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Sample records for continental tundra site

  1. Invertebrate communities of Arctic tundra ponds as related to proximity to drill site reserve pits

    International Nuclear Information System (INIS)

    Byron, E.; Williams, N.; Hoffman, R.; Elder, B.

    1994-01-01

    Aquatic invertebrate communities were assessed for diversity and abundance in North Slope tundra ponds of Prudhoe Bay, Alaska during the summer of 1992 as part of an evaluation of potential effects of exposure to petroleum drill site reserve pits (previously used for storing drill site wastes). The invertebrate communities of these shallow, tundra ponds provide abundant food for migratory, aquatic birds that use this area during the summer breeding season. The study was designed to compare abundance and diversity estimates of invertebrates in ponds surrounding the drill sites that differed in distance (and presumed exposure) to drill site reserve pits. The pits, themselves, were not sampled as part of this study. Invertebrate abundance and diversity estimates, assessed as standard biological criteria, were evaluated relative to water chemistry of the ponds, distance to the gravel pads or reserve pits, and pond morphometry. The results indicated the importance of pond morphometry in determining the structure of the invertebrate community. Shallow, exposed ponds tended to be dominated by different invertebrate communities than deeper, narrow ponds at the margins of frost polygons. In contrast, pond chemistry and relative exposure to drill sites were not predictive of invertebrate abundance or diversity

  2. Ecotypic differences in the phenology of the tundra species Eriophorum vaginatum reflect sites of origin.

    Science.gov (United States)

    Parker, Thomas C; Tang, Jianwu; Clark, Mahalia B; Moody, Michael M; Fetcher, Ned

    2017-11-01

    Eriophorum vaginatum is a tussock-forming sedge that contributes significantly to the structure and primary productivity of moist acidic tussock tundra. Locally adapted populations (ecotypes) have been identified across the geographical distribution of E. vaginatum ; however, little is known about how their growth and phenology differ over the course of a growing season. The growing season is short in the Arctic and therefore exerts a strong selection pressure on tundra species. This raises the hypothesis that the phenology of arctic species may be poorly adapted if the timing and length of the growing season change. Mature E. vaginatum tussocks from across a latitudinal gradient (65-70°N) were transplanted into a common garden at a central location (Toolik Lake, 68°38'N, 149°36'W) where half were warmed using open-top chambers. Over two growing seasons (2015 and 2016), leaf length was measured weekly to track growth rates, timing of senescence, and biomass accumulation. Growth rates were similar across ecotypes and between years and were not affected by warming. However, southern populations accumulated significantly more biomass, largely because they started to senesce later. In 2016, peak biomass and senescence of most populations occurred later than in 2015, probably induced by colder weather at the beginning of the growing season in 2016, which caused a delayed start to growth. The finish was delayed as well. Differences in phenology between populations were largely retained between years, suggesting that the amount of time that these ecotypes grow has been selected by the length of the growing seasons at their respective home sites. As potential growing seasons lengthen, E. vaginatum may be unable to respond appropriately as a result of genetic control and may have reduced fitness in the rapidly warming Arctic tundra.

  3. The surface energy balance of a polygonal tundra site in northern Siberia – Part 2: Winter

    Directory of Open Access Journals (Sweden)

    J. Boike

    2011-06-01

    Full Text Available In this study, we present the winter time surface energy balance at a polygonal tundra site in northern Siberia based on independent measurements of the net radiation, the sensible heat flux and the ground heat flux from two winter seasons. The latent heat flux is inferred from measurements of the atmospheric turbulence characteristics and a model approach. The long-wave radiation is found to be the dominant factor in the surface energy balance. The radiative losses are balanced to about 60 % by the ground heat flux and almost 40 % by the sensible heat fluxes, whereas the contribution of the latent heat flux is small. The main controlling factors of the surface energy budget are the snow cover, the cloudiness and the soil temperature gradient. Large spatial differences in the surface energy balance are observed between tundra soils and a small pond. The ground heat flux released at a freezing pond is by a factor of two higher compared to the freezing soil, whereas large differences in net radiation between the pond and soil are only observed at the end of the winter period. Differences in the surface energy balance between the two winter seasons are found to be related to differences in snow depth and cloud cover which strongly affect the temperature evolution and the freeze-up at the investigated pond.

  4. The influence of soil organic matter chemistry and site/soil properties in predicting the decomposability of tundra soils

    Science.gov (United States)

    Matamala, R.; Jastrow, J. D.; Fan, Z.; Liang, C.; Calderon, F.; Michaelson, G.; Mishra, U.; Ping, C. L.

    2017-12-01

    With the increase in high latitude warming, there is a need to better understand the potential vulnerability of soil organic matter (SOM) stored in Arctic regions. In this study, we used mid infrared spectroscopy (MidIR) to determine the influence of soil chemistry and site properties in the short-term mineralization potential of SOM stored in tundra soils. Soils from the active and permafrost layers were collected from four tundra sites on the Coastal Plain, and Arctic Foothills of the North Slope of Alaska and were incubated for 60 days at a range of temperatures. Site and soil properties including acidic versus non-acidic tundra, lowland versus upland areas, total soil organic carbon (TOC) and total nitrogen (TN) concentrations, 60-day carbon mineralization potential (CMP), MidIR spectra and the chemical composition of the SOM stored in these soils were determined. Partial least squares (PLS) models for CMP versus MidIR spectra were produced upon splitting the dataset into site and soil properties categories. We found that SOM composition determined by MidIR spectroscopy was most effective in predicting CMP for tundra soils and it was most relevant for the active-layer mineral and upper permafrost soil horizons and/or soils with C concentrations of 10% or lower. Analysis of the factor loadings and standardized beta coefficients from the CMP PLS models indicated that spectral bands associated with clay contents, phenolic OH, aliphatic, silicates, carboxylic acids, and polysaccharides were influential for lower TOC soils, but these bands were less important for higher TOC soils. High TOC soils were influenced by a combination of other factors. Our results suggest that different factors affect the short-term CMP of SOM in tundra soils depending on the amount of TOC present. We show MidIR as a powerful tool for quickly and reasonably estimating the short-term CMP of tundra soils. Widespread application of MidIR measurements to already collected and archived tundra

  5. The Cooling Capacity of Mosses: Controls on Water and Energy Fluxes in a Siberian Tundra Site

    NARCIS (Netherlands)

    Blok, D.; Heijmans, M.M.P.D.; Schaepman-Strub, G.; Ruijven, van J.; Parmentier, F.J.W.; Maximov, T.C.; Berendse, F.

    2011-01-01

    Arctic tundra vegetation composition is expected to undergo rapid changes during the coming decades because of changes in climate. Higher air temperatures generally favor growth of deciduous shrubs, often at the cost of moss growth. Mosses are considered to be very important to critical tundra

  6. Carbon dioxide exchange in three tundra sites show a dissimilar response to environmental variables

    DEFF Research Database (Denmark)

    Mbufong, Herbert Njuabe; Lund, Magnus; Christensen, Torben Røjle

    2015-01-01

    variability. An improved understanding of the control of ancillary variables on net ecosystem exchange (NEE), gross primary production (GPP) and ecosystem respiration (Re) will improve the accuracy with which CO2 exchange seasonality in Arctic tundra ecosystems is modelled. Fluxes were measured with the eddy...

  7. Short term solar radiation forecasting: Island versus continental sites

    International Nuclear Information System (INIS)

    Boland, John; David, Mathieu; Lauret, Philippe

    2016-01-01

    Due its intermittency, the large-scale integration of solar energy into electricity grids is an issue and more specifically in an insular context. Thus, forecasting the output of solar energy is a key feature to efficiently manage the supply-demand balance. In this paper, three short term forecasting procedures are applied to island locations in order to see how they perform in situations that are potentially more volatile than continental locations. Two continental locations, one coastal and one inland are chosen for comparison. At the two time scales studied, ten minute and hourly, the island locations prove to be more difficult to forecast, as shown by larger forecast errors. It is found that the three methods, one purely statistical combining Fourier series plus linear ARMA models, one combining clear sky index models plus neural net models, and a third using a clear sky index plus ARMA, give similar forecasting results. It is also suggested that there is great potential of merging modelling approaches on different horizons. - Highlights: • Solar energy forecasting is more difficult for insular than continental sites. • Fourier series plus linear ARMA models are one forecasting method tested. • Clear sky index models plus neural net models are also tested. • Clear sky index models plus linear ARMA is also an option. • All three approaches have similar skill.

  8. Site scale wetness classification of tundra regions with C-band SAR satellite data

    DEFF Research Database (Denmark)

    Widhalm, Barbara; Bartsch, Annett; Siewert, Matthias Benjamin

    2016-01-01

    A representative and consistent wetland map for the circumpolar region is required for a range of applications including modelling of permafrost properties as well as upscaling of carbon pools and fluxes. Synthetic Aperture Radar (SAR) data has been shown to be suitable for wetland mapping, espec...... resolution C-band SAR based wetness level map can be derived for tundra regions where no scattering due to tree trunks hampers the applied methodology....

  9. Tundra in the rain

    DEFF Research Database (Denmark)

    Keuper, Frida; Parmentier, Frans Jan W; Blok, Daan

    2012-01-01

    Precipitation amounts and patterns at high latitude sites have been predicted to change as a result of global climatic changes. We addressed vegetation responses to three years of experimentally increased summer precipitation in two previously unaddressed tundra types: Betula nana-dominated shrub...... tundra (northeast Siberia) and a dry Sphagnum fuscum-dominated bog (northern Sweden). Positive responses to approximately doubled ambient precipitation (an increase of 200 mm year-1) were observed at the Siberian site, for B. nana (30 % larger length increments), Salix pulchra (leaf size and length...... increments) and Arctagrostis latifolia (leaf size and specific leaf area), but none were observed at the Swedish site. Total biomass production did not increase at either of the study sites. This study corroborates studies in other tundra vegetation types and shows that despite regional differences...

  10. Enhanced biological degradation of crude oil in a Spitsbergen tundra site

    International Nuclear Information System (INIS)

    Sveum, P.; Faksness, L.-G.

    1993-01-01

    A series of oil-contaminated tundra plots on Spitsbergen was treated with combinations of five different fertilizer additives. Both organic and mineral nutrient sources were used, alone or in combination. Biological degradation of oil was recorded in all of the plots. The extent of degradation depended on the type of fertilizer added. The local conditions influence oil degradation significantly, as well as the effect of the fertilizer. Urea, SkogAN (a slow releasing fertilizer), and a blend of fish meals all give high degrees of oil degradation. Both the microbial parameters and the total heterotrophic respiration are influenced by the addition of fertilizers. 6 refs., 13 figs., 3 tabs

  11. Pulsed resources at tundra breeding sites affect winter irruptions at temperate latitudes of a top predator, the snowy owl.

    Science.gov (United States)

    Robillard, A; Therrien, J F; Gauthier, G; Clark, K M; Bêty, J

    2016-06-01

    Irruptive migration is mostly observed in species specialized on pulsed resources and is thought to be a response to unpredictable changes in food supply. We assessed two alternative hypotheses to explain the periodic winter irruptions of snowy owls Bubo scandiacus every 3-5 years in temperate North America: (a) the lack-of-food hypothesis, which states that a crash in small mammal abundance on the Arctic breeding grounds forces owls to move out of the tundra massively to search for food in winter; (b) the breeding-success hypothesis, which states that high abundance of tundra small mammals during the summer allows for high production of young, thus increasing the pool of migrants moving south the following winter. We modeled winter irruptions of snowy owls in relation to summer food resources and geographic location. Winter abundance of owls was obtained from citizen-based surveys from 1994 to 2011 and summer abundance of small mammals was collected in summer at two distant sites in Canada: Bylot Island, NU (eastern High Arctic) and Daring Lake, NWT (central Low Arctic). Winter owl abundance was positively related to prey abundance during the previous summer at both sites and tended to decrease from western to eastern temperate North America. Irruptive migration of snowy owls was therefore best explained by the breeding success hypothesis and was apparently caused by large-scale summer variations in food. Our results, combined with previous findings, suggest that the main determinants of irruptive migration may be species specific even in a guild of apparently similar species.

  12. 78 FR 8190 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Science.gov (United States)

    2013-02-05

    ... DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management [Docket No. BOEM-2012-0090] Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf (OCS) Offshore... Assessment (EA) for Commercial Wind Leasing and Site Assessment Activities on the OCS Offshore North Carolina...

  13. 77 FR 74218 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Science.gov (United States)

    2012-12-13

    ...] Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf (OCS) Offshore... initiative is designed to identify areas that appear to be suitable for wind energy leasing on the OCS, known... responsible renewable energy leasing process. More information on the ``Smart from the Start'' initiative can...

  14. Continental margin neotectonics in South Africa: a nuclear siting approach

    International Nuclear Information System (INIS)

    Andreoli, M.A.G.; Hambleton-Jones, B.B.; Anderson, N.J.B.; Faurie, J.N.; Raubenheimer, E.; Antoine, L.; Von Veh, M.W.; McMillan, I.K.

    1990-01-01

    Neotectonic activity in South Africa has only recently received attention despite the fact that a rigorous knowledge of this phenomenon could have a major impact on industrial development within certain areas. Since the early 1980s the Atomic Energy Corporation of South Africa has addressed this specific problem in the process of detailed site investigations for the licensing of six facilities related to the nuclear industry. The data indicates that there is a general correspondence in five selected areas along the South African coast between the development of Quarternary joints/faults and the degree of seismic activity recorded in each geological domain. Finally, the results provide new data that may add to a recent survey of global tectonic stresses. 13 refs., 1 fig

  15. Chloroform emissions from the Alaskan Arctic tundra

    Science.gov (United States)

    Rhew, Robert C.; Teh, Yit Arn; Abel, Triffid; Atwood, Alyssa; Mazéas, Olivier

    2008-11-01

    Chloroform (trichloromethane, CHCl3) is the second largest carrier of natural chlorine in the troposphere after methyl chloride, contributing to the reactive chlorine burden in the troposphere and to ozone destruction in the stratosphere. Here we report CHCl3 flux measurements from coastal and interior tundra sites in northern Alaska, showing that the Arctic tundra can contribute substantial amounts of CHCl3 to the atmosphere. Emissions were measured during the 2005 and 2006 growing seasons over a range of vegetation types and hydrologic conditions, from wet sedge coastal to upland tussock tundra. Overall emissions averaged 45 nmol m-2 d-1, but fluxes were highly variable, ranging from tundra. Laboratory soil core incubations show that flooded conditions sharply reduce emission rates. A rough extrapolation suggests that the tundra globally could account for 1-2% of the total estimated source of atmospheric CHCl3.

  16. Conifer seedling recruitment across a gradient from forest to alpine tundra: effects of species, provenance, and site

    Science.gov (United States)

    Castanha, C.; Torn, M.S.; Germino, M.J.; Weibel, Bettina; Kueppers, L.M.

    2013-01-01

    Background: Seedling germination and survival is a critical control on forest ecosystem boundaries, such as at the alpine–treeline ecotone. In addition, while it is known that species respond individualistically to the same suite of environmental drivers, the potential additional effect of local adaptation on seedling success has not been evaluated. Aims: To determine whether local adaptation may influence the position and movement of forest ecosystem boundaries, we quantified conifer seedling recruitment in common gardens across a subalpine forest to alpine tundra gradient at Niwot Ridge, Colorado, USA. Methods: We studied Pinus flexilis and Picea engelmannii grown from seed collected locally at High (3400 m a.s.l.) and Low (3060 m a.s.l.) elevations. We monitored emergence and survival of seeds sown directly into plots and survival of seedlings germinated indoors and transplanted after snowmelt. Results: Emergence and survival through the first growing season was greater for P. flexilis than P. engelmannii and for Low compared with High provenances. Yet survival through the second growing season was similar for both species and provenances. Seedling emergence and survival tended to be greatest in the subalpine forest and lowest in the alpine tundra. Survival was greater for transplants than for field-germinated seedlings. Conclusions: These results suggest that survival through the first few weeks is critical to the establishment of natural germinants. In addition, even small distances between seed sources can have a significant effect on early demographic performance – a factor that has rarely been considered in previous studies of tree recruitment and species range shifts.

  17. Site investigations for repositories for solid radioactive wastes in deep continental geological formations

    International Nuclear Information System (INIS)

    1982-01-01

    This report reviews the earth-science investigations and associated scientific studies that may be needed to select a repository site and confirm that its characteristics are such that it will provide a safe confinement for solidified high-level and alpha-bearing and certain other solid radioactive wastes. Site investigations, as used in this report, cover earth sciences and associated safety analyses. Other site-investigation activities are identified but not otherwise considered here. The repositories under consideration are those consisting of mined cavities in deep continental rocks for accepting wastes in the solid and packaged form. The term deep as used in this report is used solely to emphasize the distinction between the repositories discussed in this report and those for shallow-ground disposal. In general, depths under consideration here are greater than 200 metres. The term continental refers to those geological formations that occur either beneath present-day land masses and adjoining islands or beneath the shallow seas. One of the objectives of site investigations is to collect the site-specific data necessary for the different evaluations, such as modelling required to assess the long-term safety of an underground repository

  18. Hydrological patterns in warming permafrost: comparing results from a control and drained site on a floodplain tundra near Chersky, Northeast Siberia

    Science.gov (United States)

    Boelck, Sandra; Goeckede, Mathias; Hildebrandt, Anke; Vonk, Jorien; Heimann, Martin

    2017-04-01

    Permafrost areas represent a major reservoir for organic carbon. At the same time, permafrost ecosystems are very susceptible to changing climate conditions. The stability of this reservoir, i.e. changes in lateral and vertical carbon fluxes in permafrost ecosystems, largely depends on groundwater level, temperature and vegetation community. Particularly during summer when the soil thaws and a so-called active layer develops, fluctuations in carbon flux rates are often dominantly driven by water availability. Such dry soil conditions are expected to become more frequent in the future due to deepening active layers as a consequence of climate change. This could result in degradation of polygonal tundra landscape properties with channelled water transport pathways. Therefore, water table depth and the associated groundwater fluxes are crucial to understand transport patterns and to quantify the lateral export of carbon through an aquatic system. Consequently, a fundamental understanding of hydrological patterns on ecosystem structure and function is required to close the carbon balance of permafrost ecosystems. This study focuses on small-scale hydrological patterns and its influencing factors, such as topography and precipitation events. Near Chersky, Northeast Siberia, we monitored (i) a control site of floodplain tundra, and (ii) a drained site, characterised by a drainage ring which was constructed in 2004, to study the effects of water availability on the carbon cycle. This experimental disturbance simulates drainage effects following the degradation of ice-rich permafrost ecosystems under future climate change. Continuous monitoring of water table depth in drained and control areas revealed small-scale water table variations. At several key locations, we collected water samples to determine the isotopic composition (δ18O, δD) of surface water, suprapermafrost groundwater and precipitation. Furthermore, a weir at the drainage ditch was constructed to directly

  19. Where do the treeless tundra areas of northern highlands fit in the global biome system: toward an ecologically natural subdivision of the tundra biome.

    Science.gov (United States)

    Virtanen, Risto; Oksanen, Lauri; Oksanen, Tarja; Cohen, Juval; Forbes, Bruce C; Johansen, Bernt; Käyhkö, Jukka; Olofsson, Johan; Pulliainen, Jouni; Tømmervik, Hans

    2016-01-01

    delimitation problem, help in consistent characterization of research sites, and create a basis for further biogeographic and ecological research in global tundra environments.

  20. Hurricane Sandy's Fingerprint: Ripple Bedforms at an Inner Continental Shelf Sorted Bedform Field Site

    Science.gov (United States)

    DuVal, C.; Trembanis, A. C.; Beaudoin, J. D.; Schmidt, V. E.; Mayer, L. A.

    2013-12-01

    The hydrodynamics and seabed morphodynamics on the inner continental shelf and near shore environments have increasing relevance with continued development of near shore structures, offshore energy technologies and artificial reef construction. Characterizing the stresses on and response of the seabed near and around seabed objects will inform best practices for structural design, seabed mine and unexploded ordnance detection, and archaeological and benthic habitat studies. As part of an ONR funded project, Delaware's Redbird Reef is being studied for object scour and sorted bedform morphodynamics (Trembanis et al., in press). Central to this study are the effects of large storm events, such as Hurricane Sandy, which have had significant impact on the seafloor. Previous studies of inner shelf bedform dynamics have typically focused on near bed currents and bed stressors (e.g. Trembanis et al., 2004), sorted bedforms (e.g. Green et al., 2004) and object scour (e.g. Quinn, 2006; Trembanis et al., 2007; Mayer et al., 2007), but our understanding of the direct effects of objects and object scour on bedform morphodynamics is still incomplete. With prominent sorted bedform ripple fields, the Delaware Redbird artificial reef site, composed of 997 former New York City subway cars, as well as various military vehicles, tugboats, barges and ballasted tires, has made an ideal study location (Raineault et al., 2013 and 2011). Acoustic mapping of the Redbird reef three days prior to Sandy and two days after the following nor'easter, captured the extensive effects of the storms to the site, while acoustic Doppler current profilers characterized both the waves and bottom currents generated by the storm events. Results of the post-Sandy survey support the theory of sorted bedform evolution proposed by Murray and Thieler (2004). Acoustic imagery analysis indicates a highly energized and mobile bed during the storms, leading to self-organization of bedforms and creation of large

  1. Roots in the tundra

    NARCIS (Netherlands)

    Wang, Peng

    2016-01-01

    Global climate has been warming up for the last decades and it will continue in this century. The Arctic is the part of the globe that warms fastest and is more sensitive to climate warming. Aboveground productivity of Arctic tundra has been shown to increase in response to warmer climates. However,

  2. Tundra, Chapter 5

    Science.gov (United States)

    K. Nadelhoffer; L.H. Geiser

    2011-01-01

    The North American Arctic, comprising the Tundra and Arctic Cordillera ecoregions (CEC 1997, Chapter 2), covers more than 3 million km2 (300 million ha), and accounts for nearly 14 percent of the North American land mass. The North American Arctic also constitutes about 20 percent of the much larger circumpolar Arctic shared by Canada, the United...

  3. New York's TUNDRA.

    Science.gov (United States)

    Kalinowski, Thomas

    1983-01-01

    Found at the summit of some of the highest peaks of New York State's Adirondack Mountains are low-growing plants similar, and in many cases, identical to plants growing in the Arctic. Describes these plants and the environment in which they are found. Includes a color plate of alpine tundra plants. (Author/JN)

  4. The zone of tundra

    International Nuclear Information System (INIS)

    Titaeva, N.A.; Taskaev, A.I.

    1983-01-01

    Peculiarities of radionuclide migration in the zone of tundra are considered. High 232 Th content, high 232 Th/ 238 U values at low 238 U and 226 Ra concentrations in rocks are shown to be characteristic for the chosen zone. Data on methods of 238 U and 232 Th determination in natural waters, as well as content of radionuclides in water and bottom sediments are presented. Formation of soils under the conditions of mountain tundra is shown to result in noticeable redistribution of radioactive elements as well as all their isotopes. Data on U, Th, Ra isotope content in different plants and certain organs of plants are presented. Principal statistical parameters both of content of certain U, Th, Ra isotopes and their isotope relations on the whole by soil and vegetation of the investigated region are presented. When characterizing storage of isotopes of different elements in vegetation of the zone of tundra it is necessary to note that the dependence 226 Ra( 228 Ra)> 228 Th> 227 Th> 230 Th> 232 Th> 238 U> 234 U is typical for it. Intensity of radionuclide inclusion in the biogenic migration cycle in the zone of tundra is higher than in the zone of taiga

  5. Contexts for change in alpine tundra

    Science.gov (United States)

    Malanson, George P.; Rose, Jonathan P.; Schroeder, P. Jason; Fagre, Daniel B.

    2011-01-01

    Because alpine tundra is responding to climate change, a need exists to understand the meaning of observed changes. To provide context for such interpretation, the relevance of niche and neutral theories of biogeography and the continuum and classification approaches to biogeographic description are assessed. Two extensive studies of alpine tundra, from the Indian Peaks area, Colorado and Glacier National Park, Montana, are combined. The data are ordinated to describe relations. The pattern that emerges is one of a continuum of vegetation, but with the distinctions one might expect from distant sites. The relationships of the similarity of vegetation on all possible pairs of sites to the environmental differences and geographic distances are analyzed using Mantel correlations. Because distance and environmental differences in climate between the two sites are correlated, partial correlations are weak but still significant. More advanced analyses are suggested for this environment prior to interpretation of monitoring efforts such as GLORIA.

  6. Interannual changes in seafloor surficial geology at an artificial reef site on the inner continental shelf

    Science.gov (United States)

    Raineault, Nicole A.; Trembanis, Arthur C.; Miller, Douglas C.; Capone, Vince

    2013-04-01

    The influence of reef structures on seafloor surface sediments has implications for marine spatial planning and coastal development, including use of the coastal zone for offshore wind energy. We present results of interannual changes in seafloor surficial geology at the Redbird artificial reef site, located on the continental shelf offshore of Delaware Bay. The Redbird reef is composed of NYC subway cars, barges, tugboats, and other sunken objects. Since objects were added sporadically between 1996 and 2009, the survey area acts as a natural laboratory to study the evolution of the surrounding seafloor at a structural reef habitat through time. Annual side-scan surveys from 2008 through 2011, and one bathymetric survey in 2010 provide information about surface geology and morphology. Local wave and current data for this time period were analyzed to determine the main morphological agents. Automated backscatter segmentation show that three bottom types dominate and that these large-scale (>10 m) surface sediment patterns persist from year to year. Grab samples reveal that the bottom types are silty sand with clay and sandy gravel. Clear sediment and biological patterns emerged revealing the influence of the objects on the seafloor. Comet-shaped moats of sandy gravel surround single objects and grow to form large-scale coalesced patches around groups of objects. Alignment of sediment patches suggests the periodic hydrodynamic influence of seasonal storms. The abundance and diversity of organisms increases with decreasing clay/silt content. Evidence of scour includes the removal of fine sediments, the formation of moats 1-30 m in diameter and 0.5-1 m deep around the reef objects, and the >1 m settling of objects into the seafloor. Data suggest subway cars reached equilibrium with the environment in 6-7 years, but that larger objects or clusters of objects take a longer time to equilibrate and have farther-reaching effects. Knowledge of local wave and current climate

  7. Identification of unrecognized tundra fire events on the north slope of Alaska

    Science.gov (United States)

    Jones, Benjamin M.; Breen, Amy L.; Gaglioti, Benjamin V.; Mann, Daniel H.; Rocha, Adrian V.; Grosse, Guido; Arp, Christopher D.; Kunz, Michael L.; Walker, Donald A.

    2013-01-01

    Characteristics of the natural fire regime are poorly resolved in the Arctic, even though fire may play an important role cycling carbon stored in tundra vegetation and soils to the atmosphere. In the course of studying vegetation and permafrost-terrain characteristics along a chronosequence of tundra burn sites from AD 1977, 1993, and 2007 on the North Slope of Alaska, we discovered two large, previously unrecognized tundra fires. The Meade River fire burned an estimated 500 km2 and the Ketik River fire burned an estimated 1200 km2. Based on radiocarbon dating of charred twigs, analysis of historic aerial photography, and regional climate proxy data, these fires likely occurred between AD 1880 and 1920. Together, these events double the estimated burn area on the North Slope of Alaska over the last ~100 to 130 years. Assessment of vegetation succession along the century-scale chronosequence of tundra fire disturbances demonstrates for the first time on the North Slope of Alaska that tundra fires can facilitate the invasion of tundra by shrubs. Degradation of ice-rich permafrost was also evident at the fire sites and likely aided in the presumed changes of the tundra vegetation postfire. Other previously unrecognized tundra fire events likely exist in Alaska and other Arctic regions and identification of these sites is important for better understanding disturbance regimes and carbon cycling in Arctic tundra.

  8. Vegetation shifts observed in arctic tundra 17 years after fire

    Science.gov (United States)

    Barrett, Kirsten; Rocha, Adrian V.; van de Weg, Martine Janet; Shaver, Gaius

    2012-01-01

    With anticipated climate change, tundra fires are expected to occur more frequently in the future, but data on the long-term effects of fire on tundra vegetation composition are scarce. This study addresses changes in vegetation structure that have persisted for 17 years after a tundra fire on the North Slope of Alaska. Fire-related shifts in vegetation composition were assessed from remote-sensing imagery and ground observations of the burn scar and an adjacent control site. Early-season remotely sensed imagery from the burn scar exhibits a low vegetation index compared with the control site, whereas the late-season signal is slightly higher. The range and maximum vegetation index are greater in the burn scar, although the mean annual values do not differ among the sites. Ground observations revealed a greater abundance of moss in the unburned site, which may account for the high early growing season normalized difference vegetation index (NDVI) anomaly relative to the burn. The abundance of graminoid species and an absence of Betula nana in the post-fire tundra sites may also be responsible for the spectral differences observed in the remotely sensed imagery. The partial replacement of tundra by graminoid-dominated ecosystems has been predicted by the ALFRESCO model of disturbance, climate and vegetation succession.

  9. Plant and microbial uptake and allocation of organic and inorganic nitrogen related to plant growth forms and soil conditions at two subarctic tundra sites in Sweden

    DEFF Research Database (Denmark)

    Sørensen, Pernille Lærkedal; Clemmensen, Karina Engelbrecht; Michelsen, Anders

    2008-01-01

    In order to follow the uptake and allocation of N in different plant functional types and microbes in two tundra ecosystems differing in nutrient availability, we performed a 15Nlabeling experiment with three N forms and followed the partitioning of 15N label among plants, microorganisms and soil...... transported a high proportion of 15N to aboveground parts, whereas the dwarf shrubs allocated most 15N to underground storage. Enhanced 13C in Betula nana roots represents the first field evidence of uptake of intact glycine by this important circumpolar plant. Plant and microbial uptake of label...... was complementary as plants took up more inorganic than organic N, while microbes preferred organic N. Microbes initially took up a large part of the added label, but over the following four weeks microbial 15N decreased by 50% and most 15N was recovered in soil organic matter, while a smaller but slowly increasing...

  10. Tundra is a consistent source of CO2 at a site with progressive permafrost thaw during 6 years of chamber and eddy covariance measurements

    Science.gov (United States)

    Celis, Gerardo; Mauritz, Marguerite; Bracho, Rosvel; Salmon, Verity G.; Webb, Elizabeth E.; Hutchings, Jack; Natali, Susan M.; Schädel, Christina; Crummer, Kathryn G.; Schuur, Edward A. G.

    2017-06-01

    Current and future warming of high-latitude ecosystems will play an important role in climate change through feedbacks to the global carbon cycle. This study compares 6 years of CO2 flux measurements in moist acidic tundra using autochambers and eddy covariance (Tower) approaches. We found that the tundra was an annual source of CO2 to the atmosphere as indicated by net ecosystem exchange using both methods with a combined mean of 105 ± 17 g CO2 C m-2 y-1 across methods and years (Tower 87 ± 17 and Autochamber 123 ± 14). The difference between methods was largest early in the observation period, with Autochambers indicated a greater CO2 source to the atmosphere. This discrepancy diminished through time, and in the final year the Autochambers measured a greater sink strength than tower. Active layer thickness was a significant driver of net ecosystem carbon exchange, gross ecosystem primary productivity, and Reco and could account for differences between Autochamber and Tower. The stronger source initially attributed lower summer season gross primary production (GPP) during the first 3 years, coupled with lower ecosystem respiration (Reco) during the first year. The combined suppression of GPP and Reco in the first year of Autochamber measurements could be the result of the experimental setup. Root damage associated with Autochamber soil collar installation may have lowered the plant community's capacity to fix C, but recovered within 3 years. While this ecosystem was a consistent CO2 sink during the summer, CO2 emissions during the nonsummer months offset summer CO2 uptake each year.

  11. Tundra Rehabilitation in Alaska's Arctic

    Science.gov (United States)

    Lynn, L. A.

    2012-12-01

    Oil exploration in Alaska's Arctic has been conducted for more than 40 years, resulting in over 3,640 ha of gravel fill placed for roads, pads, and airstrips to support the industry. Likewise, tundra disturbance from burying power lines and by tundra vehicle travel are also common. Rehabilitation of disturbed sites began around 2002, with well over 150 ha that has been previously treated or is currently being rehabilitated. Two primary goals of rehabilitation efforts have been 1) revegetation by indigenous species, and 2) limiting thermokarst. Early efforts were concerned that removing gravel and having exposed bare ground would lead to extensive subsidence and eolian erosion. Native grass cultivars (e.g. Poa glauca, Arctagrostis latifolia, and Festuca rubra) were seeded to create vegetation cover quickly with the expectation that these grasses would survive only temporarily. The root masses and leaf litter were also expected to trap indigenous seed to enhance natural recolonization by indigenous plants. Due to the remote location of these sites, many of which are only accessible by helicopter, most are visited only two to three times following cultivation treatments, providing a limited data pool. At many sites, the total live seeded grass cover declined about 15% over the first 5¬-6 years (from around 30% to 15% cover), while total live indigenous vascular cover increased from no or trace cover to an average of 10% cover in that time. Cover of indigenous vascular plants at sites that were not seeded with native grass cultivars averaged just less than 10% after 10 years, showing no appreciable difference between the two approaches. Final surface elevations at the sites affect local hydrology and soil moisture. Other factors that influence the success of vegetation cover are proximity to the Arctic coast (salt effects), depth of remaining gravel, and changes in characteristics of the near-surface soil. Further development of rehabilitation techniques and the

  12. Can antibrowsing defense regulate the spread of woody vegetation in arctic tundra?

    Science.gov (United States)

    Bryant, John P.; Joly, Kyle; Chapin, F. Stuart; DeAngelis, Donald L.; Kielland, Knut

    2014-01-01

    Global climate warming is projected to promote the increase of woody plants, especially shrubs, in arctic tundra. Many factors may affect the extent of this increase, including browsing by mammals. We hypothesize that across the Arctic the effect of browsing will vary because of regional variation in antibrowsing chemical defense. Using birch (Betula) as a case study, we propose that browsing is unlikely to retard birch expansion in the region extending eastward from the Lena River in central Siberia across Beringia and the continental tundra of central and eastern Canada where the more effectively defended resin birches predominate. Browsing is more likely to retard birch expansion in tundra west of the Lena to Fennoscandia, Iceland, Greenland and South Baffin Island where the less effectively defended non-resin birches predominate. Evidence from the literature supports this hypothesis. We further suggest that the effect of warming on the supply of plant-available nitrogen will not significantly change either this pan-Arctic pattern of variation in antibrowsing defense or the resultant effect that browsing has on birch expansion in tundra. However, within central and east Beringia warming-caused increases in plant-available nitrogen combined with wildfire could initiate amplifying feedback loops that could accelerate shrubification of tundra by the more effectively defended resin birches. This accelerated shrubification of tundra by resin birch, if extensive, could reduce the food supply of caribou causing population declines. We conclude with a brief discussion of modeling methods that show promise in projecting invasion of tundra by woody plants.

  13. The exchange of energy, water and carbon dioxide between wet arctic tundra and the atmosphere at the Lena River Delta, Northern Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Kutzbach, L.

    2006-07-01

    The ecosystem-scale exchange fluxes of energy, water and carbon dioxide between wet arctic tundra and the atmosphere were investigated by the micrometeorological eddy covariance method. The investigation site was the centre of the Lena River Delta in Northern Siberia characterised by a polar and distinctly continental climate, very cold and ice-rich permafrost and its position at the interface between the Eurasian continent and the Arctic Ocean. The measurements were performed on the surface of a Holocene river terrace characterised by wet polygonal tundra. The soils at the site are characterised by high organic matter content, low nutrient availability and pronounced water logging. The vegetation is dominated by sedges and mosses. The fluctuations of the H{sub 2}O and CO{sub 2} concentrations were measured with a closed-path infrared gas analyser. The fast-response eddy covariance measurements were supplemented by a set of slow-response meteorological and soil-meteorological measurements. The combined datasets of the two campaigns 2003 and 2004 were used to characterise the seasonal course of the energy, water and CO{sub 2} fluxes and the underlying processes for the synthetic measurement period May 28..October 21 2004/2003 including the period of snow and soil thawing as well as the beginning of refreezing. The synthetic measurement period 2004/2003 was characterised by a long snow ablation period and a late start of the growing season. On the other hand, the growing season ended also late due to high temperatures and snow-free conditions in September. The cumulative summer energy partitioning was characterised by low net radiation, large ground heat flux, low latent heat flux and very low sensible heat flux compared to other tundra sites. These findings point out the major importance of the very cold permafrost for the summer energy budget of the tundra in Northern Siberia. (orig./SR)

  14. The Jungfraujoch high-alpine research station (3454 m) as a background clean continental site for the measurement of aerosol parameters

    Energy Technology Data Exchange (ETDEWEB)

    Nyeki, S.; Baltensperger, U.; Jost, D.T.; Weingartner, E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Colbeck, I. [Essex Univ., Colchester (United Kingdom)

    1997-09-01

    Aerosol physical parameter measurements are reported here for the first full annual set of data from the Jungfraujoch site. Comparison to NOAA background and regional stations indicate that the site may be designated as `clean continental` during the free tropospheric influenced period 03:00 -09:00. (author) figs., tab., refs.

  15. Radon-222 in boundary layer and free tropospheric continental outflow events at three ACE-Asia sites

    International Nuclear Information System (INIS)

    Zahorowski, Wlodek; Chambers, Scott; Wang Tao

    2005-01-01

    A 1-year record of hourly atmospheric radon-222 concentration observations at three ACE-Asia network sites Hok Tsui (Hong Kong), Gosan (Jeju Island) and Mauna Loa Observatory (Hawaii) is presented and discussed. The observations include the spring 2001 ACE-Asia intensive operation period. Site locations were chosen for the experimental characterization of both boundary layer (Hok Tsui, Gosan) and free tropospheric (Mauna Loa) continental outflow to the Pacific. A significant seasonal variability in background radon concentration is quantified at each site with the ratios of winter maximum to summer minimum background of 96, 15 and 3 for Hok Tsui, Gosan and Mauna Loa, respectively. Only during summer were background radon concentrations directly comparable with unperturbed marine values (20 mBq/m 3 ). The variability in radon signal was characterized at each site on diurnal to seasonal timescales. The seasonal variability in fetch regions for air masses experiencing the greatest and smallest terrestrial influence was characterized using 10-day back trajectories of air masses corresponding to radon concentrations higher (lower) than the 90th (10th) percentile value. The trajectory analyses for Hok Tsui and Gosan, as well as a direct analysis of the experimental results, further supports the previously postulated existence of a strong spatial heterogeneity in the radon source strength in East Asia. Back trajectories of free tropospheric air masses reaching Mauna Loa indicated source regions deep within the Asian continent primarily between 20 and 40 deg N. This fetch region is different from that influencing the Hok Tsui and Gosan sites. The radon concentration of air masses reaching Mauna Loa was shown to vary seasonally as well as with latitude of the predominant fetch region. Possible mechanisms of this phenomenon have been identified and include (a) seasonal variation in the radon source, (b) seasonal variation in the strength, frequency and/or efficiency of

  16. 76 FR 7226 - Commercial Wind Lease Issuance and Site Characterization Activities; Atlantic Outer Continental...

    Science.gov (United States)

    2011-02-09

    ... energy initiative to accelerate responsible renewable wind energy development on the Atlantic Outer.... The OCS Renewable Energy Development Process There are generally three phases of renewable energy development on the OCS: lease issuance, site assessment, and construction and operation of a renewable energy...

  17. Photochemical processing of organic aerosol at nearby continental sites: contrast between urban plumes and regional aerosol

    Directory of Open Access Journals (Sweden)

    J. G. Slowik

    2011-03-01

    Full Text Available As part of the BAQS-Met 2007 field campaign, Aerodyne time-of-flight aerosol mass spectrometers (ToF-AMS were deployed at two sites in southwestern Ontario from 17 June to 11 July 2007. One instrument was located at Harrow, ON, a rural, agriculture-dominated area approximately 40 km southeast of the Detroit/Windsor/Windsor urban area and 5 km north of Lake Erie. The second instrument was located at Bear Creek, ON, a rural site approximately 70 km northeast of the Harrow site and 50 km east of Detroit/Windsor. Positive matrix factorization analysis of the combined organic mass spectral dataset yields factors related to secondary organic aerosol (SOA, direct emissions, and a factor tentatively attributed to the reactive uptake of isoprene and/or condensation of its early generation reaction products. This is the first application of PMF to simultaneous AMS measurements at different sites, an approach which allows for self-consistent, direct comparison of the datasets. Case studies are utilized to investigate processing of SOA from (1 fresh emissions from Detroit/Windsor and (2 regional aerosol during periods of inter-site flow. A strong correlation is observed between SOA/excess CO and photochemical age as represented by the NOx/NOy ratio for Detroit/Windsor outflow. Although this correlation is not evident for more aged air, measurements at the two sites during inter-site transport nevertheless show evidence of continued atmospheric processing by SOA production. However, the rate of SOA production decreases with airmass age from an initial value of ~10.1 μg m−3 ppmvCO−1 h−1 for the first ~10 h of plume processing to near-zero in an aged airmass (i.e. after several days. The initial SOA production rate is comparable to the observed rate in Mexico City over similar timescales.

  18. Factors determining plant species richness in Alaskan artic tundra

    NARCIS (Netherlands)

    Welle, van der M.E.W.; Vermeulen, P.J.; Shaver, G.R.; Berendse, F.

    2003-01-01

    We studied the relationship between plant N:P ratio, soil characteristics and species richness in wet sedge and tussock tundra in northern Alaska at seven sites. We also collected data on soil characteristics, above-ground biomass, species richness and composition. The N:P ratio of the vegetation

  19. Surface carbon transformations at a site of active continental serpentinization: the Tablelands, Newfoundland, Canada

    Science.gov (United States)

    Rietze, A.; Szponar, N.; Lang, S. Q.; Kohl, L.; Morrill, P. L.

    2013-12-01

    The Tablelands in Newfoundland, Canada contain terrestrial peridotite-hosted groundwater springs associated with serpentinization. These springs act as windows into subsurface systems and provide insight into their biogeochemistry. However, at sites where ultra-basic water pools and mixes with overland flow the reactions in the pools must be considered when trying to source organic compounds. We will present data from a pool (WHC2) located in the Tablelands to determine the biogeochemical carbon transformations at this mixing site. The ultra-basic, reducing groundwater springs had higher concentrations of alkanes (C1-C4) and organic acids (acetate and formate) than the overland flow, suggesting that these organics originated from the groundwater source. A two component mixing model was developed to predict what the concentrations of alkanes and organic acids would be in the WHC2 pool based on physical mixing of groundwater and overland flow. Acetate and C2-C4 alkane concentrations were fairly well predicted by the mixing model, suggesting little consumption or production of this organic acid and these alkanes in the pool. However, methane concentrations were under predicted by the model at two sampling points in the pool, suggesting production of methane at these sites. At the same two sampling locations formate concentrations were over predicted by the model, suggesting that formate was being consumed in the pool. The water at these sampling times was highly reducing; therefore oxidation of formate was not likely responsible for the consumption of formate. Organic acid fermentation using formate is one possible sink for formate and source for methane. However, the genomic data from the site has shown little evidence for microbial methanogenesis (1). Geochemical measurements of the carbon in the pool can help elucidate the most dominant source of methane. On a Bernard plot (C1/C2+ vs. δ13CCH4 (‰)) the alkanes measured at the springs plot in the thermogenic

  20. Atmospheric oxalic acid and related secondary organic aerosols in Qinghai Lake, a continental background site in Tibet Plateau

    Science.gov (United States)

    Meng, Jingjing; Wang, Gehui; Li, Jianjun; Cheng, Chunlei; Cao, Junji

    2013-11-01

    Summertime PM2.5 aerosols collected from Qinghai Lake (3200 m a.s.l.), a remote continental site in the northeastern part of Tibetan Plateau, were analyzed for dicarboxylic acids (C2-C11), ketocarboxylic acids and α-dicarbonyals. Oxalic acid (C2) is the dominant dicarboxylic acid in the samples, followed by malonic, succinic and azelaic acids. Total dicarboxylic acids (231 ± 119 ng m-3), ketocarboxylic acids (8.4 ± 4.3 ng m-3), and α-dicarbonyls (2.7 ± 2.1 ng m-3) at the Tibetan background site are 2-5 times less than those detected in lowland areas such as 14 Chinese megacities. Compared to those in other urban and marine areas enhancements in relative abundances of C2/total diacids and diacids-C/WSOC of the PM2.5 samples suggest that organic aerosols in the region are more oxidized due to strong solar radiation. Molecular compositions and air mass trajectories demonstrate that the above secondary organic aerosols in the Qinghai Lake atmosphere are largely derived from long-range transport. Ratios of oxalic acid, glyoxal and methylglyoxal to levoglucosan in PM2.5 aerosols emitted from household burning of yak dung, a major energy source for Tibetan in the region, are 30-400 times lower than those in the ambient air, which further indicates that primary emission from biomass burning is a negligible source of atmospheric oxalic acid and α-dicarbonyls at this background site.

  1. Age of remnants of a pleistocene glacier in Bolshezemelskaya tundra

    International Nuclear Information System (INIS)

    Astakhov, V.I.; Svensen, J.I.

    2002-01-01

    The age of remnants of the pleistocene glacier in Bolshezemelskaya tundra was determined by the methods of radiocarbon and uranium-thorium dating to ascertain the age of the last continental icing of the Arctic planes on European territory of Russia. It is shown that the last glacier, that has left behind fragments of its soiled bottom in the region under review, disintegrated not later than 50 thousand years ago. The age of the maximum advance of the last glacier probably falls in the range of 80-100 thousand years ago [ru

  2. Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

    DEFF Research Database (Denmark)

    Lund, Magnus; Stiegler, Christian; Abermann, Jakob

    2017-01-01

    The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt....... For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during...

  3. Sunlight stimulates methane uptake and nitrous oxide emission from the High Arctic tundra.

    Science.gov (United States)

    Li, Fangfang; Zhu, Renbin; Bao, Tao; Wang, Qing; Xu, Hua

    2016-12-01

    Many environmental factors affecting methane (CH 4 ) and nitrous oxide (N 2 O) fluxes have been investigated during the processes of carbon and nitrogen transformation in the boreal tundra. However, effects of sunlight on CH 4 and N 2 O fluxes and their budgets were neglected in the boreal tundra. Here, summertime CH 4 and N 2 O fluxes in the presence and total absence of sunlight were investigated at the six tundra sites (DM1-DM6) on Ny-Ålesund in the High Arctic. The mean CH 4 fluxes at the tundra sites ranged from -4.7 to -158.6μg CH 4 m -2 h -1 in the presence of light, indicating that a large CH 4 sink occurred in the tundra soils. However, enhanced CH 4 emission in total absence of light occurred at all the tundra sites. The mean N 2 O fluxes ranged from 7.4 to 14.6μg N 2 O m -2 h -1 in the presence of light, whereas in the absence of light all the tundra sites generally released less N 2 O, and even significant N 2 O uptake occurred there. Soil temperature, chamber temperature and soil moisture showed no significant correlations with tundra CH 4 and N 2 O flux. The presence of sunlight increased tundra CH 4 uptake by 114.2μg CH 4 m -2 h -1 and N 2 O emission by 10.9μg N 2 O m -2 h -1 compared with total absence of light. Overall our results showed that tundra ecosystem switched from CH 4 sink and N 2 O emission source in the presence of light to CH 4 emission source and N 2 O sink in the absence of light. Therefore sunlight had an important effect on CH 4 and N 2 O budgets in the High Arctic tundra. The exclusion of sunlight might overestimate CH 4 budgets, but underestimate N 2 O budgets in the Arctic tundra ecosystem. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. Relationship of cyanobacterial and algal assemblages with vegetation in the high Arctic tundra (West Spitsbergen, Svalbard Archipelago

    Directory of Open Access Journals (Sweden)

    Richter Dorota

    2015-09-01

    Full Text Available The paper presents the results of a study of cyanobacteria and green algae assemblages occurring in various tundra types determined on the basis of mosses and vascular plants and habitat conditions. The research was carried out during summer in the years 2009-2013 on the north sea-coast of Hornsund fjord (West Spitsbergen, Svalbard Archipelago. 58 sites were studied in various tundra types differing in composition of vascular plants, mosses and in trophy and humidity. 141 cyanobacteria and green algae were noted in the research area in total. Cyanobacteria and green algae flora is a significant element of many tundra types and sometimes even dominate there. Despite its importance, it has not been hitherto taken into account in the description and classification of tundra. The aim of the present study was to demonstrate the legitimacy of using phycoflora in supplementing the descriptions of hitherto described tundra and distinguishing new tundra types. Numeric hierarchical-accumulative classification (MVSP 3.1 software methods were used to analyze the cyanobacterial and algal assemblages and their co-relations with particular tundra types. The analysis determined dominant and distinctive species in the communities in concordance with ecologically diverse types of tundra. The results show the importance of these organisms in the composition of the vegetation of tundra types and their role in the ecosystems of this part of the Arctic.

  5. Succession Stages of Tundra Plant Communities Following Wildfire Disturbance in Arctic Alaska

    Science.gov (United States)

    Breen, A. L.; Hollingsworth, T. N.; Mack, M. C.; Jones, B. M.

    2015-12-01

    Rapid climate change is affecting climate-sensitive disturbance regimes throughout the world. In particular, the impacts of climate change on Arctic disturbance regimes are poorly understood because landscape-scale disturbances are infrequent or occur in remote localities. Wildfire in Arctic Alaska is presently limited by ignition source and favorable burn weather. With rapid climate change, a lengthening growing season, and subsequent increase in plant biomass and productivity, wildfire frequency and annual area burned in tundra ecosystems is expected to increase over the next century. Yet, post-fire tundra vegetation succession is inadequately characterized except at a few point locations. We identify succession stages of tussock tundra communities following wildfire using a chronosequence of 65 relevés in 10 tundra fire scars (1971-2011) and nearby unburned tundra from sites on the Seward Peninsula and northern foothills of the Brooks Range. We used the Braun-Blanquét approach to classify plant communities, and applied nonmetric multidimentional scaling (NMDS) to identify ecological gradients underlying community differentiation. The ordination revealed a clear differentiation between unburned and burned tundra communities. Ecological gradients, reflected by ordination axes, correspond to fire history (e.g., time since last fire, number of times burned, burn severity) and a complex productivity gradient. Post-fire species richness is less than unburned tundra; primarily reflected as a decrease in lichen species and turnover of bryophyte species immediately post-fire. Species richness of grasses increases post-fire and is greatest in communities that burned more than once in the past 30 years. Shrub cover and total aboveground biomass are greatest in repeat burn sites. We review and discuss our results focusing on the implications of a changing tundra fire regime, its effect on vegetation succession trajectories, and subsequent rates of carbon sequestration and

  6. Chronic gamma-radiation impact upon the state of thyroid gland of tundra voles

    International Nuclear Information System (INIS)

    Ermakova, O.V.; Raskosha, O.V.

    2002-01-01

    The histomorphological estimation of the thyroid gland status of tundra voles living in the radiation polluted sites (30-km zone around Chernobyl nuclear plant and the Komi Republic) was given in the experiment. Nature populations of tundra voles have more high variety of the thyroid parenchyma morphological reconstructions in comparison with the experimental animals. Mechanisms of the response to the radiation influence in the nature and in the experiment are different. (author)

  7. Global assessment of experimental climate warming on tundra vegetation

    DEFF Research Database (Denmark)

    Elmendorf, S.C.; Henry, G.H.R.; Bjorkman, A.D.

    2012-01-01

    Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations...... of this approach include the apparent site-specificity of results and uncertainty about the power of short-term studies to anticipate longer term change. We address these issues with a synthesis of 61 experimental warming studies, of up to 20 years duration, in tundra sites worldwide. The response of plant groups...... to warming often differed with ambient summer temperature, soil moisture and experimental duration. Shrubs increased with warming only where ambient temperature was high, whereas graminoids increased primarily in the coldest study sites. Linear increases in effect size over time were frequently observed...

  8. A Microwave Radiance Assimilation Study for a Tundra Snowpack

    Science.gov (United States)

    Kim, Edward; Durand, Michael; Margulis, Steve; England, Anthony

    2010-01-01

    Recent studies have begun exploring the assimilation of microwave radiances for the modeling and retrieval of snow properties. At a point scale, and for short durations (i week), radiance assimilation (RA) results are encouraging. However, in order to determine how practical RA might be for snow retrievals when applied over longer durations, larger spatial scales, and/or different snow types, we must expand the scope of the tests. In this paper we use coincident microwave radiance measurements and station data from a tundra site on the North Slope of Alaska. The field data are from the 3rd Radio-brightness Energy Balance Experiment (REBEX-3) carried out in 1994-95 by the University of Michigan. This dataset will provide a test of RA over months instead of one week, and for a very different type of snow than previous snow RA studies. We will address the following questions: flow well can a snowpack physical model (SM), forced with local weather, match measured conditions for a tundra snowpack?; How well can a microwave emission model, driven by the snowpack model, match measured microwave brightnesses for a tundra snowpack?; How well does RA increase or decrease the fidelity of estimates of snow depth and temperatures for a tundra snowpack?

  9. Permafrost collapse after shrub removal shifts tundra ecosystem to a methane source

    DEFF Research Database (Denmark)

    Nauta, Ake L.; Heijmans, Monique P.D.; Blok, Daan

    2015-01-01

    Arctic tundra ecosystems are warming almost twice as fast as the global average1. Permafrost thaw and the resulting release of greenhouse gases from decomposing soil organic carbon have the potential to accelerate climate warming2,3. In recent decades, Arctic tundra ecosystems have changed rapidly4......, including expansion of woody vegetation5,6, in response to changing climate conditions. How such vegetation changes contribute to stabilization or destabilization of the permafrost is unknown. Here we present six years of field observations in a shrub removal experiment at a Siberian tundra site. Removing...... experiment demonstrate the importance of the vegetation cover for protection of the massive carbon reservoirs stored in the permafrost and illustrate the strong vulnerability of these tundra ecosystems to perturbations. If permafrost thawing can more frequently trigger such local permafrost collapse, methane...

  10. Spatiotemporal variability in surface energy balance across tundra, snow and ice in Greenland

    DEFF Research Database (Denmark)

    Lund, Magnus; Stiegler, Christian; Abermann, Jakob

    2017-01-01

    The surface energy balance (SEB) is essential for understanding the coupled cryosphere–atmosphere system in the Arctic. In this study, we investigate the spatiotemporal variability in SEB across tundra, snow and ice. During the snow-free period, the main energy sink for ice sites is surface melt....... For tundra, energy is used for sensible and latent heat flux and soil heat flux leading to permafrost thaw. Longer snow-free period increases melting of the Greenland Ice Sheet and glaciers and may promote tundra permafrost thaw. During winter, clouds have a warming effect across surface types whereas during...... summer clouds have a cooling effect over tundra and a warming effect over ice, reflecting the spatial variation in albedo. The complex interactions between factors affecting SEB across surface types remain a challenge for understanding current and future conditions. Extended monitoring activities coupled...

  11. Competition for tracer 15N in tussock tundra ecosystems

    International Nuclear Information System (INIS)

    Marion, G.M.; Miller, P.C.; Black, C.H.

    1987-01-01

    The objectives of this study were to assess the roles of plant species, time, and site on competition for tracer 15 N (without carrier) in tussock tundra ecosystems. Six experimental sites were located in northern Alaska. After one year across the experimental sites, the recovery of 15 N by litter (11.3-16.3%) and mosses (5.4-16.4%) was significantly greater than for aboveground vascular plants (2.6-5.0%). 15 N recoveries by tundra vascular plants (2.6-5.0%) were low when compared to forest trees (9-25%) which suggst that competition for nitrogen is particularly severe in these colddominated tundra ecosystems. There were no significant differences among sites in 15 N recoveries by vascular plants, by mosses, or by litter. There was a statistically significant decline in 15 N recovery with time for Vaccinium vitis-idaea and Eriophoum vaginatum between the second and third year. The shallow rooted Vaccinium vitis-ideae was more highly labeled than the deep rooted Eriophorum vaginatum. Nearness to the source of the applied 15 N played a critical role in competition for surface applied nitrogen. (author)

  12. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle.

    Science.gov (United States)

    Belshe, E F; Schuur, E A G; Bolker, B M

    2013-10-01

    Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 sources from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 sources on an annual basis. © 2013 John Wiley & Sons Ltd/CNRS.

  13. TUNDRA IN A CHANGING CLIMATE

    Directory of Open Access Journals (Sweden)

    Terry Callaghan

    2011-01-01

    Full Text Available Both palaeogeographical reconstructions and general circulation models indicate that global warming is especially strongly manifested in high latitudes. Under a 2°C increase in mean global temperature, almost the entire modern tundra zone would become potentially suitable for tree growth. Nevertheless, palaeobotanic data cannot be applied directly to estimating vegetation response to the global warming expected in the 21st century, as they characterize a quasi-equilibrium state of ecosystems, which takes several centuries to be achieved. Low migration rates of trees, damage caused by fires and insects, processes of soil drying or paludification, and influence of herbivorous animals and human activities may slow down considerably forest spread in tundra. Climate warming will probably cause a decline in the populations of Arctic species and expansion of ranges of some southern animal species into the Arctic.

  14. Deposition of ozone to tundra

    Science.gov (United States)

    Jacob, D. J.; Fan, S.-M.; Wofsy, S. C.; Spiro, P. A.; Bakwin, P. S.; Ritter, J. A.; Browell, E. V.; Gregory, G. L.; Fitzjarrald, D. R.; Moore, K. E.

    1992-01-01

    Eddy correlation measurements of O3 deposition fluxes to tundra during the Arctic Boundary Layer Expedition (ABLE 3A) are reported. The mean O3 deposition velocity was 0.24 cm/s in the daytime and 0.12 cm/s at night. The day-to-day difference in deposition velocity was driven by both atmospheric stability and surface reactivity. The mean surface resistance to O3 deposition was 2.6 s/cm in the daytime and 3.4 s/cm at night. The relatively low surface resistance at night is attributed to light-insensitive uptake of O3 at dry upland tundra surfaces. The small day-tonight difference in surface resistance is attributed to additional stomatal uptake by wet meadow tundra plants in the daytime. The mean O3 deposition flux to the world north of 60 deg N in July-August is estimated at 8.2 x 10 exp 10 molecules/sq cm/s. Suppression of photochemical loss by small anthropogenic inputs of nitrogen oxides could have a major effect on O3 concentrations in the summertime Arctic troposphere.

  15. Indicators of reproduction of the tundra vole (microtus oeconomus pallas, 1776) in Palesse state radiation-ecological reserve

    International Nuclear Information System (INIS)

    Kuchmel', S.V.

    2010-01-01

    In 2003-2007 reproductive indicators of the tundra vole in territory of Palesse state radiation-ecological reserve have been caused by factors of an inhabitancy and are peculiar to this kind on other sites of dwelling. (authors)

  16. Emissions of biogenic sulfur gases from Alaskan tundra

    Science.gov (United States)

    Hines, Mark E.; Morrison, Michael C.

    1992-01-01

    Results of sulfur emission measurements made in freshwater and marine wetlands in Alaskan tundra during the Arctic Boundary Layer Expedition 2A (ABLE 3A) in July 1988 are presented. The data indicate that this type of tundra emits very small amounts of gaseous sulfur and, when extrapolated globally, accounts for a very small percentage of the global flux of biogenic sulfur to the atmosphere. Sulfur emissions from marine sites are up to 20-fold greater than fluxes from freshwater habitats and are dominated by dimethyl sulfide (DMS). Highest emissions, with a mean of 6.0 nmol/sq m/h, occurred in water-saturated wet meadow areas. In drier upland tundra sites, highest fluxes occurred in areas inhabited by mixed vegetation and labrador tea at 3.0 nmol/sq m/h and lowest fluxes were from lichen-dominated areas at 0.9 nmol/sq m/h. DMS was the dominant gas emitted from all these sites. Emissions of DMS were highest from intertidal soils inhabited by Carex subspathacea.

  17. Aerosol properties and their impacts on surface CCN at the ARM Southern Great Plains site during the 2011 Midlatitude Continental Convective Clouds Experiment

    Science.gov (United States)

    Logan, Timothy; Dong, Xiquan; Xi, Baike

    2018-02-01

    Aerosol particles are of particular importance because of their impacts on cloud development and precipitation processes over land and ocean. Aerosol properties as well as meteorological observations from the Department of Energy Atmospheric Radiation Measurement (ARM) platform situated in the Southern Great Plains (SGP) are utilized in this study to illustrate the dependence of continental cloud condensation nuclei (CCN) number concentration ( N CCN) on aerosol type and transport pathways. ARM-SGP observations from the 2011 Midlatitude Continental Convective Clouds Experiment field campaign are presented in this study and compared with our previous work during the 2009-10 Clouds, Aerosol, and Precipitation in the Marine Boundary Layer field campaign over the current ARM Eastern North Atlantic site. Northerly winds over the SGP reflect clean, continental conditions with aerosol scattering coefficient ( σ sp) values less than 20 Mm-1 and N CCN values less than 100 cm-3. However, southerly winds over the SGP are responsible for the observed moderate to high correlation ( R) among aerosol loading ( σ sp moisture via the Gulf of Mexico, indicating a strong dependence on air mass type. NASA MERRA-2 reanalysis aerosol and chemical data are moderately to highly correlated with surface ARM-SGP data, suggesting that this facility can represent surface aerosol conditions in the SGP, especially during strong aerosol loading events that transport via the Gulf of Mexico. Future long-term investigations will help to understand the seasonal influences of air masses on aerosol, CCN, and cloud properties over land in comparison to over ocean.

  18. The role of summer precipitation and summer temperature in establishment and growth of dwarf shrub Betula nana in northeast Siberian tundra

    DEFF Research Database (Denmark)

    Li, Bingxi; Heijmans, Monique M P D; Berendse, Frank

    2016-01-01

    It is widely believed that deciduous tundra-shrub dominance is increasing in the pan-Arctic region, mainly due to rising temperature. We sampled dwarf birch (Betula nana L.) at a northeastern Siberian tundra site and used dendrochronological methods to explore the relationship between climatic...

  19. Inter-annual variability of NDVI in response to long-term warming and fertilization in wet sedge and tussock tundra.

    Science.gov (United States)

    Boelman, Natalie T; Stieglitz, Marc; Griffin, Kevin L; Shaver, Gaius R

    2005-05-01

    This study explores the relationship between the normalized difference vegetation index (NDVI) and aboveground plant biomass for tussock tundra vegetation and compares it to a previously established NDVI-biomass relationship for wet sedge tundra vegetation. In addition, we explore inter-annual variation in NDVI in both these contrasting vegetation communities. All measurements were taken across long-term experimental treatments in wet sedge and tussock tundra communities at the Toolik Lake Long Term Ecological Research (LTER) site, in northern Alaska. Over 15 years (for wet sedge tundra) and 14 years (for tussock tundra), N and P were applied in factorial experiments (N, P and N+P), air temperature was increased using greenhouses with and without N+P fertilizer, and light intensity was reduced by 50% using shade cloth. during the peak growing seasons of 2001, 2002, and 2003, NDVI measurements were made in both the wet sedge and tussock tundra experimental treatment plots, creating a 3-year time series of inter-annual variation in NDVI. We found that: (1) across all tussock experimental tundra treatments, NDVI is correlated with aboveground plant biomass (r2 = 0.59); (2) NDVI-biomass relationships for tussock and wet sedge tundra communities are community specific, and; (3) NDVI values for tussock tundra communities are typically, but not always, greater than for wet sedge tundra communities across all experimental treatments. We suggest that differences between the response of wet sedge and tussock tundra communities in the same experimental treatments result from the contrasting degree of heterogeneity in species and functional types that characterize each of these Arctic tundra vegetation communities.

  20. Cold season emissions dominate the Arctic tundra methane budget.

    Science.gov (United States)

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C; Miller, Charles E; Dinardo, Steven J; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y-W; Henderson, John M; Murphy, Patrick C; Goodrich, Jordan P; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D; Kimball, John S; Lipson, David A; Oechel, Walter C

    2016-01-05

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y(-1), ∼ 25% of global emissions from extratropical wetlands, or ∼ 6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

  1. Cold season emissions dominate the Arctic tundra methane budget

    Science.gov (United States)

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y-1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

  2. Reproduction and seedling establishment of Picea glauca across the northernmost forest-tundra region in Canada.

    Science.gov (United States)

    Walker, Xanthe; Henry, Gregory H R; McLeod, Katherine; Hofgaard, Annika

    2012-10-01

    The northern boundary of boreal forest and the ranges of tree species are expected to shift northward in response to climate warming, which will result in a decrease in the albedo of areas currently covered by tundra vegetation, an increase in terrestrial carbon sequestration, and an alteration of biodiversity in the current Low Arctic. Central to the prediction of forest expansion is an increase in the reproductive capacity and establishment of individual trees. We assessed cone production, seed viability, and transplanted seedling success of Picea glauca (Moench.) Voss. (white spruce) in the early 1990s and again in the late 2000s at four forest stand sites and eight tree island sites (clonal populations beyond present treeline) in the Mackenzie Delta region of the Northwest Territories, Canada. Over the past 20 years, average temperatures in this region have increased by 0.9 °C. This area has the northernmost forest-tundra ecotone in North America and is one of the few circumpolar regions where the northern limit of conifer trees reaches the Arctic Ocean. We found that cone production and seed viability did not change between the two periods of examination and that both variables decreased northward across the forest-tundra ecotone. Nevertheless, white spruce individuals at the northern limit of the forest-tundra ecotone produced viable seeds. Furthermore, transplanted seedlings were able to survive in the northernmost sites for 15 years, but there were no signs of natural regeneration. These results indicate that if climatic conditions continue to ameliorate, reproductive output will likely increase, but seedling establishment and forest expansion within the forest-tundra of this region is unlikely to occur without the availability of suitable recruitment sites. Processes that affect the availability of recruitment sites are likely to be important elsewhere in the circumpolar ecotone, and should be incorporated into models and predictions of climate change

  3. Developing of a VS30 map for addressing site effects for Portugal: evaluation of the effectiveness of using VS30-proxies for stable continental regions.

    Science.gov (United States)

    Vilanova, Susana; Narciso, Joao; Carvalho, Joao; Pinto, Carlos; Lopes, Isabel; Nemser, Eliza; Borges, Jose; Oliveira, Carlos

    2014-05-01

    - Sand deposits and clays, terrace deposits of Pleistocene age; and S6 - Alluvium, mud, sands, clay, silt and sand dune of Holocene age. The time-average shear-wave velocity in the upper 30m (Vs30) from the database sites range from 123m/s to 1870m/s. The variance of the distribution of Vs30 values varies significantly with the generalized geological unit, being larger S1 and S2 units. The use of proxies based either on the geological-geographical units developed for California by Wills and Clahan (2006) or on correlations with the topographic slope for stable continental regions (Wald and Allen, 2007) shows relatively unbiased total residual distributions of the logarithm of Vs30, although with a large variance. However, the performance of both methods varies significantly with the generalized geological unit analyzed. Both methods are highly biased towards lower values of Vs30 for unit S1 (hard rock). The topographic-slope method shows inconsistent bias for each generalized unit. These results are not in agreement with those of Lemoine et al. (2012) who concluded that, for stable continental regions, the topographic-slope method performance was best for rock sites (A/B NERPH class). This discrepancy points to the limitations of the database on near-surface site-conditions used in project SHARE in what concerns stable continental regions.

  4. Modeling carbon-nutrient interactions during the early recovery of tundra after fire.

    Science.gov (United States)

    Jiang, Yueyang; Rastetter, Edward B; Rocha, Adrian V; Pearce, Andrea R; Kwiatkowski, Bonnie L; Shaver, Gaius R

    2015-09-01

    Fire frequency has dramatically increased in the tundra of northern Alaska, USA, which has major implications for the carbon budget of the region and the functioning of these ecosystems, which support important wildlife species. We investigated the postfire succession of plant and soil carbon (C), nitrogen (N), and phosphorus (P) fluxes and stocks along a burn severity gradient in the 2007 Anaktuvuk River fire scar in northern Alaska. Modeling results indicated that the early regrowth of postfire tundra vegetation was limited primarily by its canopy photosynthetic potential, rather than nutrient availability, because of the initially low leaf area and relatively high inorganic N and P concentrations in soil. Our simulations indicated that the postfire recovery of tundra vegetation was sustained predominantly by the uptake of residual inorganic N (i.e., in the remaining ash), and the redistribution of N and P from soil organic matter to vegetation. Although residual nutrients in ash were higher in the severe burn than the moderate burn, the moderate burn recovered faster because of the higher remaining biomass and consequent photosynthetic potential. Residual nutrients in ash allowed both burn sites to recover and exceed the unburned site in both aboveground biomass and production five years after the fire. The investigation of interactions among postfire C, N, and P cycles has contributed to a mechanistic understanding of the response of tundra ecosystems to fire disturbance. Our study provided insight on how the trajectory of recovery of tundra from wildfire is regulated during early succession.

  5. Does earlier snowmelt lead to greater CO2 sequestration in two low Arctic tundra ecosystems?

    Science.gov (United States)

    Humphreys, Elyn R.; Lafleur, Peter M.

    2011-05-01

    Some studies have reported that spring warming and earlier snowmelt leads to increased CO2 sequestration in Arctic terrestrial ecosystems. We measured tundra-atmosphere CO2 exchange via eddy covariance at two low Arctic sites (mixed upland tundra and sedge fen) in central Canada over multiple snow-free periods to assess this hypothesis. Both sites were net sinks for atmospheric CO2 in all years (2004-2010), but with high interannual variability. Despite a large range in snowmelt date (30 days), we did not find a statistically significant correlation between seasonal accumulated net ecosystem production (NEP) and snowmelt for either site. Although many factors can influence seasonal total NEP, our analysis shows that annual variations in photosynthetic capacity, likely driven by changes in leaf area, is a dominating control at these Arctic sites. At the upland tundra site, protection of overwintering buds by a longer duration of deep snow appears to be linked to greater photosynthetic capacity and NEP. Whereas at the fen site, sedge growth benefits from earlier snowmelt resulting in a strong correlation with early season NEP and an increase in total study period NEP with increasing growing degree days. These results highlight the complexity of interannual variation in ecosystem CO2 exchange in Arctic tundra and suggest that snowmelt date alone cannot predict seasonal, or annual, NEP.

  6. Response of rhizosphere soil microbial to Deyeuxia angustifolia encroaching in two different vegetation communities in alpine tundra.

    Science.gov (United States)

    Li, Lin; Xing, Ming; Lv, Jiangwei; Wang, Xiaolong; Chen, Xia

    2017-02-21

    Deyeuxia angustifolia (Komarov) Y. L Chang is an herb species originating from the birch forests in the Changbai Mountain. Recently, this species has been found encroaching into large areas in the western slopes of the alpine tundra in the Changbai Mountain, threatening the tundra ecosystem. In this study, we systematically assessed the response of the rhizosphere soil microbial to D. angustifolia encroaching in alpine tundra by conducting experiments for two vegetation types (shrubs and herbs) by real-time PCR and Illumina Miseq sequencing methods. The treatments consisted of D. angustifolia sites (DA), native sites (NS, NH) and encroaching sites (ES, EH). Our results show that (1) Rhizosphere soil properties of the alpine tundra were significantly impacted by D. angustifolia encroaching; microbial nutrient cycling and soil bacterial communities were shaped to be suitable for D. angustifolia growth; (2) The two vegetation community rhizosphere soils responded differently to D. angustifolia encroaching; (3) By encroaching into both vegetation communities, D. angustifolia could effectively replace the native species by establishing positive plant-soil feedback. The strong adaptation and assimilative capacity contributed to D. angustifolia encroaching in the alpine tundra. Our research indicates that D. angustifolia significantly impacts the rhizosphere soil microbial of the alpine tundra.

  7. The need for a tundra treatment protocol

    International Nuclear Information System (INIS)

    Filler, D.M.

    2000-01-01

    Support services formed an integral part of the oil and natural gas industry in the Arctic. These services include the road transportation of petroleum fuels to supply pipeline pump station generators, work camps, fleet vehicles and others. At times, spill response in the tundra proves to be harmful to the environment. An incident occurred in November 1997. A tanker truck was hauling arctic-grade diesel fuel on Alaska's North Slope when it rolled over at a river crossing, spilling 20,800 liters on the frozen tundra. The in situ burning that followed polluted the subsurface soil-water matrix within the river basin. It was difficult to distinguish between petroleum pollutant and biogenic hydrocarbon contributions in the tundra. A tundra treatment manual was then developed for the proper management of land-based fuel and oil spills in the Arctic. This manual takes into account the sensitive environment of the region. 14 refs., 4 figs

  8. Potential effects of ultraviolet radiation reduction on tundra nitrous oxide and methane fluxes in maritime Antarctica.

    Science.gov (United States)

    Bao, Tao; Zhu, Renbin; Wang, Pei; Ye, Wenjuan; Ma, Dawei; Xu, Hua

    2018-02-27

    Stratospheric ozone has begun to recover in Antarctica since the implementation of the Montreal Protocol. However, the effects of ultraviolet (UV) radiation on tundra greenhouse gas fluxes are rarely reported for Polar Regions. In the present study, tundra N 2 O and CH 4 fluxes were measured under the simulated reduction of UV radiation in maritime Antarctica over the last three-year summers. Significantly enhanced N 2 O and CH 4 emissions occurred at tundra sites under the simulated reduction of UV radiation. Compared with the ambient normal UV level, a 20% reduction in UV radiation increased tundra emissions by an average of 8 μg N 2 O m -2 h -1 and 93 μg CH 4 m -2 h -1 , whereas a 50% reduction in UV radiation increased their emissions by an average of 17 μg N 2 O m -2 h -1 and 128 μg CH 4 m -2 h -1 . No statistically significant correlation (P > 0.05) was found between N 2 O and CH 4 fluxes and soil temperature, soil moisture, total carbon, total nitrogen, NO 3 - -N and NH 4 + -N contents. Our results confirmed that UV radiation intensity is an important factor affecting tundra N 2 O and CH 4 fluxes in maritime Antarctica. Exclusion of the effects of reduced UV radiation might underestimate their budgets in Polar Regions with the recovery of stratospheric ozone.

  9. Heat flow study at the Chinese Continental Scientific Drilling site: Borehole temperature, thermal conductivity, and radiogenic heat production

    Science.gov (United States)

    He, Lijuan; Hu, Shengbiao; Huang, Shaopeng; Yang, Wencai; Wang, Jiyang; Yuan, Yusong; Yang, Shuchun

    2008-02-01

    The Chinese Continental Scientific Drilling (CCSD) Project offers a unique opportunity for studying the thermal regime of the Dabie-Sulu ultrahigh-pressure metamorphic belt. In this paper, we report measurements of borehole temperature, thermal conductivity, and radiogenic heat production from the 5158 m deep main hole (CCSD MH). We have obtained six continuous temperature profiles from this borehole so far. The temperature logs show a transient mean thermal gradient that has increased from 24.38 to 25.28 K km-1 over a period of about 1.5 years. We measured thermal conductivities and radiogenic heat productions on more than 400 core samples from CCSD MH. The measured thermal conductivities range between 1.71 and 3.60 W m-1 K-1, and the radiogenic heat productions vary from 0.01 μW m-3 to over 5.0 μW m-3, with a mean value of 1.23 ± 0.82 μW m-3 for the upper 5-km layer of the crust. The heat productions in CCSD MH appear to be more rock-type than depth-dependent and, over the depth range of CCSD MH, do not fit the popular model of heat production decreasing exponentially with increasing depth. The measured heat flow decreases with depth from ˜75 mW m-2 near the surface to ˜66 mW m-2 at a depth of 4600 m. High heat flow anomalies occur at ˜1000 and ˜2300 m, and low anomalies occur at 3300-4000 m. A preliminary two-dimensional numerical model suggests that both radiogenic heat production and thermal refraction due to structural heterogeneity are at least partially responsible for the vertical variation of heat flow in CCSD MH.

  10. Carbon dioxide exchange of the Arctic tundra in the northern part of European Russia

    DEFF Research Database (Denmark)

    Kiepe, Isabell; Johansson, Paul Torbjörn; Friborg, Thomas

    , in the Pechora basin of the northern Komi Republic. The site is of lowland tundra type (underlain by permafrost) with predominating grasses, low shrubs, lichens and mosses interspersed with thermokarst lakes. The max. active layer thickness ranges from 90 cm till over 160 cm on the mineral slope and from 35 till...

  11. Global assessment of experimental climate warming on tundra vegetation: heterogeneity over space and time

    Science.gov (United States)

    Sarah C. Elmendorf; Gregory H.R. Henry; Robert D. Hollister; Robert G. Björk; Anne D. Bjorkman; Terry V. Callaghan; [and others] NO-VALUE; William Gould; Joel Mercado

    2012-01-01

    Understanding the sensitivity of tundra vegetation to climate warming is critical to forecasting future biodiversity and vegetation feedbacks to climate. In situ warming experiments accelerate climate change on a small scale to forecast responses of local plant communities. Limitations of this approach include the apparent site-specificity of results and uncertainty...

  12. Continental tectonics and continental kinetics

    International Nuclear Information System (INIS)

    Allegre, C.J.; Jaupart, C.; Paris-7 Univ., 75

    1985-01-01

    We present a model of continental growth which combines the results of geochemical studies and tectonic ideas about the evolution of continents through geological time. The process of continental growth is mainly controlled by surface phenomena. Continental material is extracted from the mantle along subduction zones at the periphery of oceans, and is destroyed in collision zones where it is remobilized and made available for subduction. We derive an equation for S, the portion of the Earth's surface occupied by continents, which reads as follows: dS/dt=a . √(1-S)-b . S. Coefficients a and b depend on the geometry of plates, on their number and on their velocities. We assume that they decrease exponentially with time with the same time-scale α. This model satisfies both geochemical and tectonic constraints, and allows the integration of several current observations in a single framework. (orig.)

  13. Seasonal changes in the radiation balance of subarctic forest and tundra

    International Nuclear Information System (INIS)

    Lafleur, P.M.; Renzetti, A.V.; Bello, R.

    1993-01-01

    This paper examines the seasonal behavior of the components of the radiation budget of subarctic tundra and open forest near Churchill, Manitoba. Data were collected between late February and August 1990. The presence of the winter snowpack is the most important factor which affects the difference in radiation balances of tundra and forest. Overall, net radiation was about four to five times larger over the forest when snow covered the ground. Albedo differences were primarily responsible for this difference in net radiation; however, somewhat smaller net longwave losses were experienced at the tundra site. The step decrease in albedo from winter to summer (i.e. snow-covered to snow-free conditions) was significant at both sites. The forest albedo decreased by about three-fold while the tundra experienced a seven-fold decrease. Net radiation at both sites increased in direct response to the albedo change. Transmissivity of the atmosphere near Churchill also appeared to change at about the same time as the loss of the snow cover and may be related to changing air masses which bring about the final snow melt

  14. Vegetation shifts observed in arctic tundra 17 years after fire

    NARCIS (Netherlands)

    Barret, K.; Rocha, A.V.; van de Weg, M.J.; Shaver, G

    2012-01-01

    With anticipated climate change, tundra fires are expected to occur more frequently in the future, but data on the long-term effects of fire on tundra vegetation composition are scarce. This study addresses changes in vegetation structure that have persisted for 17 years after a tundra fire on the

  15. The Hominin Sites and Paleolakes Drilling Project (HSPDP): Understanding the paleoenvironmental and paleoclimatic context of human origins through continental drilling

    Science.gov (United States)

    Cohen, Andrew S.; Campisano, Christopher; Asrat, Asfawossen; Arrowsmith, Ramon; Deino, Alan; Feibel, Craig; Hill, Andrew; Kingston, John; Lamb, Henry; Lowenstein, Tim; Olago, Daniel; Bernhart Owen, R.; Renaut, Robin; Schabitz, Frank; Trauth, Martin

    2015-04-01

    The influence of climate and environmental history on human evolution is an existential question that continues to be hotly debated, in part because of the paucity of high resolution records collected in close proximity to the key fossil and archaeological evidence. To address this issue and transform the scientific debate, the HSPDP was developed to collect lacustrine sediment drill cores from basins in Kenya and Ethiopia that collectively encompass critical time intervals and locations for Plio-Quaternary human evolution in East Africa. After a 17 month campaign, drilling was completed in November, 2014, with over 1750m of core collected from 11 boreholes from five areas (1930m total drilling length, avg. 91% recovery). The sites, from oldest to youngest, include 1) N. Awash, Ethiopia (~3.5-2.9Ma core interval); 2) Baringo-Tugen Hills, Kenya (~3.3-2.5Ma); 3) West Turkana, Kenya (~1.9-1.4Ma); L. Magadi, Kenya (0.8-0Ma) and the Chew Bahir Basin, Ethiopia (~0.5-0Ma). Initial core description (ICD) and sampling for geochronology, geochemistry and paleoecology studies had been completed by mid2014, with the two remaining sites (Magadi and Chew Bahir) scheduled for ICD work in early 2015. Whereas the primary scientific targets were the lacustrine deposits from the hominin-bearing basin depocenters, many intervals of paleosols (representative of low lake stands and probable arid periods) were also encountered in drill cores. Preliminary analyses of drill core sedimentology and geochemistry show both long-term lake level changes and cyclic variability in lake levels, both of which may be indicative of climatic forcing events of interest to paleoanthropologists. Authors of this abstract also include the entire HSPDP field team.

  16. Multiple Geophysical Observations by a newly developed multi-component borehole instrument at the Continental Deep Drilling Site of the CCSD, Donghai, China

    Science.gov (United States)

    Xu, J.; Zhao, Z.; Ishii, H.; Yamauchi, T.

    2004-12-01

    Multiple Geophysical Observations by a newly developed multi-component borehole instrument at the Continental Deep Drilling Site of the CCSD, Donghai, China Jiren Xu1 (+86-10-68992879; xujiren@ccsd.org.cn) Zhixin Zhao1 (+86-10-68999734; zhaozhixin@ccsd.org.cn) Hiroshi Ishii2 (+81-0572-67-3105; ishii@tries.gr.jp Tsuneo Yamauchi3 (+81-052-789-3045; yamauchi@seis.nagoya-u.ac.jp) 1 Institute of Geology, Chinese Academy of Geological Sciences, China 2 Tono Research Institute of Earthquake Science (TRIES), Japan 3 Graduate School of Environmental Studies, Nagoya University, Japan The Chinese Continental Scientific Drilling (CCSD) site is located in the Donghai area of the Dabie-Sulu belt, which is the largest UHPM belt in the world. The drilling of the main borehole with 5000m will finish in next year. Three satellite boreholes, PP1, PP2 and PP3 were drilled and various surveys have been performed in the Donghai area about 6 years ago. We are going to install a newly developed Multi-component Instrument for borehole observations in main hole near the large Tanlu fault, and establish a long-term underground observation laboratory, which is the first noiseless one in China. The seismic activity and various geophysical fields, viz. strain, geomagnetism, geothermy, tilt, pore pressure etc. will be investigated. Data from the underground laboratory will be open to scientific, engineering and public services. We will measure the initial stress in various depths of the borehole by overcoring method using a new developed wireless intelligent type strainmeter of in-situ stress. Establishing a long-term noiseless underground observation laboratory at deep borehole and investigating crustal movement in East China are important for observing the physical conditions of the earth¡_s interior and solving many social problems, such as resources, disasters and environment. Multiple geophysical observations and the study in deep borehole will speed up and develop the study on tectonics

  17. The tundra - a threat to global climate?

    International Nuclear Information System (INIS)

    Roejle Christensen, T.

    1997-01-01

    The tundra biome has an important direct influence on the global climate through its exchange of radiatively active 'greenhouse gases', carbon dioxide and methane. A number of suggestions have been raised as to how a changing climate may alter the natural state of this exchange causing significant feedback effects in a changing climate. This paper provides a brief discussion of three different issues relating to the interaction between tundra and climate. It is concluded that release of methane hydrates, permafrost degradation and major biome changes are processes which in the long term may have important effects on further development of the global climate. (au) 32 refs

  18. Tundra plant above-ground biomass and shrub dominance mapped across the North Slope of Alaska

    Science.gov (United States)

    Berner, Logan T.; Jantz, Patrick; Tape, Ken D.; Goetz, Scott J.

    2018-03-01

    Arctic tundra is becoming greener and shrubbier due to recent warming. This is impacting climate feedbacks and wildlife, yet the spatial distribution of plant biomass in tundra ecosystems is uncertain. In this study, we mapped plant and shrub above-ground biomass (AGB; kg m-2) and shrub dominance (%; shrub AGB/plant AGB) across the North Slope of Alaska by linking biomass harvests at 28 field sites with 30 m resolution Landsat satellite imagery. We first developed regression models (p accounting for ~43% of regional plant AGB. The new maps capture landscape variation in plant AGB visible in high resolution satellite and aerial imagery, notably shrubby riparian corridors. Modeled shrub AGB was strongly correlated with field measurements of shrub canopy height at 25 sites (rs  = 0.88) and with a regional map of shrub cover (rs  = 0.76). Modeled plant AGB and shrub dominance were higher in shrub tundra than graminoid tundra and increased between areas with the coldest and warmest summer air temperatures, underscoring the fact that future warming has the potential to greatly increase plant AGB and shrub dominance in this region. These new biomass maps provide a unique source of ecological information for a region undergoing rapid environmental change.

  19. Differentiation of MIS 9 and MIS 11 in the continental record: vegetational, faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex, UK.

    Science.gov (United States)

    Roe, Helen M; Coope, G Russell; Devoy, Robert J N; Harrison, Colin J O; Penkman, Kirsty E H; Preece, Richard C; Schreve, Danielle C

    2009-11-01

    Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2 degrees C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus

  20. Soils of Sub-Antarctic tundras: diversity and basic chemical characteristics

    Science.gov (United States)

    Abakumov, Evgeny; Vlasov, Dmitry; Mukhametova, Nadezhda

    2014-05-01

    Antarctic peninsula is known as specific part of Antarctica, which is characterizes by humid and relatively warm climate of so-called sub Antarctic (maritime) zone. Annual precipitation and long above zero period provides the possibility of sustainable tundra's ecosystem formation. Therefore, the soil diversity of these tundra landscapes is maximal in the whole Antarctic. Moreover, the thickness of parent material debris's is also highest and achieves a 1 or 2 meters as highest. The presence of higher vascular plants Deshampsia antarctica which is considered as one of the main edificators provides the development of humus accumulation in upper solum. Penguins activity provides an intensive soil fertilization and development of plant communities with increased density. All these factors leads to formation of specific and quite diverse soil cover in sub Antarctic tundra's. These ecosystems are presented by following permafrost affected soils: Leptosols, Lithoosols, Crysols, Gleysols, Peats and Ornhitosols. Also the post Ornhitosols are widely spreaded in subantarcic ecosystems, they forms on the penguin rockeries during the plant succession development, leaching of nutrients and organic matter mineralization. "Amphibious" soils are specific for seasonal lakes, which evaporates in the end if Australian summer. These soils have specific features of bio sediments and soils as well. Soil chemical characteristic as well as organic matter features discussed in comparison with Antacrtic continental soil in presentation.

  1. Modeling sugarcane yield with a process-based model from site to continental scale: uncertainties arising from model structure and parameter values

    Science.gov (United States)

    Valade, A.; Ciais, P.; Vuichard, N.; Viovy, N.; Caubel, A.; Huth, N.; Marin, F.; Martiné, J.-F.

    2014-06-01

    Agro-land surface models (agro-LSM) have been developed from the integration of specific crop processes into large-scale generic land surface models that allow calculating the spatial distribution and variability of energy, water and carbon fluxes within the soil-vegetation-atmosphere continuum. When developing agro-LSM models, particular attention must be given to the effects of crop phenology and management on the turbulent fluxes exchanged with the atmosphere, and the underlying water and carbon pools. A part of the uncertainty of agro-LSM models is related to their usually large number of parameters. In this study, we quantify the parameter-values uncertainty in the simulation of sugarcane biomass production with the agro-LSM ORCHIDEE-STICS, using a multi-regional approach with data from sites in Australia, La Réunion and Brazil. In ORCHIDEE-STICS, two models are chained: STICS, an agronomy model that calculates phenology and management, and ORCHIDEE, a land surface model that calculates biomass and other ecosystem variables forced by STICS phenology. First, the parameters that dominate the uncertainty of simulated biomass at harvest date are determined through a screening of 67 different parameters of both STICS and ORCHIDEE on a multi-site basis. Secondly, the uncertainty of harvested biomass attributable to those most sensitive parameters is quantified and specifically attributed to either STICS (phenology, management) or to ORCHIDEE (other ecosystem variables including biomass) through distinct Monte Carlo runs. The uncertainty on parameter values is constrained using observations by calibrating the model independently at seven sites. In a third step, a sensitivity analysis is carried out by varying the most sensitive parameters to investigate their effects at continental scale. A Monte Carlo sampling method associated with the calculation of partial ranked correlation coefficients is used to quantify the sensitivity of harvested biomass to input

  2. Modeling sugar cane yield with a process-based model from site to continental scale: uncertainties arising from model structure and parameter values

    Science.gov (United States)

    Valade, A.; Ciais, P.; Vuichard, N.; Viovy, N.; Huth, N.; Marin, F.; Martiné, J.-F.

    2014-01-01

    Agro-Land Surface Models (agro-LSM) have been developed from the integration of specific crop processes into large-scale generic land surface models that allow calculating the spatial distribution and variability of energy, water and carbon fluxes within the soil-vegetation-atmosphere continuum. When developing agro-LSM models, a particular attention must be given to the effects of crop phenology and management on the turbulent fluxes exchanged with the atmosphere, and the underlying water and carbon pools. A part of the uncertainty of Agro-LSM models is related to their usually large number of parameters. In this study, we quantify the parameter-values uncertainty in the simulation of sugar cane biomass production with the agro-LSM ORCHIDEE-STICS, using a multi-regional approach with data from sites in Australia, La Réunion and Brazil. In ORCHIDEE-STICS, two models are chained: STICS, an agronomy model that calculates phenology and management, and ORCHIDEE, a land surface model that calculates biomass and other ecosystem variables forced by STICS' phenology. First, the parameters that dominate the uncertainty of simulated biomass at harvest date are determined through a screening of 67 different parameters of both STICS and ORCHIDEE on a multi-site basis. Secondly, the uncertainty of harvested biomass attributable to those most sensitive parameters is quantified and specifically attributed to either STICS (phenology, management) or to ORCHIDEE (other ecosystem variables including biomass) through distinct Monte-Carlo runs. The uncertainty on parameter values is constrained using observations by calibrating the model independently at seven sites. In a third step, a sensitivity analysis is carried out by varying the most sensitive parameters to investigate their effects at continental scale. A Monte-Carlo sampling method associated with the calculation of Partial Ranked Correlation Coefficients is used to quantify the sensitivity of harvested biomass to input

  3. Spaceborne potential for examining taiga–tundra ecotone form and vulnerability

    OpenAIRE

    P. M. Montesano; G. Sun; R. O. Dubayah; K. J. Ranson

    2016-01-01

    In the taiga–tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density, and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, vari...

  4. Micrometeorological measurements of CH4 and CO2 exchange between the atmosphere and subarctic tundra

    Science.gov (United States)

    Fan, S. M.; Wofsy, S. C.; Bakwin, P. S.; Jacob, D. J.; Anderson, S. M.; Kebabian, P. L.; Mcmanus, J. B.; Kolb, C. E.; Fitzjarrald, D. R.

    1992-01-01

    Eddy correlation flux measurements and concentration profiles of total hydrocarbons (THC) and CO2 were combined to provide a comprehensive record of atmosphere-biosphere exchange for these gases over a 30-day period in July-August 1988 in the Yukon-Kuskokwin River Delta of Alaska. Over 90 percent of net ecosystem exchanges of THC were due to methane. Lakes and wet meadow tundra provided the major sources of methane. The average fluxes from lake, dry tundra, and wet tundra were 11 +/- 3, 29 +/- 3, and 57 +/- 6 mg CH4/sq m/d, respectively. The mean remission rate for the site was 25 mg/sq m/d. Maximum uptake of CO2 by the tundra was 1.4 gC/sq m/d between 1000 and 1500 hrs, and nocturnal respiration averaged 0.73 gC/sq m/d. Net uptake of CO2 was 0.30 gC/sq m/d for the 30 days of measurement; methane flux accounted for 6 percent of CO2 net uptake.

  5. Assessing Soil Organic C Stability at the Continental Scale: An Analysis of Soil C and Radiocarbon Profiles Across the NEON Sites

    Science.gov (United States)

    Heckman, K. A.; Gallo, A.; Hatten, J. A.; Swanston, C.; McKnight, D. M.; Strahm, B. D.; Sanclements, M.

    2017-12-01

    Soil carbon stocks have become recognized as increasingly important in the context of climate change and global C cycle modeling. As modelers seek to identify key parameters affecting the size and stability of belowground C stocks, attention has been drawn to the mineral matrix and the soil physiochemical factors influenced by it. Though clay content has often been utilized as a convenient and key explanatory variable for soil C dynamics, its utility has recently come under scrutiny as new paradigms of soil organic matter stabilization have been developed. We utilized soil cores from a range of National Ecological Observatory Network (NEON) experimental plots to examine the influence of physicochemical parameters on soil C stocks and turnover, and their relative importance in comparison to climatic variables. Soils were cored at NEON sites, sampled by genetic horizon, and density separated into light fractions (particulate organics neither occluded within aggregates nor associated with mineral surfaces), occluded fractions (particulate organics occluded within aggregates), and heavy fractions (organics associated with mineral surfaces). Bulk soils and density fractions were measured for % C and radiocarbon abundance (as a measure of C stability). Carbon and radiocarbon abundances were examined among fractions and in the context of climatic variables (temperature, precipitation, elevation) and soil physiochemical variables (% clay and pH). No direct relationships between temperature and soil C or radiocarbon abundances were found. As a whole, soil radiocarbon abundance in density fractions decreased in the order of light>heavy>occluded, highlighting the importance of both surface sorption and aggregation to the preservation of organics. Radiocarbon abundance was correlated with pH, with variance also grouping by dominate vegetation type. Soil order was also identified as an important proxy variable for C and radiocarbon abundance. Preliminary results suggest that

  6. Continental Rifts

    Science.gov (United States)

    Rosendahl, B. R.

    Continental Rifts, edited by A. M. Quennell, is a new member of the Benchmark Papers in Geology Series, edited in toto by R. W. Fairbridge. In this series the individual volume editors peruse the literature on a given topic, select a few dozen papers of ostensibly benchmark quality, and then reorder them in some sensible fashion. Some of the original papers are republished intact, but many are chopped into “McNuggets™” of information. Depending upon the volume editor, the chopping process can range from a butchering job to careful and prudent pruning. The collecting, sifting, and reorganizing tasks are, of course, equally editor-sensitive. The end product of this series is something akin to a set of Reader's Digest of Geology.

  7. Interannual Variability of Carbon Dioxide, Methane and Nitrous Oxide Fluxes in Subarctic European Russian Tundra

    Science.gov (United States)

    Marushchak, M. E.; Voigt, C.; Gil, J.; Lamprecht, R. E.; Trubnikova, T.; Virtanen, T.; Kaverin, D.; Martikainen, P. J.; Biasi, C.

    2017-12-01

    Southern tundra landscapes are particularly vulnerable to climate warming, permafrost thaw and associated landscape rearrangement due to near-zero permafrost temperatures. The large soil C and N stocks of subarctic tundra may create a positive feedback for warming if released to the atmosphere at increased rates. Subarctic tundra in European Russia is a mosaic of land cover types, which all play different roles in the regional greenhouse gas budget. Peat plateaus - massive upheaved permafrost peatlands - are large storehouses of soil carbon and nitrogen, but include also bare peat surfaces that act as hot-spots for both carbon dioxide and nitrous oxide emissions. Tundra wetlands are important for the regional greenhouse gas balance since they show high rates of methane emissions and carbon uptake. The most dominant land-form is upland tundra vegetated by shrubs, lichens and mosses, which displays a close-to-neutral balance with respect to all three greenhouse gases. The study site Seida (67°03'N, 62°56'E), located in the discontinuous permafrost zone of Northeast European Russia, incorporates all these land forms and has been an object for greenhouse gas investigations since 2007. Here, we summarize the growing season fluxes of carbon dioxide, methane and nitrous oxide measured by chamber techniques over the study years. We analyzed the flux time-series together with the local environmental data in order to understand the drivers of interannual variability. Detailed soil profile measurements of greenhouse gas concentrations, soil moisture and temperature provide insights into soil processes underlying the net emissions to the atmosphere. The multiannual time-series allows us to assess the importance of the different greenhouse gases and landforms to the overall climate forcing of the study region.

  8. Greater shrub dominance alters breeding habitat and food resources for migratory songbirds in Alaskan arctic tundra.

    Science.gov (United States)

    Boelman, Natalie T; Gough, Laura; Wingfield, John; Goetz, Scott; Asmus, Ashley; Chmura, Helen E; Krause, Jesse S; Perez, Jonathan H; Sweet, Shannan K; Guay, Kevin C

    2015-04-01

    Climate warming is affecting the Arctic in multiple ways, including via increased dominance of deciduous shrubs. Although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. To understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod community characteristics in both graminoid and shrub dominated tundra. We combined measurements of preferred nest site characteristics for Lapland longspurs (Calcarius lapponicus) and Gambel's White-crowned sparrows (Zonotrichia leucophrys gambelii) with modeled predictions for the distribution of plant community types in the Alaskan arctic foothills region for the year 2050. Lapland longspur nests were found in sedge-dominated tussock tundra where shrub height does not exceed 20 cm, whereas White-crowned sparrows nested only under shrubs between 20 cm and 1 m in height, with no preference for shrub species. Shrub canopies had higher canopy-dwelling arthropod availability (i.e. small flies and spiders) but lower ground-dwelling arthropod availability (i.e. large spiders and beetles). Since flies are the birds' preferred prey, increasing shrubs may result in a net enhancement in preferred prey availability. Acknowledging the coarse resolution of existing tundra vegetation models, we predict that by 2050 there will be a northward shift in current White-crowned sparrow habitat range and a 20-60% increase in their preferred habitat extent, while Lapland longspur habitat extent will be equivalently reduced. Our findings can be used to make first approximations of future habitat change for species with similar nesting requirements. However, we contend that as exemplified by this study's findings, existing tundra modeling tools cannot yet simulate the fine-scale habitat

  9. Environmental and vegetation controls on the spatial variability of CH4 emission from wet-sedge and tussock tundra ecosystems in the Arctic.

    Science.gov (United States)

    McEwing, Katherine Rose; Fisher, James Paul; Zona, Donatella

    Despite multiple studies investigating the environmental controls on CH 4 fluxes from arctic tundra ecosystems, the high spatial variability of CH 4 emissions is not fully understood. This makes the upscaling of CH 4 fluxes from plot to regional scale, particularly challenging. The goal of this study is to refine our knowledge of the spatial variability and controls on CH 4 emission from tundra ecosystems. CH 4 fluxes were measured in four sites across a variety of wet-sedge and tussock tundra ecosystems in Alaska using chambers and a Los Gatos CO 2 and CH 4 gas analyser. All sites were found to be sources of CH 4 , with northern sites (in Barrow) showing similar CH 4 emission rates to the southernmost site (ca. 300 km south, Ivotuk). Gross primary productivity (GPP), water level and soil temperature were the most important environmental controls on CH 4 emission. Greater vascular plant cover was linked with higher CH 4 emission, but this increased emission with increased vascular plant cover was much higher (86 %) in the drier sites, than the wettest sites (30 %), suggesting that transport and/or substrate availability were crucial limiting factors for CH 4 emission in these tundra ecosystems. Overall, this study provides an increased understanding of the fine scale spatial controls on CH 4 flux, in particular the key role that plant cover and GPP play in enhancing CH 4 emissions from tundra soils.

  10. Tundra vegetation effects on pan-Arctic albedo

    International Nuclear Information System (INIS)

    Loranty, Michael M; Goetz, Scott J; Beck, Pieter S A

    2011-01-01

    Recent field experiments in tundra ecosystems describe how increased shrub cover reduces winter albedo, and how subsequent changes in surface net radiation lead to altered rates of snowmelt. These findings imply that tundra vegetation change will alter regional energy budgets, but to date the effects have not been documented at regional or greater scales. Using satellite observations and a pan-Arctic vegetation map, we examined the effects of shrub vegetation on albedo across the terrestrial Arctic. We included vegetation classes dominated by low shrubs, dwarf shrubs, tussock-dominated graminoid tundra, and non-tussock graminoid tundra. Each class was further stratified by bioclimate subzones. Low-shrub tundra had higher normalized difference vegetation index values and earlier albedo decline in spring than dwarf-shrub tundra, but for tussock tundra, spring albedo declined earlier than for low-shrub tundra. Our results illustrate how relatively small changes in vegetation properties result in differences in albedo dynamics, regardless of shrub growth, that may lead to differences in net radiation upwards of 50 W m -2 at weekly time scales. Further, our findings imply that changes to the terrestrial Arctic energy budget during this important seasonal transition are under way regardless of whether recent satellite observed productivity trends are the result of shrub expansion. We conclude that a better understanding of changes in vegetation productivity and distribution in Arctic tundra is essential for accurately quantifying and predicting carbon and energy fluxes and associated climate feedbacks.

  11. The unseen iceberg: plant roots in arctic tundra.

    Science.gov (United States)

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F; Euskirchen, Eugenie S; McGuire, A David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey M; Wullschleger, Stan D

    2015-01-01

    Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits - including distribution, chemistry, anatomy and resource partitioning - play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions. No claim to original US Government works New Phytologist © 2014 New Phytologist Trust.

  12. Soil bacterial community composition altered by increased nutrient availability in Arctic tundra soils.

    Science.gov (United States)

    Koyama, Akihiro; Wallenstein, Matthew D; Simpson, Rodney T; Moore, John C

    2014-01-01

    The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and mineral soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than mineral soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-Proteobacteria and β-Proteobacteria was higher in fertilized than control soils, and oligotrophic Acidobacteria were less abundant in fertilized than control soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming.

  13. Soil bacterial community composition altered by increased nutrient availability in Arctic tundra soils

    Science.gov (United States)

    Koyama, Akihiro; Wallenstein, Matthew D.; Simpson, Rodney T.; Moore, John C.

    2014-01-01

    The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and mineral soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than mineral soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-Proteobacteria and β-Proteobacteria was higher in fertilized than control soils, and oligotrophic Acidobacteria were less abundant in fertilized than control soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming. PMID:25324836

  14. U.S. Tundra Biome-International Biological Program. U.S. Tundra Biome Publication List.

    Science.gov (United States)

    1983-09-01

    forage. Journal of Mammalogy, 60(4): 740-750. /Bib 35-989/ Batzli, G.O., R.G. White and F.L. Bunnell (1981) Herbivory : A strategy of tundra consum...Treat (1977) Root growth, respira- tion, and carbon dioxide evolution in an arctic tundra soil. Arctic andAlpine Research, 9(2): 129-137. (4020 and...MacLean, Jr. (1974) Ecology and evolution of social organization in arctic sandpipers. American Zoologist, 14: 185-204. (2504) /Bib 32-2828/ " Prentki, R.T

  15. Fire Severity and Soil Carbon Combustion in Boreal and Tundra Ecosystems

    Science.gov (United States)

    Walker, X. J.; Mack, M. C.; Baltzer, J. L.; Cummings, S.; Day, N.; Goetz, S.; Johnstone, J. F.; Rogers, B. M.; Turetsky, M. R.

    2016-12-01

    Climate warming in northern latitudes has led to an intensification of wildfire disturbance. Increased fire frequency, extent, and severity is expected to strongly impact the structure and function of northern ecosystems. In this study, we examined 50 sites in a recently burned tundra ecosystem of Alaska, USA and 250 sites in recently burned boreal conifer forest ecosystems of Northwest Territories, Canada. The majority of organic carbon (C) in both boreal and tundra ecosystems resides in the soil organic layer (SOL) and combustion of this layer can lead to large C emissions. Through examining multiple fire scars in different regions, ranging in moisture, elevation, and pre-fire vegetation communities, we can determine the ecosystem, landscape, and regional controls on SOL combustion and the potential shift in C storage. In this research, we use scalable SOL consumption metrics to estimate depth of burn and the associated C emissions. Preliminary results from boreal conifer sites indicate that nearly 50% of the pre-fire soil C pool was combusted and that over 75% of the total C emitted from the extreme fire year of 2014 can be attributed to combustion of the SOL. Increased combustion of SOL associated with an intensifying fire regime could shift boreal and tundra ecosystems across a C cycle threshold: from net accumulation of C from the atmosphere over multiple fire cycles, to a net loss. Understanding changes in SOL combustion and C storage is essential for assessing the consequences of an altered fire regime on permafrost dynamics, vegetation regeneration, and the initiation of successional trajectories in tundra and boreal ecosystems.

  16. THE ROLE OF THERMAL REGIMEN IN TUNDRA PLANT COMMUNITY RESTORATION

    Science.gov (United States)

    Mineral extraction activities in the Arctic regions of the world produce long-lasting ecological disturbances. Assisted recovery from such disturbances may require restoration of the tundra thermal regime. We transplanted plugs of entire root zone and live tundra plants to a dist...

  17. Methylocella tundrae sp. nov., a novel methanotrophic bacterium from acidic tundra peatlands.

    Science.gov (United States)

    Dedysh, Svetlana N; Berestovskaya, Yulia Y; Vasylieva, Lina V; Belova, Svetlana E; Khmelenina, Valentina N; Suzina, Natalia E; Trotsenko, Yuri A; Liesack, Werner; Zavarzin, George A

    2004-01-01

    A novel species, Methylocella tundrae, is proposed for three methanotrophic strains (T4T, TCh1 and TY1) isolated from acidic Sphagnum tundra peatlands. These strains are aerobic, Gram-negative, non-motile, dinitrogen-fixing rods that possess a soluble methane monooxygenase and utilize the serine pathway for carbon assimilation. Strains T4T, TCh1 and TY1 are moderately acidophilic organisms capable of growth between pH 4.2 and 7.5 (optimum 5.5-6.0) and between 5 and 30 degrees C (optimum 15 degrees C). The major phospholipid fatty acid is 18:1omega7c. The DNA G+C content of strain T4T is 63.3 mol%. The three strains possess almost identical 16S rRNA gene sequences and are most closely related to two previously identified species of Methylocella, Methylocella palustris (97% similarity) and Methylocella silvestris (97.5% similarity). DNA-DNA hybridization values of strain T4T with Methylocella palustris KT and Methylocella silvestris BL2T were respectively 27 and 36%. Thus, the tundra strains represent a novel species, for which the name Methylocella tundrae sp. nov. is proposed. Strain T4T (=DSM 15673T=NCIMB 13949T) is the type strain.

  18. Migration of Tundra Swans (Cygnus columbianus) Wintering in Japan Using Satellite Tracking: Identification of the Eastern Palearctic Flyway.

    Science.gov (United States)

    Chen, Wenbo; Doko, Tomoko; Fujita, Go; Hijikata, Naoya; Tokita, Ken-Ichi; Uchida, Kiyoshi; Konishi, Kan; Hiraoka, Emiko; Higuchi, Hiroyoshi

    2016-02-01

    Migration through the Eastern Palearctic (EP) flyway by tundra swans (Cygnus columbianus) has not been thoroughly documented. We satellite-tracked the migration of 16 tundra swans that winter in Japan. The objectives of this study were 1) to show the migration pattern of the EP flyway of tundra swans; 2) to compare this pattern with the migration pattern of whooper swans; and 3) to identify stopover sites that are important for these swans' conservation. Tundra swans were captured at Kutcharo Lake, Hokkaido, in 2009-2012 and satellite-tracked. A new method called the "MATCHED (Migratory Analytical Time Change Easy Detection) method" was developed. Based on median, the spring migration began on 18 April and ended on 27 May. Autumn migration began on 9 September and ended on 2 November. The median duration of the spring and autumn migrations were 48 and 50 days, respectively. The mean duration at one stopover site was 5.5 days and 6.8 days for the spring and autumn migrations, respectively. The number of stopover sites was 3.0 and 2.5 for the spring and autumn migrations, respectively. The mean travel distances for the spring and autumn migrations were 6471 and 6331 km, respectively. Seven migration routes passing Sakhalin, the Amur River, and/or Kamchatka were identified. There were 15, 32, and eight wintering, stopover, and breeding sites, respectively. The migration routes and staging areas of tundra swans partially overlap with those of whooper swans, whose migration patterns have been previously documented. The migration patterns of these two swan species that winter in Japan confirm the importance of the Amur River, Udyl' Lake, Shchastya Bay, Aniva Bay, zaliv Chayvo Lake, zal Piltun Lake, zaliv Baykal Lake, Kolyma River, Buyunda River, Sen-kyuyel' Lake, and northern coastal areas of the Sea of Okhotsk.

  19. Blood lead concentrations in Alaskan tundra swans: linking breeding and wintering areas with satellite telemetry

    Science.gov (United States)

    Ely, Craig R.; Franson, Christian

    2014-01-01

    Tundra swans (Cygnus columbianus) like many waterfowl species are susceptible to lead (Pb) poisoning, and Pb-induced mortality has been reported from many areas of their wintering range. Little is known however about Pb levels throughout the annual cycle of tundra swans, especially during summer when birds are on remote northern breeding areas where they are less likely to be exposed to anthropogenic sources of Pb. Our objective was to document summer Pb levels in tundra swans throughout their breeding range in Alaska to determine if there were population-specific differences in blood Pb concentrations that might pose a threat to swans and to humans that may consume them. We measured blood Pb concentrations in tundra swans at five locations in Alaska, representing birds that winter in both the Pacific Flyway and Atlantic Flyway. We also marked swans at each location with satellite transmitters and coded neck bands, to identify staging and wintering sites and determine if winter site use correlated with summer Pb concentrations. Blood Pb levels were generally low ( < 0.2 μg/ml) in swans across all breeding areas. Pb levels were lower in cygnets than adults, suggesting that swans were likely exposed to Pb on wintering areas or on return migration to Alaska, rather than on the summer breeding grounds. Blood Pb levels varied significantly across the five breeding areas, with highest concentrations in birds on the North Slope of Alaska (wintering in the Atlantic Flyway), and lowest in birds from the lower Alaska Peninsula that rarely migrate south for winter.

  20. Nitrate is an important nitrogen source for Arctic tundra plants.

    Science.gov (United States)

    Liu, Xue-Yan; Koba, Keisuke; Koyama, Lina A; Hobbie, Sarah E; Weiss, Marissa S; Inagaki, Yoshiyuki; Shaver, Gaius R; Giblin, Anne E; Hobara, Satoru; Nadelhoffer, Knute J; Sommerkorn, Martin; Rastetter, Edward B; Kling, George W; Laundre, James A; Yano, Yuriko; Makabe, Akiko; Yano, Midori; Liu, Cong-Qiang

    2018-03-27

    Plant nitrogen (N) use is a key component of the N cycle in terrestrial ecosystems. The supply of N to plants affects community species composition and ecosystem processes such as photosynthesis and carbon (C) accumulation. However, the availabilities and relative importance of different N forms to plants are not well understood. While nitrate (NO 3 - ) is a major N form used by plants worldwide, it is discounted as a N source for Arctic tundra plants because of extremely low NO 3 - concentrations in Arctic tundra soils, undetectable soil nitrification, and plant-tissue NO 3 - that is typically below detection limits. Here we reexamine NO 3 - use by tundra plants using a sensitive denitrifier method to analyze plant-tissue NO 3 - Soil-derived NO 3 - was detected in tundra plant tissues, and tundra plants took up soil NO 3 - at comparable rates to plants from relatively NO 3 - -rich ecosystems in other biomes. Nitrate assimilation determined by 15 N enrichments of leaf NO 3 - relative to soil NO 3 - accounted for 4 to 52% (as estimated by a Bayesian isotope-mixing model) of species-specific total leaf N of Alaskan tundra plants. Our finding that in situ soil NO 3 - availability for tundra plants is high has important implications for Arctic ecosystems, not only in determining species compositions, but also in determining the loss of N from soils via leaching and denitrification. Plant N uptake and soil N losses can strongly influence C uptake and accumulation in tundra soils. Accordingly, this evidence of NO 3 - availability in tundra soils is crucial for predicting C storage in tundra. Copyright © 2018 the Author(s). Published by PNAS.

  1. [Nitrogen bio-cycle in the alpine tundra ecosystem of Changbai Mountain and its comparison with arctic tundra].

    Science.gov (United States)

    Wei, Jing; Zhao, Jing-zhu; Deng, Hong-bing; Wu, Gang; Hao, Ying-jie; Shang, Wen-yan

    2005-03-01

    The nitrogen bio-cycle was discussed in the alpine tundra ecosystem of Changbai Mountain through compartment model. The alpine tundra of Changbai Mountain was compared with Arctic tundra by the common ratio of genus and species in this paper. It was found that the 89.3% of genus and 58.6% of species was the common between Changbai alpine tundra and Arctic tundra while 95.5% of lichen genus and 58.7% lichen species, 82.1% of moss genus and 76.3% of moss species, 93.1% of vascular bundle genus and 40.5% of vascular bundle species were the common, respectively, which made vegetation type or community to be similar between Changbai alpine tundra and Arctic tundra. The total storage of nitrogen was 65220.6 t in the vegetation-plant system of Changbai Mountain, of which soil pool amounted to 99.3%. The nitrogen storage of each compartment was as follows: the vegetation pool, litterfall pool and soil pool were 237.4 t, 145.3 t and 64837.9 t respectively. The transferable amounts of nitrogen were 131.7 t x a(-1), 58 t/a and 73.7 t x a(-1) in the aboveground plant, belowground root system and litterfall of alpine tundra ecosystem of Changbai Mountain.

  2. Evidence and Implications of Frequent Fires in Ancient Shrub Tundra

    Energy Technology Data Exchange (ETDEWEB)

    Higuera, P E; Brubaker, L B; Anderson, P M; Brown, T A; Kennedy, A T; Hu, F S

    2008-03-06

    Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birchdominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleo-fires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21st century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere.

  3. Recent Arctic tundra fire initiates widespread thermokarst development.

    Science.gov (United States)

    Jones, Benjamin M; Grosse, Guido; Arp, Christopher D; Miller, Eric; Liu, Lin; Hayes, Daniel J; Larsen, Christopher F

    2015-10-29

    Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions.

  4. 137Cs in alpine tundra habitats

    International Nuclear Information System (INIS)

    Allen, D.J.

    1976-01-01

    An experiment is reported that was carried out to determine the relative importance of physical habitat factors such as snow cover, wind, soil contamination and moisture, and certain plant characteristics (gross morphology and specialized morphology) in the contamination of alpine perennial, tundra vegetation by 137 Cs from worldwide fallout. The accumulations of 137 Cs and 40 K found among species of plants and soil samples in major ecological habitats of alpine tundra in Rocky Mountain National Park are shown tabulated. From this study it would appear that the 'scrubbing-out' action of precipitation and moisture in general may have enhanced direct deposition from the air and influenced foliar absorption rate. However, morphology, physiology, longevity, plant-soil interface distance, and species differences seem to play a more dominant role in radionuclide accumulation. It is difficult to accurately predict fallout behavior by monitoring vegetation 137 Cs levels. The soil (habitat) is seemingly a better indicator of 137 Cs fallout accumulation than plant species, especially when 'spot-check' sampling is employed. (U.K.)

  5. The response of Arctic vegetation and soils following an unusually severe tundra fire.

    Science.gov (United States)

    Bret-Harte, M Syndonia; Mack, Michelle C; Shaver, Gaius R; Huebner, Diane C; Johnston, Miriam; Mojica, Camilo A; Pizano, Camila; Reiskind, Julia A

    2013-08-19

    Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km(2) of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub-sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred.

  6. The response of Arctic vegetation and soils following an unusually severe tundra fire

    Science.gov (United States)

    Bret-Harte, M. Syndonia; Mack, Michelle C.; Shaver, Gaius R.; Huebner, Diane C.; Johnston, Miriam; Mojica, Camilo A.; Pizano, Camila; Reiskind, Julia A.

    2013-01-01

    Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km2 of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub–sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred. PMID:23836794

  7. Evaluation of Moderate-Resolution Imaging Spectroradiometer (MODIS) Snow Albedo Product (MCD43A) over Tundra

    Science.gov (United States)

    Wang, Zhuosen; Schaaf, Crystal B.; Chopping, Mark J.; Strahler, Alan H.; Wang, Jindi; Roman, Miguel O.; Rocha, Adrian V.; Woodcock, Curtis E.; Shuai, Yanmin

    2012-01-01

    This study assesses the MODIS standard Bidirectional Reflectance Distribution Function (BRDF)/Albedo product, and the daily Direct Broadcast BRDF/Albedo algorithm at tundra locations under large solar zenith angles and high anisotropic diffuse illumination and multiple scattering conditions. These products generally agree with ground-based albedo measurements during the snow cover period when the Solar Zenith Angle (SZA) is less than 70deg. An integrated validation strategy, including analysis of the representativeness of the surface heterogeneity, is performed to decide whether direct comparisons between field measurements and 500- m satellite products were appropriate or if the scaling of finer spatial resolution airborne or spaceborne data was necessary. Results indicate that the Root Mean Square Errors (RMSEs) are less than 0.047 during the snow covered periods for all MCD43 albedo products at several Alaskan tundra areas. The MCD43 1- day daily albedo product is particularly well suited to capture the rapidly changing surface conditions during the spring snow melt. Results also show that a full expression of the blue sky albedo is necessary at these large SZA snow covered areas because of the effects of anisotropic diffuse illumination and multiple scattering. In tundra locations with dark residue as a result of fire, the MODIS albedo values are lower than those at the unburned site from the start of snowmelt.

  8. Mapping wildfire burn severity in the Arctic Tundra from downsampled MODIS data

    Science.gov (United States)

    Kolden, Crystal A.; Rogan, John

    2013-01-01

    Wildfires are historically infrequent in the arctic tundra, but are projected to increase with climate warming. Fire effects on tundra ecosystems are poorly understood and difficult to quantify in a remote region where a short growing season severely limits ground data collection. Remote sensing has been widely utilized to characterize wildfire regimes, but primarily from the Landsat sensor, which has limited data acquisition in the Arctic. Here, coarse-resolution remotely sensed data are assessed as a means to quantify wildfire burn severity of the 2007 Anaktuvuk River Fire in Alaska, the largest tundra wildfire ever recorded on Alaska's North Slope. Data from Landsat Thematic Mapper (TM) and downsampled Moderate-resolution Imaging Spectroradiometer (MODIS) were processed to spectral indices and correlated to observed metrics of surface, subsurface, and comprehensive burn severity. Spectral indices were strongly correlated to surface severity (maximum R2 = 0.88) and slightly less strongly correlated to substrate severity. Downsampled MODIS data showed a decrease in severity one year post-fire, corroborating rapid vegetation regeneration observed on the burned site. These results indicate that widely-used spectral indices and downsampled coarse-resolution data provide a reasonable supplement to often-limited ground data collection for analysis and long-term monitoring of wildfire effects in arctic ecosystems.

  9. Evapotranspiration across plant types and geomorphological units in polygonal Arctic tundra

    Science.gov (United States)

    Raz-Yaseef, Naama; Young-Robertson, Jessica; Rahn, Thom; Sloan, Victoria; Newman, Brent; Wilson, Cathy; Wullschleger, Stan D.; Torn, Margaret S.

    2017-10-01

    Coastal tundra ecosystems are relatively flat, and yet display large spatial variability in ecosystem traits. The microtopographical differences in polygonal geomorphology produce heterogeneity in permafrost depth, soil temperature, soil moisture, soil geochemistry, and plant distribution. Few measurements have been made, however, of how water fluxes vary across polygonal tundra plant types, limiting our ability to understand and model these ecosystems. Our objective was to investigate how plant distribution and geomorphological location affect actual evapotranspiration (ET). These effects are especially critical in light of the rapid change polygonal tundra systems are experiencing with Arctic warming. At a field site near Barrow, Alaska, USA, we investigated the relationships between ET and plant cover in 2014 and 2015. ET was measured at a range of spatial and temporal scales using: (1) An eddy covariance flux tower for continuous landscape-scale monitoring; (2) An automated clear surface chamber over dry vegetation in a fixed location for continuous plot-scale monitoring; and (3) Manual measurements with a clear portable chamber in approximately 60 locations across the landscape. We found that variation in environmental conditions and plant community composition, driven by microtopographical features, has significant influence on ET. Among plant types, ET from moss-covered and inundated areas was more than twice that from other plant types. ET from troughs and low polygonal centers was significantly higher than from high polygonal centers. ET varied seasonally, with peak fluxes of 0.14 mm h-1 in July. Despite 24 hours of daylight in summer, diurnal fluctuations in incoming solar radiation and plant processes produced a diurnal cycle in ET. Combining the patterns we observed with projections for the impact of permafrost degradation on polygonal structure suggests that microtopographic changes associated with permafrost thaw have the potential to alter tundra

  10. Metals in Racomitrium lanuginosum from Arctic (SW Spitsbergen, Svalbard archipelago) and alpine (Karkonosze, SW Poland) tundra.

    Science.gov (United States)

    Wojtuń, Bronisław; Samecka-Cymerman, Aleksandra; Kolon, Krzysztof; Kempers, Alexander J

    2018-02-19

    Arctic-alpine tundra habitats are very vulnerable to the input of relatively small amounts of xenobiotics, and thus their level in such areas must be carefully controlled. Therefore, we collected the terrestrial widespread moss Racomitrium lanuginosum (Hedw.) Brid. in Spitsbergen in the Arctic moss lichen tundra and, for comparison, in the Arctic-alpine tundra in the Karkonosze (SW Poland). Concentrations of the elements Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Na, Ni, Pb, V, and Zn in this species and in the parent rock material were measured. We tested the following hypothesis: R. lanuginosum from Spitsbergen contains lower metal levels than the species from the Karkonosze collected at altitudes influenced by long-range transport from former Black Triangle industry. Principal component and classification analysis (PCCA) ordination revealed that mosses of Spitsbergen were distinguished by a significantly higher Na concentration of marine spray origin and mosses of Karkonosze were distinguished by significantly higher concentrations of Cd, Cr, Cu, Fe, Hg, Li, Mn, Pb, V, and Zn probably from long-range atmospheric transport. The influence of the polar station with a waste incinerator resulted in significantly higher Co, Li, and Ni concentrations in neighbouring mosses in comparison with this species from other sites. This investigation contributes to the use of R. lanuginosum as a bioindicator for metal contamination in Arctic and alpine tundra regions characterised by severe climate habitats with a restricted number of species. This moss enables the control of pollution usually brought solely by long-range atmospheric transport in high mountains as well as in Arctic areas.

  11. Fire disturbance effects on land surface albedo in Alaskan tundra

    Science.gov (United States)

    French, Nancy H. F.; Whitley, Matthew A.; Jenkins, Liza K.

    2016-03-01

    The study uses satellite Moderate Resolution Imaging Spectroradiometer albedo products (MCD43A3) to assess changes in albedo at two sites in the treeless tundra region of Alaska, both within the foothills region of the Brooks Range, the 2007 Anaktuvuk River Fire (ARF) and 2012 Kucher Creek Fire (KCF). Results are compared to each other and other studies to assess the magnitude of albedo change and the longevity of impact of fire on land surface albedo. In both sites there was a marked decrease of albedo in the year following the fire. In the ARF, albedo slowly increased until 4 years after the fire, when it returned to albedo values prior to the fire. For the year immediately after the fire, a threefold difference in the shortwave albedo decrease was found between the two sites. ARF showed a 45.3% decrease, while the KCF showed a 14.1% decrease in shortwave albedo, and albedo is more variable in the KCF site than ARF site 1 year after the fire. These differences are possibly the result of differences in burn severity of the two fires, wherein the ARF burned more completely with more contiguous patches of complete burn than KCF. The impact of fire on average growing season (April-September) surface shortwave forcing in the year following fire is estimated to be 13.24 ± 6.52 W m-2 at the ARF site, a forcing comparable to studies in other treeless ecosystems. Comparison to boreal studies and the implications to energy flux are discussed in the context of future increases in fire occurrence and severity in a warming climate.

  12. Continental Divide Trail

    Data.gov (United States)

    Earth Data Analysis Center, University of New Mexico — This shapefile was created to show the proximity of the Continental Divide to the Continental Divide National Scenic Trail in New Mexico. This work was done as part...

  13. Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula

    Science.gov (United States)

    Lara, Mark J.; McGuire, A. David; Euskirchen, Eugénie S.; Tweedie, Craig E.; Hinkel, Kenneth M.; Skurikhin, Alexei N.; Romanovsky, Vladimir E.; Grosse, Guido; Bolton, W. Robert; Genet, Helene

    2015-01-01

    The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006–2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 106gC-CO2 day−1(uncertainty using 95% CI is between −438.3 and −1366 106gC-CO2 day−1) and CH4 flux at 28.9 106gC-CH4 day−1(uncertainty using 95% CI is between 12.9 and 44.9 106gC-CH4 day−1), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2uptake (−166.9 106gC-CO2 day−1) and CH4 flux (2.8 106gC-CH4 day−1) with geomorphic change from

  14. Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula.

    Science.gov (United States)

    Lara, Mark J; McGuire, A David; Euskirchen, Eugenie S; Tweedie, Craig E; Hinkel, Kenneth M; Skurikhin, Alexei N; Romanovsky, Vladimir E; Grosse, Guido; Bolton, W Robert; Genet, Helene

    2015-04-01

    The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO2 and CH4 flux data were collected for the summers of 2006-2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO2 uptake occurs at -902.3 10(6) gC-CO2 day(-1) (uncertainty using 95% CI is between -438.3 and -1366 10(6) gC-CO2 day(-1)) and CH4 flux at 28.9 10(6) gC-CH4 day(-1) (uncertainty using 95% CI is between 12.9 and 44.9 10(6) gC-CH4 day(-1)), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO2 and CH4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO2 uptake (-166.9 10(6) gC-CO2 day(-1)) and CH4 flux (2.8 10(6) gC-CH4 day(-1)) with geomorphic change from low

  15. Open tundra persist, but arctic features decline-Vegetation changes in the warming Fennoscandian tundra.

    Science.gov (United States)

    Vuorinen, Katariina E M; Oksanen, Lauri; Oksanen, Tarja; Pyykönen, Anni; Olofsson, Johan; Virtanen, Risto

    2017-09-01

    In the forest-tundra ecotone of the North Fennoscandian inland, summer and winter temperatures have increased by two to three centigrades since 1965, which is expected to result in major vegetation changes. To document the expected expansion of woodlands and scrublands and its impact on the arctic vegetation, we repeated a vegetation transect study conducted in 1976 in the Darju, spanning from woodland to a summit, 200 m above the tree line. Contrary to our expectations, tree line movement was not detected, and there was no increase in willows or shrubby mountain birches, either. Nevertheless, the stability of tundra was apparent. Small-sized, poorly competing arctic species had declined, lichen cover had decreased, and vascular plants, especially evergreen ericoid dwarf shrubs, had gained ground. The novel climate seems to favour competitive clonal species and species thriving in closed vegetation, creating a community hostile for seedling establishment, but equally hostile for many arctic species, too. Preventing trees and shrubs from invading the tundra is thus not sufficient for conserving arctic biota in the changing climate. The only dependable cure is to stop the global warming. © 2017 John Wiley & Sons Ltd.

  16. Characterizing organic matter lability in Alaskan tundra soils using mid-infrared spectroscopy

    Science.gov (United States)

    Fan, Z.; Matamala, R.; Jastrow, J. D.; Liang, C.; Calderon, F.; Michaelson, G. J.; Ping, C. L.; Mishra, U.; Hofmann, S. M.

    2015-12-01

    Soils in permafrost regions contain large amounts of soil organic carbon (SOC) that is preserved in a relatively undecomposed state due to cold and often wet conditions, yet the potential lability of these SOC stocks is still largely unknown. Traditional methods of assessing SOC lability (e.g., laboratory incubation studies) are labor intensive and time consuming. Fourier-transform mid-infrared spectroscopy (MidIR) provides a means to quickly estimate SOC quantity and quality based on the wealth of spectral information. In this study, we explored the possibility of linking MidIR spectra with SOC lability in Arctic tundra soils. Soils from four sites on the North Slope of Alaska were used in this study: a wet non-acidic tundra site in the coastal plain (CP), two moist acidic tundra sites between the northern foothills and the coastal plain (HC and SH), and another moist acidic tundra site in the northern foothills (HV). Active-layer organic and mineral soils and upper permafrost soils from the four sites were incubated for 60 days at -1, 1, 4, 8 and 16 °C. Thawed soils were allowed to drain to field capacity. Carbon dioxide (CO2) production was measured throughout the study. The chemical composition (e.g., total organic carbon and nitrogen) and MidIR spectra of soil samples were obtained before and after the incubations. CO2 production varied among soils and temperatures. CO2 production was greatest at 16 °C for CP and SH organic layers and for HC and HV permafrost layers. These trends among soil layers and sites remained similar at all temperatures. We found a good correlation between MidIR and cumulative 60-day CO2 production across different soils and temperatures. Characteristic MidIR bands and band ratios previously identified in the literature were also correlated with total CO2 production. For example, several band ratios (such as the ratio of aliphatics to clay or the ratio of lignin or phenolics to minerals) in the mineral active layer were highly

  17. NPP Tundra: Toolik Lake, Alaska, 1982, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains one text file (.csv format) that provides productivity data for four contrasting tundra vegetation types studied during 1982 near Toolik Lake...

  18. NPP Tundra: Point Barrow, Alaska, 1970-1972, R1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains three data files. One file (.csv format) provides above- and below-ground biomass and leaf area index (LAI) data for a wet arctic tundra...

  19. Stem secondary growth of tundra shrubs

    DEFF Research Database (Denmark)

    Campioli, Matteo; Leblans, Niki; Michelsen, Anders

    2012-01-01

    Our knowledge of stem secondary growth of arctic shrubs (a key component of tundra net primary production, NPP) is very limited. Here, we investigated the impact of the physical elements of the environment on shrub secondary growth by comparing annual growth rates of model species from similar...... habitats at contrasting altitude, microtopography, latitude, geographical location, and soil type, in both the sub- and High Arctic. We found that secondary growth has a modest sensitivity to the environment but with large differences among species. For example, the evergreen Cassiope tetragona is affected...... by altitude, microtopography, and latitude, whereas the evergreen Empetrum hermaphroditum has rather constant secondary growth in all environments. Deciduous species seem to be most affected by microtopography. Furthermore, the impact of the environment on secondary growth differed from the impact on primary...

  20. Carbon loss from an unprecedented Arctic tundra wildfire.

    Science.gov (United States)

    Mack, Michelle C; Bret-Harte, M Syndonia; Hollingsworth, Teresa N; Jandt, Randi R; Schuur, Edward A G; Shaver, Gaius R; Verbyla, David L

    2011-07-27

    Arctic tundra soils store large amounts of carbon (C) in organic soil layers hundreds to thousands of years old that insulate, and in some cases maintain, permafrost soils. Fire has been largely absent from most of this biome since the early Holocene epoch, but its frequency and extent are increasing, probably in response to climate warming. The effect of fires on the C balance of tundra landscapes, however, remains largely unknown. The Anaktuvuk River fire in 2007 burned 1,039 square kilometres of Alaska's Arctic slope, making it the largest fire on record for the tundra biome and doubling the cumulative area burned since 1950 (ref. 5). Here we report that tundra ecosystems lost 2,016 ± 435 g C m(-2) in the fire, an amount two orders of magnitude larger than annual net C exchange in undisturbed tundra. Sixty per cent of this C loss was from soil organic matter, and radiocarbon dating of residual soil layers revealed that the maximum age of soil C lost was 50 years. Scaled to the entire burned area, the fire released approximately 2.1 teragrams of C to the atmosphere, an amount similar in magnitude to the annual net C sink for the entire Arctic tundra biome averaged over the last quarter of the twentieth century. The magnitude of ecosystem C lost by fire, relative to both ecosystem and biome-scale fluxes, demonstrates that a climate-driven increase in tundra fire disturbance may represent a positive feedback, potentially offsetting Arctic greening and influencing the net C balance of the tundra biome.

  1. Climate sensitivity of shrub growth across the tundra biome

    DEFF Research Database (Denmark)

    Myers-Smith, Isla H; Elmendorf, Sarah C; Beck, Pieter S.A.

    2015-01-01

    Rapid climate warming in the tundra biome has been linked to increasing shrub dominance1–4. Shrub expansion can modify climate by altering surface albedo, energy and water balance, and permafrost2,5–8, yet the drivers of shrub growth remain poorly understood. Dendroecological data consisting...... be incorporated into Earth system models to improve future projections of climate change impacts across the tundra biome....

  2. Carbon loss from an unprecedented Arctic tundra wildfire

    Science.gov (United States)

    Mack, Michelle C.; Bret-Harte, M. Syndonia; Hollingsworth, Teresa N.; Jandt, Randi R.; Schuur, Edward A. G.; Shaver, Gaius R.; Verbyla, David L.

    2011-07-01

    Arctic tundra soils store large amounts of carbon (C) in organic soil layers hundreds to thousands of years old that insulate, and in some cases maintain, permafrost soils. Fire has been largely absent from most of this biome since the early Holocene epoch, but its frequency and extent are increasing, probably in response to climate warming. The effect of fires on the C balance of tundra landscapes, however, remains largely unknown. The Anaktuvuk River fire in 2007 burned 1,039 square kilometres of Alaska's Arctic slope, making it the largest fire on record for the tundra biome and doubling the cumulative area burned since 1950 (ref. 5). Here we report that tundra ecosystems lost 2,016+/-435gCm-2 in the fire, an amount two orders of magnitude larger than annual net C exchange in undisturbed tundra. Sixty per cent of this C loss was from soil organic matter, and radiocarbon dating of residual soil layers revealed that the maximum age of soil C lost was 50 years. Scaled to the entire burned area, the fire released approximately 2.1teragrams of C to the atmosphere, an amount similar in magnitude to the annual net C sink for the entire Arctic tundra biome averaged over the last quarter of the twentieth century. The magnitude of ecosystem C lost by fire, relative to both ecosystem and biome-scale fluxes, demonstrates that a climate-driven increase in tundra fire disturbance may represent a positive feedback, potentially offsetting Arctic greening and influencing the net C balance of the tundra biome.

  3. Modeling long-term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition.

    Science.gov (United States)

    Jiang, Yueyang; Rastetter, Edward B; Shaver, Gaius R; Rocha, Adrian V; Zhuang, Qianlai; Kwiatkowski, Bonnie L

    2017-01-01

    To investigate the underlying mechanisms that control long-term recovery of tundra carbon (C) and nutrients after fire, we employed the Multiple Element Limitation (MEL) model to simulate 200-yr post-fire changes in the biogeochemistry of three sites along a burn severity gradient in response to increases in air temperature, CO 2 concentration, nitrogen (N) deposition, and phosphorus (P) weathering rates. The simulations were conducted for severely burned, moderately burned, and unburned arctic tundra. Our simulations indicated that recovery of C balance after fire was mainly determined by the internal redistribution of nutrients among ecosystem components (controlled by air temperature), rather than the supply of nutrients from external sources (e.g., nitrogen deposition and fixation, phosphorus weathering). Increases in air temperature and atmospheric CO 2 concentration resulted in (1) a net transfer of nutrient from soil organic matter to vegetation and (2) higher C : nutrient ratios in vegetation and soil organic matter. These changes led to gains in vegetation biomass C but net losses in soil organic C stocks. Under a warming climate, nutrients lost in wildfire were difficult to recover because the warming-induced acceleration in nutrient cycles caused further net nutrient loss from the system through leaching. In both burned and unburned tundra, the warming-caused acceleration in nutrient cycles and increases in ecosystem C stocks were eventually constrained by increases in soil C : nutrient ratios, which increased microbial retention of plant-available nutrients in the soil. Accelerated nutrient turnover, loss of C, and increasing soil temperatures will likely result in vegetation changes, which further regulate the long-term biogeochemical succession. Our analysis should help in the assessment of tundra C budgets and of the recovery of biogeochemical function following fire, which is in turn necessary for the maintenance of wildlife habitat and tundra

  4. Patterned-ground facilitates shrub expansion in Low Arctic tundra

    International Nuclear Information System (INIS)

    Frost, Gerald V; Epstein, Howard E; Walker, Donald A; Matyshak, Georgiy; Ermokhina, Ksenia

    2013-01-01

    Recent expansion of tall shrubs in Low Arctic tundra is widely seen as a response to climate warming, but shrubification is not occurring as a simple function of regional climate trends. We show that establishment of tall alder (Alnus) is strongly facilitated by small, widely distributed cryogenic disturbances associated with patterned-ground landscapes. We identified expanding and newly established shrub stands at two northwest Siberian sites and observed that virtually all new shrubs occurred on bare microsites (‘circles’) that were disturbed by frost-heave. Frost-heave associated with circles is a widespread, annual phenomenon that maintains mosaics of mineral seedbeds with warm soils and few competitors that are immediately available to shrubs during favorable climatic periods. Circle facilitation of alder recruitment also plausibly explains the development of shrublands in which alders are regularly spaced. We conclude that alder abundance and extent have increased rapidly in the northwest Siberian Low Arctic since at least the mid-20th century, despite a lack of summer warming in recent decades. Our results are consistent with findings in the North American Arctic which emphasize that the responsiveness of Low Arctic landscapes to climate change is largely determined by the frequency and extent of disturbance processes that create mineral-rich seedbeds favorable for tall shrub recruitment. Northwest Siberia has high potential for continued expansion of tall shrubs and concomitant changes to ecosystem function, due to the widespread distribution of patterned-ground landscapes. (letter)

  5. Arctic Tundra Greening and Browning at Circumpolar and Regional Scales

    Science.gov (United States)

    Epstein, H. E.; Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Yang, X.

    2017-12-01

    Remote sensing data have historically been used to assess the dynamics of arctic tundra vegetation. Until recently the scientific literature has largely described the "greening" of the Arctic; from a remote sensing perspective, an increase in the Normalized Difference Vegetation Index (NDVI), or a similar satellite-based vegetation index. Vegetation increases have been heterogeneous throughout the Arctic, and were reported to be up to 25% in certain areas over a 30-year timespan. However, more recently, arctic tundra vegetation dynamics have gotten more complex, with observations of more widespread tundra "browning" being reported. We used a combination of remote sensing data, including the Global Inventory Monitoring and Modeling System (GIMMS), as well as higher spatial resolution Landsat data, to evaluate the spatio-temporal patterns of arctic tundra vegetation dynamics (greening and browning) at circumpolar and regional scales over the past 3-4 decades. At the circumpolar scale, we focus on the spatial heterogeneity (by tundra subzone and continent) of tundra browning over the past 5-15 years, followed by a more recent recovery (greening since 2015). Landsat time series allow us to evaluate the landscape-scale heterogeneity of tundra greening and browning for northern Alaska and the Yamal Peninsula in northwestern Siberia, Russia. Multi-dataset analyses reveal that tundra greening and browning (i.e. increases or decreases in the NDVI respectively) are generated by different sets of processes. Tundra greening is largely a result of either climate warming, lengthening of the growing season, or responses to disturbances, such as fires, landslides, and freeze-thaw processes. Browning on the other hand tends to be more event-driven, such as the shorter-term decline in vegetation due to fire, insect defoliation, consumption by larger herbivores, or extreme weather events (e.g. winter warming or early summer frost damage). Browning can also be caused by local or

  6. Simulating the effects of soil organic nitrogen and grazing on arctic tundra vegetation dynamics on the Yamal Peninsula, Russia

    International Nuclear Information System (INIS)

    Yu Qin; Epstein, Howard; Walker, Donald

    2009-01-01

    Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world's largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model-ArcVeg-to evaluate how two factors (soil organic nitrogen (SON) levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (high arctic), D (northern low arctic) and E (southern low arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 deg. C caused an increase of 665 g m -2 in total biomass at the high SON site in subzone E, but only 298 g m -2 at the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g m -2 at the high SON site in contrast to 184 g m -2 at the low SON site in subzone E. Our results suggest that high SON can support greater plant biomass and plant responses to climate warming, while low SON and grazing may limit plant response to climate change. In addition to the first order factors (SON, bioclimate subzones, grazing and temporal climate warming), interactions among these significantly affect plant biomass and productivity in the arctic tundra and should not be ignored in regional scale studies.

  7. Isoprene emissions from a tundra ecosystem

    Directory of Open Access Journals (Sweden)

    M. J. Potosnak

    2013-02-01

    Full Text Available Whole-system fluxes of isoprene from a moist acidic tundra ecosystem and leaf-level emission rates of isoprene from a common species (Salix pulchra in that same ecosystem were measured during three separate field campaigns. The field campaigns were conducted during the summers of 2005, 2010 and 2011 and took place at the Toolik Field Station (68.6° N, 149.6° W on the north slope of the Brooks Range in Alaska, USA. The maximum rate of whole-system isoprene flux measured was over 1.2 mg C m−2 h−1 with an air temperature of 22 °C and a PAR level over 1500 μmol m−2 s−1. Leaf-level isoprene emission rates for S. pulchra averaged 12.4 nmol m−2 s−1 (27.4 μg C gdw−1 h−1 extrapolated to standard conditions (PAR = 1000 μmol m−2 s−1 and leaf temperature = 30 °C. Leaf-level isoprene emission rates were well characterized by the Guenther algorithm for temperature with published coefficients, but less so for light. Chamber measurements from a nearby moist acidic tundra ecosystem with little S. pulchra emitted significant amounts of isoprene, but at lower rates (0.45 mg C m−2 h−1 suggesting other significant isoprene emitters. Comparison of our results to predictions from a global model found broad agreement, but a detailed analysis revealed some significant discrepancies. An atmospheric chemistry box model predicts that the observed isoprene emissions have a significant impact on Arctic atmospheric chemistry, including a reduction of hydroxyl radical (OH concentrations. Our results support the prediction that isoprene emissions from Arctic ecosystems will increase with global climate change.

  8. Effects of Unsaturated Microtopography on Nitrate Concentrations in Tundra Ecosystems: Examples from Polygonal Terrain and Degraded Peat Plateaus

    Science.gov (United States)

    Heikoop, J. M.; Arendt, C. A.; Newman, B. D.; Charsley-Groffman, L.; Perkins, G.; Wilson, C. J.; Wullschleger, S.

    2017-12-01

    Under the auspices of the Next Generation Ecosystem Experiment - Arctic, we have been studying hydrogeochemical signals in Alaskan tundra ecosystems underlain by continuous permafrost (Barrow Environmental Observatory (BEO)) and discontinuous permafrost (Seward Peninsula). The Barrow site comprises largely saturated tundra associated with the low gradient Arctic Coastal Plain. Polygonal microtopography, however, can result in slightly raised areas that are unsaturated. In these areas we have previously demonstrated production and accumulation of nitrate, which, based on nitrate isotopic analysis, derives from microbial degradation. Our Seward Peninsula site is located in a much steeper and generally well-drained watershed. In lower-gradient areas at the top and bottom of the watershed, however, the tundra is generally saturated, likely because of the presence of underlying discontinuous permafrost inhibiting infiltration. These settings also contain microtopographic features, though in the form of degraded peat plateaus surrounded by wet graminoid sag ponds. Despite being very different microtopographic features in a very different setting with distinct vegetation, qualitatively similar nitrate accumulation patterns as seen in polygonal terrain were observed. The highest nitrate pore water concentration observed in an unsaturated peat plateau was approximately 5 mg/L, whereas subsurface pore water concentrations in surrounding sag ponds were generally below the limit of detection. Nitrate isotopes indicate this nitrate results from microbial mineralization and nitrification based on comparison to the nitrate isotopic composition of reduced nitrogen sources in the environment and the oxygen isotope composition of site pore water. Nitrate concentrations were most similar to those found in low-center polygon rims and flat-centered polygon centers at the BEO, but were significantly lower than the maximum concentrations seen in the highest and driest polygonal features

  9. 50 CFR 20.107 - Seasons, limits, and shooting hours for tundra swans.

    Science.gov (United States)

    2010-10-01

    ... tundra swans. 20.107 Section 20.107 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE..., and Shooting Hours Schedules § 20.107 Seasons, limits, and shooting hours for tundra swans. This section provides for the annual hunting of tundra swans in designated portions of the 48 contiguous United...

  10. Deep continental margin reflectors

    Science.gov (United States)

    Ewing, J.; Heirtzler, J.; Purdy, M.; Klitgord, Kim D.

    1985-01-01

    In contrast to the rarity of such observations a decade ago, seismic reflecting and refracting horizons are now being observed to Moho depths under continental shelves in a number of places. These observations provide knowledge of the entire crustal thickness from the shoreline to the oceanic crust on passive margins and supplement Consortium for Continental Reflection Profiling (COCORP)-type measurements on land.

  11. Tall shrub and tree expansion in Siberian tundra ecotones since the 1960s.

    Science.gov (United States)

    Frost, Gerald V; Epstein, Howard E

    2014-04-01

    Circumpolar expansion of tall shrubs and trees into Arctic tundra is widely thought to be occurring as a result of recent climate warming, but little quantitative evidence exists for northern Siberia, which encompasses the world's largest forest-tundra ecotonal belt. We quantified changes in tall shrub and tree canopy cover in 11, widely distributed Siberian ecotonal landscapes by comparing very high-resolution photography from the Cold War-era 'Gambit' and 'Corona' satellite surveillance systems (1965-1969) with modern imagery. We also analyzed within-landscape patterns of vegetation change to evaluate the susceptibility of different landscape components to tall shrub and tree increase. The total cover of tall shrubs and trees increased in nine of 11 ecotones. In northwest Siberia, alder (Alnus) shrubland cover increased 5.3-25.9% in five ecotones. In Taymyr and Yakutia, larch (Larix) cover increased 3.0-6.7% within three ecotones, but declined 16.8% at a fourth ecotone due to thaw of ice-rich permafrost. In Chukotka, the total cover of alder and dwarf pine (Pinus) increased 6.1% within one ecotone and was little changed at a second ecotone. Within most landscapes, shrub and tree increase was linked to specific geomorphic settings, especially those with active disturbance regimes such as permafrost patterned-ground, floodplains, and colluvial hillslopes. Mean summer temperatures increased at most ecotones since the mid-1960s, but rates of shrub and tree canopy cover expansion were not strongly correlated with temperature trends and were better correlated with mean annual precipitation. We conclude that shrub and tree cover is increasing in tundra ecotones across most of northern Siberia, but rates of increase vary widely regionally and at the landscape scale. Our results indicate that extensive changes can occur within decades in moist, shrub-dominated ecotones, as in northwest Siberia, while changes are likely to occur much more slowly in the highly continental

  12. A Comparative Review of North American Tundra Delineations

    Science.gov (United States)

    Silver, Kirk C.; Carroll, Mark

    2013-01-01

    Recent profound changes have been observed in the Arctic environment, including record low sea ice extents and high latitude greening. Studying the Arctic and how it is changing is an important element of climate change science. The Tundra, an ecoregion of the Arctic, is directly related to climate change due to its effects on the snow ice feedback mechanism and greenhouse gas cycling. Like all ecoregions, the Tundra border is shifting, yet studies and policies require clear delineation of boundaries. There are many options for ecoregion classification systems, as well as resources for creating custom maps. To help decision makers identify the best classification system possible, we present a review of North American Tundra ecoregion delineations and further explore the methodologies, purposes, limitations, and physical properties of five common ecoregion classification systems. We quantitatively compare the corresponding maps by area using a geographic information system.

  13. Future distribution of tundra refugia in northern Alaska

    Science.gov (United States)

    Hope, Andrew G.; Waltari, Eric; Payer, David C.; Cook, Joseph A.; Talbot, Sandra L.

    2013-01-01

    Climate change in the Arctic is a growing concern for natural resource conservation and management as a result of accelerated warming and associated shifts in the distribution and abundance of northern species. We introduce a predictive framework for assessing the future extent of Arctic tundra and boreal biomes in northern Alaska. We use geo-referenced museum specimens to predict the velocity of distributional change into the next century and compare predicted tundra refugial areas with current land-use. The reliability of predicted distributions, including differences between fundamental and realized niches, for two groups of species is strengthened by fossils and genetic signatures of demographic shifts. Evolutionary responses to environmental change through the late Quaternary are generally consistent with past distribution models. Predicted future refugia overlap managed areas and indicate potential hotspots for tundra diversity. To effectively assess future refugia, variable responses among closely related species to climate change warrants careful consideration of both evolutionary and ecological histories.

  14. Linkages Among Climate, Fire, and Thermoerosion in Alaskan Tundra Over the Past Three Millennia

    Science.gov (United States)

    Chipman, M. L.; Hu, F. S.

    2017-12-01

    Amplified Arctic warming may facilitate novel tundra disturbance regimes, as suggested by recent increases in the rate and extent of thermoerosion and fires in some tundra areas. Thermoerosion and wildfire can exacerbate warming by releasing large permafrost carbon stocks, and interactions between disturbance regimes can lead to complex ecosystem feedbacks. We conducted geochemical and charcoal analyses of lake sediments from an Alaskan lake to identify thermoerosion and fire events over the past 3,000 years. Thermoerosion was inferred from lake sediments in the context of modern soil data from retrogressive thaw slumps (RTS). Magnetic susceptibility (MS), Ca:K, and Ca:Sr increased with depth in modern RTS soils and were higher on recently exposed than older slump surfaces. Peaks in bulk density, % CaCO3, Ca:K, Ca:Sr, and MS values in the sediments suggest at least 18 thermoerosion events in the Loon Lake watershed over the past 3,000 years. Charcoal analysis identifies 22 fires over the same period at this site. Temporal variability in these records suggests climate-driven responses of both thermoerosion and fire disturbance regimes, with fewer RTS episodes and fire events during the Little Ice Age than the Medieval Climate Anomaly. Moreover, RTS activity lagged behind catchment fires by 20-30 years (>90% confidence interval), implying that fires facilitated thermoerosion on decadal time scales, possibly because of prolonged active-layer deepening following fire and postfire proliferation of insulative shrub cover. These results highlight the potential for complex interactions between climate, vegetation, and tundra disturbance in response to ongoing warming.

  15. Tug of war between continental gene flow and rearing site philopatry in a migratory bird: the sex-biased dispersal paradigm reconsidered.

    Science.gov (United States)

    Lecomte, Nicolas; Gauthier, Gilles; Giroux, Jean-François; Milot, Emmanuel; Bernatchez, Louis

    2009-02-01

    Nonrandom dispersal has been recently advanced as a mechanism promoting fine-scale genetic differentiation in resident populations, yet how this applies to species with high rates of dispersal is still unclear. Using a migratory species considered a classical example of male-biased dispersal (the greater snow goose, Chen caerulescens atlantica), we documented a temporally stable fine-scale genetic clustering between spatially distinct rearing sites (5-30 km apart), where family aggregates shortly after hatching. Such genetic differentiation can only arise if, in both sexes, dispersal is restricted and nonrandom, a surprising result considering that pairing occurs among mixed flocks of birds more than 3000 km away from the breeding grounds. Fine-scale genetic structure may thus occur even in migratory species with high gene flow. We further show that looking for genetic structure based on nesting sites only may be misleading. Genetically distinct individuals that segregated into different rearing sites were in fact spatially mixed during nesting. These findings provide new, scale-dependent links between genetic structure, pairing, and dispersal and show the importance of sampling different stages of the breeding cycle in order to detect a spatial genetic structure.

  16. Carbon dioxide and methane dynamics in Russian tundra

    DEFF Research Database (Denmark)

    Johansson, Paul Torbjörn; Kiepe, Isabell; Herbst, Mathias

    Russia. The area is situated at 67°N in the European part of northeast Russia within the Pechora basin. The Russian tundra region is an area which has recently been subject to many speculations in relation to climatic change effects and greenhouse gas (GHG) exchange but still little scientific......, and discuss possible implications of climatic change on this lowland tundra ecosystem. This study have been conducted as a part of the CARBO-North project (2006-2010), a project within the EU 6th framework programme, aiming at quantifying the carbon budget in Northern Russia across temporal and spatial scales....

  17. The Contribution of Old Carbon to Respiration from Alaskan Tundra Following Permafrost Thaw

    Science.gov (United States)

    Schuur, E. A.; Vogel, J. G.; Crummer, K. G.; Lee, H.; Sickman, J. O.; Dutta, K.

    2007-12-01

    More than 450 Pg of soil carbon (C) has accumulated in high latitude ecosystems after the retreat of the last major ice sheets. Recent studies suggest that, due to climate warming, these ecosystems may no longer be accumulating C, and in some cases may be losing stored C to the atmosphere. We used radiocarbon measurements of carbon dioxide to detect the age of C respired from tussock tundra near Denali National Park, Alaska. At this tundra site, permafrost has been observed to warm and thaw over the past several decades, causing the ground surface to subside as ice volume in the soil decreased. We established three sites within this area that differed in vegetation and surface topography; both characteristics varied in relation to the degree of permafrost thaw. We made radiocarbon measurements of ecosystem respiration, incubations of soil organic matter, and incubations of above and belowground plant biomass to determine the age and isotopic value of C respired from these sites. Over the study period from 2004 to 2006, ecosystem respiration radiocarbon values averaged from +35‰ to +95‰ in different months across sites. For soil incubations, surface soil radiocarbon was elevated relative both to ecosystem respiration and the current atmospheric radiocarbon value, demonstrating the significant contribution from C fixed over the past years to several decades. The deeper soil, in contrast, had respiration isotope values that averaged below zero, reflecting the significant effect of radioactive decay on the isotope content of deeper soil layers. The plant and soil incubations were combined in a multi- source mixing model to determine probable contributions from these different sources to ecosystem respiration. Deep soil respiration generally averaged between 5-15% of total ecosystem respiration, but reached as high as 40% in some months. When aggregated across the growing season, the two sites undergoing more disturbance from permafrost thaw had on average 2-3 times

  18. Seismic structure and tectonics of the continental margins of India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Chaubey, A.K.; Rao, D.G.; Reddy, P.R.

    floor belong to different lithospheric plates. Active margins are commonly the sites of tectonic activity such as earthquakes, volcanoes, mountain building and formation of new igneous rocks. Because of the mountainous terrain the continental shelf... greater proportion of the river borne sediments occur on the shelves, continental slopes, and deep sea fans where terrigenous sedimentation is dominant process. On lower slopes and continental rises, fine-grained siliciclastics commonly mixed...

  19. Site-condition map for Portugal, Western Iberia: methodology and constraints on the performance of Vs30 proxies for stable continental regions in Europe.

    Science.gov (United States)

    Vilanova, S. P.; Narciso, J.; Carvalho, J. P.; Cancela, C.; Lopes, I.; Nemser, E. S.; Borges, J.

    2014-12-01

    Information on the amplification characteristics of the near-surface formations in a regional sense is essential to adequately represent both seismic hazard maps and ground shaking maps. Due to the scarceness of shear-wave velocity data in most regions, several methods have been proposed in order to obtain first order representations of Vs30. These include the surface geology method and the topographic slope method. The latter method has become the standard way for incorporating site effects into regional studies worldwide given the convenience provided by the global Vs30 Internet server. In the framework of project SCENE we developed a shear wave velocity database for Portugal. The database consists of 87 shear-wave velocity depth profiles from a variety of lithological and geological formations. We used an iterative three-step procedure to develop the Vs30 based site-condition map: 1) to define a preliminary set of geologically defined units based on the literature; 2) to calculate the distribution of Vs30 for each unit; and 3) to perform statistical tests in order to estimate the significance of the difference in the Vs30 distribution characteristics between the units. The units were merged according to the results of the statistical tests and the procedure was repeated. We started by classifying the sites into six generalized geological units. The final set consists of three units only: F1 (igneous, metamorphic and old sedimentary rocks); F2 (Neogene and Pleistocene formations); and F3 (Holocene deposits). We used the database to evaluate the performance of Vs30 proxies. The use of proxies based either on geological units or on correlations with the topographic slope shows relatively unbiased total residual distributions of the logarithm of Vs30. However, the performance of the methods varies significantly with the generalized geological unit analyzed. Both methods are biased towards lower values of Vs30 for rock formations. The topographic-slope method is

  20. Continental drift before 1900.

    Science.gov (United States)

    Rupke, N A

    1970-07-25

    The idea that Francis Bacon and other seventeenth and eighteenth century thinkers first conceived the notion of continental drift does not stand up to close scrutiny. The few authors who expressed the idea viewed the process as a catastrophic event.

  1. Divergent hydrological responses to 20th century climate change in shallow tundra ponds, western Hudson Bay Lowlands

    Science.gov (United States)

    Wolfe, Brent B.; Light, Erin M.; Macrae, Merrin L.; Hall, Roland I.; Eichel, Kaleigh; Jasechko, Scott; White, Jerry; Fishback, LeeAnn; Edwards, Thomas W. D.

    2011-12-01

    The hydrological fate of shallow tundra lakes and ponds under conditions of continued warming remains uncertain, but has important implications for wildlife habitat and biogeochemical cycling. Observations of unprecedented pond desiccation, in particular, signify catastrophic loss of aquatic habitat in some Arctic locations. Shallow tundra ponds are a ubiquitous feature in the western Hudson Bay Lowlands (HBL), a region that has undergone intense warming over the past ˜50 years. But it remains unknown how hydrological processes in these ponds have responded. Here, we use cellulose-inferred pond water oxygen isotope records from sediment cores, informed by monitoring of modern pond water isotope compositions during the 2009 and 2010 ice-free seasons, to reconstruct hydrological conditions of four shallow tundra ponds in the western HBL over the past three centuries. Following an interval of relative hydrological stability during the early part of the records, results reveal widely differing hydrological responses to 20th century climate change among the study sites, which is largely dependent on hydrological connectivity of the basins within their respective surrounding peatlands. These findings suggest the 20th century has been characterized by an increasingly dynamic landscape that has variably influenced surface water balance - a factor that is likely to play a key role in determining the future water balance of ponds in this region.

  2. Warming of subarctic tundra increases emissions of all three important greenhouse gases - carbon dioxide, methane, and nitrous oxide.

    Science.gov (United States)

    Voigt, Carolina; Lamprecht, Richard E; Marushchak, Maija E; Lind, Saara E; Novakovskiy, Alexander; Aurela, Mika; Martikainen, Pertti J; Biasi, Christina

    2017-08-01

    Rapidly rising temperatures in the Arctic might cause a greater release of greenhouse gases (GHGs) to the atmosphere. To study the effect of warming on GHG dynamics, we deployed open-top chambers in a subarctic tundra site in Northeast European Russia. We determined carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) fluxes as well as the concentration of those gases, inorganic nitrogen (N) and dissolved organic carbon (DOC) along the soil profile. Studied tundra surfaces ranged from mineral to organic soils and from vegetated to unvegetated areas. As a result of air warming, the seasonal GHG budget of the vegetated tundra surfaces shifted from a GHG sink of -300 to -198 g CO 2 -eq m -2 to a source of 105 to 144 g CO 2 -eq m -2 . At bare peat surfaces, we observed increased release of all three GHGs. While the positive warming response was dominated by CO 2 , we provide here the first in situ evidence of increasing N 2 O emissions from tundra soils with warming. Warming promoted N 2 O release not only from bare peat, previously identified as a strong N 2 O source, but also from the abundant, vegetated peat surfaces that do not emit N 2 O under present climate. At these surfaces, elevated temperatures had an adverse effect on plant growth, resulting in lower plant N uptake and, consequently, better N availability for soil microbes. Although the warming was limited to the soil surface and did not alter thaw depth, it increased concentrations of DOC, CO 2, and CH 4 in the soil down to the permafrost table. This can be attributed to downward DOC leaching, fueling microbial activity at depth. Taken together, our results emphasize the tight linkages between plant and soil processes, and different soil layers, which need to be taken into account when predicting the climate change feedback of the Arctic. © 2016 John Wiley & Sons Ltd.

  3. Contrasting above- and belowground organic matter decomposition and carbon and nitrogen dynamics in response to warming in High Arctic tundra.

    Science.gov (United States)

    Blok, Daan; Faucherre, Samuel; Banyasz, Imre; Rinnan, Riikka; Michelsen, Anders; Elberling, Bo

    2017-12-13

    Tundra regions are projected to warm rapidly during the coming decades. The tundra biome holds the largest terrestrial carbon pool, largely contained in frozen permafrost soils. With warming, these permafrost soils may thaw and become available for microbial decomposition, potentially providing a positive feedback to global warming. Warming may directly stimulate microbial metabolism but may also indirectly stimulate organic matter turnover through increased plant productivity by soil priming from root exudates and accelerated litter turnover rates. Here, we assess the impacts of experimental warming on turnover rates of leaf litter, active layer soil and thawed permafrost sediment in two high-arctic tundra heath sites in NE-Greenland, either dominated by evergreen or deciduous shrubs. We incubated shrub leaf litter on the surface of control and warmed plots for 1 and 2 years. Active layer soil was collected from the plots to assess the effects of 8 years of field warming on soil carbon stocks. Finally, we incubated open cores filled with newly thawed permafrost soil for 2 years in the active layer of the same plots. After field incubation, we measured basal respiration rates of recovered thawed permafrost cores in the lab. Warming significantly reduced litter mass loss by 26% after 1 year incubation, but differences in litter mass loss among treatments disappeared after 2 years incubation. Warming also reduced litter nitrogen mineralization and decreased the litter carbon to nitrogen ratio. Active layer soil carbon stocks were reduced 15% by warming, while soil dissolved nitrogen was reduced by half in warmed plots. Warming had a positive legacy effect on carbon turnover rates in thawed permafrost cores, with 10% higher respiration rates measured in cores from warmed plots. These results demonstrate that warming may have contrasting effects on above- and belowground tundra carbon turnover, possibly governed by microbial resource availability. © 2017 John

  4. Ecohydrologic Changes due to Tree Expansion into Tundra in the Polar Urals, Russia

    Science.gov (United States)

    Ivanov, V. Y.; Wang, J.; El Sharif, H. A.; Liu, D.; Sheshukov, A. Y.; Mazepa, V.; Shiyatov, S.; Sokolov, A.

    2017-12-01

    The Arctic has been warming at an accelerating rate over the last several decades and the changing climate has caused the invasion of trees and shrubs into tundra across the polar regions of Alaska, Canada, and Russia. These vegetation changes may have the potential to impact regional hydrology and climate. This study aims to develop mechanistic and quantitative understanding of implications of forest encroachment into tundra. Specifically, for several areas with well-documented larch and spruce expansion in the Polar Urals and southern Yamal Peninsula of Russia over 1960-2010s, we hypothesize that the encroachment process alters the seasonality of energy budget characterized by enhanced total evapotranspiration and concomitant subsurface warming. We are collecting a comprehensive set of field observational data on micrometeorology, snow conditions, radiative fluxes, tree sap flows, soil temperature, moisture, and heat fluxes, and active layer thickness. A novel model of maximum entropy production (MEP) is used to derive the surface energy budgets as the partition of radiative fluxes into turbulent and conductive heat fluxes across the ecotone interface. We are presenting preliminary findings that illustrate the identified differences of seasonal snow and heat budget regimes for two contrasting sites: one of which has experienced a recent tree encroachment, while for the other this process has not yet occurred. Observed and modeled heat fluxes are used to inform a comprehensive physical model to study the impact of vegetation encroachment process on the permafrost dynamics.

  5. DOES NITROGEN PARTITIONING PROMOTE SPECIES DIVERSITY IN ARCTIC TUSSOCK TUNDRA?

    Science.gov (United States)

    We used 15N soil-labeling techniques to examine how the dominant species in a N-limited, tussock tundra plant community partitioned soil N, and how such partitioning may contribute to community organization. The five most productive species were well differentiated with respect ...

  6. Strong microsite control of seedling recruitment in tundra

    DEFF Research Database (Denmark)

    Graae, Bente J; Ejrnæs, Rasmus; Lang, Simone I

    2011-01-01

    gradient in dry tundra. A survey of natural seed rain and seedling density in vegetation was combined with observations of the establishment of 14 species after sowing into intact or disturbed vegetation. Although seed rain density was closely correlated with natural seedling establishment...

  7. Large tundra methane burst during onset of freezing

    DEFF Research Database (Denmark)

    Mastepanov, Mikhail; Sigsgaard, Charlotte; Dlugokencky, Edward J.

    2008-01-01

    of global atmospheric methane concentrations indicate that the observed early winter emission burst improves the agreement between the simulated seasonal cycle and atmospheric data from latitudes north of 60N. Our findings suggest that permafrost-associated freeze-in bursts of methane missions from tundra...

  8. Kevad tundras : [luuletused] / Prokopi Javtõsõi

    Index Scriptorium Estoniae

    Javtõsõi, Prokopi

    2004-01-01

    Sisu: Kevad tundras ; Virmalised ; Mulle meenus ema ; Minu rändude maa ; Oleme karjakasvatajad, "Kui olen sinu kõrval ma ..." ; "Kui askeldustest aega üle jääb ...". Eluloolisi andmeid autori kohta lk. 231. Luuletused paralleelselt eesti ja neenetsi keeles

  9. Shrub expansion in tundra ecosystems: dynamics, impacts and research priorities

    International Nuclear Information System (INIS)

    Myers-Smith, Isla H; Forbes, Bruce C; Wilmking, Martin; Hallinger, Martin; Lantz, Trevor; Blok, Daan; Sass-Klaassen, Ute; Tape, Ken D; Macias-Fauria, Marc; Lévesque, Esther; Boudreau, Stéphane; Ropars, Pascale; Hermanutz, Luise; Trant, Andrew; Collier, Laura Siegwart; Weijers, Stef; Rozema, Jelte; Rayback, Shelly A; Schmidt, Niels Martin; Schaepman-Strub, Gabriela

    2011-01-01

    Recent research using repeat photography, long-term ecological monitoring and dendrochronology has documented shrub expansion in arctic, high-latitude and alpine tundra ecosystems. Here, we (1) synthesize these findings, (2) present a conceptual framework that identifies mechanisms and constraints on shrub increase, (3) explore causes, feedbacks and implications of the increased shrub cover in tundra ecosystems, and (4) address potential lines of investigation for future research. Satellite observations from around the circumpolar Arctic, showing increased productivity, measured as changes in ‘greenness’, have coincided with a general rise in high-latitude air temperatures and have been partly attributed to increases in shrub cover. Studies indicate that warming temperatures, changes in snow cover, altered disturbance regimes as a result of permafrost thaw, tundra fires, and anthropogenic activities or changes in herbivory intensity are all contributing to observed changes in shrub abundance. A large-scale increase in shrub cover will change the structure of tundra ecosystems and alter energy fluxes, regional climate, soil–atmosphere exchange of water, carbon and nutrients, and ecological interactions between species. In order to project future rates of shrub expansion and understand the feedbacks to ecosystem and climate processes, future research should investigate the species or trait-specific responses of shrubs to climate change including: (1) the temperature sensitivity of shrub growth, (2) factors controlling the recruitment of new individuals, and (3) the relative influence of the positive and negative feedbacks involved in shrub expansion.

  10. Tracking Soil Organic Carbon Transport to Continental Margin Sediments Using Soil-Specific Hopanoid Biomarkers: a Case Study From the Congo Fan (ODP Site 1075)

    Science.gov (United States)

    Cooke, M. P.; Talbot, H. M.; Eniola, O.; Zabel, M.; Wagner, T.

    2007-12-01

    The transport and subsequent deposition of terrestrially derived organic matter into the ocean is an important but poorly constrained aspect of the modern global carbon cycle. In regions associated with large river systems it is likely that the terrestrial input of organic carbon is much more complex than commonly considered and very difficult to trace based on established geochemical proxies. It is therefore important to develop proxies that target the movement and fate of this terrestrial organic material. The identification of bacteriohopanepolyol (BHP) biomarkers unique to soil derived organic carbon (SOC) has enabled the transport of SOC into aquatic sediments to be traced. The extreme recalcitrance of BHPs enables these source specific compounds to be used on recent and ancient sediments to identify periods of high and low SOC input into sediments. BHPs are bacterial membrane compounds with a high degree of structural variability. They are analogous to steroids in eukaryotes and have been identified in over half of all bacteria studied for their presence. BHPs have a wide range of over 40 functional groups on the side chain, with up to 6 functional groups in each structure, and with methylation and unsaturation over 100 total structures have been identified1. During the BHP analysis of a wide range of soils from around the world we consistently measure high levels adenosylhopane, known to originate from purple non-sulphur, nitrogen fixing and ammonia oxidising bacteria and 2-methyl adenosyl hopane (m/z 802)2, from nitrogen fixing bacteria. Only 3 lacustrine sediments with large SOC supply from their catchments areas have been found to contain these markers in a survey of over 40 different non-marine settings. Recent studies on Late Quaternary sediments from the Congo deep sea fan (OPD site 1075, approximately 2 km water depth) provide a strong case to expect markers for SOC3. An initial analysis of the core samples confirms the presence of soil specific BHP

  11. Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution

    Science.gov (United States)

    Obrist, Daniel; Agnan, Yannick; Jiskra, Martin; Olson, Christine L.; Colegrove, Dominique P.; Hueber, Jacques; Moore, Christopher W.; Sonke, Jeroen E.; Helmig, Detlev

    2017-07-01

    Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through ‘atmospheric mercury depletion events’, or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(II)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(II) via precipitation or AMDEs. We find that deposition of Hg(0)—the form ubiquitously present in the global atmosphere—occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean.

  12. Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution.

    Science.gov (United States)

    Obrist, Daniel; Agnan, Yannick; Jiskra, Martin; Olson, Christine L; Colegrove, Dominique P; Hueber, Jacques; Moore, Christopher W; Sonke, Jeroen E; Helmig, Detlev

    2017-07-12

    Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic. It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide, raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean.

  13. Microbial functional diversity covaries with permafrost thaw-induced environmental heterogeneity in tundra soil.

    Science.gov (United States)

    Yuan, Mengting M; Zhang, Jin; Xue, Kai; Wu, Liyou; Deng, Ye; Deng, Jie; Hale, Lauren; Zhou, Xishu; He, Zhili; Yang, Yunfeng; Van Nostrand, Joy D; Schuur, Edward A G; Konstantinidis, Konstantinos T; Penton, Christopher R; Cole, James R; Tiedje, James M; Luo, Yiqi; Zhou, Jizhong

    2018-01-01

    Permafrost soil in high latitude tundra is one of the largest terrestrial carbon (C) stocks and is highly sensitive to climate warming. Understanding microbial responses to warming-induced environmental changes is critical to evaluating their influences on soil biogeochemical cycles. In this study, a functional gene array (i.e., geochip 4.2) was used to analyze the functional capacities of soil microbial communities collected from a naturally degrading permafrost region in Central Alaska. Varied thaw history was reported to be the main driver of soil and plant differences across a gradient of minimally, moderately, and extensively thawed sites. Compared with the minimally thawed site, the number of detected functional gene probes across the 15-65 cm depth profile at the moderately and extensively thawed sites decreased by 25% and 5%, while the community functional gene β-diversity increased by 34% and 45%, respectively, revealing decreased functional gene richness but increased community heterogeneity along the thaw progression. Particularly, the moderately thawed site contained microbial communities with the highest abundances of many genes involved in prokaryotic C degradation, ammonification, and nitrification processes, but lower abundances of fungal C decomposition and anaerobic-related genes. Significant correlations were observed between functional gene abundance and vascular plant primary productivity, suggesting that plant growth and species composition could be co-evolving traits together with microbial community composition. Altogether, this study reveals the complex responses of microbial functional potentials to thaw-related soil and plant changes and provides information on potential microbially mediated biogeochemical cycles in tundra ecosystems. © 2017 John Wiley & Sons Ltd.

  14. Paenibacillus tundrae sp. nov. and Paenibacillus xylanexedens sp. nov., Psychrotolerant, Xylan-Degrading, Bacteria from Alaskan Tundra

    Science.gov (United States)

    Psychrotolerant, xylan-degrading, strains of bacteria were isolated from soil beneath moist non-acidic and acidic tundra in northern Alaska. Phylogenetic analysis based on 16S rRNA gene sequences revealed that each strain belonged to the genus Paenibacillus. The highest levels of 16S rRNA gene sim...

  15. The origin of lead in the organic horizon of tundra soils: Atmospheric deposition, plant translocation from the mineral soil or soil mineral mixing?

    International Nuclear Information System (INIS)

    Klaminder, Jonatan; Farmer, John G.; MacKenzie, Angus B.

    2011-01-01

    Knowledge of the anthropogenic contribution to lead (Pb) concentrations in surface soils in high latitude ecosystems is central to our understanding of the extent of atmospheric Pb contamination. In this study, we reconstructed fallout of Pb at a remote sub-arctic region by using two ombrotrophic peat cores and assessed the extent to which this airborne Pb is able to explain the isotopic composition ( 206 Pb/ 207 Pb ratio) in the O-horizon of tundra soils. In the peat cores, long-range atmospheric fallout appeared to be the main source of Pb as indicated by temporal trends that followed the known European pollution history, i.e. accelerated fallout at the onset of industrialization and peak fallout around the 1960s-70s. The Pb isotopic composition of the O-horizon of podzolic tundra soil ( 206 Pb/ 207 Pb = 1.170 ± 0.002; mean ± SD) overlapped with that of the peat ( 206 Pb/ 207 Pb = 1.16 ± 0.01) representing a proxy for atmospheric aerosols, but was clearly different from that of the parent soil material ( 206 Pb/ 207 Pb = 1.22-1.30). This finding indicated that long-range fallout of atmospheric Pb is the main driver of Pb accumulation in podzolic tundra soil. In O-horizons of tundra soil weakly affected by cryoturbation (cryosols) however, the input of Pb from the underlying mineral soil increased as indicated by 206 Pb/ 207 Pb ratios of up to 1.20, a value closer to that of local soil minerals. Nevertheless, atmospheric Pb appeared to be the dominant source in this soil compartment. We conclude that Pb concentrations in the O-horizon of studied tundra soils - despite being much lower than in boreal soils and representative for one of the least exposed sites to atmospheric Pb contaminants in Europe - are mainly controlled by atmospheric inputs from distant anthropogenic sources. - Highlights: → We used Pb isotopic composition to aid interpretation of Pb profiles in tundra soils. → Ombrotrophic peat cores were used as records of atmospheric inputs of Pb.

  16. A synthesis of growing-season, non-growing season, and annual methane emission measurements among temperate, boreal, and tundra wetlands and uplands

    Science.gov (United States)

    Treat, C. C.; Bloom, A. A.; Marushchak, M. E.

    2017-12-01

    Wetlands are the largest natural source of methane to the atmosphere, while upland soils are a consistent sink of atmospheric methane. Wetland methane emissions are highly variable among sites, years, and temporal scales due to differences in production, oxidation, and transport pathways. Currently, process model predictions of methane emissions from wetlands remain challenging due to uncertain parameterizations of net methane production and emission processes. Here, we synthesize growing season, non-growing season, and annual methane emissions from chamber and eddy-covariance measurements for more than 150 sites in undisturbed temperate, boreal, and tundra wetlands and uplands. We compare the magnitude of fluxes among regions, wetland classifications, vegetation classifications, and environmental variables. Growing season measurements were most abundant in bogs, fens, and tundra sites, while marshes and swamps were relatively undersampled. Annual methane emissions were largest from marshes and lowest from upland mineral soils. Non-growing season emissions accounted for large fraction of annual methane emissions, especially in tundra sites. These results provide constraints for methane emissions from temporal, boreal, and arctic wetlands utilizing the numerous flux measurements conducted over the past 25 years. We find that state-of-the-art model ensembles are seasonally biased; in particular, the vast majority of models overestimate predictions of the growing season to annual wetland methane emission ratio across all biomes.

  17. The origin of lead in the organic horizon of tundra soils: atmospheric deposition, plant translocation from the mineral soil or soil mineral mixing?

    Science.gov (United States)

    Klaminder, Jonatan; Farmer, John G; MacKenzie, Angus B

    2011-09-15

    Knowledge of the anthropogenic contribution to lead (Pb) concentrations in surface soils in high latitude ecosystems is central to our understanding of the extent of atmospheric Pb contamination. In this study, we reconstructed fallout of Pb at a remote sub-arctic region by using two ombrotrophic peat cores and assessed the extent to which this airborne Pb is able to explain the isotopic composition ((206)Pb/(207)Pb ratio) in the O-horizon of tundra soils. In the peat cores, long-range atmospheric fallout appeared to be the main source of Pb as indicated by temporal trends that followed the known European pollution history, i.e. accelerated fallout at the onset of industrialization and peak fallout around the 1960s-70s. The Pb isotopic composition of the O-horizon of podzolic tundra soil ((206)Pb/(207)Pb=1.170 ± 0.002; mean ± SD) overlapped with that of the peat ((206)Pb/(207)Pb=1.16 ± 0.01) representing a proxy for atmospheric aerosols, but was clearly different from that of the parent soil material ((206)Pb/(207)Pb=1.22-1.30). This finding indicated that long-range fallout of atmospheric Pb is the main driver of Pb accumulation in podzolic tundra soil. In O-horizons of tundra soil weakly affected by cryoturbation (cryosols) however, the input of Pb from the underlying mineral soil increased as indicated by (206)Pb/(207)Pb ratios of up to 1.20, a value closer to that of local soil minerals. Nevertheless, atmospheric Pb appeared to be the dominant source in this soil compartment. We conclude that Pb concentrations in the O-horizon of studied tundra soils - despite being much lower than in boreal soils and representative for one of the least exposed sites to atmospheric Pb contaminants in Europe - are mainly controlled by atmospheric inputs from distant anthropogenic sources. Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic.

    Science.gov (United States)

    Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

    2015-01-01

    Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere.

  19. Energy fluxes in a high Arctic tundra heath subjected to strong climate warming

    Science.gov (United States)

    Lund, M.; Hansen, B. U.; Pedersen, S. H.; Stiegler, C.; Tamstorf, M. P.

    2012-12-01

    During recent decades the observed warming in the Arctic has been almost twice as large as the global average. The implications of such strong warming on surface energy balance, regulating permafrost thaw, hydrology, soil stability and carbon mineralization, need to be assessed. In Zackenberg, northeast Greenland, measurements of energy balance components in various environments have been performed since late 90's, coordinated by Zackenberg Ecological Research Operations. During 1996-2009, mean annual temperature in the area has increased by ca. 0.15 °C yr-1; while maximum thaw depth has increased by 1.4-1.8 cm yr-1. Eddy covariance measurements of energy fluxes have been performed in a Cassiope heath plant community, a commonly occurring tundra ecosystem type in circumpolar middle and high Arctic areas, in Zackenberg allowing for detailed investigations of relationships between energy fluxes and meteorological and soil physical characteristics. As the available data set spans more than a decade, possible trends in energy flux components resulting from warming related changes such as earlier snow melt, increased active layer depth and higher temperatures can be investigated. This presentation will focus on the mid-summer period from which eddy covariance measurements are available. The summer-time energy partitioning at the Zackenberg tundra heath site will be characterized using ratios of sensible, latent and ground heat flux to net radiation and Bowen ratio, whereas the surface characteristics will be described using surface resistance, McNaughton and Jarvis Ω value and Priestley-Taylor α coefficient. Furthermore, we aim to estimate the full year, all energy balance components for the tundra heath site using Snow Model (Liston and Elder 2006) for the dark winter period during which no eddy covariance measurements are available. The snow cover duration in the area is a major regulator of the energy partitioning. Early results point towards high summer

  20. Continental Mathematics League.

    Science.gov (United States)

    Quartararo, Joseph

    2002-01-01

    This article describes the activities of the Continental Mathematics League, which offers a series of meets for children in grades 3 though 9. In addition, a Calculus League and a Computer Contest are offered. The league allows schools to participate by mail so that rural schools can participate. (CR)

  1. The effect of vascular plants on carbon turnover and methane emissions from a tundra wetland

    DEFF Research Database (Denmark)

    Strom, L; Ekberg, A; Mastepanov, M

    2003-01-01

    This paper investigates how vascular plants affect carbon flow and the formation and emission of the greenhouse gas methane (CH4 ) in an arctic wet tundra ecosystem in NE Greenland. We present a field experiment where we studied, in particular, how species-specific root exudation patterns affect...... an intact peat-plant monolith system collected at the field site in NE Greenland to the laboratory, sealed it hermetically and studied the decomposition of (14) C-labelled acetate injected at the depth of methanogenic activity. After 4 h, (14) CH4 emission from the monolith could be observed. In conclusion......, allocation of recently fixed carbon to the roots of certain species of vascular plants affects substrate quality and influence CH4 formation....

  2. Carbon dioxide and methane dynamics in Russian tundra

    DEFF Research Database (Denmark)

    Johansson, Paul Torbjörn; Kiepe, Isabell; Herbst, Mathias

    Russia. The area is situated at 67°N in the European part of northeast Russia within the Pechora basin. The Russian tundra region is an area which has recently been subject to many speculations in relation to climatic change effects and greenhouse gas (GHG) exchange but still little scientific......, and discuss possible implications of climatic change on this lowland tundra ecosystem. This study have been conducted as a part of the CARBO-North project (2006-2010), a project within the EU 6th framework programme, aiming at quantifying the carbon budget in Northern Russia across temporal and spatial scales....... evidence is available from this region. At present, there are fundamental questions to answer about the CH4 concentration in the atmosphere and its oscillations and what role CH4 exchange may have under future climatic conditions, To do so, we need to better understand the ecosystem- atmosphere...

  3. Measurements and modelling of snowmelt and turbulent heat fluxes over shrub tundra

    Directory of Open Access Journals (Sweden)

    D. Bewley

    2010-07-01

    Full Text Available Measurements of snowmelt and turbulent heat fluxes were made during the snowmelt periods of two years at two neighbouring tundra sites in the Yukon, one in a sheltered location with tall shrubs exposed above deep snow and the other in an exposed location with dwarf shrubs covered by shallow snow. The snow was about twice as deep in the valley as on the plateau at the end of each winter and melted out about 10 days later. The site with buried vegetation showed a transition from air-to-surface heat transfers to surface-to-air heat transfers as bare ground became exposed during snowmelt, but there were daytime transfers of heat from the surface to the air at the site with exposed vegetation even while snow remained on the ground. A model calculating separate energy balances for snow and exposed vegetation, driven with meteorological data from the sites, is found to be able to reproduce these behaviours. Averaged over 30-day periods the model gives about 8 Wm−2 more sensible heat flux to the atmosphere for the valley site than for the plateau site. Sensitivity of simulated fluxes to model parameters describing vegetation cover and density is investigated.

  4. Outer Continental Shelf Lands Act

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data represents geographic terms used within the Outer Continental Shelf Lands Act (OCSLA or Act). The Act defines the United States outer continental shelf...

  5. Carbon-degrading enzyme activities stimulated by increased nutrient availability in Arctic tundra soils.

    Directory of Open Access Journals (Sweden)

    Akihiro Koyama

    Full Text Available Climate-induced warming of the Arctic tundra is expected to increase nutrient availability to soil microbes, which in turn may accelerate soil organic matter (SOM decomposition. We increased nutrient availability via fertilization to investigate the microbial response via soil enzyme activities. Specifically, we measured potential activities of seven enzymes at four temperatures in three soil profiles (organic, organic/mineral interface, and mineral from untreated native soils and from soils which had been fertilized with nitrogen (N and phosphorus (P since 1989 (23 years and 2006 (six years. Fertilized plots within the 1989 site received annual additions of 10 g N · m(-2 · year(-1 and 5 g P · m(-2 · year(-1. Within the 2006 site, two fertilizer regimes were established--one in which plots received 5 g N · m(-2 · year(-1 and 2.5 g P · m(-2 · year(-1 and one in which plots received 10 g N · m(-2 · year(-1 and 5 g P · m(-2 · year(-1. The fertilization treatments increased activities of enzymes hydrolyzing carbon (C-rich compounds but decreased phosphatase activities, especially in the organic soils. Activities of two enzymes that degrade N-rich compounds were not affected by the fertilization treatments. The fertilization treatments increased ratios of enzyme activities degrading C-rich compounds to those for N-rich compounds or phosphate, which could lead to changes in SOM chemistry over the long term and to losses of soil C. Accelerated SOM decomposition caused by increased nutrient availability could significantly offset predicted increased C fixation via stimulated net primary productivity in Arctic tundra ecosystems.

  6. Isotopic insights into methane production, oxidation, and emissions in Arctic polygon tundra.

    Science.gov (United States)

    Vaughn, Lydia J S; Conrad, Mark E; Bill, Markus; Torn, Margaret S

    2016-10-01

    Arctic wetlands are currently net sources of atmospheric CH4 . Due to their complex biogeochemical controls and high spatial and temporal variability, current net CH4 emissions and gross CH4 processes have been difficult to quantify, and their predicted responses to climate change remain uncertain. We investigated CH4 production, oxidation, and surface emissions in Arctic polygon tundra, across a wet-to-dry permafrost degradation gradient from low-centered (intact) to flat- and high-centered (degraded) polygons. From 3 microtopographic positions (polygon centers, rims, and troughs) along the permafrost degradation gradient, we measured surface CH4 and CO2 fluxes, concentrations and stable isotope compositions of CH4 and DIC at three depths in the soil, and soil moisture and temperature. More degraded sites had lower CH4 emissions, a different primary methanogenic pathway, and greater CH4 oxidation than did intact permafrost sites, to a greater degree than soil moisture or temperature could explain. Surface CH4 flux decreased from 64 nmol m(-2)  s(-1) in intact polygons to 7 nmol m(-2)  s(-1) in degraded polygons, and stable isotope signatures of CH4 and DIC showed that acetate cleavage dominated CH4 production in low-centered polygons, while CO2 reduction was the primary pathway in degraded polygons. We see evidence that differences in water flow and vegetation between intact and degraded polygons contributed to these observations. In contrast to many previous studies, these findings document a mechanism whereby permafrost degradation can lead to local decreases in tundra CH4 emissions. © 2016 John Wiley & Sons Ltd.

  7. Temporal changes in soil bacterial diversity and humic substances degradation in subarctic tundra soil.

    Science.gov (United States)

    Park, Ha Ju; Chae, Namyi; Sul, Woo Jun; Lee, Bang Yong; Lee, Yoo Kyung; Kim, Dockyu

    2015-04-01

    Humic substances (HS), primarily humic acids (HA) and fulvic acids (FA), are the largest constituent of soil organic matter. In microcosm systems with subarctic HS-rich tundra soil (site AK 1-75; approximately 5.6 °C during the thawing period) from Council, Alaska, the HA content significantly decreased to 48% after a 99-day incubation at 5 °C as part of a biologically mediated process. Accordingly, levels of FA, a putative byproduct of HA degradation, consistently increased to 172% during an identical incubation process. Culture-independent microbial community analysis showed that during the microcosm experiments, the relative abundance of phyla Proteobacteria (bacteria) and Euryarchaeota (archaea) largely increased, indicating their involvement in HS degradation. When the indigenous bacteria in AK 1-75 were enriched in an artificial mineral medium spiked with HA, the changes in relative abundance were most conspicuous in Proteobacteria (from 60.2 to 79.0%), specifically Betaproteobacteria-related bacteria. One hundred twenty-two HA-degrading bacterial strains, primarily from the genera Paenibacillus (phylum Firmicutes) and Pseudomonas (class Gammaproteobacteria), were cultivated from AK 1-75 and nearby sites. Through culture-dependent analysis with these bacterial isolates, we observed increasing HS-degradation rates in parallel with rising temperatures in a range of 0 °C to 20 °C, with the most notable increase occurring at 8 °C compared to 6 °C. Our results indicate that, although microbial-mediated HS degradation occurs at temperature as low as 5 °C in tundra ecosystems, increasing soil temperature caused by global climate change could enhance HS degradation rates. Extending the thawing period could also increase degradation activity, thereby directly affecting nearby microbial communities and rhizosphere environments.

  8. Breeding habitat associations and predicted distribution of an obligate tundra-breeding bird, Smith's Longspur

    Science.gov (United States)

    Wild, Teri C.; Kendall, Steven J.; Guldager, Nikki; Powell, Abby N.

    2015-01-01

    Smith's Longspur (Calcarius pictus) is a species of conservation concern which breeds in Arctic habitats that are expected to be especially vulnerable to climate change. We used bird presence and habitat data from point-transect surveys conducted at 12 sites across the Brooks Range, Alaska, 2003–2009, to identify breeding areas, describe local habitat associations, and identify suitable habitat using a predictive model of Smith's Longspur distribution. Smith's Longspurs were observed at seven sites, where they were associated with a variety of sedge–shrub habitats composed primarily of mosses, sedges, tussocks, and dwarf shrubs; erect shrubs were common but sparse. Nonmetric multidimensional scaling ordination of ground cover revealed positive associations of Smith's Longspur presence with sedges and mosses and a negative association with high cover of shrubs. To model predicted distribution, we used boosted regression trees to relate landscape variables to occurrence. Our model predicted that Smith's Longspurs may occur in valleys and foothills of the northeastern and southeastern mountains and in upland plateaus of the western mountains, and farther west than currently documented, over a predicted area no larger than 15% of the Brooks Range. With climate change, shrubs are expected to grow larger and denser, while soil moisture and moss cover are predicted to decrease. These changes may reduce Smith's Longspur habitat quality and limit distribution in the Brooks Range to poorly drained lowlands and alpine plateaus where sedge–shrub tundra is likely to persist. Conversely, northward advance of shrubs into sedge tundra may create suitable habitat, thus supporting a northward longspur distribution shift.

  9. Microbial iron oxidation in the Arctic tundra and its implications for biogeochemical cycling.

    Science.gov (United States)

    Emerson, David; Scott, Jarrod J; Benes, Joshua; Bowden, William B

    2015-12-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long -149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  10. Stratospheric ozone depletion: high arctic tundra plant species from Svalbard are not affected by enhanced UV-B after 7 years of UV-B supplementation in the field.

    NARCIS (Netherlands)

    Rozema, J.; Boelen, P.; Blokker, P.; Callaghan, T.V.; Solheim, B.; Zielke, M.

    2006-01-01

    The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78° N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996

  11. Stratospheric ozone depletion: high arctic tundra plant growth on Svalbard is not affected by enhanced UV-B after 7 years of UV-B supplementation in the field.

    NARCIS (Netherlands)

    Rozema, J.; Boelen, P.; Solheim, B.; Zielke, M.; Buskens, A.; Doorenbosch, M.; Fijn, R.; Herder, J.; Callaghan, T.V.; Bjorn, L.O.; Gwynn-Jones, D.; Broekman, R.A.; Blokker, P.; van de Poll, W.

    2006-01-01

    The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78° N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed in 1996

  12. Stratospheric ozone depletion : High arctic tundra plant growth on Svalbard is not affected by enhanced UV-B after 7 years of UV-B supplementation in the field

    NARCIS (Netherlands)

    Rozema, Jelte; Boelen, P.; Solheim, B.; Zielke, M.; Buskens, A; Doorenbosch, M.; Fijn, R.; Herder, J.; Callaghan, T.; Bjoern, L.O.; Jones, D.G.; Broekman, R.; Blokker, P.; van de Poll, W.H.

    The response of tundra plants to enhanced UV-B radiation simulating 15 and 30% ozone depletion was studied at two high arctic sites (Isdammen and Adventdalen, 78 degrees N, Svalbard).The set-up of the UV-B supplementation systems is described, consisting of large and small UV lamp arrays, installed

  13. How to preserve the tundra in a warming climate?

    Science.gov (United States)

    Käyhkö, Jukka

    2014-05-01

    The warming climate of the polar regions may change much of the current arctic-alpine tundra to forest or dense scrubland. This modification requires adaptation by traditional livelihoods such as reindeer herding, which relies on diverse, seasonal pasturelands. Vegetation change may also trigger positive warming feedbacks, where more abundant forest-scrub vegetation will decrease the global albedo. NCoE Tundra team investigates the complex climate-animal-plant interaction of the tundra ecosystem and aim to unravel the capability of herbivorous mammals to control the expansion of woody vegetation. Our interdisciplinary approach involves several work packages, whose results will be summarised in the presentation. In the ecological WPs, we study the dynamics of the natural food chains involving small herbivorous and the impacts of reindeer on the vegetation and the population dynamics of those arctic-alpine plants, which are most likely to become threatened in a warmer climate. Our study demonstrates the potential of a relatively sparse reindeer stocks (2-5 heads per km2) together with natural populations of arvicoline rodents to prevent the expansion of erect woody plants at the arctic-alpine timberline. In the climatic WPs we study the impact of grazing-dependent vegetation differences on the fraction of solar energy converted to heat. In the socio-economic WPs, we study the conditions for maintaining the economic and cultural viability of reindeer herding while managing the land use so that the arctic-alpine biota would be preserved.

  14. Regional comparison of tundra carbon budget response over the Alaska North Slope to varying environmental conditions as informed by in situ and flux tower measurements, remote sensing and biophysical modeling

    Science.gov (United States)

    Shirley, S.; Watts, J. D.; Kimball, J. S.; Zhang, Z.; Poulter, B.; Klene, A. E.; Jones, L. A.; Kim, Y.; Oechel, W. C.; Zona, D.; Euskirchen, E. S.

    2017-12-01

    A warming Arctic climate is contributing to shifts in landscape moisture and temperature regimes, a shortening of the non-frozen season, and increases in the depth of annual active layer. The changing environmental conditions make it difficult to determine whether tundra ecosystems are a carbon sink or source. At present, eddy covariance flux towers and biophysical measurements within the tower footprint provide the most direct assessment of change to the tundra carbon balance. However, these measurements have a limited spatial footprint and exist over relatively short timescales. Thus, terrestrial ecosystem models are needed to provide an improved understanding of how changes in landscape environmental conditions impact regional carbon fluxes. This study examines the primary drivers thought to affect the magnitude and variability of tundra-atmosphere CO2 and CH4 fluxes over the Alaska North Slope. Also investigated is the ability of biophysical models to capture seasonal flux characteristics over the 9 tundra tower sites examined. First, we apply a regression tree approach to ascertain which remotely sensed environmental variables best explain observed variability in the tower fluxes. Next, we compare flux estimates obtained from multiple process models including Terrestrial Carbon Flux (TCF) and the Lund-Potsdam-Jena Wald Schnee und Landschaft (LPJ-wsl), and Soil Moisture Active Passive Level 4 Carbon (SMAP L4_C) products. Our results indicate that out of 7 variables examined vegetation greenness, temperature, and moisture are more significant predictors of carbon flux magnitude over the tundra tower sites. This study found that satellite data-driven models, due to the ability of remote sensing instruments to capture the physical principles and processes driving tundra carbon flux, are more effective at estimating the magnitude and spatiotemporal variability of CO2 and CH4 fluxes in northern high latitude ecosystems.

  15. Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra.

    Science.gov (United States)

    Christiansen, Casper T; Haugwitz, Merian S; Priemé, Anders; Nielsen, Cecilie S; Elberling, Bo; Michelsen, Anders; Grogan, Paul; Blok, Daan

    2017-01-01

    Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface-incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open-top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1 year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected to increase with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by

  16. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

    Directory of Open Access Journals (Sweden)

    N. Pirk

    2017-06-01

    Full Text Available The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV that mapped ice-wedge morphology to complement eddy covariance (EC flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency flux contributions were especially pronounced during snowmelt and introduced a large bias of −46 gC m−2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem. Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (−82 gC m−2. Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

  17. Spatial variability of CO2 uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

    Science.gov (United States)

    Pirk, Norbert; Sievers, Jakob; Mertes, Jordan; Parmentier, Frans-Jan W.; Mastepanov, Mikhail; Christensen, Torben R.

    2017-06-01

    The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gC m-2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (-82 gC m-2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

  18. Detection of tundra trail damage near Barrow, Alaska using remote imagery

    Science.gov (United States)

    Hinkel, K. M.; Eisner, W. R.; Kim, C. J.

    2017-09-01

    In the past several decades, the use of all-terrain vehicles (ATVs) has proliferated in many Arctic communities in North America. One example is the village of Barrow, Alaska. This coastal community has only local roads, so all access to the interior utilizes off-road machines. These 4-wheel vehicles are the primary means of tundra traverse and transport in summer by hunters and berry-pickers, and by village residents accessing summer camps. Traveling cross-country is difficult due to the large number of thermokarst lakes, wetlands, and streams, and tundra trails tend to follow dryer higher ground while avoiding areas of high microrelief such as high-centered ice-wedge polygons. Thus, modern ATV trails tend to follow the margins of drained or partially drained thermokarst lake basins where it is flat and relatively dry, and these trails are heavily used. The deeply-ribbed tires of the heavy and powerful ATVs cause damage by destroying the vegetation and disturbing the underlying organic soil. Exposure of the dark soil enhances summer thaw and leads to local thermokarst of the ice-rich upper permafrost. The damage increases over time as vehicles continue to follow the same track, and sections eventually become unusable; this is especially true where the trail crosses ice-wedge troughs. Deep subsidence in the ponded troughs results in ATV users veering to avoid the wettest area, which leads to a widening of the damaged area. Helicopter surveys, site visits, and collection of ground penetrating radar data were combined with time series analysis of high-resolution aerial and satellite imagery for the period 1955-2014. The analysis reveals that there are 507 km of off-road trails on the Barrow Peninsula. About 50% of the total trail length was developed before 1955 in association with resource extraction, and an additional 40% were formed between 1979 and 2005 by ATVs. Segments of the more modern trail are up to 100 m wide. Damage to the tundra is especially pronounced

  19. Linking flux network measurements to continental scale simulations: ecosystem carbon dioxide exchange capacity under non-water-stressed conditions

    NARCIS (Netherlands)

    Owen, K.E.; Tenhunen, J.; Reichstein, M.; Wang, Q.; Falge, E.; Geyer, R.; Xiao, X.; Stoy, P.; Ammann, C.; Arain, A.; Aubinet, M.; Aurela, M.; Bernhofer, C.; Chojnicki, B.H.; Granier, A.; Gruenwald, T.; Hadley, J.; Heinesch, B.; Hollinger, D.; Knohl, A.; Kutsch, W.; Lohila, A.; Meyers, T.; Moors, E.J.; Moureaux, C.; Pilegaard, K.; Saigusa, N.; Verma, S.; Vesala, T.; Vogel, C.

    2007-01-01

    This paper examines long-term eddy covariance data from 18 European and 17 North American and Asian forest, wetland, tundra, grassland, and cropland sites under non-water-stressed conditions with an empirical rectangular hyperbolic light response model and a single layer two light-class

  20. Alaska North Slope Tundra Travel Model and Validation Study

    Energy Technology Data Exchange (ETDEWEB)

    Harry R. Bader; Jacynthe Guimond

    2006-03-01

    The Alaska Department of Natural Resources (DNR), Division of Mining, Land, and Water manages cross-country travel, typically associated with hydrocarbon exploration and development, on Alaska's arctic North Slope. This project is intended to provide natural resource managers with objective, quantitative data to assist decision making regarding opening of the tundra to cross-country travel. DNR designed standardized, controlled field trials, with baseline data, to investigate the relationships present between winter exploration vehicle treatments and the independent variables of ground hardness, snow depth, and snow slab thickness, as they relate to the dependent variables of active layer depth, soil moisture, and photosynthetically active radiation (a proxy for plant disturbance). Changes in the dependent variables were used as indicators of tundra disturbance. Two main tundra community types were studied: Coastal Plain (wet graminoid/moist sedge shrub) and Foothills (tussock). DNR constructed four models to address physical soil properties: two models for each main community type, one predicting change in depth of active layer and a second predicting change in soil moisture. DNR also investigated the limited potential management utility in using soil temperature, the amount of photosynthetically active radiation (PAR) absorbed by plants, and changes in microphotography as tools for the identification of disturbance in the field. DNR operated under the assumption that changes in the abiotic factors of active layer depth and soil moisture drive alteration in tundra vegetation structure and composition. Statistically significant differences in depth of active layer, soil moisture at a 15 cm depth, soil temperature at a 15 cm depth, and the absorption of photosynthetically active radiation were found among treatment cells and among treatment types. The models were unable to thoroughly investigate the interacting role between snow depth and disturbance due to a

  1. The Myanmar continental shelf

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Rao, P.S.

    the International Indian Ocean Expedition (IIOE) of the 1960’s and a more recent expedition of the Indian research Vessel ORV Sagar Kanya in 2002. The IIOE results from the Andaman Sea have been summarized by Rodolfo (1969a, 1969b) while the ORV Sagar Kanya... on the Ayeyarwady Delta also occurs during exceptional rain events. Bank overflow and Myanmar Continental Shelf 7 flooding have been controlled by construction of numerous embankments which aid freshwater and sediment discharge to the sea...

  2. Tundra fire disturbance homogonizes belowground food web structure, function and dynamics

    Science.gov (United States)

    Moore, J. C.; Pressler, Y.; Koltz, A.; Asmus, A.; Simpson, R.

    2016-12-01

    Tundra fires on Alaska's North Slope are on the rise due to increased lightning strikes since 2000. On July 16, 2007 lightning ignited the Anaktuvuk River fire, burning a 40-by-10 mile swath of tundra about 24 miles north of Toolik Field Station. The fire burned 401 square miles, was visible from space, and released more than 2.3 million tons of carbon into the atmosphere. A large amount of the organic layer of the soil was burned, changing the over all composition of the site and exposing deeper soil horizons. Due to fundamental transitions in soil characteristics and vegetation we hypothesized that the belowground food web community would be affected both in terms of biomass and location within the soil profile. Microbial biomass was reduced with burn severity. In the lower organic horizon there was a significant reduction in fungal biomass but we did not observe this effect in the upper organic soil. We did not observe a significant effect of burn severity on individual group biomass within higher trophic levels. Canonical Discriminant Analysis using the biomass estimates of the functional groups in the food webs found that the webs are becoming increasingly homogenized in the severely burned site compared to the moderately burned and unburned sites. The unburned soils differed significantly from soil at both burn sites; the greatest effects on food web structure were at the lower organic depth, whereas. We modeled the effects of the fire on soil organic matter processing rates and energy flow through the three food webs. The model estimated a decrease in C and N mineralization with fire severity, due in large part to the loss of organic material. While the organic horizon at the unburned site had 12 times greater C and N mineralization than the mineral soils, we observed little to no difference in C and N mineralization between the organic and mineral soil horizons in the moderately and severely burned sites. Our results show that the fire significantly altered

  3. Trends in NDVI and tundra community composition in the Arctic of NE Alaska between 1984 and 2009

    Science.gov (United States)

    Robert R. Pattison; Janet C. Jorgenson; Martha K. Raynolds; Jeffery M. Welker

    2015-01-01

    As Arctic ecosystems experience increases in surface air temperatures, plot-level analyses of tundra vegetation composition suggest that there are important changes occurring in tundra communities that are typified by increases in shrubs and declines in non-vascular species. At the same time analyses of NDVI indicate that the Arctic tundra is greening. Few studies have...

  4. Dynamics of aboveground phytomass of the circumpolar Arctic tundra during the past three decades

    International Nuclear Information System (INIS)

    Epstein, Howard E; Raynolds, Martha K; Walker, Donald A; Bhatt, Uma S; Tucker, Compton J; Pinzon, Jorge E

    2012-01-01

    Numerous studies have evaluated the dynamics of Arctic tundra vegetation throughout the past few decades, using remotely sensed proxies of vegetation, such as the normalized difference vegetation index (NDVI). While extremely useful, these coarse-scale satellite-derived measurements give us minimal information with regard to how these changes are being expressed on the ground, in terms of tundra structure and function. In this analysis, we used a strong regression model between NDVI and aboveground tundra phytomass, developed from extensive field-harvested measurements of vegetation biomass, to estimate the biomass dynamics of the circumpolar Arctic tundra over the period of continuous satellite records (1982–2010). We found that the southernmost tundra subzones (C–E) dominate the increases in biomass, ranging from 20 to 26%, although there was a high degree of heterogeneity across regions, floristic provinces, and vegetation types. The estimated increase in carbon of the aboveground live vegetation of 0.40 Pg C over the past three decades is substantial, although quite small relative to anthropogenic C emissions. However, a 19.8% average increase in aboveground biomass has major implications for nearly all aspects of tundra ecosystems including hydrology, active layer depths, permafrost regimes, wildlife and human use of Arctic landscapes. While spatially extensive on-the-ground measurements of tundra biomass were conducted in the development of this analysis, validation is still impossible without more repeated, long-term monitoring of Arctic tundra biomass in the field. (letter)

  5. Dynamics of Aboveground Phytomass of the Circumpolar Arctic Tundra During the Past Three Decades

    Science.gov (United States)

    Epstein, Howard E.; Raynolds, Martha K.; Walker, Donald A.; Bhatt, Uma S.; Tucker, Compton J.; Pinzon, Jorge E.

    2012-01-01

    Numerous studies have evaluated the dynamics of Arctic tundra vegetation throughout the past few decades, using remotely sensed proxies of vegetation, such as the normalized difference vegetation index (NDVI). While extremely useful, these coarse-scale satellite-derived measurements give us minimal information with regard to how these changes are being expressed on the ground, in terms of tundra structure and function. In this analysis, we used a strong regression model between NDVI and aboveground tundra phytomass, developed from extensive field-harvested measurements of vegetation biomass, to estimate the biomass dynamics of the circumpolar Arctic tundra over the period of continuous satellite records (1982-2010). We found that the southernmost tundra subzones (C-E) dominate the increases in biomass, ranging from 20 to 26%, although there was a high degree of heterogeneity across regions, floristic provinces, and vegetation types. The estimated increase in carbon of the aboveground live vegetation of 0.40 Pg C over the past three decades is substantial, although quite small relative to anthropogenic C emissions. However, a 19.8% average increase in aboveground biomass has major implications for nearly all aspects of tundra ecosystems including hydrology, active layer depths, permafrost regimes, wildlife and human use of Arctic landscapes. While spatially extensive on-the-ground measurements of tundra biomass were conducted in the development of this analysis, validation is still impossible without more repeated, long-term monitoring of Arctic tundra biomass in the field.

  6. Increased plant productivity in Alaskan tundra as a result of experimental warming of soil and permafrost

    Science.gov (United States)

    S.M. Natali; E.A.G. Schuur; R.L. Rubin

    2012-01-01

    The response of northern tundra plant communities to warming temperatures is of critical concern because permafrost ecosystems play a key role in global carbon (C) storage, and climate-induced ecological shifts in the plant community will affect the transfer of carbon-dioxide between biological and atmospheric pools. This study, which focuses on the response of tundra...

  7. Plot-scale evidence of tundra vegetation change and links to recent summer warming

    Science.gov (United States)

    Sarah C. Elmendorf; Gregory H.R. Henry; Robert D. Hollister; Robert G. Bjork; Noemie Boulanger-Lapointe; Elisabeth J. Cooper; Johannes H.C. Cornelissen; Thomas A. Day; Ellen Dorrepaal; Tatiana G. Elumeeva; Mike Gill; William A. Gould; John Harte; David S. Hik; Annika Hofgaard; David R. Johnson; Jill F. Johnstone; Ingijorg Svala Jonsdottir; Janet C. Jorgenson; Kari Klanderud; Julia A. Klein; Saewan Koh; Gaku Kudo; Mark Lara; Esther Levesque; Borgthor Magnusson; Jeremy L. May; Joel A. Mercado; Anders Michelsen; Ulf Molau; Isla H. Myers-Smith; Steven F. Oberbauer; Vladimir G. Onipchenko; Christian Rixen; Niels Martin Schmidt; Gaius R. Shaver; Marko J. Spasojevic; Pora Ellen Porhallsdottir; Anne Tolvanen; Tiffany Troxler; Craig E. Tweedie; Sandra Villareal; Carl-Henrik Wahren; Xanthe Walker; Patrick J. Webber; Jeffrey M. Welker; Sonja Wipf

    2012-01-01

    Temperature is increasing at unprecedented rates across most of the tundra biome1. Remote-sensing data indicate that contemporary climate warming has already resulted in increased productivity over much of the Arctic2,3, but plot-based evidence for vegetation transformation is not widespread. We analysed change in tundra vegetation surveyed between 1980 and 2010 in 158...

  8. Fire behavior, weather, and burn severity of the 2007 Anaktuvuk River tundra fire, North Slope, Alaska

    Science.gov (United States)

    Benjamin M. Jones; Crystal A. Kolden; Randi Jandt; John T. Abatzoglu; Frank Urban; Christopher D. Arp

    2009-01-01

    In 2007, the Anaktuvuk River Fire (ARF) became the largest recorded tundra fire on the North Slope of Alaska. The ARF burned for nearly three months, consuming more than 100,000 ha. At its peak in early September, the ARF burned at a rate of 7000 ha d-1. The conditions potentially responsible for this large tundra fire include modeled record high...

  9. Permafrost collapse after shrub removal shifts tundra ecosystem into methane source

    NARCIS (Netherlands)

    Nauta, A.L.; Heijmans, M.M.P.D.; Blok, D.; Limpens, J.; Elberling, B.; Gallagher, A.; Li, B.; Petrov, R.E.; Maximov, T.C.; van Huissteden, J.; Berendse, F.

    2015-01-01

    Arctic tundra ecosystems are warming almost twice as fast as the global average. Permafrost thaw and the resulting release of greenhouse gases from decomposing soil organic carbon have the potential to accelerate climate warming. In recent decades, Arctic tundra ecosystems have changed rapidly,

  10. Permafrost collapse after shrub removal shifts tundra ecosystem to a methane source

    NARCIS (Netherlands)

    Nauta, A.L.; Heijmans, M.M.P.D.; Blok, D.; Limpens, J.; Elberling, B.; Gallagher, A.; Li, B.; Petrov, R.E.; Maximov, T.C.; Huissteden, van J.; Berendse, F.

    2015-01-01

    Arctic tundra ecosystems are warming almost twice as fast as the global average1. Permafrost thaw and the resulting release of greenhouse gases from decomposing soil organic carbon have the potential to accelerate climate warming2, 3. In recent decades, Arctic tundra ecosystems have changed

  11. Neogene sedimentation on the outer continental margin, southern Bering Sea

    Science.gov (United States)

    Vallier, T.L.; Underwood, M.B.; Gardner, J.V.; Barron, J.A.

    1980-01-01

    Neogene sedimentary rocks and sediments from sites on the outer continental margin in the southern Bering Sea and on the Alaska Peninsula are dominated by volcanic components that probably were eroded from an emergent Aleutian Ridge. A mainland continental source is subordinate. Most sediment in the marine environment was transported to the depositional sites by longshore currents, debris flows, and turbidity currents during times when sea level was near the outermost continental shelf. Fluctuations of sea level are ascribed both to worldwide glacio-eustatic effects and to regional vertical tectonics. Large drainage systems, such as the Yukon and Kuskokwim Rivers, had little direct influence on sedimentation along the continental slope and Unmak Plateau in the southern Bering Sea. Sediments from those drainage systems probably were transported to the floor of the Aleutian Basin, to the numerous shelf basins that underlie the outer continental shelf, and to the Arctic Ocean after passing through the Bering Strait. Environments of deposition at the sites along the outer continental margin have not changed significantly since the middle Miocene. The site on the Alaska Peninsula, however, is now emergent following shallow-marine and transitional sedimentation during the Neogene. ?? 1980.

  12. Where do the treeless tundra areas of northern highlands fit in the global biome system: toward an ecologically natural subdivision of the tundra biome

    OpenAIRE

    Virtanen, Risto; Oksanen, Lauri Kalervo; Oksanen, Tarja Maarit; Cohen, Juval; Forbes, Bruce C.; Johansen, Bernt; Käyhkö, Jukka; Olofsson, Johan; Pulliainen, Jouni; Tømmervik, Hans

    2015-01-01

    This is the published version of the article. Published source: http://doi.org/10.1002/ece3.1837. According to some treatises, arctic and alpine sub-biomes are ecologically similar, whereas others find them highly dissimilar. Most peculiarly, large areas of northern tundra highlands fall outside of the two recent subdivisions of the tundra biome. We seek an ecologically natural resolution to this long-standing and far-reaching problem. We studied broad-scale patterns in climate...

  13. The Role of Explicitly Modeling Bryophytes in Simulating Carbon Exchange and Permafrost Dynamics of an Arctic Coastal Tundra at Barrow, Alaska

    Science.gov (United States)

    Yuan, F.; Thornton, P. E.; McGuire, A. D.; Oechel, W. C.; Yang, B.; Tweedie, C. E.; Rogers, A.; Norby, R. J.

    2013-12-01

    Bryophyte cover is greater than 50% in many Arctic tundra ecosystems. In regions of the Arctic where shrubs are expanding it is expected that bryophyte cover will be substantially reduced. Such a loss in cover could influence the hydrological, biogeochemical, and permafrost dynamics of Arctic tundra ecosystems. The explicit representation of bryophyte physiological and biophysical processes in large-scale ecological and land surface models is rare, and we hypothesize that the representation of bryophytes has consequences for estimates of the exchange of water, energy, and carbon by these models. This study explicitly represents the effects of bryophyte function and structure on the exchange of carbon (e.g., summer photosynthesis effects) and energy (e.g., summer insulation effects) with the atmosphere in the Community Land Model (CLM-CN). The modified model was evaluated for its ability to simulate C exchange, soil temperature, and soil moisture since the 1970s at Barrow, Alaska through comparison with data from AmeriFlux sites, USDA Soil Climate Networks observation sites at Barrow, and other sources. We also compare the outputs of the CLM-CN simulations with those of the recently developed Dynamical Organic Soil coupled Terrestrial Ecosystem Model (DOS-TEM). Overall, our evaluation indicates that bryophytes are important contributors to land-atmospheric C exchanges in Arctic tundra and that they play an important role to permafrost thermal and hydrological processes which are critical to permafrost stability. Our next step in this study is to examine the climate system effects of explicitly representing bryophyte dynamics in the land surface model. Key Words: Bryophytes, Arctic coastal tundra, Vegetation composition, Net Ecosystem Exchange, Permafrost, Land Surface Model, Terrestrial Ecosystem Model

  14. Circulation of Dirofilaria repens, Setaria tundra, and Onchocercidae species in Hungary during the period 2011-2013.

    Science.gov (United States)

    Kemenesi, Gábor; Kurucz, Kornélia; Kepner, Anett; Dallos, Bianka; Oldal, Miklós; Herczeg, Róbert; Vajdovics, Péter; Bányai, Krisztián; Jakab, Ferenc

    2015-11-30

    Dirofilaria repens and recently Dirofilaria immitis are known to be endemic in Hungary. Since there is no related research on Dirofilaria carrier mosquito species from Hungary, we conducted a three-year mosquito surveillance study between 2011 and 2013. During the study period we examined 23,139 female mosquitoes with a generic filaria-specific TaqMan PCR assay, and characterized them by sequencing a 500 bp segment of 12S rRNA. An important result of our study was the detection of Setaria tundra and D. repens along with an unidentified Onchocercidae nematode. D. repens is known to be endemic in Hungary, however, the detection of S. tundra in all sampling sites throughout the study period indicates for the first time the endemicity of this parasite in Hungary. The Onchocercidae sp. nematode showed 95% nucleotide identity with previously detected unidentified nematodes from Germany, indicating a broader geographical distribution of this nematode in Europe. D. immitis specific DNA was not detected among the screened mosquitoes in this study. Here we report 11 mosquito species as potential vector organisms for local filarial infections, including Aedes vexans, Ochlerotatus annulipes, Ochlerotatus sticticus, Coquillettidia richiardii, Anopheles hyrcanus and Ochlerotatus rusticus. Dirofilaria development unit was calculated and the potential transmission period was estimated, which ranged between 65 and 113 days between sampling seasons. A relatively high infection rate (36.8%) was identified, which is a notable finding for veterinary and human health professionals. Moreover, the results of our study widen the group of possible mosquito vector species for D. repens and S. tundra in Central Europe. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. The continental waters pollution

    International Nuclear Information System (INIS)

    Marsily, G. de

    1996-01-01

    This work deals with the continental water pollution. The sewage affect considerably the quality of some rivers water and of some basins. Moreover, a slow and general damage of natural waters has been established. The direct effects on men and on the natural medium (climatic change, aquatic ecosystems, water cycle) are given as well as the protection means (waste processing, the water-bearing bed and underground water protection, the aquatic ecosystems protection and planning) used and future to abate the water pollution. (O.L.). 17 refs., 6 tabs

  16. Radiocarbon chronology of palsas in Bol'shezemel'skaya tundra

    International Nuclear Information System (INIS)

    Vasil'chuk, Yu.K.; Vasil'chuk, A.K.; Sulerzhitskij, L.D.; Budantseva, N.A.; Volkova, E.M.; Chizhova, Yu.N.

    2003-01-01

    The age of the peat, overlapping the swelling hillocks under different geocryologic conditions in the South and North of the Bol'shezemel'skaya tundra, located in the North-East of the European part of Russia, is determined through the method of the radiocarbon dating. The similarities and differences in the paleodynamics of the swelling hillocks at various average annual ground temperatures are identified on the basis of the obtained chronological data, covering the period from 8860 years ago up to the present time [ru

  17. Recent Declines in Warming and Vegetation Greening Trends over Pan-Arctic Tundra

    Directory of Open Access Journals (Sweden)

    Igor V. Polyakov

    2013-08-01

    Full Text Available Vegetation productivity trends for the Arctic tundra are updated for the 1982–2011 period and examined in the context of land surface temperatures and coastal sea ice. Understanding mechanistic links between vegetation and climate parameters contributes to model advancements that are necessary for improving climate projections. This study employs remote sensing data: Global Inventory Modeling and Mapping Studies (GIMMS Maximum Normalized Difference Vegetation Index (MaxNDVI, Special Sensor Microwave Imager (SSM/I sea-ice concentrations, and Advanced Very High Resolution Radiometer (AVHRR radiometric surface temperatures. Spring sea ice is declining everywhere except in the Bering Sea, while summer open water area is increasing throughout the Arctic. Summer Warmth Index (SWI—sum of degree months above freezing trends from 1982 to 2011 are positive around Beringia but are negative over Eurasia from the Barents to the Laptev Seas and in parts of northern Canada. Eastern North America continues to show increased summer warmth and a corresponding steady increase in MaxNDVI. Positive MaxNDVI trends from 1982 to 2011 are generally weaker compared to trends from 1982–2008. So to better understand the changing trends, break points in the time series were quantified using the Breakfit algorithm. The most notable break points identify declines in SWI since 2003 in Eurasia and 1998 in Western North America. The Time Integrated NDVI (TI-NDVI, sum of the biweekly growing season values of MaxNDVI has declined since 2005 in Eurasia, consistent with SWI declines. Summer (June–August sea level pressure (slp averages from 1999–2011 were compared to those from 1982–1998 to reveal higher slp over Greenland and the western Arctic and generally lower pressure over the continental Arctic in the recent period. This suggests that the large-scale circulation is likely a key contributor to the cooler temperatures over Eurasia through increased summer cloud

  18. Atmospheric residence times of continental aerosols

    International Nuclear Information System (INIS)

    Balkanski, Y.J.

    1991-01-01

    The global atmospheric distributions of Rn-222 are simulated with a three-dimensional model of atmospheric transport based on the meteorology of the NASA Goddard Institute for Space Studies (GISS) general circulation model. The short-lived radioactive gas Rn-222 (half-life = 3.8d) is emitted almost exclusively from land, at a relatively uniform rate; hence it is an excellent tracer of continental influences. Lead-210 is produced by decay of Rn-222 and immediately condenses to preexisting aerosol surfaces. It provides an excellent measure of aerosol residence times in the atmosphere because its source is accurately defined by the Rn-222 distribution. Results from the three-dimensional model are compared to measurements of Rn-222 and Pb-210 atmospheric concentrations to evaluate model's long-range transport over oceanic regions and to study the deposition mechanisms of atmospheric aerosols. Model results for Rn-222 are used to examine the long-range transport of continental air over two selected oceanic regions, the subantarctic Indian Ocean and the North Pacific. It is shown that the fast transport of air from southern Africa causes substantial continental pollution at southern mid-latitudes, a region usually regarded as pristine. Air over the North Pacific is heavily impacted by continental influences year round, but the altitude at which the transport occurs varies seasonally. Observations of aerosols at island sites, which are commonly used as diagnostics of continental influences, may be misleading because they do not account for influences at high altitude and because aerosols are efficiently scavenged by deposition during transport. The study of Pb-210 focuses on defining the residence times of submicron aerosols in the troposphere. Scavenging in wet convective updrafts is found to provide the dominant sink on a global scale

  19. MODIS Tree Cover Validation for the Circumpolar Taiga-Tundra Transition Zone

    Science.gov (United States)

    Montesano, P. M.; Nelson, R.; Sun, G.; Margolis, H.; Kerber, A.; Ranson, K. J.

    2009-01-01

    A validation of the 2005 500m MODIS vegetation continuous fields (VCF) tree cover product in the circumpolar taiga-tundra ecotone was performed using high resolution Quickbird imagery. Assessing the VCF's performance near the northern limits of the boreal forest can help quantify the accuracy of the product within this vegetation transition area. The circumpolar region was divided into longitudinal zones and validation sites were selected in areas of varying tree cover where Quickbird imagery is available in Google Earth. Each site was linked to the corresponding VCF pixel and overlaid with a regular dot grid within the VCF pixel's boundary to estimate percent tree crown cover in the area. Percent tree crown cover was estimated using Quickbird imagery for 396 sites throughout the circumpolar region and related to the VCF's estimates of canopy cover for 2000-2005. Regression results of VCF inter-annual comparisons (2000-2005) and VCF-Quickbird image-interpreted estimates indicate that: (1) Pixel-level, inter-annual comparisons of VCF estimates of percent canopy cover were linearly related (mean R(sup 2) = 0.77) and exhibited an average root mean square error (RMSE) of 10.1 % and an average root mean square difference (RMSD) of 7.3%. (2) A comparison of image-interpreted percent tree crown cover estimates based on dot counts on Quickbird color images by two different interpreters were more variable (R(sup 2) = 0.73, RMSE = 14.8%, RMSD = 18.7%) than VCF inter-annual comparisons. (3) Across the circumpolar boreal region, 2005 VCF-Quickbird comparisons were linearly related, with an R(sup 2) = 0.57, a RMSE = 13.4% and a RMSD = 21.3%, with a tendency to over-estimate areas of low percent tree cover and anomalous VCF results in Scandinavia. The relationship of the VCF estimates and ground reference indicate to potential users that the VCF's tree cover values for individual pixels, particularly those below 20% tree cover, may not be precise enough to monitor 500m pixel

  20. Permafrost degradation stimulates carbon loss from experimentally warmed tundra.

    Science.gov (United States)

    Natali, Susan M; Schuur, Edward A G; Webb, Elizabeth E; Pries, Caitlin E Hicks; Crummer, Kathryn G

    2014-03-01

    A large pool of organic carbon (C) has been accumulating in the Arctic for thousands of years because cold and waterlogged conditions have protected soil organic material from microbial decomposition. As the climate warms this vast and frozen C pool is at risk of being thawed, decomposed, and released to the atmosphere as greenhouse gasses. At the same time, some C losses may be offset by warming-mediated increases in plant productivity. Plant and microbial responses to warming ultimately determine net C exchange from ecosystems, but the timing and magnitude of these responses remain uncertain. Here we show that experimental warming and permafrost (ground that remains below 0 degrees C for two or more consecutive years) degradation led to a two-fold increase in net ecosystem C uptake during the growing season. However, warming also enhanced winter respiration, which entirely offset growing-season C gains. Winter C losses may be even higher in response to actual climate warming than to our experimental manipulations, and, in that scenario, could be expected to more than double overall net C losses from tundra to the atmosphere. Our results highlight the importance of winter processes in determining whether tundra acts as a C source or sink, and demonstrate the potential magnitude of C release from the permafrost zone that might be expected in a warmer climate.

  1. Tundra swan habitat preferences during migration in North Dakota

    Science.gov (United States)

    Earnst, Susan L.

    1994-01-01

    I studied tundra swan (Cygnus columbianus columbianus) habitat preference in North Dakota during autumn migration, 1988-89. Many thousand tundra swans stop in the Prairie Pothole region during autumn migration, but swan resource use has not been quantified. I examined habitat preference in relation to an index of sago pondweed (Potamogeton pectinatus) presence, extent of open water, and wetland size. I compared habitat preference derived from counts of all swans to those derived from foraging swans only and cygnets only. Foraging swans preferred wetlands with sago pondweed (P = 0.03); the number of foraging swans per wetland was >4 times higher on wetlands with sago pondweed than on wetlands without sago. In contrast, nonforaging swans did not prefer wetlands with sago pondweed (P = 0.85) but preferred large wetlands (P = 0.02) and those with a high proportion of contiguous open water (P feeding than adults (P = 0.03) and occurred proportionately more often in smaller flocks (P = 0.04), but cygnets and adults had similar habitat preferences.

  2. Multi-Decadal Surface Water Dynamics in North American Tundra

    Science.gov (United States)

    Carroll, Mark L.; Loboda, Tatiana V.

    2017-01-01

    Over the last several decades, warming in the Arctic has outpaced the already impressive increases in global mean temperatures. The impact of these increases in temperature has been observed in a multitude of ecological changes in North American tundra including changes in vegetative cover, depth of active layer, and surface water extent. The low topographic relief and continuous permafrost create an ideal environment for the formation of small water bodies - a definitive feature of tundra surface. In this study, water bodies in Nunavut territory in northern Canada were mapped using a long-term record of remotely sensed observations at 30 meters spatial resolution from the Landsat suite of instruments. The temporal trajectories of water extent between 1985 and 2015 were assessed. Over 675,000 water bodies have been identified over the 31-year study period with over 168,000 showing a significant (probability is less than 0.05) trend in surface area. Approximately 55 percent of water bodies with a significant trend were increasing in size while the remaining 45 percent were decreasing in size. The overall net trend for water bodies with a significant trend is 0.009 hectares per year per water body.

  3. How will Shrub Expansion Impact Soil Carbon Sequestration in Arctic Tundra?

    Science.gov (United States)

    Czimczik, C. I.; Holden, S. R.; He, Y.; Randerson, J. T.

    2015-12-01

    Multiple lines of evidence suggest that plant productivity, and especially shrub abundance, is increasing in the Arctic in response to climate change. This greening is substantiated by increases in the Normalized Difference Vegetation Index, repeat photography and field observations. The implications of a greener Arctic on carbon sequestration by tundra ecosystems remain poorly understood. Here, we explore existing datasets of plant productivity and soil carbon stocks to quantify how greening, and in particular an expansion of woody shrubs, may translate to the sequestration of carbon in arctic soils. As an estimate of carbon storage in arctic tundra soils, we used the Northern Circumpolar Soil Carbon Database v2. As estimates of tundra type and productivity, we used the Circumpolar Arctic Vegetation map as well as the MODIS and Landsat Vegetation Continuous Fields, and MODIS GPP/NPP (MOD17) products. Preliminary findings suggest that in graminoid tundra and erect-shrub tundra higher shrub abundance is associated with greater soil carbon stocks. However, this relationship between shrub abundance and soil carbon is not apparent in prostrate-shrub tundra, or when comparing across graminoid tundra, erect-shrub tundra and prostrate-shrub tundra. Uncertainties originate from the extreme spatial (vertical and horizontal) heterogeneity of organic matter distribution in cryoturbated soils, the fact that (some) permafrost carbon stocks, e.g. yedoma, reflect previous rather than current vegetative cover, and small sample sizes, esp. in the High Arctic. Using Vegetation Continuous Fields and MODIS GPP/NPP (MOD17), we develop quantitative trajectories of soil carbon storage as a function of shrub cover and plant productivity in the Arctic (>60°N). We then compare our greening-derived carbon sequestration estimates to projected losses of carbon from thawing permafrost. Our findings will reduce uncertainties in the magnitude and timing of the carbon-climate feedback from the

  4. Effects of thermo-erosional disturbance on surface soil carbon and nitrogen dynamics in upland arctic tundra

    International Nuclear Information System (INIS)

    Pizano, Camila; Barón, Andrés F; Schuur, Edward A G; Crummer, Kathryn G; Mack, Michelle C

    2014-01-01

    Thaw of ice-rich permafrost soils on sloping terrain can trigger erosional disturbance events that displace large volumes of soil and sediment, kill and damage plants, and initiate secondary succession. We examined how retrogressive thaw slumps (RTS), a common form of thermo-erosional disturbance in arctic tundra, affected the local loss and re-accumulation of carbon (C) and nitrogen (N) pools in organic and surface mineral soil horizons of 18 slumps within six spatially independent sites in arctic Alaska. RTS displaced 3 kg C and 0.2 kg N per m 2 from the soil organic horizon but did not alter pools of C and N in the top 15 cm of the mineral horizon. Surface soil C pools re-accumulated rapidly (32 ± 10 g C m −2 yr −1 ) through the first 60 years of succession, reaching levels similar to undisturbed tundra 40–64 years after disturbance. Average N re-accumulation rates (2.2 ± 1.1 g N m −2 yr −1 ) were much higher than expected from atmospheric deposition and biological N fixation. Finally, plant community dominance shifted from graminoids to tall deciduous shrubs, which are likely to promote higher primary productivity, biomass accumulation, and rates of nutrient cycling. (paper)

  5. First Record of Setaria Tundra in Danish Roe Deer (Capreolus Capreolus)

    DEFF Research Database (Denmark)

    Enemark, Heidi L.; Harslund, Jakob le Fèvre; Oksanen, A.

    2011-01-01

    , and may be connected to the spreading of this parasite. In reindeer heavy worm burdens of S. tundra have been found to cause severe peritonitis and negatively affect body condition score. Thus in the light of the possible climatic changes which could result in warmer, more humid weather in Scandinavia...... described by Rejewsky (1929) and Nikander et al. (2007). Sequences of the mitochondrial 12S rRNA and cox1 genes, 454 and 595 base pairs respectively, were 99.5-99.7% identical to previously published S. tundra isolates from France and Italy. Roe deer are thought to be asymptomatic carriers of S. tundra...

  6. CHARACTERISTICS OF EVAPORATION FROM SNOW AND TUNDRA SURFACE IN SPITSBERGEN IN THE SNOWMELT SEASON 1993

    OpenAIRE

    タケウチ, ユカリ; コダマ, ユウジ; ナカバヤシ, ヒロノリ; Yukari, TAKEUCHI; Yuji, KODAMA; Hironori, NAKABAYASHI

    1995-01-01

    Meteorological conditions and evaporation from snow and tundra surfaces were measured in the tundra area in Spitsbergen from the end of May to the end of June in 1993. In this period, three types of ground surface were seen, i.e. dry snow, melting snow and snow-free tundra. Clear changes in evaporation as well as the meteorological conditions were seen with the changes in surface condition. During the dry snow period, evaporation predominated at the snow surface and the latent heat loss by ev...

  7. Consequences of artic ground squirrels on soil carbon loss from Siberian tundra

    Science.gov (United States)

    Golden, N. A.; Natali, S.; Zimov, N.

    2014-12-01

    A large pool of organic carbon (C) has been accumulating in the Arctic for thousands of years. Much of this C has been frozen in permafrost and unavailable for microbial decomposition. As the climate warms and permafrost thaws, the fate of this large C pool will be driven not only by climatic conditions, but also by ecosystem changes brought about by arctic animal populations. In this project we studied arctic ground squirrels (Spermophilus parryii), which are widely-distributed throughout the Arctic. These social mammals create subterranean burrows that mix soil layers, increase aeration, alter soil moisture and temperature, and redistribute soil nutrients, all of which may impact microbial decomposition. We examined the effects of arctic ground squirrel activity on soil C mineralization in dry heath tundra underlain by continuous permafrost in the Kolyma River watershed in northeast Siberia, Russia. Vegetation cover was greatly reduced on the ground squirrel burrows (80% of ground un-vegetated), compared to undisturbed sites (35% of ground un-vegetated). Soils from ground squirrel burrows were also significantly dryer and warmer. To examine effects of ground squirrel activity on microbial respiration, we conducted an 8-day incubation of soil fromburrows and from adjacent undisturbed tundra. In addition, we assessed the impact of nutrient addition by including treatments with low and high levels of nitrogen addition. Microbial respiration (per gram soil) was three-fold higher in incubated soils from the undisturbed sites compared to soils collected from the burrows. The lower rates of respiration from the disturbed soils may have been a result of lower carbon quality or low soil moisture. High nitrogen addition significantly increased respiration in the undisturbed soils, but not in the disturbed burrow soils, which suggests that microbial respiration in the burrow soils was not primarily limited by nitrogen. These results demonstrate the importance of wildlife

  8. Climate Variations and Alaska Tundra Vegetation Productivity Declines in Spring

    Science.gov (United States)

    Bhatt, U. S.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2015-12-01

    While sea ice has continued to decline, vegetation productivity increases have declined particularly during spring in Alaska as well as many parts of the Arctic tundra. To understand the processes behind these features we investigate spring climate variations that includes temperature, circulation patterns, and snow cover to determine how these may be contributing to spring browning. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2014. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), atmospheric reanalysis data, dynamically downscaled climate data, meteorological station data, and snow water equivalent (GlobSnow, assimilated snow data set). We analyzed the data for the full period (1982-2014) and for two sub-periods (1982-1998 and 1999-2014), which were chosen based on the declining Alaska SWI since 1998. MaxNDVI has increased from 1982-2014 over most of the Arctic but has declined from 1999 to 2014 southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but display widespread declines over the 1999-2014 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999 and these declines are particularly noteworthy during spring in Alaska. Spring declines in Alaska have been linked to increased spring snow cover that can delay greenup (Bieniek et al. 2015) but recent ground observations suggest that after an initial warming and greening, late season freezing temperature are damaging the plants. The late season freezing temperature hypothesis will be explored with meteorological climate/weather data sets for Alaska tundra regions. References P.A. Bieniek, US Bhatt, DA Walker, MK Raynolds, JC Comiso, HE Epstein, JE Pinzon, CJ Tucker, RL Thoman, H Tran, N M

  9. Dynamics of the recovery of damaged tundra vegetation. Annual progress report

    International Nuclear Information System (INIS)

    Amundsen, C.C.

    1975-01-01

    A study, begun in 1971, has been undertaken to determine the environmental factors which affect the recovery of damaged tundra vegetation. A sampling technique was developed on Amchitka Island to allow the rapid acquisition of data on species presence and frequency across areas disturbed at various times and in various ways. Attempts were made to sample across all examples of aspect, slope steepness and exposure. The data were analyzed and we concluded that there was no directional secondary succession on the Amchitka tundra, although there was vigorous recovery on organic soils. The study led to recommendations which resulted in a smaller effort than planned to reclaim damaged areas by seeding and fertilizing at a considerable financial saving and without further biological perturbation. Because of the increasing activity on tundra landscape, whether for energy production, or military or other reasons, we are expanding our sampling to other tundra areas. Immediate plans include sampling at Adak Island and Barrow, Alaska. (U.S.)

  10. Transformation of nitrogen compounds in the tundra soils of Northern Fennoscandia

    Science.gov (United States)

    Maslov, M. N.; Makarov, M. I.

    2016-07-01

    The transformation of organic nitrogen compounds in the soils of tundra ecosystems of Northern Fennoscandia has been studied under laboratory and natural conditions. Tundra soils contain significant reserves of total nitrogen, but they are poor in its extractable mineral and organic forms. The potential rates of the net mineralization and net immobilization of nitrogen by microorganisms vary among the soils and depend on the C: N ratio in the extractable organic matter and microbial biomass of soil. Under natural conditions, the rate of nitrogen net mineralization is lower than the potential rate determined under laboratory conditions by 6-25 times. The incubation of tundra soils in the presence of plants does not result in the accumulation of mineral nitrogen compounds either in the soil or in microbial biomass. This confirms the high competitive capacity of plants under conditions of limited nitrogen availability in tundra ecosystems.

  11. Dynamics of the recovery of damaged tundra vegetation. Annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Amundsen, C.C.

    1976-01-01

    A study, begun in 1971, continues to document the environmental factors which affect the recovery of damaged tundra landscapes. A measurement technique was developed on Amchitka Island to allow the rapid acquisition of data on species presence and frequency across areas disturbed at various times and in various ways. Samples across all examples of aspect, slope steepness and exposure are taken. Studies now include Adak Island and the Point Barrow area. We have concluded that there was no directional secondary succession on the Aleutian tundra, although there was vigorous recovery on organic soils. Our study led to recommendations which resulted in less intensive reclamation management at a considerable financial saving and without further biological perturbation. Because of the increasing activity on tundra landscapes, for energy extraction, transportation or production, military or other reasons, we have expanded our sampling to other tundra areas where landscape disruption is occurring or is predicted.

  12. On Sr90 migration in the soil and vegetation cover of the subarctic tundra

    International Nuclear Information System (INIS)

    Kulikov, N.V.; Molchanova, I.V.; Puskinov, L.I.

    1975-01-01

    Data are presented on the migration and distribution of strontium-90 in the soil and plants of two subarctic tundra biogeocoenoses when the radionuclide is applied artificially to the soil surface. (V.A.P.)

  13. ABoVE: Surface Water Extent, Boreal and Tundra Regions, North America, 1991-2011

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides the location and extent of surface water (open water not including vegetated wetlands) for the entire Boreal and Tundra regions of North...

  14. Tree Canopy Cover for the Circumpolar Taiga-Tundra Ecotone: 2000-2005

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides a map of selected areas with defined tree canopy cover over the circumpolar taiga-tundra ecotone (TTE). Canopy cover was derived from the...

  15. Pre-ABoVE: Arctic Vegetation Plots, IBP Tundra Biome, Barrow, Alaska, 1972-2010

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides vegetation cover and environmental plot data collected as part of the International Biological Program (IBP), U. S. Tundra Biome Program, in...

  16. Pre-ABoVE: Arctic Vegetation Plots, Burned and Unburned Tundra, Alaska, 2011-2012

    Data.gov (United States)

    National Aeronautics and Space Administration — This dataset provides environmental and vegetation data collected in late June and July of 2011 and of 2012 from study plots located in tundra fire scars and...

  17. Tree Canopy Cover for the Circumpolar Taiga-Tundra Ecotone: 2000-2005

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides a map of selected areas with defined tree canopy cover over the circumpolar taiga-tundra ecotone (TTE). Canopy cover was derived...

  18. Landscape topography structures the soil microbiome in arctic polygonal tundra

    Energy Technology Data Exchange (ETDEWEB)

    Taş, Neslihan; Prestat, Emmanuel; Wang, Shi; Wu, Yuxin; Ulrich, Craig; Kneafsey, Timothy; Tringe, Susannah G.; Torn, Margaret S.; Hubbard, Susan S.; Jansson, Janet K.

    2018-02-22

    Global temperature increases are resulting in thaw of permafrost soil in the arctic with increased emission of greenhouse gases (GHGs). Soil microorganisms are responsible for degradation of the trapped organic carbon (C) in permafrost and emission of GHG as it thaws. However, environmental factors governing microbial degradation of soil C and GHG emissions are poorly understood. Here we determined the functional potential of soil microbiomes in arctic tundra across a cryoperturbed polygonal landscape in Barrow, Alaska. Using a combination of metagenome sequencing and gas flux measurements, we found that the soil microbiome composition, diversity and functional potential varied across the polygon transect and that specific microbes and functional genes were correlated to GHG measurements. Several draft genomes of novel species were obtained with genes encoding enzymes involved in cycling of complex organic compounds. These results have larger implications for prediction of the influence of the soil microbiome on soil C flux from arctic regions undergoing environmental change.

  19. The Russian-Swedish tundra radioecology expedition 1994

    International Nuclear Information System (INIS)

    Persson, B.R.; Holm, E.; Carlsson, K.Aa.; Josefsson, D.; Roos, P.

    1995-01-01

    The expedition investigated the ecology of the anthropogenic radio nuclides 137 Cs, 90 Sr, and 239,240 Pu in the Northern Sea to explain the origin from different sources. It had been shown from an earlier expedition that the levels of 137 Cs are higher in the central Arctic Ocean than further south in Barents Sea. The question was if this was due to inflow from the Atlantic or is due to other origin. The expedition also examined the outflow of 90 Sr from the rivers along the Siberian coast in order to investigate if the permafrost enhances the run-off of radionuclides from tundra. Study of anthropogenic radionuclides in the mixing zone between fresh and salt water at the different river systems along the Siberian coast was of particular interest. Some of the results from the expedition are presented in the present paper. 3 refs., 3 figs., 3 tabs

  20. Digital Necrobacillosis in Norwegian Wild Tundra Reindeer (Rangifer tarandus tarandus)

    DEFF Research Database (Denmark)

    Handeland, K.; Boye, Mette; Bergsjø, B.

    2010-01-01

    Outbreaks of digital necrobacillosis in Norwegian wild tundra reindeer (Rangifer tarandus tarandus) are described. The outbreaks occurred in late summer and autumn 2007 and 2008, subsequent to periods with an unusually high number of days with precipitation and high air temperature. Lesions were...... of pus. Subcutaneous tissue was inflamed and oedematous with focal necrosis. Tendons, tendon sheaths, joints and periosteum of the digital bones were often affected. Animals shot during winter showed severe chronic periostitis and osteomyelitis and necrotizing deforming arthritis. Microscopically, skin...... lesions were characterized by deep ulcers with centrally located necrotic tissue, bordered by a zone of oedema and intense inflammation with granulation tissue and fibrosis. Necrosis, suppurative inflammation and oedema were found in the synovial membranes, tendons and tendon sheaths. Digital bone lesions...

  1. Metagenomics Reveals Pervasive Bacterial Populations and Reduced Community Diversity across the Alaska Tundra Ecosystem.

    Science.gov (United States)

    Johnston, Eric R; Rodriguez-R, Luis M; Luo, Chengwei; Yuan, Mengting M; Wu, Liyou; He, Zhili; Schuur, Edward A G; Luo, Yiqi; Tiedje, James M; Zhou, Jizhong; Konstantinidis, Konstantinos T

    2016-01-01

    How soil microbial communities contrast with respect to taxonomic and functional composition within and between ecosystems remains an unresolved question that is central to predicting how global anthropogenic change will affect soil functioning and services. In particular, it remains unclear how small-scale observations of soil communities based on the typical volume sampled (1-2 g) are generalizable to ecosystem-scale responses and processes. This is especially relevant for remote, northern latitude soils, which are challenging to sample and are also thought to be more vulnerable to climate change compared to temperate soils. Here, we employed well-replicated shotgun metagenome and 16S rRNA gene amplicon sequencing to characterize community composition and metabolic potential in Alaskan tundra soils, combining our own datasets with those publically available from distant tundra and temperate grassland and agriculture habitats. We found that the abundance of many taxa and metabolic functions differed substantially between tundra soil metagenomes relative to those from temperate soils, and that a high degree of OTU-sharing exists between tundra locations. Tundra soils were an order of magnitude less complex than their temperate counterparts, allowing for near-complete coverage of microbial community richness (~92% breadth) by sequencing, and the recovery of 27 high-quality, almost complete (>80% completeness) population bins. These population bins, collectively, made up to ~10% of the metagenomic datasets, and represented diverse taxonomic groups and metabolic lifestyles tuned toward sulfur cycling, hydrogen metabolism, methanotrophy, and organic matter oxidation. Several population bins, including members of Acidobacteria, Actinobacteria, and Proteobacteria, were also present in geographically distant (~100-530 km apart) tundra habitats (full genome representation and up to 99.6% genome-derived average nucleotide identity). Collectively, our results revealed that

  2. Look again: Revising ideas about the greening of Alaska’s arctic tundra

    Science.gov (United States)

    Geoffrey Koch; Robert Pattison

    2017-01-01

    Alaska’s Arctic tundra is one of the most rapidly warming regions in the world. For years, scientists have been working to interpret the effects of its changing climate and determine what these changes may mean for the rest of the planet. Coarse-scale satellite imagery of much of this region shows the tundra is becoming greener. This has been widely attributed to shrub...

  3. Spaceborne potential for examining taiga-tundra ecotone form and vulnerability

    Science.gov (United States)

    Montesano, Paul M.; Sun, Guoqing; Dubayah, Ralph O.; Ranson, K. Jon

    2016-07-01

    In the taiga-tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density, and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, variable, and widespread vegetation change warrants the application of spaceborne data including high-resolution (forest structure at the patch scale in the TTE to provide a means to examine both vertical and horizontal components of ecotone form. We demonstrate the potential of spaceborne data for integrating forest height and density to assess TTE form at the scale of forest patches across the circumpolar biome by (1) mapping forest patches in study sites along the TTE in northern Siberia with a multi-resolution suite of spaceborne data and (2) examining the uncertainty of forest patch height from this suite of data across sites of primarily diffuse TTE forms. Results demonstrate the opportunities for improving patch-scale spaceborne estimates of forest height, the vertical component of TTE form, with HRSI. The distribution of relative maximum height uncertainty based on prediction intervals is centered at ˜ 40 %, constraining the use of height for discerning differences in forest patches. We discuss this uncertainty in light of a conceptual model of general ecotone forms and highlight how the uncertainty of spaceborne estimates of height can contribute to the uncertainty in identifying TTE forms. A focus on reducing the uncertainty of height estimates in forest patches may improve depiction of TTE form, which may help explain variable forest responses in the TTE to climate change and the vulnerability of portions of the TTE to forest structure change.

  4. Spaceborne Potential for Examining Taiga-Tundra Ecotone Form and Vulnerability

    Science.gov (United States)

    Montesano, Paul M.; Sun, Guoqing; Dubayah, Ralph O.; Ranson, K. Jon

    2016-01-01

    In the taiga-tundra ecotone (TTE), site-dependent forest structure characteristics can influence the subtle and heterogeneous structural changes that occur across the broad circumpolar extent. Such changes may be related to ecotone form, described by the horizontal and vertical patterns of forest structure (e.g., tree cover, density and height) within TTE forest patches, driven by local site conditions, and linked to ecotone dynamics. The unique circumstance of subtle, variable and widespread vegetation change warrants the application of spaceborne data including high-resolution (less than 5m) spaceborne imagery (HRSI) across broad scales for examining TTE form and predicting dynamics. This study analyzes forest structure at the patch-scale in the TTE to provide a means to examine both vertical and horizontal components of ecotone form. We demonstrate the potential of spaceborne data for integrating forest height and density to assess TTE form at the scale of forest patches across the circumpolar biome by (1) mapping forest patches in study sites along the TTE in northern Siberia with a multi-resolution suite of spaceborne data, and (2) examining the uncertainty of forest patch height from this suite of data across sites of primarily diffuse TTE forms. Results demonstrate the opportunities for improving patch-scale spaceborne estimates of forest height, the vertical component of TTE form, with HRSI. The distribution of relative maximum height uncertainty based on prediction intervals is centered at approximately 40%, constraining the use of height for discerning differences in forest patches. We discuss this uncertainty in light of a conceptual model of general ecotone forms, and highlight how the uncertainty of spaceborne estimates of height can contribute to the uncertainty in identifying TTE forms. A focus on reducing the uncertainty of height estimates in forest patches may improve depiction of TTE form, which may help explain variable forest responses in the

  5. NDVI as a predictor of canopy arthropod biomass in the Alaskan arctic tundra.

    Science.gov (United States)

    Sweet, Shannan K; Asmus, Ashley; Rich, Matthew E; Wingfield, John; Gough, Laura; Boelman, Natalie T

    2015-04-01

    The physical and biological responses to rapid arctic warming are proving acute, and as such, there is a need to monitor, understand, and predict ecological responses over large spatial and temporal scales. The use of the normalized difference vegetation index (NDVI) acquired from airborne and satellite sensors addresses this need, as it is widely used as a tool for detecting and quantifying spatial and temporal dynamics of tundra vegetation cover, productivity, and phenology. Such extensive use of the NDVI to quantify vegetation characteristics suggests that it may be similarly applied to characterizing primary and secondary consumer communities. Here, we develop empirical models to predict canopy arthropod biomass with canopy-level measurements of the NDVI both across and within distinct tundra vegetation communities over four growing seasons in the Arctic Foothills region of the Brooks Range, Alaska, USA. When canopy arthropod biomass is predicted with the NDVI across all four growing seasons, our overall model that includes all four vegetation communities explains 63% of the variance in canopy arthropod biomass, whereas our models specific to each of the four vegetation communities explain 74% (moist tussock tundra), 82% (erect shrub tundra), 84% (riparian shrub tundra), and 87% (dwarf shrub tundra) of the observed variation in canopy arthropod biomass. Our field-based study suggests that measurements of the NDVI made from air- and spaceborne sensors may be able to quantify spatial and temporal variation in canopy arthropod biomass at landscape to regional scales.

  6. Continental United States Hurricane Strikes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Continental U.S. Hurricane Strikes Poster is our most popular poster which is updated annually. The poster includes all hurricanes that affected the U.S. since...

  7. Characteristics of summer-time energy exchange in a high Arctic tundra heath 2000–2010

    Directory of Open Access Journals (Sweden)

    Magnus Lund

    2014-07-01

    Full Text Available Global warming will bring about changes in surface energy balance of Arctic ecosystems, which will have implications for ecosystem structure and functioning, as well as for climate system feedback mechanisms. In this study, we present a unique, long-term (2000–2010 record of summer-time energy balance components (net radiation, R n; sensible heat flux, H; latent heat flux, LE; and soil heat flux, G from a high Arctic tundra heath in Zackenberg, Northeast Greenland. This area has been subjected to strong summer-time warming with increasing active layer depths (ALD during the last decades. We observe high energy partitioning into H, low partitioning into LE and high Bowen ratio (β=H/LE compared with other Arctic sites, associated with local climatic conditions dominated by onshore winds, slender vegetation with low transpiration activity and relatively dry soils. Surface saturation vapour pressure deficit (D s was found to be an important variable controlling within-year surface energy partitioning. Throughout the study period, we observe increasing H/R n and LE/R n and decreasing G/R n and β, related to increasing ALD and decreasing soil wetness. Thus, changes in summer-time surface energy balance partitioning in Arctic ecosystems may be of importance for the climate system.

  8. The effect of silver nanoparticles on seasonal change in arctic tundra bacterial and fungal assemblages.

    Science.gov (United States)

    Kumar, Niraj; Palmer, Gerald R; Shah, Vishal; Walker, Virginia K

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages.

  9. Effects of disturbance on ecosystem dynamics of tundra and riparian vegetation: A project in the R4D program. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, J.F.

    1995-12-31

    Models were proposed as research tools to test the basic understanding of the structure and function of arctic ecosystems, as a means for providing initial management assessments of potential response to energy-related development, and as a vehicle for extrapolation of research results to other arctic sites and landscapes. This final summary report reviews progress made on models at a variety of scales from nutrient uptake by individual roots to nutrient availability within arctic landscapes, and examines potentials and critical limitations of these models for providing insight on patch and landscape level function in tundra regions.

  10. Multi-decadal changes in tundra environments and ecosystems: Synthesis of the International Polar Year-Back to the Future Project (IPY-BTF)

    DEFF Research Database (Denmark)

    Callaghan, Terry V.; Tweedie, Craig E.; Åkerman, Jonas

    2011-01-01

    opportunity for such research through the Back to the Future (BTF) project (IPY project #512). This article synthesizes the results from 13 papers within this Ambio Special Issue. Abiotic changes include glacial recession in the Altai Mountains, Russia; increased snow depth and hardness, permafrost warming......, and increased growing season length in sub-arctic Sweden; drying of ponds in Greenland; increased nutrient availability in Alaskan tundra ponds, and warming at most locations studied. Biotic changes ranged from relatively minor plant community change at two sites in Greenland to moderate change in the Yukon...

  11. Response of a tundra ecosytem to elevated atmospheric carbon dioxide and CO2-induced climate change. Final report

    International Nuclear Information System (INIS)

    Oechel, W.C.

    1996-11-01

    The overall objective of this research was to document current patterns of CO 2 flux in selected locations of the circumpolar arctic, and to develop the information necessary to predict how these fluxes may be affected by climate change. In fulfillment of these objectives, net CO 2 flux was measured at several sites on the North Slope of Alaska during the 1990-94 growing season (June-August) to determine the local and regional patterns, of seasonal CO 2 exchange. In addition, net CO 2 flux was measured in the Russian and Icelandic Arctic to determine if the patterns of CO 2 exchange observed in Arctic Alaska were representative of the circumpolar arctic, while cold-season CO 2 flux measurements were carried out during the 1993-94 winter season to determine the magnitude of CO 2 efflux not accounted for by the growing season measurements. Manipulations of soil water table depth and surface temperature, which were identified from the extensive measurements as being the most important variables in determining the magnitude and direction of net CO 2 exchange, were carried out during the 1993-94 growing seasons in tussock and wet sedge tundra ecosystems. Finally, measurements of CH 4 flux were also measured at several of the North Slope study sites during the 1990-91 growing seasons. Measurements were made on small (e.g. 0.5 m 2 ) plots using a portable gas-exchange system and cuvette. The sample design allowed frequent measurements of net CO 2 exchange and respiration over diurnal and seasonal cycles, and a large spatial extent that incorporated both locally and regionally diverse tundra surface types. Measurements both within and between ecosystem types typically extended over soil water table depth and temperature gradients, allowing for the indirect analysis of the effects of anticipated climate change scenarios on net CO 2 exchange. In situ experiments provided a direct means for testing hypotheses

  12. Late Devonian and Triassic basalts from the southern continental ...

    Indian Academy of Sciences (India)

    In Late Devonian and Early-to-Late Triassic times, the southern continental margin of the Eastern. European Platform was the site of a basaltic volcanism in the Donbas and Fore-Caucasus areas respectively. Both volcanic piles rest unconformably upon Paleoproterozoic and Late Paleozoic units respectively, and emplaced ...

  13. Late Devonian and Triassic basalts from the southern continental ...

    Indian Academy of Sciences (India)

    In Late Devonian and Early-to-Late Triassic times, the southern continental margin of the Eastern European Platform was the site of a basaltic volcanism in the Donbas and Fore-Caucasus areas respectively. Both volcanic piles rest unconformably upon Paleoproterozoic and Late Paleozoic units respectively, and emplaced ...

  14. Water track distribution and effects on carbon dioxide flux in an eastern Siberian upland tundra landscape

    International Nuclear Information System (INIS)

    Curasi, Salvatore R; Loranty, Michael M; Natali, Susan M

    2016-01-01

    Shrub expansion in tundra ecosystems may act as a positive feedback to climate warming, the strength of which depends on its spatial extent. Recent studies have shown that shrub expansion is more likely to occur in areas with high soil moisture and nutrient availability, conditions typically found in sub-surface water channels known as water tracks. Water tracks are 5–15 m wide channels of subsurface water drainage in permafrost landscapes and are characterized by deeper seasonal thaw depth, warmer soil temperatures, and higher soil moisture and nutrient content relative to adjacent tundra. Consequently, enhanced vegetation productivity, and dominance by tall deciduous shrubs, are typical in water tracks. Quantifying the distribution of water tracks may inform investigations of the extent of shrub expansion and associated impacts on tundra ecosystem carbon cycling. Here, we quantify the distribution of water tracks and their contribution to growing season CO 2 dynamics for a Siberian tundra landscape using satellite observations, meteorological data, and field measurements. We find that water tracks occupy 7.4% of the 448 km 2 study area, and account for a slightly larger proportion of growing season carbon uptake relative to surrounding tundra. For areas inside water tracks dominated by shrubs, field observations revealed higher shrub biomass and higher ecosystem respiration and gross primary productivity relative to adjacent upland tundra. Conversely, a comparison of graminoid-dominated areas in water tracks and inter-track tundra revealed that water track locations dominated by graminoids had lower shrub biomass yet increased net uptake of CO 2 . Our results show water tracks are an important component of this landscape. Their distribution will influence ecosystem structural and functional responses to climate, and is therefore of importance for modeling. (letter)

  15. Can lemmings control the expansion of woody plants on tundra?

    Science.gov (United States)

    Oksanen, Lauri; Oksanen, Tarja; Olofsson, Johan; Virtanen, Risto; Hoset, Katrine; Tuomi, Maria; Kyrö, Kukka

    2013-04-01

    The ongoing expansion of woody vegetation in the arctic, due to global warming, creates a positive feed back loop. Increasing abundance of woody plants reduces surface albedo both directly and via speeding up snow melt. Thus a successively greater fraction of incoming solar radiation is absorbed and converted to heat. Browsing mammals - both big and small - can prevent this by consuming woody plants. However, the grazer/browser community of many tundra areas is dominated by brown/Norwegian lemmings (Lemmus spp.) which eat graminoids and mosses and cannot use woody plants as forage. It would seem a priori likely that in such areas, mammalian herbivores speed up the expansion of woody plants by improving the chances of their seedlings to get established. We studied the impact of lemmings on woody plants by constructing lemming proof exclosures within piece high-altitude tundra at Joatkanjávri, northernmost Norway. The exclosures were constructed in 1998, during a period of low lemming densities, in snow-beds, where Norwegian lemmings (L. lemmus) were the only ecologically significant herbivorous mammals. (Reindeer migrate through the area in May, when snow-beds are inaccessible for them; during the fall migration, the area represents a dead end and is therefore avoided.) We chose pairs of maximally similar vegetation patches of 0.5 by 0.5 m and randomly assigned one of each pair to become an exclosure while the other plot was left open. The initial state of the vegetation was documented by the point frequency method. In 2008, after the 2007 lemming outbreak, the same documentation was repeated; thereafter the plots were harvested, the vegetation was sorted to species, oven dried and weighed. Exclusion of lemmings resulted to pronounced increase in community level plant biomass. Evergreen woody plants were especially favored by the exclusion of lemming: their above-ground biomass in exclosures was 14 times as great as their biomass on open reference plots. The

  16. Reconstructing Rodinia by Fitting Neoproterozoic Continental Margins

    Science.gov (United States)

    Stewart, John H.

    2009-01-01

    extensional in origin, supports recognition of the Neoproterozoic fragmentation pattern of Rodinia and outlines the major continental masses that, prior to the breakup, formed the supercontinent. Using this pattern, Rodinia can be assembled by fitting the pieces together. Evidence for Neoproterozoic margins is fragmentary. The most apparent margins are marked by miogeoclinal deposits (passive-margin deposits). The margins can also be outlined by the distribution of continental-margin magmatic-arc rocks, by juvenile ocean-floor rocks, or by the presence of continent-ward extending aulacogens. Most of the continental margins described here are Neoproterozoic, and some had an older history suggesting that they were major, long-lived lithospheric flaws. In particular, the western margin of North America appears to have existed for at least 1,470 Ma and to have been reactivated many times in the Neoproterozoic and Phanerozoic. The inheritance of trends from the Mesoproterozoic by the Neoproterozoic is particularly evident along the eastern United States, where a similarity of Mesoproterozoic (Grenville) and Neoproterozoic trends, as well as Paleozoic or Mesozoic trends, is evident. The model of Rodinia presented here is based on both geologic and paleomagnetic information. Geologic evidence is based on the distribution and shape of Neoproterozoic continents and on assembling these continents so as to match the shape, history, and scale of adjoining margins. The proposed model places the Laurasian continents?Baltica, Greenland, and Laurentia?west of the South American continents (Amazonia, Rio de La Plata, and Sa? Francisco). This assembly is indicated by conjugate pairs of Grenville-age rocks on the east side of Laurentia and on the west side of South America. In the model, predominantly late Neoproterozoic magmatic-arc rocks follow the trend of the Grenville rocks. The boundary between South America and Africa is interpreted as the site of a Wilson cycle

  17. Vectors and transmission dynamics for Setaria tundra (Filarioidea; Onchocercidae, a parasite of reindeer in Finland

    Directory of Open Access Journals (Sweden)

    Kuusela Jussi

    2009-01-01

    Full Text Available Abstract Background Recent studies have revealed expansion by an array of Filarioid nematodes' into the northern boreal region of Finland. The vector-borne nematode, Setaria tundra, caused a serious disease outbreak in the Finnish reindeer population in 2003–05. The main aim of this study was to understand the outbreak dynamics and the rapid expansion of S. tundra in the sub arctic. We describe the vectors of S. tundra, and its development in vectors, for the first time. Finally we discuss the results in the context of the host-parasite ecology of S. tundra in Finland Results Development of S. tundra to the infective stage occurs in mosquitoes, (genera Aedes and Anopheles. We consider Aedes spp. the most important vectors. The prevalence of S. tundra naturally infected mosquitoes from Finland varied from 0.5 to 2.5%. The rate of development in mosquitoes was temperature-dependent. Infective larvae were present approximately 14 days after a blood meal in mosquitoes maintained at room temperature (mean 21 C, but did not develop in mosquitoes maintained outside for 22 days at a mean temperature of 14.1 C. The third-stage (infective larvae were elongated (mean length 1411 μm (SD 207, and width 28 μm (SD 2. The anterior end was blunt, and bore two liplike structures, the posterior end slight tapering with a prominent terminal papilla. Infective larvae were distributed anteriorly in the insect's body, the highest abundance being 70 larvae in one mosquito. A questionnaire survey revealed that the peak activity of Culicidae in the reindeer herding areas of Finland was from the middle of June to the end of July and that warm summer weather was associated with reindeer flocking behaviour on mosquito-rich wetlands. Conclusion In the present work, S. tundra vectors and larval development were identified and described for the first time. Aedes spp. mosquitoes likely serve as the most important and competent vectors for S. tundra in Finland. Warm summers

  18. Assessing Seasonal Backscatter Variations with Respect to Uncertainties in Soil Moisture Retrieval in Siberian Tundra Regions

    Directory of Open Access Journals (Sweden)

    Elin Högström

    2014-09-01

    Full Text Available Knowledge of surface hydrology is essential for many applications, including studies that aim to understand permafrost response to changing climate and the associated feedback mechanisms. Advanced remote sensing techniques make it possible to retrieve a range of land-surface variables, including radar retrieved soil moisture (SSM. It has been pointed out before that soil moisture retrieval from satellite data can be challenging at high latitudes, which correspond to remote areas where ground data are scarce and the applicability of satellite data of this type is essential. This study investigates backscatter variability other than associated with changing soil moisture in order to examine the possible impact on soil moisture retrieval. It focuses on issues specific to SSM retrieval in the Arctic, notably variations related to tundra lakes. ENVISAT Advanced Synthetic Aperture Radar (ASAR Wide Swath (WS, 120 m data are used to understand and quantify impacts on Metop (AAdvanced Scatterometer (ASCAT, 25 km soil moisture retrieval during the snow free period. Sites of interest are chosen according to ASAR WS availability, high or low agreement between output from the land surface model ORCHIDEE and ASCAT derived SSM. Backscatter variations are analyzed with respect to the ASCAT footprint area. It can be shown that the low model agreement is related to water fraction in most cases. No difference could be detected between periods with floating ice (in snow off situation and ice free periods at the chosen sites. The mean footprint backscatter is however impacted by partial short term surface roughness change. The water fraction correlates with backscatter deviations (relative to a smooth water surface reference image within the ASCAT footprint areas (R = 0.91

  19. Inter-annual Variability in Tundra Phenology Captured with Digital Photography

    Science.gov (United States)

    Melendez, M.; Vargas, S. A.; Tweedie, C. E.

    2012-12-01

    The need to improve multi-scale phenological monitoring of arctic terrestrial ecosystems has been a persistent research challenge. Although there has been a range of advances in remote sensing capacities over the past decade, these present costly, and sometimes logistically challenging and technically demanding solutions for arctic terrestrial ecosystems. In this poster and undergraduate research project, we demonstrate how seasonal and inter-annual variability in landscape phenology can be derived for multiple tundra ecosystems using a low-cost and low-tech kite aerial photography (KAP) system that has been developed as a contribution to the US Arctic Observing Network. Seasonal landscape phenology was observed over the Networked Info-Mechanical Systems (NIMS) grids (2 x 50 meters) located in Barrow and Atqasuk, Alaska using imagery acquired with KAP and analyzed for a range of greenness indices. Preliminary results showed that the 2G-RB greenness index correlated the best with NDVI values calculated from ground based hyperspectral reflectance measurements. 2012 had the highest 2G-RB greenness index values for both Barrow and Atqasuk sites, which correlated well with NDVI values acquired from ground-based hyperspectral reflectance measurements. Wet vegetation types showed the most interannual variability at the Atqasuk site based on the 2G-RB greenness index while in Barrow the moist vegetation types showed the most interannual variability. These results show that vegetation indices similar to those acquired from hyperspectral remote sensing platforms can be derived using low-cost and low-tech techniques. Further analysis using these same techniques is required in order to link relatively small scale vegetation dynamics measured with KAP with those documented at large scales using satellite imagery.

  20. [The processes of methane formation and oxidation in the soils of the Russian arctic tundra].

    Science.gov (United States)

    Berestovskaia, Iu Iu; Rusanov, I I; Vasil'eva, L V; Pimenov, N V

    2005-01-01

    Methane emission from the following types of tundra soils was studied: coarse humic gleyey loamy cryo soil, peaty gley soil, and peaty gleyey midloamy cryo soil of the arctic tundra. All the soils studied were found to be potential sources of atmospheric methane. The highest values of methane emission were recorded in August at a soil temperature of 8-10 degrees C. Flooded parcels were the sources of atmospheric methane throughout the observation period. The rates of methane production and oxidation in tundra soils of various types at 5 and 15 degrees C were studied by the radioisotope method. Methane oxidation was found to occur in bog water, in the green part of peat moss, and in all the soil horizons studied. Methane formation was recorded in the horizons of peat, in clay with plant roots, and in peaty moss dust of the bogey parcels. At both temperatures, the methane oxidation rate exceeded the rate of methane formation in all the horizons of the mossy-lichen tundra and of the bumpy sinkhole complex. Methanogenesis prevailed only in a sedge-peat moss bog at 15 degrees C. Enrichment bacterial cultures oxidizing methane at 5 and 15 degrees C were obtained. Different types of methanotrophic bacteria were shown to be responsible for methane oxidation under these conditions. A representative of type I methylotrophs oxidized methane at 5 degrees C, and Methylocella tundrae, a psychroactive representative of an acidophilic methanotrophic genus Methylocella, at 15 degrees C.

  1. Evidence for re-distribution of 137Cs in Alaskan tundra, lake, and marine sediments

    International Nuclear Information System (INIS)

    Cooper, L.W.; Grebmeier, J.M.; Larsen, I.L.; Solis, C.; Olsen, C.R.

    1994-01-01

    Tundra sampling conducted during 1989-1990 at Imnavait Creek, Alaska (68 o 37'N, 149 o 17'W) indicated that inventories of 137 Cs were close to expectations, based upon measured atmospheric deposition for this latitude band. Typically observed at a depth of 4-10 cm, peak accumulations of 137 Cs were associated with organic materials, above any mineral soil. Accumulated inventories of 137 Cs in tundra decreased by up to 50% along a transect to Prudhoe Bay (70 o 13'N, 148 o 30'W). Atmospheric deposition of 137 Cs decreased with latitude in the Arctic, but declines in deposition would have been relatively small over this distance (200 km). This finding suggests a recent loss of 137 Cs from tundra over the northern parts of the transect between Imnavait Creek and Prudhoe Bay. This hypothesis is supported by observations of maximum 137 Cs accumulations occurring in surface layers of the more northern tundra rather than at depth (as at Imnavait Creek), as well as by indications of higher 137 Cs accumulations in a lake inlet. On the other hand, marine sediments collected in the Bering Sea and Chukchi Seas, including the Yukon River delta region, show apparently lower inventories compared to tundra or lake sediments, although complete inventories are unavailable due to radiocesium buried to depths (>20 cm) beyond the sampling capabilities used

  2. What Does Matter?: Idols and Icons in the Nenets Tundra

    Directory of Open Access Journals (Sweden)

    Laur Vallikivi

    2011-08-01

    Full Text Available This paper examines a mission encounter in the Nenets reindeer herders’ tundra. In post-Soviet Arctic Russia, Pentecostal and Baptist missionaries of Russian and Ukrainian origin have been fighting against idolatry and trying to persuade the Nenets to burn their sacred images or khekhe’’. They claim that among the indigenous Siberians idolatry exists in its quintessential or prototypical form, as it is described in the Bible. I shall suggest that this encounter takes place in a gap, in which the Nenets and Protestant have different understandings of language and materiality. Missionaries rely simultaneously on the ‘modern’ ideology of signification and the ‘non-modern’ magic of the material. They argue that idols, which are ‘nothing’ according to the scriptures, dangerously bind the ‘pagans’’ minds. For reindeer herders, for whom sacred items occupy an important place in the family wellbeing, the main issue is how to sever the link with the spirits without doing any damage.

  3. What Does Matter?: Idols and Icons in the Nenets Tundra

    Directory of Open Access Journals (Sweden)

    Laur Vallikivi

    2011-09-01

    Full Text Available This paper examines a mission encounter in the Nenets reindeer herders’ tundra. In post-Soviet Arctic Russia, Pentecostal and Baptist missionaries of Russian and Ukrainian origin have been fighting against idolatry and trying to persuade the Nenets to burn their sacred images or khekhe’’. They claim that among the indigenous Siberians idolatry exists in its quintessential or prototypical form, as it is described in the Bible. I shall suggest that this encounter takes place in a gap, in which the Nenets and Protestant have different understandings of language and materiality. Missionaries rely simultaneously on the ‘modern’ ideology of signification and the ‘non-modern’ magic of the material. They argue that idols, which are ‘nothing’ according to the scriptures, dangerously bind the ‘pagans’’ minds. For reindeer herders, for whom sacred items occupy an important place in the family wellbeing, the main issue is how to sever the link with the spirits without doing any damage.

  4. Fractal behavior in continental crustal heat production

    Science.gov (United States)

    Vedanti, N.; Srivastava, R. P.; Pandey, O. P.; Dimri, V. P.

    2011-02-01

    The distribution of crustal heat production, which is the most important component in the elucidation of continental thermal structure, still remains a theoretical assumption. In general the heat production values must decrease with depth, but the form of decrease of heat production in the crust is not well understood. The commonly used heat production models are: "block model", in which heat production is constant from the surface to a given depth and the "exponential model", in which heat production diminishes as an exponential function of depth. The exponential model is more widely used wherein sources of the errors are heterogeneity of rock and long wavelength changes due to changes in lithology and tectonic elements, and as such exponential distribution does not work satisfactorily for the entire crust. In the present study, we analyze for the first time, deep crustal heat production data of six global areas namely Dharwar craton (India), Kaapvaal craton (South Africa), Baltic shield (Kola, Russia), Hidaka metamorphic belt (Japan), Nissho pluton (Japan) and Continental Deep Drilling site (KTB, Germany). The power spectrum of all the studied data sets exhibits power law behaviour. This would mean slower decay of heat production with depth, which conforms to the known geologic composition of the crust. Minimum value of the scaling exponent has been found for the KTB borehole, which is apparently related to higher heat production of gneisses, however for other study areas, scaling exponent is almost similar. We also found that the lower values of scaling exponents are related to higher heat production in the crust as is the case in KTB. Present finding has a direct relevance in computation of temperature-depth profiles in continental regions.

  5. The Batagay permafrost mega thaw slump: an environmental archive of the Late Pleistocene continental climate

    Science.gov (United States)

    Ashastina, Kseniia; Kienast, Frank; Römermann, Christine; Kuzmina, Svetlana; Diekmann, Bernhard; Schirrmeister, Lutz

    2017-04-01

    Palaeoenvironmental data preserved in permafrost contribute in our understanding of climate changes and their influence on the biocenoses during the Late Quaternary. Here we present cryolithological and palaeoecological results of studies carried out on a newly described permafrost exposure near Batagay about 50 km from Verkhoyansk, Sakha Republic, Russia, the town with the most continental climate recorded in the northern hemisphere. According to Günther et al. (2015), this unique exposure is the biggest mega thaw slump measured so far with the dimensions 800 m wide and 73 m deep. Only sparse data on the exposure are so far published in few articles (Novgorodov et al., 2013; Kunitsky et al., 2013; Ashastina et al., in press; Murton et al., 2016). The site is situated inWest Beringia, the Late Quaternary landmasscovered by tundra steppe and inhabited by diverse mega herbivores. We analyzed sedimentological data, plant macro- and micro-fossils together with insect remains in order to reconstruct the changes in the biome. The temporal frame for the accumulation of the sequence is provided by radiocarbon and optical stimulated luminescence dating, according to which the formation of the sequence started in the late Middle Quaternary. The features of permafrost accumulation and sedimentation give us an opportunity to propose the landscape changes responding to the climatic pulses of Pleistocene at this particular place. The shifts in vegetation from taiga to steppe associations are in a line with stadial and intersadial events. We propose a scheme of permafrost state and vegetation changes and merge it with climate variation during Late Quaternary. Ashastina, K., Schirrmeister, L., Fuchs, M., Kienast, F.: Pleistocene climate characteristics in the most continental part of the northern hemisphere: insights from cryolithological features of the Batagay mega thaw slump in the Siberian Yana Highlands. Climate of the Past, in press. doi: 10.5194/cp-2016-84. Günther, F

  6. Detection and molecular characterization of the mosquito-borne filarial nematode Setaria tundra in Danish roe deer (Capreolus capreolus)

    DEFF Research Database (Denmark)

    Enemark, Heidi Larsen; Oksanen, Antti; Chriél, Mariann

    2017-01-01

    Setaria tundra is a mosquito-borne filarial nematode of cervids in Europe. It has recently been associated with an emerging epidemic disease causing severe morbidity and mortality in reindeer and moose in Finland. Here, we present the first report of S. tundra in six roe deer (Capreolus capreolus...... capsule, worms (ranging from 2 to >20/deer) were found free in the peritoneal cavity. The worms were identified as S. tundra by morphological examination and/or molecular typing of the mitochondrial 12S rRNA and cox1 genes, which showed 99.1-99.8% identity to previously published S. tundra isolates from...... for development of parasite larvae in the mosquito vectors are expected, which may lead to increasing prevalence of S. tundra. Monitoring of this vector-borne parasite may thus be needed in order to enhance the knowledge of factors promoting its expansion and prevalence as well as predicting disease outbreaks. (C...

  7. Snowpack fluxes of methane and carbon dioxide from high Arctic tundra

    DEFF Research Database (Denmark)

    Pirk, Norbert; Tamstorf, Mikkel P; Lund, Magnus

    2016-01-01

    Measurements of the land-atmosphere exchange of the greenhouse gases methane (CH4) andcarbon dioxide (CO2) in high Arctic tundra ecosystems are particularly difficult in the cold season, resultingin large uncertainty on flux magnitudes and their controlling factors during this long, frozen period...... butdetected a pulse in the 13C-CH4stable isotopic signature of the soil’s CH4source during snowmelt, whichsuggests the release of a CH4reservoir that was strongly affected by methanotrophic microorganisms. In thepolygonal tundra of Adventdalen, the snowpack featured several ice layers, which suppressed...... togeomorphological soil cracks. Collectively, these findings suggest important ties between growing seasonand cold season greenhouse gas emissions from high Arctic tundra....

  8. Scattering Characteristics of X-, C- and L-Band PolSAR Data Examined for the Tundra Environment of the Tuktoyaktuk Peninsula, Canada

    Directory of Open Access Journals (Sweden)

    Tobias Ullmann Sarah N. Banks

    2017-06-01

    Full Text Available In this study, polarimetric Synthetic Aperture Radar (PolSAR data at X-, C- and L-Bands, acquired by the satellites: TerraSAR-X (2011, Radarsat-2 (2011, ALOS (2010 and ALOS-2 (2016, were used to characterize the tundra land cover of a test site located close to the town of Tuktoyaktuk, NWT, Canada. Using available in situ ground data collected in 2010 and 2012, we investigate PolSAR scattering characteristics of common tundra land cover classes at X-, C- and L-Bands. Several decomposition features of quad-, co-, and cross-polarized data were compared, the correlation between them was investigated, and the class separability offered by their different feature spaces was analyzed. Certain PolSAR features at each wavelength were sensitive to the land cover and exhibited distinct scattering characteristics. Use of shorter wavelength imagery (X and C was beneficial for the characterization of wetland and tundra vegetation, while L-Band data highlighted differences of the bare ground classes better. The Kennaugh Matrix decomposition applied in this study provided a unified framework to store, process, and analyze all data consistently, and the matrix offered a favorable feature space for class separation. Of all elements of the quad-polarized Kennaugh Matrix, the intensity based elements K0, K1, K2, K3 and K4 were found to be most valuable for class discrimination. These elements contributed to better class separation as indicated by an increase of the separability metrics squared Jefferys Matusita Distance and Transformed Divergence. The increase in separability was up to 57% for Radarsat-2 and up to 18% for ALOS-2 data.

  9. Potential contributions of root decomposition to the nitrogen cycle in arctic forest and tundra.

    Science.gov (United States)

    Träger, Sabrina; Milbau, Ann; Wilson, Scott D

    2017-12-01

    Plant contributions to the nitrogen (N) cycle from decomposition are likely to be altered by vegetation shifts associated with climate change. Roots account for the majority of soil organic matter input from vegetation, but little is known about differences between vegetation types in their root contributions to nutrient cycling. Here, we examine the potential contribution of fine roots to the N cycle in forest and tundra to gain insight into belowground consequences of the widely observed increase in woody vegetation that accompanies climate change in the Arctic. We combined measurements of root production from minirhizotron images with tissue analysis of roots from differing root diameter and color classes to obtain potential N input following decomposition. In addition, we tested for changes in N concentration of roots during early stages of decomposition, and investigated whether vegetation type (forest or tundra) affected changes in tissue N concentration during decomposition. For completeness, we also present respective measurements of leaves. The potential N input from roots was twofold greater in forest than in tundra, mainly due to greater root production in forest. Potential N input varied with root diameter and color, but this variation tended to be similar in forest and tundra. As for roots, the potential N input from leaves was significantly greater in forest than in tundra. Vegetation type had no effect on changes in root or leaf N concentration after 1 year of decomposition. Our results suggest that shifts in vegetation that accompany climate change in the Arctic will likely increase plant-associated potential N input both belowground and aboveground. In contrast, shifts in vegetation might not alter changes in tissue N concentration during early stages of decomposition. Overall, differences between forest and tundra in potential contribution of decomposing roots to the N cycle reinforce differences between habitats that occur for leaves.

  10. Drift of continental rafts with asymmetric heating.

    Science.gov (United States)

    Knopoff, L; Poehls, K A; Smith, R C

    1972-06-02

    A laboratory model of a lithospheric raft is propelled through a viscous asthenospheric layer with constant velocity of scaled magnitude appropriate to continental drift. The propulsion is due to differential heat concentration in the model oceanic and continental crusts.

  11. GIS- and field data based modeling of snow water equivalent in shrub tundra

    Directory of Open Access Journals (Sweden)

    Yu. A. Dvornikov

    2015-01-01

    Full Text Available An approach for snow water equivalent (SWE modelling in tundra environments has been developed for the test area on the Yamal peninsula. Detailed mapping of snow cover is very important for tundra areas under continuous permafrost conditions, because the snow cover affects the active layer thickness (ALT and the ground temperature, acting as a heat-insulating agent. The information concerning snow cover with specific regime of accumulation can support studies of ground temperature distribution and other permafrost related aspects. 

  12. Metagenomics reveals pervasive bacterial populations and reduced community diversity across the Alaska tundra ecosystem

    Directory of Open Access Journals (Sweden)

    Eric Robert Johnston

    2016-04-01

    Full Text Available How soil microbial communities contrast with respect to taxonomic and functional composition within and between ecosystems remains an unresolved question that is central to predicting how global anthropogenic change will affect soil functioning and services. In particular, it remains unclear how small-scale observations of soil communities based on the typical volume sampled (1-2 grams are generalizable to ecosystem-scale responses and processes. This is especially relevant for remote, northern latitude soils, which are challenging to sample and are also thought to be more vulnerable to climate change compared to temperate soils. Here, we employed well-replicated shotgun metagenome and 16S rRNA gene amplicon sequencing to characterize community composition and metabolic potential in Alaskan tundra soils, combining our own datasets with those publically available from distant tundra and temperate grassland and agriculture habitats. We found that the abundance of many taxa and metabolic functions differed substantially between tundra soil metagenomes relative to those from temperate soils, and that a high degree of OTU-sharing exists between tundra locations. Tundra soils were an order of magnitude less complex than their temperate counterparts, allowing for near-complete coverage of microbial community richness (~92% breadth by sequencing, and the recovery of twenty-seven high-quality, almost complete (>80% completeness population bins. These population bins, collectively, made up to ~10% of the metagenomic datasets, and represented diverse taxonomic groups and metabolic lifestyles tuned toward sulfur cycling, hydrogen metabolism, methanotrophy, and organic matter oxidation. Several population bins, including members of Acidobacteria, Actinobacteria, and Proteobacteria, were also present in geographically distant (~100-530 km apart tundra habitats (full genome representation and up to 99.6% genome-derived average nucleotide identity. Collectively

  13. Shrub Abundance Mapping in Arctic Tundra with Misr

    Science.gov (United States)

    Duchesne, R.; Chopping, M. J.; Wang, Z.; Schaaf, C.; Tape, K. D.

    2013-12-01

    Over the last 60 years an increase in shrub abundance has been observed in the Arctic tundra in connection with a rapid surface warming trend. Rapid shrub expansion may have consequences in terms of ecosystem structure and function, albedo, and feedbacks to climate; however, its rate is not yet known. The goal of this research effort is thus to map large scale changes in Arctic tundra vegetation by exploiting the structural signal in moderate resolution satellite remote sensing images from NASA's Multiangle Imaging SpectroRadiometer (MISR), mapped onto a 250m Albers Conic Equal Area grid. We present here large area shrub mapping supported by reference data collated using extensive field inventory data and high resolution panchromatic imagery. MISR Level 1B2 Terrain radiance scenes from the Terra satellite from 15 June-31 July, 2000 - 2010 were converted to surface bidirectional reflectance factors (BRF) using MISR Toolkit routines and the MISR 1 km LAND product BRFs. The red band data in all available cameras were used to invert the RossThick-LiSparse-Reciprocal BRDF model to retrieve kernel weights, model-fitting RMSE, and Weights of Determination. The reference database was constructed using aerial survey, three field campaigns (field inventory for shrub count, cover, mean radius and height), and high resolution imagery. Tall shrub number, mean crown radius, cover, and mean height estimates were obtained from QuickBird and GeoEye panchromatic image chips using the CANAPI algorithm, and calibrated using field-based estimates, thus extending the database to over eight hundred locations. Tall shrub fractional cover maps for the North Slope of Alaska were constructed using the bootstrap forest machine learning algorithm that exploits the surface information provided by MISR. The reference database was divided into two datasets for training and validation. The model derived used a set of 19 independent variables(the three kernel weights, ratios and interaction terms

  14. Permafrost collapse alters soil carbon stocks, respiration, CH4 , and N2O in upland tundra.

    Science.gov (United States)

    Abbott, Benjamin W; Jones, Jeremy B

    2015-12-01

    Release of greenhouse gases from thawing permafrost is potentially the largest terrestrial feedback to climate change and one of the most likely to occur; however, estimates of its strength vary by a factor of thirty. Some of this uncertainty stems from abrupt thaw processes known as thermokarst (permafrost collapse due to ground ice melt), which alter controls on carbon and nitrogen cycling and expose organic matter from meters below the surface. Thermokarst may affect 20-50% of tundra uplands by the end of the century; however, little is known about the effect of different thermokarst morphologies on carbon and nitrogen release. We measured soil organic matter displacement, ecosystem respiration, and soil gas concentrations at 26 upland thermokarst features on the North Slope of Alaska. Features included the three most common upland thermokarst morphologies: active-layer detachment slides, thermo-erosion gullies, and retrogressive thaw slumps. We found that thermokarst morphology interacted with landscape parameters to determine both the initial displacement of organic matter and subsequent carbon and nitrogen cycling. The large proportion of ecosystem carbon exported off-site by slumps and slides resulted in decreased ecosystem respiration postfailure, while gullies removed a smaller portion of ecosystem carbon but strongly increased respiration and N2 O concentration. Elevated N2 O in gully soils persisted through most of the growing season, indicating sustained nitrification and denitrification in disturbed soils, representing a potential noncarbon permafrost climate feedback. While upland thermokarst formation did not substantially alter redox conditions within features, it redistributed organic matter into both oxic and anoxic environments. Across morphologies, residual organic matter cover, and predisturbance respiration explained 83% of the variation in respiration response. Consistent differences between upland thermokarst types may contribute to the

  15. Water balance along a chain of tundra lakes: A 20-year isotopic perspective

    Science.gov (United States)

    Gibson, J. J.; Reid, R.

    2014-11-01

    Stable isotope measurements and isotope mass balance (IMB) calculations are presented in support of an unprecedented 20-year water balance assessment for a tailings pond and a chain of downstream lakes at the Salmita-Tundra mine site, situated near Courageous Lake, Northwest Territories, Canada (65°03‧N; 111°11‧W). The method is shown to provide a comprehensive annual and interannual perspective of water balance fluxes along a chain of lakes during the period 1991-2010, without the need for continuous streamflow gauging, and reveals important lake-order-dependent patterns of land-surface runoff, discharge accumulation, and several key diagnostic ratios, i.e., evaporation/inflow, evaporation/evapotranspiration, land-surface-runoff/precipitation and discharge/ precipitation. Lake evaporation is found to be a significant component of the water balance, accounting for between 26% and 32% of inflow to natural lakes and between 72% and 100% of inflow to mine-tailings ponds. Evaporation/evapotranspiration averages between 7% and 22% and is found to be higher in low-precipitation years, and in watersheds with a higher proportion of lakes. Runoff ratios for land-surface drainages and runoff ratios for watersheds (including lakes) ranged between 14-47% and 20-47%, respectively, and were higher in low precipitation years, in watersheds with a higher proportion of lakes, and in watersheds less affected by mining development. We propose that in general these two runoff ratios will likely converge as lake order increases and as land cover conditions become regionally representative. Notably, the study demonstrates application of IMB, validated with streamflow measurements, to constrain local water balance in a remote low-arctic region. For IMB chain-of-lakes applications, it underlines the importance of accounting for evaporatively-enriched upstream sources to avoid overestimation of evaporation losses.

  16. Transient nature of CO2 fertilization in Arctic tundra

    Science.gov (United States)

    Oechel, Walter C.; Cowles, Sid; Grulke, Nancy; Hastings, Steven J.; Lawrence, Bill; Prudhomme, Tom; Riechers, George; Strain, Boyd; Tissue, David; Vourlitis, George

    1994-10-01

    THERE has been much debate about the effect of increased atmospheric CO2 concentrations on plant net primary production1,3 and on net ecosystem CO2 flux3-10. Apparently conflicting experimental findings could be the result of differences in genetic potential11-15 and resource availability16-20, different experimental conditions21-24 and the fact that many studies have focused on individual components of the system2,21,25-27 rather than the whole ecosystem. Here we present results of an in situ experiment on the response of an intact native ecosystem to elevated CO2. An undisturbed patch of tussock tundra at Toolik Lake, Alaska, was enclosed in greenhouses in which the CO2 level, moisture and temperature could be controlled28, and was subjected to ambient (340 p.p.m.) and elevated (680 p.p.m.) levels of CO2 and temperature (+4 °C). Air humidity, precipitation and soil water table were maintained at ambient control levels. For a doubled CO2 level alone, complete homeostasis of the CO2 flux was re-established within three years, whereas the regions exposed to a combination of higher temperatures and doubled CO2 showed persistent fertilization effect on net ecosystem carbon sequestration over this time. This difference may be due to enhanced sink activity from the direct effects of higher temperatures on growth16,29-33 and to indirect effects from enhanced nutrient supply caused by increased mineralization10,11,19,27,34. These results indicate that the responses of native ecosystems to elevated CO2 may not always be positive, and are unlikely to be straightforward. Clearly, CO2 fertilization effects must always be considered in the context of genetic limitation, resource availability and other such factors.

  17. Tundra water budget and implications of precipitation underestimation

    Science.gov (United States)

    Liljedahl, Anna K.; Hinzman, Larry D.; Kane, Douglas L.; Oechel, Walter C.; Tweedie, Craig E.; Zona, Donatella

    2017-08-01

    Difficulties in obtaining accurate precipitation measurements have limited meaningful hydrologic assessment for over a century due to performance challenges of conventional snowfall and rainfall gauges in windy environments. Here, we compare snowfall observations and bias adjusted snowfall to end-of-winter snow accumulation measurements on the ground for 16 years (1999-2014) and assess the implication of precipitation underestimation on the water balance for a low-gradient tundra wetland near Utqiagvik (formerly Barrow), Alaska (2007-2009). In agreement with other studies, and not accounting for sublimation, conventional snowfall gauges captured 23-56% of end-of-winter snow accumulation. Once snowfall and rainfall are bias adjusted, long-term annual precipitation estimates more than double (from 123 to 274 mm), highlighting the risk of studies using conventional or unadjusted precipitation that dramatically under-represent water balance components. Applying conventional precipitation information to the water balance analysis produced consistent storage deficits (79 to 152 mm) that were all larger than the largest actual deficit (75 mm), which was observed in the unusually low rainfall summer of 2007. Year-to-year variability in adjusted rainfall (±33 mm) was larger than evapotranspiration (±13 mm). Measured interannual variability in partitioning of snow into runoff (29% in 2008 to 68% in 2009) in years with similar end-of-winter snow accumulation (180 and 164 mm, respectively) highlights the importance of the previous summer's rainfall (25 and 60 mm, respectively) on spring runoff production. Incorrect representation of precipitation can therefore have major implications for Arctic water budget descriptions that in turn can alter estimates of carbon and energy fluxes.

  18. Terrimonas arctica sp. nov., isolated from Arctic tundra soil.

    Science.gov (United States)

    Jiang, Fan; Qiu, Xia; Chang, Xulu; Qu, Zhihao; Ren, Lvzhi; Kan, Wenjing; Guo, Youhao; Fang, Chengxiang; Peng, Fang

    2014-11-01

    A novel, Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated R9-86(T), was isolated from tundra soil collected near Ny-Ålesund, Svalbard Archipelago, Norway (78° N). Growth occurred at 4-28 °C (optimum, 22-25 °C) and at pH 6.0-9.0 (optimum, pH 7.0). Flexirubin-type pigments were absent. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain R9-86(T) belonged to the genus Terrimonas in the family Chitinophagaceae. 16S rRNA gene sequence similarities between strain R9-86(T) and the type strains of species of the genus Terrimonas with validly published names ranged from 93.7 to 95.0%. Strain R9-86(T) contained iso-C(15:1)-G (25.7%), iso-C(15:0) (24.5%), iso-C(17:0)-3OH (18.3%) and summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c, 8.7%) as its major cellular fatty acids; phosphatidylethanolamine and an unknown polar lipid as its main polar lipids, and MK-7 as its predominant respiratory quinone. The DNA G+C content was 48.4 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain R9-86(T) is considered to represent a novel species of the genus Terrimonas, for which the name Terrimonas arctica sp. nov. is proposed. The type strain is R9-86(T) ( =CCTCC AB 2011004(T) =NRRL B-59114(T)). © 2014 IUMS.

  19. Spirosoma flavum sp. nov., isolated from Arctic tundra soil.

    Science.gov (United States)

    Zou, Rui; Zhang, Yumin; Zhou, Xueyin; Wang, Yang; Peng, Fang

    2017-12-01

    A yellow-pigmented strain, designated Y4AR-5 T , was characterized by using a polyphasic approach. The strain was isolated from a tundra soil from near Longyearbyen, Svalbard Islands, Norway. The cells were Gram-stain-negative, aerobic, rod-shaped and non-motile. Growth occurred at 4-28 °C (optimum 20 °C) and pH 6.0-9.0 (optimum pH 8.0) and with 0-0.5 % (w/v) NaCl (optimum 0 %). The major respiratory quinone was MK-7. The polar lipids were phosphatidylethanolamine (PE), an aminophospholipid (APL), a phospholipid (PL), an unidentified aminolipid (AL) and two unidentified lipids. The results of analysis of the 16S rRNA gene indicated that the novel strain was most closely related to members of the genus Spirosoma (96.2 % sequence similarity with Spirosoma endophyticum). The genomic DNA G+C content was 45.9 mol%. The major cellular fatty acids were summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c), C16 : 1ω5c, iso-C17 : 0 3-OH and iso-C15 : 0. On the basis of its phenotypic and genotypic properties, strain Y4AR-5 T should be classified as representing a novel species of the genus Spirosoma, for which the name Spirosomaflavum sp. nov. is proposed. The type strain is Y4AR-5 T (=CCTCC AB 2015352 T =KCTC 52490 T ).

  20. Mucilaginibacter antarcticus sp. nov., isolated from tundra soil.

    Science.gov (United States)

    Zheng, Ruichen; Zhao, Yiming; Wang, Liqiu; Chang, Xulu; Zhang, Yumin; Da, Xuyang; Peng, Fang

    2016-12-01

    The novel, pale yellow bacterial strain, designated S14-88T, was isolated from a tundra soil near Antarctic Peninsula, South Shetland Islands, and its taxonomic position was investigated by a genotypic and phenotypic analysis. Cells were facultatively anaerobic, Gram-stain-negative, non-motile and rod-shaped. Growth occurred at 4-28 °C (optimum at 15 °C), at pH 7.0-8.0 (optimum at 7.0) and with 0-0.6 % (w/v) NaCl (optimum, no NaCl). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S14-88T formed a lineage within the genus Mucilaginibacter. The 16S rRNA gene sequence similarity between strain S14-88T and the type strains of related species ranged from 92.2 to 96.5 %, and the 16S rRNA gene sequence of S14-88T showed highest similarity of 96.5 % to Mucilaginibacter soyangensis HME6664T. The major cellular fatty acids of strain S14-88T were iso-C15 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The major respiratory quinone was menaquinone MK-7, and the main polar lipid was phosphatidylethanolamine. The DNA G+C content of strain S14-88T was 42.3 mol%. On the basis of the evidence presented in this study, strain S14-88T is considered to represent a novel species of the genus Mucilaginibacter, for which the name Mucilaginibacter antarcticus sp. nov. is proposed. The type strain is S14-88T (=CCTCC AB 2015321T=KCTC 52232T).

  1. Roseomonas arcticisoli sp. nov., isolated from Arctic tundra soil.

    Science.gov (United States)

    Kim, Myong Chol; Rim, Songguk; Pak, Sehong; Ren, Lvzhi; Zhang, Yumin; Chang, Xulu; Li, Xuhuan; Fang, Chengxiang; Zheng, Congyi; Peng, Fang

    2016-10-01

    A pale pink, Gram-reaction-negative, non-motile, aerobic bacterium, designated MC 3624T, was isolated from a tundra soil near Ny-Ålesund, Svalbard Archipelago, Norway (78° N). Growth occurred at 10-37 °C (optimum 25-30 °C) and at pH 6.0-9.0 (optimum pH 8.0). The predominant fatty acids were C16 : 0 (17.7 %), C18 : 1ω7c 11-methyl (13.4 %), summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) (10.1 %) and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c) (38.3 %). The major respiratory quinone was ubiquinone-10, and the main polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylcholine and an unidentified aminolipids. The DNA G+C content was 68.9 mol%. Carotenoids of the spirilloxanthin series were produced. The nearest neighbour to the novel strain was Roseomonas wooponensis WW53T (94.36 % 16S rRNA gene sequence similarity). On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain MC 3624T represents a novel species of the genus Roseomonas, for which the name Roseomonas arcticisoli sp. nov. is proposed. The type strain is MC 3624T (=CCTCC AB 2014278T=LMG 28637T).

  2. A reduced-order modeling approach to represent subgrid-scale hydrological dynamics for land-surface simulations: application in a polygonal tundra landscape

    Science.gov (United States)

    Pau, G. S. H.; Bisht, G.; Riley, W. J.

    2014-09-01

    Existing land surface models (LSMs) describe physical and biological processes that occur over a wide range of spatial and temporal scales. For example, biogeochemical and hydrological processes responsible for carbon (CO2, CH4) exchanges with the atmosphere range from the molecular scale (pore-scale O2 consumption) to tens of kilometers (vegetation distribution, river networks). Additionally, many processes within LSMs are nonlinearly coupled (e.g., methane production and soil moisture dynamics), and therefore simple linear upscaling techniques can result in large prediction error. In this paper we applied a reduced-order modeling (ROM) technique known as "proper orthogonal decomposition mapping method" that reconstructs temporally resolved fine-resolution solutions based on coarse-resolution solutions. We developed four different methods and applied them to four study sites in a polygonal tundra landscape near Barrow, Alaska. Coupled surface-subsurface isothermal simulations were performed for summer months (June-September) at fine (0.25 m) and coarse (8 m) horizontal resolutions. We used simulation results from three summer seasons (1998-2000) to build ROMs of the 4-D soil moisture field for the study sites individually (single-site) and aggregated (multi-site). The results indicate that the ROM produced a significant computational speedup (> 103) with very small relative approximation error (training the ROM. We also demonstrate that our approach: (1) efficiently corrects for coarse-resolution model bias and (2) can be used for polygonal tundra sites not included in the training data set with relatively good accuracy (< 1.7% relative error), thereby allowing for the possibility of applying these ROMs across a much larger landscape. By coupling the ROMs constructed at different scales together hierarchically, this method has the potential to efficiently increase the resolution of land models for coupled climate simulations to spatial scales consistent with

  3. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    Science.gov (United States)

    Rocha, Adrian V.; Loranty, Michael M.; Higuera, Phil E.; Mack, Michelle C.; Hu, Feng Sheng; Jones, Benjamin M.; Breen, Amy L.; Rastetter, Edward B.; Goetz, Scott J.; Shaver, Gus R.

    2012-12-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

  4. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    International Nuclear Information System (INIS)

    Rocha, Adrian V; Loranty, Michael M; Higuera, Phil E; Mack, Michelle C; Hu Fengsheng; Jones, Benjamin M; Breen, Amy L; Rastetter, Edward B; Shaver, Gus R; Goetz, Scott J

    2012-01-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required. (letter)

  5. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    Science.gov (United States)

    Rocha, Adrian V.; Loranty, Michael M.; Higuera, Phil E.; Mack, Michelle C.; Hu, Feng Sheng; Jones, Benjamin M.; Breen, Amy L.; Rastetter, Edward B.; Goetz, Scott J.; Shaver, Gus R.

    2012-01-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

  6. 2015 DOE Final UF Report. Effects of Warming the Deep Soil and Permafrost on Ecosystem Carbon Balance in Alaskan Tundra. A Coupled Measurement and Modeling Approach

    Energy Technology Data Exchange (ETDEWEB)

    Schuur, Edward [Univ. of Florida, Gainesville, FL (United States)

    2015-06-11

    The major research goal of this project was to understand and quantify the fate of carbon stored in permafrost ecosystems using a combination of field and laboratory experiments to measure isotope ratios and C fluxes in a tundra ecosystem exposed to experimental warming. Field measurements centered on the establishment of a two-factor experimental warming using a snow fence and open top chambers to increase winter and summer temperatures alone, and in combination, at a tundra field site at the Eight Mile Lake watershed near Healy, Alaska. The objective of this experimental warming was to significantly raise air and deep soil temperatures and increase the depth of thaw beyond that of previous warming experiments. Detecting the loss and fate of the old permafrost C pool remains a major challenge. Because soil C has been accumulating in these ecosystems over the past 10,000 years, there is a strong difference between the radiocarbon isotopic composition of C deep in the soil profile and permafrost compared to that near the soil surface. This large range of isotopic variability is unique to radiocarbon and provides a valuable and sensitive fingerprint for detecting the loss of old soil C as permafrost thaws.

  7. Seasonal variability of leaf area index and foliar nitrogen in contrasting dry-mesic tundras

    DEFF Research Database (Denmark)

    Campioli, Matteo; Michelsen, Anders; Lemeur, Raoul

    2009-01-01

    Assimilation and exchange of carbon for arctic ecosystems depend strongly on leaf area index (LAI) and total foliar nitrogen (TFN). For dry-mesic tundras, the seasonality of these characteristics is unexplored. We addressed this knowledge gap by measuring variations of LAI and TFN at five contras...

  8. Disturbance and Recovery of Arctic Alaskan Tundra Terrain. A Review of Recent Investigations.

    Science.gov (United States)

    1987-07-01

    analogous to situations where thermal thermoerosional niches (e.g. Williams 1952, erosion has been induced by off-road vehicle Abramov 1957, Walker and...assess environmental sensitivity 283-294. across large tundra areas could be improved with Abramov , R.V. (1957) Nish: Vytaivaniya (thaw- advances in

  9. DIFFERENTIATION IN N15 UPTAKE AND THE ORGANIZATION OF AN ARCTIC TUNDRA PLANT COMMUNITY

    Science.gov (United States)

    We used N15 soil-labeling techniques to examine how the dominant species in a N-limited, tussock tundra plant community partitioned soil N, and how such partitioning may contribute to community organization. The five most abundant species were well differentiated with respect to...

  10. Spring feeding by pink-footed geese reduces carbon stocks and sink strength in tundra ecosystems

    NARCIS (Netherlands)

    Van der Wal, R.; Sjögersten, S.; Woodin, S.J.; Cooper, E.J.; Jónsdóttir, I.S.; Kuijper, D.; Fox, A.D.; Huiskes, A.H.L.

    2007-01-01

    Tundra ecosystems are widely recognized as precious areas and globally important carbon (C) sinks, yet our understanding of potential threats to these habitats and their large soil C store is limited. Land-use changes and conservation measures in temperate regions have led to a dramatic expansion of

  11. Geomorphic determinants of species composition of alpine tundra, Glacier National Park, U.S.A.

    Science.gov (United States)

    George P. Malanson,; Bengtson, Lindsey E.; Fagre, Daniel B.

    2012-01-01

    Because the distribution of alpine tundra is associated with spatially limited cold climates, global warming may threaten its local extent or existence. This notion has been challenged, however, based on observations of the diversity of alpine tundra in small areas primarily due to topographic variation. The importance of diversity in temperature or moisture conditions caused by topographic variation is an open question, and we extend this to geomorphology more generally. The extent to which geomorphic variation per se, based on relatively easily assessed indicators, can account for the variation in alpine tundra community composition is analyzed versus the inclusion of broad indicators of regional climate variation. Visual assessments of topography are quantified and reduced using principal components analysis (PCA). Observations of species cover are reduced using detrended correspondence analysis (DCA). A “best subsets” regression approach using the Akaike Information Criterion for selection of variables is compared to a simple stepwise regression with DCA scores as the dependent variable and scores on significant PCA axes plus more direct measures of topography as independent variables. Models with geographic coordinates (representing regional climate gradients) excluded explain almost as much variation in community composition as models with them included, although they are important contributors to the latter. The geomorphic variables in the model are those associated with local moisture differences such as snowbeds. The potential local variability of alpine tundra can be a buffer against climate change, but change in precipitation may be as important as change in temperature.

  12. Snowpack fluxes of methane and carbon dioxide from high Arctic tundra

    DEFF Research Database (Denmark)

    Pirk, Norbert; Tamstorf, Mikkel P.; Lund, Magnus

    2016-01-01

    butdetected a pulse in the 13C-CH4stable isotopic signature of the soil’s CH4source during snowmelt, whichsuggests the release of a CH4reservoir that was strongly affected by methanotrophic microorganisms. In thepolygonal tundra of Adventdalen, the snowpack featured several ice layers, which suppressed...

  13. Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

    NARCIS (Netherlands)

    Juszak, Inge; Eugster, Werner; Heijmans, Monique M.P.D.; Schaepman-Strub, Gabriela

    2016-01-01

    Vegetation changes, such as shrub encroachment and wetland expansion, have been observed in many Arctic tundra regions. These changes feed back to permafrost and climate. Permafrost can be protected by soil shading through vegetation as it reduces the amount of solar energy available for thawing.

  14. Leaves are just the tip of the iceberg: A review of plant roots in Arctic tundra

    Science.gov (United States)

    Iversen, C. M.; Sloan, V. L.; Sullivan, P.; Euskirchen, E. S.; McGuire, A. D.; Norby, R. J.; Walker, A. P.; Warren, J.; Wullschleger, S. D.

    2013-12-01

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, rooting dynamics remain some of the least understood aspects of plant growth in the Arctic. Our goal in this review is to synthesize the available literature on arctic roots, and also their treatment in models. Belowground plant biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Roots are shallowly distributed, and often found in a thick organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and preference for different forms of nitrogen (N) may affect plant species competition and distribution under changing environmental conditions, and should be better represented in large-scale models. Future research should focus on estimates of arctic root production and lifespan, across the diversity of tundra ecosystems that exist in the Arctic. Improved linkages between root traits and easily-measured aboveground traits will facilitate the representation of roots in large-scale land surface models, and advance our understanding of the contribution of roots to ecosystem C and N cycling in the Arctic under current and future climates.

  15. Movement of foraging Tundra Swans explained by spatial pattern in cryptic food densities

    NARCIS (Netherlands)

    Klaassen, R.H.G.; Nolet, B.A.; Bankert, D.

    2006-01-01

    We tested whether Tundra Swans use information on the spatial distribution of cryptic food items (belowground Sago pondweed tubers) to shape their movement paths. In a continuous environment, swans create their own food patches by digging craters, which they exploit in several feeding bouts. Series

  16. Response of CO2 exchange in a tussock tundra ecosystem to permafrost thaw and thermokarst development

    Science.gov (United States)

    Jason Vogel; Edward A.G. Schuur; Christian Trucco; Hanna. Lee

    2009-01-01

    Climate change in high latitudes can lead to permafrost thaw, which in ice-rich soils can result in ground subsidence, or thermokarst. In interior Alaska, we examined seasonal and annual ecosystem CO2 exchange using static and automatic chamber measurements in three areas of a moist acidic tundra ecosystem undergoing varying degrees of permafrost...

  17. Resistance and resilience of tundra plant communities to disturbance by winter seismic vehicles

    International Nuclear Information System (INIS)

    Felix, N.A.; Raynolds, M.K.; Jorgenson, J.C.; DuBois, K.E.

    1992-01-01

    Effects of winter seismic exploration on arctic tundra were evaluated on the coastal plain of the Arctic National Wildlife Refuge, four to five growing seasons after disturbance. Plant cover, active layer depths, and track depression were measured at plots representing major tundra plant communities and different levels of initial disturbance. Results are compared with the initial effects reported earlier. Little resilience was seen in any vegetation type, with no clearly decreasing trends in community dissimilarity. Active layer depths remained greater on plots in all nonriparian vegetation types, and most plots still had visible trails. Decreases in plant cover persisted on most plots, although a few species showed recovery or increases in cover above predisturbance level. Moist sedge-shrub tundra and dryas terraces had the largest community dissimilarities initially, showing the least resistance to high levels of winter vehicle disturbance. Community dissimilarity continued to increase for five seasons in moist sedge-shrub tundra, with species composition changing to higher sedge cover and lower shrub cover. The resilience amplitude may have been exceeded on four plots which had significant track depression

  18. Landscape variability of vegetation change across the forest to tundra transition of central Canada

    Science.gov (United States)

    Bonney, Mitchell Thurston

    Widespread vegetation productivity increases in tundra ecosystems and stagnation, or even productivity decreases, in boreal forest ecosystems have been detected from coarse-scale remote sensing observations over the last few decades. However, finer-scale Landsat studies have shown that these changes are heterogeneous and may be related to landscape and regional variability in climate, land cover, topography and moisture. In this study, a Landsat Normalized Difference Vegetation Index (NDVI) time-series (1984-2016) was examined for a study area spanning the entirety of the sub-Arctic boreal forest to Low Arctic tundra transition of central Canada (i.e., Yellowknife to the Arctic Ocean). NDVI trend analysis indicated that 27% of un-masked pixels in the study area exhibited a significant (p temperatures, shrubland and forest land cover, closer proximity to major drainage systems, longer distances from major lakes and lower elevations were generally more important and associated with larger positive NDVI trends. These findings indicate that the largest positive NDVI trends were primarily associated with the increased productivity of shrubby environments, especially at, and north of the forest-tundra ecotone in areas with more favorable growing conditions. Smaller and less significant NDVI trends in boreal forest environments south of the forest-tundra ecotone were likely associated with long-term recovery from fire disturbance rather than the variables analyzed here.

  19. Importance of Marine-Derived Nutrients Supplied by Planktivorous Seabirds to High Arctic Tundra Plant Communities.

    Science.gov (United States)

    Zwolicki, Adrian; Zmudczyńska-Skarbek, Katarzyna; Richard, Pierre; Stempniewicz, Lech

    2016-01-01

    We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale.

  20. CLIMATIC EFFECTS ON TUNDRA CARBON STORAGE INFERRED FROM EXPERIMENTAL DATA AND A MODEL

    Science.gov (United States)

    We used a process-based model of ecosystem carbon (C) and nitrogen (N)dynamics, MBL-GEM (Marine Biological Laboratory General Ecosystem Model), to integrated and analyze the results of several experiments that examined the response of arctic tussock tundra to manipulations of CO2...

  1. Tundra landform and vegetation productivity trend maps for the Arctic Coastal Plain of northern Alaska.

    Science.gov (United States)

    Lara, Mark J; Nitze, Ingmar; Grosse, Guido; McGuire, A David

    2018-04-10

    Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10-100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (~60,000 km 2 ) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30 m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999-2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling.

  2. Plant functional type affects nitrogen use efficiency in high-Arctic tundra

    Czech Academy of Sciences Publication Activity Database

    Oulehle, F.; Rowe, E. C.; Myška, Oldřich; Chuman, T.; Evans, C.D.

    2016-01-01

    Roč. 94, mar (2016), s. 19-28 ISSN 0038-0717 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional support: RVO:67179843 Keywords : Arctic * Nitrogen * Isotope * Mineralization * Nitrification * Tundra Subject RIV: EH - Ecology, Behaviour Impact factor: 4.857, year: 2016

  3. The effect of nutrient deposition on bacterial communities in Arctic tundra soil

    Science.gov (United States)

    Barbara J. Campbell; Shawn W. Polson; Thomas E. Hanson; Michelle C. Mack; Edward A.G. Schuur

    2010-01-01

    The microbial communities of high-latitude ecosystems are expected to experience rapid changes over the next century due to climate warming and increased deposition of reactive nitrogen, changes that will likely affect microbial community structure and function. In moist acidic tundra (MAT) soils on the North Slope of the Brooks Range, Alaska, substantial losses of C...

  4. Estimation and extrapolation of soil properties in the Siberian tundra, using field spectroscopy

    NARCIS (Netherlands)

    Bartholomeus, H.; Schaepman-Strub, G.; Blok, D.; Udaltsov, S.; Sofronov, R.

    2010-01-01

    The Siberian tundra is a complex and sensitive ecosystem. Predicted global warming will be highest in the Arctic and will severely affect permafrost environments. Due to its large spatial extent and large stocks of soil organic carbon, changes to the carbon fluxes in the Arctic will have significant

  5. Sphingomonas antarctica sp. nov., isolated from Antarctic tundra soil.

    Science.gov (United States)

    Huang, Yao; Wei, Ziyan; Danzeng, Wangmu; Kim, Myong Chol; Zhu, Guoxin; Zhang, Yumin; Liu, Zuobing; Peng, Fang

    2017-10-01

    Strain 200 T , isolated from a soil sample taken from Antarctic tundra soil around Zhongshan Station, was found to be a Gram-stain-negative, yellow-pigmented, catalase-positive, oxidase-negative, non-motile, non-spore-forming, rod-shaped and aerobic bacterium. Strain 200 T grew optimally at pH 7.0 and in the absence of NaCl on R2A. Its optimum growth temperature was 20 °C. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 200 T belonged to the genus Sphingomonas. Strain 200 T showed the highest sequence similarities to Sphingomonas kyeonggiense THG-DT81 T (95.1 %) and Sphingomonas molluscorum KMM 3882 T (95.1 %). Chemotaxonomic analysis showed that strain 200 T had characteristics typical of members of the genus Sphingomonas. Ubiquinone 10 was the predominant respiratory quinone and sym-homospermidine was the polyamine. The major polar lipids were sphingoglycolipid, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and phosphatidylcholine. The G+C content of the genomic DNA was determined to be 60.9 mol%. Strain 200 T contained C16 : 0 (31.6 %), summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c, 22.7 %), summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c, 11.2 %), C18 : 0 (7.8 %) and C14 : 0 2OH (6.7 %) as the major cellular fatty acids. On the basis of phylogenetic analysis, and physiological and biochemical characterization, strain 200 T should be classified as representing a novel species of the genus Sphingomonas, for which the name Sphingomonasantarctica sp. nov. is proposed. The type strain is 200 T (=CCTCC AB 2016064 T =KCTC 52488 T ).

  6. Assessment of tundra-taiga boundary changes using MODIS LAI data

    Science.gov (United States)

    Lee, Min-ji; Han, Kyung-Soo; Pi, Kyoung-Jin; Kim, Sang-Il; Kim, In-Hwan

    2011-11-01

    Surface of the earth temperature of the earth caused phenomenon that rise and is global warming as greenhouse gas concentration into waiting by continuous discharge of greenhouse gas increases since passing industrial revolution. While gravity about climate fluctuation is risen worldwide, place that can diminish successively biggest surface of the earth change by global warming is high latitude area of polar regions. This study observed distribution of vegetation to confirm change of tundra-taiga boundary. Tundra-taiga boundary is used to observe the transfer of vegetation pattern because it is very sensitive to human activity, natural disturbances and climate change. The circumpolar tundra-taiga boundary could observe reaction about some change. Reaction and confirmation about climate change were definite than other place. This study used Leaf Area Index(LAI) 8-Day data in August from 2000 to 2009 that acquire from Terra satellite MODerate resolution Imaging Spectroradiometer(MODIS) sensor and used Köppen Climate Map, Global Land Cover 2000 for reference data. This study conducted analysis of spatial distribution in low density vegetated areas and inter-annual / zonal analysis for using the long period data of LAI. Change of LAI was confirmed by analysis based on boundary value of LAI in study area. Development of vegetation could be confirmed by area of grown vegetation(730,325km2 ) than area of reduced vegetation(22,372km2 ) in tundra climate. Also, area was increased with the latitude 64°N~66° N as the center and around the latitude 62° N through area analysis by latitude. Vegetation of tundra-taiga boundary was general increase from 2000 to 2009. While area of reduced vegetation was a little, area of vegetation growth and development was increased significantly.

  7. Snowmelt runoff from northern alpine tundra hillslopes: major processes and methods of simulation

    Directory of Open Access Journals (Sweden)

    W. L. Quinton

    2004-01-01

    Full Text Available In northern alpine tundra, large slope gradients, late-lying snow drifts and shallow soils overlying impermeable substrates all contribute to large hillslope runoff volumes during the spring freshet. Understanding the processes and pathways of hillslope runoff in this environment is, therefore, critical to understanding the water cycle within northern alpine tundra ecosystems. This study: (a presents the results of a field study on runoff from a sub-alpine tundra hillslope with a large snow drift during the spring melt period; (b identifies the major runoff processes that must be represented in simulations of snowmelt runoff from sub-alpine tundra hillslopes; (c describes how these processes can be represented in a numerical simulation model; and d compares field measurements with modelled output to validate or refute the conceptual understanding of runoff generation embodied in the process simulations. The study was conducted at Granger Creek catchment, 15 km south of Whitehorse, Yukon Territory, Canada, on a north-facing slope below a late-lying snow drift. For the freshet period, the major processes to be represented in a runoff model include the rate of meltwater release from the late-lying snowdrift, the elevation and thickness of the saturated layer, the magnitude of the soil permeability and its variation with depth. The daily cycle of net all-wave radiation was observed to drive the diurnal pulses of melt water from the drift; this, in turn, was found to control the daily pulses of flow through the hillslope subsurface and in the stream channel. The computed rate of frost table lowering fell within the observed values; however, there was wide variation among the measured frost table depths. Spatial variability in frost table depth would result in spatial variabilities in saturated layer depth and thickness, which would, in turn, produce variations in subsurface flow rates over the slope, including preferential flowpaths. Keywords

  8. Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake.

    Science.gov (United States)

    Sweet, Shannan K; Griffin, Kevin L; Steltzer, Heidi; Gough, Laura; Boelman, Natalie T

    2015-06-01

    Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community-specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra-specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake. © 2015 John Wiley & Sons Ltd.

  9. Response of a tundra ecosystem to elevated atmospheric carbon dioxide and CO{sub 2}-induced climate change. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Oechel, W.C.

    1996-11-01

    The overall objective of this research was to document current patterns of CO{sub 2} flux in selected locations of the circumpolar arctic, and to develop the information necessary to predict how these fluxes may be affected by climate change. In fulfillment of these objectives, net CO{sub 2} flux was measured at several sites on the North Slope of Alaska during the 1990--94 growing season (June--August) to determine the local and regional patterns of seasonal CO{sub 2} exchange. In addition, net CO{sub 2} flux was measured in the Russian and Icelandic Arctic to determine if the patterns of CO{sub 2} exchange observed in Arctic Alaska were representative of the circumpolar Arctic, while cold-season CO{sub 2} flux measurements were carried out during the 1993--94 winter season to determine the magnitude of CO{sub 2} efflux not accounted for by the growing season measurements. Manipulations of soil water table depth and surface temperature, which were identified from the extensive measurements as being the most important variables in determining the magnitude and direction of net CO{sub 2} exchange, were carried out during the 1993--94 growing seasons in tussock and wet sedge tundra ecosystems. Finally, measurements of CH{sub 4} flux were also measured at several of the North Slope study sites during the 1990--91 growing seasons.

  10. Response of a tundra ecosytem to elevated atmospheric carbon dioxide and CO{sub 2}-induced climate change. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Oechel, W.C.

    1996-11-01

    The overall objective of this research was to document current patterns of CO{sub 2} flux in selected locations of the circumpolar arctic, and to develop the information necessary to predict how these fluxes may be affected by climate change. In fulfillment of these objectives, net CO{sub 2} flux was measured at several sites on the North Slope of Alaska during the 1990-94 growing season (June-August) to determine the local and regional patterns, of seasonal CO{sub 2} exchange. In addition, net CO{sub 2} flux was measured in the Russian and Icelandic Arctic to determine if the patterns of CO{sub 2} exchange observed in Arctic Alaska were representative of the circumpolar arctic, while cold-season CO{sub 2} flux measurements were carried out during the 1993-94 winter season to determine the magnitude of CO{sub 2} efflux not accounted for by the growing season measurements. Manipulations of soil water table depth and surface temperature, which were identified from the extensive measurements as being the most important variables in determining the magnitude and direction of net CO{sub 2} exchange, were carried out during the 1993-94 growing seasons in tussock and wet sedge tundra ecosystems. Finally, measurements of CH{sub 4} flux were also measured at several of the North Slope study sites during the 1990-91 growing seasons. Measurements were made on small (e.g. 0.5 m{sup 2}) plots using a portable gas-exchange system and cuvette. The sample design allowed frequent measurements of net CO{sub 2} exchange and respiration over diurnal and seasonal cycles, and a large spatial extent that incorporated both locally and regionally diverse tundra surface types. Measurements both within and between ecosystem types typically extended over soil water table depth and temperature gradients, allowing for the indirect analysis of the effects of anticipated climate change scenarios on net CO{sub 2} exchange. In situ experiments provided a direct means for testing hypotheses.

  11. Potential of radioactive and other waste disposals on the continental margin by natural dispersal processes

    International Nuclear Information System (INIS)

    Ryan, W.B.F.; Farre, J.A.

    1983-01-01

    Mass wasting, an erosional process, has recently been active at deepwater waste disposal sites on the mid-Atlantic margin of the United States. On the continental slope there is a subsea drainage network consisting of canyons, gullies, and chutes, and there are meandering channels, erosional scars, and debris aprons present on the continental rise. Fresh-looking blocks of 40 to 45 million-year-old marl and chalk (from cobble to boulder size) are strewn among canisters of low-level radioactive wastes. Some of the blocks have traveled from their original place of deposition for distances in excess of 170 km. Waste containers on the continental slope and rise cannot be considered to be disposed of permanently. The drainage network of the slope provides a natural process for collecting wastes over a catchment area, and for concentrating it with interim storage in canyons. Erosion by slumping, sliding, and debris flows ultimately will transport the wastes from the continental slope and disperse it over potentially large areas on the continental rise and abyssal plain. If it is desirable that the wastes be buried in the seafloor and isolated from the environment, then the continental slope and rise are not attractive repositories. If, however, it is deemed beneficial that the wastes ultimately be dispersed over a wide area, then the continental slope could be used as a disposal site

  12. Site scale wetness classification of tundra regions with C-band SAR satellite data

    DEFF Research Database (Denmark)

    Widhalm, Barbara; Bartsch, Annett; Siewert, Matthias Benjamin

    2016-01-01

    A representative and consistent wetland map for the circumpolar region is required for a range of applications including modelling of permafrost properties as well as upscaling of carbon pools and fluxes. Synthetic Aperture Radar (SAR) data has been shown to be suitable for wetland mapping...

  13. Mg/Ca of Continental Ostracode Shells

    Science.gov (United States)

    Ito, E.; Forester, R. M.; Marco-Barba, J.; Mezquita, F.

    2007-12-01

    Marine ionic chemistry is thought to remain constant. This, together with the belief that marine calcifiers partition Mg/Ca in a systematic manner as functions of temperature (and Mg/Ca) of water forms the basis of the Mg/Ca thermometer. In continental settings both of these assumptions are usually not true. Continental waters contain a wide variety of solutes in absolute and relative ion concentrations. Hence, waters with identical Mg/Ca may have very different concentrations of Mg and Ca and very different anions. Here we use two examples to focus on the effects of ion chemistry on Mg/Ca partitioning in continental ostracode shells and we ignore the complexities of solute evolution, which can change Mg/Ca over timescales of minutes to millennia. Palacios-Fest and Dettman (2001) conducted a monthly study of ,Cypridopsis vidua at El Yeso Lake in Sonora, Mexico. They established a relation between temperature and average shell Mg/Ca using regression analyses on averaged data. When their Mg/Ca-temperature relation is applied to monthly ,C. vidua data from Page Pond near Cleveland, Ohio, water temperatures of -8 to -1°C are obtained. The observed Mg/Ca ranges for El Yeso Lake (0.31 to 0.46) and Page Pond (0.33 to 0.46) are similar, as are their specific conductivities (700 to 850μS for El Yeso Lake; 400 to 600μS for Page Pond). However, [Ca] is 140-260 mg/L for El Yeso, but only 70-90 mg/L for Page Pond. Page Pond data, in fact, shows a good temperature shell Mg/Ca relation for .C. vidua, but the relation is different from that at El Yeso. Hence, shell Mg/Ca is a multi-valued, family of curves function of temperature and Mg/Ca of water that depends on the [Mg] and [Ca] values in water and perhaps other factors. Our second example comes from sites near Valencia, Spain and involves shell data for ,Cyprideis torosa, an estuarine ostracode that is tolerant of a wide range of salinity and can live in continental waters as long as the carbonate alkalinity to Ca ratio is

  14. Circumpolar spatio-temporal patterns and contributing climatic factors of wildfire activity in the Arctic tundra from 2001-2015

    Science.gov (United States)

    Masrur, Arif; Petrov, Andrey N.; DeGroote, John

    2018-01-01

    Recent years have seen an increased frequency of wildfire events in different parts of Arctic tundra ecosystems. Contemporary studies have largely attributed these wildfire events to the Arctic’s rapidly changing climate and increased atmospheric disturbances (i.e. thunderstorms). However, existing research has primarily examined the wildfire-climate dynamics of individual large wildfire events. No studies have investigated wildfire activity, including climatic drivers, for the entire tundra biome across multiple years, i.e. at the planetary scale. To address this limitation, this paper provides a planetary/circumpolar scale analyses of space-time patterns of tundra wildfire occurrence and climatic association in the Arctic over a 15 year period (2001-2015). In doing so, we have leveraged and analyzed NASA Terra’s MODIS active fire and MERRA climate reanalysis products at multiple temporal scales (decadal, seasonal and monthly). Our exploratory spatial data analysis found that tundra wildfire occurrence was spatially clustered and fire intensity was spatially autocorrelated across the Arctic regions. Most of the wildfire events occurred in the peak summer months (June-August). Our multi-temporal (decadal, seasonal and monthly) scale analyses provide further support to the link between climate variability and wildfire activity. Specifically, we found that warm and dry conditions in the late spring to mid-summer influenced tundra wildfire occurrence, spatio-temporal distribution, and fire intensity. Additionally, reduced average surface precipitation and soil moisture levels in the winter-spring period were associated with increased fire intensity in the following summer. These findings enrich contemporary knowledge on tundra wildfire’s spatial and seasonal patterns, and shed new light on tundra wildfire-climate relationships in the circumpolar context. Furthermore, this first pan-Arctic analysis provides a strong incentive and direction for future studies

  15. First report of Setaria tundra in roe deer (Capreolus capreolus) from the Iberian Peninsula inferred from molecular data: epidemiological implications.

    Science.gov (United States)

    Angelone-Alasaad, Samer; Jowers, Michael J; Panadero, Rosario; Pérez-Creo, Ana; Pajares, Gerardo; Díez-Baños, Pablo; Soriguer, Ramón C; Morrondo, Patrocinio

    2016-09-29

    Filarioid nematode parasites are major health hazards with important medical, veterinary and economic implications. Recently, they have been considered as indicators of climate change. In this paper, we report the first record of Setaria tundra in roe deer from the Iberian Peninsula. Adult S. tundra were collected from the peritoneal cavity during the post-mortem examination of a 2 year-old male roe deer, which belonged to a private fenced estate in La Alcarria (Guadalajara, Spain). Since 2012, the area has suffered a high roe deer decline rate (75 %), for unknown reasons. Aiming to support the morphological identification and to determine the phylogenetic position of S. tundra recovered from the roe deer, a fragment of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene from the two morphologically identified parasites was amplified, sequenced and compared with corresponding sequences of other filarioid nematode species. Phylogenetic analyses revealed that the isolate of S. tundra recovered was basal to all other formely reported Setaria tundra sequences. The presence of all other haplotypes in Northern Europe may be indicative of a South to North outbreak in Europe. This is the first report of S. tundra in roe deer from the Iberian Peninsula, with interesting phylogenetic results, which may have further implications in the epidemiological and genetic studies of these filarioid parasites. More studies are needed to explore the reasons and dynamics behind the rapid host/geographic expansion of the filarioid parasites in Europe.

  16. The Continental Drift Convection Cell

    Science.gov (United States)

    Whitehead, J. A.; Behn, M. D.

    2014-12-01

    Continents on Earth periodically assemble to form supercontinents, and then break up again into smaller continental blocks (the Wilson Cycle). Highly developed but realistic numerical models cannot resolve if continents respond passively to mantle convection or whether they modulate flow. Our simplified numerical model addresses this problem: A thermally insulating continent floats on a stress-free surface for infinite Prandtl number cellular convection with constant material properties in a chamber 8 times longer than its depth. The continent moves back and forth across the chamber driven by a "continental drift convection cell" of a form not previously described. Subduction exists at the upstream end with cold slabs dipping at an angle beneath the moving continent. Fluid moves with the continent in the upper region of this cell with return flow near the bottom. Many continent/subduction regions on Earth have these features. The drifting cell enhances vertical heat transport by approximately 30% compared to a fixed continent, especially at the core-mantle boundary, and significantly decreases lateral mantle temperature differences. However, continent drift or fixity has smaller effects on profiles of horizontally averaged temperature. Although calculations are done at Rayleigh numbers lower than expected for Earth's mantle (2x105 and 106), the drift speed extrapolates to reasonable Wilson Cycle speeds for larger Ra.

  17. Aboveground and belowground responses to nutrient additions and herbivore exclusion in Arctic tundra ecosystems in northern Alaska

    Science.gov (United States)

    Moore, J. C.; Gough, L.; Simpson, R.; Johnson, D. R.

    2011-12-01

    The Arctic has experienced significant increased regional warming over the past 30 years. Warming generally increases tundra soil nutrient availability by creating a more favorable environment for plant growth, decomposition and nutrient mineralization. Aboveground there has been a "greening" of the Arctic with increased net primary productivity (NPP), and an increase in woody vegetation. Concurrent with the changes aboveground has been an increase in root growth at lower depths and a loss of soil organic C (40 -100 g C m-2 yr-1). Given that arctic soils contain 14% of the global soil C pool, understanding the mechanisms behind shifts of this magnitude that are changing arctic soils from a net sink to a net source of atmospheric C is critical. We took an integrated multi-trophic level approach to examine how altering soil nutrients and mammalian herbivore activity affects vegetation, soil fauna, and microbial communities as well as soil physical characteristics in moist acidic (MAT) and dry heath (DH) tundra. Our work was conducted at the Arctic LTER site in northern Alaska. We sampled the nutrient (controls and annual N+P additions) and herbivore (controls and exclosures) manipulations established in 1996 after 10 years of treatment. Models that incorporated the biomass estimates from the field were used to characterize the trophic structure of the belowground food web and to estimate carbon flux among soil organisms and C-mineralization rates. Both MAT and DH exhibited significant increases in NPP and root growth and changes in vegetation structure with transitions from a mixed community to deciduous shrubs in MAT and from lichens to grasses and shrubs in DH, with nutrient additions and herbivore exclosures. Belowground responses to the treatments were dependent on ecosystem type, but exposed alterations in trophic structure that included changes in microbial biomass, the establishment of microbivorous enchytreaids, increases in root-feeding nematodes, and

  18. Ground measurements of the hemispherical-directional reflectance of Arctic snow covered tundra for the validation of satellite remote sensing products

    Science.gov (United States)

    Ball, C. P.; Marks, A. A.; Green, P.; Mac Arthur, A.; Fox, N.; King, M. D.

    2013-12-01

    Surface albedo is the hemispherical and wavelength integrated reflectance over the visible, near infrared and shortwave infrared regions of the solar spectrum. The albedo of Arctic snow can be in excess of 0.8 and it is a critical component in the global radiation budget because it determines the proportion of solar radiation absorbed, and reflected, over a large part of the Earth's surface. We present here our first results of the angularly resolved surface reflectance of Arctic snow at high solar zenith angles (~80°) suitable for the validation of satellite remote sensing products. The hemispherical directional reflectance factor (HDRF) of Arctic snow covered tundra was measured using the GonioRAdiometric Spectrometer System (GRASS) during a three-week field campaign in Ny-Ålesund, Svalbard, in March/April 2013. The measurements provide one of few existing HDRF datasets at high solar zenith angles for wind-blown Arctic snow covered tundra (conditions typical of the Arctic region), and the first ground-based measure of HDRF at Ny-Ålesund. The HDRF was recorded under clear sky conditions with 10° intervals in view zenith, and 30° intervals in view azimuth, for several typical sites over a wavelength range of 400-1500 nm at 1 nm resolution. Satellite sensors such as MODIS, AVHRR and VIIRS offer a method to monitor the surface albedo with high spatial and temporal resolution. However, snow reflectance is anisotropic and is dependent on view and illumination angle and the wavelength of the incident light. Spaceborne sensors subtend a discrete angle to the target surface and measure radiance over a limited number of narrow spectral bands. Therefore, the derivation of the surface albedo requires accurate knowledge of the surfaces bidirectional reflectance as a function of wavelength. The ultimate accuracy to which satellite sensors are able to measure snow surface properties such as albedo is dependant on the accuracy of the BRDF model, which can only be assessed

  19. Using continental land loading for routine data analysis

    Science.gov (United States)

    Petrov, L.

    2013-12-01

    The availability of the hydrological models that are updated regularly made it feasible to apply for analysis of space geodesy data a reduction for 3D displacements caused by the changes in the continental water storage on a routine basis, as it is done for a long time with ocean loading and atmospheric pressure loading. The service of the continental storage water loading was launched in 2013. The service utilizes the outputs of several hydrological models and provides the 3D time series in the form of global maps with 1-3 hour time resolution, time series for the set of ~1000 space geodesy sites, and an on-demand web-based application that allows a user to compute and download the time series of displacements for user-specified sites. The design of such a service and experience of its running are summarized. The loading series were validated by processing all available VLBI data. Results of validation are presented. Impact of using continental water storage for data reduction on estimates of other parameters, such as station velocities, is discussed.

  20. Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra.

    Science.gov (United States)

    Boelman, Natalie T; Stieglitz, Marc; Rueth, Heather M; Sommerkorn, Martin; Griffin, Kevin L; Shaver, Gaius R; Gamon, John A

    2003-05-01

    This study explores the relationship between the normalized difference vegetation index (NDVI), aboveground plant biomass, and ecosystem C fluxes including gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem production. We measured NDVI across long-term experimental treatments in wet sedge tundra at the Toolik Lake LTER site, in northern Alaska. Over 13 years, N and P were applied in factorial experiments (N, P and N + P), air temperature was increased using greenhouses with and without N + P fertilizer, and light intensity (photosynthetically active photon flux density) was reduced by 50% using shade cloth. Within each treatment plot, NDVI, aboveground biomass and whole-system CO(2) flux measurements were made at the same sampling points during the peak-growing season of 2001. We found that across all treatments, NDVI is correlated with aboveground biomass ( r(2)=0.84), GEP ( r(2)=0.75) and ER ( r(2)=0.71), providing a basis for linking remotely sensed NDVI to aboveground biomass and ecosystem carbon flux.

  1. The response of tundra springtails (Collembola, Hexapoda) to human activity on the Murman coast of the Kola Penisula, Russia

    Science.gov (United States)

    Olejniczak, Izabella; Boniecki, Paweł; Kaliszewicz, Anita; Panteleeva, Ninel

    2018-03-01

    This study was carried out in the Dalne Zelentsy settlement (69°07‧N, 36°03‧E) on the Barents Sea of the Kola Penisula in Russia. Three transects were established: the 'new garden transect'; the 'old garden transect'; and the 'settlement transect'. Overall, the number of springtails increased with distance from the 'settlement' and decreased from the 'old garden' towards the tundra. However, in the case of the 'new garden transect' there were no clear trends in springtail abundance. Eleven species of springtail were found, with Parisotoma notabilis being found at each of the studied areas along the transects. Trends in the species diversity of the springtail communities were not clear, and the values of H‧ ranged from 1.36 to 2.08. The springtail communities located 10 m from the 'new garden' and the 'old garden' were characterized by low species diversity compared with the other sites along the transects (H‧ values of 1.36 and 1.67, respectively). There were no differences in species diversity among the springtail communities along the 'settlement transect'.

  2. The structure of the bacterial heterotrophic block in tundra soils of Yamal Peninsula

    Science.gov (United States)

    Kukharenko, O. S.; Dobrovol'Skaya, T. G.; Golovchenko, A. V.; Stepanov, A. L.; Matyshak, G. V.

    2009-04-01

    The tundra cryogenic soils of Yamal Peninsula have a high pool of prokaryote microorganisms characteristic of ecosystems where the environmental conditions are unfavorable for microbiological processes. The lowering of the cultivation temperature from 20 to 5°C did not affect the number of bacteria and their taxonomic structure. Psychrotolerant gram-negative bacteria represented by oligotrophs and copiotrophs predominated in the bacterial communities. Among the bacteria of the hydrolytic block, only bacilli were isolated upon cultivation on the media. The species spectrum of the Bacillus genus was determined by the capability of its representatives for growth at low temperatures. The bacteria isolated from the cryogenic soils had a high nitrogenase activity, which increased under the lower cultivation temperature. This fact shows that the majority of the bacteria in tundra soils has adapted to functioning at low temperatures.

  3. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    Science.gov (United States)

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-01-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  4. Prevalence, transmission, and genetic diversity of blood parasites infecting tundra-nesting geese in Alaska

    Science.gov (United States)

    Ramey, Andy M.; Reed, John A.; Schmutz, Joel A.; Fondell, Tom F.; Meixell, Brandt W.; Hupp, Jerry W.; Ward, David H.; Terenzi, John; Ely, Craig R.

    2014-01-01

    A total of 842 blood samples collected from five species of tundra-nesting geese in Alaska was screened for haemosporidian parasites using molecular techniques. Parasites of the generaLeucocytozoon Danilewsky, 1890, Haemoproteus Kruse, 1890, and Plasmodium Marchiafava and Celli, 1885 were detected in 169 (20%), 3 (tundra habitats in Alaska, or alternatively, may only occur at low levels. Five haemosporidian genetic lineages shared among different species of geese sampled from two geographic areas were indicative of interspecies parasite transmission and supported broad parasite or vector distributions. However, identicalLeucocytozoon and Haemoproteus lineages on public databases were limited to waterfowl hosts suggesting constraints in the range of parasite hosts.

  5. 238U, 232Th and 226Ra behaviour in soils of mountainous tundra

    International Nuclear Information System (INIS)

    Shuktomova, I.I.; Titaeva, N.A.; Tashkaev, A.I.; Aleksakhin, R.M.

    1983-01-01

    Investigation into mountain-tundra soils of the Polar Urals for study of distribution and behaviour of natural radionuclides in them as well as search for correlations between radionuclides and physico-chemical properties of soils is conducted. It is shown that behaviour of 238 U, 232 Th, 226 Ra in soils of mountain tundra obeys general regularities of soil-formation process in any type of soils. Content of radionuclides is determined by their concentration in soil-formation rock and by the effect of talus ablations but not by the type of soils. Radionuclides in turf stained-humic soils are associated with mineral-fragmental fraction of soils, in peat-gley ones. The main part of them has sorption origin, both ways of nuclide supply are observed in turf-gley soils

  6. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    Science.gov (United States)

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-06-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  7. Tundra photosynthesis captured by satellite-observed solar-induced chlorophyll fluorescence

    Science.gov (United States)

    Luus, K. A.; Commane, R.; Parazoo, N. C.; Benmergui, J.; Euskirchen, E. S.; Frankenberg, C.; Joiner, J.; Lindaas, J.; Miller, C. E.; Oechel, W. C.; Zona, D.; Wofsy, S.; Lin, J. C.

    2017-02-01

    Accurately quantifying the timing and magnitude of respiration and photosynthesis by high-latitude ecosystems is important for understanding how a warming climate influences global carbon cycling. Data-driven estimates of photosynthesis across Arctic regions often rely on satellite-derived enhanced vegetation index (EVI); we find that satellite observations of solar-induced chlorophyll fluorescence (SIF) provide a more direct proxy for photosynthesis. We model Alaskan tundra CO2 cycling (2012-2014) according to temperature and shortwave radiation and alternately input EVI or SIF to prescribe the annual seasonal cycle of photosynthesis. We find that EVI-based seasonality indicates spring "green-up" to occur 9 days prior to SIF-based estimates, and that SIF-based estimates agree with aircraft and tower measurements of CO2. Adopting SIF, instead of EVI, for modeling the seasonal cycle of tundra photosynthesis can result in more accurate estimates of growing season duration and net carbon uptake by arctic vegetation.

  8. Psychrotolerant actinomycetes of plants and organic horizons in tundra and taiga soils

    Science.gov (United States)

    Dubrova, M. S.; Zenova, G. M.; Yakushev, A. V.; Manucharova, N. A.; Makarova, E. P.; Zvyagintsev, D. G.; Chernov, I. Yu.

    2013-08-01

    It has been revealed that in organic horizons and plants of the tundra and taiga ecosystems under low temperatures, actinomycetal complexes form. The population density of psychrotolerant actinomycetes in organic horizons and plants reaches tens and hundreds of thousands CFU/g of substrate or soil, and decreases in the sequence litters > plants > soils > undecomposed plant remains > moss growths. The mycelium length of psychrotolerant actinomycetes reaches 220 m/g of substrate. Application of the FISH method has demonstrated that metabolically active psychrotolerant bacteria of the phylum Actinobacteria constitute 30% of all metabolically active psychrotolerant representatives of the Bacterià domain of the prokaryotic microbial community of soils and plants. Psychrotolerant actinomycetes in tundra and taiga ecosystems possess antimicrobial properties.

  9. Bird communities of the arctic shrub tundra of Yamal: habitat specialists and generalists.

    Directory of Open Access Journals (Sweden)

    Vasiliy Sokolov

    Full Text Available BACKGROUND: The ratio of habitat generalists to specialists in birds has been suggested as a good indicator of ecosystem changes due to e.g. climate change and other anthropogenic perturbations. Most studies focusing on this functional component of biodiversity originate, however, from temperate regions. The Eurasian Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by domestic reindeer and growing human activity. METHODOLOGY/PRINCIPAL FINDINGS: Here we monitored bird communities in a tundra landscape harbouring shrub and open habitats in order to analyse bird habitat relationships and quantify habitat specialization. We used ordination methods to analyse habitat associations and estimated the proportions of specialists in each of the main habitats. Correspondence Analysis identified three main bird communities, inhabiting upland, lowland and dense willow shrubs. We documented a stable structure of communities despite large multiannual variations of bird density (from 90 to 175 pairs/km(2. Willow shrub thickets were a hotspot for bird density, but not for species richness. The thickets hosted many specialized species whose main distribution area was south of the tundra. CONCLUSION/SIGNIFICANCE: If current arctic changes result in a shrubification of the landscape as many studies suggested, we would expect an increase in the overall bird abundance together with an increase of local specialists, since they are associated with willow thickets. The majority of these species have a southern origin and their increase in abundance would represent a strengthening of the boreal component in the southern tundra, perhaps at the expense of species typical of the subarctic zone, which appear to be generalists within this zone.

  10. Bird Communities of the Arctic Shrub Tundra of Yamal: Habitat Specialists and Generalists

    Science.gov (United States)

    Sokolov, Vasiliy; Ehrich, Dorothée; Yoccoz, Nigel G.; Sokolov, Alexander; Lecomte, Nicolas

    2012-01-01

    Background The ratio of habitat generalists to specialists in birds has been suggested as a good indicator of ecosystem changes due to e.g. climate change and other anthropogenic perturbations. Most studies focusing on this functional component of biodiversity originate, however, from temperate regions. The Eurasian Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by domestic reindeer and growing human activity. Methodology/Principal Findings Here we monitored bird communities in a tundra landscape harbouring shrub and open habitats in order to analyse bird habitat relationships and quantify habitat specialization. We used ordination methods to analyse habitat associations and estimated the proportions of specialists in each of the main habitats. Correspondence Analysis identified three main bird communities, inhabiting upland, lowland and dense willow shrubs. We documented a stable structure of communities despite large multiannual variations of bird density (from 90 to 175 pairs/km2). Willow shrub thickets were a hotspot for bird density, but not for species richness. The thickets hosted many specialized species whose main distribution area was south of the tundra. Conclusion/Significance If current arctic changes result in a shrubification of the landscape as many studies suggested, we would expect an increase in the overall bird abundance together with an increase of local specialists, since they are associated with willow thickets. The majority of these species have a southern origin and their increase in abundance would represent a strengthening of the boreal component in the southern tundra, perhaps at the expense of species typical of the subarctic zone, which appear to be generalists within this zone. PMID:23239978

  11. Regional and landscape-scale variability of Landsat-observed vegetation dynamics in northwest Siberian tundra

    International Nuclear Information System (INIS)

    Frost, Gerald V; Epstein, Howard E; Walker, Donald A

    2014-01-01

    Widespread increases in Arctic tundra productivity have been documented for decades using coarse-scale satellite observations, but finer-scale observations indicate that changes have been very uneven, with a high degree of landscape- and regional-scale heterogeneity. Here we analyze time-series of the Normalized Difference Vegetation Index (NDVI) observed by Landsat (1984–2012), to assess landscape- and regional-scale variability of tundra vegetation dynamics in the northwest Siberian Low Arctic, a little-studied region with varied soils, landscape histories, and permafrost attributes. We also estimate spatio-temporal rates of land-cover change associated with expansion of tall alder (Alnus) shrublands, by integrating Landsat time-series with very-high-resolution imagery dating to the mid-1960s. We compiled Landsat time-series for eleven widely-distributed landscapes, and performed linear regression of NDVI values on a per-pixel basis. We found positive net NDVI trends (‘greening’) in nine of eleven landscapes. Net greening occurred in alder shrublands in all landscapes, and strong greening tended to correspond to shrublands that developed since the 1960s. Much of the spatial variability of greening within landscapes was linked to landscape physiography and permafrost attributes, while between-landscape variability largely corresponded to differences in surficial geology. We conclude that continued increases in tundra productivity in the region are likely in upland tundra landscapes with fine-textured, cryoturbated soils; these areas currently tend to support discontinuous vegetation cover, but are highly susceptible to rapid increases in vegetation cover, as well as land-cover changes associated with the development of tall shrublands. (paper)

  12. Reindeer grazing and soil nutrient cycling in boreal and tundra ecosystems

    OpenAIRE

    Stark, S. (Sari)

    2002-01-01

    Abstract In northernmost Fennoscandia, grazing by reindeer (Rangifer tarandus L.) has a substantial impact on the vegetation of boreal forests and arctic-alpine tundra heaths, which are reflected in below-ground processes, such as nutrient mineralization and soil organic matter decomposition. In the present thesis, the effects of reindeer grazing on soil nutrient cycling were studied by comparing grazed situation with an ungrazed control area in ten boreal forests a...

  13. Spatial Variability, Drivers, and Scale-Mismatch of Tundra Greenup Phenology at a Landscape Extent

    Science.gov (United States)

    Kerby, J.

    2016-12-01

    Spatial variability of plant phenology has widespread implications for landscape-level processes like herbivore foraging and the carbon cycle, but has traditionally only been quantified on small plots by human observers or at broader scales using coarse satellite imagery. Many ecological patterns vary with their scale of measurement, yet scale-dependence in vegetation emergence is poorly understood, particularly in Arctic environments. To investigate the effect of spatial grain choice on quantifying variability in tundra emergence phenology, we extracted greenness profiles from a network of 50 near-surface time-lapse cameras (Phenocams) across 40 km2 of West Greenland tundra in two years with contrasting abiotic conditions. Using this landscape-extent dataset paired with satellite-based MODIS multispectral time-series, we examined the influence of spatial grain choice on the observed timing, spatial variability, and landscape correlates of tundra green-up phenology. We matched the spatial grain of emergence time-series with three levels of ecological organization: vegetation functional-type patches (ecological `level' were analyzed simultaneously using a hierarchical Bayesian mixed modeling framework. Despite the contrasting abiotic conditions in each study year, the annual spatial variability in emergence across the broader landscape measured at fine grains was of a much greater magnitude than between year differences measured from any data-source. Coarser-grained MODIS derived metrics of vegetation greenup were much less variable between years, and were also significantly correlated with different landscape-level features than the finer grained Phenocam datasets. This first report of fine-grained vegetation emergence phenology across a broad tundra landscape extent (40 km2) reveals clear scale-dependent dynamics in the timing, variability, and environmental drivers of greenup, and offers empirical insights into how fine-grained processes may contribute to broader

  14. Effects of Climate Warming on Organic Carbon Degradation and Methylmercury Production in an Arctic Tundra Soil

    Science.gov (United States)

    Gu, B.; Yang, Z.; Lu, X.; Liang, L.; Graham, D. E.; Wullschleger, S. D.

    2016-12-01

    Climate warming increases microbial activity and stimulates the degradation of stored soil organic carbon (SOC) in Arctic tundra. Studies have shown that the rates of SOC degradation are affected by the substrate quality or chemical composition of SOC, but it remains unclear which pools of SOC are the most vulnerable to rapid breakdown and what mechanisms are involved. Additionally, little is known concerning the effects of warming on microbial mercury methylation and how it is coupled to SOC degradation. Using a suite of analytical techniques, we examined the dynamic consumption and production of labile SOC compounds, including reducing sugars, alcohols, and low-molecular-weight organic acids during an 8-month anoxic incubation with a high-centered polygon trough tundra soil from Barrow, Alaska. We show that reducing sugars and alcohols in thawed permafrost largely account for the initial rapid release of CO2 and CH4 through anaerobic fermentation, whereas the fermentation products such as acetate and formate are subsequently utilized as primary substrates for methanogenesis. Degradation of labile SOC is also found to rapidly fueling the biosynthesis of methylmercury, a potent neurotoxin in tundra soil. Mercury methylation is positively correlated to the production of CH4 and ferrous ion, suggesting the linkages among microbial pathways of methanogenesis, iron reduction, and mercury methylation. Additionally, we found that freshly amended mercury is more bioavailable and susceptible to microbial methylation than preexisting Hg, particularly in the deep mineral soil. These observations suggest that climate warming and permafrost thaw not only impact on the decomposition of stored SOC and emission of greenhouse gases but also increase production of toxic methylmercury in Arctic tundra.

  15. Call broadcasting and automated recorders as tools for anuran surveys in a subarctic tundra landscape

    Science.gov (United States)

    Mannan, R. Nicholas; Perry, Gad; Andersen, David; Boal, Clint W.

    2014-01-01

    Relatively little is known about population ecology of anurans in arctic and subarctic tundra regions, in part because it is difficult to survey anurans in these landscapes. Anuran survey protocols developed for temperate regions have limited applicability in arctic and subarctic tundra landscapes, which may lack roads and vehicle access, and experience variable and inclement weather during short anuran breeding seasons. To evaluate approaches to address some of the limitations of surveying anurans in tundra landscapes, we assessed the effectiveness of using breeding call broadcasts to increase detection of Boreal Chorus Frogs (Pseudacris maculata) and Wood Frogs (Lithobates sylvaticus) near Cape Churchill, Manitoba, Canada. We also evaluated how counts of anurans derived from automated audio recorders compared with those obtained simultaneously by observers. We detected on average 0.4 additional Wood Frogs per survey when we broadcasted calls (x̄ = 0.82, SD = 1.38), an increase of > 40% compared to surveys without broadcasts (x̄ = 1.24, SD = 1.51; Wilcoxon test; Z = 2.73, P = 0.006). In contrast, broadcasting Boreal Chorus Frog calls did not increase the number of chorus frog detections (Wilcoxon test; Z 0.90). Detections of Wood Frogs in a 100-m radius were lower via automated recorders (x̄ = 0.60, SD = 0.87 SD) than by observers during simultaneous surveys (x̄ = 0.96, SD = 1.27 Z = 2.07, P = 0.038), but those of Boreal Chorus Frogs were not different (x = 1.72, SD = 1.31;x̄ = 1.44, SD = 1.5; Z = 1.55, P > 0.121). Our results suggest that broadcasting calls can increase detection of Wood Frogs, and that automated recorders are useful in detecting both Wood Frogs and Boreal Chorus Fogs in arctic and subarctic tundra landscapes.

  16. Long-term persistence of spent lead shot in tundra wetlands

    Science.gov (United States)

    Flint, Paul L.; Schamber, Jason L.

    2010-01-01

    We seeded experimental plots with number 4 lead pellets and sampled these plots for 10 years to assess the settlement rate of pellets in tundra wetland types commonly used by foraging waterfowl. After 10 years, about 10% of pellets remained within 6 cm of the surface, but >50% remained within 10 cm. We predict that spent lead pellets will eventually become unavailable to waterfowl; however, it will likely require >25 years for all pellets to exceed depths at which waterfowl species may forage.

  17. Sedimentological context of the continental sabkhas of Abu Dhabi

    Science.gov (United States)

    Lokier, Stephen; Paul, Andreas; Bixiao, Xin

    2017-04-01

    For more than half a century, the coastal sabkhas of Abu Dhabi have been the focus of intensive research focusing on deposition, early diagenesis and the role of microbial communities. Given all of this activity, it is somewhat surprising that their continental counterparts have been largely neglected with only a brief mention in larger-scale regional studies. This study redresses this imbalance by documenting the sedimentological, mineralogical and early diagenetic characteristics of continental sabkhas that are hosted in the Rub al Khali desert of the United Arab Emirates. During reconnaissance surveys it has been established that organic-rich microbial mats and evaporite minerals, both similar to those observed in the coastal sabkha, also occur in these continental sabkha settings. Satellite imagery was utilised to identify potential field locations for surface and shallow sub surface investigation; subsequent field reconnaissance established the validity of sites in terms of anthropogenic disruption and accessibility. At each site, surface features were described in detail, particularly with reference to any microbial communities or evaporite crusts; sample pits were dug in order to document sub-surface facies geometries and to recover both sediment and pore water samples for subsequent analysis. In each pit, a range of environmental parameters was measured over a prolonged period, including surface and sub-surface temperatures, ground water salinity and dissolved oxygen. Sediment samples were subjected to a range of analyses in order to establish and quantify primary sediment composition and any early diagenetic mineral phases. The results of this study are used to build an atlas of sedimentary structures and textures that are associated with continental sabkha settings. These observations allow us to establish the defining sedimentological and early diagenetic characteristics that can be employed to identify similar depositional environments in ancient

  18. Spatial and Temporal Variation in Primary Productivity (NDVI) of Coastal Alaskan Tundra: Decreased Vegetation Growth Following Earlier Snowmelt

    Science.gov (United States)

    Gamon, John A.; Huemmrich, K. Fred; Stone, Robert S.; Tweedie, Craig E.

    2015-01-01

    In the Arctic, earlier snowmelt and longer growing seasons due to warming have been hypothesized to increase vegetation productivity. Using the Normalized Difference Vegetation Index (NDVI) from both field and satellite measurements as an indicator of vegetation phenology and productivity, we monitored spatial and temporal patterns of vegetation growth for a coastal wet sedge tundra site near Barrow, Alaska over three growing seasons (2000-2002). Contrary to expectation, earlier snowmelt did not lead to increased productivity. Instead, productivity was associated primarily with precipitation and soil moisture, and secondarily with growing degree days, which, during this period, led to reduced growth in years with earlier snowmelt. Additional moisture effects on productivity and species distribution, operating over a longer time scale, were evident in spatial NDVI patterns associated with microtopography. Lower, wetter regions dominated by graminoids were more productive than higher, drier locations having a higher percentage of lichens and mosses, despite the earlier snowmelt at the more elevated sites. These results call into question the oft-stated hypothesis that earlier arctic growing seasons will lead to greater vegetation productivity. Rather, they agree with an emerging body of evidence from recent field studies indicating that early-season, local environmental conditions, notably moisture and temperature, are primary factors determining arctic vegetation productivity. For this coastal arctic site, early growing season conditions are strongly influenced by microtopography, hydrology, and regional sea ice dynamics, and may not be easily predicted from snowmelt date or seasonal average air temperatures alone. Our comparison of field to satellite NDVI also highlights the value of in-situ monitoring of actual vegetation responses using field optical sampling to obtain detailed information on surface conditions not possible from satellite observations alone.

  19. How Continental Bank outsourced its "crown jewels.".

    Science.gov (United States)

    Huber, R L

    1993-01-01

    No industry relies more on information than banking does, yet Continental, one of America's largest banks, outsources its information technology. Why? Because that's the best way to service the customers that form the core of the bank's business, says vice chairman Dick Huber. In the late 1970s and early 1980s, Continental participated heavily with Penn Square Bank in energy investments. When falling energy prices burst Penn Square's bubble in 1982, Continental was stuck with more than $1 billion in bad loans. Eight years later when Dick Huber came on board, Continental was working hard to restore its once solid reputation. Executives had made many tough decisions already, altering the bank's focus from retail to business banking and laying off thousands of employees. Yet management still needed to cut costs and improve services to stay afloat. Regulators, investors, and analysts were watching every step. Continental executives, eager to focus on the bank's core mission of serving business customers, decided to outsource one after another in-house service--from cafeteria services to information technology. While conventional wisdom holds that banks must retain complete internal control of IT, Continental bucked this argument when it entered into a ten-year, multimillion-dollar contract with Integrated Systems Solutions Corporation. Continental is already reaping benefits from outsourcing IT. Most important, Continental staffers today focus on their true core competencies: intimate knowledge of customers' needs and relationships with customers.

  20. Humic substances elemental composition of selected taiga and tundra soils from Russian European North-East

    Directory of Open Access Journals (Sweden)

    Lodygin Evgeny

    2017-06-01

    Full Text Available Soils of Russian European North were investigated in terms of stability and quality of organic matter as well as in terms of soils organic matter elemental composi­tion. Therefore, soil humic acids (HAs, extracted from soils of different natural zones of Russian North-East were studied to characterize the degree of soil organic matter stabilization along a zonal gradient. HAs were extracted from soil of different zonal environments of the Komi Republic: south, middle and north taiga as well as south tundra. Data on elemental composition of humic acids and fulvic acids (FAs extracted from different soil types were obtained to assess humus formation mechanisms in the soils of taiga and tundra of the European North-East of Russia. The specificity of HAs elemental composition are discussed in relation to environmental conditions. The higher moisture degree of taiga soils results in the higher H/C ratio in humic substances. This reflects the reduced microbiologic activity in Albeluvisols sods and subsequent conser­vation of carbohydrate and amino acid fragments in HAs. HAs of tundra soils, shows the H/C values decreasing within the depth of the soils, which reflects increasing of aromatic compounds in HA structure of mineral soil horizons. FAs were more oxidized and contains less carbon while compared with the HAs. Humic acids, extracted from soil of different polar and boreal environments differ in terms of elemental composition winch reflects the climatic and hydrological regimes of humification.

  1. Wet meadow ecosystems contribute the majority of overwinter soil respiration from snow-scoured alpine tundra

    Science.gov (United States)

    Knowles, John F.; Blanken, Peter D.; Williams, Mark W.

    2016-04-01

    We measured soil respiration across a soil moisture gradient ranging from dry to wet snow-scoured alpine tundra soils throughout three winters and two summers. In the absence of snow accumulation, soil moisture variability was principally determined by the combination of mesotopographical hydrological focusing and shallow subsurface permeability, which resulted in a patchwork of comingled ecosystem types along a single alpine ridge. To constrain the subsequent carbon cycling variability, we compared three measures of effective diffusivity and three methods to calculate gradient method soil respiration from four typical vegetation communities. Overwinter soil respiration was primarily restricted to wet meadow locations, and a conservative estimate of the rate of overwinter soil respiration from snow-scoured wet meadow tundra was 69-90% of the maximum carbon dioxide (CO2) respired by seasonally snow-covered soils within this same catchment. This was attributed to higher overwinter soil temperatures at wet meadow locations relative to fellfield, dry meadow, and moist meadow communities, which supported liquid water and heterotrophic respiration throughout the winter. These results were corroborated by eddy covariance-based measurements that demonstrated an average of 272 g C m-2 overwinter carbon loss during the study period. As a result, we updated a conceptual model of soil respiration versus snow cover to express the potential for soil respiration variability from snow-scoured alpine tundra.

  2. CO2 flux measurements in Russian Far East tundra using eddy covariance and closed chamber techniques

    International Nuclear Information System (INIS)

    Zamolodchikov, D.G.; Karelin, D.V.

    2003-01-01

    The objective of this study was to estimate the CO 2 exchange of a tundra ecosystem in the Russian Far East using the eddy covariance technique using closed-chamber measurements as a reference. An eddy covariance tower was placed near the Lavrentiya settlement (Chukotskiy Peninsula, Russia, 65 deg 36 min N, 171 deg 04 min W) within a typical tundra landscape. During the 85 d of continuous measurements [Days 205-289, 2000] the CO 2 exchange of the studied ecosystem was found to be close to equilibrium (a carbon sink at 10.2 gC/m 2 ). In the late summer period (Days 205-240) the ecosystem sequestered 32.1 gC/m 2 , whereas in autumn (Days 241-289), it was functioning as a carbon source of 21.9 gC/m 2 . Model-based estimates of ecosystem respiration and gross primary production were obtained over the period of observations. These are the first eddy covariance-based measurements performed in the Russian tundra

  3. Modeling dynamics of tundra plant communities on the Yamal Peninsula, Russia, in response to climate change and grazing pressure

    International Nuclear Information System (INIS)

    Yu, Q; Epstein, H E; Frost, G V; Walker, D A; Forbes, B C

    2011-01-01

    Understanding the responses of the arctic tundra biome to a changing climate requires knowledge of the complex interactions among the climate, soils and biological system. This study investigates the individual and interaction effects of climate change and reindeer grazing across a variety of climate zones and soil texture types on tundra vegetation community dynamics using an arctic vegetation model that incorporates the reindeer diet, where grazing is a function of both foliar nitrogen concentration and reindeer forage preference. We found that grazing is important, in addition to the latitudinal climate gradient, in controlling tundra plant community composition, explaining about 13% of the total variance in model simulations for all arctic tundra subzones. The decrease in biomass of lichen, deciduous shrub and graminoid plant functional types caused by grazing is potentially dampened by climate warming. Moss biomass had a nonlinear response to increased grazing intensity, and such responses were stronger when warming was present. Our results suggest that evergreen shrubs may benefit from increased grazing intensity due to their low palatability, yet a growth rate sensitivity analysis suggests that changes in nutrient uptake rates may result in different shrub responses to grazing pressure. Heavy grazing caused plant communities to shift from shrub tundra toward moss, graminoid-dominated tundra in subzones C and D when evergreen shrub growth rates were decreased in the model. The response of moss, lichen and forbs to warming varied across the different subzones. Initial vegetation responses to climate change during transient warming are different from the long term equilibrium responses due to shifts in the controlling mechanisms (nutrient limitation versus competition) within tundra plant communities.

  4. Monthly hydroclimatology of the continental United States

    Science.gov (United States)

    Petersen, Thomas; Devineni, Naresh; Sankarasubramanian, A.

    2018-04-01

    Physical/semi-empirical models that do not require any calibration are of paramount need for estimating hydrological fluxes for ungauged sites. We develop semi-empirical models for estimating the mean and variance of the monthly streamflow based on Taylor Series approximation of a lumped physically based water balance model. The proposed models require mean and variance of monthly precipitation and potential evapotranspiration, co-variability of precipitation and potential evapotranspiration and regionally calibrated catchment retention sensitivity, atmospheric moisture uptake sensitivity, groundwater-partitioning factor, and the maximum soil moisture holding capacity parameters. Estimates of mean and variance of monthly streamflow using the semi-empirical equations are compared with the observed estimates for 1373 catchments in the continental United States. Analyses show that the proposed models explain the spatial variability in monthly moments for basins in lower elevations. A regionalization of parameters for each water resources region show good agreement between observed moments and model estimated moments during January, February, March and April for mean and all months except May and June for variance. Thus, the proposed relationships could be employed for understanding and estimating the monthly hydroclimatology of ungauged basins using regional parameters.

  5. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Sonal, E-mail: S.Choudhary@sheffield.ac.uk [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Management School, University of Sheffield, Conduit Road, Sheffield S10 1FL (United Kingdom); Blaud, Aimeric [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); Osborn, A. Mark [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom); School of Applied Sciences, RMIT University, PO Box 71, Bundoora, VIC 3083 (Australia); Press, Malcolm C. [School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Manchester Metropolitan University, Manchester, M15 6BH (United Kingdom); Phoenix, Gareth K. [Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN (United Kingdom)

    2016-06-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem {sup 15}N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g N m{sup −2} yr{sup −1}, applied as {sup 15}NH{sub 4}{sup 15}NO{sub 3} in Svalbard (79{sup °}N), during the summer. Separate applications of {sup 15}NO{sub 3}{sup −} and {sup 15}NH{sub 4}{sup +} were also made to determine the importance of N form in their retention. More than 95% of the total {sup 15}N applied was recovered after one growing season (~ 90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants > vascular plants > organic soil > litter > mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of {sup 15}N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater {sup 15}NO{sub 3}{sup −} than {sup 15}NH{sub 4}{sup +}, suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events

  6. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events

    International Nuclear Information System (INIS)

    Choudhary, Sonal; Blaud, Aimeric; Osborn, A. Mark; Press, Malcolm C.; Phoenix, Gareth K.

    2016-01-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem 15 N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g N m −2 yr −1 , applied as 15 NH 4 15 NO 3 in Svalbard (79 ° N), during the summer. Separate applications of 15 NO 3 − and 15 NH 4 + were also made to determine the importance of N form in their retention. More than 95% of the total 15 N applied was recovered after one growing season (~ 90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants > vascular plants > organic soil > litter > mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of 15 N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater 15 NO 3 − than 15 NH 4 + , suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. - Highlights: • High Arctic tundra demonstrated a very

  7. Effect of Freeze-Thaw Cycles on Soil Nitrogen Reactive Transport in a Polygonal Arctic Tundra Ecosystem at Barrow AK Using 3-D Coupled ALM-PFLOTRAN

    Science.gov (United States)

    Yuan, F.; Wang, G.; Painter, S. L.; Tang, G.; Xu, X.; Kumar, J.; Bisht, G.; Hammond, G. E.; Mills, R. T.; Thornton, P. E.; Wullschleger, S. D.

    2017-12-01

    In Arctic tundra ecosystem soil freezing-thawing is one of dominant physical processes through which biogeochemical (e.g., carbon and nitrogen) cycles are tightly coupled. Besides hydraulic transport, freezing-thawing can cause pore water movement and aqueous species gradients, which are additional mechanisms for soil nitrogen (N) reactive-transport in Tundra ecosystem. In this study, we have fully coupled an in-development ESM(i.e., Advanced Climate Model for Energy, ACME)'s Land Model (ALM) aboveground processes with a state-of-the-art massively parallel 3-D subsurface thermal-hydrology and reactive transport code, PFLOTRAN. The resulting coupled ALM-PFLOTRAN model is a Land Surface Model (LSM) capable of resolving 3-D soil thermal-hydrological-biogeochemical cycles. This specific version of PFLOTRAN has incorporated CLM-CN Converging Trophic Cascade (CTC) model and a full and simple but robust soil N cycle. It includes absorption-desorption for soil NH4+ and gas dissolving-degasing process as well. It also implements thermal-hydrology mode codes with three newly-modified freezing-thawing algorithms which can greatly improve computing performance in regarding to numerical stiffness at freezing-point. Here we tested the model in fully 3-D coupled mode at the Next Generation Ecosystem Experiment-Arctic (NGEE-Arctic) field intensive study site at the Barrow Environmental Observatory (BEO), AK. The simulations show that: (1) synchronous coupling of soil thermal-hydrology and biogeochemistry in 3-D can greatly impact ecosystem dynamics across polygonal tundra landscape; and (2) freezing-thawing cycles can add more complexity to the system, resulting in greater mobility of soil N vertically and laterally, depending upon local micro-topography. As a preliminary experiment, the model is also implemented for Pan-Arctic region in 1-D column mode (i.e. no lateral connection), showing significant differences compared to stand-alone ALM. The developed ALM-PFLOTRAN coupling

  8. Commercial helium reserves, continental rifting and volcanism

    Science.gov (United States)

    Ballentine, C. J.; Barry, P. H.; Hillegonds, D.; Fontijn, K.; Bluett, J.; Abraham-James, T.; Danabalan, D.; Gluyas, J.; Brennwald, M. S.; Pluess, B.; Seneshens, D.; Sherwood Lollar, B.

    2017-12-01

    Helium has many industrial applications, but notably provides the unique cooling medium for superconducting magnets in medical MRI scanners and high energy beam lines. In 2013 the global supply chainfailed to meet demand causing significant concern - the `Liquid Helium Crisis' [1]. The 2017 closure of Quatar borders, a major helium supplier, is likely to further disrupt helium supply, and accentuates the urgent need to diversify supply. Helium is found in very few natural gas reservoirs that have focused 4He produced by the dispersed decay (a-particle) of U and Th in the crust. We show here, using the example of the Rukwa section of the Tanzanian East African Rift, how continental rifting and local volcanism provides the combination of processes required to generate helium reserves. The ancient continental crust provides the source of 4He. Rifting and associated magmatism provides the tectonic and thermal mechanism to mobilise deep fluid circulation, focusing flow to the near surface along major basement faults. Helium-rich springs in the Tanzanian Great Rift Valley were first identified in the 1950's[2]. The isotopic compositions and major element chemistry of the gases from springs and seeps are consistent with their release from the crystalline basement during rifting [3]. Within the Rukwa Rift Valley, helium seeps occur in the vicinity of trapping structures that have the potential to store significant reserves of helium [3]. Soil gas surveys over 6 prospective trapping structures (1m depth, n=1486) show helium anomalies in 5 out of the 6 at levels similar to those observed over a known helium-rich gas reservoir at 1200m depth (7% He - Harley Dome, Utah). Detailed macroseep gas compositions collected over two days (n=17) at one site allows us to distinguish shallow gas contributions and shows the deep gas to contain between 8-10% helium, significantly increasing resource estimates based on uncorrected values (1.8-4.2%)[2,3]. The remainder of the deep gas is

  9. Methane and nitrous oxide fluxes from four tundra ecotopes in Ny-Ålesund of the High Arctic.

    Science.gov (United States)

    Chen, Qingqing; Zhu, Renbin; Wang, Qing; Xu, Hua

    2014-07-01

    During the summers of 2008 and 2009, net methane (CH₄) and nitrous oxide (N₂O) fluxes were investigated from 4 tundra ecotopes: normal lowland tundra (LT), bird sanctuary tundra (BT), the tundra in an abandoned coal mine (CT) and the tundra in scientific bases (ST) in Ny-Ålesund of the High Arctic. Tundra soils in CT (184.5 ± 40.0 μg CH4/(m²·hr)) and ST (367.6 ± 92.3μg CH4/(m²·hr)) showed high CH4 emissions due to the effects of human activities, whereas high CH4 uptake or low emission occurred in the soils of LT and BT. The lowland tundra soils (mean, -4.4-4.3μg N₂O/(m²·hr)) were weak N₂O sources and even sinks. Bird activity increased N₂O emissions from BT with the mean flux of 7.9μgN2O/(m(2)·hr). The mean N₂O fluxes from CT (45.4 ± 10.2 μg N₂O/(m²·hr)) and ST (78.8 ± 18.5μg N₂O/(m²·hr)) were one order of magnitude higher than those from LT and BT, indicating that human activities significantly increased N₂O emissions from tundra soils. Soil total carbon and water regime were important factors affecting CH₄ fluxes from tundra soils. The N₂O fluxes showed a significant positive correlation with ammonia nitrogen (NH₄(+)-N) contents (r=0.66, ptundra soils. The CH4 and N₂O fluxes did not correspond to the temperature variations of soil at 0-15 cm depths. Overall our results implied that human activities might have greater effects on soil CH₄ and N₂O emissions than current climate warming in Ny-Ålesund, High Arctic. Copyright © 2014. Published by Elsevier B.V.

  10. Regulation of methane production, oxidation, and emission by vascular plants and bryophytes in ponds of the northeast Siberian polygonal tundra

    Science.gov (United States)

    Knoblauch, Christian; Spott, Oliver; Evgrafova, Svetlana; Kutzbach, Lars; Pfeiffer, Eva-Maria

    2015-12-01

    Methane (CH4) production, oxidation, and emission were studied in ponds of the permafrost-affected polygonal tundra in northeast Siberia. Microbial degradation of organic matter in water-saturated soils is the most important source for the climate-relevant trace gas CH4. Although ponds and lakes cover a substantial fraction of the land surface of northern Siberia, data on CH4 fluxes from these water bodies are scarce. Summer CH4 fluxes were measured with closed chambers at the margins of ponds vegetated by vascular plants and in their centers without vascular plants. Furthermore, CH4 and oxygen concentration gradients, stable carbon isotope signatures of dissolved and emitted CH4, and microbial CH4 production and CH4 oxidation were determined. Mean summer fluxes were significantly higher at the margins of the ponds (46.1 ± 15.4 mg CH4 m-2 d-1) than at the centers (5.9 ± 8.2 mg CH4 m-2 d-1). CH4 transport was dominated by diffusion in most open water sites, but substantial ebullitive fluxes (12.0 ± 8.1 mg CH4 m-2 d-1) were detected in one pond. Plant-mediated transport accounted for 70 to 90% of total CH4 fluxes above emerged vegetation. In the absence of vascular plants, 61 to 99% of the CH4 produced in the anoxic bottom soil was consumed in a layer of the submerged moss Scorpidium scorpioides, which covered the bottoms of the ponds. The fraction of CH4 oxidized was lower at sites with vascular plants since CH4 was predominantly transported through their aerenchyma, thereby bypassing the CH4 oxidation zone in the moss layer. These results emphasize the importance of moss-associated CH4 oxidation causing low CH4 fluxes from the studied Siberian ponds.

  11. Detection and molecular characterization of the mosquito-borne filarial nematode Setaria tundra in Danish roe deer (Capreolus capreolus).

    Science.gov (United States)

    Enemark, Heidi Larsen; Oksanen, Antti; Chriél, Mariann; le Fèvre Harslund, Jakob; Woolsey, Ian David; Al-Sabi, Mohammad Nafi Solaiman

    2017-04-01

    Setaria tundra is a mosquito-borne filarial nematode of cervids in Europe. It has recently been associated with an emerging epidemic disease causing severe morbidity and mortality in reindeer and moose in Finland. Here, we present the first report of S. tundra in six roe deer ( Capreolus capreolus ) collected between October 2010 and March 2014 in Denmark. The deer originated from various localities across the country: the eastern part of the Jutland peninsular and four locations on the island Zealand. With the exception of one deer, with parasites residing in a transparent cyst just under the liver capsule, worms (ranging from 2 to >20/deer) were found free in the peritoneal cavity. The worms were identified as S. tundra by morphological examination and/or molecular typing of the mitochondrial 12S rRNA and cox1 genes, which showed 99.1-99.8% identity to previously published S. tundra isolates from Europe. Roe deer are generally considered as asymptomatic carriers and their numbers in Denmark have increased significantly in recent decades. In light of climatic changes which result in warmer, more humid weather in Scandinavia greater numbers of mosquitoes and, especially, improved conditions for development of parasite larvae in the mosquito vectors are expected, which may lead to increasing prevalence of S. tundra . Monitoring of this vector-borne parasite may thus be needed in order to enhance the knowledge of factors promoting its expansion and prevalence as well as predicting disease outbreaks.

  12. Carbon storage in permafrost and soils of the mammoth tundra-steppe biome: Role in the global carbon budget

    Science.gov (United States)

    Zimov, N. S.; Zimov, S. A.; Zimova, A. E.; Zimova, G. M.; Chuprynin, V. I.; Chapin, F. S.

    2009-01-01

    During the Last Glacial Maximum (LGM), atmospheric CO2 concentration was 80-100 ppmv lower than in pre-industrial times. At that time steppe-tundra was the most extensive biome on Earth. Some authors assume that C storage in that biome was very small, similar to today's deserts, and that the terrestrial carbon (C) reservoir increased at the Pleistocene-Holocene transition (PHT) by 400-1300 Gt. To estimate C storage in the entire steppe-tundra biome we used data of C storage in soils of this biome that persisted in permafrost of Siberia and Alaska and developed a model that describes C accumulation in soils and in permafrost. The model shows a slow but consistent C increase in soil when permafrost appears. At the PHT, C-rich frozen loess of Europe and South of Siberia thawed and lost most of its carbon. Soil carbon decreases as tundra-steppe changes to forest, steppes and tundra. As a result, over 1000 Gt C was released to the atmosphere, oceans, and other terrestrial ecosystems. The model results also show that restoring the tundra-steppe ecosystem would enhance soil C storage, while providing other important ecosystem services.

  13. Analysis Of The Land Surface Temperature And NDVI Using MODIS Data On The Arctic Tundra During The Last Decade

    Science.gov (United States)

    Mattar, C.; Duran-Alarcon, C.; Jimenez-Munoz, J. C.; Sobrino, J. A.

    2013-12-01

    The arctic tundra is one of the most sensible biome to climate conditions which has experienced important changes in the spatial distribution of temperature and vegetation in the last decades. In this paper we analyzed the spatio-temporal trend of the Land Surface Temperature (LST) and the Normalized Difference Vegetation Index (NDVI) over the arctic tundra biome during the last decade (2001-2012) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) land products MOD11C3 (LST) and MOD13C2 (NDVI) were used. Anomalies for each variable were analyzed at monthly level, and the magnitude and statistical significance of the trends were computed using the non-parametric tests of Sen's Slope and Mann-Kendal respectively. The results obtained from MODIS LST data showed a significant increase (p-value tundra in the last decade. In the case of the NDVI, the trend was positive (increase on NDVI) but statistically not significant (p-value tundra regions defined in the Circumpolar Arctic Vegetation Map have presented positive and statistically significant trends in NDVI and LST. Values of trends obtained from MODIS data over all the tundra regions were +1.10 [°C/dec] in the case of LST and +0.005 [NDVI value/dec] in the case of NDVI.

  14. Molecular detection of hematozoa infections in tundra swans relative to migration patterns and ecological conditions at breeding grounds

    Science.gov (United States)

    Ramey, Andrew M.; Ely, Craig R.; Schmutz, Joel A.; Pearce, John M.; Heard, Darryl J.

    2012-01-01

    Tundra swans (Cygnus columbianus) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska.

  15. Potential evapotranspiration and continental drying

    Science.gov (United States)

    Milly, Paul C.D.; Dunne, Krista A.

    2016-01-01

    By various measures (drought area and intensity, climatic aridity index, and climatic water deficits), some observational analyses have suggested that much of the Earth’s land has been drying during recent decades, but such drying seems inconsistent with observations of dryland greening and decreasing pan evaporation. ‘Offline’ analyses of climate-model outputs from anthropogenic climate change (ACC) experiments portend continuation of putative drying through the twenty-first century, despite an expected increase in global land precipitation. A ubiquitous increase in estimates of potential evapotranspiration (PET), driven by atmospheric warming, underlies the drying trends, but may be a methodological artefact. Here we show that the PET estimator commonly used (the Penman–Monteith PET for either an open-water surface or a reference crop) severely overpredicts the changes in non-water-stressed evapotranspiration computed in the climate models themselves in ACC experiments. This overprediction is partially due to neglect of stomatal conductance reductions commonly induced by increasing atmospheric CO2 concentrations in climate models. Our findings imply that historical and future tendencies towards continental drying, as characterized by offline-computed runoff, as well as other PET-dependent metrics, may be considerably weaker and less extensive than previously thought.

  16. Video Tutorial of Continental Food

    Science.gov (United States)

    Nurani, A. S.; Juwaedah, A.; Mahmudatussa'adah, A.

    2018-02-01

    This research is motivated by the belief in the importance of media in a learning process. Media as an intermediary serves to focus on the attention of learners. Selection of appropriate learning media is very influential on the success of the delivery of information itself both in terms of cognitive, affective and skills. Continental food is a course that studies food that comes from Europe and is very complex. To reduce verbalism and provide more real learning, then the tutorial media is needed. Media tutorials that are audio visual can provide a more concrete learning experience. The purpose of this research is to develop tutorial media in the form of video. The method used is the development method with the stages of analyzing the learning objectives, creating a story board, validating the story board, revising the story board and making video tutorial media. The results show that the making of storyboards should be very thorough, and detailed in accordance with the learning objectives to reduce errors in video capture so as to save time, cost and effort. In video capturing, lighting, shooting angles, and soundproofing make an excellent contribution to the quality of tutorial video produced. In shooting should focus more on tools, materials, and processing. Video tutorials should be interactive and two-way.

  17. Slow recovery of lichen on burned caribou winter range in Alaska tundra: potential influences of climate warming and other disturbance factors

    Science.gov (United States)

    Randi Jandt; Kyle Joly; C. Randy Meyers; Charles. Racine

    2008-01-01

    Lichen regeneration timelines are needed to establish sound fire management guidelines for caribou (Rangifer tarandus) winter range. Paired burned and unburned permanent vegetative cover transects were established after 1981, 1977, and 1972 tundra fires in northwestern Alaska to document regrowth of tundra vegetation including caribou forage...

  18. Alaska's Living Tundra. Alaska Wildlife Week, 25-29 April 1988. Unit 6: Primary Teacher's Guide; Upper Elementary Teacher's Guide; Junior/Senior High School Teacher's Guide; Supplement.

    Science.gov (United States)

    Quinlan, Susan E.

    Despite its cold and barren appearance, Alaska's tundra supports a surprising variety of insects, birds, and mammals. In this document, three teacher's guides (for primary, upper elementary, and junior and senior high schools) and a supplementary resource packet present a comprehensive unit of study on Alaska's living tundra. The five lessons in…

  19. Master function for the solid:solution equilibrium of DOC in taiga and tundra soils of N. Russia: experimental and modeling results

    Science.gov (United States)

    Oosterwoud, M. R.; van der Zee, S. E. A. T. M.; Meeussen, J. C. L.; Temminghoff, E. J. M.

    2012-04-01

    The formation and degradation of Dissolved Organic Carbon (DOC) in arctic environments is intensively investigated, in the context of DOC loading of arctic rivers and seas as well as climate change. However, chemical interaction studies are more scarce, in particular those involving modeling. We investigated DOC interactions in N. Russian taiga and tundra soils, and found that water extractable organic carbon (WEOC) comprises only a small fraction of total organic carbon, whereas DOC is again a small fraction of WEOC. The chemical composition of DOC in terms of humic, fulvic, and hydrophilic acids, the concentrations of dominant cations such as Ca and Al, and the solid iron oxide contents appear to differ profoundly for different soil horizons, as well as between taiga and tundra soils. To reconcile these differences, we processed the data with a simple Freundlich model and with advanced LCD (Ligand and Charge Distribution) modeling of DOC interactions. In the LCD modeling, a combination is made of advances such as CD-MUSIC, and Nica-Donnan approaches, that are implemented in the software ORCHESTRA (though adjusted for computational stability by us). To avoid fitting without good foundation, use is made of the generic parameterization of LCD in combination with measured, site-specific chemical data such as concentrations. We observe that the soil samples from both regions, soil types and horizons can be described with a single DOC sorption Freundlich isotherm. More interestingly, for the same set of samples, the LCD modeling enables us to cast DOC sorption into a single Master Function, that takes iron oxide content and Al and Ca concentrations of soil samples into account in a purely predictive way. Based on this Master Function, it is feasible to assess how DOC is sorbed onto the solid surface. In combination with DOC production and degradation models, our results provide a more balanced instrument to address changes in DOC loading to surface waters due to

  20. Diagnosis of the hydrology of a small Arctic basin at the tundra-taiga transition using a physically based hydrological model

    Science.gov (United States)

    Krogh, Sebastian A.; Pomeroy, John W.; Marsh, Philip

    2017-07-01

    A better understanding of cold regions hydrological processes and regimes in transitional environments is critical for predicting future Arctic freshwater fluxes under climate and vegetation change. A physically based hydrological model using the Cold Regions Hydrological Model platform was created for a small Arctic basin in the tundra-taiga transition region. The model represents snow redistribution and sublimation by wind and vegetation, snowmelt energy budget, evapotranspiration, subsurface flow through organic terrain, infiltration to frozen soils, freezing and thawing of soils, permafrost and streamflow routing. The model was used to reconstruct the basin water cycle over 28 years to understand and quantify the mass fluxes controlling its hydrological regime. Model structure and parameters were set from the current understanding of Arctic hydrology, remote sensing, field research in the basin and region, and calibration against streamflow observations. Calibration was restricted to subsurface hydraulic and storage parameters. Multi-objective evaluation of the model using observed streamflow, snow accumulation and ground freeze/thaw state showed adequate simulation. Significant spatial variability in the winter mass fluxes was found between tundra, shrubs and forested sites, particularly due to the substantial blowing snow redistribution and sublimation from the wind-swept upper basin, as well as sublimation of canopy intercepted snow from the forest (about 17% of snowfall). At the basin scale, the model showed that evapotranspiration is the largest loss of water (47%), followed by streamflow (39%) and sublimation (14%). The models streamflow performance sensitivity to a set of parameter was analysed, as well as the mean annual mass balance uncertainty associated with these parameters.

  1. Physical and biological effects of experimental crude oil spills on Low Artic tundra in the vicinity of Tuktoyaktuk, N. W. T. , Canada

    Energy Technology Data Exchange (ETDEWEB)

    Freedman, W.; Hutchinson, T.C.

    1976-10-01

    Data are presented on the effects of simulated crude oil spills on two Low Arctic terrestrial tundra plant communities near Tuktoyaktuk, Northwest Territories. Spills of fresh, unweathered crude oil had a general herbicidal effect, resulting in rapid damage to, and subsequent death of, all aboveground actively growing foliage coming in contact with the oil. Most species were defoliated. Mosses and lichens were especially susceptible and killed. However, within several weeks of the summer oil spillages, a limited number of relatively tolerant vascular plant species began to develop regrowth shoots. Summer spills were markedly more damaging than were equivalent spills made in winter. No increases were seen in active layer depth from spills made in summer. However, winter spills on one of the two sites did show consistent and statistically significant (P > 0.01) increases in depth of thaw. Examination of several key energy budget parameters at these field sites indicated consistently lower albedos and evapotranspiration and consistently higher soil surface temperatures and soil heat flux at all oil spill sites, relative to their controls. However, except for a winter spill on one site, the recorded differences were not sufficiently large in magnitude to produce significant increases in active layer thaw depths.

  2. Exploration of the continental margins of India

    Digital Repository Service at National Institute of Oceanography (India)

    Siddiquie, H.N.; Hashimi, N.H.; Vora, K.H.; Pathak, M.C.

    In mid 1970's the National Institute of Oceanography, Goa, India prepared a plan for systematic regional, geological and geophysical surveys of the continental margins of India. This involved over 75,000 km of underway (bathymetric, side scan sonar...

  3. Volatile components and continental material of planets

    International Nuclear Information System (INIS)

    Florenskiy, K.P.; Nikolayeva, O.V.

    1984-01-01

    It is shown that the continental material of the terrestrial planets varies in composition from planet to planet according to the abundances and composition of true volatiles (H 2 0, CO 2 , etc.) in the outer shells of the planets. The formation of these shells occurs very early in a planet's evolution when the role of endogenous processes is indistinct and continental materials are subject to melting and vaporizing in the absence of an atmosphere. As a result, the chemical properties of continental materials are related not only to fractionation processes but also to meltability and volatility. For planets retaining a certain quantity of true volatile components, the chemical transformation of continental material is characterized by a close interaction between impact melting vaporization and endogeneous geological processes

  4. Coordination: southeast continental shelf studies. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1981-02-01

    The objectives are to identify important physical, chemical and biological processes which affect the transfer of materials on the southeast continental shelf, determine important parameters which govern observed temporal and spatial varibility on the continental shelf, determine the extent and modes of coupling between events at the shelf break and nearshore, and determine physical, chemical and biological exchange rates on the inner shelf. Progress in meeting these research objectives is presented. (ACR)

  5. The life cycle of continental rifting as a focus for U.S.-African scientific collaboration

    Science.gov (United States)

    Abdelsalam, Mohamed G.; Atekwana, Estella A.; Keller, G. Randy; Klemperer, Simon L.

    2004-11-01

    The East African Rift System (EARS) provides the unique opportunity found nowhere else on Earth, to investigate extensional processes from incipient rifting in the Okavango Delta, Botswana, to continental breakup and creation of proto-oceanic basins 3000 km to the north in the Afar Depression in Ethiopia, Eritrea, and Djibouti.The study of continental rifts is of great interest because they represent the initial stages of continental breakup and passive margin development, they are sites for large-scale sediment accumulation, and their geomorphology may have controlled human evolution in the past and localizes geologic hazards in the present. But there is little research that provides insights into the linkage between broad geodynamic processes and the life cycle of continental rifts: We do not know why some rifts evolve into mid-ocean ridges whereas others abort their evolution to become aulacogens. Numerous studies of the EARS and other continental rifts have significantly increased our understanding of rifting processes, but we particularly lack studies of the embryonic stages of rift creation and the last stages of extension when continental breakup occurs.

  6. The Continental Market Seen from the UK

    International Nuclear Information System (INIS)

    Romieu, Michel

    1998-01-01

    In this presentation, the Chairman of a French gas company (Elf) comments on the evolution of the Continental gas market from a British point of view. He first discusses the differences between the US, British and Continental gas markets, recalls the provisions of the European Gas Directive and states why a fully competitive system is a long-term prospect in Continental Europe. Seen from the UK, the provisions of the EU directive may appear modest. Due to the long transportation, British gas companies may find it hard to compete on the gas market of Continental Europe. When Inter connector, the gas pipeline connecting the gas markets in UK and the Continent, begins operation, there will be a flow of gas from the UK to the Continent according to already signed contracts. But there may be contractual flows both ways. Gas prices will level off between the UK and Northern Europe, at least for the industry. The continental markets will change gradually, the Gas Directive and the Inter connector will help the move towards a more competitive gas industry, but the fundamentals will not change: low gas prices for the next few years, competition between the big three exporters to Continental Europe, and long-term contracts that will extend beyond 2005

  7. Nitrogen deposition but not climate warming promotes Deyeuxia angustifolia encroachment in alpine tundra of the Changbai Mountains, Northeast China.

    Science.gov (United States)

    Zong, Shengwei; Jin, Yinghua; Xu, Jiawei; Wu, Zhengfang; He, Hongshi; Du, Haibo; Wang, Lei

    2016-02-15

    Vegetation in the alpine tundra area of the Changbai Mountains, one of two alpine tundra areas in China, has undergone great changes in recent decades. The aggressive herb species Deyeuxia angustifolia (Komarov) Y. L. Chang, a narrow-leaf small reed, was currently encroaching upon the alpine landscape and threatening tundra biota. The alpine tundra of the Changbai Mountains has been experiencing a warmer climate and receiving a high load of atmospheric nitrogen deposition. In this study, we aimed to assess the respective roles of climate warming and atmospheric nitrogen deposition in promoting the upward encroachment of D. angustifolia. We conducted experiments for three years to examine the response of D. angustifolia and a native alpine shrub, Rhododendron chrysanthum, to the conditions in which temperature and nitrogen were increased. Treatments consisting of temperature increase, nitrogen addition, temperature increase combined with nitrogen addition, and controls were conducted on the D. angustifolia communities with three encroachment levels (low, medium, and high levels). Results showed that 1) D. angustifolia grew in response to added nutrients but did not grow well when temperature increased. R. chrysanthum showed negligible responses to the simulated environmental changes. 2) Compared to R. chrysanthum, D. angustifolia could effectively occupy the above-ground space by increasing tillers and growing rapidly by efficiently using nitrogen. The difference in nitrogen uptake abilities between the two species contributed to expansion of D. angustifolia. 3) D. angustifolia encroachment could deeply change the biodiversity of tundra vegetation and may eventually result in the replacement of native biota, especially with nitrogen addition. Our research indicated that nutrient perturbation may be more important than temperature perturbation in promoting D. angustifolia encroachment upon the nutrient- and species-poor alpine tundra ecosystem in the Changbai

  8. Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

    International Nuclear Information System (INIS)

    Boelman, Natalie T; Gough, Laura; McLaren, Jennie R; Greaves, Heather

    2011-01-01

    This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVI pre-leaf ), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVI demi-leaf ) and during the period of maximum leaf-out (late July, NDVI peak-leaf ). We found that: (1) NDVI pre-leaf is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVI peak-leaf is best suited to capturing variation in deciduous canopy cover; and (3) NDVI demi-leaf does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative energy balance, and wildlife

  9. Invasion of terrestrial enchytraeids into two postglacial tundras: North-eastern Greenland and the Arctic Archipelago of Canada (Enchytraeidae, Oligochaeta)

    DEFF Research Database (Denmark)

    Christensen, Bent; Dózsa-Farkas, Klára

    2006-01-01

    The aim was to study the invasion of terrestrial enchytraeids into the two postglacial tundras, North-eastern Greenland and the Arctic Archipelago of Canada. The majority of species recorded have a wide distribution in the Northern Hemisphere and the species diversity is considerably lower than...... that of potential source regions indicating either strong selection or varied dispersal ability. It appears that the Archipelago is influenced mainly from North America and North-eastern Greenland from Europe while the specialized fauna of the ancient Beringian tundra is of minor importance. The two alternative...

  10. Plant and microbial responses to nitrogen and phosphorus addition across an elevational gradient in subarctic tundra.

    Science.gov (United States)

    Sundqvist, Maja K; Liu, Zhanfeng; Giesler, Reiner; Wardle, David A

    2014-07-01

    Temperature and nutrients are major limiting factors in subarctic tundra. Experimental manipulation of nutrient availability along elevational gradients (and thus temperature) can improve our understanding of ecological responses to climate change. However, no study to date has explored impacts of nutrient addition along a tundra elevational gradient, or across contrasting vegetation types along any elevational gradient. We set up a full factorial nitrogen (N) and phosphorus (P) fertilization experiment in each of two vegetation types (heath and meadow) at 500 m, 800 m, and 1000 m elevation in northern Swedish tundra. We predicted that plant and microbial communities in heath or at lower elevations would be more responsive to N addition while communities in meadow or at higher elevations would be more responsive to P addition, and that fertilizer effects would vary more with elevation for the heath than for the meadow. Although our results provided little support for these predictions, the relationship between nutrient limitation and elevation differed between vegetation types. Most plant and microbial properties were responsive to N and/or P fertilization, but responses often varied with elevation and/or vegetation type. For instance, vegetation density significantly increased with N + P fertilization relative to the other fertilizer treatments, and this increase was greatest at the lowest elevation for the heath but at the highest elevation for the meadow. Arbuscular mycorrhizae decreased with P fertilization at 500 m for the meadow, but with all fertilizer treatments in both vegetation types at 800 m. Fungal to bacterial ratios were enhanced by N+ P fertilization for the two highest elevations in the meadow only. Additionally, microbial responses to fertilization were primarily direct rather than indirect via plant responses, pointing to a decoupled response of plant and microbial communities to nutrient addition and elevation. Because our study shows how two

  11. The Geometry of Large Tundra Lakes Observed in Historical Maps and Satellite Images

    Science.gov (United States)

    Sudakov, Ivan; Essa, Almabrok; Mander, Luke; Gong, Ming; Kariyawasam, Tharanga

    2017-10-01

    Tundra lakes are key components of the Arctic climate system because they represent a source of methane to the atmosphere. In this paper, we aim to analyze the geometry of the patterns formed by large ($>0.8$ km$^2$) tundra lakes in the Russian High Arctic. We have studied images of tundra lakes in historical maps from the State Hydrological Institute, Russia (date 1977; scale $0.21166$ km/pixel) and in Landsat satellite images derived from the Google Earth Engine (G.E.E.; date 2016; scale $0.1503$ km/pixel). The G.E.E. is a cloud-based platform for planetary-scale geospatial analysis on over four decades of Landsat data. We developed an image-processing algorithm to segment these maps and images, measure the area and perimeter of each lake, and compute the fractal dimension of the lakes in the images we have studied. Our results indicate that as lake size increases, their fractal dimension bifurcates. For lakes observed in historical maps, this bifurcation occurs among lakes larger than $100$ km$^2$ (fractal dimension $1.43$ to $1.87$). For lakes observed in satellite images this bifurcation occurs among lakes larger than $\\sim$100 km$^2$ (fractal dimension $1.31$ to $1.95$). Tundra lakes with a fractal dimension close to $2$ have a tendency to be self-similar with respect to their area--perimeter relationships. Area--perimeter measurements indicate that lakes with a length scale greater than $70$ km$^2$ are power-law distributed. Preliminary analysis of changes in lake size over time in paired lakes (lakes that were visually matched in both the historical map and the satellite imagery) indicate that some lakes in our study region have increased in size over time, whereas others have decreased in size over time. Lake size change during this 39-year time interval can be up to half the size of the lake as recorded in the historical map.

  12. The Geometry of Large Tundra Lakes Observed in Historical Maps and Satellite Images

    Directory of Open Access Journals (Sweden)

    Ivan Sudakov

    2017-10-01

    Full Text Available The climate of the Arctic is warming rapidly and this is causing major changes to the cycling of carbon and the distribution of permafrost in this region. Tundra lakes are key components of the Arctic climate system because they represent a source of methane to the atmosphere. In this paper, we aim to analyze the geometry of the patterns formed by large (> 0.8 km 2 tundra lakes in the Russian High Arctic. We have studied images of tundra lakes in historical maps from the State Hydrological Institute, Russia (date 1977; scale 0.21166 km/pixel and in Landsat satellite images derived from the Google Earth Engine (G.E.E.; date 2016; scale 0.1503 km/pixel. The G.E.E. is a cloud-based platform for planetary-scale geospatial analysis on over four decades of Landsat data. We developed an image-processing algorithm to segment these maps and images, measure the area and perimeter of each lake, and compute the fractal dimension of the lakes in the images we have studied. Our results indicate that as lake size increases, their fractal dimension bifurcates. For lakes observed in historical maps, this bifurcation occurs among lakes larger than 100 km 2 (fractal dimension 1.43 to 1.87 . For lakes observed in satellite images this bifurcation occurs among lakes larger than ∼100 km 2 (fractal dimension 1.31 to 1.95 . Tundra lakes with a fractal dimension close to 2 have a tendency to be self-similar with respect to their area–perimeter relationships. Area–perimeter measurements indicate that lakes with a length scale greater than 70 km 2 are power-law distributed. Preliminary analysis of changes in lake size over time in paired lakes (lakes that were visually matched in both the historical map and the satellite imagery indicate that some lakes in our study region have increased in size over time, whereas others have decreased in size over time. Lake size change during this 39-year time interval can be up to half the size of the lake as recorded in the

  13. Human impact on tundra environment at the Ny-Ålesund Station, Svalbard

    OpenAIRE

    Jadwiga Krzyszowska, Anna

    1989-01-01

    Studies were performed in Ny-Alesund, Spitsbergen, in June and July 1986 in order to gain an insight into the effect of activities of the polar research station on the nearby environment. It was found that chemical and mechanical factors were the most detrimental to the tundra environment. Fuel oil spills (110 m3 in 1986), which spread via surface and ground waters, were the most damaging of the chemical factors. Domestic sewage polluted the waters of Kolhamna Bay within an area of only 0.5 h...

  14. Ecosystem Respiration Rates of Arctic Tundra Mesocosms in Response to Cold-Season Temperatures

    Science.gov (United States)

    Oberbauer, S. F.; Moser, J. G.; Olivas, P. C.; Starr, G.; Mortazavi, B.

    2013-12-01

    The cold season in the Arctic extends over 8 to 9 mo, during which air temperatures often reach as low as -40 °C. However, as a result of the insulating layer created by snow cover, temperatures seldom fall below -15 °C, and are likely warm enough to support some metabolism. Little research has been conducted on arctic plants and tundra during the cold season, despite its length and the fact that warming is predicted to be greatest during this period. The primary focus of cold-season research has been on rates of winter ecosystem respiration (ER) for estimates of annual carbon balance. The majority of these measurements during the winter or at winter temperatures indicate that some respiration is occurring. Although rates are low, they may contribute substantially to the annual carbon balance because of the length of the cold season. However, estimates of respiration at low temperatures differ substantially, have been taken at different temperatures using different methodologies, and importantly almost none provide quantitative relationships across a range of temperatures. We measured respiration rates of intact arctic tundra monoliths from 15 to -15 °C at 5 °C steps to facilitate improved model estimates of tundra respiration. Six tundra monoliths (~900 cm2) taken from Toolik Field Station, Alaska were conditioned for the cold season in growth chambers at shortened photoperiods and low, but above-freezing temperatures. Desired temperatures were obtained with a combination of growth chambers and a modified freezer. The average of five samplings of [CO2] at each temperature step was used to estimate the ER rates. Measurements were conducted with a closed system using incubation periods of 30 to 180 min, depending on the temperature. Carbon dioxide concentrations were measured by syringe samples injected into a N2 gas stream flowing through an infrared gas analyzer. Rates of ER calculated on an area basis were close to zero at -15 °C, but increased steadily with

  15. Delineation of Tundra Swan Cygnus c. columbianus populations in North America: geographic boundaries and interchange

    Science.gov (United States)

    Ely, Craig R.; Sladen, William J. L.; Wilson, Heather M.; Savage, Susan E.; Sowl, Kristine M.; Henry, Bill; Schwitters, Mike; Snowden, James

    2014-01-01

    North American Tundra Swans Cygnus c. columbianus are composed of two wellrecognised populations: an Eastern Population (EP) that breeds across northern Canada and north of the Brooks Range in Alaska, which migrates to the eastern seaboard of the United States, and a Western Population (WP) that breeds in coastal regions of Alaska south of the Brooks Range and migrates to western North America. We present results of a recent major ringing effort from across the breeding range in Alaska to provide a better definition of the geographic extent of the migratory divide in Alaska. We also reassess the staging and winter distributions of these populations based on locations of birds tracked using satellite transmitters, and recent recoveries and sightings of neck-collared birds. Summer sympatry of EP and WP Tundra Swans is very limited, and largely confined to a small area in northwest Alaska. Autumn migration pathways of EP and WP Tundra swans abut in southwest Saskatchewan, a region where migrating WP birds turn west, and EP birds deviate abruptly eastward. Overall, from 1989 to 2013 inclusive, 2.6% of recoveries or resightings reported to the USGS Bird Banding Laboratory were of birds that moved from the domain of the population in which they were initially captured to within the range of the other population; a proportion roughly comparable to the results of Limpert et al. (1991) for years before 1990. Of the 70 cross-boundary movements reported since 1989, 39% were of birds marked on breeding areas and 61% were of birds marked on wintering areas. Dispersing swans (i.e. those that made crossboundary movements) did not differ with respect to age or sex from those that did not move between populations. The Brooks Range in northern Alaska effectively separates the two populations within Alaska, but climate-induced changes in tundra breeding habitats and losses of wetlands on staging areas may alter the distribution for both of these populations.

  16. Hybrid image classification technique for land-cover mapping in the Arctic tundra, North Slope, Alaska

    Science.gov (United States)

    Chaudhuri, Debasish

    Remotely sensed image classification techniques are very useful to understand vegetation patterns and species combination in the vast and mostly inaccessible arctic region. Previous researches that were done for mapping of land cover and vegetation in the remote areas of northern Alaska have considerably low accuracies compared to other biomes. The unique arctic tundra environment with short growing season length, cloud cover, low sun angles, snow and ice cover hinders the effectiveness of remote sensing studies. The majority of image classification research done in this area as reported in the literature used traditional unsupervised clustering technique with Landsat MSS data. It was also emphasized by previous researchers that SPOT/HRV-XS data lacked the spectral resolution to identify the small arctic tundra vegetation parcels. Thus, there is a motivation and research need to apply a new classification technique to develop an updated, detailed and accurate vegetation map at a higher spatial resolution i.e. SPOT-5 data. Traditional classification techniques in remotely sensed image interpretation are based on spectral reflectance values with an assumption of the training data being normally distributed. Hence it is difficult to add ancillary data in classification procedures to improve accuracy. The purpose of this dissertation was to develop a hybrid image classification approach that effectively integrates ancillary information into the classification process and combines ISODATA clustering, rule-based classifier and the Multilayer Perceptron (MLP) classifier which uses artificial neural network (ANN). The main goal was to find out the best possible combination or sequence of classifiers for typically classifying tundra type vegetation that yields higher accuracy than the existing classified vegetation map from SPOT data. Unsupervised ISODATA clustering and rule-based classification techniques were combined to produce an intermediate classified map which was

  17. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    Science.gov (United States)

    Huemmrich, Karl Fred; Gamon, John A.; Tweedie, Craig E.; Campbell, Petya K. Entcheva; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow, AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013 plus or minus 0.0002, 0.0018 plus or minus 0.0002, and 0.0012 plus or minus 0.0001 mol C mol (exp -1) absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Along the transect, area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. The patch-level statistical discriminant functions applied to in situ hyperspectral reflectance data collected along the transect successfully unmixed cover fractions of the vegetation functional types. The unmixing functions, developed from the transect data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine variability in distribution of the vegetation functional types for an area near Barrow, AK. Spatial variability of LUE was derived from the observed functional type distributions. Across this landscape, a

  18. Coincident aboveground and belowground autonomous monitoring to quantify covariability in permafrost, soil, and vegetation properties in Arctic tundra

    Science.gov (United States)

    Dafflon, Baptiste; Oktem, Rusen; Peterson, John; Ulrich, Craig; Tran, Anh Phuong; Romanovsky, Vladimir; Hubbard, Susan S.

    2017-06-01

    Coincident monitoring of the spatiotemporal distribution of and interactions between land, soil, and permafrost properties is important for advancing our understanding of ecosystem dynamics. In this study, a novel monitoring strategy was developed to quantify complex Arctic ecosystem responses to the seasonal freeze-thaw-growing season conditions. The strategy exploited autonomous measurements obtained through electrical resistivity tomography to monitor soil properties, pole-mounted optical cameras to monitor vegetation dynamics, point probes to measure soil temperature, and periodic manual measurements of thaw layer thickness, snow thickness, and soil dielectric permittivity. The spatially and temporally dense monitoring data sets revealed several insights about tundra system behavior at a site located near Barrow, AK. In the active layer, the soil electrical conductivity (a proxy for soil water content) indicated an increasing positive correlation with the green chromatic coordinate (a proxy for vegetation vigor) over the growing season, with the strongest correlation (R = 0.89) near the typical peak of the growing season. Soil conductivity and green chromatic coordinate also showed significant positive correlations with thaw depth, which is influenced by soil and surface properties. In the permafrost, soil electrical conductivity revealed annual variations in solute concentration and unfrozen water content, even at temperatures well below 0°C in saline permafrost. These conditions may contribute to an acceleration of long-term thaw in Coastal permafrost regions. Demonstration of this first aboveground and belowground geophysical monitoring approach within an Arctic ecosystem illustrates its significant potential to remotely "visualize" permafrost, soil, and vegetation ecosystem codynamics in high resolution over field relevant scales.

  19. Coupled Monitoring and Inverse Modeling to Investigate Surface - Subsurface Hydrological and Thermal Dynamics in the Arctic Tundra

    Science.gov (United States)

    Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Bisht, G.; Peterson, J.; Ulrich, C.; Romanovsky, V. E.; Kneafsey, T. J.; Wu, Y.

    2015-12-01

    Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the

  20. Fault linkage and continental breakup

    Science.gov (United States)

    Cresswell, Derren; Lymer, Gaël; Reston, Tim; Stevenson, Carl; Bull, Jonathan; Sawyer, Dale; Morgan, Julia

    2017-04-01

    The magma-poor rifted margin off the west coast of Galicia (NW Spain) has provided some of the key observations in the development of models describing the final stages of rifting and continental breakup. In 2013, we collected a 68 x 20 km 3D seismic survey across the Galicia margin, NE Atlantic. Processing through to 3D Pre-stack Time Migration (12.5 m bin-size) and 3D depth conversion reveals the key structures, including an underlying detachment fault (the S detachment), and the intra-block and inter-block faults. These data reveal multiple phases of faulting, which overlap spatially and temporally, have thinned the crust to between zero and a few km thickness, producing 'basement windows' where crustal basement has been completely pulled apart and sediments lie directly on the mantle. Two approximately N-S trending fault systems are observed: 1) a margin proximal system of two linked faults that are the upward extension (breakaway faults) of the S; in the south they form one surface that splays northward to form two faults with an intervening fault block. These faults were thus demonstrably active at one time rather than sequentially. 2) An oceanward relay structure that shows clear along strike linkage. Faults within the relay trend NE-SW and heavily dissect the basement. The main block bounding faults can be traced from the S detachment through the basement into, and heavily deforming, the syn-rift sediments where they die out, suggesting that the faults propagated up from the S detachment surface. Analysis of the fault heaves and associated maps at different structural levels show complementary fault systems. The pattern of faulting suggests a variation in main tectonic transport direction moving oceanward. This might be interpreted as a temporal change during sequential faulting, however the transfer of extension between faults and the lateral variability of fault blocks suggests that many of the faults across the 3D volume were active at least in part

  1. 77 FR 75656 - Research Lease for Renewable Energy on the Outer Continental Shelf (OCS) Offshore Virginia...

    Science.gov (United States)

    2012-12-21

    ... Lease for Renewable Energy on the Outer Continental Shelf (OCS) Offshore Virginia, Request for... obtain a lease under 30 CFR 585.238 for renewable energy research activities, including the siting of two... production of renewable energy within and around the Wind Energy Area (WEA) offshore Virginia, identified by...

  2. An assessment of the carbon balance of arctic tundra: comparisons among observations, process models, and atmospheric inversions

    Science.gov (United States)

    McGuire, A.D.; Christensen, T.R.; Hayes, D.; Heroult, A.; Euskirchen, E.; Yi, Y.; Kimball, J.S.; Koven, C.; Lafleur, P.; Miller, P.A.; Oechel, W.; Peylin, P.; Williams, M.

    2012-01-01

    Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, regional and global applications of process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of regional process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr-1 (uncertainty between a

  3. Contributions to knowledge of the continental margin of Uruguay. Uruguayan continental margin: Physiographic and seismic analysis

    International Nuclear Information System (INIS)

    Preciozzi, F

    2014-01-01

    This work is about the kind of continental margins such as a )Atlantic type passive margins which can be hard or soft b) An active or Pacific margins that because of the very frequent earthquakes develop a morphology dominated by tectonic processes. The Uruguayan continental margin belongs to a soft Atlantic margin

  4. Amino acid production exceeds plant nitrogen demand in Siberian tundra

    Science.gov (United States)

    Wild, Birgit; Eloy Alves, Ricardo J.; Bárta, Jiři; Čapek, Petr; Gentsch, Norman; Guggenberger, Georg; Hugelius, Gustaf; Knoltsch, Anna; Kuhry, Peter; Lashchinskiy, Nikolay; Mikutta, Robert; Palmtag, Juri; Prommer, Judith; Schnecker, Jörg; Shibistova, Olga; Takriti, Mounir; Urich, Tim; Richter, Andreas

    2018-03-01

    Arctic plant productivity is often limited by low soil N availability. This has been attributed to slow breakdown of N-containing polymers in litter and soil organic matter (SOM) into smaller, available units, and to shallow plant rooting constrained by permafrost and high soil moisture. Using 15N pool dilution assays, we here quantified gross amino acid and ammonium production rates in 97 active layer samples from four sites across the Siberian Arctic. We found that amino acid production in organic layers alone exceeded literature-based estimates of maximum plant N uptake 17-fold and therefore reject the hypothesis that arctic plant N limitation results from slow SOM breakdown. High microbial N use efficiency in organic layers rather suggests strong competition of microorganisms and plants in the dominant rooting zone. Deeper horizons showed lower amino acid production rates per volume, but also lower microbial N use efficiency. Permafrost thaw together with soil drainage might facilitate deeper plant rooting and uptake of previously inaccessible subsoil N, and thereby promote plant productivity in arctic ecosystems. We conclude that changes in microbial decomposer activity, microbial N utilization and plant root density with soil depth interactively control N availability for plants in the Arctic.

  5. Carbon dioxide sources from Alaska driven by increasing early winter respiration from Arctic tundra

    Science.gov (United States)

    Commane, Róisín; Lindaas, Jakob; Benmergui, Joshua; Luus, Kristina A.; Chang, Rachel Y.-W.; Daube, Bruce C.; Euskirchen, Eugénie S.; Henderson, John M.; Karion, Anna; Miller, John B.; Miller, Scot M.; Parazoo, Nicholas C.; Randerson, James T.; Sweeney, Colm; Tans, Pieter; Thoning, Kirk; Veraverbeke, Sander; Miller, Charles E.; Wofsy, Steven C.

    2017-05-01

    High-latitude ecosystems have the capacity to release large amounts of carbon dioxide (CO2) to the atmosphere in response to increasing temperatures, representing a potentially significant positive feedback within the climate system. Here, we combine aircraft and tower observations of atmospheric CO2 with remote sensing data and meteorological products to derive temporally and spatially resolved year-round CO2 fluxes across Alaska during 2012-2014. We find that tundra ecosystems were a net source of CO2 to the atmosphere annually, with especially high rates of respiration during early winter (October through December). Long-term records at Barrow, AK, suggest that CO2 emission rates from North Slope tundra have increased during the October through December period by 73% ± 11% since 1975, and are correlated with rising summer temperatures. Together, these results imply increasing early winter respiration and net annual emission of CO2 in Alaska, in response to climate warming. Our results provide evidence that the decadal-scale increase in the amplitude of the CO2 seasonal cycle may be linked with increasing biogenic emissions in the Arctic, following the growing season. Early winter respiration was not well simulated by the Earth System Models used to forecast future carbon fluxes in recent climate assessments. Therefore, these assessments may underestimate the carbon release from Arctic soils in response to a warming climate.

  6. Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska.

    Science.gov (United States)

    Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

    2014-08-01

    The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0-10 cm to 10-20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen (NH4+ and NO3-). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska. © 2014 The Authors. FEMS Microbiology Ecology published by John Wiley & Sons Ltd on behalf of the Federation of European Microbiological Societies.

  7. Effect of Tundra Fires on Stream Chemistry in Alaska's Yukon-Kuskokwim Delta

    Science.gov (United States)

    Jimmie, J. A.; Mann, P. J.; Schade, J. D.; Natali, S.; Fiske, G.; Holmes, R. M.

    2017-12-01

    Surface air temperatures in the Arctic have been increasing at approximately twice the global average, contributing to myriad changes including shifting vegetation, thawing permafrost, and altered surface and groundwater hydrology. Wildfire frequency and intensity has also been increasing, and in summer 2015, more area burned in the Yukon-Kuskowkwim Delta than in the previous 64 years combined. We investigated the impact of tundra fire on stream water chemistry, and by extension, on the movement of nutrients and organic matter between terrestrial and aquatic ecosystems. Using a high-resolution Digital Elevation Model, we characterized the contributing sub-watershed area at each of our stream water sampling locations and calculated the percent of each sub-watershed that was burned in summer 2015. We found that nitrate, ammonium, and phosphate concentrations increased with burn area in a watershed, indicating that terrestrial inputs of these constituents to aquatic systems increased following fire. Patterns were less striking for dissolved organic carbon and dissolved organic nitrogen, but there was a positive relationship between burn area and the concentration of these constituents as well. These results highlight the significant impact of tundra fires on terrestrial-aquatic linkages in the Arctic, and suggest that these impacts may increase in the future if fire in Arctic and boreal regions continues to become more common.

  8. Distinct soil bacterial communities along a small-scale elevational gradient in alpine tundra

    Directory of Open Access Journals (Sweden)

    Congcong eShen

    2015-06-01

    Full Text Available The elevational diversity pattern for microorganisms has received great attention recently but is still understudied, and phylogenetic relatedness is rarely studied for microbial elevational distributions. Using a bar-coded pyrosequencing technique, we examined the biodiversity patterns for soil bacterial communities of tundra ecosystem along 2000–2500 m elevations on Changbai Mountain in China. Bacterial taxonomic richness displayed a linear decreasing trend with increasing elevation. Phylogenetic diversity and mean nearest taxon distance (MNTD exhibited a unimodal pattern with elevation. Bacterial communities were more phylogenetically clustered than expected by chance at all elevations based on the standardized effect size of MNTD metric. The bacterial communities differed dramatically among elevations, and the community composition was significantly correlated with soil total carbon, total nitrogen, C:N ratio, and dissolved organic carbon. Multiple ordinary least squares regression analysis showed that the observed biodiversity patterns strongly correlated with soil total carbon and C:N ratio. Taken together, this is the first time that a significant bacterial diversity pattern has been observed across a small-scale elevational gradient. Our results indicated that soil carbon and nitrogen contents were the critical environmental factors affecting bacterial elevational distribution in Changbai Mountain tundra. This suggested that ecological niche-based environmental filtering processes related to soil carbon and nitrogen contents could play a dominant role in structuring bacterial communities along the elevational gradient.

  9. Sea ice, rain-on-snow and tundra reindeer nomadism in Arctic Russia.

    Science.gov (United States)

    Forbes, Bruce C; Kumpula, Timo; Meschtyb, Nina; Laptander, Roza; Macias-Fauria, Marc; Zetterberg, Pentti; Verdonen, Mariana; Skarin, Anna; Kim, Kwang-Yul; Boisvert, Linette N; Stroeve, Julienne C; Bartsch, Annett

    2016-11-01

    Sea ice loss is accelerating in the Barents and Kara Seas (BKS). Assessing potential linkages between sea ice retreat/thinning and the region's ancient and unique social-ecological systems is a pressing task. Tundra nomadism remains a vitally important livelihood for indigenous Nenets and their large reindeer herds. Warming summer air temperatures have been linked to more frequent and sustained summer high-pressure systems over West Siberia, Russia, but not to sea ice retreat. At the same time, autumn/winter rain-on-snow (ROS) events have become more frequent and intense. Here, we review evidence for autumn atmospheric warming and precipitation increases over Arctic coastal lands in proximity to BKS ice loss. Two major ROS events during November 2006 and 2013 led to massive winter reindeer mortality episodes on the Yamal Peninsula. Fieldwork with migratory herders has revealed that the ecological and socio-economic impacts from the catastrophic 2013 event will unfold for years to come. The suggested link between sea ice loss, more frequent and intense ROS events and high reindeer mortality has serious implications for the future of tundra Nenets nomadism. © 2016 The Authors.

  10. Reduced arctic tundra productivity linked with landform and climate change interactions

    Science.gov (United States)

    Lara, Mark J.; Nitze, Ingmar; Grosse, Guido; Martin, Philip; McGuire, A. David

    2018-01-01

    Arctic tundra ecosystems have experienced unprecedented change associated with climate warming over recent decades. Across the Pan-Arctic, vegetation productivity and surface greenness have trended positively over the period of satellite observation. However, since 2011 these trends have slowed considerably, showing signs of browning in many regions. It is unclear what factors are driving this change and which regions/landforms will be most sensitive to future browning. Here we provide evidence linking decadal patterns in arctic greening and browning with regional climate change and local permafrost-driven landscape heterogeneity. We analyzed the spatial variability of decadal-scale trends in surface greenness across the Arctic Coastal Plain of northern Alaska (~60,000 km²) using the Landsat archive (1999–2014), in combination with novel 30 m classifications of polygonal tundra and regional watersheds, finding landscape heterogeneity and regional climate change to be the most important factors controlling historical greenness trends. Browning was linked to increased temperature and precipitation, with the exception of young landforms (developed following lake drainage), which will likely continue to green. Spatiotemporal model forecasting suggests carbon uptake potential to be reduced in response to warmer and/or wetter climatic conditions, potentially increasing the net loss of carbon to the atmosphere, at a greater degree than previously expected.

  11. Microbial Community and Functional Gene Changes in Arctic Tundra Soils in a Microcosm Warming Experiment

    Directory of Open Access Journals (Sweden)

    Ziming Yang

    2017-09-01

    Full Text Available Microbial decomposition of soil organic carbon (SOC in thawing Arctic permafrost is important in determining greenhouse gas feedbacks of tundra ecosystems to climate. However, the changes in microbial community structure during SOC decomposition are poorly known. Here we examine these changes using frozen soils from Barrow, Alaska, USA, in anoxic microcosm incubation at −2 and 8°C for 122 days. The functional gene array GeoChip was used to determine microbial community structure and the functional genes associated with SOC degradation, methanogenesis, and Fe(III reduction. Results show that soil incubation after 122 days at 8°C significantly decreased functional gene abundance (P < 0.05 associated with SOC degradation, fermentation, methanogenesis, and iron cycling, particularly in organic-rich soil. These observations correspond well with decreases in labile SOC content (e.g., reducing sugar and ethanol, methane and CO2 production, and Fe(III reduction. In contrast, the community functional structure was largely unchanged in the −2°C incubation. Soil type (i.e., organic vs. mineral and the availability of labile SOC were among the most significant factors impacting microbial community structure. These results demonstrate the important roles of microbial community in SOC degradation and support previous findings that SOC in organic-rich Arctic tundra is highly vulnerable to microbial degradation under warming.

  12. Disentangling the coupling between sea ice and tundra productivity in Svalbard.

    Science.gov (United States)

    Macias-Fauria, Marc; Karlsen, Stein Rune; Forbes, Bruce C

    2017-08-17

    The rapid decline in Arctic sea ice poses urgent questions concerning its ecological effects, such as on tundra terrestrial productivity. However, reported sea ice/terrestrial productivity linkages have seldom been constrained, and the mechanism governing them remains elusive, with a diversity of spatial scales and metrics proposed, at times in contradiction to each other. In this study, we use spatially explicit remotely sensed sea ice concentration and high-resolution terrestrial productivity estimates (Normalised Difference Vegetation Index, NDVI) across the Svalbard Archipelago to describe local/sub-regional and large-scale components of sea ice/terrestrial productivity coupling. Whereas the local/sub-regional component is attributed to sea breeze (cold air advection from ice-covered ocean onto adjacent land during the growing season), the large-scale component might reflect co-variability of sea ice and tundra productivity due to a common forcing, such as large-scale atmospheric circulation (North Atlantic Oscillation, NAO). Our study clarifies the range of mechanisms in sea ice/terrestrial productivity coupling, allowing the generation of testable hypotheses about its past, present, and future dynamics across the Arctic.

  13. Reproductive ecology and severe pollen limitation in the polychromic tundra plant, Parrya nudicaulis (Brassicaceae.

    Directory of Open Access Journals (Sweden)

    Justin R Fulkerson

    Full Text Available Pollen limitation is predicted to be particularly severe in tundra habitats. Numerous reproductive patterns associated with alpine and arctic species, particularly mechanisms associated with reproductive assurance, are suggested to be driven by high levels of pollen limitation. We studied the reproductive ecology of Parrya nudicaulis, a species with relatively large sexual reproductive investment and a wide range of floral pigmentation, in tundra habitats in interior montane Alaska to estimate the degree of pollen limitation. The plants are self-compatible and strongly protandrous, setting almost no seed in the absence of pollinators. Supplemental hand pollinations within pollinator exclusion cages indicated no cage effect on seed production. Floral visitation rates were low in both years of study and particularly infrequent in 2010. A diversity of insects visited P. nudicaulis, though syrphid and muscid flies composed the majority of all visits. Pollen-ovule ratios and levels of heterozygosity are consistent with a mixed mating system. Pollen limitation was severe; hand pollinations increased seed production per plant five-fold. Seed-to-ovule ratios remained low following hand pollinations, indicating resource limitation is likely to also be responsible for curtailing seed set. We suggest that pollen limitation in P. nudicaulis may be the result of selection favoring an overproduction of ovules as a bet-hedging strategy in this environmental context of highly variable pollen receipt.

  14. Herbivores rescue diversity in warming tundra by modulating trait-dependent species losses and gains.

    Science.gov (United States)

    Kaarlejärvi, Elina; Eskelinen, Anu; Olofsson, Johan

    2017-09-04

    Climate warming is altering the diversity of plant communities but it remains unknown which species will be lost or gained under warming, especially considering interactions with other factors such as herbivory and nutrient availability. Here, we experimentally test effects of warming, mammalian herbivory and fertilization on tundra species richness and investigate how plant functional traits affect losses and gains. We show that herbivory reverses the impact of warming on diversity: in the presence of herbivores warming increases species richness through higher species gains and lower losses, while in the absence of herbivores warming causes higher species losses and thus decreases species richness. Herbivores promote gains of short-statured species under warming, while herbivore removal and fertilization increase losses of short-statured and resource-conservative species through light limitation. Our results demonstrate that both rarity and traits forecast species losses and gains, and mammalian herbivores are essential for preventing trait-dependent extinctions and mitigate diversity loss under warming and eutrophication.Warming can reduce plant diversity but it is unclear which species will be lost or gained under interacting global changes. Kaarlejärvi et al. manipulate temperature, herbivory and nutrients in a tundra system and find that herbivory maintains diversity under warming by reducing species losses and promoting gains.

  15. Carbon dioxide sources from Alaska driven by increasing early winter respiration from Arctic tundra.

    Science.gov (United States)

    Commane, Róisín; Lindaas, Jakob; Benmergui, Joshua; Luus, Kristina A; Chang, Rachel Y-W; Daube, Bruce C; Euskirchen, Eugénie S; Henderson, John M; Karion, Anna; Miller, John B; Miller, Scot M; Parazoo, Nicholas C; Randerson, James T; Sweeney, Colm; Tans, Pieter; Thoning, Kirk; Veraverbeke, Sander; Miller, Charles E; Wofsy, Steven C

    2017-05-23

    High-latitude ecosystems have the capacity to release large amounts of carbon dioxide (CO 2 ) to the atmosphere in response to increasing temperatures, representing a potentially significant positive feedback within the climate system. Here, we combine aircraft and tower observations of atmospheric CO 2 with remote sensing data and meteorological products to derive temporally and spatially resolved year-round CO 2 fluxes across Alaska during 2012-2014. We find that tundra ecosystems were a net source of CO 2 to the atmosphere annually, with especially high rates of respiration during early winter (October through December). Long-term records at Barrow, AK, suggest that CO 2 emission rates from North Slope tundra have increased during the October through December period by 73% ± 11% since 1975, and are correlated with rising summer temperatures. Together, these results imply increasing early winter respiration and net annual emission of CO 2 in Alaska, in response to climate warming. Our results provide evidence that the decadal-scale increase in the amplitude of the CO 2 seasonal cycle may be linked with increasing biogenic emissions in the Arctic, following the growing season. Early winter respiration was not well simulated by the Earth System Models used to forecast future carbon fluxes in recent climate assessments. Therefore, these assessments may underestimate the carbon release from Arctic soils in response to a warming climate.

  16. Physicochemical and Microbiological Characteristics of Tundra Soils on the Rybachii Peninsula

    Science.gov (United States)

    Evdokimova, G. A.; Mozgova, N. P.; Myazin, V. A.

    2018-01-01

    The Rybachii Peninsula is composed of Proterozoic sedimentary rocks and differs sharply from the rest of the Kola Peninsula in its geological structure, topographic forms, and parent rocks. It is dominated by Al-Fe-humus soils formed on moraines with an admixture of local rock fragments, including slates. Organic horizons of tundra soils in the peninsula are less acid than those on granitoids of adjacent mainland of the Kola Peninsula. The content of exchangeable calcium in the organic horizons varies from 17.4 to 68.0 cmolc/kg, and the content of water-soluble carbon reaches 400 mg/100 g amounting to 1-2% of the total soil organic matter content. The total number of bacteria in the organic horizons of tundra soils varies from 3.5 × 109 to 4.8 × 109 cells/g; and bacterial biomass varies from 0.14 to 0.19 mg/g. The length of fungal mycelium and its biomass in the organic horizons are significant (>1000 m/g soil). The biomass of fungal mycelium in the organic horizons exceeds the bacterial biomass by seven times in podzols (Albic Podzols) and by ten times in podbur (Entic Podzol), dry-peat soil (Folic Histosol), and low-moor peat soil (Sapric Histosol).

  17. 100% Retention of Snowpack Derived Nitrogen Over 10 Years in High Arctic Tundra

    Science.gov (United States)

    Choudhary, S.; Tye, A. M.; Young, S. D.; West, H. M.; Phoenix, G. K.

    2013-12-01

    Tundra ecosystems are susceptible to atmospheric nitrogen (N) deposition, increasing as a result of anthropogenic activities as well as climate change. Depositions that get accumulated within the snowpack during winter months are released in spring during snowmelt, providing a periodic input of reactive N in the melt water to such nutrient limited ecosystems. Identifying ecosystem N retention and allocation and how this change over time is important to understanding the long-term consequences of such N depositions to these ecosystems. We reanalysed 10 years later an atmospheric N deposition study established in Svalbard that in 2001 used 15N isotope tracers to determine the fate of N released from melting snowpack. Applications of 15N (99 atom%) at 0.1 and 0.5 g N m-2 were made immediately after snowmelt in 2001 as either Na15NO3 or 15NH4Cl. These applications were approximately 1 × and 5 × the yearly atmospheric deposition rates. In both the previous short-term (one week to two years after 15N tracer application) and our long-term re-sampling (10 years after 15N tracer application), ~67% of the total applied 15N was retained in the ecosystem, irrespective of the N forms or N dose. This meant the tundra had 100% long-term N retention after initial partitioning, suggesting a highly conservative N cycling. Bryophytes, followed by the organic soil horizon and then the microbial biomass formed the greatest short-term 15N sink. Maximum changes in 15N retention from the short- to long-term were observed in the microbial 15N pools, with ~75% of the 15N in soil located in its biomass during the initial partitioning (July 2001) decreasing to ~17% 10 years later. This indicates significant microbial N turnover mostly into stable humus N. In contrast, vascular plants, particularly Salix polaris, showed significant increases (~60%) in their 15N retention after 10 years, indicating a high capacity for acting as a long-term N sink in this tundra ecosystem. Because the largest

  18. THE HYDRAULIC CHARACTERISTICS AND GEOCHEMISTRY OF HYPORHEIC AND PARAFLUVIAL ZONES IN ARCTIC TUNDRA STREAMS, NORTH SLOPE, ALASKA

    Science.gov (United States)

    Sodium bromide and Rhodamine WT were used as conservative tracers to examine the hydrologic characteristics of seven tundra streams in Arctic Alaska, during the summers of 1994-1996. Continuous tracer additions were conducted in seven rivers ranging from 1st to 5th order with sam...

  19. Soil nutrients, landscape age, and Sphagno-Eriophoretum vaginati plant communities in Arctic moist-acidic Tundra landscapes

    Science.gov (United States)

    Joel Mercado-Diaz; William Gould; Grizelle Gonzalez

    2014-01-01

    Most research exploring the relationship between soil chemistry and vegetation in Alaskan Arctic tundra landscapes has focused on describing differences in soil elemental concentrations (e.g. C, N and P) of areas with contrasting vegetation types or landscape age. In this work we assess the effect of landscape age on physico-chemical parameters in organic and mineral...

  20. An application of plot-scale NDVI in predicting carbon dioxide exchange and leaf area index in heterogeneous subarctic tundra

    International Nuclear Information System (INIS)

    Dagg, J.; Lafleur, P.

    2010-01-01

    This paper reported on a study that examined the flow of carbon into and out of tundra ecosystems. It is necessary to accurately predict carbon dioxide (CO 2 ) exchange in the Tundra because of the impacts of climate change on carbon stored in permafrost. Understanding the relationships between the normalized difference vegetation index (NDVI) and vegetation and CO 2 exchange may explain how small-scale variation in vegetation community extends to remotely sensed estimates of landscape characteristics. In this study, CO 2 fluxes were measured with a portable chamber in a range of Tundra vegetation communities. Biomass and leaf area were measured with destructive harvest, and NDVI was obtained using a hand-held infrared camera. There was a weak correlation between NDVI and leaf area index in some vegetation communities, but a significant correlation between NDVI and biomass, including mosses. NDVI was found to be strongly related to photosynthetic activity and net CO 2 uptake in all vegetation groups. However, NDVI related to ecosystem respiration only in wet sedge. It was concluded that at plot scale, the ability of NDVI to predict ecosystem properties and CO 2 exchange in heterogeneous Tundra vegetation is variable.

  1. Carbon storage in permafrost and soils of the mammoth tundra-steppe biome: role in the global carbon budget

    Science.gov (United States)

    N.S. Zimov; S.A. Zimov; A.E. Zimova; G.M. Zimova; V.I. Chuprynin; F.S. Chapin

    2009-01-01

    During the Last Glacial Maximum (LGM), atmospheric CO2 concentration was 80-100 ppmv lower than in preindustrial times. At that time steppe-tundra was the most extensive biome on Earth. Some authors assume that C storage in that biome was very small, similar to today's deserts, and that the terrestrial carbon (C) reservoir increased at the...

  2. Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow–shrub interactions

    Science.gov (United States)

    Myers-Smith, Isla H; Hik, David S

    2013-01-01

    Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow–shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3-year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing ∼0.5 m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4–5°C warmer in January, and 2°C cooler in July under shrub cover. Natural shrub plots had 14–33 cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO2 fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted. PMID:24198933

  3. [CO2-exchange in tundra ecosystems of Vaygach Island during the unusually warm and dry vegetation season].

    Science.gov (United States)

    Zamolodchikov, D G

    2015-01-01

    In summer of 2013, field studies of CO2-exchange in tundra ecosystems of Vaygach Island have been conducted using the chamber method. The models are developed that establish relationships between CO2 fluxes and key ecological factors such as temperature, photosynthetic active radiation, leaf mass of vascular plants, and depth of thawing. According to the model estimates, in 2013 vegetation season tundra ecosystems of Vaygach Island have been appearing to be a CO2 source to the atmosphere (31.9 ± 17.1 g C m(-2) season(-1)) with gross primary production equal to 136.6 ± 18.9 g C m(-2) season(-1) and ecosystem respiration of 168.5 ± ± 18.4 g C m(-2) season(-1). Emission of CO2 from the soil surface (soil respiration) has been equal, on the average, to 67.3% of the ecosystem respiration. The reason behind carbon losses by tundra ecosystems seems to be unusually warm and dry weather conditions in 2013 summer. The air temperature during summer months has been twice as high as the climatic norm for 1961-1990. Last decades, researches in the circumpolar Arctic revealed a growing trend to the carbon sink from the atmosphere to tundra ecosystems. This trend can be interrupted by unusually warm weather situations becoming more frequent and of larger scale.

  4. Long-term experimental warming alters community composition of ascomycetes in Alaskan moist and dry arctic tundra.

    Science.gov (United States)

    Semenova, Tatiana A; Morgado, Luis N; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-01-01

    Arctic tundra regions have been responding to global warming with visible changes in plant community composition, including expansion of shrubs and declines in lichens and bryophytes. Even though it is well known that the majority of arctic plants are associated with their symbiotic fungi, how fungal community composition will be different with climate warming remains largely unknown. In this study, we addressed the effects of long-term (18 years) experimental warming on the community composition and taxonomic richness of soil ascomycetes in dry and moist tundra types. Using deep Ion Torrent sequencing, we quantified how OTU assemblage and richness of different orders of Ascomycota changed in response to summer warming. Experimental warming significantly altered ascomycete communities with stronger responses observed in the moist tundra compared with dry tundra. The proportion of several lichenized and moss-associated fungi decreased with warming, while the proportion of several plant and insect pathogens and saprotrophic species was higher in the warming treatment. The observed alterations in both taxonomic and ecological groups of ascomycetes are discussed in relation to previously reported warming-induced shifts in arctic plant communities, including decline in lichens and bryophytes and increase in coverage and biomass of shrubs. © 2014 John Wiley & Sons Ltd.

  5. USArray Imaging of North American Continental Crust

    Science.gov (United States)

    Ma, Xiaofei

    The layered structure and bulk composition of continental crust contains important clues about its history of mountain-building, about its magmatic evolution, and about dynamical processes that continue to happen now. Geophysical and geological features such as gravity anomalies, surface topography, lithospheric strength and the deformation that drives the earthquake cycle are all directly related to deep crustal chemistry and the movement of materials through the crust that alter that chemistry. The North American continental crust records billions of years of history of tectonic and dynamical changes. The western U.S. is currently experiencing a diverse array of dynamical processes including modification by the Yellowstone hotspot, shortening and extension related to Pacific coast subduction and transform boundary shear, and plate interior seismicity driven by flow of the lower crust and upper mantle. The midcontinent and eastern U.S. is mostly stable but records a history of ancient continental collision and rifting. EarthScope's USArray seismic deployment has collected massive amounts of data across the entire United States that illuminates the deep continental crust, lithosphere and deeper mantle. This study uses EarthScope data to investigate the thickness and composition of the continental crust, including properties of its upper and lower layers. One-layer and two-layer models of crustal properties exhibit interesting relationships to the history of North American continental formation and recent tectonic activities that promise to significantly improve our understanding of the deep processes that shape the Earth's surface. Model results show that seismic velocity ratios are unusually low in the lower crust under the western U.S. Cordillera. Further modeling of how chemistry affects the seismic velocity ratio at temperatures and pressures found in the lower crust suggests that low seismic velocity ratios occur when water is mixed into the mineral matrix

  6. Atlantic continental margin of the United States

    Science.gov (United States)

    Grow, John A.; Sheridan, Robert E.; Palmer, A.R.

    1982-01-01

    The objective of this Decade of North American Geology (D-NAG) volume will be to focus on the Mesozoic and Cenozoic evolution of the U.S. Atlantic continental margin, including the onshore coastal plain, related onshore Triassic-Jurassic rift grabens, and the offshore basins and platforms. Following multiple compressional tectonic episodes between Africa and North America during the Paleozoic Era that formed the Appalachian Mountains, the Mesozoic and Cenozoic Eras were dominated by tensional tectonic processes that separated Africa and North America. Extensional rifting during Triassic and Early Jurassic times resulted in numerous tensional grabens both onshore and offshore, which filled with nonmarine continental red beds, lacustrine deposits, and volcanic flows and debris. The final stage of this breakup between Africa and North America occurred beneath the present outer continental shelf and continental slope during Early or Middle Jurassic time when sea-floor spreading began to form new oceanic crust and lithosophere between the two continents as they drifted apart. Postrift subsidence of the marginal basins continued in response to cooling of the lithosphere and sedimentary loading.Geophysical surveys and oil-exploration drilling along the U.S. Atlantic continental margin during the past 5 years are beginning to answer many questions concerning its deep structure and stratigraphy and how it evolved during the rifting and early sea-floor-spreading stages of the separation of this region from Africa. Earlier geophysical studies of the U.S. continental margin used marine refraction and submarine gravity measurements. Single-channel seismic-reflection, marine magnetic, aeromagnetic, and continuous gravity measurements became available during the 1960s.

  7. Continental drift under the Third Reich.

    Science.gov (United States)

    Buffetaut, Eric

    2003-12-01

    Contrary to what happened in many other countries in the 1930s and 1940s, Alfred Wegener's theory of continental drift was not generally rejected in Nazi Germany, although several leading German geologists of the time did not accept it. It was actually presented as the modern view of Earth history in books and magazine articles aimed at the general public. Although outlandish geological theories such as Hörbiger's Welteislehre were favoured by some Nazi dignitaries, they were not widely accepted in scientific circles. On the other hand, continental drift received official support under the Third Reich, at a time when it was ignored or ridiculed by most earth scientists outside Germany.

  8. Do the pyramids show continental drift?

    Science.gov (United States)

    Pawley, G S; Abrahamsen, N

    1973-03-02

    The mystery of the orientation of the Great Pyramids of Giza has remained unexplained for many decades. The general alignment is 4 minutes west of north. It is argued that this is not a builders' error but is caused by movement over the centuries. Modern theories of continental drift do not predict quite such large movements, but other causes of polar wandering give even smaller shifts. Thus, continental drift is the most likely explanation, although somewhat implausible, especially as relevant measurements have been made over a 50-year period, whereas geophysical measurements of sea-floor spreading relate to million-year time scales.

  9. MAGSAT anomaly map and continental drift

    Science.gov (United States)

    Lemouel, J. L. (Principal Investigator); Galdeano, A.; Ducruix, J.

    1981-01-01

    Anomaly maps of high quality are needed to display unambiguously the so called long wave length anomalies. The anomalies were analyzed in terms of continental drift and the nature of their sources is discussed. The map presented confirms the thinness of the oceanic magnetized layer. Continental magnetic anomalies are characterized by elongated structures generally of east-west trend. Paleomagnetic reconstruction shows that the anomalies found in India, Australia, and Antarctic exhibit a fair consistency with the African anomalies. It is also shown that anomalies are locked under the continents and have a fixed geometry.

  10. Continental Growth and Recycling in Convergent Orogens with Large Turbidite Fans on Oceanic Crust

    Directory of Open Access Journals (Sweden)

    Ben D. Goscombe

    2013-07-01

    Full Text Available Convergent plate margins where large turbidite fans with slivers of oceanic basement are accreted to continents represent important sites of continental crustal growth and recycling. Crust accreted in these settings is dominated by an upper layer of recycled crustal and arc detritus (turbidites underlain by a layer of tectonically imbricated upper oceanic crust and/or thinned continental crust. When oceanic crust is converted to lower continental crust it represents a juvenile addition to the continental growth budget. This two-tiered accreted crust is often the same thickness as average continental crustal and is isostatically balanced near sea level. The Paleozoic Lachlan Orogen of eastern Australia is the archetypical example of a tubidite-dominated accretionary orogeny. The Neoproterozoic-Cambrian Damaran Orogen of SW Africa is similar to the Lachlan Orogen except that it was incorporated into Gondwana via a continent-continent collision. The Mesozoic Rangitatan Orogen of New Zealand illustrates the transition of convergent margin from a Lachlan-type to more typical accretionary wedge type orogen. The spatial and temporal variations in deformation, metamorphism, and magmatism across these orogens illustrate how large volumes of turbidite and their relict oceanic basement eventually become stable continental crust. The timing of deformation and metamorphism recorded in these rocks reflects the crustal thickening phase, whereas post-tectonic magmatism constrains the timing of chemical maturation and cratonization. Cratonization of continental crust is fostered because turbidites represent fertile sources for felsic magmatism. Recognition of similar orogens in the Proterozoic and Archean is important for the evaluation of crustal growth models, particularly for those based on detrital zircon age patterns, because crustal growth by accretion of upper oceanic crust or mafic underplating does not readily result in the addition of voluminous zircon

  11. How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra.

    Directory of Open Access Journals (Sweden)

    John-André Henden

    Full Text Available The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation

  12. Detection and molecular characterization of the mosquito-borne filarial nematode Setaria tundra in Danish roe deer (Capreolus capreolus

    Directory of Open Access Journals (Sweden)

    Heidi Larsen Enemark

    2017-04-01

    Full Text Available Setaria tundra is a mosquito-borne filarial nematode of cervids in Europe. It has recently been associated with an emerging epidemic disease causing severe morbidity and mortality in reindeer and moose in Finland. Here, we present the first report of S. tundra in six roe deer (Capreolus capreolus collected between October 2010 and March 2014 in Denmark. The deer originated from various localities across the country: the eastern part of the Jutland peninsular and four locations on the island Zealand. With the exception of one deer, with parasites residing in a transparent cyst just under the liver capsule, worms (ranging from 2 to >20/deer were found free in the peritoneal cavity. The worms were identified as S. tundra by morphological examination and/or molecular typing of the mitochondrial 12S rRNA and cox1 genes, which showed 99.1–99.8% identity to previously published S. tundra isolates from Europe. Roe deer are generally considered as asymptomatic carriers and their numbers in Denmark have increased significantly in recent decades. In light of climatic changes which result in warmer, more humid weather in Scandinavia greater numbers of mosquitoes and, especially, improved conditions for development of parasite larvae in the mosquito vectors are expected, which may lead to increasing prevalence of S. tundra. Monitoring of this vector-borne parasite may thus be needed in order to enhance the knowledge of factors promoting its expansion and prevalence as well as predicting disease outbreaks.

  13. Satellite-Based Evidence for Shrub and Graminoid Tundra Expansion in Northern Quebec from 1986-2010

    Science.gov (United States)

    McManus, K. M.; Morton, D. C.; Masek, J. G.; Wang, D.; Sexton, J. O.; Nagol, J.; Ropars, P.; Boudreau, S.

    2012-01-01

    Global vegetation models predict rapid poleward migration of tundra and boreal forest vegetation in response to climate warming. Local plot and air-photo studies have documented recent changes in high-latitude vegetation composition and structure, consistent with warming trends. To bridge these two scales of inference, we analyzed a 24-year (1986-2010) Landsat time series in a latitudinal transect across the boreal forest-tundra biome boundary in northern Quebec province, Canada. This region has experienced rapid warming during both winter and summer months during the last forty years. Using a per-pixel (30 m) trend analysis, 30% of the observable (cloud-free) land area experienced a significant (p tundra contributed preferentially to the greening trend, while forested areas were less likely to show significant trends in NDVI. These trends reflect increasing leaf area, rather than an increase in growing season length, because Landsat data were restricted to peak-summer conditions. The average NDVI trend (0.007/yr) corresponds to a leaf-area index (LAI) increase of 0.6 based on the regional relationship between LAI and NDVI from the Moderate Resolution Spectroradiometer (MODIS). Across the entire transect, the area-averaged LAI increase was 0.2 during 1986-2010. A higher area-averaged LAI change (0.3) within the shrub-tundra portion of the transect represents a 20-60% relative increase in LAI during the last two decades. Our Landsat-based analysis subdivides the overall high-latitude greening trend into changes in peak-summer greenness by cover type. Different responses within and among shrub, graminoid, and tree-dominated cover types in this study indicate important fine-scale heterogeneity in vegetation growth. Although our findings are consistent with community shifts in low-biomass vegetation types over multi-decadal time scales, the response in tundra and forest ecosystems to recent warming was not uniform.

  14. Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska.

    Science.gov (United States)

    Morgado, Luis N; Semenova, Tatiana A; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-02-01

    Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage. © 2014 The Authors. Global Change

  15. Plastic bimodal xylogenesis in conifers from continental Mediterranean climates.

    Science.gov (United States)

    Camarero, Jesús Julio; Olano, José Miguel; Parras, Alfonso

    2010-01-01

    *Seasonal radial-increment and xylogenesis data can help to elucidate how climate modulates wood formation in conifers. Few xylogenesis studies have assessed how plastic xylogenesis is in sympatric conifer species from continental Mediterranean areas, where low winter temperatures and summer drought constrain growth. *Here, we analysed intra-annual patterns of secondary growth in sympatric conifer species (Juniperus thurifera, Pinus halepensis and Pinus sylvestris). Two field sites (xeric and mesic) were evaluated using dendrometers, microcores and climatic data. *A bimodal pattern of xylogenesis characterized by spring and autumn precipitation and subsequent cambial reactivation was detected in J. thurifera at both study sites and in P. halepensis at the xeric site, but was absent in P. sylvestris where growth was largely controlled by day length. In the xeric site J. thurifera exhibited an increased response to water availability in autumn relative to P. halepensis and summer cambial suppression was more marked in J. thurifera than in P. halepensis. *Juniperus thurifera exhibited increased plasticity in its xylogenesis pattern compared with sympatric pines, enabling this species to occupy sites with more variable climatic conditions. The plastic xylogenesis patterns of junipers in drought-stressed areas may also provide them with a competitive advantage against co-occurring pines.

  16. Western Ross Sea continental slope gravity currents

    Science.gov (United States)

    Gordon, Arnold L.; Orsi, Alejandro H.; Muench, Robin; Huber, Bruce A.; Zambianchi, Enrico; Visbeck, Martin

    2009-06-01

    Antarctic Bottom Water of the world ocean is derived from dense Shelf Water that is carried downslope by gravity currents at specific sites along the Antarctic margins. Data gathered by the AnSlope and CLIMA programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the Ross Sea when High Salinity Shelf Water exits the shelf through Drygalski Trough. Joides Trough, immediately to the east, offers an additional escape route for less saline Shelf Water, while the Glomar Challenger Trough still farther east is a major pathway for export of the once supercooled low-salinity Ice Shelf Water that forms under the Ross Ice Shelf. The Drygalski Trough gravity currents increase in thickness from ˜100 to ˜400 m on proceeding downslope from ˜600 m (the shelf break) to 1200 m (upper slope) sea floor depth, while turning sharply to the west in response to the Coriolis force during their descent. The mean current pathway trends ˜35° downslope from isobaths. Benthic-layer current and thickness are correlated with the bottom water salinity, which exerts the primary control over the benthic-layer density. A 1-year time series of bottom-water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of Shelf Water export through Drygalski Trough. These cold (34.75) pulses correlate with strong downslope bottom flow. Extreme examples occurred during austral summer/fall 2003, comprising concentrated High Salinity Shelf Water (-1.9 °C; 34.79) and approaching 1.5 m s -1 at descent angles as large as ˜60° relative to the isobaths. Such events were most common during November-May, consistent with a northward shift in position of the dense Shelf Water during austral summer. The coldest, saltiest bottom water was measured from mid-April to mid-May 2003. The summer/fall export of High Salinity Shelf Water observed in 2004 was less than that seen in 2003. This difference, if real

  17. Does NDVI reflect variation in the structural attributes associated with increasing shrub dominance in arctic tundra?

    Energy Technology Data Exchange (ETDEWEB)

    Boelman, Natalie T [Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY 10964 (United States); Gough, Laura; McLaren, Jennie R [Department of Biology, University of Texas at Arlington, Arlington, TX 76019 (United States); Greaves, Heather, E-mail: nboelman@ldeo.columbia.edu [Department of Forest Ecosystems and Society, Oregon State University, 321 Richardson Hall, Corvallis, OR 97331 (United States)

    2011-07-15

    This study explores relationships between the normalized difference vegetation index (NDVI) and structural characteristics associated with deciduous shrub dominance in arctic tundra. Our structural measures of shrub dominance are stature, branch abundance, aerial per cent woody stem cover (deciduous and evergreen species), and per cent deciduous shrub canopy cover. All measurements were taken across a suite of transects that together represent a gradient of deciduous shrub height. The transects include tussock tundra shrub and riparian shrub tundra communities located in the northern foothills of the Brooks Range, in northern Alaska. Plot-level NDVI measurements were made in 2010 during the snow-free period prior to deciduous shrub leaf-out (early June, NDVI{sub pre-leaf}), at the point in the growing season when canopy NDVI has reached half of its maximum growing season value (mid-June, NDVI{sub demi-leaf}) and during the period of maximum leaf-out (late July, NDVI{sub peak-leaf}). We found that: (1) NDVI{sub pre-leaf} is best suited to capturing variation in the per cent woody stem cover, maximum shrub height, and branch abundance, particularly between 10 and 50 cm height in the canopy; (2) NDVI{sub peak-leaf} is best suited to capturing variation in deciduous canopy cover; and (3) NDVI{sub demi-leaf} does not capture variability in any of our measures of shrub dominance. These findings suggest that in situ NDVI measurements made prior to deciduous canopy leaf-out could be used to identify small differences in maximum shrub height, woody stem cover, and branch abundance (particularly between 10 and 50 cm height in the canopy). Because shrubs are increasing in size and regional extent in several regions of the Arctic, investigation into spectrally based tools for monitoring these changes are worthwhile as they provide a first step towards development of remotely sensed techniques for quantifying associated changes in regional carbon cycling, albedo, radiative

  18. Thaw pond dynamics and carbon emissions in a Siberian lowland tundra landscape

    Science.gov (United States)

    van Huissteden, Ko; Heijmans, Monique; Dean, Josh; Meisel, Ove; Goovaerts, Arne; Parmentier, Frans-Jan; Schaepman-Strub, Gabriela; Belelli Marchesini, Luca; Kononov, Alexander; Maximov, Trofim; Borges, Alberto; Bouillon, Steven

    2017-04-01

    Arctic climate change induces drastic changes in permafrost surface wetness. As a result of thawing ground ice bodies, ice wedge troughs and thaw ponds are formed. Alternatively, ongoing thaw may enhance drainage as a result of increased interconnectedness of thawing ice wedge troughs, as inferred from a model study (Liljedahl et al., 2016, Nature Geoscience, DOI: 10.1038/NGEO2674). However, a recent review highlighted the limited predictability of consequences of thawing permafrost on hydrology (Walvoord and Kurylyk, 2016, Vadose Zone J., DOI:10.2136/vzj2016.01.0010). Overall, these changes in tundra wetness modify carbon cycling in the Arctic and in particular the emissions of CO2 and CH4 to the atmosphere, providing a possibly positive feedback on climate change. Here we present the results of a combined remote sensing, geomorphological, vegetation and biogechemical study of thaw ponds in Arctic Siberian tundra, at Kytalyk research station near Chokurdakh, Indigirka lowlands. The station is located in an area dominated by Pleistocene ice-rich 'yedoma' sediments and drained thaw lake bottoms of Holocene age. The development of three types of ponds in the Kytalyk area (polygon centre ponds, ice wedge troughs and thaw ponds) has been traced with high resolution satellite and aerial imagery. The remote sensing data show net areal expansion of all types of ponds. Next to formation of new ponds, local vegetation change from dry vegetation types to wet, sedge-dominated vegetation is common. Thawing ice wedges and thaw ponds show an increase in area and number at most studied locations. In particular the area of polygon centre ponds increased strongly between 2010 and 2015, but this is highly sensitive to antecedent precipitation conditions. Despite a nearly 60% increase of the area of thawing ice wedge troughs, there is no evidence of decreasing water surfaces by increasing drainage through connected ice wedge troughs. The number of thaw ponds shows an equilibrium

  19. Understanding Pan-Arctic Tundra Vegetation Change Through Long-term Remotely Sensed Data

    Science.gov (United States)

    Bhatt, U.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2012-12-01

    The goal of this paper is to present an analysis of the seasonality of tundra vegetation variability and change using long-term remotely sensed data as well as ground based measurements and reanalyses. An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI). Coherent variability between NDVI, springtime coastal sea ice (passive microwave) and land surface temperatures (AVHRR) has also been established. Satellite based snow and cloud cover data sets are being incorporated into this analysis. The Arctic tundra is divided into domains based on Treshnikov divisions that are modified based on floristic provinces. There is notable heterogeneity in Pan-Arctic vegetation and climate trends, which necessitates a regional analysis. This study uses remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2010. The GIMMS NDVI3g data has been corrected for biases during the spring and fall, with special focus on the Arctic. Trends of Maximum NDVI (MaxNDVI), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), and open water area are calculated for the Pan Arctic. Remotely sensed snow data trends suggest varying patterns throughout the Arctic and may in part explain the heterogeneous MaxNDVI trends. Standard climate data (station, reanalysis, and model data) and ground observations are used in the analysis to provide additional support for hypothesized mechanisms. Overall, we find that trends over the 30-year record are changing as evidenced by the following examples from recent years. The sea ice decline has increased in Eurasia and slowed in North America. The weekly AVHRR landsurface temperatures reveal that there has been summer cooling over Eurasia and that the warming over North America has slowed. The MaxNDVI rates of change have diverged between N. America and Eurasia

  20. Decadal changes in tundra land cover on Yamal Peninsula, Northwest Siberia

    Science.gov (United States)

    Forbes, B. C.; Kumpula, T.; Macias-Fauria, M.

    2017-12-01

    The Yamal-Nenets Okrug in Russia has experienced significant changes in land use and climate in recent decades. Average year-round air temperatures have increased ca. 2°C since the 1970's, with much - but not all - of the warming taking place in winter. In association with ongoing summer warming, the annual growth of erect deciduous shrubs has been accelerating while growing season seasonality has diminished, characterized by shifts in the spatial patterns of key phenological parameters. We prepared LANDSAT-derived land cover classifications for 1988 and 2014 using change detection analysis, supported by extensive ground truthing bolstered with data from Very High-Resolution (VHR) imagery (e.g. Quickbird-2, Worldview-2/3). Research was conducted within summer reindeer pastures utilized by the Yarsalinksi sovhoz, whose animals are collectively owned, as well as many privately-owned herds. The area represents bioclimatic Subzone D of the Circumpolar Arctic Vegetation Map and covers about 8500 km2. This is a key subzone for several reasons: (1) it includes Bovanenkovo, the first and largest gas deposit on Yamal to be developed; (2) it is a zone of extremely active periglacial processes (e.g. active layer detachment slides, lake drainage and recent methane-mediated craters); and (3) it is characterized by steadily increasing growth of tall willow shrubs (Salix spp.), which comprise an important source of fodder by reindeer migrating through the area in summer. These results are unique as our dataset: (1) covers sizable inland regions lying entirely within the Russian tundra zone; (2) derives from extensive ground truthing; and (3) treats all plant taxonomic groups (vascular, bryophytes, lichens) at the plot scale. Here we present the first such classifications, based on LANDSAT images from 1988 and 2014. We identify 16 classes ranging from bare ground and drained lakes, anthropogenic disturbances, through several wetland types, to various dwarf and erect tundra shrub

  1. Demographic outcomes of diverse migration strategies assessed in a metapopulation of tundra swans.

    Science.gov (United States)

    Ely, Craig R; Meixell, Brandt W

    2016-01-01

    Migration is a prominent aspect of the life history of many avian species, but the demographic consequences of variable migration strategies have only infrequently been investigated, and rarely when using modern technological and analytical methods for assessing survival, movement patterns, and long-term productivity in the context of life history theory. We monitored the fates of 50 satellite-implanted tundra swans (Cygnus columbianus) over 4 years from five disparate breeding areas in Alaska, and used known-fate analyses to estimate monthly survival probability relative to migration distance, breeding area, migratory flyway, breeding status, and age. We specifically tested whether migratory birds face a trade-off, whereby long-distance migrants realize higher survival rates at the cost of lower productivity because of reduced time on breeding areas relative to birds that migrate shorter distances and spend more time on breeding areas. Annual migration distances varied significantly among breeding areas (1020 to 12720 km), and were strongly negatively correlated with time spent on breeding areas (r = -0.986). Estimates of annual survival probability varied by wintering area (Pacific coast, Alaska Peninsula, and Eastern seaboard) and ranged from 0.79 (95%CI: 0.70-0.88) to 1.0, depending on criteria used to discern mortalities from radio failures. We did not find evidence for a linear relationship between migration distance and survival as swans from the breeding areas with the shortest and longest migration distances had the highest survival probabilities. Survival was lower in the first year post-marking than in subsequent years, but there was not support for seasonal differences in survival. Productivity varied among breeding populations and was generally inversely correlated to survival, but not migration distance or time spent on breeding areas. Tundra swans conformed to a major tenet of life history theory, as populations with the highest survival

  2. Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra.

    Science.gov (United States)

    Blanc-Betes, Elena; Welker, Jeffrey M; Sturchio, Neil C; Chanton, Jeffrey P; Gonzalez-Meler, Miquel A

    2016-08-01

    Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH4 emissions may represent a significant climate forcing feedback, long-term impacts of changes in snow accumulation on CH4 fluxes remain uncertain. We measured ecosystem CH4 fluxes and soil CH4 and CO2 concentrations and (13) C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH4 flux over the growing season (Jun-Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O2 levels and increasing thaw depth. Soil moisture, through changes in soil %O2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH4 (Fox) by 75-120% compared to Ambient, switching the system from a small source to a net CH4 sink (21 ± 2 and -31 ± 1 mg CH4  m(-2)  season(-1) at Ambient and RS). Deeper snow reduced Fox by 35-40% and 90-100% in medium- (MS) and high- (HS) snow additions relative to Ambient, contributing to increasing the CH4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH4  m(-2)  season(-1) at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant-mediated CH4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw-induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently

  3. Exchange of CO2 in Arctic tundra: impacts of meteorological variations and biological disturbance

    Science.gov (United States)

    López-Blanco, Efrén; Lund, Magnus; Williams, Mathew; Tamstorf, Mikkel P.; Westergaard-Nielsen, Andreas; Exbrayat, Jean-François; Hansen, Birger U.; Christensen, Torben R.

    2017-10-01

    An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating -30 g C m-2 on average (range of -17 to -41 g C m-2) during the years 2008-2015, except 2011 (source of 41 g C m-2), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (-182 to -316 g C m-2) and Reco (144 to 279 g C m-2) were > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.

  4. Wegener and his Theory of Continental Drift

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 7. Wegener and his Theory of Continental Drift. Ramesh Chander. General Article Volume 4 Issue 7 July 1999 pp 24-41. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/004/07/0024-0041 ...

  5. Plate Tectonics and Continental Drift: Classroom Ideas.

    Science.gov (United States)

    Stout, Prentice K.

    1983-01-01

    Suggests various classroom studies related to plate tectonics and continental drift, including comments on and sources of resource materials useful in teaching the topics. A complete list of magazine articles on the topics from the Sawyer Marine Resource Collection may be obtained by contacting the author. (JN)

  6. Wegener and his Theory of Continental Drift

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 12. Wegener and his Theory of Continental Drift. Ramesh Chander. Volume 10 Issue 12 December 2005 pp 58-75. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/010/12/0058-0075 ...

  7. Coordination: Southeast Continental Shelf studies. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, D.W.

    1981-02-01

    An overview of the Oceanograhic Program of Skidaway Institute of Oceanograhy is presented. Included are the current five year plan for studies of the Southeast Continental Shelf, a summary of research accomplishments, proposed research for 1981-1982, current status of the Savannah Navigational Light Tower, and a list of publications. (ACR)

  8. Root zone of a continental rift

    DEFF Research Database (Denmark)

    Kirsch, Moritz; Svenningsen, Olaf

    2016-01-01

    Mafic magmatic rocks formed between ca. 615 and 560 Ma along the Neoproterozoic margins of Baltica and Laurentia are classically attributed to continental rifting heralding the opening of the Iapetus Ocean. We report new data for the Kebnekaise Intrusive Complex (KIC) exposed in the Seve Nappes i...

  9. CAR LEADEX Level 1C Artic Sea Ice and Tundra Radiation Measurements (CAR_LEADEX_L1C) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — CAR LEADEX mission measured bidirectional reflectance functions for four common arctic surfaces: snow covered sea ice, melt season sea ice, snow covered tundra, and...

  10. 75 FR 1076 - Outer Continental Shelf Civil Penalties

    Science.gov (United States)

    2010-01-08

    ... initiate civil penalty proceedings; however, violations that cause injury, death, or environmental damage... DEPARTMENT OF THE INTERIOR Minerals Management Service Outer Continental Shelf Civil Penalties... daily civil penalty assessment. SUMMARY: The Outer Continental Shelf Lands Act requires the MMS to...

  11. Changing Seasonality of Panarctic Tundra Vegetation in Relationship to Climatic Variables

    Science.gov (United States)

    Bhatt, Uma S.; Walker, Donald A.; Raynolds, Martha K.; Bieniek, Peter A.; Epstein, Howard E.; Comiso, Josefino C.; Pinzon, Jorge E.; Tucker, Compton J.; Steele, Michael; Ermold, Wendy; hide

    2017-01-01

    Potential climate drivers of Arctic tundra vegetation productivity are investigated to understand recent greening and browning trends documented by maximum normalized difference vegetation index (NDVI) (MaxNDVI) and time-integrated NDVI (TI-NDVI) for 19822015. Over this period, summer sea ice has continued to decline while oceanic heat content has increased. The increases in summer warmth index (SWI) and NDVI have not been uniform over the satellite record. SWI increased from 1982 to the mid-1990s and remained relatively flat from 1998 onwards until a recent upturn. While MaxNDVI displays positive trends from 19822015, TI-NDVI increased from 1982 until 2001 and has declined since. The data for the first and second halves of the record were analyzed and compared spatially for changing trends with a focus on the growing season. Negative trends for MaxNDVI and TI-NDVI were more common during 19992015 compared to 19821998.

  12. A continuous-flow periphyton bioassay: tests of nutrient limitation in a tundra stream

    International Nuclear Information System (INIS)

    Peterson, B.J.; Hobbie, J.E.; Corliss, T.L.; Kriet, K.

    1983-01-01

    The effect of added nutrients on the periphyton of a tundra stream was tested during July and August. Flow-through systems consisting of a bank of clear plastic tubes containing racks of microscope slides were suspended from floats in the stream. Nutrients were enriched in the experimental tubes by siphoning concentrated nutrient solutions from Mariotte bottles into the upstream end of each tube. Slides from each tube were assayed at 2-6 day intervals for chlorophyll content and photosynthetic 14 CO 2 uptake. Levels of chlorophyll and CO 2 uptake were significantly higher than the controls both in the tubes with 10μg PO 4 -P>liter -1 of stream water and in those with P plus 100 μg NH 4 NO 3 -N.liter. Nitrogen alone gave no stimulation

  13. Fungi benefit from two decades of increased nutrient availability in tundra heath soil

    DEFF Research Database (Denmark)

    Rinnan, Riikka; Michelsen, Anders; Bååth, Erland

    2013-01-01

    If microbial degradation of carbon substrates in arctic soil is stimulated by climatic warming, this would be a significant positive feedback on global change. With data from a climate change experiment in Northern Sweden we show that warming and enhanced soil nutrient availability, which...... is a predicted long-term consequence of climatic warming and mimicked by fertilization, both increase soil microbial biomass. However, while fertilization increased the relative abundance of fungi, warming caused only a minimal shift in the microbial community composition based on the phospholipid fatty acid...... of complex organic compounds such as vanillin, while warming has had no such effects. Furthermore, the NLFA-to-PLFA ratio for (13)C-incorporation from acetate increased in warmed plots but not in fertilized ones. Thus, fertilization cannot be used as a proxy for effects on warming in arctic tundra soils...

  14. Influence of iron redox cycling on organo-mineral associations in Arctic tundra soil

    Science.gov (United States)

    Herndon, Elizabeth; AlBashaireh, Amineh; Singer, David; Roy Chowdhury, Taniya; Gu, Baohua; Graham, David

    2017-06-01

    Arctic tundra stores large quantities of soil organic matter under varying redox conditions. As the climate warms, these carbon reservoirs are susceptible to increased rates of decomposition and release to the atmosphere as the greenhouse gases carbon dioxide (CO2) and methane (CH4). Geochemical interactions between soil organic matter and minerals influence decomposition in many environments but remain poorly understood in Arctic tundra systems and are not considered in decomposition models. The accumulation of iron (Fe) oxyhydroxides and organo-iron precipitates at redox interfaces may be particularly important for carbon cycling given that ferric iron [Fe(III)] species can enhance decomposition by serving as terminal electron acceptors in anoxic soils or inhibit microbial decomposition by binding organic molecules. Here, we examine chemical properties of solid-phase Fe and organic matter in organic and mineral horizons within the seasonally thawed active layer of Arctic tundra on the North Slope of Alaska. Spectroscopic techniques, including micro-X-ray fluorescence (μXRF) mapping, micro-X-ray absorption near-edge structure (μXANES) spectroscopy, and Fourier transform infrared spectroscopy (FTIR), were coupled with chemical sequential extractions and physical density fractionations to evaluate the spatial distribution and speciation of Fe-bearing phases and associated organic matter in soils. Organic horizons were enriched in poorly crystalline and crystalline iron oxides, and approximately 60% of total Fe stored in organic horizons was calculated to derive from upward translocation from anoxic mineral horizons. Ferrihydrite and goethite were present as coatings on mineral grains and plant debris, and in aggregates with clays and particulate organic matter. Minor amounts of ferrous iron [Fe(II)] were present in iron sulfides (i.e., pyrite and greigite) in mineral horizon soils and iron phosphates (vivianite) in organic horizons. Concentrations of organic

  15. Doubled volatile organic compound emissions from subarctic tundra under simulated climate warming

    DEFF Research Database (Denmark)

    Faubert, Patrick; Tiiva, Paivi; Rinnan, Åsmund

    2010-01-01

    • Biogenic volatile organic compound (BVOC) emissions from arctic ecosystems are important in view of their role in global atmospheric chemistry and unknown feedbacks to global warming. These cold ecosystems are hotspots of climate warming, which will be more severe here than averaged over...... the globe. We assess the effects of climatic warming on non-methane BVOC emissions from a subarctic heath. • We performed ecosystem-based chamber measurements and gas chromatography-mass spectrometry (GC-MS) analyses of the BVOCs collected on adsorbent over two growing seasons at a wet subarctic tundra...... heath hosting a long-term warming and mountain birch (Betula pubescens ssp. czerepanovii) litter addition experiment. • The relatively low emissions of monoterpenes and sesquiterpenes were doubled in response to an air temperature increment of only 1.9-2.5°C, while litter addition had a minor influence...

  16. Circumpolar arctic tundra biomass and productivity dynamics in response to projected climate change and herbivory.

    Science.gov (United States)

    Yu, Qin; Epstein, Howard; Engstrom, Ryan; Walker, Donald

    2017-09-01

    Satellite remote sensing data have indicated a general 'greening' trend in the arctic tundra biome. However, the observed changes based on remote sensing are the result of multiple environmental drivers, and the effects of individual controls such as warming, herbivory, and other disturbances on changes in vegetation biomass, community structure, and ecosystem function remain unclear. We apply ArcVeg, an arctic tundra vegetation dynamics model, to estimate potential changes in vegetation biomass and net primary production (NPP) at the plant community and functional type levels. ArcVeg is driven by soil nitrogen output from the Terrestrial Ecosystem Model, existing densities of Rangifer populations, and projected summer temperature changes by the NCAR CCSM4.0 general circulation model across the Arctic. We quantified the changes in aboveground biomass and NPP resulting from (i) observed herbivory only; (ii) projected climate change only; and (iii) coupled effects of projected climate change and herbivory. We evaluated model outputs of the absolute and relative differences in biomass and NPP by country, bioclimate subzone, and floristic province. Estimated potential biomass increases resulting from temperature increase only are approximately 5% greater than the biomass modeled due to coupled warming and herbivory. Such potential increases are greater in areas currently occupied by large or dense Rangifer herds such as the Nenets-occupied regions in Russia (27% greater vegetation increase without herbivores). In addition, herbivory modulates shifts in plant community structure caused by warming. Plant functional types such as shrubs and mosses were affected to a greater degree than other functional types by either warming or herbivory or coupled effects of the two. © 2017 John Wiley & Sons Ltd.

  17. Implications of a lightning-rich tundra biome for permafrost carbon and vegetation dynamics

    Science.gov (United States)

    Chen, Y.; Veraverbeke, S.; Randerson, J. T.

    2017-12-01

    Lightning is a major ignition source of wildfires in circumpolar boreal forests but rarely occurs in arctic tundra. While theoretical and empirical work suggests that climate change will increase lightning strikes in temperate regions, much less is known about future changes in lightning across terrestrial ecosystems at high northern latitudes. Here we analyzed the spatial and temporal patterns of lightning flash rate (FR) from the satellite observations and surface detection networks. Regression models between the observed FR from the Optical Transient Detector on the MicroLab-1 satellite (later renamed OV-1) and meteorological parameters, including surface temperature (T), convective available potential energy (CAPE), and convective precipitation (CP) from ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-interim reanalysis, were established and assessed. We found that FR had significant linear correlations with CAPE and CP, and a strong non-linear relationship with T. The statistical model based on T and CP can reproduce most of the spatial and temporal variability in FR in the circumpolar region. By using the regression model and meteorological predictions from 24 earth system models in the Coupled Model Intercomparison Project Phase 5 (CMIP5), we estimated the spatial distribution of FR by the end of the 21st century. Due to increases in surface temperature and convection, modeled FR shows substantial increase in northern biomes, including a 338% change in arctic tundra and a 185% change in regions with permafrost soil carbon reservoirs. These changes highlight a new mechanism by which permafrost carbon is vulnerable to the sustained impacts of climate warming. Increased fire in a warmer and lightning-rich future near the treeline has the potential to accelerate the northward migration of trees, which may further enhance warming and the abundance of lightning strikes.

  18. Vegetation-associated impacts on arctic tundra bacterial and microeukaryotic communities.

    Science.gov (United States)

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Chu, Haiyan; Neufeld, Josh D; Walker, Virginia K; Grogan, Paul

    2015-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H') were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure. Copyright © 2015, American Society for Microbiology. All Rights

  19. Object-Based Mapping of the Circumpolar Taiga-Tundra Ecotone with MODIS Tree Cover

    Science.gov (United States)

    Ranson, K. J.; Montesano, P. M.; Nelson, R.

    2011-01-01

    The circumpolar taiga tundra ecotone was delineated using an image-segmentation-based mapping approach with multi-annual MODIS Vegetation Continuous Fields (VCF) tree cover data. Circumpolar tree canopy cover (TCC) throughout the ecotone was derived by averaging MODIS VCF data from 2000 to 2005 and adjusting the averaged values using linear equations relating MODIS TCC to Quickbird-derived tree cover estimates. The adjustment helped mitigate VCF's overestimation of tree cover in lightly forested regions. An image segmentation procedure was used to group pixels representing similar tree cover into polygonal features (segmentation objects) that form the map of the transition zone. Each polygon represents an area much larger than the 500 m MODIS pixel and characterizes the patterns of sparse forest patches on a regional scale. Those polygons near the boreal/tundra interface with either (1) mean adjusted TCC values from5 to 20%, or (2) mean adjusted TCC values greater than 5% but with a standard deviation less than 5% were used to identify the ecotone. Comparisons of the adjusted average tree cover data were made with (1) two existing tree line definitions aggregated for each 1 degree longitudinal interval in North America and Eurasia, (2) Landsat-derived Canadian proportion of forest cover for Canada, and (3) with canopy cover estimates extracted from airborne profiling lidar data that transected 1238 of the TCC polygons. The adjusted TCC from MODIS VCF shows, on average, less than 12% TCC for all but one regional zone at the intersection with independently delineated tree lines. Adjusted values track closely with Canadian proportion of forest cover data in areas of low tree cover. A comparison of the 1238 TCC polygons with profiling lidar measurements yielded an overall accuracy of 67.7%.

  20. Water uptake of Alaskan tundra evergreens during the winter-spring transition.

    Science.gov (United States)

    Moser, Jonathan G; Oberbauer, Steven F; Sternberg, Leonel da S L; Ellsworth, Patrick Z; Starr, Gregory; Mortazavi, Behzad; Olivas, Paulo C

    2016-02-01

    The cold season in the Arctic extends over 8 to 9 mo, yet little is known about vascular plant physiology during this period. Evergreen species photosynthesize under the snow, implying that they are exchanging water with the atmosphere. However, liquid water available for plant uptake may be limited at this time. The study objective was to determine whether evergreen plants are actively taking up water while under snow and/or immediately following snowmelt during spring thaw. In two in situ experiments, one at the plot level and another at the individual species level, (2)H-labeled water was used as a tracer injected beneath the snow, after which plant stems and leaves were tested for the presence of the label. In separate experiments, excised shoots of evergreen species were exposed to (2)H-labeled water for ∼5 s or 60 min and tested for foliar uptake of the label. In both the plot-level and the species-level experiments, some (2)H-labeled water was found in leaves and stems. Additionally, excised individual plant shoots exposed to labeled water for 60 min took up significantly more (2)H-label than shoots exposed ∼5 s. Evergreen tundra plants take up water under snow cover, some via roots, but also likely by foliar uptake. The ability to take up water in the subnivean environment allows evergreen tundra plants to take advantage of mild spring conditions under the snow and replenish carbon lost by winter respiration. © 2016 Botanical Society of America.

  1. Age-specific survival of tundra swans on the lower Alaska Peninsula

    Science.gov (United States)

    Meixell, Brandt W.; Lindberg, Mark S.; Conn, Paul B.; Dau, Christian P.; Sarvis, John E.; Sowl, Kristine M.

    2013-01-01

    The population of Tundra Swans (Cygnus columbianus columbianus) breeding on the lower Alaska Peninsula represents the southern extremity of the species' range and is uniquely nonmigratory. We used data on recaptures, resightings, and recoveries of neck-collared Tundra Swans on the lower Alaska Peninsula to estimate collar loss, annual apparent survival, and other demographic parameters for the years 1978–1989. Annual collar loss was greater for adult males fitted with either the thinner collar type (0.34) or the thicker collar type (0.15) than for other age/sex classes (thinner: 0.10, thicker: 0.04). The apparent mean probability of survival of adults (0.61) was higher than that of immatures (0.41) and for both age classes varied considerably by year (adult range: 0.44–0.95, immature range: 0.25–0.90). To assess effects of permanent emigration by age and breeding class, we analyzed post hoc the encounter histories of swans known to breed in our study area. The apparent mean survival of known breeders (0.65) was generally higher than that of the entire marked sample but still varied considerably by year (range 0.26–1.00) and indicated that permanent emigration of breeding swans was likely. We suggest that reductions in apparent survival probability were influenced primarily by high and variable rates of permanent emigration and that immigration by swans from elsewhere may be important in sustaining a breeding population at and near Izembek National Wildlife Refuge.

  2. Shrub encroachment in Arctic tundra: Betula nana effects on above- and belowground litter decomposition.

    Science.gov (United States)

    McLaren, Jennie R; Buckeridge, Kate M; van de Weg, Martine J; Shaver, Gaius R; Schimel, Joshua P; Gough, Laura

    2017-05-01

    Rapid arctic vegetation change as a result of global warming includes an increase in the cover and biomass of deciduous shrubs. Increases in shrub abundance will result in a proportional increase of shrub litter in the litter community, potentially affecting carbon turnover rates in arctic ecosystems. We investigated the effects of leaf and root litter of a deciduous shrub, Betula nana, on decomposition, by examining species-specific decomposition patterns, as well as effects of Betula litter on the decomposition of other species. We conducted a 2-yr decomposition experiment in moist acidic tundra in northern Alaska, where we decomposed three tundra species (Vaccinium vitis-idaea, Rhododendron palustre, and Eriophorum vaginatum) alone and in combination with Betula litter. Decomposition patterns for leaf and root litter were determined using three different measures of decomposition (mass loss, respiration, extracellular enzyme activity). We report faster decomposition of Betula leaf litter compared to other species, with support for species differences coming from all three measures of decomposition. Mixing effects were less consistent among the measures, with negative mixing effects shown only for mass loss. In contrast, there were few species differences or mixing effects for root decomposition. Overall, we attribute longer-term litter mass loss patterns to patterns created by early decomposition processes in the first winter. We note numerous differences for species patterns between leaf and root decomposition, indicating that conclusions from leaf litter experiments should not be extrapolated to below-ground decomposition. The high decomposition rates of Betula leaf litter aboveground, and relatively similar decomposition rates of multiple species below, suggest a potential for increases in turnover in the fast-decomposing carbon pool of leaves and fine roots as the dominance of deciduous shrubs in the Arctic increases, but this outcome may be tempered by

  3. Arctic biodiversity: Increasing richness accompanies shrinking refugia for a cold-associated tundra fauna

    Science.gov (United States)

    Hope, Andrew; Waltari, Eric; Malaney, Jason L.; Payer, David C.; Cook, J.A.; Talbot, Sandra L.

    2015-01-01

    As ancestral biodiversity responded dynamically to late-Quaternary climate changes, so are extant organisms responding to the warming trajectory of the Anthropocene. Ecological predictive modeling, statistical hypothesis tests, and genetic signatures of demographic change can provide a powerful integrated toolset for investigating these biodiversity responses to climate change, and relative resiliency across different communities. Within the biotic province of Beringia, we analyzed specimen localities and DNA sequences from 28 mammal species associated with boreal forest and Arctic tundra biomes to assess both historical distributional and evolutionary responses and then forecasted future changes based on statistical assessments of past and present trajectories, and quantified distributional and demographic changes in relation to major management regions within the study area. We addressed three sets of hypotheses associated with aspects of methodological, biological, and socio-political importance by asking (1) what is the consistency among implications of predicted changes based on the results of both ecological and evolutionary analyses; (2) what are the ecological and evolutionary implications of climate change considering either total regional diversity or distinct communities associated with major biomes; and (3) are there differences in management implications across regions? Our results indicate increasing Arctic richness through time that highlights a potential state shift across the Arctic landscape. However, within distinct ecological communities, we found a predicted decline in the range and effective population size of tundra species into several discrete refugial areas. Consistency in results based on a combination of both ecological and evolutionary approaches demonstrates increased statistical confidence by applying cross-discipline comparative analyses to conservation of biodiversity, particularly considering variable management regimes that seek

  4. 78 FR 6227 - Importation of Fresh Apricots From Continental Spain

    Science.gov (United States)

    2013-01-30

    .... Mitigations for C. funebrana Under proposed Sec. 319.56-58(f), APHIS would require the NPPO of Spain to use.... APHIS-2011-0132] RIN 0579-AD62 Importation of Fresh Apricots From Continental Spain AGENCY: Animal and... continental Spain. As a condition of entry, fresh apricots from continental Spain would have to be produced in...

  5. 78 FR 32184 - Importation of Fresh Apricots From Continental Spain

    Science.gov (United States)

    2013-05-29

    .... APHIS-2011-0132] RIN 0579-AD62 Importation of Fresh Apricots From Continental Spain AGENCY: Animal and... United States of fresh apricots from continental Spain. This action will allow interested persons... importation of fruits and vegetables to allow the importation of fresh apricots from continental Spain into...

  6. 78 FR 32183 - Importation of Avocados From Continental Spain

    Science.gov (United States)

    2013-05-29

    .... APHIS-2012-0002] RIN 0579-AD63 Importation of Avocados From Continental Spain AGENCY: Animal and Plant... continental Spain (excluding the Balearic Islands and Canary Islands) into the United States. This action will... avocados from continental Spain (excluding the Balearic Islands and Canary Islands) into the United States...

  7. Contributions to knowledge of the continental margin of Uruguay. Description of background samples in the continental margin of Uruguay

    International Nuclear Information System (INIS)

    Preciozzi, F

    2015-01-01

    This study provide data concerning of the background sediments of the continental margin of Uruguay. There were carried out different works with witnesses in order to extract various sediment samples from the continental shelf

  8. Potential alternative energy technologies on the Outer Continental Shelf.

    Energy Technology Data Exchange (ETDEWEB)

    Elcock, D.; Environmental Assessment

    2007-04-20

    This technical memorandum (TM) describes the technology requirements for three alternative energy technologies for which pilot and/or commercial projects on the U.S. Outer Continental Shelf (OCS) are likely to be proposed within the next five to seven years. For each of the alternative technologies--wind, wave, and ocean current--the TM first presents an overview. After each technology-specific overview, it describes the technology requirements for four development phases: site monitoring and testing, construction, operation, and decommissioning. For each phase, the report covers the following topics (where data are available): facility description, electricity generated, ocean area (surface and bottom) occupied, resource requirements, emissions and noise sources, hazardous materials stored or used, transportation requirements, and accident potential. Where appropriate, the TM distinguishes between pilot-scale (or demonstration-scale) facilities and commercial-scale facilities.

  9. The role of deep nitrogen and dynamic rooting profiles on vegetation dynamics and productivity in response to permafrost thaw and climate change in Arctic tundra

    Science.gov (United States)

    Hewitt, R. E.; Helene, G.; Taylor, D. L.; McGuire, A. D.; Mack, M. C.

    2017-12-01

    The release of permafrost-derived nitrogen (N) has the potential to fertilize tundra vegetation, modulating plant competition, stimulating productivity, and offsetting carbon losses from thawing permafrost. Dynamic rooting, mycorrhizal interactions, and coupling of N availability and root N uptake have been identified as gaps in ecosystem models. As a first step towards understanding whether Arctic plants can access deep permafrost-derived N, we characterized rooting profiles and quantified acquisition of 15N tracer applied at the permafrost boundary by moist acidic tundra plants subjected to almost three decades of warming at Toolik Lake, Alaska. In the ambient control plots the vegetation biomass is distributed between five plant functional types (PFTs): sedges, evergreen and deciduous shrubs, mosses and in lower abundance, forbs. The warming treatment has resulted in the increase of deciduous shrub biomass and the loss of sedges, evergreen shrubs, and mosses. We harvested roots by depth increment down to the top of the permafrost. Roots were classified by size class and PFT. The average thaw depth in the warmed plots was 58.3 cm ± 6.4 S.E., close to 18 cm deeper than the average thaw depth in the ambient plots (40.8 cm ± 1.8 S.E.). Across treatments the deepest rooting species was Rubus chamaemorus (ambient 40.8 cm ± 1.8 S.E., warmed 50.3 cm ± 9.8 S.E.), a non-mycorrhizal forb, followed by Eriophorum vaginatum, a non-mycorrhizal sedge. Ectomycorrhizal deciduous and ericoid mycorrhizal evergreen shrubs were rooted at more shallow depths. Deeply rooted non-mycorrhizal species had the greatest uptake of 15N tracer within 24 hours across treatments. Tracer uptake was greatest for roots of E. vaginatum in ambient plots and R. chamaemorus in warmed plots. Root profiles were integrated into a process-based ecosystem model coupled with a dynamic vegetation model. Functions modeling dynamic rooting profile relative to thaw depth were implemented for each PFT. The

  10. A survey of entomopathogenic nematode species in continental Portugal.

    Science.gov (United States)

    Valadas, V; Laranjo, M; Mota, M; Oliveira, S

    2014-09-01

    Entomopathogenic nematodes (EPN) are lethal parasites of insects, used as biocontrol agents. The objectives of this work were to survey the presence of EPN in continental Portugal and to characterize the different species. Of the 791 soil samples collected throughout continental Portugal, 53 were positive for EPN. Steinernema feltiae and Heterorhabditis bacteriophora were the two most abundant species. Analysis of EPN geographical distribution revealed an association between nematode species and vegetation type. Heterorhabditis bacteriophora was mostly found in the Alentejo region while S. feltiae was present in land occupied by agriculture with natural vegetation, broadleaved forest, mixed forest and transitional woodland-shrub, agro-forestry areas, complex cultivated patterns and non-irrigated arable land. Although no clear association was found between species and soil type, S. feltiae was typically recovered from cambisols and H. bacteriophora was more abundant in lithosols. Sequencing of the internal transcribed spacer (ITS) region indicated that S. feltiae was the most abundant species, followed by H. bacteriophora. Steinernema intermedium and S. kraussei were each isolated from one site and Steinernema sp. from two sites. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COXI) and cytochrome b (cytb) genes, was performed to evaluate the genetic diversity of S. feltiae and H. bacteriophora. No significant genetic diversity was found among H. bacteriophora isolates. However, COXI seems to be the best marker to study genetic diversity of S. feltiae. This survey contributes to the understanding of EPN distribution in Europe.

  11. Geocryological hazards and destructive exogenic geological processes on lines of linear constructions of tundra and forest-tundra zones of Western Siberia

    Science.gov (United States)

    Ospennikov, E. N.; Hilimonjuk, V. Z.

    2009-04-01

    Economic development of northern oil-and gas-bearing regions, even by application of shift method, is accompanied by a construction of the linear transport systems including automobile- and railways. Construction of such roads is connected with the risks caused by the whole complex of hazards, defined by the environmental features of the region, including flat surface with strong marshiness, development of a peat, fine-grained and easily eroded friable sedimentations, as well as by complicated geocryological conditions. Geocryological conditions of Western Siberia area are characterized by a rather high heterogeneity. This implies the strong variability of permafrost soils distribution, their thickness and continuity, depths of seasonal thawing and frost penetration, and also intact development of geocryological processes and phenomena. Thermokarst, thermo erosion and thermo-abrasion develop in the natural conditions. These processes are caused by partial degradation of permafrost. A frost heave also occurs during their seasonal or long-term freezing. Failure of an environment, which is always peculiar to construction of the roads, causes reorganization of geocryological systems that is accompanied by occurrence of dangerous geocryological processes, such as technogenic thermokarst (with formation of various negative forms of a relief: from fine subsidence up to small and average sized lakes), frost heave ground (with formation frost mound in height up to 0,5 - 1,5 meters and more), thermal erosion (gullies and ravines with volume of the born material up to several thousand cubic meters). Development of these destructive processes in a road stripes leads to emergencies owing to deformations and destructions of an earthen cloth, and to failure of natural tundra and forest-tundra ecosystems. The methodical approaches based on typification and zoning of the area by its environmental complex have been developed for an estimation of geocryological hazards at linear

  12. Revegetation and soil development on anthropogenic disturbances in shrub tundra, 50 years following construction of the CANOL No. 1 pipeline, N.W.T

    International Nuclear Information System (INIS)

    Harper, K.A.

    1994-01-01

    An intensive study of long-term revegetation patterns of erect deciduous shrub tundra on anthropogenic disturbances was conducted in the summer of 1993 within the CANOL pipeline corridor, Northwest Territories. Soil development, primary and secondary succession were investigated on 10 m by 20 m sites in vehicle tracks and borrow pits. Data were collected on the cover of all vascular and non-vascular species. Soil temperature, pH, organic matter, moisture and particle size composition were determined. Patterns in plant species composition and soil characteristics among disturbance types were examined using detrended correspondence analysis. The importance of the measured abiotic factors in explaining the differences in species composition was revealed by canonical correspondence analysis. Significant differences in species composition were evident among disturbance types. Different taxonomic groups exhibited different responses to disturbance. Soil samples in linear disturbances were analogous to those in undisturbed areas. Warmer, drier and less acidic soils in borrow pits contained less organic matter and fine particles than undisturbed soils. Soil temperature was considered the most important measured environmental variable in accounting for the revegetation patterns on disturbance with the microclimate stations. Comparison with a similar study on revegetation in the CANOL corridor in 1978 suggest that revegetation and soil development are proceeding faster on linear disturbances than borrow pits. 150 figs., 37 figs., 28 tabs

  13. Moroccan crustal response to continental drift.

    Science.gov (United States)

    Kanes, W H; Saadi, M; Ehrlich, E; Alem, A

    1973-06-01

    The formation and development of a zone of spreading beneath the continental crust resulted in the breakup of Pangea and formation of the Atlantic Ocean. The crust of Morocco bears an extremely complete record of the crustal response to this episode of mantle dynamics. Structural and related depositional patterns indicate that the African margin had stabilized by the Middle Jurassic as a marine carbonate environment; that it was dominated by tensile stresses in the early Mesozoic, resulting in two fault systems paralleling the Atlantic and Mediterranean margins and a basin and range structural-depositional style; and that it was affected by late Paleozoic metamorphism and intrusion. Mesozoic events record the latter portion of African involvement in the spreading episode; late Paleozoic thermal orogenesis might reflect the earlier events in the initiation of the spreading center and its development beneath significant continental crust. In that case, more than 100 million years were required for mantle dynamics to break up Pangea.

  14. Regional magnetic anomaly constraints on continental rifting

    Science.gov (United States)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  15. Precipitation of Continental Origin over South America

    Science.gov (United States)

    Martinez-Agudelo, J. A.; Dominguez, F.

    2012-12-01

    The Amazon forest receives high amounts of moisture from the tropical Atlantic. A significant part of this moisture is returned back to the atmosphere by the forest, and further redistributed to the rest of the continent by the meridional flow imposed by the Andes. Thus, the land-atmosphere interaction between the Amazon forest and the large-scale flow affects not only the forest itself but also the downstream regions. We develop a method to quantify the precipitation of continental origin over South America, and identify the contribution that selected source regions make to continental precipitation. The average annual cycle of precipitation of continental origin for the five-year period 2000-2004 shows a band of high values aligned along the northwest-southeast direction, from southern Peru to northeastern Argentina. The lowest values of precipitation of continental origin occur upstream, over the northeastern coast of South America. Precipitation that originates as moisture from the Amazon forest shows maximum values over the western side of the Amazon, east of the Andes, especially over southern Peru. The Amazon forest also contributes to precipitation over La Plata River Basin (LPRB) and the Pacific coast of Colombia. During its dry season, up to 29.3% of the precipitation over LPRB originates as moisture from the Amazon forest. Throughout the year, the contributions to precipitation over LPRB by the Amazon forest and LPRB (recycled precipitation) are in the same range, but out of phase. The average contribution of the rest of the continent to precipitation over LPRB is smaller but of the same order as that of the Amazon and LPRB.

  16. Landscape modelling at Regional to Continental scales

    Science.gov (United States)

    Kirkby, M. J.

    Most work on simulating landscape evolution has been focused at scales of about 1 Ha, there are still limitations, particularly in understanding the links between hillslope process rates and climate, soils and channel initiation. However, the need for integration with GCM outputs and with Continental Geosystems now imposes an urgent need for scaling up to Regional and Continental scales. This is reinforced by a need to incorporate estimates of soil erosion and desertification rates into national and supra-national policy. Relevant time-scales range from decadal to geological. Approaches at these regional to continental scales are critical to a fuller collaboration between geomorphologists and others interested in Continental Geosystems. Two approaches to the problem of scaling up are presented here for discussion. The first (MEDRUSH) is to embed representative hillslope flow strips into sub-catchments within a larger catchment of up to 5,000 km2. The second is to link one-dimensional models of SVAT type within DEMs at up to global scales (CSEP/SEDWEB). The MEDRUSH model is being developed as part of the EU Desertification Programme (MEDALUS project), primarily for semi-natural vegetation in southern Europe over time spans of up to 100 years. Catchments of up to 2500 km2 are divided into 50-200 sub-catchments on the basis of flow paths derived from DEMs with a horizontal resolution of 50 m or better. Within each sub-catchment a representative flow strip is selected and Hydrology, Sediment Transport and Vegetation change are simulated in detail for the flow strip, using a 1 hour time step. Changes within each flow strip are transferred back to the appropriate sub-catchment and flows of water and sediment are then routed through the channel network, generating changes in flood plain morphology.

  17. Ocean processes at the Antarctic continental slope.

    Science.gov (United States)

    Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

    2014-07-13

    The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

  18. Net Primary Production and Carbon Stocks for Subarctic Mesic-Dry Tundras with Contrasting Microtopography, Altitude, and Dominant Species

    DEFF Research Database (Denmark)

    Campioli, Matteo; Michelsen, Anders; Demey, A

    2009-01-01

    Mesic-dry tundras are widespread in the Arctic but detailed assessments of net primary production (NPP) and ecosystem carbon (C) stocks are lacking. We addressed this lack of knowledge by determining the seasonal dynamics of aboveground vascular NPP, annual NPP, and whole-ecosystem C stocks in five...... mesic-dry tundras in Northern Sweden with contrasting microtopography, altitude, and dominant species. Those measurements were paralleled by the stock assessments of nitrogen (N), the limiting nutrient. The vascular production was determined by harvest or in situ growing units, whereas the nonvascular...... hermaphroditum is more productive than Cassiope tetragona vegetation. Although the large majority of the apical NPP occurred in early-mid season (85%), production of stems and evergreen leaves proceeded until about 2 weeks before senescence. Most of the vascular vegetation was belowground (80%), whereas most...

  19. Radiocesium and 129I along the Russian coast. Preliminary results from th Swedish-Russian tundra ecology expedition

    International Nuclear Information System (INIS)

    Josefsson, D.; Holm, E.; Persson, B.R.; Roos, P.; Kilius, L.

    1995-01-01

    During the summer 1994 a joint Swedish-Russian expedition, Tundra Ecology 94, examined the coast of the Siberian tundra. The cruise passed the Barents Sea, the Kara Sea, The Laptev Sea and reached 170 o E in the East Siberian Sea. Most of the projects dealt with land based research which lead to a ship route close to the shore. The sampling was performed both offshore and onshore, but with emphasis on sea water and sediment sampling. At approximately 30 stations water samples were taken both at the surface and in near bottom water for the determination of 134 Cs, 137 Cs, 90 Sr, 129 I and 239,240 P concentrations. At these stations also sediment cores were taken. Some of the results from the expedition are presented in the present paper. 1 fig., 1 tab

  20. A boreal invasion in response to climate change? Range shifts and community effects in the borderland between forest and tundra.

    Science.gov (United States)

    Elmhagen, Bodil; Kindberg, Jonas; Hellström, Peter; Angerbjörn, Anders

    2015-01-01

    It has been hypothesized that climate warming will allow southern species to advance north and invade northern ecosystems. We review the changes in the Swedish mammal and bird community in boreal forest and alpine tundra since the nineteenth century, as well as suggested drivers of change. Observed changes include (1) range expansion and increased abundance in southern birds, ungulates, and carnivores; (2) range contraction and decline in northern birds and carnivores; and (3) abundance decline or periodically disrupted dynamics in cyclic populations of small and medium-sized mammals and birds. The first warm spell, 1930-1960, stands out as a period of substantial faunal change. However, in addition to climate warming, suggested drivers of change include land use and other anthropogenic factors. We hypothesize all these drivers interacted, primarily favoring southern generalists. Future research should aim to distinguish between effects of climate and land-use change in boreal and tundra ecosystems.

  1. The continental lithosphere: a geochemical perspective

    International Nuclear Information System (INIS)

    Hawkesworth, C.J.; Person, G.; Turner, S.P.; Calsteren, P. Van; Gallagher, K.

    1993-01-01

    The lithosphere is the cool strong outler layer of the Earth that is effectively a boundary layer to the convecting interior. The evidence from mantle xenoliths and continental basalts is that the lower continental crust and uppermost mantle are different beneath Archaen and proterozoic areas. Mantle xenoliths from Archaen terrains, principally the Kaapvaal craton in southern Africa, are significantly depleted in Fe and other major elements which are concentrated in basalts. Nd and Os isotope data on inclusions in diamonds and peridoties respectively, indicate that such mantle is as old as the overlying Archaen crust. Since it appears to have been coupled to the overlying crust, and to have been isolated from the homogenising effects of convection for long periods of time, it is inferred to be within the continental lithosphere. The mantle lithosphere beneath Proterozoic and younger areas is less depleted in major elements, and so it is more fertile, less buoyant, and therefore thinner, than the Archaen mantle lithosphere. (author). 136 refs, 14 figs

  2. Continental Deformation in Madagascar from GNSS Observations

    Science.gov (United States)

    Stamps, D. S.; Rajaonarison, T.; Rambolamanana, G.; Herimitsinjo, N.; Carrillo, R.; Jesmok, G.

    2015-12-01

    D.S. Stamps, T. Rajaonarison, G. Rambolamanana Madagascar is the easternmost continental segment of the East African Rift System (EARS). Plate reconstructions assume the continental island behaves as a rigid block, but studies of geologically recent kinematics suggest Madagascar undergoes extension related to the broader EARS. In this work we test for rigidity of Madagascar in two steps. First, we quantify surface motions using a novel dataset of episodic and continuous GNSS observations that span Madagascar from north to south. We established a countrywide network of precision benchmarks fixed in bedrock and with open skyview in 2010 that we measured for 48-72 hours with dual frequency receivers. The benchmarks were remeasured in 2012 and 2014. We processed the episodic GNSS data with ABPO, the only continuous GNSS station in Madagascar with >2.5 years of data, for millimeter precision positions and velocities at 7 locations using GAMIT-GLOBK. Our velocity field shows 2 mm/yr of differential motion between southern and northern Madagascar. Second, we test a suite of kinematic predictions from previous studies and find residual velocities are greater than 95% uncertainties. We also calculate angular velocity vectors assuming Madagascar moves with the Lwandle plate or the Somalian plate. Our new velocity field in Madagascar is inconsistent with all models that assume plate rigidity at the 95% uncertainty level; this result indicates the continental island undergoes statistically significant internal deformation.

  3. Disentangling the mechanisms of the coupling between sea ice and tundra productivity: cold air advection vs. arctic amplification.

    Science.gov (United States)

    Macias-Fauria, M.; Karlsen, S. R.; Forbes, B. C.

    2016-12-01

    Changes in arctic terrestrial productivity have been associated with the decline in sea ice extent, concentration, and volume observed at a pan-Arctic scale during the last decades, on the basis that most tundra ecosystems lay close to the sea. However the mechanisms for this coupling remain elusive, and despite overall trend agreements between different components of the Arctic system, no clear hypothesis has successfully explained the heterogeneous spatial and temporal patterns of sea ice and tundra productivity. Here we propose two mechanisms through which sea ice might influence tundra productivity: (1) by advecting cold air from sea ice to the adjacent land during the growing season (cold air advection, local-to-regional control); (2) via changes in the regional climate linked to the snow-ice albedo feedbacks (arctic amplification, regional-to-pan-Arctic controls). We used 8-day Normalised Difference Vegetation Index (NDVI MODIS) and concurrent sea ice concentration data (Norwegian Sea Ice Service) to test the relative influence of cold air advection vs. arctic amplification over the Svalbard Archipelago (period 2000-2014). Singular Value Decomposition (SVD) analyses suggest that cold air advection affects tundra productivity in regions/periods where/when sea ice is close to the adjacent land during the growing season, whereas a more regional signal appears when sea ice is distant ( >100km) from the coast. Further analyses were performed using the same approach over the pan-Arctic region using bi-weekly NDVI (GIMMS-NDVI3g) and sea ice extent (NASA/JAXA dataset; period 1981-2015). We interpret that cold air advection locally causes temperatures in the adjacent land to drop ("true coupling"), whereas in the arctic amplification scenario both NDVI and regional sea ice concentration are collinearly related to warmer, regional-to-pan-Arctic temperatures. Our results offer a mechanism that successfully explains NDVI/sea ice coupling and its heterogeneous spatial and

  4. Water chemistry of tundra lakes in the periglacial zone of the Bellsund Fiord (Svalbard) in the summer of 2013.

    Science.gov (United States)

    Szumińska, Danuta; Szopińska, Małgorzata; Lehmann-Konera, Sara; Franczak, Łukasz; Kociuba, Waldemar; Chmiel, Stanisław; Kalinowski, Paweł; Polkowska, Żaneta

    2018-05-15

    Climate changes observed in the Arctic (e.g. permafrost degradation, glacier retreat) may have significant influence on sensitive polar wetlands. The main objectives of this paper are defining chemical features of water within six small arctic lakes located in Bellsund (Svalbard) in the area of continuous permafrost occurrence. The unique environmental conditions of the study area offer an opportunity to observe phenomena influencing water chemistry, such as: chemical weathering, permafrost thawing, marine aerosols, atmospheric deposition and biological inputs. In the water samples collected during the summer 2013, detailed tundra lake water chemistry characteristics regarding ions, trace elements, pH and specific electrolytic conductivity (SEC 25 ) analysis were determined. Moreover, water chemistry of the studied lakes was compared to the water samples from the Tyvjobekken Creek and precipitation water samples. As a final step of data analysis, Principal Component Analysis (PCA) was performed. Detailed chemical analysis allowed us to conclude what follows: (1) Ca 2+ , Mg 2+ , SO 4 2- , Sr are of geogenic origin, (2) NO 3 - present in tundra lakes and the Tyvjobekken Creek water samples (ranging from 0.31 to 1.69mgL - 1 and from 0.25 to 1.58mgL - 1 respectively) may be of mixed origin, i.e. from biological processes and permafrost thawing, (3) high contribution of non-sea-salt SO 4 2- >80% in majority of studied samples indicate considerable inflow of sulphate-rich air to the study area, (4) high content of chlorides in tundra lakes (range: 25.6-32.0% meqL - 1 ) indicates marine aerosol influence, (5) PCA result shows that atmospheric transport may constitute a source of Mn, Co, Ni, Cu, Ga, Ba and Cd. However, further detailed inter-season and multi-seasonal study of tundra lakes in the Arctic are recommended. Especially in terms of detailed differentiation of sources influence (atmospheric transport vs. permafrost degradation). Copyright © 2017 Elsevier B.V. All

  5. Continental fragmentation and the strontium isotopic evolution of seawater.

    Science.gov (United States)

    Eric, H.; Jean Pascal, C.

    2008-12-01

    The time evolution of the strontium isotopic composition of seawater over the last 600 million years has the form of an asymmetric trough. The values are highest in the Cambrian and recent and lowest in the Jurassic. Superimposed on this trend are a number of smaller oscillations. The mechanisms responsible for these global isotopic fluctuations are subject to much debates. In order to get a quantitative picture of the changing paleogeography, we have characterized land-ocean distributions over Late Proterozoic to Phanerozoic times from measurement of perimeters and areas of continental fragments, based on paleomagnetic reconstructions. These measurements served to calculate geophysically constrainted breakup and scatter indexes of continental land masses from 0 to 1100 Ma (Cogne and Humler, 2008). Both parameters (strontium isotopic ratios of seawater and continental fragmentation indexes) are obviously highly correlated during the last 600 Ma. Low continental dispersion (that is large continental land masses) are associated with low seawater strontium isotopic ratios (that is when the continental inputs to oceans are minimum) and high continental dispersion (that is relatively small and widely distributed continents) with high seawater strontium isotopic ratios (that is when the continental input to ocean is maximum). Importantly, this first order evolution appears to conflict with the common idea of mountains erosion as a source for radiogenic strontium to oceans because high strontium isotopic ratios in seawater correspond to period of maximum dispersion of continents and not with period of general collisions. At first glance, it would seem that continental erosion increases with the degree of continental dispersion. Models showing that continental precipitation increases when continental masses are smaller and more widely dispersed and/or the length of continental margins available for rivers to carry continental material to oceans are thus favoured in order

  6. Cesium-137 inventories in Alaskan Tundra, lake and marine sediments: An indicator of recent organic material transport?

    International Nuclear Information System (INIS)

    Grebmeier, J.M.; Cooper, L.W.; Larsen, I.L.; Solis, C.; Olsen, C.R.

    1993-01-01

    Tundra sampling was accomplished in 1989--1990 at Imnavait Creek, Alaska (68 degree 37' N, 149 degree 17' W). Inventories of 137 Cs (102--162 mBq/cm 2 ) are close to expectations, based upon measured atmospheric deposition for this latitude. Accumulated inventories of 137 Cs in tundra decrease by up to 50% along a transect to Prudhoe Bay (70 degree 13' N, 148 degree 30' W). Atmospheric deposition of 137 Cs decreased with latitude in the Arctic, but declines in deposition would have been relatively small over this distance (200 km). This suggests a recent loss of 137 Cs and possibly associated organic matter from tundra over the northern portions of the transect between Imnavait Creek and Prudhoe Bay. Sediments from Toolik Lake (68 degree 38' N, 149 degree 38' W) showed widely varying 137 Cs inventories, from a low of 22 mBq/cm 2 away from the lake inlet, to a high between 140 to >200 mBq/cm 2 near the main stream inflow. This was indicative of recent accumulation of cesium and possibly organic material associated with it in arctic lakes, although additional sampling is needed

  7. Diurnal patterns of gas-exchange and metabolic pools in tundra plants during three phases of the arctic growing season.

    Science.gov (United States)

    Patankar, Rajit; Mortazavi, Behzad; Oberbauer, Steven F; Starr, Gregory

    2013-02-01

    Arctic tundra plant communities are subject to a short growing season that is the primary period in which carbon is sequestered for growth and survival. This period is often characterized by 24-h photoperiods for several months a year. To compensate for the short growing season tundra plants may extend their carbon uptake capacity on a diurnal basis, but whether this is true remains unknown. Here, we examined in situ diurnal patterns of physiological activity and foliar metabolites during the early, mid, and late growing season in seven arctic species under light-saturated conditions. We found clear diurnal patterns in photosynthesis and respiration, with midday peaks and midnight lulls indicative of circadian regulation. Diurnal patterns in foliar metabolite concentrations were less distinct between the species and across seasons, suggesting that metabolic pools are likely governed by proximate external factors. This understanding of diurnal physiology will also enhance the parameterization of process-based models, which will aid in better predicting future carbon dynamics for the tundra. This becomes even more critical considering the rapid changes that are occurring circumpolarly that are altering plant community structure, function, and ultimately regional and global carbon budgets.

  8. ‘Blood’ Kinship and Kinship in Christ’s Blood: Nomadic Evangelism in the Nenets Tundra

    Directory of Open Access Journals (Sweden)

    Tatiana Vagramenko

    2017-06-01

    Full Text Available The article addresses a conflicting encounter of two ideologies of kinship, ‘natural’ and ‘religious’, among the newly established Evangelical communities of Nenets in the Polar Ural and Yamal tundra. An ideology of Christian kinship, as an outcome of ‘spiritual re-birth’, was introduced through Nenets religious conversion. The article argues that although the born-again experience often turned against ancestral traditions and Nenets traditional kinship ties, the Nenets kinship system became a platform upon which the conversion mechanism was furthered and determined in the Nenets tundra. The article examines missionary initiatives and Nenets religiosity as kin-based activities, the outcome of which was twofold. On one side, it was the realignment of Nenets traditional kinship networks. On other side, it was the indigenisation of the Christian concept of kinship according to native internal cultural logic. Evangelical communities in the tundra were plunged into the traditional practices of Nenets kinship networks, economic exchanges, and marriage alliances. Through negotiation of traditional Nenets kinship and Christian kinship, converted Nenets developed new imaginaries, new forms of exchanges, and even new forms of mobility.

  9. Diurnal patterns of gas-exchange and metabolic pools in tundra plants during three phases of the arctic growing season

    Science.gov (United States)

    Patankar, Rajit; Mortazavi, Behzad; Oberbauer, Steven F; Starr, Gregory

    2013-01-01

    Arctic tundra plant communities are subject to a short growing season that is the primary period in which carbon is sequestered for growth and survival. This period is often characterized by 24-h photoperiods for several months a year. To compensate for the short growing season tundra plants may extend their carbon uptake capacity on a diurnal basis, but whether this is true remains unknown. Here, we examined in situ diurnal patterns of physiological activity and foliar metabolites during the early, mid, and late growing season in seven arctic species under light-saturated conditions. We found clear diurnal patterns in photosynthesis and respiration, with midday peaks and midnight lulls indicative of circadian regulation. Diurnal patterns in foliar metabolite concentrations were less distinct between the species and across seasons, suggesting that metabolic pools are likely governed by proximate external factors. This understanding of diurnal physiology will also enhance the parameterization of process-based models, which will aid in better predicting future carbon dynamics for the tundra. This becomes even more critical considering the rapid changes that are occurring circumpolarly that are altering plant community structure, function, and ultimately regional and global carbon budgets. PMID:23467719

  10. Eurasian continental background and regionally polluted levels of ozone and CO observed in northeast Asia

    Science.gov (United States)

    Pochanart, Pakpong; Kato, Shungo; Katsuno, Takao; Akimoto, Hajime

    The roles of Eurasian/Siberian continental air masses transport and the impact of large-scale East Asian anthropogenic emissions on tropospheric ozone and carbon monoxide levels in northeast Asia were investigated. Seasonal behaviors of O 3 and CO mixing ratios in background continental (BC) air masses and regionally polluted continental (RPC) air masses were identified using trajectory analyses of Eurasian continental air masses and multi-year O 3 and CO data observed at Happo, a mountain site in Japan. RPC air masses show significantly higher O 3 and CO mixing ratios (annual average of 53.9±6.0 and 200±41 ppb, respectively) than BC air masses (44.4±3.6 and 167±17 ppb, respectively). Large scale anthropogenic emissions in East Asia are suggested to contribute about 10 ppb of photochemical O 3 and 32 ppb of CO at Happo. A comparative study of O 3 and CO observed at other sites, i.e., Oki Islands and Mondy in northeast Asia, showed similarities suggesting that O 3 mixing ratios in BC air masses at Happo could be representative for remote northeast Asia. However, CO mixing ratios in BC air masses at Happo are higher than the background level in Siberia. The overestimate is probably related to an increase in the CO baseline gradient between Siberia and the East Asia Pacific rim, and perturbations by sub-grid scale pollution transport and regional-scale boreal forest fires in Siberia when the background continental air masses are transported to Japan.

  11. The Changing Seasonality of Tundra Nutrient Cycling: Implications for Arctic Ecosystem Function

    Science.gov (United States)

    Weintraub, M. N.; Steltzer, H.; Sullivan, P.; Schimel, J.; Wallenstein, M. D.; Darrouzet-Nardi, A.; Segal, A. D.

    2011-12-01

    Arctic soils contain large stores of carbon (C) and may act as a significant CO2 source with warming. However, the key to understanding tundra soil processes is nitrogen (N), as both plant growth and decomposition are N limited. However, current models of tundra ecosystems assume that while N limits plant growth, C limits decomposition. In addition, N availability is strongly seasonal with relatively high concentrations early in the growing season followed by a pronounced crash. We need to understand the controls on this seasonality to predict responses to climate change, but there are multiple questions that need answers: 1) What causes the seasonality in N? 2) Does microbial activity switch seasonally between C and N limitation? 3) How will a lengthening of the growing season alter overall ecosystem C and N dynamics, as a result of differential extension of the periods before and after the nutrient crash? We hypothesized that microbial activity is C limited early in the growing season, when N availability is higher and root exudate C is unavailable, and that microbial activity becomes N limited in response to plant N uptake and immobilization stimulated by root C. To address these questions we are conducting an accelerated snow-melt X warming field experiment in an Alaskan moist acidic arctic tundra community, and following plant and soil dynamics. Changes in the timing of C and N interactions in the different treatments will enable us to develop an enhanced mechanistic understanding of why the nutrient crash occurs and what the implications are for a lengthening of the arctic growing season. In 2010 we successfully accelerated snowmelt by 4 days. Both earlier snowmelt and warming accelerated early season plant life history events, with a few exceptions. However, responses to the combined treatment could not always be predicted from single factor effects. End of season life history events occurred later in response to the treatments, again with a few exceptions

  12. Comparison of Forest and Tundra Ecosystems Npp with Remote Sensing and Ground Observation Data

    Science.gov (United States)

    Ivanova, Yuliya; Ovchinnikova, Nataly; Kryazhimskiy, Fedor; Maklakov, Kirill

    2012-07-01

    In this study we compared two models for NPP estimate: an estimate based on satellite data and an estimate based on biomass calculation for tundra in the Yamal Peninsula and for forest ecosystems at the West Sayan Mountains. Ground NPP estimates were done for the same study areas which made it possible to identify the most significant parameters, specific to each model, that affect the estimates. The main difficulty in NPP-related studies is that current NPP values in an ecosystem cannot be determined exactly. Estimates, however, are feasible, and they can be made using a variety of methods. Thus, it seems important to see the ways in which these methods are different from each other and to find out how close the resulting values are. If these are dissimilar, the parameters used to make NPP estimates should be compared in order to identify the stage that can give rise to defects and errors, and to under- and overestimates. In this study we estimated NPP using the following two approaches: NPP calculation based on ground-truth measurements, such as calculation of plant phytomass on the studied area based on morphometric measurements (height, stem diameter, crown volume, etc.) and variations in this phytomass over a certain time period. NPP calculation based on satellite remote sensing data, using the data of satellite spectral channels and the data on underlying terrain. In this study we used MODIS/TERRA 8-day composite images, namely MOD09A1 and MOD11A2, with the spatial resolution 500 m and 1 km, respectively, obtained from EOS Data Gateway. Different models evaluate NPP using different physical values, with dissimilar temporal and spatial distributions. The NPP values evaluated by two models differ inherently. We used both of the models: GLO-PEM end MODIS-NPP. The study area is situated in the south of the Krasnoyarskii Krai, at the West Sayan Mountains, where the Institute of Forest SB RAS has been conducting observations since 1960. In this area altitudinal

  13. Environmental heterogeneity explains the genetic structure of Continental and Mediterranean populations of Fraxinus angustifolia Vahl.

    Science.gov (United States)

    Temunović, Martina; Franjić, Jozo; Satovic, Zlatko; Grgurev, Marin; Frascaria-Lacoste, Nathalie; Fernández-Manjarrés, Juan F

    2012-01-01

    Tree species with wide distributions often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in a wind-pollinated Mediterranean tree species, Fraxinus angustifolia Vahl, within a recognised glacial refugium in Croatia. We sampled 11 populations from environmentally divergent habitats within the Continental and Mediterranean biogeographical regions. We combined genetic data analyses based on nuclear microsatellite loci, multivariate statistics on environmental data and ecological niche modelling (ENM). We identified a geographic structure with a high genetic diversity and low differentiation in the Continental region, which contrasted with the significantly lower genetic diversity and higher population divergence in the Mediterranean region. The positive and significant correlation between environmental and genetic distances after controlling for geographic distance suggests an important influence of ecological divergence of the sites in shaping genetic variation. The ENM provided support for niche differentiation between the populations from the Continental and Mediterranean regions, suggesting that contemporary populations may represent two divergent ecotypes. Ecotype differentiation was also supported by multivariate environmental and genetic distance analyses. Our results suggest that despite extensive gene flow in continental areas, long-term stability of heterogeneous environments have likely promoted genetic divergence of ashes in this region and can explain the present-day genetic variation patterns of these ancient populations.

  14. Environmental heterogeneity explains the genetic structure of Continental and Mediterranean populations of Fraxinus angustifolia Vahl.

    Directory of Open Access Journals (Sweden)

    Martina Temunović

    Full Text Available Tree species with wide distributions often exhibit different levels of genetic structuring correlated to their environment. However, understanding how environmental heterogeneity influences genetic variation is difficult because the effects of gene flow, drift and selection are confounded. We investigated the genetic variation and its ecological correlates in a wind-pollinated Mediterranean tree species, Fraxinus angustifolia Vahl, within a recognised glacial refugium in Croatia. We sampled 11 populations from environmentally divergent habitats within the Continental and Mediterranean biogeographical regions. We combined genetic data analyses based on nuclear microsatellite loci, multivariate statistics on environmental data and ecological niche modelling (ENM. We identified a geographic structure with a high genetic diversity and low differentiation in the Continental region, which contrasted with the significantly lower genetic diversity and higher population divergence in the Mediterranean region. The positive and significant correlation between environmental and genetic distances after controlling for geographic distance suggests an important influence of ecological divergence of the sites in shaping genetic variation. The ENM provided support for niche differentiation between the populations from the Continental and Mediterranean regions, suggesting that contemporary populations may represent two divergent ecotypes. Ecotype differentiation was also supported by multivariate environmental and genetic distance analyses. Our results suggest that despite extensive gene flow in continental areas, long-term stability of heterogeneous environments have likely promoted genetic divergence of ashes in this region and can explain the present-day genetic variation patterns of these ancient populations.

  15. Changing snow cover in tundra ecosystems tips the Arctic carbon balance

    Science.gov (United States)

    Zona, D.; Hufkens, K.; Gioli, B.; Kalhori, A. A. M.; Oechel, W. C.

    2014-12-01

    The Arctic environment has witnessed important changes due to global warming, resulting in increased surface air temperatures and rain events which both exacerbate snow cover deterioration (Semmens et al, 2013; Rennert et al, 2009; White et al, 2007; Min et al, 2008; Sharp et al, 2013; Schaeffer et al, 2013). Snow cover duration is declining by almost 20% per decade, a far higher rate than model estimates (Derksen and Brown, 2012). Concomitant with increasing temperatures and decreasing snow cover duration, the length of the arctic growing season is reported to have increased by 1.1 - 4.9 days per decade since 1951 (Menzel et al, 2006), and, plant productivity and CO2 uptake from arctic vegetation are strongly influenced by changes in growing season length (Myneni et al., 1997; Schaefer et al., 2005; Euskirchen et al., 2006). Based on more than a decade of eddy flux measurements in Arctic tundra ecosystems across the North slope of Alaska, and remotely sensed snow cover data, we show that earlier snow melt in the spring increase C uptake while an extended snow free period in autumn is associated with a higher C loss. Here we present the impacts of changes in snow cover dynamics between spring and autumn in arctic tundra ecosystems on the carbon dynamics and net C balance of the Alaskan Arctic. ReferencesDerksen, C., Brown R. (2012) Geophys. Res. Lett., doi:10.1029/2012GL053387 Euskirchen, E.S., et al. (2006) Glob. Change Biol., 12, 731-750. Menzel, A., et al. 2006. Glob. Change Biol., 12, 1969-1976. Min SK, Zhang X, Zweirs F (2008) Science 320: 518-520. Rennert K J, Roe G, Putkonen J and Bitz C M (2009) J. Clim. 22 2302-15. Schaefer, K., Denning A.S., Leonard O. (2005) Global Biogeochem. Cycles, 19, GB3017. Schaeffer, S. M., Sharp, E., Schimel, J. P. & Welker, J. M. (2013). Soil- plant N processes in a High Arctic ecosystem, NW Greenland are altered by long-term experimental warming and higher rainfall. Glob. Change Biol., 11, 3529-39. doi: 10.1111/gcb.12318

  16. Spectral determination of concentrations of functionally diverse pigments in increasingly complex arctic tundra canopies.

    Science.gov (United States)

    Boelman, Natalie T; Magney, Troy S; Logan, Barry A; Griffin, Kevin L; Eitel, Jan U H; Greaves, Heather; Prager, Case M; Vierling, Lee A

    2016-09-01

    As the Arctic warms, tundra vegetation is becoming taller and more structurally complex, as tall deciduous shrubs become increasingly dominant. Emerging studies reveal that shrubs exhibit photosynthetic resource partitioning, akin to forests, that may need accounting for in the "big leaf" net ecosystem exchange models. We conducted a lab experiment on sun and shade leaves from S. pulchra shrubs to determine the influence of both constitutive (slowly changing bulk carotenoid and chlorophyll pools) and facultative (rapidly changing xanthophyll cycle) pigment pools on a suite of spectral vegetation indices, to devise a rapid means of estimating within canopy resource partitioning. We found that: (1) the PRI of dark-adapted shade leaves (PRIo) was double that of sun leaves, and that PRIo was sensitive to variation among sun and shade leaves in both xanthophyll cycle pool size (V + A + Z) (r (2) = 0.59) and Chla/b (r (2) = 0.64); (2) A corrected PRI (difference between dark and illuminated leaves, ΔPRI) was more sensitive to variation among sun and shade leaves in changes to the epoxidation state of their xanthophyll cycle pigments (dEPS) (r (2) = 0.78, RMSE = 0.007) compared to the uncorrected PRI of illuminated leaves (PRI) (r (2) = 0.34, RMSE = 0.02); and (3) the SR680 index was correlated with each of (V + A + Z), lutein, bulk carotenoids, (V + A + Z)/(Chla + b), and Chla/b (r (2) range = 0.52-0.69). We suggest that ΔPRI be employed as a proxy for facultative pigment dynamics, and the SR680 for the estimation of constitutive pigment pools. We contribute the first Arctic-specific information on disentangling PRI-pigment relationships, and offer insight into how spectral indices can assess resource partitioning within shrub tundra canopies.

  17. Domibacillus tundrae sp. nov., isolated from active layer soil of tussock tundra in Alaska, and emended description of the genus Domibacillus.

    Science.gov (United States)

    Gyeong, Hye Ryeon; Baek, Kiwoon; Hwang, Chung Yeon; Park, Key Hun; Kim, Hye Min; Lee, Hong Kum; Lee, Yoo Kyung

    2015-10-01

    A novel Gram-stain-positive, spore-forming, aerobic, motile and rod-shaped bacterium designated strain PAMC 80007T was isolated from an active layer soil sample of Council, Alaska. Optimal growth of strain PAMC 80007T was observed at 30 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain PAMC 80007T belonged to the genus Domibacillus. This strain was closely related to Domibacillus enclensis (98.3 %), Domibacillus robiginosus (98.3 %) and Domibacillus indicus (97.2 %). Genomic DNA G+C content was 43.5 mol% and genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed that strain PAMC 80007T is clearly distinguished from the closely related species of the genus Domibacillus. The major fatty acids (>5 %) were iso-C15 : 0 (24.7 %), C16 : 1ω11c (16.8 %), anteiso-C15 : 0 (16.5 %), C16 : 0 (15.6 %) and anteiso-C17 : 0 (8.7 %). The major respiratory isoprenoid quinones were menaquinone-6 (MK-6) and menaquinone-7 (MK-7), and the polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, phospholipid and two unidentified lipids. meso-Diaminopimelic acid (type A1γ) was present in the cell-wall peptidoglycan, and the major whole-cell sugar was ribose with a minor quantity of glucose. Results from a polyphasic study suggested that strain PAMC 80007T represents a novel species of the genus Domibacillus for which the name Domibacillus tundrae sp. nov. is proposed. The type strain is PAMC 80007T ( = JCM 30371T = KCTC 33549T = DSM 29572T). An emended description of the genus Domibacillus is also provided.

  18. Stable Continental Region Earthquakes in South China

    Science.gov (United States)

    Liu, L.

    This paper reviews some remarkable characteristics of earthquakes in a Stable Continental Region (SCR) of the South China Block (SCB). The kernel of the SCB is the Yangtze platform solidified in late Proterozoic time, with continental growth to the southeast by a series of fold belts in Paleozoic time. The facts that the deviatoric stress is low, the orientations of the major tectonic features in the SCB are substantially normal to the maximum horizontal principal stress, and a relatively uniform crust, seem to be the major reasons for lack of significant seismicity in most regions of the SCB. Earthquakes in this region are mainly associated with three seismic zones: (1) the Southeast China Coast seismic zone related to Guangdong-Fujian coastal folding belt (associated with Eurasia-Philippine Sea plate collision); (2) the Southern Yellow Sea seismic zone associated with continental shelf rifts and basins; and (3) the Downstream Yangtze River seismic zone spatially coinciding with Tertiary rifts and basin development. All three seismic zones are close to one or two major economic and population centers in the SCB so that they pose significant seismic hazards. Earthquake focal mechanisms in the SCB are consistent with strike-slip to normal faulting stress regimes. Because of the global and national economic significance of the SCB and its dense population, the seismic hazard of the region is of outstanding importance. Comparing the SCB with another less developed region, a pending earthquake with the same size and tectonic setting would cause substantially more severe social and economic losses in the SCB. This paper also compiles an inventory of historic moderate to great earthquakes in the SCB; most of the data are not widely available in English literature.

  19. Crew coordination concepts: Continental Airlines CRM training

    Science.gov (United States)

    Christian, Darryl; Morgan, Alice

    1987-01-01

    The outline of the crew coordination concepts at Continental airlines is: (1) Present relevant theory: Contained in a pre-work package and in lecture/discussion form during the work course, (2) Discuss case examples: Contained in the pre-work for study and use during the course; and (3) Simulate practice problems: Introduced during the course as the beginning of an ongoing process. These concepts which are designed to address the problem pilots have in understanding the interaction between situations and their own theories of practice are briefly discussed.

  20. Disappearing Arctic tundra ponds: Fine-scale analysis of surface hydrology in drained thaw lake basins over a 65 year period (1948-2013)

    Science.gov (United States)

    Andresen, Christian G.; Lougheed, Vanessa L.

    2015-03-01

    Long-term fine-scale dynamics of surface hydrology in Arctic tundra ponds (less than 1 ha) are largely unknown; however, these small water bodies may contribute substantially to carbon fluxes, energy balance, and biodiversity in the Arctic system. Change in pond area and abundance across the upper Barrow Peninsula, Alaska, was assessed by comparing historic aerial imagery (1948) and modern submeter resolution satellite imagery (2002, 2008, and 2010). This was complemented by photogrammetric analysis of low-altitude kite-borne imagery in combination with field observations (2010-2013) of pond water and thaw depth transects in seven ponds of the International Biological Program historic research site. Over 2800 ponds in 22 drained thaw lake basins (DTLB) with different geological ages were analyzed. We observed a net decrease of 30.3% in area and 17.1% in number of ponds over the 62 year period. The inclusion of field observations of pond areas in 1972 from a historic research site confirms the linear downward trend in area. Pond area and number were dependent on the age of DTLB; however, changes through time were independent of DTLB age, with potential long-term implications for the hypothesized geomorphologic landscape succession of the thaw lake cycle. These losses were coincident with increases in air temperature, active layer, and density and cover of aquatic emergent plants in ponds. Increased evaporation due to warmer and longer summers, permafrost degradation, and transpiration from encroaching aquatic emergent macrophytes are likely the factors contributing to the decline in surface area and number of ponds.

  1. Ozone pollution around a coastal region of South China Sea: interaction between marine and continental air

    Science.gov (United States)

    Wang, Hao; Lyu, Xiaopu; Guo, Hai; Wang, Yu; Zou, Shichun; Ling, Zhenhao; Wang, Xinming; Jiang, Fei; Zeren, Yangzong; Pan, Wenzhuo; Huang, Xiaobo; Shen, Jin

    2018-03-01

    Marine atmosphere is usually considered to be a clean environment, but this study indicates that the near-coast waters of the South China Sea (SCS) suffer from even worse air quality than coastal cities. The analyses were based on concurrent field measurements of target air pollutants and meteorological parameters conducted at a suburban site (Tung Chung, TC) and a nearby marine site (Wan Shan, WS) from August to November 2013. The observations showed that the levels of primary air pollutants were significantly lower at WS than those at TC, while the ozone (O3) value was greater at WS. Higher O3 levels at WS were attributed to the weaker NO titration and higher O3 production rate because of stronger oxidative capacity of the atmosphere. However, O3 episodes were concurrently observed at both sites under certain meteorological conditions, such as tropical cyclones, continental anticyclones and sea-land breezes (SLBs). Driven by these synoptic systems and mesoscale recirculations, the interaction between continental and marine air masses profoundly changed the atmospheric composition and subsequently influenced the formation and redistribution of O3 in the coastal areas. When continental air intruded into marine atmosphere, the O3 pollution was magnified over the SCS, and the elevated O3 ( > 100 ppbv) could overspread the sea boundary layer ˜ 8 times the area of Hong Kong. In some cases, the exaggerated O3 pollution over the SCS was recirculated to the coastal inshore by sea breeze, leading to aggravated O3 pollution in coastal cities. The findings are applicable to similar mesoscale environments around the world where the maritime atmosphere is potentially influenced by severe continental air pollution.

  2. Investigating Continental Margins: An Activity to Help Students Better Understand the Continental Margins of North America

    Science.gov (United States)

    Poli, Maria-Serena; Capodivacca, Marco

    2011-01-01

    Continental margins are an important part of the ocean floor. They separate the land above sea level from the deep ocean basins below and occupy about 11% of Earth's surface. They are also economically important, as they harbor both mineral resources and some of the most valuable fisheries in the world. In this article students investigate North…

  3. Fungi benefit from two decades of increased nutrient availability in tundra heath soil.

    Science.gov (United States)

    Rinnan, Riikka; Michelsen, Anders; Bååth, Erland

    2013-01-01

    If microbial degradation of carbon substrates in arctic soil is stimulated by climatic warming, this would be a significant positive feedback on global change. With data from a climate change experiment in Northern Sweden we show that warming and enhanced soil nutrient availability, which is a predicted long-term consequence of climatic warming and mimicked by fertilization, both increase soil microbial biomass. However, while fertilization increased the relative abundance of fungi, warming caused only a minimal shift in the microbial community composition based on the phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) profiles. The function of the microbial community was also differently affected, as indicated by stable isotope probing of PLFA and NLFA. We demonstrate that two decades of fertilization have favored fungi relative to bacteria, and increased the turnover of complex organic compounds such as vanillin, while warming has had no such effects. Furthermore, the NLFA-to-PLFA ratio for (13)C-incorporation from acetate increased in warmed plots but not in fertilized ones. Thus, fertilization cannot be used as a proxy for effects on warming in arctic tundra soils. Furthermore, the different functional responses suggest that the biomass increase found in both fertilized and warmed plots was mediated via different mechanisms.

  4. Fungi benefit from two decades of increased nutrient availability in tundra heath soil.

    Directory of Open Access Journals (Sweden)

    Riikka Rinnan

    Full Text Available If microbial degradation of carbon substrates in arctic soil is stimulated by climatic warming, this would be a significant positive feedback on global change. With data from a climate change experiment in Northern Sweden we show that warming and enhanced soil nutrient availability, which is a predicted long-term consequence of climatic warming and mimicked by fertilization, both increase soil microbial biomass. However, while fertilization increased the relative abundance of fungi, warming caused only a minimal shift in the microbial community composition based on the phospholipid fatty acid (PLFA and neutral lipid fatty acid (NLFA profiles. The function of the microbial community was also differently affected, as indicated by stable isotope probing of PLFA and NLFA. We demonstrate that two decades of fertilization have favored fungi relative to bacteria, and increased the turnover of complex organic compounds such as vanillin, while warming has had no such effects. Furthermore, the NLFA-to-PLFA ratio for (13C-incorporation from acetate increased in warmed plots but not in fertilized ones. Thus, fertilization cannot be used as a proxy for effects on warming in arctic tundra soils. Furthermore, the different functional responses suggest that the biomass increase found in both fertilized and warmed plots was mediated via different mechanisms.

  5. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    Energy Technology Data Exchange (ETDEWEB)

    Lipson, David A.; Raab, Theodore K.; Parker , Melanie; Kelley , Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-07-21

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska, and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography, but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes).

  6. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    Energy Technology Data Exchange (ETDEWEB)

    Lipson, David A.; Raab, Theodore K.; Parker , Melanie; Kelley , Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-08-01

    Summary This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes,

  7. Long-term warming restructures Arctic tundra without changing net soil carbon storage.

    Science.gov (United States)

    Sistla, Seeta A; Moore, John C; Simpson, Rodney T; Gough, Laura; Shaver, Gaius R; Schimel, Joshua P

    2013-05-30

    High latitudes contain nearly half of global soil carbon, prompting interest in understanding how the Arctic terrestrial carbon balance will respond to rising temperatures. Low temperatures suppress the activity of soil biota, retarding decomposition and nitrogen release, which limits plant and microbial growth. Warming initially accelerates decomposition, increasing nitrogen availability, productivity and woody-plant dominance. However, these responses may be transitory, because coupled abiotic-biotic feedback loops that alter soil-temperature dynamics and change the structure and activity of soil communities, can develop. Here we report the results of a two-decade summer warming experiment in an Alaskan tundra ecosystem. Warming increased plant biomass and woody dominance, indirectly increased winter soil temperature, homogenized the soil trophic structure across horizons and suppressed surface-soil-decomposer activity, but did not change total soil carbon or nitrogen stocks, thereby increasing net ecosystem carbon storage. Notably, the strongest effects were in the mineral horizon, where warming increased decomposer activity and carbon stock: a 'biotic awakening' at depth.

  8. Identification of Previously Unknown Groups of Microorganisms Under the Tundra Snowpack

    Science.gov (United States)

    Schmidt, S.; Schadt, C. W.; Lipson, D. A.; Martin, A. P.

    2003-12-01

    Recent work has shown that microbial communities are active under snow. In fact, in some tundra soils these organisms reach their year-round peak in late winter. These communities can function at temperatures down to at least -5° C and are fuelled by dead plant material laid down in the Autumn. Until now the identity of these cold adapted microbial communities was a complete mystery. We used microbiological and molecular techniques to elucidate the phylogenetic composition of these under-snow microbial communities. At the broadest taxonomic level, we show that fungi dominate the under-snow world. More detailed molecular analyses revealed a high diversity within the fungi and we identified three clades that constitute major new groups of fungi (at the subphylum or class level) that have not been previously described or cultured. An abundance of hitherto unknown fungi that are active beneath the snow significantly broadens our understanding of both the diversity and biogeochemical functioning of fungi in cold environments.

  9. Doubled volatile organic compound emissions from subarctic tundra under simulated climate warming.

    Science.gov (United States)

    Faubert, Patrick; Tiiva, Päivi; Rinnan, Asmund; Michelsen, Anders; Holopainen, Jarmo K; Rinnan, Riikka

    2010-07-01

    *Biogenic volatile organic compound (BVOC) emissions from arctic ecosystems are important in view of their role in global atmospheric chemistry and unknown feedbacks to global warming. These cold ecosystems are hotspots of climate warming, which will be more severe here than averaged over the globe. We assess the effects of climatic warming on non-methane BVOC emissions from a subarctic heath. *We performed ecosystem-based chamber measurements and gas chromatography-mass spectrometry (GC-MS) analyses of the BVOCs collected on adsorbent over two growing seasons at a wet subarctic tundra heath hosting a long-term warming and mountain birch (Betula pubescens ssp. czerepanovii) litter addition experiment. *The relatively low emissions of monoterpenes and sesquiterpenes were doubled in response to an air temperature increment of only 1.9-2.5 degrees C, while litter addition had a minor influence. BVOC emissions were seasonal, and warming combined with litter addition triggered emissions of specific compounds. *The unexpectedly high rate of release of BVOCs measured in this conservative warming scenario is far above the estimates produced by the current models, which underlines the importance of a focus on BVOC emissions during climate change. The observed changes have implications for ecological interactions and feedback effects on climate change via impacts on aerosol formation and indirect greenhouse effects.

  10. [Methanotrophs of the psychrophilic microbial community of the Russian Arctic tundra].

    Science.gov (United States)

    Berestovskaia, Iu Iu; Vasil'eva, L V; Chestnykh, O V; Zavarzin, G A

    2002-01-01

    In tundra, at a low temperature, there exists a slowly developing methanotrophic community. Methane-oxidizing bacteria are associated with plants growing at high humidity, such as sedge and sphagnum; no methonotrophs were found in polytrichous and aulacomnious mosses and lichens, typical of more arid areas. The methanotrophic bacterial community inhabits definite soil horizons, from moss dust to peat formed from it. Potential ability of the methanotrophic community to oxidize methane at 5 degrees C enhances with the depth of the soil profile in spite of the decreasing soil temperature. The methanotrophic community was found to gradually adapt to various temperatures due to the presence of different methane-oxidizing bacteria in its composition. Depending on the temperature and pH, different methanotrophs occupy different econiches. Within a temperature range from 5 to 15 degrees C, three morphologically distinct groups of methanotrophs could be distinguished. At pH 5-7 and 5-15 degrees C, forms morphologically similar to Methylobacter psychrophilus predominated, whereas at the acidic pH 4-6 and 10-15 degrees C, bipolar cells typical of Methylocella palustris were mostly found. The third group of methanotrophic bacteria growing at pH 5-7 and 5-10 degrees C was represented by a novel methanotroph whole large coccoid cells had a thick mucous capsule.

  11. Potential of Immobilized Whole-Cell Methylocella tundrae as a Biocatalyst for Methanol Production from Methane.

    Science.gov (United States)

    Mardina, Primata; Li, Jinglin; Patel, Sanjay K S; Kim, In-Won; Lee, Jung-Kul; Selvaraj, Chandrabose

    2016-07-28

    Methanol is a versatile compound that can be biologically synthesized from methane (CH4) by methanotrophs using a low energy-consuming and environment-friendly process. Methylocella tundrae is a type II methanotroph that can utilize CH4 as a carbon and energy source. Methanol is produced in the first step of the metabolic pathway of methanotrophs and is further oxidized into formaldehyde. Several parameters must be optimized to achieve high methanol production. In this study, we optimized the production conditions and process parameters for methanol production. The optimum incubation time, substrate, pH, agitation rate, temperature, phosphate buffer and sodium formate concentration, and cell concentration were determined to be 24 h, 50% CH4, pH 7, 150 rpm, 30°C, 100 mM and 50 mM, and 18 mg/ml, respectively. The optimization of these parameters significantly improved methanol production from 0.66 to 5.18 mM. The use of alginate-encapsulated cells resulted in enhanced methanol production stability and reusability of cells after five cycles of reuse under batch culture conditions.

  12. Biological methanol production by immobilized Methylocella tundrae using simulated biohythane as a feed.

    Science.gov (United States)

    Patel, Sanjay K S; Singh, Raushan K; Kumar, Ashok; Jeong, Jae-Hoon; Jeong, Seong Hun; Kalia, Vipin C; Kim, In-Won; Lee, Jung-Kul

    2017-10-01

    Biohythane may be used as an alternative feed for methanol production instead of costly pure methane. In this study, methanol production potential of Methylocella tundrae immobilized through covalent immobilization, adsorption, and encapsulation was evaluated. Cells covalently immobilized on groundnut shells and chitosan showed a relative methanol production potential of 83.9 and 91.6%, respectively, compared to that of free cells. The maximum methanol production by free cells and cells covalently immobilized on groundnut shells and chitosan was 6.73, 6.20, and 7.23mM, respectively, using simulated biohythane as a feed. Under repeated batch conditions of eight cycles, cells covalently immobilized on chitosan and groundnut shells, and cells encapsulated in sodium-alginate resulted in significantly higher cumulative methanol production of 37.76, 31.80, and 25.58mM, respectively, than free cells (18.57mM). This is the first report on immobilization of methanotrophs on groundnut shells and its application in methanol production using biohythane as a feed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Moss Mediates the Influence of Shrub Species on Soil Properties and Processes in Alpine Tundra.

    Science.gov (United States)

    Bueno, C Guillermo; Williamson, Scott N; Barrio, Isabel C; Helgadóttir, Ágústa; HiK, David S

    2016-01-01

    In tundra ecosystems, bryophytes influence soil processes directly and indirectly through interactions with overstory shrub species. We experimentally manipulated moss cover and measured seasonal soil properties and processes under two species of deciduous shrubs with contrasting canopy structures, Salix planifolia pulchra and Betula glandulosa-nana complex. Soil properties (seasonal temperature, moisture and C:N ratios) and processes (seasonal litter decomposition and soil respiration) were measured over twelve months. Shrub species identity had the largest influence on summer soil temperatures and soil respiration rates, which were higher under Salix canopies. Mosses were associated with lower soil moisture irrespective of shrub identity, but modulated the effects of shrubs on winter soil temperatures and soil C:N ratios so that moss cover reduced differences in soil winter temperatures between shrub species and reduced C:N ratios under Betula but not under Salix canopies. Our results suggest a central role of mosses in mediating soil properties and processes, with their influence depending on shrub species identity. Such species-dependent effects need to be accounted for when forecasting vegetation dynamics under ongoing environmental changes.

  14. Calibration and Validation of Landsat Tree Cover in the Taiga-Tundra Ecotone

    Science.gov (United States)

    Montesano, Paul Mannix; Neigh, Christopher S. R.; Sexton, Joseph; Feng, Min; Channan, Saurabh; Ranson, Kenneth J.; Townshend, John R.

    2016-01-01

    Monitoring current forest characteristics in the taiga-tundra ecotone (TTE) at multiple scales is critical for understanding its vulnerability to structural changes. A 30 m spatial resolution Landsat-based tree canopy cover map has been calibrated and validated in the TTE with reference tree cover data from airborne LiDAR and high resolution spaceborne images across the full range of boreal forest tree cover. This domain-specific calibration model used estimates of forest height to determine reference forest cover that best matched Landsat estimates. The model removed the systematic under-estimation of tree canopy cover greater than 80% and indicated that Landsat estimates of tree canopy cover more closely matched canopies at least 2 m in height rather than 5 m. The validation improved estimates of uncertainty in tree canopy cover in discontinuous TTE forests for three temporal epochs (2000, 2005, and 2010) by reducing systematic errors, leading to increases in tree canopy cover uncertainty. Average pixel-level uncertainties in tree canopy cover were 29.0%, 27.1% and 31.1% for the 2000, 2005 and 2010 epochs, respectively. Maps from these calibrated data improve the uncertainty associated with Landsat tree canopy cover estimates in the discontinuous forests of the circumpolar TTE.

  15. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils.

    Science.gov (United States)

    Lipson, David A; Raab, Theodore K; Parker, Melanie; Kelley, Scott T; Brislawn, Colin J; Jansson, Janet

    2015-08-01

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes). © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

  16. Heterogeneity of carbon loss and its temperature sensitivity in East-European subarctic tundra soils.

    Science.gov (United States)

    Diáková, Kateřina; Čapek, Petr; Kohoutová, Iva; Mpamah, Promise A; Bárta, Jiří; Biasi, Christina; Martikainen, Pertti J; Šantrůčková, Hana

    2016-09-01

    Arctic peatlands store large stocks of organic carbon which are vulnerable to the climate change but their fate is uncertain. There is increasing evidence that a part of it will be lost as a result of faster microbial mineralization. We studied the vulnerability of 3500-5900 years old bare peat uplifted from permafrost layers by cryogenic processes to the surface of an arctic peat plateau. We aimed to find biotic and abiotic drivers of CLOSS from old peat and compare them with those of adjacent, young vegetated soils of the peat plateau and mineral tundra. The soils were incubated in laboratory at three temperatures (4°C, 12°C and 20°C) and two oxygen levels (aerobic, anaerobic). CLOSS was monitored and soil parameters (organic carbon quality, nutrient availability, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools) were determined. We found that CLOSS from the old peat was constrained by low microbial biomass representing only 0.22% of organic carbon. CLOSS was only slightly reduced by the absence of oxygen and exponentially increased with temperature, showing the same temperature sensitivity under both aerobic and anaerobic conditions. We conclude that carbon in the old bare peat is stabilized by a combination of physical, chemical and biological controls including soil compaction, organic carbon quality, low microbial biomass and the absence of plants. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. On the influence of the tundra on the EnEV

    International Nuclear Information System (INIS)

    Genath, B.

    2004-01-01

    This extensive article discusses the European General Energy-Efficiency Guidelines for Buildings that are to be implemented in national legislation by 2006. This extensive article looks at questions concerning the implementation of these guidelines, which not only limit the amount of primary energy used for heating, but also that used for air-conditioning and lighting. The new regulations are compared with the existing German EnEV energy-efficiency regulations. The advantages and the weak points of the latter are discussed. Several special cases are quoted and improvements are suggested, including the adoption of the best part-implementations from existing national regulations. The interdisciplinary approach necessary is discussed. Also the effects of the EU-EnEV on emissions trading is looked at. The situation concerning CO 2 and global warming in Russia is examined in the light of emissions-trading efforts - and even the climatic pros and cons of letting the permafrost of the tundra melt are discussed

  18. Calibration and Validation of Landsat Tree Cover in the Taiga−Tundra Ecotone

    Directory of Open Access Journals (Sweden)

    Paul Mannix Montesano

    2016-06-01

    Full Text Available Monitoring current forest characteristics in the taiga−tundra ecotone (TTE at multiple scales is critical for understanding its vulnerability to structural changes. A 30 m spatial resolution Landsat-based tree canopy cover map has been calibrated and validated in the TTE with reference tree cover data from airborne LiDAR and high resolution spaceborne images across the full range of boreal forest tree cover. This domain-specific calibration model used estimates of forest height to determine reference forest cover that best matched Landsat estimates. The model removed the systematic under-estimation of tree canopy cover >80% and indicated that Landsat estimates of tree canopy cover more closely matched canopies at least 2 m in height rather than 5 m. The validation improved estimates of uncertainty in tree canopy cover in discontinuous TTE forests for three temporal epochs (2000, 2005, and 2010 by reducing systematic errors, leading to increases in tree canopy cover uncertainty. Average pixel-level uncertainties in tree canopy cover were 29.0%, 27.1% and 31.1% for the 2000, 2005 and 2010 epochs, respectively. Maps from these calibrated data improve the uncertainty associated with Landsat tree canopy cover estimates in the discontinuous forests of the circumpolar TTE.

  19. Geological features and geophysical signatures of continental margins of India

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.

    margins of India, with which some of the main geological features of continental margins have been modified. This article provides a brief review on theory of plate tectonics for understanding the process of intra- continental breakup..., thereby the results are discussed for classification of the margins. The Theory of Plate Tectonics The theory of continental drift, which paves the way for discovery of plate tectonics, was put forward by Alfred Lother Wegener as early as in 1912...

  20. A Spatial Model of Erosion and Sedimentation on Continental Margins

    National Research Council Canada - National Science Library

    Pratson, Lincoln

    1999-01-01

    .... A computer model that simulates the evolution of continental slope morphology under the interaction of sedimentation, slope failure, and sediment flow erosion has been constructed and validated...

  1. A vision for a continental energy strategy

    International Nuclear Information System (INIS)

    Klein, R.; Tobin, B.; Angevine, G.; Fryer, K.; Martin, L.T.

    2008-01-01

    This paper presented a vision with respect to a continental energy strategy and the principles and goals that must underlie such a strategy. These principles include relying on signals emanating from energy markets to guide investment; limiting the role of government to that of ensuring that the policy and institutional framework is conducive to the development and operation of competitive and innovative energy markets; and ensuring free and open energy trade in energy commodities, both within the continent and with the rest of the world. The paper also identified a number of important factors that, would shape and condition continental energy development and trade. The paper provided an overview of the North American energy use and supply situation for the following resources: oil; natural gas; electricity; coal; nuclear power; hydroelectricity; geothermal energy; wind power; solar power; and ethanol. It also discussed the contribution of the North American Free Trade Agreement (NAFTA) through increased natural gas exports. It was concluded that given the petroleum resources of the three countries and their increased value because of higher oil and gas prices, there was considerable incentive for Canada, the United States, and Mexico to streamline regulations in order to facilitate the efficient development, transportation, and use of the continent's energy resources in accordance with market conditions. 38 refs., 2 tabs., 21 figs

  2. A vision for a continental energy strategy

    Energy Technology Data Exchange (ETDEWEB)

    Klein, R. [Borden Ladner Gervais LLP, Calgary, AB (Canada); Tobin, B. [Fraser Milner Casgrain LLP. Toronto, ON (Canada); Angevine, G. [Angevine Economic Consulting Ltd., Calgary, AB (Canada); Fryer, K.; Martin, L.T. [Fraser Inst., Vancouver, BC (Canada)] (eds.)

    2008-02-15

    This paper presented a vision with respect to a continental energy strategy and the principles and goals that must underlie such a strategy. These principles include relying on signals emanating from energy markets to guide investment; limiting the role of government to that of ensuring that the policy and institutional framework is conducive to the development and operation of competitive and innovative energy markets; and ensuring free and open energy trade in energy commodities, both within the continent and with the rest of the world. The paper also identified a number of important factors that, would shape and condition continental energy development and trade