Performances of some warm-season turfgrasses under ...

African Journals Online (AJOL)

STORAGESEVER

2009-09-15

Sep 15, 2009 ... Main characteristics of mediterranean climate are represented by mild, rainy ... the warm-season turfgrasses with low water use rate and. *Corresponding ..... Lawns and Golf, Sleeping Bear Press, Chelsea, MI. Busey P (2003).

Effects of Seasonal and Perennial Grazing on Soil Fauna Community and Microbial Biomass Carbon in the Subalpine Meadows of Yunnan, Southwest China

Institute of Scientific and Technical Information of China (English)

LIU Shengjie; YANG Xiaodong; Anthony R.IVES; FENG Zhili; SHA Liqing

2017-01-01

Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems.A field soil survey was conducted to compare microbial biomass carbon (Cmin) and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province,China:perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing.A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices,including treatments of no mowing,perennial grazing (NM + G),mowing followed by seasonal grazing (M + G),mowing and no grazing (M + NG),and no mowing or grazing (NM + NG).The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site.The experiment results showed that in comparison to non-grazing treatments (M + NG and NM + NG),grazing (NM + G and M + G) reduced total fauna density (by 150 individuals m-2) and the number of taxonomic groups present (by 0.32 taxa m-2).Mowing decreased Cmin (by 0.31 mg g-1).Furthermore,the NM + G treatment (perennial grazing) had the lowest density of Collembola (16.24 individuals m-2),one of the two most common taxonomic groups,although other taxonomic groups responded differently to the treatments.Treatment effects on soil fauna were consistent with those on above-ground grasses,in which C:N ratios were greatly reduced by grazing,with this effect being the greatest for the NM + G treatment.In contrast,different grazing treatments had little effect on C:N ratio of soil.Furthermore,the traditional grazing method (mowing followed by seasonal grazing) may have less severe effects on some taxonomic groups than perennial grazing.Therefore,an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.

Responses of Seasonal Precipitation Intensity to Global Warming

Science.gov (United States)

Lan, Chia-Wei; Lo, Min-Hui; Chou, Chia

2016-04-01

Under global warming, the water vapor increases with rising temperature at the rate of 7%/K. Most previous studies focus on the spatial differences of precipitation and suggest that wet regions become wetter and dry regions become drier. Our recent studies show a temporal disparity of global precipitation, which the wet season becomes wetter and dry season becomes drier; therefore, the annual range increases. However, such changes in the annual range are not homogeneous globally, and in fact, the drier trend over the ocean is much larger than that over the land, where the dry season does not become drier. Such precipitation change over land is likely because of decreased omega at 500hPa (more upward motion) in the reanalysis datasets from 1980 to 2013. The trends of vertical velocity and moist static energy profile over the increased precipitation regions become more unstable. The instability is most likely attributed to the change in specific humility below 400hPa. Further, we will use Coupled Model Intercomparison Project Phase 5 (CMIP5) archives to investigate whether the precipitation responses in dry season are different between the ocean and land under global warming.

Greenhouse gas flux under warm-season perennial C4 grasses across different soil and climate gradients on the Islands of Hawaii

Science.gov (United States)

Pawlowski, M. N.; Crow, S. E.; Sumiyoshi, Y.; Wells, J.; Kikkawa, H. R.

2011-12-01

Agricultural soils can serve as either a sink or a source for atmospheric carbon (C) and other greenhouse gases (GHG). This is particularly true for tropical soils where influences from climate and soil gradients are wide ranging. Current estimates of GHG flux from soil are often under or overestimated due to high variability in sample sites and inconsistencies in land use and vegetation type, making extrapolation to new study systems difficult. This work aimed to identify patterns of trace fluxes of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) across two soil types and three species of warm season perennial C4 grasses: Pennisetum purpureum (Napier grass), Panicum maximum (Guinea grass) and Saccharum officinarum (sugar cane) on the islands of Oahu and Maui in Hawaii. Multiple static vented chambers were installed into replicate plots for each species; flux measurements were made during the growth, fertilization and harvest cycles at set time intervals for one hour and analyzed by gas chromatography. Initial results from Oahu indicate no significant differences in CO2 flux between the P. maximum and P. purpureum species after fertilization or at full growth. We observed an average flux of 143 mg m-2 h-1 and 155 mg m-2 h-1 for P. maximum and P. purpureum respectively at full growth for CO2 and 1.7 μg m-2 h-1and 0.3 μg m-2 h-1 for N2O. Additionally, N2O rates sampled after a typical fertilizer application were significantly greater than at full growth (p=0.0005) with flux rates of 25.2 μg m2h-1 and 30.3 μg m2h-1 for P. maximum and P. purpureum respectively. With a global warming potential of 310 for N2O, even short-term spikes following fertilizer application can cause long lasting effects of GHG emission from agricultural soils. CH4 flux was negligible for all species on the Oahu plots during these sample periods. Globally, water limitation is a major factor influencing the potential productivity of agricultural crops and the sustainability of

Warm-season severe wind events in Germany

Science.gov (United States)

Gatzen, Christoph

2013-04-01

A 15-year data set of wind measurements was analyzed with regard to warm season severe wind gusts in Germany. For April to September of the years 1997 to 2011, 1035 wind measurements of 26 m/s or greater were found. These wind reports were associated with 268 wind events. In total, 252 convective wind events contributed to 837 (81%) of the wind reports, 16 non-convective synoptic-scale wind events contributed to 198 reports (19%). Severe wind events were found with synoptic situations characterized by rather strong mid-level flow and advancing mid-level troughs. Severe convective wind events were analyzed using radar images and classified with respect to the observed radar structure. The most important convective mode was squall lines that were associated with one third of all severe wind gusts, followed by groups, bow echo complexes, and bow echoes. Supercells and cells were not associated with many wind reports. The low contribution of isolated cells indicates that rather large-scale forcing by synoptic-scale features like fronts is important for German severe wind events. Bow echoes were found to be present for 58% of all wind reports. The movement speed of bow echoes indicated a large variation with a maximum speed of 33 m/s. Extreme wind events as well as events with more than 15 wind reports were found to be related to higher movement speeds. Concentrating on the most intense events, derechos seem to be very important to the warm season wind threat in Germany. Convective events with a path length of more than 400 km contributed to 36% of all warm-season wind gusts in this data set. Furthermore, eight of nine extreme gusts exceeding 40 m/s were recorded with derecho events.

SEASONALITY OF ANNUAL PLANT ESTABLISHMENT INFLUENCES THE INTERACTIONBETWEEN THE NON-NATIVE ANNUAL GRASS BROMUS MADRITENSIS SSP. RUBENS AND MOJAVE DESERT PERENNIALS

Energy Technology Data Exchange (ETDEWEB)

L A. DEFALCO; G. C. FERNANDEZ; R. S. NOWAK

2004-01-01

Competition between native and non-native species can change the composition and structure of plant communities, but in deserts the timing of non-native plant establishment can modulate their impacts to native species. In a field experiment, we varied densities of the non-native annual grass Bromus madritensis ssp. rubens around individuals of three native perennials--Larrea iridentata, Achnatherum hymenoides, and Pleuraphis rigida--in either winter or spring. Additional plots were prepared for the Same perennial species and seasons, but with a mixture of native annual species. Relative growth rates of perennial shoots (RGRs) declined with increasing Bromus biomass when Bromus that was established in winter had 2-3 mo of growth and high water use before perennial growth began. However, this high water use did not significantly reduce water potentials for the perennials, suggesting Bromus that established earlier depleted other soil resources, such as N, otherwise used by perennial plants. Spring-established Bromus had low biomass even at higher densities and did not effectively reduce RGRs, resulting in an overall lower impact to perennials than when Bromus was established in winter. Similarly, growth and reproduction of perennials with mixed annuals as neighbors did not differ from those with Bromus neighbors of equivalent biomass, but densities of these annuals did not support the high biomass necessary to reduce perennial growth. Thus, impacts of native Mojave Desert annuals to perennials are expected to be lower than those of Bromus because seed dormancy and narrow requirements for seedling survivorship produce densities and biomass lower than those achieved by Bromus. In comparing the effects of Bromus among perennial species, the impact of increased Bromus biomass on RGR was lower for Larrea than for the two perennial grasses, probably because Lurrea maintains low growth rates throughout the year, even after Bromus has completed its life cycle. This contrasts

The potential of perennial cave ice in isotope palaeoclimatology

International Nuclear Information System (INIS)

Yonge, Charles J.; MacDonald, William D.

1999-01-01

Perennial ice from caves on and to the east of the Canadian Great Divide yield delta O 18 and delta D values which are usually high measurements where compared with the average precipitation for the region. Furthermore, these ice data fall below and along lines of lower slope than the Global Meteoric Water Line. To explain the observed relationships, we propose the following process. a vapour-ice isotopic fractionation mechanism operates on warm season vapour when it precipitates as hoar ice on entering the caves. The subsequent fall of hoar to the cave floor through mechanical overloading along with ice derived from ground-water seepage (with a mean annual isotopic composition), results in massive ice formation of a mixed composition. This mixed composition is what is observed in the characteristic relationships found here. Such findings suggest that a warm versus cold climate interpretation for ancient cave ice may be the opposite of that found in the more familiar polar and glacial ice caves. (Author) 3 figs., 1 tab., 12 refs

Intake, digestibility, and nitrogen retention by sheep supplemented with warm-season legume haylages or soybean meal.

Science.gov (United States)

Foster, J L; Adesogan, A T; Carter, J N; Blount, A R; Myer, R O; Phatak, S C

2009-09-01

The high cost of commercial supplements necessitates evaluation of alternatives for ruminant livestock fed poor quality warm-season grasses. This study determined how supplementing bahiagrass haylage (Paspalum notatum Flügge cv. Tifton 9) with soybean [Glycine max (L.) Merr.] meal or warm-season legume haylages affected the performance of lambs. Forty-two Dorper x Katadhin lambs (27.5 +/- 5 kg) were fed for ad libitum intake of bahiagrass haylage (67.8% NDF, 9.6% CP) alone (control) or supplemented with soybean meal (18.8% NDF, 51.4% CP) or haylages of annual peanut [Arachis hypogaea (L.) cv. Florida MDR98; 39.6% NDF, 18.7% CP], cowpea [Vigna unguiculata (L.) Walp. cv. Iron clay; 44.1% NDF, 16.0% CP], perennial peanut (Arachis glabrata Benth. cv. Florigraze; 40.0% NDF, 15.8% CP), or pigeonpea [Cajanus cajan (L.) Millsp. cv. GA-2; 65.0% NDF, 13.7% CP]. Haylages were harvested at the optimal maturity for maximizing yield and nutritive value, wilted to 45% DM, baled, wrapped in polyethylene plastic, and ensiled for 180 d. Legumes were fed at 50% of the dietary DM, and soybean meal was fed at 8% of the dietary DM to match the average CP concentration (12.8%) of legume haylage-supplemented diets. Lambs were fed each diet for a 14-d adaptation period and a 7-d data collection period. Each diet was fed to 7 lambs in period 1 and 4 lambs in period 2. Pigeonpea haylage supplementation decreased (P haylages increased (P haylage, all supplements increased (P haylage supplementation, but unaffected (P = 0.05) by other supplements. Efficiency of microbial protein synthesis was unaffected (P = 0.05) by diet. Ruminal ammonia concentration was increased (P = 0.01) by all supplements, but only soybean meal and annual peanut haylage increased (P haylages are promising protein supplements for growing lambs.

Warm season chloride concentrations in stream habitats of freshwater mussel species at risk

International Nuclear Information System (INIS)

Todd, Aaron K.; Kaltenecker, M. Georgina

2012-01-01

Warm season (May–October) chloride concentrations were assessed in stream habitats of freshwater mussel species at risk in southern Ontario, Canada. Significant increases in concentrations were observed at 96% of 24 long-term (1975–2009) monitoring sites. Concentrations were described as a function of road density indicating an anthropogenic source of chloride. Linear regression showed that 36% of the variation of concentrations was explained by road salt use by the provincial transportation ministry. Results suggest that long-term road salt use and retention is contributing to a gradual increase in baseline chloride concentrations in at risk mussel habitats. Exposure of sensitive mussel larvae (glochidia) to increasing chloride concentrations may affect recruitment to at risk mussel populations. - Highlights: ► Warm season chloride concentrations were assessed in habitats of mussel species at risk. ► Concentrations increased significantly at 96% of 24 long-term monitoring sites. ► Concentrations increased with increases in road density and road salt use. ► Retention of road salt likely contributed to elevated warm season concentrations. ► Glochidia exposure to increasing concentrations may affect mussel reproduction. - Warm season chloride concentrations increased in southern Ontario streams with road salt use, such that reproduction of freshwater mussel species at risk may be affected.

A new mechanism for warm-season precipitation response to global warming based on convection-permitting simulations

Science.gov (United States)

Dai, Aiguo; Rasmussen, Roy M.; Liu, Changhai; Ikeda, Kyoko; Prein, Andreas F.

2017-08-01

Climate models project increasing precipitation intensity but decreasing frequency as greenhouse gases increase. However, the exact mechanism for the frequency decrease remains unclear. Here we investigate this by analyzing hourly data from regional climate change simulations with 4 km grid spacing covering most of North America using the Weather Research and Forecasting model. The model was forced with present and future boundary conditions, with the latter being derived by adding the CMIP5 19-model ensemble mean changes to the ERA-interim reanalysis. The model reproduces well the observed seasonal and spatial variations in precipitation frequency and histograms, and the dry interval between rain events over the contiguous US. Results show that overall precipitation frequency indeed decreases during the warm season mainly due to fewer light-moderate precipitation (0.1 2.0 mm/h) events, while heavy (2 10 mm/h) events increase. Dry spells become longer and more frequent, together with a reduction in time-mean relative humidity (RH) in the lower troposphere during the warm season. The increased dry hours and decreased RH lead to a reduction in overall precipitation frequency and also for light-moderate precipitation events, while water vapor-induced increases in precipitation intensity and the positive latent heating feedback in intense storms may be responsible for the large increase in intense precipitation. The size of intense storms increases while their number decreases in the future climate, which helps explain the increase in local frequency of heavy precipitation. The results generally support a new hypothesis for future warm-season precipitation: each rainstorm removes ≥7% more moisture from the air per 1 K local warming, and surface evaporation and moisture advection take slightly longer than currently to replenish the depleted moisture before the next storm forms, leading to longer dry spells and a reduction in precipitation frequency, as well as

Striking Seasonality in the Secular Warming of the Northern Continents: Structure and Mechanisms

Science.gov (United States)

Nigam, S.; Thomas, N. P.

2017-12-01

The linear trend in twentieth-century surface air temperature (SAT)—a key secular warming signal— exhibits striking seasonal variations over Northern Hemisphere continents; SAT trends are pronounced in winter and spring but notably weaker in summer and fall. The SAT trends in historical twentieth-century climate simulations informing the Intergovernmental Panel for Climate Change's Fifth Assessment show varied (and often unrealistic) strength and structure, and markedly weaker seasonal variation. The large intra-ensemble spread of winter SAT trends in some historical simulations was surprising, especially in the context of century-long linear trends, with implications for the detection of the secular warming signal. The striking seasonality of observed secular warming over northern continents warrants an explanation and the representation of related processes in climate models. Here, the seasonality of SAT trends over North America is shown to result from land surface-hydroclimate interactions and, to an extent, also from the secular change in low-level atmospheric circulation and related thermal advection. It is argued that the winter dormancy and summer vigor of the hydrologic cycle over middle- to high-latitude continents permit different responses to the additional incident radiative energy from increasing greenhouse gas concentrations. The seasonal cycle of climate, despite its monotony, provides an expanded phase space for the exposition of the dynamical and thermodynamical processes generating secular warming, and an exceptional cost-effective opportunity for benchmarking climate projection models.

Seasonal Variation of Provitamin D2 and Vitamin D2 in Perennial Ryegrass (Lolium perenne L.)

DEFF Research Database (Denmark)

Jäpelt, Rie Bak; Didion, Thomas; Smedsgaard, Jørn

2011-01-01

Ergosterol (provitamin D(2)) is converted to vitamin D(2) in grass by exposure to UV light. Six varieties of perennial ryegrass (Lolium perenne L.) were harvested four times during the season, and the contents of vitamin D(2) and ergosterol were analyzed by a sensitive and selective liquid...... chromatography tandem mass spectrometry method. Weather factors were recorded, and a principal component analysis was performed to study which factors were important for the formation of vitamin D(2). The results suggest that a combination of weather factors is involved and that the contents of ergosterol...... and vitamin D(2) change more than a factor of 10 during the season. These results demonstrate that grass potentially can be a significant source of vitamin D for grazing animals and animals fed on silage and hay....

Harvesting Effects on Species Composition and Distribution of Cover Attributes in Mixed Native Warm-Season Grass Stands

Directory of Open Access Journals (Sweden)

Vitalis W. Temu

2015-05-01

Full Text Available Managing grasslands for forage and ground-nesting bird habitat requires appropriate defoliation strategies. Subsequent early-summer species composition in mixed stands of native warm-season grasses (Indiangrass (IG, Sorghastrum nutans, big bluestem (BB, Andropogon gerardii and little bluestem (LB, Schizachyrium scoparium responding to harvest intervals (treatments, 30, 40, 60, 90 or 120 d and durations (years in production was assessed. Over three years, phased May harvestings were initiated on sets of randomized plots, ≥90 cm apart, in five replications (blocks to produce one-, two- and three-year-old stands. Two weeks after harvest, the frequencies of occurrence of plant species, litter and bare ground, diagonally across each plot (line intercept, were compared. Harvest intervals did not influence proportions of dominant plant species, occurrence of major plant types or litter, but increased that of bare ground patches. Harvest duration increased the occurrence of herbaceous forbs and bare ground patches, decreased that of tall-growing forbs and litter, but without affecting that of perennial grasses, following a year with more September rainfall. Data suggest that one- or two-year full-season forage harvesting may not compromise subsequent breeding habitat for bobwhites and other ground-nesting birds in similar stands. It may take longer than a year’s rest for similar stands to recover from such changes in species composition.

Native herbaceous perennials as ornamentals

DEFF Research Database (Denmark)

Larsen, Bjarne; Ørgaard, Marian

2013-01-01

Gardening with native perennials is a way to bring nature closer to urban citizens and bring up reflections on nature in a busy world. During three seasons of trialing Salvia pratensis, Dianthus deltoides, Campanula trachelium, Vincetoxicum hirundinaria, Saxifraga granulata, Plantago media and P...

Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

Science.gov (United States)

Kwok, R.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

The impact of global warming on seasonality of ocean primary production

Directory of Open Access Journals (Sweden)

S. Henson

2013-06-01

Full Text Available The seasonal cycle (i.e. phenology of oceanic primary production (PP is expected to change in response to climate warming. Here, we use output from 6 global biogeochemical models to examine the response in the seasonal amplitude of PP and timing of peak PP to the IPCC AR5 warming scenario. We also investigate whether trends in PP phenology may be more rapidly detectable than trends in annual mean PP. The seasonal amplitude of PP decreases by an average of 1–2% per year by 2100 in most biomes, with the exception of the Arctic which sees an increase of ~1% per year. This is accompanied by an advance in the timing of peak PP by ~0.5–1 months by 2100 over much of the globe, and particularly pronounced in the Arctic. These changes are driven by an increase in seasonal amplitude of sea surface temperature (where the maxima get hotter faster than the minima and a decrease in the seasonal amplitude of the mixed layer depth and surface nitrate concentration. Our results indicate a transformation of currently strongly seasonal (bloom forming regions, typically found at high latitudes, into weakly seasonal (non-bloom regions, characteristic of contemporary subtropical conditions. On average, 36 yr of data are needed to detect a climate-change-driven trend in the seasonal amplitude of PP, compared to 32 yr for mean annual PP. Monthly resolution model output is found to be inadequate for resolving phenological changes. We conclude that analysis of phytoplankton seasonality is not necessarily a shortcut to detecting climate change impacts on ocean productivity.

Changes of biomass in some perennial grass species. | M.C. ...

African Journals Online (AJOL)

Patterns of seasonal herbaceous biomass change in a burned, ungrazed savanna woodland are reported. A standard clipping technique was used and material farmed in the current season was separated from that formed in the previous season for three perennial grass species: Brachiaria nigropedata, Andropogon ...

The responses of microbial temperature relationships to seasonal change and winter warming in a temperate grassland.

Science.gov (United States)

Birgander, Johanna; Olsson, Pål Axel; Rousk, Johannes

2018-01-18

Microorganisms dominate the decomposition of organic matter and their activities are strongly influenced by temperature. As the carbon (C) flux from soil to the atmosphere due to microbial activity is substantial, understanding temperature relationships of microbial processes is critical. It has been shown that microbial temperature relationships in soil correlate with the climate, and microorganisms in field experiments become more warm-tolerant in response to chronic warming. It is also known that microbial temperature relationships reflect the seasons in aquatic ecosystems, but to date this has not been investigated in soil. Although climate change predictions suggest that temperatures will be mostly affected during winter in temperate ecosystems, no assessments exist of the responses of microbial temperature relationships to winter warming. We investigated the responses of the temperature relationships of bacterial growth, fungal growth, and respiration in a temperate grassland to seasonal change, and to 2 years' winter warming. The warming treatments increased winter soil temperatures by 5-6°C, corresponding to 3°C warming of the mean annual temperature. Microbial temperature relationships and temperature sensitivities (Q 10 ) could be accurately established, but did not respond to winter warming or to seasonal temperature change, despite significant shifts in the microbial community structure. The lack of response to winter warming that we demonstrate, and the strong response to chronic warming treatments previously shown, together suggest that it is the peak annual soil temperature that influences the microbial temperature relationships, and that temperatures during colder seasons will have little impact. Thus, mean annual temperatures are poor predictors for microbial temperature relationships. Instead, the intensity of summer heat-spells in temperate systems is likely to shape the microbial temperature relationships that govern the soil-atmosphere C

Seasonality of change: Summer warming rates do not fully represent effects of climate change on lake temperatures

Science.gov (United States)

Winslow, Luke; Read, Jordan S.; Hansen, Gretchen J. A.; Rose, Kevin C.; Robertson, Dale M.

2017-01-01

Responses in lake temperatures to climate warming have primarily been characterized using seasonal metrics of surface-water temperatures such as summertime or stratified period average temperatures. However, climate warming may not affect water temperatures equally across seasons or depths. We analyzed a long-term dataset (1981–2015) of biweekly water temperature data in six temperate lakes in Wisconsin, U.S.A. to understand (1) variability in monthly rates of surface- and deep-water warming, (2) how those rates compared to summertime average trends, and (3) if monthly heterogeneity in water temperature trends can be predicted by heterogeneity in air temperature trends. Monthly surface-water temperature warming rates varied across the open-water season, ranging from 0.013 in August to 0.073°C yr−1 in September (standard deviation [SD]: 0.025°C yr−1). Deep-water trends during summer varied less among months (SD: 0.006°C yr−1), but varied broadly among lakes (–0.056°C yr−1 to 0.035°C yr−1, SD: 0.034°C yr−1). Trends in monthly surface-water temperatures were well correlated with air temperature trends, suggesting monthly air temperature trends, for which data exist at broad scales, may be a proxy for seasonal patterns in surface-water temperature trends during the open water season in lakes similar to those studied here. Seasonally variable warming has broad implications for how ecological processes respond to climate change, because phenological events such as fish spawning and phytoplankton succession respond to specific, seasonal temperature cues.

Comparative seasonal variations of spectral signatures of broad-leaved and coniferous stands from Landsat data. Comparison with other perennial environments

International Nuclear Information System (INIS)

Chaume, R.; Combeau, A.

1984-01-01

Spectral signatures of two distinct forest test areas were identified from digital data including 15 LANDSAT scenes covering the same geographical area: a broad-leaved forest (oak and beech) and a coniferous forest (scotch pine). Seasonal variations of the signatures were examined and were expressed in terms of various data: date, solar height and phenological state of vegetation cover. Results were compared to these obtained from other perennial surface conditions (grassland, bare soils) . Range of the seasonal variations of radiance is noted, as well as evolutionary peculiarities on each band and between themes. Rationing of spectral bands (particularly MSS 5 and 7) and their variation with time are specified [fr

Characterization of water quality and suspended sediment during cold-season flows, warm-season flows, and stormflows in the Fountain and Monument Creek watersheds, Colorado, 2007–2015

Science.gov (United States)

Miller, Lisa D.; Stogner, Sr., Robert W.

2017-09-01

From 2007 through 2015, the U.S. Geological Survey, in cooperation with Colorado Springs City Engineering, conducted a study in the Fountain and Monument Creek watersheds, Colorado, to characterize surface-water quality and suspended-sediment conditions for three different streamflow regimes with an emphasis on characterizing water quality during storm runoff. Data collected during this study were used to evaluate the effects of stormflows and wastewater-treatment effluent discharge on Fountain and Monument Creeks in the Colorado Springs, Colorado, area. Water-quality samples were collected at 2 sites on Upper Fountain Creek, 2 sites on Monument Creek, 3 sites on Lower Fountain Creek, and 13 tributary sites during 3 flow regimes: cold-season flow (November–April), warm-season flow (May–October), and stormflow from 2007 through 2015. During 2015, additional samples were collected and analyzed for Escherichia coli (E. coli) during dry weather conditions at 41 sites, located in E. coli impaired stream reaches, to help identify source areas and scope of the impairment.Concentrations of E. coli, total arsenic, and dissolved copper, selenium, and zinc in surface-water samples were compared to Colorado in-stream standards. Stormflow concentrations of E. coli frequently exceeded the recreational use standard of 126 colonies per 100 milliliters at main-stem and tributary sites by more than an order of magnitude. Even though median E. coli concentrations in warm-season flow samples were lower than median concentrations in storm-flow samples, the water quality standard for E. coli was still exceeded at most main-stem sites and many tributary sites during warm-season flows. Six samples (three warm-season flow and three stormflow samples) collected from Upper Fountain Creek, upstream from the confluence of Monument Creek, and two stormflow samples collected from Lower Fountain Creek, downstream from the confluence with Monument Creek, exceeded the acute water

Winter Season Mortality: Will Climate Warming Bring Benefits?

Science.gov (United States)

Kinney, Patrick L; Schwartz, Joel; Pascal, Mathilde; Petkova, Elisaveta; Tertre, Alain Le; Medina, Sylvia; Vautard, Robert

2015-06-01

Extreme heat events are associated with spikes in mortality, yet death rates are on average highest during the coldest months of the year. Under the assumption that most winter excess mortality is due to cold temperature, many previous studies have concluded that winter mortality will substantially decline in a warming climate. We analyzed whether and to what extent cold temperatures are associated with excess winter mortality across multiple cities and over multiple years within individual cities, using daily temperature and mortality data from 36 US cities (1985-2006) and 3 French cities (1971-2007). Comparing across cities, we found that excess winter mortality did not depend on seasonal temperature range, and was no lower in warmer vs. colder cities, suggesting that temperature is not a key driver of winter excess mortality. Using regression models within monthly strata, we found that variability in daily mortality within cities was not strongly influenced by winter temperature. Finally we found that inadequate control for seasonality in analyses of the effects of cold temperatures led to spuriously large assumed cold effects, and erroneous attribution of winter mortality to cold temperatures. Our findings suggest that reductions in cold-related mortality under warming climate may be much smaller than some have assumed. This should be of interest to researchers and policy makers concerned with projecting future health effects of climate change and developing relevant adaptation strategies.

Seasonal exposure to drought and air warming affects soil Collembola and mites.

Directory of Open Access Journals (Sweden)

Guo-Liang Xu

Full Text Available Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4 °C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length ≤ 0.20 mm increased, but the percentage of large mites (body length >0.40 mm decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type.

Seasonal Exposure to Drought and Air Warming Affects Soil Collembola and Mites

Science.gov (United States)

Xu, Guo-Liang; Kuster, Thomas M.; Günthardt-Goerg, Madeleine S.; Dobbertin, Matthias; Li, Mai-He

2012-01-01

Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment) at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4°C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length 0.20 mm) increased, but the percentage of large mites (body length >0.40 mm) decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type. PMID:22905210

Seasonal exposure to drought and air warming affects soil Collembola and mites.

Science.gov (United States)

Xu, Guo-Liang; Kuster, Thomas M; Günthardt-Goerg, Madeleine S; Dobbertin, Matthias; Li, Mai-He

2012-01-01

Global environmental changes affect not only the aboveground but also the belowground components of ecosystems. The effects of seasonal drought and air warming on the genus level richness of Collembola, and on the abundance and biomass of the community of Collembola and mites were studied in an acidic and a calcareous forest soil in a model oak-ecosystem experiment (the Querco experiment) at the Swiss Federal Research Institute WSL in Birmensdorf. The experiment included four climate treatments: control, drought with a 60% reduction in rainfall, air warming with a seasonal temperature increase of 1.4 °C, and air warming + drought. Soil water content was greatly reduced by drought. Soil surface temperature was slightly increased by both the air warming and the drought treatment. Soil mesofauna samples were taken at the end of the first experimental year. Drought was found to increase the abundance of the microarthropod fauna, but reduce the biomass of the community. The percentage of small mites (body length ≤ 0.20 mm) increased, but the percentage of large mites (body length >0.40 mm) decreased under drought. Air warming had only minor effects on the fauna. All climate treatments significantly reduced the richness of Collembola and the biomass of Collembola and mites in acidic soil, but not in calcareous soil. Drought appeared to have a negative impact on soil microarthropod fauna, but the effects of climate change on soil fauna may vary with the soil type.

Chronic environmental stress enhances tolerance to seasonal gradual warming in marine mussels.

Directory of Open Access Journals (Sweden)

Ionan Marigómez

Full Text Available In global climate change scenarios, seawater warming acts in concert with multiple stress sources, which may enhance the susceptibility of marine biota to thermal stress. Here, the responsiveness to seasonal gradual warming was investigated in temperate mussels from a chronically stressed population in comparison with a healthy one. Stressed and healthy mussels were subjected to gradual temperature elevation for 8 days (1°C per day; fall: 16-24°C, winter: 12-20°C, summer: 20-28°C and kept at elevated temperature for 3 weeks. Healthy mussels experienced thermal stress and entered the time-limited survival period in the fall, became acclimated in winter and exhibited sublethal damage in summer. In stressed mussels, thermal stress and subsequent health deterioration were elicited in the fall but no transition into the critical period of time-limited survival was observed. Stressed mussels did not become acclimated to 20°C in winter, when they experienced low-to-moderate thermal stress, and did not experience sublethal damage at 28°C in summer, showing instead signs of metabolic rate depression. Overall, although the thermal threshold was lowered in chronically stressed mussels, they exhibited enhanced tolerance to seasonal gradual warming, especially in summer. These results challenge current assumptions on the susceptibility of marine biota to the interactive effects of seawater warming and pollution.

On the shortening of Indian summer monsoon season in a warming scenario

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Sabeerali, C. T.; Ajayamohan, R. S.

2018-03-01

Assessing the future projections of the length of rainy season (LRS) has paramount societal impact considering its potential to alter the seasonal mean rainfall over the Indian subcontinent. Here, we explored the projections of LRS using both historical and Representative Concentration Pathways 8.5 (RCP8.5) simulations of the Coupled Model Intercomparison Project Phase5 (CMIP5). RCP8.5 simulations project shortening of the LRS of Indian summer monsoon by altering the timing of onset and withdrawal dates. Most CMIP5 RCP8.5 model simulations indicate a faster warming rate over the western tropical Indian Ocean compared to other regions of the Indian Ocean. It is found that the pronounced western Indian Ocean warming and associated increase in convection results in warmer upper troposphere over the Indian Ocean compared to the Indian subcontinent, reducing the meridional gradient in upper tropospheric temperature (UTT) over the Asian summer monsoon (ASM) domain. The weakening of the meridional gradient in UTT induces weakening of easterly vertical wind shear over the ASM domain during first and last phase of monsoon, facilitate delayed (advanced) monsoon onset (withdrawal) dates, ensues the shortening of LRS of the Indian summer monsoon in a warming scenario.

Grassland bird productivity in warm season grass fields in southwest Wisconsin

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Byers, Carolyn M.; Ribic, Christine; Sample, David W.; Dadisman, John D.; Guttery, Michael

2017-01-01

Surrogate grasslands established through federal set-aside programs, such as U.S. Department of Agriculture's Conservation Reserve Program (CRP), provide important habitat for grassland birds. Warm season grass CRP fields as a group have the potential for providing a continuum of habitat structure for breeding birds, depending on how the fields are managed and their floristic composition. We studied the nesting activity of four obligate grassland bird species, Bobolink (Dolichonyx oryzivorus), Eastern Meadowlark (Sturnella magna), Grasshopper Sparrow (Ammodramus savannarum), and Henslow's Sparrow (A. henslowii), in relation to vegetative composition and fire management in warm season CRP fields in southwest Wisconsin during 2009–2011. Intraspecific variation in apparent nest density was related to the number of years since the field was burned. Apparent Grasshopper Sparrow nest density was highest in the breeding season immediately following spring burns, apparent Henslow's Sparrow nest density was highest 1 y post burn, and apparent Bobolink and Eastern Meadowlark nest densities were higher in post fire years one to three. Grasshopper Sparrow nest density was highest on sites with more diverse vegetation, specifically prairie forbs, and on sites with shorter less dense vegetation. Bobolink, Eastern Meadowlark, and Henslow's Sparrow apparent nest densities were higher on sites with deeper litter; litter was the vegetative component that was most affected by spring burns. Overall nest success was 0.487 for Bobolink (22 d nesting period), 0.478 for Eastern Meadowlark (25 d nesting period), 0.507 for Grasshopper Sparrow (22 d nesting period), and 0.151 for Henslow's Sparrow (21 d nesting period). The major nest predators were grassland-associated species: thirteen-lined ground squirrel (Ictidomys tridecemlineatus), striped skunk (Mephitis mephitis), milk snake (Lampropeltis triangulum), American badger (Taxidea taxus), and western fox snake (Elaphe vulpina). Overall

Transcriptional Profiling and Identification of Heat-Responsive Genes in Perennial Ryegrass by RNA-Sequencing

Directory of Open Access Journals (Sweden)

Kehua Wang

2017-06-01

Full Text Available Perennial ryegrass (Lolium perenne is one of the most widely used forage and turf grasses in the world due to its desirable agronomic qualities. However, as a cool-season perennial grass species, high temperature is a major factor limiting its performance in warmer and transition regions. In this study, a de novo transcriptome was generated using a cDNA library constructed from perennial ryegrass leaves subjected to short-term heat stress treatment. Then the expression profiling and identification of perennial ryegrass heat response genes by digital gene expression analyses was performed. The goal of this work was to produce expression profiles of high temperature stress responsive genes in perennial ryegrass leaves and further identify the potentially important candidate genes with altered levels of transcript, such as those genes involved in transcriptional regulation, antioxidant responses, plant hormones and signal transduction, and cellular metabolism. The de novo assembly of perennial ryegrass transcriptome in this study obtained more total and annotated unigenes compared to previously published ones. Many DEGs identified were genes that are known to respond to heat stress in plants, including HSFs, HSPs, and antioxidant related genes. In the meanwhile, we also identified four gene candidates mainly involved in C4 carbon fixation, and one TOR gene. Their exact roles in plant heat stress response need to dissect further. This study would be important by providing the gene resources for improving heat stress tolerance in both perennial ryegrass and other cool-season perennial grass plants.

Positive feedback of greenhouse gas balances to warming is determined by non-growing season emissions in an alpine meadow

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Niu, S.; Wang, J.; Quan, Q.; Chen, W.; Wen, X.; Yu, G.

2017-12-01

Large uncertainties exist in the sources and sinks of greenhouse gases (CO2, CH4, N2O) in response to climate warming and human activity. So far, numerous previous studies have evaluated the CO2 budget, but little attention has paid to CH4 and N2O budgets and the concurrent balance of these three gases in combination, especially in the non-growing season. Here, we synthesized eddy covariance measurement with the automatic chamber measurements of CO2, CH4, and N2O exposed to three levels of temperature treatments (ambient, +1.5 °C, +2.5 °C) and two disturbance treatments (ummowing, mowing) in an alpine meadow on the Tibetan Plateau. We have found that warming caused increase in CH4 uptake and decrease in N2O emission offset little of the enhancement in CO2 emission, triggering a positive feedback to climate warming. Warming switches the ecosystem from a net sink (-17 ± 14 g CO2-eq m-2 yr-1) in the control to a net source of greenhouse gases of 94 ± 36 gCO2-eq m-2 yr-1 in the plots with +1.5 °C warming treatment, and 177 ± 6 gCO2-eq m-2 yr-1 in the plots with +2.5 °C warming treatment. The changes in the non-growing season balance, rather than those in the growing season, dominate the warming responses of annual greehouse gas balance. And this is not changed by mowing. The dominant role of responses of winter greenhouse gas balance in the positive feedback of ecosystem to climate warming highlights that greenhouse gas balance in cold season has to be considered when assessing climate-carbon cycle feedback.

Artificial asymmetric warming reduces nectar yield in a Tibetan alpine species of Asteraceae.

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Mu, Junpeng; Peng, Youhong; Xi, Xinqiang; Wu, Xinwei; Li, Guoyong; Niklas, Karl J; Sun, Shucun

2015-11-01

Asymmetric warming is one of the distinguishing features of global climate change, in which winter and night-time temperatures are predicted to increase more than summer and diurnal temperatures. Winter warming weakens vernalization and hence decreases the potential to flower for some perennial herbs, and night warming can reduce carbohydrate concentrations in storage organs. This study therefore hypothesized that asymmetric warming should act to reduce flower number and nectar production per flower in a perennial herb, Saussurea nigrescens, a key nectar plant for pollinators in Tibetan alpine meadows. A long-term (6 years) warming experiment was conducted using open-top chambers placed in a natural meadow and manipulated to achieve asymmetric increases in temperature, as follows: a mean annual increase of 0·7 and 2·7 °C during the growing and non-growing seasons, respectively, combined with an increase of 1·6 and 2·8 °C in the daytime and night-time, respectively, from June to August. Measurements were taken of nectar volume and concentration (sucrose content), and also of leaf non-structural carbohydrate content and plant morphology. Six years of experimental warming resulted in reductions in nectar volume per floret (64·7 % of control), floret number per capitulum (8·7 %) and capitulum number per plant (32·5 %), whereas nectar concentration remained unchanged. Depletion of leaf non-structural carbohydrates was significantly higher in the warmed than in the ambient condition. Overall plant density was also reduced by warming, which, when combined with reductions in flower development and nectar volumes, led to a reduction of ∼90 % in nectar production per unit area. The negative effect of asymmetric warming on nectar yields in S. nigrescens may be explained by a concomitant depletion of leaf non-structural carbohydrates. The results thus highlight a novel aspect of how climate change might affect plant-pollinator interactions and plant

Observed decreases in the Canadian outdoor skating season due to recent winter warming

International Nuclear Information System (INIS)

Damyanov, Nikolay N; Mysak, Lawrence A; Damon Matthews, H

2012-01-01

Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada. (letter)

Observed decreases in the Canadian outdoor skating season due to recent winter warming

Science.gov (United States)

Damyanov, Nikolay N.; Damon Matthews, H.; Mysak, Lawrence A.

2012-03-01

Global warming has the potential to negatively affect one of Canada’s primary sources of winter recreation: hockey and ice skating on outdoor rinks. Observed changes in winter temperatures in Canada suggest changes in the meteorological conditions required to support the creation and maintenance of outdoor skating rinks; while there have been observed increases in the ice-free period of several natural water bodies, there has been no study of potential trends in the duration of the season supporting the construction of outdoor skating rinks. Here we show that the outdoor skating season (OSS) in Canada has significantly shortened in many regions of the country as a result of changing climate conditions. We first established a meteorological criterion for the beginning, and a proxy for the length of the OSS. We extracted this information from daily maximum temperature observations from 1951 to 2005, and tested it for significant changes over time due to global warming as well as due to changes in patterns of large-scale natural climate variability. We found that many locations have seen a statistically significant decrease in the OSS length, particularly in Southwest and Central Canada. This suggests that future global warming has the potential to significantly compromise the viability of outdoor skating in Canada.

Annual warm-season grasses vary for forage yield, quality, and competitiveness with weeds

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Warm-season annual grasses may be suitable as herbicide-free forage crops. A two-year field study was conducted to determine whether tillage system and nitrogen (N) fertilizer application method influenced crop and weed biomass, water use, water use efficiency (WUE), and forage quality of three war...

Observed changes in seasonal heat waves and warm temperature extremes in the Romanian Carpathians

Science.gov (United States)

Micu, Dana; Birsan, Marius-Victor; Dumitrescu, Alexandru; Cheval, Sorin

2015-04-01

Extreme high temperature have a large impact on environment and human activities, especially in high elevation areas particularly sensitive to the recent climate warming. The climate of the Romanian Carpathians became warmer particularly in winter, spring and summer, exibiting a significant increasing frequency of warm extremes. The paper investigates the seasonal changes in the frequency, duration and intensity of heat waves in relation to the shifts in the daily distribution of maximum temperatures over a 50-year period of meteorological observations (1961-2010). The paper uses the heat wave definition recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI) and exploits the gridded daily dataset of maximum temperature at 0.1° resolution (~10 km) developed in the framework of the CarpatClim project (www.carpatclim.eu). The seasonal changes in heat waves behavior were identified using the Mann-Kendall non-parametric trend test. The results suggest an increase in heat wave frequency and a lengthening of intervals affected by warm temperature extremes all over the study region, which are explained by the shifts in the upper (extreme) tail of the daily maximum temperature distribution in most seasons. The trends are consistent across the region and are well correlated to the positive phases of the East Atlantic Oscillation. Our results are in good agreement with the previous temperature-related studies concerning the Carpathian region. This study was realized within the framework of the project GENCLIM, financed by UEFISCDI, code PN-II 151/2014.

Spatial variability and trends of seasonal snowmelt processes over Antarctic sea ice observed by satellite scatterometers

Science.gov (United States)

Arndt, S.; Haas, C.

2017-12-01

Snow is one of the key drivers determining the seasonal energy and mass budgets of sea ice in the Southern Ocean. Here, we analyze radar backscatter time series from the European Remote Sensing Satellites (ERS)-1 and-2 scatterometers, from the Quick Scatterometer (QSCAT), and from the Advanced Scatterometer (ASCAT) in order to observe the regional and inter-annual variability of Antarctic snowmelt processes from 1992 to 2014. On perennial ice, seasonal backscatter changes show two different snowmelt stages: A weak backscatter rise indicating the initial warming and metamorphosis of the snowpack (pre-melt), followed by a rapid rise indicating the onset of internal snowmelt and thaw-freeze cycles (snowmelt). In contrast, similar seasonal backscatter cycles are absent on seasonal ice, preventing the periodic retrieval of spring/summer transitions. This may be due to the dominance of ice bottom melt over snowmelt, leading to flooding and ice disintegration before strong snowmelt sets in. Resulting snowmelt onset dates on perennial sea ice show the expected latitudinal gradient from early melt onsets (mid-November) in the northern Weddell Sea towards late (end-December) or even absent snowmelt conditions further south. This result is likely related to seasonal variations in solar shortwave radiation (absorption). In addition, observations with different microwave frequencies allow to detect changing snow properties at different depths. We show that short wavelengths of passive microwave observations indicate earlier pre-melt and snowmelt onset dates than longer wavelength scatterometer observations, in response to earlier warming of upper snow layers compared to lower snow layers. Similarly, pre-melt and snowmelt onset dates retrieved from Ku-Band radars were earlier by an average of 11 and 23 days, respectively, than those retrieved from C-Band. This time difference was used to correct melt onset dates retrieved from Ku-Band to compile a consistent time series from

Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing.

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Bintanja, R; Krikken, F

2016-12-02

Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-albedo and lapse-rate feedbacks. Here we use a state-of-the-art global climate model in idealized seasonal forcing simulations to show that Arctic warming (especially in winter) and sea ice decline are particularly sensitive to radiative forcing in spring, during which the energy is effectively 'absorbed' by the ocean (through sea ice melt and ocean warming, amplified by the ice-albedo feedback) and consequently released to the lower atmosphere in autumn and winter, mainly along the sea ice periphery. In contrast, winter radiative forcing causes a more uniform response centered over the Arctic Ocean. This finding suggests that intermodel differences in simulated Arctic (winter) warming can to a considerable degree be attributed to model uncertainties in Arctic radiative fluxes, which peak in summer.

The occurrence of large branchiopod crustaceans in perennial pans ...

African Journals Online (AJOL)

Pans are isolated, shallow depressions that are endorheic in nature. Because of the natural hydrological functioning of pans, these systems are usually restricted to arid regions and complete desiccation occurs seasonally. In the eastern provinces of South Africa many pans are perennial in nature often remaining inundated ...

Seasonal body size reductions with warming covary with major body size gradients in arthropod species

DEFF Research Database (Denmark)

Horne, Curtis R.; Hirst, Andrew G.; Atkinson, David

2017-01-01

experience different developmental conditions. Yet, unlike other size patterns, these common seasonal temperature–size gradients have never been collectively analysed. We undertake the largest analysis to date of seasonal temperature-size gradients in multivoltine arthropods, including 102 aquatic...... and terrestrial species from 71 global locations. Adult size declines in warmer seasons in 86% of the species examined. Aquatic species show approximately 2.5-fold greater reduction in size per °C of warming than terrestrial species, supporting the hypothesis that greater oxygen limitation in water than in air...

Incorporating residual temperature and specific humidity in predicting weather-dependent warm-season electricity consumption

Science.gov (United States)

Guan, Huade; Beecham, Simon; Xu, Hanqiu; Ingleton, Greg

2017-02-01

Climate warming and increasing variability challenges the electricity supply in warm seasons. A good quantitative representation of the relationship between warm-season electricity consumption and weather condition provides necessary information for long-term electricity planning and short-term electricity management. In this study, an extended version of cooling degree days (ECDD) is proposed for better characterisation of this relationship. The ECDD includes temperature, residual temperature and specific humidity effects. The residual temperature is introduced for the first time to reflect the building thermal inertia effect on electricity consumption. The study is based on the electricity consumption data of four multiple-street city blocks and three office buildings. It is found that the residual temperature effect is about 20% of the current-day temperature effect at the block scale, and increases with a large variation at the building scale. Investigation of this residual temperature effect provides insight to the influence of building designs and structures on electricity consumption. The specific humidity effect appears to be more important at the building scale than at the block scale. A building with high energy performance does not necessarily have low specific humidity dependence. The new ECDD better reflects the weather dependence of electricity consumption than the conventional CDD method.

Seasonal variations in methane fluxes in response to summer warming and leaf litter addition in a subarctic heath ecosystem

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Pedersen, Emily Pickering; Elberling, Bo; Michelsen, Anders

2017-08-01

Methane (CH4) is a powerful greenhouse gas controlled by both biotic and abiotic processes. Few studies have investigated CH4 fluxes in subarctic heath ecosystems, and climate change-induced shifts in CH4 flux and the overall carbon budget are therefore largely unknown. Hence, there is an urgent need for long-term in situ experiments allowing for the study of ecosystem processes over time scales relevant to environmental change. Here we present in situ CH4 and CO2 flux measurements from a wet heath ecosystem in northern Sweden subjected to 16 years of manipulations, including summer warming with open-top chambers, birch leaf litter addition, and the combination thereof. Throughout the snow-free season, the ecosystem was a net sink of CH4 and CO2 (CH4 -0.27 mg C m-2 d-1; net ecosystem exchange -1827 mg C m-2 d-1), with highest CH4 uptake rates (-0.70 mg C m-2 d-1) during fall. Warming enhanced net CO2 flux, while net CH4 flux was governed by soil moisture. Litter addition and the combination with warming significantly increased CH4 uptake rates, explained by a pronounced soil drying effect of up to 32% relative to ambient conditions. Both warming and litter addition also increased the seasonal average concentration of dissolved organic carbon in the soil. The site was a carbon sink with a net uptake of 60 g C m-2 over the snow-free season. However, warming reduced net carbon uptake by 77%, suggesting that this ecosystem type might shift from snow-free season sink to source with increasing summer temperatures.

Comparing soil organic carbon dynamics in perennial grasses and shrubs in a saline-alkaline arid region, northwestern China.

Science.gov (United States)

Zhou, Yong; Pei, Zhiqin; Su, Jiaqi; Zhang, Jingli; Zheng, Yuanrun; Ni, Jian; Xiao, Chunwang; Wang, Renzhong

2012-01-01

Although semi-arid and arid regions account for about 40% of terrestrial surface of the Earth and contain approximately 10% of the global soil organic carbon stock, our understanding of soil organic carbon dynamics in these regions is limited. A field experiment was conducted to compare soil organic carbon dynamics between a perennial grass community dominated by Cleistogenes squarrosa and an adjacent shrub community co-dominated by Reaumuria soongorica and Haloxylon ammodendron, two typical plant life forms in arid ecosystems of saline-alkaline arid regions in northwestern China during the growing season 2010. We found that both fine root biomass and necromass in two life forms varied greatly during the growing season. Annual fine root production in the perennial grasses was 45.6% significantly higher than in the shrubs, and fine root turnover rates were 2.52 and 2.17 yr(-1) for the perennial grasses and the shrubs, respectively. Floor mass was significantly higher in the perennial grasses than in the shrubs due to the decomposition rate of leaf litter in the perennial grasses was 61.8% lower than in the shrubs even though no significance was detected in litterfall production. Soil microbial biomass and activity demonstrated a strong seasonal variation with larger values in May and September and minimum values in the dry month of July. Observed higher soil organic carbon stocks in the perennial grasses (1.32 Kg C m(-2)) than in the shrubs (1.12 Kg C m(-2)) might be attributed to both greater inputs of poor quality litter that is relatively resistant to decay and the lower ability of microorganism to decompose these organic matter. Our results suggest that the perennial grasses might accumulate more soil organic carbon with time than the shrubs because of larger amounts of inputs from litter and slower return of carbon through decomposition.

Disruption of the European climate seasonal clock in a warming world

Science.gov (United States)

Cattiaux, J.; Cassou, C.

2015-12-01

Strength and inland penetration of the oceanic westerly flow over Europe control a large part of the temperature variability over most of the continent. Reduced westerlies, linked to high-pressure anomalies over Scandinavia, induce cold conditions in winter and warm conditions in summer. Here we propose to define the onset of these two seasons as the calendar day where the daily circulation/temperature relationship over Western Europe switches sign. According to this meteorologically-based metrics assessed from several observational datasets, we provide robust evidence for an earlier summer onset by ~10 days between the 1960s and 2000s. Results from model ensemble simulations dedicated to detection-attribution show that this calendar advance is incompatible with the sole internal climate variability and can be attributed to anthropogenic forcings. Late winter snow disappearance over Eastern Europe affects cold air intrusion to the West when easterlies blow, and is mainly responsible for the observed present-day and near-future summer advance. Our findings agree with phenological-based trends (earlier spring events) reported for many living species over Europe, for which they provide a novel dynamical interpretation beyond the traditionally evoked global warming effect. Based on business-as-usual scenario, a seasonal shift of ~25 days is expected by 2100 for summer onset, while no clear signal arises for winter onset.

Effect of Lactic Acid Lactobacillus Preservative and Moisture Level at Baling on In-situ Digestibility of Crabgrass Hay by Heifers.

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Common crabgrass (Digitaria ciliaris [Retz.] Koel.) is a warm-season annual that offers an advantage over many perennial warm-season grasses because of its greater nutritive value and high palatability. However, little is known about how baling crabgrass hay at high moisture affects ruminal forage ...

Comparison of signaling interactions determining annual and perennial plant growth in response to low temperature

Directory of Open Access Journals (Sweden)

Astrid eWingler

2015-01-01

Full Text Available Low temperature inhibits plant growth despite the fact that considerable rates of photosynthetic activity can be maintained. Instead of lower rates of photosynthesis, active inhibition of cell division and expansion is primarily responsible for reduced growth. This results in sink limitation and enables plants to accumulate carbohydrates that act as compatible solutes or are stored throughout the winter to enable re-growth in spring. Regulation of growth in response to temperature therefore requires coordination with carbon metabolism, e.g. via the signaling metabolite trehalose-6-phosphate. The phytohormones gibberellins (GA and jasmonate (JA play an important role in regulating growth in response to temperature. Growth restriction at low temperature is mainly mediated by DELLA proteins, whose degradation is promoted by GA. For annual plants, it has been shown that the GA/DELLA pathway interacts with JA signaling and C-repeat binding factor (CBF dependent cold acclimation, but these interactions have not been explored in detail for perennials. Growth regulation in response to seasonal factors is, however, particularly important in perennials, especially at high latitudes. In autumn, growth cessation in trees is caused by shortening of the daylength in interaction with phytohormone signaling. In perennial grasses seasonal differences in the sensitivity to GA may enable enhanced growth in spring. This review provides an overview of the signaling interactions that determine plant growth at low temperature and highlights gaps in our knowledge, especially concerning the seasonality of signaling responses in perennial plants.

Predicting the occurrence of cold water patches at intermittent and ephemeral tributary confluences with warm rivers

Science.gov (United States)

Small, cold tributary streams can provide important thermal refuge habitat for cold-water fishes such as Pacific salmon (Oncorhynchus spp.) residing in warm, downstream receiving waters. We investigated the potential function of small perennial and non-perennial tributary stream...

Productivity and carbon footprint of perennial grass-forage legume intercropping strategies with high or low nitrogen fertilizer input

DEFF Research Database (Denmark)

Hauggaard-Nielsen, Henrik; Lachouani, Petra; Knudsen, Marie Trydeman

2016-01-01

with either a high or a low rate of mineral nitrogen (N) fertilizer. Life cycle assessment (LCA) was used to evaluate the carbon footprint (global warming potential) of the grassland management including measured nitrous oxide (N2O) emissions after sward incorporation. Without applying any mineral N......A three-season field experiment was established and repeated twice with spring barley used as cover crop for different perennial grass-legume intercrops followed by a full year pasture cropping and winter wheat after sward incorporation. Two fertilization regimes were applied with plots fertilized...... carbon footprint. Thus, a reduction in N fertilizer application rates in the low input systems offsets increased N2O emissions after forage legume treatments compared to grass plots due to the N fertilizer production-related emissions. When including the subsequent wheat yield in the total aboveground...

An Update to the Warm-Season Convective Wind Climatology of KSC/CCAFS

Science.gov (United States)

Lupo, Kevin

2012-01-01

Total of 1100 convective events in the 17-year warm-season climatology at KSC/CCAFS. July and August typically are the peak of convective events, May being the minimum. Warning and non-warning level convective winds are more likely to occur in the late afternoon (1900-2000Z). Southwesterly flow regimes and wind directions produce the strongest winds. Storms moving from southwesterly direction tend to produce more warning level winds than those moving from the northerly and easterly directions.

Global warming related transient albedo feedback in the Arctic and its relation to the seasonality of sea ice

Science.gov (United States)

Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

2015-04-01

The Arctic is warming two to three times faster than the global average. Arctic sea ice cover is very sensitive to this warming and has reached historic minima in late summer in recent years (i.e. 2007, 2012). Considering that the Arctic Ocean is mainly ice-covered and that the albedo of sea ice is very high compared to that of open water, the change in sea ice cover is very likely to have a strong impact on the local surface albedo feedback. Here we quantify the temporal changes in surface albedo feedback in response to global warming. Usually feedbacks are evaluated as being representative and constant for long time periods, but we show here that the strength of climate feedbacks in fact varies strongly with time. For instance, time series of the amplitude of the surface albedo feedback, derived from future climate simulations (CIMP5, RCP8.5 up to year 2300) using a kernel method, peaks around the year 2100. This maximum is likely caused by an increased seasonality in sea-ice cover that is inherently associated with sea ice retreat. We demonstrate that the Arctic average surface albedo has a strong seasonal signature with a maximum in spring and a minimum in late summer/autumn. In winter when incoming solar radiation is minimal the surface albedo doesn't have an important effect on the energy balance of the climate system. The annual mean surface albedo is thus determined by the seasonality of both downwelling shortwave radiation and sea ice cover. As sea ice cover reduces the seasonal signature is modified, the transient part from maximum sea ice cover to its minimum is shortened and sharpened. The sea ice cover is reduced when downwelling shortwave radiation is maximum and thus the annual surface albedo is drastically smaller. Consequently the change in annual surface albedo with time will become larger and so will the surface albedo feedback. We conclude that a stronger seasonality in sea ice leads to a stronger surface albedo feedback, which accelerates

Projected warming portends seasonal shifts of stream temperatures in the Crown of the Continent Ecosystem, USA and Canada

Science.gov (United States)

Jones, Leslie A.; Muhlfeld, Clint C.; Marshall, Lucy A.

2017-01-01

Climate warming is expected to increase stream temperatures in mountainous regions of western North America, yet the degree to which future climate change may influence seasonal patterns of stream temperature is uncertain. In this study, a spatially explicit statistical model framework was integrated with empirical stream temperature data (approximately four million bi-hourly recordings) and high-resolution climate and land surface data to estimate monthly stream temperatures and potential change under future climate scenarios in the Crown of the Continent Ecosystem, USA and Canada (72,000 km2). Moderate and extreme warming scenarios forecast increasing stream temperatures during spring, summer, and fall, with the largest increases predicted during summer (July, August, and September). Additionally, thermal regimes characteristic of current August temperatures, the warmest month of the year, may be exceeded during July and September, suggesting an earlier and extended duration of warm summer stream temperatures. Models estimate that the largest magnitude of temperature warming relative to current conditions may be observed during the shoulder months of winter (April and November). Summer stream temperature warming is likely to be most pronounced in glacial-fed streams where models predict the largest magnitude (> 50%) of change due to the loss of alpine glaciers. We provide the first broad-scale analysis of seasonal climate effects on spatiotemporal patterns of stream temperature in the Crown of the Continent Ecosystem for better understanding climate change impacts on freshwater habitats and guiding conservation and climate adaptation strategies.

Interactive effects of warming and increased precipitation on community structure and composition in an annual forb dominated desert steppe.

Directory of Open Access Journals (Sweden)

Yanhui Hou

Full Text Available To better understand how warming, increased precipitation and their interactions influence community structure and composition, a field experiment simulating hydrothermal interactions was conducted at an annual forb dominated desert steppe in northern China over 2 years. Increased precipitation increased species richness while warming significantly decreased species richness, and their effects were additive rather than interactive. Although interannual variations in weather conditions may have a major affect on plant community composition on short term experiments, warming and precipitation treatments affected individual species and functional group composition. Warming caused C4 grasses such as Cleistogenes squarrosa to increase while increased precipitation caused the proportions of non-perennial C3 plants like Artemisia capillaris to decrease and perennial C4 plants to increase.

Design and performance of combined infrared canopy and belowground warming in the B4WarmED (Boreal Forest Warming at an Ecotone in Danger) experiment.

Science.gov (United States)

Rich, Roy L; Stefanski, Artur; Montgomery, Rebecca A; Hobbie, Sarah E; Kimball, Bruce A; Reich, Peter B

2015-06-01

Conducting manipulative climate change experiments in complex vegetation is challenging, given considerable temporal and spatial heterogeneity. One specific challenge involves warming of both plants and soils to depth. We describe the design and performance of an open-air warming experiment called Boreal Forest Warming at an Ecotone in Danger (B4WarmED) that addresses the potential for projected climate warming to alter tree function, species composition, and ecosystem processes at the boreal-temperate ecotone. The experiment includes two forested sites in northern Minnesota, USA, with plots in both open (recently clear-cut) and closed canopy habitats, where seedlings of 11 tree species were planted into native ground vegetation. Treatments include three target levels of plant canopy and soil warming (ambient, +1.7°C, +3.4°C). Warming was achieved by independent feedback control of voltage input to aboveground infrared heaters and belowground buried resistance heating cables in each of 72-7.0 m(2) plots. The treatments emulated patterns of observed diurnal, seasonal, and annual temperatures but with superimposed warming. For the 2009 to 2011 field seasons, we achieved temperature elevations near our targets with growing season overall mean differences (∆Tbelow ) of +1.84°C and +3.66°C at 10 cm soil depth and (∆T(above) ) of +1.82°C and +3.45°C for the plant canopies. We also achieved measured soil warming to at least 1 m depth. Aboveground treatment stability and control were better during nighttime than daytime and in closed vs. open canopy sites in part due to calmer conditions. Heating efficacy in open canopy areas was reduced with increasing canopy complexity and size. Results of this study suggest the warming approach is scalable: it should work well in small-statured vegetation such as grasslands, desert, agricultural crops, and tree saplings (<5 m tall). © 2015 John Wiley & Sons Ltd.

The influence of the bottom cold water on the seasonal variability of the Tsushima warm current

Science.gov (United States)

Isobe, Atsuhiko

1995-06-01

Previous studies have concluded that the volume transport and surface current velocity of the Tsushima Warm Current are at a maximum between summer and autumn and at a minimum between winter and spring. Each study has obtained these results indirectly, using the sea level difference across the Tsushima-Korea Strait or dynamic calculation. Numerical experiments are performed to estimate the seasonal variability in the sea level difference caused by the Bottom Cold Water (BCW), which intrudes from the Sea of Japan along the Korean coast in the bottom layer. These experiments basically treat the baroclinic adjustment problem of the BCW in a rectangular cross section perpendicular to the axis (northeast-southwest direction) of the Tsushima-Korea Strait. It is a five-layer model for summer and a two-layer model for winter. The initial conditions and parameters in models are chosen so as to match the calculated velocity-density fields with the observed velocity-density fields [Isobe A., S. Tawara, A. Kaneko and M. Kawano (1994) Continental Shelf Research, 14, 23-35.]. Consequently, the experiments prove that the observed seasonal variability in the sea level difference across the Tsushima-Korea Strait largely contains the baroclinic motion caused by the BCW. It should be noted that the position of the BCW also plays an important role in producing a considerable seasonal variation of the sea level difference. It is critical to remove the baroclinic contribution from the observed sea level differences across the Tsushima-Korea Strait in order to estimate the seasonal variation in the volume transport of the Tsushima Warm Current.

The central and eastern Arabian Sea as a perennial source of atmospheric carbon dioxide

Digital Repository Service at National Institute of Oceanography (India)

Sarma, V.V.S.S.; DileepKumar, M.; George, M.D.

circulation and biological production. In all seasons, the pCO sub(2) is higher in surface waters of the Arabian Sea, except along the Indian coast in the southwest monsoon, than that in atmosphere, and thus this region appears to be a perennial source...

Impacts of second-generation biofuel feedstock production in the central U.S. on the hydrologic cycle and global warming mitigation potential

Science.gov (United States)

Harding, K. J.; Twine, T. E.; VanLoocke, A.; Bagley, J. E.; Hill, J.

2016-10-01

Biofuel feedstocks provide a renewable energy source that can reduce fossil fuel emissions; however, if produced on a large scale they can also impact local to regional water and carbon budgets. Simulation results for 2005-2014 from a regional weather model adapted to simulate the growth of two perennial grass biofuel feedstocks suggest that replacing at least half the current annual cropland with these grasses would increase water use efficiency and drive greater rainfall downwind of perturbed grid cells, but increased evapotranspiration (ET) might switch the Mississippi River basin from having a net warm-season surplus of water (precipitation minus ET) to a net deficit. While this scenario reduces land required for biofuel feedstock production relative to current use for maize grain ethanol production, it only offsets approximately one decade of projected anthropogenic warming and increased water vapor results in greater atmospheric heat content.

Cumulative drought and land-use impacts on perennial vegetation across a North American dryland region

Science.gov (United States)

Munson, Seth M.; Long, A. Lexine; Wallace, Cynthia; Webb, Robert H.

2016-01-01

Question The decline and loss of perennial vegetation in dryland ecosystems due to global change pressures can alter ecosystem properties and initiate land degradation processes. We tracked changes of perennial vegetation using remote sensing to address the question of how prolonged drought and land-use intensification have affected perennial vegetation cover across a desert region in the early 21st century? Location Mojave Desert, southeastern California, southern Nevada, southwestern Utah and northwestern Arizona, USA. Methods We coupled the Moderate-Resolution Imaging Spectroradiometer Enhanced Vegetation Index (MODIS-EVI) with ground-based measurements of perennial vegetation cover taken in about 2000 and about 2010. Using the difference between these years, we determined perennial vegetation changes in the early 21st century and related these shifts to climate, soil and landscape properties, and patterns of land use. Results We found a good fit between MODIS-EVI and perennial vegetation cover (2000: R2 = 0.83 and 2010: R2 = 0.74). The southwestern, far southeastern and central Mojave Desert had large declines in perennial vegetation cover in the early 21st century, while the northeastern and southeastern portions of the desert had increases. These changes were explained by 10-yr precipitation anomalies, particularly in the cool season and during extreme dry or wet years. Areas heavily impacted by visitor use or wildfire lost perennial vegetation cover, and vegetation in protected areas increased to a greater degree than in unprotected areas. Conclusions We find that we can extrapolate previously documented declines of perennial plant cover to an entire desert, and demonstrate that prolonged water shortages coupled with land-use intensification create identifiable patterns of vegetation change in dryland regions.

Warm season grass establishment (in one year without the weeds)

International Nuclear Information System (INIS)

Downing, D.

1998-01-01

Native warm season grasses, big bluestem and indian, were established by the broadcast method on a relatively large area (130 acres) of reclaimed coal surface-mined land in Perry County, Illinois. Existing vegetation was controlled using two quarts of Round-Up and 12 ounces of Plateau per acre the first week of May. Five pounds of pure live seed of both species were applied by airflow using 100 pounds per acre of 0-46-0 and 100 pounds per acre of 0-0-60, primarily to carry the seed. The surface was cultipacked to insure good seed to soil contact. Planting was initiated and completed the last week of June. An estimated 95% to 100% ground cover was evident by mid to late August. By mid September, numerous big blue stem flower/seed stalks were noticeable

Integrated production of warm season grasses and agroforestry for biomass production

Energy Technology Data Exchange (ETDEWEB)

Samson, R.; Omielan, J. [Resource Efficient Agricultural Production-Canada, Ste, Anne de Bellevue, Quebec (Canada); Girouard, P.; Henning, J. [McGill Univ., Ste. Anne de Bellevue, Quebec (Canada)

1993-12-31

Increased research on C{sub 3} and C{sub 4} perennial biomass crops is generating a significant amount of information on the potential of these crops to produce large quantities of low cost biomass. In many parts of North America it appears that both C{sub 3} and C{sub 4} species are limited by water availability particularly on marginal soils. In much of North America, rainfall is exceeded by evaporation. High transpiration rates by fast growing trees and rainfall interception by the canopy appear to indicate that this can further exacerbate the problem of water availability. C{sub 4} perennial grasses appear to have distinct advantages over C{sub 3} species planted in monoculture systems particularly on marginal soils. C{sub 4} grasses historically predominated over much of the land that is now available for biomass production because of their adaptation to low humidity environments and periods of low soil moisture. The planting of short rotation forestry (SRF) species in an energy agroforestry system is proposed as an alternative production strategy which could potentially alleviate many of the problems associated with SRF monocultures. Energy agroforestry would be complementary to both production of conventional farm crops and C{sub 4} perennial biomass crops because of beneficial microclimatic effects.

Effects of Global Warming on Predatory Bugs Supported by Data Across Geographic and Seasonal Climatic Gradients

Science.gov (United States)

Schuldiner-Harpaz, Tarryn; Coll, Moshe

2013-01-01

Global warming may affect species abundance and distribution, as well as temperature-dependent morphometric traits. In this study, we first used historical data to document changes in Orius (Heteroptera: Anthocoridae) species assemblage and individual morphometric traits over the past seven decades in Israel. We then tested whether these changes could have been temperature driven by searching for similar patterns across seasonal and geographic climatic gradients in a present survey. The historical records indicated a shift in the relative abundance of dominant Orius species; the relative abundance of O. albidipennis, a desert-adapted species, increased while that of O. laevigatus decreased in recent decades by 6 and 10–15 folds, respectively. These shifts coincided with an overall increase of up to 2.1°C in mean daily temperatures over the last 25 years in Israel. Similar trends were found in contemporary data across two other climatic gradients, seasonal and geographic; O. albidipennis dominated Orius assemblages under warm conditions. Finally, specimens collected in the present survey were significantly smaller than those from the 1980’s, corresponding to significantly smaller individuals collected now during warmer than colder seasons. Taken together, results provide strong support to the hypothesis that temperature is the most likely driver of the observed shifts in species composition and body sizes because (1) historical changes in both species assemblage and body size were associated with rising temperatures in the study region over the last few decades; and (2) similar changes were observed as a result of contemporary drivers that are associated with temperature. PMID:23805249

Exploring the Factors Driving Seasonal Farmland Abandonment: A Case Study at the Regional Level in Hunan Province, Central China

OpenAIRE

Yu, Zhonglei; Liu, Lei; Zhang, Hua; Liang, Jinshe

2017-01-01

Farmland abandonment, including perennial and seasonal abandonment, is an important process of land use change that matters most to food security. Although there is a great deal of studies on farmland abandonment, seasonal abandonment, which is as serious as perennial abandonment, has attracted little academic attention. This paper takes Hunan Province in central China as its study area and uses a spatial regression model to examine the driving factors of seasonal farmland abandonment at the ...

Characterization of gene expression associated with drought avoidance and tolerance traits in a perennial grass species.

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Peng Zhou

Full Text Available To understand molecular mechanisms of perennial grass adaptation to drought stress, genes associated with drought avoidance or tolerance traits were identified and their expression patterns were characterized in C4 hybrid bermudagrass [Cynodon dactylon (L. Pers.×C. transvaalensis Burtt Davy, cv. Tifway] and common bermudagrass (C. dactylon, cv. C299. Plants of drought-tolerant 'Tifway' and drought-sensitive 'C299' were exposed to drought for 5 d (mild stress and 10 d (severe stress by withholding irrigation in a growth chamber. 'Tifway' maintained significantly lower electrolyte leakage and higher relative water content than 'C299' at both 5 and 10 d of drought stress. Four cDNA libraries via suppression subtractive hybridization analysis were constructed and identified 277 drought-responsive genes in the two genotypes at 5 and 10 d of drought stress, which were mainly classified into the functional categories of stress defense, metabolism, osmoregulation, membrane system, signal and regulator, structural protein, protein synthesis and degradation, and energy metabolism. Quantitative-PCR analysis confirmed the expression of 36 drought up-regulated genes that were more highly expressed in drought-tolerant 'Tifway' than drought-sensitive 'C299', including those for drought avoidance traits, such as cuticle wax formation (CER1 and sterol desaturase, for drought tolerance traits, such as dehydration-protective proteins (dehydrins, HVA-22-like protein and oxidative stress defense (superoxide dismutase, dehydroascorbate reductase, 2-Cys peroxiredoxins, and for stress signaling (EREBP-4 like protein and WRKY transcription factor. The results suggest that the expression of genes for stress signaling, cuticle wax accumulation, antioxidant defense, and dehydration-protective protein accumulation could be critically important for warm-season perennial grass adaptation to long-term drought stress.

Persistence of Overseeded Cool-Season Grasses in Bermudagrass Turf

OpenAIRE

Thomas Serensits; Matthew Cutulle; Jeffrey F. Derr

2011-01-01

Cool-season grass species are commonly overseeded into bermudagrass turf for winter color. When the overseeded grass persists beyond the spring; however, it becomes a weed. The ability of perennial ryegrass, Italian (annual) ryegrass, intermediate ryegrass, and hybrid bluegrass to persist in bermudagrass one year after seeding was determined. Perennial ryegrass, intermediate ryegrass, and Italian ryegrass produced acceptable ground cover in the spring after fall seeding. Hybrid bluegrass di...

Managing for Multifunctionality in Perennial Grain Crops

Science.gov (United States)

Ryan, Matthew R; Crews, Timothy E; Culman, Steven W; DeHaan, Lee R; Hayes, Richard C; Jungers, Jacob M; Bakker, Matthew G

2018-01-01

Abstract Plant breeders are increasing yields and improving agronomic traits in several perennial grain crops, the first of which is now being incorporated into commercial food products. Integration strategies and management guidelines are needed to optimize production of these new crops, which differ substantially from both annual grain crops and perennial forages. To offset relatively low grain yields, perennial grain cropping systems should be multifunctional. Growing perennial grains for several years to regenerate soil health before rotating to annual crops and growing perennial grains on sloped land and ecologically sensitive areas to reduce soil erosion and nutrient losses are two strategies that can provide ecosystem services and support multifunctionality. Several perennial cereals can be used to produce both grain and forage, and these dual-purpose crops can be intercropped with legumes for additional benefits. Highly diverse perennial grain polycultures can further enhance ecosystem services, but increased management complexity might limit their adoption. PMID:29662249

Recent Progress in Perennial Buckwheat Development

Directory of Open Access Journals (Sweden)

Qing-Fu Chen

2018-02-01

Full Text Available Grains in the genus Fagopyrum have benefits to human health and are an excellent gluten-free raw material. Of all cereal foods, this genus has the highest total content of amino-acid nutrients necessary for humans; nutrients that are resistant to digestion (protein and starch resulting in their sustained release; higher dietary fiber content than key cereals, and is rich in a special healthy ingredient (flavonoids. Fagopyrum includes 24 species of which five are perennial. Among them, golden buckwheat (F.cymosum complex is the most important perennial buckwheat, which is not only used in Chinese medicine, but also has great potential in healthy food crop. In order to provide some clues for perennial crop studies and their industry development, this paper presents the state of perennial buckwheat research in terms of taxonomy; natural chemical products and pharmacological and health functions; genetics and evolution; breeding; and product development and utilization. The great advances such as successful interspecific crossing and its subsequent new perennial buckwheat varieties will speed up the development of the perennial buckwheat industry.

A comparative study of AMF diversity in annual and perennial plant species from semiarid gypsum soils.

Science.gov (United States)

Alguacil, M. M.; Torrecillas, E.; Roldán, A.; Díaz, G.; Torres, P.

2012-04-01

The arbuscular mycorrhizal fungi (AMF) communities composition regulate plant interactions and determine the structure of plant communities. In this study we analysed the diversity of AMF in the roots of two perennial gypsophyte plant species, Herniaria fruticosa and Senecio auricula, and an annual herbaceous species, Bromus rubens, growing in a gypsum soil from a semiarid area. The objective was to determine whether perennial and annual host plants support different AMF communities in their roots and whether there are AMF species that might be indicators of specific functional plant roles in these ecosystems. The roots were analysed by nested PCR, cloning, sequencing of the ribosomal DNA small subunit region and phylogenetic analysis. Twenty AMF sequence types, belonging to the Glomus group A, Glomus group B, Diversisporaceae, Acaulosporaceae, Archaeosporaceae and Paraglomeraceae, were identified. Both gypsophyte perennial species had differing compositions of the AMF community and higher diversity when compared with the annual species, showing preferential selection by specific AMF sequences types. B. rubens did not show host specificity, sharing the full composition of its AMF community with both perennial plant species. Seasonal variations in the competitiveness of AM fungi could explain the observed differences in AMF community composition, but this is still a working hypothesis that requires the analysis of further data obtained from a higher number of both annual and perennial plant species in order to be fully tested.

Nutritive value, fermentation characteristics, and in situ disappearance kinetics of ensiled warm-season legumes and bahiagrass.

Science.gov (United States)

Foster, J L; Carter, J N; Sollenberger, L E; Blount, A R; Myer, R O; Maddox, M K; Phatak, S C; Adesogan, A T

2011-04-01

This study determined the nutritive value, ensiling characteristics, and in situ disappearance kinetics of bahiagrass (Paspalum notatum Flügge 'Tifton 9'), perennial peanut (Arachis glabrata Benth. 'Florigraze'), annual peanut [Arachis hypogaea (L.) 'FL MDR 98'], cowpea [Vigna unguiculata (L.) Walp. 'Iron clay'], and pigeonpea [Cajanus cajan (L.) Millsp. 'GA-2']. All forages were harvested at maturity stages that optimized dry matter (DM) yield and nutritive value. After harvest, forages were wilted to 45% DM, and 4 replicate bales of each legume and 8 bales of bahiagrass were wrapped in polyethylene and ensiled for 180 d. After each bale was opened, the forage was thoroughly mixed, and representative subsamples were taken for laboratory analysis and in situ incubation. Wilting and ensiling decreased the rumen-undegradable protein, water-soluble carbohydrate, crude protein (CP), and in vitro true digestibility (IVTD) of bahiagrass, perennial peanut, and cowpea, and increased their neutral detergent fiber (NDF) concentrations. Among haylages, CP concentration was greatest for annual peanut, followed by perennial peanut and cowpea, and least for bahiagrass. In contrast, NDF concentration was greater in bahiagrass than in legumes. Pigeonpea had the greatest NDF concentration among legumes and lowest IVTD of all haylages. All haylages were aerobically stable for at least 84 h, but pH was lower in perennial peanut and cowpea than in pigeonpea. Ammonia-N concentrations tended to be greater in legume haylages than in bahiagrass haylage. Butyrate concentration was greater in annual and perennial peanut than in bahiagrass. Total VFA concentration was greater in annual and perennial peanut and cowpea haylages than in bahiagrass haylage. Undegradable DM fractions were greater and extent of DM degradation was lower in bahiagrass and pigeonpea than in other haylages but lag time and degradation rates did not differ. Annual and perennial peanut and cowpea haylages were as

Multi-century cool- and warm-season rainfall reconstructions for Australia's major climatic regions

Science.gov (United States)

Freund, Mandy; Henley, Benjamin J.; Karoly, David J.; Allen, Kathryn J.; Baker, Patrick J.

2017-11-01

Australian seasonal rainfall is strongly affected by large-scale ocean-atmosphere climate influences. In this study, we exploit the links between these precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the past. We use an extensive network of palaeoclimate records from the Southern Hemisphere to reconstruct cool (April-September) and warm (October-March) season rainfall in eight natural resource management (NRM) regions spanning the Australian continent. Our bi-seasonal rainfall reconstruction aligns well with independent early documentary sources and existing reconstructions. Critically, this reconstruction allows us, for the first time, to place recent observations at a bi-seasonal temporal resolution into a pre-instrumental context, across the entire continent of Australia. We find that recent 30- and 50-year trends towards wetter conditions in tropical northern Australia are highly unusual in the multi-century context of our reconstruction. Recent cool-season drying trends in parts of southern Australia are very unusual, although not unprecedented, across the multi-century context. We also use our reconstruction to investigate the spatial and temporal extent of historical drought events. Our reconstruction reveals that the spatial extent and duration of the Millennium Drought (1997-2009) appears either very much below average or unprecedented in southern Australia over at least the last 400 years. Our reconstruction identifies a number of severe droughts over the past several centuries that vary widely in their spatial footprint, highlighting the high degree of diversity in historical droughts across the Australian continent. We document distinct characteristics of major droughts in terms of their spatial extent, duration, intensity, and seasonality. Compared to the three largest droughts in the instrumental period (Federation Drought

Multi-century cool- and warm-season rainfall reconstructions for Australia's major climatic regions

Directory of Open Access Journals (Sweden)

M. Freund

2017-11-01

Full Text Available Australian seasonal rainfall is strongly affected by large-scale ocean–atmosphere climate influences. In this study, we exploit the links between these precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the past. We use an extensive network of palaeoclimate records from the Southern Hemisphere to reconstruct cool (April–September and warm (October–March season rainfall in eight natural resource management (NRM regions spanning the Australian continent. Our bi-seasonal rainfall reconstruction aligns well with independent early documentary sources and existing reconstructions. Critically, this reconstruction allows us, for the first time, to place recent observations at a bi-seasonal temporal resolution into a pre-instrumental context, across the entire continent of Australia. We find that recent 30- and 50-year trends towards wetter conditions in tropical northern Australia are highly unusual in the multi-century context of our reconstruction. Recent cool-season drying trends in parts of southern Australia are very unusual, although not unprecedented, across the multi-century context. We also use our reconstruction to investigate the spatial and temporal extent of historical drought events. Our reconstruction reveals that the spatial extent and duration of the Millennium Drought (1997–2009 appears either very much below average or unprecedented in southern Australia over at least the last 400 years. Our reconstruction identifies a number of severe droughts over the past several centuries that vary widely in their spatial footprint, highlighting the high degree of diversity in historical droughts across the Australian continent. We document distinct characteristics of major droughts in terms of their spatial extent, duration, intensity, and seasonality. Compared to the three largest droughts in the instrumental

Seasonal hydroclimatic impacts of Sun Corridor expansion

International Nuclear Information System (INIS)

Georgescu, M; Mahalov, A; Moustaoui, M

2012-01-01

Conversion of natural to urban land forms imparts influence on local and regional hydroclimate via modification of the surface energy and water balance, and consideration of such effects due to rapidly expanding megapolitan areas is necessary in light of the growing global share of urban inhabitants. Based on a suite of ensemble-based, multi-year simulations using the Weather Research and Forecasting (WRF) model, we quantify seasonally varying hydroclimatic impacts of the most rapidly expanding megapolitan area in the US: Arizona’s Sun Corridor, centered upon the Greater Phoenix metropolitan area. Using a scenario-based urban expansion approach that accounts for the full range of Sun Corridor growth uncertainty through 2050, we show that built environment induced warming for the maximum development scenario is greatest during the summer season (regionally averaged warming over AZ exceeds 1 °C). Warming remains significant during the spring and fall seasons (regionally averaged warming over AZ approaches 0.9 °C during both seasons), and is least during the winter season (regionally averaged warming over AZ of 0.5 °C). Impacts from a minimum expansion scenario are reduced, with regionally averaged warming ranging between 0.1 and 0.3 °C for all seasons except winter, when no warming impacts are diagnosed. Integration of highly reflective cool roofs within the built environment, increasingly recognized as a cost-effective option intended to offset the warming influence of urban complexes, reduces urban-induced warming considerably. However, impacts on the hydrologic cycle are aggravated via enhanced evapotranspiration reduction, leading to a 4% total accumulated precipitation decrease relative to the non-adaptive maximum expansion scenario. Our results highlight potentially unintended consequences of this adaptation approach within rapidly expanding megapolitan areas, and emphasize the need for undeniably sustainable development paths that account for

Amplified Arctic warming by phytoplankton under greenhouse warming.

Science.gov (United States)

Park, Jong-Yeon; Kug, Jong-Seong; Bader, Jürgen; Rolph, Rebecca; Kwon, Minho

2015-05-12

Phytoplankton have attracted increasing attention in climate science due to their impacts on climate systems. A new generation of climate models can now provide estimates of future climate change, considering the biological feedbacks through the development of the coupled physical-ecosystem model. Here we present the geophysical impact of phytoplankton, which is often overlooked in future climate projections. A suite of future warming experiments using a fully coupled ocean-atmosphere model that interacts with a marine ecosystem model reveals that the future phytoplankton change influenced by greenhouse warming can amplify Arctic surface warming considerably. The warming-induced sea ice melting and the corresponding increase in shortwave radiation penetrating into the ocean both result in a longer phytoplankton growing season in the Arctic. In turn, the increase in Arctic phytoplankton warms the ocean surface layer through direct biological heating, triggering additional positive feedbacks in the Arctic, and consequently intensifying the Arctic warming further. Our results establish the presence of marine phytoplankton as an important potential driver of the future Arctic climate changes.

Spatial and temporal characteristics of warm season convection over Pearl River Delta region, China, based on 3 years of operational radar data

Science.gov (United States)

Chen, Xingchao; Zhao, Kun; Xue, Ming

2014-11-01

This study examines the temporal and spatial characteristics and distributions of convection over the Pearl River Delta region of Guangzhou, China, during the May-September warm season, using, for the first time for such a purpose, 3 years of operational Doppler radar data in the region. Results show that convective features occur most frequently along the southern coast and the windward slope of the eastern mountainous area of Pearl River Delta, with the highest frequency occurring in June and the lowest in September among the 5 months. The spatial frequency distribution pattern also roughly matches the accumulated precipitation pattern. The occurrence of convection in this region also exhibits strong diurnal cycles. During May and June, the diurnal distribution is bimodal, with the maximum frequency occurring in the early afternoon and a secondary peak occurring between midnight and early morning. The secondary peak is much weaker in July, August, and September. Convection near the coast is found to occur preferentially on days when a southerly low-level jet (LLJ) exists, especially during the Meiyu season. Warm, moist, and unstable air is transported from the ocean to land by LLJs on these days, and the lifting along the coast by convergence induced by differential surface friction between the land and ocean is believed to be the primary cause for the high frequency along the coast. In contrast, the high frequency over mountainous area is believed to be due to orographic lifting of generally southerly flows during the warm season.

How does the dengue vector mosquito Aedes albopictus respond to global warming?

Science.gov (United States)

Jia, Pengfei; Chen, Xiang; Chen, Jin; Lu, Liang; Liu, Qiyong; Tan, Xiaoyue

2017-03-11

Global warming has a marked influence on the life cycle of epidemic vectors as well as their interactions with human beings. The Aedes albopictus mosquito as the vector of dengue fever surged exponentially in the last decade, raising ecological and epistemological concerns of how climate change altered its growth rate and population dynamics. As the global warming pattern is considerably uneven across four seasons, with a confirmed stronger effect in winter, an emerging need arises as to exploring how the seasonal warming effects influence the annual development of Ae. albopictus. The model consolidates a 35-year climate dataset and designs fifteen warming patterns that increase the temperature of selected seasons. Based on a recently developed mechanistic population model of Ae. albopictus, the model simulates the thermal reaction of blood-fed adults by systematically increasing the temperature from 0.5 to 5 °C at an interval of 0.5 °C in each warming pattern. The results show the warming effects are different across seasons. The warming effects in spring and winter facilitate the development of the species by shortening the diapause period. The warming effect in summer is primarily negative by inhibiting mosquito development. The warming effect in autumn is considerably mixed. However, these warming effects cannot carry over to the following year, possibly due to the fact that under the extreme weather in winter the mosquito fully ceases from development and survives in terms of diapause eggs. As the historical pattern of global warming manifests seasonal fluctuations, this study provides corroborating and previously ignored evidence of how such seasonality affects the mosquito development. Understanding this short-term temperature-driven mechanism as one chain of the transmission events is critical to refining the thermal reaction norms of the epidemic vector under global warming as well as developing effective mosquito prevention and control strategies.

Seasonal patterns in soil N availability in the arctic tundra in response to accelerated snowmelt and warming

Science.gov (United States)

Darrouzet-Nardi, A.; Wallenstein, M. D.; Steltzer, H.; Sullivan, P.; Melle, C.; Segal, A.; Weintraub, M. N.

2010-12-01

Arctic soils contain large stocks of carbon (C) and may act as a significant CO2 source in response to climate warming. However, nitrogen (N) availability limits both plant growth and decomposition in many Arctic sites, and may thus be a key constraint on climate-carbon feedbacks. While current models of tundra ecosystems and their responses to climate change assume that N limits plant growth and C limits decomposition, there is strong evidence to the contrary showing that N can also limit decomposition. For example, the production of both new microbial biomass and enzymes that degrade organic matter appear to be limited by N during the summer. N availability is strongly seasonal: we have previously observed relatively high availability early in the growing season followed by a pronounced crash in tussock tundra soils. To investigate the drivers of N availability throughout the season, we used a field manipulation of tussock tundra growing season length (~4 days acceleration of snowmelt) and air temperature (open top chambers) and a laboratory soil N addition in both early and late season. Nutrient availability throughout the field season was measured at high temporal resolution (25 measurements from soil thaw through early plant senescence). Results from a laboratory experiment in which N was added to early season and late season soils suggests that soil respiration is in fact N limited at both times of the season, though this limitation is temperature dependent with effects most pronounced at 10°C. High-resolution measurements of nutrients in the soil solution and extractable N throughout the season showed that although a nutrient crash in N can be observed mid-season, N availability can still fluctuate later in the season. Finally, effects of the extended growing season and increased air temperature have so far had few effects on soil nutrient N dynamics throughout the summer growing season, suggesting either an insensitivity of N availability to these

Investigating the Sustainability of Perennial Agriculture

Science.gov (United States)

Sutherlin, C. E.; Brunsell, N. A.; De Oliveira, G.; Crews, T.; Vico, G.

2017-12-01

The changing climate leads to uncertainties concerning the sustainability of certain agricultural resources, and with the additional stresses of an increasing global population, uncertainty in food security will greatly increase. To adhere to future food demands in the face of this changing climate, perennial agriculture has been a proposed solution. However, it is equally important to assure that perennial agriculture is not negatively affecting the climate in exchange for this proposed more robust food source. We chose to examine the interactions between perennial and annual agricultural crops by focusing on the efficiency of exchanges with the atmosphere. This is done using the omega decoupling factor for 4 different sites as a way of quantifying the contributions of radiation and stomatal conductance over the resulting water and carbon cycles. This gives us an indication of how the plant canopy is interacting with, and influencing the local microclimate. Ultimately, this should give us an indication of the ability of perennial crops to aid in the climate mitigation process. We hypothesized that the perennial site chosen would have omega values more similar to the omega values of a natural grassland rather than an annual crop site. Using AmeriFlux towers to determine the canopy values needed to calculate the omega decoupling factor, we focused on the Kernza perennial crops being grown at the Land Institute in Salina, Kansas (KLS), in comparison to a natural grassland in Manhattan, Kansas (KON), a typical land cover model in Lawrence, Kansas (KFS), and an annual crop site in Lamont, Oklahoma (ARM). These results will allow us to move forward in the investigation of perennial crops as a sustainable food source.

Nonintrusive field experiments show different plant responses to warming and drought among sites, seasons, and species in a north-south European gradient

DEFF Research Database (Denmark)

Penuelas, J.; Gordon, C.; Llorens, L.

2004-01-01

-limited. In the water-stressed southern site, there was no increase in total aboveground plant biomass growth as expected since warming increases water loss, and temperatures in those ecosystems are already close to the optimum for photosynthesis. The southern site presented instead the most negative response...... a 15% increase in total aboveground plant biomass growth in the UK site. Both direct and indirect effects of warming, such as longer growth season and increased nutrient availability, are likely to be particularly important in this and the other northern sites which tend to be temperature...... to the drought treatment consisting of a soil moisture reduction at the peak of the growing season ranging from 33% in the Spanish site to 82% in The Netherlands site. In the Spanish site there was a 14% decrease in total aboveground plant biomass growth relative to control. Flowering was decreased by drought...

Trophic strategy of Atlantirivulus riograndensis (Cyprinodontiformes: Rivulidae, a non-annual rivulid threatened by extinction, in a perennial environment, Brazil

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Laísa Wociechoski Cavalheiro

Full Text Available ABSTRACT Rivulidae includes non-annual fish of perennial habitats and annual fish of temporary wetlands. The objective of this research was to investigate the trophic strategy of Atlantirivulus riograndensis in a perennial environment. Sampling occurred in an environmental conservation unit in the Pampa biome, Brazil. Quantification of the diet followed the volumetric method. Consumption of autochthonous material as the main food source of the species followed the pattern of Rivulidae. Species is zooplanktonic when young. Food spectrum is broadened and insectivorousness increases with ontogeny, revealing a specialist trend in the feeding strategy of A. riograndensis. The most diverse feeding occurs in the spring and summer seasons in which the presence of larger fish was more frequent than in other seasons. The increased consumption of microcrustaceans in the fall was related to smaller individuals, captured in greater quantities in this post-reproductive period. The lowest diversity of dietary items occurs during the winter and may reflect the lower diversity of food resources available in this season or the transition from juvenile to adult diet, with consumption of autochthonous Diptera by medium sized fish.

Protozoans bacterivory in a subtropical environment during a dry/cold and a rainy/warm season

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Karina F. Hisatugo

2014-01-01

Full Text Available In aquatic ecosystems, bacteria are controlled by several organisms in the food chain, such as protozoa, that use them as food source. This study aimed to quantify the ingestion and clearance rates of bacteria by ciliates and heterotrophic nanoflagellates (HNF in a subtropical freshwater reservoir (Monjolinho reservoir -São Carlos -Brazil during one year period, in order to verify their importance as consumers and controllers of bacteria in two seasons, a dry/cold and a rainy/warm one. For this purpose, in situ bacterivory experiments were carried out bimonthly using fluorescently labeled bacteria with 5-(4,6 diclorotriazin-2yl aminofluorescein (DTAF. Although ciliates have shown the highest individual ingestion and clearance rates, bacterivory was dominated by HNF, who showed higher population ingestion rates (mean of 9,140 bacteria h-1mL-1 when compared to ciliates (mean of 492 bacteria h-1mL-1. The greater predation impact on bacterial communities was caused mainly by the small HNF (< 5 µm population, especially in the rainy season, probably due to the abundances of these organisms, the precipitation, trophic index state and water temperature that were higher in this period. Thus, the protozoan densities together with environmental variables were extremely relevant in determining the seasonal pattern of bacterivory in Monjolinho reservoir.

Genomics: a potential panacea for the perennial problem.

Science.gov (United States)

McClure, Kendra A; Sawler, Jason; Gardner, Kyle M; Money, Daniel; Myles, Sean

2014-10-01

Perennial crops represent important fresh and processed food sources worldwide, but advancements in breeding perennials are often impeded due to their very nature. The perennial crops we rely on most for food take several years to reach production maturity and require large spaces to grow, which make breeding new cultivars costly compared with most annual crops. Because breeding perennials is inefficient and expensive, they are often grown in monocultures consisting of small numbers of elite cultivars that are vegetatively propagated for decades or even centuries. This practice puts many perennial crops at risk for calamity since they remain stationary in the face of evolving pest and disease pressures. Although there is tremendous genetic diversity available to them, perennial crop breeders often struggle to generate commercially successful cultivars in a timely and cost-effective manner because of the high costs of breeding. Moreover, consumers often expect the same cultivars to be available indefinitely, and there is often little or no incentive for growers and retailers to take the risk of adopting new cultivars. While genomics studies linking DNA variants to commercially important traits have been performed in diverse perennial crops, the translation of these studies into accelerated breeding of improved cultivars has been limited. Here we explain the "perennial problem" in detail and demonstrate how modern genomics tools can significantly improve the cost effectiveness of breeding perennial crops and thereby prevent crucial food sources from succumbing to the perils of perpetual propagation. © 2014 Botanical Society of America, Inc.

Persistence of Overseeded Cool-Season Grasses in Bermudagrass Turf

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Thomas Serensits

2011-01-01

Full Text Available Cool-season grass species are commonly overseeded into bermudagrass turf for winter color. When the overseeded grass persists beyond the spring; however, it becomes a weed. The ability of perennial ryegrass, Italian (annual ryegrass, intermediate ryegrass, and hybrid bluegrass to persist in bermudagrass one year after seeding was determined. Perennial ryegrass, intermediate ryegrass, and Italian ryegrass produced acceptable ground cover in the spring after fall seeding. Hybrid bluegrass did not establish well, resulting in unacceptable cover. Perennial ryegrass generally persisted the most one year after seeding, either because of summer survival of plants or because of new germination the following fall. Plant counts one year after seeding were greater in the higher seeding rate treatment compared to the lower seeding treatment rate of perennial ryegrass, suggesting new germination had occurred. Plant counts one year after seeding plots with intermediate ryegrass or Italian ryegrass were attributed primarily to latent germination and not summer survival. Applications of foramsulfuron generally did not prevent overseeded species stand one year after seeding, supporting the conclusion of new germination. Although quality is less with intermediate ryegrass compared to perennial ryegrass, it transitions out easier than perennial ryegrass, resulting in fewer surviving plants one year later.

Landscape control of nitrous oxide emissions during the transition from conservation reserve program to perennial grasses for bioenergy

Science.gov (United States)

Debasish Saha; Benjamin M. Rau; Jason P. Kaye; Felipe Montes; Paul R. Adler; Armen R. Kemanian

2016-01-01

Future liquid fuel demand from renewable sources may, in part, be met by converting the seasonally wet portions of the landscape currently managed for soil and water conservation to perennial energy crops. However, this shift may increase nitrous oxide (N2O) emissions, thus limiting the carbon (C) benefits of energy crops. Particularly high emissions may occur during...

Intensified Arctic warming under greenhouse warming by vegetation–atmosphere–sea ice interaction

International Nuclear Information System (INIS)

Jeong, Jee-Hoon; Kug, Jong-Seong; Linderholm, Hans W; Chen, Deliang; Kim, Baek-Min; Jun, Sang-Yoon

2014-01-01

Observations and modeling studies indicate that enhanced vegetation activities over high latitudes under an elevated CO 2 concentration accelerate surface warming by reducing the surface albedo. In this study, we suggest that vegetation-atmosphere-sea ice interactions over high latitudes can induce an additional amplification of Arctic warming. Our hypothesis is tested by a series of coupled vegetation-climate model simulations under 2xCO 2 environments. The increased vegetation activities over high latitudes under a 2xCO 2 condition induce additional surface warming and turbulent heat fluxes to the atmosphere, which are transported to the Arctic through the atmosphere. This causes additional sea-ice melting and upper-ocean warming during the warm season. As a consequence, the Arctic and high-latitude warming is greatly amplified in the following winter and spring, which further promotes vegetation activities the following year. We conclude that the vegetation-atmosphere-sea ice interaction gives rise to additional positive feedback of the Arctic amplification. (letter)

Drought mitigation in perennial crops by fertilization and adjustments of regional yield models for future climate variability

Science.gov (United States)

Kantola, I. B.; Blanc-Betes, E.; Gomez-Casanovas, N.; Masters, M. D.; Bernacchi, C.; DeLucia, E. H.

2017-12-01

Increased variability and intensity of precipitation in the Midwest agricultural belt due to climate change is a major concern. The success of perennial bioenergy crops in replacing maize for bioethanol production is dependent on sustained yields that exceed maize, and the marketing of perennial crops often emphasizes the resilience of perennial agriculture to climate stressors. Land conversion from maize for bioethanol to Miscanthus x giganteus (miscanthus) increases yields and annual evapotranspiration rates (ET). However, establishment of miscanthus also increases biome water use efficiency (the ratio between net ecosystem productivity after harvest and ET), due to greater belowground biomass in miscanthus than in maize or soybean. In 2012, a widespread drought reduced the yield of 5-year-old miscanthus plots in central Illinois by 36% compared to the previous two years. Eddy covariance data indicated continued soil water deficit during the hydrologically-normal growing season in 2013 and miscanthus yield failed to rebound as expected, lagging behind pre-drought yields by an average of 53% over the next three years. In early 2014, nitrogen fertilizer was applied to half of mature (7-year-old) miscanthus plots in an effort to improve yields. In plots with annual post-emergence application of 60 kg ha-1 of urea, peak biomass was 29% greater than unfertilized miscanthus in 2014, and 113% greater in 2015, achieving statistically similar yields to the pre-drought average. Regional-scale models of perennial crop productivity use 30-year climate averages that are inadequate for predicting long-term effects of short-term extremes on perennial crops. Modeled predictions of perennial crop productivity incorporating repeated extreme weather events, observed crop response, and the use of management practices to mitigate water deficit demonstrate divergent effects on predicted yields.

Seasonal and inter-annual photosynthetic response of representative C4 species to soil water content and leaf nitrogen concentration across a tropical seasonal floodplain

NARCIS (Netherlands)

Mantlana, K.B.; Arneth, A.; Veenendaal, E.M.; Wohland, P.; Wolski, P.; Kolle, O.; Lloyd, J.

2008-01-01

We examined the seasonal and inter-annual variation of leaf-level photosynthetic characteristics of three C4 perennial species, Cyperus articulatus, Panicum repens and Imperata cylindrica, and their response to environmental variables, to determine comparative physiological responses of plants

Winter warming delays dormancy release, advances budburst, alters carbohydrate metabolism and reduces yield in a temperate shrub

DEFF Research Database (Denmark)

Pagter, Majken; Andersen, Uffe Brandt; Andersen, Lillie

2015-01-01

Global climate models predict an increase in the mean surface air temperature, with a disproportionate increase during winter. Since temperature is a major driver of phenological events in temperate woody perennials, warming is likely to induce changes in a range of these events. We investigated ...

EFFECT OF PRE-COOLING ON REPEAT-SPRINT PERFORMANCE IN SEASONALLY ACCLIMATISED MALES DURING AN OUTDOOR SIMULATED TEAM-SPORT PROTOCOL IN WARM CONDITIONS

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Carly J. Brade

2013-09-01

Full Text Available Whether precooling is beneficial for exercise performance in warm climates when heat acclimatised is unclear. The purpose of this study was to determine the effect of precooling on repeat-sprint performance during a simulated team-sport circuit performed outdoors in warm, dry field conditions in seasonally acclimatised males (n = 10. They performed two trials, one with precooling (PC; ice slushy and cooling jacket and another without (CONT. Trials began with a 30-min baseline/cooling period followed by an 80 min repeat-sprint protocol, comprising 4 x 20-min quarters, with 2 x 5-min quarter breaks and a 10-min half-time recovery/cooling period. A clear and substantial (negative; PC slower effect was recorded for first quarter circuit time. Clear and trivial effects were recorded for overall circuit time, third and fourth quarter sprint times and fourth quarter best sprint time, otherwise unclear and trivial effects were recorded for remaining performance variables. Core temperature was moderately lower (Cohen's d=0.67; 90% CL=-1.27, 0.23 in PC at the end of the precooling period and quarter 1. No differences were found for mean skin temperature, heart rate, thermal sensation, or rating of perceived exertion, however, moderate Cohen's d effect sizes suggested a greater sweat loss in PC compared with CONT. In conclusion, repeat- sprint performance was neither clearly nor substantially improved in seasonally acclimatised players by using a combination of internal and external cooling methods prior to and during exercise performed in the field in warm, dry conditions. Of practical importance, precooling appears unnecessary for repeat-sprint performance if athletes are seasonally acclimatised or artificially acclimated to heat, as it provides no additional benefit

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations.

Science.gov (United States)

Tsyganov, Andrey N; Aerts, Rien; Nijs, Ivan; Cornelissen, Johannes H C; Beyens, Louis

2012-05-01

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental field climate manipulations. All manipulations were accomplished using open top chambers in a dry blanket bog located in the sub-Arctic (Abisko, Sweden). We estimated sensitivity of abundance, diversity and assemblage structure of living and empty shell assemblages of testate amoebae in the living and decaying layers of Sphagnum. Our results show that, in a sub-arctic climate, testate amoebae are more sensitive to climate changes in the growing season than in winter. Summer warming reduced species richness and shifted assemblage composition towards predominance of xerophilous species for the living and empty shell assemblages in both layers. The higher soil temperatures during the growing season also decreased abundance of empty shells in both layers hinting at a possible increase in their decomposition rates. Thus, although possible effects of climate changes on preservation of empty shells should always be taken into account, species diversity and structure of testate amoeba assemblages in dry subarctic bogs are sensitive proxies for climatic changes during the growing season. Copyright © 2011 Elsevier GmbH. All rights reserved.

Forage yield and nitrogen nutrition dynamics of warm-season native forage genotypes under two shading levels and in full sunlight

OpenAIRE

Barro,Raquel Santiago; Varella,Alexandre Costa; Lemaire,Gilles; Medeiros,Renato Borges de; Saibro,João Carlos de; Nabinger,Carlos; Bangel,Felipe Villamil; Carassai,Igor Justin

2012-01-01

The successful achievement of a highly productive understorey pasture in silvopastoral systems depends on the use of well-adapted forage genotypes, showing good agronomic performance and persistence under shading and grazing. In this study, the herbage dry matter yield (DMY) and nitrogen nutrition dynamics were determined in three native warm-season grasses (Paspalum regnellii, Paspalum dilatatum and Paspalum notatum) and a forage legume (Arachis pintoi) under two shading levels compared with...

Impediments to hybridization between Napiergrass (Pennisetum purpureum Schum.) and other Pennisetum species

Science.gov (United States)

Napiergrass (Pennisetum purpureum Schum.) is a robust, perennial, warm-season grass that grows throughout the tropical and sub-tropical regions of the world. Some genotypes have sufficient winter hardiness to survive winters in the Gulf coast region of the United States. However, germplasm with in...

Composition and structural features of condensed tannins from Texas legumes exhibiting methane abatement activity during in vitro rumen digestion

Science.gov (United States)

Previous studies showed that a series of purified condensed tannins (CTs) from warm-season perennial legumes exhibited high variability in their modulation of methane production during in vitro rumen digestion. The molecular weight difference of these CTs did not provide correlation with either the ...

Warming slowdown over the Tibetan plateau in recent decades

Science.gov (United States)

Liu, Yaojie; Zhang, Yangjian; Zhu, Juntao; Huang, Ke; Zu, Jiaxing; Chen, Ning; Cong, Nan; Stegehuis, Annemiek Irene

2018-03-01

As the recent global warming hiatus and the warming on high elevations are attracting worldwide attention, this study examined the robustness of the warming slowdown over the Tibetan plateau (TP) and its related driving forces. By integrating multiple-source data from 1982 to 2015 and using trend analysis, we found that the mean temperature (T mean), maximum temperature (T max) and minimum temperature (T min) showed a slowdown of the warming trend around 1998, during the period of the global warming hiatus. This was found over both the growing season (GS) and non-growing season (NGS) and suggested a robust warming hiatus over the TP. Due to the differences in trends of T max and T min, the trend of diurnal temperature range (DTR) also shifted after 1998, especially during the GS temperature. The warming rate was spatially heterogeneous. The northern TP (NTP) experienced more warming than the southern TP (STP) in all seasons from 1982 to 1998, while the pattern was reversed in the period from 1998 to 2015. Water vapour was found to be the main driving force for the trend in T mean and T min by influencing downward long wave radiation. Sunshine duration was the main driving force behind the trend in T max and DTR through a change in downward shortwave radiation that altered the energy source of daytime temperature. Water vapour was the major driving force for temperature change over the NTP, while over the STP, sunshine duration dominated the temperature trend.

The Effect of Passive Design Strategies on Thermal Performance of Female Secondary School Buildings during Warm Season in Hot Dry Climate

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Sahar eZahiri

2016-03-01

Full Text Available This paper describes a series of field studies and simulation analysis to improve the thermal performance of school buildings in the city of Tehran in Iran during warm season. The field studies used on-site measurement and questionnaire-based survey in the warm spring season in a typical female secondary school building. The on-site monitoring assessed the indoor air temperature and humidity levels of six classrooms while the occupants completed questionnaires covering their thermal sensations and thermal preferences. Moreover, thermal simulation analysis was also carried out to evaluate and improve the thermal performance of the classrooms based on the students’ thermal requirements and passive design strategies. In this study, the environmental design guidelines for female secondary school buildings were introduced for the hot and dry climate of Tehran, using passive design strategies. The study shows that the application of passive design strategies including south and south-east orientation, 10cm thermal insulation in wall and 5cm in the roof, and the combination of 30cm side fins and overhangs as a solar shading devices, as well as all-day ventilation strategy and the use of thermal mass materials with 25cm-30cm thickness, has considerable impact on indoor air temperatures in warm season in Tehran and keeps the indoor environment in an acceptable thermal condition. The results of the field studies also indicated that most of the occupants found their thermal environment not to be comfortable and the simulation results showed that passive design techniques had a significant influence on the indoor air temperature and can keep it in an acceptable range based on the female students’ thermal requirement. Therefore, in order to enhance the indoor environment and to increase the learning performance of the students, it is necessary to use the appropriate passive design strategies, which also reduce the need for mechanical systems and

Specificity Responses of Grasshoppers in Temperate Grasslands to Diel Asymmetric Warming

Science.gov (United States)

Wu, Tingjuan; Hao, Shuguang; Sun, Osbert Jianxin; Kang, Le

2012-01-01

Background Global warming is characterized by not only an increase in the daily mean temperature, but also a diel asymmetric pattern. However, most of the current studies on climate change have only concerned with the mean values of the warming trend. Although many studies have been conducted concerning the responses of insects to climate change, studies that address the issue of diel asymmetric warming under field conditions are not found in the literature. Methodology/Principal Findings We conducted a field climate manipulative experiment and investigated developmental and demographic responses to diel asymmetric warming in three grasshopper species (an early-season species Dasyhippus barbipes, a mid-season species Oedaleus asiaticus, and a late-season species Chorthippus fallax). It was found that warming generally advanced the development of eggs and nymphs, but had no apparent impacts on the hatching rate of eggs, the emergence rate of nymphs and the survival and fecundity of adults in all the three species. Nighttime warming was more effective in advancing egg development than the daytime warming. The emergence time of adults was differentially advanced by warming in the three species; it was advanced by 5.64 days in C. fallax, 3.55 days in O. asiaticus, and 1.96 days in D. barbipes. This phenological advancement was associated with increases in the effective GDDs accumulation. Conclusions/Significance Results in this study indicate that the responses of the three grasshopper species to warming are influenced by several factors, including species traits, developmental stage, and the thermal sensitivity of the species. Moreover, species with diapausing eggs are less responsive to changes in temperature regimes, suggesting that development of diapausing eggs is a protective mechanism in early-season grasshopper for avoiding the risk of pre-winter hatching. Our results highlight the need to consider the complex relationships between climate change and

Season exerts differential effects of ocean acidification and warming on growth and carbon metabolism of the seaweed Fucus vesiculosus in the western Baltic Sea

Directory of Open Access Journals (Sweden)

Angelika eGraiff

2015-12-01

Full Text Available Warming and acidification of the oceans as a consequence of increasing CO2-concentrations occur at large scales. Numerous studies have shown the impact of single stressors on individual species. However, studies on the combined effect of multiple stressors on a multi-species assemblage, which is ecologically much more realistic and relevant, are still scarce. Therefore, we orthogonally crossed the two factors warming and acidification in mesocosm experiments and studied their single and combined impact on the brown alga Fucus vesiculosus associated with its natural community (epiphytes and mesograzers in the Baltic Sea in all seasons (from April 2013 to April 2014. We superimposed our treatment factors onto the natural fluctuations of all environmental variables present in the Benthocosms in so-called delta-treatments. Thereby we compared the physiological responses of F. vesiculosus (growth and metabolites to the single and combined effects of natural Kiel Fjord temperatures and pCO2 conditions with a 5 °C temperature increase and/or pCO2 increase treatment (1100 ppm in the headspace above the mesocosms. Responses were also related to the factor photoperiod which changes over the course of the year. Our results demonstrate complex seasonal pattern. Elevated pCO2 positively affected growth of F. vesiculosus alone and/or interactively with warming. The response direction (additive, synergistic or antagonistic, however, depended on season and daylength. The effects were most obvious when plants were actively growing during spring and early summer. Our study revealed for the first time that it is crucial to always consider the impact of variable environmental conditions throughout all seasons. In summary, our study indicates that in future F. vesiculosus will be more affected by detrimental summer heat-waves than by ocean acidification although the latter consequently enhances growth throughout the year. The mainly negative influence of rising

Dynamic response of wind turbine towers in warm permafrost

Institute of Scientific and Technical Information of China (English)

Benjamin Still; ZhaoHui Joey Yang; Simon Evans; FuJun Niu

2014-01-01

Wind is a great source of renewable energy in western Alaska. Consistent winds blow across the barren tundra underlain by warm permafrost in the winter season, when the energy demand is the highest. Foundation engineering in warm permafrost has always been a challenge in wind energy development. Degrading warm permafrost poses engineering issues to design, construction, and operation of wind turbines. This paper describes the foundation design of a wind turbine built in western Alaska. It presents a sys-tem for response monitoring and load assessment, and data collected from September 2013 to March 2014. The dynamic proper-ties are assessed based on the monitoring data, and seasonal changes in the dynamic properties of the turbine tower-foundation system and likely resonance between the spinning blades and the tower structure are discussed. These analyses of a wind turbine in warm permafrost are valuable for designing or retrofitting of foundations in warm permafrost.

Sustainable Production of Switchgrass for Biomass Energy

Science.gov (United States)

Switchgrass (Panicum virgatum L.) is a C4 grass native to the North American tallgrass prairies, which historically extended from Mexico to Canada. It is the model perennial warm-season grass for biomass energy. USDA-ARS in Lincoln, NE has studied switchgrass continuously since 1936. Plot-scale rese...

Production and supply logistics of switchgrass as an energy feedstock

Science.gov (United States)

Switchgrass (Panicum virgatum L.) is a warm-season (C4), perennial grass that is native to the tallgrass ecoregion of North America (Figure 1). Historically, switchgrass has been used for summer forage, hay, ensiling, or in conservation plantings. At the end of the 20th century, switchgrass was de...

Antibiosis among selected paspalum taxa to the fall armyworm (Lepidoptera: Noctuidae)

Science.gov (United States)

Twenty six accessions of the warm-season perennial grass, Paspalum spp., were evaluated for response to the fall armyworm Spodoptera frugiperda (J. E. Smith), an important pest of turfgrass. In growth chamber, excised clipping studies, P. vaginatum 03-539-31 and P. vaginatum 03-525-22 were the most ...

Experimental winter warming modifies thermal performance and primes acorn ants for warm weather

DEFF Research Database (Denmark)

MacLean, Heidi J.; Penick, Clint A.; Dunn, Robert R.

2017-01-01

The frequency of warm winter days is increasing under global climate change, but how organisms respond to warmer winters is not well understood. Most studies focus on growing season responses to warming. Locomotor performance is often highly sensitive to temperature, and can determine fitness...... outcomes through a variety of mechanisms including resource acquisition and predator escape. As a consequence, locomotor performance, and its impacts on fitness, may be strongly affected by winter warming in winter-active species. Here we use the acorn ant, Temnothorax curvispinosus, to explore how thermal...... performance (temperature-driven plasticity) in running speed is influenced by experimental winter warming of 3–5 °C above ambient in a field setting. We used running speed as a measure of performance as it is a common locomotor trait that influences acquisition of nest sites and food in acorn ants...

Determination of microbial protein in perennial ryegrass silage

NARCIS (Netherlands)

Driehuis, F.; Wikselaar, van P.G.

2001-01-01

The microbial matter fraction was determined in perennial ryegrass silages of different dry-matter (DM) contents, ensiled with or without Lactobacillus plantarum. 15N-Leucine and the bacterial cell wall constituent diaminopimelic acid (DAPA) were used as markers for microbial-N. Perennial ryegrass

Differential metabolic responses of perennial grass Cynodon transvaalensis×Cynodon dactylon (C₄) and Poa Pratensis (C₃) to heat stress.

Science.gov (United States)

Du, Hongmei; Wang, Zhaolong; Yu, Wenjuan; Liu, Yimin; Huang, Bingru

2011-03-01

Differential metabolic responses to heat stress may be associated with variations in heat tolerance between cool-season (C₃) and warm-season (C₄) perennial grass species. The main objective of this study was to identify metabolites associated with differential heat tolerance between C₄ bermudagrass and C₃ Kentucky bluegrass by performing metabolite profile analysis using gas chromatography-mass spectrometry. Plants of Kentucky bluegrass (Poa Pratensis'Midnight') and hybrid bermudagrass (Cynodon transvaalensis x Cynodon dactylon'Tifdwarf') were grown under optimum temperature conditions (20/15 °C for Kentucky bluegrass and 30/25 °C for bermudagrass) or heat stress (35/30 °C for Kentucky bluegrass and 45/40 °C for bermudagrass). Physiological responses to heat stress were evaluated by visual rating of grass quality, measuring photochemical efficiency (variable fluorescence to maximal fluorescence) and electrolyte leakage. All of these parameters indicated that bermudagrass exhibited better heat tolerance than Kentucky bluegrass. The metabolite analysis of leaf polar extracts revealed 36 heat-responsive metabolites identified in both grass species, mainly consisting of organic acids, amino acids, sugars and sugar alcohols. Most metabolites showed higher accumulation in bermudagrass compared with Kentucky bluegrass, especially following long-term (18 days) heat stress. The differentially accumulated metabolites included seven sugars (sucrose, fructose, galactose, floridoside, melibiose, maltose and xylose), a sugar alcohol (inositol), six organic acids (malic acid, citric acid, threonic acid, galacturonic acid, isocitric acid and methyl malonic acid) and nine amino acids (Asn, Ala, Val, Thr, γ-aminobutyric acid, IIe, Gly, Lys and Met). The differential accumulation of those metabolites could be associated with the differential heat tolerance between C₃ Kentucky bluegrass and C₄ bermudagrass. Copyright © Physiologia Plantarum 2010.

Terrestrial carbon cycle affected by non-uniform climate warming

International Nuclear Information System (INIS)

Jianyang Xia; Yiqi Luo; Jiquan Chen; Shilong Piao; Ciais, Philippe; Shiqiang Wan

2014-01-01

Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30 degrees and 90 degrees N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research. (authors)

Seasonal timing in a warming world : plasticity of seasonal timing of growth and reproduction

OpenAIRE

Salis, L.

2015-01-01

In seasonal environments the timing of various biological processes is crucial for growth, survival and reproductive success of an individual. Nowadays, rapid large-scale climate change is altering species’ seasonal timing (phenology) in many eco¬systems. In this thesis Lucia Salis focuses on the study of seasonal timing in the food chain of the oak-winter moth-great tit. As temperature increased over the last decades, both phenologies of the host plant, the oak, and the herbivorous insect, t...

Dynamics of Necrophagous Insect and Tissue Bacteria for Postmortem Interval Estimation During the Warm Season in Romania.

Science.gov (United States)

Iancu, Lavinia; Sahlean, Tiberiu; Purcarea, Cristina

2016-01-01

The estimation of postmortem interval (PMI) is affected by several factors including the cause of death, the place where the body lay after death, and the weather conditions during decomposition. Given the climatic differences among biogeographic locations, the understanding of necrophagous insect species biology and ecology is required when estimating PMI. The current experimental model was developed in Romania during the warm season in an outdoor location. The aim of the study was to identify the necrophagous insect species diversity and dynamics, and to detect the bacterial species present during decomposition in order to determine if their presence or incidence timing could be useful to estimate PMI. The decomposition process of domestic swine carcasses was monitored throughout a 14-wk period (10 July-10 October 2013), along with a daily record of meteorological parameters. The chronological succession of necrophagous entomofauna comprised nine Diptera species, with the dominant presence of Chrysomya albiceps (Wiedemann 1819) (Calliphoridae), while only two Coleoptera species were identified, Dermestes undulatus (L. 1758) and Creophilus maxillosus Brahm 1970. The bacterial diversity and dynamics from the mouth and rectum tissues, and third-instar dipteran larvae were identified using denaturing gradient gel electrophoresis analysis and sequencing of bacterial 16S rRNA gene fragments. Throughout the decomposition process, two main bacterial chronological groups were differentiated, represented by Firmicutes and Gammaproteobacteria. Twenty-six taxa from the rectal cavity and 22 from the mouth cavity were identified, with the dominant phylum in both these cavities corresponding to Firmicutes. The present data strengthen the postmortem entomological and microbial information for the warm season in this temperate-continental area, as well as the role of microbes in carcass decomposition. © The Authors 2015. Published by Oxford University Press on behalf of

Foliar glyphosate treatment alters transcript and hormone profiles in crown buds of leafy spurge and induces dwarfed and bushy phenotypes throughout its perennial life cycle

Science.gov (United States)

Leafy spurge (Euphorbia esula) is an invasive weed of North America and its perennial nature is attributed to underground adventitious buds (UABs) that undergo seasonal cycles of para-, endo- and eco-dormancy. Recommended field rates of glyphosate (~1 kg/ha) destroys above-ground shoots of leafy spu...

Perennial Grass Bioenergy Cropping on Wet Marginal Land

NARCIS (Netherlands)

Das, Srabani; Teuffer, Karin; Stoof, Cathelijne R.; Walter, Michael F.; Walter, M.T.; Steenhuis, Tammo S.; Richards, Brian K.

2018-01-01

The control of soil moisture, vegetation type, and prior land use on soil health parameters of perennial grass cropping systems on marginal lands is not well known. A fallow wetness-prone marginal site in New York (USA) was converted to perennial grass bioenergy feedstock production. Quadruplicate

Corresponding Relation between Warm Season Precipitation Extremes and Surface Air Temperature in South China

Institute of Scientific and Technical Information of China (English)

SUN; Wei; LI; Jian; YU; Ru-Cong

2013-01-01

Hourly data of 42 rain gauges over South China during 1966–2005 were used to analyze the corresponding relation between precipitation extremes and surface air temperature in the warm season(May to October).The results show that below 25℃,both daily and hourly precipitation extremes in South China increase with rising temperature.More extreme events transit to the two-time Clausius-Clapeyron(CC)relationship at lower temperatures.Daily as well as hourly precipitation extremes have a decreasing tendency nearly above 25℃,among which the decrease of hourly extremes is much more significant.In order to investigate the efects of rainfall durations,hourly precipitation extremes are presented by short duration and long duration precipitation,respectively.Results show that the dramatic decrease of hourly rainfall intensities above 25℃ is mainly caused by short duration precipitation,and long duration precipitation extremes rarely occur in South China when surface air temperature surpasses 28℃.

Seasonal variation in standardized litter decomposition and effects of elevation and land use at Mount Kilimanjaro

Science.gov (United States)

Becker, Joscha; Kuzyakov, Yakov

2017-04-01

Decomposition is one of most important ecological steps in organic matter and nutrient cycles, but studies and reliable data from tropical regions in Africa are still scarce. At the global scale, litter decomposition and recycling is controlled by climatic factors and land-use intensity. These factors can be linked to specific ecosystem characteristics along the unique elevation gradient of Mt. Kilimanjaro. Our objectives were to assess the effects of climatic conditions (i.e. elevation) and land-use intensity on C turnover and stabilization and investigated the seasonal variations. Tea-bag Index (see www.teatime4science.org) was used to measure decomposition of a standardized litter substrate by microorganisms and mesofauna coffee plantations or cloud forest (S=0.11) respectively and strongly increased again to a maximum of S=0.41 in the alpine helichrysum ecosystem. During all seasons, we found the highest decomposition rates at mid elevation. However, during both warm seasons the peak is shifted upslope. Savanna experienced the strongest seasonal variation, with 23 times higher S-values in dry- compared to rainy season. Mean annual k-values increased for about 30% with increasing land-use intensity. C stabilization in Mt. Kilimanjaro ecosystems is strongly dependent on seasonal moisture limitation (lower slope) and perennial temperature limitation (alpine zone). Ecosystems at mid elevation (around 1920 & 2120m) represent the interception zone of optimal moisture and temperature conditions. High input and fast turnover drive the C sequestration in these ecosystems, while restrains on decomposition control the C turnover in lower and higher elevation zones. Land-use intensification decreases stabilization from new C inputs in transition zones from savanna to maize monocultures and from traditional homegardens to large-scale coffee plantations.

Free boundary models for mosquito range movement driven by climate warming.

Science.gov (United States)

Bao, Wendi; Du, Yihong; Lin, Zhigui; Zhu, Huaiping

2018-03-01

As vectors, mosquitoes transmit numerous mosquito-borne diseases. Among the many factors affecting the distribution and density of mosquitoes, climate change and warming have been increasingly recognized as major ones. In this paper, we make use of three diffusive logistic models with free boundary in one space dimension to explore the impact of climate warming on the movement of mosquito range. First, a general model incorporating temperature change with location and time is introduced. In order to gain insights of the model, a simplified version of the model with the change of temperature depending only on location is analyzed theoretically, for which the dynamical behavior is completely determined and presented. The general model can be modified into a more realistic one of seasonal succession type, to take into account of the seasonal changes of mosquito movements during each year, where the general model applies only for the time period of the warm seasons of the year, and during the cold season, the mosquito range is fixed and the population is assumed to be in a hibernating status. For both the general model and the seasonal succession model, our numerical simulations indicate that the long-time dynamical behavior is qualitatively similar to the simplified model, and the effect of climate warming on the movement of mosquitoes can be easily captured. Moreover, our analysis reveals that hibernating enhances the chances of survival and successful spreading of the mosquitoes, but it slows down the spreading speed.

Association of Candidate Genes With Submergence Response in Perennial Ryegrass

Directory of Open Access Journals (Sweden)

Xicheng Wang

2017-05-01

Full Text Available Perennial ryegrass is a popular cool-season grass species due to its high quality for forage and turf. The objective of this study was to identify associations of candidate genes with growth and physiological traits to submergence stress and recovery after de-submergence in a global collection of 94 perennial ryegrass accessions. Accessions varied largely in leaf color, plant height (HT, leaf fresh weight (LFW, leaf dry weight (LDW, and chlorophyll fluorescence (Fv/Fm at 7 days of submergence and in HT, LFW and LDW at 7 days of recovery in two experiments. Among 26 candidate genes tested by various models, single nucleotide polymorphisms (SNPs in 10 genes showed significant associations with traits including 16 associations for control, 10 for submergence, and 8 for recovery. Under submergence, Lp1-SST encoding sucrose:sucrose 1-fructosyltransferase and LpGA20ox encoding gibberellin 20-oxidase were associated with LFW and LDW, and LpACO1 encoding 1-aminocyclopropane-1-carboxylic acid oxidase was associated with LFW. Associations between Lp1-SST and HT, Lp6G-FFT encoding fructan:fructan 6G-fructosyltransferase and Fv/Fm, LpCAT encoding catalase and HT were also detected under submergence stress. Upon de-submergence, Lp1-SST, Lp6G-FFT, and LpPIP1 encoding plasma membrane intrinsic protein type 1 were associated with LFW or LDW, while LpCBF1b encoding C-repeat binding factor were associated with HT. Nine significant SNPs in Lp1-SST, Lp6G-FFT, LpCAT, and LpACO1 resulted in amino acid changes with five substitutions found in Lp1-SST under submergence or recovery. The results indicated that allelic diversity in genes involved in carbohydrate and antioxidant metabolism, ethylene and gibberellin biosynthesis, and transcript factor could contribute to growth variations in perennial ryegrass under submergence stress and recovery after de-submergence.

Seasonal timing in a warming world : Plasticity of seasonal timing of growth and reproduction

NARCIS (Netherlands)

Salis, Lucia

2015-01-01

In seasonal environments the timing of various biological processes is crucial for growth, survival and reproductive success of an individual. Nowadays, rapid large-scale climate change is altering species’ seasonal timing (phenology) in many eco¬systems. In this thesis Lucia Salis focuses on the

Seasonality in ocean microbial communities.

Science.gov (United States)

Giovannoni, Stephen J; Vergin, Kevin L

2012-02-10

Ocean warming occurs every year in seasonal cycles that can help us to understand long-term responses of plankton to climate change. Rhythmic seasonal patterns of microbial community turnover are revealed when high-resolution measurements of microbial plankton diversity are applied to samples collected in lengthy time series. Seasonal cycles in microbial plankton are complex, but the expansion of fixed ocean stations monitoring long-term change and the development of automated instrumentation are providing the time-series data needed to understand how these cycles vary across broad geographical scales. By accumulating data and using predictive modeling, we gain insights into changes that will occur as the ocean surface continues to warm and as the extent and duration of ocean stratification increase. These developments will enable marine scientists to predict changes in geochemical cycles mediated by microbial communities and to gauge their broader impacts.

Mean surface fields of heat budget components over the warm pool in the Bay of Bengal during post-monsoon season

Digital Repository Service at National Institute of Oceanography (India)

Sadhuram, Y.; Rao, D.P.; Rao, B.P.

Andaman Islands and in the MT area there is an association between SST and Q n . But, off Sri Lanka warmer waters were noticed eventhough Q n was negative. This gives a clue that the role of advection plays a dominant role in the maintenance of SST.... Maintenance of warmwaters could be due to the transport of heat from North to South during post-monsoon season. Individual contributions from advection and air-sea fluxes towards SST would throw better light on the formation of warm pool in Bay of Bengal...

Whole-stream metabolism of a perennial spring-fed aufeis field in Alaska, with coincident surface and subsurface flow

Science.gov (United States)

Hendrickson, P. J.; Gooseff, M. N.; Huryn, A. D.

2017-12-01

Aufeis (icings or naleds) are seasonal arctic and sub-arctic features that accumulate through repeated overflow and freeze events of river or spring discharge. Aufeis fields, defined as the substrate on which aufeis form and the overlaying ice, have been studied to mitigate impacts on engineering structures; however, ecological characteristics and functions of aufeis fields are poorly understood. The perennial springs that supply warm water to aufeis fields create unique fluvial habitats, and are thought to act as winter and summer oases for biota. To investigate ecosystem function, we measured whole-stream metabolism at the Kuparuk River Aufeis (North Slope, AK), a large ( 5 km2) field composed of cobble substrate and predominately subsurface flow dynamics. The single-station open channel diel oxygen method was utilized at several dissolved oxygen (DO) stations located within and downstream of the aufeis field. DO loggers were installed in August 2016, and data downloaded summer 2017. Daily ecosystem respiration (ER), gross primary production (GPP) and reaeration rates were modeled using BASE, a package freely available in the open-source software R. Preliminary results support net heterotrophy during a two-week period of DO measurements in the fall season when minimum ice extent is observed. GPP, ER, and net metabolism are greater at the upstream reach near the spring source (P/R = 0.53), and decrease as flow moves downstream. As flow exits the aufeis field, surface and subsurface flow are incorporated into the metabolism model, and indicate the stream system becomes dependent on autochthonous production (P/R = 0.91). Current work is directed towards spring and summer discharge and metabolic parameter estimation, which is associated with maximum ice extent and rapid melting of the aufeis feature.

Productivity and carbon footprint of perennial grass-forage legume intercropping strategies with high or low nitrogen fertilizer input.

Science.gov (United States)

Hauggaard-Nielsen, Henrik; Lachouani, Petra; Knudsen, Marie Trydeman; Ambus, Per; Boelt, Birte; Gislum, René

2016-01-15

A three-season field experiment was established and repeated twice with spring barley used as cover crop for different perennial grass-legume intercrops followed by a full year pasture cropping and winter wheat after sward incorporation. Two fertilization regimes were applied with plots fertilized with either a high or a low rate of mineral nitrogen (N) fertilizer. Life cycle assessment (LCA) was used to evaluate the carbon footprint (global warming potential) of the grassland management including measured nitrous oxide (N2O) emissions after sward incorporation. Without applying any mineral N fertilizer, the forage legume pure stand, especially red clover, was able to produce about 15 t above ground dry matter ha(-1) year(-1) saving around 325 kg mineral Nfertilizer ha(-1) compared to the cocksfoot and tall fescue grass treatments. The pure stand ryegrass yielded around 3t DM more than red clover in the high fertilizer treatment. Nitrous oxide emissions were highest in the treatments containing legumes. The LCA showed that the low input N systems had markedly lower carbon footprint values than crops from the high N input system with the pure stand legumes without N fertilization having the lowest carbon footprint. Thus, a reduction in N fertilizer application rates in the low input systems offsets increased N2O emissions after forage legume treatments compared to grass plots due to the N fertilizer production-related emissions. When including the subsequent wheat yield in the total aboveground production across the three-season rotation, the pure stand red clover without N application and pure stand ryegrass treatments with the highest N input equalled. The present study illustrate how leguminous biological nitrogen fixation (BNF) represents an important low impact renewable N source without reducing crop yields and thereby farmers earnings. Copyright © 2015. Published by Elsevier B.V.

Tradeoffs between water requirements and yield stability in annual vs. perennial crops

Science.gov (United States)

Vico, Giulia; Brunsell, Nathaniel A.

2018-02-01

Population growth and changes in climate and diets will likely further increase the pressure on agriculture and water resources globally. Currently, staple crops are obtained from annuals plants. A shift towards perennial crops may enhance many ecosystem services, but at the cost of higher water requirements and lower yields. It is still unclear when the advantages of perennial crops overcome their disadvantages and perennial crops are thus a sustainable solution. Here we combine a probabilistic description of the soil water balance and crop development with an extensive dataset of traits of congeneric annuals and perennials to identify the conditions for which perennial crops are more viable than annual ones with reference to yield, yield stability, and effective use of water. We show that the larger and more developed roots of perennial crops allow a better exploitation of soil water resources and a reduction of yield variability with respect to annual species, but their yields remain lower when considering grain crops. Furthermore, perennial crops have higher and more variable irrigation requirements and lower water productivity. These results are important to understand the potential consequences for yield, its stability, and water resource use of a shift from annual to perennial crops and, more generally, if perennial crops may be more resilient than annual crops in the face of climatic fluctuations.

Evaulation of perennial pepperweed (Lepidium latifolium) management in a seasonal wetland in San Francisco Estuary prior to restoration of tidal hydrology

Science.gov (United States)

Herbicide applications have shown potential for control and management of invasive perennial pepperweed (Lepidium latifolium) in rangelands and tidal wetlands. However, reported efficacy of management methods varies widely, and the effects of more recently labeled aquatic herbicides on non-target ve...

Aerosol Indirect Effect on Warm Clouds over Eastern China Using Combined CALIOP and MODIS Observations

Science.gov (United States)

Guo, Jianping; Wang, Fu; Huang, Jingfeng; Li, Xiaowen

2015-04-01

Aerosol, one of key components of the climate system, is highly variable, both temporally and spatially. It often exerts great influences on the cloud-precipitation chain processes by serving as CCN/IN, altering cloud microphysics and its life cycle. Yet, the aerosol indirect effect on clouds remains largely unknown, because the initial changes in clouds due to aerosols may be enhanced or dampened by such feedback processes as modified cloud dynamics, or evaporation of the smaller droplets due to the competition for water vapor. In this study, we attempted to quantify the aerosol effects on warm cloud over eastern China, based on near-simultaneous retrievals from MODIS/AQUA, CALIOP/CALIPSO and CPR/CLOUDSAT during the period 2006 to 2010. The seasonality of aerosol from ground-based PM10 is quite different from that estimated from MODIS AOD. This result is corroborated by lower level profile of aerosol occurrence frequency from CALIOP, indicating the significant role CALIOP could play in aerosol-cloud interaction. The combined use of CALIOP and CPR facilitate the process to exactly determine the (vertical) position of warm cloud relative to aerosol, out of six scenarios in terms of aerosol-cloud mixing status in terms of aerosol-cloud mixing status, which shows as follows: AO (Aerosol only), CO (Cloud only), SASC (Single aerosol-single cloud), SADC (single aerosol-double cloud), DASC (double aerosol-single cloud), and others. Results shows that about 54% of all the cases belong to mixed status, among all the collocated aerosol-cloud cases. Under mixed condition, a boomerang shape is observed, i.e., reduced cloud droplet radius (CDR) is associated with increasing aerosol at moderate aerosol pollution (AODcases. We categorize dataset into warm-season and cold-season subsets to figure out how the boomerang shape varies with season. For moderate aerosol loading (AODMixed" cases is greater during cold season (denoted by a large slope), as compared with that during warm

The regulation of seasonal flowering in the Rosaceae.

Science.gov (United States)

Kurokura, Takeshi; Mimida, Naozumi; Battey, Nicholas H; Hytönen, Timo

2013-11-01

Molecular mechanisms regulating the flowering process have been extensively studied in model annual plants; in perennials, however, understanding of the molecular mechanisms controlling flowering has just started to emerge. Here we review the current state of flowering research in perennial plants of the rose family (Rosaceae), which is one of the most economically important families of horticultural plants. Strawberry (Fragaria spp.), raspberry (Rubus spp.), rose (Rosa spp.), and apple (Malus spp.) are used to illustrate how photoperiod and temperature control seasonal flowering in rosaceous crops. We highlight recent molecular studies which have revealed homologues of terminal flower1 (TFL1) to be major regulators of both the juvenile to adult, and the vegetative to reproductive transitions in various rosaceous species. Additionally, recent advances in understanding of the regulation of TFL1 are discussed.

Seasonal modulation of the Asian summer monsoon between the Medieval Warm Period and Little Ice Age: a multi model study

Science.gov (United States)

Kamae, Youichi; Kawana, Toshi; Oshiro, Megumi; Ueda, Hiroaki

2017-12-01

Instrumental and proxy records indicate remarkable global climate variability over the last millennium, influenced by solar irradiance, Earth's orbital parameters, volcanic eruptions and human activities. Numerical model simulations and proxy data suggest an enhanced Asian summer monsoon during the Medieval Warm Period (MWP) compared to the Little Ice Age (LIA). Using multiple climate model simulations, we show that anomalous seasonal insolation over the Northern Hemisphere due to a long cycle of orbital parameters results in a modulation of the Asian summer monsoon transition between the MWP and LIA. Ten climate model simulations prescribing historical radiative forcing that includes orbital parameters consistently reproduce an enhanced MWP Asian monsoon in late summer and a weakened monsoon in early summer. Weakened, then enhanced Northern Hemisphere insolation before and after June leads to a seasonally asymmetric temperature response over the Eurasian continent, resulting in a seasonal reversal of the signs of MWP-LIA anomalies in land-sea thermal contrast, atmospheric circulation, and rainfall from early to late summer. This seasonal asymmetry in monsoon response is consistently found among the different climate models and is reproduced by an idealized model simulation forced solely by orbital parameters. The results of this study indicate that slow variation in the Earth's orbital parameters contributes to centennial variability in the Asian monsoon transition.[Figure not available: see fulltext.

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations.

NARCIS (Netherlands)

Tsyganov, A.N.; Aerts, R.; Nijs, I.; Cornelissen, J.H.C.; Beyens, L.

2012-01-01

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming,

Relationship between altitude and intensity of malaria transmission in the Usambara Mountains, Tanzania

DEFF Research Database (Denmark)

Bødker, Rene; Akida, J.; Shayo, D.

2003-01-01

the holoendemic lowland and the hypoendemic highland plateau. Lowland transmission was perennial with a significant peak in the cool season after the long rains in May, when vectors densities were high. In the highlands, low temperatures prevented parasite development in mosquitoes during the cool season rains......, and highland transmission was therefore limited to the warm dry season when vector densities were low. The primary effect of increasing altitude was a log-linear reduction in vector abundance and, to a lesser extent, a reduction in the proportion of infective mosquitoes. Highland malaria transmission...

Fitossociologia de uma área de floresta estacional perenifólia na fazenda Amoreiras, Querência, MT Seasonal perennial forest site phytossociology in the amareiras farm, Querência, Mato Grosso state, Brazil

Directory of Open Access Journals (Sweden)

Sustanis Horn Kunz

2010-08-01

Full Text Available As florestas do sul da Amazônia, onde se encontra a Floresta Estacional Perenifólia, têm grande influência sobre a manutenção do equilíbrio físico regional e são as que mais estão ameaçadas pela ação antrópica, além de serem pouco conhecidas em relação à sua estrutura. Diante disso, objetivou-se estudar a estrutura fitossociológica de um trecho de Floresta Estacional Perenifólia na Bacia do Rio das Pacas em Querência, MT. A amostragem da vegetação consistiu na distribuição de 200 pontos quadrantes, sendo amostrados os indivíduos com diâmetro à altura de 1,30 m do solo (DAP ? 10 cm. A densidade total da área amostrada foi de 736 ind./ha, distribuídos em 58 espécies, 45 gêneros e 31 famílias. As espécies de maior Valor de Importância (VI, Ocotea leucoxylon (Sw. Laness., Trattinickia glaziovii Swart, Ouratea discophora Ducke, Xylopia amazonica R.E. Fr. e Myrcia multiflora (Lam. DC. corresponderam a 28,45% do VI total e também ocorreram em outros trechos de Floresta Estacional Perenifólia em Gaúcha do Norte, MT, porém não com a mesma representatividade. O índice de Shannon (3,51 pode ser considerado baixo por se tratar de Floresta Amazônica, mas a equabilidade de Pielou (0,86 evidenciou que a comunidade arbórea apresentava alta heterogeneidade florística.The Southern Amazon forests, where the Seasonal Perennial Forest occurs, has great influence on the maintenance of the regional physical equilibrium and they are among forests most threatened by anthropic action and are little known in relation to their structure. In this context, the objective of this work was to study phytosociological structure of a Seasonal Perennial Forest area in the Rio das Pacas Basin at Querência, state of Mato Grosso, Brazil. The vegetation sampling was composed of the distribution of 200 center quarter points, all individuals with DAP (diameter to height breast equal or superior to 10 cm were considered. The total density of

Assessing Water-use Relationships in a Perennial Kernza Field

Science.gov (United States)

De Oliveira, G.; Brunsell, N. A.; Sutherlin, C. E.; Crews, T.; Vico, G.

2017-12-01

Perennial grain/forage crops can sustain high yields without replanting for 3-10 years or more, resulting in potentially important environmental benefits. Although previous research has been conducted in perennial food crops, the coupling between these ecosystems and the atmosphere is not well understood. The objective of this study was to evaluate the magnitude and temporal variability of the water-use relationships in a perennial Kernza wheatgrass crop in Salina, north-central region of Kansas (KS), USA. The study period comprised approximately 4.5 years (May 2012-October 2016) of eddy covariance observations collected at the US-KLS AmeriFlux tower. In particular, we examine the water-use efficiency, carbon and water fluxes in relation to the local environmental factors, such as vapor pressure deficit, soil moisture, air temperature, etc. An analysis of the correspondence between accumulated precipitation (PPT) and ET in the perennial crop indicated a most likely low surface runoff and that there were other sources of water for plant intake in addition to the annual PPT, i.e., deep water. In this sense, we highlight that the long roots observed in perennial crops may facilitate the water uptake in the deeper soil layers, providing extra resources for the plant growth especially when the rainfall indices are low. The results obtained in this work are important in order to better understand the hydrologic cycle of perennial agroecosystems as well as to understand the benefits and disadvantages in relation to annual crops particularly under changing climatic conditions.

The Role of Frozen Soil in Groundwater Discharge Predictions for Warming Alpine Watersheds

Science.gov (United States)

Evans, Sarah G.; Ge, Shemin; Voss, Clifford I.; Molotch, Noah P.

2018-03-01

Climate warming may alter the quantity and timing of groundwater discharge to streams in high alpine watersheds due to changes in the timing of the duration of seasonal freezing in the subsurface and snowmelt recharge. It is imperative to understand the effects of seasonal freezing and recharge on groundwater discharge to streams in warming alpine watersheds as streamflow originating from these watersheds is a critical water resource for downstream users. This study evaluates how climate warming may alter groundwater discharge due to changes in seasonally frozen ground and snowmelt using a 2-D coupled flow and heat transport model with freeze and thaw capabilities for variably saturated media. The model is applied to a representative snowmelt-dominated watershed in the Rocky Mountains of central Colorado, USA, with snowmelt time series reconstructed from a 12 year data set of hydrometeorological records and satellite-derived snow covered area. Model analyses indicate that the duration of seasonal freezing in the subsurface controls groundwater discharge to streams, while snowmelt timing controls groundwater discharge to hillslope faces. Climate warming causes changes to subsurface ice content and duration, rerouting groundwater flow paths but not altering the total magnitude of future groundwater discharge outside of the bounds of hydrologic parameter uncertainties. These findings suggest that frozen soil routines play an important role for predicting the future location of groundwater discharge in watersheds underlain by seasonally frozen ground.

The role of frozen soil in groundwater discharge predictions for warming alpine watersheds

Science.gov (United States)

Evans, Sarah G.; Ge, Shemin; Voss, Clifford I.; Molotch, Noah P.

2018-01-01

Climate warming may alter the quantity and timing of groundwater discharge to streams in high alpine watersheds due to changes in the timing of the duration of seasonal freezing in the subsurface and snowmelt recharge. It is imperative to understand the effects of seasonal freezing and recharge on groundwater discharge to streams in warming alpine watersheds as streamflow originating from these watersheds is a critical water resource for downstream users. This study evaluates how climate warming may alter groundwater discharge due to changes in seasonally frozen ground and snowmelt using a 2‐D coupled flow and heat transport model with freeze and thaw capabilities for variably saturated media. The model is applied to a representative snowmelt‐dominated watershed in the Rocky Mountains of central Colorado, USA, with snowmelt time series reconstructed from a 12 year data set of hydrometeorological records and satellite‐derived snow covered area. Model analyses indicate that the duration of seasonal freezing in the subsurface controls groundwater discharge to streams, while snowmelt timing controls groundwater discharge to hillslope faces. Climate warming causes changes to subsurface ice content and duration, rerouting groundwater flow paths but not altering the total magnitude of future groundwater discharge outside of the bounds of hydrologic parameter uncertainties. These findings suggest that frozen soil routines play an important role for predicting the future location of groundwater discharge in watersheds underlain by seasonally frozen ground.

Seasonal forecasts: communicating current climate variability in southern Africa

CSIR Research Space (South Africa)

Landman, WA

2011-11-01

Full Text Available seasonal time scale. Seasonal climate forecasts are defined as probabilistic predictions of how much rain is expected during the season and how warm or cool it will be, based primarily on the principle that the ocean (sea-surface temperatures) influences...

Integrated rice-duck farming mitigates the global warming potential in rice season.

Science.gov (United States)

Xu, Guochun; Liu, Xin; Wang, Qiangsheng; Yu, Xichen; Hang, Yuhao

2017-01-01

Integrated rice-duck farming (IRDF), as a mode of ecological agriculture, is an important way to realize sustainable development of agriculture. A 2-year split-plot field experiment was performed to evaluate the effects of IRDF on methane (CH 4 ) and nitrous oxide (N 2 O) emissions and its ecological mechanism in rice season. This experiment was conducted with two rice farming systems (FS) of IRDF and conventional farming (CF) under four paddy-upland rotation systems (PUR): rice-fallow (RF), annual straw incorporating in rice-wheat rotation system (RWS), annual straw-based biogas residues incorporating in rice-wheat rotation system (RWB), and rice-green manure (RGM). During the rice growing seasons, IRDF decreased the CH 4 emission by 8.80-16.68%, while increased the N 2 O emission by 4.23-15.20%, when compared to CF. Given that CH 4 emission contributed to 85.83-96.22% of global warming potential (GWP), the strong reduction in CH 4 emission led to a significantly lower GWP of IRDF as compared to CF. The reason for this trend was because IRDF has significant effect on dissolved oxygen (DO) and soil redox potential (Eh), which were two pivotal factors for CH 4 and N 2 O emissions in this study. The IRDF not only mitigates the GWP, but also increases the rice yield by 0.76-2.43% compared to CF. Moreover, compared to RWS system, RF, RWB and RGM systems significantly reduced CH 4 emission by 50.17%, 44.89% and 39.51%, respectively, while increased N 2 O emission by 10.58%, 14.60% and 23.90%, respectively. And RWS system had the highest GWP. These findings suggest that mitigating GWP and improving rice yield could be simultaneously achieved by the IRDF, and employing suitable PUR would benefit for relieving greenhouse effect. Copyright © 2016 Elsevier B.V. All rights reserved.

The genome and transcriptome of perennial ryegrass mitochondria

DEFF Research Database (Denmark)

Islam, Md. Shofiqul; Studer, Bruno; Byrne, Stephen

2013-01-01

Background: Perennial ryegrass (Lolium perenne L.) is one of the most important forage and turf grass species of temperate regions worldwide. Its mitochondrial genome is inherited maternally and contains genes that can influence traits of agricultural importance. Moreover, the DNA sequence...... and annotation of the complete mitochondrial genome from perennial ryegrass. Results: Intact mitochondria from perennial ryegrass leaves were isolated and used for mtDNA extraction. The mitochondrial genome was sequenced to a 167-fold coverage using the Roche 454 GS-FLX Titanium platform, and assembled...... of mitochondrial genomes has been established and compared for a large number of species in order to characterize evolutionary relationships.Therefore, it is crucial to understand the organization of the mitochondrial genome and how it varies between and within species. Here, we report the first de novo assembly...

Irrigation enhances local warming with greater nocturnal warming effects than daytime cooling effects

Science.gov (United States)

Chen, Xing; Jeong, Su-Jong

2018-02-01

To meet the growing demand for food, land is being managed to be more productive using agricultural intensification practices, such as the use of irrigation. Understanding the specific environmental impacts of irrigation is a critical part of using it as a sustainable way to provide food security. However, our knowledge of irrigation effects on climate is still limited to daytime effects. This is a critical issue to define the effects of irrigation on warming related to greenhouse gases (GHGs). This study shows that irrigation led to an increasing temperature (0.002 °C year-1) by enhancing nighttime warming (0.009 °C year-1) more than daytime cooling (-0.007 °C year-1) during the dry season from 1961-2004 over the North China Plain (NCP), which is one of largest irrigated areas in the world. By implementing irrigation processes in regional climate model simulations, the consistent warming effect of irrigation on nighttime temperatures over the NCP was shown to match observations. The intensive nocturnal warming is attributed to energy storage in the wetter soil during the daytime, which contributed to the nighttime surface warming. Our results suggest that irrigation could locally amplify the warming related to GHGs, and this effect should be taken into account in future climate change projections.

Development of new techniques of using irradiation in the genetic improvement of warm season grasses and an assessment of the genetic and cytogenetic effects. Progress report, May 1, 1975--April 30, 1976

International Nuclear Information System (INIS)

Burton, G.W.; Hanna, W.W.

1976-06-01

Irradiation ( 60 Coγ source) was used for the genetic improvement of several warm season grasses and pearl millet. Results of plant breeding experiments using radioinduced mutants of Bermuda grass and millet are reported

Future vegetation ecosystem response to warming climate over the Tibetan Plateau

Science.gov (United States)

Bao, Y.; Gao, Y.; Wang, Y.

2017-12-01

The amplified vegetation response to climate variability has been found over the Tibetan Plateau (TP) in recent decades. In this study, the potential impacts of 21st century climate change on the vegetation ecosystem over the TP are assessed based on the dynamic vegetation outputs of models from Coupled Model Intercomparison Project Phase 5 (CMIP5), and the sensitivity of the TP vegetation in response to warming climate was investigated. Models project a continuous and accelerating greening in future, especially in the eastern TP, which closely associates with the plant type upgrade due to the pronouncing warming in growing season.Vegetation leaf area index (LAI) increase well follows the global warming, suggesting the warming climate instead of co2 fertilization controlls the future TP plant growth. The warming spring may advance the start of green-up day and extend the growing season length. More carbon accumulation in vegetation and soil will intensify the TP carbon cycle and will keep it as a carbon sink in future. Keywords: Leaf Area Index (LAI), Climate Change, Global Dynamic Vegetation Models (DGVMs), CMIP5, Tibetan Plateau (TP)

Belowground Water Dynamics Under Contrasting Annual and Perennial Plant Communities in an Agriculturally-Dominated Landscape

Science.gov (United States)

Mora, G.; Asbjornsen, H.; Helmers, M. J.; Shepherd, G. W.

2005-12-01

The conversion from grasslands and forests to row-crops in the Midwest has affected soil water cycling because plant characteristics are one of the main parameters determining soil storage capacity, infiltration rates, and surface runoff. Little is known, however, about the extent of modification of soil water dynamics under different plant communities. To address this important issue, we are documenting soil water dynamics under contrasting perennial and annual plant communities in an agriculturally-dominated landscape. Measurements of soil moisture and depths of uptake of source water were obtained for six vegetative cover types (corn and soybean field, brome pasture, degraded savanna, restored savanna, and restored prairie) at the Neal Smith National Wildlife Refuge in Prairie City, Iowa. The depths of uptake of soil water were determined on the basis of oxygen isotope composition of soil water and stem water. Measurements were performed once a month during an entire growing season. Preliminary results indicate that soil water present under the different vegetation types show similar profiles with depth during the dry months. Soil water in the upper 5 cm is enriched in oxygen-18 by about 5 per mil relative to soil water at 100 cm. Our preliminary results also indicate that the isotopic composition of stem water from annual plants is typically higher by about 2 per mil relative to that of stem water from perennial plants during the dry period. Whereas the oxygen isotopic composition for corn stem water is -5.49 per mil, that for elm and oak stem water is -7.62 and -7.51 per mil, respectively. The higher isotope values for corn suggest that annual crop plants are withdrawing water from shallower soil horizons relative to perennial plants. Moreover, our preliminary data suggest lower moisture content in soil under annual plant cover. We propose that the presence of deeper roots in the perennial vegetation allows these plants to tap into deeper water sources when

Projected changes of thermal growing season over Northern Eurasia in a 1.5 °C and 2 °C warming world

Science.gov (United States)

Zhou, Baiquan; Zhai, Panmao; Chen, Yang; Yu, Rong

2018-03-01

Projected changes of the thermal growing season (TGS) over Northern Eurasia at 1.5 °C and 2 °C global warming levels are investigated using 22 CMIP5 models under both RCP4.5 and RCP8.5 scenarios. The multi-model mean projections indicate Northern Eurasia will experience extended and intensified TGSs in a warmer world. The prolongation of TGSs under 1.5 °C and 2 °C warming is attributed to both earlier onset and later termination, with the latter factor playing a dominating role. Interestingly, earlier onset is of greater importance under RCP4.5 than under RCP8.5 in prolonging TGS as the world warms by an additional 0.5 °C. Under both RCPs, growing degree day sum (GDD) above 5 °C is anticipated to increase by 0 °C-450 °C days and 0 °C-650 °C days over Northern Eurasia at 1.5 °C and 2 °C warming, respectively. However, effective GDD (EGDD) which accumulates optimum temperature for the growth of wheat, exhibits a decline in the south of Central Asia under warmer climates. Therefore, for wheat production over Northern Eurasia, adverse effects incurred by scorching temperatures and resultant inadequacy in water availability may counteract benefits from lengthening and warming TGS. In response to a future 1.5 °C and 2 °C warmer world, proper management and scientifically-tailored adaptation are imperative to optimize local-regional agricultural production.

Seasonal and cryopreservation impacts on semen quality in boars

Science.gov (United States)

Seasonal boar infertility occurs worldwide and contributes to economic loss to the pork industry. The current study evaluated cooled vs cryopreserved semen quality of 11 Duroc boars collected in June (cool season) and August 2014 (warm season). Semen was cooled to 16°C (cooled) or frozen over liquid...

Estimated Perennial Streams of Idaho and Related Geospatial Datasets

Science.gov (United States)

Rea, Alan; Skinner, Kenneth D.

2009-01-01

The perennial or intermittent status of a stream has bearing on many regulatory requirements. Because of changing technologies over time, cartographic representation of perennial/intermittent status of streams on U.S. Geological Survey (USGS) topographic maps is not always accurate and (or) consistent from one map sheet to another. Idaho Administrative Code defines an intermittent stream as one having a 7-day, 2-year low flow (7Q2) less than 0.1 cubic feet per second. To establish consistency with the Idaho Administrative Code, the USGS developed regional regression equations for Idaho streams for several low-flow statistics, including 7Q2. Using these regression equations, the 7Q2 streamflow may be estimated for naturally flowing streams anywhere in Idaho to help determine perennial/intermittent status of streams. Using these equations in conjunction with a Geographic Information System (GIS) technique known as weighted flow accumulation allows for an automated and continuous estimation of 7Q2 streamflow at all points along a stream, which in turn can be used to determine if a stream is intermittent or perennial according to the Idaho Administrative Code operational definition. The selected regression equations were applied to create continuous grids of 7Q2 estimates for the eight low-flow regression regions of Idaho. By applying the 0.1 ft3/s criterion, the perennial streams have been estimated in each low-flow region. Uncertainty in the estimates is shown by identifying a 'transitional' zone, corresponding to flow estimates of 0.1 ft3/s plus and minus one standard error. Considerable additional uncertainty exists in the model of perennial streams presented in this report. The regression models provide overall estimates based on general trends within each regression region. These models do not include local factors such as a large spring or a losing reach that may greatly affect flows at any given point. Site-specific flow data, assuming a sufficient period of

Establishment techniques in under-sown perennial ryegrass for seed production

DEFF Research Database (Denmark)

Deleuran, Lise C; Boelt, Birte

2009-01-01

Establishment methods have proven to be of major importance for grass-seed production. The objective of this research was to test the effect of different sowing techniques on plant establishment and the subsequent seed yield. Perennial ryegrass (Lolium perenne L.) is used as the model grass due...... to its large importance in Danish agriculture. In a three-year trial six different methods of under-sowing of perennial ryegrass in a spring barley cover crop were employed. Perennial ryegrass was either sown directly at different depths within the spring barley (Hordeum vulgare L.) rows or placed 2, 6......, or 12 cm from the spring barley rows. Results of dry-matter yield indicate that the best establishment of the grass occurred when placing the grass 6 or 12 cm from the cover-crop row, and this is of importance in less vigorous grasses. Overall, no seed-yield difference has been observed for perennial...

Relict Mountain Permafrost Area (Loess Plateau, China) Exhibits High Ecosystem Respiration Rates and Accelerating Rates in Response to Warming

Science.gov (United States)

Mu, Cuicui; Wu, Xiaodong; Zhao, Qian; Smoak, Joseph M.; Yang, Yulong; Hu, Lian; Zhong, Wen; Liu, Guimin; Xu, Haiyan; Zhang, Tingjun

2017-10-01

Relict permafrost regions are characterized by thin permafrost and relatively high temperatures. Understanding the ecosystem respiration rate (ERR) and its relationship with soil hydrothermal conditions in these areas can provide knowledge regarding the permafrost carbon cycle in a warming world. In this study, we examined a permafrost area, a boundary area, and a seasonally frozen ground area within a relict permafrost region on the east edge of the Qinghai-Tibetan Plateau, China. Measurements from July 2015 to September 2016 showed that the mean annual ecosystem CO2 emissions for the boundary area were greater than the permafrost area. The Q10 value of the ERRs in the seasonally frozen ground area was greater than the permafrost area, indicating that the carbon emissions in the nonpermafrost areas were more sensitive to warming. The 1 year open-top chamber (OTC) warming increased soil temperatures in both the permafrost and seasonally frozen ground areas throughout the year, and the warming increased the ERRs by 1.18 (0.99-1.38, with interquartile range) and 1.13 (0.75-1.54, with interquartile range) μmol CO2 m-2 s-1 in permafrost and seasonally frozen ground areas, respectively. The OTC warming increased annual ERRs by approximately 50% for both permafrost and seasonally frozen ground areas with half the increase occurring during the nongrowing seasons. These results suggest that the ERRs in relict permafrost are high in comparison with arctic regions, and the carbon balance in relict permafrost areas could be greatly changed by climate warming.

Relative effects of precipitation variability and warming on tallgrass prairie ecosystem function

Directory of Open Access Journals (Sweden)

P. A. Fay

2011-10-01

Full Text Available Precipitation and temperature drive many aspects of terrestrial ecosystem function. Climate change scenarios predict increasing precipitation variability and temperature, and long term experiments are required to evaluate the ecosystem consequences of interannual climate variation, increased growing season (intra-annual rainfall variability, and warming. We present results from an experiment applying increased growing season rainfall variability and year round warming in native tallgrass prairie. During ten years of study, total growing season rainfall varied 2-fold, and we found ~50–200% interannual variability in plant growth and aboveground net primary productivity (ANPP, leaf carbon assimilation (A_CO2, and soil CO₂ efflux (J_CO2 despite only ~40% variation in mean volumetric soil water content (0–15 cm, Θ₁₅. Interannual variation in soil moisture was thus amplified in most measures of ecosystem response. Differences between years in Θ₁₅ explained the greatest portion (14–52% of the variation in these processes. Experimentally increased intra-annual season rainfall variability doubled the amplitude of intra-annual soil moisture variation and reduced Θ₁₅ by 15%, causing most ecosystem processes to decrease 8–40% in some or all years with increased rainfall variability compared to ambient rainfall timing, suggesting reduced ecosystem rainfall use efficiency. Warming treatments increased soil temperature at 5 cm depth, particularly during spring, fall, and winter. Warming advanced canopy green up in spring, increased winter J_CO2, and reduced summer J_CO2 and forb ANPP, suggesting that the effects of warming differed in cooler versus warmer parts of the year. We conclude that (1 major ecosystem processes in this grassland may be substantially altered by predicted changes in

A Decade of Carbon Flux Measurements with Annual and Perennial Crop Rotations on the Canadian Prairies

Science.gov (United States)

Amiro, B. D.; Tenuta, M.; Gao, X.; Gervais, M.

2016-12-01

The Fluxnet database has over 100 cropland sites, some of which have long-term (over a decade) measurements. Carbon neutrality is one goal of sustainable agriculture, although measurements over many annual cropping systems have indicated that soil carbon is often lost. Croplands are complex systems because the CO2 exchange depends on the type of crop, soil, weather, and management decisions such as planting date, nutrient fertilization and pest management strategy. Crop rotations are often used to decrease pest pressure, and can range from a simple 2-crop system, to have 4 or more crops in series. Carbon dioxide exchange has been measured using the flux-gradient technique since 2006 in agricultural systems in Manitoba, Canada. Two cropping systems are being followed: one that is a rotation of annual crops (corn, faba bean, spring wheat, rapeseed, barley, spring wheat, corn, soybean, spring wheat, soybean); and the other with a perennial phase of alfalfa/grass in years 3 to 6. Net ecosystem production ranged from a gain of 330 g C m-2 y-1 in corn to a loss of 75 g C m-2 y-1 in a poor spring-wheat crop. Over a decade, net ecosystem production for the annual cropping system was not significantly different from zero (carbon neutral), but the addition of the perennial phase increased the sink to 130 g C m-2 y-1. Once harvest removals were included, there was a net loss of carbon ranging from 77 g C m-2 y-1 in the annual system to 52 g C m-2 y-1 in the annual-perennial system; but neither of these were significantly different from zero. Termination of the perennial phase of the rotation only caused short-term increases in respiration. We conclude that both these systems were close to carbon-neutral over a decade even though they were tilled with a short growing season (90 to 130 days). We discuss the need for more datasets on agricultural systems to inform management options to increase the soil carbon sink.

Changes in the seasonality of Arctic sea ice and temperature

Science.gov (United States)

Bintanja, R.

2012-04-01

Observations show that the Arctic sea ice cover is currently declining as a result of climate warming. According to climate models, this retreat will continue and possibly accelerate in the near-future. However, the magnitude of this decline is not the same throughout the year. With temperatures near or above the freezing point, summertime Arctic sea ice will quickly diminish. However, at temperatures well below freezing, the sea ice cover during winter will exhibit a much weaker decline. In the future, the sea ice seasonal cycle will be no ice in summer, and thin one-year ice in winter. Hence, the seasonal cycle in sea ice cover will increase with ongoing climate warming. This in itself leads to an increased summer-winter contrast in surface air temperature, because changes in sea ice have a dominant influence on Arctic temperature and its seasonality. Currently, the annual amplitude in air temperature is decreasing, however, because winters warm faster than summer. With ongoing summer sea ice reductions there will come a time when the annual temperature amplitude will increase again because of the large seasonal changes in sea ice. This suggests that changes in the seasonal cycle in Arctic sea ice and temperature are closely, and intricately, connected. Future changes in Arctic seasonality (will) have an profound effect on flora, fauna, humans and economic activities.

[Characteristics and adaptation of seasonal drought in southern China under the background of climate change. V. Seasonal drought characteristics division and assessment in southern China].

Science.gov (United States)

Huang, Wan-Hua; Sui, Yue; Yang, Xiao-Guang; Dai, Shu-Wei; Li, Mao-Song

2013-10-01

Zoning seasonal drought based on the study of drought characteristics can provide theoretical basis for formulating drought mitigation plans and improving disaster reduction technologies in different arid zones under global climate change. Based on the National standard of meteorological drought indices and agricultural drought indices and the 1959-2008 meteorological data from 268 meteorological stations in southern China, this paper analyzed the climatic background and distribution characteristics of seasonal drought in southern China, and made a three-level division of seasonal drought in this region by the methods of combining comprehensive factors and main factors, stepwise screening indices, comprehensive disaster analysis, and clustering analysis. The first-level division was with the annual aridity index and seasonal aridity index as the main indices and with the precipitation during entire year and main crop growing season as the auxiliary indices, dividing the southern China into four primary zones, including semi-arid zone, sub-humid zone, humid zone, and super-humid zone. On this basis, the four primary zones were subdivided into nine second-level zones, including one semi-arid area-temperate-cold semi-arid hilly area in Sichuan-Yunnan Plateau, three sub-humid areas of warm sub-humid area in the north of the Yangtze River, warm-tropical sub-humid area in South China, and temperate-cold sub-humid plateau area in Southwest China, three humid areas of temperate-tropical humid area in the Yangtze River Basin, warm-tropical humid area in South China, and warm humid hilly area in Southwest China, and two super-humid areas of warm-tropical super-humid area in South China and temperate-cold super-humid hilly area in the south of the Yangtze River and Southwest China. According to the frequency and intensity of multiple drought indices, the second-level zones were further divided into 29 third-level zones. The distribution of each seasonal drought zone was

[Effects of Warming and Straw Application on Soil Respiration and Enzyme Activity in a Winter Wheat Cropland].

Science.gov (United States)

Chen, Shu-tao; Sang, Lin; Zhang, Xu; Hu, Zheng-hua

2016-02-15

In order to investigate the effects of warming and straw application on soil respiration and enzyme activity, a field experiment was performed from November 2014 to May 2015. Four treatments, which were control (CK), warming, straw application, and warming and straw application, were arranged in field. Seasonal variability in soil respiration, soil temperature and soil moisture for different treatments were measured. Urease, invertase, and catalase activities for different treatments were measured at the elongation, booting, and anthesis stages. The results showed that soil respiration in different treatments had similar seasonal variation patterns. Seasonal mean soil respiration rates for the CK, warming, straw application, and warming and straw application treatments were 1.46, 1.96, 1.92, and 2.45 micromol x (m2 x s)(-1), respectively. ANOVA indicated that both warming and straw applications significantly (P soil respiration compared to the control treatment. The relationship between soil respiration and soil temperature in different treatments fitted with the exponential regression function. The exponential regression functions explained 34.3%, 28.1%, 24.6%, and 32.0% variations of soil respiration for CK, warming, straw application, and warming and straw application treatments, respectively. Warming and straw applications significantly (P soil respiration and urease activity fitted with a linear regression function, with the P value of 0.061. The relationship between soil respiration and invertase (P = 0.013), and between soil respiration and catalase activity (P = 0.002) fitted well with linear regression functions.

Seasonally asymmetric enhancement of northern vegetation productivity

Science.gov (United States)

Park, T.; Myneni, R.

2017-12-01

Multiple evidences of widespread greening and increasing terrestrial carbon uptake have been documented. In particular, enhanced gross productivity of northern vegetation has been a critical role leading to observed carbon uptake trend. However, seasonal photosynthetic activity and its contribution to observed annual carbon uptake trend and interannual variability are not well understood. Here, we introduce a multiple-source of datasets including ground, atmospheric and satellite observations, and multiple process-based global vegetation models to understand how seasonal variation of land surface vegetation controls a large-scale carbon exchange. Our analysis clearly shows a seasonally asymmetric enhancement of northern vegetation productivity in growing season during last decades. Particularly, increasing gross productivity in late spring and early summer is obvious and dominant driver explaining observed trend and variability. We observe more asymmetric productivity enhancement in warmer region and this spatially varying asymmetricity in northern vegetation are likely explained by canopy development rate, thermal and light availability. These results imply that continued warming may facilitate amplifying asymmetric vegetation activity and cause these trends to become more pervasive, in turn warming induced regime shift in northern land.

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.

Distribution and seasonal change of the Tsugaru warm current water off Rokkasho

International Nuclear Information System (INIS)

Shima, Shigeki; Nakayama, Tomoharu; Iseda, Kenichi; Nishizawa, Keisuke; Gasa, Shinichi; Suto, Kazuhiko; Sakurai, Satoshi; Oguri, Kazumasa; Kouzuma, Kiyotake

2000-01-01

The first commercial spent fuel reprocessing plant in Japan is being installed in Rokkasho-mura, Aomori Prefecture. Decontaminated liquid effluents in its operation will be released into a sea. In accessing the environmental impact of radionuclides discharged into a sea, it is important that the patterns of water movements around the discharge outlet are clarified. This area off Rokkasho is an open coast, where the Tsugaru Warm Current Water (TWC), the cold Oyashio and the warm Kuroshio Extension meet. Therefore, it is considered that complicated water circulations will be formed around the region of the wastewater outlet. Current structures of the coastal water near the ocean outlet were investigated by use of mooring current meters/ADCPs, a towing-ADCP, and some CTD observations. In addition, extensive observations with CTD and a shipboard ADCP were made in detail around the off Rokkasho (Shimokita Peninsula) to evaluate the distribution and the seasonal change of the TWC. These observations were carried out five times in September 1997 to August 1999. Gyre mode and coastal mode of the TWC experimentally pointed out by Conlon are found by those investigations. In the gyre mode, the large eddy more than 100 km in diameter is found in the east part of the Tsugaru Strait, which has the vertical structure of 1,000 m in depth. From the current measurements by shipboard ADCP, the velocity of the TWC was more than three knots and the width of its fastest region about 30km at that mode. On the other hand, in the coastal mode, the TWC flows along the continental slope off Rokkasho (ca five miles off the coast) and is about 400m thick in depth. The TWC affects the layers below the sill depth of the Tsugaru Strait. In the gyre mode the TWC flows northward along the slope off Rokkasho, however, around the coastal zone standing near to the outlet, southward flow was observed predominantly. At the coastal mode, the northward flow was mostly observed around the coastal area

Agroecology of Novel Annual and Perennial Crops for Biomass Production

DEFF Research Database (Denmark)

Manevski, Kiril; Jørgensen, Uffe; Lærke, Poul Erik

The agroecological potential of many crops under sustainable intensification has not been investigated. This study investigates such potential for novel annual and perennial crops grown for biomass production.......The agroecological potential of many crops under sustainable intensification has not been investigated. This study investigates such potential for novel annual and perennial crops grown for biomass production....

Autumn photosynthetic decline and growth cessation in seedlings of white spruce are decoupled under warming and photoperiod manipulations.

Science.gov (United States)

Stinziano, Joseph R; Way, Danielle A

2017-08-01

Climate warming is expected to increase the seasonal duration of photosynthetic carbon fixation and tree growth in high-latitude forests. However, photoperiod, a crucial cue for seasonality, will remain constant, which may constrain tree responses to warming. We investigated the effects of temperature and photoperiod on weekly changes in photosynthetic capacity, leaf biochemistry and growth in seedlings of a boreal evergreen conifer, white spruce [Picea glauca (Moench) Voss]. Warming delayed autumn declines in photosynthetic capacity, extending the period when seedlings had high carbon uptake. While photoperiod was correlated with photosynthetic capacity, short photoperiods did not constrain the maintenance of high photosynthetic capacity under warming. Rubisco concentration dynamics were affected by temperature but not photoperiod, while leaf pigment concentrations were unaffected by treatments. Respiration rates at 25 °C were stimulated by photoperiod, although respiration at the growth temperatures was increased in warming treatments. Seedling growth was stimulated by increased photoperiod and suppressed by warming. We demonstrate that temperature is a stronger control on the seasonal timing of photosynthetic down-regulation than is photoperiod. Thus, while warming can stimulate carbon uptake in boreal conifers, the extra carbon may be directed towards respiration rather than biomass, potentially limiting carbon sequestration under climate change. © 2017 John Wiley & Sons Ltd.

Impact of climate change on mid-twenty-first century growing seasons in Africa

Energy Technology Data Exchange (ETDEWEB)

Cook, Kerry H.; Vizy, Edward K. [The University of Texas at Austin, Department of Geological Sciences, Jackson School of Geosciences, Austin, TX (United States)

2012-12-15

Changes in growing seasons for 2041-2060 across Africa are projected using a regional climate model at 90-km resolution, and confidence in the predictions is evaluated. The response is highly regional over West Africa, with decreases in growing season days up to 20% in the western Guinean coast and some regions to the east experiencing 5-10% increases. A longer growing season up to 30% in the central and eastern Sahel is predicted, with shorter seasons in parts of the western Sahel. In East Africa, the short rains (boreal fall) growing season is extended as the Indian Ocean warms, but anomalous mid-tropospheric moisture divergence and a northward shift of Sahel rainfall severely curtails the long rains (boreal spring) season. Enhanced rainfall in January and February increases the growing season in the Congo basin by 5-15% in association with enhanced southwesterly moisture transport from the tropical Atlantic. In Angola and the southern Congo basin, 40-80% reductions in austral spring growing season days are associated with reduced precipitation and increased evapotranspiration. Large simulated reductions in growing season over southeastern Africa are judged to be inaccurate because they occur due to a reduction in rainfall in winter which is over-produced in the model. Only small decreases in the actual growing season are simulated when evapotranspiration increases in the warmer climate. The continent-wide changes in growing season are primarily the result of increased evapotranspiration over the warmed land, changes in the intensity and seasonal cycle of the thermal low, and warming of the Indian Ocean. (orig.)

Control of perennial weeds by mechanical methods and anaerobic soil disinfection

NARCIS (Netherlands)

Huiting, H.F.; Bleeker, P.O.; Riemens, M.M.

2011-01-01

Perennial weeds are difficult to control and ask for a specific approach. During the most recent years it has even become a great challenge to control these weeds in conventional farming systems, although in comparison effective perennial weed control in organic farming systems remains more

Projections of Seasonal Patterns in Temperature- Related Deaths for Manhattan, New York

Science.gov (United States)

Li, Tiantian; Horton, Radley M.; Kinney, Patrick L.

2013-01-01

Global average temperatures have been rising for the past half-century, and the warming trend has accelerated in recent decades. Further warming is expected over the next few decades, with significant regional variations. These warming trends will probably result in more frequent, intense and persistent periods of hot temperatures in summer, and generally higher temperatures in winter. Daily death counts in cities increase markedly when temperatures reach levels that are very high relative to what is normal in a given location. Relatively cold temperatures also seem to carry risk. Rising temperatures may result in more heat-related mortality but may also reduce cold-related mortality, and the net impact on annual mortality remains uncertain. Here we use 16 downscaled global climate models and two emissions scenarios to estimate present and future seasonal patterns in temperature-related mortality in Manhattan, New York. All 32 projections yielded warm-season increases and cold-season decreases in temperature-related mortality, with positive net annual temperature-related deaths in all cases. Monthly analyses showed that the largest percentage increases may occur in May and September. These results suggest that, over a range of models and scenarios of future greenhouse gas emissions, increases in heat-related mortality could outweigh reductions in cold-related mortality, with shifting seasonal patterns.

Predicting seed yield in perennial ryegrass using repeated canopy reflectance measurements and PLSR

DEFF Research Database (Denmark)

Gislum, René; Deleuran, Lise Christina; Boelt, Birte

2009-01-01

with first year seed crops using three sowing rates and three spring nitrogen (N) application rates. PLSR models were developed for each year and showed correlation coefficients of 0.71, 0.76, and 0.92, respectively. Regression coefficients showed in these experiments that the optimum time for canopy...... reflectance measurements was from approximately 600 cumulative growing degree-days (CGDD) to approximately 900 CGDD. This is the period just before and at heading of the seed crop. Furthermore, regression coefficients showed that information about N and water is important. The results support the development......Repeated canopy reflectance measurements together with partial least-squares regression (PLSR) were used to predict seed yield in perennial ryegrass (Lolium perenne L.). The measurements were performed during the spring and summer growing seasons of 2001 to 2003 in three field experiments...

Global warming and climate change: control methods

International Nuclear Information System (INIS)

Laal, M.; Aliramaie, A.

2008-01-01

This paper aimed at finding causes of global warming and ways to bring it under control. Data based on scientific opinion as given by synthesis reports of news, articles, web sites, and books. global warming is the observed and projected increases in average temperature of Earth's atmosphere and oceans. Carbon dioxide and other air pollution that is collecting in the atmosphere like a thickening blanket, trapping the sun's heat and causing the planet to warm up. Pollution is one of the biggest man-made problems. Burning fossil fuels is the main factor of pollution. As average temperature increases, habitats, species and people are threatened by drought, changes in rainfall, altered seasons, and more violent storms and floods. Indeed the life cycle of nuclear power results in relatively little pollution. Energy efficiency, solar, wind and other renewable fuels are other weapons against global warming . Human activity, primarily burning fossil fuels, is the major driving factor in global warming . Curtailing the release of carbon dioxide into the atmosphere by reducing use of oil, gasoline, coal and employment of alternate energy, sources are the tools for keeping global warming under control. global warming can be slowed and stopped, with practical actions thal yield a cleaner, healthier atmosphere

Effects of recent warm and cold spells on European plant phenology

Science.gov (United States)

Menzel, A.; Estrella, N.; Seifert, H.

2009-04-01

Numerous studies have concurrently documented a progressively earlier start for vegetation activity in spring and a lengthening of the growing season during the last 2 to 5 decades in the temperate northern hemisphere. In contrast to climatic factors influencing autumn phenology, the climate signal controlling spring and summer phenology is fairly well understood: nearly all phenophases correlate with temperatures in the preceding 1 to 3 months. The changes currently experienced by emergence of vegetation may reach 6 to 8 d per °C. But how will this well-known, often linearly described relationship change in case of more frequent and more stronger temperature extremes? We thus studied the temperature response of European phenological records to cold and warm spells using the COST725 data base (www.cost725.org). We restricted our analysis to the time period 1951-2006 due to the relatively better coverage of Europe by phenological records. Up to now, 20 European countries contributed more than 7 Mio. phenological observations to this data base including 64 species and 22 different phases. The phenological observations compiled originated from different sources and phenological networks. Unfortunately there is no entire coverage and the data are very lumped. Cold and warm spells were identified using daily mean temperature data (1951-2006) on a 0.5° grid for Europe provided by the EU-FP6 project ENSEMBLES (http://www.ensembles-eu.org, http://eca.knmi.nl). The study area covered Europe and was limited to 40°E. For the whole study period, mean monthly and seasonal mean temperatures well as the corresponding standard deviations were calculated for each grid point. The annual monthly or seasonal temperature at a grid point was defined as cold (very cold, warm, very warm) by its deviation from the long-term average (more than 1.5 or 3sd, respectively). Warm and cold spells were selected when either the percentages of crossing 1.5sd were greater than 50% for the total

Effects of global warming on ancient mammalian communities and their environments.

Directory of Open Access Journals (Sweden)

Larisa R G DeSantis

2009-06-01

Full Text Available Current global warming affects the composition and dynamics of mammalian communities and can increase extinction risk; however, long-term effects of warming on mammals are less understood. Dietary reconstructions inferred from stable isotopes of fossil herbivorous mammalian tooth enamel document environmental and climatic changes in ancient ecosystems, including C(3/C(4 transitions and relative seasonality.Here, we use stable carbon and oxygen isotopes preserved in fossil teeth to document the magnitude of mammalian dietary shifts and ancient floral change during geologically documented glacial and interglacial periods during the Pliocene (approximately 1.9 million years ago and Pleistocene (approximately 1.3 million years ago in Florida. Stable isotope data demonstrate increased aridity, increased C(4 grass consumption, inter-faunal dietary partitioning, increased isotopic niche breadth of mixed feeders, niche partitioning of phylogenetically similar taxa, and differences in relative seasonality with warming.Our data show that global warming resulted in dramatic vegetation and dietary changes even at lower latitudes (approximately 28 degrees N. Our results also question the use of models that predict the long term decline and extinction of species based on the assumption that niches are conserved over time. These findings have immediate relevance to clarifying possible biotic responses to current global warming in modern ecosystems.

Comparing and contrasting Holocene and Eemian warm periods with greenhouse-gas-induced warming

International Nuclear Information System (INIS)

MacCracken, M.C.; Kutzbach, J.

1990-01-01

Periods of the past that are estimated to have been warmer than present are of great potential interest for comparison with simulations of future climates associated with greenhouse-gas-induced warming. Certain features of the climates of the mid-Holocene and Eemian periods, both interglacial maxima, are described. The simulated climatic responses to both types of forcing, in terms of land/ocean and latitudinal averages, are also compared. The zonal average and annual (or seasonal) average radiation fluxes associated with the different-from-present orbital conditions that existed for those interglacials are compared to the radiation flux associated with CO 2 -induced warming. There are some similarities but also significant differences in the two types of radiation flux perturbations, and there are both similarities and differences in the simulated climatic responses

Holocene landscape response to seasonality of storms in the Mojave Desert

Science.gov (United States)

Miller, D.M.; Schmidt, K.M.; Mahan, S.A.; McGeehin, J.P.; Owen, L.A.; Barron, J.A.; Lehmkuhl, F.; Lohrer, R.

2010-01-01

New optically stimulated and radiocarbon ages for alluvial fan and lake deposits in the Mojave Desert are presented, which greatly improves the temporal resolution of surface processes. The new Mojave Desert climate-landscape record is particularly detailed for the late Holocene. Evidence from ephemeral lake deposits and landforms indicates times of sustained stream flow during a wet interval of the latter part of the Medieval Warm Period at ca. AD 1290 and during the Little Ice Age at ca. AD 1650. The former lakes postdate megadroughts of the Medieval Warm Period, whereas the latter match the Maunder Minimum of the Little Ice Age. Periods of alluvial fan aggradation across the Mojave Desert are 14-9 cal ka and 6-3 cal ka. This timing largely correlates to times of increased sea-surface temperatures in the Gulf of California and enhanced warm-season monsoons. This correlation suggests that sustained alluvial fan aggradation may be driven by intense summer-season storms. These data suggest that the close proximity of the Mojave Desert to the Pacific Ocean and the Gulf of California promotes a partitioning of landscape-process responses to climate forcings that vary with seasonality of the dominant storms. Cool-season Pacific frontal storms cause river flow, ephemeral lakes, and fan incision, whereas periods of intense warm-season storms cause hillslope erosion and alluvial fan aggradation. The proposed landscape-process partitioning has important implications for hazard mitigation given that climate change may increase sea-surface temperatures in the Gulf of California, which indirectly could increase future alluvial fan aggradation.

Evaluation of Warm Season Turfgrass under Different Irrigation Regimes in Arid Region

Directory of Open Access Journals (Sweden)

Abdullah Mohd Hassan ALSHEHHI

2010-09-01

Full Text Available Turfgrasses play a very important role in enhancing quality of life in modern urban living. Water quantity is the most important challenge worldwide in establishing and maintaining quality turf. The present study was aimed to test the performance of three warm season turfgrasses under four water levels for plantation in arid zones. Pits (48 measuring 1m length x 1m width x 0.6 m depth were planted with four replications of Common Bermuda grass (Cynodon dactylon, Tifway Bermuda grass (Cynodon dactylon x transvaalensis and Seashore Paspalum grass (Paspalum vaginatum in complete randomized design (CRD. Irrigation was done daily with 15 l/plot during the first 4 weeks (establishment period and four irrigation levels (5, 10, and 15, 20 l/lot were maintained in the following 8 weeks (treatment period. Physical parameters (canopy temperatures, ambient temperature, leaf area, shoot production and relative water content were measured once in two week as well as the visual quality (shoot color, shoot density and shoot uniformity was assessed, however, chlorophyll analysis was done in the end of the study. It was found that temperature has significant effect on performance of turfgrasses. Canopy temperature was higher than ambient temperature in the three turfgrasses but it has different level in each variety. Five liter of water per day per square meter gave acceptable turf quality when ambient temperature ranged from 20 to 33�C. Seashore paspalum performed best followed by Tifway Bermuda grass and common Bermuda grass respectively.

Specific immunotherapy has long-term preventive effect of seasonal and perennial asthma

DEFF Research Database (Denmark)

Jacobsen, L; Niggemann, B; Dreborg, S

2007-01-01

BACKGROUND: 3-year subcutaneous specific immunotherapy (SIT) in children with seasonal allergic rhinoconjunctivitis reduced the risk of developing asthma during treatment and 2 years after discontinuation of SIT (5-year follow-up) indicating long-term preventive effect of SIT. OBJECTIVE: We......: Specific immunotherapy has long-term clinical effects and the potential of preventing development of asthma in children with allergic rhino conjunctivitis up to 7 years after treatment termination....

Supporting Agricultural Ecosystem Services through the Integration of Perennial Polycultures into Crop Rotations

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Peter Weißhuhn

2017-12-01

Full Text Available This review analyzes the potential role and long-term effects of field perennial polycultures (mixtures in agricultural systems, with the aim of reducing the trade-offs between provisioning and regulating ecosystem services. First, crop rotations are identified as a suitable tool for the assessment of the long-term effects of perennial polycultures on ecosystem services, which are not visible at the single-crop level. Second, the ability of perennial polycultures to support ecosystem services when used in crop rotations is quantified through eight agricultural ecosystem services. Legume–grass mixtures and wildflower mixtures are used as examples of perennial polycultures, and compared with silage maize as a typical crop for biomass production. Perennial polycultures enhance soil fertility, soil protection, climate regulation, pollination, pest and weed control, and landscape aesthetics compared with maize. They also score lower for biomass production compared with maize, which confirms the trade-off between provisioning and regulating ecosystem services. However, the additional positive factors provided by perennial polycultures, such as reduced costs for mineral fertilizer, pesticides, and soil tillage, and a significant preceding crop effect that increases the yields of subsequent crops, should be taken into account. However, a full assessment of agricultural ecosystem services requires a more holistic analysis that is beyond the capabilities of current frameworks.

Exploring the Factors Driving Seasonal Farmland Abandonment: A Case Study at the Regional Level in Hunan Province, Central China

Directory of Open Access Journals (Sweden)

Zhonglei Yu

2017-01-01

Full Text Available Farmland abandonment, including perennial and seasonal abandonment, is an important process of land use change that matters most to food security. Although there is a great deal of studies on farmland abandonment, seasonal abandonment, which is as serious as perennial abandonment, has attracted little academic attention. This paper takes Hunan Province in central China as its study area and uses a spatial regression model to examine the driving factors of seasonal farmland abandonment at the county level. Our results show that farmland abandonment has striking spatial relativity, and there are two clustering zones with a high index of farmland abandonment (IFA in the Dongting plain and the basin in south-central Hunan, while a clustering zone of low IFA can be found in the mountains of southwest Hunan. Farmland abandonment at the regional level is negatively affected by the land productive potentialities, proportion of mechanized planting, ratio of effective irrigation, and distance to provincial capital, while it is positively associated with the variables mountainous terrain, per capita farmland area, and labor shortage. Additionally, farmland abandonment is also affected by adjacent areas through its spatial dependence. In short, seasonal farmland abandonment is also driven integratedly by the socioeconomic and environmental dimensions and spatial interaction of farm abandonment.

Totally impermeable film (TIF reduces emissions in perennial crop fumigation

Directory of Open Access Journals (Sweden)

Suduan Gao

2013-10-01

Full Text Available Many perennial nursery fields and replanted orchards and vineyards in California are treated with preplant soil fumigants to control soilborne pests. In annual crops, such as strawberry, covering fumigated fields with totally impermeable film (TIF has shown promise in controlling emissions and improving fumigant distribution in soil. The objective of this research was to optimize the use of TIF for perennial crops via three field trials. TIF reduced peak emission flux and cumulative emissions by > 90% relative to polyethylene tarp during a 2-week covering period. After the TIF was cut, emissions were greatly reduced compared to when tarps were cut after 6 days. TIF maintained higher fumigant concentrations under tarp and in the soil than polyethylene film. The results indicate that TIF can increase fumigation efficiency for perennial crop growers.

Development of new techniques of using irradiation in the genetic improvement of warm season grasses, the assessment of their genetic and cytogenetic effects and biomass production from grass. Annual progress report, November 1, 1979 to October 31, 1980

International Nuclear Information System (INIS)

Burton, G.W.; Hanna, W.W.

1980-01-01

New techniques are described for using irradiation and chemical mutagens in the genetic improvement of several warm season grasses. Genetic and cytogenetic effects of these treatments are also being studied

Adaptive management of perennial pepperweed for endangered specias and tidal marsh recovery

Science.gov (United States)

Perennial pepperweed has invaded a wide range of habitat types in the far west. In the San Francisco Estuary, dense infestations have impacted sensitive tidal wetlands and compromised endangered species recovery efforts. An adaptive management effort to reduce perennial pepperweed was initiated by...

Seasonal Changes in Central England Temperatures

DEFF Research Database (Denmark)

Proietti, Tommaso; Hillebrand, Eric

The aim of this paper is to assess how climate change is reflected in the variation of the seasonal patterns of the monthly Central England Temperature time series between 1772 and 2013. In particular, we model changes in the amplitude and phase of the seasonal cycle. Starting from the seminal work...... by Thomson (“The Seasons, Global Temperature and Precession”, Science, 7 April 1995, vol 268, p. 59–68), a number of studies have documented a shift in the phase of the annual cycle implying an earlier onset of the spring season at various European locations. A significant reduction in the amplitude...... and stochastic trends, as well as seasonally varying autocorrelation and residual variances. The model can be summarized as containing a permanent and a transitory component, where global warming is captured in the permanent component, on which the seasons load differentially. The phase of the seasonal cycle...

Anthropogenic Warming Impacts on Today's Sierra Nevada Snowpack and Flood Severity

Science.gov (United States)

Huang, X.; Hall, A. D.; Berg, N.

2017-12-01

Focusing on this recent extreme wet year over California, this study investigates the warming impacts on the snowpack and the flood severity over the Sierra Nevada (SN), where the majority of the precipitation occurs during the winter season and early spring. One of our goals is to quantify anthropogenic warming impacts on the snow water equivalent (SWE) including recent historical warming and prescribed future projected warming scenarios; This work also explores to what extent flooding risk has increased under those warming cases. With a good representation of the historical precipitation and snowpack over the Sierra Nevada from the historical reference run at 9km (using WRF), the results from the offline Noah-MP simulations with perturbed near-surface temperatures reveal magnificent impacts of warming to the loss of the average snowpack. The reduction of the SWE under warming mainly results from the decreased rain-to-snow conversion with a weaker effect from increased snowmelt. Compared to the natural case, the past industrial warming decreased the maximum SWE by about one-fifth averaged over the study area. Future continuing warming can result in around one-third reduction of current maximum SWE under RCP4.5 emissions scenario, and the loss can reach to two-thirds under RCP8.5 as a "business-as-usual" condition. The impact of past warming is particularly outstanding over the North SN region where precipitation dominates and over the middle elevation regions where the snow mainly distributes. In the future, the warming impact on SWE progresses to higher regions, and so to the south and east. Under the business-as-usual scenario, the projected mid-elevation snowpack almost disappears by April 1st with even high-elevation snow reduced by about half. Along with the loss of the snowpack, as the temperature warms, floods can also intensify with increased early season runoff especially under heavy-rainy days caused by the weakened rain-to-snow processes and

Environmental DNA (eDNA) Detection Probability Is Influenced by Seasonal Activity of Organisms.

Science.gov (United States)

de Souza, Lesley S; Godwin, James C; Renshaw, Mark A; Larson, Eric

2016-01-01

Environmental DNA (eDNA) holds great promise for conservation applications like the monitoring of invasive or imperiled species, yet this emerging technique requires ongoing testing in order to determine the contexts over which it is effective. For example, little research to date has evaluated how seasonality of organism behavior or activity may influence detection probability of eDNA. We applied eDNA to survey for two highly imperiled species endemic to the upper Black Warrior River basin in Alabama, US: the Black Warrior Waterdog (Necturus alabamensis) and the Flattened Musk Turtle (Sternotherus depressus). Importantly, these species have contrasting patterns of seasonal activity, with N. alabamensis more active in the cool season (October-April) and S. depressus more active in the warm season (May-September). We surveyed sites historically occupied by these species across cool and warm seasons over two years with replicated eDNA water samples, which were analyzed in the laboratory using species-specific quantitative PCR (qPCR) assays. We then used occupancy estimation with detection probability modeling to evaluate both the effects of landscape attributes on organism presence and season of sampling on detection probability of eDNA. Importantly, we found that season strongly affected eDNA detection probability for both species, with N. alabamensis having higher eDNA detection probabilities during the cool season and S. depressus have higher eDNA detection probabilities during the warm season. These results illustrate the influence of organismal behavior or activity on eDNA detection in the environment and identify an important role for basic natural history in designing eDNA monitoring programs.

Microbial biomass dynamics dominate N cycle responses to warming in a sub-arctic peatland

Science.gov (United States)

Weedon, J. T.; Aerts, R.; Kowalchuk, G. K.; van Bodegom, P. M.

2012-04-01

The balance of primary production and decomposition in sub-arctic peatlands may shift with climate change. Nitrogen availability will modulate this shift, but little is known about the drivers of soil nitrogen dynamics in these environments, and how they are influenced by rising soil temperatures. We used a long-term open top chamber warming experiment in Abisko, Sweden, to test for the interactive effects of spring warming, summer warming and winter snow addition on soil organic and inorganic nitrogen fluxes, potential activities of carbon and nitrogen cycle enzymes, and the structure of the soil-borne microbial communities. Summer warming increased the flux of soil organic nitrogen over the growing season, while simultaneously causing a seasonal decrease in microbial biomass, suggesting that N flux is driven by large late-season dieback of microbes. This change in N cycle dynamics was not reflected in any of the measured potential enzyme activities. Moreover, the soil microbial community structure was stable across treatments, suggesting non-specific microbial dieback. To further test whether the observed patterns were driven by direct temperature effects or indirect effects (via microbial biomass dynamics), we conducted follow-up controlled experiments in soil mesocosms. Experimental additions of dead microbial cells had stronger effects on N pool sizes and enzyme activities than either plant litter addition or a 5 °C alteration in incubation temperatures. Peat respiration was positively affected by both substrate addition and higher incubation temperatures, but the temperature-only effect was not sufficient to account for the increases in respiration observed in previous field experiments. We conclude that warming effects on peatland N cycling (and to some extent C cycling) are dominated by indirect effects, acting through alterations to the seasonal flux of microbe-derived organic matter. We propose that climate change models of soil carbon and nitrogen

The changing seasonal climate in the Arctic.

Science.gov (United States)

Bintanja, R; van der Linden, E C

2013-01-01

Ongoing and projected greenhouse warming clearly manifests itself in the Arctic regions, which warm faster than any other part of the world. One of the key features of amplified Arctic warming concerns Arctic winter warming (AWW), which exceeds summer warming by at least a factor of 4. Here we use observation-driven reanalyses and state-of-the-art climate models in a variety of standardised climate change simulations to show that AWW is strongly linked to winter sea ice retreat through the associated release of surplus ocean heat gained in summer through the ice-albedo feedback (~25%), and to infrared radiation feedbacks (~75%). Arctic summer warming is surprisingly modest, even after summer sea ice has completely disappeared. Quantifying the seasonally varying changes in Arctic temperature and sea ice and the associated feedbacks helps to more accurately quantify the likelihood of Arctic's climate changes, and to assess their impact on local ecosystems and socio-economic activities.

Bacterial endophytes of perennial crops for management of plant disease

OpenAIRE

Melnick, Rachel L.; Bailey, B.A.; Backman, Paul A.

2013-01-01

Metadata only record Bacterial endophytes, microorganisms which inhabit the internal tissues of plants, can suppress disease and are often used as a biological control in annual crops. Less research, however, has been applied to the use of bacterial endophytes to prevent disease in perennial crops, which presents a more complex challenge. However, exploration of their potential as a biological control in perennial crops has been limited. This chapter assembles current knowledge on the subj...

The perennial ryegrass GenomeZipper: targeted use of genome resources for comparative grass genomics.

Science.gov (United States)

Pfeifer, Matthias; Martis, Mihaela; Asp, Torben; Mayer, Klaus F X; Lübberstedt, Thomas; Byrne, Stephen; Frei, Ursula; Studer, Bruno

2013-02-01

Whole-genome sequences established for model and major crop species constitute a key resource for advanced genomic research. For outbreeding forage and turf grass species like ryegrasses (Lolium spp.), such resources have yet to be developed. Here, we present a model of the perennial ryegrass (Lolium perenne) genome on the basis of conserved synteny to barley (Hordeum vulgare) and the model grass genome Brachypodium (Brachypodium distachyon) as well as rice (Oryza sativa) and sorghum (Sorghum bicolor). A transcriptome-based genetic linkage map of perennial ryegrass served as a scaffold to establish the chromosomal arrangement of syntenic genes from model grass species. This scaffold revealed a high degree of synteny and macrocollinearity and was then utilized to anchor a collection of perennial ryegrass genes in silico to their predicted genome positions. This resulted in the unambiguous assignment of 3,315 out of 8,876 previously unmapped genes to the respective chromosomes. In total, the GenomeZipper incorporates 4,035 conserved grass gene loci, which were used for the first genome-wide sequence divergence analysis between perennial ryegrass, barley, Brachypodium, rice, and sorghum. The perennial ryegrass GenomeZipper is an ordered, information-rich genome scaffold, facilitating map-based cloning and genome assembly in perennial ryegrass and closely related Poaceae species. It also represents a milestone in describing synteny between perennial ryegrass and fully sequenced model grass genomes, thereby increasing our understanding of genome organization and evolution in the most important temperate forage and turf grass species.

Seasonal Variations in Color Preference.

Science.gov (United States)

Schloss, Karen B; Nelson, Rolf; Parker, Laura; Heck, Isobel A; Palmer, Stephen E

2017-08-01

We investigated how color preferences vary according to season and whether those changes could be explained by the ecological valence theory (EVT). To do so, we assessed the same participants' preferences for the same colors during fall, winter, spring, and summer in the northeastern United States, where there are large seasonal changes in environmental colors. Seasonal differences were most pronounced between fall and the other three seasons. Participants liked fall-associated dark-warm colors-for example, dark-red, dark-orange (brown), dark-yellow (olive), and dark-chartreuse-more during fall than other seasons. The EVT could explain these changes with a modified version of Palmer and Schloss' (2010) weighted affective valence estimate (WAVE) procedure that added an activation term to the WAVE equation. The results indicate that color preferences change according to season, as color-associated objects become more/less activated in the observer. These seasonal changes in color preferences could not be characterized by overall shifts in weights along cone-contrast axes. Copyright © 2016 Cognitive Science Society, Inc.

Cold-season solar input and ambivalent thermal behavior brought by climber greenwalls

International Nuclear Information System (INIS)

Jim, C.Y.

2015-01-01

Most greenwall studies focus on cooling and energy conservation in the warm season, and tropical cold-season has received little attention. This field-experimental study in humid-subtropical Hong Kong evaluated winter thermal behavior of climber greenwalls. Orientation and weather factors regulated solar-irradiation regimes with critical impact on vegetation thermal responses. Temperature differentiation occurred mainly on sunny day, with subdued variations on cloudy and rainy days. The south greenwall on sunny day received the highest solar-energy input, bringing divergent surface temperature in three climber species. The daytime descending cooling sequence was: Control-air > Pyrostegia venusta > Bauhinia corymbosa > Ficus pumila > Control-surface. Heat-sink effect related to foliage-thickness and moisture-content influenced climber thermal responses. Exceeding a solar-irradiance threshold of 500 Wm"−"2 was a prerequisite for notable solar-warming and transpiration-cooling, bringing well-differentiated climber-surface temperature. Cooling of vegetation-surface and Anterior-ambient-air was contrasted by warming behind the greenwall. Posterior-airgap with trapped stagnant air and Posterior-concrete-surface were warmed consistently above control concrete-surface on sunny and cloudy days. This winter passive warming mechanism denotes a new dimension in thermal benefits operating behind the greenwall. The thermal-gradient can transmit heat into indoor space, with benefits on human comfort, health and energy conservation. - Highlights: • Cold-season thermal regimes and benefits of climber greenwalls in tropics was studied. • Greenwall plots were installed as a field-experiment to evaluated six related factors. • Descending cooling sequence: Pyrostegia venusta > Bauhinia corymbosa > Ficus pumila. • Solar radiation intensity and foliage heat-sink effect determined climber cooling. • Posterior airgap and Posterior concrete-surface were warmed to provide indoor

Birth seasonality and offspring production in threatened neotropical primates related to climate

Science.gov (United States)

Wiederholt, R.; Post, E.

2011-01-01

Given the threatened status of many primate species, the impacts of global warming on primate reproduction and, consequently, population growth should be of concern. We examined relations between climatic variability and birth seasonality, offspring production, and infant sex ratios in two ateline primates, northern muriquis, and woolly monkeys. In both species, the annual birth season was delayed by dry conditions and El Ni??o years, and delayed birth seasons were linked to lower birth rates. Additionally, increased mean annual temperatures were associated with lower birth rates for northern muriquis. Offspring sex ratios varied with climatic conditions in both species, but in different ways: directly in woolly monkeys and indirectly in northern muriquis. Woolly monkeys displayed an increase in the proportion of males among offspring in association with El Ni??o events, whereas in northern muriquis, increases in the proportion of males among offspring were associated with delayed onset of the birth season, which itself was related, although weakly, to warm, dry conditions. These results illustrate that global warming, increased drought frequency, and changes in the frequency of El Ni??o events could limit primate reproductive output, threatening the persistence and recovery of ateline primate populations. ?? 2011 Blackwell Publishing Ltd.

Inter-simple sequence repeat (ISSR) loci mapping in the genome of perennial ryegrass

DEFF Research Database (Denmark)

Pivorienė, O; Pašakinskienė, I; Brazauskas, G

2008-01-01

The aim of this study was to identify and characterize new ISSR markers and their loci in the genome of perennial ryegrass. A subsample of the VrnA F2 mapping family of perennial ryegrass comprising 92 individuals was used to develop a linkage map including inter-simple sequence repeat markers...... demonstrated a 70% similarity to the Hordeum vulgare germin gene GerA. Inter-SSR mapping will provide useful information for gene targeting, quantitative trait loci mapping and marker-assisted selection in perennial ryegrass....

Development of new techniques of using irradiation in the genetic improvement of warm season grasses and an assessment of the genetic and cytogenetic effects. Annual report, August 1, 1976--October 31, 1977

International Nuclear Information System (INIS)

Burton, G.W.; Hanna, W.W.

1977-08-01

New techniques of using irradiation in the genetic improvement of several warm season grasses are described. The economic value of radiation induced plant mutants and the genetic and cytogenetic effects of these treatments are discussed. Alterations in protein quality in pearl millet grain and improved varieties of Bermuda grass following radiation treatment are reported

Perennial Pepperweed Patches - San Francisco Estuary [ds295

Data.gov (United States)

California Natural Resource Agency — This layer contains polygon data for the perennial pepperweed (Lepidium latifolium) database. This database represents distribution data collected within the areas...

Herbaceous energy crops in humid lower South USA

Energy Technology Data Exchange (ETDEWEB)

Prine, G.M.; Woodard, K.R. [Univ. of Florida, Gainesville, FL (United States)

1993-12-31

The humid lower South has the long warm growing season and high rainfall conditions needed for producing high-yielding perennial herbaceous grasses and shrubs. Many potential biomass plants were evaluated during a ten-year period. Perennial tall grasses such as elephantgrass (Pennisetum purpureum), sugarcane and energycane (Saccharum spp.) and the leguminous shrub Leucaena leucocephala were the highest in biomass production. These perennial crops often have top growth killed by winter freezes and regenerate from underground parts. The tall grasses have high yields because of linear crop growth rates of 18 to 27 g m{sup 2} d{sup {minus}1} for long periods (140 to 196 d) each season. Tall grasses must be planted vegetatively, which is more costly than seed propagation, however, once established, they may persist for many seasons. Oven dry biomass yields have varied from 20 to 45 Mg ha{sup {minus}1} yr{sup {minus}1} in colder subtropical to mild temperate locations to over 60 Mg ha{sup {minus}1} yr{sup {minus}1} in the lower portion of the Florida peninsular. Highest biomass yields have been produced when irrigated with sewage effluent or when grown on phosphatic clay and muck soils in south Florida. The energy content of 1 Mg of oven dry tall grass and leucaena is equivalent to that of about 112 and 123 gallons of number 2 diesel fuel, respectively.

Soil water status under perennial and annual pastures on an acid duplex soil

International Nuclear Information System (INIS)

Heng, L.K.; White, R.E.; Chen, D.

2000-01-01

A comprehensive field study of soil water balance, nitrogen (N) cycling, pasture management and animal production was carried out on an acid duplex soil at Book Book near Wagga Wagga in southern New South Wales. The experiment, carried out over a 3-year period, tested the hypothesis that sown perennial grass pastures improve the sustainability of a grazing system through better use of water and N. The treatments were: annual pastures without lime (AP-), annual pastures with lime (AP+), perennial pastures without lime (PP-) and perennial pastures with lime (PP+). Soil water measurement was made using a neutron probe on one set of the treatments comprising four adjacent paddocks. Over three winter and spring periods, the results showed that perennial grass pastures, especially PP+, consistently extracted about 40 mm more soil water each year than did the annual grass pastures. As a result, surface runoff, sub-surface flow and deep drainage (percolation below 180 cm depth) were about 40 mm less from the perennial pastures. The soil water status of the four pasture treatments was simulated reasonably well using a simple soil water model. Together with the long-term simulation of deep drainage, using past meteorological records, it is shown that proper management of perennial pastures can reduce recharge to groundwater and make pastoral systems more sustainable in the high rainfall zone. However, to completely reduce recharge, more-deeply rooted plants or trees are needed. (author)

Investigation on seasonal variation of thermal-induced strain in flexible pavements based on field and laboratory measurements

Directory of Open Access Journals (Sweden)

Simita Biswas

2016-09-01

Full Text Available Pavement temperature variation has a large influence on the structural response of flexible pavements. Daily and seasonal temperature fluctuation causes expansion and contraction of pavement material, which then leads to the generation of thermal strain. In this study, field observation and laboratory tests were conducted to investigate seasonal variation of thermal-induced strain in flexible pavement. Field observations were conducted at the Integrated Road Research Facility (IRRF’s test road in Edmonton, Alberta, Canada, which is fully equipped with structural and environmental monitoring instruments. The main objective of the field study was to compare the variation of thermal-induced strain in warm and cold seasons. Field results indicated that thermal-induced strain is 1.4–2.0 times greater in cold seasons than in warm seasons following the same pavement temperature variations; however, strain generation rate was greater in warm seasons. Laboratory testing of asphalt slab and cylindrical samples produced comparable ratios. Moreover, field observation and laboratory testing showed a similar trend of temperature and thermal strain variations. Keywords: Thermal-induced strain, Asphalt strain gauge, Field observation, Flexible pavement, Laboratory testing, Seasonal variation

Evaporite deposition in a shallow perennial lake, Qaidam basin, western China

Energy Technology Data Exchange (ETDEWEB)

Schubel, K.A.; Lowenstein, T.K. (SUNY, Binghampton, NY (United States)); Spencer, R.J. (Univ. of Calgary, Alberta (Canada)); Pengxi, Z. (Institute of Salt Lakes, Xining (China))

1991-03-01

Evaporites accumulate in ephemeral saline-pans, shallow perennial lakes or lagoons, and deep perennial systems. Continuous brine trench exposures of Holocene evaporites from the Qaidam basin provide criteria for the recognition of shallow perennial lake sediments. Based on Landsat photographs, lateral extent of beds (at least 7 km), and sequence thicknesses (maximum 2.5 m), the paleolake is interpreted to have been less than 2.5 m deep and at least 120 km{sup 2} in area. Sediments consist of laminated siliciclastic mud overlain by mud-halite couplets (mm- to cm-scale layers), which represent one vertical shallowing- and concentrating-upwards sequence. The basal laminite marks the onset of deposition in this shallow perennial paleolake. Syndepositional halite textures and fabrics in the overlying mud-halite couplets include cumulates, rafts, and chevrons, draped by mud laminae, and halite layers truncated by horizontal dissolution surfaces (increasing in frequency upwards). Paleolake brines, determined from fluid inclusion melting temperatures, are Na-Mg-Cl-rich and evolve from 0.84 m Mg{sup 2} to 1.52 m Mg{sup 2+} (near the surface). Combinations of the following criteria may be used for the recognition of shallow, nonstratified, perennial lake sediments: lateral continuity of layers; muds undisrupted by subaerial exposure; vertical bottom-growth of halite; halite layers conformably overlain by mud; halite layers truncated by nonuniformly spaced horizontal dissolution surfaces; erosional scours and channels filled with cross-laminated gypsum, halite, and siliciclastic sand and mud; and salinity fluctuations over small stratigraphic intervals within an overall concentrating-upwards sequence.

0-6613 : evaluate binder and mixture aging for warm mix asphalt.

Science.gov (United States)

2013-08-01

Warm mix asphalt (WMA) technologies employ reduced : mixing and placement temperatures, thereby allowing : reduced fuel consumption, enhanced compaction, : increased haul distances, and an extended paving : season. However, there have been issues of ...

Scaling Potential Evapotranspiration with Greenhouse Warming (Invited)

Science.gov (United States)

Scheff, J.; Frierson, D. M.

2013-12-01

Potential evapotranspiration (PET) is a supply-independent measure of the evaporative demand of a terrestrial climate, of basic importance in climatology, hydrology, and agriculture. Future increases in PET from greenhouse warming are often cited as key drivers of global trends toward drought and aridity. The present work computes recent and business-as-usual-future Penman-Monteith (i.e. physically-based) PET fields at 3-hourly resolution in 14 modern global climate models. The %-change in local annual-mean PET over the upcoming century is almost always positive, modally low double-digit in magnitude, usually increasing with latitude, yet quite divergent between models. These patterns are understood as follows. In every model, the global field of PET %-change is found to be dominated by the direct, positive effects of constant-relative-humidity warming (via increasing vapor pressure deficit and increasing Clausius-Clapeyron slope.) This direct-warming term very accurately scales as the PET-weighted (warm-season daytime) local warming, times 5-6% per degree (related to the Clausius-Clapeyron equation), times an analytic factor ranging from about 0.25 in warm climates to 0.75 in cold climates, plus a small correction. With warming of several degrees, this product is of low double-digit magnitude, and the strong temperature dependence gives the latitude dependence. Similarly, the inter-model spread in the amount of warming gives most of the spread in this term. Additional spread in the total change comes from strong disagreement on radiation, relative-humidity, and windspeed changes, which make smaller yet substantial contributions to the full PET %-change fields.

Linkage Between Hourly Precipitation Events and Atmospheric Temperature Changes over China during the Warm Season

Science.gov (United States)

Miao, Chiyuan; Sun, Qiaohong; Borthwick, Alistair G. L.; Duan, Qingyun

2016-01-01

We investigated changes in the temporospatial features of hourly precipitation during the warm season over mainland China. The frequency and amount of hourly precipitation displayed latitudinal zonation, especially for light and moderate precipitation, which showed successive downward change over time in northeastern and southern China. Changes in the precipitation amount resulted mainly from changes in frequency rather than changes in intensity. We also evaluated the linkage between hourly precipitation and temperature variations and found that hourly precipitation extreme was more sensitive to temperature than other categories of precipitation. A strong dependency of hourly precipitation on temperature occurred at temperatures colder than the median daily temperature; in such cases, regression slopes were greater than the Clausius-Clapeyron (C-C) relation of 7% per degree Celsius. Regression slopes for 31.6%, 59.8%, 96.9%, and 99.1% of all stations were greater than 7% per degree Celsius for the 75th, 90th, 99th, and 99.9th percentiles for precipitation, respectively. The mean regression slopes within the 99.9th percentile of precipitation were three times the C-C rate. Hourly precipitation showed a strong negative relationship with daily maximum temperature and the diurnal temperature range at most stations, whereas the equivalent correlation for daily minimum temperature was weak. PMID:26931350

[Effects of diurnal warming on soil N2O emission in soybean field].

Science.gov (United States)

Hu, Zheng-Hua; Zhou, Ying-Ping; Cui, Hai-Ling; Chen, Shu-Tao; Xiao, Qi-Tao; Liu, Yan

2013-08-01

To investigate the impact of experimental warming on N2O emission from soil of soybean field, outdoor experiments with simulating diurnal warming were conducted, and static dark chamber-gas chromatograph method was used to measure N2O emission fluxes. Results indicated that: the diurnal warming did not change the seasonal pattern of N2O emissions from soil. In the whole growing season, comparing to the control treatment (CK), the warming treatment (T) significantly enhanced the N2O flux and the cumulative amount of N2O by 17.31% (P = 0.019), and 20.27% (P = 0.005), respectively. The significant correlations were found between soil N2O emission and soil temperature, moisture. The temperature sensitivity values of soil N2O emission under CK and T treatments were 3.75 and 4.10, respectively. In whole growing stage, T treatment significantly increased the crop aboveground and total biomass, the nitrate reductase activity, and total nitrogen in leaves, while significantly decreased NO3(-) -N content in leaves. T treatment significantly increased soil NO3(-) -N content, but had no significant effect on soil organic carbon and total nitrogen contents. The results of this study suggested that diurnal warming enhanced N2O emission from soil in soybean field.

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.

Root proliferation in native perennial grasses of arid Patagonia, Argentina

Institute of Scientific and Technical Information of China (English)

Yanina A. TORRES; Mara M. MUJICA; Sandra S. BAIONI; Jos ENTO; Mara N. FIORETTI; Guillermo TUCAT; Carlos A. BUSSO; Oscar A. MONTENEGRO; Leticia ITHURRART; Hugo D. GIORGETTI; Gustavo RODRGUEZ; Diego BENTIVEGNA; Roberto E. BREVEDAN; Osvaldo A. FERNNDEZ

2014-01-01

Pappophorum vaginatum is the most abundant C4 perennial grass desirable to livestock in rangelands of northeastern Patagonia, Argentina. We hypothesized that (1) defoliation reduce net primary productivity, and root length density and weight in the native species, and (2) root net primary productivity, and root length density and weight, are greater in P. vaginatum than in the other, less desirable, native species (i.e., Aristida spegazzinii, A. subulata and Sporobolus cryptandrus). Plants of all species were either exposed or not to a severe defoliation twice a year during two growing seasons. Root proliferation was measured using the cylinder method. Cylindrical, iron structures, wrapped up using nylon mesh, were buried diagonally from the periphery to the center on individual plants. These structures, initially filled with soil without any organic residue, were dug up from the soil on 25 April 2008, after two successive defoliations in mid-spring 2007. During the second growing season (2008-2009), cylinders were destructively harvested on 4 April 2009, after one or two defoliations in mid-and/or late-spring, respectively. Roots grown into the cylinders were obtained after washing the soil manually. Defoliation during two successive years did reduce the study variables only after plants of all species were defoliated twice, which supported the first hypothesis. The greater root net primary productivity, root length den-sity and weight in P. vaginatum than in the other native species, in support of the second hypothesis, could help to explain its greater abundance in rangelands of Argentina.

Seasonal soil moisture patterns in contrasting habitats in the Willamette Valley, Oregon

Science.gov (United States)

Changing seasonal soil moisture regimes caused by global warming may alter plant community composition in sensitive habitats such as wetlands and oak savannas. To evaluate such changes, an understanding of typical seasonal soil moisture regimes is necessary. The primary objective...

Perennial wheat lines have highly admixed population structure and elevated rates of outcrossing.

Science.gov (United States)

Perennial wheat has been proposed to alleviate long standing issues with soil erosion in annual cropping systems, while supporting rural communities and providing grain farmers with a marketable climate-resilient crop. The Washington State University perennial wheat breeding program has created sev...

Perennial ryegrass for dairy cows: effects of cultivar on herbage intake during grazing

NARCIS (Netherlands)

Smit, H.J.

2005-01-01

Keywords:Perennial ryegrass, Lolium perenne , sward morphology, sward cutting, n-alkanes, herbage intake, selection, preference.Perennial ryegrass ( Lolium perenne L.) is the most important species for feeding dairy cows. The majority of the farmers in the Netherlands graze their

Seasonal and inter-annual temperature variability in the bottom waters over the western Black Sea shelf

Directory of Open Access Journals (Sweden)

G. I. Shapiro

2011-09-01

Full Text Available Long-term changes in the state of the Bottom Shelf Water (BSW on the Western shelf of the Black Sea are assessed using analysis of intra-seasonal and inter-annual temperature variations. For the purpose of this study the BSW is defined as such shelf water mass between the seabed and the upper mixed layer (bounded by the σ_θ = 14.2 isopycnal which has limited ability to mix vertically with oxygen-rich surface waters during the warm season due to formation of a seasonal pycnocline. A long-term time series of temperature anomalies in the BSW is constructed from in-situ observations taken over the 2nd half of the 20th century. The BSW is shown to occupy nearly half of the shelf area during the summer stratification period (May–November.The results reveal a warm phase in the 1960s/70s, followed by a cold phase between 1985 and 1995 and a further warming after 1995. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter convection is well preserved over the following months in the deep sea, the signal of winter cooling in the BSW significantly reduces during the warm season. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. It is shown that temperature in the BSW is stronger correlated with the temperature of Cold Intermediate Waters (CIW in the deep sea than with the severity of the previous winters, thus indicating that the isopycnal exchanges with the deep sea are more important for inter-annual/inter-decadal variability of the BSW on the western Black Sea shelf than effects of winter convection on the shelf itself.

Range shifts and global warming: ecological responses of Empetrum nigrum L. to experimental warming at its northern (high Arctic) and southern (Atlantic) geographical range margin

International Nuclear Information System (INIS)

Buizer, Bert; Weijers, Stef; Van Bodegom, Peter M; Van Breda, Johan; De Korte, Maarten; Van Rijckevorsel, Jaap; Rozema, Jelte; Alsos, Inger Greve; Eidesen, Pernille Bronken

2012-01-01

Global change is expected to lead to range shifts of plant species. The ecological mechanisms underpinning these shifts are currently not well understood. Here, we compared ecological responses possibly underlying southern range contraction and northern range expansion of Empetrum nigrum, a key species in northern heathlands, which may be related to global change. We hypothesized a negative response to warming in the ‘south’ (i.e. the Netherlands) and a positive response at the northern range margin (the tundra on Svalbard). Open top chambers (OTCs) were used to simulate global warming. In the ‘south’, OTC warming caused enhanced shoot growth and growth rate, biomass increment, advanced phenology, larger and heavier berries of Empetrum, while its growing season was extended by 75 days. Under OTC warming co-occurring Calluna vulgaris also showed an increased growing season length (by 98 days) as well as increased shoot growth rate and biomass growth, plant cover and height. Still, we found no evidence for increased competitiveness relative to Empetrum. In the ‘north’, Empetrum responded with increased shoot and biomass growth, enhanced berry development and ripening to warming. These responses exceeded those of co-occurring Cassiope tetragona with the exception of its biomass response. The direct and indirect ecological responses found do not readily explain the observed northward retreat of Empetrum at the southern range margin. The direct ecological responses found at its northern range margin are, on the other hand, in line with the increased occurrences of this species on Svalbard. (letter)

Responses of Ecosystem CO2 Fluxes to Short-Term Experimental Warming and Nitrogen Enrichment in an Alpine Meadow, Northern Tibet Plateau

Science.gov (United States)

Shi, Peili; Jiang, Jing; Song, Minghua; Xiong, Dingpeng; Ma, Weiling; Fu, Gang; Zhang, Xianzhou; Shen, Zhenxi

2013-01-01

Over the past decades, the Tibetan Plateau has experienced pronounced warming, yet the extent to which warming will affect alpine ecosystems depends on how warming interacts with other influential global change factors, such as nitrogen (N) deposition. A long-term warming and N manipulation experiment was established to investigate the interactive effects of warming and N deposition on alpine meadow. Open-top chambers were used to simulate warming. N addition, warming, N addition × warming, and a control were set up. In OTCs, daytime air and soil temperature were warmed by 2.0°C and 1.6°C above ambient conditions, but soil moisture was decreased by 4.95 m3 m−3. N addition enhanced ecosystem respiration (Reco); nevertheless, warming significantly decreased Reco. The decline of Reco resulting from warming was cancelled out by N addition in late growing season. Our results suggested that N addition enhanced Reco by increasing soil N availability and plant production, whereas warming decreased Reco through lowering soil moisture, soil N supply potential, and suppression of plant activity. Furthermore, season-specific responses of Reco indicated that warming and N deposition caused by future global change may have complicated influence on carbon cycles in alpine ecosystems. PMID:24459432

A Systematic Review of Perennial Staple Crops Literature Using Topic Modeling and Bibliometric Analysis

Science.gov (United States)

2016-01-01

Research on perennial staple crops has increased in the past ten years due to their potential to improve ecosystem services in agricultural systems. However, multiple past breeding efforts as well as research on traditional ratoon systems mean there is already a broad body of literature on perennial crops. In this review, we compare the development of research on perennial staple crops, including wheat, rice, rye, sorghum, and pigeon pea. We utilized the advanced search capabilities of Web of Science, Scopus, ScienceDirect, and Agricola to gather a library of 914 articles published from 1930 to the present. We analyzed the metadata in the entire library and in collections of literature on each crop to understand trends in research and publishing. In addition, we applied topic modeling to the article abstracts, a type of text analysis that identifies frequently co-occurring terms and latent topics. We found: 1.) Research on perennials is increasing overall, but individual crops have each seen periods of heightened interest and research activity; 2.) Specialist journals play an important role in supporting early research efforts. Research often begins within communities of specialists or breeders for the individual crop before transitioning to a more general scientific audience; 3.) Existing perennial agricultural systems and their domesticated crop material, such as ratoon rice systems, can provide a useful foundation for breeding efforts, accelerating the development of truly perennial crops and farming systems; 4.) Primary research is lacking for crops that are produced on a smaller scale globally, such as pigeon pea and sorghum, and on the ecosystem service benefits of perennial agricultural systems. PMID:27213283

The Performance of Early-Generation Perennial Winter Cereals at 21 Sites across Four Continents

Directory of Open Access Journals (Sweden)

Richard C. Hayes

2018-04-01

Full Text Available A network of 21 experiments was established across nine countries on four continents and spanning both hemispheres, to evaluate the relative performance of early generation perennial cereal material derived from wheat, rye, and barley and to inform future breeding strategies. The experimental lines were grown in replicated single rows, and first year production and phenology characteristics as well as yield and persistence for up to three years were monitored. The study showed that the existing experimental material is all relatively short-lived (≤3 years, with environments that are milder in summer and winter generally conferring greater longevity. No pedigree was superior across this diverse network of sites although better performing lines at the higher latitude sites were generally derived from Thinopyrum intermedium. By contrast, at lower latitudes the superior lines were generally derived from Th. ponticum and Th. elongatum parentage. The study observed a poor relationship between year 1 performance and productivity in later years, highlighting the need for perennial cereal material with greater longevity to underpin future experimental evaluation, and the importance for breeding programs to emphasize post-year 1 performance in their selections. Hybrid lines derived from the tetraploid durum wheat generally showed greater longevity than derivatives of hexaploid wheat, highlighting potential for greater use of Triticum turgidum in perennial wheat breeding. We advocate a model in future breeding initiatives that develops perennial cereal genotypes for specific target environments rather than a generic product for one global market. These products may include a diversity of cultivars derived from locally adapted annual and perennial parents. In this scenario the breeding program may have access to only a limited range of adapted perennial grass parents. In other situations, such as at very high latitude environments, perennial crops derived

A transcriptome map of perennial ryegrass (Lolium perenne L.

Directory of Open Access Journals (Sweden)

Studer Bruno

2012-04-01

Full Text Available Abstract Background Single nucleotide polymorphisms (SNPs are increasingly becoming the DNA marker system of choice due to their prevalence in the genome and their ability to be used in highly multiplexed genotyping assays. Although needed in high numbers for genome-wide marker profiles and genomics-assisted breeding, a surprisingly low number of validated SNPs are currently available for perennial ryegrass. Results A perennial ryegrass unigene set representing 9,399 genes was used as a reference for the assembly of 802,156 high quality reads generated by 454 transcriptome sequencing and for in silico SNP discovery. Out of more than 15,433 SNPs in 1,778 unigenes fulfilling highly stringent assembly and detection parameters, a total of 768 SNP markers were selected for GoldenGate genotyping in 184 individuals of the perennial ryegrass mapping population VrnA, a population being previously evaluated for important agronomic traits. A total of 592 (77% of the SNPs tested were successfully called with a cluster separation above 0.9. Of these, 509 (86% genic SNP markers segregated in the VrnA mapping population, out of which 495 were assigned to map positions. The genetic linkage map presented here comprises a total of 838 DNA markers (767 gene-derived markers and spans 750 centi Mogan (cM with an average marker interval distance of less than 0.9 cM. Moreover, it locates 732 expressed genes involved in a broad range of molecular functions of different biological processes in the perennial ryegrass genome. Conclusions Here, we present an efficient approach of using next generation sequencing (NGS data for SNP discovery, and the successful design of a 768-plex Illumina GoldenGate genotyping assay in a complex genome. The ryegrass SNPs along with the corresponding transcribed sequences represent a milestone in the establishment of genetic and genomics resources available for this species and constitute a further step towards molecular breeding

Identification of a seasonal pattern to brain metastases

Directory of Open Access Journals (Sweden)

Sakellakis M

2016-03-01

Full Text Available Minas Sakellakis,1 Angelos Koutras,1 Maria Pittaka,2 Dimitrios Kardamakis,2 Melpomeni Kalofonou,1 Haralabos P Kalofonos,1 Despina Spyropoulou2 1Division of Oncology, Department of Medicine, 2Department of Radiation Oncology, University Hospital, Patras Medical School, Rion, Patras, GreeceWe have previously tested our hypothesis that there is a seasonality in the incidence of carcinomatous meningitis.1 Although further validation is needed in a larger cohort, we found that leptomeningeal metastasis occurred more often during warm months of the year which, in the case of Greece, is the period generally marked with the larger daytime length.1 Carcinomatous meningitis is closely related to brain metastasis, and a logical question is whether warm season is marked by a greater propensity also for brain metastasis.2 

Direct control of perennial weeds between crops - Implication for organic farming

DEFF Research Database (Denmark)

Melander, Bo; Holst, Niels; Rasmussen, Ilse Ankjær

2012-01-01

and ending the strategy with mouldboard ploughing in the succeeding spring. Grain yields did not differ among the treatments in the two experiments as a result of the generally high effectiveness exerted by the control strategies. Especially post-harvest control strategies based on rotating weed devices...... and mouldboard ploughing appear to be effective solutions against mixed stands of perennials on sandy soils but they do not comply with optimal nutrient management in organic cropping. Therefore, intensive autumn cultivation is only relevant where a perennial weed problem is uncontrollable by other means.......Perennial weeds can be a major constraint to organic crop production and direct control actions applied between crops can then be necessary to reduce the problems. We conducted two experiments, one on a sandy loam and one on a sandy soil in Denmark, with the aim of studying the efficacy...

Energy balance and cost-benefit analysis of biogas production from perennial energy crops pretreated by wet oxidation

DEFF Research Database (Denmark)

Uellendahl, Hinrich; Wang, Guangtao; Møller, Henrik B.

2008-01-01

Perennial crops need far less energy to plant, require less fertilizer and pesticides, and show a lower negative environmental impact compared with annual crops like for example corn. This makes the cultivation of perennial crops as energy crops more sustainable than the use of annual crops....... The conversion into biogas in anaerobic digestion plants shows however much lower specific methane yields for the raw perennial crops like miscanthus and willow due to their lignocellulosic structure. Without pretreatment the net energy gain is therefore lower for the perennials than for corn. When applying wet...... oxidation to the perennial crops, however, the specific methane yield increases significantly and the ratio of energy output to input and of costs to benefit for the whole chain of biomass supply and conversion into biogas becomes higher than for corn. This will make the use of perennial crops as energy...

Global warming: it's not only size that matters

Science.gov (United States)

Hegerl, Gabriele C.

2011-09-01

impacts than temperatures that have occurred frequently due to internal climate variability. Determining when exactly temperatures enter unusual ranges may be done in many different ways (and the paper shows several, and more could be imagined), but the main result of first local emergence in low latitudes remains robust. A worrying factor is that the regions where the signal is expected to emerge first, or is already emerging are largely regions in Africa, parts of South and Central America, and the Maritime Continent; regions that are vulnerable to climate change for a variety of regions (see IPCC 2007), and regions which contribute generally little to global greenhouse gas emissions. In contrast, strong emissions of greenhouse gases occur in regions of low warming-to-variability ratio. To get even closer to the relevance of this finding for impacts, it would be interesting to place the emergence of highly unusual summer temperatures in the context not of internal variability, but in the context of variability experienced by the climate system prior to the 20th century, as, e.g. documented in palaeoclimatic reconstructions and simulated in simulations of the last millennium (see Jansen et al 2007). External forcing has moved the temperature range around more strongly for some regions and in some seasons than others. For example, while reconstructions of summer temperatures in Europe appear to show small long-term variations, winter shows deep drops in temperature in the little Ice Age and a long-term increase since then (Luterbacher et al 2004), which was at least partly caused by external forcing (Hegerl et al 2011a) and therefore 'natural variability' may be different from internal variability. A further interesting question in attempts to provide a climate-based proxy for impacts of climate change is: to what extent does the rapidity of change matter, and how does it compare to trends due to natural variability? It is reasonable to assume that fast changes impact

Water Use and Water-Use Efficiency of Three Perennial Bioenergy Grass Crops in Florida

Directory of Open Access Journals (Sweden)

Jerry M. Bennett

2012-10-01

Full Text Available Over two-thirds of human water withdrawals are estimated to be used for agricultural production, which is expected to increase as demand for renewable liquid fuels from agricultural crops intensifies. Despite the potential implications of bioenergy crop production on water resources, few data are available on water use of perennial bioenergy grass crops. Therefore, the objective of this study was to compare dry matter yield, water use, and water-use efficiency (WUE of elephantgrass, energycane, and giant reed, grown under field conditions for two growing seasons in North Central Florida. Using scaled sap flow sensor data, water use ranged from about 850 to 1150 mm during the growing season, and was generally greater for giant reed and less for elephantgrass. Despite similar or greater water use by giant reed, dry biomass yields of 35 to 40 Mg ha−1 were significantly greater for energycane and elephantgrass, resulting in greater WUE. Overall, water use by the bioenergy crops was greater than the rainfall received during the study, indicating that irrigation will be needed in the region to achieve optimal yields. Species differ in water use and WUE and species selection can play an important role with regard to potential consequences for water resources.

A farm-level analysis of economic and agronomic impacts of gradual climate warming

International Nuclear Information System (INIS)

Kaiser, H.M.; Sampath, R.; Riha, S.J.; Wilks, D.S.; Rossiter, D.G.

1993-01-01

The potential economic and agronomic impacts of gradual climate warming are examined at the farm level. Three models of the relevant climatic, agronomic, and economic processes are developed and linked to address climate change impacts and agricultural adaptability. Several climate warming severity. The results indicate that grain farmers in southern Minnesota can effectively adapt to a gradually changing climate (warmer and either wetter or drier) by adopting later maturing cultivars, changing crop mix, and altering the timing of field operations to take advantage of a longer growing season resulting from climate warming

Decadal warming causes a consistent and persistent shift from heterotrophic to autotrophic respiration in contrasting permafrost ecosystems.

Science.gov (United States)

Hicks Pries, Caitlin E; van Logtestijn, Richard S P; Schuur, Edward A G; Natali, Susan M; Cornelissen, Johannes H C; Aerts, Rien; Dorrepaal, Ellen

2015-12-01

Soil carbon in permafrost ecosystems has the potential to become a major positive feedback to climate change if permafrost thaw increases heterotrophic decomposition. However, warming can also stimulate autotrophic production leading to increased ecosystem carbon storage-a negative climate change feedback. Few studies partitioning ecosystem respiration examine decadal warming effects or compare responses among ecosystems. Here, we first examined how 11 years of warming during different seasons affected autotrophic and heterotrophic respiration in a bryophyte-dominated peatland in Abisko, Sweden. We used natural abundance radiocarbon to partition ecosystem respiration into autotrophic respiration, associated with production, and heterotrophic decomposition. Summertime warming decreased the age of carbon respired by the ecosystem due to increased proportional contributions from autotrophic and young soil respiration and decreased proportional contributions from old soil. Summertime warming's large effect was due to not only warmer air temperatures during the growing season, but also to warmer deep soils year-round. Second, we compared ecosystem respiration responses between two contrasting ecosystems, the Abisko peatland and a tussock-dominated tundra in Healy, Alaska. Each ecosystem had two different timescales of warming (permafrost ecosystems. © 2015 John Wiley & Sons Ltd.

A generic model for estimating biomass accumulation and greenhouse gas emissions from perennial crops

Science.gov (United States)

Ledo, Alicia; Heathcote, Richard; Hastings, Astley; Smith, Pete; Hillier, Jonathan

2017-04-01

Agriculture is essential to maintain humankind but is, at the same time, a substantial emitter of greenhouse gas (GHG) emissions. With a rising global population, the need for agriculture to provide secure food and energy supply is one of the main human challenges. At the same time, it is the only sector which has significant potential for negative emissions through the sequestration of carbon and offsetting via supply of feedstock for energy production. Perennial crops accumulate carbon during their lifetime and enhance organic soil carbon increase via root senescence and decomposition. However, inconsistency in accounting for this stored biomass undermines efforts to assess the benefits of such cropping systems when applied at scale. A consequence of this exclusion is that efforts to manage this important carbon stock are neglected. Detailed information on carbon balance is crucial to identify the main processes responsible for greenhouse gas emissions in order to develop strategic mitigation programs. Perennial crops systems represent 30% in area of total global crop systems, a considerable amount to be ignored. Furthermore, they have a major standing both in the bioenergy and global food industries. In this study, we first present a generic model to calculate the carbon balance and GHGs emissions from perennial crops, covering both food and bioenergy crops. The model is composed of two simple process-based sub-models, to cover perennial grasses and other perennial woody plants. The first is a generic individual based sub-model (IBM) covering crops in which the yield is the fruit and the plant biomass is an unharvested residue. Trees, shrubs and climbers fall into this category. The second model is a generic area based sub-model (ABM) covering perennial grasses, in which the harvested part includes some of the plant parts in which the carbon storage is accounted. Most second generation perennial bioenergy crops fall into this category. Both generic sub

A Bayesian modelling method for post-processing daily sub-seasonal to seasonal rainfall forecasts from global climate models and evaluation for 12 Australian catchments

Science.gov (United States)

Schepen, Andrew; Zhao, Tongtiegang; Wang, Quan J.; Robertson, David E.

2018-03-01

Rainfall forecasts are an integral part of hydrological forecasting systems at sub-seasonal to seasonal timescales. In seasonal forecasting, global climate models (GCMs) are now the go-to source for rainfall forecasts. For hydrological applications however, GCM forecasts are often biased and unreliable in uncertainty spread, and calibration is therefore required before use. There are sophisticated statistical techniques for calibrating monthly and seasonal aggregations of the forecasts. However, calibration of seasonal forecasts at the daily time step typically uses very simple statistical methods or climate analogue methods. These methods generally lack the sophistication to achieve unbiased, reliable and coherent forecasts of daily amounts and seasonal accumulated totals. In this study, we propose and evaluate a Rainfall Post-Processing method for Seasonal forecasts (RPP-S), which is based on the Bayesian joint probability modelling approach for calibrating daily forecasts and the Schaake Shuffle for connecting the daily ensemble members of different lead times. We apply the method to post-process ACCESS-S forecasts for 12 perennial and ephemeral catchments across Australia and for 12 initialisation dates. RPP-S significantly reduces bias in raw forecasts and improves both skill and reliability. RPP-S forecasts are also more skilful and reliable than forecasts derived from ACCESS-S forecasts that have been post-processed using quantile mapping, especially for monthly and seasonal accumulations. Several opportunities to improve the robustness and skill of RPP-S are identified. The new RPP-S post-processed forecasts will be used in ensemble sub-seasonal to seasonal streamflow applications.

Potential phytoextraction and phytostabilization of perennial peanut on copper-contaminated vineyard soils and copper mining waste.

Science.gov (United States)

Andreazza, Robson; Bortolon, Leandro; Pieniz, Simone; Giacometti, Marcelo; Roehrs, Dione D; Lambais, Mácio R; Camargo, Flávio A O

2011-12-01

This study sought to evaluate the potential of perennial peanut (Arachis pintoi) for copper phytoremediation in vineyard soils (Inceptisol and Mollisol) contaminated with copper and copper mining waste. Our results showed high phytomass production of perennial peanut in both vineyard soils. Macronutrient uptakes were not negatively affected by perennial peanut cultivated in all contaminated soils. Plants cultivated in Mollisol showed high copper concentrations in the roots and shoots of 475 and 52 mg kg(-1), respectively. Perennial peanut plants showed low translocation factor values for Cu, although these plants showed high bioaccumulation factor (BCF) for both vineyard soils, Inceptisol and Mollisol, with BCF values of 3.83 and 3.24, respectively, being characterized as a copper hyperaccumulator plant in these soils. Copper phytoextraction from Inceptisol soil was the highest for both roots and entire plant biomass, with more than 800 mg kg(-1) of copper in whole plant. The highest potential copper phytoextraction by perennial peanut was in Inceptisol soil with copper removal of 2,500 g ha(-1). Also, perennial peanut showed high potential for copper phytoremoval in copper mining waste and Mollisol with 1,700 and 1,500 g of copper per hectare, respectively. In addition, perennial peanuts characterized high potential for phytoextraction and phytostabilization of copper in vineyard soils and copper mining waste.

Soil warming for utilization and dissipation of waste heat in Pennsylvania

International Nuclear Information System (INIS)

DeWalle, D.R.; Chapura, A.M. Jr.

1978-01-01

The feasibility of using soil warming for utilization and dissipation of reject heat from power plants was demonstrated in a year-long test operation of a field prototype in Pennsylvania. A parallel network of 5-mm-diam polyethylene pipes was buried at a 0.3-m depth and with 0.6-m spacing in the soil covering a 15- x 60-m area to convey hot water simulating condenser cooling water from a power plant. Crop response to the heated soil varied: Snap beans and warm season forage crops such as sudangrass responded with increased yields, while cool season forage crops experienced decreased yields. Winter wheat yields were also increased, but winter barley was winter-killed due to delayed development of cold tolerance in the warm soil. Heat dissipation from the buried pipes was primarily by thermal conduction to the soil surface. Rates of heat loss from the buried pipes were most accurately predicted using an equation that included an explicit term for heat conduction below the pipes. Estimated soil warming land area necessary to dissipate all the reject heat from a 33% efficiency, 1500-MW electrical power plant based on minimum measured summer heat loss rates was 76 km 2 compared to the economic optimum of 18.2 km 2 determined as the least-cost system

Changes in Intense Precipitation Events in West Africa and the central U.S. under Global Warming

Energy Technology Data Exchange (ETDEWEB)

Cook, Kerry H. [Univ. of Texas, Austin, TX (United States); Vizy, Edward [Univ. of Texas, Austin, TX (United States)

2016-02-08

The purpose of the proposed project is to improve our understanding of the physical processes and large-scale connectivity of changes in intense precipitation events (high rainfall rates) under global warming in West Africa and the central U.S., including relationships with low-frequency modes of variability. This is in response to the requested subject area #2 “simulation of climate extremes under a changing climate … to better quantify the frequency, duration, and intensity of extreme events under climate change and elucidate the role of low frequency climate variability in modulating extremes.” We will use a regional climate model and emphasize an understanding of the physical processes that lead to an intensification of rainfall. The project objectives are as follows: 1. Understand the processes responsible for simulated changes in warm-season rainfall intensity and frequency over West Africa and the Central U.S. associated with greenhouse gas-induced global warming 2. Understand the relationship between changes in warm-season rainfall intensity and frequency, which generally occur on regional space scales, and the larger-scale global warming signal by considering modifications of low-frequency modes of variability. 3. Relate changes simulated on regional space scales to global-scale theories of how and why atmospheric moisture levels and rainfall should change as climate warms.

BVOCs emission in a semi-arid grassland under climate warming and nitrogen deposition

Directory of Open Access Journals (Sweden)

H. J. Wang

2012-04-01

Full Text Available Biogenic volatile organic compounds (BVOCs profoundly affect atmospheric chemistry and ecosystem functioning. BVOCs emission and their responses to global change are still unclear in grasslands, which cover one quarter of the Earth's land surface and are currently undergoing the largest changes. Over two growing seasons, we conducted a field experiment in a semi-arid grassland (Inner Mongolia, China to examine the emission and the responses of BVOCs emissions to warming and nitrogen deposition. The natural emission rate (NER of monoterpene (dominant BVOCs here is 107 ± 16 μg m⁻² h⁻¹ in drought 2007, and 266 ± 53 μg m⁻² h⁻¹ in wet 2008, respectively. Warming decreased the standard emission factor (SEF by 24% in 2007, while it increased by 43% in 2008. The exacerbated soil moisture loss caused by warming in dry season might be responsible for the decrease of SEF in 2007. A possible threshold of soil moisture (8.2% (v/v, which controls the direction of warming effects on monoterpene emission, existed in the semiarid grassland. Nitrogen deposition decreased the coverage of Artemisia frigida and hence reduced the NER by 24% across the two growing seasons. These results suggest that the grasslands dominated by the extended Artemisia frigida are an important source for BVOCs, while the responses of their emissions to global changes are more uncertain since they depend on multifactorial in-situ conditions.

Seasonal trends of atmospheric nitrogen dioxide and sulfur dioxide over North Santa Clara, Cuba.

Science.gov (United States)

Alejo, Daniellys; Morales, Mayra C; de la Torre, Jorge B; Grau, Ricardo; Bencs, László; Van Grieken, René; Van Espen, Piet; Sosa, Dismey; Nuñez, Vladimir

2013-07-01

Atmospheric nitrogen dioxide (NO2) and sulfur dioxide (SO2) levels were monitored simultaneously by means of Radiello passive samplers at six sites of Santa Clara city, Cuba, in the cold and the warm seasons in 2010. The dissolved ionic forms of NO2 and SO2 as nitrate and sulfite plus sulfate, respectively, were determined by means of ion chromatography. Analysis of NO2 as nitrite was also performed by UV-Vis spectrophotometry. For NO2, significant t tests show good agreement between the results of IC and UV-Vis methods. The NO2 and SO2 concentrations peaked in the cold season, while their minimum levels were experienced in the warm season. The pollutant levels do not exceed the maximum allowable limit of the Cuban Standard 39:1999, i.e., 40 μg/m(3) and 50 μg/m(3) for NO2 and SO2, respectively. The lowest pollutant concentrations obtained in the warm season can be attributed to an increase in their removal via precipitation (scavenging) while to the decreased traffic density and industrial emission during the summer holidays (e.g., July and August).

Seasonal variability of rocky reef fish assemblages: Detecting functional and structural changes due to fishing effects

Science.gov (United States)

Henriques, Sofia; Pais, Miguel Pessanha; Costa, Maria José; Cabral, Henrique Nogueira

2013-05-01

The present study analyzed the effects of seasonal variation on the stability of fish-based metrics and their capability to detect changes in fish assemblages, which is yet poorly understood despite the general idea that guilds are more resilient to natural variability than species abundances. Three zones subject to different levels of fishing pressure inside the Arrábida Marine Protected Area (MPA) were sampled seasonally. The results showed differences between warm (summer and autumn) and cold (winter and spring) seasons, with the autumn clearly standing out. In general, the values of the metrics density of juveniles, density of invertebrate feeders and density of omnivores increased in warm seasons, which can be attributed to differences in recruitment patterns, spawning migrations and feeding activity among seasons. The density of generalist/opportunistic individuals was sensitive to the effect of fishing, with higher values at zones with the lowest level of protection, while the density of individuals with high commercial value only responded to fishing in the autumn, due to a cumulative result of both juveniles and adults abundances during this season. Overall, this study showed that seasonal variability affects structural and functional features of the fish assemblage and that might influence the detection of changes as a result of anthropogenic pressures. The choice of a specific season, during warm sea conditions after the spawning period (July-October), seems to be more adequate to assess changes on rocky-reef fish assemblages.

Mapping the temporary and perennial character of whole river networks

Science.gov (United States)

González-Ferreras, A. M.; Barquín, J.

2017-08-01

Knowledge of the spatial distribution of temporary and perennial river channels in a whole catchment is important for effective integrated basin management and river biodiversity conservation. However, this information is usually not available or is incomplete. In this study, we present a statistically based methodology to classify river segments from a whole river network (Deva-Cares catchment, Northern Spain) as temporary or perennial. This method is based on an a priori classification of a subset of river segments as temporary or perennial, using field surveys and aerial images, and then running Random Forest models to predict classification membership for the rest of the river network. The independent variables and the river network were derived following a computer-based geospatial simulation of riverine landscapes. The model results show high values of overall accuracy, sensitivity, and specificity for the evaluation of the fitted model to the training and testing data set (≥0.9). The most important independent variables were catchment area, area occupied by broadleaf forest, minimum monthly precipitation in August, and average catchment elevation. The final map shows 7525 temporary river segments (1012.5 km) and 3731 perennial river segments (662.5 km). A subsequent validation of the mapping results using River Habitat Survey data and expert knowledge supported the validity of the proposed maps. We conclude that the proposed methodology is a valid method for mapping the limits of flow permanence that could substantially increase our understanding of the spatial links between terrestrial and aquatic interfaces, improving the research, management, and conservation of river biodiversity and functioning.

A Bayesian modelling method for post-processing daily sub-seasonal to seasonal rainfall forecasts from global climate models and evaluation for 12 Australian catchments

Directory of Open Access Journals (Sweden)

A. Schepen

2018-03-01

Full Text Available Rainfall forecasts are an integral part of hydrological forecasting systems at sub-seasonal to seasonal timescales. In seasonal forecasting, global climate models (GCMs are now the go-to source for rainfall forecasts. For hydrological applications however, GCM forecasts are often biased and unreliable in uncertainty spread, and calibration is therefore required before use. There are sophisticated statistical techniques for calibrating monthly and seasonal aggregations of the forecasts. However, calibration of seasonal forecasts at the daily time step typically uses very simple statistical methods or climate analogue methods. These methods generally lack the sophistication to achieve unbiased, reliable and coherent forecasts of daily amounts and seasonal accumulated totals. In this study, we propose and evaluate a Rainfall Post-Processing method for Seasonal forecasts (RPP-S, which is based on the Bayesian joint probability modelling approach for calibrating daily forecasts and the Schaake Shuffle for connecting the daily ensemble members of different lead times. We apply the method to post-process ACCESS-S forecasts for 12 perennial and ephemeral catchments across Australia and for 12 initialisation dates. RPP-S significantly reduces bias in raw forecasts and improves both skill and reliability. RPP-S forecasts are also more skilful and reliable than forecasts derived from ACCESS-S forecasts that have been post-processed using quantile mapping, especially for monthly and seasonal accumulations. Several opportunities to improve the robustness and skill of RPP-S are identified. The new RPP-S post-processed forecasts will be used in ensemble sub-seasonal to seasonal streamflow applications.

Boreal and temperate trees show strong acclimation of respiration to warming.

Science.gov (United States)

Reich, Peter B; Sendall, Kerrie M; Stefanski, Artur; Wei, Xiaorong; Rich, Roy L; Montgomery, Rebecca A

2016-03-31

Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 °C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated.

Moisture rivals temperature in limiting photosynthesis by trees establishing beyond their cold-edge range limit under ambient and warmed conditions.

Science.gov (United States)

Moyes, Andrew B; Germino, Matthew J; Kueppers, Lara M

2015-09-01

Climate change is altering plant species distributions globally, and warming is expected to promote uphill shifts in mountain trees. However, at many cold-edge range limits, such as alpine treelines in the western United States, tree establishment may be colimited by low temperature and low moisture, making recruitment patterns with warming difficult to predict. We measured response functions linking carbon (C) assimilation and temperature- and moisture-related microclimatic factors for limber pine (Pinus flexilis) seedlings growing in a heating × watering experiment within and above the alpine treeline. We then extrapolated these response functions using observed microclimate conditions to estimate the net effects of warming and associated soil drying on C assimilation across an entire growing season. Moisture and temperature limitations were each estimated to reduce potential growing season C gain from a theoretical upper limit by 15-30% (c. 50% combined). Warming above current treeline conditions provided relatively little benefit to modeled net assimilation, whereas assimilation was sensitive to either wetter or drier conditions. Summer precipitation may be at least as important as temperature in constraining C gain by establishing subalpine trees at and above current alpine treelines as seasonally dry subalpine and alpine ecosystems continue to warm. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Energy-conserving perennial agriculture for marginal land in southern Appalachia. Final technical report

Energy Technology Data Exchange (ETDEWEB)

Williams, G.

1982-01-30

USDA economists predict the end of surplus farm production in the US within this decade. More and more marginal land will be cropped to provide feed for the growing world population and to produce energy. Much of this potential cropland in Southern Appalachia is poorly suited to annual crops, such as corn. Perennial crops are much better suited to steep, rocky, and wet sites. Research was undertaken on the theoretical potentials of perennial species with high predicted yields of protein, carbohydrates, or oils. Several candidate staple perennial crops for marginal land in Southern Appalachia were identified, and estimates were made of their yields, energy input requirements, and general suitabilities. Cropping systems incorporating honeylocust, persimmon, mulberry, jujube, and beech were compared with corn cropping systems. It appears that these candidate staple perennials show distinct advantages for energy conservation and environmental preservation. Detailed economic analyses must await actual demonstration trials, but preliminary indications for ethanol conversion systems with honeylocust are encouraging. It is suggested that short-term loans to farmers undertaking this new type of agriculture would be appropriate to solve cash-flow problems.

Global Warming on Triton

Science.gov (United States)

Elliot, J. L.; Hammel, H. B.; Wasserman, L. H.; Franz, O. G.; McDonald, S. W.; Person, M. J.; Olkin, C. B.; Dunham, E. J.; Spencer, J. R.; Stansberry, J. A.;

The Forecasting of Adaptation Potential of Herbaceous Perennials

Directory of Open Access Journals (Sweden)

Belykh, O. A.

2013-04-01

Full Text Available This work investigates the problem of the ecobiomorph productive features formation of perennial herbs Ranunculaceae family forecasting on the basis of quantitative connections of species parameters with the leading geomorphological factors of South Siberia environment.

Disentangling Seasonality and Mean Annual Precipitation in the Indo-Pacific Warm Pool: Insights from Coupled Plant Wax C and H Isotope Measurements

Science.gov (United States)

Galy, V.; Oppo, D.; Dubois, N.; Arbuszewski, J. A.; Mohtadi, M.; Schefuss, E.; Rosenthal, Y.; Linsley, B. K.

2016-12-01

There is ample evidence suggesting that rainfall distribution across the Indo-Pacific Warm Pool (IPWP) - a key component of the global climate system - has substantially varied over the last deglaciation. Yet, the precise nature of these hydroclimate changes remains to be elucidated. In particular, the relative importance of variations in precipitation seasonality versus annual precipitation amount is essentially unknown. Here we use a set of surface sediments from the IPWP covering a wide range of modern hydroclimate conditions to evaluate how plant wax stable isotope composition records rainfall distribution in the area. We focus on long chain fatty acids, which are exclusively produced by vascular plants living on nearby land and delivered to the ocean by rivers. We relate the C (δ13C) and H (δD) isotope composition of long chain fatty acids preserved in surface sediments to modern precipitation distribution and stable isotope composition in their respective source area. We show that: 1) δ13C values reflect vegetation distribution (in particular the relative abundance of C3 and C4 plants) and are primarily recording precipitation seasonality (Dubois et al., 2014) and, 2) once corrected for plant fractionation effects, δD values reflect the amount-weighted average stable isotope composition of precipitation and are primarily recording annual precipitation amounts. We propose that combining the C and H isotope composition of long chain fatty acids thus allows independent reconstructions of precipitation seasonality and annual amounts in the IPWP. The practical implications for reconstructing past hydroclimate in the IPWP will be discussed.

Cool seasons are related to poor prognosis in patients with infective endocarditis

Science.gov (United States)

Chen, Su-Jung; Chao, Tze-Fan; Lin, Yenn-Jiang; Lo, Li-Wei; Hu, Yu-Feng; Tuan, Ta-Chuan; Hsu, Tsui-Lieh; Yu, Wen-Chung; Leu, Hsin-Bang; Chang, Shih-Lin; Chen, Shih-Ann

2012-09-01

Many cardiac diseases demonstrate seasonal variations in the incidence and mortality. This study was designed to investigate whether the mortality of infective endocarditis (IE) was higher in cool seasons and to evaluate the effects of cool climate for IE. We enrolled 100 IE patients with vegetations in our hospital. The temperatures of the IE episodes were defined as the monthly average temperatures of the admission days. The average temperatures in the cool (fall/winter) and warm seasons (spring/summer) were 19.2°C and 27.6°C, respectively. In addition, patients admitted with the diagnosis of IE were identified from the National Health Insurance Research Database (NHIRD) and the in-hospital mortality rates in cool and warm seasons were compared to validate the findings derived from the data of our hospital. The mortality rate for IE was significantly higher in fall/winter than in spring/summer which presents consistently in the patient population of our hospital (32.7% versus 12.5%, p = 0.017) and from NHIRD (10.4% versus 4.6%, p = 0.019). IE episodes which occurred during cool seasons presented with a higher rate of heart failure (44.2% versus 22.9%, p = 0.025) and D-dimer level (5.5 ± 3.8 versus 2.4 ± 1.8 μg/ml, p = 0.017) at admission than that of warm seasons. These results may reflect the impact of temperatures during the pre-hospitalized period on the disease process. In the multivariate analysis, Staphylococcal infection, left ventricular hypertrophy, left ventricular systolic dysfunction and temperature were the independent predictors of mortalities in IE patients.

Phytoplankton response to winter warming modified by large-bodied zooplankton: an experimental microcosm study

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Hu He

2015-03-01

Full Text Available While several field investigations have demonstrated significant effects of cool season (winter or spring warming on phytoplankton development, the role played by large-bodied zooplankton grazers for the responses of phytoplankton to winter warming is ambiguous. We conducted an outdoor experiment to compare the effect of winter warming (heating by 3°C in combination with presence and absence of Daphnia grazing (D. similis on phytoplankton standing crops and community structure under eutrophic conditions. When Daphnia were absent, warming was associated with significant increases in phytoplankton biomass and cyanobacterial dominance. In contrast, when Daphnia were present, warming effects on phytoplankton dynamics were offset by warming-enhanced grazing, resulting in no significant change in biomass or taxonomic dominance. These results emphasize that large-bodied zooplankton like Daphnia spp. may play an important role in modulating the interactions between climate warming and phytoplankton dynamics in nutrient rich lake ecosystems.

Global Warming Attenuates the Tropical Atlantic-Pacific Teleconnection

Science.gov (United States)

Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju

2016-01-01

Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread warming intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by warming in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global warming. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like warming of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse warming continues, the trend in the tropical Pacific as well as the development of ENSO will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection. PMID:26838053

Global Warming Attenuates the Tropical Atlantic-Pacific Teleconnection.

Science.gov (United States)

Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju

2016-02-03

Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread warming intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by warming in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global warming. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like warming of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse warming continues, the trend in the tropical Pacific as well as the development of ENSO will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection.

Perennial peanut (Arachis glabrata Benth.) contains polyphenol oxidase (PPO) and PPO substrates that can reduce post-harvest proteolysis.

Science.gov (United States)

Sullivan, Michael L; Foster, Jamie L

2013-08-15

Studies of perennial peanut (Arachis glabrata Benth.) suggest its hay and haylage have greater levels of rumen undegraded protein (RUP) than other legume forages such as alfalfa (Medicago sativa L.). Greater RUP can result in more efficient nitrogen utilization by ruminant animals with positive economic and environmental effects. We sought to determine whether, like red clover (Trifolium pretense L.), perennial peanut contains polyphenol oxidase (PPO) and PPO substrates that might be responsible for increased RUP. Perennial peanut extracts contain immunologically detectible PPO protein and high levels of PPO activity (>100 nkatal mg(-1) protein). Addition of caffeic acid (PPO substrate) to perennial peanut extracts depleted of endogenous substrates reduced proteolysis by 90%. Addition of phenolics prepared from perennial peanut leaves to extracts of either transgenic PPO-expressing or control (non-expressing) alfalfa showed peanut phenolics could reduce proteolysis >70% in a PPO-dependent manner. Two abundant likely PPO substrates are present in perennial peanut leaves including caftaric acid. Perennial peanut contains PPO and PPO substrates that together are capable of inhibiting post-harvest proteolysis, suggesting a possible mechanism for increased RUP in this forage. Research related to optimizing the PPO system in other forage crops will likely be applicable to perennial peanut. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

How does the dengue vector mosquito Aedes albopictus respond to global warming?

OpenAIRE

Jia, Pengfei; Chen, Xiang; Chen, Jin; Lu, Liang; Liu, Qiyong; Tan, Xiaoyue

2017-01-01

Background Global warming has a marked influence on the life cycle of epidemic vectors as well as their interactions with human beings. The Aedes albopictus mosquito as the vector of dengue fever surged exponentially in the last decade, raising ecological and epistemological concerns of how climate change altered its growth rate and population dynamics. As the global warming pattern is considerably uneven across four seasons, with a confirmed stronger effect in winter, an emerging need arises...

Response of organic matter quality in permafrost soils to warming

Science.gov (United States)

Plaza, C.; Pegoraro, E.; Schuur, E.

2016-12-01

Global warming is predicted to thaw large quantities of the perennially frozen organic matter stored in northern permafrost soils. Upon thaw, this organic matter will be exposed to lateral export to water bodies and to microbial decomposition, which may exacerbate climate change by releasing significant amounts of greenhouse gases. To gain an insight into these processes, we investigated how the quality of permafrost soil organic matter responded to five years of warming. In particular, we sampled control and experimentally warmed soils in 2009 and 2013 from an experiment established in 2008 in a moist acidic tundra ecosystem in Healy, Alaska. We examined surface organic (0 to 15 cm), deep organic (15 to 35 cm), and mineral soil layers (35 to 55 cm) separately by means of stable isotope analysis (δ13C and δ15N) and solid-state 13C nuclear magnetic resonance. Compared to the control, the experimental warming did not affect the isotopic and molecular composition of soil organic matter across the depth profile. However, we did find significant changes with time. In particular, in the surface organic layer, δ13C decreased and alkyl/O-alkyl ratio increased from 2009 to 2013, which indicated variations in soil organic sources (e.g., changes in vegetation) and accelerated decomposition. In the deep organic layer, we found a slight increase in δ15N with time. In the mineral layer, δ13C values decreased slightly, whereas alkyl C/O-alkyl ratio increased, suggesting a preferential loss of relatively more degraded organic matter fractions probably by lateral transport by water flowing through the soil. Acknowledgements: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 654132. Web site: http://vulcan.comule.com

On tropical cyclone frequency and the warm pool area

Directory of Open Access Journals (Sweden)

R. E. Benestad

2009-04-01

Full Text Available The proposition that the rate of tropical cyclogenesis increases with the size of the "warm pool" is tested by comparing the seasonal variation of the warm pool area with the seasonality of the number of tropical cyclones. An analysis based on empirical data from the Northern Hemisphere is presented, where the warm pool associated with tropical cyclone activity is defined as the area, A, enclosed by the 26.5°C SST isotherm. Similar analysis was applied to the temperature weighted area A_T with similar results.

An intriguing non-linear relationship of high statistical significance was found between the temperature weighted area in the North Atlantic and the North-West Pacific on the one hand and the number of cyclones, N, in the same ocean basin on the other, but this pattern was not found over the North Indian Ocean. A simple statistical model was developed, based on the historical relationship between N and A. The simple model was then validated against independent inter-annual variations in the seasonal cyclone counts in the North Atlantic, but the correlation was not statistically significant in the North-West Pacific. No correlation, however, was found between N and A in the North Indian Ocean.

A non-linear relationship between the cyclone number and temperature weighted area may in some ocean basins explain both why there has not been any linear trend in the number of cyclones over time as well as the recent upturn in the number of Atlantic hurricanes. The results also suggest that the notion of the number of tropical cyclones being insensitive to the area A is a misconception.

The Indo-Pacific Warm Pool: critical to world oceanography and world climate

Science.gov (United States)

De Deckker, Patrick

2016-12-01

The Indo-Pacific Warm Pool holds a unique place on the globe. It is a large area [>30 × 106 km2] that is characterised by permanent surface temperature >28 °C and is therefore called the `heat engine' of the globe. High convective clouds which can reach altitudes up to 15 km generate much latent heat in the process of convection and this area is therefore called the `steam engine' of the world. Seasonal and contrasting monsoonal activity over the region is the cause for a broad seasonal change of surface salinities, and since the area lies along the path of the Great Ocean Conveyor Belt, it is coined the `dilution' basin due to the high incidence of tropical rain and, away from the equator, tropical cyclones contribute to a significant drop in sea water salinity. Discussion about what may happen in the future of the Warm Pool under global warming is presented together with a description of the Warm Pool during the past, such as the Last Glacial Maximum when sea levels had dropped by ~125 m. A call for urgent monitoring of the IPWP area is justified on the grounds of the significance of this area for global oceanographic and climatological processes, but also because of the concerned threats to human population living there.

Tracking Changes in Dissolved Organic Matter Patterns in Perennial Headwater Streams Throughout a Hydrologic Year Using In-situ Sensors and Optical Properties

Science.gov (United States)

Armstrong, A.; Epting, S.; Hosen, J. D.; Palmer, M.

2015-12-01

Dissolved organic matter (DOM) plays a central role in freshwater streams but key questions remain unanswered about temporal patterns in its quantity and composition. DOM in perennial streams in the temperate zone is a complex mixture reflecting a variety of sources such as leached plant material, organic matter from surrounding soils, and microbial processes in the streams themselves. Headwater perennial streams in the Tuckahoe Creek watershed of the Atlantic coastal plain (Maryland, USA) drain a mosaic of land cover types including row crops, forests, and both forested and marshy small depressional wetlands. Wetland-stream surface hydrologic connections generally occur between mid-fall and late spring, coinciding with peak wetland hydrologic expression (i.e. highest groundwater levels and surface inundation extent). When inundated, these wetlands contain high DOM concentrations, and surface connections may serve as conduits for downstream export. We hypothesized that changes in wetland-stream surface hydrologic connectivity would affect patterns of DOM concentration and composition in these streams. We deployed 6 sondes equipped with fluorescent DOM sensors in 4 perennial streams, 1 forested wetland, and the larger downstream channel draining all study sites for the 2015 water year. The 4 headwater streams drain areas containing forested wetlands and have documented temporary channel connections. Combined with baseflow and stormflow sampling, the sondes provided 15 minute estimates of dissolved organic carbon (DOC) concentrations. This resolution provided insights into patterns of DOC concentration across temporal scales from daily rhythms to seasonal changes, during both baseflow and storm conditions. Discrete measurements of absorbance and fluorescence provided information about DOM composition throughout the study. Together these measurements give a detailed record of DOM dynamics in multiple perennial headwater streams for an entire year. This information

Effects of chicory/perennial ryegrass swards compared with perennial ryegrass swards on the performance and carcass quality of grazing beef steers.

Directory of Open Access Journals (Sweden)

Christina L Marley

Full Text Available An experiment investigated whether the inclusion of chicory (Cichorium intybus in swards grazed by beef steers altered their performance, carcass characteristics or parasitism when compared to steers grazing perennial ryegrass (Lolium perenne. Triplicate 2-ha plots were established with a chicory/ryegrass mix or ryegrass control. Forty-eight Belgian Blue-cross steers were used in the first grazing season and a core group (n = 36 were retained for finishing in the second grazing season. The experiment comprised of a standardisation and measurement period. During standardisation, steers grazed a ryegrass/white clover pasture as one group. Animals were allocated to treatment on the basis of liveweight, body condition and faecal egg counts (FEC determined 7 days prior to the measurement period. The measurement period ran from 25 May until 28 September 2010 and 12 April until 11 October 2011 in the first and second grazing year. Steers were weighed every 14 days at pasture or 28 days during housing. In the first grazing year, faecal samples were collected for FEC and parasite cultures. At the end of the first grazing year, individual blood samples were taken to determine O. ostertagi antibody and plasma pepsinogen levels. During winter, animals were housed as one group and fed silage. In the second grazing year, steers were slaughtered when deemed to reach fat class 3. Data on steer performance showed no differences in daily live-weight gain which averaged 1.04 kg/day. The conformation, fat grade and killing out proportion of beef steers grazing chicory/ryegrass or ryegrass were not found to differ. No differences in FEC, O. ostertagi antibody or plasma pepsinogen levels of beef steers grazing either chicory/ryegrass or ryegrass were observed. Overall, there were no detrimental effects of including chicory in swards grazed by beef cattle on their performance, carcass characteristics or helminth parasitism, when compared with steers grazing ryegrass.

Seasonal cycles of pelagic production and consumption

Science.gov (United States)

Longhurst, Alan

Comprehensive seasonal cycles of production and consumption in the pelagial require the ocean to be partitioned. This can be done rationally at two levels: into four primary ecological domains (three oceanic and one coastal), or about fifty biogeochemical provinces. The domains differ in their characteristic seasonal cycles of stability, nutrient supply and illumination, while provinces are defined by ocean currents, fronts, topography and recurrent features in the sea surface chlorophyll field. For each of these compartments, seasonal cycles of photic depth, primary production and accumulation (or loss) of algal biomass were obtained from the climatological CZCS chlorophyll field and other data and these, together with mixed layer depths, rendered characteristic seasonal cycles of production and consumption, which can be grouped into eight models: i - polar irradiance-mediated production peak; ii - nutrient-limited spring production peak; iii - winter-spring production with nutrient limitation; iv - small amplitude response to trade wind seasonality; v - large amplitude response to monsoon reversal; vi - canonical spring-fall blooms of mid-latitude continental shelves; vii - topography-forced summer production; viii - intermittent production at coastal divergences. For higher latitudes, these models suggest that the observed late-summer ‘blooms’ result not from a renewal of primary production rate, but from a relaxation of grazing pressure; in mid-latitudes, the observed ‘winter’ bloom represents chlorophyll accumulation at a season when loss terms are apparently smaller than during the period of peak primary production rate which occurs later, in spring. Where an episodic seasonal increase in rate of primary production occurs, as in the Arabian Sea, algal biomass accumulation may brief, lasting only until consumption is fully re-established. Only in the low latitude oligotrophic ocean are production and consumption perennially and closely coupled.

Ionomics: Genes and QTLs controlling heavy metal uptake in perennial grasses grown on phytoxic soil

Science.gov (United States)

Perennial grasses occupy diverse soils throughout the world, including many sites contaminated with heavy metals. Uncovering the genetic architecture of QTLs controlling mineral homoeostasis is critical for understanding the biochemical pathways that determine the elemental profiles of perennial pl...

Transgenic perennial biofuel feedstocks and strategies for bioconfinement

Science.gov (United States)

The use of transgenic tools for the improvement of plant feedstocks will be required to realize the full economic and environmental benefits of cellulosic and other biofuels, particularly from perennial plants. Traits that are targets for improvement of biofuels crops include he...

Submesoscale processes promote seasonal restratification in the Subantarctic Ocean

CSIR Research Space (South Africa)

Du Plessis, M

2017-04-01

Full Text Available Traditionally, the mechanism driving the seasonal restratification of the Southern Ocean mixed layer (ML) is thought to be the onset of springtime warming. Recent developments in numerical modeling and North Atlantic observations have shown...

Diagnostics, taxonomy, nomenclature and distribution of perennial Sesuvium (Aizoaceae) in Africa

Science.gov (United States)

Sukhorukov, Alexander P.; Nilova, Maya V.; Erst, Andrey S.; Kushunina, Maria; Baider, Cláudia; Verloove, Filip; Salas-Pascual, Marcos; Belyaeva, Irina V.; Krinitsina, Anastasiya A.; Bruyns, Peter V.; Klak, Cornelia

2018-01-01

Abstract The taxonomy of perennial Sesuvium species in Africa has been poorly investigated until now. Previously five perennial species of Sesuvium were recognised in Africa (S. congense, S. crithmoides, S. mesembryanthemoides, S. portulacastrum, and S. sesuvioides). Based on the differing number of stamens, S. ayresii is accepted here as being distinct from S. portulacastrum. Field observations in Angola also led the authors to conclude that S. crystallinum and S. mesembryanthemoides are conspecific with S. crithmoides. A new subspecies, Sesuvium portulacastrum subsp. persoonii, is described from West Africa (Cape Verde, Gambia, Guinea-Bissau, Mauritania, Senegal). The molecular phylogeny indicates the position of S. portulacastrum subsp. persoonii within the “American lineage” as a part of the Sesuvium portulacastrum complex which needs further studies. A diagnostic key and taxonomic notes are provided for the six perennial species of Sesuvium found in Africa and recognised by the authors (S. ayresii, S. congense, S. crithmoides, S. portulacastrum subsp. portulacastrum, S. portulacastrum subsp. persoonii, S. verrucosum and the facultatively short-lived S. sesuvioides). The distribution of S. crithmoides, previously considered to be endemic to Angola, is now confirmed for the seashores of Republic of Congo and DR Congo. The American species S. verrucosum is reported for the first time for Africa (the Macaronesian islands: Cape Verde and the Canaries). It is locally naturalised in Gran Canaria, being a potentially invasive species. These findings as well as new records of S. verrucosum from Asia and the Pacific Islands confirm its proneness to transcontinental introduction. Lectotypes of S. brevifolium, S. crithmoides, S. crystallinum and S. mesembryanthemoides are selected. The seed micromorphology and anatomy of the perennial African species is studied. Compared to the seeds of some annual African Sesuvium investigated earlier, those of perennial species are

Focus: Assessing the regional impacts of global warming

International Nuclear Information System (INIS)

Woo, Mingko

1992-01-01

Five studies are presented which assess the impacts of global warming on physical, economic, and social systems in Canada. A study on the use of climatic change scenarios to estimate ecoclimatic impacts was carried out. These scenarios may include synthetic scenarios produced from historical data, global climate model (GCM) simulations, and hybrid scenarios. The advantages and drawbacks of various scenarios are discussed along with the criteria for selecting impact assessment models. An examination of water resources in the Great Lakes and the Saskatchewan River subbasin uses case studies of two areas that have experienced wide hydrological variations due to climatic variability in order to determine the impacts of global warming scenarios on net basin supply. Problems of developing regional models are discussed and results of projected changes in net basin supply are presented for GCM-based simulations and hypothetical warming scenarios. A study of the impacts of climate warming on transportation and the regional economy in northern Canada uses stochastic models to provide examples of how Mackenzie River barge traffic will be affected. The economic impacts of the resultant lengthened shipping season are outlined under three scenarios. The implications of climatic change on Ontario agriculture are assessed according to GCM scenarios. Results are presented for crop yields and production as well as land resource suitability. Finally, sociocultural implications of global warming on the Arctic and the Inuit are summarized, with reference to a past warming episode occurring around the year 1000. 45 refs., 4 figs., 3 tabs

Global warming and allergy in Asia Minor.

Science.gov (United States)

Bajin, Munir Demir; Cingi, Cemal; Oghan, Fatih; Gurbuz, Melek Kezban

2013-01-01

The earth is warming, and it is warming quickly. Epidemiological studies have demonstrated that global warming is correlated with the frequency of pollen-induced respiratory allergy and allergic diseases. There is a body of evidence suggesting that the prevalence of allergic diseases induced by pollens is increasing in developed countries, a trend that is also evident in the Mediterranean area. Because of its mild winters and sunny days with dry summers, the Mediterranean area is different from the areas of central and northern Europe. Classical examples of allergenic pollen-producing plants of the Mediterranean climate include Parietaria, Olea and Cupressaceae. Asia Minor is a Mediterranean region that connects Asia and Europe, and it includes considerable coastal areas. Gramineae pollens are the major cause of seasonal allergic rhinitis in Asia Minor, affecting 1.3-6.4 % of the population, in accordance with other European regions. This article emphasizes the importance of global climate change and anticipated increases in the prevalence and severity of allergic disease in Asia Minor, mediated through worsening air pollution and altered local and regional pollen production, from an otolaryngologic perspective.

Performance Measures of Warm Asphalt Mixtures for Safe and Reliable Freight Transportation

Science.gov (United States)

2009-04-01

Warm mix asphalt (WMA) is an emerging technology that can allow asphalt to flow at a lower temperature for mixing, placing and compaction. The advantages of WMA include reduced fuel consumption, less carbon dioxide emission, longer paving season, lon...

Global Warming Induced Changes in Rainfall Characteristics in IPCC AR5 Models

Science.gov (United States)

Lau, William K. M.; Wu, Jenny, H.-T.; Kim, Kyu-Myong

2012-01-01

Changes in rainfall characteristic induced by global warming are examined from outputs of IPCC AR5 models. Different scenarios of climate warming including a high emissions scenario (RCP 8.5), a medium mitigation scenario (RCP 4.5), and 1% per year CO2 increase are compared to 20th century simulations (historical). Results show that even though the spatial distribution of monthly rainfall anomalies vary greatly among models, the ensemble mean from a sizable sample (about 10) of AR5 models show a robust signal attributable to GHG warming featuring a shift in the global rainfall probability distribution function (PDF) with significant increase (>100%) in very heavy rain, reduction (10-20% ) in moderate rain and increase in light to very light rains. Changes in extreme rainfall as a function of seasons and latitudes are also examined, and are similar to the non-seasonal stratified data, but with more specific spatial dependence. These results are consistent from TRMM and GPCP rainfall observations suggesting that extreme rainfall events are occurring more frequently with wet areas getting wetter and dry-area-getting drier in a GHG induced warmer climate.

The Perennial Ryegrass GenomeZipper: Targeted Use of Genome Resources for Comparative Grass Genomics1[C][W

Science.gov (United States)

Pfeifer, Matthias; Martis, Mihaela; Asp, Torben; Mayer, Klaus F.X.; Lübberstedt, Thomas; Byrne, Stephen; Frei, Ursula; Studer, Bruno

2013-01-01

Whole-genome sequences established for model and major crop species constitute a key resource for advanced genomic research. For outbreeding forage and turf grass species like ryegrasses (Lolium spp.), such resources have yet to be developed. Here, we present a model of the perennial ryegrass (Lolium perenne) genome on the basis of conserved synteny to barley (Hordeum vulgare) and the model grass genome Brachypodium (Brachypodium distachyon) as well as rice (Oryza sativa) and sorghum (Sorghum bicolor). A transcriptome-based genetic linkage map of perennial ryegrass served as a scaffold to establish the chromosomal arrangement of syntenic genes from model grass species. This scaffold revealed a high degree of synteny and macrocollinearity and was then utilized to anchor a collection of perennial ryegrass genes in silico to their predicted genome positions. This resulted in the unambiguous assignment of 3,315 out of 8,876 previously unmapped genes to the respective chromosomes. In total, the GenomeZipper incorporates 4,035 conserved grass gene loci, which were used for the first genome-wide sequence divergence analysis between perennial ryegrass, barley, Brachypodium, rice, and sorghum. The perennial ryegrass GenomeZipper is an ordered, information-rich genome scaffold, facilitating map-based cloning and genome assembly in perennial ryegrass and closely related Poaceae species. It also represents a milestone in describing synteny between perennial ryegrass and fully sequenced model grass genomes, thereby increasing our understanding of genome organization and evolution in the most important temperate forage and turf grass species. PMID:23184232

Perennial grasses traits as functional markers of grazing intensity in basaltic grasslands of Uruguay Rasgos de gramíneas perennes como marcadores funcionales de la intensidad de pastoreo en pastizales de basalto en Uruguay

Directory of Open Access Journals (Sweden)

Martin Jaurena

2012-12-01

Full Text Available Natural grasslands in the basaltic region of Uruguay are threatened by an increase in stocking rates and changes in land use. To assess the effect of grazing intensification, plant functional types are proposed as simple tools to aid the monitoring and management of vegetation. In the present study we evaluated the effect of stocking rate increase at community level taking into account plant traits of 23 dominant perennial grass species. In order to identify plant functional types, we determined the grazing response in an experiment with two wethers stocking rates (0.78 and 1.56 livestock units ha-1 quantifying species cover and traits values. Leaf dry matter content (LDMC and specific leaf area (SLA were the traits that best described the perennial grasses response to the stocking rate increase and therefore are suggested to be used as functional markers. Three functional types were identified. Low stocking rates were related to functional type A (tall, warm season species with low SLA and high LDMC and functional type B (tall, cool-season species, with intermediate levels of leaf traits. On the other hand, high stocking rate encouraged functional type C (prostrate, warm season species, with high SLA and low LDMC. The classification of a highly diverse community into three functional types and the selection of traits as functional markers candidates is an innovative approach to develop simple and general methods to diagnosis the state of basaltic grasslands in Uruguay and to advise on its management.Las praderas naturales de la region bas áltica de Uruguay están amenazadas por el incremento de la carga animal y cambios en el uso del suelo. Para evaluar el efecto del pastoreo se han propuesto los grupos funcionales como una herramienta simple para el monitoreo y manejo de la vegetación. El presente estudio evaluó el efecto del incremento de la carga animal considerando rasgos de 23 especies de gramineas perennes dominantes. Para identificar

Genomics-Assisted Exploitation of Heterosis in Perennial Ryegrass (Lolium perenne L.)

DEFF Research Database (Denmark)

Islam, Md. Shofiqul

ryegrass for the development of improved varieties. During his PhD studies, Mohammad Shofiqul Islam studied the feasibility of developing novel hybrid breeding schemes based on cytoplasmic male sterility (CMS) systems in perennial ryegrass. He successfully completed the assembly and annotation of a male......-fertile perennial ryegrass mitochondrial genome, and identified candidate genes responsible for the CMS phenotype by comparing male-fertile and male-sterile mitochondrial genomes. His findings constitute a good basis for continuing research to produce hybrid grass varieties to address the future needs......, breeding activities have been carried out to improve the population and develop synthetic varieties. This does not fully exploit the potential of heterosis, however. Hybrid breeding is an alternative strategy and provides opportunities to fully exploit the genetically available heterosis in perennial...

Early onset of significant local warming in low latitude countries

International Nuclear Information System (INIS)

Mahlstein, I; Knutti, R; Solomon, S; Portmann, R W

2011-01-01

The Earth is warming on average, and most of the global warming of the past half-century can very likely be attributed to human influence. But the climate in particular locations is much more variable, raising the question of where and when local changes could become perceptible enough to be obvious to people in the form of local warming that exceeds interannual variability; indeed only a few studies have addressed the significance of local signals relative to variability. It is well known that the largest total warming is expected to occur in high latitudes, but high latitudes are also subject to the largest variability, delaying the emergence of significant changes there. Here we show that due to the small temperature variability from one year to another, the earliest emergence of significant warming occurs in the summer season in low latitude countries (∼25 deg. S-25 deg. N). We also show that a local warming signal that exceeds past variability is emerging at present, or will likely emerge in the next two decades, in many tropical countries. Further, for most countries worldwide, a mean global warming of 1 deg. C is sufficient for a significant temperature change, which is less than the total warming projected for any economically plausible emission scenario. The most strongly affected countries emit small amounts of CO 2 per capita and have therefore contributed little to the changes in climate that they are beginning to experience.

A comparative simple method for human bioclimatic conditions applied to seasonally hot/warm cities of Mexico

Energy Technology Data Exchange (ETDEWEB)

Tejeda Martinez, A. [Universidad Veracruzana, Xalapa, Veracruz (Mexico); Garcia Cueto, O.R. [Universidad Autonoma de Baja California, Mexicali, B.C. (Mexico)

2002-01-01

The climate of a region is an environmental resource with important implications for things such as thermal comfort, health and productivity of the population. In this work, the bioclimatic comfort was evaluated for seven seasonally warm/hot cities of Mexico by means of the following current indexes: Discomfort Index, Enthalpy Index and Heat Strain Index. Also, the periods during which it is necessary to use air conditioning in the studied cities were calculated from estimated global radiation and hourly data of temperature and relative humidity which made it possible to establish them with high precision. Finally, the useful of the Heat Strain Index is shown. It is a simple index needing available meteorological data to compare bioclimatic conditions of similar sites. [Spanish] El clima regional tiene implicaciones en el confort, la salud y la productividad de la poblacion. En este articulo se presentan las evaluaciones bioclimaticas comparativas de siete ciudades calidas de Mexico. Se aplicaron los indices bioclimaticos de disconfort, entalpia y esfuerzo frente al calor. Se calcularon los periodos para los cuales es necesario el uso de aire acondicionado, a partir de estimaciones de radiacion solar global y de temperatura y humedad horarias medias mensuales. Finalmente se muestra la utilidad y calidad del Indice de esfuerzo frente al calor, el cual requiere solo de datos climatologicos comunes para poder comparar condiciones bioclimaticas de sitios similares.

Effects of warming on N2O fluxes in a boreal peatland of Permafrost region, Northeast China.

Science.gov (United States)

Cui, Qian; Song, Changchun; Wang, Xianwei; Shi, Fuxi; Yu, Xueyang; Tan, Wenwen

2018-03-01

Climate warming is expected to increasingly influence boreal peatlands and alter their greenhouse gases emissions. However, the effects of warming on N 2 O fluxes and the N 2 O budgets were ignored in boreal peatlands. Therefore, in a boreal peatland of permafrost zone in Northeast China, a simulated warming experiment was conducted to investigate the effects of warming on N 2 O fluxes in Betula. Fruticosa community (B. Fruticosa) and Ledum. palustre community (L. palustre) during the growing seasons from 2013 to 2015. Results showed that warming treatment increased air temperature at 1.5m aboveground and soil temperature at 5cm depth by 0.6°C and 2°C, respectively. The average seasonal N 2 O fluxes ranged from 6.62 to 9.34μgm -2 h -1 in the warming plot and ranged from 0.41 to 4.55μgm -2 h -1 in the control plots. Warming treatment increased N 2 O fluxes by 147% and transformed the boreal peatlands from a N 2 O sink to a source. The primary driving factors for N 2 O fluxes were soil temperature and active layer depth, whereas soil moisture showed a weak correlation with N 2 O fluxes. The results indicated that warming promoted N 2 O fluxes by increasing soil temperature and active layer depth in a boreal peatland of permafrost zone in Northeast China. Moreover, elevated N 2 O fluxes persisted in this region will potentially drive a noncarbon feedback to ongoing climate change. Copyright © 2017 Elsevier B.V. All rights reserved.

Fire Safety During the Holiday Season | Poster

Science.gov (United States)

Winter is here, and that means holiday decorations, a warm hearth, and (hopefully) plenty of homecooked meals. Unfortunately, winter also brings numerous fire hazards both at work and around the house. This year, as you shop, decorate, and celebrate, keep these safety tips in mind to ensure a safe and enjoyable holiday season.

A warm-season comparison of WRF coupled to the CLM4.0, Noah-MP, and Bucket hydrology land surface schemes over the central USA

Science.gov (United States)

Van Den Broeke, Matthew S.; Kalin, Andrew; Alavez, Jose Abraham Torres; Oglesby, Robert; Hu, Qi

2017-11-01

In climate modeling studies, there is a need to choose a suitable land surface model (LSM) while adhering to available resources. In this study, the viability of three LSM options (Community Land Model version 4.0 [CLM4.0], Noah-MP, and the five-layer thermal diffusion [Bucket] scheme) in the Weather Research and Forecasting model version 3.6 (WRF3.6) was examined for the warm season in a domain centered on the central USA. Model output was compared to Parameter-elevation Relationships on Independent Slopes Model (PRISM) data, a gridded observational dataset including mean monthly temperature and total monthly precipitation. Model output temperature, precipitation, latent heat (LH) flux, sensible heat (SH) flux, and soil water content (SWC) were compared to observations from sites in the Central and Southern Great Plains region. An overall warm bias was found in CLM4.0 and Noah-MP, with a cool bias of larger magnitude in the Bucket model. These three LSMs produced similar patterns of wet and dry biases. Model output of SWC and LH/SH fluxes were compared to observations, and did not show a consistent bias. Both sophisticated LSMs appear to be viable options for simulating the effects of land use change in the central USA.

Aquifer Thermal Energy Storage for Seasonal Thermal Energy Balance

Science.gov (United States)

Rostampour, Vahab; Bloemendal, Martin; Keviczky, Tamas

2017-04-01

Aquifer Thermal Energy Storage (ATES) systems allow storing large quantities of thermal energy in subsurface aquifers enabling significant energy savings and greenhouse gas reductions. This is achieved by injection and extraction of water into and from saturated underground aquifers, simultaneously. An ATES system consists of two wells and operates in a seasonal mode. One well is used for the storage of cold water, the other one for the storage of heat. In warm seasons, cold water is extracted from the cold well to provide cooling to a building. The temperature of the extracted cold water increases as it passes through the building climate control systems and then gets simultaneously, injected back into the warm well. This procedure is reversed during cold seasons where the flow direction is reversed such that the warmer water is extracted from the warm well to provide heating to a building. From the perspective of building climate comfort systems, an ATES system is considered as a seasonal storage system that can be a heat source or sink, or as a storage for thermal energy. This leads to an interesting and challenging optimal control problem of the building climate comfort system that can be used to develop a seasonal-based energy management strategy. In [1] we develop a control-oriented model to predict thermal energy balance in a building climate control system integrated with ATES. Such a model however cannot cope with off-nominal but realistic situations such as when the wells are completely depleted, or the start-up phase of newly installed wells, etc., leading to direct usage of aquifer ambient temperature. Building upon our previous work in [1], we here extend the mathematical model for ATES system to handle the above mentioned more realistic situations. Using our improved models, one can more precisely predict system behavior and apply optimal control strategies to manage the building climate comfort along with energy savings and greenhouse gas reductions

Allium hookeri , Thw. Enum. A lesser known terrestrial perennial ...

African Journals Online (AJOL)

A lesser known terrestrial perennial herb used as food and its ethnobotanical ... from the wilderness, for consumption and traditional healing of various ailments. ... plants, the lifestyles of the people are changed and they prefer 'junk foods'.

Interaction between seed dormancy-release mechanism, environment and seed bank strategy for a widely distributed perennial legume, Parkinsonia aculeata (Caesalpinaceae).

Science.gov (United States)

Van Klinken, Rieks D; Lukitsch, Bert; Cook, Carly

2008-08-01

Parkinsonia aculeata (Caesalpinaceae) is a perennial legume with seeds that have hard-seeded (physical) dormancy and are potentially very long-lived. Seed dormancy is a characteristic that can both help maximize the probability of seedling establishment and spread the risk of recruitment failure across years (bet-hedging). In this study, dormancy-release patterns are described across the diverse environments in which this species occurs in order to test whether wet heat (incubation under wet, warm-to-hot, conditions) alone can explain those patterns, and in order to determine the likely ecological role of physical dormancy across this species distribution. A seed burial trial was conducted across the full environmental distribution of P. aculeata in Australia (arid to wet-dry tropics, uplands to wetlands, soil surface to 10 cm deep). Wet heat explained the pattern of dormancy release across all environments. Most seeds stored in the laboratory remained dormant throughout the trial (at least 84 %). Dormancy release was quickest for seeds buried during the wet season at relatively high rainfall, upland sites (only 3 % of seeds remained dormant after 35 d). The longest-lived seeds were in wetlands (9 % remained dormant after almost 4 years) and on the soil surface (57 % after 2 years). There was no consistent correlation between increased aridity and rate of dormancy release. The results suggest that physical dormancy in P. aculeata is a mechanism for maximizing seedling establishment rather than a bet-hedging strategy. However, seed persistence can occur in environmental refuges where dormancy-release cues are weak and conditions for germination and establishment are poor (e.g. under dense vegetation or in more arid micro-environments) or unsuitable (e.g. when seeds are inundated or on the soil surface). Risks of recruitment failure in suboptimal environments could therefore be reduced by inter-year fluctuations in microclimate or seed movement.

Temperature effects on seaweed-sustaining top-down control vary with season.

Science.gov (United States)

Werner, Franziska J; Graiff, Angelika; Matthiessen, Birte

2016-03-01

Rising seawater temperature and CO2 concentrations (ocean acidification) represent two of the most influential factors impacting marine ecosystems in the face of global climate change. In ecological climate change research, full-factorial experiments performed across seasons in multispecies, cross-trophic-level settings are essential as they permit a more realistic estimation of direct and indirect effects as well as the relative importance of the effects of both major environmental stressors on ecosystems. In benthic mesocosm experiments, we tested the responses of coastal Baltic Sea Fucus vesiculosus communities to elevated seawater temperature and CO2 concentrations across four seasons of one year. While increasing [CO2] levels had only minor effects, warming had strong and persistent effects on grazers, and the resulting effects on the Fucus community were found to be season dependent. In late summer, a temperature-driven collapse of grazers caused a cascading effect from the consumers to the foundation species, resulting in overgrowth of Fucus thalli by epiphytes. In fall/winter (outside the growing season of epiphytes), intensified grazing under warming resulted in a significant reduction in Fucus biomass. Thus, we were able to confirm the prediction that future increases in water temperatures will influence marine food-web processes by altering top-down control, but we were also able to show that specific consequences for food-web structure depend on the season. Since F. vesiculosus is the dominant habitat-forming brown algal system in the Baltic Sea, its potential decline under global warming implies a loss of key functions and services such as provision of nutrient storage, substrate, food, shelter, and nursery grounds for a diverse community of marine invertebrates and fish in Baltic Sea coastal waters.

Experimental climate warming decreases photosynthetic efficiency of lichens in an arid South African ecosystem.

Science.gov (United States)

Maphangwa, Khumbudzo Walter; Musil, Charles F; Raitt, Lincoln; Zedda, Luciana

2012-05-01

Elevated temperatures and diminished precipitation amounts accompanying climate warming in arid ecosystems are expected to have adverse effects on the photosynthesis of lichen species sensitive to elevated temperature and/or water limitation. This premise was tested by artificially elevating temperatures (increase 2.1-3.8°C) and reducing the amounts of fog and dew precipitation (decrease 30.1-31.9%), in an approximation of future climate warming scenarios, using transparent hexagonal open-top warming chambers placed around natural populations of four lichen species (Xanthoparmelia austroafricana, X. hyporhytida , Xanthoparmelia. sp., Xanthomaculina hottentotta) at a dry inland site and two lichen species (Teloschistes capensis and Ramalina sp.) at a humid coastal site in the arid South African Succulent Karoo Biome. Effective photosynthetic quantum yields ([Formula: see text]) were measured hourly throughout the day at monthly intervals in pre-hydrated lichens present in the open-top warming chambers and in controls which comprised demarcated plots of equivalent open-top warming chamber dimensions constructed from 5-cm-diameter mesh steel fencing. The cumulative effects of the elevated temperatures and diminished precipitation amounts in the open-top warming chambers resulted in significant decreases in lichen [Formula: see text]. The decreases were more pronounced in lichens from the dry inland site (decline 34.1-46.1%) than in those from the humid coastal site (decline 11.3-13.7%), most frequent and prominent in lichens at both sites during the dry summer season, and generally of greatest magnitude at or after the solar noon in all seasons. Based on these results, we conclude that climate warming interacting with reduced precipitation will negatively affect carbon balances in endemic lichens by increasing desiccation damage and reducing photosynthetic activity time, leading to increased incidences of mortality.

[The innovation of warm disease theory in the Ming Dynasty before Wen yi lun On Pestilence].

Science.gov (United States)

Zhang, Zhi-bin

2008-10-01

Some doctors of the Ming dynasty raised subversive doubts against the traditional viewpoints of "exogenous cold disease is warm-heat" before the emergence of Wen yi lun (On Pestilence), holding that warm-heat disease "is contracted in different seasons instead of being transformed from cold to warm and/or heat". The conception of the separation of warm-heat disease and exogenous cold disease had changed from obscure to clear. As the idea became clear, the recognition on the new affection of warm, heat, summer-heat, pestilent pathogen was formed, and the idea that the pathogens of summer-heat and warm entered the human body through the mouth and nostrils was put forward. The six-channel syndrome differentiation of warm disease and the five sweat-resolving methods in pestilence raised by the doctors of this period are the aspects of the differential diagnosis of syndrome and treatment in warm diseases, and deserve to be paid attention to.

Coupled prediction of flood response and debris flow initiation during warm and cold season events in the Southern Appalachians, USA

Science.gov (United States)

Tao, J.; Barros, A. P.

2013-07-01

Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas warm season events are clearly associated with heavy rainfall intensity, the same cannot be said for the cold season events. Instead, there is a relationship between large (cumulative) rainfall events independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. The first objective of this study is to investigate this hypothesis. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These events were selected due to the optimal availability of rainfall observations, availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions, and because they are representative of events that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions necessary for the initiation of slope instability, and should therefore be considered explicitly in landslide hazard assessments. Moreover, the relationships between slope stability and interflow are

Soil Temperature Manipulation to Study Global Warming Effects in Arable Land

DEFF Research Database (Denmark)

Patil, R H; Laegdsmand, M; Olesen, Jørgen E

2013-01-01

in a plough layer. Temperature sensors were placed at 0.05, 0.1 and 0.25 m depths in soil, and 0.1 m above the soil surface in all plots, which were connected to an automated data logger. Soil-warming setup was able to maintain a mean seasonal temperature difference of 5.0 ± 0.005℃ between heated and control......-ground vegetation response as this method heats only the soil. Therefore, using infrared heaters seems to represent natural climate warming (both air and soil) much more closely and may be used for future climate manipulation field studies....

Soil temperature manipulation to study global warming effects in arable land

DEFF Research Database (Denmark)

Patil, Raveendra H.; Laegdsmand, Mette; Olesen, Jørgen Eivind

2013-01-01

in a plough layer. Temperature sensors were placed at 0.05, 0.1 and 0.25 m depths in soil, and 0.1 m above the soil surface in all plots, which were connected to an automated data logger. Soil-warming setup was able to maintain a mean seasonal temperature difference of 5.0 ± 0.005 oC between heated...... that of above-ground vegetation response as this method heats only the soil. Therefore, using infrared heaters seems to represent natural climate warming (both air and soil) much more closely and may be used for future climate manipulation field studies....

FORWINE - Statistical Downscaling of Seasonal forecasts for wine

Science.gov (United States)

Cardoso, Rita M.; Soares, Pedro M. M.; Miranda, Pedro M. A.

2016-04-01

The most renowned viticulture regions in the Iberian Peninsula have a long standing tradition in winemaking and are considered world-class grapevine (Vitis Vinifera L.) producing regions. Portugal is the 11th wine producer in the world, with internationally acclaimed wines, such as Port wine, and vineyards across the whole territory. Climate is widely acknowledged of one of the most important factors for grapevine development and growth (Fraga et al. 2014a and b; Jackson et al. 1993; Keller 2010). During the growing season (April-October in the Northern Hemisphere) of this perennial and deciduous crop, the climatic conditions are responsible for numerous morphologically and physiological changes. Anomalously low February-March mean temperature, anomalously high May mean temperature and anomalously high March precipitation tend to be favourable to wine production in the Douro Valley. Seasonal forecast of precipitation and temperature tailored to fit critical thresholds, for crucial seasons, can be used to inform management practices (viz. phytosanitary measures, land operations, marketing campaigns) and develop a wine production forecast. Statistical downscaling of precipitation, maximum, minimum temperatures is used to model wine production following Santos et al. (2013) and to calculate bioclimatic indices. The skill of the ensemble forecast is evaluated through anomaly correlation, ROC area, spread-error ratio and CRPS

Seasonal and elevational contrasts in temperature trends in Central Chile between 1979 and 2015

Science.gov (United States)

Burger, F.; Brock, B.; Montecinos, A.

2018-03-01

We analyze trends in temperature from 18 temperature stations and one upper air sounding site at 30°-35° S in central Chile between 1979-2015, to explore geographical and season temperature trends and their controls, using regional ocean-atmosphere indices. Significant warming trends are widespread at inland stations, while trends are non-significant or negative at coastal sites, as found in previous studies. However, ubiquitous warming across the region in the past 8 years, suggests the recent period of coastal cooling has ended. Significant warming trends are largely restricted to austral spring, summer and autumn seasons, with very few significant positive or negative trends in winter identified. Autumn warming is notably strong in the Andes, which, together with significant warming in spring, could help to explain the negative mass balance of snow and glaciers in the region. A strong Pacific maritime influence on regional temperature trends is inferred through correlation with the Interdecadal Pacific Oscillation (IPO) index and coastal sea surface temperature, but the strength of this influence rapidly diminishes inland, and the majority of valley, and all Andes, sites are independent of the IPO index. Instead, valley and Andes sites, and mid-troposphere temperature in the coastal radiosonde profile, show correlation with the autumn Antarctic Oscillation which, in its current positive phase, promotes subsidence and warming at the latitude of central Chile.

Water runoff vs modern climatic warming in mountainous cryolithic zone in North-East Russia

Science.gov (United States)

Glotov, V. E.; Glotova, L. P.

2018-01-01

The article presents the results of studying the effects of current climatic warming for both surface and subsurface water runoffs in North-East Russia, where the Main Watershed of the Earth separates it into the Arctic and Pacific continental slopes. The process of climatic warming is testified by continuous weather records during 80-100 years and longer periods. Over the Arctic slope and in the northern areas of the Pacific slope, climatic warming results in a decline in a total runoff of rivers whereas the ground-water recharge becomes greater in winter low-level conditions. In the southern Pacific slope and in the Sea of Okhotsk basin, the effect of climatic warming is an overall increase in total runoff including its subsurface constituents. We believe these peculiar characters of river runoff there to be related to the cryolithic zone environments. Over the Arctic slope and the northern Pacific slope, where cryolithic zone is continuous, the total runoff has its subsurface constituent as basically resulting from discharge of ground waters hosted in seasonally thawing rocks. Warmer climatic conditions favor growth of vegetation that needs more water for the processes of evapotranspiration and evaporation from rocky surfaces in summer seasons. In the Sea of Okhotsk basin, where the cryolithic zone is discontinuous, not only ground waters in seasonally thawing layers, but also continuous taliks and subpermafrost waters participate in processes of river recharges. As a result, a greater biological productivity of vegetation cover does not have any effect on ground-water supply and river recharge processes. If a steady climate warming is provided, a continuous cryolithic zone can presumably degrade into a discontinuous and then into an island-type permafrost layer. Under such a scenario, there will be a general increase in the total runoff and its subsurface constituent. From geoecological viewpoints, a greater runoff will have quite positive effects, whereas some

Lake seasonality across the Tibetan Plateau and their varying relationship with regional mass changes and local hydrology

Science.gov (United States)

Lei, Yanbin; Yao, Tandong; Yang, Kun; Sheng, Yongwei; Kleinherenbrink, Marcel; Yi, Shuang; Bird, Broxton W.; Zhang, Xiaowen; Zhu, La; Zhang, Guoqing

2017-01-01

The recent growth and deepening of inland lakes in the Tibetan Plateau (TP) may be a salient indicator of the consequences of climate change. The seasonal dynamics of these lakes is poorly understood despite this being potentially crucial for disentangling contributions from glacier melt and precipitation, which are all sensitive to climate, to lake water budget. Using in situ observations, satellite altimetry and gravimetry data, we identified two patterns of lake level seasonality. In the central, northern, and northeastern TP, lake levels are characterized by considerable increases during warm seasons and decreases during cold seasons, which is consistent with regional mass changes related to monsoon precipitation and evaporation. In the northwestern TP, however, lake levels exhibit dramatic increases during both warm and cold seasons, which deviate from regional mass changes. This appears to be more connected with high spring snowfall and large summer glacier melt. The variable lake level response to different drivers indicates heterogeneous sensitivity to climate change between the northwestern TP and other regions.

Preliminary Results of a U.S. Deep South Warm Season Deep Convective Initiation Modeling Experiment using NASA SPoRT Initialization Datasets for Operational National Weather Service Local Model Runs

Science.gov (United States)

Medlin, Jeffrey M.; Wood, Lance; Zavodsky, Brad; Case, Jon; Molthan, Andrew

2012-01-01

The initiation of deep convection during the warm season is a forecast challenge in the relative high instability and low wind shear environment of the U.S. Deep South. Despite improved knowledge of the character of well known mesoscale features such as local sea-, bay- and land-breezes, observations show the evolution of these features fall well short in fully describing the location of first initiates. A joint collaborative modeling effort among the NWS offices in Mobile, AL, and Houston, TX, and NASA s Short-term Prediction Research and Transition (SPoRT) Center was undertaken during the 2012 warm season to examine the impact of certain NASA produced products on the Weather Research and Forecasting Environmental Modeling System. The NASA products were: a 4-km Land Information System data, a 1-km sea surface temperature analysis, and a 4-km greenness vegetation fraction analysis. Similar domains were established over the southeast Texas and Alabama coastlines, each with a 9 km outer grid spacing and a 3 km inner nest spacing. The model was run at each NWS office once per day out to 24 hours from 0600 UTC, using the NCEP Global Forecast System for initial and boundary conditions. Control runs without the NASA products were made at the NASA SPoRT Center. The NCAR Model Evaluation Tools verification package was used to evaluate both the forecast timing and location of the first initiates, with a focus on the impacts of the NASA products on the model forecasts. Select case studies will be presented to highlight the influence of the products.

Magnitude and pattern of Arctic warming governed by the seasonality of radiative forcing

NARCIS (Netherlands)

Bintanja, R.; Krikken, F.

2016-01-01

Observed and projected climate warming is strongest in the Arctic regions, peaking in autumn/winter. Attempts to explain this feature have focused primarily on identifying the associated climate feedbacks, particularly the ice-Albedo and lapse-rate feedbacks. Here we use a state-of-The-Art global

Seeding method influences warm-season grass abundance and distribution but not local diversity in grassland restoration

Science.gov (United States)

Yurkonis, Kathryn A.; Wilsey, Brian J.; Moloney, Kirk A.; Drobney, Pauline; Larson, Diane L.

2010-01-01

Ecological theory predicts that the arrangement of seedlings in newly restored communities may influence future species diversity and composition. We test the prediction that smaller distances between neighboring seeds in drill seeded grassland plantings would result in lower species diversity, greater weed abundance, and larger conspecific patch sizes than otherwise similar broadcast seeded plantings. A diverse grassland seed mix was either drill seeded, which places seeds in equally spaced rows, or broadcast seeded, which spreads seeds across the ground surface, into 24 plots in each of three sites in 2005. In summer 2007, we measured species abundance in a 1 m2 quadrat in each plot and mapped common species within the quadrat by recording the most abundant species in each of 64 cells. Quadrat-scale diversity and weed abundance were similar between drilled and broadcast plots, suggesting that processes that limited establishment and controlled invasion were not affected by such fine-scale seed distribution. However, native warm-season (C4) grasses were more abundant and occurred in less compact patches in drilled plots. This difference in C4 grass abundance and distribution may result from increased germination or vegetative propagation of C4 grasses in drilled plots. Our findings suggest that local plant density may control fine-scale heterogeneity and species composition in restored grasslands, processes that need to be further investigated to determine whether seed distributions can be manipulated to increase diversity in restored grasslands.

Sensitivity of Pliocene Arctic climate to orbital forcing, atmospheric CO2 and sea ice albedo parameterisation

Science.gov (United States)

Howell, Fergus W.; Haywood, Alan M.; Dowsett, Harry J.; Pickering, Steven J.

2016-01-01

General circulation model (GCM) simulations of the mid-Pliocene Warm Period (mPWP, 3.264 to 3.025 Myr ago) do not reproduce the magnitude of Northern Hemisphere high latitude surface air and sea surface temperature (SAT and SST) warming that proxy data indicate. There is also large uncertainty regarding the state of sea ice cover in the mPWP. Evidence for both perennial and seasonal mPWP Arctic sea ice is found through analyses of marine sediments, whilst in a multi-model ensemble of mPWP climate simulations, half of the ensemble simulated ice-free summer Arctic conditions. Given the strong influence that sea ice exerts on high latitude temperatures, an understanding of the nature of mPWP Arctic sea ice would be highly beneficial.

Evaluation of seasonal exergy efficiency of air handing unit

Directory of Open Access Journals (Sweden)

Kęstutis Genys

2015-10-01

Full Text Available The article deals with the air handling unit seasonal exergy efficiency. TRNSYS simulation tool is used to evaluate it. The object of research is air treatment device used to treat an air for the ventilation of laboratory. The mathematical model of air handling unit using TRNSYS simulation tool was developed when the technical parameters of air handling unit and energy exchange in it were analysed. The developed model according to the made observations during the warm and cold periods was tested and validation of elements was performed. The simulation of air handling unit operation after the verification of reliability and permitted tolerances was performed. The control mechanisim which allows simulating the operation of air handling unit during cold and warm periods of the year was made. The mathematical algorithm for calculation of air handling unit exergy efficiency coefficient applying the principles of exergy analysis was developed. The seasonal exergy efficiency of air handling unit equal to 3.94 percent during the simulation was obtained.

Perennial Environment Observatory

International Nuclear Information System (INIS)

Plas, Frederic

2014-07-01

The Perennial Environment Observatory [Observatoire Perenne de l'Environnement - OPE] is a unique approach and infrastructure developed and implemented by ANDRA, the French National Radioactive Waste Management Agency, as part of its overall project of deep geological disposal for radioactive waste. Its current mission is to assess the initial state of the rural (forest, pasture, open-field and aquatic) environment, prior to repository construction. This will be followed in 2017 (pending construction authorizations) and for a period exceeding a century, by monitoring of any impact the repository may have on the environment. In addition to serving its own industrial purpose of environmental monitoring, ANDRA also opens the OPE approach, infrastructure and acquired knowledge (database...) to the scientific community to support further research on long term evolution of the environment subjected to natural and anthropogenic stresses, and to contribute to a better understanding of the interaction between the various compartments of the environment

Introducing perennial biomass crops into agricultural landscapes to address water quality challenges and provide other environmental services: Integrating perennial bioenergy crops into agricultural landscapes

Energy Technology Data Exchange (ETDEWEB)

Cacho, J. F. [Environmental Science Division, Argonne National Laboratory, Lemont IL USA; Negri, M. C. [Environmental Science Division, Argonne National Laboratory, Lemont IL USA; Zumpf, C. R. [Environmental Science Division, Argonne National Laboratory, Lemont IL USA; Campbell, P. [Environmental Science Division, Argonne National Laboratory, Lemont IL USA

2017-11-29

The world is faced with a difficult multiple challenge of meeting nutritional, energy, and other basic needs, under a limited land and water budget, of between 9 and 10 billion people in the next three decades, mitigating impacts of climate change, and making agricultural production resilient. More productivity is expected from agricultural lands, but intensification of production could further impact the integrity of our finite surface water and groundwater resources. Integrating perennial bioenergy crops in agricultural lands could provide biomass for biofuel and potential improvements on the sustainability of commodity crop production. This article provides an overview of ways in which research has shown that perennial bioenergy grasses and short rotation woody crops can be incorporated into agricultural production systems with reduced indirect land use change, while increasing water quality benefits. Current challenges and opportunities as well as future directions are also highlighted.

Economic and conservation implications of converting exotic forages to native warm-season grass

Directory of Open Access Journals (Sweden)

Adrian P. Monroe

2017-07-01

Full Text Available Intensive agriculture can have negative environmental consequences such as nonpoint source pollution and the simplification of biotic communities, and land sharing posits that conservation can be enhanced by integrating agricultural productivity and biodiversity on the same land. In the Southeastern United States, native warm-season grasses (NWSG may be a land sharing alternative to exotic forages currently in production because of greater livestock gains with lower fertilizer inputs, and habitat for grassland birds. However, uncertainty regarding costs and risk poses an important barrier to incorporating NWSG in livestock operations. We evaluated the economic and conservation implications of NWSG conversion among small, operational-scale pastures (6.8–10.5 ha during 2011–2012 at the Prairie Research Unit in Monroe Co., Mississippi (USA. We used partial budgets to compare the marginal rate of return (MRRe from converting exotic grass pastures to either a NWSG monoculture of Indiangrass (Sorghastrum nutans or a NWSG mix of Indiangrass, little bluestem (Schizachyrium scoparium, and big bluestem (Andropogon gerardii. We similarly compared changes in productivity of dickcissels (Spiza americana, a grassland bird specializing in tall structure. Average daily gain (ADG of steers and revenue were consistently higher for NWSG treatments than exotic grass pasture, but ADG declined between years. Indiangrass pastures yielded consistently positive MRRe, indicating producers would receive 16–24% return on investment. Marginal rate of return was lower for mixed NWSG (−12 to 3%, driven by slightly lower livestock ADG and higher establishment costs than for Indiangrass. Sensitivity analyses indicated that MRRe also was influenced by cattle selling price. Conversely, mixed NWSG increased dickcissel productivity by a greater degree than Indiangrass per amount invested in NWSG conversion, suggesting a tradeoff between livestock and dickcissel production

Outdoor thermal comfort in public space in warm-humid Guayaquil, Ecuador

Science.gov (United States)

Johansson, Erik; Yahia, Moohammed Wasim; Arroyo, Ivette; Bengs, Christer

2018-03-01

The thermal environment outdoors affects human comfort and health. Mental and physical performance is reduced at high levels of air temperature being a problem especially in tropical climates. This paper deals with human comfort in the warm-humid city of Guayaquil, Ecuador. The main aim was to examine the influence of urban micrometeorological conditions on people's subjective thermal perception and to compare it with two thermal comfort indices: the physiologically equivalent temperature (PET) and the standard effective temperature (SET*). The outdoor thermal comfort was assessed through micrometeorological measurements of air temperature, humidity, mean radiant temperature and wind speed together with a questionnaire survey consisting of 544 interviews conducted in five public places of the city during both the dry and rainy seasons. The neutral and preferred values as well as the upper comfort limits of PET and SET* were determined. For both indices, the neutral values and upper thermal comfort limits were lower during the rainy season, whereas the preferred values were higher during the rainy season. Regardless of season, the neutral values of PET and SET* are above the theoretical neutral value of each index. The results show that local people accept thermal conditions which are above acceptable comfort limits in temperate climates and that the subjective thermal perception varies within a wide range. It is clear, however, that the majority of the people in Guayaquil experience the outdoor thermal environment during daytime as too warm, and therefore, it is important to promote an urban design which creates shade and ventilation.

Modeling the Thickness of Perennial Ice Covers on Stratified Lakes of the Taylor Valley, Antarctica

Science.gov (United States)

Obryk, M. K.; Doran, P. T.; Hicks, J. A.; McKay, C. P.; Priscu, J. C.

2016-01-01

A one-dimensional ice cover model was developed to predict and constrain drivers of long term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 years (between 1996 and 2012) of ice thickness changes for west lobe of Lake Bonney (average ice thickness = 3.53 m; RMSE = 0.09 m, n = 118) and Lake Fryxell (average ice thickness = 4.22 m; RMSE = 0.21 m, n = 128). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (temperature cooling or warming). As such, shallow (< 20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.

Impacts of +2 °C global warming on winter tourism demand in Europe

NARCIS (Netherlands)

Damm, Andrea; Greuell, Wouter; Landgren, Oskar; Prettenthaler, Franz

2017-01-01

Increasing temperatures and snow scarce winter seasons challenge the winter tourism industry. In this study the impacts of +2 °C global warming on winter tourism demand in Europe's ski tourism related NUTS-3 regions are quantified. Using time series regression models, the relationship between

Microclimate impacts of passive warming methods in Antarctica: implications for climate change studies

NARCIS (Netherlands)

Bokhorst, S.; Huiskes, A.H.L.; Convey, P.; Sinclair, B.J.; Lebouvier, M.; van de Vijver, B.; Wall, D.H.

2011-01-01

Passive chambers are used to examine the impacts of summer warming in Antarctica but, so far, impacts occurring outside the growing season, or related to extreme temperatures, have not been reported, despite their potentially large biological significance. In this review, we synthesise and discuss

Effects of different re-warm up activities in football players' performance.

Directory of Open Access Journals (Sweden)

Eduardo Abade

Full Text Available Warm up routines are commonly used to optimize football performance and prevent injuries. Yet, official pre-match protocols may require players to passively rest for approximately 10 to 15 minutes between the warm up and the beginning of the match. Therefore, the aim of this study was to explore the effect of different re-warm up activities on the physical performance of football players. Twenty-Two Portuguese elite under-19 football players participated in the study conducted during the competitive season. Different re-warm up protocols were performed 6 minutes after the same standardized warm up in 4 consecutive days in a crossover controlled approach: without, eccentric, plyometric and repeated changes of direction. Vertical jump and Sprint performances were tested immediately after warm up and 12 minutes after warm up. Results showed that repeated changes of direction and plyometrics presented beneficial effects to jump and sprint. Different practical implications may be taken from the eccentric protocol since a vertical jump impairment was observed, suggesting a possibly harmful effect. The absence of re-warm up activities may be detrimental to players' physical performance. However, the inclusion of re-warm up prior to match is a complex issue, since the manipulation of volume, intensity and recovery may positively or negatively affect the subsequent performance. In fact, this exploratory study shows that eccentric exercise may be harmful for physical performance when performed prior a football match. However, plyometric and repeated changes of direction exercises seem to be simple, quick and efficient activities to attenuate losses in vertical jump and sprint capacity after warm up. Coaches should aim to develop individual optimal exercise modes in order to optimize physical performance after re warm activities.

An assessment of global warming stress on Caribbean coral reef ecosystems

Energy Technology Data Exchange (ETDEWEB)

Atwood, D.K.; Hendec, J.C.; Mendez, A. (NOAA, Miami, FL (USA). Atlantic Oceanography and Meteorology Laboratory)

1992-07-01

There is evidence that stress on coral reef ecosystems in the Caribbean region is increasing. Recently numerous authors have stated that the major stress results from 'abnormally high' seasonal sea surface temperatures (SST) and have implicated global warming as a cause, stating that recent episodes of coral bleaching result therefrom. However, an analysis of available SST data sets shows no discernible warming trend that could cause an increase in coral bleaching. Given the lack of long-term records synoptic with observations of coral ecosystem health, there is insufficient evidence available to label temperatures observed in coincidence with recent regional bleaching events as 'abnormally' high.

An assessment of global warming stress on Caribbean coral reef ecosystems

Energy Technology Data Exchange (ETDEWEB)

Atwood, D K; Hendec, J C; Mendez, A [NOAA, Miami, FL (USA). Atlantic Oceanography and Meteorology Laboratory

1992-07-01

There is evidence that stress on coral reef ecosystems in the Caribbean region is increasing. Recently numerous authors have stated that the major stress results from 'abnormally high' seasonal sea surface temperatures (SST) and have implicated global warming as a cause, stating that recent episodes of coral bleaching result therefrom. However, an analysis of available SST data sets shows no discernible warming trend that could cause an increase in coral bleaching. Given the lack of long-term records synoptic with observations of coral ecosystem health, there is insufficient evidence available to label temperatures observed in coincidence with recent regional bleaching events as 'abnormally' high.

Seasonal temperature extremes in Potsdam

Science.gov (United States)

Kundzewicz, Zbigniew; Huang, Shaochun

2010-12-01

The awareness of global warming is well established and results from the observations made on thousands of stations. This paper complements the large-scale results by examining a long time-series of high-quality temperature data from the Secular Meteorological Station in Potsdam, where observation records over the last 117 years, i.e., from January 1893 are available. Tendencies of change in seasonal temperature-related climate extremes are demonstrated. "Cold" extremes have become less frequent and less severe than in the past, while "warm" extremes have become more frequent and more severe. Moreover, the interval of the occurrence of frost has been decreasing, while the interval of the occurrence of hot days has been increasing. However, many changes are not statistically significant, since the variability of temperature indices at the Potsdam station has been very strong.

Trends in airborne pollen and pollen-season-related features of anemophilous species in Jaen (south Spain): A 23-year perspective

Science.gov (United States)

Ruiz-Valenzuela, Luis; Aguilera, Fátima

2018-05-01

Over the last few decades, global warming is prompting phenological changes in numerous plant species across Europe, and a trend towards rising airborne pollen concentrations has been detected. This study, focused on the most frequent pollen types from arboreal and herbaceous species in the airborne spectrum of Jaen (southern Spain), revealed significant changes in airborne pollen intensity and duration of the pollen season over the 23-year study period. Here Cupressaceae, Olea, Pinus, Platanus, Quercus as arboreal taxa and Plantago as herbaceous taxa were the most important with notable changes of at least three pollen season characteristics. Airborne pollen trends from arboreal taxa with high to very high allergenic potential are rising in line with the local temperature increasing trend, and their pollen seasons tend to end later and last longer. However, both the pollen concentrations and the duration of the pollen season of some herbaceous taxa are declining. The climate conditions projected for south Europe under different greenhouse emissions scenarios could continue to prompt greater pollen release and longer pollen season in tree species, especially those that flowering in winter and early spring, but these warming trends might be adverse for the local development of some herbaceous species and favorable for others sharing the same ecological niche. If similar warming trends accompany long-term climate change, greater exposure times to seasonal allergens may occur with subsequent effects on health.

Warming and provenance limit tree recruitment across and beyond the elevation range of subalpine forest.

Science.gov (United States)

Kueppers, Lara M; Conlisk, Erin; Castanha, Cristina; Moyes, Andrew B; Germino, Matthew J; de Valpine, Perry; Torn, Margaret S; Mitton, Jeffry B

2017-06-01

Climate niche models project that subalpine forest ranges will extend upslope with climate warming. These projections assume that the climate suitable for adult trees will be adequate for forest regeneration, ignoring climate requirements for seedling recruitment, a potential demographic bottleneck. Moreover, local genetic adaptation is expected to facilitate range expansion, with tree populations at the upper forest edge providing the seed best adapted to the alpine. Here, we test these expectations using a novel combination of common gardens, seeded with two widely distributed subalpine conifers, and climate manipulations replicated at three elevations. Infrared heaters raised temperatures in heated plots, but raised temperatures more in the forest than at or above treeline because strong winds at high elevation reduced heating efficiency. Watering increased season-average soil moisture similarly across sites. Contrary to expectations, warming reduced Engelmann spruce recruitment at and above treeline, as well as in the forest. Warming reduced limber pine first-year recruitment in the forest, but had no net effect on fourth-year recruitment at any site. Watering during the snow-free season alleviated some negative effects of warming, indicating that warming exacerbated water limitations. Contrary to expectations of local adaptation, low-elevation seeds of both species initially recruited more strongly than high-elevation seeds across the elevation gradient, although the low-provenance advantage diminished by the fourth year for Engelmann spruce, likely due to small sample sizes. High- and low-elevation provenances responded similarly to warming across sites for Engelmann spruce, but differently for limber pine. In the context of increasing tree mortality, lower recruitment at all elevations with warming, combined with lower quality, high-provenance seed being most available for colonizing the alpine, portends range contraction for Engelmann spruce. The lower

In a warming climate, just how predictable are temperature extremes at weather and seasonal time scales?

CSIR Research Space (South Africa)

Landman, WA

2011-10-01

Full Text Available stream_source_info Landman7_2011.pdf.txt stream_content_type text/plain stream_size 3538 Content-Encoding ISO-8859-1 stream_name Landman7_2011.pdf.txt Content-Type text/plain; charset=ISO-8859-1 In a warming climate... at UK Met Office N9 members SA Japan UKUSA USA Brazil* SA SASA * IBSA-Ocean In use Near future Far future VCM/UTCM ENSEMBLES Strong anthropogenically forced warming trends have been observed over southern Africa and are projected...

De novo assembly of the perennial ryegrass transcriptome using an RNA-Seq strategy.

Directory of Open Access Journals (Sweden)

Jacqueline D Farrell

Full Text Available Perennial ryegrass is a highly heterozygous outbreeding grass species used for turf and forage production. Heterozygosity can affect de-Bruijn graph assembly making de novo transcriptome assembly of species such as perennial ryegrass challenging. Creating a reference transcriptome from a homozygous perennial ryegrass genotype can circumvent the challenge of heterozygosity. The goals of this study were to perform RNA-sequencing on multiple tissues from a highly inbred genotype to develop a reference transcriptome. This was complemented with RNA-sequencing of a highly heterozygous genotype for SNP calling.De novo transcriptome assembly of the inbred genotype created 185,833 transcripts with an average length of 830 base pairs. Within the inbred reference transcriptome 78,560 predicted open reading frames were found of which 24,434 were predicted as complete. Functional annotation found 50,890 transcripts with a BLASTp hit from the Swiss-Prot non-redundant database, 58,941 transcripts with a Pfam protein domain and 1,151 transcripts encoding putative secreted peptides. To evaluate the reference transcriptome we targeted the high-affinity K+ transporter gene family and found multiple orthologs. Using the longest unique open reading frames as the reference sequence, 64,242 single nucleotide polymorphisms were found. One thousand sixty one open reading frames from the inbred genotype contained heterozygous sites, confirming the high degree of homozygosity.Our study has developed an annotated, comprehensive transcriptome reference for perennial ryegrass that can aid in determining genetic variation, expression analysis, genome annotation, and gene mapping.

Sibship Characteristics and Risk of Allergic Rhinitis and Asthma

DEFF Research Database (Denmark)

Westergaard, Tine; Rostgaard, Klaus; Wohlfahrt, Jan

2005-01-01

asthma; birth order; hypersensitivity; rhinitis; allergic; perennial; rhinitis; allergic; seasonal; risk factors; siblings......asthma; birth order; hypersensitivity; rhinitis; allergic; perennial; rhinitis; allergic; seasonal; risk factors; siblings...

Soil-surface CO2 flux and growth in a boreal Norway spruce stand: Effects of soil warming and nutrition

International Nuclear Information System (INIS)

Stroemgren, M.

2001-01-01

Global warming is predicted to affect the carbon balance of forests. A change in the carbon balance would give a positive or negative feedback to the greenhouse effect, which would affect global warming. The effects of long-term soil warming on growth, nutrient and soil-surface CO 2 flux (R) dynamics were studied in irrigated (I) and irrigated-fertilised (IL) stands of Norway spruce in northern Sweden. Soil temperature on heated plots (Ih and ILh) was maintained 5 deg C above that on unheated plots (Ic and ILc) from May to October, by heating cables. After six years' soil warming, stemwood production increased by 100% and 50% in the I and IL treatment, respectively. The main production increase occurred at the beginning of the season, probably as an effect of the earlier increase in soil temperature. In the 1h treatment, however, the growth increase was evident during the entire season. The effect of increased nitrogen (N) mineralisation on annual growth appeared to be stronger than the direct effect of warming. From 1995-2000, the total amount of N stored in aboveground tree parts increased by 100 and 475 kg N/ha on Ic and ILc plots, respectively. During the same period, 450 kg N fertiliser was added to the ILc plot. Soil warming increased the total amount of N stored in aboveground tree parts by 50 kg N/ha, independently of nutrient treatment. Soil warming did not significantly increase R, except in early spring, when R was 30-50% higher on heated compared to unheated plots. The extended growing season, however, increased annual respiration (RA) by 12-30% throughout. RA losses were estimated to be 0.6-0.7 kg C/ha/year. Use of relationships between R and soil temperature, derived from unheated plots, overestimated RA on heated plots by 50-80%. These results suggest that acclimation of root or microbial respiration or both to temperature had occurred, but the exact process(es) and their relative contribution are still unclear. In conclusion, the study showed that

Genetic variation, population structure, and linkage disequilibrium in European elite germplasm of perennial ryegrass

DEFF Research Database (Denmark)

Brazauskas, Gintaras; Lenk, Ingo; Pedersen, Morten Greve

2011-01-01

Perennial ryegrass (Lolium perenne L.) is a highly valued temperate climate grass species grown as forage crop and for amenity uses. Due to its outbreeding nature and recent domestication, a high degree of genetic diversity is expected among cultivars. The aim of this study was to assess the extent...... of linkage disequilibrium (LD) within European elite germplasm and to evaluate the appropriate methodology for genetic association mapping in perennial ryegrass. A high level of genetic diversity was observed in a set of 380 perennial ryegrass elite genotypes when genotyped with 40 SSRs and 2 STS markers...... and occurred within 0.4 cM across European varieties, when population structure was taken into consideration. However, an extended LD of up to 6.6 cM was detected within the variety Aberdart. High genetic diversity and rapid LD decay provide means for high resolution association mapping in elite materials...

Antarctica: Cooling or Warming?

Science.gov (United States)

Bunde, Armin; Ludescher, Josef; Franzke, Christian

2013-04-01

We consider the 14 longest instrumental monthly mean temperature records from the Antarctica and analyse their correlation properties by wavelet and detrended fluctuation analysis. We show that the stations in the western and the eastern part of the Antarctica show significant long-term memory governed by Hurst exponents close to 0.8 and 0.65, respectively. In contrast, the temperature records at the inner part of the continent (South Pole and Vostok), resemble white noise. We use linear regression to estimate the respective temperature differences in the records per decade (i) for the annual data, (ii) for the summer and (iii) for the winter season. Using a recent approach by Lennartz and Bunde [1] we estimate the respective probabilities that these temperature differences can be exceeded naturally without inferring an external (anthropogenic) trend. We find that the warming in the western part of the continent and the cooling at the South Pole is due to a gradually changes in the cold extremes. For the winter months, both cooling and warming are well outside the 95 percent confidence interval, pointing to an anthropogenic origin. In the eastern Antarctica, the temperature increases and decreases are modest and well within the 95 percent confidence interval. [1] S. Lennartz and A. Bunde, Phys. Rev. E 84, 021129 (2011)

Observational Analysis of Cloud and Precipitation in Midlatitude Cyclones: Northern Versus Southern Hemisphere Warm Fronts

Science.gov (United States)

Naud, Catherine M.; Posselt, Derek J.; van den Heever, Susan C.

2012-01-01

Extratropical cyclones are responsible for most of the precipitation and wind damage in the midlatitudes during the cold season, but there are still uncertainties on how they will change in a warming climate. An ubiquitous problem amongst General Circulation Models (GCMs) is a lack of cloudiness over the southern oceans that may be in part caused by a lack of clouds in cyclones. We analyze CloudSat, CALIPSO and AMSR-E observations for 3 austral and boreal cold seasons and composite cloud frequency of occurrence and precipitation at the warm fronts for northern and southern hemisphere oceanic cyclones. We find that cloud frequency of occurrence and precipitation rate are similar in the early stage of the cyclone life cycle in both northern and southern hemispheres. As cyclones evolve and reach their mature stage, cloudiness and precipitation at the warm front increase in the northern hemisphere but decrease in the southern hemisphere. This is partly caused by lower amounts of precipitable water being available to southern hemisphere cyclones, and smaller increases in wind speed as the cyclones evolve. Southern hemisphere cloud occurrence at the warm front is found to be more sensitive to the amount of moisture in the warm sector than to wind speeds. This suggests that cloudiness in southern hemisphere storms may be more susceptible to changes in atmospheric water vapor content, and thus to changes in surface temperature than their northern hemisphere counterparts. These differences between northern and southern hemisphere cyclones are statistically robust, indicating A-Train-based analyses as useful tools for evaluation of GCMs in the next IPCC report.

The influence of season and living environment on children's urinary 1-hydroxypyrene levels in Ulaanbaatar, Mongolia.

Science.gov (United States)

Chen, Yi-Ting; Huang, Yu-Kai; Luvsan, Munkh-Erdene; Gombojav, Enkhjargal; Ochir, Chimedsuren; Bulgan, Jargal; Chan, Chang-Chuan

2015-02-01

Heating indoor living environments elevates air pollution in Ulaanbaatar, Mongolia. This study was conducted to investigate the influence of season and living environment on children's urinary 1-hydroxypyrene (1-OHP) levels in Ulaanbaatar, Mongolia. Our study subjects were 320 children aged 11-15 years living in gers, brick houses and apartments, in ger and non-ger areas of Ulaanbaatar. Spot urine samples and questionnaires were collected three times from each subject in three seasons, September (warm) and December (cold) in 2011 and March (moderate) in 2012. Urinary 1-OHP was analyzed by high-performance liquid chromatography with fluorescent detection (HPLC/FLD). Generalized estimating equation (GEE) models were applied to estimate the seasonal and residential effects on 1-OHP levels, adjusting for demographic and environmental factors. Children's urinary 1-OHP levels showed significant seasonal differences with 0.30 ± 0.57 μmol/mol creatinine in cold season, 0.14 ± 0.12 μmol/mol creatinine in moderate season, and 0.14 ± 0.21 μmol/mol creatinine in warm season. After controlling confounding factors, the GEE model showed that season, living area, and housing type had significant influence on children's urinary 1-OHP levels. Urinary 1-OHP levels in the cold and moderate seasons were, respectively 2.13 and 1.37 times higher than the warm season. Urinary 1-OHP levels for children living in ger areas were 1.27 times higher than those living in non-ger areas. Children who lived in gers or brick houses had 1.58 and 1.34 times higher 1-OHP levels, respectively, compared with those living in apartments. Children's urinary 1-OHP levels were associated with either estimated NO2 or SO2 concentrations at their home addresses in Ulaanbaatar. Mongolian children's urinary 1-OHP levels were significantly elevated during the cold season, and for those living in ger areas, gers, or brick houses in Ulaanbaatar. Children's urinary 1-OHP levels were associated PAH co

The Perennial Ryegrass GenomeZipper – Targeted Use of Genome Resources for Comparative Grass Genomics

DEFF Research Database (Denmark)

Pfeiffer, Matthias; Martis, Mihaela; Asp, Torben

2013-01-01

(Lolium perenne) genome on the basis of conserved synteny to barley (Hordeum vulgare) and the model grass genome Brachypodium (Brachypodium distachyon) as well as rice (Oryza sativa) and sorghum (Sorghum bicolor). A transcriptome-based genetic linkage map of perennial ryegrass served as a scaffold......Whole-genome sequences established for model and major crop species constitute a key resource for advanced genomic research. For outbreeding forage and turf grass species like ryegrasses (Lolium spp.), such resources have yet to be developed. Here, we present a model of the perennial ryegrass...... to establish the chromosomal arrangement of syntenic genes from model grass species. This scaffold revealed a high degree of synteny and macrocollinearity and was then utilized to anchor a collection of perennial ryegrass genes in silico to their predicted genome positions. This resulted in the unambiguous...

Genomic prediction in families of perennial ryegrass based on genotyping-by-sequencing

DEFF Research Database (Denmark)

Ashraf, Bilal

In this thesis we investigate the potential for genomic prediction in perennial ryegrass using genotyping-by-sequencing (GBS) data. Association method based on family-based breeding systems was developed, genomic heritabilities, genomic prediction accurancies and effects of some key factors wer...... explored. Results show that low sequencing depth caused underestimation of allele substitution effects in GWAS and overestimation of genomic heritability in prediction studies. Other factors susch as SNP marker density, population structure and size of training population influenced accuracy of genomic...... prediction. Overall, GBS allows for genomic prediction in breeding families of perennial ryegrass and holds good potential to expedite genetic gain and encourage the application of genomic prediction...

Energy balance and cost-benefit analysis of biogas production from perennial energy crops pretreated by wet oxidation

DEFF Research Database (Denmark)

Uellendahl, Hinrich; Wang, Guangtao; Møller, H.B.

2008-01-01

. The conversion into biogas in anaerobic digestion plants shows however much lower specific methane yields for the raw perennial crops like miscanthus and willow due to their lignocellulosic structure. Without pretreatment the net energy gain is therefore lower for the perennials than for corn. When applying wet...

Coupled prediction of flood response and debris flow initiation during warm- and cold-season events in the Southern Appalachians, USA

Science.gov (United States)

Tao, J.; Barros, A. P.

2014-01-01

Debris flows associated with rainstorms are a frequent and devastating hazard in the Southern Appalachians in the United States. Whereas warm-season events are clearly associated with heavy rainfall intensity, the same cannot be said for the cold-season events. Instead, there is a relationship between large (cumulative) rainfall events independently of season, and thus hydrometeorological regime, and debris flows. This suggests that the dynamics of subsurface hydrologic processes play an important role as a trigger mechanism, specifically through soil moisture redistribution by interflow. We further hypothesize that the transient mass fluxes associated with the temporal-spatial dynamics of interflow govern the timing of shallow landslide initiation, and subsequent debris flow mobilization. The first objective of this study is to investigate this relationship. The second objective is to assess the physical basis for a regional coupled flood prediction and debris flow warning system. For this purpose, uncalibrated model simulations of well-documented debris flows in headwater catchments of the Southern Appalachians using a 3-D surface-groundwater hydrologic model coupled with slope stability models are examined in detail. Specifically, we focus on two vulnerable headwater catchments that experience frequent debris flows, the Big Creek and the Jonathan Creek in the Upper Pigeon River Basin, North Carolina, and three distinct weather systems: an extremely heavy summertime convective storm in 2011; a persistent winter storm lasting several days; and a severe winter storm in 2009. These events were selected due to the optimal availability of rainfall observations; availability of detailed field surveys of the landslides shortly after they occurred, which can be used to evaluate model predictions; and because they are representative of events that cause major economic losses in the region. The model results substantiate that interflow is a useful prognostic of conditions

Detecting the permafrost carbon feedback: talik formation and increased cold-season respiration as precursors to sink-to-source transitions

Science.gov (United States)

Parazoo, Nicholas C.; Koven, Charles D.; Lawrence, David M.; Romanovsky, Vladimir; Miller, Charles E.

2018-01-01

Thaw and release of permafrost carbon (C) due to climate change is likely to offset increased vegetation C uptake in northern high-latitude (NHL) terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a subsurface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost-affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM) version 4.5, a permafrost and biogeochemistry model, in comparison to long-term deep borehole data along North American and Siberian transects, to investigate thaw-driven C sources in NHL ( > 55° N) from 2000 to 2300. Widespread talik at depth is projected across most of the NHL permafrost region (14 million km2) by 2300, 6.2 million km2 of which is projected to become a long-term C source, emitting 10 Pg C by 2100, 50 Pg C by 2200, and 120 Pg C by 2300, with few signs of slowing. Roughly half of the projected C source region is in predominantly warm sub-Arctic permafrost following talik onset. This region emits only 20 Pg C by 2300, but the CLM4.5 estimate may be biased low by not accounting for deep C in yedoma. Accelerated decomposition of deep soil C following talik onset shifts the ecosystem C balance away from surface dominant processes (photosynthesis and litter respiration), but sink-to-source transition dates are delayed by 20-200 years by high ecosystem productivity, such that talik peaks early ( ˜ 2050s, although borehole data suggest sooner) and C source transition peaks late ( ˜ 2150-2200). The remaining C source region in cold northern Arctic permafrost, which shifts to a net

Cool-Season Turfgrass Species and Cultivars: Response to Simulated Traffic in Central Italy

Directory of Open Access Journals (Sweden)

Carlo F. Cereti

2010-03-01

Full Text Available Turfgrass species differ greatly in their ability to withstand the abrasion and compaction of traffic. Wear tolerance of turfgrass species and cultivars has been evaluated abroad by many researchers, while only few and partial studies have been conducted in Italy. Field experiment was carried out in Viterbo in 2001, 2002 and 2003 to evaluate the effect of the simulated traffic on 110 varieties belonging to four turfgrass cool-season species: tall fescue (Festuca arundinacea Schreb., fine fescues (Festuca rubra L. ssp. rubra Gaud., ssp. commutata Gaud., ssp. tricophylla Gaud., perennial ryegrass (Lolium perenne L. and Kentucky bluegrass (Poa pratensis L.. Shoot density, visual turfgrass quality and thatch thickness were the major characters recorded to estimate wear tolerance. Traffic was simulated using a device containing three rollers pulled by a small tractor. The traffic simulator weighed 564 kg and applied a pressure of about 3 MPa. Results indicated that perennial ryegrass and tall fescue had high wear tolerance and low statistical variation among cultivars. Kentucky bluegrass showed an average wear tolerance owing to its shoot density and good recovery potential. In spite of their high shoot density, fine fescues exhibited poor wear tolerance because of their scarce resistance to high temperatures which are typical of the Mediterranean climate in late spring and summer. This study enabled a preliminary selection of the most suitable cool-season grasses and cultivars for trafficked and non-trafficked areas in Central Italy and highlighted that different turfgrass species have different wear tolerance mechanisms.

Farmer perceptions on factors influencing water scarcity for goats in resource-limited communal farming environments.

Science.gov (United States)

Mdletshe, Zwelethu Mfanafuthi; Ndlela, Sithembile Zenith; Nsahlai, Ignatius Verla; Chimonyo, Michael

2018-05-09

The objective of the study was to compare factors influencing water scarcity for goats in areas where there are seasonal and perennial rivers under resource-limited communal farming environments. Data were collected using a structured questionnaire (n = 285) administered randomly to smallholder goat farmers from areas with seasonal and perennial rivers. Ceremonies was ranked as the major reason for keeping goats. Water scarcity was ranked the major constraint to goat production in areas with seasonal rivers when compared to areas with perennial rivers (P goat drinking in areas with seasonal and perennial river systems during cool dry and rainy seasons. Rivers were ranked as an important water source for goat drinking where there are seasonal and perennial river systems during the cool dry season. Households located close (≤ 3 km) to the nearest water source reported drinking water for goats a scarce resource. These results show that river systems, season and distance to the nearest water source from a household were factors perceived by farmers to influence water scarcity for goats in resource-limited communal farming environments. Farmers should explore water-saving strategies such as recycling wastewater from kitchens and bathrooms as an alternative water source. The government may assist farmers through sinking boreholes to supply water for both humans and livestock.

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

Science.gov (United States)

Carlson, Henrik; Caballero, Rodrigo

2017-08-01

Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2-thin clouds or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has ˜ 11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

Defoliation effects of perennial grasses – continuing confusion | DL ...

African Journals Online (AJOL)

Although an adequate knowledge of growth patterns and defoliation effects in perennial grasses is a prerequisite for the rational use of veld and pastures for animal production, our knowledge of this subject is far from adequate. The results of various physiological and clipping studies on tropical and sub-tropical grasses are ...

Reconsidering the generation time hypothesis based on nuclear ribosomal ITS sequence comparisons in annual and perennial angiosperms

Directory of Open Access Journals (Sweden)

Fiz-Palacios Omar

2008-12-01

Full Text Available Abstract Background Differences in plant annual/perennial habit are hypothesized to cause a generation time effect on divergence rates. Previous studies that compared rates of divergence for internal transcribed spacer (ITS1 and ITS2 sequences of nuclear ribosomal DNA (nrDNA in angiosperms have reached contradictory conclusions about whether differences in generation times (or other life history features are associated with divergence rate heterogeneity. We compared annual/perennial ITS divergence rates using published sequence data, employing sampling criteria to control for possible artifacts that might obscure any actual rate variation caused by annual/perennial differences. Results Relative rate tests employing ITS sequences from 16 phylogenetically-independent annual/perennial species pairs rejected rate homogeneity in only a few comparisons, with annuals more frequently exhibiting faster substitution rates. Treating branch length differences categorically (annual faster or perennial faster regardless of magnitude with a sign test often indicated an excess of annuals with faster substitution rates. Annuals showed an approximately 1.6-fold rate acceleration in nucleotide substitution models for ITS. Relative rates of three nuclear loci and two chloroplast regions for the annual Arabidopsis thaliana compared with two closely related Arabidopsis perennials indicated that divergence was faster for the annual. In contrast, A. thaliana ITS divergence rates were sometimes faster and sometimes slower than the perennial. In simulations, divergence rate differences of at least 3.5-fold were required to reject rate constancy in > 80 % of replicates using a nucleotide substitution model observed for the combination of ITS1 and ITS2. Simulations also showed that categorical treatment of branch length differences detected rate heterogeneity > 80% of the time with a 1.5-fold or greater rate difference. Conclusion Although rate homogeneity was not rejected

Soil carbon under perennial pastures; benchmarking the influence of pasture age and management

Science.gov (United States)

Orgill, Susan E.; Spoljaric, Nancy; Kelly, Georgina

2015-07-01

This paper reports baseline soil carbon stocks from a field survey of 19 sites; 8 pairs/triplet in the Monaro region of New South Wales. Site comparisons were selected by the Monaro Farming Systems group to demonstrate the influence of land management on soil carbon, and included: nutrient management, liming, pasture age and cropping history. Soil carbon stocks varied with parent material and with land management. The fertilised (phosphorus) native perennial pasture had a greater stock of soil carbon compared with the unfertilised site; 46.8 vs 40.4 Mg.C.ha to 0.50 m. However, the introduced perennial pasture which had been limed had a lower stock of soil carbon compared with the unlimed site; 62.8 vs 66.7 Mg.C.ha to 0.50 m. There was a greater stock of soil carbon under two of the three younger (35 yr old) pastures. Cropped sites did not have lower soil carbon stocks at all sites; however, this survey was conducted after three years of above average annual rainfall and most sites had been cropped for less than three years. At all sites more than 20% of the total carbon stock to 0.50 m was in the 0.30 to 0.50 m soil layer highlighting the importance of considering this soil layer when investigating the implications of land management on soil carbon. Our baseline data indicates that nutrient management may increase soil carbon under perennial pastures and highlights the importance of perennial pastures for soil carbon sequestration regardless of age.

A zero-power warming chamber for investigating plant responses to rising temperature

Directory of Open Access Journals (Sweden)

K. F. Lewin

2017-09-01

Full Text Available Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by  ∼  1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be  ∼  2–3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our zero-power warming (ZPW chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. During the thaw season on the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tunable, enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming

A zero-power warming chamber for investigating plant responses to rising temperature

Science.gov (United States)

Lewin, Keith F.; McMahon, Andrew M.; Ely, Kim S.; Serbin, Shawn P.; Rogers, Alistair

2017-09-01

Advances in understanding and model representation of plant and ecosystem responses to rising temperature have typically required temperature manipulation of research plots, particularly when considering warming scenarios that exceed current climate envelopes. In remote or logistically challenging locations, passive warming using solar radiation is often the only viable approach for temperature manipulation. However, current passive warming approaches are only able to elevate the mean daily air temperature by ˜ 1.5 °C. Motivated by our need to understand temperature acclimation in the Arctic, where warming has been markedly greater than the global average and where future warming is projected to be ˜ 2-3 °C by the middle of the century; we have developed an alternative approach to passive warming. Our zero-power warming (ZPW) chamber requires no electrical power for fully autonomous operation. It uses a novel system of internal and external heat exchangers that allow differential actuation of pistons in coupled cylinders to control chamber venting. This enables the ZPW chamber venting to respond to the difference between the external and internal air temperatures, thereby increasing the potential for warming and eliminating the risk of overheating. During the thaw season on the coastal tundra of northern Alaska our ZPW chamber was able to elevate the mean daily air temperature 2.6 °C above ambient, double the warming achieved by an adjacent passively warmed control chamber that lacked our hydraulic system. We describe the construction, evaluation and performance of our ZPW chamber and discuss the impact of potential artefacts associated with the design and its operation on the Arctic tundra. The approach we describe is highly flexible and tunable, enabling customization for use in many different environments where significantly greater temperature manipulation than that possible with existing passive warming approaches is desired.

Seasonal and inter-annual temperature variability in the bottom waters over the Black Sea shelf

Science.gov (United States)

Shapiro, G. I.; Wobus, F.; Aleynik, D. L.

2011-02-01

Long-term changes in the state of the Bottom Shelf Water (BSW) on the Western shelf of the Black Sea are assessed using analysis of intra- and inter-annual variations of temperature as well as their relations to physical parameters of both shelf and deep-sea waters. First, large data sets of in-situ observations over the 20th century are compiled into high-resolution monthly climatology at different depth levels. Then, the temperature anomalies from the climatic mean are calculated and aggregated into spatial compartments and seasonal bins to reveal temporal evolution of the BSW. For the purpose of this study the BSW is defined as such shelf water body between the seabed and the upper mixed layer (bounded by the σθ = 14.2 isopycnal) which has limited ability to mix vertically with oxygen-rich surface waters during the warm season (May-November) due to the formation of a seasonal pycnocline. The effects of atmospheric processes at the surface on the BSW are hence suppressed as well as the action of the "biological pump". The vertical extent of the near- bottom waters is determined based on energy considerations and the structure of the seasonal pycnocline, whilst the horizontal extent is controlled by the shelf break, where strong along-slope currents hinder exchanges with the deep sea. The BSW is shown to occupy nearly half of the area of the shelf during the summer stratification period. The potential of the BSW to ventilate horizontally during the warm season with the deep-sea waters is assessed using isopycnic analysis of temperature variations. A long-term time series of temperature anomalies in the BSW is constructed from observations during the May-November period for the 2nd half of the 20th century. The results reveal a warm phase in the 1960s/70s, followed by cooling of the BSW during 1980-2001. The transition between the warm and cold periods coincides with a regime shift in the Black Sea ecosystem. While it was confirmed that the memory of winter

Amplified warming projections for high altitude regions of the northern hemisphere mid-latitudes from CMIP5 models

International Nuclear Information System (INIS)

Rangwala, Imtiaz; Sinsky, Eric; Miller, James R

2013-01-01

We use output from global climate models available from the Coupled Model Intercomparison Project Phase 5 (CMIP5) for three different greenhouse gas emission scenarios to investigate whether the projected warming in mountains by the end of the 21st century is significantly different from that in low elevation regions. To remove the effects of latitudinal variation in warming rates, we focus on seasonal changes in the mid-latitude band of the northern hemisphere between 27.5° N and 40° N, where the two major mountain systems are the Tibetan Plateau/Himalayas in Asia and the Rocky Mountains in the United States. Results from the multi-model ensemble indicate that warming rates in mountains will be enhanced relative to non-mountain regions at the same latitude, particularly during the cold season. The strongest correlations of enhanced warming with elevation are obtained for the daily minimum temperature during winter, with the largest increases found for the Tibetan Plateau/Himalayas. The model projections indicate that this occurs, in part, because of proportionally greater increases in downward longwave radiation at higher elevations in response to increases in water vapor. The mechanisms for enhanced increases in winter and spring maximum temperatures in the Rockies appear to be influenced more by increases in surface absorption of solar radiation owing to a reduced snow cover. Furthermore, the amplification of warming with elevation is greater for a higher greenhouse gas emission scenario. (letter)

Indo-Pacific sea surface temperature influences on failed consecutive rainy seasons over eastern Africa

Science.gov (United States)

Hoell, Andrew; Funk, Christopher C.

2014-01-01

Rainfall over eastern Africa (10°S–10°N; 35°E–50°E) is bimodal, with seasonal maxima during the "long rains" of March–April–May (MAM) and the "short rains" of October–November–December (OND). Below average precipitation during consecutive long and short rains seasons over eastern Africa can have devastating long-term impacts on water availability and agriculture. Here, we examine the forcing of drought during consecutive long and short rains seasons over eastern Africa by Indo-Pacific sea surface temperatures (SSTs). The forcing of eastern Africa precipitation and circulation by SSTs is tested using ten ensemble simulations of a global weather forecast model forced by 1950–2010 observed global SSTs. Since the 1980s, Indo-Pacific SSTs have forced more frequent droughts spanning consecutive long and short rains seasons over eastern Africa. The increased frequency of dry conditions is linked to warming SSTs over the Indo-west Pacific and to a lesser degree to Pacific Decadal Variability. During MAM, long-term warming of tropical west Pacific SSTs from 1950–2010 has forced statistically significant precipitation reductions over eastern Africa. The warming west Pacific SSTs have forced changes in the regional lower tropospheric circulation by weakening the Somali Jet, which has reduced moisture and rainfall over the Horn of Africa. During OND, reductions in precipitation over recent decades are oftentimes overshadowed by strong year-to-year precipitation variability forced by the Indian Ocean Dipole and the El Niño–Southern Oscillation.

Perennial filter strips reduce nitrate levels in soil and shallow groundwater after grassland-to-cropland conversion.

Science.gov (United States)

Zhou, Xiaobo; Helmers, Matthew J; Asbjornsen, Heidi; Kolka, Randy; Tomer, Mark D

2010-01-01

Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland-to-cropland conversion on nitrate-nitrogen (NO3-N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO3-N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed-scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20 PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (Bromus L.) cover for at least 10 yr. Nonperennial areas were maintained under a no-till 2-yr corn (Zea mays L.)--soybean [Glycine max. (L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO3-N concentration from 2005 to 2008. The results indicated significant increases in NO3-N concentration in soil and groundwater following grassland-to-cropland conversion. Nitrate-nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long-term monitoring is needed to observe and understand the full response to land-use conversion.

Soil warming increased whole-tree water use of Pinus cembra at the treeline in the Central Tyrolean Alps.

Science.gov (United States)

Wieser, Gerhard; Grams, Thorsten E E; Matyssek, Rainer; Oberhuber, Walter; Gruber, Andreas

2015-03-01

This study quantified the effect of soil warming on sap flow density (Qs) of Pinus cembra L. at the treeline in the Central Tyrolean Alps. To enhance soil temperature we installed a transparent roof construction above the forest floor around six trees. Six other trees served as controls in the absence of any manipulation. Roofing enhanced growing season mean soil temperature by 1.6, 1.3 and 1.0 °C at 5, 10 and 20 cm soil depth, respectively, while soil water availability was not affected. Sap flow density (using Granier-type thermal dissipation probes) and environmental parameters were monitored throughout three growing seasons. During the first year of treatment, no warming effect was detected on Qs. However, soil warming caused Qs to increase significantly by 11 and 19% above levels in control trees during the second and third year, respectively. This effect appeared to result from warming-induced root production, a reduction in viscosity and perhaps an increase also in root hydraulic conductivity. Hardly affected were leaf-level net CO2 uptake rate and conductance for water vapour, so that water-use efficiency stayed unchanged as confirmed by needle δ(13)C analysis. We conclude that tree water loss will increase with soil warming, which may alter the water balance within the treeline ecotone of the Central Austrian Alps in a future warming environment. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Recent increased warming of the Alaskan marine Arctic due to midlatitude linkages

Science.gov (United States)

Overland, James E.; Wang, Muyin; Ballinger, Thomas J.

2018-01-01

Alaskan Arctic waters have participated in hemispheric-wide Arctic warming over the last two decades at over two times the rate of global warming. During 2008-13, this relative warming occurred only north of the Bering Strait and the atmospheric Arctic front that forms a north-south thermal barrier. This front separates the southeastern Bering Sea temperatures from Arctic air masses. Model projections show that future temperatures in the Chukchi and Beaufort seas continue to warm at a rate greater than the global rate, reaching a change of +4°C by 2040 relative to the 1981-2010 mean. Offshore at 74°N, climate models project the open water duration season to increase from a current average of three months to five months by 2040. These rates are occasionally enhanced by midlatitude connections. Beginning in August 2014, additional Arctic warming was initiated due to increased SST anomalies in the North Pacific and associated shifts to southerly winds over Alaska, especially in winter 2015-16. While global warming and equatorial teleconnections are implicated in North Pacific SSTs, the ending of the 2014-16 North Pacific warm event demonstrates the importance of internal, chaotic atmospheric natural variability on weather conditions in any given year. Impacts from global warming on Alaskan Arctic temperature increases and sea-ice and snow loss, with occasional North Pacific support, are projected to continue to propagate through the marine ecosystem in the foreseeable future. The ecological and societal consequences of such changes show a radical departure from the current Arctic environment.

Acclimation and soil moisture constrain sugar maple root respiration in experimentally warmed soil.

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Jarvi, Mickey P; Burton, Andrew J

2013-09-01

The response of root respiration to warmer soil can affect ecosystem carbon (C) allocation and the strength of positive feedbacks between climatic warming and soil CO2 efflux. This study sought to determine whether fine-root (maple (Acer saccharum Marsh.)-dominated northern hardwood forest would adjust to experimentally warmed soil, reducing C return to the atmosphere at the ecosystem scale to levels lower than that would be expected using an exponential temperature response function. Infrared heating lamps were used to warm the soil (+4 to +5 °C) in a mature sugar maple forest in a fully factorial design, including water additions used to offset the effects of warming-induced dry soil. Fine-root-specific respiration rates, root biomass, root nitrogen (N) concentration, soil temperature and soil moisture were measured from 2009 to 2011, with experimental treatments conducted from late 2010 to 2011. Partial acclimation of fine-root respiration to soil warming occurred, with soil moisture deficit further constraining specific respiration rates in heated plots. Fine-root biomass and N concentration remained unchanged. Over the 2011 growing season, ecosystem root respiration was not significantly greater in warmed soil. This result would not be predicted by models that allow respiration to increase exponentially with temperature and do not directly reduce root respiration in drier soil.

Nephrolithiasis, stone composition, meteorology, and seasons in Malta: Is there any connection?

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Buttigieg, Jesmar; Attard, Stephanie; Carachi, Alexander; Galea, Ruth; Fava, Stephen

2016-01-01

The effect of seasons and meteorology on the incidence of nephrolithiasis has been studied in various regions around the globe, but seldom in the Mediterranean. This retrospective analysis aims at investigating these putative effects in the Maltese Islands, whose climate is typically Mediterranean, followed by a systematic review of the literature. Submission rate and chemical composition of all kidney stones after spontaneous passage or surgical removal between January 2009 and December 2011 were analyzed according to seasons and corresponding meteorology. A total of 389 stones were analyzed. A higher stone submission rate was observed in summer compared to winter (31.6% vs. 20.8%, P = 0.0008) and in the warm period compared to the cold period (57.1% vs. 42.9%, P = 0.0001). Significant correlation was established between the monthly number of stones and mean monthly maximum temperature (r = 0.50, P = 0.002), mean monthly temperature (r = 0.49, P = 0.003) and mean monthly Humidex (r = 0.49, P = 0.007). Humidex was found to be an independent predictor for stone submission (β = 0.49, P = 0.007). The majority of stones contained calcium (83.3%), combined with oxalate (77.6%), phosphate (14.7%), and carbonate (2.8%). Some stones (11.8%) contained a mixture of >1 negatively charged molecules. Urate (11.6%), cysteine (4.6%), and ammonium-magnesium-phosphate (0.5%) constituted the rest. There was no association between chemical composition and seasons. Literature review included 25 articles. Higher ambient temperature and warm seasons were the most commonly encountered risk factors for both presentation and etiology of nephrolithiasis. A significant positive correlation was noted between ambient temperature and stone submission rate, which was significantly higher during the warm months in Malta.

Seasonal variation of the protozooplanktonic community in a tropical oligotrophic environment (Ilha Solteira reservoir, Brazil).

Science.gov (United States)

Mansano, A S; Hisatugo, K F; Leite, M A; Luzia, A P; Regali-Seleghim, M H

2013-05-01

The seasonal variation of the protozooplanktonic community (ciliates and testate amoebae) was studied in a tropical oligotrophic reservoir in Brazil, which was under the influence of two contrasting climatic seasons (rainy/warm and dry/cold). The aim of this study was to evaluate the effect of these climatic changes on physical, chemical and biological variables in the dynamic of this community. The highest mean density of total protozoans occurred in the rainy/warm season (5683.2 ind L-1), while the lowest was in the dry/cold (2016.0 ind L-1). Considering the seasonal variations, the protozoan groups that are truly planktonic, such as the oligotrichs (Spirotrichea), predominated in the dry season, whereas during the rainy season, due to the material input and resuspension of sediment, sessile protozoans of the Peritrichia group were the most important ones. The dominant protozoans were Urotricha globosa, Cothurnia annulata, Pseudodifflugia sp. and Halteria grandinella. The highest densities of H. grandinella were associated with more oxygenated and transparent water conditions, while the highest densities of C. annulata occurred in sites with high turbidity, pH and trophic state index (TSI). The study demonstrated that density and composition of protozooplanktonic species and groups of the reservoir suffered seasonal variation due to the environmental variables (mainly temperature, turbidity, water transparency, dissolved oxygen and TSI) and the biological variables (e.g. morphological characteristics, eating habits and escape strategies from predation of the species).

Late Cretaceous seasonal ocean variability from the Arctic.

Science.gov (United States)

Davies, Andrew; Kemp, Alan E S; Pike, Jennifer

2009-07-09

The modern Arctic Ocean is regarded as a barometer of global change and amplifier of global warming and therefore records of past Arctic change are critical for palaeoclimate reconstruction. Little is known of the state of the Arctic Ocean in the greenhouse period of the Late Cretaceous epoch (65-99 million years ago), yet records from such times may yield important clues to Arctic Ocean behaviour in near-future warmer climates. Here we present a seasonally resolved Cretaceous sedimentary record from the Alpha ridge of the Arctic Ocean. This palaeo-sediment trap provides new insight into the workings of the Cretaceous marine biological carbon pump. Seasonal primary production was dominated by diatom algae but was not related to upwelling as was previously hypothesized. Rather, production occurred within a stratified water column, involving specially adapted species in blooms resembling those of the modern North Pacific subtropical gyre, or those indicated for the Mediterranean sapropels. With increased CO(2) levels and warming currently driving increased stratification in the global ocean, this style of production that is adapted to stratification may become more widespread. Our evidence for seasonal diatom production and flux testify to an ice-free summer, but thin accumulations of terrigenous sediment within the diatom ooze are consistent with the presence of intermittent sea ice in the winter, supporting a wide body of evidence for low temperatures in the Late Cretaceous Arctic Ocean, rather than recent suggestions of a 15 degrees C mean annual temperature at this time.

A model study of the seasonality of sea surface temperature and circulation in the Atlantic North-Eastern Tropical Upwelling System.

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Saliou eFaye

2015-09-01

Full Text Available The climatological seasonal cycle of the sea surface temperature (SST in the north-eastern tropical Atlantic (7-25°N, 26-12°W is studied using a mixed layer heat budget in a regional ocean general circulation model. The region, which experiences one of the larger SST cycle in the tropics, forms the main part of the Guinea Gyre. It is characterized by a seasonally varying open ocean and coastal upwelling system, driven by the movements of the intertropical convergence zone (ITCZ. The model annual mean heat budget has two regimes schematically. South of roughly 12°N, advection of equatorial waters, mostly warm, and warming by vertical mixing, is balanced by net air-sea flux. In the rest of the domain, a cooling by vertical mixing, reinforced by advection at the coast, is balanced by the air-sea fluxes. Regarding the seasonal cycle, within a narrow continental band, in zonal mean, the SST early decrease (from September, depending on latitude, until December is driven by upwelling dynamics off Senegal and Mauritania (15°-20°N, and instead by air-sea fluxes north and south of these latitudes. Paradoxically, the later peaks of upwelling intensity (from March to July, with increasing latitude essentially damp the warming phase, driven by air-sea fluxes. The open ocean cycle to the west, is entirely driven by the seasonal net air-sea fluxes. The oceanic processes significantly oppose it, but for winter north of ~18°N. Vertical mixing in summer-autumn tends to cool (warm the surface north (south of the ITCZ, and advective cooling or warming by the geostrophic Guinea Gyre currents and the Ekman drift. This analysis supports previous findings on the importance of air-sea fluxes offshore. It mainly offers quantitative elements on the modulation of the SST seasonal cycle by the ocean circulation, and particularly by the upwelling dynamics.Keywords: SST, upwelling, circulation, heat budget, observations, modeling

Growth and phenology of three dwarf shrub species in a six-year soil warming experiment at the alpine treeline.

Science.gov (United States)

Anadon-Rosell, Alba; Rixen, Christian; Cherubini, Paolo; Wipf, Sonja; Hagedorn, Frank; Dawes, Melissa A

2014-01-01

Global warming can have substantial impacts on the phenological and growth patterns of alpine and Arctic species, resulting in shifts in plant community composition and ecosystem dynamics. We evaluated the effects of a six-year experimental soil warming treatment (+4°C, 2007-2012) on the phenology and growth of three co-dominant dwarf shrub species growing in the understory of Larix decidua and Pinus uncinata at treeline in the Swiss Alps. We monitored vegetative and reproductive phenology of Vaccinium myrtillus, Vaccinium gaultherioides and Empetrum hermaphroditum throughout the early growing season of 2012 and, following a major harvest at peak season, we measured the biomass of above-ground ramet fractions. For all six years of soil warming we measured annual shoot growth of the three species and analyzed ramet age and xylem ring width of V. myrtillus. Our results show that phenology of the three species was more influenced by snowmelt timing, and also by plot tree species (Larix or Pinus) in the case of V. myrtillus, than by soil warming. However, the warming treatment led to increased V. myrtillus total above-ground ramet biomass (+36% in 2012), especially new shoot biomass (+63% in 2012), as well as increased new shoot increment length and xylem ring width (+22% and +41%, respectively; average for 2007-2012). These results indicate enhanced overall growth of V. myrtillus under soil warming that was sustained over six years and was not caused by an extended growing period in early summer. In contrast, E. hermaphroditum only showed a positive shoot growth response to warming in 2011 (+21%), and V. gaultherioides showed no significant growth response. Our results indicate that V. myrtillus might have a competitive advantage over the less responsive co-occurring dwarf shrub species under future global warming.

Growth and phenology of three dwarf shrub species in a six-year soil warming experiment at the alpine treeline.

Directory of Open Access Journals (Sweden)

Alba Anadon-Rosell

Full Text Available Global warming can have substantial impacts on the phenological and growth patterns of alpine and Arctic species, resulting in shifts in plant community composition and ecosystem dynamics. We evaluated the effects of a six-year experimental soil warming treatment (+4°C, 2007-2012 on the phenology and growth of three co-dominant dwarf shrub species growing in the understory of Larix decidua and Pinus uncinata at treeline in the Swiss Alps. We monitored vegetative and reproductive phenology of Vaccinium myrtillus, Vaccinium gaultherioides and Empetrum hermaphroditum throughout the early growing season of 2012 and, following a major harvest at peak season, we measured the biomass of above-ground ramet fractions. For all six years of soil warming we measured annual shoot growth of the three species and analyzed ramet age and xylem ring width of V. myrtillus. Our results show that phenology of the three species was more influenced by snowmelt timing, and also by plot tree species (Larix or Pinus in the case of V. myrtillus, than by soil warming. However, the warming treatment led to increased V. myrtillus total above-ground ramet biomass (+36% in 2012, especially new shoot biomass (+63% in 2012, as well as increased new shoot increment length and xylem ring width (+22% and +41%, respectively; average for 2007-2012. These results indicate enhanced overall growth of V. myrtillus under soil warming that was sustained over six years and was not caused by an extended growing period in early summer. In contrast, E. hermaphroditum only showed a positive shoot growth response to warming in 2011 (+21%, and V. gaultherioides showed no significant growth response. Our results indicate that V. myrtillus might have a competitive advantage over the less responsive co-occurring dwarf shrub species under future global warming.

Interference between perennial grassland and Lavandula stoechas subsp. pedunculata seedlings: a case of spatial segregation cause by competition

Science.gov (United States)

Sánchez, Ana M.; Peco, Begoña

2004-07-01

This paper analyses the relationship between Lavandula stoechas subsp. pedunculata, a common Mediterranean scrub species in central Iberia, and perennial grasslands. While Lavandula gives rise to almost monospecific formations in intermediate and upper hill zones, perennial grasses occupy the low areas. The proposed explanatory hypothesis for this spatial distribution is that the scrub is unable to establish itself in grasslands with heavy spatial occupation. We designed two experiments to test this hypothesis, one which analysed the effect of perennial grass cover on Lavandula establishment, and another which focused on its influence on previously implanted seedling survival and growth, distinguishing the effect of shoot and root interference. The results show negative interference during establishment and later in the use of light and nutrients. This results in a very low overall survival probability, with only 1.4% of seedlings surviving the first growth period. This low success rate explains the existence of a clear spatial segregation between scrub patches and perennial-dominated grasslands.

Trends in land surface phenology and atmospheric CO2 seasonality in the Northern Hemisphere terrestrial ecosystems

Science.gov (United States)

Gonsamo, A.; Chen, J. M.

2017-12-01

Northern terrestrial ecosystems have shown global warming-induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO2 uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystems on the atmospheric CO2 concentration and 13C/12C isotope ratio seasonality. Atmospheric CO2 and 13C/12C seasonality is controlled by vegetation phenology, but is not identical because growth will typically commence some time before and terminate some time after the net carbon exchange changes sign in spring and autumn, respectively. Here, we use 34-year satellite normalized difference vegetation index (NDVI) observations to determine how changes in vegetation productivity and phenology affect both the atmospheric CO2 and 13C/12C seasonality. Differences and similarities in recent trends of CO2 and 13C/12C seasonality and vegetation phenology will be discussed. Furthermore, we use the NDVI observations, and atmospheric CO2 and 13C/12C data to show the trends and variability of the timing of peak season plant activity. Preliminary results show that the peak season plant activity of the Northern Hemisphere extra-tropical terrestrial ecosystems is shifting towards spring, largely in response to the warming-induced advance of the start of growing season. Besides, the spring-ward shift of the peak plant activity is contributing the most to the increasing peak season productivity. In other words, earlier start of growing season is highly linked to earlier arrival of peak of season and higher NDVI. Changes in the timing of peak season plant activity are expected to disrupt the synchrony of biotic interaction and exert strong biophysical feedbacks on climate by modifying the surface albedo and energy budget.

Effect of pre-grazing herbage mass on dairy cow performance, grass dry matter production and output from perennial ryegrass (Lolium perenne L.) pastures.

Science.gov (United States)

Wims, C M; Delaby, L; Boland, T M; O'Donovan, M

2014-01-01

A grazing study was undertaken to examine the effect of maintaining three levels of pre-grazing herbage mass (HM) on dairy cow performance, grass dry matter (DM) production and output from perennial ryegrass (Lolium perenne L.) pastures. Cows were randomly assigned to one of three pre-grazing HM treatments: 1150 - Low HM (L), 1400 - Medium HM (M) or 2000 kg DM/ha - High HM (H). Herbage accumulation under grazing was lowest (Ppastures required more grass silage supplementation during the grazing season (+73 kg DM/cow) to overcome pasture deficits due to lower pasture growth rates (Ppasture intake, although cows grazing the L pastures had to graze a greater daily area (Ppasture reduces pasture DM production and at a system level may increase the requirement for imported feed.

Response of snow-dependent hydrologic extremes to continued global warming

Energy Technology Data Exchange (ETDEWEB)

Diffenbaugh, Noah [Stanford University; Scherer, Martin [Stanford University; Ashfaq, Moetasim [ORNL

2012-01-01

Snow accumulation is critical for water availability in the Northern Hemisphere1,2, raising concern that global warming could have important impacts on natural and human systems in snow-dependent regions1,3. Although regional hydrologic changes have been observed (for example, refs 1,3 5), the time of emergence of extreme changes in snow accumulation and melt remains a key unknown for assessing climate- change impacts3,6,7. We find that the CMIP5 global climate model ensemble exhibits an imminent shift towards low snow years in the Northern Hemisphere, with areas of western North America, northeastern Europe and the Greater Himalaya showing the strongest emergence during the near- termdecadesandat2 Cglobalwarming.Theoccurrenceof extremely low snow years becomes widespread by the late twenty-first century, as do the occurrences of extremely high early-season snowmelt and runoff (implying increasing flood risk), and extremely low late-season snowmelt and runoff (implying increasing water stress). Our results suggest that many snow-dependent regions of the Northern Hemisphere are likely to experience increasing stress from low snow years within the next three decades, and from extreme changes in snow-dominated water resources if global warming exceeds 2 C above the pre-industrial baseline.

Implications of global warming for the climate of African rainforests.

Science.gov (United States)

James, Rachel; Washington, Richard; Rowell, David P

2013-01-01

African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions.

Exceptional Air Mass Transport and Dynamical Drivers of an Extreme Wintertime Arctic Warm Event

Science.gov (United States)

Binder, Hanin; Boettcher, Maxi; Grams, Christian M.; Joos, Hanna; Pfahl, Stephan; Wernli, Heini

2017-12-01

At the turn of the years 2015/2016, maximum surface temperature in the Arctic reached record-high values, exceeding the melting point, which led to a strong reduction of the Arctic sea ice extent in the middle of the cold season. Here we show, using a Lagrangian method, that a combination of very different airstreams contributed to this event: (i) warm low-level air of subtropical origin, (ii) initially cold low-level air of polar origin heated by surface fluxes, and (iii) strongly descending air heated by adiabatic compression. The poleward transport of these warm airstreams occurred along an intense low-level jet between a series of cyclones and a quasi-stationary anticyclone. The complex 3-D configuration that enabled this transport was facilitated by continuous warm conveyor belt ascent into the upper part of the anticyclone. This study emphasizes the combined role of multiple transport processes and transient synoptic-scale dynamics for establishing an extreme Arctic warm event.

Indonesian vegetation response to changes in rainfall seasonality over the past 25,000 years

Science.gov (United States)

Dubois, Nathalie; Oppo, Delia W.; Galy, Valier V.; Mohtadi, Mahyar; van der Kaars, Sander; Tierney, Jessica E.; Rosenthal, Yair; Eglinton, Timothy I.; Lückge, Andreas; Linsley, Braddock K.

2014-07-01

The hydrologic response to climate forcing in the Indo-Pacific warm pool region has varied spatially over the past 25,000 years. For example, drier conditions are inferred on Java and Borneo for the period following the end of the Last Glacial Maximum, whereas wetter conditions are reconstructed for northwest Australia. The response of vegetation to these past rainfall variations is poorly constrained. Using a suite of 30 surface marine sediment samples from throughout the Indo-Pacific warm pool, we demonstrate that today the stable isotopic composition of vascular plant fatty acids (δ13CFA) reflects the regional vegetation composition. This in turn is controlled by the seasonality of rainfall consistent with dry season water stress. Applying this proxy in a sediment core from offshore northeast Borneo, we show broadly similar vegetation cover during the Last Glacial Maximum and the Holocene, suggesting that, despite generally drier glacial conditions, there was no pronounced dry season. In contrast, δ13CFA and pollen data from a core off the coast of Sumba indicate an expansion of C4 herbs during the most recent glaciation, implying enhanced aridity and water stress during the dry season. Holocene vegetation trends are also consistent with a response to dry season water stress. We therefore conclude that vegetation in tropical monsoon regions is susceptible to increases in water stress arising from an enhanced seasonality of rainfall, as has occurred in past decades.

Effects of Nitrogen Rate and Regrowth Interval on Perennial Ryegrass Fatty Acid Content during the Growing Season

NARCIS (Netherlands)

Witkowska, I.M.; Wever, C.J.G.; Gort, G.; Elgersma, A.

2008-01-01

The content of fatty acids (FA) in herbage is important for forage quality and animal-source foods, but there is a lack of knowledge on effects of agronomic practices, and on environmental factors related to seasonal variation in FA concentrations and FA composition. This research investigated the

Interannual Similarity in the Martian Atmosphere During the Dust Storm Season

Science.gov (United States)

Kass, D. M.; Kleinboehl, A.; McCleese, D. J.; Schofield, J. T.; Smith, M. D.

2016-01-01

We find that during the dusty season on Mars (southern spring and summer) of years without a global dust storm there are three large regional-scale dust storms. The storms are labeled A, B, and C in seasonal order. This classification is based on examining the zonal mean 50 Pa (approximately 25 km) daytime temperature retrievals from TES/MGS and MCS/MRO over 6 Mars Years. Regional-scale storms are defined as events where the temperature exceeds 200 K. Examining the MCS dust field at 50 Pa indicates that warming in the Southern Hemisphere is dominated by direct heating, while northern high latitude warming is a dynamical response. A storms are springtime planet encircling Southern Hemisphere events. B storms are southern polar events that begin near perihelion and last through the solstice. C storms are southern summertime events starting well after the end of the B storm. C storms show the most interannual variability.

Genetic Loci Governing Androgenic Capacity in Perennial Ryegrass (Lolium perenne L.

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Rachel F. Begheyn

2018-06-01

Full Text Available Immature pollen can be induced to switch developmental pathways from gametogenesis to embryogenesis and subsequently regenerate into homozygous, diploid plants. Such androgenic production of doubled haploids is particularly useful for species where inbreeding is hampered by effective self-incompatibility systems. Therefore, increasing the generally low androgenic capacity of perennial ryegrass (Lolium perenne L. germplasm would enable the efficient production of homozygous plant material, so that a more effective exploitation of heterosis through hybrid breeding schemes can be realized. Here, we present the results of a genome-wide association study in a heterozygous, multiparental population of perennial ryegrass (n = 391 segregating for androgenic capacity. Genotyping-by-sequencing was used to interrogate gene- dense genomic regions and revealed over 1,100 polymorphic sites. Between one and 10 quantitative trait loci (QTL were identified for anther response, embryo and total plant production, green and albino plant production and regeneration. Most traits were under polygenic control, although a major QTL on linkage group 5 was associated with green plant regeneration. Distinct genetic factors seem to affect green and albino plant recovery. Two intriguing candidate genes, encoding chromatin binding domains of the developmental phase transition regulator, Polycomb Repressive Complex 2, were identified. Our results shed the first light on the molecular mechanisms behind perennial ryegrass microspore embryogenesis and enable marker-assisted introgression of androgenic capacity into recalcitrant germplasm of this forage crop of global significance.

A phenological timetable of oak growth under experimental drought and air warming.

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Thomas M Kuster

Full Text Available Climate change is expected to increase temperature and decrease summer precipitation in Central Europe. Little is known about how warming and drought will affect phenological patterns of oaks, which are considered to possess excellent adaptability to these climatic changes. Here, we investigated bud burst and intra-annual shoot growth of Quercus robur, Q. petraea and Q. pubescens grown on two different forest soils and exposed to air warming and drought. Phenological development was assessed over the course of three growing seasons. Warming advanced bud burst by 1-3 days °C⁻¹ and led to an earlier start of intra-annual shoot growth. Despite this phenological shift, total time span of annual growth and shoot biomass were not affected. Drought changed the frequency and intensity of intra-annual shoot growth and advanced bud burst in the subsequent spring of a severe summer drought by 1-2 days. After re-wetting, shoot growth recovered within a few days, demonstrating the superior drought tolerance of this tree genus. Our findings show that phenological patterns of oaks are modified by warming and drought but also suggest that ontogenetic factors and/or limitations of water and nutrients counteract warming effects on the biomass and the entire span of annual shoot growth.

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

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H. Carlson

2017-08-01

Full Text Available Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO2 concentrations or more modest CO2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO2 (which we refer to as the greenhouse gas (GHG scenario and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the low CO2–thin clouds or LCTC scenario . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has  ∼  11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

Global warming and the forest fire business in Canada

International Nuclear Information System (INIS)

Stocks, B.J.

1991-01-01

The current forest fire situation in Canada is outlined, and an attempt is made to predict the impact of global warming on the forest fire business in Canada. Despite the development of extremely sophisticated provincial and territorial fire management systems, forest fires continue to exert a tremendous influence on the Canadian forest resource. Research into the relationship between climate warming and forest fires has fallen into two categories: the effect of future global warming on fire weather severity, and the current contribution of forest fires to global atmospheric greenhouse gas budgets. A 46% increase in seasonal fire severity across Canada is suggested under a doubled atmospheric carbon dioxide concentration scenario. Approximately 89% of carbon released to the atmosphere by forest fire burning is in the form of carbon dioxide, 9% is carbon monoxide, and the remaining carbon is released as methane or non-methane hydrocarbons. It is estimated that forest fires in northern circumpolar countries contribute from 1-2% of the carbon released globally through biomass burning. Fire may be the agent by which a northerly shift of forest vegetation in Canada occurs. 13 refs., 2 figs

Seasonal climate signals from multiple tree ring metrics: A case study of Pinus ponderosa in the upper Columbia River Basin

Science.gov (United States)

Dannenberg, Matthew P.; Wise, Erika K.

2016-04-01

Projected changes in the seasonality of hydroclimatic regimes are likely to have important implications for water resources and terrestrial ecosystems in the U.S. Pacific Northwest. The tree ring record, which has frequently been used to position recent changes in a longer-term context, typically relies on signals embedded in the total ring width of tree rings. Additional climatic inferences at a subannual temporal scale can be made using alternative tree ring metrics such as earlywood and latewood widths and the density of tree ring latewood. Here we examine seasonal precipitation and temperature signals embedded in total ring width, earlywood width, adjusted latewood width, and blue intensity chronologies from a network of six Pinus ponderosa sites in and surrounding the upper Columbia River Basin of the U.S. Pacific Northwest. We also evaluate the potential for combining multiple tree ring metrics together in reconstructions of past cool- and warm-season precipitation. The common signal among all metrics and sites is related to warm-season precipitation. Earlywood and latewood widths differ primarily in their sensitivity to conditions in the year prior to growth. Total and earlywood widths from the lowest elevation sites also reflect cool-season moisture. Effective correlation analyses and composite-plus-scale tests suggest that combining multiple tree ring metrics together may improve reconstructions of warm-season precipitation. For cool-season precipitation, total ring width alone explains more variance than any other individual metric or combination of metrics. The composite-plus-scale tests show that variance-scaled precipitation reconstructions in the upper Columbia River Basin may be asymmetric in their ability to capture extreme events.

Remotely Sensed Northern Vegetation Response to Changing Climate: Growing Season and Productivity Perspective

Science.gov (United States)

Ganguly, S.; Park, Taejin; Choi, Sungho; Bi, Jian; Knyazikhin, Yuri; Myneni, Ranga

2016-01-01

Vegetation growing season and maximum photosynthetic state determine spatiotemporal variability of seasonal total gross primary productivity of vegetation. Recent warming induced impacts accelerate shifts on growing season and physiological status over Northern vegetated land. Thus, understanding and quantifying these changes are very important. Here, we first investigate how vegetation growing season and maximum photosynthesis state are evolved and how such components contribute on inter-annual variation of seasonal total gross primary productivity. Furthermore, seasonally different response of northern vegetation to changing temperature and water availability is also investigated. We utilized both long-term remotely sensed data to extract larger scale growing season metrics (growing season start, end and duration) and productivity (i.e., growing season summed vegetation index, GSSVI) for answering these questions. We find that regionally diverged growing season shift and maximum photosynthetic state contribute differently characterized productivity inter-annual variability and trend. Also seasonally different response of vegetation gives different view of spatially varying interaction between vegetation and climate. These results highlight spatially and temporally varying vegetation dynamics and are reflective of biome-specific responses of northern vegetation to changing climate.

Latitudinal range influences the seasonal variation in the foraging behavior of marine top predators.

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Stella Villegas-Amtmann

Full Text Available Non-migratory resident species should be capable of modifying their foraging behavior to accommodate changes in prey abundance and availability associated with a changing environment. Populations that are better adapted to change will have higher foraging success and greater potential for survival in the face of climate change. We studied two species of resident central place foragers from temperate and equatorial regions with differing population trends and prey availability associated to season, the California sea lion (Zalophus californianus (CSL whose population is increasing and the endangered Galapagos sea lion (Zalophus wollebaeki (GSL whose population is declining. To determine their response to environmental change, we studied and compared their diving behavior using time-depth recorders and satellite location tags and their diet by measuring C and N isotope ratios during a warm and a cold season. Based on latitudinal differences in oceanographic productivity, we hypothesized that the seasonal variation in foraging behavior would differ for these two species. CSL exhibited greater seasonal variability in their foraging behavior as seen in changes to their diving behavior, foraging areas and diet between seasons. Conversely, GSL did not change their diving behavior between seasons, presenting three foraging strategies (shallow, deep and bottom divers during both. GSL exhibited greater dive and foraging effort than CSL. We suggest that during the warm and less productive season a greater range of foraging behaviors in CSL was associated with greater competition for prey, which relaxed during the cold season when resource availability was greater. GSL foraging specialization suggests that resources are limited throughout the year due to lower primary production and lower seasonal variation in productivity compared to CSL. These latitudinal differences influence their foraging success, pup survival and population growth reflected in

Cultivar by environment effects of perennial ryegrass cultivars selected for high water soluble carbohydrates managed under differing precipitation levels

Science.gov (United States)

Historic results of perennial ryegrass (Lolium perenne L.) breeding include improved disease resistance, biomass, and nutritional quality. Yet, lack of tolerance to water stress limits its wise use. Recent efforts to increase water soluble carbohydrate (WSC) content in perennial ryegrass may incre...

Ocean warming and acidification synergistically increase coral mortality

Science.gov (United States)

Prada, F.; Caroselli, E.; Mengoli, S.; Brizi, L.; Fantazzini, P.; Capaccioni, B.; Pasquini, L.; Fabricius, K. E.; Dubinsky, Z.; Falini, G.; Goffredo, S.

2017-01-01

Organisms that accumulate calcium carbonate structures are particularly vulnerable to ocean warming (OW) and ocean acidification (OA), potentially reducing the socioeconomic benefits of ecosystems reliant on these taxa. Since rising atmospheric CO2 is responsible for global warming and increasing ocean acidity, to correctly predict how OW and OA will affect marine organisms, their possible interactive effects must be assessed. Here we investigate, in the field, the combined temperature (range: 16-26 °C) and acidification (range: pHTS 8.1-7.4) effects on mortality and growth of Mediterranean coral species transplanted, in different seasonal periods, along a natural pH gradient generated by a CO2 vent. We show a synergistic adverse effect on mortality rates (up to 60%), for solitary and colonial, symbiotic and asymbiotic corals, suggesting that high seawater temperatures may have increased their metabolic rates which, in conjunction with decreasing pH, could have led to rapid deterioration of cellular processes and performance. The net calcification rate of the symbiotic species was not affected by decreasing pH, regardless of temperature, while in the two asymbiotic species it was negatively affected by increasing acidification and temperature, suggesting that symbiotic corals may be more tolerant to increasing warming and acidifying conditions compared to asymbiotic ones.

Seasonal dynamics and life histories of pelagic cladocerans (Crustacea; Cladocera in an acid boreal lake

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Jens Petter NILSSEN

2011-02-01

Full Text Available In the surveyed anthropogenic acidified Lake Gjerstadvann with pH ≈ 5.2 situated in southern Norway, spatial and temporal distribution of three characteristic planktonic cladocerans inhabiting acidified boreal biotopes, Bosmina longispina, Holopedium gibberum, and Diaphanosoma brachyurum, were studied over a period of one year. The major pelagic predator was Eurasian perch, Perca fluviatilis. The local perch probably balanced the cladoceran community and facilitated co-existence of all three species of cladocerans by removing significant portions of B. longispina, which could also be the case in similar types of boreal lakes. Invertebrate predators such as the dipteran larvae Chaoborus flavicans and carnivorous copepods did not seem to influence the cladoceran community. B. longispina was perennial, whereas both H. gibberum and D. brachyurum were recorded only during the ice-free period. The life cycle of these free-living pelagic species ranged from 2-3 in D. brachyurum, 3 in H. gibberum to approximately 6 annual generations in B. longispina. Wintering took place as resting eggs in D. brachyurum and H. gibberum, while B. longispina produced resting eggs in addition to an active planktonic stay. The warm water tolerant D. brachyurum was mainly distributed above the thermocline, whereas H. gibberum also inhabited deeper strata, and B. longispina most vertical strata of the lake. Maximum seasonal clutch volume of B. longispina coincided in time with peak in food abundance and may be a useful parameter to identify planktonic food availability in such lakes. Knowledge of the autecology and life history of species is fundamental for understanding ecosystem stress, such as anthropogenic acidification and recovery through liming or by natural causes. Seasonal depth isoplots combined with life history studies of commonly co-occurring cladoceran species from natural acid and anthropogenic acidified lakes on the Northern Hemisphere seem to be uncommon

Genetic markers for flowering in perennial ryegrass

DEFF Research Database (Denmark)

Paina, Cristiana; Byrne, Stephen; Andersen, Jeppe Reitan

2011-01-01

Perennial ryegrass (Lolium perenne L.) is the principal forage grass utilized in Danish agriculture and underpins the beef and dairy sectors. It is characterized as having high digestibility, high nutritional value, and high productivity during vegetative growth. However, at the reproductive growth...... genes will be converted to molecular markers and mapped in an existing mapping population previously characterized for flowering time and vernalization response. References: Amasino, R.M., Michaels S.D. (2010). The Timing of Flowering. Plant Physiology 154: 516–520 Greenup, A., W. Peacock, W.J., Dennis...

The effects of perennial ryegrass and alfalfa on microbial abundance and diversity in petroleum contaminated soil

International Nuclear Information System (INIS)

Kirk, Jennifer L.; Klironomos, John N.; Lee, Hung; Trevors, Jack T.

2005-01-01

Enhanced rhizosphere degradation uses plants to stimulate the rhizosphere microbial community to degrade organic contaminants. We measured changes in microbial communities caused by the addition of two species of plants in a soil contaminated with 31,000 ppm of total petroleum hydrocarbons. Perennial ryegrass and/or alfalfa increased the number of rhizosphere bacteria in the hydrocarbon-contaminated soil. These plants also increased the number of bacteria capable of petroleum degradation as estimated by the most probable number (MPN) method. Eco-Biolog plates did not detect changes in metabolic diversity between bulk and rhizosphere samples but denaturing gradient gel electrophoresis (DGGE) analysis of PCR-amplified partial 16S rDNA sequences indicated a shift in the bacterial community in the rhizosphere samples. Dice coefficient matrices derived from DGGE profiles showed similarities between the rhizospheres of alfalfa and perennial ryegrass/alfalfa mixture in the contaminated soil at week seven. Perennial ryegrass and perennial ryegrass/alfalfa mixture caused the greatest change in the rhizosphere bacterial community as determined by DGGE analysis. We concluded that plants altered the microbial population; these changes were plant-specific and could contribute to degradation of petroleum hydrocarbons in contaminated soil. - Plant-specific changes in microbial populations on roots affect degradation of petroleum hydrocarbons in contaminated soil

Changing seasonality patterns in Central Europe from Miocene Climate Optimum to Miocene Climate Transition deduced from the Crassostrea isotope archive

Science.gov (United States)

Harzhauser, Mathias; Piller, Werner E.; Müllegger, Stefan; Grunert, Patrick; Micheels, Arne

2011-03-01

The Western Tethyan estuarine oyster Crassostrea gryphoides is an excellent climate archive due to its large size and rapid growth. It is geologically long lived and allows a stable isotope-based insight into climatic trends during the Miocene. Herein we utilised the climate archive of 5 oyster shells from the Miocene Climate Optimum (MCO) and the subsequent Miocene Climate Transition (MCT) to evaluate changes of seasonality patterns. MCO shells exhibit highly regular seasonal rhythms of warm-wet and dry-cool seasons. Optimal conditions resulted in extraordinary growth rates of the oysters. δ 13C profiles are in phase with δ 18O although phytoplankton blooms may cause a slight offset. Estuarine waters during the MCO in Central Europe display a seasonal temperature range of c. 9-10 °C. Absolute water temperatures have ranged from 17 to 19 °C during cool seasons and up to 28 °C in warm seasons. Already during the early phase of the MCO, the growth rates are distinctly declining, although gigantic and extremely old shells have been formed at that time. Still, a very regular and well expressed seasonality is dominating the isotope profiles, but episodically occurring extreme climate events influence the environments. The seasonal temperature range is still c. 9 °C but the cool season temperature seems to be slightly lower (16 °C) and the warm season water temperature does not exceed c. 25 °C. In the later MCT at c. 12.5-12.0 Ma the seasonality pattern is breaking down and is replaced by successions of dry years with irregular precipitation events. No correlation between δ 18O and δ 13C is documented maybe due to a suboptimal nutrition level which would explain the low growth rates and small sizes. The amplitude of seasonal temperature range is decreasing to 5-8 °C. No clear cooling trend can be postulated for that time as the winter season water temperatures range from 15 to 20 °C. This may point to unstable precipitation rhythms on a multi-annual to

PERPHECLIM ACCAF Project - Perennial fruit crops and forest phenology evolution facing climatic changes

Science.gov (United States)

Garcia de Cortazar-Atauri, Iñaki; Audergon, Jean Marc; Bertuzzi, Patrick; Anger, Christel; Bonhomme, Marc; Chuine, Isabelle; Davi, Hendrik; Delzon, Sylvain; Duchêne, Eric; Legave, Jean Michel; Raynal, Hélène; Pichot, Christian; Van Leeuwen, Cornelis; Perpheclim Team

2015-04-01

Phenology is a bio-indicator of climate evolutions. Measurements of phenological stages on perennial species provide actually significant illustrations and assessments of the impact of climate change. Phenology is also one of the main key characteristics of the capacity of adaptation of perennial species, generating questions about their consequences on plant growth and development or on fruit quality. Predicting phenology evolution and adaptative capacities of perennial species need to override three main methodological limitations: 1) existing observations and associated databases are scattered and sometimes incomplete, rendering difficult implementation of multi-site study of genotype-environment interaction analyses; 2) there are not common protocols to observe phenological stages; 3) access to generic phenological models platforms is still very limited. In this context, the PERPHECLIM project, which is funded by the Adapting Agriculture and Forestry to Climate Change Meta-Program (ACCAF) from INRA (French National Institute of Agronomic Research), has the objective to develop the necessary infrastructure at INRA level (observatories, information system, modeling tools) to enable partners to study the phenology of various perennial species (grapevine, fruit trees and forest trees). Currently the PERPHECLIM project involves 27 research units in France. The main activities currently developed are: define protocols and observation forms to observe phenology for various species of interest for the project; organizing observation training; develop generic modeling solutions to simulate phenology (Phenological Modelling Platform and modelling platform solutions); support in building research projects at national and international level; develop environment/genotype observation networks for fruit trees species; develop an information system managing data and documentation concerning phenology. Finally, PERPHECLIM project aims to build strong collaborations with public

Seasonal alterations in host range and fidelity in the polyphagous mirid bug, Apolygus lucorum (Heteroptera: Miridae.

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Hongsheng Pan

Full Text Available In herbivorous insects, host plant switching is commonly observed and plays an important role in their annual life cycle. However, much remains to be learned about seasonal host switching of various pestiferous arthropods under natural conditions. From 2006 until 2012, we assessed Apolygus lucorum (Meyer-Dür host plant use in successive spring, summer and winter seasons at one single location (Langfang, China. Data were used to quantify changes in host plant breadth and host fidelity between seasons. Host fidelity of A. lucorum differed between seasons, with 87.9% of spring hosts also used in the summer and 36.1% of summer hosts used in winter. In contrast, as little as 25.6% host plant species were shared between winter and spring. Annual herbaceous plants are most often used for overwintering, while perennial woody plants are relatively important for initial population build-up in the spring. Our study contributes to an improved understanding of evolutionary interactions between A. lucorum and its host plants and lays the groundwork for the design of population management strategies for this important pest in myriad crops.

Next steps in determining the overall sustainability of perennial bioenergy crops

Science.gov (United States)

Perennial bioenergy crops are being developed and evaluated in the United States to partially offset petroleum transport fuels. Accurate accounting of upstream and downstream greenhouse gas (GHG) emissions is necessary to measure the overall carbon intensity of new biofuel feedstocks. For example, c...

20th-Century Climate Change over Africa: Seasonal Variation in Hydroclimate Trends and Sahara Desert Extent

Science.gov (United States)

Nigam, S.; Thomas, N. P.

2017-12-01

Twentieth-century trends in seasonal temperature and precipitation over the African continent are analyzed from observational data sets and historical climate simulations. Given the agricultural economy of the continent, a seasonal perspective is adopted as it is more pertinent than an annual-average one which can mask off-setting but agriculturally-sensitive seasonal hydroclimate variations. Examination of linear trends in seasonal surface air temperature (SAT) shows that heat stress has increased in several regions, including Sudan and Northern Africa where largest SAT trends occur in the warm season. Broadly speaking, the northern continent has warmed more than the southern one in all seasons. Precipitation trends are varied but notable declining trends are found in the countries along the Gulf of Guinea, especially in the source region of Niger river in West Africa, and in the Congo river basin. Rainfall over the African Great Lakes - one of the largest freshwater repositories - has however increased. We show that the Sahara Desert has expanded significantly over the 20th century - by 12-20% depending on the season. The desert expanded southward in summer, reflecting retreat of the northern edge of the Sahel rainfall belt; and to the north in winter, indicating potential impact of the widening of the Tropics. Specific mechanisms driving the expansion in each season are investigated. Finally, this observational analysis is used to evaluate the state-of-the-art climate models from a comparison of the 20th-century hydroclimate trends with those manifest in historical climate simulations. The evaluation shows that modeling regional hydroclimate change over the Africa continent remains challenging.

Diversity and structure of microcrustacean assemblages (Cladocera and Copepoda and limnological variability in perennial and intermittent pools in a semi-arid region, Bahia, Brazil

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Nadson R. Simões

2011-12-01

Full Text Available Temporary wetlands undergo recurrent drought due to the scarcity of water, which disrupts the hydrological connectivity with adjacent aquatic systems. However, some environments retain water for longer periods, allowing greater persistence of the community. The current study evaluated differences in the microcrustacean assemblages and limnological variability between perennial and intermittent pools in a semi-arid region of Brazil. The abiotic features (water temperature, pH, total alkalinity, electrical conductivity and depth of intermittent pools were affected more than perennial pools due to loss of water volume. This may have contributed to a higher average richness and diversity index in some intermittent pools and differences in the structure of the assemblages. The lowest species richness and diversity were recorded where physical factors, such as a large quantity of suspended solids and variability in the electrical conductivity of the water and pH, make the environment unsuitable for these organisms. These results suggest that community development in intermittent pools is interrupted by the dry season; when the water returns, due to rainfall or rising groundwater, each pond undergoes a different process of colonization. In these circumstances, the biological importance of temporary aquatic environments is clear, since such pools provide shelters and have an important role in the maintenance of the regional diversity of aquatic environments.

Rhetorical Transcendence Revisited: The "Thin Red Line" as Perennial Philosophy.

Science.gov (United States)

Stroud, Scott R.

Fifteen years ago, J. H. Rushing published a seminal article addressing the fragmentation within contemporary society and the ways in which myths (films) may address this exigence. The exigence of fragmentation is relieved, according to her analysis, by mediated recourse to the perennial philosophy of monistic holism that is found across the…

Declining global warming effects on the phenology of spring leaf unfolding.

Science.gov (United States)

Fu, Yongshuo H; Zhao, Hongfang; Piao, Shilong; Peaucelle, Marc; Peng, Shushi; Zhou, Guiyun; Ciais, Philippe; Huang, Mengtian; Menzel, Annette; Peñuelas, Josep; Song, Yang; Vitasse, Yann; Zeng, Zhenzhong; Janssens, Ivan A

2015-10-01

Earlier spring leaf unfolding is a frequently observed response of plants to climate warming. Many deciduous tree species require chilling for dormancy release, and warming-related reductions in chilling may counteract the advance of leaf unfolding in response to warming. Empirical evidence for this, however, is limited to saplings or twigs in climate-controlled chambers. Using long-term in situ observations of leaf unfolding for seven dominant European tree species at 1,245 sites, here we show that the apparent response of leaf unfolding to climate warming (ST, expressed in days advance of leaf unfolding per °C warming) has significantly decreased from 1980 to 2013 in all monitored tree species. Averaged across all species and sites, ST decreased by 40% from 4.0 ± 1.8 days °C(-1) during 1980-1994 to 2.3 ± 1.6 days °C(-1) during 1999-2013. The declining ST was also simulated by chilling-based phenology models, albeit with a weaker decline (24-30%) than observed in situ. The reduction in ST is likely to be partly attributable to reduced chilling. Nonetheless, other mechanisms may also have a role, such as 'photoperiod limitation' mechanisms that may become ultimately limiting when leaf unfolding dates occur too early in the season. Our results provide empirical evidence for a declining ST, but also suggest that the predicted strong winter warming in the future may further reduce ST and therefore result in a slowdown in the advance of tree spring phenology.

Path and correlation analysis of perennial ryegrass (Lolium perenne L.) seed yield components

DEFF Research Database (Denmark)

Abel, Simon; Gislum, René; Boelt, Birte

2017-01-01

Maximum perennial ryegrass seed production potential is substantially greater than harvested yields with harvested yields representing only 20% of calculated potential. Similar to wheat, maize and other agriculturally important crops, seed yield is highly dependent on a number of interacting seed...... yield components. This research was performed to apply and describe path analysis of perennial ryegrass seed yield components in relation to harvested seed yields. Utilising extensive yield components which included subdividing reproductive inflorescences into five size categories, path analysis...... was undertaken assuming a unidirectional causal-admissible relationship between seed yield components and harvested seed yield in six commercial seed production fields. Both spikelets per inflorescence and florets per spikelet had a significant (p seed yield; however, total...

Dynamics behind warming of the southeastern Arabian Sea and its interruption based on in situ measurements

Science.gov (United States)

Mathew, Simi; Natesan, Usha; Latha, Ganesan; Venkatesan, Ramasamy

2018-05-01

A study of the inter-annual variability of the warming of the southeastern Arabian Sea (SEAS) during the spring transition months was carried out from 2013 to 2015 based on in situ data from moored buoys. An attempt was made to identify the roles of the different variables in the warming of the SEAS (e.g., net heat flux, advection, entrainment, and thickness of the barrier layer during the previous northeast monsoon season). The intense freshening of the SEAS (approximately 2 PSU) occurring in each December, together with the presence of a downwelling Rossby wave, supports the formation of a thick barrier layer during the northeast monsoon season. It is known that the barrier layer thickness, varying each year, plays a major role in the spring warming of the SEAS. Interestingly, an anomalously thick barrier layer occurred during the northeast monsoon season of 2012-2013. However, the highest sea surface temperature (31 °C) was recorded during the last week of April 2015, while the lowest sea surface temperature (29.7 °C) was recorded during the last week of May 2013. The mixed layer heat budget analysis during the spring transition months proved that the intense warming has been mainly supported by the net heat flux, not by other factors like advection and entrainment. The inter-annual variability analysis of the net heat flux and its components, averaged over a box region of the SEAS, showed a substantial latent heat flux release and a reduction in net shortwave radiation in 2013. Both factors contributed to the negative net heat flux. Strong breaks in the warming were also observed in May due to the entrainment of cold sub-surface waters. These events are associated with the cyclonic eddy persisting over the SEAS during the same time. The entrainment term, favoring the cooling, was stronger in 2015 than that in 2013 and 2014. The surface temperatures measured in 2013 were lower than those in 2014 and 2015 despite the presence of a thick barrier layer. The

Impact of ocean acidification and warming on the productivity of a rock pool community.

Science.gov (United States)

Legrand, Erwann; Riera, Pascal; Bohner, Olivier; Coudret, Jérôme; Schlicklin, Ferdinand; Derrien, Marie; Martin, Sophie

2018-05-01

This study examined experimentally the combined effect of ocean acidification and warming on the productivity of rock pool multi-specific assemblages, composed of coralline algae, fleshy algae, and grazers. Natural rock pool communities experience high environmental fluctuations. This may confer physiological advantage to rock pool communities when facing predicted acidification and warming. The effect of ocean acidification and warming have been assessed at both individual and assemblage level to examine the importance of species interactions in the response of assemblages. We hypothesized that rock pool assemblages have physiological advantage when facing predicted ocean acidification and warming. Species exhibited species-specific responses to increased temperature and pCO 2 . Increased temperature and pCO 2 have no effect on assemblage photosynthesis, which was mostly influenced by fleshy algal primary production. The response of coralline algae to ocean acidification and warming depended on the season, which evidenced the importance of physiological adaptations to their environment in their response to climate change. We suggest that rock pool assemblages are relatively robust to changes in temperature and pCO 2 , in terms of primary production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Global warming in the context of 2000 years of Australian alpine temperature and snow cover.

Science.gov (United States)

McGowan, Hamish; Callow, John Nikolaus; Soderholm, Joshua; McGrath, Gavan; Campbell, Micheline; Zhao, Jian-Xin

2018-03-13

Annual resolution reconstructions of alpine temperatures are rare, particularly for the Southern Hemisphere, while no snow cover reconstructions exist. These records are essential to place in context the impact of anthropogenic global warming against historical major natural climate events such as the Roman Warm Period (RWP), Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Here we show for a marginal alpine region of Australia using a carbon isotope speleothem reconstruction, warming over the past five decades has experienced equivalent magnitude of temperature change and snow cover decline to the RWP and MCA. The current rate of warming is unmatched for the past 2000 years and seasonal snow cover is at a minimum. On scales of several decades, mean maximum temperatures have undergone considerable change ≈ ± 0.8 °C highlighting local scale susceptibility to rapid temperature change, evidence of which is often masked in regional to hemisphere scale temperature reconstructions.

Physical mechanisms of spring and summertime drought related with the global warming over the northern America

Science.gov (United States)

Choi, W.; Kim, K. Y.

2017-12-01

Drought during the growing season (spring through summer) is severe natural hazard in the large cropland over the northern America. It is important to understand how the drought is related with the global warming and how it will change in the future. This study aims to investigate the physical mechanism of global warming impact on the spring and summertime drought over the northern America using Cyclostationary Empirical Orthogonal Function (CSEOF) analysis. The Northern Hemisphere surface warming, the most dominant mode of the surface air temperature, has resulted in decreased relative humidity and precipitation over the mid-latitude region of North America. For the viewpoint of atmospheric water demand, soil moisture and evaporation have also decreased significantly, exacerbating vulnerability of drought. These consistent features of changes in water demand and supply related with the global warming can provide a possibility of credible insight for future drought change.

Energizing marginal soils: A perennial cropping system for Sida hermaphrodita

Science.gov (United States)

Nabel, Moritz; Poorter, Hendrik; Temperton, Vicky; Schrey, Silvia D.; Koller, Robert; Schurr, Ulrich; Jablonowski, Nicolai D.

2017-04-01

As a way to avoid land use conflicts, the use of marginal soils for the production of plant biomass can be a sustainable alternative to conventional biomass production (e.g. maize). However, new cropping strategies have to be found that meet the challenge of crop production under marginal soil conditions. We aim for increased soil fertility by the use of the perennial crop Sida hermaphrodita in combination with organic fertilization and legume intercropping to produce substantial biomass yield. We present results of a three-year outdoor mesocosm experiment testing the perennial energy crop Sida hermaphrodita grown on a marginal model substrate (sand) with four kinds of fertilization (Digestate broadcast, Digestate Depot, mineral NPK and unfertilized control) in combination with legume intercropping. After three years, organic fertilization (via biogas digestate) compared to mineral fertilization (NPK), reduced the nitrate concentration in leachate and increased the soil carbon content. Biomass yields of Sida were 25% higher when fertilized organically, compared to mineral fertilizer. In general, digestate broadcast application reduced root growth and the wettability of the sandy substrate. However, when digestate was applied locally as depot to the rhizosphere, root growth increased and the wettability of the sandy substrate was preserved. Depot fertilization increased biomass yield by 10% compared to digestate broadcast fertilization. We intercropped Sida with various legumes (Trifolium repens, Trifolium pratense, Melilotus spp. and Medicago sativa) to enable biological nitrogen fixation and make the cropping system independent from synthetically produced fertilizers. We could show that Medicago sativa grown on marginal substrate fixed large amounts of N, especially when fertilized organically, whereas mineral fertilization suppressed biological nitrogen fixation. We conclude that the perennial energy crop Sida in combination with organic fertilization has great

Detecting the permafrost carbon feedback: talik formation and increased cold-season respiration as precursors to sink-to-source transitions

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N. C. Parazoo

2018-01-01

Full Text Available Thaw and release of permafrost carbon (C due to climate change is likely to offset increased vegetation C uptake in northern high-latitude (NHL terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a subsurface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost-affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM version 4.5, a permafrost and biogeochemistry model, in comparison to long-term deep borehole data along North American and Siberian transects, to investigate thaw-driven C sources in NHL ( >  55° N from 2000 to 2300. Widespread talik at depth is projected across most of the NHL permafrost region (14 million km2 by 2300, 6.2 million km2 of which is projected to become a long-term C source, emitting 10 Pg C by 2100, 50 Pg C by 2200, and 120 Pg C by 2300, with few signs of slowing. Roughly half of the projected C source region is in predominantly warm sub-Arctic permafrost following talik onset. This region emits only 20 Pg C by 2300, but the CLM4.5 estimate may be biased low by not accounting for deep C in yedoma. Accelerated decomposition of deep soil C following talik onset shifts the ecosystem C balance away from surface dominant processes (photosynthesis and litter respiration, but sink-to-source transition dates are delayed by 20–200 years by high ecosystem productivity, such that talik peaks early ( ∼  2050s, although borehole data suggest sooner and C source transition peaks late ( ∼  2150–2200. The

Compensatory mechanisms mitigate the effect of warming and drought on wood formation.

Science.gov (United States)

Balducci, Lorena; Cuny, Henri E; Rathgeber, Cyrille B K; Deslauriers, Annie; Giovannelli, Alessio; Rossi, Sergio

2016-06-01

Because of global warming, high-latitude ecosystems are expected to experience increases in temperature and drought events. Wood formation will have to adjust to these new climatic constraints to maintain tree mechanical stability and long-distance water transport. The aim of this study is to understand the dynamic processes involved in wood formation under warming and drought. Xylogenesis, gas exchange, water relations and wood anatomy of black spruce [Picea mariana (Mill.) B.S.P.] saplings were monitored during a greenhouse experiment where temperature was increased during daytime or night-time (+6 °C) combined with a drought period. The kinetics of tracheid development expressed as rate and duration of the xylogenesis sub-processes were quantified using generalized additive models. Drought and warming had a strong influence on cell production, but little effect on wood anatomy. The increase in cell production rate under warmer temperatures, and especially during the night-time warming at the end of the growing season, resulted in wider tree-rings. However, the strong compensation between rates and durations of cell differentiation processes mitigates warming and drought effects on tree-ring structure. Our results allowed quantification of how wood formation kinetics is regulated when water and heat stress increase, allowing trees to adapt to future environmental conditions. © 2015 John Wiley & Sons Ltd.

Perennial ryegrass for dairy cows: Intake, milk production and nitrogen utilization

NARCIS (Netherlands)

Tas, B.M.

2005-01-01

Keywords: perennial ryegrass, dairy cows, intake, digestibility milk production, nitrogen utilisation.In the Netherlands, grass is one of the main roughages in the diet of high productive dairy cows. Grass is associated with two main problems: the limited dry matter intake (DMI)

Daytime warming has stronger negative effects on soil nematodes than night-time warming

OpenAIRE

Yan, Xiumin; Wang, Kehong; Song, Lihong; Wang, Xuefeng; Wu, Donghui

2017-01-01

Warming of the climate system is unequivocal, that is, stronger warming during night-time than during daytime. Here we focus on how soil nematodes respond to the current asymmetric warming. A field infrared heating experiment was performed in the western of the Songnen Plain, Northeast China. Three warming modes, i.e. daytime warming, night-time warming and diurnal warming, were taken to perform the asymmetric warming condition. Our results showed that the daytime and diurnal warming treatmen...

PERENNIAL HELIANTHUS TAXA IN TÂRGU-MURES CITY AND ITS SURROUNDINGS

Directory of Open Access Journals (Sweden)

FILEP RITA

2010-12-01

Full Text Available Although in the neighbouring countries several perennial Helianthus taxa have been recorded in the last decade, in Romania only three have been identified so far. The literature and herbaria data of Târgu-Mures date back to the end of the XIXth century, and only refer to H. × multiflorus and H. tuberosus. The aim of this study was to identify the perennial Helianthus taxa in this region and to prepare their current distribution map. The survey was conducted in Târgu Mures city and the neighbouring villages: Livezeni, Sântana de Mures, Sâncraiu de Mures, Sângeorgiu de Mures, and Corunca. Four taxa were identified: H. pauciflorus Nutt., H. × laetiflorus Pers., H. tuberosus L. s.str., and Helianthus tuberosus L. s.l. The first two taxa are cultivated as ornamental plants, H. tuberosus s. str. is cultivated in a few farms, whereas H. tuberosus s. l. is an invasive species that spreads along the rivers.

Evaluation of Seed and Forage Yield of Perennial Plants with Low Water Requirement in Abandoned Farming Lands

Directory of Open Access Journals (Sweden)

Ali gazanchian

2017-10-01

Full Text Available Introduction Drought is a natural phenomenon in arid and semi-arid regions of the world. It is created by low precipitation, high evaporation and reduced soil moisture. Today, they are the major threats to agricultural lands due to fluctuations in rainfall, limited water resources, wells salinization and subsequently abandoned farming lands. Iran is located on the world's dry belt and more than 90 percent of its area is located in the arid and semi-arid climatic regions. It has been reported that the annual rate of soil erosion is up to 33 tons per hectare and 5 to 6 times more than the standard limit. Also, 90% of the country's protein production comes from animals sources. Due to the lack of adequate forage production, the main burden of protein production is imposed on the natural resources and pastures. Therefore, In order to enhance soil stabilization and maintain its fertility, optimum use of off-season precipitations, preventing the flow of water and protecting the abandoned farming lands from the flood risk, increasing the water permeability in the soil, and helping to feed the underwater aquifers and finally the production of forage and seeds, the development of perennial plants cultivation is an important conservative practice. The aim of this study is to emphasize on the selection of the best perennial forage species with low water requirements and acceptable performance for renovation of the abandoned farming lands and moving towards sustainable agriculture approaches. Materials and Methods In this experiment, 10 species of perennial grasses (Agropyron elongatum Host., Secale montanum Guss., Festuca arundinaceae Schreb., Dactylis glomerata L., Agropyron intermedium Host., Agropyron repense L., Agropyron cristatum L., Panicum antidutale Retz., Bromus inermis Leyss., Bromus riparius Rehmann, Agropyron cristatum L. and two legumes includes Trifolium pratense L., Onobrychis sativa Lam. were studied at Asatan-e-Ghods Razavi farm in

Factors Influencing Knowledge, Food Safety Practices and Food Preferences During Warm Weather of Salmonella and Campylobacter Cases in South Australia.

Science.gov (United States)

Milazzo, Adriana; Giles, Lynne C; Zhang, Ying; Koehler, Ann P; Hiller, Janet E; Bi, Peng

2017-03-01

To assess food safety practices, food shopping preferences, and eating behaviors of people diagnosed with Salmonella or Campylobacter infection in the warm seasons, and to identify socioeconomic factors associated with behavior and practices. A cross-sectional survey was conducted among Salmonella and Campylobacter cases with onset of illness from January 1 to March 31, 2013. Multivariable logistic regression analyses examined relationships between socioeconomic position and food safety knowledge and practices, shopping and food preferences, and preferences, perceptions, and knowledge about food safety information on warm days. Respondents in our study engaged in unsafe personal and food hygiene practices. They also carried out unsafe food preparation practices, and had poor knowledge of foods associated with an increased risk of foodborne illness. Socioeconomic position did not influence food safety practices. We found that people's reported eating behaviors and food preferences were influenced by warm weather. Our study has explored preferences and practices related to food safety in the warm season months. This is important given that warmer ambient temperatures are projected to rise, both globally and in Australia, and will have a substantial effect on the burden of infectious gastroenteritis including foodborne disease. Our results provide information about modifiable behaviors for the prevention of foodborne illness in the household in the warm weather and the need for information to be disseminated across the general population. An understanding of the knowledge and factors associated with human behavior during warmer weather is critical for public health interventions on foodborne prevention.

A Proteomics Sample Preparation Method for Mature, Recalcitrant Leaves of Perennial Plants

Science.gov (United States)

Na, Zhang; Chengying, Lao; Bo, Wang; Dingxiang, Peng; Lijun, Liu

2014-01-01

Sample preparation is key to the success of proteomics studies. In the present study, two sample preparation methods were tested for their suitability on the mature, recalcitrant leaves of six representative perennial plants (grape, plum, pear, peach, orange, and ramie). An improved sample preparation method was obtained: Tris and Triton X-100 were added together instead of CHAPS to the lysis buffer, and a 20% TCA-water solution and 100% precooled acetone were added after the protein extraction for the further purification of protein. This method effectively eliminates nonprotein impurities and obtains a clear two-dimensional gel electrophoresis array. The method facilitates the separation of high-molecular-weight proteins and increases the resolution of low-abundance proteins. This method provides a widely applicable and economically feasible technology for the proteomic study of the mature, recalcitrant leaves of perennial plants. PMID:25028960

A proteomics sample preparation method for mature, recalcitrant leaves of perennial plants.

Directory of Open Access Journals (Sweden)

Deng Gang

Full Text Available Sample preparation is key to the success of proteomics studies. In the present study, two sample preparation methods were tested for their suitability on the mature, recalcitrant leaves of six representative perennial plants (grape, plum, pear, peach, orange, and ramie. An improved sample preparation method was obtained: Tris and Triton X-100 were added together instead of CHAPS to the lysis buffer, and a 20% TCA-water solution and 100% precooled acetone were added after the protein extraction for the further purification of protein. This method effectively eliminates nonprotein impurities and obtains a clear two-dimensional gel electrophoresis array. The method facilitates the separation of high-molecular-weight proteins and increases the resolution of low-abundance proteins. This method provides a widely applicable and economically feasible technology for the proteomic study of the mature, recalcitrant leaves of perennial plants.

Effects of experimental warming and nitrogen addition on soil respiration and CH4 fluxes from crop rotations of winter wheat–soybean/fallow

DEFF Research Database (Denmark)

Liu, L; Hu, C; Yang, P

2015-01-01

Soil respiration and CH4 emissions play a significant role in the global carbon balance. However, in situ studies in agricultural soils on responses of soil respiration and CH4 fluxes to climate warming are still sparse, especially from long-term studies with year-round heating. A warming...... by affecting soil NH4 concentration. Across years, CH4 emissions were negatively correlated with soil temperature in N1 treatment. Soil respiration showed clear seasonal fluctuations, with the largest emissions during summer and smallest in winter. Warming and nitrogen fertilization had no significant effects...... on total cumulative soil CO2 fluxes. Soil respiration was positively correlated with microbial biomass C, and microbial biomass C was not affected significantly by warming or nitrogen addition. The lack of significant effects of warming on soil respiration may have resulted from: (1) warming-induced soil...

Development of new techniques of using irradiation in the genetic improvement of warm season grasses and an assessment of the genetic and cytogenetic effects. Progress report, November 1, 1977--October 31, 1978

International Nuclear Information System (INIS)

Hanna, W.W.; Burton, G.W.

1978-05-01

Progress is reported on plant breeding programs for the genetic improvement of warm season grasses using irradiation as a tool. Data are included from studies on alteration of the protein quantity and quality in pearl millet grain by irradiation and mutation breeding; the effects of nitrogen and genotype on pearl millet grain; the effects of seed size on quality in pearl millet; irradiation breeding of sterile triploid turf Bermuda grasses; irradiation breeding of sterile coastcross-1, a forage grass, to increase winter hardiness; use of irradiation to induce resistance to rust disease; and an economic assessment of irradiation-induced mutants for plant breeding programs

Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status

DEFF Research Database (Denmark)

Albert, Kristian Rost; Ro-Poulsen, H.; Mikkelsen, Teis Nørgaard

2011-01-01

The impact of elevated CO2, periodic drought and warming on photosynthesis and leaf characteristics of the evergreen dwarf shrub Calluna vulgaris in a temperate heath ecosystem was investigated. Photosynthesis was reduced by drought in midsummer and increased by elevated CO2 throughout the growing...... season, whereas warming only stimulated photosynthesis early in the year. At the beginning and end of the growing season, a T × CO2 interaction synergistically stimulated plant carbon uptake in the combination of warming and elevated CO2. At peak drought, the D × CO2 interaction antagonistically down......-regulated photosynthesis, suggesting a limited ability of elevated CO2 to counteract the negative effect of drought. The response of photosynthesis in the full factorial combination (TDCO2) could be explained by the main effect of experimental treatments (T, D, CO2) and the two-factor interactions (D × CO2, T × CO2...

Energy from biomass: Results of two-years trials on annual and perennial Herba ceous species

International Nuclear Information System (INIS)

Angelini, L.; Ceccarini, L.; Oggiano, N.; Bonari, E.

1994-01-01

In the framework of the PRisCa Project (Alternative Crops Research Project) a number of germ plasm collections were set up at the Department of Agronomy of the University of Pisa in order to identify annual and perennial herbaceous species utilizable for electric energy production. The first results deriving from trials carried out in 1992-93 are reported. The following species were used: 1) Annual: Sorghum bicolor, Hibiscus cannabinus, Pennisetum americanum, Kochia scoparia. 2) Perennial: Cynara cardunculus, Helianthus tuberosus, Miscantus sinensis, Arundo donax. Almost all species tested were represented by several genotypes. The total amount of species and genotype tested was 16. On all species, main phenological, biometric and productive determinations were performed. The hypothesized final use was intended to be electric power production by direct combustion and/or gasification. In addition, specific calorific value was also determined by adiabatic calorimeter as well as chemical composition of dry matter and ash composition. Species showing high yield potential, both from the quantitative and qualitative point of view, were Sorghum bicolor and Kochia scoparia (among annuals), as well as Miscanthus sinensis and Arundo donax (among perennials). Total dry matter yield ranged from about 23 tha -1 in the annual species to about 56 tha -1 in the perennials. The highest total calorific power obtainable from dry epigeic biomass was measured in Sorghum bicolor and Arundo donax - 4023 Kcal Kg -1 and 4166 Kcal Kg -1 respectively. The preliminary results suggest that vegetable biomass is environmentally-friendly and could contribute significantly to the world energy needs. (author)

Warm Season Storms, Floods, and Tributary Sand Inputs below Glen Canyon Dam: Investigating Salience to Adaptive Management in the Context of a 10-Year Long Controlled Flooding Experiment in Grand Canyon National Park, AZ, USA

Science.gov (United States)

Jain, S.; Melis, T. S.; Topping, D. J.; Pulwarty, R. S.; Eischeid, J.

2013-12-01

The planning and decision processes in the Glen Canyon Dam Adaptive Management Program (GCDAMP) strive to balance numerous, often competing, objectives, such as, water supply, hydropower generation, low flow maintenance, maximizing conservation of downstream tributary sand supply, endangered native fish, and other sociocultural resources of Glen Canyon National Recreation Area and Grand Canyon National Park. In this context, use of monitored and predictive information on the warm season floods (at point-to-regional scales) has been identified as lead-information for a new 10-year long controlled flooding experiment (termed the High-Flow Experiment Protocol) intended to determine management options for rebuilding and maintaining sandbars in Grand Canyon; an adaptive strategy that can potentially facilitate improved planning and dam operations. In this work, we focus on a key concern identified by the GCDAMP, related to the timing and volume of tributary sand input from the Paria and Little Colorado Rivers (located 26 and 124 km below the dam, respectively) into the Colorado River in Grand Canyon National Park. Episodic and intraseasonal variations (with links to equatorial and sub-tropical Pacific sea surface temperature variability) in the southwest hydroclimatology are investigated to understand the magnitude, timing and spatial scales of warm season floods from this relatively small, but prolific sand producing drainage of the semi-arid Colorado Plateau. The coupled variations of the flood-driven sediment input (magnitude and timing) from these two drainages into the Colorado River are also investigated. The physical processes, including diagnosis of storms and moisture sources, are mapped alongside the planning and decision processes for the ongoing experimental flood releases from the Glen Canyon Dam which are aimed at achieving restoration and maintenance of sandbars and instream ecology. The GCDAMP represents one of the most visible and widely recognized

Nitrous oxide emission and soil carbon sequestration from herbaceous perennial biofuel feedstocks

Science.gov (United States)

Greenhouse gas (GHG) mitigation and renewable, domestic fuels are needed in the United States. Switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerdardii Vitman) are potential bioenergy feedstocks that may meet this need. However, managing perennial grasses for feedstock requires nitro...

Detecting Climate Signals in Precipitation Extremes from TRMM (1998-2013) - Increasing Contrast Between Wet and Dry Extremes During the "Global Warming Hiatus"

Science.gov (United States)

Wu, Huey-Tzu Jenny; Lau, William K.-M.

2016-01-01

We investigate changes in daily precipitation extremes using Tropical Rainfall Measuring Mission (TRMM) data (1998-2013), which coincides with the "global warming hiatus." Results show a change in probability distribution functions of local precipitation events (LPEs) during this period consistent with previous global warming studies, indicating increasing contrast between wet and dry extremes, with more intense LPE, less moderate LPE, and more dry (no rain) days globally. Analyses for land and ocean separately reveal more complex and nuanced changes over land, characterized by a strong positive trend (+12.0% per decade, 99% confidence level (c.l.)) in frequency of extreme LPEs over the Northern Hemisphere extratropics during the wet season but a negative global trend (-6.6% per decade, 95% c.l.) during the dry season. A significant global drying trend (3.2% per decade, 99% c.l.) over land is also found during the dry season. Regions of pronounced increased dry events include western and central U.S., northeastern Asia, and Southern Europe/Mediterranean.

Increasing potential of biomass burning over Sumatra, Indonesia induced by anthropogenic tropical warming

International Nuclear Information System (INIS)

Lestari, R Kartika; Watanabe, Masahiro; Kimoto, Masahide; Imada, Yukiko; Shiogama, Hideo; Field, Robert D; Takemura, Toshihiko

2014-01-01

Uncontrolled biomass burning in Indonesia during drought periods damages the landscape, degrades regional air quality, and acts as a disproportionately large source of greenhouse gas emissions. The expansion of forest fires is mostly observed in October in Sumatra favored by persistent droughts during the dry season from June to November. The contribution of anthropogenic warming to the probability of severe droughts is not yet clear. Here, we show evidence that past events in Sumatra were exacerbated by anthropogenic warming and that they will become more frequent under a future emissions scenario. By conducting two sets of atmospheric general circulation model ensemble experiments driven by observed sea surface temperature for 1960–2011, one with and one without an anthropogenic warming component, we found that a recent weakening of the Walker circulation associated with tropical ocean warming increased the probability of severe droughts in Sumatra, despite increasing tropical-mean precipitation. A future increase in the frequency of droughts is then suggested from our analyses of the Coupled Model Intercomparison Project Phase 5 model ensembles. Increasing precipitation to the north of the equator accompanies drier conditions over Indonesia, amplified by enhanced ocean surface warming in the central equatorial Pacific. The resultant precipitation decrease leads to a ∼25% increase in severe drought events from 1951–2000 to 2001–2050. Our results therefore indicate the global warming impact to a potential of wide-spreading forest fires over Indonesia, which requires mitigation policy for disaster prevention. (letter)

Daytime warming has stronger negative effects on soil nematodes than night-time warming

Science.gov (United States)

Yan, Xiumin; Wang, Kehong; Song, Lihong; Wang, Xuefeng; Wu, Donghui

2017-03-01

Warming of the climate system is unequivocal, that is, stronger warming during night-time than during daytime. Here we focus on how soil nematodes respond to the current asymmetric warming. A field infrared heating experiment was performed in the western of the Songnen Plain, Northeast China. Three warming modes, i.e. daytime warming, night-time warming and diurnal warming, were taken to perform the asymmetric warming condition. Our results showed that the daytime and diurnal warming treatment significantly decreased soil nematodes density, and night-time warming treatment marginally affected the density. The response of bacterivorous nematode and fungivorous nematode to experimental warming showed the same trend with the total density. Redundancy analysis revealed an opposite effect of soil moisture and soil temperature, and the most important of soil moisture and temperature in night-time among the measured environment factors, affecting soil nematode community. Our findings suggested that daily minimum temperature and warming induced drying are most important factors affecting soil nematode community under the current global asymmetric warming.

Drilling comparison in "warm ice" and drill design comparison

DEFF Research Database (Denmark)

Augustin, L.; Motoyama, H.; Wilhelms, F.

2007-01-01

For the deep ice-core drilling community, the 2005/06 Antarctic season was an exciting and fruitful one. In three different Antarctic locations, Dome Fuji, EPICA DML and Vostok, deep drillings approached bedrock (the ice-water interface in the case of Vostok), emulating what had previously been...... achieved at NorthGRIP, Greenland, (summer 2003 and 2004) and at EPICA Dome C2, Antarctica (season 2004/05). For the first time in ice-core drilling history, three different types of drill (KEMS, JARE and EPICA) simultaneously reached the depth of 'warm ice' under high pressure. After excellent progress...... at each site, the drilling rate dropped and the drilling teams had to deal with refrozen ice on cutters and drill heads. Drills have different limits and perform differently. In this comparative study, we examine depth, pressure, temperature, pump flow and cutting speed. Finally, we compare a few...

Clumped Isotope Thermometry Reveals Variations in Soil Carbonate Seasonal Biases Over >4 km of Relief in the Semi-Arid Andes of Central Chile

Science.gov (United States)

Burgener, L. K.; Huntington, K. W.; Hoke, G. D.; Schauer, A. J.; Ringham, M. C.; Latorre Hidalgo, C.; Díaz, F.

2015-12-01

The application of carbonate clumped isotope thermometry to soil carbonates has the potential to shed new light on questions regarding terrestrial paleoclimate. In order to better utilize this paleoclimate tool, outstanding questions regarding seasonal biases in soil carbonate formation and the relationship between soil carbonate formation temperatures (T(Δ47)) and surface temperatures must be resolved. We address these questions by comparing C, O, and clumped isotope data from Holocene/modern soil carbonates to modern meteorological data. The data were collected along a 170 km transect with >4 km of relief in central Chile (~30°S). Previous studies have suggested that soil carbonates should record a warm season bias and form in isotopic equilibrium with soil water and soil CO2. We identify two discrete climate zones separated by the local winter snow line (~3200 m). Below this boundary, precipitation falls as rain and soil carbonate T(Δ47) values at depths >40 cm resemble summer soil temperatures; at higher elevations, precipitation falls as snow and T(Δ47) values resemble mean annual soil temperatures. Soil carbonates from the highest sample site (4700 m), which is devoid of vegetation and located near perennial snow fields, yield anomalous δ18O, δ13C, and T(Δ47) values, indicative of kinetic isotope effects that we attribute to cryogenic carbonate formation. Our results suggest that soil carbonates from depths temperature and precipitation, and should not be used as paleotemperature proxies. These findings (1) highlight the role of soil moisture in modulating soil carbonate formation and the resulting T(Δ47) values, (2) underscore the importance of understanding past soil moisture conditions when attempting to reconstruct paleotemperatures using carbonate clumped isotope thermometry, and (3) suggest that soil carbonates from high elevation or high latitude sites may form under non-equilibrium conditions.

The relationship of lightning activity and short-duration rainfall events during warm seasons over the Beijing metropolitan region

Science.gov (United States)

Wu, Fan; Cui, Xiaopeng; Zhang, Da-Lin; Qiao, Lin

2017-10-01

The relationship between lightning activity and rainfall associated with 2925 short-duration rainfall (SDR) events over the Beijing metropolitan region (BMR) is examined during the warm seasons of 2006-2007, using the cloud-to-ground (CG) and intracloud (IC) lightning data from Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR)-3000 and 5-min rainfall data from automatic weather stations (AWSs). An optimal radius of 10 km around selected AWSs is used to determine the lightning-rainfall relationship. The lightning-rainfall correlations vary significantly, depending upon the intensity of SDR events. That is, correlation coefficient (R 0.7) for the short-duration heavy rainfall (SDHR, i.e., ≥ 20 mm h- 1) events is found higher than that (R 0.4) for the weak SDR (i.e., 5-10 mm h- 1) events, and lower percentage of the SDHR events (< 10%) than the weak SDR events (40-50%) are observed with few flashes. Significant time-lagged correlations between lightning and rainfall are also found. About 80% of the SDR events could reach their highest correlation coefficients when the associated lightning flashes shift at time lags of < 25 min before and after rainfall begins. Those events with lightning preceding rainfall account for 50-60% of the total SDR events. Better lightning-rainfall correlations can be attained when time lags are incorporated, with the use of total (CG and IC) lightning data. These results appear to have important implications for improving the nowcast of SDHR events.

Assessing the magnitude and timing of anthropogenic warming of a shallow aquifer: example from Virginia Beach, USA

Science.gov (United States)

Eggleston, John R.; McCoy, Kurt J.

2015-01-01

Groundwater temperature measurements in a shallow coastal aquifer in Virginia Beach, Virginia, USA, suggest groundwater warming of +4.1 °C relative to deeper geothermal gradients. Observed warming is related to timing and depth of influence of two potential thermal drivers—atmospheric temperature increases and urbanization. Results indicate that up to 30 % of groundwater warming at the water table can be attributed to atmospheric warming while up to 70 % of warming can be attributed to urbanization. Groundwater temperature readings to 30-m depth correlate positively with percentage of impervious cover and negatively with percentage of tree canopy cover; thus, these two land-use metrics explain up to 70 % of warming at the water table. Analytical and numerical modeling results indicate that an average vertical groundwater temperature profile for the study area, constructed from repeat measurement at 11 locations over 15 months, is consistent with the timing of land-use change over the past century in Virginia Beach. The magnitude of human-induced warming at the water table (+4.1 °C) is twice the current seasonal temperature variation, indicating the potential for ecological impacts on wetlands and estuaries receiving groundwater discharge from shallow aquifers.

Observed and Projected Changes in Thermal Growing Degree-Days and Growing Season and Their Divergent Responses to Warming over China

Science.gov (United States)

Deng, H.

2017-12-01

Vegetation growth and phenology are largely regulated by the growing degree-days (GDD) and growing season (GS). By choosing 0°C, 5°C and 10°C, three key based temperatures (Tb) for vegetation growth, the GDD and GS in China during the observed period (1960-2011) were developed using homogenized daily mean temperatures (Td) in 536 meteorological stations. In addition, the GDD10 and GS10 in China were projected under the representative concentration pathway scenarios (RCPs) during 1961-2099, using the Td (0.5°×0.5°) derived from five general circulation models (GCMs), after model evaluation. Advance in the start of the growing season (SOS; 4.86-6.71 days; SOS0 > SOS5 > SOS10) and delay in the end of the growing season (EOS; 4.32-6.19 days; EOS0 GDD5 > GDD10), in China as a whole. Each observed variation has a substantial acceleration mostly in 1987 or 1996, and a speed reduction or a trend reversal in the early 2000s. Increases in the GDD10 and GS10 would continue in the 21st century, causing northward shifts in the temperature zones. Finally in the long-term (2071-2099), the nationally average GDD10 and GS10 would be 279.1°C·d higher and 16.5 d longer for RCP 2.6, and 964.4°C·d higher and 50.3 d longer for RCP 8.5, relative to 1981-2010. Regionally, the GDD enhancement were stronger in the tropics, east, northeast and northwest China during the observed period, and tend to be in southern China in the future. The largest GS extensions are consistently in the eastern and southern parts of the Tibetan Alpine zone, particularly in the future. During the observed period, advance in SOS and delay in EOS drove the GS extensions in the eastern monsoon zone and northwest arid/semi-arid zone respectively. In the future, an advanced SOS drives the GS extension in the northern (> ca. 33°N) Tibetan Alpine zone, the mountainous areas in northeast China, and south of the Tropic of Cancer. The GDD and GS showed positive sensitivity to the temperature (GDD0 > GDD5 > GDD10

A century of ocean warming on Florida Keys coral reefs: historic in situ observations

Science.gov (United States)

Kuffner, Ilsa B.; Lidz, Barbara H.; Hudson, J. Harold; Anderson, Jeffery S.

2015-01-01

There is strong evidence that global climate change over the last several decades has caused shifts in species distributions, species extinctions, and alterations in the functioning of ecosystems. However, because of high variability on short (i.e., diurnal, seasonal, and annual) timescales as well as the recency of a comprehensive instrumental record, it is difficult to detect or provide evidence for long-term, site-specific trends in ocean temperature. Here we analyze five in situ datasets from Florida Keys coral reef habitats, including historic measurements taken by lighthouse keepers, to provide three independent lines of evidence supporting approximately 0.8 °C of warming in sea surface temperature (SST) over the last century. Results indicate that the warming observed in the records between 1878 and 2012 can be fully accounted for by the warming observed in recent decades (from 1975 to 2007), documented using in situ thermographs on a mid-shore patch reef. The magnitude of warming revealed here is similar to that found in other SST datasets from the region and to that observed in global mean surface temperature. The geologic context and significance of recent ocean warming to coral growth and population dynamics are discussed, as is the future prognosis for the Florida reef tract.

Cultivar effects of perennial ryegrass on herbage intake by grazing dairy cows

NARCIS (Netherlands)

Smit, H.J.

2006-01-01

Perennial ryegrass is the most abundant grass species in temperate climates. An increased herbage intake of dairy cows by breeding new cultivars could have a large potential impact on agriculture. The effects of cultivars on sward structure, nutritive value, physical characteristics and disease

The Change in Oceanic O2 Inventory Associated with Recent Global Warming

Science.gov (United States)

Keeling, Ralph; Garcia, Hernan

2002-01-01

Oceans general circulation models predict that global warming may cause a decrease in the oceanic O2 inventory and an associated O2 outgassing. An independent argument is presented here in support of this prediction based on observational evidence of the ocean's biogeochemical response to natural warming. On time scales from seasonal to centennial, natural O2 flux/heat flux ratios are shown to occur in a range of 2 to 10 nmol O2 per Joule of warming, with larger ratios typically occurring at higher latitudes and over longer time scales. The ratios are several times larger than would be expected solely from the effect of heating on the O2 solubility, indicating that most of the O2 exchange is biologically mediated through links between heating and stratification. The change in oceanic O2 inventory through the 1990's is estimated to be 0.3 - 0.4 x 10(exp 14) mol O2 per year based on scaling the observed anomalous long-term ocean warming by natural O2 flux/heating ratios and allowing for uncertainty due to decadal variability. Implications are discussed for carbon budgets based on observed changes in atmospheric O2/N2 ratio and based on observed changes in ocean dissolved inorganic carbon.

How Vulnerable is Perennial Sea Ice? Insights from Earth's Late Cenozoic Natural Experiments (Invited)

Science.gov (United States)

Brigham-Grette, J.; Polyak, L. V.; Caissie, B.; Sharko, C. J.; Petsch, S.

2010-12-01

Island at 80oN, correspond to the peak of Pliocene warming (~3.2 Ma). Marine SST and land-based flora suggest repeated intervals of seasonally ice free conditions during the Pliocene and parts of the Pleistocene. During the last interglacial, the Arctic Ocean may have also experienced periods of seasonal ice cover. These conditions may have been repeated during the early Holocene when elevated insolation produced transient warming across the high Arctic. This challenges many reconstructions based solely on deep ocean cores.

Variations of polycyclic aromatic hydrocarbons in ambient air during haze and non-haze episodes in warm seasons in Hangzhou, China.

Science.gov (United States)

Lu, Hao; Wang, Shengsheng; Wu, Zuliang; Yao, Shuiliang; Han, Jingyi; Tang, Xiujuan; Jiang, Boqiong

2017-01-01

To investigate the characteristics of polycyclic aromatic hydrocarbons (PAHs) during haze episodes in warm seasons, daily PM 2.5 and gaseous samples were collected from March to September 2015 in Hangzhou, China. Daily samples were further divided into four groups by the definition of haze according to visibility and relative humidity (RH), including non-haze (visibility, >10 km), light haze (visibility, 8-10 km, RH <90 %), medium haze (visibility, 5-8 km, RH <90 %), and heavy haze (visibility, <5 km, RH <90 %). Significantly higher concentrations of PM 2.5 -bound PAHs were found in haze days, but the mean PM 2.5 -bound PAH concentrations obviously decreased with the aggravation of haze pollution from light to heavy. The gas/particle partitioning coefficients of PAHs decreased from light-haze to heavy-haze episodes, which indicated that PM 2.5 -bound PAHs were restricted to adhere to the particulate phase with the aggravation of haze pollution. Absorption was considered the main mechanism of gas/particle partitioning of PAHs from gaseous to particulate phase. Analysis of air mass transport indicated that the PM 2.5 -bound PAH pollution in haze days was largely from regional sources but also significantly affected by long-range air mass transport. The inhalation cancer risk associated with PAHs exceeded the acceptable risk level markedly in both haze and non-haze days.

Bioenergy production from perennial energy crops: a consequential LCA of 12 bioenergy scenarios including land use changes.

Science.gov (United States)

Tonini, Davide; Hamelin, Lorie; Wenzel, Henrik; Astrup, Thomas

2012-12-18

In the endeavor of optimizing the sustainability of bioenergy production in Denmark, this consequential life cycle assessment (LCA) evaluated the environmental impacts associated with the production of heat and electricity from one hectare of Danish arable land cultivated with three perennial crops: ryegrass (Lolium perenne), willow (Salix viminalis) and Miscanthus giganteus. For each, four conversion pathways were assessed against a fossil fuel reference: (I) anaerobic co-digestion with manure, (II) gasification, (III) combustion in small-to-medium scale biomass combined heat and power (CHP) plants and IV) co-firing in large scale coal-fired CHP plants. Soil carbon changes, direct and indirect land use changes as well as uncertainty analysis (sensitivity, MonteCarlo) were included in the LCA. Results showed that global warming was the bottleneck impact, where only two scenarios, namely willow and Miscanthus co-firing, allowed for an improvement as compared with the reference (-82 and -45 t CO₂-eq. ha⁻¹, respectively). The indirect land use changes impact was quantified as 310 ± 170 t CO₂-eq. ha⁻¹, representing a paramount average of 41% of the induced greenhouse gas emissions. The uncertainty analysis confirmed the results robustness and highlighted the indirect land use changes uncertainty as the only uncertainty that can significantly change the outcome of the LCA results.

El Niño Southern Oscillation (ENSO and global warming

Directory of Open Access Journals (Sweden)

B. Nyenzi

2006-01-01

Full Text Available It is widely accepted by the international scientific community that human activities have increased atmospheric concentrations of greenhouse gases (GHG and aerosols since the pre-industrial era. This increase has contributed to most of the warming (0.6±0.2°C observed over the 20th century, land areas warming more than the oceans, with the 1990s very likely to be the warmest decade of the 20th century (IPCC, 2001. How this warming influences the occurrence, severity and frequency of ENSO episodes remains highly uncertain. The IPCC (2001 assessment of the scientific literature found insufficient evidence to suggest any direct attribution between increase in ENSO events that occurred in the last 20 to 30 years of the 20th century and global warming (IPCC, 2001. However, assessments carried out since then (e.g. IPCC Fourth Assessment Report (AR4, in preparations suggest El Niño events have become more frequent, persistent and intense during the last 20 to 30 years compared to the previous 100 years. Attribution to global warming, however, remains highly uncertain. Efforts to simulate and model past, present and future behaviour of ENSO under a warming world due to enhanced GHG concentrations produce conflicting results. Since substantial internally-generated variability of ENSO behaviour on multi-decadal to century timescales occurs in long, unforced atmospheric-oceanic general circulation model (AOGCM simulations, the attribution of past and future changes in ENSO amplitude and frequency to external forcing like GHG concentrations cannot be made with certainty. Such attribution would require extensive use of ensemble climate experiments or long experiments with stabilised GHG forcing. Although there are now better ENSO simulations in AOGCM, further model improvements are needed to simulate a more realistic Pacific climatology and seasonal cycle of the key modes influencing the climate of the region, as well as more realistic ENSO variability

Effects of short term and long term soil warming on ecosystem phenology of a sub-arctic grassland: an NDVI-based approach

Science.gov (United States)

Leblans, Niki; Sigurdsson, Bjarni D.; Janssens, Ivan A.

2014-05-01

Phenology has been defined as the study of the timing of recurring biological events and the causes of their timing with regard to abiotic and biotic factors. Ecosystem phenology, including the onset of the growing season and its senescence in autumn, plays an important role in the carbon, water and energy exchange between biosphere and atmosphere at higher latitudes. Factors that influence ecosystem phenology can therefore induce important climate-controlling feedback mechanisms. Global surface temperatures have been predicted to increase in the coming decades. Hence, a better understanding of the effect of temperature on ecosystem phenology is essential. Natural geothermal soil temperature gradients in Iceland offer a unique opportunity to study the soil temperature (Ts) dependence of ecosystem phenology and distinguish short-term (transient) warming effects (in recently established Ts gradients) from long-term (permanent) effects (in centuries-old Ts gradients). This research was performed in the framework of an international research project (ForHot; www.forhot.is). ForHot includes two natural grassland areas with gradients in Ts, dominated by Festuca sp., Agrostis sp.. The first warmed area was created in 2008, when an earthquake in S-Iceland caused geothermal systems to be shifted to previously cold soils. The second area is located about 3 km away from this newly warmed grassland. For this area, there are proofs that the natural soil warming has been continuous for at least 300 year. In the present study we focus on Ts elevation gradients of +0 to +10°C. The experiment consists of five transects with five temperature levels (+0,+1,+3,+5 and +10°C) in the two aforementioned grassland ecosystems (n=25 in each grassland). From April until November 2013, weekly measurements of the normalized difference vegetation index (NDVI) were taken. In the short-term warmed grassland, the greening of the vegetation was 36 days advanced at +10°C Ts and the date of 50

Recent global-warming hiatus tied to equatorial Pacific surface cooling.

Science.gov (United States)

Kosaka, Yu; Xie, Shang-Ping

2013-09-19

Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century, challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming, but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970-2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, the multi-decadal warming trend is very likely to continue with greenhouse gas increase.

Large Plankton Enhance Heterotrophy Under Experimental Warming in a Temperate Coastal Ecosystem

KAUST Repository

Huete-Stauffer, Tamara Megan

2017-12-15

Microbes are key players in oceanic carbon fluxes. Temperate ecosystems are seasonally variable and thus suitable for testing the effect of warming on microbial carbon fluxes at contrasting oceanographic conditions. In four experiments conducted in February, April, August and October 2013 in coastal NE Atlantic waters, we monitored microbial plankton stocks and daily rates of primary production, bacterial heterotrophic production and respiration at in situ temperature and at 2 and 4°C over ambient values during 4-day incubations. Ambient total primary production (TPP) exceeded total community respiration (< 200 µm, TR) in winter and fall but not in spring and summer. The bacterial contribution to ecosystem carbon fluxes was low, with bacterial production representing on average 6.9 ± 3.2% of TPP and bacterial respiration (between 0.8 and 0.2 µm) contributing on average 35 ± 7% to TR. Warming did not result in a uniform increase in the variables considered, and most significant effects were found only for the 4°C increase. In the summer and fall experiments, under warm and nutrient-deficient conditions, the net TPP/TR ratio decreased by 39 and 34% in the 4°C treatment, mainly due to the increase in respiration of large organisms rather than bacteria. Our results indicate that the interaction of temperature and substrate availability in determining microbial carbon fluxes has a strong seasonal component in temperate planktonic ecosystems, with temperature having a more pronounced effect and generating a shift toward net heterotrophy under more oligotrophic conditions as found in summer and early fall.

Investigate the plant biomass response to climate warming in permafrost ecosystem using matrix-based data assimilation

Science.gov (United States)

Lu, X.; Du, Z.; Schuur, E.; Luo, Y.

2017-12-01

Permafrost is one of the most vulnerable regions on the earth with over 40% world soil C represented in this region. Future climate warming potentially has a great impact on this region. On one hand, rising temperature accelerates permafrost soil thaw and release more C from land. On the other hand, warming may also increase the plant growing season length and therefore negatively feedback to climate change by increasing annual land C uptake. However, whether permafrost vegetation biomass change in response to warming can sequester more C has not been well understood. Manipulated air warming experiments reported that air warming has very limited impacts on grass land productivity and biomass growth in permafrost region [Mauritz et al., 2017]. It is hard to reveal the mechanisms behind the limited air warming response directly from experiment data. We employ a vegetation C cycle matrix model based on Community land model 4.5 (CLM4.5) and data assimilation technique to investigate how much do phenology and physiology processes contribute to the response respectively. Our results indicate phenology contributes the most in response to warming. The shift of vegetation parameter distributions after 2012 indicate vegetation acclimation may explain the modest response in plant biomass to air warming. The results suggest future model development need to take vegetation acclimation more seriously. The novel matrix-based model allows data assimilation to be conducted more efficiently. It provides more functional understanding of the models as well as the mechanism behind experiment data.

Anaerobic co-digestion of perennials: Methane potential and digestate nitrogen fertilizer value

DEFF Research Database (Denmark)

Muller-Stover, Dorette Sophie; Sun, Guotao; Kroff, Pablo

2016-01-01

Co-digestion of crop biomass improves the traditional manure-based biogas yield due to an increased content of easily degradable carbon compounds. In this study, the methane potential of three perennials (grass, legumes, and grass+legume) was determined using various amounts together with animal ...

Artificial climate warming positively affects arbuscular mycorrhizae but decreases soil aggregate water stability in an annual grassland

Energy Technology Data Exchange (ETDEWEB)

Rillig, M.C.; Wright, S.F.; Shaw, M.R.; Field, C.B.

2002-04-01

Despite the importance of arbuscular mycorrhizae to the functioning of terrestrial ecosystems (e.g. nutrient uptake, soil aggregation), and the increasing evidence of global warming, responses of arbuscular mycorrhizal fungi (AMF) to climate warming are poorly understood. In a field experiment using infrared heaters, we found effects of warming on AMF after one growing season in an annual grassland, in the absence of any effects on measured root parameters (weight, length, average diameter). AMF soil hyphal length was increased by over 40% in the warmed plots, accompanied by a strong trend for AMF root colonization increase. In the following year, root weight was again not significantly changed, and AMF root colonization increased significantly in the warmed plots. Concentration of the soil protein glomalin, a glycoprotein produced by AMF hyphae with importance in soil aggregation, was decreased in the warmed plots. Soil aggregate water stability, measured for five diameter size classes, was also decreased significantly. In the following year, soil aggregate weight in two size classes was decreased significantly, but the effect size was very small. These results indicate that ecosystem warming may have stimulated carbon allocation to AMF. Other factors either influenced glomalin decomposition or production, hence influencing the role of these symbionts in soil aggregation. The observed small changes in soil aggregation, if widespread among terrestrial ecosystems, could have important consequences for soil carbon storage and erosion in a warmed climate, especially if there are cumulative effects of warming. (au)

The effects of warming and nitrogen addition on soil nitrogen cycling in a temperate grassland, northeastern China.

Directory of Open Access Journals (Sweden)

Lin-Na Ma

Full Text Available Both climate warming and atmospheric nitrogen (N deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood.A field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland.Interactions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem.

A Contribution by Ice Nuclei to Global Warming

Science.gov (United States)

Zeng, Xiping; Tao, Wei-Kuo; Zhang, Minghua; Hou, Arthur Y.; Xie, Shaocheng; Lang, Stephen; Li, Xiaowen; Starr, David O.; Li, Xiaofan

2009-01-01

Ice nuclei (IN) significantly affect clouds via supercooled droplets, that in turn modulate atmospheric radiation and thus climate change. Since the IN effect is relatively strong in stratiform clouds but weak in convective ones, the overall effect depends on the ratio of stratiform to convective cloud amount. In this paper, 10 years of TRMM (Tropical Rainfall Measuring Mission) satellite data are analyzed to confirm that stratiform precipitation fraction increases with increasing latitude, which implies that the IN effect is stronger at higher latitudes. To quantitatively evaluate the IN effect versus latitude, large-scale forcing data from ten field campaigns are used to drive a CRM (cloud-resolving model) to generate longterm cloud simulations. As revealed in the simulations, the increase in the net downward radiative flux at the TOA (top of the atmosphere) from doubling the current IN concentrations is larger at higher latitude, which is attributed to the meridional tendency in the stratiform precipitation fraction. Surface warming from doubling the IN concentrations, based on the radiative balance of the globe, is compared with that from anthropogenic COZ . It is found that the former effect is stronger than the latter in middle and high latitudes but not in the Tropics. With regard to the impact of IN on global warming, there are two factors to consider: the radiative effect from increasing the IN concentration and the increase in IN concentration itself. The former relies on cloud ensembles and thus varies mainly with latitude. In contrast, the latter relies on IN sources (e.g., the land surface distribution) and thus varies not only with latitude but also longitude. Global desertification and industrialization provide clues on the geographic variation of the increase in IN concentration since pre-industrial times. Thus, their effect on global warming can be inferred and then be compared with observations. A general match in geographic and seasonal

Impacts of managing perennial grasses in the northern Midwest United States for bioenergy on soil organic C and nitrous oxide emission

Science.gov (United States)

In the USA perennial grasses [e.g., switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerdardii Vitman)] are proposed as cellulosic feedstock. Perennial grasses are often touted as being low input and as having a C-neutral foot print, but managing them as bioenergy feedstock means addin...

Selecting native perennial plants for ecological intensification in Mediterranean greenhouse horticulture.

Science.gov (United States)

Rodríguez, E; González, M; Paredes, D; Campos, M; Benítez, E

2017-12-04

Natural control by predators and parasitoids provides an important and often unnoticed ecosystem service to agricultural landscapes by reducing pest populations in crops. The current model of horticultural intensification in south-eastern Spain produces high yields but has also resulted in a landscape almost completely covered by plastic. Promoting natural areas among greenhouses could enhance biodiversity, by being beneficial insects, and reduce pest pressure outdoors. The first step is to ascertain how pests and their natural enemies (NEs) use Mediterranean vegetation for selecting the best plants for pest suppression outdoors. The abundance of the two major horticultural pests, the tobacco whitefly, Bemisia tabaci, and the western flower thrips, Frankliniella occidentalis, together with their NEs, were assayed in 22 flowering perennial plants, which were newly planted in an experimental field surrounded by greenhouses. Eight plant species were identified as the most critical species for sustaining pest populations outdoors. A set of five plant species supported a medium level of pests, and another set of ten plant species supported the lowest level of both pests. Tobacco whitefly occurred in a few plants species, whereas western flower thrips occurred on almost all the plant species studied, and was favoured by the presence of flowers in perennial plants. The results suggest that plant diversity may provide relatively few acceptable host plants for tobacco whitefly than for western flower thrips. NEs were generally collected in plants that also supported abundance of pests, indicating that host/prey availability, more than food resources from flowers, was a stronger predictor of NE abundance in perennial plants. Field trials using the plants with the lowest host acceptance by pests are needed in order to ascertain whether pest abundance outdoors is reduced.

Perennial soybean seeds coated with high doses of boron and zinc ...

African Journals Online (AJOL)

The objective of this work was to study combinations of high doses of boron (B) and zinc (Zn) in the recoating of perennial soybean seeds, in order to provide these nutrients to the future plants. The physical, physiological and nutritional characteristics of the coated seeds and initial development of plants in a greenhouse ...

Global warming

International Nuclear Information System (INIS)

Anon.

1992-01-01

Canada's Green Plan strategy for dealing with global warming is being implemented as a multidepartmental partnership involving all Canadians and the international community. Many of the elements of this strategy are built on an existing base of activities predating the Green Plan. Elements of the strategy include programs to limit emissions of greenhouse gases, such as initiatives to encourage more energy-efficient practices and development of alternate fuel sources; studies and policy developments to help Canadians prepare and adapt to climate change; research on the global warming phenomenon; and stimulation of international action on global warming, including obligations arising out of the Framework Convention on Climate Change. All the program elements have been approved, funded, and announced. Major achievements to date are summarized, including improvements in the Energy Efficiency Act, studies on the socioeconomic impacts of global warming, and participation in monitoring networks. Milestones associated with the remaining global warming initiatives are listed

Responses of soil CO2 fluxes to short-term experimental warming in alpine steppe ecosystem, Northern Tibet.

Science.gov (United States)

Lu, Xuyang; Fan, Jihui; Yan, Yan; Wang, Xiaodan

2013-01-01

Soil carbon dioxide (CO2) emission is one of the largest fluxes in the global carbon cycle. Therefore small changes in the size of this flux can have a large effect on atmospheric CO2 concentrations and potentially constitute a powerful positive feedback to the climate system. Soil CO2 fluxes in the alpine steppe ecosystem of Northern Tibet and their responses to short-term experimental warming were investigated during the growing season in 2011. The results showed that the total soil CO2 emission fluxes during the entire growing season were 55.82 and 104.31 g C m(-2) for the control and warming plots, respectively. Thus, the soil CO2 emission fluxes increased 86.86% with the air temperature increasing 3.74°C. Moreover, the temperature sensitivity coefficient (Q 10) of the control and warming plots were 2.10 and 1.41, respectively. The soil temperature and soil moisture could partially explain the temporal variations of soil CO2 fluxes. The relationship between the temporal variation of soil CO2 fluxes and the soil temperature can be described by exponential equation. These results suggest that warming significantly promoted soil CO2 emission in the alpine steppe ecosystem of Northern Tibet and indicate that this alpine ecosystem is very vulnerable to climate change. In addition, soil temperature and soil moisture are the key factors that controls soil organic matter decomposition and soil CO2 emission, but temperature sensitivity significantly decreases due to the rise in temperature.

Contrasting effects of summer and winter warming on body mass explain population dynamics in a food-limited Arctic herbivore.

Science.gov (United States)

Albon, Steve D; Irvine, R Justin; Halvorsen, Odd; Langvatn, Rolf; Loe, Leif E; Ropstad, Erik; Veiberg, Vebjørn; van der Wal, René; Bjørkvoll, Eirin M; Duff, Elizabeth I; Hansen, Brage B; Lee, Aline M; Tveraa, Torkild; Stien, Audun

2017-04-01

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain-on-snow) can cause 'icing', restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a 'barometer' of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between-year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long-term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to 'rain-on-snow' events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density-dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important 'missing' mechanistic link in the current understanding of the population biology of a

A shorter snowfall season associated with higher air temperatures over northern Eurasia

International Nuclear Information System (INIS)

Ye Hengchun; Cohen, Judah

2013-01-01

The temperature sensitivity of the snowfall season (start, end, duration) over northern Eurasia (the former USSR) is analyzed from synoptic records of 547 stations from 1966 to 2000. The results find significant correlations between temperature and snowfall season at approximately 56% of stations (61% for the starting date and 56% for the ending date) with a mean snowfall season duration temperature sensitivity of −6.2 days °C −1 split over the start (2.8 days) and end periods (−3.4 days). Temperature sensitivity was observed to increase with stations’ mean seasonal air temperature, with the strongest relationships at locations of around 6 °C temperature. This implies that increasing air temperature in fall and spring will delay the onset and hasten the end of snowfall events, and reduces the snowfall season length by 6.2 days for each degree of increase. This study also clarifies that the increasing trend in snowfall season length during 1936/37–1994 over northern European Russia and central Siberia revealed in an earlier study is unlikely to be associated with warming in spring and fall seasons. (letter)

Effects of dairy manure management in annual and perennial cropping systems on soil microbial communities associated with in situ N2O fluxes

Science.gov (United States)

Dunfield, Kari; Thompson, Karen; Bent, Elizabeth; Abalos, Diego; Wagner-Riddle, Claudia

2016-04-01

Liquid dairy manure (LDM) application and ploughing events may affect soil microbial community functioning differently between perennial and annual cropping systems due to plant-specific characteristics stimulating changes in microbial community structure. Understanding how these microbial communities change in response to varied management, and how these changes relate to in situ N2O fluxes may allow the creation of predictive models for use in the development of best management practices (BMPs) to decrease nitrogen (N) losses through choice of crop, plough, and LDM practices. Our objectives were to contrast changes in the population sizes and community structures of genes associated with nitrifier (amoA, crenamoA) and denitrifier (nirK, nirS, nosZ) communities in differently managed annual and perennial fields demonstrating variation in N2O flux, and to determine if differences in these microbial communities were linked to the observed variation in N2O fluxes. Soil was sampled in 2012 and in 2014 in a 4-ha spring-applied LDM grass-legume (perennial) plot and two 4-ha corn (annual) treatments under fall or spring LDM application. Soil DNA was extracted and used to target N-cycling genes via qPCR (n=6) and for next-generation sequencing (Illumina Miseq) (n=3). Significantly higher field-scale N2O fluxes were observed in the annual plots compared to the perennial system; however N2O fluxes increased after plough down of the perennial plot. Nonmetric multidimensional scaling (NMS) indicated differences in N-cycling communities between annual and perennial cropping systems, and some communities became similar between annual and perennial plots after ploughing. Shifts in these communities demonstrated relationships with agricultural management, which were associated with differences in N2O flux. Indicator species analysis was used to identify operational taxonomic units (OTUs) most responsible for community shifts related to management. Nitrifying and denitrifying soil

Seasonal ozone uptake by a warm-temperate mixed deciduous and evergreen broadleaf forest in western Japan estimated by the Penman–Monteith approach combined with a photosynthesis-dependent stomatal model

International Nuclear Information System (INIS)

Kitao, Mitsutoshi; Komatsu, Masabumi; Hoshika, Yasutomo; Yazaki, Kenichi; Yoshimura, Kenichi; Fujii, Saori; Miyama, Takafumi; Kominami, Yuji

2014-01-01

Canopy-level stomatal conductance over a warm-temperate mixed deciduous and evergreen broadleaf forest in Japan was estimated by the Penman–Monteith approach, as compensated by a semi-empirical photosynthesis-dependent stomatal model, where photosynthesis, relative humidity, and CO 2 concentration were assumed to regulate stomatal conductance. This approach, using eddy covariance data and routine meteorological observations at a flux tower site, permits the continuous estimation of canopy-level O 3 uptake, even when the Penman–Monteith approach is unavailable (i.e. in case of direct evaporation from soil or wet leaves). Distortion was observed between the AOT40 exposure index and O 3 uptake through stomata, as AOT40 peaked in April, but with O 3 uptake occurring in July. Thus, leaf pre-maturation in the predominant deciduous broadleaf tree species (Quercus serrata) might suppress O 3 uptake in springtime, even when the highest O 3 concentrations were observed. -- Highlights: • We estimate canopy-level O 3 uptake in a warm-temperate mixed forest in Japan. • The Penman–Monteith approach is compensated by a photosynthesis-dependent model. • Stomatal conductance can be estimated, even in a partly-opened or wet canopy. • The estimated O 3 dose peaks in summer though O 3 exposure peaks in spring. -- Estimation of seasonal O 3 uptake over a mixed-temperate forest compensated by a photosynthesis-dependent stomatal model

Linking resilience theory and diffusion of innovations theory to understand the potential for perennials in the U.S. Corn Belt

Science.gov (United States)

Ryan C. Atwell; Lisa A. Schulte; Lynne M. Westphal

2009-01-01

In the last 200 yr, more than 80% of the land in the U.S. Corn Belt agro-ecosystem has been converted from natural perennial vegetation to intensive agricultural production of row crops. Despite research showing how re-integration of perennial vegetation, e.g., cover crops, pasture, riparian buffers, and restored wetlands, at strategic landscape positions can bolster...

Adaptation to seasonality and the winter freeze

Directory of Open Access Journals (Sweden)

Jill Christine Preston

2013-06-01

Full Text Available Flowering plants initially diversified during the Mesozoic era at least 140 million years ago in regions of the world where temperate seasonal environments were not encountered. Since then several cooling events resulted in the contraction of warm and wet environments and the establishment of novel temperate zones in both hemispheres. In response, less than half of modern angiosperm families have members that evolved specific adaptations to cold seasonal climates, including cold acclimation, freezing tolerance, endodormancy, and vernalization responsiveness. Despite compelling evidence for multiple independent origins, the level of genetic constraint on the evolution of adaptations to seasonal cold is not well understood. However, the recent increase in molecular genetic studies examining the response of model and crop species to seasonal cold offers new insight into the evolutionary lability of these traits. This insight has major implications for our understanding of complex trait evolution, and the potential role of local adaptation in response to past and future climate change. In this review, we discuss the biochemical, morphological, and developmental basis of adaptations to seasonal cold, and synthesize recent literature on the genetic basis of these traits in a phylogenomic context. We find evidence for multiple genetic links between distinct physiological responses to cold, possibly reinforcing the coordinated expression of these traits. Furthermore, repeated recruitment of the same or similar ancestral pathways suggests that land plants might be somewhat pre-adapted to dealing with temperature stress, perhaps making inducible cold traits relatively easy to evolve.

Lagging adaptation to warming climate in Arabidopsis thaliana.

Science.gov (United States)

Wilczek, Amity M; Cooper, Martha D; Korves, Tonia M; Schmitt, Johanna

2014-06-03

If climate change outpaces the rate of adaptive evolution within a site, populations previously well adapted to local conditions may decline or disappear, and banked seeds from those populations will be unsuitable for restoring them. However, if such adaptational lag has occurred, immigrants from historically warmer climates will outperform natives and may provide genetic potential for evolutionary rescue. We tested for lagging adaptation to warming climate using banked seeds of the annual weed Arabidopsis thaliana in common garden experiments in four sites across the species' native European range: Valencia, Spain; Norwich, United Kingdom; Halle, Germany; and Oulu, Finland. Genotypes originating from geographic regions near the planting site had high relative fitness in each site, direct evidence for broad-scale geographic adaptation in this model species. However, genotypes originating in sites historically warmer than the planting site had higher average relative fitness than local genotypes in every site, especially at the northern range limit in Finland. This result suggests that local adaptive optima have shifted rapidly with recent warming across the species' native range. Climatic optima also differed among seasonal germination cohorts within the Norwich site, suggesting that populations occurring where summer germination is common may have greater evolutionary potential to persist under future warming. If adaptational lag has occurred over just a few decades in banked seeds of an annual species, it may be an important consideration for managing longer-lived species, as well as for attempts to conserve threatened populations through ex situ preservation.

Fructan metabolism and changes in fructan composition during cold acclimation in perennial ryegrass

DEFF Research Database (Denmark)

Abeynayake, Shamila; Etzerodt, Thomas; Jonavičienė, Kristina

2015-01-01

. The ecotype ‘Falster’, adapted to cold climates, increased total fructan content and produced more fructans (DP˃7) in the roots than the variety ‘Veyo’, adapted to warmer climates suggesting that accumulation of fructans in roots, especially the high-DP fructans as an adaptive trait for plant recovery after......Perennial ryegrass (Lolium perenne L.) produces high levels of fructans as a mixture of oligomers with different degrees of polymerization (DP). The present study describes the analysis of the compositional changes in the full spectrum of fructan oligomers, fructan distribution between above ground...... biomass (top) and the roots, and the transcription of candidate genes involved in fructan metabolism during cold acclimation in perennial ryegrass variety ‘Veyo’ and ecotype ‘Falster’ from distinct geographical origins. We observed changes in fructan composition and induction of low-DP fructans...

Climate and tourism in the Black Forest during the warm season.

Science.gov (United States)

Endler, Christina; Matzarakis, Andreas

2011-03-01

Climate, climate change and tourism all interact. Part of the public discussion about climate change focusses on the tourism sector, with direct and indirect impacts being of equally high relevance. Climate and tourism are closely linked. Thus, climate is a very decisive factor in choices both of destination and of type of journey (active holidays, wellness, and city tours) in the tourism sector. However, whether choices about destinations or types of trip will alter with climate change is difficult to predict. Future climates can be simulated and projected, and the tendencies of climate parameters can be estimated using global and regional climate models. In this paper, the focus is on climate change in the mountainous regions of southwest Germany - the Black Forest. The Black Forest is one of the low mountain ranges where both winter and summer tourism are vulnerable to climate change due to its southern location; the strongest climatic changes are expected in areas covering the south and southwest of Germany. Moreover, as the choice of destination is highly dependent on good weather, a climatic assessment for tourism is essential. Thus, the aim of this study was to estimate climatic changes in mountainous regions during summer, especially for tourism and recreation. The assessment method was based on human-biometeorology as well as tourism-climatologic approaches. Regional climate simulations based on the regional climate model REMO were used for tourism-related climatic analyses. Emission scenarios A1B and B1 were considered for the time period 2021 to 2050, compared to the 30-year base period of 1971-2000, particularly for the warm period of the year, defined here as the months of March-November. In this study, we quantified the frequency, but not the means, of climate parameters. The study results show that global and regional warming is reflected in an increase in annual mean air temperature, especially in autumn. Changes in the spring show a slight negative

Study on absorption and translocation amounts of 2,4-D on perennial weed( Glycyrrhiza glabra) by 19 C- labelled herbicides tracer technique

International Nuclear Information System (INIS)

Ahari Mostafavi, H.; Fatholahi, H.; Naserian, B.

2004-01-01

Glycyrrhiza glabra a perennial broad leaf weed, is very difficult to control due to it's powerful root system. The best chemical treatment to perennial weeds control is the application of systemic herbicides and their effect is related to amount of permeability and mobility

Antarctic Circumpolar Current Dynamics and Their Relation to Antarctic Ice Sheet and Perennial Sea-Ice Variability in the Central Drake Passage During the Last Climate Cycle

Science.gov (United States)

Kuhn, G.; Wu, S.; Hass, H. C.; Klages, J. P.; Zheng, X.; Arz, H. W.; Esper, O.; Hillenbrand, C. D.; Lange, C.; Lamy, F.; Lohmann, G.; Müller, J.; McCave, I. N. N.; Nürnberg, D.; Roberts, J.; Tiedemann, R.; Timmermann, A.; Titschack, J.; Zhang, X.

2017-12-01

The evolution of the Antarctic Ice Sheet during the last climate cycle and the interrelation to global atmospheric and ocean circulation remains controversial and plays an important role for our understanding of ice sheet response to modern global warming. The timing and sequence of deglacial warming is relevant for understanding the variability and sensitivity of the Antarctic Ice Sheet to climatic changes, and the continuing rise of atmospheric greenhouse gas concentrations. The Antarctic Ice Sheet is a pivotal component of the global water budget. Freshwater fluxes from the ice sheet may affect the Antarctic Circumpolar Current (ACC), which is strongly impacted by the westerly wind belt in the Southern Hemisphere (SHWW) and constricted to its narrowest extent in the Drake Passage. The flow of ACC water masses through Drake Passage is, therefore, crucial for advancing our understanding of the Southern Ocean's role in global meridional overturning circulation and global climate change. In order to address orbital and millennial-scale variability of the Antarctic ice sheet and the ACC, we applied a multi-proxy approach on a sediment core from the central Drake Passage including grain size, iceberg-rafted debris, mineral dust, bulk chemical and mineralogical composition, and physical properties. In combination with already published and new sediment records from the Drake Passage and Scotia Sea, as well as high-resolution data from Antarctic ice cores (WDC, EDML), we now have evidence that during glacial times a more northerly extent of the perennial sea-ice zone decreased ACC current velocities in the central Drake Passage. During deglaciation the SHWW shifted southwards due to a decreasing temperature gradient between subtropical and polar latitudes caused by sea ice and ice sheet decline. This in turn caused Southern Hemisphere warming, a more vigorous ACC, stronger Southern Ocean ventilation, and warm Circumpolar Deep Water (CDW) upwelling on Antarctic shelves

Returning succession to downy brome dominated rangelands: roadblocks to perennial grass establishment

Science.gov (United States)

The most common cause of successional retrogression in the Great Basin is wildfires fueled by downy brome (Bromus tectorum). Downy brome invasion has reduced fire intervals from an estimated 60-100 years down to 5-10 years. Our previous research found that establishment of long-lived perennial grass...

Impact of Environmental Changes and Global Warming on Temperature in Pakistan

Directory of Open Access Journals (Sweden)

Ishtiaq Hassan

2011-01-01

Full Text Available Environmental changes and global warming have direct impact on human life. Estimation of these changes in various parameters of hydrologic cycle is necessary for future planning and development of a country. In this paper the impact of environmental changes and global warming on temperatures of Pakistan has been studied. The temperature changes in Pakistan have been extracted from simulations made using EdGCM model developed at Columbia University. Simulation study to the end of 21st century is executed using the model for GHG (Greenhouse Gases scenario with doubled_CO2 and scenario of Modern_Predicted SST (Sea Surface Temperature. The model analysis has been carried out for seasonal and annual changes for an average of last 5 years period from 2096-2100. Maps are generated to depict global temperature variations. The study divides Pakistan into five (05 main areas for twenty six (26 stations. A part-plan of globe focusing Pakistan is generated showing the five divisions for twenty six (26 data stations of Pakistan. This part plan is made compatible with grid-box resolution of EdGCM. Eagle-Point Engineering software has been used to generate isohyets of interval (0.5oC for downscaling GCM (Global Climate Model grid data to data stations. The station values of different seasons and annual changes are then compared with the values of base period data to determine changes in temperature. It is observed that impact of global environmental changes on temperature are higher (i.e. there is an increase in annual temperature for double_CO2 experiment at places near the Arabian Sea than areas located away from this sea. It is also observed that the temperature increase will be more in winter than that in other seasons for Pakistan.

Thermal comfort of people in the hot and humid area of China-impacts of season, climate, and thermal history.

Science.gov (United States)

Zhang, Y; Chen, H; Wang, J; Meng, Q

2016-10-01

We conducted a climate chamber study on the thermal comfort of people in the hot and humid area of China. Sixty subjects from naturally ventilated buildings and buildings with split air conditioners participated in the study, and identical experiments were conducted in a climate chamber in both summer and winter. Psychological and physiological responses were observed over a wide range of conditions, and the impacts of season, climate, and thermal history on human thermal comfort were analyzed. Seasonal and climatic heat acclimatization was confirmed, but they were found to have no significant impacts on human thermal sensation and comfort. The outdoor thermal history was much less important than the indoor thermal history in regard to human thermal sensation, and the indoor thermal history in all seasons of a year played a key role in shaping the subjects' sensations in a wide range of thermal conditions. A warmer indoor thermal history in warm seasons produced a higher neutral temperature, a lower thermal sensitivity, and lower thermal sensations in warm conditions. The comfort and acceptable conditions were identified for people in the hot and humid area of China. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Nasal budesonide offers superior symptom relief in perennial allergic rhinitis in comparison to nasal azelastine.

Science.gov (United States)

Stern, M A; Wade, A G; Ridout, S M; Cambell, L M

1998-10-01

Allergic rhinitis is usually treated with oral antihistamines or nasal steroids. Topically active nasal antihistamine is a new treatment modality for allergic rhinitis. The efficacy in comparison to well established topical treatment alternatives is not fully known. To compare the efficacy of intranasally administered azelastine to budesonide, at their respectively recommended dosage, on the symptoms of perennial rhinitis patients. A placebo-controlled, randomized, parallel group study was conducted to compare the efficacy and tolerability of intranasal budesonide aqueous suspension (256 microg once daily) with azelastine hydrochloride nasal spray (280 microg twice daily (560 microg/day)) and with placebo in the treatment of perennial allergic rhinitis. The 195 patients (with at least a 2-year history of perennial allergic rhinitis) recorded individual nasal symptom scores, the degree of symptom control achieved and any adverse events experienced over a 2-week baseline period and a 6-week treatment period. Following treatment, the reductions in mean combined and individual nasal symptom scores from baseline values were significantly greater in the budesonide group compared with the placebo group (P < .0001 for all variables except runny nose P = .01). In patients treated with budesonide, there were also significantly larger reductions from baseline values in combined nasal symptom scores (P < .01) and in scores for all individual nasal symptoms (P < or = .05) compared with those treated with azelastine. The reductions from baseline in both combined and individual nasal symptom scores did not differ between azelastine and placebo. The study medications were well tolerated, producing no unexpected or serious treatment-related adverse events. A once-daily dose of 256 microg of intranasal budesonide aqueous suspension is significantly more effective at relieving the symptoms of perennial allergic rhinitis compared with a twice daily dose of 280 microg of azelastine

Nitrogen removal and nitrate leaching for two perennial, sod-based forage systems receiving dairy effluent.

Science.gov (United States)

Woodard, Kenneth R; French, Edwin C; Sweat, Lewin A; Graetz, Donald A; Sollenberger, Lynn E; Macoon, Bisoondat; Portier, Kenneth M; Rymph, Stuart J; Wade, Brett L; Prine, Gordon M; Van Horn, Harold H

2003-01-01

In northern Florida, year-round forage systems are used in dairy effluent sprayfields to reduce nitrate leaching. Our purpose was to quantify forage N removal and monitor nitrate N (NO3(-)-N) concentration below the rooting zone for two perennial, sod-based, triple-cropping systems over four 12-mo cycles (1996-2000). The soil is an excessively drained Kershaw sand (thermic, uncoated Typic Quartzip-samment). Effluent N rates were 500, 690, and 910 kg ha(-1) per cycle. Differences in N removal between a corn (Zea mays L.)-bermudagrass (Cynodon spp.)-rye (Secale cereale L.) system (CBR) and corn-perennial peanut (Arachis glabrata Benth.)-rye system (CPR) were primarily related to the performance of the perennial forages. Nitrogen removal of corn (125-170 kg ha(-1)) and rye (62-90 kg ha(-1)) was relatively stable between systems and among cycles. The greatest N removal was measured for CBR in the first cycle (408 kg ha(-1)), with the bermudagrass removing an average of 191 kg N ha(-1). In later cycles, N removal for bermudagrass declined because dry matter (DM) yield declined. Yield and N removal of perennial peanut increased over the four cycles. Nitrate N concentrations below the rooting zone were lower for CBR than CPR in the first two cycles, but differences were inconsistent in the latter two. The CBR system maintained low NO3(-)-N leaching in the first cycle when the bermudagrass was the most productive; however, it was not a sustainable system for long-term prevention of NO3(-)-N leaching due to declining bermudagrass yield in subsequent cycles. For CPR, effluent N rates > or = 500 kg ha(-1) yr(-1) have the potential to negatively affect ground water quality.

Evaluating winter/spring seeding of a native perennial bunchgrass in the sagebrush steppe

Science.gov (United States)

Sagebrush (Artemisia tridentata Nutt.) plant communities in the US Great Basin region are being severely impacted by increasingly frequent wildfires in association with the expansion of exotic annual grasses. Maintenance of native perennial bunchgrasses is key to controlling annual grass expansion,...

Beclomethasone Dipropionate Nasal Aerosol in Patients with Perennial Allergic Rhinitis (BALANCE) study: 6-month results.

Science.gov (United States)

Bukstein, Donald; Parikh, Ruchir; Eid, Sherrine; Ferro, Thomas; Morello, Jean-Pierre

2016-01-01

Perennial allergic rhinitis (PAR) exerts significant quality-of-life and economic burdens on society. Beclomethasone dipropionate (BDP) nasal aerosol is the first nonaqueous, hydrofluoroalkane-propelled intranasal corticosteroid approved for patients in the United States to treat PAR and seasonal allergic rhinitis. To evaluate real-world effectiveness of BDP nasal aerosol from the patient's perspective by using a postmarketing observational registry. Patients (N = 824) from 43 U.S. study sites completed monthly patient-reported outcome instruments, including the Rhinitis Control Assessment Test (primary outcome variable), Treatment Satisfaction Questionnaire for Medication, Work Productivity and Activity Impairment Questionnaire plus Classroom Impairment Questions: Allergy-Specific, Pittsburgh Sleep Quality Index, and Mini Rhinoconjunctivitis Quality of Life Questionnaire for 6 months. The primary outcome assessment (Rhinitis Control Assessment Test score) (N = 527) indicated significant symptomatic improvement over baseline beginning at month 1 (p 78.8% of respondents who achieved clinically meaningful improvement over 6 months. Secondary outcome measures Mini Rhinoconjunctivitis Quality of Life Questionnaire (p Work Productivity and Activity Impairment Questionnaire plus Classroom Impairment Questions: Allergy-Specific, with the exception of work time missed and class time missed, were significantly (p life, work, and school-related activities, and is associated with high patient satisfaction, reduced productivity loss and activity impairment, and improvement in sleep quality.

Rapid warming accelerates tree growth decline in semi-arid forests of Inner Asia.

Science.gov (United States)

Liu, Hongyan; Park Williams, A; Allen, Craig D; Guo, Dali; Wu, Xiuchen; Anenkhonov, Oleg A; Liang, Eryuan; Sandanov, Denis V; Yin, Yi; Qi, Zhaohuan; Badmaeva, Natalya K

2013-08-01

Forests around the world are subject to risk of high rates of tree growth decline and increased tree mortality from combinations of climate warming and drought, notably in semi-arid settings. Here, we assess how climate warming has affected tree growth in one of the world's most extensive zones of semi-arid forests, in Inner Asia, a region where lack of data limits our understanding of how climate change may impact forests. We show that pervasive tree growth declines since 1994 in Inner Asia have been confined to semi-arid forests, where growing season water stress has been rising due to warming-induced increases in atmospheric moisture demand. A causal link between increasing drought and declining growth at semi-arid sites is corroborated by correlation analyses comparing annual climate data to records of tree-ring widths. These ring-width records tend to be substantially more sensitive to drought variability at semi-arid sites than at semi-humid sites. Fire occurrence and insect/pathogen attacks have increased in tandem with the most recent (2007-2009) documented episode of tree mortality. If warming in Inner Asia continues, further increases in forest stress and tree mortality could be expected, potentially driving the eventual regional loss of current semi-arid forests. © 2013 John Wiley & Sons Ltd.

Seasonal prediction of the Leeuwin Current using the POAMA dynamical seasonal forecast model

Energy Technology Data Exchange (ETDEWEB)

Hendon, Harry H.; Wang, Guomin [Centre for Australian Weather and Climate Research, Bureau of Meteorology, PO Box 1289, Melbourne (Australia)

2010-06-15

The potential for predicting interannual variations of the Leeuwin Current along the west coast of Australia is addressed. The Leeuwin Current flows poleward against the prevailing winds and transports warm-fresh tropical water southward along the coast, which has a great impact on local climate and ecosystems. Variations of the current are tightly tied to El Nino/La Nina (weak during El Nino and strong during La Nina). Skilful seasonal prediction of the Leeuwin Current to 9-month lead time is achieved by empirical downscaling of dynamical coupled model forecasts of El Nino and the associated upper ocean heat content anomalies off the north west coast of Australia from the Australian Bureau of Meteorology Predictive Ocean Atmosphere Model for Australia (POAMA) seasonal forecast system. Prediction of the Leeuwin Current is possible because the heat content fluctuations off the north west coast are the primary driver of interannual annual variations of the current and these heat content variations are tightly tied to the occurrence of El Nino/La Nina. POAMA can skilfully predict both the occurrence of El Nino/La Nina and the subsequent transmission of the heat content anomalies from the Pacific onto the north west coast. (orig.)

American lay conceptions of global warming

International Nuclear Information System (INIS)

Kempton, W.

1990-01-01

Ethnographic interviews were conducted with Americans from all walks of life in order to understand how ordinary citizens conceptualize global climate change and make value judgments about it. Most informants had heard of the greenhouse effect, but they held fundamental misconceptions that were shared across individuals. Many of these misconceptions derive from the process of fitting a new concept, global warming, into four preexisting categories: stratospheric ozone depletion, plant photosynthesis, tropospheric pollution, and personally-experienced seasonal and geographic temperature variation. Informants readily accepted that human activities could change climate and weather patterns. Indeed, most reported they had already observed changes in weather patterns, some citing space shots or atomic bomb testing as causes. Few informants connected the greenhouse effect to energy or fuel consumption, although the connection was easily understood when explained by the interviewers

Calculation of probability density functions for temperature and precipitation change under global warming

International Nuclear Information System (INIS)

Watterson, Ian G.

2007-01-01

Full text: he IPCC Fourth Assessment Report (Meehl ef al. 2007) presents multi-model means of the CMIP3 simulations as projections of the global climate change over the 21st century under several SRES emission scenarios. To assess the possible range of change for Australia based on the CMIP3 ensemble, we can follow Whetton etal. (2005) and use the 'pattern scaling' approach, which separates the uncertainty in the global mean warming from that in the local change per degree of warming. This study presents several ways of representing these two factors as probability density functions (PDFs). The beta distribution, a smooth, bounded, function allowing skewness, is found to provide a useful representation of the range of CMIP3 results. A weighting of models based on their skill in simulating seasonal means in the present climate over Australia is included. Dessai ef al. (2005) and others have used Monte-Carlo sampling to recombine such global warming and scaled change factors into values of net change. Here, we use a direct integration of the product across the joint probability space defined by the two PDFs. The result is a cumulative distribution function (CDF) for change, for each variable, location, and season. The median of this distribution provides a best estimate of change, while the 10th and 90th percentiles represent a likely range. The probability of exceeding a specified threshold can also be extracted from the CDF. The presentation focuses on changes in Australian temperature and precipitation at 2070 under the A1B scenario. However, the assumption of linearity behind pattern scaling allows results for different scenarios and times to be simply obtained. In the case of precipitation, which must remain non-negative, a simple modification of the calculations (based on decreases being exponential with warming) is used to avoid unrealistic results. These approaches are currently being used for the new CSIRO/ Bureau of Meteorology climate projections

Thirty-Three Years of Ocean Benthic Warming Along the U.S. Northeast Continental Shelf and Slope: Patterns, Drivers, and Ecological Consequences

Science.gov (United States)

Kavanaugh, Maria T.; Rheuban, Jennie E.; Luis, Kelly M. A.; Doney, Scott C.

2017-12-01

The U.S. Northeast Continental Shelf is experiencing rapid warming, with potentially profound consequences to marine ecosystems. While satellites document multiple scales of spatial and temporal variability on the surface, our understanding of the status, trends, and drivers of the benthic environmental change remains limited. We interpolated sparse benthic temperature data along the New England Shelf and upper Slope using a seasonally dynamic, regionally specific multiple linear regression model that merged in situ and remote sensing data. The statistical model predicted nearly 90% of the variability of the data, resulting in a synoptic time series spanning over three decades from 1982 to 2014. Benthic temperatures increased throughout the domain, including in the Gulf of Maine. Rates of benthic warming ranged from 0.1 to 0.4°C per decade, with fastest rates occurring in shallow, nearshore regions and on Georges Bank, the latter exceeding rates observed in the surface. Rates of benthic warming were up to 1.6 times faster in winter than the rest of the year in many regions, with important implications for disease occurrence and energetics of overwintering species. Drivers of warming varied over the domain. In southern New England and the mid-Atlantic shallow Shelf regions, benthic warming was tightly coupled to changes in SST, whereas both regional and basin-scale changes in ocean circulation affect temperatures in the Gulf of Maine, the Continental Shelf, and Georges Banks. These results highlight data gaps, the current feasibility of prediction from remotely sensed variables, and the need for improved understanding on how climate may affect seasonally specific ecological processes.

Transcription Through The Eye Of A Needle: Daily And Annual Cycles Of Gene Expression Variation In Douglas-Fir Needles

OpenAIRE

Dolan, Peter; Cronn, Richard; Denver, Dee; Clair, J.; Neale, David; Wegrzyn, Jill; Jogdeo, Sanjuro

2017-01-01

Background: Perennial growth in plants is the product of interdependent cycles of daily and annual stimuli that induce cycles of growth and dormancy. In conifers, needles are the key perennial organ that integrates daily and seasonal signals from light, temperature, and water availability. To understand the relationship between seasonal rhythms and seasonal gene expression responses in conifers, we examined diurnal and circannual needle mRNA accumulation in Douglas-fir (Pseudotsuga menziesii)...

Unexpected Impacts of Global warming on Extreme Warm Spells

Science.gov (United States)

Sardeshmukh, P. D.; Compo, G. P.; McColl, C.; Penland, C.

2017-12-01

It is generally presumed that the likelihood of extreme warm spells around the globe has increased, and will continue to increase, due to global warming. However, we find that this is generally not true in three very different types of global observational datasets and uncoupled atmospheric model simulations of the 1959 to 2012 period with prescribed observed global SSTs, sea ice, and radiative forcing changes. While extreme warm spells indeed became more common in many regions, in many other regions their likelihood remained almost the same or even decreased from the first half to the second half of this period. Such regions of unexpected changes covered nearly 40 percent of the globe in both winter and summer. The basic reason for this was a decrease of temperature variability in such regions that offset or even negated the effect of the mean temperature shift on extreme warm spell probabilities. The possibility of such an impact on extreme value probabilities was highlighted in a recent paper by Sardeshmukh, Compo, and Penland (Journal of Climate 2015). The consistency of the changes in extreme warm spell probabilities among the different observational datasets and model simulations examined suggests that they are robust regional aspects of global warming associated with atmospheric circulation changes. This highlights the need for climate models to represent not just the mean regional temperature signals but also the changes in subseasonal temperature variability associated with global warming. However, current climate models (both CMIP3 and CMIP5) generally underestimate the magnitude of the changes in the atmospheric circulation and associated temperature variability. A likely major cause of this is their continuing underestimation of the magnitude of the spatial variation of tropical SST trends. By generating an overly spatially bland tropical SST warming in response to changes in radiative forcing, the models spuriously mute tropically

Effect of nutritional density and season on the performance of young rabbit does before the first mating - doi: 10.4025/actascianimsci.v35i4.19101 Effect of nutritional density and season on the performance of young rabbit does before the first mating - doi: 10.4025/actascianimsci.v35i4.19101

Directory of Open Access Journals (Sweden)

Paulo Sergio dos Santos Teixeira

2013-10-01

Full Text Available The objective was to evaluate the effect of nutritional density and season on the performance of young rabbit does before the first mating. Forty-eight females from the Botucatu Genetic Group were used in each season (warm or cool, starting at the age of 70 days, housed in groups of four per cage up to 119 days, and reared individually from 120 to 140 days of age. The high-density diet was formulated to contain, on a 90% DM basis, 18.4% CP, 16.5% ADF and 2,500 kcal DE kg-1; whereas the low-density diet was formulated to contain 14.7% CP, 24% ADF and 2,000 kcal DE kg-1. The experiment was conducted according to a 2x2 factorial design (two diets x two seasons with repeated measures (weeks. The high-density diet promoted lower feed intake, higher final weight, and higher daily weight gain, adjusted for constant intake. But these facts alone do not warrant using a high-density diet for growing rabbit does, because it could have a negative impact during the reproductive phase. In the warm season, there was a reduction in feed intake and an improvement in feed efficiency. Along time, however, the mean body weight of does was similar in the two seasons.  The objective was to evaluate the effect of nutritional density and season on the performance of young rabbit does before the first mating. Forty-eight females from the Botucatu Genetic Group were used in each season (warm or cool, starting at the age of 70 days, housed in groups of four per cage up to 119 days, and reared individually from 120 to 140 days of age. The high-density diet was formulated to contain, on a 90% DM basis, 18.4% CP, 16.5% ADF and 2,500 kcal DE kg-1; whereas the low-density diet was formulated to contain 14.7% CP, 24% ADF and 2,000 kcal DE kg-1. The experiment was conducted according to a 2x2 factorial design (two diets x two seasons with repeated measures (weeks. The high-density diet promoted lower feed intake, higher final weight, and higher daily weight gain, adjusted for

Quantitative Trait Locus (QTL meta-analysis and comparative genomics for candidate gene prediction in perennial ryegrass (Lolium perenne L.

Directory of Open Access Journals (Sweden)

Shinozuka Hiroshi

2012-11-01

Full Text Available Abstract Background In crop species, QTL analysis is commonly used for identification of factors contributing to variation of agronomically important traits. As an important pasture species, a large number of QTLs have been reported for perennial ryegrass based on analysis of biparental mapping populations. Further characterisation of those QTLs is, however, essential for utilisation in varietal improvement programs. Results A bibliographic survey of perennial ryegrass trait-dissection studies identified a total of 560 QTLs from previously published papers, of which 189, 270 and 101 were classified as morphology-, physiology- and resistance/tolerance-related loci, respectively. The collected dataset permitted a subsequent meta-QTL study and implementation of a cross-species candidate gene identification approach. A meta-QTL analysis based on use of the BioMercator software was performed to identify two consensus regions for pathogen resistance traits. Genes that are candidates for causal polymorphism underpinning perennial ryegrass QTLs were identified through in silico comparative mapping using rice databases, and 7 genes were assigned to the p150/112 reference map. Markers linked to the LpDGL1, LpPh1 and LpPIPK1 genes were located close to plant size, leaf extension time and heading date-related QTLs, respectively, suggesting that these genes may be functionally associated with important agronomic traits in perennial ryegrass. Conclusions Functional markers are valuable for QTL meta-analysis and comparative genomics. Enrichment of such genetic markers may permit further detailed characterisation of QTLs. The outcomes of QTL meta-analysis and comparative genomics studies may be useful for accelerated development of novel perennial ryegrass cultivars with desirable traits.

Using radiative signatures to diagnose the cause of warming during the 2013-2014 Californian drought

Science.gov (United States)

Wolf, Sebastian; Yin, Dongqin; Roderick, Michael L.

2017-10-01

California recently experienced among the worst droughts of the last century, with exceptional precipitation deficits and co-occurring record high temperatures. The dry conditions caused severe water shortages in one of the economically most important agricultural regions of the US. It has recently been hypothesized that anthropogenic warming is increasing the likelihood of such extreme droughts in California, or more specifically, that warmer temperatures from the enhanced greenhouse effect intensify drought conditions. However, separating the cause and effect is difficult because the dry conditions lead to a reduction in evaporative cooling that contributes to the warming. Here we investigate and compare the forcing of long-term greenhouse-induced warming with the short-term warming during the 2013-2014 Californian drought. We use the concept of radiative signatures to investigate the source of the radiative perturbation during the drought, relate the signatures to expected changes due to anthropogenic warming, and assess the cause of warming based on observed changes in the surface energy balance compared to the period 2001-2012. We found that the recent meteorological drought based on precipitation deficits was characterised by an increase in incoming shortwave radiation coupled with a decline in incoming longwave radiation, which contributed to record warm temperatures. In contrast, climate models project that anthropogenic warming is accompanied by little change in incoming shortwave but a large increase in incoming longwave radiation. The warming during the drought was associated with increased incoming shortwave radiation in combination with reduced evaporative cooling from water deficits, which enhanced surface temperatures and sensible heat transfer to the atmosphere. Our analyses demonstrate that radiative signatures are a powerful tool to differentiate the source of perturbations in the surface energy balance at monthly to seasonal time scales.

Regimes of seasonal air-sea interaction and implications for performance of forced simulations

Energy Technology Data Exchange (ETDEWEB)

Wu, Renguang [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); Kirtman, Ben P. [Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); George Mason University, School of Computational Sciences, Fairfax, VA (United States)

2007-09-15

Sea surface temperature (SST) anomalies can induce anomalous convection through surface evaporation and low-level moisture convergence. This SST forcing of the atmosphere is indicated in a positive local rainfall-SST correlation. Anomalous convection can feedback on SST through cloud-radiation and wind-evaporation effects and wind-induced oceanic mixing and upwelling. These atmospheric feedbacks are reflected in a negative local rainfall-SST tendency correlation. As such, the simultaneous rainfall-SST and rainfall-SST tendency correlations can indicate the nature of local air-sea interactions. Based on the magnitude of simultaneous rainfall-SST and rainfall-SST tendency correlations, the present study identifies three distinct regimes of local air-sea interactions. The relative importance of SST forcing and atmospheric forcing differs in these regimes. In the equatorial central-eastern Pacific and, to a smaller degree, in the western equatorial Indian Ocean, SST forcing dominates throughout the year and the surface heat flux acts mainly as a damping term. In the tropical Indo-western Pacific Ocean regions, SST forcing and atmospheric forcing dominate alternatively in different seasons. Atmospheric forcing dominates in the local warm/rainy season. SST forcing dominates with a positive wind-evaporation feedback during the transition to the cold/dry season. SST forcing also dominates during the transition to the warm/rainy season but with a negative cloud-radiation feedback. The performance of atmospheric general circulation model simulations forced by observed SST is closely linked to the regime of air-sea interaction. The forced simulations have good performance when SST forcing dominates. The performance is low or poor when atmospheric forcing dominates. (orig.)

[Temporal and spatial change of climate resources and meteorological disasters under climate change during winter crop growing season in Guangdong Province, China.

Science.gov (United States)

Wang, Hua; Chen, Hui Hua; Tang, Li Sheng; Wang, Juan Huai; Tang, Hai Yan

2018-01-01

Trend analysis method was applied to analyze the general variation characteristics of the climate resources and meteorological disasters of growing season of the winter planting in Guangdong before (1961-1996) and after climate warming (1997-2015). Percentile method was employed to determine thresholds for extreme cold and drought in major planting regions, and the characteristics of extreme disasters since climate warming were analyzed. The results showed that, by comparing 1997-2015 with 1961-1996, the heat value in winter growing season increased significantly. The belt with a higher heat value, where the average temperature was ≥15 ℃ and accumulated temperature was ≥2200 ℃·d, covered the main winter production regions as Shaoguan, Zhanjiang, Maoming, Huizhou, Meizhou and Guangzhou. Meanwhile, the precipitation witnessed a slight increase. The regions with precipitations of 250-350 mm included Zhanjiang, Maoming, Huizhou, Guangzhou and Meizhou. Chilling injury in the winter planting season in the regions decreased, the belt with an accumulated chilling of climate resources and the occurrence law of meteorological disasters in growing season.

Covariability of seasonal temperature and precipitation over the Iberian Peninsula in high-resolution regional climate simulations (1001-2099)

Science.gov (United States)

Fernández-Montes, S.; Gómez-Navarro, J. J.; Rodrigo, F. S.; García-Valero, J. A.; Montávez, J. P.

2017-04-01

Precipitation and surface temperature are interdependent variables, both as a response to atmospheric dynamics and due to intrinsic thermodynamic relationships and feedbacks between them. This study analyzes the covariability of seasonal temperature (T) and precipitation (P) across the Iberian Peninsula (IP) using regional climate paleosimulations for the period 1001-1990, driven by reconstructions of external forcings. Future climate (1990-2099) was simulated according to SRES scenarios A2 and B2. These simulations enable exploring, at high spatial resolution, robust and physically consistent relationships. In winter, positive P-T correlations dominate west-central IP (Pearson correlation coefficient ρ = + 0.43, for 1001-1990), due to prevalent cold-dry and warm-wet conditions, while this relationship weakens and become negative towards mountainous, northern and eastern regions. In autumn, negative correlations appear in similar regions as in winter, whereas for summer they extend also to the N/NW of the IP. In spring, the whole IP depicts significant negative correlations, strongest for eastern regions (ρ = - 0.51). This is due to prevalent frequency of warm-dry and cold-wet modes in these regions and seasons. At the temporal scale, regional correlation series between seasonal anomalies of temperature and precipitation (assessed in 31 years running windows in 1001-1990) show very large multidecadal variability. For winter and spring, periodicities of about 50-60 years arise. The frequency of warm-dry and cold-wet modes appears correlated with the North Atlantic Oscillation (NAO), explaining mainly co-variability changes in spring. For winter and some regions in autumn, maximum and minimum P-T correlations appear in periods with enhanced meridional or easterly circulation (low or high pressure anomalies in the Mediterranean and Europe). In spring and summer, the Atlantic Multidecadal Oscillation shows some fingerprint on the frequency of warm/cold modes. For

Abiotic factors affect the recruitment and biomass of perennial grass and evergreen shrub seedlings in denuded areas of Patagonian Monte rangelands.

Science.gov (United States)

Bosco, Tomás; Bertiller, Mónica Beatriz; Carrera, Analía Lorena

2018-07-15

Assessing the ability of key species to cope with environmental stresses in disturbed areas is an important issue for recovery of degraded arid ecosystem. Our objective was to evaluate the effect of soil moisture, exposure to UV radiation, and presence/absence of litter with different chemistry on soil N, recruitment and biomass of seedlings of perennial grass (Poa ligularis and Nassella tenuis) and evergreen shrub species (Atriplex lampa and Larrea divaricata) in denuded areas. We carried out a microcosm experiment with soil blocks (28 cm depth) sowed with seeds of the target species, subjected to different levels of litter type (perennial grass-evergreen shrub mixture, evergreen shrub mixture, and no litter), UV radiation (near ambient and reduced UV), and soil water (high: 15-25% and low 5-15%). Periodically, during 6 months, we assessed soil-N (total and inorganic) at two depths and species seedling recruitment at microcosms. Additionally, emerged seedlings of each species were transplanted to individual pots containing soil and subjected to the same previous factors during 12 months. Then, all plants were harvested and biomass assessed. Only inorganic soil-N at the upper soil varied among treatments increasing with the presence of evergreen shrub litter, exposure to ambient UV, and high soil water. Inorganic soil-N, promoted by near ambient UV and high soil water, had a positive effect on recruitment of perennial grasses and A. lampa. Both litter types promoted the recruitment of perennial grasses. Evergreen shrub litter and high soil water promoted the recruitment of L. divaricata. Seedling biomass of perennial grasses increased with high soil water and reduced UV. Ambient UV had positive or null effects on biomass of evergreen shrub seedlings. High soil water increased biomass of L. divaricata seedlings. We concluded that soil water appeared as the most limiting factor for seedling recruitment of all species whereas inorganic soil N limited the

Photographs and herbarium specimens as tools to document phenological changes in response to global warming.

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Miller-Rushing, Abraham J; Primack, Richard B; Primack, Daniel; Mukunda, Sharda

2006-11-01

Global warming is affecting natural systems across the world. Of the biological responses to warming, changes in the timing of phenological events such as flowering are among the most sensitive. Despite the recognized importance of phenological changes, the limited number of long-term records of phenological events has restricted research on the topic in most areas of the world. In a previous study in Boston (American Journal of Botany 91: 1260-1264), we used herbarium specimens and one season of field observations to show that plants flowered earlier as the climate warmed over the past 100 yr. In our new study, we found that two extra years of data did not strengthen the explanatory power of the analysis. Analysis of herbarium specimens without any field data yielded results similar to analyses that included field observations. In addition, we found that photographs of cultivated and wild plants in Massachusetts, data similar to that contained in herbarium specimens, show changes in flowering times that closely match independent data on the same species in the same locations. Dated photographs of plants in flower represent a new resource to extend the range of species and localities addressed in global-warming research.

Seasonality in the relationship between El Nino and Indian Ocean dipole

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Roxy, Mathew [Centro-Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Indian Institute of Tropical Meteorology, Centre for Climate Change Research, Pune (India); Gualdi, Silvio; Navarra, Antonio [Centro-Euro-Mediterraneo per i Cambiamenti Climatici, Bologna (Italy); Istituto Nazionale di Geofisica e Vulcanologia, Bologna (Italy); Lee Drbohlav, Hae-Kyung [University of Hawaii at Manoa, International Pacific Research Center, Honolulu, HI (United States)

2011-07-15

The seasonal change in the relationship between El Nino and Indian Ocean dipole (IOD) is examined using the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40), and the twentieth century simulations (20c3m) from the Geophysical Fluid Dynamics Laboratory Coupled Model, version 2.1. It is found that, both in ERA-40 and the model simulations, the correlation between El Nino (Nino3 index) and the eastern part of the IOD (90-110 E; 10 S-equator) is predominantly positive from January to June, and then changes to negative from July to December. Correlation maps of atmospheric and oceanic variables with respect to the Nino3 index are constructed for each season in order to examine the spatial structure of their seasonal response to El Nino. The occurrence of El Nino conditions during January to March induces low-level anti-cyclonic circulation anomalies over the southeastern Indian Ocean, which counteracts the climatological cyclonic circulation in that region. As a result, evaporation decreases and the southeastern Indian Ocean warms up as the El Nino proceeds, and weaken the development of a positive phase of an IOD. This warming of the southeastern Indian Ocean associated with the El Nino does not exist past June because the climatological winds there develop into the monsoon-type flow, enhancing the anomalous circulation over the region. Furthermore, the development of El Nino from July to September induces upwelling in the southeastern Indian Ocean, thereby contributing to further cooling of the region during the summer season. This results in the enhancement of a positive phase of an IOD. Once the climatological circulation shifts from the boreal summer to winter mode, the negative correlation between El Nino and SST of the southeastern Indian Ocean changes back to a positive one. (orig.)

Perennial growth of hermatypic corals at Rottnest Island, Western Australia (32°S

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Claire L. Ross

2015-02-01

Full Text Available To assess the viability of high latitude environments as coral refugia, we report measurements of seasonal changes in seawater parameters (temperature, light, and carbonate chemistry together with calcification rates for two coral species, Acropora yongei and Pocillopora damicornis from the southernmost geographical limit of these species at Salmon Bay, Rottnest Island (32°S in Western Australia. Changes in buoyant weight were normalised to colony surface areas as determined from both X-ray computed tomography and geometric estimation. Extension rates for A. yongei averaged 51 ± 4 mm y−1 and were comparable to rates reported for Acroporid coral at other tropical and high latitude locations. Mean rates of calcification for both A. yongei and P. damicornis in winter were comparable to both the preceding and following summers despite a mean seasonal temperature range of ∼6 °C (18.2°–24.3 °C and more than two-fold changes in the intensity of downwelling light. Seasonal calcification rates for A. yongei (1.31–2.02 mg CaCO3 cm−2 d−1 and P. damicornis (0.34–0.90 mg CaCO3 cm−2 d−1 at Salmon Bay, Rottnest Island were comparable to rates from similar taxa in more tropical environments; however, they appeared to decline sharply once summer temperatures exceeded 23 °C. A coral bleaching event observed in December 2013 provided further evidence of how coral at Rottnest Island are still vulnerable to the deleterious effects of episodic warming despite its high latitude location. Thus, while corals at Rottnest Island can sustain robust year-round rates of coral growth, even over cool winter temperatures of 18°–19 °C, there may be limits on the extent that such environments can provide refuge against the longer term impacts of anthropogenic climate change.

Magnitudes and timing of seasonal peak snowpack water equivalents in Arizona: A preliminary study of the possible effects of recent climatic change

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Peter F. Ffolliott; Gerald J. Gottfried