75 FR 55736 - Mark Twain National Forest; Missouri; Integrated Non-Native Invasive Plant Project

Science.gov (United States)

2010-09-14

... DEPARTMENT OF AGRICULTURE Forest Service Mark Twain National Forest; Missouri; Integrated Non... notice of intent initiates the scoping process, which guides the development of the environmental impact... information to MTNF world wide Web site. Four comment letters were received in response to that solicitation...

Carbon in Amazon forests: unexpected seasonal fluxes and disturbance-induced losses.

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S. R. Saleska; S. D. Miller; D. M. Matross; M. L. Goulden; S. C. Wofsy; H. R. da Rocha; P. B. de Camargo; P. Crill; B. C. Daube; H. C. de Freitas; L. Hutyra; M. Keller; V. Kirchhoff; M. Menton; J. W. Munger; H. E. Pyle; A. H. Rice; H. Silva

2003-01-01

The net ecosystem exchange of carbon dioxide was measured by eddy covariance methods for 3 years in two old-growth forest sites near Santarém, Brazil. Carbon was lost in the wet season and gained in the dry season, which was opposite to the seasonal cycles of both tree growth and model predictions. The 3-year average carbon loss was 1.3 (confidence...

Phenological synchrony and seasonality of understory Rubiaceae in the Atlantic Forest, Bahia, Brazil

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Heitor Scarpati Liuth

2013-03-01

Full Text Available In tropical forests with low seasonality, climatic variables generally exert a weak influence on the phenology of species. The seasonality of phenophases in closely related taxa can be controlled by phylogenetic constraints in such environments. In this study, our aim was to describe the phenology of Rubiaceae in the understory of the Atlantic Forest in the southern part of Bahia, Brazil, as well as to evaluate the seasonality and phenological synchrony of this family. For two years, we observed 90 individuals belonging to 13 species, in an area of 0.2 ha. Leaf flushing and leaf fall did not demonstrate any seasonality, were continuous for most species and correlated with few of the climatic variables. Flowering was seasonal and correlated positively with all climatic variables. Species exhibited seasonality for this phenophase with high flowering overlap among species of Psychotria, indicating an aggregated pattern for this genus. Fruiting was also seasonal and correlated with all the climatic variables, unripe fruit development peaking at the beginning of the season during which humidity is highest and fruit ripening peaking in the season during which humidity is slightly lower. The vegetative and flowering patterns observed in the study area are commonly seen in other tropical forests. The reproductive seasonality of this family can facilitate the attraction of biotic agents, as postulated in the facilitation hypothesis. Our results demonstrate that climatic variables influenced the phenological patterns observed here, although the high reproductive seasonality and interspecific synchrony, especially in congeneric species, raises the possibility that phylogenetic proximity plays a role in the pattern of the family Rubiaceae.

Effects of Forest Gaps on Litter Lignin and Cellulose Dynamics Vary Seasonally in an Alpine Forest

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Han Li

2016-01-01

Full Text Available To understand how forest gaps and the associated canopy control litter lignin and cellulose dynamics by redistributing the winter snow coverage and hydrothermal conditions in the growing season, a field litterbag trial was conducted in the alpine Minjiang fir (Abies faxoniana Rehder and E.H. Wilson forest in a transitional area located in the upper reaches of the Yangtze River and the eastern Tibetan Plateau. Over the first year of litter decomposition, the litter exhibited absolute cellulose loss and absolute lignin accumulation except for the red birch litter. The changes in litter cellulose and lignin were significantly affected by the interactions among gap position, period and species. Litter cellulose exhibited a greater loss in the winter with the highest daily loss rate observed during the snow cover period. Both cellulose and lignin exhibited greater changes under the deep snow cover at the gap center in the winter, but the opposite pattern occurred under the closed canopy in the growing season. The results suggest that decreased snowpack seasonality due to winter warming may limit litter cellulose and lignin degradation in alpine forest ecosystems, which could further inhibit litter decomposition. As a result, the ongoing winter warming and gap vanishing would slow soil carbon sequestration from foliar litter in cold biomes.

Seasonal changes in camera-based indices from an open canopy black spruce forest in Alaska, and comparison with indices from a closed canopy evergreen coniferous forest in Japan

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Nagai, Shin; Nakai, Taro; Saitoh, Taku M.; Busey, Robert C.; Kobayashi, Hideki; Suzuki, Rikie; Muraoka, Hiroyuki; Kim, Yongwon

2013-06-01

Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests.

Effects of site preparation subsoiling and prescribed burning on survival and growth of shortleaf pine in the Mark Twain National Forest: results after 20 growing seasons

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David Gwaze; Ross Melick; Lynn McClure; Charly Studyvin; David Massengele

2007-01-01

The objective of this study was to evaluate the effect of subsoiling (ripping) and prescribed burning on height, survival, diameter, volume, and competition of planted shortleaf pine (Pinus echinata Mill.). The study was established at the Salem Ranger District, Mark Twain National Forest. The treatments were subsoil/burn, burn, and control with no...

Earlier Snowmelt Changes the Ratio Between Early and Late Season Forest Productivity

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Knowles, J. F.; Molotch, N. P.; Trujillo, E.; Litvak, M. E.

2017-12-01

Future projections of declining snowpack and increasing potential evaporation associated with climate warming are predicted to advance the timing of snowmelt in mountain ecosystems globally. This scenario has direct implications for snowmelt-driven forest productivity, but the net effect of temporally shifting moisture dynamics is unknown with respect to the annual carbon balance. Accordingly, this study uses both satellite- and tower-based observations to document the forest productivity response to snowpack and potential evaporation variability between 1989 and 2012 throughout the southern Rocky Mountain ecoregion, USA. These results show that a combination of low snow accumulation and record high potential evaporation in 2012 resulted in the 34-year minimum ecosystem productivity that could be indicative of future conditions. Moreover, early and late season productivity were significantly and inversely related, suggesting that future shifts toward earlier or reduced snowmelt could increase late-season moisture stress to vegetation and thus restrict productivity despite a longer growing season. This relationship was further subject to modification by summer precipitation, and the controls on the early/late season productivity ratio are explored within the context of ecosystem carbon storage in the future. Any perturbation to the carbon cycle at this scale represents a potential feedback to climate change since snow-covered forests represent an important global carbon sink.

Seasonal variation of ozone deposition to a tropical rain forest in southwest Amazonia

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U. Rummel

2007-10-01

Full Text Available Within the project EUropean Studies on Trace gases and Atmospheric CHemistry as a contribution to Large-scale Biosphere-atmosphere experiment in Amazonia (LBA-EUSTACH, we performed tower-based eddy covariance measurements of O₃ flux above an Amazonian primary rain forest at the end of the wet and dry season. Ozone deposition revealed distinct seasonal differences in the magnitude and diel variation. In the wet season, the rain forest was an effective O₃ sink with a mean daytime (midday maximum deposition velocity of 2.3 cm s⁻¹, and a corresponding O₃ flux of −11 nmol m⁻² s⁻¹. At the end of the dry season, the ozone mixing ratio was about four times higher (up to maximum values of 80 ppb than in the wet season, as a consequence of strong regional biomass burning activity. However, the typical maximum daytime deposition flux was very similar to the wet season. This results from a strong limitation of daytime O₃ deposition due to reduced plant stomatal aperture as a response to large values of the specific humidity deficit. As a result, the average midday deposition velocity in the dry burning season was only 0.5 cm s⁻¹. The large diel ozone variation caused large canopy storage effects that masked the true diel variation of ozone deposition mechanisms in the measured eddy covariance flux, and for which corrections had to be made. In general, stomatal aperture was sufficient to explain the largest part of daytime ozone deposition. However, during nighttime, chemical reaction with nitrogen monoxide (NO was found to contribute substantially to the O₃ sink in the rain forest canopy. Further contributions were from non-stomatal plant uptake and other processes that could not be clearly identified.

Measurements, made simultaneously on a 22 years old cattle pasture enabled the spatially and temporally direct comparison of O₃

Vegetation and Lepidoptera in Seasonally Dry Tropical Forests. Community structure along climate zones, forest succession and seasonality in the Southern Yucatán, Mexico

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Essens, T.; Leyequien, E.; Pozo, C.

2010-01-01

Seasonally dry tropical forests are worldwide recognized as important ecosystems for biodiversity conservation. Increasing agricultural activities (e.g., slash-and-burn agriculture) leads to a heterogeneous landscape matrix; and as ecological succession takes over in abandoned fields, plant and

Seasonal Effects of Habitat on Sources and Rates of Snowshoe Hare Predation in Alaskan Boreal Forests.

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Dashiell Feierabend

Full Text Available Survival and predation of snowshoe hares (Lepus americanus has been widely studied, yet there has been little quantification of the changes in vulnerability of hares to specific predators that may result from seasonal changes in vegetation and cover. We investigated survival and causes of mortalities of snowshoe hares during the late increase, peak, and decline of a population in interior Alaska. From June 2008 to May 2012, we radio-tagged 288 adult and older juvenile hares in early successional and black spruce (Picea mariana forests and, using known-fate methods in program MARK, evaluated 85 survival models that included variables for sex, age, and body condition of hares, as well as trapping site, month, season, year, snowfall, snow depth, and air temperature. We compared the models using Akaike's information criterion with correction for small sample size. Model results indicated that month, capture site, and body condition were the most important variables in explaining survival rates. Survival was highest in July, and more generally during summer, when alternative prey was available to predators of hares. Low survival rates coincided with molting periods, breeding activity in the spring, and the introduction of juveniles to the sample population in the fall. We identified predation as the cause of mortality in 86% of hare deaths. When the source of predation could be determined, hares were killed more often by goshawks (Accipiter gentilis than other predators in early successional forest (30%, and more often by lynx (Lynx canadensis than other predators in black spruce forest (31%. Great horned owls (Bubo virginianus and coyotes (Canis latrans represented smaller proportions of hare predation, and non-predatory causes were a minor source (3% of mortality. Because hares rely on vegetative cover for concealment from predators, we measured cover in predation sites and habitats that the hares occupied and concluded that habitat type had a

Seasonal dynamics of ant community structure in the Moroccan Argan Forest.

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El Keroumi, Abderrahim; Naamani, Khalid; Soummane, Hassna; Dahbi, Abdallah

2012-01-01

In this study we describe the structure and composition of ant communities in the endemic Moroccan Argan forest, using pitfall traps sampling technique throughout the four seasons between May 2006 and February 2007. The study focused on two distinct climatic habitats within the Essaouira Argan forest, a semi-continental site at Lahssinate, and a coastal site at Boutazarte. Thirteen different ant species were identified, belonging to seven genera. Monomorium subopacum Smith and Tapinoma simrothi Krausse-Heldrungen (Hymenoptera: Formicidae) were the most abundant and behaviorally dominant ant species in the arganeraie. In addition, more specimens were captured in the semi-continental site than in the coastal area. However, no significant difference was observed in species richness, evenness, or diversity between both sites. Composition and community structure showed clear seasonal dynamics. The number of species, their abundance, their diversity, and their evenness per Argan tree were significantly dissimilar among seasons. The richness (except between summer and autumn), and the abundance and the evenness of ant species among communities, showed a significant difference between the dry period (summer and spring) and the rainy period (winter and autumn). Higher abundance and richness values occurred in the dry period of the year. Ant species dominance and seasonal climatic variations in the arganeraie might be among the main factors affecting the composition, structure, and foraging activity of ant communities. This study, together with recent findings on ant predation behavior below Argan trees, highlights the promising use of dominant ant species as potential agents of Mediterranean fruit fly bio-control in the Argan forest and surrounding ecosystems.

Detecting leaf phenology of seasonally moist tropical forests in South America with multi-temporal MODIS images.

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Xiangming Xiao; Stephen Hagen; Qingyuan Zhang; Michael Keller; Berrien Moore III

2006-01-01

Leaf phenology of tropical evergreen forests affects carbon and water fluxes. In an earlier study of a seasonally moist evergreen tropical forest site in the Amazon basin, time series data of Enhanced Vegetation Index (EVI) from the VEGETATION and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors showed an unexpected seasonal pattern, with higher EVI in the...

The seasonality of butterflies in a semi-evergreen forest: Gibbon Wildlife Sanctuary, Assam, northeastern India

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Arun P. Singh

2015-01-01

Full Text Available A study spanning 3.7 years on the butterflies of Gibbon Wildlife Sanctuary GWS (21km2, a semi-evergreen forest, in Jorhat District of Assam, northeastern India revealed 211 species of butterflies belonging to 115 genera including 19 papilionids and seven ‘rare’ and ‘very rare’ species as per Evans list of the Indian sub-continent (Great Blue Mime Papilio paradoxa telearchus; Brown Forest BobScobura woolletti; Snowy Angle Darpa pteria dealbatahas; Constable Dichorragia nesimachus; Grey Baron Euthalia anosia anosia; Sylhet Oakblue Arhopala silhetensis; Branded Yamfly Yasoda tripunctata. The butterflies showed a strong seasonality pattern in this forest with only one significant peak during the post monsoon (September-October when 118 species were in flight inside the forest which slowly declined to 92 species in November-December. Another peak (102 species was visible after winter from March to April. Species composition showed least similarity between pre-monsoon (March-May and post-monsoon (October-November seasons. The number of papilionid species were greater from July to December as compared from January to June. The findings of this study suggest that the pattern of seasonality in a semi-evergreen forest in northeastern India is distinct from that of the sub-tropical lowland forest in the Himalaya. Favourable logistics and rich diversity in GWS points to its rich potential in promoting ‘butterfly inclusive ecotourism’ in this remnant forest.

Upland Forest Linkages to Seasonal Wetlands: Litter Flux, Processing, and Food Quality

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Brian J. Palik; Darold P. Batzer; Christel Kern

2005-01-01

The flux of materials across ecosystem boundaries has significant effects on recipient systems. Because of edge effects, seasonal wetlands in upland forest are good systems to explore these linkages. The purpose of this study was to examine flux of coarse particulate organic matter as litter fall into seasonal wetlands in Minnesota, and the relationship of this flux to...

Seasonal patterns of leaf gas exchange and water relations in dry rain forest trees of contrasting leaf phenology.

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Choat, Brendan; Ball, Marilyn C; Luly, Jon G; Donnelly, Christine F; Holtum, Joseph A M

2006-05-01

Diurnal and seasonal patterns of leaf gas exchange and water relations were examined in tree species of contrasting leaf phenology growing in a seasonally dry tropical rain forest in north-eastern Australia. Two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret. were studied. The deciduous species had higher specific leaf areas and maximum photosynthetic rates per leaf dry mass in the wet season than the evergreens. During the transition from wet season to dry season, total canopy area was reduced by 70-90% in the deciduous species and stomatal conductance (g(s)) and assimilation rate (A) were markedly lower in the remaining leaves. Deciduous species maintained daytime leaf water potentials (Psi(L)) at close to or above wet season values by a combination of stomatal regulation and reduction in leaf area. Thus, the timing of leaf drop in deciduous species was not associated with large negative values of daytime Psi(L) (greater than -1.6 MPa) or predawn Psi(L) (greater than -1.0 MPa). The deciduous species appeared sensitive to small perturbations in soil and leaf water status that signalled the onset of drought. The evergreen species were less sensitive to the onset of drought and g(s) values were not significantly lower during the transitional period. In the dry season, the evergreen species maintained their canopies despite increasing water-stress; however, unlike Eucalyptus species from northern Australian savannas, A and g(s) were significantly lower than wet season values.

Seasonal dynamics of water use efficiency of typical forest and grassland ecosystems in China

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Zhu, Xianjin; Wang, Qiufeng; Hu, Zhongmin; Han, Shijie; Yan, Junhua; Wang, Yanfen; Zhao, Liang

2014-01-01

We selected four sites of ChinaFLUX representing four major ecosystem types in China-Changbaishan temperate broad-leaved Korean pine mixed forest (CBS), Dinghushan subtropical evergreen broadleaved forest (DHS), Inner Mongolia temperate steppe (NM), and Haibei alpine shrub-meadow (HBGC)-to study the seasonal dynamics of ecosystem water use efficiency (WUE = GPP/ET, where GPP is gross primary productivity and ET is evapotranspiration) and factors affecting it. Our seasonal dynamics results indicated single-peak variation of WUE in CBS, NM, and HBGC, which were affected by air temperature (Ta) and leaf area index (LAI), through their effects on the partitioning of evapotranspiration (ET) into transpiration (T) (i.e., T/ET). In DHS, WUE was higher at the beginning and the end of the year, and minimum in summer. Ta and soil water content affected the seasonal dynamics of WUE through their effects on GPP/T. Our results indicate that seasonal dynamics of WUE were different because factors affecting the seasonal dyn...

Annual and Seasonal Changes in the Structure of Litter-Dwelling Ant Assemblages (Hymenoptera: Formicidae in Atlantic Semideciduous Forests

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Flávio Siqueira de Castro

2012-01-01

Full Text Available We surveyed ant fauna in the leaf litter in an Atlantic Semideciduous forest in the State Park of Rio Doce (PERD. The work aimed to produce basic information about habitat effects on diversity, as well as about how the ant fauna in a such buffered forest habitat, as the litter layer, could respond the climate variation in a short and long term. We sampled two years in two distinct forest physiognomies, which respond to different geomorphologic backgrounds, in dry and rainy seasons. Species composition, richness and abundance of these forests were distinct. However, both forests hosted similar numbers of rare and specialized, habitat demanding species, thus suggesting both are similarly well preserved, despite distinct physiognomies. However, the lower and more open forest was, more susceptible to dry season effects, showing a steeper decline in species numbers in such season, but similar numbers in the wet seasons. The pattern varied between years, which corroborates the hypothesis of a strongly variable community in response to subtle climatic variation among years. The present results are baselines for future long term monitoring projects, and could support protocols for early warnings of global climatic changes effects on biodiversity.

Seasonality and microhabitat selection in a forest-dwelling salamander

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Basile, Marco; Romano, Antonio; Costa, Andrea; Posillico, Mario; Scinti Roger, Daniele; Crisci, Aldo; Raimondi, Ranieri; Altea, Tiziana; Garfì, Vittorio; Santopuoli, Giovanni; Marchetti, Marco; Salvidio, Sebastiano; De Cinti, Bruno; Matteucci, Giorgio

2017-10-01

Many small terrestrial vertebrates exhibit limited spatial movement and are considerably exposed to changes in local environmental variables. Among such vertebrates, amphibians at present experience a dramatic decline due to their limited resilience to environmental change. Since the local survival and abundance of amphibians is intrinsically related to the availability of shelters, conservation plans need to take microhabitat requirements into account. In order to gain insight into the terrestrial ecology of the spectacled salamander Salamandrina perspicillata and to identify appropriate forest management strategies, we investigated the salamander's seasonal variability in habitat use of trees as shelters in relation to tree features (size, buttresses, basal holes) and environmental variables in a beech forest in Italy. We used the occupancy approach to assess tree suitability on a non-conventional spatial scale. Our approach provides fine-grained parameters of microhabitat suitability and elucidates many aspects of the salamander's terrestrial ecology . Occupancy changed with the annual life cycle and was higher in autumn than in spring, when females were found closer to the stream in the study area. Salamanders showed a seasonal pattern regarding the trees they occupied and a clear preference for trees with a larger diameter and more burrows. With respect to forest management, we suggest maintaining a suitable number of trees with a trunk diameter exceeding 30 cm. A practice of selective logging along the banks of streams could help maintain an adequate quantity of the appropriate microhabitat. Furthermore, in areas with a presence of salamanders, a good forest management plan requires leaving an adequate buffer zone around streams, which should be wider in autumn than in spring.

Diverse patterns of stored water use among saplings in seasonally dry tropical forests.

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Wolfe, Brett T; Kursar, Thomas A

2015-12-01

Tree species in seasonally dry tropical forests likely vary in their drought-survival mechanisms. Drought-deciduousness, which reduces water loss, and low wood density, which may permit dependence on stored water, are considered key traits. For saplings of six species at two distinct sites, we studied these and two associated traits: the seasonal amount of water released per stem volume ("water released") and the hydraulic capacitance of the stem (C). Two deciduous species with low stem density, Cavanillesia platanifolia and Bursera simaruba, had high C and high dry-season stem water potential (Ψ(stem)), but differed in dry-season water released. C. platanifolia did not use stored water during the dry season whereas B. simaruba, in a drier forest, released stored water. In both, water released was highest while flushing leaves, suggesting that stored water supports leaf flushing. In contrast, two deciduous species with intermediate stem density, Annona hayesii and Genipa americana, had intermediate C, low dry-season Ψ(stem), and high seasonal change in water released. Meanwhile, two evergreen species with intermediate stem density, Cojoba rufescens and Astronium graveolens, had relatively low C, low dry-season Ψ(stem), and intermediate seasonal change in water released. Thus, at least three, distinct stored-water-use strategies were observed. Additionally, bark relative water content (RWC) decreased along with Ψ(stem) during the dry season while xylem RWC did not change, suggesting that bark-stored water buffers Ψ(stem) seasonally. Together these results suggest that seasonal use of stored water and change in Ψ(stem) are associated with functional groups that are characterized by combinations of deciduousness and stem density.

Curve Numbers for Nine Mountainous Eastern United States Watersheds: Seasonal Variation and Forest Cutting

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Many engineers and hydrologists use the curve number method to estimate runoff from ungaged watersheds; however, the method does not explicitly account for the influence of season or forest cutting on runoff. This study of observed rainfall and runoff for small, forested watershe...

Soil charcoal as long-term pyrogenic carbon storage in Amazonian seasonal forests.

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Turcios, Maryory M; Jaramillo, Margarita M A; do Vale, José F; Fearnside, Philip M; Barbosa, Reinaldo Imbrozio

2016-01-01

Forest fires (paleo + modern) have caused charcoal particles to accumulate in the soil vertical profile in Amazonia. This forest compartment is a long-term carbon reservoir with an important role in global carbon balance. Estimates of stocks remain uncertain in forests that have not been altered by deforestation but that have been impacted by understory fires and selective logging. We estimated the stock of pyrogenic carbon derived from charcoal accumulated in the soil profile of seasonal forest fragments impacted by fire and selective logging in the northern portion of Brazilian Amazonia. Sixty-nine soil cores to 1-m depth were collected in 12 forest fragments of different sizes. Charcoal stocks averaged 3.45 ± 2.17 Mg ha(-1) (2.24 ± 1.41 Mg C ha(-1) ). Pyrogenic carbon was not directly related to the size of the forest fragments. This carbon is equivalent to 1.40% (0.25% to 4.04%) of the carbon stocked in aboveground live tree biomass in these fragments. The vertical distribution of pyrogenic carbon indicates an exponential model, where the 0-30 cm depth range has 60% of the total stored. The total area of Brazil's Amazonian seasonal forests and ecotones not altered by deforestation implies 65-286 Tg of pyrogenic carbon accumulated along the soil vertical profile. This is 1.2-2.3 times the total amount of residual pyrogenic carbon formed by biomass burning worldwide in 1 year. Our analysis suggests that the accumulated charcoal in the soil vertical profile in Amazonian forests is a substantial pyrogenic carbon pool that needs to be considered in global carbon models. © 2015 John Wiley & Sons Ltd.

Water, energy and CO2 exchange over a seasonally flooded forest in the Sahel.

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Kergoat, L.; Le Dantec, V.; Timouk, F.; Hiernaux, P.; Mougin, E.; Manuela, G.; Diawara, M.

2014-12-01

In semi-arid areas like the Sahel, perennial water bodies and temporary-flooded lowlands are critical for a number of activities. In some cases, their existence is simply a necessary condition for human societies to establish. They also play an important role in the water and carbon cycle and have strong ecological values. As a result of the strong multi-decadal drought that impacted the Sahel in the 70' to 90', a paradoxical increase of ponds and surface runoff has been observed ("Less rain, more water in the ponds", Gardelle 2010). In spite of this, there are excessively few data documenting the consequence of such a paradox on the water and carbon cycle. Here we present 2 years of eddy covariance data collected over the Kelma flooded Acacia forest in the Sahel (15.50 °N), in the frame of the AMMA project. The flooded forest is compared to the other major component of this Sahelian landscape: a grassland and a rocky outcrop sites. All sites are involved in the ALMIP2 data/LSM model comparison. The seasonal cycle of the flooded forest strongly departs from the surroundings grassland and bare soil sites. Before the rain season, the forest displays the strongest net radiation and sensible heat flux. Air temperature within the canopy reaches extremely high values. During the flood, it turns to the lowest sensible heat flux. In fact, due to an oasis effect, this flux is negative during the late flood. Water fluxes turn from almost zero in the dry season to strong evaporation during the flood, since it uses additional energy provided by negative sensible heat flux. The eddy covariance fluxes are consistent with sap flow data, showing that the flood greatly increases the length of the growing season. CO2 fluxes over the forest were twice as large as over the grassland, and the growing season was also longer, giving a much larger annual photosynthesis. In view of these data and data over surroundings grasslands and bare soil, as well as data from a long-term ecological

Pennsylvanian coniferopsid forests in sabkha facies reveal the nature of seasonal tropical biome

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Falcon-Lang, H. J.; Jud, N.A.; John, Nelson W.; DiMichele, W.A.; Chaney, D.S.; Lucas, S.G.

2011-01-01

Pennsylvanian fossil forests are known from hundreds of sites across tropical Pangea, but nearly all comprise remains of humid Coal Forests. Here we report a unique occurrence of seasonally dry vegetation, preserved in growth position along >5 km of strike, in the Pennsylvanian (early Kasimovian, Missourian) of New Mexico (United States). Analyses of stump anatomy, diameter, and spatial density, coupled with observations of vascular traces and associated megaflora, show that this was a deciduous, mixed-age, coniferopsid woodland (~100 trees per hectare) with an open canopy. The coniferopsids colonized coastal sabkha facies and show tree rings, confirming growth under seasonally dry conditions. Such woodlands probably served as the source of coniferopsids that replaced Coal Forests farther east in central Pangea during drier climate phases. Thus, the newly discovered woodland helps unravel biome-scale vegetation dynamics and allows calibration of climate models. ?? 2011 Geological Society of America.

Energy balance and evaporation of a short-rotation willow forest. Variation with season and stand development

Energy Technology Data Exchange (ETDEWEB)

Iritz, Z.

1996-10-01

Energy balance and evaporation of a short-rotation willow (Salix viminalis L.) forest was studied in relation to season and stand development. The developmental stage of the forest stand considerably influenced how the energy, received as net radiation, was partitioned between the connective fluxes and the storage components. The main part of the available energy was utilised for evaporation during most of the season. Only at the beginning of the season did the willow forest supply heat to the atmosphere. Later in the season, energy was taken from air and utilised for evaporation, which resulted in negative sensible heat fluxes. Soil heat storage was also a significant term in the energy balance and also strongly depended on canopy development. Changes in energy partitioning relative to leaf area indices indicated the existence of a threshold value for leaf area index of the developing canopy. The analysis suggested that the canopy of the willow forest could be considered as closed at a leaf area index of 2. It was further found that evaporation from well-irrigated willow forest occurred also during night-time, particularly in windy and dry weather conditions. The sources of nocturnal evaporation were both the canopy, i.e. indicating non-closed stomata, and the soil surface. Partitioning of the total evaporation into components was investigated using a physically-based model with a two-layer aboveground representation and a two-layer soil module. The model estimates evaporation with respect to developmental stage of the willow stand and also takes into account the interaction between the fluxes from the canopy and the soil surface. Good performance of the model indicated that, after further testing in drier conditions, it could be used as a tool for analysing the prerequisites for energy-forest establishment, and practical management of energy forest stands. 37 refs, 9 figs

From leaf longevity to canopy seasonality: a carbon optimality phenology model for tropical evergreen forests

Science.gov (United States)

Xu, X.; Medvigy, D.; Wu, J.; Wright, S. J.; Kitajima, K.; Pacala, S. W.

2016-12-01

Tropical evergreen forests play a key role in the global carbon, water and energy cycles. Despite apparent evergreenness, this biome shows strong seasonality in leaf litter and photosynthesis. Recent studies have suggested that this seasonality is not directly related to environmental variability but is dominated by seasonal changes of leaf development and senescence. Meanwhile, current terrestrial biosphere models (TBMs) can not capture this pattern because leaf life cycle is highly underrepresented. One challenge to model this leaf life cycle is the remarkable diversity in leaf longevity, ranging from several weeks to multiple years. Ecologists have proposed models where leaf longevity is regarded as a strategy to optimize carbon gain. However previous optimality models can not be readily integrated into TBMs because (i) there are still large biases in predicted leaf longevity and (ii) it is never tested whether the carbon optimality model can capture the observed seasonality in leaf demography and canopy photosynthesis. In this study, we develop a new carbon optimality model for leaf demography. The novelty of our approach is two-fold. First, we incorporate a mechanistic photosynthesis model that can better estimate leaf carbon gain. Second, we consider the interspecific variations in leaf senescence rate, which strongly influence the modelled optimal carbon gain. We test our model with a leaf trait database for Panamanian evergreen forests. Then, we apply the model at seasonal scale and compare simulated seasonality of leaf litter and canopy photosynthesis with in-situ observations from several Amazonian forest sites. We find that (i) compared with original optimality model, the regression slope between observed and predicted leaf longevity increases from 0.15 to 1.04 in our new model and (ii) that our new model can capture the observed seasonal variations of leaf demography and canopy photosynthesis. Our results suggest that the phenology in tropical evergreen

Water-use advantage for lianas over trees in tropical seasonal forests

NARCIS (Netherlands)

Chen, Y.J.; Cao, K.F.; Schnitzer, S.A.; Fan, Z.X.; Zhang, J.L.; Bongers, F.

2015-01-01

•Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco-physiological mechanisms associated with lianas coping with water deficits are poorly understood. •We examined soil water partitioning, sap flow, and canopy eco-physiological properties for 99 individuals of 15

The importance of forest disturbance for the recruitment of the large arborescent palm Attalea maripa in a seasonally-dry Amazonian forest

OpenAIRE

Salm,Rodolfo

2005-01-01

The hypothesis that forest disturbance is important for the recruitment of the large arborescent palms Attalea maripa was tested with a natural experiment in the Pinkaití site (7º 46'S; 51º 57'W), a seasonally-dry Amazonian forest. A 8,000 m long trail, that crosses, in its lower half, an open forest along the Pinkaití stream bottomlands and, on its upper half, a dense forest on a hill, was divided in 160 0.15 ha (50x30 m) sampling units. At each unit, adult palms were counted and percentage ...

Seasonal Variability of Ground Water Levels in the Puszcza Zielonka Forest

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Grajewski Sylwester

2014-07-01

Full Text Available The paper presents results of studies on seasonal variability of ground water tables recorded in long-term observations of water levels in the Puszcza Zielonka forest complex. The Puszcza Zielonka Forest is located in the middle part of the Warta basin in the central part of the Wielkopolska region. Its western boundary is located approx. 6 km north-east of Poznań. The area is situated in the western part of the Wielkopolska-Mazovian climatic region. The natural landscape is of young glacial type of Pleistocene and Holocene formation. For this reason parent materials for soils in this area were mainly postglacial drifts, deposits coming from the Poznań stage of the Würm glaciation. In terms of granulometric composition these were mainly low clayey sands deposited on loose sands with an admixture of gravel and eroded sandy clay. Scots pine is the dominant species. Oaks, alders, larches and scarce spruces are also found in this area. Predominant sites include fresh mixed forest, fresh mixed coniferous forest, fresh broadleaved forest and alder swamp forest.

Simulation of the Unexpected Photosynthetic Seasonality in Amazonian Evergreen Forests by Using an Improved Diffuse Fraction-Based Light Use Efficiency Model

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Yan, Hao; Wang, Shao-Qiang; da Rocha, Humberto R.; Rap, Alexandru; Bonal, Damien; Butt, Nathalie; Coupe, Natalia Restrepo; Shugart, Herman H.

2017-11-01

Understanding the mechanism of photosynthetic seasonality in Amazonian evergreen forests is critical for its formulation in global climate and carbon cycle models. However, the control of the unexpected photosynthetic seasonality is highly uncertain. Here we use eddy-covariance data across a network of Amazonian research sites and a novel evapotranspiration (E) and two-leaf-photosynthesis-coupled model to investigate links between photosynthetic seasonality and climate factors on monthly scales. It reproduces the GPP seasonality (R2 = 0.45-0.69) with a root-mean-square error (RMSE) of 0.67-1.25 g C m-2 d-1 and a Bias of -0.03-1.04 g C m-2 d-1 for four evergreen forest sites. We find that the proportion of diffuse and direct sunlight governs the photosynthetic seasonality via their interaction with sunlit and shaded leaves, supported by a proof that canopy light use efficiency (LUE) has a strong linear relationship with the fraction of diffuse sunlight for Amazonian evergreen forests. In the transition from dry season to rainy season, incident total radiation (Q) decreased while LUE and diffuse fraction increased, which produced the large seasonal increase ( 34%) in GPP of evergreen forests. We conclude that diffuse radiation is an important environmental driver of the photosynthetic seasonality in tropical Amazon forests yet depending on light utilization by sunlit and shaded leaves. Besides, the GPP model simulates the precipitation-dominated GPP seasonality (R2 = 0.40-0.69) at pasture and savanna sites. These findings present an improved physiological method to relate light components with GPP in tropical Amazon.

Seasonal pattern of anthropogenic salinization in temperate forested headwater streams.

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Timpano, Anthony J; Zipper, Carl E; Soucek, David J; Schoenholtz, Stephen H

2018-04-15

Salinization of freshwaters by human activities is of growing concern globally. Consequences of salt pollution include adverse effects to aquatic biodiversity, ecosystem function, human health, and ecosystem services. In headwater streams of the temperate forests of eastern USA, elevated specific conductance (SC), a surrogate measurement for the major dissolved ions composing salinity, has been linked to decreased diversity of aquatic insects. However, such linkages have typically been based on limited numbers of SC measurements that do not quantify intra-annual variation. Effective management of salinization requires tools to accurately monitor and predict salinity while accounting for temporal variability. Toward that end, high-frequency SC data were collected within the central Appalachian coalfield over 4 years at 25 forested headwater streams spanning a gradient of salinity. A sinusoidal periodic function was used to model the annual cycle of SC, averaged across years and streams. The resultant model revealed that, on average, salinity deviated approximately ±20% from annual mean levels across all years and streams, with minimum SC occurring in late winter and peak SC occurring in late summer. The pattern was evident in headwater streams influenced by surface coal mining, unmined headwater reference streams with low salinity, and larger-order salinized rivers draining the study area. The pattern was strongly responsive to varying seasonal dilution as driven by catchment evapotranspiration, an effect that was amplified slightly in unmined catchments with greater relative forest cover. Evaluation of alternative sampling intervals indicated that discrete sampling can approximate the model performance afforded by high-frequency data but model error increases rapidly as discrete sampling intervals exceed 30 days. This study demonstrates that intra-annual variation of salinity in temperate forested headwater streams of Appalachia USA follows a natural seasonal

Hydrologic response to and recovery from differing silvicultural systems in a deciduous forest landscape with seasonal snow cover

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Buttle, J. M.; Beall, F. D.; Webster, K. L.; Hazlett, P. W.; Creed, I. F.; Semkin, R. G.; Jeffries, D. S.

2018-02-01

Hydrological consequences of alternative harvesting strategies in deciduous forest landscapes with seasonal snow cover have received relatively little attention. Most forest harvesting experiments in landscapes with seasonal snow cover have focused on clearcutting in coniferous forests. Few have examined alternative strategies such as selection or shelterwood cutting in deciduous stands whose hydrologic responses to harvesting may differ from those of conifers. This study presents results from a 31-year examination of hydrological response to and recovery from alternative harvesting strategies in a deciduous forest landscape with seasonal snow cover in central Ontario, Canada. A quantitative means of assessing hydrologic recovery to harvesting is also developed. Clearcutting resulted in increased water year (WY) runoff. This was accompanied by increased runoff in all seasons, with greatest relative increases in Summer. Direct runoff and baseflow from treatment catchments generally increased following harvesting, although annual peak streamflow did not. Largest increases in WY runoff and seasonal runoff as well as direct runoff and baseflow generally occurred in the selection harvest catchment, likely as a result of interception of hillslope runoff by a forest access road and redirection to the stream channel. Hydrologic recovery appeared to begin towards the end of the experimental period for several streamflow metrics but was incomplete for all harvesting strategies 15 years after harvesting. Geochemical tracing indicated that harvesting enhanced the relative importance of surface and near-surface water pathways on catchment slopes for all treatments, with the clearcut catchment showing the most pronounced and prolonged response. Such insights into water partitioning between flow pathways may assist assessments of the ecological and biogeochemical consequences of forest disturbance.

Diversity and aboveground biomass of lianas in the tropical seasonal rain forests of Xishuangbanna, SW China.

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Lü, Xiao-Tao; Tang, Jian-Wei; Feng, Zhi-Li; Li, Mai-He

2009-01-01

Lianas are important components of tropical forests and have significant impacts on the diversity, structure and dynamics of tropical forests. The present study documented the liana flora in a Chinese tropical region. Species richness, abundance, size-class distribution and spatial patterns of lianas were investigated in three 1-ha plots in tropical seasonal rain forests in Xishuangbanna, SW China. All lianas with > or = 2 cm diameter at breast height (dbh) were measured, tagged and identified. A total of 458 liana stems belonging to 95 species (ranging from 38 to 50 species/ha), 59 genera and 32 families were recorded in the three plots. The most well-represented families were Loganiaceae, Annonceae, Papilionaceae, Apocynaceae and Rhamnaceae. Papilionaceae (14 species recorded) was the most important family in the study forests. The population density, basal area and importance value index (IVI) varied greatly across the three plots. Strychnos cathayensis, Byttneria grandifolia and Bousigonia mekongensis were the dominant species in terms of IVI across the three plots. The mean aboveground biomass of lianas (3 396 kg/ha) accounted for 1.4% of the total community above-ground biomass. The abundance, diversity and biomass of lianas in Xishuangbanna tropical seasonal rain forests are lower than those in tropical moist and wet forests, but higher than those in tropical dry forests. This study provides new data on lianas from a geographical region that has been little-studied. Our findings emphasize that other factors beyond the amount and seasonality of precipitation should be included when considering the liana abundance patterns across scales.

Quantifying responses of dung beetles to fire disturbance in tropical forests: the importance of trapping method and seasonality.

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de Andrade, Rafael Barreto; Barlow, Jos; Louzada, Julio; Vaz-de-Mello, Fernando Zagury; Souza, Mateus; Silveira, Juliana M; Cochrane, Mark A

2011-01-01

Understanding how biodiversity responds to environmental changes is essential to provide the evidence-base that underpins conservation initiatives. The present study provides a standardized comparison between unbaited flight intercept traps (FIT) and baited pitfall traps (BPT) for sampling dung beetles. We examine the effectiveness of the two to assess fire disturbance effects and how trap performance is affected by seasonality. The study was carried out in a transitional forest between Cerrado (Brazilian Savanna) and Amazon Forest. Dung beetles were collected during one wet and one dry sampling season. The two methods sampled different portions of the local beetle assemblage. Both FIT and BPT were sensitive to fire disturbance during the wet season, but only BPT detected community differences during the dry season. Both traps showed similar correlation with environmental factors. Our results indicate that seasonality had a stronger effect than trap type, with BPT more effective and robust under low population numbers, and FIT more sensitive to fine scale heterogeneity patterns. This study shows the strengths and weaknesses of two commonly used methodologies for sampling dung beetles in tropical forests, as well as highlighting the importance of seasonality in shaping the results obtained by both sampling strategies.

Seasonality in the dung beetle community in a Brazilian tropical dry forest: Do small changes make a difference?

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Medina, Anderson Matos; Lopes, Priscila Paixão

2014-01-01

Dung beetle (Coleoptera: Scarabaeoidea: Scarabaeinae) activity is influenced by rainfall seasonality. We hypothesized that rainfall might also play a major role in regulating the community structure of this group. In this study, we describe seasonal changes in the richness, composition, and structure of the Scarabaeinae community in a Brazilian tropical dry forest. A fragment of arboreal Caatinga was sampled using baited pitfall traps during the early dry season (EDS), late dry season (LDS), early wet season (EWS), and middle wet season (MWS). We compared the dung beetle community in each season in relationship to species richness, rank-dominance, curves, and composition. We collected 1352 Scarabaeinae individuals , belonging to 15 species. Dichotomius aff. laevicollis Felsche (Coleoptera: Scarabaeidae) was the dominant species, representing 73.89% of the individuals. There were no seasonal changes in the rank dominance curves; all had a single dominant species and a few species with low abundance, typical for arid areas. Estimated richness was highest in MWS, followed by EWS. Dry-season samples (EDS and LDS) had lower richness, with no significant difference between the dry seasons. Although species richness increased as the habitat became wetter, the difference between the wet and dry seasons was small, which differs completely from the findings of other studies in Neotropical dry forests, where almost all species cease activities in the dry season. Species composition changes were found in non-metric multidimensional scaling and sustained by analysis of similarity. All the seasons had pairwise differences in composition, with the exception of EDS and MWS, which indicates that the dung beetle community in this fragment requires more than three months of drought to trigger changes in species composition; this is probably due to small changes in the forest canopy. There was no difference in composition between EDS and MWS. As in other tropical dry forests, although

Comparison of Ant Community Diversity and Functional Group Composition Associated to Land Use Change in a Seasonally Dry Oak Forest.

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Cuautle, M; Vergara, C H; Badano, E I

2016-04-01

Ants have been used to assess land use conversion, because they reflect environmental change, and their response to these changes have been useful in the identification of bioindicators. We evaluated ant diversity and composition associated to different land use change in a temperate forest (above 2000 m asl) in Mexico. The study was carried out in "Flor del Bosque" Park a vegetation mosaic of native Oak Forests and introduced Eucalyptus and grasslands. Species richness, dominance and diversity rarefaction curves, based on ant morphospecies and functional groups, were constructed and compared among the three vegetation types, for the rainy and the dry seasons of 2008-2009. Jaccard and Sorensen incidence-based indices were calculated to obtain similarity values among all the habitats. The Oak Forest was a rich dominant community, both in species and functional groups; the Eucalyptus plantation was diverse with low dominance. The most seasonality habitat was the grassland, with low species and high functional group diversity during the dry seasons, but the reverse pattern during the wet season. The Oak Forest was more similar to the Eucalyptus plantation than to the grassland, particularly during the dry season. Oak Forests are dominated by Cold Climate Specialists, specifically Prenolepis imparis (Say). The Eucalyptus and the grassland are characterized by generalized Myrmicinae, as Pheidole spp. and Monomorium ebenium (Forel). The conservation of the native Oak Forest is primordial for the maintenance of Cold Climate Specialist ant communities. The microclimatic conditions in this forest, probably, prevented the invasion by opportunistic species.

Amazon forest structure generates diurnal and seasonal variability in light utilization

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Douglas C. Morton; Jeremy Rubio; Bruce D. Cook; Jean-Philippe Gastellu-Etchegorry; Marcos Longo; Hyeungu Choi; Maria Hunter; Michael Keller

2016-01-01

The complex three-dimensional (3-D) structure of tropical forests generates a diversity of light environments for canopy and understory trees. Understanding diurnal and seasonal changes in light availability is critical for interpreting measurements of net ecosystem exchange and improving ecosystem models. Here, we used the Discrete Anisotropic Radiative Transfer (DART...

High NDVI and Potential Canopy Photosynthesis of South American Subtropical Forests despite Seasonal Changes in Leaf Area Index and Air Temperature

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Piedad M. Cristiano

2014-02-01

Full Text Available The canopy photosynthesis and carbon balance of the subtropical forests are not well studied compared to temperate and tropical forest ecosystems. The main objective of this study was to assess the seasonal dynamics of Normalized Difference Vegetation Index (NDVI and potential canopy photosynthesis in relation to seasonal changes in leaf area index (LAI, chlorophyll concentration, and air temperatures of NE Argentina subtropical forests throughout the year. We included in the analysis several tree plantations (Pinus, Eucalyptus and Araucaria species that are known to have high productivity. Field studies in native forests and tree plantations were conducted; stem growth rates, LAI and leaf chlorophyll concentration were measured. MODIS satellite-derived LAI (1 km SIN Grid and NDVI (250m SIN Grid from February 2000 to 2012 were used as a proxy of seasonal dynamics of potential photosynthetic activity at the stand level. The remote sensing LAI of the subtropical forests decreased every year from 6 to 5 during the cold season, similar to field LAI measurements, when temperatures were 10 °C lower than during the summer. The yearly maximum NDVI values were observed during a few months in autumn and spring (March through May and November, respectively because high and low air temperatures may have a small detrimental effect on photosynthetic activity during both the warm and the cold seasons. Leaf chlorophyll concentration was higher during the cold season than the warm season which may have a compensatory effect on the seasonal variation of the NDVI values. The NDVI of the subtropical forest stands remained high and fairly constant throughout the year (the intra-annual coefficient of variation was 1.9%, and were comparable to the values of high-yield tree plantations. These results suggest that the humid subtropical forests in NE Argentina potentially could maintain high canopy photosynthetic activity throughout the year and thus this ecosystem may

Forest structure and carbon dynamics in Amazonian tropical rain forests.

Science.gov (United States)

Vieira, Simone; de Camargo, Plinio Barbosa; Selhorst, Diogo; da Silva, Roseana; Hutyra, Lucy; Chambers, Jeffrey Q; Brown, I Foster; Higuchi, Niro; dos Santos, Joaquim; Wofsy, Steven C; Trumbore, Susan E; Martinelli, Luiz Antonio

2004-08-01

Living trees constitute one of the major stocks of carbon in tropical forests. A better understanding of variations in the dynamics and structure of tropical forests is necessary for predicting the potential for these ecosystems to lose or store carbon, and for understanding how they recover from disturbance. Amazonian tropical forests occur over a vast area that encompasses differences in topography, climate, and geologic substrate. We observed large differences in forest structure, biomass, and tree growth rates in permanent plots situated in the eastern (near Santarém, Pará), central (near Manaus, Amazonas) and southwestern (near Rio Branco, Acre) Amazon, which differed in dry season length, as well as other factors. Forests at the two sites experiencing longer dry seasons, near Rio Branco and Santarém, had lower stem frequencies (460 and 466 ha(-1) respectively), less biodiversity (Shannon-Wiener diversity index), and smaller aboveground C stocks (140.6 and 122.1 Mg C ha(-1)) than the Manaus site (626 trees ha(-1), 180.1 Mg C ha(-1)), which had less seasonal variation in rainfall. The forests experiencing longer dry seasons also stored a greater proportion of the total biomass in trees with >50 cm diameter (41-45 vs 30% in Manaus). Rates of annual addition of C to living trees calculated from monthly dendrometer band measurements were 1.9 (Manaus), 2.8 (Santarém), and 2.6 (Rio Branco) Mg C ha(-1) year(-1). At all sites, trees in the 10-30 cm diameter class accounted for the highest proportion of annual growth (38, 55 and 56% in Manaus, Rio Branco and Santarém, respectively). Growth showed marked seasonality, with largest stem diameter increment in the wet season and smallest in the dry season, though this may be confounded by seasonal variation in wood water content. Year-to-year variations in C allocated to stem growth ranged from nearly zero in Rio Branco, to 0.8 Mg C ha(-1) year(-1) in Manaus (40% of annual mean) and 0.9 Mg C ha(-1) year(-1) (33% of

Effects of seasonality on drosophilids (Insecta, Diptera) in the northern part of the Atlantic Forest, Brazil.

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Coutinho-Silva, R D; Montes, M A; Oliveira, G F; de Carvalho-Neto, F G; Rohde, C; Garcia, A C L

2017-10-01

Seasonality is an important aspect associated with population dynamic and structure of tropical insect assemblages. This study evaluated the effects of seasonality on abundance, richness, diversity and composition of an insect group, drosophilids, including species native to the Neotropical region and exotic ones. Three preserved fragments of the northern Atlantic Forest were surveyed, where temperatures are above 20 °C throughout the year and rainfall regimes define two seasons (dry and rainy). As opposed to other studies about arthropods in tropical regions, we observed that abundance of drosophilids was significantly higher in the dry season, possibly due to biological aspects and the colonization strategy adopted by the exotic species in these environments. Contrarily to abundance, we did not observe a seasonal pattern for richness. As for other parts of the Atlantic Forest, the most representative Neotropical species (Drosophila willistoni, D. sturtevanti, D. paulistorum and D. prosaltans) were significantly more abundant in the rainy season. Among the most abundant exotic species, D. malerkotliana, Zaprionus indianus and Scaptodrosophila latifasciaeformis were more importantly represented the dry season, while D. simulans was more abundant in the rainy period. The seasonality patterns exhibited by the most abundant species were compared to findings published in other studies. Our results indicate that exotic species were significantly more abundant in the dry season, while native ones exhibited an opposite pattern.

Mobbing call experiment suggests the enhancement of forest bird movement by tree cover in urban landscapes across seasons

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Atsushi Shimazaki

2017-06-01

Full Text Available Local scale movement behavior is an important basis to predict large-scale bird movements in heterogeneous landscapes. Here we conducted playback experiments using mobbing calls to estimate the probability that forest birds would cross a 50-m urban area during three seasons (breeding, dispersal, and wintering seasons with varying amounts of tree cover, building area, and electric wire density. We examined the responses of four forest resident species: Marsh Tit (Poecile palustris, Varied Tit (Sittiparus varius, Japanese Tit (P. minor, and Eurasian Nuthatch (Sitta europaea in central Hokkaido, northern Japan. We carried out and analyzed 250 playback experiments that attracted 618 individuals. Our results showed that tree cover increased the crossing probability of three species other than Varied Tit. Building area and electric wire density had no detectable effect on crossing probability for four species. Seasonal difference in the crossing probability was found only for Varied Tit, and the probability was the highest in the breeding season. These results suggest that the positive effect of tree cover on the crossing probability would be consistent across seasons. We therefore conclude that planting trees would be an effective way to promote forest bird movement within an urban landscape.

Habitat degradation and seasonality affect physiological stress levels of Eulemur collaris in littoral forest fragments.

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Michela Balestri

Full Text Available The littoral forest on sandy soil is among the most threatened habitats in Madagascar and, as such, it represents a hot-spot within a conservation hot-spot. Assessing the health of the resident lemur fauna is not only critical for the long-term viability of these populations, but also necessary for the future re-habilitation of this unique habitat. Since the Endangered collared brown lemur, Eulemur collaris, is the largest seed disperser of the Malagasy south-eastern littoral forest its survival in this habitat is crucial. In this study we compared fecal glucocorticoid metabolite (fGCM levels, a measure of physiological stress and potential early indicator of population health, between groups of collared brown lemurs living in a degraded forest fragment and groups occurring in a more preserved area. For this, we analysed 279 fecal samples collected year-round from 4 groups of collared brown lemurs using a validated 11-oxoetiocholanolone enzyme immunoassay and tested if fGCM levels were influenced by reproductive stages, phenological seasons, sex, and habitat degradation. The lemurs living in the degraded forest had significantly higher fGCM levels than those living in the more preserved area. In particular, the highest fGCM levels were found during the mating season in all animals and in females during gestation in the degraded forest. Since mating and gestation are both occurring during the lean season in the littoral forest, these results likely reflect a combination of ecological and reproductive pressures. Our findings provide a clear indication that habitat degradation has additive effects to the challenges found in the natural habitat. Since increased stress hormone output may have long-term negative effects on population health and reproduction, our data emphasize the need for and may add to the development of effective conservation plans for the species.

Habitat degradation and seasonality affect physiological stress levels of Eulemur collaris in littoral forest fragments.

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Balestri, Michela; Barresi, Marta; Campera, Marco; Serra, Valentina; Ramanamanjato, Jean Baptiste; Heistermann, Michael; Donati, Giuseppe

2014-01-01

The littoral forest on sandy soil is among the most threatened habitats in Madagascar and, as such, it represents a hot-spot within a conservation hot-spot. Assessing the health of the resident lemur fauna is not only critical for the long-term viability of these populations, but also necessary for the future re-habilitation of this unique habitat. Since the Endangered collared brown lemur, Eulemur collaris, is the largest seed disperser of the Malagasy south-eastern littoral forest its survival in this habitat is crucial. In this study we compared fecal glucocorticoid metabolite (fGCM) levels, a measure of physiological stress and potential early indicator of population health, between groups of collared brown lemurs living in a degraded forest fragment and groups occurring in a more preserved area. For this, we analysed 279 fecal samples collected year-round from 4 groups of collared brown lemurs using a validated 11-oxoetiocholanolone enzyme immunoassay and tested if fGCM levels were influenced by reproductive stages, phenological seasons, sex, and habitat degradation. The lemurs living in the degraded forest had significantly higher fGCM levels than those living in the more preserved area. In particular, the highest fGCM levels were found during the mating season in all animals and in females during gestation in the degraded forest. Since mating and gestation are both occurring during the lean season in the littoral forest, these results likely reflect a combination of ecological and reproductive pressures. Our findings provide a clear indication that habitat degradation has additive effects to the challenges found in the natural habitat. Since increased stress hormone output may have long-term negative effects on population health and reproduction, our data emphasize the need for and may add to the development of effective conservation plans for the species.

Seasonal and spatial variation in broadleaf forest model parameters

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Groenendijk, M.; van der Molen, M. K.; Dolman, A. J.

2009-04-01

Process based, coupled ecosystem carbon, energy and water cycle models are used with the ultimate goal to project the effect of future climate change on the terrestrial carbon cycle. A typical dilemma in such exercises is how much detail the model must be given to describe the observations reasonably realistic while also be general. We use a simple vegetation model (5PM) with five model parameters to study the variability of the parameters. These parameters are derived from the observed carbon and water fluxes from the FLUXNET database. For 15 broadleaf forests the model parameters were derived for different time resolutions. It appears that in general for all forests, the correlation coefficient between observed and simulated carbon and water fluxes improves with a higher parameter time resolution. The quality of the simulations is thus always better when a higher time resolution is used. These results show that annual parameters are not capable of properly describing weather effects on ecosystem fluxes, and that two day time resolution yields the best results. A first indication of the climate constraints can be found by the seasonal variation of the covariance between Jm, which describes the maximum electron transport for photosynthesis, and climate variables. A general seasonality we found is that during winter the covariance with all climate variables is zero. Jm increases rapidly after initial spring warming, resulting in a large covariance with air temperature and global radiation. During summer Jm is less variable, but co-varies negatively with air temperature and vapour pressure deficit and positively with soil water content. A temperature response appears during spring and autumn for broadleaf forests. This shows that an annual model parameter cannot be representative for the entire year. And relations with mean annual temperature are not possible. During summer the photosynthesis parameters are constrained by water availability, soil water content and

Northern California redwood forests provide important seasonal habitat for migrant bats

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Theodore J. Weller; Craig A. Stricker

2012-01-01

Bats are known to roost in redwood forests year-round, but their activities outside the summer season are poorly understood. To improve understanding of the use of redwoods by resident and migrant bats, we conducted 74 mist net surveys between February 2008 and October 2010. Captures were dominated by Yuma myotis (M. yumanensis) in the summer and...

Variations in soil carbon sequestration and their determinants along a precipitation gradient in seasonally dry tropical forest ecosystems.

Science.gov (United States)

Campo, Julio; Merino, Agustín

2016-05-01

The effect of precipitation regime on the C cycle of tropical forests is poorly understood, despite the existence of models that suggest a drier climate may substantially alter the source-sink function of these ecosystems. Along a precipitation regime gradient containing 12 mature seasonally dry tropical forests growing under otherwise similar conditions (similar annual temperature, rainfall seasonality, and geological substrate), we analyzed the influence of variation in annual precipitation (1240 to 642 mm) and duration of seasonal drought on soil C. We investigated litterfall, decomposition in the forest floor, and C storage in the mineral soil, and analyzed the dependence of these processes and pools on precipitation. Litterfall decreased slightly - about 10% - from stands with 1240 mm yr(-1) to those with 642 mm yr(-1), while the decomposition decreased by 56%. Reduced precipitation strongly affected C storage and basal respiration in the mineral soil. Higher soil C storage at the drier sites was also related to the higher chemical recalcitrance of litter (fine roots and forest floor) and the presence of charcoal across sites, suggesting an important indirect influence of climate on C sequestration. Basal respiration was controlled by the amount of recalcitrant organic matter in the mineral soil. We conclude that in these forest ecosystems, the long-term consequences of decreased precipitation would be an increase in organic layer and mineral soil C storage, mainly due to lower decomposition and higher chemical recalcitrance of organic matter, resulting from changes in litter composition and, likely also, wildfire patterns. This could turn these seasonally dry tropical forests into significant soil C sinks under the predicted longer drought periods if primary productivity is maintained. © 2016 John Wiley & Sons Ltd.

Investigating the role of evergreen and deciduous forests in the increasing trend in atmospheric CO2 seasonal amplitude

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Welp, L.; Calle, L.; Graven, H. D.; Poulter, B.

2017-12-01

The seasonal amplitude of Northern Hemisphere atmospheric CO2 concentrations has systematically increased over the last several decades, indicating that the timing and amplitude of net CO2 uptake and release by northern terrestrial ecosystems has changed substantially. Remote sensing, dynamic vegetation modeling, and in-situ studies have explored how changes in phenology, expansion of woody vegetation, and changes in species composition and disturbance regimes, among others, are driven by changes in climate and CO2. Despite these efforts, ecosystem models have not been able to reproduce observed atmospheric CO2 changes. Furthermore, the implications for the source/sink balance of northern ecosystems remains unclear. Changing proportions of evergreen and deciduous tree cover in response to climate change could be one of the key mechanisms that have given rise to amplified atmospheric CO2 seasonality. These two different plant functional types (PFTs) have different carbon uptake seasonal patterns and also different sensitivities to climate change, but are often lumped together as one forest type in global ecosystem models. We will demonstrate the potential that shifting distributions of evergreen and deciduous forests can have on the amplitude of atmospheric CO2. We will show phase differences in the net CO2 seasonal uptake using CO2 flux data from paired evergreen/deciduous eddy covariance towers. We will use simulations of evergreen and deciduous PFTs from the LPJ dynamic vegetation model to explore how climate change may influence the abundance and CO2 fluxes of each. Model results show that the area of deciduous forests is predicted to have increased, and the seasonal amplitude of CO2 fluxes has increased as well. The impact of surface flux seasonal variability on atmospheric CO2 amplitude is examined by transporting fluxes from each forest PFT through the TM3 transport model. The timing of the most intense CO2 uptake leads to an enhanced effect of deciduous

Assessing seasonality of biochemical CO2 exchange model parameters from micrometeorological flux observations at boreal coniferous forest

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T. Vesala

2008-12-01

Full Text Available The seasonality of the NEE of the northern boreal coniferous forests was investigated by means of inversion modelling using eddy covariance data. Eddy covariance data was used to optimize the biochemical model parameters. Our study sites consisted of three Scots pine (l. Pinus sylvestris forests and one Norway spruce (l. Picea abies forest that were located in Finland and Sweden. We obtained temperature and seasonal dependence for the biochemical model parameters: the maximum rate of carboxylation (Vc(max and the maximum rate of electron transport (Jmax. Both of the parameters were optimized without assumptions about their mutual magnitude. The values obtained for the biochemical model parameters were similar at all the sites during summer time. To describe seasonality, different temperature fits were made for the spring, summer and autumn periods. During summer, average Jmax across the sites was 54.0 μmol m−2 s−1 (variance 31.2 μmol m−2 s−1 and Vc(max was 12.0 μmol m−2 s−1 (variance 6.6 μmol m−2 s−1 at 17°C. The sensitivity of the model to LAI and atmospheric soil water stress was also studied. The impact of seasonality on annual GPP was 17% when only summertime parameterization was used throughout the year compared to seasonally changing parameterizations.

Mapping Spatial Distribution of Larch Plantations from Multi-Seasonal Landsat-8 OLI Imagery and Multi-Scale Textures Using Random Forests

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Tian Gao

2015-02-01

Full Text Available The knowledge about spatial distribution of plantation forests is critical for forest management, monitoring programs and functional assessment. This study demonstrates the potential of multi-seasonal (spring, summer, autumn and winter Landsat-8 Operational Land Imager imageries with random forests (RF modeling to map larch plantations (LP in a typical plantation forest landscape in North China. The spectral bands and two types of textures were applied for creating 675 input variables of RF. An accuracy of 92.7% for LP, with a Kappa coefficient of 0.834, was attained using the RF model. A RF-based importance assessment reveals that the spectral bands and bivariate textural features calculated by pseudo-cross variogram (PC strongly promoted forest class-separability, whereas the univariate textural features influenced weakly. A feature selection strategy eliminated 93% of variables, and then a subset of the 47 most essential variables was generated. In this subset, PC texture derived from summer and winter appeared the most frequently, suggesting that this variability in growing peak season and non-growing season can effectively enhance forest class-separability. A RF classifier applied to the subset led to 91.9% accuracy for LP, with a Kappa coefficient of 0.829. This study provides an insight into approaches for discriminating plantation forests with phenological behaviors.

Seasonal changes in the radiation balance of subarctic forest and tundra

International Nuclear Information System (INIS)

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

1993-01-01

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

Seasonal variation in soil and plant water potentials in a Bolivian tropical moist and dry forest

NARCIS (Netherlands)

Markesteijn, L.; Iraipi, J.; Bongers, F.; Poorter, L.

2010-01-01

We determined seasonal variation in soil matric potentials (¿soil) along a topographical gradient and with soil depth in a Bolivian tropical dry (1160 mm y-1 rain) and moist forest (1580 mm y-1). In each forest we analysed the effect of drought on predawn leaf water potentials (¿pd) and drought

Preliminary assessment of mercury accumulation in Massachusetts and Minnesota seasonal forest pools

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Robert T. Brooks; Susan L. Eggert; Keith H. Nislow; Randall K. Kolka; Celia Y. Chen; Darren M. Ward

2012-01-01

Seasonal forest pools (SFPs) are common, widespread, and provide critical habitat for amphibians and invertebrates. The ephemeral hydrology of SFPs has been identified as an important factor in the production of biologically active methylmercury (MeHg). To investigate mercury (Hg) in SFPs, we collected water, fine benthic organic matter (FBOM), detrital materials, and...

Spatial and seasonal variations of leaf area index (LAI) in subtropical secondary forests related to floristic composition and stand characters

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Zhu, Wenjuan; Xiang, Wenhua; Pan, Qiong; Zeng, Yelin; Ouyang, Shuai; Lei, Pifeng; Deng, Xiangwen; Fang, Xi; Peng, Changhui

2016-07-01

Leaf area index (LAI) is an important parameter related to carbon, water, and energy exchange between canopy and atmosphere and is widely applied in process models that simulate production and hydrological cycles in forest ecosystems. However, fine-scale spatial heterogeneity of LAI and its controlling factors have yet to be fully understood in Chinese subtropical forests. We used hemispherical photography to measure LAI values in three subtropical forests (Pinus massoniana-Lithocarpus glaber coniferous and evergreen broadleaved mixed forests, Choerospondias axillaris deciduous broadleaved forests, and L. glaber-Cyclobalanopsis glauca evergreen broadleaved forests) from April 2014 to January 2015. Spatial heterogeneity of LAI and its controlling factors were analysed using geostatistical methods and the generalised additive models (GAMs) respectively. Our results showed that LAI values differed greatly in the three forests and their seasonal variations were consistent with plant phenology. LAI values exhibited strong spatial autocorrelation for the three forests measured in January and for the L. glaber-C. glauca forest in April, July, and October. Obvious patch distribution pattern of LAI values occurred in three forests during the non-growing period and this pattern gradually dwindled in the growing season. Stem number, crown coverage, proportion of evergreen conifer species on basal area basis, proportion of deciduous species on basal area basis, and forest types affected the spatial variations in LAI values in January, while stem number and proportion of deciduous species on basal area basis affected the spatial variations in LAI values in July. Floristic composition, spatial heterogeneity, and seasonal variations should be considered for sampling strategy in indirect LAI measurement and application of LAI to simulate functional processes in subtropical forests.

Fast changes in seasonal forest communities due to soil moisture increase after damming

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Vagner Santiago do Vale

2013-12-01

Full Text Available Local changes caused by dams can have drastic consequences for ecosystems, not only because they change the water regime but also the modification on lakeshore areas. Thus, this work aimed to determine the changes in soil moisture after damming, to understand the consequences of this modification on the arboreal community of dry forests, some of the most endangered systems on the planet. We studied these changes in soil moisture and the arboreal community in three dry forests in the Araguari River Basin, after two dams construction in 2005 and 2006, and the potential effects on these forests. For this, plots of 20m x10m were distributed close to the impoundment margin and perpendicular to the dam margin in two deciduous dry forests and one semi-deciduous dry forest located in Southeastern Brazil, totaling 3.6ha sampled. Besides, soil analysis were undertaken before and after impoundment at three different depths 0-10, 20-30 and 40-50cm. A tree minimum DBH of 4.77cm community inventory was made before T0 and at two T2 and four T4 years after damming. Annual dynamic rates of all communities were calculated, and statistical tests were used to determine changes in soil moisture and tree communities. The analyses confirmed soil moisture increases in all forests, especially during the dry season and at sites closer to the reservoir; besides, an increase in basal area due to the fast growth of many trees was observed. The highest turnover occurred in the first two years after impoundment, mainly due to the higher tree mortality especially of those closer to the dam margin. All forests showed reductions in dynamic rates for subsequent years T2-T4, indicating that these forests tended to stabilize after a strong initial impact. The modifications were more extensive in the deciduous forests, probably because the dry period resulted more rigorous in these forests when compared to semideciduous forest. The new shorelines created by damming increased soil

Heterogeneity in fire severity within early season and late season prescribed burns in a mixed-conifer forest

Science.gov (United States)

Knapp, E.E.; Keeley, J.E.

2006-01-01

Structural heterogeneity in forests of the Sierra Nevada was historically produced through variation in fire regimes and local environmental factors. The amount of heterogeneity that prescription burning can achieve might now be more limited owing to high fuel loads and increased fuel continuity. Topography, woody fuel loading, and vegetative composition were quantified in plots within replicated early and late season burn units. Two indices of fire severity were evaluated in the same plots after the burns. Scorch height ranged from 2.8 to 25.4 m in early season plots and 3.1 to 38.5 m in late season plots, whereas percentage of ground surface burned ranged from 24 to 96% in early season plots and from 47 to 100% in late season plots. Scorch height was greatest in areas with steeper slopes, higher basal area of live trees, high percentage of basal area composed of pine, and more small woody fuel. Percentage of area burned was greatest in areas with less bare ground and rock cover (more fuel continuity), steeper slopes, and units burned in the fall (lower fuel moisture). Thus topographic and biotic factors still contribute to the abundant heterogeneity in fire severity with prescribed burning, even under the current high fuel loading conditions. Burning areas with high fuel loads in early season when fuels are moister may lead to patterns of heterogeneity in fire effects that more closely approximate the expected patchiness of historical fires.

Phytossociology of wood community in Seasonal Dry Montane Forest in Paraiba, Brazil

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Maria do Carmo Learth Cunha

2013-06-01

Full Text Available The Pico do Jabre Seasonally Dry Montane Forest in Paraiba state, Brazil, the highest regional elevation, 1197 m, distant 360 km the sea was assessed aiming to survey its phytosociology and woody structure. In 36 systematic sampling plots, 10x50m, individuals, Dbh > 4.8cm, had their diameters and height measured. Botanical samples were collected during five years and vouchers were deposited at the Paraiba Federal University Herbaria (JPB. It was found 2050 trees distributed in 64 species of 51 genera of 31 families, which accounted for 1138 ind.ha-1 and 22.45 m2.ha -1. Diversity and equability were assessed as H' = 3.17 nats.ind-1 and J' = 0.76 similar to some others regional seasonally dry montane forest communities. Malpighiaceae, Myrtaceae, Erythroxylaceae, Vochysiaceae, Celastraceae, Rutaceae, Sapindaceae e Fabaceae-Faboideae stood out and summed 66.72% of the total VI. Byrsonima nitidifolia, Eugenia ligustrina, Calisthene microphylla, Maytenus distichophylla and Erythroxylum mucronatum species accounted for 120.79 (40.3% of the total VI. B. nitidifolia ecological dominance is firstly reported in the Brazilian northeast region.

Fish movement in an Atlantic Forest stream

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Rosana Mazzoni

2018-03-01

Full Text Available ABSTRACT Given the importance of fish movement to the dynamics and maintenance of stream dwelling fish communities from the Atlantic Forest, we analysed patterns of fish movement in a coastal stream from Southeastern Brazil, using mark-recapture technique. Displacement distance of each species were presented and discussed considering seasonal (rainy and dry and body size patterns. We marked 10 species along the stream and recaptured 440 (34.6% of the 1,270 marked fishes. The species with significant number of upstream moving individuals were Astyanax janeiroensis, Characidium interruptum, Astyanax hastatus, Parotocinclus maculicauda and Awaous tajasica. Only Pimelodella lateristriga presented significant differences between resident and moving individuals. Characidium interruptum and A. tajasica demonstrated greater downstream and upstream movement, respectively, moving up to 2,100 m. Even after controlling for species identity we found no significant correlation between fish length and individual displacement distance. Fishes moved longer distances during the rainy season, in accordance to the breeding season. Patterns of fish movement were in agreement to life-history traits of many of the studied species and can be reflecting specific behaviour and morphologies.

Effects of seasonal variation of photosynthetic capacity on the carbon fluxes of a temperate deciduous forest

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David Medvigy; Su-Jong Jeong; Kenneth L. Clark; Nicholas S. Skowronski; Karina V. R. Schäfer

2013-01-01

Seasonal variation in photosynthetic capacity is an important part of the overall seasonal variability of temperate deciduous forests. However, it has only recently been introduced in a few terrestrial biosphere models, and many models still do not include it. The biases that result from this omission are not well understood. In this study, we use the Ecosystem...

Conversion of tropical lowland forest reduces nutrient return through litterfall, and alters nutrient use efficiency and seasonality of net primary production.

Science.gov (United States)

Kotowska, Martyna M; Leuschner, Christoph; Triadiati, Triadiati; Hertel, Dietrich

2016-02-01

Tropical landscapes are not only rapidly transformed by ongoing land-use change, but are additionally confronted by increasing seasonal climate variation. There is an increasing demand for studies analyzing the effects and feedbacks on ecosystem functioning of large-scale conversions of tropical natural forest into intensively managed cash crop agriculture. We analyzed the seasonality of aboveground litterfall, fine root litter production, and aboveground woody biomass production (ANPP(woody)) in natural lowland forests, rubber agroforests under natural tree cover ("jungle rubber"), rubber and oil palm monocultures along a forest-to-agriculture transformation gradient in Sumatra. We hypothesized that the temporal fluctuation of litter production increases with increasing land-use intensity, while the associated nutrient fluxes and nutrient use efficiency (NUE) decrease. Indeed, the seasonal variation of aboveground litter production and ANPP(woody) increased from the natural forest to the plantations, while aboveground litterfall generally decreased. Nutrient return through aboveground litter was mostly highest in the natural forest; however, it was significantly lower only in rubber plantations. NUE of N, P and K was lowest in the oil palm plantations, with natural forest and the rubber systems showing comparably high values. Root litter production was generally lower than leaf litter production in all systems, while the root-to-leaf ratio of litter C flux increased along the land-use intensity gradient. Our results suggest that nutrient and C cycles are more directly affected by climate seasonality in species-poor agricultural systems than in species-rich forests, and therefore might be more susceptible to inter-annual climate fluctuation and climate change.

Asynchronous response of tropical forest leaf phenology to seasonal and el Niño-driven drought.

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Stephanie Pau

2010-06-01

Full Text Available The Hawaiian Islands are an ideal location to study the response of tropical forests to climate variability because of their extreme isolation in the middle of the Pacific, which makes them especially sensitive to El Niño-Southern Oscillation (ENSO. Most research examining the response of tropical forests to drought or El Niño have focused on rainforests, however, tropical dry forests cover a large area of the tropics and may respond very differently than rainforests. We use satellite-derived Normalized Difference Vegetation Index (NDVI from February 2000-February 2009 to show that rainforests and dry forests in the Hawaiian Islands exhibit asynchronous responses in leaf phenology to seasonal and El Niño-driven drought. Dry forest NDVI was more tightly coupled with precipitation compared to rainforest NDVI. Rainforest cloud frequency was negatively correlated with the degree of asynchronicity (Delta(NDVI between forest types, most strongly at a 1-month lag. Rainforest green-up and dry forest brown-down was particularly apparent during the 2002-003 El Niño. The spatial pattern of NDVI response to the NINO 3.4 Sea Surface Temperature (SST index during 2002-2003 showed that the leeward side exhibited significant negative correlations to increased SSTs, whereas the windward side exhibited significant positive correlations to increased SSTs, most evident at an 8 to 9-month lag. This study demonstrates that different tropical forest types exhibit asynchronous responses to seasonal and El Niño-driven drought, and suggests that mechanisms controlling dry forest leaf phenology are related to water-limitation, whereas rainforests are more light-limited.

Analysis of Seasonal Soil Organic Carbon Content at Bukit Jeriau Forest, Fraser Hill, Pahang

International Nuclear Information System (INIS)

Ahmad Adnan Mohamed; Ahmad Adnan Mohamed; Sahibin Abd Rahim; David Allan Aitman; Mohd Khairul Amri Kamarudin; Mohd Khairul Amri Kamarudin

2016-01-01

Soil carbon is the carbon held within the soil, primarily in association with its organic content. The total soil organic carbon study was determined in a plot at Bukit Jeriau forest in Bukit Fraser, Pahang, Malaysia. The aim of this study is to determine the changing of soil organic carbon between wet season and dry season. Soil organic carbon was fined out using titrimetric determination. The soil organic carbon content in wet season is 223.24 t/ ha while dry season is 217.90 t/ ha. The soil pH range in wet season is between 4.32 to 4.45 and in dry season in 3.95 to 4.08 which is considered acidic. Correlation analysis showed that soil organic carbon value is influenced by pH value and climate. Correlation analysis between clay and soil organic carbon with depth showed positively significant differences and clay are very much influenced soil organic carbon content. Correlation analysis between electrical conductivity and soil organic carbon content showed negative significantly difference on wet season and positively significant different in dry season. (author)

SEASONAL AND TOPOGRAPHYCAL VARIATION OF THE LITTER NUTRIENT CONTENTS OF A ATLANTIC FOREST FRAGMENT

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Rosângela A. Tristão Borém

2002-01-01

Full Text Available ABSTRACT: The objective of this work was to study the effects of forest degradation on the supplyand contents of nutrients in the litter of two toposequences. The study area is located in a fragment ofthe Atlantic Forest, in Silva Jardim, State of Rio de Janeiro, Brazil (42°31'W and 22°31'S. The twotoposequences are under low and high degrees of human intervention. They were divided in lower,middle and upper slope, and the vegetation sampled with plots of 600m2. The litter was collected forquantitative and qualitative characterisation using a wood frame of 0,25m2 randomly distributedwithin the sample plots. Litter collection was carried out in two distinct dates in order to capture seasonalpatterns. The average litter production did not differ significantly between the toposequences.The total litter production was higher at the end of the dry season, and lower at the end of the rainyseason, indicating the seasonal pattern of the forest. The chemical analyses showed that the nutrientscontents varied widely between the toposequences. The lower and middle slope of the toposequenceunder high degree of human intervention presented the highest nutrient contents in the litter.

Effects of land use change and seasonality of precipitation on soil nitrogen in a dry tropical forest area in the Western Llanos of Venezuela.

Science.gov (United States)

González-Pedraza, Ana Francisca; Dezzeo, Nelda

2014-01-01

We evaluated changes of different soil nitrogen forms (total N, available ammonium and nitrate, total N in microbial biomass, and soil N mineralization) after conversion of semideciduous dry tropical forest in 5- and 18-year-old pastures (YP and OP, resp.) in the western Llanos of Venezuela. This evaluation was made at early rainy season, at end rainy season, and during dry season. With few exceptions, no significant differences were detected in the total N in the three study sites. Compared to forest soils, YP showed ammonium losses from 4.2 to 62.9% and nitrate losses from 20.0 to 77.8%, depending on the season of the year. In OP, the ammonium content increased from 50.0 to 69.0% at the end of the rainy season and decreased during the dry season between 25.0 and 55.5%, whereas the nitrate content increased significantly at early rainy season. The net mineralization and the potentially mineralizable N were significantly higher (P forest and YP, which would indicate a better quality of the substrate in OP for mineralization. The mineralization rate constant was higher in YP than in forest and OP. This could be associated with a reduced capacity of these soils to preserve the available nitrogen.

Plant diversity patterns in neotropical dry forests and their conservation implications

Science.gov (United States)

K. Banda-R; A. Delgado-Salinas; K. G. Dexter; R. Linares-Palomino; A. Oliveira-Filho; D. Prado; M. Pullan; C. Quintana; R. Riina; G. M. Rodriguez M.; J. Weintritt; P. Acevedo-Rodriguez; J. Adarve; E. Alvarez; A. Aranguren B.; J. C. Arteaga; G. Aymard; A. Castano; N. Ceballos-Mago; A. Cogollo; H. Cuadros; F. Delgado; W. Devia; H. Duenas; L. Fajardo; A. Fernandez; M. A. Fernandez; J. Franklin; E. H. Freid; L. A. Galetti; R. Gonto; R. Gonzalez-M.; R. Graveson; E. H. Helmer; A. Idarraga; R. Lopez; H. Marcano-Vega; O. G. Martinez; H. M. Maturo; M. McDonald; K. McLaren; O. Melo; F. Mijares; V. Mogni; D. Molina; N. d. P. Moreno; J. M. Nassar; D. M. Neves; L. J. Oakley; M. Oatham; A. R. Olvera-Luna; F. F. Pezzini; O. J. R. Dominguez; M. E. Rios; O. Rivera; N. Rodriguez; A. Rojas; T. Sarkinen; R. Sanchez; M. Smith; C. Vargas; B. Villanueva; R. T. Pennington

2016-01-01

Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than...

Post-fire regeneration in seasonally dry tropical forest fragments in southeastern Brazil.

Science.gov (United States)

Costa, Mayke B; Menezes, Luis Fernando T DE; Nascimento, Marcelo T

2017-01-01

Seasonally dry tropical forest is one of the highly threatened biome. However, studies on the effect of fire on these tree communities are still scarce. In this context, a floristic and structural survey in three forest areas in the southeast of Brazil that were affected by fire between 14 and 25 years ago was performed with the objective of evaluating post-fire regeneration. In each site, five systematically placed plots (25 m x 25 m each) were established. The more recently burnt site had significantly lower values of richness and diversity than the other two sites. However, the sites did not differ in density and basal area. Annona dolabripetala, Astronium concinnum, Joannesia princeps and Polyandrococos caudescens were within the 10 most important species for the three sites. Comparing these data with adjacent mature forests, the results indicated differences both in structural and floristic aspects, suggesting that the time after fire was not sufficient for recuperation of these areas. The recovery process indicate at least 190 years for areas return to basal area values close to those observed in mature forests nearby.

Phenology of two Ficus species in seasonal semi-deciduous forest in Southern Brazil

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E. Bianchini

Full Text Available Abstract We analyzed the phenology of Ficus adhatodifolia Schott ex Spreng. (23 fig tree and F. eximia Schott (12 fig tree for 74 months in a remnant of seasonal semi-deciduous forest (23°27’S and 51°15’W, Southern Brazil and discussed their importance to frugivorous. Leaf drop, leaf flush, syconia production and dispersal were recorded. These phenophases occurred year-round, but seasonal peaks were recorded in both leaf phenophases for F. eximia and leaf flushing for F. adhatodifolia. Climatic variables analyzed were positively correlated with reproductive phenophases of F. adhatodifolia and negatively correlated with the vegetative phenophases of F. eximia. In despite of environmental seasonality, little seasonality in the phenology of two species was observed, especially in the reproductive phenology. Both species were important to frugivorous, but F. adhatodifolia can play a relevant role in the remnant.

Modeling seasonal surface temperature variations in secondary tropical dry forests

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Cao, Sen; Sanchez-Azofeifa, Arturo

2017-10-01

Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15-20 K higher than in the wet season at SRNP. We found that the early successional stages were about 6-8 K warmer than the intermediate successional stages and were 9-10 K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0-1 K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

Successional and seasonal variations in soil and litter microbial community structure and function during tropical postagricultural forest regeneration: a multiyear study.

Science.gov (United States)

Smith, A Peyton; Marín-Spiotta, Erika; Balser, Teri

2015-09-01

Soil microorganisms regulate fundamental biochemical processes in plant litter decomposition and soil organic matter (SOM) transformations. Understanding how microbial communities respond to changes in vegetation is critical for improving predictions of how land-cover change affects belowground carbon storage and nutrient availability. We measured intra- and interannual variability in soil and forest litter microbial community composition and activity via phospholipid fatty acid analysis (PLFA) and extracellular enzyme activity across a well-replicated, long-term chronosequence of secondary forests growing on abandoned pastures in the wet subtropical forest life zone of Puerto Rico. Microbial community PLFA structure differed between young secondary forests and older secondary and primary forests, following successional shifts in tree species composition. These successional patterns held across seasons, but the microbial groups driving these patterns differed over time. Microbial community composition from the forest litter differed greatly from those in the soil, but did not show the same successional trends. Extracellular enzyme activity did not differ with forest succession, but varied by season with greater rates of potential activity in the dry seasons. We found few robust significant relationships among microbial community parameters and soil pH, moisture, carbon, and nitrogen concentrations. Observed inter- and intrannual variability in microbial community structure and activity reveal the importance of a multiple, temporal sampling strategy when investigating microbial community dynamics with land-use change. Successional control over microbial composition with forest recovery suggests strong links between above and belowground communities. © 2015 John Wiley & Sons Ltd.

Climate change in winter versus the growing-season leads to different effects on soil microbial activity in northern hardwood forests

Science.gov (United States)

Sorensen, P. O.; Templer, P. H.; Finzi, A.

2014-12-01

Mean winter air temperatures have risen by approximately 2.5˚ C per decade over the last fifty years in the northeastern U.S., reducing the maximum depth of winter snowpack by approximately 26 cm over this period and the duration of winter snow cover by 3.6 to 4.2 days per decade. Forest soils in this region are projected to experience a greater number of freeze-thaw cycles and lower minimum winter soil temperatures as the depth and duration of winter snow cover declines in the next century. Climate change is likely to result not only in lower soil temperatures during winter, but also higher soil temperatures during the growing-season. We conducted two complementary experiments to determine how colder soils in winter and warmer soils in the growing-season affect microbial activity in hardwood forests at Harvard Forest, MA and Hubbard Brook Experimental Forest, NH. A combination of removing snow via shoveling and buried heating cables were used to induce freeze-thaw events during winter and to warm soils 5˚C above ambient temperatures during the growing-season. Increasing the depth and duration of soil frost via snow-removal resulted in short-term reductions in soil nitrogen (N) production via microbial proteolytic enzyme activity and net N mineralization following snowmelt, prior to tree leaf-out. Declining mass specific rates of carbon (C) and N mineralization associated with five years of snow removal at Hubbard Brook Experimental Forest may be an indication of microbial physiological adaptation to winter climate change. Freeze-thaw cycles during winter reduced microbial extracellular enzyme activity and the temperature sensitivity of microbial C and N mineralization during the growing-season, potentially offsetting nutrient and soil C losses due to soil warming in the growing-season. Our multiple experimental approaches show that winter climate change is likely to contribute to reduced microbial activity in northern hardwood forests.

Temporal dynamics and leaf trait variability in Neotropical dry forests

Science.gov (United States)

Hesketh, Michael Sean

This thesis explores the variability of leaf traits resulting from changes in season, ecosystem successional stage, and site characteristics. In chapter two, I present a review of the use of remote sensing analysis for the evaluation of Neotropical dry forests. Here, I stress the conclusion, drawn from studies on land cover characterization, biodiversity assessment, and evaluation of forest structural characteristics, that addressing temporal variability in spectral properties is an essential element in the monitoring of these ecosystems. Chapter three describes the effect of wet-dry seasonality on spectral classification of tree and liana species. Highly accurate classification (> 80%) was possible using data from either the wet or dry season. However, this accuracy decreased by a factor of ten when data from the wet season was classified using an algorithm trained on the dry, or vice versa. I also address the potential creation of a spectral taxonomy of species, but found that any clustering based on spectral properties resulted in markedly different arrangements in the wet and dry seasons. In chapter 4, I address the variation present in both physical and spectral leaf traits according to changes in forest successional stage at dry forest sites in Mexico and Costa Rica. I found significant differences in leaf traits between successional stages, but more strongly so in Costa Rica. This variability deceased the accuracy of spectral classification of tree species by a factor of four when classifying data using an algorithm trained on a different successional stage. Chapter 5 shows the influence of seasonality and succession on trait variability in Mexico. Differences in leaf traits between successional stages were found to be greater during the dry season, but were sufficient in both seasons to negatively influence spectral classification of tree species. Throughout this thesis, I show clear and unambiguous evidence of the variability of key physical and spectral

Seasonal abundance and development of the Asian longhorned beetle and natural enemy prevalence in different forest types in China

Science.gov (United States)

Houping Liu; Leah S. Bauer; Tonghai Zhao; Ruitong Gao; Therese M. Poland

2016-01-01

Seasonal abundance and population development of the Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), and prevalence of its natural enemies were studied on Hankow willow (Salix matsudana Koidz.) at an urban forest site (Anci) and a rural forest site (Tangerli) in Hebei province...

Seasonal and inter-annual dynamics of growth, non-structural carbohydrates and C stable isotopes in a Mediterranean beech forest.

Science.gov (United States)

Scartazza, Andrea; Moscatello, Stefano; Matteucci, Giorgio; Battistelli, Alberto; Brugnoli, Enrico

2013-07-01

Seasonal and inter-annual dynamics of growth, non-structural carbohydrates (NSC) and carbon isotope composition (δ(13)C) of NSC were studied in a beech forest of Central Italy over a 2-year period characterized by different environmental conditions. The net C assimilated by forest trees was mainly used to sustain growth early in the season and to accumulate storage carbohydrates in trunk and root wood in the later part of the season, before leaf shedding. Growth and NSC concentration dynamics were only slightly affected by the reduced soil water content (SWC) during the drier year. Conversely, the carbon isotope analysis on NSC revealed seasonal and inter-annual variations of photosynthetic and post-carboxylation fractionation processes, with a significant increase in δ(13)C of wood and leaf soluble sugars in the drier summer year than in the wetter one. The highly significant correlation between δ(13)C of leaf soluble sugars and SWC suggests a decrease of the canopy C isotope discrimination and, hence, an increased water-use efficiency with decreasing soil water availability. This may be a relevant trait for maintaining an acceptable plant water status and a relatively high C sink capacity during dry seasonal periods. Our results suggest a short- to medium-term homeostatic response of the Collelongo beech stand to variations in water availability and solar radiation, indicating that this Mediterranean forest was able to adjust carbon-water balance in order to prevent C depletion and to sustain plant growth and reserve accumulation during relatively dry seasons.

Seasonal variations of leaf and canopy properties tracked by ground-based NDVI imagery in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Heskel, Mary; Sun, Shucun; Tang, Jianwu

2017-04-28

Changes in plant phenology affect the carbon flux of terrestrial forest ecosystems due to the link between the growing season length and vegetation productivity. Digital camera imagery, which can be acquired frequently, has been used to monitor seasonal and annual changes in forest canopy phenology and track critical phenological events. However, quantitative assessment of the structural and biochemical controls of the phenological patterns in camera images has rarely been done. In this study, we used an NDVI (Normalized Difference Vegetation Index) camera to monitor daily variations of vegetation reflectance at visible and near-infrared (NIR) bands with high spatial and temporal resolutions, and found that the infrared camera based NDVI (camera-NDVI) agreed well with the leaf expansion process that was measured by independent manual observations at Harvard Forest, Massachusetts, USA. We also measured the seasonality of canopy structural (leaf area index, LAI) and biochemical properties (leaf chlorophyll and nitrogen content). We found significant linear relationships between camera-NDVI and leaf chlorophyll concentration, and between camera-NDVI and leaf nitrogen content, though weaker relationships between camera-NDVI and LAI. Therefore, we recommend ground-based camera-NDVI as a powerful tool for long-term, near surface observations to monitor canopy development and to estimate leaf chlorophyll, nitrogen status, and LAI.

CO2 efflux from subterranean nests of ant communities in a seasonal tropical forest, Thailand

OpenAIRE

Hasin, Sasitorn; Ohashi, Mizue; Yamada, Akinori; Hashimoto, Yoshiaki; Tasen, Wattanachai; Kume, Tomonori; Yamane, Seiki

2014-01-01

Many ant species construct subterranean nests. The presence of their nests may explain soil respiration “hot spots”, an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determi...

Ecological consequences of alternative fuel reduction treatments in seasonally dry forests: the national fire and fire surrogate study

Science.gov (United States)

J.D. McIver; C.J. Fettig

2010-01-01

This special issue of Forest Science features the national Fire and Fire Surrogate study (FFS), a niultisite, multivariate research project that evaluates the ecological consequences of prescribed fire and its mechanical surrogates in seasonally dry forests of the United States. The need for a comprehensive national FFS study stemmed from concern that information on...

Estimating seasonal variations in cloud droplet number concentration over the boreal forest from satellite observations

NARCIS (Netherlands)

Janssen, R.; Ganzeveld, L.N.; Kabat, P.; Kulmala, M.; Nieminen, T.; Roebeling, R.A.

2011-01-01

Seasonal variations in cloud droplet number concentration (NCD) in low-level stratiform clouds over the boreal forest are estimated from MODIS observations of cloud optical and microphysical properties, using a sub-adiabatic cloud model to interpret vertical profiles of cloud properties. An

Age-dependent leaf physiology and consequences for crown-scale carbon uptake during the dry season in an Amazon evergreen forest.

Science.gov (United States)

Albert, Loren P; Wu, Jin; Prohaska, Neill; de Camargo, Plinio Barbosa; Huxman, Travis E; Tribuzy, Edgard S; Ivanov, Valeriy Y; Oliveira, Rafael S; Garcia, Sabrina; Smith, Marielle N; Oliveira Junior, Raimundo Cosme; Restrepo-Coupe, Natalia; da Silva, Rodrigo; Stark, Scott C; Martins, Giordane A; Penha, Deliane V; Saleska, Scott R

2018-03-04

Satellite and tower-based metrics of forest-scale photosynthesis generally increase with dry season progression across central Amazônia, but the underlying mechanisms lack consensus. We conducted demographic surveys of leaf age composition, and measured the age dependence of leaf physiology in broadleaf canopy trees of abundant species at a central eastern Amazon site. Using a novel leaf-to-branch scaling approach, we used these data to independently test the much-debated hypothesis - arising from satellite and tower-based observations - that leaf phenology could explain the forest-scale pattern of dry season photosynthesis. Stomatal conductance and biochemical parameters of photosynthesis were higher for recently mature leaves than for old leaves. Most branches had multiple leaf age categories simultaneously present, and the number of recently mature leaves increased as the dry season progressed because old leaves were exchanged for new leaves. These findings provide the first direct field evidence that branch-scale photosynthetic capacity increases during the dry season, with a magnitude consistent with increases in ecosystem-scale photosynthetic capacity derived from flux towers. Interactions between leaf age-dependent physiology and shifting leaf age-demographic composition are sufficient to explain the dry season photosynthetic capacity pattern at this site, and should be considered in vegetation models of tropical evergreen forests. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Seasonality of temperate forest photosynthesis and daytime respiration.

Science.gov (United States)

Wehr, R; Munger, J W; McManus, J B; Nelson, D D; Zahniser, M S; Davidson, E A; Wofsy, S C; Saleska, S R

2016-06-30

Terrestrial ecosystems currently offset one-quarter of anthropogenic carbon dioxide (CO2) emissions because of a slight imbalance between global terrestrial photosynthesis and respiration. Understanding what controls these two biological fluxes is therefore crucial to predicting climate change. Yet there is no way of directly measuring the photosynthesis or daytime respiration of a whole ecosystem of interacting organisms; instead, these fluxes are generally inferred from measurements of net ecosystem-atmosphere CO2 exchange (NEE), in a way that is based on assumed ecosystem-scale responses to the environment. The consequent view of temperate deciduous forests (an important CO2 sink) is that, first, ecosystem respiration is greater during the day than at night; and second, ecosystem photosynthetic light-use efficiency peaks after leaf expansion in spring and then declines, presumably because of leaf ageing or water stress. This view has underlain the development of terrestrial biosphere models used in climate prediction and of remote sensing indices of global biosphere productivity. Here, we use new isotopic instrumentation to determine ecosystem photosynthesis and daytime respiration in a temperate deciduous forest over a three-year period. We find that ecosystem respiration is lower during the day than at night-the first robust evidence of the inhibition of leaf respiration by light at the ecosystem scale. Because they do not capture this effect, standard approaches overestimate ecosystem photosynthesis and daytime respiration in the first half of the growing season at our site, and inaccurately portray ecosystem photosynthetic light-use efficiency. These findings revise our understanding of forest-atmosphere carbon exchange, and provide a basis for investigating how leaf-level physiological dynamics manifest at the canopy scale in other ecosystems.

Seasonal dynamics of soil CO2 emission in the boreal forests in Central Siberia

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Makhnykina, A. V.; Prokishkin, A. S.; Zyryanov, V.; Verkhovets, S. V.

2016-12-01

A large amount of carbon in soil is released to the atmosphere through soil respiration, which is the main pathway of transferring carbon from terrestrial ecosystems (Comstedt et al., 2011). Considering that boreal forests is a large terrestrial sink (Tans et al., 1990) and represent approximately 11 % of the Earth's total land area (Gower et al., 2001), even a small change in soil respiration could significantly intensify - or mitigate - current atmospheric increases of CO2, with potential feedbacks to climate change. The objectives of the present study are: (a) to study the dynamic of CO2emission from the soil surface during summer season (from May to October); (b) to identify the reaction of soil respiration to different amount of precipitation as the main limiting factor in the region. The research was carried out in the pine forests in Central Siberia (60°N, 90°E), Russia. Sample plots were represented by the lichen pine forest, moss pine forest, mixed forest and anthropogenic destroyed area. We used the automated soil CO2 flux system based on the infrared gas analyzer LI-8100 for measuring the soil efflux. Soil temperature was measured with Soil Temperature Probe Type E in three depths 5, 10, 15 cm. Volumetric soil moisture was measured with Theta Probe Model ML2. The presence and type of ground cover substantially affects the value of soil respiration fluxes. The carbon dioxide emission from the soil surface averaged was 5.4 ±2.3 μmol CO2 m-2 s-1. The destroyed area without plant cover demonstrated the lowest soil respiration (0.1-5.6 μmol CO2 m-2 s-1). The lowest soil respiration among forested areas was observed in the feathermoss pine forest. The lichen pine forest soil respiration was characterized by averages values. The maximum soil respiration values and seasonal fluctuations were obtained in the mixed forest (2.3-29.3 μmol CO2 m-2 s-1). The analysis of relation between soil CO2 efflux and amount of precipitation showed that the site without any

Tree mortality from fire and bark beetles following early and late season prescribed fires in a Sierra Nevada mixed-conifer forest

Science.gov (United States)

Schwilk, Dylan W.; Knapp, Eric E.; Ferrenberg, Scott; Keeley, Jon E.; Caprio, Anthony C.

2006-01-01

Over the last century, fire exclusion in the forests of the Sierra Nevada has allowed surface fuels to accumulate and has led to increased tree density. Stand composition has also been altered as shade tolerant tree species crowd out shade intolerant species. To restore forest structure and reduce the risk of large, intense fires, managers have increasingly used prescription burning. Most fires prior to EuroAmerican settlement occurred during the late summer and early fall and most prescribed burning has taken place during the latter part of this period. Poor air quality and lack of suitable burn windows during the fall, however, have resulted in a need to conduct more prescription burning earlier in the season. Previous reports have suggested that burning during the time when trees are actively growing may increase mortality rates due to fine root damage and/or bark beetle activity. This study examines the effects of fire on tree mortality and bark beetle attacks under prescription burning during early and late season. Replicated early season burn, late season burn and unburned control plots were established in an old-growth mixed conifer forest in the Sierra Nevada that had not experienced a fire in over 120 years. Although prescribed burns resulted in significant mortality of particularly the smallest tree size classes, no difference between early and late season burns was detected. Direct mortality due to fire was associated with fire intensity. Secondary mortality due to bark beetles was not significantly correlated with fire intensity. The probability of bark beetle attack on pines did not differ between early and late season burns, while the probability of bark beetle attack on firs was greater following early season burns. Overall tree mortality appeared to be primarily the result of fire intensity rather than tree phenology at the time of the burns. Early season burns are generally conducted under higher fuel moisture conditions, leading to less fuel

Chlorophyll fluorescence tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Zhang, Yongguang; Heskel, Mary A; Lu, Xiaoliang; Munger, J William; Sun, Shucun; Tang, Jianwu

2017-07-01

Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf-level ChlF was linked with canopy-scale solar-induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts, USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R 2  = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively; P chlorophyll content (R 2  = 0.65 for canopy GPP SIF and chlorophyll content; P < 0.0001), leaf area index (LAI) (R 2  = 0.35 for canopy GPP SIF and LAI; P < 0.0001), and normalized difference vegetation index (NDVI) (R 2  = 0.36 for canopy GPP SIF and NDVI; P < 0.0001). Our results suggest that ChlF can be a powerful tool to track photosynthetic rates at leaf, canopy, and ecosystem scales. © 2016 John Wiley & Sons Ltd.

Stand-level gas-exchange responses to seasonal drought in very young versus old Douglas-fir forests of the Pacific Northwest, USA

Science.gov (United States)

Sonia Wharton; Matt Schroeder; Ken Bible; Matthias Falk; Kyaw Tha Paw U

2009-01-01

This study examines how stand age affects ecosystem mass and energy exchange response to seasonal drought in three adjacent Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. The sites include two early seral (ES) stands (0 to 15 years old) and an old-growth (OG) (~450 to 500 years old) forest in the Wind River Experimental Forest,...

Seasonality, diaspore traits and the structure of plant-frugivore networks in Neotropical savanna forest

Science.gov (United States)

Darosci, Adriano Antonio Brito; Bruna, Emilio M.; Motta-Junior, José Carlos; Ferreira, Cristiane da Silva; Blake, John Gilman; Munhoz, Cássia Beatriz Rodrigues

2017-10-01

Complex frugivory networks are common in heterogeneous environments, but how the structure of those networks varies due to seasonality and other environmental factors remains unclear. For example, seasonal variation in rainfall can influence fruit production and diaspore characteristics, which could alter the quantity and quality of resources available to different animals in the network and, hence, network structure. We investigated how a frugivory network varied seasonally in Brazilian savanna (Cerrado), where there are well-defined dry and wet seasons and fructification mainly during the rainy season for most tree species. We recorded fruit consumption by animals during the dry and wet seasons in two different gallery forests and used these data to test the hypotheses that connectance, links per species and nestedness would be higher in the dry season than rainy season due to low available food in the former that would be consumed by various species of frugivores. Concomitantly, we also measured seed width and lipid content from diaspores of the fruiting trees to determine if these characteristics influenced interaction properties between fruiting trees and frugivores. Among the measured network parameters, connectance, links per species and specialization varied between seasons in one site but not in the other, indicating that seasonal variation in networks is not necessarily consistent over time or space. The number of tree species with small diaspores with high lipid content differed between seasons, and those characteristics were key factors increasing the interaction parameter of fruiting trees. We suggest that network stability between seasons may be related to local frugivore diversity, resource availability, and fruit quality.

Seasonal measurements of organic acid fluxes over a ponderosa pine forest

Science.gov (United States)

Fulgham, S. R.; Brophy, P.; Link, M.; Ortega, J. V.; Farmer, D.

2016-12-01

The biosphere acts as both a source and a sink of oxidized organic compounds. Ignoring dry deposition leads to overestimation of secondary organic aerosols by aerosol models, while ignoring emission sources underestimates the budget of organic acids. Developing parameterizations for oxidized organic dry deposition and emission requires observational constraints. Although biosphere parameters are impacted by seasonal variability, most reactive, trace-gas exchange measurements are made for only short periods of time in the main growing season. Here we make fast (5 - 10 Hz) and sensitive (e.g. 0.73 ppt mean limit of detection for formic acid with 10 s averaging) eddy covariance measurements of gas-phase organic acids and other oxidized organic species with a high resolution Time-of-Flight Chemical Ionization Mass Spectrometer with acetate and iodide reagent ions. Measurements were made in 4 - 6 week campaigns over five seasons from summer 2015 to fall 2016 as part of the Seasonal Particles in Forests Flux studY (SPIFFY) at the Manitou Experimental Forest Observatory near Woodland Park, Colorado. Permeation tubes were used for online calibration of carboxylic acids including formic (C1), propionic (C3), butyric (C4), methacrylic (CH2C(CH3)COOH), valeric (C5), and heptanoic (C7) acids. Average daytime mixing ratios for formic acid were 100 ± 100 ppt in winter and 1500 ± 1000 ppt in summer 2016. Upward fluxes of formic acid were observed throughout the experiment, daytime averages and standard deviations ranging from 1900 ± 1000 ppt cm s-1 in winter to 170 ± 130 ppt cm s-1 in spring. Propionic (22 ± 22 ppt cm s-1), butyric (17 ± 16 ppt cm s-1), and methacrylic (3.5 ± 6.1 ppt cm s-1) acids exhibit a mix of upward, near-zero, and downward fluxes. Fluxes were exponentially correlated to temperature, suggesting an ecosystem-scale source of these acids. We also measure exchange velocities of a broad suite of other oxidized organic compounds (31.99 m/z to 311.523 m/z in

Seasonality of Central Amazon Forest Leaf Flush Using Tower-Mounted RGB Camera

Science.gov (United States)

Wu, J.; Nelson, B. W.; Tavares, J. V.; Valeriano, D. M.; Lopes, A. P.; Marostica, S. F.; Martins, G.; Prohaska, N.; Albert, L.; De Araujo, A. C.; Manzi, A. O.; Saleska, S. R.; Huete, A. R.

2014-12-01

Tower-mounted RGB cameras can contribute data to the debate on seasonality of photosynthesis in Amazon upland forests and to improved modelling of forest response to climate change. In late 2010 we began monitoring upper crown surfaces of ~65 living trees or vines from a 54m tall eddy-flux tower on a well-drained clay-soil plateau. This Central Amazon site (60.2091 W, 2.6092 S) is in a large forest reserve. We deployed a Stardot Netcam XL RGB camera with a 1024 x 768 resolution CMOS sensor, 66o HFOV lens, fixed oblique south view, fixed iris, fixed white balance and auto-exposure. Images were logged every 15 seconds to a passively cooled FitPC2i with heat-tolerant SSD drive. Camera and PC automatically rebooted after power outages. Here we report results for two full years, from 1 Dec 2011 through 30 Nov 2013. Images in six day intervals were selected near local noon for homogeneous diffuse lighting under cloudy sky and for a standard reflected radiance (± 10%). Crowns showing two easily recognized phenophases were tallied: (1) massive flushing of new light-green leaves and (2) complete or nearly complete leaf loss. On average, 60% of live crowns flushed a massive amount of new leaves each year. Each crown flush was completed within 30 days. During the five driest months (Jun-Oct), 44% of all live crowns, on average, exhibited such massive leaf flush. In the five wettest months (Dec-Apr) only 11% of live crowns mass-flushed new leaves. In each year 23% of all live crowns became deciduous, usually a brief (1-2 week) preamble to flushing. Additional crowns lost old dark-green leaves partially and more gradually, becoming semi-deciduous prior to flushing. From these two years of camera data we infer that highly efficient leaves of 2-6 months age (high maximum carboxylation rate) are most abundant from the late dry season (October) through the mid wet season (March). This coincides with peak annual photosynthesis (Gross Ecosystem Productivity) reported for this same

[Effect of seasonal high temperature and drought on carbon flux of bamboo forest ecosystem in subtropical region].

Science.gov (United States)

Chen, Xiao-feng; Jiang, Hong; Niu, Xiao-dong; Zhang, Jin-meng; Liu, Yu-li; Fang, Cheng-yuan

2016-02-01

The carbon flux of subtropical bamboo forest ecosystem was continuously measured using eddy covariance technique in Anji County of Zhejiang Province, China. The monthly net ecosystem productivity (NEP), ecosystem respiration (Re) and gross ecosystem productivity (GEP) data from 2011 to 2013 were selected to analyze the impacts of seasonal high temperature and drought on the carbon flux of bamboo forest ecosystem. The results showed that there were big differences among annual NEP of bamboo forest from 2011 to 2013. Because of the asynchronization of precipitation and heat, the seasonal high temperature and drought in July and August of 2013 caused significant decline in NEP by 59.9% and 80.0% when compared with the same months in 2011. Correlation analysis of the NEP, Re, GEP and environmental factors suggested that the atmosphere temperatures were significantly correlated with Re and GEP in 2011 and 2013 (P<0.05). However, to air and soil moisture, Re and GEP had different responses, that was, GEP was more vulnerable by the decrease of the soil moisture compared with Re. Besides, the raising of saturation vapour pressure promoted the Re modestly but inhibited the GEP, which was supposed to be the main reason for NEP decrease of bamboo forest ecosystem in Anji, from July to August in 2013.

SHIFTS OF START AND END OF SEASON IN RESPONSE TO AIR TEMPERATURE VARIATION BASED ON GIMMS DATASET IN HYRCANIAN FORESTS

Directory of Open Access Journals (Sweden)

K. H. Kiapasha

2017-09-01

Full Text Available Climate change is one of the most important environmental challenges in the world and forest as a dynamic phenomenon is influenced by environmental changes. The Hyrcanian forests is a unique natural heritage of global importance and we need monitoring this region. The objective of this study was to detect start and end of season trends in Hyrcanian forests of Iran based on biweekly GIMMS (Global Inventory Modeling and Mapping Studies NDVI3g in the period 1981-2012. In order to find response of vegetation activity to local temperature variations, we used air temperature provided from I.R. Iran Meteorological Organization (IRIMO. At the first step in order to remove the existing gap from the original time series, the iterative Interpolation for Data Reconstruction (IDR model was applied to GIMMS and temperature dataset. Then we applied significant Mann Kendall test to determine significant trend for each pixel of GIMMS and temperature datasets over the Hyrcanian forests. The results demonstrated that start and end of season (SOS & EOS respectively derived from GIMMS3g NDVI time series increased by -0.16 and +0.41 days per year respectively. The trends derived from temperature time series indicated increasing trend in the whole of this region. Results of this study showed that global warming and its effect on growth and photosynthetic activity can increased the vegetation activity in our study area. Otherwise extension of the growing season, including an earlier start of the growing season, later autumn and higher rate of production increased NDVI value during the study period.

Caatinga Revisited: Ecology and Conservation of an Important Seasonal Dry Forest

Science.gov (United States)

de Albuquerque, Ulysses Paulino; de Lima Araújo, Elcida; El-Deir, Ana Carla Asfora; de Lima, André Luiz Alves; Souto, Antonio; Bezerra, Bruna Martins; Ferraz, Elba Maria Nogueira; Maria Xavier Freire, Eliza; Sampaio, Everardo Valadares de Sá Barreto; Las-Casas, Flor Maria Guedes; de Moura, Geraldo Jorge Barbosa; Pereira, Glauco Alves; de Melo, Joabe Gomes; Alves Ramos, Marcelo; Rodal, Maria Jesus Nogueira; Schiel, Nicola; de Lyra-Neves, Rachel Maria; Alves, Rômulo Romeu Nóbrega; de Azevedo-Júnior, Severino Mendes; Telino Júnior, Wallace Rodrigues; Severi, William

2012-01-01

Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest) hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga. PMID:22919296

Caatinga Revisited: Ecology and Conservation of an Important Seasonal Dry Forest

Directory of Open Access Journals (Sweden)

Ulysses Paulino de Albuquerque

2012-01-01

Full Text Available Besides its extreme climate conditions, the Caatinga (a type of tropical seasonal forest hosts an impressive faunal and floristic biodiversity. In the last 50 years there has been a considerable increase in the number of studies in the area. Here we aimed to present a review of these studies, focusing on four main fields: vertebrate ecology, plant ecology, human ecology, and ethnobiology. Furthermore, we identify directions for future research. We hope that the present paper will help defining actions and strategies for the conservation of the biological diversity of the Caatinga.

Seasonal variation in the atmospheric deposition of inorganic constituents and canopy interactions in a Japanese cedar forest

International Nuclear Information System (INIS)

Sase, Hiroyuki; Takahashi, Akiomi; Sato, Masahiko; Kobayashi, Hiroyasu; Nakata, Makoto; Totsuka, Tsumugu

2008-01-01

The seasonal changes in throughfall (TF) and stemflow (SF) chemistry and the canopy interactions of K + and N compounds were studied in a Japanese cedar forest near the Sea of Japan. The fluxes of most ions, including non-sea-salt SO 4 2- , from TF, SF, and rainfall showed distinct seasonal trends, increasing from autumn to winter, owing to the seasonal west wind, while the fluxes of NH 4 + and K + ions from TF + SF might have a large effect of canopy interactions. The contact angle (CA) of water droplets on leaves decreased with leaf aging, suggesting that surface wettability increases with leaf age. The K + concentration in TF was negatively correlated with the CA of 1-year-old leaves, while the NH 4 + concentration was positively correlated with the CA. The net fluxes of NH 4 + and NO 3 - from TF were positively correlated with the CA. The increase in wettability may accelerate leaching of K + or uptake of NH 4 + . - Leaf surface properties may contribute to the ion transport process of the forest canopy

WET AND DRY SEASON ECOSYSTEM LEVEL FLUXES OF ISOPRENE AND MONOTERPENES FROM A SOUTHEAST ASIAN SECONDARY FOREST AND RUBBER TREE PLANTATION

Science.gov (United States)

Canopy scale fluxes of isoprene and monoterpenes were investigated in both wet and dry seasons above a rubber tree (Hevea brasiliensis)/secondary tropical forest in the Yunnan province of southwestern China. Drought conditions were unusually high during the dry season experiment....

Constructing seasonal LAI trajectory by data-model fusion for global evergreen needle-leaf forests

Science.gov (United States)

Wang, R.; Chen, J.; Mo, G.

2010-12-01

For decades, advancements in optical remote sensors made it possible to produce maps of a biophysical parameter--the Leaf Area Index (LAI), which is critically necessary in regional and global modeling of exchanges of carbon, water, energy and other substances, across large areas in a fast way. Quite a few global LAI products have been generated since 2000, e.g. GLOBCARBON (Deng et al., 2006), MODIS Collection 5 (Shabanov et al., 2007), CYCLOPES (Baret et al., 2007), etc. Albeit these progresses, the basic physics behind the technology restrains it from accurate estimation of LAI in winter, especially for northern high-latitude evergreen needle-leaf forests. Underestimation of winter LAI in these regions has been reported in literature (Yang et al., 2000; Cohen et al., 2003; Tian et al., 2004; Weiss et al., 2007; Pisek et al., 2007), and the distortion is usually attributed to the variations of canopy reflectance caused by understory change (Weiss et al., 2007) as well as by the presence of ice and snow on leaves and ground (Cohen, 2003; Tian et al., 2004). Seasonal changes in leaf pigments can also be another reason for low LAI retrieved in winter. Low conifer LAI values in winter retrieved from remote sensing make them unusable for surface energy budget calculations. To avoid these drawbacks of remote sensing approaches, we attempt to reconstruct the seasonal LAI trajectory through model-data fusion. A 1-degree LAI map of global evergreen needle-leaf forests at 10-day interval is produced based on the carbon allocation principle in trees. With net primary productivity (NPP) calculated by the Boreal Ecosystems Productivity Simulator (BEPS) (Chen et al., 1999), carbon allocated to needles is quantitatively evaluated and then can be further transformed into LAI using the specific leaf area (SLA). A leaf-fall scheme is developed to mimic the carbon loss caused by falling needles throughout the year. The seasonally maximum LAI from remote sensing data for each pixel

Species biogeography predicts drought responses in a seasonally dry tropical forest

Science.gov (United States)

Schwartz, N.; Powers, J. S.; Vargas, G.; Xu, X.; Smith, C. M.; Brodribb, T.; Werden, L. K.; Becknell, J.; Medvigy, D.

2017-12-01

The timing, distribution, and amount of rainfall in the seasonal tropics have shifted in recent years, with consequences for seasonally dry tropical forests (SDTF). SDTF are sensitive to changing rainfall regimes and drought conditions, but sensitivity to drought varies substantially across species. One potential explanation of species differences is that species that experience dry conditions more frequently throughout their range will be better able to cope with drought than species from wetter climates, because species from drier climates will be better adapted to drought. An El-Niño induced drought in 2015 presented an opportunity to assess species-level differences in mortality in SDTF, and to ask whether the ranges of rainfall conditions species experience and the average rainfall regimes in species' ranges predict differences in mortality rates in Costa Rican SDTF. We used field plot data from northwest Costa Rica to determine species' level mortality rates. Mortality rates ranged substantially across species, with some species having no dead individuals to as high as 50% mortality. To quantify rainfall conditions across species' ranges, we used species occurrence data from the Global Biodiversity Information Facility, and rainfall data from the Chelsa climate dataset. We found that while the average and range of mean annual rainfall across species ranges did not predict drought-induced mortality in the field plots, across-range averages of the seasonality index, a measure of rainfall seasonality, was strongly correlated with species-level drought mortality (r = -0.62, p < 0.05), with species from more strongly seasonal climates experiencing less severe drought mortality. Furthermore, we found that the seasonality index was a stronger predictor of mortality than any individual functional trait we considered. This result shows that species' biogeography may be an important factor for how species will respond to future drought, and may be a more integrative

Plant diversity patterns in neotropical dry forests and their conservation implications.

Science.gov (United States)

Banda-R, Karina; Delgado-Salinas, Alfonso; Dexter, Kyle G; Linares-Palomino, Reynaldo; Oliveira-Filho, Ary; Prado, Darién; Pullan, Martin; Quintana, Catalina; Riina, Ricarda; Rodríguez M, Gina M; Weintritt, Julia; Acevedo-Rodríguez, Pedro; Adarve, Juan; Álvarez, Esteban; Aranguren B, Anairamiz; Arteaga, Julián Camilo; Aymard, Gerardo; Castaño, Alejandro; Ceballos-Mago, Natalia; Cogollo, Álvaro; Cuadros, Hermes; Delgado, Freddy; Devia, Wilson; Dueñas, Hilda; Fajardo, Laurie; Fernández, Ángel; Fernández, Miller Ángel; Franklin, Janet; Freid, Ethan H; Galetti, Luciano A; Gonto, Reina; González-M, Roy; Graveson, Roger; Helmer, Eileen H; Idárraga, Álvaro; López, René; Marcano-Vega, Humfredo; Martínez, Olga G; Maturo, Hernán M; McDonald, Morag; McLaren, Kurt; Melo, Omar; Mijares, Francisco; Mogni, Virginia; Molina, Diego; Moreno, Natalia Del Pilar; Nassar, Jafet M; Neves, Danilo M; Oakley, Luis J; Oatham, Michael; Olvera-Luna, Alma Rosa; Pezzini, Flávia F; Dominguez, Orlando Joel Reyes; Ríos, María Elvira; Rivera, Orlando; Rodríguez, Nelly; Rojas, Alicia; Särkinen, Tiina; Sánchez, Roberto; Smith, Melvin; Vargas, Carlos; Villanueva, Boris; Pennington, R Toby

2016-09-23

Seasonally dry tropical forests are distributed across Latin America and the Caribbean and are highly threatened, with less than 10% of their original extent remaining in many countries. Using 835 inventories covering 4660 species of woody plants, we show marked floristic turnover among inventories and regions, which may be higher than in other neotropical biomes, such as savanna. Such high floristic turnover indicates that numerous conservation areas across many countries will be needed to protect the full diversity of tropical dry forests. Our results provide a scientific framework within which national decision-makers can contextualize the floristic significance of their dry forest at a regional and continental scale. Copyright © 2016, American Association for the Advancement of Science.

Seasonal Belowground Ecosystem and Eco-enzymatic Responses to Soil pH and Phosphorus Availability in Temperate Hardwood Forests

Science.gov (United States)

Smemo, K. A.; Deforest, J. L.; Petersen, S. L.; Burke, D.; Hewins, C.; Kluber, L. A.; Kyker, S. R.

2013-12-01

Atmospheric acid deposition can increase phosphorus (P) limitation in temperate hardwood forests by increasing N availability, and therefore P demand, and/or by decreasing pH and occluding inorganic P. However, only recently have studies demonstrated that P limitation can occur in temperate forests and very little is known about the temporal aspects of P dynamics in acidic forest soils and how seasonal shifts in nutrient availability and demand influence microbial investment in extracellular enzymes. The objectives of this study were to investigate how P availability and soil pH influence seasonal patterns of nutrient cycling and soil microbial activity in hardwood forests that experience chronic acid deposition. We experimentally manipulated soil pH, P, or both for three years and examined soil treatment responses in fall, winter, spring, early summer, and late summer. We found that site (glaciated versus unglaciated) and treatment had the most significant influence on nutrient pools and cycling. In general, nutrient pools were higher in glaciated soils than unglaciated for measured nutrients, including total C and N (2-3 times higher), extractable inorganic nitrogen, and readily available P. Treatment had no impact on total C and N pools in either region, but did affect other measured nutrients such as ammonium, which was greatest in the elevated pH treatment for both sites. As expected, readily available P pools were highest in the elevated P treatments (3 fold increase in both sites), but raising pH decreased available P pools in the glaciated site. Raising soil pH increased both net N mineralization rates and net P mineralization rates, regardless of site. Nitrification responses were complex, but we observed an overall significant nitrification increase under elevated pH, particularly in the growing season. Extracellular enzyme activity showed more seasonal patterns than site and treatment effects, exhibiting significant growing season activity reductions for

ABOVE GROUND BIOMASS MICRONUTRIENTS IN A SEASONAL SUBTROPICAL FOREST

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Hamilton Luiz Munari Vogel

2015-06-01

Full Text Available In the above ground biomass of a native forest or plantation are stored large quantities of nutrients, with few studies in the literature, especially concerning micronutrients. The present work aimed to quantify the micronutrients in above ground biomass in a Seasonal Subtropical forest in Itaara-RS, Brazil. For the above ground biomass evaluation, 20 trees of five different diameter classes were felled. The above ground biomass was separated in the following compartments: stem wood, stem bark, branches and leaves. The contents of B, Cu, Fe, Mn and Zn in the biomass samples were determined. The stock of micronutrients in the biomass for each component was obtained based on the estimated dry biomass, multiplied by the nutrient content. The total production of above ground biomass was estimated at 210.0 Mg.ha-1. The branches, stem wood, stem bark and leaves corresponded to 48.8, 43.3, 5.4 and 2.4% of the above ground biomass. The lower levels of B, Cu, Fe and Mn are in stem wood, except for Zn; in the branches and trunk wood are the largest stocks of B, Cu, Fe and Mn. In the branches, leaves and trunk bark are stored most micronutrients, pointing to the importance of these to remain on the soil.

Assessing the Impact of Forest Change and Climate Variability on Dry Season Runoff by an Improved Single Watershed Approach: A Comparative Study in Two Large Watersheds, China

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Yiping Hou

2018-01-01

Full Text Available Extensive studies on hydrological responses to forest change have been published for centuries, yet partitioning the hydrological effects of forest change, climate variability and other factors in a large watershed remains a challenge. In this study, we developed a single watershed approach combining the modified double mass curve (MDMC and the time series multivariate autoregressive integrated moving average model (ARIMAX to separate the impact of forest change, climate variability and other factors on dry season runoff variation in two large watersheds in China. The Zagunao watershed was examined for the deforestation effect, while the Meijiang watershed was examined to study the hydrological impact of reforestation. The key findings are: (1 both deforestation and reforestation led to significant reductions in dry season runoff, while climate variability yielded positive effects in the studied watersheds; (2 the hydrological response to forest change varied over time due to changes in soil infiltration and evapotranspiration after vegetation regeneration; (3 changes of subalpine natural forests produced greater impact on dry season runoff than alteration of planted forests. These findings are beneficial to water resource and forest management under climate change and highlight a better planning of forest operations and management incorporated trade-off between carbon and water in different forests.

CO2 efflux from subterranean nests of ant communities in a seasonal tropical forest, Thailand.

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Hasin, Sasitorn; Ohashi, Mizue; Yamada, Akinori; Hashimoto, Yoshiaki; Tasen, Wattanachai; Kume, Tomonori; Yamane, Seiki

2014-10-01

Many ant species construct subterranean nests. The presence of their nests may explain soil respiration "hot spots", an important factor in the high CO2 efflux from tropical forests. However, no studies have directly measured CO2 efflux from ant nests. We established 61 experimental plots containing 13 subterranean ant species to evaluate the CO2 efflux from subterranean ant nests in a tropical seasonal forest, Thailand. We examined differences in nest CO2 efflux among ant species. We determined the effects of environmental factors on nest CO2 efflux and calculated an index of nest structure. The mean CO2 efflux from nests was significantly higher than those from the surrounding soil in the wet and dry seasons. The CO2 efflux was species-specific, showing significant differences among the 13 ant species. The soil moisture content significantly affected nest CO2 efflux, but there was no clear relationship between nest CO2 efflux and nest soil temperature. The diameter of the nest entrance hole affected CO2 efflux. However, there was no significant difference in CO2 efflux rates between single-hole and multiple-hole nests. Our results suggest that in a tropical forest ecosystem the increase in CO2 efflux from subterranean ant nests is caused by species-specific activity of ants, the nest soil environment, and nest structure.

Forest fire situation analysis over forest reserve land in Tomsk petroleum province

International Nuclear Information System (INIS)

Pasko, O A; Baranova, A V

2015-01-01

The paper delivers the analysis of space-time characteristics of forest fire ignition and spread in the North of Tomsk oblast, i.e. petroleum production area (Kargasok, Parabel and Teguldet districts). It also presents long-term and seasonal forest fire behavior including fire ignition and spread frequency (annual and seasonal), the fire season duration and their zonality. The main driving factors of forest fire ignition both human and natural ones are revealed

Seasonal abundance and activity of pill millipedes ( Arthrosphaera magna) in mixed plantation and semi-evergreen forest of southern India

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Ashwini, Krishna M.; Sridhar, Kandikere R.

2006-01-01

Seasonal occurrence and activity of endemic pill millipedes ( Arthrosphaera magna) were examined in organically managed mixed plantation and semi-evergreen forest reserve in southwest India between November 1996 and September 1998. Abundance and biomass of millipedes were highest in both habitats during monsoon season. Soil moisture, conductivity, organic carbon, phosphate, potassium, calcium and magnesium were higher in plantation than in forest. Millipede abundance and biomass were about 12 and 7 times higher in plantation than in forest, respectively ( P 0.05). Millipede abundance and biomass were positively correlated with rainfall ( P = 0.01). Besides rainfall, millipedes in plantation were positively correlated with soil moisture as well as temperature ( P = 0.001). Among the associated fauna with pill millipedes, earthworms rank first followed by soil bugs in both habitats. Since pill millipedes are sensitive to narrow ecological changes, the organic farming strategies followed in mixed plantation and commonly practiced in South India seem not deleterious for the endangered pill millipedes Arthrosphaera and reduce the risk of local extinctions.

Effects of fire disturbance on soil respiration in the non-growing season in a Larix gmelinii forest in the Daxing'an Mountains, China.

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Hu, Tongxin; Sun, Long; Hu, Haiqing; Guo, Futao

2017-01-01

In boreal forests, fire is an important part of the ecosystem that greatly influences soil respiration, which in turn affects the carbon balance. Wildfire can have a significant effect on soil respiration and it depends on the fire severity and environmental factors (soil temperature and snow water equivalent) after fire disturbance. In this study, we quantified post-fire soil respiration during the non-growing season (from November to April) in a Larix gmelinii forest in Daxing'an Mountains of China. Soil respiration was measured in the snow-covered and snow-free conditions with varying degrees of natural burn severity forests. We found that soil respiration decreases as burn severity increases. The estimated annual C efflux also decreased with increased burn severity. Soil respiration during the non-growing season approximately accounted for 4%-5% of the annual C efflux in all site types. Soil temperature (at 5 cm depth) was the predominant determinant of non-growing season soil respiration change in this area. Soil temperature and snow water equivalent could explain 73%-79% of the soil respiration variability in winter snow-covering period (November to March). Mean spring freeze-thaw cycle (FTC) period (April) soil respiration contributed 63% of the non-growing season C efflux. Our finding is key for understanding and predicting the potential change in the response of boreal forest ecosystems to fire disturbance under future climate change.

Fires in Seasonally Dry Tropical Forest: Testing the Varying Constraints Hypothesis across a Regional Rainfall Gradient.

Science.gov (United States)

Mondal, Nandita; Sukumar, Raman

2016-01-01

The "varying constraints hypothesis" of fire in natural ecosystems postulates that the extent of fire in an ecosystem would differ according to the relative contribution of fuel load and fuel moisture available, factors that vary globally along a spatial gradient of climatic conditions. We examined if the globally widespread seasonally dry tropical forests (SDTFs) can be placed as a single entity in this framework by analyzing environmental influences on fire extent in a structurally diverse SDTF landscape in the Western Ghats of southern India, representative of similar forests in monsoonal south and southeast Asia. We used logistic regression to model fire extent with factors that represent fuel load and fuel moisture at two levels-the overall landscape and within four defined moisture regimes (between 700 and1700 mm yr-1)-using a dataset of area burnt and seasonal rainfall from 1990 to 2010. The landscape scale model showed that the extent of fire in a given year within this SDTF is dependent on the combined interaction of seasonal rainfall and extent burnt the previous year. Within individual moisture regimes the relative contribution of these factors to the annual extent burnt varied-early dry season rainfall (i.e., fuel moisture) was the predominant factor in the wettest regime, while wet season rainfall (i.e., fuel load) had a large influence on fire extent in the driest regime. Thus, the diverse structural vegetation types associated with SDTFs across a wide range of rainfall regimes would have to be examined at finer regional or local scales to understand the specific environmental drivers of fire. Our results could be extended to investigating fire-climate relationships in STDFs of monsoonal Asia.

Water uptake and transport in lianas and co-occurring trees of a seasonally dry tropical forest.

Science.gov (United States)

José Luis Andrade; Frederick C. Meinzer; Guillermo Goldstein; Stefan A. Schnitzer

2005-01-01

Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island, Panama. Stable hydrogen isotope composition (δD) of xylem and soil water, soil volumetric water content (θv), and basal sap flow were measured during the 1997 and...

[Seasonal variation of soil respiration and its components in tropical rain forest and rubber plantation in Xishuangbanna, Yunnan].

Science.gov (United States)

Lu, Hua-Zheng; Sha, Li-Qing; Wang, Jun; Hu, Wen-Yan; Wu, Bing-Xia

2009-10-01

By using trenching method and infrared gas analyzer, this paper studied the seasonal variation of soil respiration (SR), including root respiration (RR) and heterotrophic respiration (HR), in tropical seasonal rain forest (RF) and rubber (Hevea brasiliensis) plantation (RP) in Xishuangbanna of Yunnan, China. The results showed that the SR and HR rates were significantly higher in RF than in RP (P dry-hot season > foggy season, but the RR rate was rainy season > foggy season > dry-hot season in RF, and foggy season > rainy season > dry-hot season in RP. The contribution of RR to SR in RF (29%) was much lower than that in RP (42%, P < 0.01), while the contribution of HR to SR was 71% in RF and 58% in RP. When the soil temperature at 5 cm depth varied from 12 degrees C to 32 degrees C, the Q10 values for SR, HR, and RR rates were higher in RF than in RP. HR had the highest Q10 value, while RR had the lowest one.

Seasonal energetic stress in a tropical forest primate: proximate causes and evolutionary implications.

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Steffen Foerster

Full Text Available Animals facing seasonal variation in food availability experience selective pressures that favor behavioral adjustments such as migration, changes in activity, or shifts in diet. Eclectic omnivores such as many primates can process low-quality fallback food when preferred food is unavailable. Such dietary flexibility, however, may be insufficient to eliminate constraints on reproduction even for species that live in relatively permissive environments, such as moist tropical forests. Focusing on a forest-dwelling primate with a flexible diet (Cercopithecus mitis we investigated whether females experience seasonal energetic stress and how it may relate to reproductive seasonality. We used fecal glucocorticoids (fGCs as an indicator of energetic stress, controlling for the potentially confounding effects of social interactions and reproductive state. We modeled within-female fGC variation with General Linear Mixed Models, evaluating changes in feeding behavior and food availability as main effects. Regardless of reproductive state, fGCs increased when females shifted their diet towards fallback foods (mature leaves and other non-preferred items and when they spent more time feeding, while fGCs decreased with feeding time on preferred items (insects, fruits, young leaves and with the availability of young leaves. Changes in fruit availability had no general effects on fGCs, likely because fruits were sought out regardless of availability. As predicted, females in the energetically demanding stages of late pregnancy and early lactation showed greater increases in fGCs between periods of low versus high availability of fruits and young leaves than females in other reproductive states. Potential social stressors had no measurable effects on fGCs. Preliminary evidence suggests that seasonal energetic stress may affect the timing of infant independence from mothers and contribute to unusually long inter-birth intervals compared to closely related species

Seasonal energetic stress in a tropical forest primate: proximate causes and evolutionary implications.

Science.gov (United States)

Foerster, Steffen; Cords, Marina; Monfort, Steven L

2012-01-01

Animals facing seasonal variation in food availability experience selective pressures that favor behavioral adjustments such as migration, changes in activity, or shifts in diet. Eclectic omnivores such as many primates can process low-quality fallback food when preferred food is unavailable. Such dietary flexibility, however, may be insufficient to eliminate constraints on reproduction even for species that live in relatively permissive environments, such as moist tropical forests. Focusing on a forest-dwelling primate with a flexible diet (Cercopithecus mitis) we investigated whether females experience seasonal energetic stress and how it may relate to reproductive seasonality. We used fecal glucocorticoids (fGCs) as an indicator of energetic stress, controlling for the potentially confounding effects of social interactions and reproductive state. We modeled within-female fGC variation with General Linear Mixed Models, evaluating changes in feeding behavior and food availability as main effects. Regardless of reproductive state, fGCs increased when females shifted their diet towards fallback foods (mature leaves and other non-preferred items) and when they spent more time feeding, while fGCs decreased with feeding time on preferred items (insects, fruits, young leaves) and with the availability of young leaves. Changes in fruit availability had no general effects on fGCs, likely because fruits were sought out regardless of availability. As predicted, females in the energetically demanding stages of late pregnancy and early lactation showed greater increases in fGCs between periods of low versus high availability of fruits and young leaves than females in other reproductive states. Potential social stressors had no measurable effects on fGCs. Preliminary evidence suggests that seasonal energetic stress may affect the timing of infant independence from mothers and contribute to unusually long inter-birth intervals compared to closely related species of similar body

Soil fauna as an indicator of soil quality in forest stands, pasture and secondary forest

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Felipe Vieira da Cunha Neto

2012-11-01

Full Text Available The interactions between soil invertebrates and environmental variations are relatively unknown in the assessment of soil quality. The objective of this study was to evaluate soil quality in areas with different soil management systems, based on soil fauna as indicator, in Além Paraíba, Minas Gerais, Brazil. The soil invertebrate community was sampled using pitfall traps, in the dry and rainy seasons, from areas with five vegetation types (acacia, mimosa, eucalyptus, pasture, and secondary forest. The abundance of organisms and the total and average richness, Shannon's diversity index, the Pielou uniformity index, and change index V were determined. The fauna was most abundant in the areas of secondary forest and mimosa plantations in the dry season (111.3 and 31.7 individuals per trap per day, respectively. In the rainy season, the abundance of organisms in the three vegetation types did not differ. The highest values of average and total richness were recorded in the secondary forest in the dry season and in the mimosa stand in the rainy season. Shannon's index ranged from 1.57 in areas with acacia and eucalyptus in the rainy season to 3.19 in the eucalyptus area in the dry season. The uniformity index was highest in forest stands (eucalyptus, acacia and mimosa in the dry season, but higher in the rainy season in the pasture and secondary forest than in the forest stands. The change index V indicated that the percentage of extremely inhibited groups was lowest in the area with mimosa, both in the dry and rainy season (36 and 23 %, respectively. Of all forest stands, the mimosa area had the most abundant soil fauna.

Floristics and biogeography of vegetation in seasonally dry tropical regions

DEFF Research Database (Denmark)

Dexter, K.G.; Smart, B.; Baldauf, C.

2015-01-01

To provide an inter-continental overview of the floristics and biogeography of drought-adapted tropical vegetation formations, we compiled a dataset of inventory plots in South America (n=93), Africa (n=84), and Asia (n=92) from savannas (subject to fire), seasonally dry tropical forests (not...... similar vegetation formations (e.g. savannas) are floristically highly dissimilar. Neotropical moist forest, savanna and seasonally dry tropical forest are floristically distinct, but elsewhere there is no clear floristic division of savanna and seasonally dry tropical forest, though moist and dry...... of the ecology, biology and conservation of savannas and seasonally dry tropical forests may be difficult....

Effects of fire disturbance on soil respiration in the non-growing season in a Larix gmelinii forest in the Daxing'an Mountains, China.

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Tongxin Hu

Full Text Available In boreal forests, fire is an important part of the ecosystem that greatly influences soil respiration, which in turn affects the carbon balance. Wildfire can have a significant effect on soil respiration and it depends on the fire severity and environmental factors (soil temperature and snow water equivalent after fire disturbance. In this study, we quantified post-fire soil respiration during the non-growing season (from November to April in a Larix gmelinii forest in Daxing'an Mountains of China. Soil respiration was measured in the snow-covered and snow-free conditions with varying degrees of natural burn severity forests. We found that soil respiration decreases as burn severity increases. The estimated annual C efflux also decreased with increased burn severity. Soil respiration during the non-growing season approximately accounted for 4%-5% of the annual C efflux in all site types. Soil temperature (at 5 cm depth was the predominant determinant of non-growing season soil respiration change in this area. Soil temperature and snow water equivalent could explain 73%-79% of the soil respiration variability in winter snow-covering period (November to March. Mean spring freeze-thaw cycle (FTC period (April soil respiration contributed 63% of the non-growing season C efflux. Our finding is key for understanding and predicting the potential change in the response of boreal forest ecosystems to fire disturbance under future climate change.

Seasonal and depth effects on some parameters of a forest soil

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Dimas Augusto Morozin Zaia

2009-03-01

Full Text Available The main goal of this paper is to study the effect of wet/dry season and the depth on several parameters of the forest soil. This work has shown that the concentration of Al3+ increases and that the concentration of exchangeable cations (Ca2+, Mg2+ and pHs (distilled water and CaCl2 decreases with the increase in depth and that these results are correlated. The concentrations of exchangeable cations (Al3+, Ca2+, Mg2+ and organic matter (OM are affected by dry/wet season. Rain increases the solubility of organic carbon, thus decreasing OM and releasing exchangeable cations (Al3+, Ca2+, Mg2+. P (available shows an increase in its concentration with an increase in depth. The low concentration of P (available in the soil samples could be due to the low pH of the soils. The value of pHpzc is influenced by exchangeable cations (Al3+, Ca2+, Mg2+, and the pHs (CaCl2 and distilled water are higher than pHpzc. This means that the net charge of these soils is negative. CEC and CECpotential decrease with the increase in depth in most soil samples. For mostly of the samples, the season (wet/dry does not affect CEC, CECpotential, K+, or Na+.

Seasonal photochemical transformations of nitrogen species in a forest stream and lake.

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Petr Porcal

Full Text Available The photochemical release of inorganic nitrogen from dissolved organic matter is an important source of bio-available nitrogen (N in N-limited aquatic ecosystems. We conducted photochemical experiments and used mathematical models based on pseudo-first-order reaction kinetics to quantify the photochemical transformations of individual N species and their seasonal effects on N cycling in a mountain forest stream and lake (Plešné Lake, Czech Republic. Results from laboratory experiments on photochemical changes in N speciation were compared to measured lake N budgets. Concentrations of organic nitrogen (Norg; 40-58 µmol L-1 decreased from 3 to 26% during 48-hour laboratory irradiation (an equivalent of 4-5 days of natural solar insolation due to photochemical mineralization to ammonium (NH4+ and other N forms (Nx; possibly N oxides and N2. In addition to Norg mineralization, Nx also originated from photochemical nitrate (NO3- reduction. Laboratory exposure of a first-order forest stream water samples showed a high amount of seasonality, with the maximum rates of Norg mineralization and NH4+ production in winter and spring, and the maximum NO3- reduction occurring in summer. These photochemical changes could have an ecologically significant effect on NH4+ concentrations in streams (doubling their terrestrial fluxes from soils and on concentrations of dissolved Norg in the lake. In contrast, photochemical reactions reduced NO3- fluxes by a negligible (<1% amount and had a negligible effect on the aquatic cycle of this N form.

Fire decreases arthropod abundance but increases diversity: Early and late season prescribed fire effects in a Sierra Nevada mixed-conifer forest

Science.gov (United States)

Ferrenberg, Scott; Schwilk, Dylan W.; Knapp, Eric E.; Groth, Eric; Keeley, Jon E.

2006-01-01

Prior to fire suppression in the 20th century, the mixed-conifer forests of the Sierra Nevada, California, U.S.A., historically burned in frequent fires that typically occurred during the late summer and early fall. Fire managers have been attempting to restore natural ecosystem processes through prescription burning, and have often favored burning during the fall in order to mimic historical fire regimes. Increasingly, however, prescription burning is also being done during the late spring and early summer in order to expand the window of opportunity for needed fuel reduction burning. The effect of prescribed fires outside of the historical fire season on forest arthropods is not known. The objective of this study was to compare the short-term effects of prescribed fires ignited in the early and late fire season on forest floor arthropods. Arthropod abundance and diversity were assessed using pitfall trapping in replicated burn units in Sequoia National Park, California. Overall, abundance of arthropods was lower in the burn treatments than in the unburned control. However, diversity tended to be greater in the burn treatments. Fire also altered the relative abundances of arthropod feeding guilds. No significant differences in arthropod community structure were found between early and late season burn treatments. Instead, changes in the arthropod community appeared to be driven largely by changes in fuel loading, vegetation, and habitat heterogeneity, all of which differed more between the burned and unburned treatments than between early and late season burn treatments.

Growing season length as a key factor of cumulative net ecosystem exchange over the pine forest ecosystems in Europe

Czech Academy of Sciences Publication Activity Database

Danielewska, A.; Urbaniak, M.; Olejnik, Janusz

2015-01-01

Roč. 29, č. 2 (2015), s. 129-135 ISSN 0236-8722 Institutional support: RVO:67179843 Keywords : forest * carbon dioxide * eddy covariance * growing season length Subject RIV: EH - Ecology, Behaviour Impact factor: 1.067, year: 2015

Floristic structure and biomass distribution of a tropical seasonal rain forest in Xishuangbanna, southwest China

Energy Technology Data Exchange (ETDEWEB)

Shanmughavel, P.; Zheng Zheng; Sha Liqing; Cao Min [Chinese Academy of Sciences, Kunming (China). Dept. of Forest Ecology

2001-07-01

The aim of this research was to study the forest community structure, tree species diversity and biomass production of a tropical seasonal rain forest in Xishuangbanna, southwest China. The community structure showed a diversified species composition and supported many species of economic significance. This tropical rain forest in closely related to Malaysian forests. The biomass and its distribution were studied using standard regression analysis and the clear-cut method for shrubs and herbs. The total biomass was 360.9 t/ha and its allocation in different layers was: tree layer 352.5 t/ha, shrub layer 4.7 t/ha, liana 3.1 t/ha and herb layer 0.5 t/ha. Most of the biomass was concentrated in the trees: stem 241.2 t/ha, root 69.6 t/ha, branch 37.2 t/ha and leaves 4.3 t/ha. The DBH class allocation of the tree biomass was concentrated in the middle DBH class. The biomass of six DBH classes from 20 to 80 cm was 255.4 t/ha. There are twenty-six species with biomass over 0.5% of the total biomass of the tree layer, and three species with biomass over 5%, i.e., Pometia tomentosa, Barringtonia macrostachya (5.4%) and Terminalia myriocarpa (5.2%). Data on stem, branch, leaves and root of the individual tree species were used to develop regression models. D{sup 2}H was found to be the best estimator of the biomass in this tropical rain forest. However, higher biomass figures have been reported from tropical forests elsewhere e.g., 415-520 t/ha in the tropical forests of Cambodia, the tropical moist mixed dipterocarp forests, and the tropical moist logged moist evergreen-high, medium, and low yield forests of Sri Lanka. In some forests, lower accumulation of biomass was reported, e.g., 10-295 t/ha in the tropical moist forests of Bangladesh, the tropical moist dense forest of Cambodia, the tropical dry forests of India, the tropical moist forests of Peninsular-Malaysia, the tropical moist mixed dipterocarp forests of Sarawak-Malaysia, the tropical evergreen forests of

Seasonal Changes in Microbial Community Structure in Freshwater Stream Sediment in a North Carolina River Basin

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John P. Bucci

2014-01-01

Full Text Available This study examined seasonal differences in microbial community structure in the sediment of three streams in North Carolina’s Neuse River Basin. Microbes that reside in sediment are at the base of the food chain and have a profound influence on the health of freshwater stream environments. Terminal-Restriction Fragment Length Polymorphism (T-RFLP, molecular fingerprint analysis of 16S rRNA genes was used to examine the diversity of bacterial species in stream sediment. Sediment was sampled in both wet and dry seasons from an agricultural (Bear, mixed urban (Crabtree and forested (Marks Creek, and the microbiota examined. Gamma, Alpha and Beta proteobacteria were prevalent species of microbial taxa represented among all sites. Actinobacteria was the next most prevalent species observed, with greater occurrence in dry compared to the wet season. Discernable clustering was observed of Marks and Bear Creek samples collected during the wetter period (September–April, which corresponded with a period of higher precipitation and cooler surface water temperatures. Although not statistically significant, microbial community structure appeared different between season (ANOSIM, R = 0.60; p < 0.10. Principal components analysis confirmed this pattern and showed that the bacterial groups were separated by wet and dry seasonal periods. These results suggest seasonal differences among the microbial community structure in sediment of freshwater streams and that these communities may respond to changes in precipitation during wetter periods.

Role of burning season on initial understory vegetation response to prescribed fire in a mixed conifer forest

Science.gov (United States)

Knapp, E.E.; Schwilk, D.W.; Kane, J.M.; Keeley, J.E.

2007-01-01

Although the majority of fires in the western United States historically occurred during the late summer or early fall when fuels were dry and plants were dormant or nearly so, early-season prescribed burns are often ignited when fuels are still moist and plants are actively growing. The purpose of this study was to determine if burn season influences postfire vegetation recovery. Replicated early-season burn, late-season burn, and unburned control units were established in a mixed conifer forest, and understory vegetation was evaluated before and after treatment. Vegetation generally recovered rapidly after prescribed burning. However, late-season burns resulted in a temporary but significant drop in cover and a decline in species richness at the 1 m 2 scale in the following year. For two of the several taxa that were negatively affected by burning, the reduction in frequency was greater after late-season than early-season burns. Early-season burns may have moderated the effect of fire by consuming less fuel and lessening the amount of soil heating. Our results suggest that, when burned under high fuel loading conditions, many plant species respond more strongly to differences in fire intensity and severity than to timing of the burn relative to stage of plant growth. ?? 2007 NRC.

Evaluating the utility and seasonality of NDVI values for assessing post-disturbance recovery in a subalpine forest.

Science.gov (United States)

Buma, Brian

2012-06-01

Forest disturbances around the world have the potential to alter forest type and cover, with impacts on diversity, carbon storage, and landscape composition. These disturbances, especially fire, are common and often large, making ground investigation of forest recovery difficult. Remote sensing offers a means to monitor forest recovery in real time, over the entire landscape. Typically, recovery monitoring via remote sensing consists of measuring vegetation indices (e.g., NDVI) or index-derived metrics, with the assumption that recovery in NDVI (for example) is a meaningful measure of ecosystem recovery. This study tests that assumption using MODIS 16-day imagery from 2000 to 2010 in the area of the Colorado's Routt National Forest Hinman burn (2002) and seedling density counts taken in the same area. Results indicate that NDVI is rarely correlated with forest recovery, and is dominated by annual and perennial forb cover, although topography complicates analysis. Utility of NDVI as a means to delineate areas of recovery or non-recovery are in doubt, as bootstrapped analysis indicates distinguishing power only slightly better than random. NDVI in revegetation analyses should carefully consider the ecology and seasonal patterns of the system in question.

Evaporation components of a boreal forest: variations during the growing season

Science.gov (United States)

Grelle, A.; Lundberg, A.; Lindroth, A.; Morén, A.-S.; Cienciala, E.

1997-10-01

To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.

Fire, climate and vegetation linkages in the Bolivian Chiquitano seasonally dry tropical forest.

Science.gov (United States)

Power, M J; Whitney, B S; Mayle, F E; Neves, D M; de Boer, E J; Maclean, K S

2016-06-05

South American seasonally dry tropical forests (SDTFs) are critically endangered, with only a small proportion of their original distribution remaining. This paper presents a 12 000 year reconstruction of climate change, fire and vegetation dynamics in the Bolivian Chiquitano SDTF, based upon pollen and charcoal analysis, to examine the resilience of this ecosystem to drought and fire. Our analysis demonstrates a complex relationship between climate, fire and floristic composition over multi-millennial time scales, and reveals that moisture variability is the dominant control upon community turnover in this ecosystem. Maximum drought during the Early Holocene, consistent with regional drought reconstructions, correlates with a period of significant fire activity between 8000 and 7000 cal yr BP which resulted in a decrease in SDTF diversity. As fire activity declined but severe regional droughts persisted through the Middle Holocene, SDTFs, including Anadenanthera and Astronium, became firmly established in the Bolivian lowlands. The trend of decreasing fire activity during the last two millennia promotes the idea among forest ecologists that SDTFs are threatened by fire. Our analysis shows that the Chiquitano seasonally dry biome has been more resilient to Holocene changes in climate and fire regime than previously assumed, but raises questions over whether this resilience will continue in the future under increased temperatures and drought coupled with a higher frequency anthropogenic fire regime.This article is part of the themed issue 'The interaction of fire and mankind'. © 2016 The Author(s).

Detrimental effects of low atmospheric humidity and forest fire on a community of western Himalayan butterflies

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P. Smetacek

2011-04-01

Full Text Available Compared to previous years, the period from October 2008 to March 2009 showed marked reductions in species number and population size in the butterfly community of the Maheshkhan Reserve Forest, Nainital District, Uttarakhand. Desiccation of pupae due to abnormally low atmospheric humidity after the failure of seasonal rains appears to have been a major cause of this reduction. The drop in humidity also appears to be linked to the unusual spread of fires affecting broadleaf forests, one of which in May 2009 wiped out the remaining Maheshkhan butterfly community.

Strong carbon sink of monsoon tropical seasonal forest in Southern Vietnam

Science.gov (United States)

Deshcherevskaya, Olga; Anichkin, Alexandr; Avilov, Vitaly; Duy Dinh, Ba; Luu Do, Phong; Huan Tran, Cong; Kurbatova, Julia

2014-05-01

EC procedures were applied to the raw 10-Hz data, including time-lag compensation, block average, WPL-correction, planar fit, low- and high-frequency corrections etc. in EddyPro software (LI-COR Inc., USA). Calculated fluxes with bad quality flags (more than 6 of 9) were excluded. Spikes due to rains, instrument malfunction were removed too. Storage of CO2 from the surface to the measurement level which is very significant in tall tropical forest was added to the flux. Then low-turbulence correction was applied with u*-threshold of 0.178 m s-1. After these steps only 43 % of 30-min data of 2012 still presented, so the rate of gaps was 57 % (mainly at night and in rains). Data were gapfilled using on-line tool at the web-site of Max-Plank Institute, Germany and Flux-Analysis Tool, Japan. Different gap-filling procedures (non-linear regressions, look-up tables, model evaluation, artificial gaps-method) as well as u*-threshold shifting from 0 to 0.25 resulted in drift of 2012 net carbon exchange total from -296 to -612 g C m-2 (strong carbon sink still remain). Unfortunately, the situation of more then 50 % of gaps in CO2 flux is usual for tropical EC stations because of frequent calm nights. So, a gap-filling algorithm is extremely important for evaluation of long-term totals. We found for Vietnamese data that even few spikes which were not removed before gap-filling can change all-year total by up to 20-50 g m-2 year-1. Especially 'powerful' are big positive values at night in rare-occurred good turbulence. Possibly these values are physical. But they influence regressions in look-up table method dramatically because amount of data in peak of rainy season in night-time is too small. So, the gap-filling algorithm happened to be very sensitive to spikes. Additionally, striking was the fact that storage of CO2 appeared to be the main factor influencing 1-year totals after gap-filling procedure. Taking storage into account shifted the 2012 sum from +182 to -402 g m-2 year

Seasonal Snowpack Dynamics and Runoff in a Maritime Forested Basin, Niigata, Japan

Science.gov (United States)

Whitaker, A. C.; Sugiyama, H.

2005-12-01

Seasonal snowpack dynamics are described through field measurements under contrasting canopy conditions for a mountainous catchment in the Japan Sea region. Microclimatic data, snow accumulation, albedo and lysimeter runoff is given through three complete winter seasons 2002-05 in: (1) mature cedar stand, (2) larch stand, and (3) regenerating cedar stand or opening. The accumulation and melt of seasonal snowpack strongly influences streamflow runoff during December to May, including winter base-flow, mid-winter melt, rain-on-snow, and diurnal peaks driven by radiation melt in spring. Lysimeter runoff at all sites is characterised by constant ground melt of 0.8-1.0 mm/day. Rapid response to mid-winter melt or rainfall shows that the snowpack remains in a ripe or near-ripe condition throughout the snowcover season. Hourly and daily lysimeter discharge was greatest during rain-on-snow with the majority of runoff due to rainfall passing through the snowpack as opposed to snowmelt. For both rain-on-snow and radiation melt events lysimeter discharge was generally greatest at the open site, although there were exceptions such as during interception melt events. During radiation melt instantaneous discharge was up to 4.0 times greater in the opening compared to the mature cedar, and 48-hour discharge was up to 2.5 times greater. Perhaps characteristic of maritime climates, forest interception melt is shown to be important in addition to sublimation in reducing snow accumulation beneath dense canopies. While sublimation represents a loss from the catchment water balance, interception melt percolates through the snowpack and contributes to soil moisture during the winter season. Strong differences in microclimate and snowpack albedo persisted between cedar, larch and open sites, and it is suggested further work is needed to account for this in hydrological simulation models.

Nutrient intake and balancing among female Colobus angolensis palliatus inhabiting structurally distinct forest areas: Effects of group, season, and reproductive state.

Science.gov (United States)

Dunham, Noah T; Rodriguez-Saona, Luis E

2018-06-08

Understanding intraspecific behavioral and dietary variation is critical for assessing primate populations' abilities to persist in habitats characterized by increasing anthropogenic disturbances. While it is evident that some species exhibit considerable dietary flexibility (in terms of species-specific plant parts) in relation to habitat disturbance, it is unclear if primates are characterized by similar variation and flexibility regarding nutrient intake. This study examined the effects of group, season, and reproductive state on nutrient intake and balancing in adult female Colobus angolensis palliatus in the Diani Forest, Kenya. During July 2014 to December 2015, estimates of nutrient intake were recorded for eight females from three groups inhabiting structurally and ecologically distinct forest areas differing in tree species composition and density. There were differences in metabolizable energy (ME) and macronutrient intakes among groups, seasons, and reproductive states. Most notably, females inhabiting one of the more disturbed forest areas consumed less ME and macronutrients compared to females in the more intact forest area. Contrary to prediction, females in early lactation consumed significantly less ME and macronutrients compared to non-lactating and late lactation females. Despite differences in macronutrient intake, the relative contribution of macronutrients to ME were generally more conservative among groups, seasons, and reproductive states. Average daily intake ratios of non-protein energy to available protein ranged from approximately 3.5:1-4.3:1 among groups. These results indicate that female C. a. palliatus demonstrate a consistent nutrient balancing strategy despite significant intergroup differences in consumption of species-specific plant parts. Data from additional colobine species inhabiting different forest types are required to assess the extent to which nutrient balancing is constrained by phylogeny or is more flexible to local

Stratification and seasonal stability of diverse bacterial communities in a Pinus merkusii (pine) forest soil in central Java, Indonesia.

NARCIS (Netherlands)

Krave, A.S.; Lin, B.; Braster, M.; Laverman, A.M.; van Straalen, N.M.; Roling, W.F.M.; van Verseveld, H.W.

2002-01-01

In Java, Indonesia, many nutrient-poor soils are intensively reforested with Pinus merkusii (pine). Information on nutrient cycles and microorganisms involved in these cycles will benefit the management of these important forests. Here, seasonal effects on the stratification of bacterial community

Combustion efficiency and emission factors for wildfire-season fires in mixed conifer forests of the northern Rocky Mountains, US

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S. P. Urbanski

2013-07-01

Full Text Available In the US, wildfires and prescribed burning present significant challenges to air regulatory agencies attempting to achieve and maintain compliance with air quality regulations. Fire emission factors (EF are essential input for the emission models used to develop wildland fire emission inventories. Most previous studies quantifying wildland fire EF of temperate ecosystems have focused on emissions from prescribed burning conducted outside of the wildfire season. Little information is available on EF for wildfires in temperate forests of the conterminous US. The goal of this work is to provide information on emissions from wildfire-season forest fires in the northern Rocky Mountains, US. In August 2011, we deployed airborne chemistry instruments and sampled emissions over eight days from three wildfires and a prescribed fire that occurred in mixed conifer forests of the northern Rocky Mountains. We measured the combustion efficiency, quantified as the modified combustion efficiency (MCE, and EF for CO2, CO, and CH4. Our study average values for MCE, EFCO2, EFCO, and EFCH4 were 0.883, 1596 g kg−1, 135 g kg−1, 7.30 g kg−1, respectively. Compared with previous field studies of prescribed fires in temperate forests, the fires sampled in our study had significantly lower MCE and EFCO2 and significantly higher EFCO and EFCH4. The fires sampled in this study burned in areas reported to have moderate to heavy components of standing dead trees and down dead wood due to insect activity and previous fire, but fuel consumption data was not available. However, an analysis of MCE and fuel consumption data from 18 prescribed fires reported in the literature indicates that the availability of coarse fuels and conditions favorable for the combustion of these fuels favors low MCE fires. This analysis suggests that fuel composition was an important factor contributing to the low MCE of the fires measured in this study. This study only measured EF for CO2, CO

Reducing the uncertainty of parameters controlling seasonal carbon and water fluxes in Chinese forests and its implication for simulated climate sensitivities

Science.gov (United States)

Li, Yue; Yang, Hui; Wang, Tao; MacBean, Natasha; Bacour, Cédric; Ciais, Philippe; Zhang, Yiping; Zhou, Guangsheng; Piao, Shilong

2017-08-01

Reducing parameter uncertainty of process-based terrestrial ecosystem models (TEMs) is one of the primary targets for accurately estimating carbon budgets and predicting ecosystem responses to climate change. However, parameters in TEMs are rarely constrained by observations from Chinese forest ecosystems, which are important carbon sink over the northern hemispheric land. In this study, eddy covariance data from six forest sites in China are used to optimize parameters of the ORganizing Carbon and Hydrology In Dynamics EcosystEms TEM. The model-data assimilation through parameter optimization largely reduces the prior model errors and improves the simulated seasonal cycle and summer diurnal cycle of net ecosystem exchange, latent heat fluxes, and gross primary production and ecosystem respiration. Climate change experiments based on the optimized model are deployed to indicate that forest net primary production (NPP) is suppressed in response to warming in the southern China but stimulated in the northeastern China. Altered precipitation has an asymmetric impact on forest NPP at sites in water-limited regions, with the optimization-induced reduction in response of NPP to precipitation decline being as large as 61% at a deciduous broadleaf forest site. We find that seasonal optimization alters forest carbon cycle responses to environmental change, with the parameter optimization consistently reducing the simulated positive response of heterotrophic respiration to warming. Evaluations from independent observations suggest that improving model structure still matters most for long-term carbon stock and its changes, in particular, nutrient- and age-related changes of photosynthetic rates, carbon allocation, and tree mortality.

Using interviews and biological sign surveys to infer seasonal use of forested and agricultural portions of a human-dominated landscape by Asian elephants in Nepal

Science.gov (United States)

Lamichhane, Babu Ram; Subedi, Naresh; Pokheral, Chiranjibi Prasad; Dhakal, Maheshwar; Acharya, Krishna Prasad; Pradhan, Narendra Man Babu; Smith, James L. David; Malla, Sabita; Thakuri, Bishnu Singh; Yackulic, Charles B.

2018-01-01

Understanding how wide-ranging animals use landscapes in which human use is highly heterogeneous is important for determining patterns of human–wildlife conflict and designing mitigation strategies. Here, we show how biological sign surveys in forested components of a human-dominated landscape can be combined with human interviews in agricultural portions of a landscape to provide a full picture of seasonal use of different landscape components by wide-ranging animals and resulting human–wildlife conflict. We selected Asian elephants (Elephas maximus) in Nepal to illustrate this approach. Asian elephants are threatened throughout their geographic range, and there are large gaps in our understanding of their landscape-scale habitat use. We identified all potential elephant habitat in Nepal and divided the potential habitat into sampling units based on a 10 km by 10 km grid. Forested areas within grids were surveyed for signs of elephant use, and local villagers were interviewed regarding elephant use of agricultural areas and instances of conflict. Data were analyzed using single-season and multi-season (dynamic) occupancy models. A single-season occupancy model applied to data from 139 partially or wholly forested grid cells estimated that 0.57 of grid cells were used by elephants. Dynamic occupancy models fit to data from interviews across 158 grid cells estimated that monthly use of non-forested, human-dominated areas over the preceding year varied between 0.43 and 0.82 with a minimum in February and maximum in October. Seasonal patterns of crop raiding by elephants coincided with monthly elephant use of human-dominated areas, and serious instances of human–wildlife conflict were common. Efforts to mitigate human–elephant conflict in Nepal are likely to be most effective if they are concentrated during August through December when elephant use of human-dominated landscapes and human–elephant conflict are most common.

Use of the space by the opossum Didelphis aurita Wied-Newied (Mammalia, Marsupialia in a mixed forest fragment of southern Brazil

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Cáceres Nilton Carlos

2003-01-01

Full Text Available Use of the space by the opossum Didelphis aurita Wied-Newied, 1826 (Mammalia, Marsupialia in a mixed forest fragment of southern Brazil. The space use of the marsupial Didelphis aurita was studied in a forest fragment of southern Brazil from February 1995 to January 1996. The method used was the 'distribution utilization' in which each trap was set in 38 x 38 m quadrats. Captures of each marked individual in each point give information on its habitat use. Food availability was searched and compared to the habitat utilization and to the food consumption of opossums. Distribution patterns of captures (aggregated to random and spatial overlap between individuals were searched. Results showed aggregated distributions of individuals, particularly females, in the fragment. Females used exclusively the fragment during the drier season. Opossums tend to not choose the sites with highest food availability to establish home ranges. Spatial overlap was usually low between forest resident and neighbouring resident females, but much lower during the breeding season (only forest resident females in an apparently pattern of territoriality. Hence, core areas of females decreased in size during the breeding season. Males probably searched primarily for mates during the breeding season being less opportunistic than females in feeding habits, yet their space use did not correlate to food consumption.

Forest meteorology research within the Oak Ridge site, eastern deciduous forest biome, USIBP

International Nuclear Information System (INIS)

Hutchison, B.A.; Matt, D.R.

1977-01-01

The data presented here indicate that the diurnal trends in forest microclimate are dominated by the diurnal trend in incident solar radiation amounts and the diurnal changes in solar elevations. Absolute values of these microclimatic variables, on the other hand, reflect strongly, the synoptic climatic conditions present and, to a lesser degree, the interactions among synoptic climatic parameters, forest structure, forest physiology, and soil moisture conditions. The seasonal changes in forest microclimate are the result of changes in incident radiation amounts, earth-sun geometry, and phenological change in forest structure along with seasonal changes in synoptic climatic parameters. The temporal and spatial variations of solar radiation within and above a deciduous forest composed predominately of tulip poplar (biriodendron tulipifera) were documented and on attempt was made to relate the variations to forest structure

Feeding patterns of red deer along altitudinal gradient in the Bohemian Forest: the effect of habitat and season

Czech Academy of Sciences Publication Activity Database

Krojerová-Prokešová, Jarmila; Barančeková, Miroslava; Šustr, P.; Heurich, M.

2010-01-01

Roč. 16, č. 2 (2010), s. 173-184 ISSN 0909-6396 R&D Projects: GA MŠk LC06073 Institutional research plan: CEZ:AV0Z60930519 Keywords : Bavarian Forest National Park * red deer * PCA * seasonal and spatial variation * Šumava National Park Subject RIV: EG - Zoology Impact factor: 0.697, year: 2010

Effects of riparian buffers on hydrology of northern seasonal ponds

Science.gov (United States)

Randall K. Kolka; Brian J. Palik; Daniel P. Tersteeg; James C. Bell

2011-01-01

Although seasonal ponds are common in northern, glaciated, forested landscapes, forest management guidelines are generally lacking for these systems. The objective of this study was to determine the effect of riparian buffer type on seasonal pond hydrology following harvest of the adjacent upland forest. A replicated block design consisting of four buffer treatments...

Seasonal Pattern of Decomposition and N, P, and C Dynamics in Leaf litter in a Mongolian Oak Forest and a Korean Pine Plantation

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Jaeeun Sohng

2014-10-01

Full Text Available Distinct seasons and diverse tree species characterize temperate deciduous forests in NE Asia, but large areas of deciduous forests have been converted to conifer plantations. This study was conducted to understand the effects of seasons and tree species on leaf litter decomposition in a temperate forest. Using the litterbag method, the decomposition rate and nitrogen, phosphorous, and carbon dynamics of Mongolian oak (Quercus mongolica, Korean pine (Pinus koraiensis, and their mixed leaf litter were compared for 24 months in a Mongolian oak stand, an adjacent Korean pine plantation, and a Mongolian oak—Korean pine mixed stand. The decomposition rates of all the leaf litter types followed a pattern of distinct seasonal changes: most leaf litter decomposition occurred during the summer. Tree species was less influential on the leaf litter decomposition. The decomposition rates among different leaf litter types within the same stand were not significantly different, indicating no mixed litter effect. The immobilization of leaf litter N and P lasted for 14 months. Mongolian oak leaf litter and Korean pine leaf litter showed different N and P contents and dynamics during the decomposition, and soil P2O5 was highest in the Korean pine plantation, suggesting effects of plantation on soil nutrient budget.

The role of arbuscular mycorrhizal fungi on the early-stage restoration of seasonally dry tropical forest in Chamela, Mexico

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Pilar Huante

2012-04-01

Full Text Available It was evaluated the effect of two different sources of local inocula from two contrasting sites (mature forest, pasture of arbuscular mycorrhizae fungi (AMF and a non-mycorrhizal control on the plant growth of six woody species differing in functional characteristics (slow-, intermediate- and fast-growth, when introduced in a seasonally tropical dry forest (STDF converted into abandoned pasture. Six plots (12 X 12m were set as AMF inoculum source. Six replicates of six different species arranged in a Latin Square design were set in each plot. Plant height, cover area and the number of leaves produced by individual plant was measured monthly during the first growing season in each treatment. Species differed in their ability to benefit from AMF and the largest responsiveness in plant height and leaf production was exhibited by the slow-growing species Swietenia humilis, Hintonia latiflora and Cordia alliodora. At the end of the growing season (November, the plant height of the fast growing species Tabebuia donnel-smithii, Ceiba pentandra and Guazuma ulmifolia were not influenced by AMF. However, inocula of AMF increased leaf production of all plant species regardless the functional characteristics of the species, suggesting a better exploitation of above-ground space and generating a light limited environment under the canopy, which contributed to pasture suppression. Inoculation of seedlings planted in abandoned pasture areas is recommended for ecological restoration due to the high responsiveness of seedling growth in most of species. Use of forest inoculum with its higher diversity of AMF could accelerate the ecological restoration of the above and below-ground comunities.

Identifying spatial clustering properties of the 1997-2003 Liguria (Northern Italy) forest-fire sequence

International Nuclear Information System (INIS)

Telesca, Luciano; Amatulli, Giuseppe; Lasaponara, Rosa; Lovallo, Michele; Santulli, Adriano

2007-01-01

The spatial clustering of the forest-fire sequence (1997-2003) of Liguria Region (Northern Italy) has been analysed using the correlation dimension D C , calculated by means of the correlation integral method. Studying the variations of this parameter, we recognize the presence of a strong variability of the spatial clusterization, modulated by seasonal cycles. Furthermore, we found that the larger fires (size >400 ha) mark the cyclic behaviour of the correlation dimension

Diversity and aboveground biomass of lianas in the tropical seasonal rain forests of Xishuangbanna, SW China

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Xiao-Tao Lü

2009-06-01

Full Text Available Lianas are important components of tropical forests and have significant impacts on the diversity, structure and dynamics of tropical forests. The present study documented the liana flora in a Chinese tropical region. Species richness, abundance, size-class distribution and spatial patterns of lianas were investigated in three 1-ha plots in tropical seasonal rain forests in Xishuangbanna, SW China. All lianas with = 2 cm diameter at breast height (dbh were measured, tagged and identified. A total of 458 liana stems belonging to 95 species (ranging from 38 to 50 species/ha, 59 genera and 32 families were recorded in the three plots. The most well-represented families were Loganiaceae, Annonceae, Papilionaceae, Apocynaceae and Rhamnaceae. Papilionaceae (14 species recorded was the most important family in the study forests. The population density, basal area and importance value index (IVI varied greatly across the three plots. Strychnos cathayensis, Byttneria grandifolia and Bousigonia mekongensis were the dominant species in terms of IVI across the three plots. The mean aboveground biomass of lianas (3 396 kg/ha accounted for 1.4% of the total community aboveground biomass. The abundance, diversity and biomass of lianas in Xishuangbanna tropical seasonal rain forests are lower than those in tropical moist and wet forests, but higher than those in tropical dry forests. This study provides new data on lianas from a geographical region that has been little-studied. Our findings emphasize that other factors beyond the amount and seasonality of precipitation should be included when considering the liana abundance patterns across scales. Rev. Biol. Trop. 57 (1-2: 211-222. Epub 2009 June 30.Las lianas son componentes importantes de los bosques tropicales y tienen importantes impactos en la diversidad, la estructura y la dinámica de los bosques tropicales. El presente estudio documenta la flora de lianas en una región tropical estacional china. La

Temporal variability of the NPP-GPP ratio at seasonal and interannual time scales in a temperate beech forest

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M. Campioli

2011-09-01

Full Text Available The allocation of carbon (C taken up by the tree canopy for respiration and production of tree organs with different construction and maintenance costs, life span and decomposition rate, crucially affects the residence time of C in forests and their C cycling rate. The carbon-use efficiency, or ratio between net primary production (NPP and gross primary production (GPP, represents a convenient way to analyse the C allocation at the stand level. In this study, we extend the current knowledge on the NPP-GPP ratio in forests by assessing the temporal variability of the NPP-GPP ratio at interannual (for 8 years and seasonal (for 1 year scales for a young temperate beech stand, reporting dynamics for both leaves and woody organs, in particular stems. NPP was determined with biometric methods/litter traps, whereas the GPP was estimated via the eddy covariance micrometeorological technique.

The interannual variability of the proportion of C allocated to leaf NPP, wood NPP and leaf plus wood NPP (on average 11% yr⁻¹, 29% yr⁻¹ and 39% yr⁻¹, respectively was significant among years with up to 12% yr⁻¹ variation in NPP-GPP ratio. Studies focusing on the comparison of NPP-GPP ratio among forests and models using fixed allocation schemes should take into account the possibility of such relevant interannual variability. Multiple linear regressions indicated that the NPP-GPP ratio of leaves and wood significantly correlated with environmental conditions. Previous year drought and air temperature explained about half of the NPP-GPP variability of leaves and wood, respectively, whereas the NPP-GPP ratio was not decreased by severe drought, with large NPP-GPP ratio on 2003 due mainly to low GPP. During the period between early May and mid June, the majority of GPP was allocated to leaf and stem NPP, whereas these sinks were of little importance later on. Improved estimation of seasonal GPP and of the

Synchrony, compensatory dynamics, and the functional trait basis of phenological diversity in a tropical dry forest tree community: effects of rainfall seasonality

Science.gov (United States)

Lasky, Jesse R.; Uriarte, María; Muscarella, Robert

2016-11-01

Interspecific variation in phenology is a key axis of functional diversity, potentially mediating how communities respond to climate change. The diverse drivers of phenology act across multiple temporal scales. For example, abiotic constraints favor synchronous reproduction (positive covariance among species), while biotic interactions can favor synchrony or compensatory dynamics (negative covariance). We used wavelet analyses to examine phenology of community flower and seed production for 45 tree species across multiple temporal scales in a tropical dry forest in Puerto Rico with marked rainfall seasonality. We asked three questions: (1) do species exhibit synchronous or compensatory temporal dynamics in reproduction, (2) do interspecific differences in phenology reflect variable responses to rainfall, and (3) is interspecific variation in phenology and response to a major drought associated with functional traits that mediate responses to moisture? Community-level flowering was synchronized at seasonal scales (˜5-6 mo) and at short scales (˜1 mo, following rainfall). However, seed rain exhibited significant compensatory dynamics at intraseasonal scales (˜3 mo), suggesting interspecific variation in temporal niches. Species with large leaves (associated with sensitivity to water deficit) peaked in reproduction synchronously with the peak of seasonal rainfall (˜5 mo scale). By contrast, species with high wood specific gravity (associated with drought resistance) tended to flower in drier periods. Flowering of tall species and those with large leaves was most tightly linked to intraseasonal (˜2 mo scale) rainfall fluctuations. Although the 2015 drought dramatically reduced community-wide reproduction, functional traits were not associated with the magnitude of species-specific declines. Our results suggest opposing drivers of synchronous versus compensatory dynamics at different temporal scales. Phenology associations with functional traits indicated that

Solar radiation in forest and pasture areas in the Amazonia

International Nuclear Information System (INIS)

Feitosa, J.R.P.; Costa, R.F. da; Fisch, G.; Souza, S.S. de; Nobre, C.A.

1998-01-01

The average daytime behavior of the global incident radiation (Rg) over grassland (NS) and forest (RJ) in Rondonia State during dry and wet seasons were analyzed. The data set originated from the ABRACOS Project’s automatic meteorological stations in years 1992 through 1996. Results showed that incident radiation is smaller in pasture than in forest (17.1MJ m -2 dia -1 pasture versus 18.3M Jm -2 dia -1 forest) during the dry season. In the wet season, incident radiation is smaller than dry season, with 16.9MJ m -2 dia -1 for pasture and 17.1MJ m -2 dia -1 for forest. Atmospheric transmittance in pasture was smaller than forest (0.58 versus 0.66) in the dry season. This difference is equivalent a reduction of 2.8M Jm -2 dia -1 in the surface incident radiation. In the wet season the transmittances were 0.52 for the pasture and 0.50 for the forest. (author) [pt

Forest Fires Darken Snow for Years following Disturbance: Magnitude, Duration, and Composition of Light Absorbing Impurities in Seasonal Snow across a Chronosequence of Burned Forests in the Colorado River Headwaters

Science.gov (United States)

Gleason, K. E.; Arienzo, M. M.; Chellman, N.; McConnell, J.

2017-12-01

Charred forests shed black carbon and burned debris, which accumulates and concentrates on winter snowpack, reducing snow surface albedo, and subsequently increasing snowmelt rates, and advancing the date of snow disappearance. Forest fires have occurred across vast areas of the seasonal snow zone in recent decades, however we do not understand the long-term implications of burned forests in montane headwaters to snow hydrology and downstream water resources. Across a chronosequence of nine burned forests in the Colorado River Headwaters, we sampled snow throughout the complete snowpack profile to conserve the composition, properties, and vertical stratigraphy of impurities in the snowpack during maximum snow accumulation. Using state-of-the-art geochemical analyses, we determined the magnitude, composition, and particle size distribution of black carbon, dust, and other impurities in the snowpack relative to years-since fire. Forest fires continue to darken snow for many years following fire, however the magnitude, composition, and particle size distribution of impurities change through time, altering the post-fire radiative forcing on snow as a burned forest ages.

Interactions between fleshy fruits and frugivores in a tropical seasonal forest in Thailand.

Science.gov (United States)

Kitamura, Shumpei; Yumoto, Takakazu; Poonswad, Pilai; Chuailua, Phitaya; Plongmai, Kamol; Maruhashi, Tamaki; Noma, Naohiko

2002-12-01

Large frugivores are considered to be important seed dispersers for many tropical plant species. Their roles as seed dispersers are not well known in Southeast Asia, where degraded landscapes typically lack these animals. Interactions between 259 (65 families) vertebrate-dispersed fruits and frugivorous animals (including 7 species of bulbul, 1 species of pigeon, 4 species of hornbill, 2 species of squirrel, 3 species of civet, 2 species of gibbon, 1 species of macaque, 2 species of bear, 2 species of deer, and 1 species of elephant) were studied for 3 years in a tropical seasonal forest in Khao Yai National Park, Thailand. The purpose was to examine the dietary overlaps among the large frugivores and the characteristics of fruits they consumed. Most fruit species are eaten by various kinds of frugivores; no close relationship between a particular fruit and a frugivore was found. The number of frugivore groups that served a given plant species was negatively correlated with seed size. Additionally, the fruit/seed diameters consumed by bulbuls were significantly smaller than consumed by the other nine groups. These trends of fruit characteristics were consistent with those observed elsewhere in Southeast Asia: small fruits and large, soft fruits with many small seeds are consumed by a wide spectrum of frugivores while larger fruits with a single large seed are consumed by relatively few potential dispersers. Importantly, these large, single-seed fruits are not consumed by the small frugivores that thrive in small forest fragments and degraded areas in Southeast Asia. To insure the natural seed dispersal process in the forest, an evaluation of all frugivore groups in the forest is urgently needed in Southeast Asia.

How Does Dung Beetle (Coleoptera: Scarabaeidae) Diversity Vary Along a Rainy Season in a Tropical Dry Forest?

Science.gov (United States)

Novais, Samuel M A; Evangelista, Lucas A; Reis-Júnior, Ronaldo; Neves, Frederico S

2016-01-01

Dung beetle community dynamics are determined by regional rainfall patterns. However, little is known about the temporal dynamics of these communities in tropical dry forests (TDFs). This study was designed to test the following predictions: 1) Peak diversity of dung beetle species occurs early in the wet season, with a decrease in diversity (α and β) and abundance throughout the season; 2) Nestedness is the primary process determining β-diversity, with species sampled in the middle and the end of the wet season representing subsets of the early wet season community. Dung beetles were collected in a TDF in the northern Minas Gerais state, Brazil over three sampling events (December 2009, February and April 2010). We sampled 2,018 dung beetles belonging to 39 species and distributed among 15 genera. Scarabaeinae α-diversity and abundance were highest in December and equivalent between February and April, while β-diversity among plots increased along the wet season. The importance of nestedness and species turnover varies between pairs of sample periods as the main process of temporal β-diversity. Most species collected in the middle and end of the wet season were found in greater abundance in early wet season. Thus, the dung beetle community becomes more homogeneous at the beginning of the wet season, and as the season advances, higher resource scarcity limits population size, which likely results in a smaller foraging range, increasing β-diversity. Our results demonstrate high synchronism between the dung beetle life cycle and seasonality of environmental conditions throughout the wet season in a TDF, where the onset of rains determines adult emergence for most species. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America.

Vascular species composition of a contact zone between Seasonal and Araucaria forests in Guaraciaba, Far West of Santa Catarina state, southern Brazil

OpenAIRE

Gnigler, Luciana; Caddah, Mayara

2015-01-01

A floristic survey was carried out in a contact area between Araucaria Forest and Seasonal Forest areas, in the municipality of Guaraciaba, Far West of Santa Catarina state, southern Brazil. We provide a checklist containing 108 species and 42 plant families for the area. Families with the most encountered number of species were Myrtaceae (eight species), Solanaceae (eight), Euphorbiaceae (seven) and Poaceae (six). Two species are classified as endangered of extinction, following IUCN criteri...

Seasonal variability in physiological and anatomical traits contributes to invasion success of Prosopis juliflora in tropical dry forest.

Science.gov (United States)

Oliveira, Marciel T; Souza, Gustavo M; Pereira, Silvia; Oliveira, Deborah A S; Figueiredo-Lima, Karla V; Arruda, Emília; Santos, Mauro G

2017-03-01

We investigated whether there were consistent differences in the physiological and anatomical traits and phenotypic variability of an invasive (Prosopis juliflora (Sw.) DC.) and native species (Anadenanthera colubrina (Vell.) Brenan) in response to seasonality in a tropical dry forest. The water potential, organic solutes, gas exchange, enzymes of the antioxidant system, products of oxidative stress and anatomical parameters were evaluated in both species in response to seasonality. An analysis of physiological responses indicated that the invasive P. juliflora exhibited higher response in net photosynthetic rate to that of the native species between seasons. Higher values of water potential of the invasive species than those of the native species in the dry season indicate a more efficient mechanism for water regulation in the invasive species. The invasive species exhibits a thicker cuticle and trichomes, which can reduce transpiration. In combination, the increased epidermal thickness and the decreased thickness of the parenchyma in the dry season may contribute to water saving. Our data suggest a higher variability in anatomical traits in the invasive species as a response to seasonality, whereas physiological traits did not present a clear pattern of response. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

SEASONAL PATTERNS AND VERTICAL PROFILE OF SOIL WATER UPTAKE AND UTILIZATION BY YOUNG AND OLD DOUGLAS-FIR AND PONDEROSA PINE FORESTS

Science.gov (United States)

Water availability has a strong influence on the distribution of forest tree species across the landscape. However, we do not understand how seasonal patterns of water utilization by tree species are related to their drought tolerance. In the Pacific Northwest, Douglas-fir occu...

Understanding the Response of Photosynthetic Metabolism in Tropical Forests to Seasonal Climate Variations. Final Report

Energy Technology Data Exchange (ETDEWEB)

Dye, Dennis [U.S. Geological Survey, Menlo Park, CA (United States); Ivanov, Valeriy [Univ. of Michigan, Ann Arbor, MI (United States); Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Huete, Alfredo [Univ. of Arizona, Tucson, AZ (United States); Univ. of Technology, Sydney NSW (Australia)

2017-03-31

This U.S-Brazil collaboration for GOAmazon has investigated a deceptively simple question: what controls the response of photosynthesis in Amazon tropical forests to seasonal variations in climate? In the past this question has been difficult to answer with modern earth system process models. We hypothesized that observed dry season increases in photosynthetic capacity are controlled by the phenology of leaf flush and litter fall, from which the seasonal pattern of LAI emerges. Our results confirm this hypothesis (Wu et al., 2016). Synthesis of data collected throughout the 3-year project period continues through December 31, 2017 under no-cost extensions granted to the project teams at University of Michigan and University of Arizona (Award 2). The USGS component (Award 1) ceased on the final date of the project performance period, December 31, 2016. This report summarizes the overall activities and achievements of the project, and constitutes the final project report for the USGS component. The University of Michigan will submit a separate final report that includes additional results and deliverables achieved during the period of their and the University of Arizona’s no-cost extension, which will end on December 31, 2017.

Step process for selecting and testing surrogates and indicators of afrotemperate forest invertebrate diversity.

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Charmaine Uys

Full Text Available BACKGROUND: The diversity and complexity of invertebrate communities usually result in their exclusion from conservation activities. Here we provide a step process for assessing predominantly ground-dwelling Afrotemperate forest invertebrates' (earthworms, centipedes, millipedes, ants, molluscs potential as surrogates for conservation and indicators for monitoring. We also evaluated sampling methods (soil and litter samples, pitfall traps, active searching quadrats and tree beating and temporal (seasonal effects. METHODOLOGY/PRINCIPAL FINDINGS: Lack of congruence of species richness across taxa indicated poor surrogacy potential for any of the focus taxa. Based on abundance and richness, seasonal stability, and ease of sampling, molluscs were the most appropriate taxon for use in monitoring of disturbance impacts. Mollusc richness was highest in March (Antipodal late summer wet season. The most effective and efficient methods were active searching quadrats and searching litter samples. We tested the effectiveness of molluscs as indicators for monitoring by contrasting species richness and community structure in burned relative to unburned forests. Both species richness and community structure changed significantly with burning. Some mollusc species (e.g. Macroptychia africana showed marked negative responses to burning, and these species have potential for use as indicators. CONCLUSIONS/SIGNIFICANCE: Despite habitat type (i.e., Afrotemperate forest being constant, species richness and community structure varied across forest patches. Therefore, in conservation planning, setting targets for coarse filter features (e.g., habitat type requires fine filter features (e.g., localities for individual species. This is especially true for limited mobility taxa such as those studied here. Molluscs have high potential for indicators for monitoring, and this requires broader study.

Evapotranspiration seasonality across the Amazon Basin

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Eiji Maeda, Eduardo; Ma, Xuanlong; Wagner, Fabien Hubert; Kim, Hyungjun; Oki, Taikan; Eamus, Derek; Huete, Alfredo

2017-06-01

Evapotranspiration (ET) of Amazon forests is a main driver of regional climate patterns and an important indicator of ecosystem functioning. Despite its importance, the seasonal variability of ET over Amazon forests, and its relationship with environmental drivers, is still poorly understood. In this study, we carry out a water balance approach to analyse seasonal patterns in ET and their relationships with water and energy drivers over five sub-basins across the Amazon Basin. We used in situ measurements of river discharge, and remotely sensed estimates of terrestrial water storage, rainfall, and solar radiation. We show that the characteristics of ET seasonality in all sub-basins differ in timing and magnitude. The highest mean annual ET was found in the northern Rio Negro basin (˜ 1497 mm year-1) and the lowest values in the Solimões River basin (˜ 986 mm year-1). For the first time in a basin-scale study, using observational data, we show that factors limiting ET vary across climatic gradients in the Amazon, confirming local-scale eddy covariance studies. Both annual mean and seasonality in ET are driven by a combination of energy and water availability, as neither rainfall nor radiation alone could explain patterns in ET. In southern basins, despite seasonal rainfall deficits, deep root water uptake allows increasing rates of ET during the dry season, when radiation is usually higher than in the wet season. We demonstrate contrasting ET seasonality with satellite greenness across Amazon forests, with strong asynchronous relationships in ever-wet watersheds, and positive correlations observed in seasonally dry watersheds. Finally, we compared our results with estimates obtained by two ET models, and we conclude that neither of the two tested models could provide a consistent representation of ET seasonal patterns across the Amazon.

Biome-Scale Forest Properties in Amazonia Based on Field and Satellite Observations

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Liana O. Anderson

2012-05-01

Full Text Available Amazonian forests are extremely heterogeneous at different spatial scales. This review intends to present the large-scale patterns of the ecosystem properties of Amazonia, and focuses on two parts of the main components of the net primary production: the long-lived carbon pools (wood and short-lived pools (leaves. First, the focus is on forest biophysical properties, and secondly, on the macro-scale leaf phenological patterns of these forests, looking at field measurements and bringing into discussion the recent findings derived from remote sensing dataset. Finally, I discuss the results of the three major droughts that hit Amazonia in the last 15 years. The panorama that emerges from this review suggests that slow growing forests in central and eastern Amazonia, where soils are poorer, have significantly higher above ground biomass and higher wood density, trees are higher and present lower proportions of large-leaved species than stands in northwest and southwest Amazonia. However, the opposite pattern is observed in relation to forest productivity and dynamism, which is higher in western Amazonia than in central and eastern forests. The spatial patterns on leaf phenology across Amazonia are less marked. Field data from different forest formations showed that new leaf production can be unrelated to climate seasonality, timed with radiation, timed with rainfall and/or river levels. Oppositely, satellite images exhibited a large-scale synchronized peak in new leaf production during the dry season. Satellite data and field measurements bring contrasting results for the 2005 drought. Discussions on data processing and filtering, aerosols effects and a combined analysis with field and satellite images are presented. It is suggested that to improve the understanding of the large-scale patterns on Amazonian forests, integrative analyses that combine new technologies in remote sensing and long-term field ecological data are imperative.

Forest vegetation of Xishuangbanna, south China

Institute of Scientific and Technical Information of China (English)

Zhu Hua

2006-01-01

Xishuangbanna of southern Yunnan is biogeographically located at a transitional zone from tropical southeast (SE) Asia to subtropical east Asia and is at the junction of the Indian and Burmese plates of Gondwana and the Eurasian plate of Laurasia. The region, though surprisingly far from the equator and at a relatively high altitude, has a rich tropical flora and a typical tropical rain forest in the lowland areas. Based on physiognomic and ecological characteristics, floristic composition and habitats combined, the primary vegetation in Xishuangbanna can be organized into four main vegetation types: tropical rain forest, tropical seasonal moist forest, tropical montane evergreen broad-leaved forest and tropical monsoon forest. The tropical rain forest can be classified into two subtypes, i.e. a tropical seasonal rain forest in the lowlands and a tropical montane rain forest at higher elevations. The tropical seasonal rain forest has almost the same forest profile and physiognomic characteristics as equatorial lowland rain forests and is a type of truly tropical rain forest. Because of conspicuous similarity on ecological and floristic characteristics, the tropical rain forest in Xishuangbanna is a type of tropical Asian rain forest. However, since the tropical rain forest of Xishuangbanna occurs at the northern edge of tropical SE Asia, it differs from typical lowland rain forests in equatorial areas in having some deciduous trees in the canopy layer, fewer megaphanerophytes and epiphytes but more abundant lianas and more plants with microphyll. It is a type of semi-evergreen rain forest at the northern edge of the tropical zone. The tropical montane rain forest occurs at wet montane habitats and is similar to the lower montane rain forest in equatorial Asia in floristic composition and physiognomy. It is a type of lower montane rain forests within the broader category of tropical rain forests. The tropical seasonal moist forest occurs on middle and upper

Large forest patches promote breeding success of a terrestrial mammal in urban landscapes.

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Masashi Soga

Full Text Available Despite a marked increase in the focus toward biodiversity conservation in fragmented landscapes, studies that confirm species breeding success are scarce and limited. In this paper, we asked whether local (area of forest patches and landscape (amount of suitable habitat surrounding of focal patches factors affect the breeding success of raccoon dogs (Nyctereutes procyonoides in Tokyo, Central Japan. The breeding success of raccoon dogs is easy to judge as adults travel with pups during the breeding season. We selected 21 forest patches (3.3-797.8 ha as study sites. In each forest patch, we used infra-red-triggered cameras for a total of 60 camera days per site. We inspected each photo to determine whether it was of an adult or a pup. Although we found adult raccoon dogs in all 21 forest patches, pups were found only in 13 patches. To estimate probability of occurrence and detection for raccoon in 21 forest fragments, we used single season site occupancy models in PRESENCE program. Model selection based on AIC and model averaging showed that the occupancy probability of pups was positively affected by patch area. This result suggests that large forests improve breeding success of raccoon dogs. A major reason for the low habitat value of small, isolated patches may be the low availability of food sources and the high risk of being killed on the roads in such areas. Understanding the effects of local and landscape parameters on species breeding success may help us to devise and implement effective long-term conservation and management plans.

Seasonal variation of CO{sub 2} flux between air and temperate forest

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Susumo; Murayama, Shohei; Kondo, Hiroaki [National Inst. for Resources and Environment, Ibaraki (Japan)

1995-12-31

Carbon dioxide, which is a very important greenhouse gas, contributes approximately 55 % to the problem of global warming. The knowledge to the sources and sinks of carbon on a global basis is very poor. IPCC (1994) suggested that unknown 1.5-2.0 GtC/year may be sunk in terrestrial ecosystem, in particular, in the Northern Hemisphere. As can be seen from a recent estimation of the carbon fluxes in the terrestrial biosphere, there is a high degree of uncertainty in the magnitude. The clear evidence for it has not been shown yet by IPCC (1994). However, based on the gradient of CO{sub 2}, as a function of latitude, main CO{sub 2} sink can be thought to be in the terrestrial biosphere, in the middle to high latitude of the Northern Hemisphere. As can be seen from a recent estimation of the carbon fluxes in the terrestrial biosphere, there is a high degree of uncertainty in the magnitude. From this view, more investigation of the role of the temperate forest on the CO{sub 2} balance is inevitable. In this presentation, the seasonal variation of CO{sub 2} flux between air and biosphere in temperate deciduous forest in Japan is intended to be elucidated. (author)

Seasonal variation of CO{sub 2} flux between air and temperate forest

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Susumo; Murayama, Shohei; Kondo, Hiroaki [National Inst. for Resources and Environment, Ibaraki (Japan)

1996-12-31

Carbon dioxide, which is a very important greenhouse gas, contributes approximately 55 % to the problem of global warming. The knowledge to the sources and sinks of carbon on a global basis is very poor. IPCC (1994) suggested that unknown 1.5-2.0 GtC/year may be sunk in terrestrial ecosystem, in particular, in the Northern Hemisphere. As can be seen from a recent estimation of the carbon fluxes in the terrestrial biosphere, there is a high degree of uncertainty in the magnitude. The clear evidence for it has not been shown yet by IPCC (1994). However, based on the gradient of CO{sub 2}, as a function of latitude, main CO{sub 2} sink can be thought to be in the terrestrial biosphere, in the middle to high latitude of the Northern Hemisphere. As can be seen from a recent estimation of the carbon fluxes in the terrestrial biosphere, there is a high degree of uncertainty in the magnitude. From this view, more investigation of the role of the temperate forest on the CO{sub 2} balance is inevitable. In this presentation, the seasonal variation of CO{sub 2} flux between air and biosphere in temperate deciduous forest in Japan is intended to be elucidated. (author)

[Regulation effect of forest vegetation on watershed runoff in the Loess Plateau].

Science.gov (United States)

Huang, Mingbin; Liu, Xianzhao

2002-09-01

The runoff and rainfall data of typical forested and non-forested watersheds in Ziwuling region, which is located in the hinterland of the Loess Plateau, were used to analyze their annual runoff variation comparatively. The result showed that the annual distribution of runoff in forested watersheds was uniform, compared with that in non-forested watersheds. The total runoff in flood season decreased by 8.88 mm and 7.1 mm. Regression analyses between runoff in dried-up season and rainfall in flood season or in dried-up season showed that the rainfall in flood season in forested watersheds could be changed into underground runoff by forest vegetation, and increased the runoff in dried-up season. The annual variation of runoff also indicated that the total effect of forest vegetation on dried-up runoff complement from October to December was 1.69 mm and 0.5 mm, and that from January to May was not significant.

Black carbon content in a ponderosa pine forest of eastern Oregon with varying seasons and intervals of prescribed burns

Science.gov (United States)

Matosziuk, L.; Hatten, J. A.

2016-12-01

Soil carbon represents a significant component of the global carbon cycle. While fire-based disturbance of forest ecosystems acts as a carbon source, the increased temperatures can initiate molecular changes to forest biomass that convert fast cycling organic carbon into more stable forms such as black carbon (BC), a product of incomplete combustion that contains highly-condensed aromatic structures and very low hydrogen and oxygen content. Such forms of carbon can remain in the soil for hundred to thousands of years, effectively creating a long-term carbon sink. The goal of this project is to understand how specific characteristics of prescribed burns, specifically the season of burn and the interval between burns, affect the formation, structure, and retention of these slowly degrading forms of carbon in the soil. Both O-horizon (forest floor) and mineral soil (0-15 cm cores) samples were collected from a season and interval of burn study in Malheur National Forest. The study area is divided into six replicate units, each of which is sub-divided into four treatment areas and a control. Beginning in 1997, each treatment area was subjected to: i) spring burns at five-year intervals, ii) fall burns at five-year intervals, iii) spring burns at 15-year intervals, or iv) fall burns at 15-year intervals. The bulk density, pH, and C/N content of each soil were measured to assess the effect of the burn treatments on the soil. Additionally, the amount and molecular structure of BC in each sample was quantified using the distribution of specific molecular markers (benzene polycarboxylic acids or BPCAs) that are present in the soil following acid digestion.

The specificity of host-bat fly interaction networks across vegetation and seasonal variation.

Science.gov (United States)

Zarazúa-Carbajal, Mariana; Saldaña-Vázquez, Romeo A; Sandoval-Ruiz, César A; Stoner, Kathryn E; Benitez-Malvido, Julieta

2016-10-01

Vegetation type and seasonality promote changes in the species composition and abundance of parasite hosts. However, it is poorly known how these variables affect host-parasite interaction networks. This information is important to understand the dynamics of parasite-host relationships according to biotic and abiotic changes. We compared the specialization of host-bat fly interaction networks, as well as bat fly and host species composition between upland dry forest and riparian forest and between dry and rainy seasons in a tropical dry forest in Jalisco, Mexico. Bat flies were surveyed by direct collection from bats. Our results showed that host-bat fly interaction networks were more specialized in upland dry forest compared to riparian forest. Bat fly species composition was different between the dry and rainy seasons, while host species composition was different between upland dry forest and riparian forest. The higher specialization in upland dry forest could be related to the differences in bat host species composition and their respective roosting habits. Variation in the composition of bat fly species between dry and rainy seasons coincides with the seasonal shifts in their species richness. Our study confirms the high specialization of host-bat fly interactions and shows the importance of biotic and abiotic factors to understand the dynamics of parasite-host interactions.

Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin

Science.gov (United States)

Arn Teh, Yit; Murphy, Wayne A.; Berrio, Juan-Carlos; Boom, Arnoud; Page, Susan E.

2017-08-01

The Amazon plays a critical role in global atmospheric budgets of methane (CH4) and nitrous oxide (N2O). However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs), one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH4 and N2O fluxes from lowland tropical peatlands in the Pastaza-Marañón foreland basin (PMFB) in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH4 and N2O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole) vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH4 emissions averaged 36.05 ± 3.09 mg CH4-C m-2 day-1 across the entire dataset, with diffusive CH4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH4 averaged 973.3 ± 161.4 mg CH4-C m-2 day-1 and did not vary significantly among vegetation types or between seasons. Diffusive CH4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH4-C m-2 day-1), followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH4-C m-2 day-1), forested (short pole) vegetation (31.6 ± 6.6 mg CH4-C m-2 day-1), and forested vegetation (29.8 ± 10.0 mg CH4-C m-2 day-1). Diffusive CH4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher dry season (47.2 ± 5.4 mg CH4-C m-2 day-1 and 85.5 ± 26.4 mg CH4-C m-2 day-1, respectively) compared to wet season emissions

An Ecological Comparison of Floristic Composition in Seasonal Semideciduous Forest in Southeast Brazil: Implications for Conservation

OpenAIRE

Lopes, Sérgio de Faria; Schiavini, Ivan; Oliveira, Ana Paula; Vale, Vagner Santiago

2012-01-01

We examined floristic patterns of ten seasonal semideciduous forest sites in southeastern Brazil and conducted a central sampling of one hectare for each site, where we took samples and identified all individual living trees with DBH (diameter at breast height, 1.30 m) ≥4.8 cm. Arboreal flora totaled 242 species, 163 genera, and 58 families. Fabaceae (38 species) and Myrtaceae (20 species) were families with the largest number of species. Only Copaifera langsdorffii and Hymenaea courbaril occ...

Pan-Tropical Analysis of Climate Effects on Seasonal Tree Growth

Science.gov (United States)

Wagner, Fabien; Rossi, Vivien; Aubry-Kientz, Mélaine; Bonal, Damien; Dalitz, Helmut; Gliniars, Robert; Stahl, Clément; Trabucco, Antonio; Hérault, Bruno

2014-01-01

Climate models predict a range of changes in tropical forest regions, including increased average temperatures, decreased total precipitation, reduced soil moisture and alterations in seasonal climate variations. These changes are directly related to the increase in anthropogenic greenhouse gas concentrations, primarily CO2. Assessing seasonal forest growth responses to climate is of utmost importance because woody tissues, produced by photosynthesis from atmospheric CO2, water and light, constitute the main component of carbon sequestration in the forest ecosystem. In this paper, we combine intra-annual tree growth measurements from published tree growth data and the corresponding monthly climate data for 25 pan-tropical forest sites. This meta-analysis is designed to find the shared climate drivers of tree growth and their relative importance across pan-tropical forests in order to improve carbon uptake models in a global change context. Tree growth reveals significant intra-annual seasonality at seasonally dry sites or in wet tropical forests. Of the overall variation in tree growth, 28.7% was explained by the site effect, i.e. the tree growth average per site. The best predictive model included four climate variables: precipitation, solar radiation (estimated with extrasolar radiation reaching the atmosphere), temperature amplitude and relative soil water content. This model explained more than 50% of the tree growth variations across tropical forests. Precipitation and solar radiation are the main seasonal drivers of tree growth, causing 19.8% and 16.3% of the tree growth variations. Both have a significant positive association with tree growth. These findings suggest that forest productivity due to tropical tree growth will be reduced in the future if climate extremes, such as droughts, become more frequent. PMID:24670981

Composition and seasonal phenology of a nonindigenous root-feeding weevil (Coleoptera: Curculionidae) complex in northern hardwood forests in the Great Lakes Region

Science.gov (United States)

R. A. Pinski; W. J. Mattson; K. F. Raffa

2005-01-01

Phyllobius oblongus (L.), Polydrusus sericeus (Schaller), and Sciaphilus asperatus (Bonsdorff) comprise a complex of nonindigenous root-feeding weevils in northern hardwood forests of the Great Lakes region. Little is known about their detailed biology, seasonality, relative abundance, and distribution patterns....

Phytosociology analysis of a fragment of Seasonal Deciduous Forest: Parque Estadual do Turvo, RS, Brazil

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Rafaelo Balbinot

2016-06-01

Full Text Available The ecosystem formed by the Seasonal Deciduous Forest (SDF predominates in the region of Alto Uruguay in Rio Grande do Sul State, Brazil. This study aimed to analyze descriptively the floristic composition and the phytosociology of trees from a fragment of SDF present in Parque Estadual do Turvo (PET located in the Municipality of Derrubadas, Rio Grande do Sul State (Yucumã forest. We used the method of fixed area, based on 18 sample units with 1,000 m2 installed randomly oriented by the main road of the park. All wood species with diameter at 1.3 m above ground level (DBH greater than 10 cm were measured and identified. It was observed the presence of 842 individuals belonging to 32 families, 67 genera and 83 species (12% were not identified. The families with the highest number of species were Fabaceae, Euphorbiaceae, Meliaceae, Myrtaceae and Sapindaceae. Shannon index estimated was 3.72.

Radiation budget, soil heat flux and latent heat flux at the forest floor in warm, temperate mixed forest

International Nuclear Information System (INIS)

Tamai, K.; Abe, T.; Araki, M.; Ito, H.

1998-01-01

Seasonal changes in the radiation budget and soil heat flux of a forest floor were measured in a mixed forest located in Kyoto, Japan. The basal area at breast height in the survey forest was about 15·82 m 2 ha −1 , for evergreen trees, and 12·46 m 2 ha −1 , for deciduous trees. The sky view factor was 16 and 22% at the survey site in the foliate and defoliate seasons, respectively. The small difference between the sky view factor in the two seasons was reflected in the seasonal change in the radiation budget of the forest floor. Namely, the net long-wave radiation changed rapidly in leafing and falling days, and the rate of net short-wave radiation was highest in April. The distinctive characteristic of the radiation budget was that the rates of available radiation in the daytime and at night were almost equal in September and October. Latent heat flux at the forest floor was estimated to be around 94 MJ m −2 annually, from our measurement with the simulation model. (author)

Phylobetadiversity among forest types in the Brazilian Atlantic Forest complex.

Science.gov (United States)

Duarte, Leandro Da Silva; Bergamin, Rodrigo Scarton; Marcilio-Silva, Vinícius; Seger, Guilherme Dubal Dos Santos; Marques, Márcia Cristina Mendes

2014-01-01

Phylobetadiversity is defined as the phylogenetic resemblance between communities or biomes. Analyzing phylobetadiversity patterns among different vegetation physiognomies within a single biome is crucial to understand the historical affinities between them. Based on the widely accepted idea that different forest physiognomies within the Southern Brazilian Atlantic Forest constitute different facies of a single biome, we hypothesize that more recent phylogenetic nodes should drive phylobetadiversity gradients between the different forest types within the Atlantic Forest, as the phylogenetic divergence among those forest types is biogeographically recent. We compiled information from 206 checklists describing the occurrence of shrub/tree species across three different forest physiognomies within the Southern Brazilian Atlantic Forest (Dense, Mixed and Seasonal forests). We analyzed intra-site phylogenetic structure (phylogenetic diversity, net relatedness index and nearest taxon index) and phylobetadiversity between plots located at different forest types, using five different methods differing in sensitivity to either basal or terminal nodes (phylogenetic fuzzy weighting, COMDIST, COMDISTNT, UniFrac and Rao's H). Mixed forests showed higher phylogenetic diversity and overdispersion than the other forest types. Furthermore, all forest types differed from each other in relation phylobetadiversity patterns, particularly when phylobetadiversity methods more sensitive to terminal nodes were employed. Mixed forests tended to show higher phylogenetic differentiation to Dense and Seasonal forests than these latter from each other. The higher phylogenetic diversity and phylobetadiversity levels found in Mixed forests when compared to the others likely result from the biogeographical origin of several taxa occurring in these forests. On one hand, Mixed forests shelter several temperate taxa, like the conifers Araucaria and Podocarpus. On the other hand, tropical groups, like

Forest litter stocks in Korean pine-broad-leaved forests of the southern Sikhote Alin

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A. V. Ivanov

2015-10-01

Full Text Available The article presents the data on the forest litter of the Korean pine-broad-leaved forests of the South of Primorsky krai. The focus of the research is plantations dominated by Korean pine; areas of the main tree species with ages of 50, 80, 130 and 200 years were selected. The dynamics of the forest litter stock in the pine and broadleaved forests of different ages according to the measurement results for the season in 2014 is stated. In the studied plantation, the forest litter stock varies between 9.7–20.3 t ha-1. The greatest value of the forest litter stock is recorded in old-growth cedar forest (200 years. Relatively high power and the stock of litter are typical for young Korean pine forest that can explain the lower speed of the litter properties change against the dynamics of taxation indicators of the forest stand. The difference between the amount of the litter in the 200-year-old and remaining pine trees are statistically significant at p = 0.05. The dependence of the litter power on the age is not revealed. The coefficient of the forest litter decomposition ranges from 2.55–10.60 that characterizes the high speed of its rotting. The highest coefficient of the litter decomposition has an old-growing pine forest. The schedule of seasonal humidity fluctuations of the forest litter on the chosen plot is made; with increasing cedar forest age, the volumetric moisture content of the forest litter increases; volumetric moisture content on the plots remain relatively unchanged during the season. The area of the Korean pine forests of Primorsky State Academy of Agriculture is 6835 ha. The amount of carbon stock in the forest litter is 38.7 thousand tons C. in this area, while the system of regional assessment of the forest carbon balance estimates this index as 24.3 tons С. The data obtained can be used to adjust the coefficients of regional assessment of the forest carbon balance for cedar forests of Primorsky krai.

Effects of Repeated Growing Season Prescribed Fire on the Structure and Composition of Pine–Hardwood Forests in the Southeastern Piedmont, USA

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Matthew J. Reilly

2016-12-01

Full Text Available We examined the effects of repeated growing season prescribed fire on the structure and composition of mixed pine–hardwood forests in the southeastern Piedmont region, Georgia, USA. Plots were burned two to four times over an eight-year period with low intensity surface fires during one of four six-week long periods from early April to mid-September. Density of saplings (0.25–11.6 cm diameter at breast height was significantly reduced after one or two fires during the first four-year period. Sapling density declined with additional burning over the next four years, but density of mesic hardwoods including sweetgum (Liquidambar styraciflua and red maple (Acer rubrum remained relatively high (~865 stems ha−1. Repeated burning had little effect on density or basal area of trees (≥11.7 cm dbh and changes in overstory structure were limited to small increases in the quadratic mean diameter of all trees and pines. We found little evidence to suggest differential effects on structure or composition due to timing of burn within the growing season. Although repeated growing season burning alters midstory structure and composition, burning alone is unlikely to result in immediate shifts in overstory composition or structure in mixed pine–hardwood forests of the southeastern Piedmont region.

Response of frugivorous primates to changes in fruit supply in a northern Amazonian forest.

Science.gov (United States)

Mourthé, I

2014-08-01

Few attempts have been made to understand how spatiotemporal changes in fruit supply influence frugivores in tropical forests. The marked spatiotemporal variation in fruit supply can affect frugivore abundance and distribution, but studies addressing the effects of this variation on primates are scarce. The present study aimed to investigate how the spatiotemporal distribution of fruits influences the local distribution of three frugivorous primates in the eastern part of the Maracá Ecological Station, a highly seasonal Amazonian rainforest. Specifically, it was hypothesised that primate distribution will track changes in fruit supply, resulting that sites with high fruit availability should be heavily used by primates. During a 1-year study, fruit supply (ground fruit surveys) and primate density (line-transects) were monitored in twelve 2 km-long transects at monthly intervals. Fruit supply varied seasonally, being low during the dry season. The density of Ateles belzebuth was positively related to fruit supply during fruit shortage, but Cebus olivaceus and Alouatta macconnelli did not follow the same pattern. The supply of Sapotaceae fruit was an important component determining local distribution of A. belzebuth during the overall fruit shortage. Highly frugivorous primates such as A. belzebuth respond to seasonal decline in fruit supply by congregating at places with high fruit supply in this forest, particularly, those with many individuals of species of Sapotaceae. This study underscores the importance of small-scale spatiotemporal changes of fruit supply as a key component of frugivorous primate ecology in highly seasonal environments.

Water cycle observations in forest watersheds of Cambodia

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Shimizu, A.; Tamai, K.; Kabeya, N.; Shimizu, T.; Iida, S. I.

2015-12-01

The Lower Mekong River flows through Cambodia, where forests cover ~60% of the country and are believed to have a marked effect on the water cycle. These tropical seasonal forests in the Cambodian flat lands are very precious in the Indochinese Peninsula as few forests of this type remain. However, few hydrological observations have been conducted in these areas. In Cambodia, deciduous and evergreen forests make up 42% and 33% of the total forest area, respectively. We established experimental watersheds both in deciduous and evergreen forests containing meteorological observation towers in Cambodia and collected various observational data since 2003 (O'Krieng, deciduous forest watershed including a 30-m-high observation tower, 2,245 km2; Stung Chinit, evergreen forest watershed including a 60-m-high observation tower, 3,700 km2 including three small watersheds). The basic data from these sites included various kinds of information related to the composition of vegetation, soil characteristics, etc. Hydrologic data was collected and linked to the above data; the main hydrologic research results follow. The water budget for each watershed was determined using an observational rainfall and runoff dataset. The evapotranspiration rate in an evergreen forest was obtained using various observational methods including the Bowen energy-balance ratio and the bandpass eddy covariance method. The annual evapotranspiration of evergreen forests, estimated using the Bowen energy-balance ratio method and water balance, was about 1100-1200 mm, corresponding to 70-80% of annual rainfall. While considering the importance of the presence of evergreen forest, we conducted sap flow measurements to analyze the transpiration process that maintains water uptake through root systems that reach to depths exceeding 8 m. Characteristics of the evaporation from the forest floor that form an important element of the evaporation system were estimated in both evergreen and deciduous forests.

Seasonal Precipitation Variability Effects on Carbon Exchange in a Tropical Dry Forest of Northwest Mexico

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Verduzco, V.; Garatuza-Payan, J.; Yépez, E. A.; Watts, C. J.; Rodriguez, J. C.; Robles-Morua, A.; Vivoni, E. R.

2015-12-01

The Tropical Dry Forest (TDF) cover a large area in tropical and subtropical regions in the Americas and its productivity is thought to have an important contribution to the atmospheric carbon fluxes. However, due to this ecosystem complex dynamics, our understanding about the mechanisms controlling net ecosystem exchange is limited. In this study, five years of continue water and carbon fluxes measurements from eddy covariance complemented with remotely sensed vegetation greenness were used to investigate the ecosystem carbon balance of a TDF in the North American Monsoon region under different hydro climatic conditions. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer a predominant heterotrophic control owed to high decomposition of accumulated labile soil organic matter from prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production over the year, but can be overwhelmed by the strength of the primary productivity during the monsoon season. Precipitation characteristics during the monsoon have significant controls on sustaining carbon fixation in the TDF ecosystem into the fall season. A threshold of ~350 to 400 mm of summer precipitation was identify to switch the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This research points at the needs for understanding the potential effects of changing seasonal precipitation patterns on ecosystem dynamics and carbon sequestration in subtropical regions.

Foggy days and dry nights determine crown-level water balance in a seasonal tropical Montane cloud forest.

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Gotsch, Sybil G; Asbjornsen, Heidi; Holwerda, Friso; Goldsmith, Gregory R; Weintraub, Alexis E; Dawson, Todd E

2014-01-01

The ecophysiology of tropical montane cloud forest (TMCF) trees is influenced by crown-level microclimate factors including regular mist/fog water inputs, and large variations in evaporative demand, which in turn can significantly impact water balance. We investigated the effect of such microclimatic factors on canopy ecophysiology and branch-level water balance in the dry season of a seasonal TMCF in Veracruz, Mexico, by quantifying both water inputs (via foliar uptake, FU) and outputs (day- and night-time transpiration, NT). Measurements of sap flow, stomatal conductance, leaf water potential and pressure-volume relations were obtained in Quercus lanceifolia, a canopy-dominant tree species. Our results indicate that FU occurred 34% of the time and led to the recovery of 9% (24 ± 9.1 L) of all the dry-season water transpired from individual branches. Capacity for FU was independently verified for seven additional common tree species. NT accounted for approximately 17% (46 L) of dry-season water loss. There was a strong correlation between FU and the duration of leaf wetness events (fog and/or rain), as well as between NT and the night-time vapour pressure deficit. Our results show the clear importance of fog and NT for the canopy water relations of Q. lanceifolia. © 2013 John Wiley & Sons Ltd.

Seasonal variation of infiltration capacities of soils in western Oregon.

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Michael G. Johnson; Robert L. Beschta

1981-01-01

Infiltration capacities were 50 percent greater during fall than during summer for forest soils of western Oregon. These results contrast with those measured in other studies. In forested areas, investigators should be aware of potentially large seasonal changes in infiltration capacities. Such seasonal changes may exceed effects due to applied treatments (logging,...

Boreal forest fires in 1997 and 1998: a seasonal comparison using transport model simulations and measurement data

Directory of Open Access Journals (Sweden)

N. Spichtinger

2004-01-01

Full Text Available Forest fire emissions have a strong impact on the concentrations of trace gases and aerosols in the atmosphere. In order to quantify the influence of boreal forest fire emissions on the atmospheric composition, the fire seasons of 1997 and 1998 are compared in this paper. Fire activity in 1998 was very strong, especially over Canada and Eastern Siberia, whereas it was much weaker in 1997. According to burned area estimates the burning in 1998 was more than six times as intense as in 1997. Based on hot spot locations derived from ATSR (Along Track Scanning Radiometer data and official burned area data, fire emissions were estimated and their transport was simulated with a Lagrangian tracer transport model. Siberian and Canadian forest fire tracers were distinguished to investigate the transport of both separately. The fire emissions were transported even over intercontinental distances. Due to the El Niño induced meteorological situation, transport from Siberia to Canada was enhanced in 1998. Siberian fire emissions were transported towards Canada and contributed concentrations more than twice as high as those due to Canada's own CO emissions by fires. In 1998 both tracers arrive at higher latitudes over Europe, which is due to a higher North Atlantic Oscillation (NAO index in 1998. The simulated emission plumes are compared to CMDL (Climate Monitoring and Diagnostics Laboratory CO2 and CO data, Total Ozone Mapping Spectrometer (TOMS aerosol index (AI data and Global Ozone Monitoring Experiment (GOME tropospheric NO2 and HCHO columns. All the data show clearly enhanced signals during the burning season of 1998 compared to 1997. The results of the model simulation are in good agreement with ground-based as well as satellite-based measurements.

Stand-Level Gas-Exchange Responses to Seasonal Drought in Very Young Versus Old Douglas-fir Forests of the Pacific Northwest, USA

Energy Technology Data Exchange (ETDEWEB)

Wharton, S; Schroeder, M; Bible, K; Falk, M; Paw U, K T

2009-02-23

This study examines how stand age affects ecosystem mass and energy exchange response to seasonal drought in three adjacent Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forests. The sites include two early seral stands (ES) (0-15 years old) and an old-growth (OG) ({approx} 450-500) forest in the Wind River Experiment Forest, Washington, USA. We use eddy covariance flux measurements of carbon dioxide (F{sub NEE}), latent energy ({lambda}E) and sensible heat (H) to derive evapotranspiration rate (E{sub T}), bowen ratio ({beta}), water use efficiency (WUE), canopy conductance (G{sub c}), the Priestley-Taylor coefficient ({alpha}) and a canopy decoupling factor ({Omega}). The canopy and bulk parameters are examined to see how ecophysiological responses to water stress, including changes in available soil water ({theta}{sub r}) and vapor pressure deficit ({delta}e) differ among the two forest successional-stages. Despite very different rainfall patterns in 2006 and 2007, we observed distinct successional-stage relationships between E{sub T}, {alpha}, and G{sub c} to {delta}e and {theta}{sub r} during both years. The largest stand differences were (1) higher morning G{sub c} (> 10 mm s{sup -1}) at the OG forest coinciding with higher CO{sub 2} uptake (F{sub NEE} = -9 to -6 {micro}mol m{sup -2} s{sup -1}) but a strong negative response in G{sub c} to moderate {delta}e later in the day and a subsequent reduction in E{sub T}, and (2) higher E{sub T} at the ES stands because midday canopy conductance did not decrease until very low water availability levels (<30%) were reached at the end of the summer. Our results suggest that early seral stands are more likely than mature forests to experience declines in production if the summer drought becomes longer or intensifies because water conserving ecophysiological responses were only observed at the very end of the seasonal drought period in the youngest stands.

Water availability not fruitfall modulates the dry season distribution of frugivorous terrestrial vertebrates in a lowland Amazon forest.

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Omar Stalin Landázuri Paredes

Full Text Available Terrestrial vertebrate frugivores constitute one of the major guilds in tropical forests. Previous studies show that the meso-scale distribution of this group is only weakly explained by variables such as altitude and tree basal area in lowland Amazon forests. For the first time we test whether seasonally limiting resources (water and fallen fruit affect the dry season distribution in 25 species of terrestrial vertebrates. To examine the effects of the spatial availability of fruit and water on terrestrial vertebrates we used a standardized, regularly spaced arrangement of camera-traps within 25km2 of lowland Amazon forest. Generalized linear models (GLMs were then used to examine the influence of four variables (altitude, distance to large rivers, distance to nearest water, and presence vs absence of fruits on the number of photos on five functional groups (all frugivores, small, medium, large and very large frugivores and on seven of the most abundant frugivore species (Cuniculus paca, Dasyprocta leporina, Mazama americana, Mazama nemorivaga, Myoprocta acouchy, Pecari tajacu and Psophia crepitans. A total of 279 independent photos of 25 species were obtained from 900 camera-trap days. For most species and three functional groups, the variation in the number of photos per camera was significantly but weakly explained by the GLMs (deviance explained ranging from 6.2 to 48.8%. Generally, we found that the presence of water availability was more important than the presence of fallen fruit for the groups and species studied. Medium frugivores, large-bodied frugivores, and two of the more abundant species (C. paca and P. crepitans were recorded more frequently closer to water bodies; while none of the functional groups nor the most abundant species showed any significant relationship with the presence of fallen fruit. Two functional groups and two of the seven most common frugivore species assessed in the GLMs showed significant results with species

Water availability not fruitfall modulates the dry season distribution of frugivorous terrestrial vertebrates in a lowland Amazon forest.

Science.gov (United States)

Paredes, Omar Stalin Landázuri; Norris, Darren; Oliveira, Tadeu Gomes de; Michalski, Fernanda

2017-01-01

Terrestrial vertebrate frugivores constitute one of the major guilds in tropical forests. Previous studies show that the meso-scale distribution of this group is only weakly explained by variables such as altitude and tree basal area in lowland Amazon forests. For the first time we test whether seasonally limiting resources (water and fallen fruit) affect the dry season distribution in 25 species of terrestrial vertebrates. To examine the effects of the spatial availability of fruit and water on terrestrial vertebrates we used a standardized, regularly spaced arrangement of camera-traps within 25km2 of lowland Amazon forest. Generalized linear models (GLMs) were then used to examine the influence of four variables (altitude, distance to large rivers, distance to nearest water, and presence vs absence of fruits) on the number of photos on five functional groups (all frugivores, small, medium, large and very large frugivores) and on seven of the most abundant frugivore species (Cuniculus paca, Dasyprocta leporina, Mazama americana, Mazama nemorivaga, Myoprocta acouchy, Pecari tajacu and Psophia crepitans). A total of 279 independent photos of 25 species were obtained from 900 camera-trap days. For most species and three functional groups, the variation in the number of photos per camera was significantly but weakly explained by the GLMs (deviance explained ranging from 6.2 to 48.8%). Generally, we found that the presence of water availability was more important than the presence of fallen fruit for the groups and species studied. Medium frugivores, large-bodied frugivores, and two of the more abundant species (C. paca and P. crepitans) were recorded more frequently closer to water bodies; while none of the functional groups nor the most abundant species showed any significant relationship with the presence of fallen fruit. Two functional groups and two of the seven most common frugivore species assessed in the GLMs showed significant results with species

Air contaminants and litter fall decomposition in urban forest areas: The case of São Paulo - SP, Brazil.

Science.gov (United States)

Lamano Ferreira, Maurício; Portella Ribeiro, Andreza; Rodrigues Albuquerque, Caroline; Ferreira, Ana Paula do Nascimento Lamano; Figueira, Rubens César Lopes; Lafortezza, Raffaele

2017-05-01

factors. Precipitation appeared to be an important factor to disperse air pollutants; one method to better regulate this process is the development and integration of green infrastructure at city level, which might contribute to nature-based solutions. Results suggest that although the Curucutu forest is not very far from the MRSP, which could result in heavy metal levels similar to those observed in the Guarapiranga forest, the weather conditions, geographic location and rainfall rates might act as efficient physical barriers against the dispersion of pollutants in the urban area. However, it is important to highlight that in the period studied (2012-2013), MRSP presented unusual features during the winter period marked by the highest levels of precipitation which was due to several numbers of frontal systems and also due to their permanence for a couple days in the region. Thus, it is recommended to continue this study in order to obtain a database for characterizing the seasonal variation of air pollution levels in the litter fall and their adverse effects on ecosystem processes in these remnants of the Atlantic Forest. Copyright © 2017 Elsevier Inc. All rights reserved.

Demography of a forest elephant population

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Turkalo, Andrea K.; Wrege, Peter H.

2018-01-01

African forest elephants face severe threats from illegal killing for ivory and bushmeat and habitat conversion. Due to their cryptic nature and inaccessible range, little information on the biology of this species has been collected despite its iconic status. Compiling individual based monitoring data collected over 20 years from the Dzanga Bai population in Central African Republic, we summarize sex and age specific survivorship and female age specific fecundity for a cohort of 1625 individually identified elephants. Annual mortality (average = 3.5%) and natality (average = 5.3%) were lower and markedly less variable relative to rates reported for savanna elephant populations. New individuals consistently entered the study system, leading to a 2.5% average annual increase in the registered population. Calf sex ratios among known birth did not differ from parity. A weak seasonal signal in births was detected suggesting increased conceptions during the wet season. Inter-calf intervals and age of primiparity were longer relative to savanna elephant populations. Within the population, females between the ages of 25–39 demonstrated the shortest inter-calf intervals and highest fecundity, and previous calf sex had no influence on the interval. Calf survivorship was high (97%) the first two years after birth and did not differ by sex. Male and female survival began to differ by the age of 13 years, and males demonstrated significantly lower survival relative to females by the age of 20. It is suspected these differences are driven by human selection for ivory. Forest elephants were found to have one of the longest generation times recorded for any species at 31 years. These data provide fundamental understanding of forest elephant demography, providing baseline data for projecting population status and trends. PMID:29447207

Seasonal variability in methane and nitrous oxide fluxes from tropical peatlands in the western Amazon basin

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Y. A. Teh

2017-08-01

Full Text Available The Amazon plays a critical role in global atmospheric budgets of methane (CH4 and nitrous oxide (N2O. However, while we have a relatively good understanding of the continental-scale flux of these greenhouse gases (GHGs, one of the key gaps in knowledge is the specific contribution of peatland ecosystems to the regional budgets of these GHGs. Here we report CH4 and N2O fluxes from lowland tropical peatlands in the Pastaza–Marañón foreland basin (PMFB in Peru, one of the largest peatland complexes in the Amazon basin. The goal of this research was to quantify the range and magnitude of CH4 and N2O fluxes from this region, assess seasonal trends in trace gas exchange, and determine the role of different environmental variables in driving GHG flux. Trace gas fluxes were determined from the most numerically dominant peatland vegetation types in the region: forested vegetation, forested (short pole vegetation, Mauritia flexuosa-dominated palm swamp, and mixed palm swamp. Data were collected in both wet and dry seasons over the course of four field campaigns from 2012 to 2014. Diffusive CH4 emissions averaged 36.05 ± 3.09 mg CH4–C m−2 day−1 across the entire dataset, with diffusive CH4 flux varying significantly among vegetation types and between seasons. Net ebullition of CH4 averaged 973.3 ± 161.4 mg CH4–C m−2 day−1 and did not vary significantly among vegetation types or between seasons. Diffusive CH4 flux was greatest for mixed palm swamp (52.0 ± 16.0 mg CH4–C m−2 day−1, followed by M. flexuosa palm swamp (36.7 ± 3.9 mg CH4–C m−2 day−1, forested (short pole vegetation (31.6 ± 6.6 mg CH4–C m−2 day−1, and forested vegetation (29.8 ± 10.0 mg CH4–C m−2 day−1. Diffusive CH4 flux also showed marked seasonality, with divergent seasonal patterns among ecosystems. Forested vegetation and mixed palm swamp showed significantly higher

Marking behavior of Andean bears in an Ecuadorian cloud forest

NARCIS (Netherlands)

Filipczyková, Eva; Heitkonig, Ignas; Castellanos, Armando; Hantson, Wouter; Steyaert, Sam M.J.G.

2017-01-01

Very little is known about marking behavior of the endangered Andean bear (Tremarctos ornatus). Here, we present a first detailed description of Andean bear marking behavior obtained using camera traps. From November 2012 to April 2013, we inspected 16 bear trails in the Napo province of eastern

Microscopic saw mark analysis: an empirical approach.

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Love, Jennifer C; Derrick, Sharon M; Wiersema, Jason M; Peters, Charles

2015-01-01

Microscopic saw mark analysis is a well published and generally accepted qualitative analytical method. However, little research has focused on identifying and mitigating potential sources of error associated with the method. The presented study proposes the use of classification trees and random forest classifiers as an optimal, statistically sound approach to mitigate the potential for error of variability and outcome error in microscopic saw mark analysis. The statistical model was applied to 58 experimental saw marks created with four types of saws. The saw marks were made in fresh human femurs obtained through anatomical gift and were analyzed using a Keyence digital microscope. The statistical approach weighed the variables based on discriminatory value and produced decision trees with an associated outcome error rate of 8.62-17.82%. © 2014 American Academy of Forensic Sciences.

Three Decades of Remote Sensing Based Tropical Forests Phenological Patterns and Trends

Science.gov (United States)

Didan, K.

2010-12-01

The faint climatic seasonality of tropical rain forests is believed to be the reason these biomes lack strong and detectable seasonality. Forest seasonality is a critical element of ecosystem functions. It moderates the echo-hydrology, carbon, and nutrient exchange of the area. While deciduous forests exhibit distinct and strong seasonality, tropical forests do not, yet they play a large role in the cycling of energy and mass. Tropical forests represent a large percentage of vegetated land and their importance to the Earth system stems from their biological diversity, their habitat role, their role in regulating global weather, and the role they play in carbon storage. While Tropical forests are well buffered by their sheer size, their vulnerability to climate change is exacerbated by the human pressure. All of this begs the questions of what are the patterns and characteristic of tropical forests phenology and are there any detectable trends over the last three decades of synoptic remote sensing. These three decades comprise different episodes of droughts and an ever increasing level of human encroachment. In so far understanding the function and dynamic of these biomes, field studies continue to play a major role, but synoptic remote sensing is emerging as a viable tool to addressing the spatial and temporal scale associated with this problem. Recent studies of Brazilian rainforest with synoptic remote sensing point to a sizable seasonal signal coincident with the dry season. However, these studies were not extensive in time or space and did not look at other rainforests. Using data from AVHRR and MODIS, we generated a 30 year record of the 2 bands Enhance Vegetation Index (EVI2), and analyzed the patterns and trends of land surface phenology across all tropical forests using the homogeneous phenology cluster approach. We chose EVI because of its superior performance over these dense forests, and we selected the homogeneous phenology cluster approach to abate the

The hydrologic bench-mark program; a standard to evaluate time-series trends in selected water-quality constituents for streams in Georgia

Science.gov (United States)

Buell, G.R.; Grams, S.C.

1985-01-01

Significant temporal trends in monthly pH, specific conductance, total alkalinity, hardness, total nitrite-plus-nitrite nitrogen, and total phosphorus measurements at five stream sites in Georgia were identified using a rank correlation technique, the seasonal Kendall test and slope estimator. These sites include a U.S. Geological Survey Hydrologic Bench-Mark site, Falling Creek near Juliette, and four periodic water-quality monitoring sites. Comparison of raw data trends with streamflow-residual trends and, where applicable, with chemical-discharge trends (instantaneous fluxes) shws that some of these trends are responses to factors other than changing streamflow. Percentages of forested, agricultural, and urban cover with each basin did not change much during the periods of water-quality record, and therefore these non-flow-related trends are not obviously related to changes in land cover or land use. Flow-residual water-quality trends at the Hydrologic Bench-Mark site and at the Chattooga River site probably indicate basin reponses to changes in the chemical quality of atmospheric deposition. These two basins are predominantly forested and have received little recent human use. Observed trends at the other three sites probably indicate basin responses to various land uses and water uses associated with agricultural and urban land or to changes in specific uses. (USGS)

Above Canopy Emissions of Isoprene and Monoterpenes from a Southeast Asian Tropical Forest

Science.gov (United States)

Baker, B.; Johnson, C.; Cai, Z.; Guenther, A.; Greenberg, J.; Bai, J.; Li, Q.

2003-12-01

Fluxes of isoprene were measured using the eddy covariance technique and an ozone chemiluminescence isoprene sensor above a secondary tropical forest/rubber tree plantation located in the Xishuangbanna region of southern China during the wet and dry seasons. Fluxes of monoterpenes were inferred from ambient boundary layer concentrations (wet season) and from relaxed eddy accumulation measurements (dry season). Isoprene emissions were comparable to what has been observed from other tropical forests in Africa and South America. In this forest, monoterpene emissions were much higher during the wet season due to the senescence of the rubber trees during the dry season. These flux measurements represent the first ecosystem level flux measurements reported from Southeast Asian tropical forests.

Determining the annual periodicity of growth rings in seven tree species of a tropical moist forest in Santa Cruz, Bolivia

Energy Technology Data Exchange (ETDEWEB)

Lopez, L.; Villalba, R.; Pena-Claros, M.

2012-07-01

To determine the annual periodicity of growth rings in seven tree species from a tropical moist forest in Santa Cruz, Bolivia, a fire scar was used as a marker point to verify the annual nature of tree rings. The number of tree rings formed between the 1995 fire scar and the collection of the cross sections in 2002 was visually identified. The seven species showed annual growth rings. In most cases, boundaries between rings were marked by the presence of marginal parenchyma and wall-thick ed fibers formed at the end of the growing season. Growth lenses and false rings were recorded in some species. Tree rings can be carefully used in Santa Cruz forests to determine rates of growth. This information is crucial for defining forest management practices in tropical regions. (Author) 21 refs.

The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs.

Directory of Open Access Journals (Sweden)

Gabriela Silva Ribeiro Gonçalves

Full Text Available Understanding the processes that influence species diversity is still a challenge in ecological studies. However, there are two main theories to discuss this topic, the niche theory and the neutral theory. Our objective was to understand the importance of environmental and spatial processes in structuring bird communities within the hydrological seasons in dry forest areas in northeastern Brazil. The study was conducted in two National Parks, the Serra da Capivara and Serra das Confusões National Parks, where 36 areas were sampled in different seasons (dry, dry/rainy transition, rainy, rainy/dry transition, in 2012 and 2013. We found with our results that bird species richness is higher in the rainy season and lower during the dry season, indicating a strong influence of seasonality, a pattern also found for environmental heterogeneity. Richness was explained by local environmental factors, while species composition was explained by environmental and spatial factors. The environmental factors were more important in explaining variations in composition. Climate change predictions have currently pointed out frequent drought events and a rise in global temperature by 2050, which would lead to changes in species behavior and to increasing desertification in some regions, including the Caatinga. In addition, the high deforestation rates and the low level of representativeness of the Caatinga in the conservation units negatively affects bird communities. This scenario has demonstrated how climatic factors affect individuals, and, therefore, should be the starting point for conservation initiatives to be developed in xeric environments.

The role of climate and environmental variables in structuring bird assemblages in the Seasonally Dry Tropical Forests (SDTFs).

Science.gov (United States)

Gonçalves, Gabriela Silva Ribeiro; Cerqueira, Pablo Vieira; Brasil, Leandro Schlemmer; Santos, Marcos Pérsio Dantas

2017-01-01

Understanding the processes that influence species diversity is still a challenge in ecological studies. However, there are two main theories to discuss this topic, the niche theory and the neutral theory. Our objective was to understand the importance of environmental and spatial processes in structuring bird communities within the hydrological seasons in dry forest areas in northeastern Brazil. The study was conducted in two National Parks, the Serra da Capivara and Serra das Confusões National Parks, where 36 areas were sampled in different seasons (dry, dry/rainy transition, rainy, rainy/dry transition), in 2012 and 2013. We found with our results that bird species richness is higher in the rainy season and lower during the dry season, indicating a strong influence of seasonality, a pattern also found for environmental heterogeneity. Richness was explained by local environmental factors, while species composition was explained by environmental and spatial factors. The environmental factors were more important in explaining variations in composition. Climate change predictions have currently pointed out frequent drought events and a rise in global temperature by 2050, which would lead to changes in species behavior and to increasing desertification in some regions, including the Caatinga. In addition, the high deforestation rates and the low level of representativeness of the Caatinga in the conservation units negatively affects bird communities. This scenario has demonstrated how climatic factors affect individuals, and, therefore, should be the starting point for conservation initiatives to be developed in xeric environments.

Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils

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Brzostek, Edward R.; Finzi, Adrien C.

2012-03-01

Increasing soil temperature has the potential to alter the activity of the extracellular enzymes that mobilize nitrogen (N) from soil organic matter (SOM) and ultimately the availability of N for primary production. Proteolytic enzymes depolymerize N from proteinaceous components of SOM into amino acids, and their activity is a principal driver of the within-system cycle of soil N. The objectives of this study were to investigate whether the soils of temperate forest tree species differ in the temperature sensitivity of proteolytic enzyme activity over the growing season and the role of substrate limitation in regulating temperature sensitivity. Across species and sampling dates, proteolytic enzyme activity had relatively low sensitivity to temperature with a mean activation energy (Ea) of 33.5 kJ mol-1. Ea declined in white ash, American beech, and eastern hemlock soils across the growing season as soils warmed. By contrast, Eain sugar maple soil increased across the growing season. We used these data to develop a species-specific empirical model of proteolytic enzyme activity for the 2009 calendar year and studied the interactive effects of soil temperature (ambient or +5°C) and substrate limitation (ambient or elevated protein) on enzyme activity. Declines in substrate limitation had a larger single-factor effect on proteolytic enzyme activity than temperature, particularly in the spring. There was, however, a large synergistic effect of increasing temperature and substrate supply on proteolytic enzyme activity. Our results suggest limited increases in N availability with climate warming unless there is a parallel increase in the availability of protein substrates.

Effects of repeated growing season prescribed fire on the structure and composition of pine-hardwood forests in the southeastern Piedmont, USA

Science.gov (United States)

Matthew Reilly; Kenneth Outcalt; Joseph O’Brien; Dale Wade

2016-01-01

We examined the effects of repeated growing season prescribed fire on the structure and composition of mixed pine–hardwood forests in the southeastern Piedmont region, Georgia, USA. Plots were burned two to four times over an eight-year period with low intensity surface fires during one of four six-week long periods from early April to mid-September. Density...

Assessing socioeconomic impacts of climate change on U.S. forests, wood-product markets, and forest recreation

Science.gov (United States)

Lloyd C. Irland; Darius Adams; Ralph Alig; Carter J. Betz; Chi-Chung Chen; Mark Hutchins; Bruce A. McCarl; Ken Skog; Brent L. Sohngen

2001-01-01

In this paper we discuss the problems of projecting social and economic changes affecting forests and review recent efforts to assess the wood-market impacts of possible climate changes. To illustrate the range of conditions encountered in projecting socioeconomic change linked to forests, we consider two markedly different uses: forest products markets and forest...

Tropical dry forest recovery : processes and causes of change

NARCIS (Netherlands)

Lebrija Trejos, E.E.

2009-01-01

Seasonally dry areas are one of the preferred zones for human inhabitance in the tropics. Large forest areas are converted to other land uses and many are covered by secondary forests that grow naturally after cessation of disturbance. Surprisingly, secondary succession in these strongly seasonal

The Forest Fire Problem of Degrading Tain II Forest Reserve in Ghana

African Journals Online (AJOL)

Agribotix GCS 068

2010-01-11

Jan 11, 2010 ... informal practice was done before the 1982/83 dry season when the country ..... Tain II Forest Reserve forms part of the Dry Semi-Deciduous Fire ...... 2003/08; Forest Resources Development Service Working Paper FFM/2. .... Environment, Resources and Development Thailand. web.idrc.ca/uploads/user-.

The Tetramerium lineage (Acanthaceae: Justicieae) does not support the Pleistocene Arc hypothesis for South American seasonally dry forests.

Science.gov (United States)

Côrtes, Ana Luiza A; Rapini, Alessandro; Daniel, Thomas F

2015-06-01

The Tetramerium lineage (Acanthaceae) presents a striking ecological structuring in South America, with groups concentrated in moist forests or in seasonally dry forests. In this study, we investigate the circumscription and relationships of the South American genera as a basis for better understanding historic interactions between dry and moist biomes in the Neotropics. We dated the ancestral distribution of the Tetramerium lineage based on one nuclear and four plastid DNA regions. Maximum parsimony, maximum likelihood, and Bayesian inference analyses were performed for this study using 104 terminals. Phylogenetic divergences were dated using a relaxed molecular clock approach and ancestral distributions obtained from dispersal-vicariance analyses. The genera Pachystachys, Schaueria, and Thyrsacanthus are nonmonophyletic. A dry forest lineage dispersed from North America to South America and reached the southwestern part of the continent between the end of the Miocene and beginning of the Pleistocene. This period coincides with the segregation between Amazonian and Atlantic moist forests that established the geographic structure currently found in the group. The South American genera Pachystachys, Schaueria, and Thyrsacanthus need to be recircumscribed. The congruence among biogeographical events found for the Tetramerium lineage suggests that the dry forest centers currently dispersed throughout South America are relatively old remnants, probably isolated since the Neogene, much earlier than the Last Glacial Maximum postulated by the Pleistocene Arc hypothesis. In addition to exploring the Pleistocene Arc hypothesis, this research also informs evolution in a lineage with numerous geographically restricted and threatened species. © 2015 Botanical Society of America, Inc.

A preliminary early-season flower-visitation web for the Kirindy Forest, Madagascar

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Mary V. Price

2010-08-01

Full Text Available Tropical dry deciduous forest is an endangered ecosystem whose plant-pollinator relationships are little known. We characterised a portion of the web of interactions between flowering plants and flower visitors in the Kirindy Forest of the Menabe region of west-central Madagascar. Taking a plant-centered approach, we observed individuals of the 5 most abundant native plant species that were coming into flower at the end of the annual dry season, and recorded all identifiable flower-visitors. Taking a visitor-centered approach, we walked a network of established trails and listened for distinctive calls of a common flower-visiting bird, noting the plant species visited. The former approach revealed connections among the early-flowering species via birds and insects, whereas the latter confirmed these connections and added an additional plant species. Flowers of the 6 plant species were visited on average by 5.5 animal species, while 10 visitor species for which we had reasonable samples frequented on average the flowers of 3.3 plant species. These qualitative results resemble those reported from other temperate and tropical webs, in that interactions appeared to be relatively generalised by pollinator species and body plan (e.g., birds vs. bees. Also in agreement, the visitation web was significantly nested, with more-specialised species tending to interact with mutualistic partners that were themselves more generalised. In addition to documenting previously-unreported interactions, therefore, this preliminary web conforms to more widespread patterns emerging for pollination systems at the community level.

Correlations of Rainfall and Forest Type with Papilionid Assemblages in Assam in Northeast India

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Kamini Kusum Barua

2010-01-01

Full Text Available No comprehensive community studies have been done on the butterflies of the tropical monsoon forests of the East Himalayan region. We described the Papilionidae at one site within the continuous moist deciduous forest belt of Northeast India and their variation with season and forest type. We surveyed 20 permanent line transects, varying with respect to canopy openness and observed levels of disturbance. A total sample effort of 131 days during the dry and wet seasons of a two-year study resulted in 18,373 individuals identified from 28 Papilionidae species. Constrained canonical correspondence ordination was used to examine the effects of season, forest type, rainfall, year, altitude, and geographical position on the species assemblages. Results showed that rainfall, forest type, and season accounted for most variance in papilionid abundance. Rainfall was strongly correlated with the abundance of some species. Nine species were associated with gaps, 16 species were restricted to closed forest, and three species were encountered in both gaps and closed forest. Six species with narrow geographic range were found only in closed forest. The results confirm the strong seasonality of continental Southeast Asian butterfly assemblages.

Asynchronous Amazon Forest Canopy Phenology Indicates Adaptation to Both Water and Light Availability

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Jones, M. O.; Kimball, J. S.; Nemani, R. R.

2015-12-01

Amazon forests represent nearly half of all tropical vegetation biomass and, through photosynthesis and respiration, annually process more than twice the amount of estimated carbon (CO2) from fossil fuel emissions. Yet the seasonality of Amazon canopy cover, and the extent to which seasonal fluctuations in water availability and photosynthetically active radiation influence these processes, is still poorly understood. Implementing six remotely sensed data sets spanning nine years (2003-2011), with reported field and flux tower data, we show that southern equatorial Amazon forests exhibit a distinctive seasonal signal. Seasonal timing of water availability, canopy biomass growth and net leaf flush are asynchronous in regions with short dry seasons and become more synchronous across a west-to-east longitudinal moisture gradient of increasing dry season length. Forest cover is responsive to seasonal disparities in both water and solar radiation availability, temporally adjusting net leaf flush to maximize use of these generally abundant resources, while reducing drought susceptibility. An accurate characterization of this asynchronous behavior allows for improved understanding of canopy phenology across contiguous tropical forests and their sensitivity to climate variability and drought. These insights can also inform land surface models to provide a more accurate representation of seasonal forest carbon allocation strategies responsive to environmental drivers.

Improved understanding of drought controls on seasonal variation in Mediterranean forest canopy CO2 and water fluxes through combined in situ measurements and ecosystem modelling

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S. Sabate

2009-08-01

Full Text Available Water stress is a defining characteristic of Mediterranean ecosystems, and is likely to become more severe in the coming decades. Simulation models are key tools for making predictions, but our current understanding of how soil moisture controls ecosystem functioning is not sufficient to adequately constrain parameterisations. Canopy-scale flux data from four forest ecosystems with Mediterranean-type climates were used in order to analyse the physiological controls on carbon and water flues through the year. Significant non-stomatal limitations on photosynthesis were detected, along with lesser changes in the conductance-assimilation relationship. New model parameterisations were derived and implemented in two contrasting modelling approaches. The effectiveness of two models, one a dynamic global vegetation model ("ORCHIDEE", and the other a forest growth model particularly developed for Mediterranean simulations ("GOTILWA+", was assessed and modelled canopy responses to seasonal changes in soil moisture were analysed in comparison with in situ flux measurements. In contrast to commonly held assumptions, we find that changing the ratio of conductance to assimilation under natural, seasonally-developing, soil moisture stress is not sufficient to reproduce forest canopy CO2 and water fluxes. However, accurate predictions of both CO2 and water fluxes under all soil moisture levels encountered in the field are obtained if photosynthetic capacity is assumed to vary with soil moisture. This new parameterisation has important consequences for simulated responses of carbon and water fluxes to seasonal soil moisture stress, and should greatly improve our ability to anticipate future impacts of climate changes on the functioning of ecosystems in Mediterranean-type climates.

Phyllostomid Bat Occurrence in Successional Stages of Neotropical Dry Forests

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Avila-Cabadilla, Luis Daniel; Stoner, Kathryn Elizabeth; Nassar, Jafet M.; Espírito-Santo, Mario M.; Alvarez-Añorve, Mariana Yolotl; Aranguren, Carla I.; Henry, Mickael; González-Carcacía, José A.; Dolabela Falcão, Luiz A.; Sanchez-Azofeifa, Gerardo Arturo

2014-01-01

Tropical dry forests (TDFs) are highly endangered tropical ecosystems being replaced by a complex mosaic of patches of different successional stages, agricultural fields and pasturelands. In this context, it is urgent to understand how taxa playing critical ecosystem roles respond to habitat modification. Because Phyllostomid bats provide important ecosystem services (e.g. facilitate gene flow among plant populations and promote forest regeneration), in this study we aimed to identify potential patterns on their response to TDF transformation in sites representing four different successional stages (initial, early, intermediate and late) in three Neotropical regions: México, Venezuela and Brazil. We evaluated bat occurrence at the species, ensemble (abundance) and assemblage level (species richness and composition, guild composition). We also evaluated how bat occurrence was modulated by the marked seasonality of TDFs. In general, we found high seasonal and regional specificities in phyllostomid occurrence, driven by specificities at species and guild levels. For example, highest frugivore abundance occurred in the early stage of the moistest TDF, while highest nectarivore abundance occurred in the same stage of the driest TDF. The high regional specificity of phyllostomid responses could arise from: (1) the distinctive environmental conditions of each region, (2) the specific behavior and ecological requirements of the regional bat species, (3) the composition, structure and phenological patterns of plant assemblages in the different stages, and (4) the regional landscape composition and configuration. We conclude that, in tropical seasonal environments, it is imperative to perform long-term studies considering seasonal variations in environmental conditions and plant phenology, as well as the role of landscape attributes. This approach will allow us to identify potential patterns in bat responses to habitat modification, which constitute an invaluable tool for

Phyllostomid bat occurrence in successional stages of neotropical dry forests.

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Luis Daniel Avila-Cabadilla

Full Text Available Tropical dry forests (TDFs are highly endangered tropical ecosystems being replaced by a complex mosaic of patches of different successional stages, agricultural fields and pasturelands. In this context, it is urgent to understand how taxa playing critical ecosystem roles respond to habitat modification. Because Phyllostomid bats provide important ecosystem services (e.g. facilitate gene flow among plant populations and promote forest regeneration, in this study we aimed to identify potential patterns on their response to TDF transformation in sites representing four different successional stages (initial, early, intermediate and late in three Neotropical regions: México, Venezuela and Brazil. We evaluated bat occurrence at the species, ensemble (abundance and assemblage level (species richness and composition, guild composition. We also evaluated how bat occurrence was modulated by the marked seasonality of TDFs. In general, we found high seasonal and regional specificities in phyllostomid occurrence, driven by specificities at species and guild levels. For example, highest frugivore abundance occurred in the early stage of the moistest TDF, while highest nectarivore abundance occurred in the same stage of the driest TDF. The high regional specificity of phyllostomid responses could arise from: (1 the distinctive environmental conditions of each region, (2 the specific behavior and ecological requirements of the regional bat species, (3 the composition, structure and phenological patterns of plant assemblages in the different stages, and (4 the regional landscape composition and configuration. We conclude that, in tropical seasonal environments, it is imperative to perform long-term studies considering seasonal variations in environmental conditions and plant phenology, as well as the role of landscape attributes. This approach will allow us to identify potential patterns in bat responses to habitat modification, which constitute an invaluable

Environmental filtering of eudicot lineages underlies phylogenetic clustering in tropical South American flooded forests.

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Aldana, Ana M; Carlucci, Marcos B; Fine, Paul V A; Stevenson, Pablo R

2017-02-01

The phylogenetic community assembly approach has been used to elucidate the role of ecological and historical processes in shaping tropical tree communities. Recent studies have shown that stressful environments, such as seasonally dry, white-sand and flooded forests tend to be phylogenetically clustered, arguing for niche conservatism as the main driver for this pattern. Very few studies have attempted to identify the lineages that contribute to such assembly patterns. We aimed to improve our understanding of the assembly of flooded forest tree communities in Northern South America by asking the following questions: are seasonally flooded forests phylogenetically clustered? If so, which angiosperm lineages are over-represented in seasonally flooded forests? To assess our hypotheses, we investigated seasonally flooded and terra firme forests from the Magdalena, Orinoco and Amazon Basins, in Colombia. Our results show that, regardless of the river basin in which they are located, seasonally flooded forests of Northern South America tend to be phylogenetically clustered, which means that the more abundant taxa in these forests are more closely related to each other than expected by chance. Based on our alpha and beta phylodiversity analyses we interpret that eudicots are more likely to adapt to extreme environments such as seasonally flooded forests, which indicates the importance of environmental filtering in the assembly of the Neotropical flora.

Do Reductions in Dry Season Transpiration Allow Shallow Soil Water Uptake to Persist in a Tropical Lower Montane Cloud Forest?

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Munoz Villers, L. E.; Holwerda, F.; Alvarado-Barrientos, M. S.; Goldsmith, G. R.; Geissert Kientz, D. R.; González Martínez, T. M.; Dawson, T. E.

2016-12-01

Tropical montane cloud forests (TMCF) are ecosystems particularly sensitive to climate change; however, the effects of warmer and drier conditions on TMCF water cycling remain poorly understood. To investigate the plant functional response to reduced water availability, we conducted a study during the mid to late dry season (2014) in the lower limit (1,325 m asl) of the TMCF belt (1200-2500 m asl) in central Veracruz, Mexico. The temporal variation of transpiration rates of dominant upper canopy and mid-story tree species, depth of water uptake, as well as tree water sources were examined using micrometeorological, sapflow and soil moisture measurements, in combination with data on stable isotope (δ18O and δ2H) composition of rain, tree xylem, soil (bulk and low suction-lysimeter) and stream water. The sapflow data suggest that crown conductances decreased as temperature and vapor pressure deficit increased, and soil moisture decreased from the mid to late dry season. Across all samplings (January 21, April 12 and 26), upper canopy species (Quercus spp.) showed more depleted (negative) isotope values compared to mid-story trees (Carpinus tropicalis). Overall, we found that the evaporated soil water pool was the main source for the trees. Furthermore, our MixSIAR Bayesian mixing model results showed that the depth of tree water uptake changed over the course of the dry season. Unexpectedly, a shift in water uptake from deeper (60-120 cm depth) to shallower soil water (0-30 cm) sources was observed, coinciding with the decreases in transpiration rates towards the end of the dry season. A larger reduction in deep soil water contributions was observed for upper canopy trees (from 70±14 to 22±15%) than for mid-story species (from 10±13 to 7±10%). The use of shallow soil water by trees during the dry season seems consistent with the greater root biomass and higher macronutrient concentrations found in the first 10 cm of the soil profiles. These findings are an

Forested wetland habitat

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Duberstein, Jamie A.; Krauss, Ken W.; Kennish, Michael J.

2015-01-01

A forested wetland (swamp) is a forest where soils are saturated or flooded for at least a portion of the growing season, and vegetation, dominated by trees, is adapted to tolerate flooded conditions. A tidal freshwater forested wetland is a forested wetland that experiences frequent but short-term surface flooding via tidal action, with average salinity of soil porewater less than 0.5 g/l. It is known locally as tidal várzea in the Amazon delta, Brazil. A tidal saltwater forested wetland (mangrove forest) is a forested wetland that experiences frequent but short-term surface flooding via tidal action, with average salinity often exceeding 3 g/l and reaching levels that can exceed seawater. Mangrove ecosystems are composed of facultative halophytes that generally experience better growth at moderate salinity concentrations.

Forest structure, stand composition, and climate-growth response in montane forests of Jiuzhaigou National Nature Reserve, China.

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Mark W Schwartz

Full Text Available Montane forests of western China provide an opportunity to establish baseline studies for climate change. The region is being impacted by climate change, air pollution, and significant human impacts from tourism. We analyzed forest stand structure and climate-growth relationships from Jiuzhaigou National Nature Reserve in northwestern Sichuan province, along the eastern edge of the Tibetan plateau. We conducted a survey to characterize forest stand diversity and structure in plots occurring between 2050 and 3350 m in elevation. We also evaluated seedling and sapling recruitment and tree-ring data from four conifer species to assess: 1 whether the forest appears in transition toward increased hardwood composition; 2 if conifers appear stressed by recent climate change relative to hardwoods; and 3 how growth of four dominant species responds to recent climate. Our study is complicated by clear evidence of 20(th century timber extraction. Focusing on regions lacking evidence of logging, we found a diverse suite of conifers (Pinus, Abies, Juniperus, Picea, and Larix strongly dominate the forest overstory. We found population size structures for most conifer tree species to be consistent with self-replacement and not providing evidence of shifting composition toward hardwoods. Climate-growth analyses indicate increased growth with cool temperatures in summer and fall. Warmer temperatures during the growing season could negatively impact conifer growth, indicating possible seasonal climate water deficit as a constraint on growth. In contrast, however, we found little relationship to seasonal precipitation. Projected warming does not yet have a discernible signal on trends in tree growth rates, but slower growth with warmer growing season climates suggests reduced potential future forest growth.

Seasonal dynamics, age structure and reproduction of four Carabus species (Coleoptera: Carabidae) living in forested landscapes in Hungary

DEFF Research Database (Denmark)

Kádár, Ferenc; Fazekas, Judit P.; Sárospataki, Miklós

2015-01-01

Seasonal dynamics and reproductive phenological parameters of four Carabus species (C. convexus, C. coriaceus, C. germarii and C. hortensis) common in Hungary were studied by pitfall trapping and dissection. Beetles were collected in an abandoned apple orchard and in the bordering oak forest near...... Budapest (Central Hungary), in 1988–1991. The sex ratio was male-dominated, but this was significant only for C. coriaceus. The catch of C. germarii adults showed relatively short activity period with unimodal curve, but activity was longer and bimodal for the other three species. Adults of C. germarii...

Are optical indices good proxies of seasonal changes in carbon fluxes and stress-related physiological status in a beech forest?

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Nestola, E; Scartazza, A; Di Baccio, D; Castagna, A; Ranieri, A; Cammarano, M; Mazzenga, F; Matteucci, G; Calfapietra, C

2018-01-15

This study investigates the functionality of a Mediterranean-mountain beech forest in Central Italy using simultaneous determinations of optical measurements, carbon (C) fluxes, leaf eco-physiological and biochemical traits during two growing seasons (2014-2015). Meteorological variables showed significant differences between the two growing seasons, highlighting a heat stress coupled with a reduced water availability in mid-summer 2015. As a result, a different C sink capacity of the forest was observed between the two years of study, due to the differences in stressful conditions and the related plant physiological status. Spectral indices related to vegetation (VIs, classified in structural, chlorophyll and carotenoid indices) were computed at top canopy level and used to track CO 2 fluxes and physiological changes. Optical indices related to structure (EVI 2, RDVI, DVI and MCARI 1) were found to better track Net Ecosystem Exchange (NEE) variations for 2014, while indices related to chlorophylls (SR red edge, CL red edge, MTCI and DR) provided better results for 2015. This suggests that when environmental conditions are not limiting for forest sink capacity, structural parameters are more strictly connected to C uptake, while under stress conditions indices related to functional features (e.g., chlorophyll content) become more relevant. Chlorophyll indices calculated with red edge bands (SR red edge, NDVI red edge, DR, CL red edge) resulted to be highly correlated with leaf nitrogen content (R 2 >0.70), while weaker, although significant, correlations were found with chlorophyll content. Carotenoid indices (PRI and PSRI) were strongly correlated with both chlorophylls and carotenoids content, suggesting that these indices are good proxies of the shifting pigment composition related to changes in soil moisture, heat stress and senescence. Our work suggests the importance of integrating different methods as a successful approach to understand how changing climatic

Climate controls on forest productivity along the climate gradient of the western Sierra Nevada

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Kelly, A. E.; Goulden, M. L.

2010-12-01

The broad climate gradient of the slopes of the western Sierra Nevada mountains supports ecosystems spanning extremes of productivity, biomass, and function. We are using this natural environmental gradient to understand how climate controls NPP, aboveground biomass, species' range limits, and phenology. Our experimental approach combines eddy covariance, sap flow, dendrometer, and litterfall measurements in combination with soil and hydrological data from the Southern Sierra Critical Zone Observatory (SSCZO). We have found that above about 2500 m, forest productivity is limited by winter cold, while below 1200 m, productivity is likely limited by summer drought. The sweet spot between these elevations has a nearly year-long growing season despite a snowpack that persists for as long as six months. Our results show that small differences in temperature can markedly alter the water balance and productivity of mixed conifer forests.

Seasonal variations of gas exchange and water relations in deciduous and evergreen trees in monsoonal dry forests of Thailand.

Science.gov (United States)

Ishida, Atsushi; Harayama, Hisanori; Yazaki, Kenichi; Ladpala, Phanumard; Sasrisang, Amornrat; Kaewpakasit, Kanokwan; Panuthai, Samreong; Staporn, Duriya; Maeda, Takahisa; Gamo, Minoru; Diloksumpun, Sapit; Puangchit, Ladawan; Ishizuka, Moriyoshi

2010-08-01

This study compared leaf gas exchange, leaf hydraulic conductance, twig hydraulic conductivity and leaf osmotic potential at full turgor between two drought-deciduous trees, Vitex peduncularis Wall. and Xylia xylocarpa (Roxb.) W. Theob., and two evergreen trees, Hopea ferrea Lanessan and Syzygium cumini (L.) Skeels, at the uppermost canopies in tropical dry forests in Thailand. The aims were to examine (i) whether leaf and twig hydraulic properties differ in relation to leaf phenology and (ii) whether xylem cavitation is a determinant of leaf shedding during the dry season. The variations in almost all hydraulic traits were more dependent on species than on leaf phenology. Evergreen Hopea exhibited the lowest leaf-area-specific twig hydraulic conductivity (leaf-area-specific K(twig)), lamina hydraulic conductance (K(lamina)) and leaf osmotic potential at full turgor (Ψ(o)) among species, whereas evergreen Syzygium exhibited the highest leaf-area-specific K(twig), K(lamina) and Ψ(o). Deciduous Xylia had the highest sapwood-area-specific K(twig), along with the lowest Huber value (sapwood area/leaf area). More negative osmotic Ψ(o) and leaf osmotic adjustment during the dry season were found in deciduous Vitex and evergreen Hopea, accompanied by low sapwood-area-specific K(twig). Regarding seasonal changes in hydraulics, no remarkable decrease in K(lamina) and K(twig) was found during the dry season in any species. Results suggest that leaf shedding during the dry season is not always associated with extensive xylem cavitation.

Tree species diversity in a seasonally-dry forest: the case of the Pinkaití site, in the Kayapó Indigenous Area, Southeastern limits of the Amazon

OpenAIRE

Salm,Rodolfo

2004-01-01

This study investigates patterns of forest structure and tree species diversity in an anthropogenic palm grove and undisturbed areas at the seasonally-dry Pinkaití research station, in the Kayapó Indigenous Area. This site, managed by the Conservation International do Brasil, is the most southeastern site floristically surveyed in the Amazon until now. The secondary and a nearby undisturbed forest were sampled in a group of 52 floristic plots of 0.0625-ha (25x25-m) where all trees with DBH > ...

Soil respiration in tropical seasonal rain forest in Xishuangbanna, SW China

Institute of Scientific and Technical Information of China (English)

SHA; Liqing; ZHENG; Zheng; TANG; Jianwei; WANG; Yinghong

2005-01-01

With the static opaque chamber and gas chromatography technique, from January 2003 to January 2004 soil respiration was investigated in a tropical seasonal rain forest in Xishuangbanna, SW China. In this study three treatments were applied, each with three replicates: A (bare soil), B (soil+litter), and C (soil+litter+seedling). The results showed that soil respiration varied seasonally, low from December 2003 to February 2004, and high from June to July 2004. The annual average values of CO2 efflux from soil respiration differed among the treatments at 1% level, with the rank of C (14642 mgCO2· m-2. h-1)＞B (12807 mgCO2· m-2. h-1)＞A (9532 mgCO2· m-2. h-1). Diurnal variation in soil respiration was not apparent due to little diurnal temperate change in Xishuangbanna. There was a parabola relationship between soil respiration and soil moisture at 1% level. Soil respiration rates were higher when soil moisture ranged from 35% to 45%. There was an exponential relationship between soil respiration and soil temperature (at a depth of 5cm in mineral soil) at 1% level. The calculated Q1o values in this study,ranging from 2.03 to 2.36, were very near to those of tropical soil reported. The CO2 efflux in 2003was 5.34 kgCO2· m-2. a-1 from soil plus litter plus seedling, of them 3.48 kgCO2· m-2. a-1 from soil (accounting for 62.5%), 1.19 kgCO2· m-2. a-1 from litter (22.3%) and 0.67 kgCO2·m-2. a-1 from seedling (12.5%).

Seasonal Patterns of Sporophyte Growth, Fertility, Fouling, and Mortality of Saccharina latissima in Skagerrak, Norway: Implications for Forest Recovery

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Guri Sogn Andersen

2011-01-01

Full Text Available On the Skagerrak coast the kelp Saccharina latissima has suffered severe stand reductions over the last decade, resulting in loss of important habitats. In the present study, healthy kelp plants were transplanted into four deforested areas and their patterns of growth, reproduction, and survival were monitored through subsequent seasons. Our main objective was to establish whether the kelp plants were able to grow and mature in deforested areas. We observed normal patterns of growth and maturation at all study sites. However, heavy fouling by epiphytes occurred each summer, followed by high kelp mortality. The study shows that the seasonal variations and the life stage timing of S. latissima make formation of self-sustainable populations impossible in the present environment. Most noteworthy, we suggest that fouling by epiphytes is involved in the lack of kelp forest recovery in Skagerrak, Norway.

Marked seasonal variation in the wild mouse gut microbiota.

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Maurice, Corinne F; Knowles, Sarah C L; Ladau, Joshua; Pollard, Katherine S; Fenton, Andy; Pedersen, Amy B; Turnbaugh, Peter J

2015-11-01

Recent studies have provided an unprecedented view of the microbial communities colonizing captive mice; yet the host and environmental factors that shape the rodent gut microbiota in their natural habitat remain largely unexplored. Here, we present results from a 2-year 16 S ribosomal RNA gene sequencing-based survey of wild wood mice (Apodemus sylvaticus) in two nearby woodlands. Similar to other mammals, wild mice were colonized by 10 bacterial phyla and dominated by the Firmicutes, Bacteroidetes and Proteobacteria. Within the Firmicutes, the Lactobacillus genus was most abundant. Putative bacterial pathogens were widespread and often abundant members of the wild mouse gut microbiota. Among a suite of extrinsic (environmental) and intrinsic (host-related) factors examined, seasonal changes dominated in driving qualitative and quantitative differences in the gut microbiota. In both years examined, we observed a strong seasonal shift in gut microbial community structure, potentially due to the transition from an insect- to a seed-based diet. This involved decreased levels of Lactobacillus, and increased levels of Alistipes (Bacteroidetes phylum) and Helicobacter. We also detected more subtle but statistically significant associations between the gut microbiota and biogeography, sex, reproductive status and co-colonization with enteric nematodes. These results suggest that environmental factors have a major role in shaping temporal variations in microbial community structure within natural populations.

Seasonal changes in plant-water relations influence patterns of leaf display in Miombo woodlands: evidence of water conservative strategies.

Science.gov (United States)

Vinya, Royd; Malhi, Yadvinder; Brown, Nick D; Fisher, Joshua B; Brodribb, Timothy; Aragão, Luiz E O C

2018-06-15

Water availability has frequently been linked to seasonal leaf display in seasonally dry ecosystems, but there have been few ecohydrological investigations of this link. Miombo woodland is a dominant seasonally dry tropical forest ecosystem type in southern Africa; however, there are few data on the relationship between seasonal dynamics in plant-water relations and patterns of leaf display for Miombo woodland. Here we investigate this relationship among nine key Miombo woodland tree species differing in drought tolerance ability and leaf phenology. Results of this study showed that seasonal patterns of leaf phenology varied significantly with seasonal changes in stem water relations among the nine species. Leaf shedding coincided with the attainment of seasonal minimum stem water potential. Leaf flush occurred following xylem rehydration at the peak of the dry season suggesting that endogenous plant factors play a pivotal role in seasonal leaf display in this forest type. Drought-tolerant deciduous species suffered significantly higher seasonal losses in xylem hydraulic conductivity than the drought-intolerant semi-evergreen tree species (P water stress in seasonally dry tropical forests selects for water conservative traits that protect the vulnerable xylem transport system. Therefore, seasonal rhythms in xylem transport dictate patterns of leaf display in seasonally dry tropical forests.

Viewing Forests Through a Historical Lens

Science.gov (United States)

Noreen Parks; Eric [< em> featured scientist< /em> ]. Knapp

2009-01-01

Past records on fire-resilient, biodiverse stands could offer models for the future.  This year marks the centennial of the Forest Service’s nationwide network of 80 experimental forests and ranges, which serve as field laboratories for long-term studies on the science and management of national forests. At the Stanislaus-Tuolumne Experimental Forest in the central...

Influence of spring phenology on seasonal and annual carbon balance in two contrasting New England forests.

Science.gov (United States)

Richardson, Andrew D; Hollinger, David Y; Dail, D Bryan; Lee, John T; Munger, J William; O'keefe, John

2009-03-01

Spring phenology is thought to exert a major influence on the carbon (C) balance of temperate and boreal ecosystems. We investigated this hypothesis using four spring onset phenological indicators in conjunction with surface-atmosphere CO(2) exchange data from the conifer-dominated Howland Forest and deciduous-dominated Harvard Forest AmeriFlux sites. All phenological measures, including CO(2) source-sink transition dates, could be well predicted on the basis of a simple two-parameter spring warming model, indicating good potential for improving the representation of phenological transitions and their dynamic responsiveness to climate variability in land surface models. The date at which canopy-scale photosynthetic capacity reached a threshold value of 12 micromol m(-2) s(-1) was better correlated with spring and annual flux integrals than were either deciduous or coniferous bud burst dates. For all phenological indicators, earlier spring onset consistently, but not always significantly, resulted in higher gross primary productivity (GPP) and ecosystem respiration (RE) for both seasonal (spring months, April-June) and annual flux integrals. The increase in RE was less than that in GPP; depending on the phenological indicator used, a one-day advance in spring onset increased springtime net ecosystem productivity (NEP) by 2-4 g C m(-2) day(-1). In general, we could not detect significant differences between the two forest types in response to earlier spring, although the response to earlier spring was generally more pronounced for Harvard Forest than for Howland Forest, suggesting that future climate warming may favor deciduous species over coniferous species, at least in this region. The effect of earlier spring tended to be about twice as large when annual rather than springtime flux integrals were considered. This result is suggestive of both immediate and lagged effects of earlier spring onset on ecosystem C cycling, perhaps as a result of accelerated N cycling

Wet season water distribution in a tropical Andean cloud forest of Boyacá (Colombia) during the dry climate of El Niño

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Garcia-Santos, G.; Berdugo, M. B.

2010-07-01

Fog has been demonstrated as the only source of moisture during the dry climate of El Niño in the tropical Andean cloud forest of Boyacá region in Colombia, yet its importance for the forest is virtually unknown. We assessed fog water distribution during the wet season inside the forest and outside in a practically deforested area. Water intercepted by plant was measured at different vertical stratus. Soil moisture in the first centimetres was also measured. During the anomalous drier wet season there was lack of rainfall and the total recorded cloud water was lower compared with the same period during the previous year. Our results indicated that the upper part of the forest mass intercepts most of the fog water compared with lower stratus when the fog event starts. However upper most stratus became rapidly drier after the event, which is explained because water is released to the atmosphere due to high heat atmosphere-leaves interface fluctuations caused by wind and solar radiation, flows towards a different water potential and drips from the leaves. Low amount of fog dripped from tree foliage into the soil, indicating a large water storage capacity of the epiphyte and bryophyte vegetation. Despite the small amount of throughfall, understory vegetation and litter remained wet, which might be explained by the water flowing through the epiphyte vegetation or the high capacity of the understory to absorb moisture from the air. Soil water did not infiltrate in depth, which underlines the importance of fog as water and cool source for seedling growth and shallow rooted understory species, especially during drier conditions.

Natural and near natural tropical forest values

Science.gov (United States)

Daniel H. Henning

2011-01-01

This paper identifies and describes some of the values associated with tropical rain forests in their natural and near-natural conditions. Tropical rain forests are moist forests in the humid tropics where temperature and rainfall are high and the dry season is short. These closed (non-logged) and broad-leaved forests are a global resource. Located almost entirely in...

Effects of climate change on Forest Service strategic goals

Science.gov (United States)

Forest Service U.S. Department of Agriculture

2010-01-01

Climate change affects forests and grasslands in many ways. Changes in temperature and precipitation affect plant productivity as well as some species' habitat. Changes in key climate variables affect the length of the fire season and the seasonality of National Forest hydrological regimes. Also, invasive species tend to adapt to climate change more easily and...

Influence of physiological phenology on the seasonal pattern of ecosystem respiration in deciduous forests.

Science.gov (United States)

Migliavacca, Mirco; Reichstein, Markus; Richardson, Andrew D; Mahecha, Miguel D; Cremonese, Edoardo; Delpierre, Nicolas; Galvagno, Marta; Law, Beverly E; Wohlfahrt, Georg; Black, T Andrew; Carvalhais, Nuno; Ceccherini, Guido; Chen, Jiquan; Gobron, Nadine; Koffi, Ernest; Munger, J William; Perez-Priego, Oscar; Robustelli, Monica; Tomelleri, Enrico; Cescatti, Alessandro

2015-01-01

Understanding the environmental and biotic drivers of respiration at the ecosystem level is a prerequisite to further improve scenarios of the global carbon cycle. In this study we investigated the relevance of physiological phenology, defined as seasonal changes in plant physiological properties, for explaining the temporal dynamics of ecosystem respiration (RECO) in deciduous forests. Previous studies showed that empirical RECO models can be substantially improved by considering the biotic dependency of RECO on the short-term productivity (e.g., daily gross primary production, GPP) in addition to the well-known environmental controls of temperature and water availability. Here, we use a model-data integration approach to investigate the added value of physiological phenology, represented by the first temporal derivative of GPP, or alternatively of the fraction of absorbed photosynthetically active radiation, for modeling RECO at 19 deciduous broadleaved forests in the FLUXNET La Thuile database. The new data-oriented semiempirical model leads to an 8% decrease in root mean square error (RMSE) and a 6% increase in the modeling efficiency (EF) of modeled RECO when compared to a version of the model that does not consider the physiological phenology. The reduction of the model-observation bias occurred mainly at the monthly time scale, and in spring and summer, while a smaller reduction was observed at the annual time scale. The proposed approach did not improve the model performance at several sites, and we identified as potential causes the plant canopy heterogeneity and the use of air temperature as a driver of ecosystem respiration instead of soil temperature. However, in the majority of sites the model-error remained unchanged regardless of the driving temperature. Overall, our results point toward the potential for improving current approaches for modeling RECO in deciduous forests by including the phenological cycle of the canopy. © 2014 John Wiley & Sons

Seasonal cycles of isoprene concentrations in the Amazonian rainforest

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Trostdorf, C. R.; Gatti, L. V.; Yamazaki, A.; Potosnak, M. J.; Guenther, A.; Martins, W. C.; Munger, J. W.

2004-03-01

Tropical forests are an important global source of volatile organic compounds (VOCs) and other atmospheric trace gases. The high biodiversity in tropical rainforests complicates the extrapolation of biogenic volatile organic compound (BVOC) emissions from leaf-level measurements to landscape and regional or global scales. In Amazónia, a significant fraction of the carbon emitted from the biosphere to the atmosphere is emitted in the form of BVOCs, and the knowledge of these emissions is important to our understanding of tropical and global atmospheric chemistry and carbon cycling. As part of the Large scale Biosphere-atmosphere experiment in Amazónia (LBA). VOC concentrations were measured at two sites near Santarém, Para State, Brazil. The two sites are located in the National Forest of Tapajós, the first corresponding to primary forest and the second to a forest, that was selectively logged. The samples were collected simultaneously at heights of 65 and 55 m (20 and 10 m above forest canopy, respectively). The average isoprene mixing ratio was 2.2-2.5 ppb at the two sites and the standard deviations within a site ranged from 1 to 1.2 ppb. A strong seasonality of isoprene mixing ratio was observed and associated with the wet and dry seasons. The lowest mixing ratios were found during the transition between the wet to dry season, while at the start of the biomass burning season the mixing ratios increase. A qualitative analysis of a one dimensional model demonstrates that the seasonal cycle in concentrations reflects changes in isoprene production by the ecosystem, not changes in boundary layer dynamics or chemistry. The magnitude of the cycle indicates that the physiological capacity of the ecosystem to emit isoprene may depend on water availability although phenological changes could also contribute to the observed variations. A simple 1-D model that assumes mean daytime isoprene fluxes of 1.5 mg m-2h-1 and 0.9 mg m-2h-1 scaled by an algorithm depending on

Habitat selection by owls in a seasonal semi-deciduous forest in southern Brazil

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W. Menq

Full Text Available Abstract This paper tested the hypothesis that the structural components of vegetation have impact over the distribution of owl species in a fragment of a semi-deciduous seasonal forest. This paper also determined which vegetation variables contributed to the spatial distribution of owl species. It was developed in the Perobas Biological Reserve (PBR between September and December 2011. To conduct the owl census, a playback technique was applied at hearing points distributed to cover different vegetation types in the study area. A total of 56 individual owls of six species were recorded: Tropical Screech-Owl (Megascops choliba, Black-capped Screech-Owl (Megascops atricapilla, Tawny-browed Owl (Pulsatrix koeniswaldiana, Ferruginous Pygmy-Owl (Glaucidium brasilianum, Mottled Owl (Strix virgata and Stygian Owl (Asio stygius. The results suggest that the variables of vegetation structure have impact on the occurrence of owls. The canopy height, the presence of hollow trees, fallen trees and glades are the most important structural components influencing owl distribution in the sampled area.

Seasonal and inter-annual variations in methyl mercury concentrations in zooplankton from boreal lakes impacted by deforestation or natural forest fires.

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Garcia, Edenise; Carignan, Richard; Lean, David R S

2007-08-01

We compared the effects of natural and anthropogenic watershed disturbances on methyl mercury (MeHg) concentration in bulk zooplankton from boreal Shield lakes. MeHg in zooplankton was monitored for three years in nine lakes impacted by deforestation, in nine lakes impacted by wildfire, and in twenty lakes with undisturbed catchments. Lakes were sampled during spring, mid- and late summer. MeHg in zooplankton showed a seasonal trend: concentrations were the lowest in spring, then peaked in mid-summer and decreased in late summer. Over the three study years, MeHg concentrations observed in mid-summer in zooplankton from forest harvested lakes were significantly higher than in reference and fire-impacted lakes, whereas differences between these two groups of lakes were not significant. The pattern of distribution of MeHg in zooplankton during the different seasons paralleled that of dissolved organic carbon (DOC), which is known as a vector of Hg from watershed soils to lake water. Besides DOC, MeHg in zooplankton also showed a positive significant correlation with epilimnetic temperature and sulfate concentrations. An inter-annual decreasing trend in MeHg was observed in zooplankton from reference and fire-impacted lakes. In forest harvested lakes, however, MeHg concentrations remained higher and nearly constant over three years following the impact. Overall these results indicate that the MeHg pulse observed in zooplankton following deforestation by harvesting is relatively long-lived, and may have repercussions to the accumulation of MeHg along the food chain. Therefore, potential effects of deforestation on the Hg contamination of fish should be taken into account in forest management practices.

Impacts of short-rotation early-growing season prescribed fire on a ground nesting bird in the central hardwoods region of North America

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Pittman, H. Tyler; Krementz, David G.

2016-01-01

Landscape-scale short-rotation early-growing season prescribed fire, hereafter prescribed fire, in upland hardwood forests represents a recent shift in management strategies across eastern upland forests. Not only does this strategy depart from dormant season to growing season prescriptions, but the strategy also moves from stand-scale to landscape-scale implementation (>1,000 ha). This being so, agencies are making considerable commitments in terms of time and resources to this management strategy, but the effects on wildlife in upland forests, especially those dominated by hardwood canopy species, are relatively unknown. We initiated our study to assess whether this management strategy affects eastern wild turkey reproductive ecology on the Ozark-St. Francis National Forest. We marked 67 wild turkey hens with Global Positioning System (GPS) Platform Transmitting Terminals in 2012 and 2013 to document exposure to prescribed fire, and estimate daily nest survival, nest success, and nest-site selection. We estimated these reproductive parameters in forest units managed with prescribed fire (treated) and units absent of prescribed fire (untreated). Of 60 initial nest attempts monitored, none were destroyed or exposed to prescribed fire because a majority of fires occurred early than a majority of the nesting activity. We found nest success was greater in untreated units than treated units (36.4% versus 14.6%). We did not find any habitat characteristic differences between successful and unsuccessful nest-sites. We found that nest-site selection criteria differed between treated and untreated units. Visual concealment and woody ground cover were common selection criteria in both treated and untreated units. However, in treated units wild turkey selected nest-sites with fewer small shrubs (20 cm DBH) but not in untreated units. In untreated units wild turkey selected nest-sites with more large shrubs (≥5cm ground diameter) but did not select for small shrubs or large

Impacts of Short-Rotation Early-Growing Season Prescribed Fire on a Ground Nesting Bird in the Central Hardwoods Region of North America.

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H Tyler Pittman

Full Text Available Landscape-scale short-rotation early-growing season prescribed fire, hereafter prescribed fire, in upland hardwood forests represents a recent shift in management strategies across eastern upland forests. Not only does this strategy depart from dormant season to growing season prescriptions, but the strategy also moves from stand-scale to landscape-scale implementation (>1,000 ha. This being so, agencies are making considerable commitments in terms of time and resources to this management strategy, but the effects on wildlife in upland forests, especially those dominated by hardwood canopy species, are relatively unknown. We initiated our study to assess whether this management strategy affects eastern wild turkey reproductive ecology on the Ozark-St. Francis National Forest. We marked 67 wild turkey hens with Global Positioning System (GPS Platform Transmitting Terminals in 2012 and 2013 to document exposure to prescribed fire, and estimate daily nest survival, nest success, and nest-site selection. We estimated these reproductive parameters in forest units managed with prescribed fire (treated and units absent of prescribed fire (untreated. Of 60 initial nest attempts monitored, none were destroyed or exposed to prescribed fire because a majority of fires occurred early than a majority of the nesting activity. We found nest success was greater in untreated units than treated units (36.4% versus 14.6%. We did not find any habitat characteristic differences between successful and unsuccessful nest-sites. We found that nest-site selection criteria differed between treated and untreated units. Visual concealment and woody ground cover were common selection criteria in both treated and untreated units. However, in treated units wild turkey selected nest-sites with fewer small shrubs (20 cm DBH but not in untreated units. In untreated units wild turkey selected nest-sites with more large shrubs (≥5 cm ground diameter but did not select for small

Impacts of Short-Rotation Early-Growing Season Prescribed Fire on a Ground Nesting Bird in the Central Hardwoods Region of North America.

Science.gov (United States)

Pittman, H Tyler; Krementz, David G

2016-01-01

Landscape-scale short-rotation early-growing season prescribed fire, hereafter prescribed fire, in upland hardwood forests represents a recent shift in management strategies across eastern upland forests. Not only does this strategy depart from dormant season to growing season prescriptions, but the strategy also moves from stand-scale to landscape-scale implementation (>1,000 ha). This being so, agencies are making considerable commitments in terms of time and resources to this management strategy, but the effects on wildlife in upland forests, especially those dominated by hardwood canopy species, are relatively unknown. We initiated our study to assess whether this management strategy affects eastern wild turkey reproductive ecology on the Ozark-St. Francis National Forest. We marked 67 wild turkey hens with Global Positioning System (GPS) Platform Transmitting Terminals in 2012 and 2013 to document exposure to prescribed fire, and estimate daily nest survival, nest success, and nest-site selection. We estimated these reproductive parameters in forest units managed with prescribed fire (treated) and units absent of prescribed fire (untreated). Of 60 initial nest attempts monitored, none were destroyed or exposed to prescribed fire because a majority of fires occurred early than a majority of the nesting activity. We found nest success was greater in untreated units than treated units (36.4% versus 14.6%). We did not find any habitat characteristic differences between successful and unsuccessful nest-sites. We found that nest-site selection criteria differed between treated and untreated units. Visual concealment and woody ground cover were common selection criteria in both treated and untreated units. However, in treated units wild turkey selected nest-sites with fewer small shrubs (20 cm DBH) but not in untreated units. In untreated units wild turkey selected nest-sites with more large shrubs (≥5 cm ground diameter) but did not select for small shrubs or

Scope on the Skies: Changing of the Seasons

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Riddle, Bob

2011-01-01

Learn the astronomy behind the changing of the seasons. Students know that we mark the change of seasons with the position of the Sun over certain parts of the Earth. The specific time and date for the change of seasons is determined by the position of the Sun, not above the horizon necessarily, nor geographically, but rather where the Sun is…

Seasonal variation in diversity and abundance of understorey birds ...

African Journals Online (AJOL)

Our findings suggest that in a situation where there is no natural forest, an exotic plantation with suitable indigenous understorey cover can help in protection of birds, including endemic and near-endemic species. Keywords: birds, conservation, Eastern Arc Mountains, plantation, seasonal altitudinal migration, seasons, ...

Caribbean dry forest networking: an opportunity for conservation

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K. Banda-Rodriguez; J. Weintritt; R.T. Pennington

2016-01-01

Seasonally dry tropical forest is the most threatened tropical forest in the world. Though its overall plant species diversity is lower than in neighboring biomes such as rain forest, species endemism can be high, and its conservation has often been neglected. Caribbean dry forests face diverse threats including tourism, agriculture, and climate change. The Latin...

Phenology of selected herbaceous species of northern Wisconsin deciduous forests and forest roads

International Nuclear Information System (INIS)

Zavitkovski, J.

1977-01-01

Vegetative and reproductive phenophases were observed from 1970 to 1974 on 30 native and 8 introduced herbaceous species growing under deciduous forests and on an abandoned logging road in the Enterprise Radiation Forest in northern Wisconsin. Forest herbs started growing in the same order each year, but logging-road herbs varied. Growth initiation was more variable in the early-starting than in the late-starting species. In most years logging-road herbs started growth a few days earlier than forest herbs. Initiation of flowering of the 38 species was bimodal, culminating around mid-May for forest species and around mid-July for logging-road species. In general, the annual start of flowering varied less than the start of vegetative growth. Duration of flowering of most species was variable, however. Seed ripening times varied strikingly among species, ranging from 11 days for Taraxacum officinale to 101 days for Iris versicolor. Seeds of forest herbs took longer to ripen than those of logging-road species. On the basis of growth initiation of the 6 earliest species, spring arrival in 1970 to 1974 differed by 26 days and appeared to be related to snow disappearance. The growing season of most species paralleled cumulative current-year (May--July) and last-year (August--September) precipitation. Multiple regression analyses between precipitation and average length of growing season explained 87 percent of the total variation for forest herbs and 69 percent of that for logging-road herbs

Asynchronous Amazon forest canopy phenology indicates adaptation to both water and light availability

International Nuclear Information System (INIS)

Jones, Matthew O; Kimball, John S; Nemani, Ramakrishna R

2014-01-01

Amazon forests represent nearly half of all tropical vegetation biomass and, through photosynthesis and respiration, annually process more than twice the amount of estimated carbon (CO 2 ) from fossil fuel emissions. Yet the seasonality of Amazon canopy cover, and the extent to which seasonal fluctuations in water availability and photosynthetically available radiation influence these processes, is still poorly understood. Implementing six remotely sensed data sets spanning nine years (2003–2011), with reported field and flux tower data, we show that southern equatorial Amazon forests exhibit a distinctive seasonal signal. Seasonal timing of water availability, canopy biomass growth and net leaf flush are asynchronous in regions with short dry seasons and become more synchronous across a west-to-east longitudinal moisture gradient of increasing dry season. Forest cover is responsive to seasonal disparities in both water and solar radiation availability, temporally adjusting net leaf flush to maximize use of these generally abundant resources, while reducing drought susceptibility. An accurate characterization of this asynchronous behavior allows for improved understanding of canopy phenology across contiguous tropical forests and their sensitivity to climate variability and drought. (letter)

Factors affecting seasonal habitat use, and predicted range of two tropical deer in Indonesian rainforest

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Rahman, Dede Aulia; Gonzalez, Georges; Haryono, Mohammad; Muhtarom, Aom; Firdaus, Asep Yayus; Aulagnier, Stéphane

2017-07-01

There is an urgent recognized need for conservation of tropical forest deer. In order to identify some environmental factors affecting conservation, we analyzed the seasonal habitat use of two Indonesian deer species, Axis kuhlii in Bawean Island and Muntiacus muntjak in south-western Java Island, in response to several physical, climatic, biological, and anthropogenic variables. Camera trapping was performed in different habitat types during both wet and dry season to record these elusive species. The highest number of photographs was recorded in secondary forest and during the dry season for both Bawean deer and red muntjac. In models, anthropogenic and climatic variables were the main predictors of habitat use. Distances to cultivated area and to settlement were the most important for A. kuhlii in the dry season. Distances to cultivated area and annual rainfall were significant for M. muntjak in both seasons. Then we modelled their predictive range using Maximum entropy modelling (Maxent). We concluded that forest landscape is the fundamental scale for deer management, and that secondary forests are potentially important landscape elements for deer conservation. Important areas for conservation were identified accounting of habitat transformation in both study areas.

Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae

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Marga Born

2010-07-01

Full Text Available Seasonal rainfall affects tropical forest dynamics and behaviorof species that are part of these ecosystems. The positive correlation between amphibian activity patterns and rainfall has been demonstrated repeatedly. Members of Dendrobatidae, a clade of Neotropical dart-poison frogs, are well known for their habitat use and behavior during the rainy season, but their behavior during the dry season has received little attention. We studied habitat use and diet of the dendrobatid frog Dendrobates tinctorius in French Guiana during the rainy and dry seasons. Unlike many other dendrobatid frogs, D. tinctorius does not maintain territories for the entire rainy season. Both sexes colonize recently formed canopy-gaps and stay in these forest patches for only a few weeks. The frogs inthese patches consume a great diversity of prey, consisting of ants, beetles, wasps, insect larvae, and mites. During the dry season, frogs move to retreat sites in mature forest, such as palm bracts and tree holes. The frogs are less active and consume fewer prey items in the dry season, and they consume fewer wasps and insect larvae, but more termites. Ants are the most common prey items during both the wet and dry seasons. We discuss the effects of shifts in seasonal habitat use on the territorial behavior of dendrobatid frogs.

Seasonal dynamics of common ground beetles (Coleoptera: Carabidae) along an urbanisation gradient near Sorø, Zealand, Denmark

DEFF Research Database (Denmark)

Elek, Zoltan; Howe, Andy G.; Enggaard, Mattias

2017-01-01

The seasonal activity of six carabid species (Nebria brevicollis, Carabus nemoralis, C. hortensis, C. coriaceus, Pterostichus melanarius and Abax parallelepipedus) was studied along an urbanisation gradient (rural forest – suburban forest – forest fragments in urban park) in Sorø, Denmark, during...... and between the years (C. nemoralis, N. brevicollis and P. melanarius). In four out of six studied species, 2005 was less favourable than 2004. Spring activity in the urban habitat started earlier than in the suburban or forested ones. Abetter understanding of urban green infrastructures in biodiversity...... assessments may need the study of seasonality in order to distinguish whether the bioindicator’s responses are to habitat quality or stochastic seasonal events....

Stand, species, and individual traits impact transpiration in historically disturbed forests.

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Blakely, B.; Rocha, A. V.; McLachlan, J. S.

2017-12-01

Historic logging disturbances have changed the structure and species composition of most Northern temperate forests. These changes impact the process of transpiration - which in turn impacts canopy surface temperature - but the links among structure, composition, and transpiration remain unclear. For this reason, ecosystem models typically use simplified structure and composition to simulate the impact of disturbances on forest transpiration. However, such simplifications ignore real variability among stands, species, and individual trees that may strongly influence transpiration across spatial and temporal scales. To capture this variability, we monitored transpiration in 48 individual trees of multiple species in both undisturbed (400+ yr) and historically logged (80 - 120 yr) forests. Using modern and historic forest surveys, we upscaled our observations to stand and regional scales to identify the key changes impacting transpiration. We extended these inferences by establishing a relationship between transpiration and measured surface temperature, linking disturbance-induced changes in structure and composition to local and regional climate. Despite greater potential evapotranspiration and basal area, undisturbed forest transpired less than disturbed (logged) forest. Transpiration was a strong predictor of surface temperature, and the canopy surface was warmer in undisturbed forest. Transpiration differences among disturbed and undisturbed forests resulted from (1) lesser transpiration and dampened seasonality in evergreen species (2) greater transpiration in younger individuals within a species, and (3) strong transpiration by large individuals. When transpiration was scaled to the stand or regional level in a simplified manner (e.g. a single transpiration rate for all deciduous individuals), the resulting estimates differed markedly from the original. Stand- species- and individual-level traits are therefore essential for understanding how transpiration and

Different Patterns of Changes in the Dry Season Diameter at Breast Height of Dominant and Evergreen Tree Species in a Mature Subtropical Forest in South China

Institute of Scientific and Technical Information of China (English)

Jun-Hua Yan; Guo-Yi Zhou; De-Qiang Zhang; Xu-Li Tang; Xu Wang

2006-01-01

Information on changes in diameter at breast height (DBH) is important for net primary production (NPP)estimates, timing of forest inventory, and forest management. In the present study, patterns of DBH change were measured under field conditions during the dry season for three dominant and native tree species in a monsoon evergreen broad-leaved forest in the Dinghushan Biosphere Reserve. For each tree species,different patterns of DBH change were observed. In the case of the fast-growing tree species Castanopsis chinensis Hance, large diurnal fluctuations occur, with a peak DBH in the early morning (around 05:00 h) that decreases to a minimum by about 14:00 h. Both Schima superba Gardn. et Chemp and Cryptocarya chinensis (Hance) Hemsl. exhibited less diurnal swelling and shrinkage. Diurnal fluctuations for these species were observed on a few occasions over the period of observation. Graphical comparisons and statistical analysis of changes in DBH with meteorological variables indicate that for different trees, the different changes in DBH observed responded to different meteorological variables. Large stem changes were found to occur for Ca. chinensis trees that were associated with variations in solar radiation. However, both S. superba and Cr. chinensis were found to be less sensitive to solar radiation. Changes in the DBH of these two species were found to be controlled mainly by soil temperature and soil moisture. During the later dry season, with a lower soil temperature and soil moisture, all three tree species stopped growing and only negligible shrinkage, expansion, or fluctuation occurred, suggesting that the optimum time to measure tree growth in the Dinghushan Biosphere Reserve is the later dry season.

Diagnosing the Role of Transpiration in the Transition from Dry to Wet Season Over the Amazon Using Satellite Observations

Science.gov (United States)

Wright, J. S.; Fu, R.; Yin, L.; Chae, J.

2013-12-01

Reanalysis data indicates that land surface evapotranspiration plays a key role in determining the timing of wet season onset over the Amazon. Here, we use satellite observations of water vapor and its stable isotopes, carbon dioxide, leaf area index, and precipitation together with reanalysis data to explore the importance of transpiration in initiating the transition from dry season to wet season over the Amazon. The growth of vegetation in this region is primarily limited by the availability of sunlight rather than the availability of soil moisture, so that the increase of solar radiation during the dry season coincides with dramatic increases in leaf area index within forested ecosystems. This period of plant growth is accompanied by uptake of carbon dioxide and enrichment of heavy isotopes in water vapor, particularly near the land surface. Reanalysis data indicate that this pre-wet season enrichment of HDO is accompanied by sharp increases in the surface latent heat flux, which eventually triggers sporadic moist convection. The transport of transpiration-enriched near-surface air by this convection causes a dramatic increase in free-tropospheric HDO in late August and September. September also marks transition points in the annual cycles of leaf area index (maximum) and carbon dioxide (minimum). The increase in convective activity during this period creates convergence, enhancing moisture transport into the region and initiating the wet season.

Fog Water Is Important in Maintaining the Water Budgets of Vascular Epiphytes in an Asian Tropical Karst Forests during the Dry Season

Directory of Open Access Journals (Sweden)

Yi Wu

2018-05-01

Full Text Available Fog may be an important source of water for forest vascular epiphytes on trees, because they lack direct access to sources of soil water, but little is known about the water use proportions from various sources and potential water uptake pathways in epiphytes. Here, we analyzed leaf carbon isotope ratios as a measure of water use efficiency (WUE, proportions of fog, rain, and soil water use, and foliar water uptake (FWU in species of epiphyte and their host trees in a tropical karst dwarf forest in China during the dry season. We found that the WUE, as represented by leaf δ13C, was generally enriched in the epiphyte species compared to their host trees. Epiphytes used substantial proportions of fog water, whereas water use in the host trees was dominated by soil water. The leaves of epiphytes and host trees absorbed water following immersion in water for 3 h and FWU possibly related to foliar epicuticular structures, such as fungal endophytes. Our results show a divergence of water use strategies between epiphytes and their hosts and highlight the importance of fog water for epiphytes during the dry season and under a climate change scenario with a reduced occurrence of fog events.

Water-use dynamics of a peat swamp forest and a dune forest in Maputaland, South Africa

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A. D. Clulow

2013-05-01

Full Text Available Peat swamp forests are the second rarest forest type found in South Africa while dune forests have been under severe threat through mining and agriculture. Both forest types exist in the conservation area, and World Heritage site, known as the iSimangaliso Wetland Park on the East coast of South Africa. The area is prone to severe droughts (Taylor et al., 2006 and recent attempts to understand the local water balance revealed that there was insufficient information on the water use of the indigenous forests of the area. The peat swamp forest and dune forest sites studied in this research were located within close proximity to each other, yet, are characterised by different landscape positions in terms of water availability. The coastal dune forest soil profile was generally dry and sandy and the tree roots did not have access to the water table. In contrast the peat swamp forest is located in an interdunal wetland where the trees have permanent access to water. The climate at both sites is subtropical with a mean annual precipitation of 1200 mm yr−1. However, over 20 months of measurement, the first summer (October 2009 to March 2010 was drier (424 versus 735 mm than the second summer (October 2010 to March 2011 emphasising the variability of the rainfall in the area and providing a wide range of conditions measured. The sap flow of an evergreen, overstory Syzygium cordatum and a semi-deciduous, understory Shirakiopsis elliptica were measured in the peat swamp forest using the heat ratio method. The Syzygium cordatum water use was not highly seasonal and the daily maximum water use ranged from approximately 30 L d−1 in winter to 45 L d−1 in summer whereas the extit{Shirakiopsis elliptica} water use was more seasonal at 2 L d−1 in winter and 12 L d−1 in summer. The water use of the Syzygium cordatum was not influenced by seasonal rainfall variations and was actually higher in the drier summer (October 2009 to March 2010. Three trees of

DRY DEPOSITION OF POLLUTANTS TO FORESTS

Science.gov (United States)

We report on the results of an extensive field campaign to measure dry deposition of ozone and sulfur dioxide to a sample of forest types in the United States. Measurements were made for full growing seasons over a deciduous forest in Pennsylvania and a mixed deciduous-conifer...

Tropical Montane Cloud Forests: Hydrometeorological variability in three neighbouring catchments with different forest cover

Science.gov (United States)

Ramírez, Beatriz H.; Teuling, Adriaan J.; Ganzeveld, Laurens; Hegger, Zita; Leemans, Rik

2017-09-01

Mountain areas are characterized by a large heterogeneity in hydrological and meteorological conditions. This heterogeneity is currently poorly represented by gauging networks and by the coarse scale of global and regional climate and hydrological models. Tropical Montane Cloud Forests (TMCFs) are found in a narrow elevation range and are characterized by persistent fog. Their water balance depends on local and upwind temperatures and moisture, therefore, changes in these parameters will alter TMCF hydrology. Until recently the hydrological functioning of TMCFs was mainly studied in coastal regions, while continental TMCFs were largely ignored. This study contributes to fill this gap by focusing on a TMCF which is located on the northern eastern Andes at an elevation of 1550-2300 m asl, in the Orinoco river basin highlands. In this study, we describe the spatial and seasonal meteorological variability, analyse the corresponding catchment hydrological response to different land cover, and perform a sensitivity analysis on uncertainties related to rainfall interpolation, catchment area estimation and streamflow measurements. Hydro-meteorological measurements, including hourly solar radiation, temperature, relative humidity, wind speed, precipitation, soil moisture and streamflow, were collected from June 2013 to May 2014 at three gauged neighbouring catchments with contrasting TMCF/grassland cover and less than 250 m elevation difference. We found wetter and less seasonally contrasting conditions at higher elevations, indicating a positive relation between elevation and fog or rainfall persistence. This pattern is similar to that of other eastern Andean TMCFs, however, the study site had higher wet season rainfall and lower dry season rainfall suggesting that upwind contrasts in land cover and moisture can influence the meteorological conditions at eastern Andean TMCFs. Contrasting streamflow dynamics between the studied catchments reflect the overall system response

Stress tolerance and ecophysiological ability of an invader and a native species in a seasonally dry tropical forest.

Science.gov (United States)

Oliveira, Marciel Teixeira; Matzek, Virginia; Dias Medeiros, Camila; Rivas, Rebeca; Falcão, Hiram Marinho; Santos, Mauro Guida

2014-01-01

Ecophysiological traits of Prosopis juliflora (Sw.) DC. and a phylogenetically and ecologically similar native species, Anadenanthera colubrina (Vell.) Brenan, were studied to understand the invasive species' success in caatinga, a seasonally dry tropical forest ecosystem of the Brazilian Northeast. To determine if the invader exhibited a superior resource-capture or a resource-conservative strategy, we measured biophysical and biochemical parameters in both species during dry and wet months over the course of two years. The results show that P. juliflora benefits from a flexible strategy in which it frequently outperforms the native species in resource capture traits under favorable conditions (e.g., photosynthesis), while also showing better stress tolerance (e.g., antioxidant activity) and water-use efficiency in unfavorable conditions. In addition, across both seasons the invasive has the advantage over the native with higher chlorophyll/carotenoids and chlorophyll a/b ratios, percent N, and leaf protein. We conclude that Prosopis juliflora utilizes light, water and nutrients more efficiently than Anadenanthera colubrina, and suffers lower intensity oxidative stress in environments with reduced water availability and high light radiation.

Hydrologic and forest management controls on DOC dynamics in the small watersheds of the H.J. Andrews Experimental Forest, OR

Science.gov (United States)

Lajtha, K.; Jones, J. A.

2016-12-01

Dissolved organic carbon (DOC) export from hillslopes to streams is an important component of the carbon cycle of a catchment and may be a critical source of energy for the aquatic food web in receiving waters. Using a long-term record of DOC and other dissolved nutrients and elements from paired watersheds from the H.J. Andrews Experimental Forest in Oregon, we explored hydrologic, climatic, and land-use controls on seasonal and inter-annual patterns of DOC flux in a seasonally dry ecosystem. Seasonal patterns of DOC flux demonstrated source limitations to DOC export, with DOC concentrations highest immediately following the first rains after a dry summer, and lowest after winter rains. In contrast, more geochemically-controlled elements showed simple dilution-concentration patterns with no seasonal hysteresis. Inter-annual patterns of DOC flux, however, did not provide evidence of source limitation, with DOC flux within a watershed tightly correlated to total discharge but not temperature. Among watersheds, forest harvest, even over 50 years ago, significantly reduced DOC flux but not fluxes of other elements including N; this response was linked to the loading of coarse woody debris to the forest floor. Chemical fingerprinting of DOC revealed that old-growth watersheds had higher fluxes of DOC characteristic of forest floor organic materials, likely delivered to streams through more surficial preferential flow pathways not subject to microbial alteration, respiration, or sorption losses. Taken together these results suggest that the biogeochemical composition of forested streams reflects both current hydrologic patterns and also processes that occurred many decades ago within the catchment.

The role of fire-return interval and season of burn in snag dynamics in a south Florida slash pine forest

Science.gov (United States)

Lloyd, John D.; Slater, Gary L.; Snyder, James R.

2012-01-01

Standing dead trees, or snags, are an important habitat element for many animal species. In many ecosystems, fire is a primary driver of snag population dynamics because it can both create and consume snags. The objective of this study was to examine how variation in two key components of the fire regime—fire-return interval and season of burn—affected population dynamics of snags. Using a factorial design, we exposed 1 ha plots, located within larger burn units in a south Florida slash pine (Pinus elliottii var. densa Little and Dorman) forest, to prescribed fire applied at two intervals (approximately 3-year intervals vs. approximately 6-year intervals) and during two seasons (wet season vs. dry season) over a 12- to 13-year period. We found no consistent effect of fire season or frequency on the density of lightly to moderately decayed or heavily decayed snags, suggesting that variation in these elements of the fire regime at the scale we considered is relatively unimportant in the dynamics of snag populations. However, our confidence in these findings is limited by small sample sizes, potentially confounding effects of unmeasured variation in fire behavior and effects (e.g., intensity, severity, synergy with drought cycles) and wide variation in responses within a treatment level. The generalizing of our findings is also limited by the narrow range of treatment levels considered. Future experiments incorporating a wider range of fire regimes and directly quantifying fire intensity would prove useful in identifying more clearly the role of fire in shaping the dynamics of snag populations.

Landscape fragmentation, severe drought, and the new Amazon forest fire regime.

Science.gov (United States)

Alencar, Ane A; Brando, Paulo M; Asner, Gregory P; Putz, Francis E

2015-09-01

Changes in weather and land use are transforming the spatial and temporal characteristics of fire regimes in Amazonia, with important effects on the functioning of dense (i.e., closed-canopy), open-canopy, and transitional forests across the Basin. To quantify, document, and describe the characteristics and recent changes in forest fire regimes, we sampled 6 million ha of these three representative forests of the eastern and southern edges of the Amazon using 24 years (1983-2007) of satellite-derived annual forest fire scar maps and 16 years of monthly hot pixel information (1992-2007). Our results reveal that changes in forest fire regime properties differentially affected these three forest types in terms of area burned and fire scar size, frequency, and seasonality. During the study period, forest fires burned 15% (0.3 million ha), 44% (1 million ha), and 46% (0.6 million ha) of dense, open, and transitional forests, respectively. Total forest area burned and fire scar size tended to increase over time (even in years of average rainfall in open canopy and transitional forests). In dense forests, most of the temporal variability in fire regime properties was linked to El Nino Southern Oscillation (ENSO)-related droughts. Compared with dense forests, transitional and open forests experienced fires twice as frequently, with at least 20% of these forests' areas burning two or more times during the 24-year study period. Open and transitional forests also experienced higher deforestation rates than dense forests. During drier years, the end of the dry season was delayed by about a month, which resulted in larger burn scars and increases in overall area burned later in the season. These observations suggest that climate-mediated forest flammability is enhanced by landscape fragmentation caused by deforestation, as observed for open and transitional forests in the Eastern portion of the Amazon Basin.

An enhanced forest classification scheme for modeling vegetation-climate interactions based on national forest inventory data

Science.gov (United States)

Majasalmi, Titta; Eisner, Stephanie; Astrup, Rasmus; Fridman, Jonas; Bright, Ryan M.

2018-01-01

Forest management affects the distribution of tree species and the age class of a forest, shaping its overall structure and functioning and in turn the surface-atmosphere exchanges of mass, energy, and momentum. In order to attribute climate effects to anthropogenic activities like forest management, good accounts of forest structure are necessary. Here, using Fennoscandia as a case study, we make use of Fennoscandic National Forest Inventory (NFI) data to systematically classify forest cover into groups of similar aboveground forest structure. An enhanced forest classification scheme and related lookup table (LUT) of key forest structural attributes (i.e., maximum growing season leaf area index (LAImax), basal-area-weighted mean tree height, tree crown length, and total stem volume) was developed, and the classification was applied for multisource NFI (MS-NFI) maps from Norway, Sweden, and Finland. To provide a complete surface representation, our product was integrated with the European Space Agency Climate Change Initiative Land Cover (ESA CCI LC) map of present day land cover (v.2.0.7). Comparison of the ESA LC and our enhanced LC products (https://doi.org/10.21350/7zZEy5w3) showed that forest extent notably (κ = 0.55, accuracy 0.64) differed between the two products. To demonstrate the potential of our enhanced LC product to improve the description of the maximum growing season LAI (LAImax) of managed forests in Fennoscandia, we compared our LAImax map with reference LAImax maps created using the ESA LC product (and related cross-walking table) and PFT-dependent LAImax values used in three leading land models. Comparison of the LAImax maps showed that our product provides a spatially more realistic description of LAImax in managed Fennoscandian forests compared to reference maps. This study presents an approach to account for the transient nature of forest structural attributes due to human intervention in different land models.

Landscape-moderated bird nest predation in hedges and forest edges

Science.gov (United States)

Ludwig, Martin; Schlinkert, Hella; Holzschuh, Andrea; Fischer, Christina; Scherber, Christoph; Trnka, Alfréd; Tscharntke, Teja; Batáry, Péter

2012-11-01

Landscape-scale agricultural intensification has caused severe declines in biodiversity. Hedges and forest remnants may mitigate biodiversity loss by enhancing landscape heterogeneity and providing habitat to a wide range of species, including birds. However, nest predation, the major cause of reproductive failure of birds, has been shown to be higher in forest edges than in forest interiors. Little is known about how spatial arrangement (configuration) of hedges affects the avian nest predation. We performed an experiment with artificial ground and elevated nests (resembling yellowhammer and whitethroat nests) baited with quail and plasticine eggs. Nests were placed in three habitat types with different degrees of isolation from forests: forest edges, hedges connected to forests and hedges isolated from forests. Nest predation was highest in forest edges, lowest in hedges connected to forests and intermediate in isolated hedges. In the early breeding season, we found similar nest predation on ground and elevated nests, but in the late breeding season nest predation was higher on ground nests than on elevated nests. Small mammals were the main predators of ground nests and appeared to be responsible for the increase in predation from early to late breeding season, whereas the elevated nests were mainly depredated by small birds and small mammals. High predation pressure at forest edges was probably caused by both forest and open-landscape predators. The influence of forest predators may be lower at hedges, leading to lower predation pressure than in forest edges. Higher predation pressure in isolated than connected hedges might be an effect of concentration of predators in these isolated habitats. We conclude that landscape configuration of hedges is important in nest predation, with connected hedges allowing higher survival than isolated hedges and forest edges.

Seasonal variation in soil seed bank size and species composition of selected habitat types in Maputaland, South Africa

Directory of Open Access Journals (Sweden)

M. J. S. Kellerman

2007-08-01

Full Text Available Seasonal variation in seed bank size and species composition of five selected habitat types within the Tembe Elephant Park. South Africa, was investigated. At three-month intervals, soil samples were randomly collected from five different habitat types: a, Licuati forest; b, Licuati thicket; c, a bare or sparsely vegetated zone surrounding the forest edge, referred to as the forest/grassland ecotone; d, grassland; and e, open woodland. Most species in the seed bank flora were either grasses, sedges, or forbs, with hardly any evidence of woody species. The Licuati forest and thicket soils produced the lowest seed densities in all seasons.  Licuati forest and grassland seed banks showed a two-fold seasonal variation in size, those of the Licuati thicket and woodland a three-fold variation in size, whereas the forest/grassland ecotone maintained a relatively large seed bank all year round. The woodland seed bank had the highest species richness, whereas the Licuati forest and thicket soils were poor in species. Generally, it was found that the greatest correspondence in species composition was between the Licuati forest and thicket, as well as the forest/grassland ecotone and grassland seed bank floras.

A Passive Microwave L-Band Boreal Forest Freeze/Thaw and Vegetation Phenology Study

Science.gov (United States)

Roy, A.; Sonnentag, O.; Pappas, C.; Mavrovic, A.; Royer, A.; Berg, A. A.; Rowlandson, T. L.; Lemay, J.; Helgason, W.; Barr, A.; Black, T. A.; Derksen, C.; Toose, P.

2016-12-01

The boreal forest is the second largest land biome in the world and thus plays a major role in the global and regional climate systems. The extent, timing and duration of seasonal freeze/thaw (F/T) state influences vegetation developmental stages (phenology) and, consequently, constitute an important control on how boreal forest ecosystems exchange carbon, water and energy with the atmosphere. The effective retrieval of seasonal F/T state from L-Band radiometry was demonstrated using satellite mission. However, disentangling the seasonally differing contributions from forest overstory and understory vegetation, and the soil surface to the satellite signal remains challenging. Here we present initial results from a radiometer field campaign to improve our understanding of the L-Band derived boreal forest F/T signal and vegetation phenology. Two L-Band surface-based radiometers (SBR) are installed on a micrometeorological tower at the Southern Old Black Spruce site in central Saskatchewan over the 2016-2017 F/T season. One radiometer unit is installed on the flux tower so it views forest including all overstory and understory vegetation and the moss-covered ground surface. A second radiometer unit is installed within the boreal forest overstory, viewing the understory and the ground surface. The objectives of our study are (i) to disentangle the L-Band F/T signal contribution of boreal forest overstory from the understory and ground surface, (ii) to link the L-Band F/T signal to related boreal forest structural and functional characteristics, and (iii) to investigate the use of the L-Band signal to characterize boreal forest carbon, water and energy fluxes. The SBR observations above and within the forest canopy are used to retrieve the transmissivity (γ) and the scattering albedo (ω), two parameters that describe the emission of the forest canopy though the F/T season. These two forest parameters are compared with boreal forest structural and functional

[Characteristics of floor litter and soil arthropod community in different types ot subtropical forest in Ailao Mountain of Yunnan, Southwest China].

Science.gov (United States)

Yang, Zhao; Yang, Xiao-Dong

2011-11-01

By using line transect method, an investigation was conducted on the floor litter and soil arthropod community in a mid mountain wet evergreen broad-leaved forest, a mossy dwarf forest, and a Populus bonatii forest in Ailao Mountain of Yunnan in April (dry and hot season), June (rainy season), and December (dry and cold season), 2005. In both dry and rainy seasons, the existing floor litter mass, C storage, and C/N ratio in the three forests all increased in the order of mossy dwarf forest > P. bonatii forest > evergreen broad-leaved forest, but the N storage had less difference. In the floor litter layer of the forests, Acari and Collembola were the dominant groups of soil arthropod community, while Diptera larvae, Coleoptera, ants, and Homoptera were the common groups. The Sorenson coefficients of soil arthropod community in the three forests were extremely great. No significant differences were observed in the soil arthropod density (ind x m(-2)) in the floor litter layer among the three forests, but the relative density (ind x g(-1)) of soil arthropods was higher in the evergreen broad-leaved forest and P. bonatii forest than in the mossy dwarf forest. In the three forests, the density of soil arthropods was significantly higher in dry season than in rainy season, but the Shannon diversity index had less difference. There were significant positive correlations between the existing floor litter mass and the individual density (ind x m(-2)) and dominant groups of soil arthropod communities in dry and hot season (April), but negative correlations between the existing floor litter mass and the relative density (ind x g(-1)) of soil arthropod communities and Acari in dry and cold season (December). The individual densities of Collembola and Coleoptera also had positive correlations with the N storage of the existing floor litter mass in the three forests. It was considered that the floor litter and the development of soil arthropod community in the litter layer of

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks

Science.gov (United States)

Zemp, Delphine Clara; Schleussner, Carl-Friedrich; Barbosa, Henrique M. J.; Hirota, Marina; Montade, Vincent; Sampaio, Gilvan; Staal, Arie; Wang-Erlandsson, Lan; Rammig, Anja

2017-03-01

Reduced rainfall increases the risk of forest dieback, while in return forest loss might intensify regional droughts. The consequences of this vegetation-atmosphere feedback for the stability of the Amazon forest are still unclear. Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. We apply a novel complex-network approach, in which Amazon forest patches are linked by observation-based atmospheric water fluxes. Our results suggest that the risk of self-amplified forest loss is reduced with increasing heterogeneity in the response of forest patches to reduced rainfall. Under dry-season Amazonian rainfall reductions, comparable to Last Glacial Maximum conditions, additional forest loss due to self-amplified effects occurs in 10-13% of the Amazon basin. Although our findings do not indicate that the projected rainfall changes for the end of the twenty-first century will lead to complete Amazon dieback, they suggest that frequent extreme drought events have the potential to destabilize large parts of the Amazon forest.

Variations of net ecosystem production due to seasonal precipitation differences in a tropical dry forest of northwest Mexico

Science.gov (United States)

Verduzco, Vivian S.; Garatuza-Payán, Jaime; Yépez, Enrico A.; Watts, Christopher J.; Rodríguez, Julio C.; Robles-Morua, Agustin; Vivoni, Enrique R.

2015-10-01

Due to their large extent and high primary productivity, tropical dry forests (TDF) are important contributors to atmospheric carbon exchanges in subtropical and tropical regions. In northwest Mexico, a bimodal precipitation regime that includes winter precipitation derived from Pacific storms and summer precipitation from the North American monsoon (NAM) couples water availability with ecosystem processes. We investigated the net ecosystem production of a TDF ecosystem using a 4.5 year record of water and carbon fluxes obtained from the eddy covariance method complemented with remotely sensed data. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer that respiration is mainly due to decomposition of soil organic matter accumulated from the prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production but can be overwhelmed by the strength of the primary productivity during the NAM. Precipitation characteristics during NAM have significant controls on sustaining carbon fixation in the TDF into the fall season. We identified that a threshold of ~350 to 400 mm of monsoon precipitation leads to a switch in the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This monsoonal precipitation threshold is typically exceeded one out of every 2 years. The close coupling of winter and summer periods with respect to carbon fluxes suggests that the annual carbon balance is dependent on precipitation amounts in both seasons in TDF ecosystems.

Hematological alterations in broiler chicks during different seasons supplemented with herbal formulations

Directory of Open Access Journals (Sweden)

Nidhi Singh1

2008-08-01

Full Text Available The study was conducted on Vencobb broiler chicks to ascertain the antistress affects of Zist, Zeetress and a combination of Amla and Turmeric during summer, rainy and winter seasons and thereby the haematological changes of birds revealed that during all the three seasons a marked improvement in Haemoglobin was encountered in all the three groups where herbal preparations were supplemented. A marked increase in the lymphocyte count occurred during summer and winter seasons in all the experimental groups of bird as compared to the control group. The heterophil count was decreased with the supplementation of herbal formulations in the feed irrespective of the seasons encountered in the season. This decrease in heterophil count was highly significant in seasons like summer, winter and rainy. This observation proves the hepato-stimulatory, hepato protective and immuno modulating effects of herbal preparations. [Veterinary World 2008; 1(4.000: 110-112

Influences of Herbivory and Canopy Opening Size on Forest Regeneration in a Southern Bottomland Hardwood Forest

Science.gov (United States)

Steven B. Castleberry; W. Mark Ford; Carl V. Miller; Winston P. Smith

2000-01-01

We examined the effects of white-tailed deer (Odocoileus virginianus) browsing and canopy opening size on relative abundance and diversity of woody and herbaceous regeneration in various sized forest openings in a southern, bottomland hardwood forest over three growing seasons (1995-1997). We created 36 canopy openings (gaps), ranging from 7 to 40m...

Fluctuations in daily energy intake do not cause physiological stress in a Neotropical primate living in a seasonal forest.

Science.gov (United States)

Martínez-Mota, Rodolfo; Righini, Nicoletta; Palme, Rupert

2016-12-01

Animals may face periods of nutritional stress due to short-term food shortage and/or low energy consumption associated with seasonal fluctuations in resource availability. We tested the hypothesis that periods of restricted macronutrient and energy intake result in energy deficits and physiological stress in wild black howler monkeys (Alouatta pigra) inhabiting seasonal tropical semi-deciduous forests. We conducted full-day follows of focal animals recording feeding rates, time spent feeding, and total amount of food ingested. We carried out nutritional analysis of foods collected from feeding trees and calculated the daily nutrient and energy intake of each focal individual. Fecal glucocorticoid metabolites (fGCM) of focal animals were used as an indicator of physiological stress. We found that fluctuations in daily energy intake across seasons did not have significant effects on fGCM of individuals. However, protein intake was negatively associated with fGCM, highlighting the interplay among macronutrients, metabolism, and the endocrine system. Fecal glucocorticoid metabolites were also positively related to fruit availability, but this relationship was most likely due to social stress associated with intergroup encounters and resource defense that occurred when preferred trees were fruiting. Behavioral strategies such as dietary shifts and nutrient mixing, and metabolic adaptations such as low energy expenditure allowed individuals to fulfill their minimum energy requirements even during periods of decreased resource availability and intake. The present study suggests that seasonal variations in food, macronutrient, and energy acquisition may have limited physiological costs for animals that exploit different types of plant resources such as howler monkeys.

Concentración estacional de micronutrientes en hojas de cuatro especies forestales del Parque Chaqueño, Argentina Seasonal micronutrients concentration in leaves of four forest species from Parque Chaqueño, Argentina

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Juan Prause

2012-09-01

the functioning of forest ecosystems. Leaves of different forest species observe specific chemical composition, and some seasonal differences in biomass production, may be related to climate fluctuations and/or changes in plant phenology and the variation on nutrient contents. The objective of this study was to analyze the seasonal variability of Fe, Mn, Cu and Zn concentrations in leaves of Gleditsia amorphoides (Ga; Patagonula americana (Pa; Maclura tinctoria (Mt and Astronium balansae (Ab from Colonia Benítez Strict Nature Reserve (Chaco, Argentina. The leaves of each forest species were collected monthly, dried at 70ºC and their weight by tree species were recorded. Samples for analytical determinations were prepared by humid oxidation of organic substances from vegetal nets, using oxidant acids such as ternary mixture of HNO3-H2SO4-HClO4. After digestion, total micronutrients leaves concentrations were determined by atomic absortion spectrophotometry. Leaves Fe highest values were detected during fall in Mt (76.1mg/kg, Pa (75.2mg/kg, Ab (59.5mg/kg and Ga (45.3mg/kg. Highest foliar concentrations of Mn were detected in Pa (54.0mg/kg, Ga (50.0mg/kg, Mt (48.0mg/kg, and Ab with the lower Mn concentration (39.7mg/ kg. No significant differences were found for Cu between the different forest species, standing for Pa (11.3mg/ kg, Ga and Mt (11.0mg/kg and Ab (10.4mg/kg. With regard to leaves Zn, highest concentrations were found in Mt (347.4mg/kg, Ga (319.9mg/kg, Pa (280.2mg/kg and Ab (255.7mg/kg. Generally, a marked seasonal variation was observed for Mn and Cu concentrations (except in Ga and Zn (except in Pa, with no statistical differences for Fe. in the species studied, the concentration of micronutrients analyzed showed a marked and erratic seasonal variation, attributed to the relationship established between the native species, and the strong influence of the environment over a long period of time, especially temperature and rainfall.

Seasonality and structure of the arthropod community in a forested ...

African Journals Online (AJOL)

The structure of an arthropod community in the forest floor vegetation was studied in a low altitude (about 700 m a.s.l.) forest valley in the Uluguru Mountains near Morogoro, Tanzania, by monthly sweep net sampling during one year (December 1996-November 1997). The community structure of arthropods changed ...

Organic halogens in spruce forest throughfall

DEFF Research Database (Denmark)

Öberg, G.; Johansen, C.; Grøn, C.

1998-01-01

. No relationship between the position of the collectors and the forest edge or dominating wind-direction was found, suggesting that dry deposition was not a major source. The concentration of organic halogens was related to that of organic carbon and decreased from the tree-trunk and outwards. In addition......, the concentrations were higher during the growing season than during the dormant season. This indicates that the major part of the organic carbon and organic halogens in spruce forest throughfall originates from canopy leachates or other internal sources. (C) 1998 Elsevier Science Ltd.......Deposition of dissolved organic halogens by throughfall was determined in a small spruce forest site in Denmark (56 degrees 28'N, 8 degrees 24'E). The mean annual deposition of dissolved organic halogens was 377 g ha(-1)yr(-1), and larger than the general deposition by precipitation...

Influence of wildfires in the boreal forests of Eastern Siberia on atmospheric aerosol parameters

Science.gov (United States)

Tomshin, Oleg A.; Solovyev, Vladimir S.

2017-11-01

The results of studies of the dynamics of forest fires in the boreal forests of Yakutia (Eastern Siberia) for 2001-2016 are presented. Variations of aerosol optical thickness (AOT), aerosol index (AI) and total carbon monoxide content during May-September were studied depending on the different forest fire activity level. It is shown that the seasonal variations of AOT, AI and CO in the most fire-dangerous years differ significantly from the fire seasons when forest fire activity was medium or low.

Food preferences of winter bird communities in different forest types.

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Swen C Renner

Full Text Available Food availability for forest birds is a function of habitat type, forest management regime, and season. In winter, it is also impacted by variations in the weather. In the current study we assessed the food preferences of wild bird populations in two types of forest (spruce and beech during the months of November 2010 to April 2011 in the Schwäbische Alb Biodiversity Exploratory, south-western Germany. Our aim was to investigate whether local bird communities preferred fat-rich, carbohydrate-rich or wild fruits and to determine how forest structure, seasonality and local weather conditions affected food preferences. We found higher bird activity in beech forests for the eleven resident species. We observed a clear preference for fat-rich food for all birds in both forest types. Snow cover affected activity at food stations but did not affect food preferences. Periods of extreme low temperatures increased activity.

Soil moisture in sessile oak forest gaps

Science.gov (United States)

Zagyvainé Kiss, Katalin Anita; Vastag, Viktor; Gribovszki, Zoltán; Kalicz, Péter

2015-04-01

By social demands are being promoted the aspects of the natural forest management. In forestry the concept of continuous forest has been an accepted principle also in Hungary since the last decades. The first step from even-aged stand to continuous forest can be the forest regeneration based on gap cutting, so small openings are formed in a forest due to forestry interventions. This new stand structure modifies the hydrological conditions for the regrowth. Without canopy and due to the decreasing amounts of forest litter the interception is less significant so higher amount of precipitation reaching the soil. This research focuses on soil moisture patterns caused by gaps. The spatio-temporal variability of soil water content is measured in gaps and in surrounding sessile oak (Quercus petraea) forest stand. Soil moisture was determined with manual soil moisture meter which use Time-Domain Reflectometry (TDR) technology. The three different sizes gaps (G1: 10m, G2: 20m, G3: 30m) was opened next to Sopron on the Dalos Hill in Hungary. First, it was determined that there is difference in soil moisture between forest stand and gaps. Second, it was defined that how the gap size influences the soil moisture content. To explore the short term variability of soil moisture, two 24-hour (in growing season) and a 48-hour (in dormant season) field campaign were also performed in case of the medium-sized G2 gap along two/four transects. Subdaily changes of soil moisture were performed. The measured soil moisture pattern was compared with the radiation pattern. It was found that the non-illuminated areas were wetter and in the dormant season the subdaily changes cease. According to our measurements, in the gap there is more available water than under the forest stand due to the less evaporation and interception loss. Acknowledgements: The research was supported by TÁMOP-4.2.2.A-11/1/KONV-2012-0004 and AGRARKLIMA.2 VKSZ_12-1-2013-0034.

Mast fruiting of large ectomycorrhizal African rain forest trees: importance of dry season intensity, and the resource-limitation hypothesis.

Science.gov (United States)

Newbery, David M; Chuyong, George B; Zimmermann, Lukas

2006-01-01

Mast fruiting is a distinctive reproductive trait in trees. This rain forest study, at a nutrient-poor site with a seasonal climate in tropical Africa, provides new insights into the causes of this mode of phenological patterning. At Korup, Cameroon, 150 trees of the large, ectomycorrhizal caesalp, Microberlinia bisulcata, were recorded almost monthly for leafing, flowering and fruiting during 1995-2000. The series was extended to 1988-2004 with less detailed data. Individual transitions in phenology were analysed. Masting occurred when the dry season before fruiting was drier, and the one before that was wetter, than average. Intervals between events were usually 2 or 3 yr. Masting was associated with early leaf exchange, followed by mass flowering, and was highly synchronous in the population. Trees at higher elevation showed more fruiting. Output declined between 1995 and 2000. Mast fruiting in M. bisulcata appears to be driven by climate variation and is regulated by internal tree processes. The resource-limitation hypothesis was supported. An 'alternative bearing' system seems to underlie masting. That ectomycorrhizal habit facilitates masting in trees is strongly implied.

Combining stable isotope and carbohydrate analyses in phloem sap and fine roots to study seasonal changes of source-sink relationships in a Mediterranean beech forest.

Science.gov (United States)

Scartazza, Andrea; Moscatello, Stefano; Matteucci, Giorgio; Battistelli, Alberto; Brugnoli, Enrico

2015-08-01

Carbon isotope composition (δ(13)C) and carbohydrate content of phloem sap and fine roots were measured in a Mediterranean beech (Fagus sylvatica L.) forest throughout the growing season to study seasonal changes of source-sink relationships. Seasonal variations of δ(13)C and content of phloem sap sugars, collected during the daylight period, reflected the changes in soil and plant water status. The correlation between δ(13)C and content of phloem sap sugars, collected from plants belonging to different social classes, was significantly positive only during the driest month of July. In this month, δ(13)C of phloem sap sugars was inversely related to the increment of trunk radial growth and positively related to δ(13)C of fine roots. We conclude that the relationship between δ(13)C and the amount of phloem sap sugars is affected by a combination of causes, such as sink strength, tree social class, changes in phloem anatomy and transport capacity, and phloem loading of sugars to restore sieve tube turgor following the reduced plant water potential under drought conditions. However, δ(13)C and sugar composition of fine roots suggested that phloem transport of leaf sucrose to this belowground component was not impaired by mild drought and that sucrose was in a large part allocated towards fine roots in July, depending on tree social class. Hence, fine roots could represent a functional carbon sink during the dry seasonal periods, when transport and use of assimilates in other sink tissues are reduced. These results indicate a strict link between above- and belowground processes and highlight a rapid response of this Mediterranean forest to changes in environmental drivers to regulate source-sink relationships and carbon sink capacity. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Root hydraulic vulnerability regulation of whole-plant conductance along hillslope gradients within subalpine and montane forests

Science.gov (United States)

Beverly, D.; Speckman, H. N.; Ewers, B. E.

2017-12-01

Ecosystem-scale models often rely on root vulnerability or whole-plant conductance for simulating seasonal evapotranspiration declines via constraints of water uptake and vegetation mortality. Further, many of these ecosystem models rely on single, unvarying, hydraulic parameter estimates for modeling large areas. Ring-porous species have shown seasonal variability in root vulnerability (percent loss of conductivity; PLC) and whole-plant conductance (Kw) but simulations of coniferous forest typically rely on point measurements. This assumption for coniferous forest is not likely true because of seasonal variability caused by phenology and environmental stresses and the potential for cavitation fatigue is not considered. Moreover, many of these dynamics have only been considered for stems even though roots are often the most vulnerable segments of the pathway for conifers. We hypothesized that seasonally dynamic whole-plant conductance along hillslope gradients in coniferous forests are regulated by cavitation fatigue within the roots resulting in seasonal increases in vulnerability. To test the hypothesis, a subalpine mixed forest (3000 m.a.s.l) and montane forest (2550 m.a.s.l.) were monitored between 2015-2017 to quantify PLC and Kw along the hillslope gradients of 300 m and 50 m, respectively. Forest plots were instrumented with 35 Granier-type sapflow sensors. Seasonal sampling campaigns occurred to quantify PLC through centrifuge techniques and Kw through Darcy's law approximations with pre-dawn and diurnal leaf water potentials. Downslope roots exhibit a 33% decrease in maximal conductivity corresponding to the approximately 50% decrease in whole-plant conductance suggesting seasonal soil dry-down limitations within the downslope stands. Upslope stands had no to little change in root vulnerability or decrease in whole-plant conductance as soil water limitations occur immediately following snowmelt, thus limiting hydraulic conductance throughout the growing

Seasonal and Daily Dynamics of the CO2 Emission from Soils of Pinus koraiensis Forests in the South of the Sikhote-Alin Range

Science.gov (United States)

Ivanov, A. V.; Braun, M.; Tataurov, V. A.

2018-03-01

The presented study shows the results of measuring soil respiration in typical burozems (Dystric Cambisols) under mixed Korean pine-broadleaved forests in the southern part of the Primorskii (Far East) region of Russia growing under conditions of monsoon climate. The measurements were performed in 2014-2016 by the chamber method with the use of a portable infrared gas analyzer. Relative and total values of the CO2 efflux from the soil surface on four model plots were determined. The intensity of summer emission varied from 2.25 to 10.97 μmol/(m2 s), and the total CO2 efflux from the soils of four plots varied from 18.84 to 25.56 mol/m2. It is shown that a larger part of seasonal variability in the soil respiration is controlled by the soil temperature ( R 2 = 0.5-0.7); the soil water content also has a significant influence on the CO2 emission determining about 10% of its temporal variability. The daily dynamics of soil respiration under the old-age (200 yrs) forest have a significant relationship with the soil temperature ( R 2 = 0.51). The pyrogenic transformation of Pinus koraiensis forests into low-value oak forests is accompanied by an increase in the CO2 efflux from the soil.

Measuring forest and wild product contributions to household welfare

DEFF Research Database (Denmark)

Bakkegaard, Riyong Kim; Hogarth, Nicholas J.; Bong, Indah Waty

2017-01-01

in the lowest bracket. Consumption of forest products and importance as a coping strategy was higher in the most upstream village, where sale of forest products in times of shock was more marked in the most downstream village (where forest coping strategies were also least important). The Forestry Modules...

Disentangling the environmental heterogeneity, floristic distinctiveness and current threats of tropical dry forests in Colombia

Science.gov (United States)

González-M, Roy; García, Hernando; Isaacs, Paola; Cuadros, Hermes; López-Camacho, René; Rodríguez, Nelly; Pérez, Karen; Mijares, Francisco; Castaño-Naranjo, Alejandro; Jurado, Rubén; Idárraga-Piedrahíta, Álvaro; Rojas, Alicia; Vergara, Hernando; Pizano, Camila

2018-04-01

Tropical dry forests (TDFs) have been defined as a single biome occurring mostly in the lowlands where there is a marked period of drought during the year. In the Neotropics, dry forests occur across contrasting biogeographical regions that contain high beta diversity and endemism, but also strong anthropogenic pressures that threaten their biodiversity and ecological integrity. In Colombia, TDFs occur across six regions with contrasting soils, climate, and anthropogenic pressures, therefore being ideal for studying how these variables relate to dry forest species composition, successional stage and conservation status. Here, we explore the variation in climate and soil conditions, floristic composition, forest fragment size and shape, successional stage and anthropogenic pressures in 571 dry forest fragments across Colombia. We found that TDFs should not be classified solely on rainfall seasonality, as high variation in precipitation and temperature were correlated with soil characteristics. In fact, based on environmental factors and floristic composition, the dry forests of Colombia are clustered in three distinctive groups, with high species turnover across and within regions, as reported for other TDF regions of the Neotropics. Widely distributed TDF species were found to be generalists favored by forest disturbance and the early successional stages of dry forests. On the other hand, TDF fragments were not only small in size, but highly irregular in shape in all regions, and comprising mostly early and intermediate successional stages, with very little mature forest left at the national level. At all sites, we detected at least seven anthropogenic disturbances with agriculture, cattle ranching and human infrastructure being the most pressing disturbances throughout the country. Thus, although environmental factors and floristic composition of dry forests vary across regions at the national level, dry forests are equally threatened by deforestation, degradation

An Ecological Comparison of Floristic Composition in Seasonal Semideciduous Forest in Southeast Brazil: Implications for Conservation

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Sérgio de Faria Lopes

2012-01-01

Full Text Available We examined floristic patterns of ten seasonal semideciduous forest sites in southeastern Brazil and conducted a central sampling of one hectare for each site, where we took samples and identified all individual living trees with DBH (diameter at breast height, 1.30 m ≥4.8 cm. Arboreal flora totaled 242 species, 163 genera, and 58 families. Fabaceae (38 species and Myrtaceae (20 species were families with the largest number of species. Only Copaifera langsdorffii and Hymenaea courbaril occurred at all sites. Multivariate analysis (detrended correspondence analysis and cluster analysis using two-way indicator species analysis (TWINSPAN indicated the formation of a group containing seven fragments in which Siparuna guianensis was the indicator species. This analysis revealed that similarities between studied fragments were due mainly to the successional stage of the community.

High but not dry: diverse epiphytic bromeliad adaptations to exposure within a seasonally dry tropical forest community.

Science.gov (United States)

Reyes-García, C; Mejia-Chang, M; Griffiths, H

2012-02-01

• Vascular epiphytes have developed distinct lifeforms to maximize water uptake and storage, particularly when delivered as pulses of precipitation, dewfall or fog. The seasonally dry forest of Chamela, Mexico, has a community of epiphytic bromeliads with Crassulacean acid metabolism showing diverse morphologies and stratification within the canopy. We hypothesize that niche differentiation may be related to the capacity to use fog and dew effectively to perform photosynthesis and to maintain water status. • Four Tillandsia species with either 'tank' or 'atmospheric' lifeforms were studied using seasonal field data and glasshouse experimentation, and compared on the basis of water use, leaf water δ(18) O, photosynthetic and morphological traits. • The atmospheric species, Tillandsia eistetteri, with narrow leaves and the lowest succulence, was restricted to the upper canopy, but displayed the widest range of physiological responses to pulses of precipitation and fog, and was a fog-catching 'nebulophyte'. The other atmospheric species, Tillandsia intermedia, was highly succulent, restricted to the lower canopy and with a narrower range of physiological responses. Both upper canopy tank species relied on tank water and stomatal closure to avoid desiccation. • Niche differentiation was related to capacity for water storage, dependence on fog or dewfall and physiological plasticity. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Effects of climate and forest structure on palms, bromeliads and bamboos in Atlantic Forest fragments of Northeastern Brazil.

Science.gov (United States)

Hilário, R R; Toledo, J J

2016-01-01

Palms, bromeliads and bamboos are key elements of tropical forests and understanding the effects of climate, anthropogenic pressure and forest structure on these groups is crucial to forecast structural changes in tropical forests. Therefore, we investigated the effects of these factors on the abundance of these groups in 22 Atlantic forest fragments of Northeastern Brazil. Abundance of bromeliads and bamboos were assessed through indexes. Palms were counted within a radius of 20 m. We also obtained measures of vegetation structure, fragment size, annual precipitation, precipitation seasonality and human population density. We tested the effects of these predictors on plant groups using path analysis. Palm abundance was higher in taller forests with larger trees, closed canopy and sparse understory, which may be a result of the presence of seed dispersers and specific attributes of local palm species. Bromeliads were negatively affected by both annual precipitation and precipitation seasonality, what may reflect adaptations of these plants to use water efficiently, but also the need to capture water in a regular basis. Bamboos were not related to any predictor variable. As climate and forest structure affected the abundance of bromeliads and palms, human-induced climatic changes and disturbances in forest structure may modify the abundance of these groups. In addition, soil properties and direct measurements of human disturbance should be used in future studies in order to improve the predictability of models about plant groups in Northeastern Atlantic Forest.

Prolonged limitation of tree growth due to warmer spring in semi-arid mountain forests of Tianshan, northwest China

International Nuclear Information System (INIS)

Wu Xiuchen; Liu Hongyan; Wang Yufu; Deng Minghua

2013-01-01

Based on radial tree growth measurements in nine plots of area 625 m 2 (369 trees in total) and climate data, we explored the possibly changing effects of climate on regional tree growth in the temperate continental semi-arid mountain forests in the Tianshan Mountains in northwest China during 1933–2005. Tree growth in our study region is generally limited by the soil water content of pre- and early growing season (February–July). Remarkably, moving correlation functions identified a clear temporal change in the relationship between tree growth and mean April temperature. Tree growth showed a significant (p < 0.05) and negative relationship to mean April temperature since approximately the beginning of the 1970s, which indicated that the semi-arid mountain forests are suffering a prolonged growth limitation in recent years accompanying spring warming. This prolonged limitation of tree growth was attributed to the effects of soil water limitation in early spring (March–April) caused by the rapid spring warming. Warming-induced prolonged drought stress contributes, to a large part, to the marked reduction of regional basal area increment (BAI) in recent years and a much slower growth rate in young trees. Our results highlight that the increasing water limitation induced by spring warming on tree growth most likely aggravated the marked reduction in tree growth. This work provides a better understanding of the effects of spring warming on tree growth in temperate continental semi-arid forests. (letter)

Short dry spells in the wet season increase mortality of tropical pioneer seedlings.

Science.gov (United States)

Engelbrecht, Bettina M J; Dalling, James W; Pearson, Timothy R H; Wolf, Robert L; Gálvez, David A; Koehler, Tobias; Tyree, Melvin T; Kursar, Thomas A

2006-06-01

Variation in plant species performance in response to water availability offers a potential axis for temporal and spatial habitat partitioning and may therefore affect community composition in tropical forests. We hypothesized that short dry spells during the wet season are a significant source of mortality for the newly emerging seedlings of pioneer species that recruit in treefall gaps in tropical forests. An analysis of a 49-year rainfall record for three forests across a rainfall gradient in central Panama confirmed that dry spells of > or = 10 days during the wet season occur on average once a year in a deciduous forest, and once every other year in a semi-deciduous moist and an evergreen wet forest. The effect of wet season dry spells on the recruitment of pioneers was investigated by comparing seedling survival in rain-protected dry plots and irrigated control plots in four large artificially created treefall gaps in a semi-deciduous tropical forest. In rain-protected plots surface soil layers dried rapidly, leading to a strong gradient in water potential within the upper 10 cm of soil. Seedling survival for six pioneer species was significantly lower in rain-protected than in irrigated control plots after only 4 days. The strength of the irrigation effect differed among species, and first became apparent 3-10 days after treatments started. Root allocation patterns were significantly, or marginally significantly, different between species and between two groups of larger and smaller seeded species. However, they were not correlated with seedling drought sensitivity, suggesting allocation is not a key trait for drought sensitivity in pioneer seedlings. Our data provide strong evidence that short dry spells in the wet season differentially affect seedling survivorship of pioneer species, and may therefore have important implications to seedling demography and community dynamics.

The effect of local and landscape-level characteristics on the abundance of forest birds in early-successional habitats during the post-fledging season in western Massachusetts.

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Michelle A Labbe

Full Text Available Many species of mature forest-nesting birds ("forest birds" undergo a pronounced shift in habitat use during the post-fledging period and move from their forest nesting sites into areas of early-successional vegetation. Mortality is high during this period, thus understanding the resource requirements of post-fledging birds has implications for conservation. Efforts to identify predictors of abundance of forest birds in patches of early-successional habitats have so far been equivocal, yet these previous studies have primarily focused on contiguously forested landscapes and the potential for landscape-scale influences in more fragmented and modified landscapes is largely unknown. Landscape composition can have a strong influence on the abundance and productivity of forest birds during the nesting period, and could therefore affect the number of forest birds in the landscape available to colonize early-successional habitats during the post-fledging period. Therefore, the inclusion of landscape characteristics should increase the explanatory power of models of forest bird abundance in early-successional habitat patches during the post-fledging period. We examined forest bird abundance and body condition in relation to landscape and habitat characteristics of 15 early-successional sites during the post-fledging season in Massachusetts. The abundance of forest birds was influenced by within-patch habitat characteristics, however the explanatory power of these models was significantly increased by the inclusion of landscape fragmentation and the abundance of forest birds in adjacent forest during the nesting period for some species and age groups. Our findings show that including factors beyond the patch scale can explain additional variation in the abundance of forest birds in early-successional habitats during the post-fledging period. We conclude that landscape composition should be considered when siting early-successional habitat to maximize its

The Effect of Local and Landscape-Level Characteristics on the Abundance of Forest Birds in Early-Successional Habitats during the Post-Fledging Season in Western Massachusetts

Science.gov (United States)

Labbe, Michelle A.; King, David I.

2014-01-01

Many species of mature forest-nesting birds (“forest birds”) undergo a pronounced shift in habitat use during the post-fledging period and move from their forest nesting sites into areas of early-successional vegetation. Mortality is high during this period, thus understanding the resource requirements of post-fledging birds has implications for conservation. Efforts to identify predictors of abundance of forest birds in patches of early-successional habitats have so far been equivocal, yet these previous studies have primarily focused on contiguously forested landscapes and the potential for landscape-scale influences in more fragmented and modified landscapes is largely unknown. Landscape composition can have a strong influence on the abundance and productivity of forest birds during the nesting period, and could therefore affect the number of forest birds in the landscape available to colonize early-successional habitats during the post-fledging period. Therefore, the inclusion of landscape characteristics should increase the explanatory power of models of forest bird abundance in early-successional habitat patches during the post-fledging period. We examined forest bird abundance and body condition in relation to landscape and habitat characteristics of 15 early-successional sites during the post-fledging season in Massachusetts. The abundance of forest birds was influenced by within-patch habitat characteristics, however the explanatory power of these models was significantly increased by the inclusion of landscape fragmentation and the abundance of forest birds in adjacent forest during the nesting period for some species and age groups. Our findings show that including factors beyond the patch scale can explain additional variation in the abundance of forest birds in early-successional habitats during the post-fledging period. We conclude that landscape composition should be considered when siting early-successional habitat to maximize its benefit to

Landscape controls on the timing of spring, autumn, and growing season length in mid-Atlantic forests

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Elmore, A.J.; Guinn, S.M.; Minsley, B.J.; Richardson, A.D.

2012-01-01

The timing of spring leaf development, trajectories of summer leaf area, and the timing of autumn senescence have profound impacts to the water, carbon, and energy balance of ecosystems, and are likely influenced by global climate change. Limited field-based and remote-sensing observations have suggested complex spatial patterns related to geographic features that influence climate. However, much of this variability occurs at spatial scales that inhibit a detailed understanding of even the dominant drivers. Recognizing these limitations, we used nonlinear inverse modeling of medium-resolution remote sensing data, organized by day of year, to explore the influence of climate-related landscape factors on the timing of spring and autumn leaf-area trajectories in mid-Atlantic, USA forests. We also examined the extent to which declining summer greenness (greendown) degrades the precision and accuracy of observations of autumn offset of greenness. Of the dominant drivers of landscape phenology, elevation was the strongest, explaining up to 70% of the spatial variation in the onset of greenness. Urban land cover was second in importance, influencing spring onset and autumn offset to a distance of 32 km from large cities. Distance to tidal water also influenced phenological timing, but only within ~5 km of shorelines. Additionally, we observed that (i) growing season length unexpectedly increases with increasing elevation at elevations below 275 m; (ii) along gradients in urban land cover, timing of autumn offset has a stronger effect on growing season length than does timing of spring onset; and (iii) summer greendown introduces bias and uncertainty into observations of the autumn offset of greenness. These results demonstrate the power of medium grain analyses of landscape-scale phenology for understanding environmental controls on growing season length, and predicting how these might be affected by climate change.

Self-amplified Amazon forest loss due to vegetation-atmosphere feedbacks

OpenAIRE

Zemp, Delphine Clara; Schleussner, Carl Friedrich; Barbosa, Henrique M J; Hirota, Marina; Montade, Vincent; Sampaio, Gilvan; Staal, Arie; Wang-Erlandsson, L.; Rammig, Anja

2017-01-01

Reduced rainfall increases the risk of forest dieback, while in return forest loss might intensify regional droughts. The consequences of this vegetation–atmosphere feedback for the stability of the Amazon forest are still unclear. Here we show that the risk of self-amplified Amazon forest loss increases nonlinearly with dry-season intensification. We apply a novel complexnetwork approach, in which Amazon forest patches are linked by observation-based atmospheric water fluxes. ...

Monitoring temporal Vegetation changes in Lao tropical forests

International Nuclear Information System (INIS)

Phompila, Chittana; Lewis, Megan; Clarke, Kenneth; Ostendorf, Bertram

2014-01-01

Studies on changes in vegetation are essential for understanding the interaction between humans and the environment. These studies provide key information for land use assessment, terrestrial ecosystem monitoring, carbon flux modelling and impacts of global climate change. The primary purpose of this study was to detect temporal vegetation changes in tropical forests in the southern part of Lao PDR from 2001-2012. The study investigated the annual vegetation phenological response of dominant land cover types across the study area and relationships to seasonal precipitation and temperature. Improved understanding of intra-annual patterns of vegetation variation was useful to detect longer term changes in vegetation. The breaks for additive season and trend (BFAST) approach was implemented to detect changes in these land cover types throughout the 2001-2012 period. We used the enhanced vegetation index (EVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) (MOD13Q1 products) and monthly rainfall and temperature data obtained from the Meteorology and Hydrology Department, Ministry of Agriculture-Forestry, published by Lao National Statistical Centre in this research. EVI well documented the annual seasonal growth of vegetation and clearly distinguished the characteristic phenology of four different land use types; native forest, plantation, agriculture and mixed wooded/cleared area. Native forests maintained high EVI throughout the year, while plantations, wooded/cleared areas and agriculture showed greater inter-annual variation, with minimum EVI at the end of the dry season in April and maximum EVI in September-October, around two months after the wet season peak in rainfall. The BFAST analysis detected abrupt temporal changes in vegetation in the tropical forests, especially in a large conversion of mixed wooded/cleared area into plantation. Within the study area from 2001-2012 there has been an overall decreasing trend of vegetation cover for

Removal rates of native and exotic dung by dung beetles (Scarabaeidae: Scarabaeinae) in a fragmented tropical rain forest.

Science.gov (United States)

Amézquita, Sandra; Favila, Mario E

2010-04-01

Many studies have evaluated the effect of forest fragmentation on dung beetle assemblage structure. However, few have analyzed how forest fragmentation affects the processes carried out by these insects in tropical forests where their food sources consist mainly of dung produced by native herbivore mammals. With the conversion of forests to pastures, cattle dung has become an exotic alternative and abundant food for dung beetles. This study compares dung removal rates of native (monkey) and exotic (cow) dung in different-sized fragments of tropical rain forests, during the dry and rainy seasons at the Los Tuxtlas Biosphere Reserve. Dung removal rates were affected by season, dung type, and the interaction between resource type and season. During the dry season, the removal rates of monkey dung were somewhat similar than during the rainy season, whereas the removal rates of cow dung were much higher during the rainy season. Dung beetle biomass and species richness were almost three times greater in monkey dung than in cow dung. Monkey dung attracted species belonging to the dweller, roller, and tunneler guilds; cow dung attracted mostly tunnelers. Therefore, the use of exotic dung may result in a biased misconception of the rates of dung removal in tropical forest and an underestimation of dung beetle diversity. This study highlights the importance of working with natural tropical forest resources when attempting to identify realistic tendencies concerning processes in natural habitats and those modified by fragmentation and by other human activities.

Hydrological Controls on Floodplain Forest Phenology Assessed using Remotely Sensed Vegetation Indices

Science.gov (United States)

Lemon, M. G.; Keim, R.

2017-12-01

Although specific controls are not well understood, the phenology of temperate forests is generally thought to be controlled by photoperiod and temperature, although recent research suggests that soil moisture may also be important. The phenological controls of forested wetlands have not been thoroughly studied, and may be more controlled by site hydrology than other forests. For this study, remotely sensed vegetation indices were used to investigate hydrological controls on start-of-season timing, growing season length, and end-of-season timing at five floodplains in Louisiana, Arkansas, and Texas. A simple spring green-up model was used to determine the null spring start of season time for each site as a function of land surface temperature and photoperiod, or two remotely sensed indices: MODIS phenology data product and the MODIS Nadir Bidirectional Reflectance Distribution Function-Adjusted Reflectance (NBAR) product. Preliminary results indicate that topographically lower areas within the floodplain with higher flood frequency experience later start-of-season timing. In addition, start-of-season is delayed in wet years relative to predicted timing based solely on temperature and photoperiod. The consequences for these controls unclear, but results suggest hydrological controls on floodplain ecosystem structure and carbon budgets are likely at least partially expressed by variations in growing season length.

Traffic noise affects forest bird species in a protected tropical forest

Directory of Open Access Journals (Sweden)

J. Edgardo Arévalo

2011-06-01

Full Text Available The construction of roads near protected forest areas alters ecosystem function by creating habitat fragmentation and through several direct and indirect negative effects such as increased pollution, animal mortality through collisions, disturbance caused by excessive noise and wind turbulence. Noise in particular may have strong negative effects on animal groups such as frogs and birds, that rely on sound for communication as it can negatively interfere with vocalizations used for territorial defense or courtship. Thus, birds are expected to be less abundant close to the road where noise levels are high. In this study, we examined the effects of road traffic noise levels on forest bird species in a protected tropical forest in Costa Rica. Data collection was conducted in a forest segment of the Carara National Park adjacent to the Coastal Highway. We carried out 120 ten minute bird surveys and measured road noise levels 192 times from the 19th to the 23rd of April and from the 21st to the 28th of November, 2008. To maximize bird detection for the species richness estimates we operated six 12m standard mist nets simultaneously with the surveys. The overall mist-netting effort was 240net/h. In addition, we estimated traffic volumes by tallying the number of vehicles passing by the edge of the park using 24 one hour counts throughout the study. We found that the relative abundance of birds and bird species richness decreased significantly with the increasing traffic noise in the dry and wet season. Noise decreased significantly and in a logarithmic way with distance from the road in both seasons. However, noise levels at any given distance were significantly higher in the dry compared to the wet season. Our results suggest that noise might be an important factor influencing road bird avoidance as measured by species richness and relative abundance. Since the protected forest in question is located in a national park subjected to tourist visitation

Climate and Vegetation Effects on Temperate Mountain Forest ...

Science.gov (United States)

Current forest composition may be resilient to typical climatic variability; however, climate trends, combined with projected changes in species composition, may increase tree vulnerability to water stress. A shift in forest composition toward tree species with higher water use has implications for biogenic emissions and deposition of reactive nitrogen and carbon compounds. Forest evapotranspiration (ET) can vary greatly at daily and seasonal time scales, but compared to carbon fluxes, often exhibits relatively consistent inter-annual behavior. The processes controlling ET involve the combined effects of physical and biological factors. Atmospheric conditions that promote high ET, consisting of high radiation and vapor pressure deficit (D), are often characterized by rainless periods when soil water supply to vegetation may be limiting and plant stomata may close to prevent excessive water loss. In contrast, periods of high ecosystem water availability require frequent precipitation and are characterized by low D. Thus, the combination of these contrasting conditions throughout a growing season may explain some of the consistency in ET. Additionally, vegetation composition is also an important factor in determining ET. In mixed species forests, physiological differences in water use strategies (e.g. isohydric/anisohydric species) can produce conservative water use throughout wet and dry phases of the growing season. Furthermore, transpiration by evergreen specie

Characterization of free amino acids, bacteria and fungi in size-segregated atmospheric aerosols in boreal forest: seasonal patterns, abundances and size distributions

Science.gov (United States)

Helin, Aku; Sietiö, Outi-Maaria; Heinonsalo, Jussi; Bäck, Jaana; Riekkola, Marja-Liisa; Parshintsev, Jevgeni

2017-11-01

Primary biological aerosol particles (PBAPs) are ubiquitous in the atmosphere and constitute ˜ 30 % of atmospheric aerosol particle mass in sizes > 1 µm. PBAP components, such as bacteria, fungi and pollen, may affect the climate by acting as cloud-active particles, thus having an effect on cloud and precipitation formation processes. In this study, size-segregated aerosol samples ( 10 µm) were collected in boreal forest (Hyytiälä, Finland) during a 9-month period covering all seasons and analysed for free amino acids (FAAs), DNA concentration and microorganism (bacteria, Pseudomonas and fungi). Measurements were performed using tandem mass spectrometry, spectrophotometry and qPCR, respectively. Meteorological parameters and statistical analysis were used to study their atmospheric implication for results. Distinct annual patterns of PBAP components were observed, late spring and autumn being seasons of dominant occurrence. Elevated abundances of FAAs and bacteria were observed during the local pollen season, whereas fungi were observed at the highest level during autumn. Meteorological parameters such as air and soil temperature, radiation and rainfall were observed to possess a close relationship with PBAP abundances on an annual scale.

Forest fire risk zonation mapping using remote sensing technology

Science.gov (United States)

Chandra, Sunil; Arora, M. K.

2006-12-01

Forest fires cause major losses to forest cover and disturb the ecological balance in our region. Rise in temperature during summer season causing increased dryness, increased activity of human beings in the forest areas, and the type of forest cover in the Garhwal Himalayas are some of the reasons that lead to forest fires. Therefore, generation of forest fire risk maps becomes necessary so that preventive measures can be taken at appropriate time. These risk maps shall indicate the zonation of the areas which are in very high, high, medium and low risk zones with regard to forest fire in the region. In this paper, an attempt has been made to generate the forest fire risk maps based on remote sensing data and other geographical variables responsible for the occurrence of fire. These include altitude, temperature and soil variations. Key thematic data layers pertaining to these variables have been generated using various techniques. A rule-based approach has been used and implemented in GIS environment to estimate fuel load and fuel index leading to the derivation of fire risk zonation index and subsequently to fire risk zonation maps. The fire risk maps thus generated have been validated on the ground for forest types as well as for forest fire risk areas. These maps would help the state forest departments in prioritizing their strategy for combating forest fires particularly during the fire seasons.

Frugivory by the black-eared opossum Didelphis aurita in the Atlantic Forest of southern Brazil: Roles of sex, season and sympatric species

Directory of Open Access Journals (Sweden)

Nilton C. Cáceres

2009-06-01

Full Text Available http://dx.doi.org/10.5007/2175-7925.2009v22n3p203 Our objective in this study was to examine the frugivory performed by the black-eared opossum, Didelphis aurita Wied-Neuwied, 1826, in an area of the coastal Atlantic Forest of southern Brazil, including differences between sexes, seasonal variation, and relationships to other sympatric marsupials. We collected 63 fecal samples from a trap grid over a six-month period and analyzed seed presence, seed number and richness,  and diversity of fruit species in feces. Diversity of fruit items was estimated by the Shannon index. Results showed a high variability in fruit consumption along the seasons, but no sexual difference in consumption. Sympatric marsupial species, including D. aurita, showed substantial differences in frugivory which may be related to body size, space use and differences in the foraging behavior of such species.

Diversity in plant hydraulic traits explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests.

Science.gov (United States)

Xu, Xiangtao; Medvigy, David; Powers, Jennifer S; Becknell, Justin M; Guan, Kaiyu

2016-10-01

We assessed whether diversity in plant hydraulic traits can explain the observed diversity in plant responses to water stress in seasonally dry tropical forests (SDTFs). The Ecosystem Demography model 2 (ED2) was updated with a trait-driven mechanistic plant hydraulic module, as well as novel drought-phenology and plant water stress schemes. Four plant functional types were parameterized on the basis of meta-analysis of plant hydraulic traits. Simulations from both the original and the updated ED2 were evaluated against 5 yr of field data from a Costa Rican SDTF site and remote-sensing data over Central America. The updated model generated realistic plant hydraulic dynamics, such as leaf water potential and stem sap flow. Compared with the original ED2, predictions from our novel trait-driven model matched better with observed growth, phenology and their variations among functional groups. Most notably, the original ED2 produced unrealistically small leaf area index (LAI) and underestimated cumulative leaf litter. Both of these biases were corrected by the updated model. The updated model was also better able to simulate spatial patterns of LAI dynamics in Central America. Plant hydraulic traits are intercorrelated in SDTFs. Mechanistic incorporation of plant hydraulic traits is necessary for the simulation of spatiotemporal patterns of vegetation dynamics in SDTFs in vegetation models. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Characteristics of Sediment Transportation in Two Contrasting Oak Forested Watersheds in the Lesser Central Himalaya, India

Science.gov (United States)

Qazi, N. U. Q.; Bruijnzeel, S., Sr.; Rai, S. P., Sr.

2015-12-01

Sediment transfer from mountainous areas to lowland areas is one of the most important geomorphological processes globally with the bulk of the sediment yield from such areas typically deriving from mass wastage processes. This study presents monthly, seasonal and annual variations in sediment transport (both suspended load and bedload) as well as dissolved loads over three consecutive water years (2008-2011) for two small forested watersheds with contrasting levels of forest disturbance in the Lesser Himalaya of Northwest India. Seasonal and annual suspended sediment yields were strongly influenced by amounts of rainfall and streamflow and showed a 10-63 fold range between wet and dry years. Of the annual load, some 93% was produced on average during the monsoon season (June-September). Sediment production by the disturbed forest catchment was 1.9-fold (suspended sediment) to 5.9-fold (bedload) higher than that for the well-stocked forest catchment. By contrast, dissolved loads varied much less between years, seasons (although minimal during the dry summer season), and degree of forest disturbance. Total mechanical denudation rates were 1.6 times and 4.6 times larger than chemical denudation rates for the little disturbed and the heavily disturbed forest catchment, respectively whereas overall denudation rates were estimated at 0.69 and 1.04 mm per 1000 years, respectively.

Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

Science.gov (United States)

Tang Che Ing, A.; Stoy, P. C.; Melling, L.

2014-12-01

Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

Anthropometric measurements of adolescents from two Amazonian ecosystems: variations according to seasonality.

Science.gov (United States)

Silva, Hilton P; Veiga, Gloria V; Kac, Gilberto; Pereira, Rosangela A

2010-03-01

This paper aims to describe the nutritional status of Caboclo adolescents living in two areas of the Amazon Basin. Two cross-sectional studies, the first in the dry and the second in the wet season, were carried out in two Amazonian ecosystems: the forest and black water ecosystem, and the floodplain and white water ecosystem. Measurements of weight, stature, arm circumference and triceps, subscapular and suprailiac skinfolds were performed on 247 adolescents (10-19 years of age). Nutritional status was classified using body mass index according to international criteria and the prevalence of underweight and overweight was estimated. Linear mixed effects models were used with the anthropometric measurements as dependent variables and time interval, place of residence, sex, age and stature variation as independent variables. During the wet season, the prevalence of overweight among girls was higher in the forest (42%) than in the floodplain (9%). Longitudinal linear regression models showed that the arm circumference measurement was influenced both by seasonality and location, revealing that the increment between dry and wet seasons was less pronounced in the floodplain. At the time of the study, overweight already constituted a major public health concern among girls living in the forest area. In order to develop adequate public health policies for this important segment of the Amazon population further studies are necessary to investigate the role of environment and seasonality on the growth and nutritional status of adolescents.

A SEASONAL COMPARISON OF THE PHYSICAL DAMAGES ON RESIDUAL TREES AND SEEDLINGS DUE TO LOGGING OPERATION USING URUS MIII FOREST SKYLINE IN ARTVIN REGION

OpenAIRE

Habip Eroğlu; Ufuk Özcan Öztürk

2008-01-01

In this paper, the physical damages of logging activities using Urus MIII forest skylines on residual trees and seedlings were evaluated through comparison between harvesting operations took place in winter and summer seasons in Artvin region. In order to achieve our aims, both in winter and summer, 4 representative plots were taken in the harvesting areas using Urus MIII skyline. Physical damages caused by logging to residual trees and seedling were noted. Damage classes for the residual tr...

[Odocoileus virginianus diet (Artiodactyla: Cervidae) in a temperate forest of Northern Oaxaca, Mexico].

Science.gov (United States)

González, Graciela; Briones-Salas, Miguel

2012-03-01

The Sierra Madre de Oaxaca region, located in the Northern state of Oaxaca, Mexico, is an area of forest ecosystems subject to high exploitation rates, although in some areas its temperate forests are conserved by indigenous community initiatives that live there. We analyzed the diet of white tailed-deer (Odocoileus virginianus) in the localities of Santa Catarina Lachatao and San Miguel Amatlán from June 1998 to August 1999. Sampling was done during both the wet and dry seasons, and included the observation of browsing traces (238 observations), microhistological analysis of deer feces (28 deer pellet-groups), and two stomach content analysis. The annual diet of white-tailed deer was composed of 42 species from 23 botanical families. The most represented families in the diet of this deer were Fagaceae, Asteraceae, Ericaceae and Fabaceae. There were significant differences in the alpha diversity of the diet during the wet and dry seasons (H'=2.957 and H'=1.832, respectively). The similarity percentage between seasons was 56%. Differences in plant species frequency were significantly higher during the wet season. Herbaceous plants made up the greatest percentage of all the species consumed. The preferred species throughout the year were Senecio sp. (shrub), Sedum dendroideum (herbaceous), Arctostaphylos pungens (shrub) and Satureja macrostema (shrub). Diet species richness was found to be lower than that observed in a tropical forest (Venezuela), tropical dry forest (Mexico) and temperate deciduous and mixed forest (Mexico), but similar to the diet species richness observed in a tropical dry forest (Costa Rica) and temperate coniferous and deciduous forests (USA).

Rainfall model investigation and scenario analyses of the effect of government reforestation policy on seasonal rainfalls: A case study from Northern Thailand

Science.gov (United States)

Duangdai, Eakkapong; Likasiri, Chulin

2017-03-01

In this work, 4 models for predicting rainfall amounts are investigated and compared using Northern Thailand's seasonal rainfall data for 1973-2008. Two models, global temperature, forest area and seasonal rainfall (TFR) and modified TFR based on a system of differential equations, give the relationships between global temperature, Northern Thailand's forest cover and seasonal rainfalls in the region. The other two models studied are time series and Autoregressive Moving Average (ARMA) models. All models are validated using the k-fold cross validation method with the resulting errors being 0.971233, 0.740891, 2.376415 and 2.430891 for time series, ARMA, TFR and modified TFR models, respectively. Under Business as Usual (BaU) scenario, seasonal rainfalls in Northern Thailand are projected through the year 2020 using all 4 models. TFR and modified TFR models are also used to further analyze how global temperature rise and government reforestation policy affect seasonal rainfalls in the region. Rainfall projections obtained via the two models are also compared with those from the International Panel on Climate Change (IPCC) under IS92a scenario. Results obtained through a mathematical model for global temperature, forest area and seasonal rainfall show that the higher the forest cover, the less fluctuation there is between rainy-season and summer rainfalls. Moreover, growth in forest cover also correlates with an increase in summer rainfalls. An investigation into the relationship between main crop productions and rainfalls in dry and rainy seasons indicates that if the rainy-season rainfall is high, that year's main-crop rice production will decrease but the second-crop rice, maize, sugarcane and soybean productions will increase in the following year.

Abiotic factors influencing tropical dry forests regeneration

Directory of Open Access Journals (Sweden)

Ceccon Eliane

2006-01-01

Full Text Available Tropical dry forests represent nearly half the tropical forests in the world and are the ecosystems registering the greatest deterioration from the anthropogenic exploitation of the land. This paper presents a review on the dynamics of tropical dry forests regeneration and the main abiotic factors influencing this regeneration, such as seasonal nature, soil fertility and humidity, and natural and anthropic disturbances. The main purpose is to clearly understand an important part of TDF succession dynamics.

Análise da dinâmica sazonal de fitofisionomias do bioma Mata Atlântica com base em índices de vegetação do sensor MODIS/TERRA / Analysis of the seasonal dynamics of some Atlantic Forest biome physiognomies with basis of vegetation indices derived from MOD

Directory of Open Access Journals (Sweden)

Elói Lennon Dalla Nora

2010-08-01

and with a climatic database (temperature and precipitation, for each physiognomy. The results showed that the fragments of seasonal deciduous forest and mixed rain forest present a common seasonal pattern, however, with variations of amplitude in relation to each index. The EVI was more sensible and hence, more efficient to annual variations of the vegetation compared to the NDVI. For both forest formations a positive correlation between profile EVI and NDVI with variations of temperature was established. The spectral/temporal dynamic showed a marked contrast under distinct seasonal conditions converging with the pattern presented for the vegetation indices. Data indicate potentialities of the use of MODIS sensor for the continuous monitoring of the south forest formations with moderate space resolution and high temporal resolution.

Water flow and energy balance for a tropical dry semideciduous forest

Science.gov (United States)

Andrade, J. L.; Garruña-Hernandez, R.; Leon-Palomo, M.; Us-Santamaria, R.; Sima, J. L.

2013-05-01

Tropical forests cool down locally because increase water evaporation from the soil to the atmosphere, reduce albedo and help forming clouds that reflect solar radiation back to the atmosphere; this, aligned to the carbon catchment, increase forests value. We will present an estimation of the sap flow and energy balance for the tropical dry semideciduous forest at Kiuic, Yucatan, Mexico during a year. We use a meteorological tower equipped with a rain gauge, temperature and relative humidity, heat flow plates, thermocouples and volumetric soil water content. We recorded net radiation and soil heat flux and estimated sensible heat and latent heat. Besides, we estimated latent heat by measuring sap flow directly in tres using disispation constant heat probes during the rainy season. Results show the influence of the seasonality on net radiation, air temperatura and vapor pressure deficit, because during the dry season his variables were higher and with more duation than during the rainy and early dry season. Sap flow was different for trees belonging to the family Fabaceae compared to trees from other families.

Bayesian estimation of seasonal course of canopy leaf area index from hyperspectral satellite data

Science.gov (United States)

Varvia, Petri; Rautiainen, Miina; Seppänen, Aku

2018-03-01

In this paper, Bayesian inversion of a physically-based forest reflectance model is investigated to estimate of boreal forest canopy leaf area index (LAI) from EO-1 Hyperion hyperspectral data. The data consist of multiple forest stands with different species compositions and structures, imaged in three phases of the growing season. The Bayesian estimates of canopy LAI are compared to reference estimates based on a spectral vegetation index. The forest reflectance model contains also other unknown variables in addition to LAI, for example leaf single scattering albedo and understory reflectance. In the Bayesian approach, these variables are estimated simultaneously with LAI. The feasibility and seasonal variation of these estimates is also examined. Credible intervals for the estimates are also calculated and evaluated. The results show that the Bayesian inversion approach is significantly better than using a comparable spectral vegetation index regression.

Compilation of woody species occurring in the Brazilian Atlantic Forest complex

OpenAIRE

Bergamin, Rodrigo Scarton; Da Silva Duarte, Leandro; Marcilio-Silva, Vinicius; Dos Santos Seger, Guilherme Dubal; Liebsch, Dieter; Marques, Márcia C. M.

2015-01-01

The Atlantic Forest is a hotspot for biodiversity conservation because of its high levels of endemism and threatened areas. Three main forest types, differentiated by their floras, compose the Atlantic Forest: ‘Atlantic Forest’ sensu strictu, ‘Araucaria Mixed Forest’ and ‘Seasonal Forest’. The flora comprises taxa from the Amazon forest, Cerrado gallery forests and the Andean region, which makes the Atlantic Forest a relevant study system for ecologists and biogeographers. Here, we present da...

Breeding season concerns and response to forest management: Can forest management produce more breeding birds? Ornitologia Neotropical

Science.gov (United States)

J.L. Larkin; P.B. Wood; T.J. Boves; J. Sheehan; D.A. Buehler

2012-01-01

Cerulean Warblers (Setophaga cerulea), one of the fastest declining avian species in North America, are associated with heterogeneous canopies in mature hardwood forests. However, the age of most second and third-growth forests in eastern North American is not sufficient for natural tree mortality to maintain structurally diverse canopies. Previous research suggests...

Aboveground Biomass and Litterfall Dynamics in Secondary Forest ...

African Journals Online (AJOL)

The differences in aboveground biomass, litterfall patterns and the seasonality of litterfall in three secondary forest fields aged 1, 5 and 10 years of age regenerating from degraded abandoned rubber plantation and a mature forest were studied in southern Nigeria. This is with a view to understanding the possibility of ...

Dependence of Soil Respiration on Soil Temperature and Soil Moisture in Successional Forests in Southern China

Institute of Scientific and Technical Information of China (English)

Xu-Li Tang; Guo-Yi Zhou; Shu-Guang Liu; De-Qiang Zhang; Shi-Zhong Liu; Jiong Li; Cun-Yu Zhou

2006-01-01

The spatial and temporal variations in soil respiration and its relationship with biophysical factors in forests near the Tropic of Cancer remain highly uncertain. To contribute towards an improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured in three successional subtropical forests at the Dinghushan Nature Reserve (DNR) in southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared in successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates in the cool dry season (October-March). Soil respiration measured at these forests showed a clear increasing trend with the progressive succession. Annual mean (± SD) soil respiration rate in the DNR forests was (9.0±4.6) Mg CO2-C/hm2 per year, ranging from (6.1±3.2) Mg CO2-C/hm2 per year in early successional forests to (10.7±4.9) Mg CO2-C/hm2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation in DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture increased with progressive succession processes. This increase is caused, in part, by abundant respirators in advanced-successional forest, where more soil moisture is needed to maintain their activities.

Dependence of soil respiration on soil temperature and soil moisture in successional forests in Southern China

Science.gov (United States)

Tang, X.-L.; Zhou, G.-Y.; Liu, S.-G.; Zhang, D.-Q.; Liu, S.-Z.; Li, Ji; Zhou, C.-Y.

2006-01-01

The spatial and temporal variations in soil respiration and its relationship with biophysical factors in forests near the Tropic of Cancer remain highly uncertain. To contribute towards an improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured in three successional subtropical forests at the Dinghushan Nature Reserve (DNR) in southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and its biophysical dependence in these forests. The relationships between biophysical factors and soil respiration rates were compared in successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates in the cool dry season (October-March). Soil respiration measured at these forests showed a clear increasing trend with the progressive succession. Annual mean (±SD) soil respiration rate in the DNR forests was (9.0 ± 4.6) Mg CO2-C/hm2per year, ranging from (6.1 ± 3.2) Mg CO2-C/hm2per year in early successional forests to (10.7 ± 4.9) Mg CO2-C/hm2 per year in advanced successional forests. Soil respiration was correlated with both soil temperature and moisture. The T/M model, where the two biophysical variables are driving factors, accounted for 74%-82% of soil respiration variation in DNR forests. Temperature sensitivity decreased along progressive succession stages, suggesting that advanced-successional forests have a good ability to adjust to temperature. In contrast, moisture increased with progressive succession processes. This increase is caused, in part, by abundant respirators in advanced-successional forest, where more soil moisture is needed to maintain their activities.

Factors influencing density of the Northern Mealy Amazon in three forest types of a modified rainforest landscape in Mesoamerica

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Miguel Ángel. De Labra-Hernández

2017-06-01

Full Text Available The high rate of conversion of tropical moist forest to secondary forest makes it imperative to evaluate forest metric relationships of species dependent on primary, old-growth forest. The threatened Northern Mealy Amazon (Amazona guatemalae is the largest mainland parrot, and occurs in tropical moist forests of Mesoamerica that are increasingly being converted to secondary forest. However, the consequences of forest conversion for this recently taxonomically separated parrot species are poorly understood. We measured forest metrics of primary evergreen, riparian, and secondary tropical moist forest in Los Chimalapas, Mexico. We also used point counts to estimate density of Northern Mealy Amazons in each forest type during the nonbreeding (Sept 2013 and breeding (March 2014 seasons. We then examined how parrot density was influenced by forest structure and composition, and how parrots used forest types within tropical moist forest. Overall, parrot density was high in the breeding season, with few parrots present during the nonbreeding season. During the breeding season, primary forest had significantly greater density of 18.9 parrots/km² in evergreen forest and 35.9 parrots/km² in riparian forest, compared with only 3.4 parrots/km² in secondary forest. Secondary forest had significantly lower tree species richness, density, diameter, total height, and major branch ramification height, as well as distinct tree species composition compared with both types of primary forest. The number of parrots recorded at point counts was related to density of large, tall trees, characteristic of primary forest, and parrots used riparian forest more than expected by availability. Hence, the increased conversion of tropical moist forest to secondary forest is likely to lead to reduced densities of forest-dependent species such as the Northern Mealy Amazon. Furthermore, the species' requirement for primary tropical moist forest highlights the need to reevaluate

Arthropod abundance and seasonal bird use of bottomland forest harvest gaps

Science.gov (United States)

Christopher E. Moorman; Liessa T. Woen; John C. Kilgo; James L. Hanula; Scott Horn; Michael D. Ulyshen

2012-01-01

We investigated the influence of arthropod abundance and vegetation structure on shifts in avian use of canopy gap, gap edge, and surrounding forest understory in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. We compared captures of foliage-gleaning birds among locations during four periods (spring migration, breeding, post-breeding, and...

Operational Forest Monitoring in Siberia Using Multi-source Earth Observation Data

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C. Hüttich

2014-08-01

Full Text Available Forest cover disturbance rates are increasing in the forests of Siberia due to intensification of human activities and climate change. In this paper two satellite data sources were used for automated forest cover change detection. Annual ALOS PALSAR backscatter mosaics (2007–2010 were used for yearly forest loss monitoring. Time series of the Enhanced Vegetation Index (EVI, 2000–2014 from the Moderate Resolution Imaging Spectroradiometer (MODIS were integrated in a web-based data middleware system to assess the capabilities of a near-real time detection of forest disturbances using the break point detection by additive season and trends (Bfast method. The SAR-based average accuracy of the forest loss detection was 70 %, whereas the MODIS-based change assessment using breakpoint detection achieved average accuracies of 50 % for trend-based breakpoints and 43.4 % for season-based breakpoints. It was demonstrated that SAR remote sensing is a highly accurate tool for up-to-date forest monitoring. Web-based data middleware systems like the Earth Observation Monitor, linked with MODIS time series, provide access and easy-to-use tools for on demand change monitoring in remote Siberian forests.

Environmental determinants of tropical forest and savanna distribution: A quantitative model evaluation and its implication

Science.gov (United States)

Zeng, Zhenzhong; Chen, Anping; Piao, Shilong; Rabin, Sam; Shen, Zehao

2014-07-01

The distributions of tropical ecosystems are rapidly being altered by climate change and anthropogenic activities. One possible trend—the loss of tropical forests and replacement by savannas—could result in significant shifts in ecosystem services and biodiversity loss. However, the influence and the relative importance of environmental factors in regulating the distribution of tropical forest and savanna biomes are still poorly understood, which makes it difficult to predict future tropical forest and savanna distributions in the context of climate change. Here we use boosted regression trees to quantitatively evaluate the importance of environmental predictors—mainly climatic, edaphic, and fire factors—for the tropical forest-savanna distribution at a mesoscale across the tropics (between 15°N and 35°S). Our results demonstrate that climate alone can explain most of the distribution of tropical forest and savanna at the scale considered; dry season average precipitation is the single most important determinant across tropical Asia-Australia, Africa, and South America. Given the strong tendency of increased seasonality and decreased dry season precipitation predicted by global climate models, we estimate that about 28% of what is now tropical forest would likely be lost to savanna by the late 21st century under the future scenario considered. This study highlights the importance of climate seasonality and interannual variability in predicting the distribution of tropical forest and savanna, supporting the climate as the primary driver in the savanna biogeography.

Temperature as a potent driver of regional forest drought stress and tree mortality

Science.gov (United States)

Williams, A. Park; Allen, Craig D.; Macalady, Alison K.; Griffin, Daniel; Woodhouse, Connie A.; Meko, David M.; Swetnam, Thomas W.; Rauscher, Sara A.; Seager, Richard; Grissino-Mayer, Henri D.; Dean, Jeffrey S.; Cook, Edward R.; Gangodagamage, Chandana; Cai, Michael; McDowell, Nathan G.

2012-01-01

s the climate changes, drought may reduce tree productivity and survival across many forest ecosystems; however, the relative influence of specific climate parameters on forest decline is poorly understood. We derive a forest drought-stress index (FDSI) for the southwestern United States using a comprehensive tree-ring data set representing AD 1000-2007. The FDSI is approximately equally influenced by the warm-season vapour-pressure deficit (largely controlled by temperature) and cold-season precipitation, together explaining 82% of the FDSI variability. Correspondence between the FDSI and measures of forest productivity, mortality, bark-beetle outbreak and wildfire validate the FDSI as a holistic forest-vigour indicator. If the vapour-pressure deficit continues increasing as projected by climate models, the mean forest drought-stress by the 2050s will exceed that of the most severe droughts in the past 1,000 years. Collectively, the results foreshadow twenty-first-century changes in forest structures and compositions, with transition of forests in the southwestern United States, and perhaps water-limited forests globally, towards distributions unfamiliar to modern civilization.

Modelling of 137Cs behaviour in forest ecosystems and prediction of its accumulation in forest products

International Nuclear Information System (INIS)

Spiridonov, S.I.; Fesenko, S.V.; Gontarenko, I.A.; Avila, R.

2001-01-01

A mathematical model of 137 Cs migration in forest ecosystem contaminated due to the Chernobyl accident presented, which describes the behaviour of this radionuclide in the forest litter-soil system, tress, and forest animals. The model's parameters for different types of forest ecosystems are estimated and model's adequacy is tested through the use of independent experimental data. The sensitivity of the model's output variables is analyzed to variations in the most significant parameters. The differences in the seasonal and mean annual dynamics of 137 Cs concentration in muscles of roe deers and mooses are shown to be defined by specific features of the diets of these animals and variations in 137 Cs content in the main diet components [ru

Chronic human disturbance affects plant trait distribution in a seasonally dry tropical forest

Science.gov (United States)

Sfair, Julia C.; de Bello, Francesco; de França, Thaysa Q.; Baldauf, Cristina; Tabarelli, Marcelo

2018-02-01

The effects of human disturbance on biodiversity can be mediated by environmental conditions, such as water availability, climate and nutrients. In general, disturbed, dry or nutrient-depleted soils areas tend to have lower taxonomic diversity. However, little is known about how these environmental conditions affect functional composition and intraspecific variability in tropical dry forests. We studied a seasonally dry tropical forest (SDTF) under chronic anthropogenic disturbance (CAD) along rainfall and soil nutrient gradients to understand how these factors influence the taxonomic and functional composition. Specifically we evaluated two aspects of CAD, wood extraction and livestock pressure (goat and cattle grazing), along soil fertility and rainfall gradients on shrub and tree traits, considering species turnover and intraspecific variability. In addition, we also tested how the traits of eight populations of the most frequent species are affected by wood extraction, livestock pressure, rainfall and soil fertility. In general, although CAD and environmental gradients affected each trait of the most widespread species differently, the most abundant species also had a greater variation of traits. Considering species turnover, wood extraction is associated with species with a smaller leaf area and lower investment in leaf mass, probably due to the indirect effects of this disturbance type on the vegetation, i.e. the removal of branches and woody debris clears the vegetation, favouring species that minimize water loss. Livestock pressure, on the other hand, affected intraspecific variation: the herbivory caused by goats and cattle promoted individuals which invest more in wood density and leaf mass. In this case, the change of functional composition observed is a direct effect of the disturbance, such as the decrease of palatable plant abundance by goat and cattle herbivory. In synthesis, CAD, rainfall and soil fertility can affect trait distribution at community

Does the reproductive season account for more records of birds in a marked seasonal climate landscape in the state of São Paulo, Brazil?

Directory of Open Access Journals (Sweden)

Vagner Cavarzere

2013-01-01

Full Text Available Investigators have reported that birds from temperate regions are more detectable during their breeding seasons, which should be used to adequately survey avifaunas. In the state of São Paulo, southeastern Brazil, the rainiest months of the year are usually associated with a peak in the reproduction of birds. To test the hypothesis that birds are equally detectable throughout the year, I conducted transect counts of birds in a predominantly open Cerrado landscape in São Paulo during 2005 and 2006. There was no significant difference in the number of species or individuals between breeding (rainy and nonbreeding (dry seasons; 24% of the species with > 50 contacts was likely to be recorded more often in a particular season. Unlike temperate regions, where vocal behavior plays an important role in detections of birds during and after reproductive seasons, my results suggest that Cerrado birds may be evenly detected throughout the year.

NotaMark industrial laser marking system: a new security marking technology

Science.gov (United States)

Moreau, Vincent G.

2004-06-01

Up until now, the only variable alphanumeric data which could be added to banknotes was the number, applied by means of impact typographical numbering boxes. As an additional process or an alternative to this mechanical method, a non-contact laser marking process can be used offering high quality and greater levels of flexibility. For this purpose KBA-GIORI propose an exclusive laser marking solution called NotaMark. The laser marking process NotaMark is the ideal solution for applying variable data and personalizing banknotes (or any other security documents) with a very high resolution, for extremely large production volumes. A completely integrated solution has been developed comprised of laser light sources, marking head units, and covers and extraction systems. NotaMark allows the marking of variable data by removing locally and selectively, specific printed materials leaving the substrate itself untouched. A wide range of materials has already been tested extensively. NotaMark is a new security feature which is easy to identify and difficult to counterfeit, and which complies with the standard mechanical and chemical resistance tests in the security printing industry as well as with other major soiling tests. The laser marking process opens up a whole new range of design possibilities and can be used to create a primary security feature such as numbering, or to enhance the value of existing features.

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 

Scent-marking by coyotes, Canis latrans: the influence of social and ecological factors

Science.gov (United States)

Gese; Ruff

1997-11-01

We observed 49 coyotes, Canis latransfrom five resident packs for 2456 h and five transient coyotes for 51 h from January 1991 to June 1993 in the Lamar River Valley, Yellowstone National Park, Wyoming, U.S.A. During these observations we recorded 3042 urinations, 451 defecations, 446 ground scratches and 743 double-marks. The rate of scent-marking (via urination) was influenced by the social organization (resident versus transient) to which the coyote belonged, the social class (alpha, beta or pup) of the animal and the time of the year. Transient coyotes scent-marked at a lower rate than did members of a resident pack. Within the resident packs, alpha coyotes scent-marked at a higher rate than beta coyotes (adults and yearlings subordinant to alphas, but dominant over pups) and pups. Alpha coyotes increased their rate of marking during the breeding season; beta and pup coyotes performed scent-marks at a relatively constant rate throughout the year. There was no influence of social class or time of year on the rate of defecation. The rate of double-marking was highest among alpha coyotes with a peak during the breeding season. Alpha coyotes ground-scratched at a higher rate than did beta and pup coyotes. Alpha and beta coyotes scent-marked more than expected along the periphery of the territory compared to the interior; pups marked in the interior and edge in proportion to expected frequencies. Double-marking and ground-scratching were higher than expected along the periphery of the territory. The distribution of defecations was not different from expected along the edge versus the interior of the territory. Pack size did not influence the rate of scent-marking performed by individuals in the pack or by the alpha pair. We concluded that alpha coyotes were the primary members of the resident pack involved in scent-marking. The large coyote packs and the high rate of marking by the alpha pairs were parallel to the scent-marking behaviour displayed by wolves, C

Arthropod vertical stratification in temperate deciduous forests: Implications for conservation oriented management

Science.gov (United States)

Ulyshen Michael

2011-01-01

Studies on the vertical distribution patterns of arthropods in temperate deciduous forests reveal highly stratified (i.e., unevenly vertically distributed) communities. These patterns are determined by multiple factors acting simultaneously, including: (1) time (forest age, season, time of day); (2) forest structure (height, vertical foliage complexity, plant surface...

Impacts of Land Cover and Seasonal Variation on Maximum Air Temperature Estimation Using MODIS Imagery

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Yulin Cai

2017-03-01

Full Text Available Daily maximum surface air temperature (Tamax is a crucial factor for understanding complex land surface processes under rapid climate change. Remote detection of Tamax has widely relied on the empirical relationship between air temperature and land surface temperature (LST, a product derived from remote sensing. However, little is known about how such a relationship is affected by the high heterogeneity in landscapes and dynamics in seasonality. This study aims to advance our understanding of the roles of land cover and seasonal variation in the estimation of Tamax using the MODIS (Moderate Resolution Imaging Spectroradiometer LST product. We developed statistical models to link Tamax and LST in the middle and lower reaches of the Yangtze River in China for five major land-cover types (i.e., forest, shrub, water, impervious surface, cropland, and grassland and two seasons (i.e., growing season and non-growing season. Results show that the performance of modeling the Tamax-LST relationship was highly dependent on land cover and seasonal variation. Estimating Tamax over grasslands and water bodies achieved superior performance; while uncertainties were high over forested lands that contained extensive heterogeneity in species types, plant structure, and topography. We further found that all the land-cover specific models developed for the plant non-growing season outperformed the corresponding models developed for the growing season. Discrepancies in model performance mainly occurred in the vegetated areas (forest, cropland, and shrub, suggesting an important role of plant phenology in defining the statistical relationship between Tamax and LST. For impervious surfaces, the challenge of capturing the high spatial heterogeneity in urban settings using the low-resolution MODIS data made Tamax estimation a difficult task, which was especially true in the growing season.

Effect of water stress on seedling growth in two species with different abundances: the importance of Stress Resistance Syndrome in seasonally dry tropical forest

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Wanessa Nepomuceno Ferreira

2015-09-01

Full Text Available ABSTRACTIn seasonally dry tropical forests, species carrying attributes of Stress Resistance Syndrome (SRS may have ecological advantages over species demanding high quantities of resources. In such forests, Poincianella bracteosa is abundant, while Libidibia ferrea has low abundance; therefore, we hypothesized that P. bracteosa has characteristics of low-resource species, while L. ferrea has characteristics of high-resource species. To test this hypothesis, we assessed morphological and physiological traits of seedlings of these species under different water regimes (100%, 70%, 40%, and 10% field capacity over 85 days. For most of the studied variables we observed significant decreases with increasing water stress, and these reductions were greater in L. ferrea. As expected, L. ferreamaximized their growth with increased water supply, while P. bracteosa maintained slower growth and had minor adjustments in biomass allocation, characteristics representative of low-resource species that are less sensitive to stress. We observed that specific leaf area, biomass allocation to roots, and root/shoot ratio were higher in L. ferrea, while biomass allocation to leaves and photosynthesis were higher in P. bracteosa. Results suggest that the attributes of SRS can facilitate high abundance of P. bracteosa in dry forest.

Seasonality of Lutzomyia fairtigi (Diptera: Psychodidae: Phlebotominae), a species endemic to Eastern Colombia.

Science.gov (United States)

Molina, Jorge Alberto; Ortiz, Mario Iván; Guhl, Felipe

2008-08-01

The bionomics of sand flies (Diptera: Phlebotominae) was studied monthly for two consecutive years in alluvial gallery forests in the department of Casanare, Northeastern Colombia. A total of 2,365 specimens and 10 species were captured using CDC light traps and Shannon traps, and from diurnal resting places, and human landing collections. Lutzomyia fairtigi Martins (55%), Lutzomyia micropyga (Mangabeira) (20.9%), and Lutzomyia antunesi (Coutinho) (13.5%) were the predominant species in the region. Lutzomyia flaviscutellata and Lutzomyia panamensis, potential vectors of Leishmania in Colombia and neighboring countries, were also collected, but in low numbers. Lu. fairtigi is an endemic species to Colombia, and minimal data are available on its biology and distribution. The present study provides additional information about Lu. fairtigi, such as the diurnal activity displayed by females on cloudy days, the greater density during the rainy season (April to October), marked anthropophilia, and the presence of flagellates in the midgut of one female.

[The scent marking of territory of gerbils: a comparative analysis exemplified by 4 species of the genus Meriones].

Science.gov (United States)

Gromov, V S

1997-01-01

Sex-age and seasonal variability of the ventral glands and different stereotypes of scent marking behaviour in four Meriones species (M. unguiculatus, M. meridianus, M. libycus, M. tamariscinus) have been studied in nature and under semi-natural conditions. Two major ways of olfactory marking are considered: by secretion of the ventral glands and by "signal heaps" with urine and feces. Intraspecific and inter-species variability of marking activity is investigated. The ventral glands start to function at the period of preparation of a generative system to reproduction. The peak of secretary activity of gland and maximum of two types of marking activity is observed in spring and early summer, i.e. the period of active reproduction. The maximum of two types of the marking activity is observed during this period. In M. tamariscinus and M. meridianus the marking by the ventral gland is prevailing mode of the territory scent marking, while Mongolian gerbils (M. unguiculatus) prefer to use "signal heaps" Libyan gerbils (M. libycus) in this relation take an intermediate position. At the non-productive period a level of marking activity is on 10-20 times lower than at the reproductive season. Besides hormonal, social factors were also important for regulation of marking activity. By influence of these factors the differences in the level of marking activity in high-rank and low-rank individuals and differences in patterns of a spatial distribution of scent marks in individuals of different hierarchical rank is explained. Functional significance of various ways of territory scent marking is discussed.

Vertical stratification of bat assemblages in flooded and unflooded Amazonian forests

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Maria João Ramos PEREIRA, João Tiago MARQUES, Jorge M. PALMEIRIM

2010-08-01

Full Text Available Tropical rainforests usually have multiple strata that results in a vertical stratification of ecological opportunities for animals. We investigated if this stratification influences the way bats use the vertical space in flooded and unflooded forests of the Central Amazon. Using mist-nets set in the canopy (17 to 35 m high and in the understorey (0 to 3 m high we sampled four sites in upland unflooded forests (terra firme, three in forests seasonally flooded by nutrient-rich water (várzea, and three in forests seasonally flooded by nutrient-poor water (igapó. Using rarefaction curves we found that species richness in the understorey and canopy were very similar. An ordination analysis clearly separated the bat assemblages of the canopy from those of the understorey in both flooded and unflooded habitats. Gleaning carnivores were clearly associated with the understorey, whereas frugivores were abundant in both strata. Of the frugivores, Carollinae and some Stenodermatinae were understorey specialists, but several Stenodermatinae mostly used the canopy. The first group mainly includes species that, in general, feed on fruits of understorey shrubs, whereas the second group feed on figs and other canopy fruits. We conclude that vertical stratification in bat communities occurs even within forests with lower canopy heights, such as Amazonian seasonally flooded forests, and that the vertical distribution of bat species is closely related to their diet and foraging behaviour [Current Zoology 56 (4: 469–478, 2010].

Forest fires and lightning activity during the outstanding 2003 and 2005 fire seasons

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Russo, Ana; Ramos, Alexandre; Trigo, Ricardo

2013-04-01

discharges location which were extracted from the Portuguese Lightning Location System that has been in service since June of 2002 and is operated by the national weather service - Instituto de Meteorologia (IM). The main objective of this work is to analyze for possible relations between the PRFD and the Portuguese lightning database for the 2003 and 2005 extreme fire seasons. In particularly we were able to verify the forest fires labeled as "ignited by lightning" by comparing its location to the lightning discharges location database. Furthermore we have also investigated possible fire ignition by lightning discharges that have not yet been labeled in the PRFD by comparing daily data from both datasets.

Drivers of methane uptake by montane forest soils in the Peruvian Andes

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Jones, Sam; Diem, Torsten; Huaraca Quispe, Lidia; Cahuana, Adan; Meir, Patrick; Teh, Yit

2016-04-01

The exchange of methane between the soils of humid tropical forests and the atmosphere is relatively poorly documented. This is particularly true of montane settings where variations between uptake and emission of atmospheric methane have been observed. Whilst most of these ecosystems appear to function as net sinks for atmospheric methane, some act as considerable sources. In regions like the Andes, humid montane forests are extensive and a better understanding of the magnitude and controls on soil-atmosphere methane exchange is required. We report methane fluxes from upper montane cloud forest (2811 - 2962 m asl), lower montane cloud forest (1532 - 1786 m asl), and premontane forest (1070 - 1088 m asl) soils in south-eastern Peru. Between 1000 and 3000 m asl, mean annual air temperature and total annual precipitation decrease from 24 ° C and 5000 mm to 12 ° C and 1700 mm. The study region experiences a pronounced wet season between October and April. Monthly measurements of soil-atmosphere gas exchange, soil moisture, soil temperature, soil oxygen concentration, available ammonium and available nitrate were made from February 2011 in the upper and lower montane cloud forests and July 2011 in the premontane forest to June 2013. These soils acted as sinks for atmospheric methane with mean net fluxes for wet and dry season, respectively, of -2.1 (0.2) and -1.5 (0.1) mg CH4 m-2 d-1 in the upper montane forest; -1.5 (0.2) and -1.4 (0.1) mg CH4 m-2 d-1in the lower montane forest; and -0.3 (0.2) and -0.2 (0.2) mg CH4 m-2 d-1 in the premontane forest. Spatial variations among forest types were related to available nitrate and water-filled pore space suggesting that nitrate inhibition of oxidation or constraints on the diffusional supply of methane to methanotrophic communities may be important controls on methane cycling in these soils. Seasonality in methane exchange, with weaker uptake related to increased water-filled pore space and soil temperature during the wet

Inventory of forest and rangeland and detection of forest stress. [Colorado and California

Science.gov (United States)

Heller, R. C.; Aldrich, R. C.; Weber, F. P.; Driscoll, R. S. (Principal Investigator)

1974-01-01

The author has identified the following significant results. Disturbances in a forest environment that cause reductions in forest area, timber volume, and timber growth can be detected on ERTS-1 combined color composites. However, detection depends on comparing a conventional aerial photograph taken at some base year with an ERTS-1 image taken in some subsequent year. In a test made on the Atlanta site, 1:63,360 scale aerial photo index sheets made in 1966 were compared with ERTS-1 image 1264-15445 (April 1973). Five factors were found important to detection reliability: (1) the quality of the imagery; (2) the season of the imagery; (3) the size of the disturbed area; (4) the number of years since the disturbances; and (5) the type of cutting treatment. Of 209 disturbances verified on aerial photography, 165 (or approximately 80%) were detected on the ERTS-1 image by one independent interpreter. Improved training and additional experience in using this low resolution imagery should improve detection. Of the two seasons of data studies (fall and early spring), early spring is the best for detecting land use changes. Generally speaking, winter, early spring, and early summer are the best times of year for detecting forest disturbances.

THE VEGETATION OF LAMBUSANGO FOREST, BUTON, INDONESIA

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ANDREW POWLING

2016-01-01

Full Text Available POWLING, A., PHILLIPS, A., PRITCHETT, R., SEGAR, S. T., WHEELER, R. & MARDIASTUTI, A. 2015. Thevegetation of Lambusango Forest, Buton, Indonesia. Reinwardtia 14(2: 265 – 286. ― Lambusango Forest is a tropicalrainforest on the island of Buton, which lies close to south east Sulawesi. The forest covers an area of about 95.000 ha,with different parts of the forest having different levels of conservation protection. It lies on rocks of both calcareous(limestone and non-calcareous (sandstone, conglomerate, peridotite and chert nature, which give rise to soils withvarying pH values, nutrient levels and water-holding capacities. The climate is seasonal, with a dry season of threemonths and considerable year-to-year variability due to El Niño and La Niña events. The vegetation on the differentsoils and in different habitats has been studied. Over 300 species of vascular plants found in the forest and surroundingareas are listed, including trees and shrubs, herbs, climbers, epiphytes, ferns and club-mosses. Two genera, Calamuswith 18 species and Ficus with 29 species, are particularly species-rich, apparently due to their ability to occupy numerousedaphic and ecological niches. Species of these two genera are also good colonists and so better able to reachButon in the recent past than other species. The plants of the forest indicate that Buton is floristically very similar toSulawesi, with at least 83% of the species found in the forest also being known from Sulawesi. Most of the plant familiesand genera present on Buton are common in SE Asia, indicating colonisation primarily from that continent. Manyfewer families and genera have colonised from the Australasian continent. The conservation of plant diversity is necessaryfor the forest to continue as a functioning ecosystem, to the benefit of the animals of the forest and also the localpeople.

Effect of fragmentation on the Costa Rican dry forest avifauna

OpenAIRE

Barrantes, Gilbert; Ocampo, Diego; Ram?rez-Fern?ndez, Jos? D.; Fuchs, Eric J.

2016-01-01

Deforestation and changes in land use have reduced the tropical dry forest to isolated forest patches in northwestern Costa Rica. We examined the effect of patch area and length of the dry season on nestedness of the entire avian community, forest fragment assemblages, and species occupancy across fragments for the entire native avifauna, and for a subset of forest dependent species. Species richness was independent of both fragment area and distance between fragments. Similarity in bird comm...

Tropical savannas and dry forests.

Science.gov (United States)

Pennington, R Toby; Lehmann, Caroline E R; Rowland, Lucy M

2018-05-07

In the tropics, research, conservation and public attention focus on rain forests, but this neglects that half of the global tropics have a seasonally dry climate. These regions are home to dry forests and savannas (Figures 1 and 2), and are the focus of this Primer. The attention given to rain forests is understandable. Their high species diversity, sheer stature and luxuriance thrill biologists today as much as they did the first explorers in the Age of Discovery. Although dry forest and savanna may make less of a first impression, they support a fascinating diversity of plant strategies to cope with stress and disturbance including fire, drought and herbivory. Savannas played a fundamental role in human evolution, and across Africa and India they support iconic megafauna. Copyright © 2018 Elsevier Ltd. All rights reserved.

Do seasonal changes in light availability influence the inverse leafing phenology of the neotropical dry forest understory shrub Bonellia nervosa (Theophrastaceae?

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Oscar M Chaves

2008-03-01

Full Text Available In tropical dry forests most plants are deciduous during the dry season and flush leaves with the onset of the rains. In Costa Rica, the only species displaying the opposite pattern is Bonellia nervosa. To determine if seasonal changes in light availability are associated with the leaf and reproductive phenology of this species, we monitored leaf production, survival, and life span, as well as flower and fruit production from April 2000 to October 2001 in Santa Rosa National Park. Leaf flushing and flower bud production took place shortly after the autumnal equinox when day length starts to decrease. Leaves began expansion at the end of the wet season, and plants reached 70 % of their maximum leaf area at the beginning of the dry season, maintaining their foliage throughout the entire dry period. Leaf shedding occurred gradually during the first three months of the wet season. Leaf flushing and shedding showed high synchrony, with leaf numbers being related to light availability. Maximum leaf production coincided with peaks in radiation during the middle of the dry season. Decreasing day length induces highly synchronous flower bud emergence in dry forest species, but this is the first study indicating induction of leaf flushing by declining day length. Rev. Biol. Trop. 56 (1: 257-268. Epub 2008 March 31.En los bosques tropicales secos la mayoría de las plantas pierden sus hojas durante la estación seca y las producen con el inicio de las lluvias. En Costa Rica la única especie que muestra el patrón fenológico inverso es Bonellia nervosa. Para determinar si los cambios estacionales en la disponibilidad de luz estaban asociados con la fenología foliar y reproductiva en esta especie, monitoreamos la producción y sobrevivencia de hojas, así como la producción de flores y frutos de abril del 2000 a octubre del 2001 en el Parque Nacional Santa Rosa. La producción de hojas y botones florales ocurrió poco después del equinoccio de oto

Forest Floor Carbon Exchange of a Boreal Black Spruce Forest in Eastern Canada

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Bergeron, O.; Margolis, H. A.; Coursolle, C.

2009-06-01

This study reports continuous automated measurements of forest floor carbon (C) exchange over feathermoss, lichen, and sphagnum micro-sites in a black spruce forest in eastern North America during snow-free periods over three years. The response of soil respiration (Rs-auto) and forest floor photosynthesis (Pff) to environmental factors was determined. The seasonal contributions of scaled up Rs-auto adjusted for spatial representativeness (Rs-adj) and Pff (Pff-eco) relative to that of total ecosystem respiration (Re) and photosynthesis (Peco), respectively, were also quantified. Shallow soil temperature explained 67-86% of the variation in Rs-auto for all ground cover types, while deeper soil temperatures were related to Rs-auto only for the feathermoss micro-sites. Base respiration was consistently lower under feathermoss, intermediate under sphagnum, and higher under lichen during all three years. The Rs-adj/Re ratio increased from spring through autumn and ranged from 0.85 to 0.87 annually for the snow-free period. The Rs-adj/Re ratio was negatively correlated with the difference between air and shallow soil temperature and this correlation was more pronounced in autumn than summer and spring. Maximum photosynthetic capacity of the forest floor (Pffmax) saturated at low irradiance levels (~200 μmol m-2 s-1) and decreased with increasing air temperature and vapor pressure deficit for all three ground cover types, suggesting that Pff was more limited by desiccation than by light availability. Pffmax was lowest for sphagnum, intermediate for feathermoss, and highest for lichen for two of the three years. Pff normalized for light peaked at air temperatures of 5-8°C, suggesting that this is the optimal temperature range for Pff. The Pff-eco/Peco ratio varied seasonally from 13 to 24% and reached a minimum in mid-summer when both air temperature and Peco were at their maximum. On an annual basis, Pff-eco accounted for 17-18% of Peco depending on the year and the

The Prefrontal Cortex Activity and Psychological Effects of Viewing Forest Landscapes in Autumn Season.

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Joung, Dawou; Kim, Geonwoo; Choi, Yoonho; Lim, HyoJin; Park, Soonjoo; Woo, Jong-Min; Park, Bum-Jin

2015-06-26

Recently reported research indicate that forest environments have physiological and psychological relaxing effects compared to urban environments. However, some researchers claim that the stress of the subjects from being watched by others during measurements can affect the measurement result in urban experiments conducted in the center of a street. The present study was conducted to determine whether forest environments have physiological and psychological relaxing effects, using comparison of viewing a forest area with viewing an urban area from the roof of an urban building without being watched by others. Near-infrared spectroscopy (NIRS) measurement was performed on subjects while they viewed scenery for 15 min at each experimental site (urban and forest areas). Subjective assessments were performed after the NIRS measurement was complete. Total hemoglobin and oxyhemoglobin concentrations were significantly lower in the forest area than in the urban area. For semantic differential in subjective assessments, feelings of "comfortable", "natural", and "soothed" were significantly higher in the forest area than in the urban area, and for profile of mood states, negative emotions were significantly lower in the forest area than in the urban area. The results of physiological and psychological measurements show that viewing the forest enabled effective relaxation.

Longleaf pine restoration in context comparisons of frequent fire forests

Science.gov (United States)

Seth Bigelow; Michael C. Stambaugh; Joseph J. O' Brien; Andrew J. Larson; Michael A. Battaglia

2018-01-01

To see a frequent-fire forest burn for the first time is to experience a remarkable teat of nature. Most people are accustomed to the slow change of forests with the seasons, not the instantaneous conversion of green and brown plant mass to smoke and char. Yet to visit such a forest a week after it bums is to see bright green shoots emerging, highlighted against a...

Seasonal variation in the number of captures of Artibeus lituratus (Olfers, 1818 and Sturnira lilium (E. Geoffroy, 1810 (Chiroptera: Phyllostomidae in the upper strata of an Atlantic Forest remnant in southern Brazil

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Fernando Carvalho

2014-09-01

Full Text Available This study aimed to analyze the occurrence of seasonal variations in the number of captures of Artibeus lituratus and Sturnira lilium in the upper strata of an Atlantic Forest remnant in southern Brazil. It was conducted in the town of Pedras Grandes, in the southern end of Santa Catarina. The chiropterans were captured with mist nets installed in the canopy and subcanopy. To check whether there were differences in the number of captures between seasons, we used the chi-square test (χ2, with a significance level of 0.05, and, whenever needed, partial χ2 tests. Artibeus lituratus showed significant differences between seasons, and the largest number of captures occurs in autumn. For S. lilium we did not observe statistically significant differences. The seasonal variation found out for A. lituratus may be related to its diet, which is based on fruits whose availability has seasonal variations. For S. lilium, besides the diet, mainly based on plants that do not have seasonal variations with regard to fruit availability, the altitude of the study area and its variations in temperature also seem to explain the absence of seasonal variation.

Observations of climate, albedo, and surface radiation over cleared and undisturbed Amazonian forest

International Nuclear Information System (INIS)

Bastable, H.G.; Shuttleworth, W.J.; Dallarosa, R.L.G.; Fisch, G.; Nobre, C.A.

1993-01-01

Measurements from the first comparative study of climate over Amazonian tropical forest and an embedded deforested clearing are presented. Observations comprise a continuous 60-day run of data from mid-October to mid-December 1990, covering the end of the dry season and the beginning of the wet season. Mean hourly observations are calculated for the whole period; and for two 10-day periods, one in the dry season and one at the start of the wet season. Much greater variation in weather variables was observed at the clearing compared with over the forest. While the mean values of temperature and specific humidity deficit differed by less than 1°C and 1 g kg −1 respectively, their daily ranges at the clearing were twice those at the forest. Mean daily albedo of the forest was 13.1 per cent, agreeing well with other tropical forest measurements, and of the clearing was 16.3 per cent, somewhat lower than the values currently being used in GCMs. The surface energy balance was investigated and mean available energy calculated for each site. The significant difference in the daily pattern of net radiation between the sites was found to be at least as much due to differences in the longwave radiation balance as to differences in albedo. The diurnal pattern of net radiation therefore changed between dry and wet periods as the higher plant water stress experienced by clearing vegetation altered the daily temperature cycle

Dinâmica sazonal da produção e decomposição de serrapilheira em floresta tropical de transição Seasonal dynamics of the litterfall production and decomposition in tropical transitional forest

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Luciana Sanches

2009-04-01

Full Text Available Em função de se analisar a produção, dinâmica e decomposição de serrapilheira em busca da sazonalidade do microclima em uma floresta tropical de transição Amazônia Cerrado, propõe-se estimar a produção de serrapilheira, por meio de caixas de coleta de 1 m² e o acúmulo de serrapilheira sobre o solo por meio de quadrantes de 25 x 25 cm, distribuídos aleatoriamente. Determinaram-se a constante de decaimento (K, o coeficiente de retorno de serrapilheira (K L e a constante de decomposição (K'. Com o emprego de bolsas de nylon preenchidas com folhas de espécies de relevância na floresta (Tovomita schomburgkki e Brosimium lactescens estudou-se a decomposição de folhas e se monitaram os fatores ambientais por meio de equipamentos instalados em uma torre micrometeorológica. A produção de serrapilheira não só se apresentou de forma sazonal, com significativa influência da umidade relativa do ar e da precipitação, em uma floresta de transição, mas foi majoritariamente composta de folhas seguidas de galhos e miscelânea (flores e frutos. A decomposição de folhas em florestas tropicais foi acelerada em ambas as estações, seca-úmida e úmida-seca, sendo a velocidade de decomposição das folhas maior na estação úmida-seca.The objective of this study was to analyze the production, dynamics and litter decomposition as a function of the seasonality of the microclimate in a transitional tropical forest of Amazonia Cerrado. Estimate of litterfall was carried out with collection boxes of 1 m² and floor forest mass with quadrants of 25 x 25 cm distributed randomly. The decline constant (K, litter turnover rate (K L and litter decomposition rate (K' were determined by estimation of litterfall and forest floor litter mass. Leaf decomposition was studied by litter bags with leaves of species of relevance (Tovomita schomburgkki and Brosimium lactescens in the forest. The analysis of the environmental factors was measured through

Hydro-chemical cycle of forest ecosystem in the Norikura Highlands

Science.gov (United States)

Muramoto, Michiko; Nara, Maiko; Asari, Tomoko; Suzuki, Keisuke

Because of precipitation serves as a major vehicle of nutrient input into the forest ecosystem, the accurate measurement of its volume and ion concentration is of prime importance in an evaluation of any bio-geochemical cycle. Therefore, chemistry of the precipitation and throughfall of forest ecosystem was investigated in the Norikura Highlands. The investigation period was from January, 2003 to October, 2006. The throughfall volume in growing season and dormant season were 86 % and 93 % of the precipitation volume. Throughfall pH increased with increasing K+ concentration showed that H+ was held within the canopy by cation exchange reaction. And the concentration level of K+, Mg2+ and Ca2+ in the throughfall was much higher than that in the precipitation. It was the cause of canopy leaching. In growing season, proportions of canopy leaching of K+, Mg2+ and Ca2+ were 95 %, 70 % and 43 % of the throughfall deposition respectively. At Coniferous site, the flux of dry deposition was higher in dormant season than growing season. It is suggested that aerosol of the atmosphere and leaf area might be influenced.

The role of phytophysiognomies and seasonality on the structure of ground-dwelling anuran (Amphibia) in the Pampa biome, Southern Brazil.

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Maragno, Franciéle P; Santos, Tiago G; Cechin, Sonia Z

2013-09-01

Considering that habitat use by amphibians is related both with climate and environmental features, we tested the hypothesis that anuran assemblages found in different phytophysiognomies and in different seasons vary in structure. Additionally, we searched for species which can be indicators of habitat and seasons. The study was conducted in the Pampa biome, southern Brazil. Sampling was done through pitfall traps placed in three phytophysiognomies: grassland, ecotone grassland/forest; and forest. The seasonality factor was created by grouping months in warn and cold seasons. Sixteen species were found and the assemblages were influenced both by phytophysiognomies and climatic seasonality. In a paired comparison, the three phytophysiognomies differed in structure of assemblage from each other. Physalaemus henselii, P. riograndensis, Pseudopaludicola falcipes and Pseudis minuta were indicators of ecotone. Leptodactylus gracilis and Physalaemus biligonigerus were indicators of grassland. None species was indicator of forest. Most of the species were indicators of warm season: Elachistocleis bicolor, Leptodactylus fuscus, L. gracilis, L. latinasus, L. latrans, L. mystacinus, Physalaemus biligonigerus, P. cuvieri and Pseudis minuta. None species was indicator of cold season. We found that even for species of open areas, as Pampa, heterogeneous phytophysiognomies are important for maintaining abundance and constancy of populations of anuran.

Marked seasonality of Cyclospora cayetanensis infections: ten-year observation of hospital cases, Honduras.

Science.gov (United States)

Kaminsky, Rina Girard; Lagos, Javier; Raudales Santos, Gabriela; Urrutia, Samuel

2016-02-04

Document seasonality occurrence and epidemiologic characteristics of Cyclospora cayetanensis infections during a 10-year period from patients consulting at the University Hospital, Honduras. Retrospective non interventional hospital-based study analyzed laboratory results from the period 2002 to 2011 of fresh and Ziehl-Nielsen carbolfuchsin stained routine stool samples received for parasitologic examination. Sporadically a sample with numerous oocysts was allowed to sporulate in 2.5 % potassium dichromate confirming the presence of bi-cystic bi-zoic oocysts. A total of 35,157 fecal samples were examined during a ten-year span, of which a third (28.4 %) was stained by the Ziehl-Neelsen carbolfuchsin method diagnosing a total of 125 (1.3 %) C.cayetanensis infections. A statistically significant apparent seasonality was observed most years during May to August (range p < 0.036-0.001), with 83.3 % of 125 cases occurring in those rainy months. All C. cayetanensis cases came from urban poor neighborhoods; male/female relation was 1:1 except in 2006, when all patients were females (p = 0.05; r(2) = 22,448). Forty four point eight percent of the stool samples were diarrheic or liquid and 65.6 % infections were identified in children 10 years old or less. Enteric helminths and protozoa co-infected Cyclospora positive patients in 52 instances.: 8 % Ascaris lumbricoides, 8 % Giardia duodenalis, 23.2 % Blastocystis spp. and less frequently Entamoeba histolytica/E. dispar, Strongyloides stercoralis, and Trichuris trichiura. Results suggest a seasonal pattern for Cyclospora infections diagnosed in a clinical setting during the rainy months in Tegucigalpa and surrounding areas. Community studies should be conducted to support or dispute these observations.

Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest.

Science.gov (United States)

Schilling, Erik M; Waring, Bonnie G; Schilling, Jonathan S; Powers, Jennifer S

2016-09-01

We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.

Global Trends in Seasonality of Normalized Difference Vegetation Index (NDVI, 1982–2011

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Assaf Anyamba

2013-09-01

Full Text Available A 30-year series of global monthly Normalized Difference Vegetation Index (NDVI imagery derived from the Global Inventory Modeling and Mapping Studies (GIMMS NDVI3g archive was analyzed for the presence of trends in changing seasonality. Using the Seasonal Trend Analysis (STA procedure, over half (56.30% of land surfaces were found to exhibit significant trends. Almost half (46.10% of the significant trends belonged to three classes of seasonal trends (or changes. Class 1 consisted of areas that experienced a uniform increase in NDVI throughout the year, and was primarily associated with forested areas, particularly broadleaf forests. Class 2 consisted of areas experiencing an increase in the amplitude of the annual seasonal signal whereby increases in NDVI in the green season were balanced by decreases in the brown season. These areas were found primarily in grassland and shrubland regions. Class 3 was found primarily in the Taiga and Tundra biomes and exhibited increases in the annual summer peak in NDVI. While no single attribution of cause could be determined for each of these classes, it was evident that they are primarily found in natural areas (as opposed to anthropogenic land cover conversions and that they are consistent with climate-related ameliorations of growing conditions during the study period.

Seasonal contrasts in the response of coffee ants to agroforestry shade-tree management.

Science.gov (United States)

Teodoro, A V; Sousa-Souto, L; Klein, A-M; Tscharntke, T

2010-12-01

In many tropical landscapes, agroforestry systems are the last forested ecosystems, providing shade, having higher humidity, mitigating potential droughts, and possessing more species than any other crop system. Here, we tested the hypothesis that higher levels of shade and associated humidity in agroforestry enhance coffee ant richness more during the dry than rainy season, comparing ant richness in 22 plots of three coffee agroforestry types in coastal Ecuador: simple-shade agroforests (intensively managed with low tree species diversity), complex-shade agroforests (extensively managed with intermediate tree species diversity) and abandoned coffee agroforests (abandoned for 10-15 yr and resembling secondary forests). Seasonality affected responses of ant richness but not composition to agroforestry management, in that most species were observed in abandoned coffee agroforests in the dry season. In the rainy season, however, most species were found in simple-shade agroforests, and complex agroforestry being intermediate. Foraging coffee ants species composition did not change differently according to agroforestry type and season. Results show that shade appears to be most important in the dry seasons, while a mosaic of different land-use types may provide adequate environmental conditions to ant species, maximizing landscape-wide richness throughout the year. © 2010 Entomological Society of America

Mapping forest transition trends in Okomu reserve using Landsat ...

African Journals Online (AJOL)

DR. ALEX O. ONOJEGHUO

1 Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, United ... and improve upon the technical capacity of forest managers to improve forest management. Overall, the .... cloud cover or were totally free of such and acquired within the same season (as was the case in this ... Green (2), red (3) and.

The role of forest humus in watershed management in New England

Science.gov (United States)

G. R., Jr. Trimble; Howard W. Lull

1956-01-01

Forest humus is one of the most interesting components of the forest environment. Its surface serves as a depository for leaf fall and needle fall, with successive depths marking stages of transmutation from the freshly fallen to the decomposed. And humus is responsive: humus type and depth are indicators of forest treatment and, to some extent, of site quality....

Richness and Abundance of Ichneumonidae in a Fragmented Tropical Rain Forest.

Science.gov (United States)

Ruiz-Guerra, B; Hanson, P; Guevara, R; Dirzo, R

2013-10-01

Because of the magnitude of land use currently occurring in tropical regions, the local loss of animal species due to habitat fragmentation has been widely studied, particularly in the case of vertebrates. Many invertebrate groups and the ichneumonid wasps in particular, however, have been poorly studied in this context, despite the fact that they are one of the most species-rich groups and play an important role as regulators of other insect populations. Here, we recorded the taxonomic composition of ichneumonid parasitoids and assessed their species richness, abundance, similarity, and dominance in the Los Tuxtlas tropical rain forest, Mexico. We compared two forest types: a continuous forest (640 ha) and a forest fragment (19 ha). We sampled ichneumonids using four malaise traps in both forest types during the dry (September-October) and rainy (March-April) seasons. A total of 104 individuals of Ichneumonidae belonging to 11 subfamilies, 18 genera, and 42 species were collected in the continuous forest and 11 subfamilies, 15 genera, and 24 species were collected in the forest fragment. Species richness, abundance, and diversity of ichneumonids were greater in the continuous forest than in the forest fragment. We did not detect differences between seasons. Species rank/abundance curves showed that the ichneumonid community between the forest types was different. Species similarity between forest types was low. The most dominant species in continuous forest was Neotheronia sp., whereas in the forest fragment, it was Orthocentrus sp. Changes in the ichneumonid wasp community may compromise important tropical ecosystem processes.

Response of Amazon Fires to the 2015/2016 El Niño and Evaluation of a Seasonal Fire Season Severity Forecast

Science.gov (United States)

Randerson, J. T.

2016-12-01

Recent work has established that year-to-year variability in drought and fire within the Amazon responds to a dual forcing from ocean-atmosphere interactions in the tropical Pacific and North Atlantic. Teleconnections between the Pacific and the Amazon are strongest between October and March, when El Niño contributes to below-average precipitation during the wet season. A reduced build-up of soil moisture during the wet season, in turn, may limit water availability and transpiration in tropical forests during the following dry season, lowering surface humidity, drying fuels, and allowing fires to spread more easily through the understory. The delayed influence of soil moisture through this land - atmosphere coupling provides a means to predict fire season severity 3-6 months before the onset of the dry season. With the aim of creating new opportunities for forest conservation, we have developed an experimental seasonal fire forecasting system for the Amazon. The 2016 fire season severity forecast, released in June by UCI and NASA, predicts unusually high risk across eastern Peru, northern Bolivia, and Brazil. Several surface and satellite data streams confirm that El Niño teleconnections had a significant impact on wet season hydrology within the Amazon. Rainfall observations from the Global Precipitation Climatology Centre provided evidence that cumulative precipitation deficits during August-April were 1 to 2 standard deviations below the long-term mean for most of the basin. These observations were corroborated by strong negative terrestrial water storage anomalies measured by the Gravity Recovery and Climate Experiment, and by fluorescence and vegetation index observations from other sensors that indicated elevated canopy stress. By August 3rd, satellite observations showed above average fire activity in most, but not all, forecast regions. Using additional satellite observations that become available later this year, we plan to describe the full spatial and

Forest Type and Tree Characteristics Determine the Vertical Distribution of Epiphytic Lichen Biomass in Subtropical Forests

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Su Li

2017-11-01

Full Text Available Epiphytic lichens are an important component in subtropical forests and contribute greatly to forest biodiversity and biomass. However, information on epiphytic lichens still remains scarce in forest conservation owing to the difficulty of accessing all canopy layers for direct observation. Here, epiphytic lichens were quantified on 73 whole trees in five forest types in Southwest China to clarify the vertical stratification of their biomass in subtropical forests. Lichen biomass was significantly influenced by forest type and host attributes, varying from 187.11 to 8.55 g∙tree−1 among forest types and from 289.81 to <0.01 g∙tree−1 among tree species. The vertical stratification of lichen biomass was also determined by forest type, which peaked at the top in primary Lithocarpus forest and middle-aged oak secondary forest and in the middle upper heights in other forests. Overall, the proportion of lichen biomass accounted for 73.17–100.00% of total lichen biomass on branches and 0.00–26.83% on trunks in five forests, and 64.53–100.00% and 0.00–35.47% on eight host species. Seven functional groups showed marked and various responses to tree height between and among forest types. This information improves our understanding of the distribution of epiphytic lichens in forest ecosystems and the promotion of forest management in subtropical China.

Contributions of water supply from the weathered bedrock zone to forest soil quality

Science.gov (United States)

James H. Witty; Robert C. Graham; Kenneth R. Hubbert; James A. Doolittle; Jonathan A. Wald

2003-01-01

One measure of forest soil quality is the ability of the soil to support tree growth. In mediterranean-type ecosystems, such as most of California's forests, there is virtually no rainfall during the summer growing season, so trees must rely on water stored within the substrate. Water is the primary limitation to productivity in these forests. Many forest soils in...

Seasonal snow accumulation in the mid-latitude forested catchment

Czech Academy of Sciences Publication Activity Database

Šípek, Václav; Tesař, Miroslav

2014-01-01

Roč. 69, č. 11 (2014), s. 1562-1569 ISSN 0006-3088 R&D Projects: GA TA ČR TA02021451 Institutional support: RVO:67985874 Keywords : snow depth * snow water equivalent * forested catchment Subject RIV: DA - Hydrology ; Limnology Impact factor: 0.827, year: 2014

Processes governing yearly variations in carbon sequestration at a temperate deciduous forest

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Barr, J. G.; Fuentes, J. D.; Staebler, R.; Lee, X.

2001-12-01

Since 1995, processes governing the net ecosystem exchange (NEE) of carbon dioxide have been continuously investigated at the CFB Borden temperate mixed deciduous forest in Ontario, Canada. On a yearly basis, the rates of NEE for this forest range from 0.3 to 2.5 t C ha-1. For the 1996 to 1999 period, the forest sequestered the most carbon and had the greatest seasonal carbon dioxide flux in 1997. This seasonal flux is defined as the average daily rate of NEE over the course of the growing period and is the single most important factor governing yearly NEE. Such factors as soil temperature, timing of soil thawing, and respiratory processes exert only minor influences on the yearly variability in NEE. In this presentation, we will provide evidence to support the hypothesis that maximum Rubisco capacity per unit foliage element is one key control on the NEE variability. Additionally, changes in diffuse photosysnthetically active irradiance contribute to the variability observed in NEE. We will present results from both data analyses and outputs from a biospheric modeling system which was employed to investigate seasonal rates of NEE for the Borden forest.

Layout Guide for Burnt and Un-burnt Tropical Forest: The Diversity of Forest Plants and Insetcs for Sustainable Environmental

Science.gov (United States)

Watiniasih, N. L.; Tambunan, J.; Merdana, I. M.; Antara, I. N. G.

2018-04-01

Forest fire is a common phenomenon in tropical forest likes in Indonesia. Beside the effect of soaring heat and lack of rain during dry season due to the tropical climate, farming system is also reported as one reason of forest fire in Indonesia. People of surrounding areas and neighbouring countries are suffering from the effect of forest fire. Plants and animals are the most suffer from this occurrence that they cannot escape. This study aimed to investigate the effect of previously burnt and un-burnt tropical forest in Borneo Island on the plant and insect diversity of the tropical forest. The result of the study found that the plants in previously burnt forest area was dominated by one species, while higher and more stable plant diversity was found in un-burnt forest. Although the number of individual insects was higher in previously burnt tropical forest, but the insects was more diverse in un-burnt tropical forest. The alteration of environmental conditions in previously burnt and un-burnt forest indicate that the energy held in natural forest support higher number and more stable insects than previously burnt forest.

Dry-season retreat and dietary shift of the dart-poison frog Dendrobates tinctorius (Anura: Dendrobatidae)

NARCIS (Netherlands)

Born, M.; Bongers, F.; Poelman, E.H.; Sterck, F.J.

2010-01-01

Dry-season retreat and dietary shift of the dart-poison frog Delldrobates tillCtOrillS (Anura: Dendrobatidae). Seasonal rainfall affects tropical forest dynamics and behavior of species that are part of these ecosystems. TIle positive correlation between amphibian ac tivity pattems and rainfall has

Forest fires and air quality issues in southern Europe

Science.gov (United States)

Ana Isabel Miranda; Enrico Marchi; Marco Ferretti; Millán M. Millán

2009-01-01

Each summer forest fires in southern Europe emit large quantities of pollutants to the atmosphere. These fires can generate a number of air pollution episodes as measured by air quality monitoring networks. We analyzed the impact of forest fires on air quality of specific regions of southern Europe. Data from several summer seasons were studied with the aim of...

Characterization of biomass burning aerosols from forest fire in Indonesia

Science.gov (United States)

Fujii, Y.; Iriana, W.; Okumura, M.; Lestari, P.; Tohno, S.; Akira, M.; Okuda, T.

2012-12-01

Biomass burning (forest fire, wild fire) is a major source of pollutants, generating an estimate of 104 Tg per year of aerosol particles worldwide. These particles have adverse human health effects and can affect the radiation budget and climate directly and indirectly. Eighty percent of biomass burning aerosols are generated in the tropics and about thirty percent of them originate in the tropical regions of Asia (Andreae, 1991). Several recent studies have reported on the organic compositions of biomass burning aerosols in the tropical regions of South America and Africa, however, there is little data about forest fire aerosols in the tropical regions of Asia. It is important to characterize biomass burning aerosols in the tropical regions of Asia because the aerosol properties vary between fires depending on type and moisture of wood, combustion phase, wind conditions, and several other variables (Reid et al., 2005). We have characterized PM2.5 fractions of biomass burning aerosols emitted from forest fire in Indonesia. During the dry season in 2012, PM2.5 aerosols from several forest fires occurring in Riau, Sumatra, Indonesia were collected on quartz and teflon filters with two mini-volume samplers. Background aerosols in forest were sampled during transition period of rainy season to dry season (baseline period). Samples were analyzed with several analytical instruments. The carbonaceous content (organic and elemental carbon, OC and EC) of the aerosols was analyzed by a thermal optical reflectance technique using IMPROVE protocol. The metal, inorganic ion and organic components of the aerosols were analyzed by X-ray Fluorescence (XRF), ion chromatography and gas chromatography-mass spectrometry, respectively. There was a great difference of chemical composition between forest fire and non-forest fire samples. Smoke aerosols for forest fires events were composed of ~ 45 % OC and ~ 2.5 % EC. On the other hand, background aerosols for baseline periods were

Forest pathology in Hawaii

Science.gov (United States)

Gardner, D.E.

2003-01-01

Native Hawaiian forests are characterised by a high degree of endemism, including pathogens as well as their hosts. With the exceptions of koa (Acacia koa Gray), possibly maile (Alyxia oliviformis Gaud.), and, in the past, sandalwood (Santalum spp.), forest species are of little commercial value. On the other hand, these forests are immensely important from a cultural, ecological, and evolutionary standpoint. Forest disease research was lacking during the mid-twentieth century, but increased markedly with the recognition of ohia (Metrosideros polymorpha Gaud.) decline in the 1970s. Because many pathogens are themselves endemic, or are assumed to be, having evolved with their hosts, research emphasis in natural areas is on understanding host-parasite interactions and evolutionary influences, rather than disease control. Aside from management of native forests, attempts at establishing a commercial forest industry have included importation of several species of pine, Araucaria, and Eucalyptus as timber crops, and of numerous ornamentals. Diseases of these species have been introduced with their hosts. The attacking of native species by introduced pathogens is problematic - for example, Armillaria mellea (Vahl ex Fr.) Que??l. on koa and mamane (Sophora chrysophylla (Salisb.) Seem.). Much work remains to be done in both native and commercial aspects of Hawaiian forest pathology.

Plastic debris retention and exportation by a mangrove forest patch

International Nuclear Information System (INIS)

Ivar do Sul, Juliana A.; Costa, Monica F.; Silva-Cavalcanti, Jacqueline S.; Araújo, Maria Christina B.

2014-01-01

Highlights: • Estuaries and mangrove forests are rarely studied for marine plastic debris loads. • Types of plastic items and mangrove forest habitats determine the potential of debris retention. • Mangrove habitats are temporary sinks of plastic debris from river and marine origins. • Plastics rapidly accumulate in mangrove forest, but are exported slowly. • Fauna and fishers using mangrove forest habitats are at risk of interaction with plastic debris. -- Abstract: An experiment observed the behavior of selected tagged plastic items deliberately released in different habitats of a tropical mangrove forest in NE Brazil in late rainy (September) and late dry (March) seasons. Significant differences were not reported among seasons. However, marine debris retention varied among habitats, according to characteristics such as hydrodynamic (i.e., flow rates and volume transported) and relative vegetation (Rhizophora mangle) height and density. The highest grounds retained significantly more items when compared to the borders of the river and the tidal creek. Among the used tagged items, PET bottles were more observed and margarine tubs were less observed, being easily transported to adjacent habitats. Plastic bags were the items most retained near the releasing site. The balance between items retained and items lost was positive, demonstrating that mangrove forests tend to retain plastic marine debris for long periods (months-years)

Carabid beetle assemblages in three environments in the Araucaria humid forest of southern Brazil

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Rodrigo Milton Moraes

2013-03-01

Full Text Available Carabid beetle assemblages in three environments in the Araucaria humid forest of southern Brazil. Carabidae is composed mainly by ground-dwelling predator beetles. It is the fourth most diverse group within Coleoptera, but its diversity in the Neotropical region is understudied. Here we describe and analyze the diversity of carabid beetles in a region of subtropical rain forest dominated by Araucaria angustifolia with different landscapes. Three areas were chosen in an environmental integrity gradient: primary forests, secondary forests and old Pinus plantations. Pitfall traps were taken monthly, in a total of 14 samples per area. 1733 adult carabid beetles, belonging to 18 species, were sampled. There were differences in richness and abundance between the sampled areas. The total scores followed the same tendency: primary forests (14 species/747 individuals, secondary forests (13/631 and Pinus forests (10/355. An analysis of similarity shows differences in species composition, for both areas and seasons. Galerita lacordarei was the most abundant species for all samples and seasons. Carabid species show similar responses in accordance with habitat heterogeneity and disturbance. The abundance of Galerita lacordarei was influenced by temperature, for all sampled sites. Environmental changes affect the carabid assemblages and decrease diversity, possibly interfering in local dynamics. Seasonality patterns seem to indicate an increase in individual movement during summer, probably in search of resources. It is suggested that microhabitat patchiness is probably an important factor affecting carabid beetle diversity at small spatial scales.

Litter decomposing fungi in sal (Shorea robusta forests of central India

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RAM KEERTI VERMA

2011-11-01

Full Text Available Soni KK, Pyasi A, Verma RK. 2011. Litter decomposing fungi in sal (Shorea robusta forests of central India. Nusantara Bioscience 3: 136-144. The present study aim on isolation and identification of fungi associated with decomposition of litter of sal forest in central India. Season wise successional changes in litter mycoflora were determined for four main seasons of the year namely, March-May, June-August, September-November and December-February. Fungi like Aspergillus flavus, A. niger and Rhizopus stolonifer were associated with litter decomposition throughout the year, while Aspergillus fumigatus, Cladosporium cladosporioides, C. oxysporum, Curvularia indica, and C. lunata were recorded in three seasons. Some fungi including ectomycorrhiza forming occur only in the rainy season (June-August these are Astraeus hygrometricus, Boletus fallax, Calvatia elata, Colletotrichum dematium, Corticium rolfsii, Mycena roseus, Periconia minutissima, Russula emetica, Scleroderma bovista, S. geaster, S. verrucosum, Scopulariopsis alba and four sterile fungi. Fungi like Alternaria citri, Gleocladium virens, Helicosporium phragmitis and Pithomyces cortarum were rarely recorded only in one season.

Regeneration of monsoon rain forest in northern Australia: the sapling bank

Energy Technology Data Exchange (ETDEWEB)

Russell-Smith, J. [Conservation Commission of the Northern Territory, Palmerston, NT (Australia)

1996-12-01

As part of a wider study examining regeneration pathways in monsoon rain forest vegetation in northern Australia, a one-off, dry season census of saplings was undertaken along transects sampled at each of 33 relatively undisturbed sites broadly representative of the range of regional monsoon rain forest vegetation. Four floristic quadrat groups were derived through TWINSPAN classification. Subsequent analyses involved: (1) comparison of mean dry season stockings of juveniles occurring in different rain forest types, and their structural and environmental correlates; (2) comparison of the contributions of different life forms, and the influence of clonal reproduction in the sapling regeneration banks of different forest types; and (3) exploration of relationships between the distributions of saplings of common tree species with respect to seed bank, floristic, structural, and environmental variables. While data presented here require cautious interpretation given that processes of seedling/sapling recruitment and mortality are highly dynamic, sapling banks were found to be most dense on coarse-textured, moist soils, and least dense on coarse-textured, seasonally dry soils. Canopy cover and fire impact were shown to be highly influential on sapling distribution, especially for saplings of tree species and those growing on seasonally dry sites. Sapling densities were little influenced by proximity to rain forest margins, except for shrubs. The potential for clonal reproduction was significantly greater on dry sites, especially for trees. The majority of saplings sampled were derived from relatively few common, non-clonal, canopy tree species. Sapling distributions of 20 out of 23 common tree species were clumped in the vicinity of conspecific adults; for most species the strength of this relationship was greater than that for any other variable. 55 refs, 1 fig, 6 tabs

Consistency of Vegetation Index Seasonality Across the Amazon Rainforest

Science.gov (United States)

Maeda, Eduardo Eiji; Moura, Yhasmin Mendes; Wagner, Fabien; Hilker, Thomas; Lyapustin, Alexei I.; Wang, Yujie; Chave, Jerome; Mottus, Matti; Aragao, Luiz E.O.C.; Shimabukuro, Yosio

2016-01-01

Vegetation indices (VIs) calculated from remotely sensed reflectance are widely used tools for characterizing the extent and status of vegetated areas. Recently, however, their capability to monitor the Amazon forest phenology has been intensely scrutinized. In this study, we analyze the consistency of VIs seasonal patterns obtained from two MODIS products: the Collection 5 BRDF product (MCD43) and the Multi-Angle Implementation of Atmospheric Correction algorithm (MAIAC). The spatio-temporal patterns of the VIs were also compared with field measured leaf litterfall, gross ecosystem productivity and active microwave data. Our results show that significant seasonal patterns are observed in all VIs after the removal of view-illumination effects and cloud contamination. However, we demonstrate inconsistencies in the characteristics of seasonal patterns between different VIs and MODIS products. We demonstrate that differences in the original reflectance band values form a major source of discrepancy between MODIS VI products. The MAIAC atmospheric correction algorithm significantly reduces noise signals in the red and blue bands. Another important source of discrepancy is caused by differences in the availability of clear-sky data, as the MAIAC product allows increased availability of valid pixels in the equatorial Amazon. Finally, differences in VIs seasonal patterns were also caused by MODIS collection 5 calibration degradation. The correlation of remote sensing and field data also varied spatially, leading to different temporal offsets between VIs, active microwave and field measured data. We conclude that recent improvements in the MAIAC product have led to changes in the characteristics of spatio-temporal patterns of VIs seasonality across the Amazon forest, when compared to the MCD43 product. Nevertheless, despite improved quality and reduced uncertainties in the MAIAC product, a robust biophysical interpretation of VIs seasonality is still missing.

Consistency of vegetation index seasonality across the Amazon rainforest

Science.gov (United States)

Maeda, Eduardo Eiji; Moura, Yhasmin Mendes; Wagner, Fabien; Hilker, Thomas; Lyapustin, Alexei I.; Wang, Yujie; Chave, Jérôme; Mõttus, Matti; Aragão, Luiz E. O. C.; Shimabukuro, Yosio

2016-10-01

Vegetation indices (VIs) calculated from remotely sensed reflectance are widely used tools for characterizing the extent and status of vegetated areas. Recently, however, their capability to monitor the Amazon forest phenology has been intensely scrutinized. In this study, we analyze the consistency of VIs seasonal patterns obtained from two MODIS products: the Collection 5 BRDF product (MCD43) and the Multi-Angle Implementation of Atmospheric Correction algorithm (MAIAC). The spatio-temporal patterns of the VIs were also compared with field measured leaf litterfall, gross ecosystem productivity and active microwave data. Our results show that significant seasonal patterns are observed in all VIs after the removal of view-illumination effects and cloud contamination. However, we demonstrate inconsistencies in the characteristics of seasonal patterns between different VIs and MODIS products. We demonstrate that differences in the original reflectance band values form a major source of discrepancy between MODIS VI products. The MAIAC atmospheric correction algorithm significantly reduces noise signals in the red and blue bands. Another important source of discrepancy is caused by differences in the availability of clear-sky data, as the MAIAC product allows increased availability of valid pixels in the equatorial Amazon. Finally, differences in VIs seasonal patterns were also caused by MODIS collection 5 calibration degradation. The correlation of remote sensing and field data also varied spatially, leading to different temporal offsets between VIs, active microwave and field measured data. We conclude that recent improvements in the MAIAC product have led to changes in the characteristics of spatio-temporal patterns of VIs seasonality across the Amazon forest, when compared to the MCD43 product. Nevertheless, despite improved quality and reduced uncertainties in the MAIAC product, a robust biophysical interpretation of VIs seasonality is still missing.

Seasonal precipitation patterns along pathways of South American low-level jets and aerial rivers

Science.gov (United States)

Poveda, Germán.; Jaramillo, Liliana; Vallejo, Luisa F.

2014-01-01

We study the seasonal dynamics of the eastern Pacific (CHOCO) and Caribbean low-level jets (LLJ), and aerial rivers (AR) acting on tropical and subtropical South America. Using the ERA-Interim reanalysis (1979-2012), we show that the convergence of both LLJs over the eastern Pacific-western Colombia contributes to the explanation of the region's world-record rainfall. Diverse variables involved in the transport and storage of moisture permit the identification of an AR over northern South America involving a midtropospheric easterly jet that connects the Atlantic and Pacific Oceans across the Andes, with stronger activity in April to August. Other major seasonal AR pathways constitute part of a large gyre originating over the tropical North Atlantic, veering to the southeast over the eastern Andes and reaching regions of northern Argentina and southeastern Brazil. We illustrate the distribution of average seasonal precipitation along the LLJs and AR pathways with data from the Tropical Rainfall Measuring Mission (1998-2011), combined with considerations of CAPE, topography, and land cover. In addition, the theory of the biotic pump of atmospheric moisture (BiPAM) is tested at seasonal time scales, and found to hold in 8 out of 12 ARs, and 22 out of 32 forest-covered tracks (64% in distance) along the ARs. Deviations from BiPAM's predictions of rainfall distribution are explained by the effects of topography, orography, and land cover types different from forests. Our results lend a strong observational support to the BiPAM theory at seasonal time scales over South American forested flat lands.

Climatic potential for tourism in the Black Forest, Germany — winter season

Science.gov (United States)

Endler, Christina; Matzarakis, Andreas

2011-05-01

Climate change, whether natural or human-caused, will have an impact on human life, including recreation and tourism among other things. In this study, methods from biometeorology and tourism climatology are used to assess the effect of a changed climate on tourism and recreation in particular. The study area is the Black Forest mountainous region of south-west Germany, which is well known for its tourist and recreational assets. Climate model projections for the 2021-2050 period based on REMO-UBA simulations with a high spatial resolution of 10 km are compared to a 30-year reference period (1971-2000) using the IPCC emission scenarios A1B and B1. The results show that the mean winter air temperature will increase by up to 1.8°C, which is the most pronounced warming compared to the other seasons. The annual precipitation amount will increase marginally by 5% in the A1B scenario and 10% in the B1 scenario. Winter precipitation contributes about 10% (A1B) and 30% (B1) to variations in annual precipitation. Although the results show that winter precipitation will increase slightly, snow days affecting skiing will be reduced on average by approximately 40% due to regional warming. Cold stress will be reduced on average by up to 25%. The result is that the thermal environment will be advanced, and warmer winters are likely to lead to an upward altitudinal shift of ski resorts and winter sport activities, thus displacing land-use currently dedicated to nature conservation.

Effects of reforestation on ammonia-oxidizing microbial community composition and abundance in subtropical acidic forest soils.

Science.gov (United States)

Wu, Ruo-Nan; Meng, Han; Wang, Yong-Feng; Gu, Ji-Dong

2018-06-01

Forest ecosystems have great ecological values in mitigation of climate change and protection of biodiversity of flora and fauna; re-forestry is commonly used to enhance the sequestration of atmospheric CO 2 into forest storage biomass. Therefore, seasonal and spatial dynamics of the major microbial players in nitrification, ammonia-oxidizing archaea (AOA) and bacteria (AOB), in acidic soils of young and matured revegetated forests were investigated to elucidate the changes of microbial communities during forest restoration, and compared to delineate the patterns of community shifts under the influences of environmental factors. AOA were more abundant than AOB in both young and matured revegetated forest soils in both summer and winter seasons. In summer, however, the abundance of amoA-AOA decreased remarkably (p < 0.01), ranging from 1.90 (± 0.07) × 10 8 copies per gram dry soil in matured forest to 5.04 (± 0.43) × 10 8 copies per gram dry soil in young forest, and amoA-AOB was below detection limits to obtain any meaningful values. Moreover, exchangeable Al 3+ and organic matter were found to regulate the physiologically functional nitrifiers, especially AOA abundance in acidic forest soils. AOB community in winter showed stronger correlation with the restoration status of revegetated forests and AOA community dominated by Nitrosotalea devanaterra, in contrast, was more sensitive to the seasonal and spatial variations of environmental factors. These results enrich the current knowledge of nitrification during re-forestry and provide valuable information to developmental status of revegetated forests for management through microbial analysis.

Man biting rate seasonal variation of malaria vectors in Roraima, Brazil

Directory of Open Access Journals (Sweden)

Fábio Saito Monteiro de Barros

2007-06-01

Full Text Available Malaria control has been directed towards regional actions where more detailed knowledge of local determinants of transmission is of primary importance. This is a short report on range distribution and biting indices for Anopheles darlingi and An. albitarsis during the dry and rainy season that follows river level variation in a savanna/alluvial forest malaria system area in the Northern Amazon Basin. Distribution range and adult biting indices were at their highest during the rainy season for both An. darlingi and An. albitarsis. During the rainy season the neighboring alluvial forest was extensively flooded. This coincided with highest rates in malaria transmission with case clustering near the river. As the river receded, anopheline distribution range and density decreased. This decrease in distribution and density corresponded to a malaria decrease in the near area. An exponential regression function was derived to permit estimations of An. darlingi distribution over specified distances. Anopheline spatio-temporal variations lead to uneven malaria case distribution and are of important implications for control strategies.

Relating ring width of Mediterranean evergreen species to seasonal and annual variations of precipitation and temperature

NARCIS (Netherlands)

Nijland, W.; Jansma, E.; Addink, E.A.; Domínguez Delmás, M.; Jong, S.M. de

2011-01-01

Plant growth in Mediterranean landscapes is limited by the typical summer-dry climate. Forests in these areas are only marginally productive and may be quite susceptible to modern climate change. To improve our understanding of forest sensitivity to annual and seasonal climatic variability, we

Photoprotection related to xanthophyll cycle pigments in epiphytic orchids acclimated at different light microenvironments in two tropical dry forests of the Yucatan Peninsula, Mexico.

Science.gov (United States)

de la Rosa-Manzano, Edilia; Andrade, José Luis; García-Mendoza, Ernesto; Zotz, Gerhard; Reyes-García, Casandra

2015-12-01

Epiphytic orchids from dry forests of Yucatán show considerable photoprotective plasticity during the dry season, which depends on leaf morphology and host tree deciduousness. Nocturnal retention of antheraxanthin and zeaxanthin was detected for the first time in epiphytic orchids. In tropical dry forests, epiphytes experience dramatic changes in light intensity: photosynthetic photon flux density may be up to an order of magnitude higher in the dry season compared to the wet season. To address the seasonal changes of xanthophyll cycle (XC) pigments and photosynthesis that occur throughout the year, leaves of five epiphytic orchid species were studied during the early dry, dry and wet seasons in a deciduous and a semi-deciduous tropical forests at two vertical strata on the host trees (3.5 and 1.5 m height). Differences in XC pigment concentrations and photosynthesis (maximum quantum efficiency of photosystem II; F v/F m) were larger among seasons than between vertical strata in both forests. Antheraxanthin and zeaxanthin retention reflected the stressful conditions of the epiphytic microhabitat, and it is described here in epiphytes for the first time. During the dry season, both XC pigment concentrations and photosystem II heat dissipation of absorbed energy increased in orchids in the deciduous forest, while F v/F m and nocturnal acidification (ΔH(+)) decreased, clearly as a response to excessive light and drought. Concentrations of XC pigments were higher than those in orchids with similar leaf shape in semi-deciduous forest. There, only Encyclia nematocaulon and Lophiaris oerstedii showed somewhat reduced F v/F m. No changes in ΔH(+) and F v/F m were detected in Cohniella ascendens throughout the year. This species, which commonly grows in forests with less open canopies, showed leaf tilting that diminished light interception. Light conditions in the uppermost parts of the canopy probably limit the distribution of epiphytic orchids and the retention of

Ground Monitoring Neotropical Dry Forests: A Sensor Network for Forest and Microclimate Dynamics in Semi-Arid Environments (Enviro-Net°)

Science.gov (United States)

Rankine, C. J.; Sánchez-Azofeifa, G.

2011-12-01

In the face of unprecedented global change driven by anthropogenic pressure on natural systems it has become imperative to monitor and better understand potential shifts in ecosystem functioning and services from local to global scales. The utilization of automated sensors technologies offers numerous advantages over traditional on-site ecosystem surveying techniques and, as a result, sensor networks are becoming a powerful tool in environmental monitoring programs. Tropical forests, renowned for their biodiversity, are important regulators of land-atmosphere fluxes yet the seasonally dry tropical forests, which account for 40% of forested ecosystems in the American tropics, have been severely degraded over the past several decades and not much is known of their capacity to recover. With less than 1% of these forests protected, our ability to monitor the dynamics and quantify changes in the remaining primary and recovering secondary tropical dry forests is vital to understanding mechanisms of ecosystem stress responses and climate feedback with respect to annual productivity and desertification processes in the tropics. The remote sensing component of the Tropi-Dry: Human and Biophysical Dimensions of Tropical Dry Forests in the Americas research network supports a network of long-term tropical ecosystem monitoring platforms which focus on the dynamics of seasonally dry tropical forests in the Americas. With over 25 sensor station deployments operating across a latitudinal gradient in Mexico, Costa Rica, Brazil, and Argentina continuously collecting hyper-temporal sensory input based on standardized deployment parameters, this monitoring system is unique among tropical environments. Technologies used in the network include optical canopy phenology towers, understory wireless sensing networks, above and below ground microclimate stations, and digital cameras. Sensory data streams are uploaded to a cyber-infrastructure initiative, denominated Enviro-Net°, for data

Tracing the Sources of Atmospheric Phosphorus Deposition to a Tropical Rain Forest in Panama Using Stable Oxygen Isotopes.

Science.gov (United States)

Gross, A; Turner, B L; Goren, T; Berry, A; Angert, A

2016-02-02

Atmospheric dust deposition can be a significant source of phosphorus (P) in some tropical forests, so information on the origins and solubility of atmospheric P is needed to understand and predict patterns of forest productivity under future climate scenarios. We characterized atmospheric dust P across a seasonal cycle in a tropical lowland rain forest on Barro Colorado Nature Monument (BCNM), Republic of Panama. We traced P sources by combining remote sensing imagery with the first measurements of stable oxygen isotopes in soluble inorganic phosphate (δ(18)OP) in dust. In addition, we measured soluble inorganic and organic P concentrations in fine (1 μm) aerosol fractions and used this data to estimate the contribution of P inputs from dust deposition to the forest P budget. Aerosol dry mass was greater in the dry season (December to April, 5.6-15.7 μg m(-3)) than the wet season (May to November, 3.1-7.1 μg m(-3)). In contrast, soluble P concentrations in the aerosols were lower in the dry season (980-1880 μg P g(-1)) than the wet season (1170-3380 μg P g(-1)). The δ(18)OP of dry-season aerosols resembled that of nearby forest soils (∼19.5‰), suggesting a local origin. In the wet season, when the Trans-Atlantic Saharan dust belt moves north close to Panama, the δ(18)OP of aerosols was considerably lower (∼15.5‰), suggesting a significant contribution of long-distance dust P transport. Using satellite retrieved aerosol optical depth (AOD) and the P concentrations in aerosols we sampled in periods when Saharan dust was evident we estimate that the monthly P input from long distance dust transport during the period with highest Saharan dust deposition is 88 ± 31 g P ha(-1) month(-1), equivalent to between 10 and 29% of the P in monthly litter fall in nearby forests. These findings have important implications for our understanding of modern nutrient budgets and the productivity of tropical forests in the region under future climate scenarios.

[On the seasonality of dermatoses: a retrospective analysis of search engine query data depending on the season].

Science.gov (United States)

Köhler, M J; Springer, S; Kaatz, M

2014-09-01

The volume of search engine queries about disease-relevant items reflects public interest and correlates with disease prevalence as proven by the example of flu (influenza). Other influences include media attention or holidays. The present work investigates if the seasonality of prevalence or symptom severity of dermatoses correlates with search engine query data. The relative weekly volume of dermatological relevant search terms was assessed by the online tool Google Trends for the years 2009-2013. For each item, the degree of seasonality was calculated via frequency analysis and a geometric approach. Many dermatoses show a marked seasonality, reflected by search engine query volumes. Unexpected seasonal variations of these queries suggest a previously unknown variability of the respective disease prevalence. Furthermore, using the example of allergic rhinitis, a close correlation of search engine query data with actual pollen count can be demonstrated. In many cases, search engine query data are appropriate to estimate seasonal variability in prevalence of common dermatoses. This finding may be useful for real-time analysis and formation of hypotheses concerning pathogenetic or symptom aggravating mechanisms and may thus contribute to improvement of diagnostics and prevention of skin diseases.

Seasonal Variation of Cistus ladanifer L. Diterpenes

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Juan Carlos Alías

2012-07-01

Full Text Available The exudate of Cistus ladanifer L. consists mainly of two families of secondary metabolites: flavonoids and diterpenes. The amount of flavonoids present in the leaves has a marked seasonal variation, being maximum in summer and minimum in winter. In the present study, we demonstrate that the amount of diterpenes varies seasonally, but with a different pattern: maximum concentration in winter and minimum in spring-summer. The experiments under controlled conditions have shown that temperature influences diterpene production, and in particular, low temperatures. Given this pattern, the functions that these compounds perform in C. ladanifer are probably different.

Nematode communities of natural and managed beech forests - a pilot study

DEFF Research Database (Denmark)

Strandmark, Lisa Bjørnlund; Madsen, Mette Vestergård; Johansson, Sanne

2002-01-01

forests is discussed. We suggest dead wood input to be the driving variable leading to the observed differences in the nematode community between managed and natural forests of Zealand, Denmark. The marked site differences found in this study emphasizes the need to carefully choose reference areas where...

Tropical montane forest conversion affects spatial and temporal nitrogen dynamics in Kenyan headwater catchment

Science.gov (United States)

Jacobs, Suzanne; Weeser, Björn; Breuer, Lutz; Butterbach-Bahl, Klaus; Guzha, Alphonce; Rufino, Mariana

2017-04-01

Deforestation and land use change (LUC) are often stated as major contributors to changes in water quality, although other catchment characteristics such as topography, geology and climate can also play a role. Understanding how stream water chemistry is affected by LUC is essential for sustainable water management and land use planning. However, there is often a lack of reliable data, especially in less studied regions such as East Africa. This study focuses on three sub-catchments (27-36 km2) with different land use types (natural forest, smallholder agriculture and tea/tree plantations) nested in a 1023 km2 headwater catchment in the Mau Forest Complex, Kenya's largest closed-canopy indigenous tropical montane forest. In the past decades approx. 25% of the natural forest was lost due to land use change. We studied seasonal, diurnal and spatial patterns of total dissolved nitrogen (TDN), nitrate (NO3-N) and dissolved organic nitrogen (DON) using a combination of high-resolution in-situ measurements, bi-weekly stream water samples and spatial sampling campaigns. Multiple linear regression analysis of the spatial data indicates that land use shows a strong influence on TDN and nitrate, while DON is more influenced by precipitation. Highest TDN and nitrate concentrations are found in tea plantations, followed by smallholder agriculture and natural forest. This ranking does not change throughout the year, though concentrations of TDN and nitrate are respectively 27.6 and 25.4% lower in all catchments during the dry season. Maximum Overlap Discrete Wavelet Transform (MODWT) analysis of the high resolution nitrate data revealed a seasonal effect on diurnal patterns in the natural forest catchment, where the daily peak shifts from early morning in the wet season to mid-afternoon in the dry season. The smallholder and tea catchment do not exhibit clear diurnal patterns. The results suggest that land use affects dissolved nitrogen concentrations, leading to higher N

Fluxes of energy, H2O, and CO2 between the atmosphere and the monsoon tropical forest in Southern Vietnam.

Science.gov (United States)

Kurbatova, Yu A; Kuricheva, O A; Avilov, V K; Dinh, Ba Duy; Kuznetsov, A N

2015-01-01

The 2.5-year dynamics of heat, water and carbon dioxide fluxes in the tropical monsoon semi-evergreen forest in Southern Vietnam obtained by means of continuous eddy covariance observations using standard procedures of FLUXNET global network are analyzed. The features of wet seasons during the measurement period were close to long-term average ones, but dry seasons had a great heterogeneity. The maximal duration of the period with little precipitation was 4 months. The annual radiation balance in the south of Vietnam exceeded the balance at all stations of FLUXNET in tropical forests, except one. Annual evapotranspiration in monsoon forest of south of Vietnam is approximately equal to the evaporation of the rain forests of Central Amazonia. During the wet season evapotranspiration spent 80% of the radiation balance, and in the driest months this value decreased to 50%. In the dry season reduction of evapotranspiration and gross primary production was relatively small due to photosynthesizing trees of 2-4 canopy sub-layers. For the first time a large net sink of carbon dioxide from the atmosphere in the monsoon forest ecosystem was identified.

CO2 and water vapor exchange of a larch forest in northern Japan

International Nuclear Information System (INIS)

Hirano, Takashi; Hirata, Ryuichi; Harazono, Yoshinobu

2003-01-01

In the northern part of East Asia, forests dominated by larch are extensively distributed and probably play an important role in the global carbon cycle. However, a knowledge of the CO 2 balance of larch forests based on long-term flux measurements is very restricted in East Asia. Thus, a long-term flux measurement has been started in 2000 at a larch plantation on a flat terrain in Hokkaido, Japan to obtain more information on the CO 2 and energy balances of larch forests. From September 2000 to August 2001 the net ecosystem CO 2 exchange (NEE) changed seasonally in accordance with the annual cycles of phenology and climate. NEE was negative for six months of the growing season, May-September; the larch ecosystem was a carbon sink with a peak intensity of -0.38 mol m 2 d1 for this period. In the leafless season from November to April the forest ecosystem was a carbon source with an intensity ranging between 0 and 0.05 mol/m 2 /d. Annual NEE from September 2000 to August 2001 was 24.4 to 32.4 mol m 2 /yr (= 293 to 389 gC/m 2 /yr); this value is compatible with those reported from other temperate forests. Annual evapotranspiration for the same period was 367 mm, which was only 29% of annual precipitation

The behavior of 137Cs in the soil-forest plants system

International Nuclear Information System (INIS)

Spiridonov, S.; Fesenko, S.; Avila, R.

1999-01-01

A model has been developed which simulates the behavior of 137 Cs in forest litter and soil, as well as seasonal and long-term dynamics of 137 CS content in forest plants. The long-term cycles of 137 CS migration are described as an integrated result of multiple annual cycles. The model results demonstrate a satisfactory coincidence with the experimental data. A set of model parameters is provided for each of four different types of forest (coniferous and deciduous forest; automorphic and semi-hydromorphic landscapes). The model allows an evaluation of the effects of countermeasures implemented in the contaminated forest. Refs. 1 (author)

Vegetation composition and soil nutrients status from polyculture to ...

African Journals Online (AJOL)

The findings revealed that the change in micro-environmental conditions as influenced by attitude and seasonality has marked effect on status and release of nutrients in the soil of representative forest stands at markedly difference. The ambient and soil temperature was sharply greater at high altitude (Upper Shillong) and ...

Floristic composition of the dry tropical forest in biological reserve (sanctuary "Los Besotes" and phenology of the dominant arboreal species (Valledupar, Cesar, Colombia

Directory of Open Access Journals (Sweden)

Mary Lee Berdugo Lattke

2015-01-01

Full Text Available Based on the floristic composition and structural aspects, the formation tropical dry forest of the reserve "Los Besotes" (Valledupar, Cesar; 248 y 1046m of altitude was characterized. In 35 individuals from nine dominant tree species in two forest types, the phenological characteristics were assessed. Seven monitoring were performed along one year according to the scheme of distribution of rainfall. The leaf fall in the forests of Myrcianthes aff. fragrans and Brosimum alicastrum did not exceed 20% regardless of the climatic period (drought or rainy seasons. In others dominant understory species the leaf fall was less than 40%, thus species of the canopy are classified as evergreen while those of the understory as semideciduous. Blooming peaked during the dry season while fruit production peaked during the two rainy seasons. In the forest ofBursera simaruba and Pterocarpus acapulcensis the leaf fall exceeded 60% in the dry season, while in the rainy season was only 30%. The leaf fall increased to 60% in others dominant understory species. Both canopy as well as understory species are deciduous. Blooming was observed during the dry season (December to March, and July, but it is also likely to occur in October; fruit production was observed at the end of the rainy season. In the tropical dry forest formation evergreen plant communities with low values of leaf fall (40% and deciduous communities with values greater than 60% are recognized.

Forest fires in 2017: a useful lesson

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Battipaglia G

2017-08-01

Full Text Available Forest fires in 2017: a useful lesson. Forest fires, together with the decline of silviculture practice, are one of the most important natural disturbances affecting Mediterranean forests. The year 2017 is shaping up to be a record breaking fire season all around Southern Europe and especially in Italy for the sheer amount of hectares burned. Here we discuss about the importance of forest fire management, highlighting the role of prescribed burning and mechanical treatment (e.g., manual removal, thinning in reducing the risk of high-intensity wildfires. We report on the successful applications of those fire management techniques on the pinewoods of Vesuvio National Park and Castel Fusano Natural Reserve. The information compiled in the present article aims to demonstrate the potential relevance and impact of forest resources management for fire hazard reduction and shows the necessity of strong interaction among not only the scientific community, but also forest managers, decision makers and the civic responsibility of society at large.

Seasonal organic pig production with a local breed

DEFF Research Database (Denmark)

Kongsted, Anne Grete; Claudi-Magnussen, C.; Horsted, Klaus

2009-01-01

It is important that organic pork differs markedly from conventional pork regarding taste, appearance and production methods in order to overcome the heavy price competition. That is the hypothesis behind thecurrent project. A seasonal outdoor rearing system based on a traditional and local breed...... to the modern genotype and thefat of the Black-Spotted pig was characterised as having a special nutty taste. In conclusion, preliminaryresults indicate that the local breed differs markedly with respect to several meat quality aspects comparedto the modern breed but also shows clear disadvantages regarding...

Spatial distribution and interspecific associations of tree species in a tropical seasonal rain forest of China.

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Guoyu Lan

Full Text Available Studying the spatial pattern and interspecific associations of plant species may provide valuable insights into processes and mechanisms that maintain species coexistence. Point pattern analysis was used to analyze the spatial distribution patterns of twenty dominant tree species, their interspecific spatial associations and changes across life stages in a 20-ha permanent plot of seasonal tropical rainforest in Xishuangbanna, China, to test mechanisms maintaining species coexistence. Torus-translation tests were used to quantify positive or negative associations of the species to topographic habitats. The results showed: (1 fourteen of the twenty tree species were negatively (or positively associated with one or two of the topographic variables, which evidences that the niche contributes to the spatial pattern of these species. (2 Most saplings of the study species showed a significantly clumped distribution at small scales (0-10 m which was lost at larger scales (10-30 m. (3 The degree of spatial clumping deceases from saplings, to poles, to adults indicates that density-dependent mortality of the offspring is ubiquitous in species. (4 It is notable that a high number of positive small-scale interactions were found among the twenty species. For saplings, 42.6% of all combinations of species pairs showed positive associations at neighborhood scales up to five meters, but only 38.4% were negative. For poles and adults, positive associations at these distances still made up 45.5% and 29.5%, respectively. In conclusion, there is considerable evidence for the presence of positive interactions among the tree species, which suggests that species herd protection may occur in our plot. In addition, niche assembly and limited dispersal (likely contribute to the spatial patterns of tree species in the tropical seasonal rain forest in Xishuangbanna, China.

Parameterization of Leaf-Level Gas Exchange for Plant Functional Groups From Amazonian Seasonal Tropical Rain Forest

Science.gov (United States)

Domingues, T. F.; Berry, J. A.; Ometto, J. P.; Martinelli, L. A.; Ehleringer, J. R.

2004-12-01

Plant communities exert strong influence over the magnitude of carbon and water cycling through ecosystems by controlling photosynthetic gas exchange and respiratory processes. Leaf-level gas exchange fluxes result from a combination of physiological properties, such as carboxylation capacity, respiration rates and hydraulic conductivity, interacting with environmental drivers such as water and light availability, leaf-to-air vapor pressure deficit, and temperature. Carbon balance models concerned with ecosystem-scale responses have as a common feature the description of eco-physiological properties of vegetation. Here we focus on the parameterization of ecophysiological gas-exchange properties of plant functional groups from a pristine Amazonian seasonally dry tropical rain forest ecosystem (FLONA-Tapajós, Santarém, PA, Brazil). The parameters were specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, photosynthetic carboxylation capacity, dark respiration rates, and stomatal conductance to water vapor. Our plant functional groupings were lianas at the top of the canopy, trees at the top of the canopy, mid-canopy trees and undestory trees. Within the functional groups, we found no evidence that leaves acclimated to seasonal changes in precipitation. However, there were life-form dependent distinctions when a combination of parameters was included. Top-canopy lianas were statistically different from top-canopy trees for leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and stomatal conductance to water vapor, suggesting that lianas are more conservative in the use of water, causing a stomatal limitation on photosynthetic assimilation. Top-canopy, mid canopy and understory groupings were distinct for specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and photosynthetic carboxylation capacity. The recognition that plant

Chaco Chachalaca (Ortalis canicollis, Wagler, 1830 feeding ecology in a gallery forest in the South Pantanal (Brazil

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J. Ragusa-Netto

Full Text Available Cracids are generalist frugivores, which often exploit plant food resources such as flowers and leaves, mainly when fruit production declines. The Chaco chachalaca (Ortalis canicollis is the most abundant cracid in the Pantanal (Brazil, and particularly common in the gallery forests. However, the factors related to their occurrence in this habitat type are unclear. In this study I describe the feeding habits and feeding niche breadth fluctuations of the Chaco chachalaca in relation to food resources abundance and diversity at the Miranda river gallery forest (Southern Pantanal. I also analyzed the relationships between Chaco chachalacas feeding activity and food resources abundance. This parameter (flowers and fruits exhibited significant seasonal differences of abundance in which flowers were plentiful at the end of the dry, while fruits were abundant during the early wet season. However, food resources diversity to Chaco chachalacas exhibited no seasonal difference. Their feeding activity paralleled the availability of food resources, so that when some items were massively available an enhanced number of Chaco chachalacas foraged in the gallery forest, particularly during the prolonged dry season when they extensively used flowers and Genipa americana fruits. In fact, the Chaco chachalaca feeding niche breadth value presented low values in this period, while high values were common in the rest of the year. The flexible diet of this cracid, potentially favors their year round presence in the gallery forest, mainly during the prolonged dry season when the propensity for famine might be high. Since the Chaco chachalaca is among the largest and most abundant canopy frugivores in the gallery forest, it may contribute to forest regeneration, an underscored role due to the impact of annual floods and meandering dynamics on tree loss.

Abundance and frugivory of the toco toucan (Ramphastos toco in a gallery forest in Brazil's Southern Pantanal

Directory of Open Access Journals (Sweden)

J. Ragusa-Netto

Full Text Available Unlike other toucan species, the Toco toucan (Ramphastos toco - the largest Ramphastidae - usually inhabits dry semi-open areas. This conspicuous canopy frugivore uses a large home range that includes a variety of vegetation types, among which gallery forests are widely cited as important to this species. However, the factors relating to the occurrence of Toco toucans in such habitats are unclear. I studied the abundance of Toco toucans as well as the availability of fleshy fruit in a gallery forest in the southern Pantanal (sub-region of Miranda, Brazil, in order to assess the relationship between these parameters. Also, I examined toucan foraging activity to analyze its relationship with both toucan abundance and fruit availability. The presence of the Toco toucan was more common in the gallery forest from the middle to the end of the dry season and during the middle of the wet season. Toucans foraged for fleshy fruits, mainly Genipa americana, Ficus luschnatiana, and Cecropia pachystachya fruits, feeding mostly on G. americana (by far the favorite food resource and F. luschnatiana fruits during the dry season, while C. pachystachya fruits were important in the wet season. Toco toucans foraged particularly heavily (> 80% of foraging activity on G. americana fruits during the latter part of the dry season, when fleshy fruit availability declined sharply. Toco toucan abundance in the gallery forest was associated with the availability of the most commonly consumed fleshy fruits, and also with its foraging activity. This finding suggests that the Toco toucan moved to the gallery forest periodically in response to the availability of abundant food resources, especially the G. americana fruits widely available and exploited during the severely dry season. Therefore, these fruits potentially contribute to Toco toucan persistence in the South Pantanal during the harshest period of the year.

Abundance and frugivory of the Toco toucan (Ramphastos toco) in a gallery forest in Brazil's southern Pantanal.

Science.gov (United States)

Ragusa-Netto, J

2006-02-01

Unlike other toucan species, the Toco toucan (Ramphastos toco)--the largest Ramphastidae--usually inhabits dry semi-open areas. This conspicuous canopy frugivore uses a large home range that includes a variety of vegetation types, among which gallery forests are widely cited as important to this species. However, the factors relating to the occurrence of Toco toucans in such habitats are unclear. I studied the abundance of Toco toucans as well as the availability of fleshy fruit in a gallery forest in the southern Pantanal (sub-region of Miranda, Brazil), in order to assess the relationship between these parameters. Also, I examined toucan foraging activity to analyze its relationship with both toucan abundance and fruit availability. The presence of the Toco toucan was more common in the gallery forest from the middle to the end of the dry season and during the middle of the wet season. Toucans foraged for fleshy fruits, mainly Genipa americana, Ficus luschnatiana, and Cecropia pachystachya fruits, feeding mostly on G. americana (by far the favorite food resource) and F. luschnatiana fruits during the dry season, while C. pachystachya fruits were important in the wet season. Toco toucans foraged particularly heavily (> 80% of foraging activity) on G. americana fruits during the latter part of the dry season, when fleshy fruit availability declined sharply. Toco toucan abundance in the gallery forest was associated with the availability of the most commonly consumed fleshy fruits, and also with its foraging activity. This finding suggests that the Toco toucan moved to the gallery forest periodically in response to the availability of abundant food resources, especially the G. americana fruits widely available and exploited during the severely dry season. Therefore, these fruits potentially contribute to Toco toucan persistence in the South Pantanal during the harshest period of the year.