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Sample records for arctic vegetation types

  1. Radiation budget and soil heat fluxes in different Arctic tundra vegetation types

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Iturrate Garcia, Maitane; Gastellu-Etchegorry, Jean-Philippe; Schaepman, Michael E.; Schaepman-Strub, Gabriela

    2016-04-01

    While solar radiation is one of the primary energy sources for warming and thawing permafrost soil, the amount of shortwave radiation reaching the soil is reduced by vegetation shading. Climate change has led to greening, shrub expansion and encroachment in many Arctic tundra regions and further changes are anticipated. These vegetation changes feed back to the atmosphere and permafrost as they modify the surface energy budget. However, canopy transmittance of solar radiation has rarely been measured or modelled for a variety of tundra vegetation types. We assessed the radiation budget of the most common vegetation types at the Kytalyk field site in North-East Siberia (70.8°N, 147.5°E) with field measurements and 3D radiative transfer modelling and linked it to soil heat fluxes. Our results show that Arctic tundra vegetation types differ in canopy albedo and transmittance as well as in soil heat flux and active layer thickness. Tussock sedges transmitted on average 56% of the incoming light and dwarf shrubs 27%. For wet sedges we found that the litter layer was very important as it reduced the average transmittance to only 6%. Model output indicated that both, albedo and transmittance, also depend on the spatial aggregation of vegetation types. We found that permafrost thaw was more strongly related to soil properties than to canopy shading. The presented radiative transfer model allows quantifying effects of the vegetation layer on the surface radiation budget in permafrost areas. The parametrised model can account for diverse vegetation types and variation of properties within types. Our results highlight small scale radiation budget and permafrost thaw variability which are indicated and partly caused by vegetation. As changes in species composition and biomass increase can influence thaw rates, small scale patterns should be considered in assessments of climate-vegetation-permafrost feedbacks.

  2. The Circumpolar Arctic vegetation map

    USGS Publications Warehouse

    Walker, Donald A.; Raynolds, Martha K.; Daniels, F.J.A.; Einarsson, E.; Elvebakk, A.; Gould, W.A.; Katenin, A.E.; Kholod, S.S.; Markon, C.J.; Melnikov, E.S.; Moskalenko, N.G.; Talbot, S. S.; Yurtsev, B.A.; Bliss, L.C.; Edlund, S.A.; Zoltai, S.C.; Wilhelm, M.; Bay, C.; Gudjonsson, G.; Ananjeva, G.V.; Drozdov, D.S.; Konchenko, L.A.; Korostelev, Y.V.; Ponomareva, O.E.; Matveyeva, N.V.; Safranova, I.N.; Shelkunova, R.; Polezhaev, A.N.; Johansen, B.E.; Maier, H.A.; Murray, D.F.; Fleming, Michael D.; Trahan, N.G.; Charron, T.M.; Lauritzen, S.M.; Vairin, B.A.

    2005-01-01

    Question: What are the major vegetation units in the Arctic, what is their composition, and how are they distributed among major bioclimate subzones and countries? Location: The Arctic tundra region, north of the tree line. Methods: A photo-interpretive approach was used to delineate the vegetation onto an Advanced Very High Resolution Radiometer (AVHRR) base image. Mapping experts within nine Arctic regions prepared draft maps using geographic information technology (ArcInfo) of their portion of the Arctic, and these were later synthesized to make the final map. Area analysis of the map was done according to bioclimate subzones, and country. The integrated mapping procedures resulted in other maps of vegetation, topography, soils, landscapes, lake cover, substrate pH, and above-ground biomass. Results: The final map was published at 1:7 500 000 scale map. Within the Arctic (total area = 7.11 x 106 km 2), about 5.05 ?? 106 km2 is vegetated. The remainder is ice covered. The map legend generally portrays the zonal vegetation within each map polygon. About 26% of the vegetated area is erect shrublands, 18% peaty graminoid tundras, 13% mountain complexes, 12% barrens, 11% mineral graminoid tundras, 11% prostrate-shrub tundras, and 7% wetlands. Canada has by far the most terrain in the High Arctic mostly associated with abundant barren types and prostrate dwarf-shrub tundra, whereas Russia has the largest area in the Low Arctic, predominantly low-shrub tundra. Conclusions: The CAVM is the first vegetation map of an entire global biome at a comparable resolution. The consistent treatment of the vegetation across the circumpolar Arctic, abundant ancillary material, and digital database should promote the application to numerous land-use, and climate-change applications and will make updating the map relatively easy. ?? IAVS; Opulus Press.

  3. The impact of vegetation type on the shortwave radiation balance of the Arctic tundra

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Schaepman-Strub, Gabriela

    2015-04-01

    Profound changes in vegetation composition in the Arctic tundra have been observed and are predicted in a warmer future climate. Shrub expansion may positively feed back to climate warming by decreasing the shortwave albedo. On the other hand, permafrost protection through soil shading by shrubs has been discussed in literature. Several studies compared the average radiation balance across vegetation zones. However, variation within vegetation zones may be as important as differences between vegetation zones. The lowland tundra ecosystem at the Kytalyk research site (NE Siberia) is dominated by two vegetation types (dwarf shrub (Betula nana) and wet sedge (Eriophorum angustifolium)) organised in patches at a scale of about 10m. We investigated the shortwave radiation balance of both types separately and related it to the 11 year data set of the fluxtower with a mixed footprint. In addition to canopy albedo, we measured canopy transmittance below dwarf shrubs and wet sedges to quantify the often discussed effect of soil shading. Our results show that at our field site, wet sedge vegetation is shading the soil more efficiently than dwarf shrubs due to multi-year standing litter. While we measured an average transmission of 36% of the incoming shortwave radiation below dwarf shrubs, the transmission of wet sedge was 28%. Wet sedge summer albedo was on average 16% higher than dwarf shrub albedo. Additionally, the snow melted 10 days later in the sedge patches, leading to large albedo differences in the second half of May 2014. Our analysis shows, that cloud cover is the second most important control on albedo and transmittance of both vegetation types. Clouds reduced the summer albedo of both vegetation types across all zenith angles. On average, the growing season albedo was about 11% higher on clear sky days as compared to overcast days whereas the transmittance was about 23% lower. As cloud cover is expected to change with climate change, field studies of the cloud

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

    PubMed

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere. PMID:26376204

  6. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya P. K.; Landis, David; Middleton, Elizabeth

    2012-01-01

    Climate change in tundra regions may alter vegetation species composition and ecosystem carbon balance. Remote sensing provides critical tools for monitoring these changes as optical signals provide a way to scale from plot measurements to regional patterns. Gas exchange measurements of pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK, show three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012 0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Further, discriminant analysis of patch reflectance identifies five spectral bands that can separate each vegetation functional type as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. Patch-level statistical discriminant functions applied to in situ hyperspectral reflectance successfully unmixed cover fractions of the vegetation functional types. These functions, developed from the tram data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine regional variability in distribution of the vegetation functional types and from those distributions, the variability of LUE. Across the landscape, there was a fivefold variation in tundra LUE that was correlated to a spectral vegetation index developed to detect vegetation chlorophyll content.

  7. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl Fred; Gamon, John A.; Tweedie, Craig E.; Campbell, Petya K. Entcheva; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow, AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013 plus or minus 0.0002, 0.0018 plus or minus 0.0002, and 0.0012 plus or minus 0.0001 mol C mol (exp -1) absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Along the transect, area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. The patch-level statistical discriminant functions applied to in situ hyperspectral reflectance data collected along the transect successfully unmixed cover fractions of the vegetation functional types. The unmixing functions, developed from the transect data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine variability in distribution of the vegetation functional types for an area near Barrow, AK. Spatial variability of LUE was derived from the observed functional type distributions. Across this landscape, a

  8. Design and Development of a Spectral Library for Different Vegetation and Landcover Types for Arctic, Antarctic and Chihuahua Desert Ecosystem

    NASA Astrophysics Data System (ADS)

    Matharasi, K.; Goswami, S.; Gamon, J.; Vargas, S.; Marin, R.; Lin, D.; Tweedie, C. E.

    2008-12-01

    All objects on the Earth's surface absorb and reflect portions of the electromagnetic spectrum. Depending on the composition of the material, every material has its characteristic spectral profile. The characteristic spectral profile for vegetation is often used to study how vegetation patterns at large spatial scales affect ecosystem structure and function. Analysis of spectroscopic data from the laboratory, and from various other platforms like aircraft or spacecraft, requires a knowledge base that consists of different characteristic spectral profiles for known different materials. This study reports on establishment of an online and searchable spectral library for a range of plant species and landcover types in the Arctic, Anatarctic and Chihuahuan desert ecosystems. Field data were collected from Arctic Alaska, the Antarctic Peninsula and the Chihuahuan desert in the visible to near infrared (IR) range using a handheld portable spectrometer. The data have been archived in a database created using postgre sql with have been made publicly available on a plone web-interface. This poster describes the data collected in more detail and offers instruction to users who wish to make use of this free online resource.

  9. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya K.; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012+/-0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals.

  10. New views on changing Arctic vegetation

    NASA Astrophysics Data System (ADS)

    Kennedy, Robert E.

    2012-03-01

    ). While the USGS archive has been dominated by imagery from the United States, recent efforts by the USGS to repatriate data stored in international archives are adding new historical images to the archive every day. With persistence and the goodwill of collaborating countries, this effort may someday allow analyses similar to that of Fraser et al across broader expanses of the Earth, providing further insights into the mechanisms and manifestations of climate change. References Chapin F S et al 2000 Arctic and boreal ecosystems of western North America as components of the climate system Glob. Change Biol. 6 211-23 Coops N C and Waring R H 2011 A process-based approach to estimate lodgepole pine (Pinus contorta Dougl.) distribution in the Pacific Northwest under climate change Clim. Change 105 313-28 de Beurs K M and Henebry G M 2010 A land surface phenology assessment of the northern polar regions using MODIS reflectance time series Can. J. Remote Sens. 36 S87-110 Forbes B C, Fauria M M and Zetterberg P 2010 Russian Arctic warming and 'greening' are closely tracked by tundra shrub willows Glob. Change Biol. 16 1542-54 Fraser R H et al 2011 Detecting long-term changes to vegetation in northern Canada using the Landsat satellite image archive Environ. Res. Lett. 6 045502 Goodwin N R, Magnussen S, Coops N C and Wulder M A 2010 Curve fitting of time-series Landsat imagery for characterizing a mountain pine beetle infestation Int. J. Remote Sens. 31 3263-71 Hais M, Jonášová M, Langhammer J and Kuèera T 2009 Comparison of two types of forest disturbance using multitemporal Landsat TM/ETMC imagery and field vegetation data Remote Sens. Environ. 113 835-45 Hansen M C, Stehman S V and Potapov P V 2010 Quantification of global gross forest cover loss Proc. Natl Acad. Sci. 107 8650-5 Huang C, Goward S N, Masek J G, Thomas N, Zhu Z and Vogelmann J E 2010 An automated approach for reconstructing recent forest disturbance history using dense Landsat time series stacks Remote Sens

  11. Arctic and Alpine Vegetations: Similarities, Differences, and Susceptibility to Disturbance

    ERIC Educational Resources Information Center

    Billings, W. D.

    1973-01-01

    Discusses environmental and biological aspects of arctic and alpine vegetations in the New World between the equator and the Arctic Ocean, considering their similarities, differences, and susceptibility to disturbance by man. (JR)

  12. The Alaska Arctic Vegetation Archive (AVA-AK)

    DOE PAGESBeta

    Walker, Donald; Breen, Amy; Druckenmiller, Lisa; Wirth, Lisa W.; Fisher, Will; Raynolds, Martha K.; Sibik, Jozef; Walker, Marilyn D.; Hennekens, Stephan; Boggs, Keith; et al

    2016-05-17

    The Alaska Arctic Vegetation Archive (AVA-AK, GIVD-ID: NA-US-014) is a free, publically available database archive of vegetation-plot data from the Arctic tundra region of northern Alaska. The archive currently contains 24 datasets with 3,026 non-overlapping plots. Of these, 74% have geolocation data with 25-m or better precision. Species cover data and header data are stored in a Turboveg database. A standardized Pan Arctic Species List provides a consistent nomenclature for vascular plants, bryophytes, and lichens in the archive. A web-based online Alaska Arctic Geoecological Atlas (AGA-AK) allows viewing and downloading the species data in a variety of formats, and providesmore » access to a wide variety of ancillary data. We conducted a preliminary cluster analysis of the first 16 datasets (1,613 plots) to examine how the spectrum of derived clusters is related to the suite of datasets, habitat types, and environmental gradients. Here, we present the contents of the archive, assess its strengths and weaknesses, and provide three supplementary files that include the data dictionary, a list of habitat types, an overview of the datasets, and details of the cluster analysis.« less

  13. Arctic Vegetation Change and Feedbacks under Future Climate (Invited)

    NASA Astrophysics Data System (ADS)

    Goetz, S. J.; Loranty, M. M.; Beck, P.; Phillips, S.; Damoulas, T.; Pearson, R. G.

    2013-12-01

    Arctic surface air temperatures have risen at approximately twice the global rate, produce multiple climate feedbacks, e.g. via expansion of woody shrubs and trees into the tundra biome increasing surface net shortwave radiation due to reductions in albedo. To explore the feedbacks of future Arctic vegetation change on climate, we modeled vegetation type distribution across the circumpolar domain using machine-learning ecological niche models at moderately fine (4.5 x 4.5 km) spatial resolution. Vegetation was resolved into four classes of graminoids, four classes of shrubs, and two classes of tree cover. Comparison of observed and modeled classes under present climate revealed strong predictive performance. When simulating into the 2050s under scenarios of restricted tree dispersal and climate change, we found vegetation in 48-69% of our study area would shift to a different physiognomic class. Under an equilibrium scenario with unrestricted dispersal 57-84% of the area is predicted to shift to a different class. This latter scenario is supported by evidence of rapid shifts to larger growth-forms due to rapid colonization due to long-distance dispersal, expansion from refugia, and favorable conditions for establishment following disturbance like tundra fires and thermal erosion related to permafrost thaw. Distributions of lower-lying vegetation classes with sparse plant cover are predicted to contract in some places as larger shrubs and trees expand their ranges, but this outcome is mostly restricted to regions that do not have more northerly land masses to which vegetation could shift as trees and larger shrubs migrate from the south. We also estimated future changes in albedo, evapotranspiration and above-ground biomass, each of which would change substantially with our predicted widespread redistribution of Arctic vegetation. In terms of climate feedbacks, the predicted increases in ET were relatively small, and predicted maximum total increases in biomass (1

  14. Vegetation greening in the Canadian Arctic related to decadal warming.

    PubMed

    Jia, Gensuo J; Epstein, Howard E; Walker, Donald A

    2009-12-01

    This study is presented within the context that climate warming and sea-ice decline has been occurring throughout much of the Arctic over the past several decades, and that terrestrial ecosystems at high latitudes are sensitive to the resultant alterations in surface temperatures. Results are from analyzing interannual satellite records of vegetation greenness across a bioclimate gradient of the Canadian Arctic over the period of 1982-2006. Here, we combine multi-scale sub-pixel analysis and remote sensing time-series analysis to investigate recent decadal changes in vegetation greenness along spatial gradients of summer temperature and vegetation. Linear autoregression temporal analysis of vegetation greenness was performed with relatively "pure" vegetation pixels of Advanced Very High Resolution Radiometer (AVHRR) data, spanning Low Arctic, High Arctic and polar desert ecosystems. Vegetation greenness generally increased over tundra ecosystems in the past two decades. Peak annual greenness increased 0.49-0.79%/yr over the High Arctic where prostrate dwarf shrubs, forbs, mosses and lichens dominate and 0.46-0.67%/yr over the Low Arctic where erect dwarf shrubs and graminoids dominate. However, magnitudes of vegetation greenness differ with length of time series and periods considered, indicating a nonlinear response of terrestrial ecosystems to climate change. The decadal increases of greenness reflect increasing vegetation production during the peak of the growing season, and were likely driven by the recent warming.

  15. Arctic Browning: vegetation damage and implications for carbon balance.

    NASA Astrophysics Data System (ADS)

    Treharne, Rachael; Bjerke, Jarle; Emberson, Lisa; Tømmervik, Hans; Phoenix, Gareth

    2016-04-01

    'Arctic browning' is the loss of biomass and canopy in Arctic ecosystems. This process is often driven by climatic and biological extreme events - notably extreme winter warm periods, winter frost-drought and severe outbreaks of defoliating insects. Evidence suggests that browning is becoming increasingly frequent and severe at the pan-arctic scale, a view supported by observations from more intensely observed regions, with major and unprecedented vegetation damage reported at landscape (>1000km2) and regional (Nordic Arctic Region) scales in recent years. Critically, the damage caused by these extreme events is in direct opposition to 'Arctic greening', the well-established increase in productivity and shrub abundance observed at high latitudes in response to long-term warming. This opposition creates uncertainty as to future anticipated vegetation change in the Arctic, with implications for Arctic carbon balance. As high latitude ecosystems store around twice as much carbon as the atmosphere, and vegetation impacts are key to determining rates of loss or gain of ecosystem carbon stocks, Arctic browning has the potential to influence the role of these ecosystems in global climate. There is therefore a clear need for a quantitative understanding of the impacts of browning events on key ecosystem carbon fluxes. To address this, field sites were chosen in central and northern Norway and in Svalbard, in areas known to have been affected by either climatic extremes or insect outbreak and subsequent browning in the past four years. Sites were chosen along a latitudinal gradient to capture both conditions already causing vegetation browning throughout the Norwegian Arctic, and conditions currently common at lower latitudes which are likely to become more damaging further North as climate change progresses. At each site the response of Net Ecosystem CO2 Exchange to light was measured using a LiCor LI6400 Portable Photosynthesis system and a custom vegetation chamber with

  16. Vegetation, plant biomass, and net primary productivity patterns in the Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Gould, W. A.; Raynolds, M.; Walker, D. A.

    2003-01-01

    We have developed maps of dominant vegetation types, plant functional types, percent vegetation cover, aboveground plant biomass, and above and belowground annual net primary productivity for Canada north of the northern limit of trees. The area mapped covers 2.5 million km2 including glaciers. Ice-free land covers 2.3 million km2 and represents 42% of all ice-free land in the Circumpolar Arctic. The maps combine information on climate, soils, geology, hydrology, remotely sensed vegetation classifications, previous vegetation studies, and regional expertise to define polygons drawn using photo-interpretation of a 1:4,000,000 scale advanced very high resolution radiometer (AVHRR) color infrared image basemap. Polygons are linked to vegetation description, associated properties, and descriptive literature through a series of lookup tables in a graphic information systems (GIS) database developed as a component of the Circumpolar Arctic Vegetation Map (CAVM) project. Polygons are classified into 20 landcover types including 17 vegetation types. Half of the region is sparsely vegetated (<50% vegetation cover), primarily in the High Arctic (bioclimatic subzones A-C). Whereas most (86%) of the estimated aboveground plant biomass (1.5 × 1015 g) and 87% of the estimated above and belowground annual net primary productivity (2.28 × 1014 g yr-1) are concentrated in the Low Arctic (subzones D and E). The maps present more explicit spatial patterns of vegetation and ecosystem attributes than have been previously available, the GIS database is useful in summarizing ecosystem properties and can be easily updated and integrated into circumpolar mapping efforts, and the derived estimates fall within the range of current published estimates.

  17. Modelling tundra vegetation response to recent arctic warming.

    PubMed

    Miller, Paul A; Smith, Benjamin

    2012-01-01

    The Arctic land area has warmed by > 1 °C in the last 30 years and there is evidence that this has led to increased productivity and stature of tundra vegetation and reduced albedo, effecting a positive (amplifying) feedback to climate warming. We applied an individual-based dynamic vegetation model over the Arctic forced by observed climate and atmospheric CO(2) for 1980-2006. Averaged over the study area, the model simulated increases in primary production and leaf area index, and an increasing representation of shrubs and trees in vegetation. The main underlying mechanism was a warming-driven increase in growing season length, enhancing the production of shrubs and trees to the detriment of shaded ground-level vegetation. The simulated vegetation changes were estimated to correspond to a 1.75 % decline in snow-season albedo. Implications for modelling future climate impacts on Arctic ecosystems and for the incorporation of biogeophysical feedback mechanisms in Arctic system models are discussed. PMID:22864701

  18. Vegetation-Associated Impacts on Arctic Tundra Bacterial and Microeukaryotic Communities

    PubMed Central

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Neufeld, Josh D.; Walker, Virginia K.

    2014-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H′) were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure. PMID:25362064

  19. Vegetation-associated impacts on arctic tundra bacterial and microeukaryotic communities.

    PubMed

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Chu, Haiyan; Neufeld, Josh D; Walker, Virginia K; Grogan, Paul

    2015-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H') were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure. PMID:25362064

  20. Vegetation-associated impacts on arctic tundra bacterial and microeukaryotic communities.

    PubMed

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Chu, Haiyan; Neufeld, Josh D; Walker, Virginia K; Grogan, Paul

    2015-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H') were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure.

  1. Impact of Holocene climate variability on Arctic vegetation

    NASA Astrophysics Data System (ADS)

    Gajewski, K.

    2015-10-01

    This paper summarizes current knowledge about the postglacial history of the vegetation of the Canadian Arctic Archipelago (CAA) and Greenland. Available pollen data were used to understand the initial migration of taxa across the Arctic, how the plant biodiversity responded to Holocene climate variability, and how past climate variability affected primary production of the vegetation. Current evidence suggests that most of the flora arrived in the area during the Holocene from Europe or refugia south or west of the region immediately after local deglaciation, indicating rapid dispersal of propagules to the region from distant sources. There is some evidence of shrub species arriving later in Greenland, but it is not clear if this is dispersal limited or a response to past climates. Subsequent climate variability had little effect on biodiversity across the CAA, with some evidence of local extinctions in areas of Greenland in the late Holocene. The most significant impact of climate changes is on vegetation density and/or plant production.

  2. Fifty thousand years of Arctic vegetation and megafaunal diet.

    PubMed

    Willerslev, Eske; Davison, John; Moora, Mari; Zobel, Martin; Coissac, Eric; Edwards, Mary E; Lorenzen, Eline D; Vestergård, Mette; Gussarova, Galina; Haile, James; Craine, Joseph; Gielly, Ludovic; Boessenkool, Sanne; Epp, Laura S; Pearman, Peter B; Cheddadi, Rachid; Murray, David; Bråthen, Kari Anne; Yoccoz, Nigel; Binney, Heather; Cruaud, Corinne; Wincker, Patrick; Goslar, Tomasz; Alsos, Inger Greve; Bellemain, Eva; Brysting, Anne Krag; Elven, Reidar; Sønstebø, Jørn Henrik; Murton, Julian; Sher, Andrei; Rasmussen, Morten; Rønn, Regin; Mourier, Tobias; Cooper, Alan; Austin, Jeremy; Möller, Per; Froese, Duane; Zazula, Grant; Pompanon, François; Rioux, Delphine; Niderkorn, Vincent; Tikhonov, Alexei; Savvinov, Grigoriy; Roberts, Richard G; MacPhee, Ross D E; Gilbert, M Thomas P; Kjær, Kurt H; Orlando, Ludovic; Brochmann, Christian; Taberlet, Pierre

    2014-02-01

    Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25-15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe.

  3. Fifty thousand years of Arctic vegetation and megafaunal diet.

    PubMed

    Willerslev, Eske; Davison, John; Moora, Mari; Zobel, Martin; Coissac, Eric; Edwards, Mary E; Lorenzen, Eline D; Vestergård, Mette; Gussarova, Galina; Haile, James; Craine, Joseph; Gielly, Ludovic; Boessenkool, Sanne; Epp, Laura S; Pearman, Peter B; Cheddadi, Rachid; Murray, David; Bråthen, Kari Anne; Yoccoz, Nigel; Binney, Heather; Cruaud, Corinne; Wincker, Patrick; Goslar, Tomasz; Alsos, Inger Greve; Bellemain, Eva; Brysting, Anne Krag; Elven, Reidar; Sønstebø, Jørn Henrik; Murton, Julian; Sher, Andrei; Rasmussen, Morten; Rønn, Regin; Mourier, Tobias; Cooper, Alan; Austin, Jeremy; Möller, Per; Froese, Duane; Zazula, Grant; Pompanon, François; Rioux, Delphine; Niderkorn, Vincent; Tikhonov, Alexei; Savvinov, Grigoriy; Roberts, Richard G; MacPhee, Ross D E; Gilbert, M Thomas P; Kjær, Kurt H; Orlando, Ludovic; Brochmann, Christian; Taberlet, Pierre

    2014-02-01

    Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25-15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe. PMID:24499916

  4. Will Arctic ground squirrels impede or accelerate climate-induced vegetation changes to the Arctic tundra?

    NASA Astrophysics Data System (ADS)

    Dalton, J.; Flower, C. E.; Brown, J.; Gonzalez-Meler, M. A.; Whelan, C.

    2014-12-01

    Considerable attention has been given to the climate feedbacks associated with predicted vegetation shifts in the Arctic tundra in response to global environmental change. However, little is known regarding the extent to which consumers can facilitate or respond to shrub expansion. Arctic ground squirrels, the largest and most northern ground squirrel, are abundant and widespread throughout the North American tundra. Their broad diet of seeds, flowers, herbage, bird's eggs and meat speaks to the need to breed, feed, and fatten in a span of some 12-16 weeks that separate their 8-9 month bouts of hibernation with the potential consequence to impact ecosystem dynamics. Therefore Arctic ground squirrels are a good candidate to evaluate whether consumers are mere responders (bottom-up effects) or drivers (top-down) of the observed and predicted vegetation changes. As a start towards this question, we measured the foraging intensity (giving-up densities) of Arctic ground squirrels in experimental food patches within which the squirrels experience diminishing returns as they seek the raisins and peanuts that we provided at the Toolik Lake field station in northern Alaska. If the squirrels show their highest feeding intensity in the shrubs, they may impede vegetation shifts by slowing the establishment and expansion of shrubs in the tundra. Conversely, if they show their lowest feeding intensity within shrub dominated areas, they may accelerate vegetation shifts. We found neither. Feeding intensity varied most among transects and times of day, and least along a tundra-to-shrub vegetation gradient. This suggests that the impacts of squirrels will be heterogeneous - in places responders and in others drivers. We should not be surprised then to see patches of accelerated and impeded vegetation changes in the tundra ecosystem. Some of these patterns may be predictable from the foraging behavior of Arctic ground squirrels.

  5. High Arctic Hillslope-Wetland Linkages: Types, Patterns and Importance

    NASA Astrophysics Data System (ADS)

    Young, K. L.; Abnizova, A.

    2012-12-01

    High Arctic wetlands are lush areas in an otherwise barren landscape. They help to store and replenish water and they serve as significant resting and breeding grounds for migratory birds. In addition, they provide rich grazing grounds for arctic fauna such as muskox and caribou. Arctic wetlands can be small, patchy grounds of wet vegetation or they can encompass large zones characterized by lakes, ponds, wet meadows, and, often times, they are inter-mixed with areas of dry ground. While seasonal snowmelt continues to remain the most critical source of water for recharging ponds, lakes, and meadows in these environments, less is known about the role of lateral inputs of water into low-lying wetlands, namely water flowing into these wetland ecosystems from adjacent hillslopes, which often surround them. This paper will review the different modes of hillslope runoff into both patchy and regional-scale wetlands including late-lying snowbeds, snow-filled creeks, and both small and large (>1st order) streams. It will draw upon field results from four arctic islands (Ellesmere, Cornwallis, Somerset and Bathurst Island) and a research period which spans from the mid'90s until present. Our study will evaluate seasonal and inter-seasonal patterns of snowmelt driven discharge (initiation, duration), timing, and magnitude of peak flows, in addition to stream response to rainfall and dry episodes. The impacts of these lateral water sources for a range of wetlands (ponds, wet meadows) will include an analysis of water level fluctuations (frequency, duration), shrinkage/expansion rates, and water quality. Finally, this study will surmise how these types of lateral hillslope inflows might shift in the future and suggest the impact of these changes on the sustainability of High Arctic wetland terrain.

  6. Modelling high arctic percent vegetation cover using field digital images and high resolution satellite data

    NASA Astrophysics Data System (ADS)

    Liu, Nanfeng; Treitz, Paul

    2016-10-01

    In this study, digital images collected at a study site in the Canadian High Arctic were processed and classified to examine the spatial-temporal patterns of percent vegetation cover (PVC). To obtain the PVC of different plant functional groups (i.e., forbs, graminoids/sedges and mosses), field near infrared-green-blue (NGB) digital images were classified using an object-based image analysis (OBIA) approach. The PVC analyses comparing different vegetation types confirmed: (i) the polar semi-desert exhibited the lowest PVC with a large proportion of bare soil/rock cover; (ii) the mesic tundra cover consisted of approximately 60% mosses; and (iii) the wet sedge consisted almost exclusively of graminoids and sedges. As expected, the PVC and green normalized difference vegetation index (GNDVI; (RNIR - RGreen)/(RNIR + RGreen)), derived from field NGB digital images, increased during the summer growing season for each vegetation type: i.e., ∼5% (0.01) for polar semi-desert; ∼10% (0.04) for mesic tundra; and ∼12% (0.03) for wet sedge respectively. PVC derived from field images was found to be strongly correlated with WorldView-2 derived normalized difference spectral indices (NDSI; (Rx - Ry)/(Rx + Ry)), where Rx is the reflectance of the red edge (724.1 nm) or near infrared (832.9 nm and 949.3 nm) bands; Ry is the reflectance of the yellow (607.7 nm) or red (658.8 nm) bands with R2's ranging from 0.74 to 0.81. NDSIs that incorporated the yellow band (607.7 nm) performed slightly better than the NDSIs without, indicating that this band may be more useful for investigating Arctic vegetation that often includes large proportions of senescent vegetation throughout the growing season.

  7. Spatial variation in vegetation productivity trends, fire disturbance, and soil carbon across arctic-boreal permafrost ecosystems

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Liberman-Cribbin, Wil; Berner, Logan T.; Natali, Susan M.; Goetz, Scott J.; Alexander, Heather D.; Kholodov, Alexander L.

    2016-09-01

    In arctic tundra and boreal forest ecosystems vegetation structural and functional influences on the surface energy balance can strongly influence permafrost soil temperatures. As such, vegetation changes will likely play an important role in permafrost soil carbon dynamics and associated climate feedbacks. Processes that lead to changes in vegetation, such as wildfire or ecosystem responses to rising temperatures, are of critical importance to understanding the impacts of arctic and boreal ecosystems on future climate. Yet these processes vary within and between ecosystems and this variability has not been systematically characterized across the arctic-boreal region. Here we quantify the distribution of vegetation productivity trends, wildfire, and near-surface soil carbon, by vegetation type, across the zones of continuous and discontinuous permafrost. Siberian larch forests contain more than one quarter of permafrost soil carbon in areas of continuous permafrost. We observe pervasive positive trends in vegetation productivity in areas of continuous permafrost, whereas areas underlain by discontinuous permafrost have proportionally less positive productivity trends and an increase in areas exhibiting negative productivity trends. Fire affects a much smaller proportion of the total area and thus a smaller amount of permafrost soil carbon, with the vast majority occurring in deciduous needleleaf forests. Our results indicate that vegetation productivity trends may be linked to permafrost distribution, fire affects a relatively small proportion of permafrost soil carbon, and Siberian larch forests will play a crucial role in the strength of the permafrost carbon climate feedback.

  8. Crustal types of the Circumpolar Arctic

    NASA Astrophysics Data System (ADS)

    Kashubin, Sergey; Pavlenkova, Ninel; Petrov, Oleg; Milshtein, Evgenia; Shokalsky, Sergey; Erinchek, Yuri

    2016-04-01

    Deep seismic studies revealed unusual crustal structure in the Arctic Ocean. The thin (about 10 km) oceanic crust with seismic velocities Vp= 6.8-7.2 km/s is observed only in the narrow mid-oceanic ridge zone (the Gakkel ridge). The thick (25-35 km) continental crust covers the whole continental margins and the central part of the ocean. The continental type of the magnetic field with large local anomalies of different signs and irregular shapes is also observed in this area. However, the crust of the central Arctic (the Lomonosov, Mendeleev and Alpha ridges) differ from the crust of the Eurasia by the lower thickness of the upper granite-gneiss layer (velocities Vp=6.0-6.6 km/s): it is only 5-7 km in comparison with 15-20 km in the continent. The origin of such crust may be explained in two ways. Most frequently it is accounted for by the destruction and transformation of the continental crust by the basification that implies the enrichment of the crust by the rocks of basic composition from the mantle and the metamorphization of the continental rocks at the higher temperature and pressure. But in the central part of the Arctic Ocean the crust looks as an original one. The regular form of the large ridges and the continental type magnetic field were not destroyed by the basification processes which are usually irregular and most intensive in some local zones. The basification origin may be proposed for the Canadian and the South-Barents deep sedimentary basins with "suboceanic" crust (10-15 km of sediments and 10-15 km of the lower crust with Vp= 6.8-7.2 km/s). The other basins which stretch along fault zones outlined the central deep water part of the Arctic Ocean have the ''subcontinental' crust: the thickness of the granite-gneiss layer decreases in these basins and sometimes the high velocity intrusions are observed in the lower parts. The different crustal types are observed in the North Atlantic where the oceanic crust with linear magnetic anomalies is

  9. Phenological dynamics of arctic tundra vegetation and its implications on satellite imagery interpretation

    NASA Astrophysics Data System (ADS)

    Juutinen, Sari; Aurela, Mika; Mikola, Juha; Räsänen, Aleksi; Virtanen, Tarmo

    2016-04-01

    Remote sensing is a key methodology when monitoring the responses of arctic ecosystems to climatic warming. The short growing season and rapid vegetation development, however, set demands to the timing of image acquisition in the arctic. We used multispectral very high spatial resolution satellite images to study the effect of vegetation phenology on the spectral reflectance and image interpretation in the low arctic tundra in coastal Siberia (Tiksi, 71°35'39"N, 128°53'17"E). The study site mainly consists of peatlands, tussock, dwarf shrub, and grass tundra, and stony areas with some lichen and shrub patches. We tested the hypotheses that (1) plant phenology is responsive to the interannual weather variation and (2) the phenological state of vegetation has an impact on satellite image interpretation and the ability to distinguish between the plant communities. We used an empirical transfer function with temperature sums as drivers to reconstruct daily leaf area index (LAI) for the different plant communities for years 2005, and 2010-2014 based on measured LAI development in summer 2014. Satellite images, taken during growing seasons, were acquired for two years having late and early spring, and short and long growing season, respectively. LAI dynamics showed considerable interannual variation due to weather variation, and particularly the relative contribution of graminoid dominated communities was sensitive to these phenology shifts. We have also analyzed the differences in the reflectance values between the two satellite images taking account the LAI dynamics. These results will increase our understanding of the pitfalls that may arise from the timing of image acquisition when interpreting the vegetation structure in a heterogeneous tundra landscape. Very high spatial resolution multispectral images are available at reasonable cost, but not in high temporal resolution, which may lead to compromises when matching ground truth and the imagery. On the other hand

  10. Recovery and archiving key Arctic Alaska vegetation map and plot data for the Arctic-Boreal Vulnerability Field Experiment (ABoVE)

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Breen, A. L.; Broderson, D.; Epstein, H. E.; Fisher, W.; Grunblatt, J.; Heinrichs, T.; Raynolds, M. K.; Walker, M. D.; Wirth, L.

    2013-12-01

    Abundant ground-based information will be needed to inform remote-sensing and modeling studies of NASA's Arctic-Boreal Vulnerability Experiment (ABoVE). A large body of plot and map data collected by the Alaska Geobotany Center (AGC) and collaborators from the Arctic regions of Alaska and the circumpolar Arctic over the past several decades is being archived and made accessible to scientists and the public via the Geographic Information Network of Alaska's (GINA's) 'Catalog' display and portal system. We are building two main types of data archives: Vegetation Plot Archive: For the plot information we use a Turboveg database to construct the Alaska portion of the international Arctic Vegetation Archive (AVA) http://www.geobotany.uaf.edu/ava/. High quality plot data and non-digital legacy datasets in danger of being lost have highest priority for entry into the archive. A key aspect of the database is the PanArctic Species List (PASL-1), developed specifically for the AVA to provide a standard of species nomenclature for the entire Arctic biome. A wide variety of reports, documents, and ancillary data are linked to each plot's geographic location. Geoecological Map Archive: This database includes maps and remote sensing products and links to other relevant data associated with the maps, mainly those produced by the Alaska Geobotany Center. Map data include GIS shape files of vegetation, land-cover, soils, landforms and other categorical variables and digital raster data of elevation, multispectral satellite-derived data, and data products and metadata associated with these. The map archive will contain all the information that is currently in the hierarchical Toolik-Arctic Geobotanical Atlas (T-AGA) in Alaska http://www.arcticatlas.org, plus several additions that are in the process of development and will be combined with GINA's already substantial holdings of spatial data from northern Alaska. The Geoecological Atlas Portal uses GINA's Catalog tool to develop a

  11. Trends of Vegetation Greenness in the Arctic from 1982-2005

    NASA Astrophysics Data System (ADS)

    Jia, G. J.; Epstein, H. E.; Walker, D. A.

    2007-12-01

    The Arctic region has experienced a continuous trend of warming during the past 30 years. Meanwhile, many areas of the Arctic are undergoing large-scale industrial development, e.g. oil and gas exploration, at a rapid pace, indicating an increasing human pressure and land use changes even in this frontier wilderness. Major questions face arctic terrestrial ecologists are what will happen to the tundra ecosystems as the global climate warms and what will happen to the indigenous people way of life as land cover changes proceed? Here, we combine multi-scale sub-pixel analysis and remote sensing time-series analysis to investigate recent decadal changes in vegetation photosynthetic activity along spatial gradients of summer temperature and vegetation in the Arctic. The datasets used here are NASA Gimms data at 8 km pixel resolution and MODIS land cover data. Fractional vegetation cover was analyzed in order to select homogenously vegetated areas of tundra and autoregression analysis was performed on time series of those homogenous pixels. Only pixels below 70 degree north were included for 2004-2005 due to calibration errors occurred beyond 70 degree north for those years. Linear trends in Arctic tundra vegetation greenness over period 1982-2005 were positive. However, there were different magnitudes between Eurasia and North America. The rate of change was +0.64%/yr over North American Arctic compared to +0.44%/yr over Eurasian Arctic. Vegetation productivities increase from north to south along bioclimatic gradient, therefore, greenness is much higher in areas below 70 degree north compared to entire tundra biome. Higher rates of greening in High Arctic contributed to a stronger positive trend in the longer time series. The rate of greening detected here was higher than that reported in previous studies. This is likely due to two reasons: 1) we restricted our study area in tundra biome only with a phenological tundra-taiga boundary identification approach, therefore

  12. Relationships between declining summer sea ice, increasing temperatures and changing vegetation in the Siberian Arctic tundra from MODIS time series (2000-11)

    NASA Astrophysics Data System (ADS)

    Dutrieux, L. P.; Bartholomeus, H.; Herold, M.; Verbesselt, J.

    2012-12-01

    The concern about Arctic greening has grown recently as the phenomenon is thought to have significant influence on global climate via atmospheric carbon emissions. Earlier work on Arctic vegetation highlighted the role of summer sea ice decline in the enhanced warming and greening phenomena observed in the region, but did not contain enough details for spatially characterizing the interactions between sea ice, temperature and vegetation photosynthetic absorption. By using 1 km resolution data from the Moderate Resolution Imaging Spectrometer (MODIS) as a primary data source, this study presents detailed maps of vegetation and temperature trends for the Siberian Arctic region, using the time integrated normalized difference vegetation index (TI-NDVI) and summer warmth index (SWI) calculated for the period 2000-11 to represent vegetation greenness and temperature respectively. Spatio-temporal relationships between the two indices and summer sea ice conditions were investigated with transects at eight locations using sea ice concentration data from the Special Sensor Microwave/Imager (SSM/I). In addition, the derived vegetation and temperature trends were compared among major Arctic vegetation types and bioclimate subzones. The fine resolution trend map produced confirms the overall greening (+1% yr-1) and warming (+0.27% yr-1) of the region, reported in previous studies, but also reveals browning areas. The causes of such local decreases in vegetation, while surrounding areas are experiencing the opposite reaction to changing conditions, are still unclear. Overall correlations between sea ice concentration and SWI as well as TI-NDVI decreased in strength with increasing distance from the coast, with a particularly pronounced pattern in the case of SWI. SWI appears to be driving TI-NDVI in many cases, but not systematically, highlighting the presence of limiting factors other than temperature for plant growth in the region. Further unravelling those limiting factors

  13. The role of mosses in carbon uptake and partitioning in arctic vegetation.

    PubMed

    Street, Lorna E; Subke, Jens-Arne; Sommerkorn, Martin; Sloan, Victoria; Ducrotoy, Helene; Phoenix, Gareth K; Williams, Mathew

    2013-07-01

    The Arctic is already experiencing changes in plant community composition, so understanding the contribution of different vegetation components to carbon (C) cycling is essential in order to accurately quantify ecosystem C balance. Mosses contribute substantially to biomass, but their impact on carbon use efficiency (CUE) - the proportion of gross primary productivity (GPP) incorporated into growth - and aboveground versus belowground C partitioning is poorly known. We used (13) C pulse-labelling to trace assimilated C in mosses (Sphagnum sect. Acutifolia and Pleurozium schreberi) and in dwarf shrub-P. schreberi vegetation in sub-Arctic Finland. Based on (13) C pools and fluxes, we quantified the contribution of mosses to GPP, CUE and partitioning. Mosses incorporated 20 ± 9% of total ecosystem GPP into biomass. CUE of Sphagnum was 68-71%, that of P. schreberi was 62-81% and that of dwarf shrub-P. schreberi vegetation was 58-74%. Incorporation of C belowground was 10 ± 2% of GPP, while vascular plants alone incorporated 15 ± 4% of their fixed C belowground. We have demonstrated that mosses strongly influence C uptake and retention in Arctic dwarf shrub vegetation. They increase CUE, and the fraction of GPP partitioned aboveground. Arctic C models must include mosses to accurately represent ecosystem C dynamics.

  14. How will the greening of the Arctic affect an important prey species and disturbance agent? Vegetation effects on arctic ground squirrels.

    PubMed

    Wheeler, H C; Chipperfield, J D; Roland, C; Svenning, J-C

    2015-07-01

    Increases in terrestrial primary productivity across the Arctic and northern alpine ecosystems are leading to altered vegetation composition and stature. Changes in vegetation stature may affect predator-prey interactions via changes in the prey's ability to detect predators, changes in predation pressure, predator identity and predator foraging strategy. Changes in productivity and vegetation composition may also affect herbivores via effects on forage availability and quality. We investigated if height-dependent effects of forage and non-forage vegetation determine burrowing extent and activity of arctic ground squirrels (Urocitellus parryii). We collected data on burrow networks and activity of arctic ground squirrels across long-term vegetation monitoring sites in Denali National Park and Preserve, Alaska. The implications of height-specific cover of potential forage and non-forage vegetation on burrowing behaviour and habitat suitability for arctic ground squirrels were investigated using hierarchical Bayesian modelling. Increased cover of forbs was associated with more burrows and burrow systems, and higher activity of systems, for all forb heights. No other potential forage functional group was related to burrow distribution and activity. In contrast, height-dependent negative effects of non-forage vegetation were observed, with cover over 50-cm height negatively affecting the number of burrows, systems and system activity. Our results demonstrate that increases in vegetation productivity have dual, potentially counteracting effects on arctic ground squirrels via changes in forage and vegetation stature. Importantly, increases in tall-growing woody vegetation (shrubs and trees) have clear negative effects, whereas increases in forb should benefit arctic ground squirrels. PMID:25666700

  15. How will the greening of the Arctic affect an important prey species and disturbance agent? Vegetation effects on arctic ground squirrels.

    PubMed

    Wheeler, H C; Chipperfield, J D; Roland, C; Svenning, J-C

    2015-07-01

    Increases in terrestrial primary productivity across the Arctic and northern alpine ecosystems are leading to altered vegetation composition and stature. Changes in vegetation stature may affect predator-prey interactions via changes in the prey's ability to detect predators, changes in predation pressure, predator identity and predator foraging strategy. Changes in productivity and vegetation composition may also affect herbivores via effects on forage availability and quality. We investigated if height-dependent effects of forage and non-forage vegetation determine burrowing extent and activity of arctic ground squirrels (Urocitellus parryii). We collected data on burrow networks and activity of arctic ground squirrels across long-term vegetation monitoring sites in Denali National Park and Preserve, Alaska. The implications of height-specific cover of potential forage and non-forage vegetation on burrowing behaviour and habitat suitability for arctic ground squirrels were investigated using hierarchical Bayesian modelling. Increased cover of forbs was associated with more burrows and burrow systems, and higher activity of systems, for all forb heights. No other potential forage functional group was related to burrow distribution and activity. In contrast, height-dependent negative effects of non-forage vegetation were observed, with cover over 50-cm height negatively affecting the number of burrows, systems and system activity. Our results demonstrate that increases in vegetation productivity have dual, potentially counteracting effects on arctic ground squirrels via changes in forage and vegetation stature. Importantly, increases in tall-growing woody vegetation (shrubs and trees) have clear negative effects, whereas increases in forb should benefit arctic ground squirrels.

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

    USGS Publications Warehouse

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

    2012-01-01

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

  17. Circumpolar Arctic vegetation: a hierarchic review and roadmap toward an internationally consistent approach to survey, archive and classify tundra plot data

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Daniëls, F. J. A.; Alsos, I.; Bhatt, U. S.; Breen, A. L.; Buchhorn, M.; Bültmann, H.; Druckenmiller, L. A.; Edwards, M. E.; Ehrich, D.; Epstein, H. E.; Gould, W. A.; Ims, R. A.; Meltofte, H.; Raynolds, M. K.; Sibik, J.; Talbot, S. S.; Webber, P. J.

    2016-05-01

    Satellite-derived remote-sensing products are providing a modern circumpolar perspective of Arctic vegetation and its changes, but this new view is dependent on a long heritage of ground-based observations in the Arctic. Several products of the Conservation of Arctic Flora and Fauna are key to our current understanding. We review aspects of the PanArctic Flora, the Circumpolar Arctic Vegetation Map, the Arctic Biodiversity Assessment, and the Arctic Vegetation Archive (AVA) as they relate to efforts to describe and map the vegetation, plant biomass, and biodiversity of the Arctic at circumpolar, regional, landscape and plot scales. Cornerstones for all these tools are ground-based plant-species and plant-community surveys. The AVA is in progress and will store plot-based vegetation observations in a public-accessible database for vegetation classification, modeling, diversity studies, and other applications. We present the current status of the Alaska Arctic Vegetation Archive (AVA-AK), as a regional example for the panarctic archive, and with a roadmap for a coordinated international approach to survey, archive and classify Arctic vegetation. We note the need for more consistent standards of plot-based observations, and make several recommendations to improve the linkage between plot-based observations biodiversity studies and satellite-based observations of Arctic vegetation.

  18. Ecosystem-Vegetation Dynamics in sub-arctic Stordalen Mire, Sweden

    NASA Astrophysics Data System (ADS)

    Mugnani, M. P.; Varner, R. K.; Steele, K.; Frey, S. D.; Crill, P. M.

    2012-12-01

    Increased global temperatures have contributed to the thaw of permafrost and a subsequent atmospheric release of stored methane (CH4) from sub-arctic ecosystems. Palsas, small frost uplifted mounds that support specialized dry-tolerant vegetation species, degrade when permafrost thaws, allowing other species such a Sphagnum and Eriophorum to encroach on the microhabitats and outcompete other species, altering the carbon feedback into the thin arctic soil. Other climate change-related events including increased precipitation, seasonal temperature abnormalities and changes in humidity and nutrient availability may alter vegetation dynamics in terms of diversity and abundance in sub-arctic regions. During July 2012, measurements of vegetation composition and species abundance estimates were made in Stordalen Mire (68° 21' N, 19° 03' E), Abisko Sweden, two hundred kilometers north of the Arctic Circle. The mire is an area of discontinuous permafrost populated by micro-ecosystems that vary in vegetation species and abundance depending on growth conditions. All ecosystems provide beneficial services to support a range of life forms including rodents, birds, insects and reindeer. Five representative ecosystems of the mire were chosen to conduct studies on vegetation diversity and percent cover-based abundance: palsa, Eriophorum-dominated fen, Sphagnum-dominated peatland, lakeshore edge and lakeside heath. In each ecosystem vegetation species were recorded in six transects with quadrats along with a corresponding percent cover estimation and scale number based on the Braun-Blanquet percent cover method. To determine nutrient dynamics between ecosystems, soil peat samples were also taken at random from all ecosystem transects. These were analyzed for carbon and inorganic nitrogen as well as ammonium and nitrate. In the vegetation data analysis, the Shannon-Wiener Diversity Index showed that the lakeside heath ecosystem was the most diverse and even in species distribution

  19. Mapping plant functional type distributions in Arctic ecosystems using WorldView-2 satellite imagery and unsupervised clustering

    NASA Astrophysics Data System (ADS)

    Langford, Z.; Kumar, J.; Hoffman, F. M.; Sloan, V. L.; Norby, R. J.; Wullschleger, S. D.

    2014-12-01

    The Arctic has emerged as an important focal point for the study of climate change. Arctic vegetation is particularly sensitive to warming conditions and likely to exhibit shifts in species composition, phenology and productivity under changing climate. Modeling of Arctic tundra vegetation requires representation of the heterogeneous tundra landscape, which includes representation of individual plant functional types (PFT). Vegetation exhibits unique spectral characteristics that can be harnessed to discriminate plant types and develop quantitative vegetation indices, such as the Normalized Difference Vegetation Index. We have combined high resolution multi-spectral remote sensing from the WorldView-2 satellite with LiDAR-derived digital elevation models to characterize the tundra landscape in four 100m X 100m sites within the Barrow Environmental Observatory, a 3021 hectare research reserve located at the northern most location on the Alaskan Arctic Coastal Plain. Classification of landscape PFT's using spectral and topographic characteristics yields spatial regions with expectedly similar vegetation characteristics. A field campaign was conducted during peak growing season (June - August) to collect vegetation surveys from a number of 1m x 1m plots in the study region, which were then analyzed for distribution of vegetation types in the plots. Statistical relationships were developed between spectral and topographic characteristics and vegetation type distributions at the vegetation plots. These derived relationships were employed to statistically upscale the vegetation distributions for the landscape based on spectral characteristics. We will describe two versions of PFT upscaling from WorldView-2 imagery: 1) a version computed from multiple imagery through the growing season and 2) a version computed from a single image in the middle of the growing season. This approach allowed us to test the degree to which including phenology helps predict PFT distribution

  20. Feedbacks Between Microenvironment and Plant Functional Type and Implications for CO2 Flux in Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Squires, E.; Rodenheizer, H.; Natali, S.; Mann, P.

    2013-12-01

    Future climate models predict a warmer, drier Arctic, with resultant shifts in vegetative composition and implications for ecosystem carbon budgets. The impact of vegetation change, however, may depend on which plant functional groups are favored in a warming Arctic. Physiological and functional differences between plant groups influence both the local microenvironment and, on a broader scale, whole-ecosystem CO2 flux. We examined the interactions between plants and their microenvironment, and analyzed the effect of these interactions on both soil microbial communities and CO2 flux across different functional groups. Physical and biological aspects of the microenvironment differed between plant functional groups. Lichen patches were characterized by deeper thaw depths, lower soil moisture, greater thermal conductivity, and a thinner organic layer than mosses. To better understand the development of these plant-environment interactions, we conducted a reciprocal transplant experiment, switching multiple lichen and moss patches. Temporal changes in environmental parameters at these sites will demonstrate how different plants modify their environment and will help identify associated implications for soil microbial communities and CO2 flux. We measured CO2 flux and used Biolog assays to examine soil microbial communities in undisturbed patches of mosses, lichens, and shrubs. Patches of birch shrubs had more negative net ecosystem exchange, signifying a carbon sink. Soils from alder shrubs and mosses hosted more active microbial communities than soils under birch shrubs and lichens. These results suggest a strong link between environment, plant functional type, and C cycling. Understanding how this relationship differs among plant functional types is an important part of predicting ecosystem carbon budgets as Arctic vegetation composition shifts in response to climate change.

  1. Pan-Arctic linkages between snow accumulation and growing season air temperature, soil moisture and vegetation

    NASA Astrophysics Data System (ADS)

    Luus, K. A.; Gel, Y.; Lin, J. C.; Kelly, R. E. J.; Duguay, C. R.

    2013-01-01

    Arctic field studies have indicated that the air temperature, soil moisture and vegetation at a site influence the quantity of snow accumulated, and that snow accumulation can alter growing season soil moisture and vegetation. Climate change is predicted to bring about warmer air temperatures, greater snow accumulation and northward movements of the shrub and tree lines. Understanding the response of northern environments to changes in snow and growing season land surface characteristics requires: (1) insights into the present-day linkages between snow and growing season land surface characteristics; and (2) the ability to continue to monitor these associations over time across the vast pan-Arctic. The objective of this study was therefore to examine the pan-Arctic (north of 60° N) linkages between two temporally distinct data products created from AMSR-E satellite passive microwave observations: GlobSnow snow water equivalent, and NTSG (growing season air temperature, soil moisture and vegetation transmissivity). Due to the complex and interconnected nature of processes determining snow and growing season land surface characteristics, these associations were analyzed using the modern non-parametric technique of Alternating Conditional Expectations (ACE), as this approach does not impose a predefined analytic form. Findings indicate that regions with lower vegetation transmissivity (more biomass) at the start and end of the growing season tend to accumulate less snow at the start and end of the snow season, possibly due to interception and shading. Warmer air temperatures at the start and end of the growing season were associated with diminished snow accumulation at the start and end of the snow season. High latitude sites with warmer mean annual growing season temperatures tended to accumulate more snow, probably due to the greater availability of water vapor for snow season precipitation at warmer locations. Regions with drier soils preceding snow onset tended

  2. Interactions between herbivory and warming in aboveground biomass production of arctic vegetation

    PubMed Central

    Pedersen, Christian; Post, Eric

    2008-01-01

    Background Many studies investigating the ecosystem effects of global climate change have focused on arctic ecosystems because the Arctic is expected to undergo the earliest and most pronounced changes in response to increasing global temperatures, and arctic ecosystems are considerably limited by low temperatures and permafrost. In these nutrient limited systems, a warmer climate is expected to increase plant biomass production, primarily through increases in shrubs over graminoids and forbs. But, the influence of vertebrate and invertebrate herbivores has been largely absent in studies investigating the effects of vegetation responses to climate change, despite the fact that herbivory can have a major influence on plant community composition, biomass and nutrient cycling. Here, we present results from a multi-annual field experiment investigating the effects of vertebrate herbivory on plant biomass response to simulated climate warming in arctic Greenland. Results The results after four years of treatments did not give any clear evidence of increased biomass of shrubs in response climate warming. Nor did our study indicate that vertebrate grazing mediated any increased domination of shrubs over other functional plant groups in response to warming. However, our results indicate an important role of insect outbreaks on aboveground biomass. Intense caterpillar foraging from a two-year outbreak of the moth Eurois occulta during two growing seasons may have concealed any treatment effects. However, there was some evidence suggesting that vertebrate herbivores constrain the biomass production of shrubs over graminoids and forbs. Conclusion Although inconclusive, our results were likely constrained by the overwhelming influence of an unexpected caterpillar outbreak on aboveground biomass. It is likely that the role of large vertebrate herbivores in vegetation response to warming will become more evident as this experiment proceeds and the plant community recovers from

  3. Large herbivore grazing affects the vegetation structure and greenhouse gas balance in a high arctic mire

    NASA Astrophysics Data System (ADS)

    Falk, Julie Maria; Schmidt, Niels Martin; Christensen, Torben R.; Ström, Lena

    2015-04-01

    Herbivory is an important part of most ecosystems and affects the ecosystems’ carbon balance both directly and indirectly. Little is known about herbivory and its impact on the carbon balance in high arctic mire ecosystems. We hypothesized that trampling and grazing by large herbivores influences the vegetation density and composition and thereby also the carbon balance. In 2010, we established fenced exclosures in high arctic Greenland to prevent muskoxen (Ovibos moschatus) from grazing. During the growing seasons of 2011 to 2013 we measured CO2 and CH4 fluxes in these ungrazed blocks and compared them to blocks subjected to natural grazing. Additionally, we measured depth of the water table and active layer, soil temperature, and in 2011 and 2013 an inventory of the vegetation density and composition were made. In 2013 a significant decrease in total number of vascular plant (33-44%) and Eriophorum scheuchzeri (51-53%) tillers were found in ungrazed plots, the moss-layer and amount of litter had also increased substantially in these plots. This resulted in a significant decrease in net ecosystem uptake of CO2 (47%) and likewise a decrease in CH4 emission (44%) in ungrazed plots in 2013. While the future of the muskoxen in a changing arctic is unknown, this experiment points to a potentially large effect of large herbivores on the carbon balance in natural Arctic ecosystems. It thus sheds light on the importance of grazing mammals, and hence adds to our understanding of natural ecosystem greenhouse gas balance in the past and in the future.

  4. Inclusion of Additional Plant Species and Trait Information in Dynamic Vegetation Modeling of Arctic Tundra and Boreal Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Patil, V.; Roach, J.; Griffith, B.; McGuire, A. D.

    2015-12-01

    Dynamic vegetation models (DVMs) have been developed to model the ecophysiological characteristics of plant functional types in terrestrial ecosystems. They have frequently been used to answer questions pertaining to processes such as disturbance, plant succession, and community composition under historical and future climate scenarios. While DVMs have proved useful in these types of applications, it has often been questioned if additional detail, such as including plant dynamics at the species-level and/or including species-specific traits would make these models more accurate and/or broadly applicable. A sub-question associated with this issue is, 'How many species, or what degree of functional diversity, should we incorporate to sustain ecosystem function in modeled ecosystems?' Here, we focus on how the inclusion of additional plant species and trait information may strengthen dynamic vegetation modeling in applications pertaining to: (1) forage for caribou in northern Alaska, (2) above- and belowground carbon storage in the boreal forest and lake margin wetlands of interior Alaska, and (3) arctic tundra and boreal forest leaf phenology. While the inclusion of additional information generally proved valuable in these three applications, this additional detail depends on field data that may not always be available and may also result in increased computational complexity. Therefore, it is important to assess these possible limitations against the perceived need for additional plant species and trait information in the development and application of dynamic vegetation models.

  5. Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect

    PubMed Central

    Swann, Abigail L.; Fung, Inez Y.; Levis, Samuel; Bonan, Gordon B.; Doney, Scott C.

    2010-01-01

    Arctic climate is projected to change dramatically in the next 100 years and increases in temperature will likely lead to changes in the distribution and makeup of the Arctic biosphere. A largely deciduous ecosystem has been suggested as a possible landscape for future Arctic vegetation and is seen in paleo-records of warm times in the past. Here we use a global climate model with an interactive terrestrial biosphere to investigate the effects of adding deciduous trees on bare ground at high northern latitudes. We find that the top-of-atmosphere radiative imbalance from enhanced transpiration (associated with the expanded forest cover) is up to 1.5 times larger than the forcing due to albedo change from the forest. Furthermore, the greenhouse warming by additional water vapor melts sea-ice and triggers a positive feedback through changes in ocean albedo and evaporation. Land surface albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration of water vapor and feedbacks from the ocean and sea-ice. PMID:20080628

  6. Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect.

    PubMed

    Swann, Abigail L; Fung, Inez Y; Levis, Samuel; Bonan, Gordon B; Doney, Scott C

    2010-01-26

    Arctic climate is projected to change dramatically in the next 100 years and increases in temperature will likely lead to changes in the distribution and makeup of the Arctic biosphere. A largely deciduous ecosystem has been suggested as a possible landscape for future Arctic vegetation and is seen in paleo-records of warm times in the past. Here we use a global climate model with an interactive terrestrial biosphere to investigate the effects of adding deciduous trees on bare ground at high northern latitudes. We find that the top-of-atmosphere radiative imbalance from enhanced transpiration (associated with the expanded forest cover) is up to 1.5 times larger than the forcing due to albedo change from the forest. Furthermore, the greenhouse warming by additional water vapor melts sea-ice and triggers a positive feedback through changes in ocean albedo and evaporation. Land surface albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration of water vapor and feedbacks from the ocean and sea-ice.

  7. Vegetation types in coastal Louisiana in 2013

    USGS Publications Warehouse

    Sasser, Charles E.; Visser, Jenneke M.; Mouton, Edmond; Linscombe, Jeb; Hartley, Steve B.

    2014-01-01

    During the summer of 2013, the U.S. Geological Survey, Louisiana State University, University of Louisiana at Lafayette, and the Louisiana Department of Wildlife and Fisheries Coastal and Nongame Resources Division jointly completed an aerial survey to collect data on 2013 vegetation types in coastal Louisiana. Plant species were listed and their abundance classified. On the basis of species composition and abundance, each marsh sampling station was assigned a marsh type: fresh, intermediate, brackish, or saline (saltwater) marsh. The current map presents the data collected in this effort.

  8. Vegetation biomass, leaf area index, and NDVI patterns and relationships along two latitudinal transects in arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Walker, D. A.; Raynolds, M. K.; Kelley, A. M.; Jia, G.; Ping, C.; Michaelson, G.; Leibman, M. O.; Kaarlejärvi, E.; Khomutov, A.; Kuss, P.; Moskalenko, N.; Orekhov, P.; Matyshak, G.; Forbes, B. C.; Yu, Q.

    2009-12-01

    Analyses of vegetation properties along climatic gradients provide first order approximations as to how vegetation might respond to a temporally dynamic climate. Until recently, no systematic study of tundra vegetation had been conducted along bioclimatic transects that represent the full latitudinal extent of the arctic tundra biome. Since 1999, we have been collecting data on arctic tundra vegetation and soil properties along two such transects, the North American Arctic Transect (NAAT) and the Yamal Arctic Transect (YAT). The NAAT spans the arctic tundra from the Low Arctic of the North Slope of Alaska to the polar desert of Cape Isachsen on Ellef Ringnes Island in the Canadian Archipelago. The Yamal Arctic Transect located in northwest Siberia, Russia, presently ranges from the forest-tundra transition at Nadym to the High Arctic tundra on Belyy Ostrov off the north coast of the Yamal Peninsula. The summer warmth indices (SWI - sum of mean monthly temperatures greater than 0°C) range from approximately 40 °C months to 3 °C months from south to north. For largely zonal sites along these transects, we systematically collected leaf area index (LAI-2000 Plant Canopy Analyzer), normalized difference vegetation index (NDVI - PSII hand-held spectro-radiometer), and vegetation biomass (clip harvests). Site-averaged LAI ranges from 1.08 to 0 along the transects, yet can be highly variable at the landscape scale. Site-averaged NDVI ranges from 0.67 to 0.26 along the transects, and is less variable than LAI at the landscape scale. Total aboveground live biomass ranges from approximately 700 g m-2 to < 50 g m-2 along the NAAT, and from approximately 1100 g m-2 to < 400 g m-2 along the YAT (not including tree biomass at Nadym). LAI and NDVI are highly correlated logarithmically (r = 0.80) for the entire dataset. LAI is significantly related to total aboveground (live plus dead) vascular plant biomass, although there is some variability in the data (r = 0.63). NDVI is

  9. A Survey of Submerged Aquatic Vegetation in Three Sub-arctic Lakes near Abisko, Sweden

    NASA Astrophysics Data System (ADS)

    Sampson, J.; Stilson, K.; Varner, R. K.; Crill, P. M.; Wik, M.; Crawford, M.

    2014-12-01

    We surveyed the submerged aquatic vegetation (SAV) in three sub-arctic lakes (Mellan Harrsjön, Inre Harrsjön, and Villasjön) located near Abisko in northern Sweden. Samples were collected using an extended rake, after which they were photographed and the plants identified. We also collected environmental data including temperature, dissolved oxygen, and secchi depth. Percent cover of SAV was taken twice using a 0.5 m. quadrat in shallow areas to track the changes in vegetation growth over time. In addition, we tested surface sediment samples for grain size and carbon, hydrogen, nitrogen, and sulfur composition. The percent cover of SAV in Mellan Harrsjön varied from 36%-49% and in Inre Harrsjön it averaged 19%. Across all three lakes, the average percent clay, silt, and sand was 3.8%, 50.1%, 46%, respectively. Because little research similar to this has been conducted in the area in such a comprehensive manner, these results are important to establish a baseline. Furthermore, these data will help establish how the SAV and environmental data may contribute to methane production and emission in these sub-arctic lakes.

  10. Vegetation Types in Coastal Louisiana in 2007

    USGS Publications Warehouse

    Sasser, Charles E.; Visser, Jenneke M.; Mouton, Edmond; Linscombe, Jeb; Hartley, Steve B.

    2008-01-01

    During the summer and fall of 2007, the U.S. Geological Survey, the Louisiana State University Agricultural Center, and the Louisiana Department of Wildlife and Fisheries Fur and Refuge Division jointly completed an aerial survey to collect data on 2007 vegetation types in coastal Louisiana. The current map presents the data collected in this effort. The 2007 aerial survey was conducted by using techniques developed over the last thirty years while conducting similar vegetation surveys. Transects flown were oriented in a north-south direction and spaced 1.87 mi (3 km) apart and covered coastal marshes from the Texas State line to the Mississippi State line and from the northern extent of fresh marshes to the southern end of saline (saltwater) marshes on the beaches of the Gulf of Mexico or of coastal bays. Navigation along these transects and to each sampling site was accomplished by using Global Positioning System (GPS) technology and geographic information system (GIS) software. As the surveyors reached each sampling station, observed areas of marsh were assigned as fresh, intermediate, brackish, or saline (saltwater) types, and dominant plant species were listed and ranked according to abundance. Delineations of marsh boundaries usually followed natural levees, bayous, or other features that impede or restrict water flow.

  11. Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

    USGS Publications Warehouse

    Stow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.; Noyle, B.; Silapaswan, C.; Douglas, D.; Griffith, B.; Jia, G.; Epstein, H.; Walker, D.; Daeschner, S.; Petersen, A.; Zhou, L.; Myneni, R.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. ?? 2003 Elsevier Inc. All rights reserved.

  12. Remote sensing of vegetation and land-cover change in Arctic tundra ecosystems

    USGS Publications Warehouse

    Checkstow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.

  13. Landscape dynamics in the Arctic foothills: Landscape evolution and vegetation succession on disturbances

    SciTech Connect

    Walker, D.A.; Walker, M.D.

    1990-10-20

    This document contains a summary of research accomplished by the University of Colorado's Institute of Arctic and Alpine Research (INSTAAR) Joint Facility for Regional Ecosystem Analysis (JFREA) for the Department of Energy's R D research program for 1989--1990. Aerial photographs, orthophoto topographic maps, and digital elevation models (DEMs) of the Toolik Lake region site were prepared by Aeromap US at 1:500 and 1:5000 scales. During August 1990, the region surrounding Toolik Lake was mapped at 1:5000 scale, and the intensive research grid was mapped at 1:500 scale. Mapped variables include vegetation, landforms, surface forms, and percentage surface water. Soil data from the Imnavait Creek and Toolik Lake sites are central to the analysis of landscape evolution. Soils were collected from the base of the O horizon at 72 gridpoints on the 1:500-scale map area at Imnavait Creek, and 85 grid points at Toolik Lake. Soils are being analyzed for percentage moisture, pH (saturated paste), electrical conductivity, percentage organic matter, nitrate, nitrogen, phosphorus, potassium, iron, manganese, copper. Soils were also collected from 81 permanent plots (199 horizons) which will be used for vegetation-environmental analyses. Permanent 1 {times} 1-meter point-quadrat plots were established at 85 points of the Toolik Lake grid. Data from the plots will be stratified according to slope position and terrain unit and used to compare vegetation structure and cover on different aged surfaces. Work continued on the study of the effects of road dust on tundra vegetation. 28 figs.

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-08-19

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

  16. Impact of interactive vegetation phenology on the simulated pan-Arctic land surface state

    NASA Astrophysics Data System (ADS)

    Teufel, Bernardo; Sushama, Laxmi

    2016-04-01

    The pan-Arctic land surface is undergoing rapid changes in a warming climate, with near-surface permafrost projected to degrade significantly during the 21st century. This can have important impacts on the regional climate and hydrology through various feedbacks, including vegetation-related feedbacks. In this study, the impact of interactive phenology on the land surface state, including near-surface permafrost, is assessed by comparing two simulations of the Canadian Land Surface Scheme (CLASS) - one with interactive phenology, modelled using the Canadian Terrestrial Ecosystem Model (CTEM), and the other with prescribed phenology. These simulations are performed for the 1979-2012 period, using atmospheric forcing from ECMWF's ERA-Interim reanalysis. The impact of interactive phenology on projected changes to the land surface state are also assessed by comparing two simulations of CLASS (with and without interactive phenology), spanning the 1961-2100 period, driven by atmospheric forcing from a transient climate change simulation of the 5th generation Canadian Regional Climate Model (CRCM5) for the Representative Concentration Pathway 8.5 (RCP8.5). Comparison of the CLASS coupled to CTEM simulation with available observational estimates of plant area index, primary productivity, spatial distribution of permafrost and active layer thickness suggests that the model captures reasonably well the general distribution of vegetation and permafrost. Significant differences in evapotranspiration, leading to differences in runoff, soil temperature and active layer thickness are noted when comparing CLASS simulations with and without interactive phenology. Furthermore, the CLASS simulations with and without interactive phenology for RCP8.5 show extensive near-surface permafrost degradation by the end of the 21st century, with slightly accelerated degradation of permafrost in the simulation with interactive phenology, pointing towards a positive feedback of changes in

  17. Early Cretaceous vegetation and climate change at high latitude: palynological evidence from Isachsen Formation, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Galloway, Jennifer M.; Tullius, Dylan N.; Evenchick, Carol A.; Swindles, Graeme T.; Hadlari, Thomas; Embry, Ashton

    2015-04-01

    Understanding the behaviour of global climate during relatively warm periods in Earth's history, such as the Cretaceous Period, advances our overall understanding of the climate system and provides insight on drivers of climate change over geologic time. While it has been suggested that the Valanginian Age represents the first episode of Cretaceous greenhouse climate conditions with relatively equable warm temperatures, mounting evidence suggests that this time was relatively cool. A paucity of paleoclimate data currently exists for polar regions compared to mid- and low-latitudes and this is particularly true for the Canadian Arctic. There is also a lack of information about the terrestrial realm as most paleoclimate studies have been based on marine material. Here we present quantitative pollen and spore data obtained from the marginal marine and deltaic-fluvial Isachsen Formation of the Sverdrup Basin, Canadian Arctic, to better understand the long-term vegetation and climate history of polar regions during the warm but variable Early Cretaceous (Valanginian to Early Aptian). Detrended correspondence analysis of main pollen and spore taxa is used to derive three ecological groupings influenced by moisture and disturbance based on the botanical affinities of palynomorphs: 1) a mixed coniferous assemblage containing both lowland and upland components; 2) a conifer-filicopsid community that likely grew in dynamic lowland habitats; and, 3) a mature dry lowland community composed of Cheirolepidaceans. Stratigraphic changes in the relative abundance of pollen and spore taxa reflect climate variability in this polar region during the ~20 Mya history of the Isachsen Formation. The late Valanginian was relatively cool and moist and promoted lowland conifer-filicopsid communities. Warming in the Hauterivian resulted in the expansion coniferous communities in well-drained or arid hinterlands. A return to relatively cool and moist conditions in the Barremian resulted in the

  18. Multisite comparison of drivers of methane emissions from wetlands in the European Arctic: influence of vegetation community and water table.

    NASA Astrophysics Data System (ADS)

    Dinsmore, Kerry; Drewer, Julia; Leeson, Sarah; Skiba, Ute; Levy, Pete; George, Charles

    2014-05-01

    Arctic and sub arctic wetlands are a major source of atmospheric CH4 and therefore have the potential to be important in controlling global radiative forcing. Furthermore, the strong links between wetland CH4 emissions and vegetation community, hydrology and temperature suggest potentially large feedbacks between climate change and future emissions. Quantifying current emissions over large spatial scales and predicting future climatic feedbacks requires a fundamental understanding of the ground based drivers of plot scale emissions. The MAMM project (Methane in the Arctic: Measurements and Modelling) aims to understand and quantify current CH4 emissions and future climatic impacts by combining both ground and aircraft measurements across the European Arctic with regional computer modelling. Here we present results from the ground-based MAMM measurement campaigns, analysing chamber-measured CH4 emissions from two sites in the European Arctic/Sub-Arctic region (Sodankylä, Finland; Stordalen Mire, Sweden) from growing seasons in 2012 and 2013. A total of 85 wetland static chambers were deployed across the two field sites; 39 at Sodankylä (67° 22'01' N, 26° 3'06' E) in 2012 and 46 at Stordalen Mire (68° 21'20' N, 19° 02'56' E) in 2013. Chamber design, protocol and deployment were the same across both sites. Chambers were located at sites chosen strategically to cover the local range of water table depths and vegetation communities. A total of 18 and 15 repeated measurements were made at each chamber in Sodankylä and Stordalen Mire, respectively, over the snow-free season. Preliminary results show a large range of CH4 fluxes across both sites ranging from a CH4 uptake of up to 0.07 and 0.06 mg CH4-C m-2 hr-1 to emissions of 17.3 and 44.2 mg CH4-C m-2 hr-1 in Sodankylä and Stordalen Mire, respectively. Empirical models based on vegetation community, water table depth, temperature and soil nutrient availability (Plant Root Simulator Probes, PRSTM) have been

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

    NASA Astrophysics Data System (ADS)

    Yu, Qin; Epstein, Howard; Walker, Donald

    2009-10-01

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

  20. Correlations between the Heterogeneity of Permafrost Thaw Depth and Vegetation in Boreal Forests and Arctic Tundra in Alaska.

    NASA Astrophysics Data System (ADS)

    Uy, K. L. Q.; Natali, S.; Kholodov, A. L.; Loranty, M. M.

    2015-12-01

    Global climate change induces rapid large scale changes in the far Northern regions of the globe, which include the thickening of the active layer of arctic and subarctic soils. Active layer depth, in turn, drives many changes to the hydrology and geochemistry of the soil, making an understanding of this layer essential to boreal forest and arctic tundra ecology. Because the structure of plant communities can affect the thermal attributes of the soil, they may drive variations in active layer depth. For instance, trees and tussocks create shade, which reduces temperatures, but also hold snow, which increases temperature through insulation; these aspects of vegetation can increase or decrease summer thaw. The goal of this project is to investigate correlations between the degree of heterogeneity of active layer depths, organic layer thickness, and aboveground vegetation to determine how these facets of Northern ecosystems interact at the ecosystem scale. Permafrost thaw and organic layer depths were measured along 20m transects in twenty-four boreal forest and tundra sites in Alaska. Aboveground vegetation along these transects was characterized by measuring tree diameter at breast height (DBH), tussock dimensions, and understory biomass. Using the coefficient of variation as a measure of heterogeneity, we found a positive correlation between thaw depth variability and tussock volume variability, but little correlation between the former and tree DBH variability. Soil organic layer depth variability was also positively correlated with thaw depth variability, but weakly correlated with tree and tussock heterogeneity. These data suggest that low vegetation and organic layer control the degree of variability in permafrost thaw at the ecosystem scale. Vegetation can thus affect the microtopography of permafrost and future changes in the plant community that affect vegetation heterogeneity will drive corresponding changes in the variability of the soil.

  1. Pan-Arctic linkages between snow accumulation and growing-season air temperature, soil moisture and vegetation

    NASA Astrophysics Data System (ADS)

    Luus, K. A.; Gel, Y.; Lin, J. C.; Kelly, R. E. J.; Duguay, C. R.

    2013-11-01

    Arctic field studies have indicated that the air temperature, soil moisture and vegetation at a site influence the quantity of snow accumulated, and that snow accumulation can alter growing-season soil moisture and vegetation. Climate change is predicted to bring about warmer air temperatures, greater snow accumulation and northward movements of the shrub and tree lines. Understanding the responses of northern environments to changes in snow and growing-season land surface characteristics requires: (1) insights into the present-day linkages between snow and growing-season land surface characteristics; and (2) the ability to continue to monitor these associations over time across the vast pan-Arctic. The objective of this study was therefore to examine the pan-Arctic (north of 60° N) linkages between two temporally distinct data products created from AMSR-E satellite passive microwave observations: GlobSnow snow water equivalent (SWE), and NTSG growing-season AMSR-E Land Parameters (air temperature, soil moisture and vegetation transmissivity). Due to the complex and interconnected nature of processes determining snow and growing-season land surface characteristics, these associations were analyzed using the modern nonparametric technique of alternating conditional expectations (ACE), as this approach does not impose a predefined analytic form. Findings indicate that regions with lower vegetation transmissivity (more biomass) at the start and end of the growing season tend to accumulate less snow at the start and end of the snow season, possibly due to interception and sublimation. Warmer air temperatures at the start and end of the growing season were associated with diminished snow accumulation at the start and end of the snow season. High latitude sites with warmer mean annual growing-season temperatures tended to accumulate more snow, probably due to the greater availability of water vapor for snow season precipitation at warmer locations. Regions with drier

  2. Classification of vegetation types in military region

    NASA Astrophysics Data System (ADS)

    Gonçalves, Miguel; Silva, Jose Silvestre; Bioucas-Dias, Jose

    2015-10-01

    In decision-making process regarding planning and execution of military operations, the terrain is a determining factor. Aerial photographs are a source of vital information for the success of an operation in hostile region, namely when the cartographic information behind enemy lines is scarce or non-existent. The objective of present work is the development of a tool capable of processing aerial photos. The methodology implemented starts with feature extraction, followed by the application of an automatic selector of features. The next step, using the k-fold cross validation technique, estimates the input parameters for the following classifiers: Sparse Multinomial Logist Regression (SMLR), K Nearest Neighbor (KNN), Linear Classifier using Principal Component Expansion on the Joint Data (PCLDC) and Multi-Class Support Vector Machine (MSVM). These classifiers were used in two different studies with distinct objectives: discrimination of vegetation's density and identification of vegetation's main components. It was found that the best classifier on the first approach is the Sparse Logistic Multinomial Regression (SMLR). On the second approach, the implemented methodology applied to high resolution images showed that the better performance was achieved by KNN classifier and PCLDC. Comparing the two approaches there is a multiscale issue, in which for different resolutions, the best solution to the problem requires different classifiers and the extraction of different features.

  3. Use of the Normalized Difference Vegetation Index to Assess Vegetative Nutritive Value in Halophytic Graminoid Habitat across Alaska's Arctic Coastal Plain

    NASA Astrophysics Data System (ADS)

    Hogrefe, K. R.; Ward, D. H.; Budde, M. E.; Ruthrauff, D. R.; Hupp, J. W.

    2015-12-01

    Climate change will likely alter the seasonal nutrient abundance and general distribution of halophytic graminoid (salt marsh) habitat across the Arctic Coastal Plain. Halophytic graminoids are key forage for newly hatched Black Brant, Lesser Snow and Greater White-fronted Geese and the timing and degree of seasonal nutrient abundance in these plants is critical for gosling growth and survival. After 5 years of research (culminating in 2015) under the USGS Alaska Science Center's Changing Arctic Ecosystems Initiative, we found strong relationships between the Normalized Difference Vegetation Index (NDVI) and nutrient abundance (N g/m2) and availability (%N) in halophytic graminoid habitat. The relationships between NDVI and nutrient abundance and availability were strong whether using NDVI derived from high (spectrometer), moderate (WorldView-2 satellite) or low (eMODIS satellite) resolution data. Correlations established and validated at one location were used to predict nutrient abundance using NDVI readings from other locations, allowing interpretation of satellite derived NDVI in terms of nutrient abundance across broad areas of mapped salt marsh habitat. Further, NDVI seasonal timelines were used to predict the timing of peak nutrient availability using the period of most rapid increase in NDVI value. Currently, we are using WorldView-2 imagery to create vegetation maps of the central Arctic coastal zone (~20 km inland) of Alaska, covering approximately 1000 km of coastline, with a focus on identifying all salt marshes. Such maps will enable monitoring programs and allow for modeling to predict spatial and temporal changes in halophytic graminoid habitat and the nutrients available to geese in the early stages of life.

  4. Trends in the normalized difference vegetation index (NDVI) associated with urban development in arctic and subarctic Western Siberia

    NASA Astrophysics Data System (ADS)

    Outten, S.; Miles, V.; Ezau, I.

    2015-12-01

    Changes in normalized difference vegetation index (NDVI) in the high Arctic have been reliably documented, with widespread "greening" (increase in NDVI), specifically along the northern rim of Eurasia and Alaska. Whereas in West Siberia south of 65N, widespread "browning" (decrease in NDVI) has been noted, although the causes remain largely unclear. In this study we report results of statistical analysis of the spatial and temporal changes in NDVI around 28 major urban areas in the arctic and subarctic Western Siberia. Exploration and exploitation of oil and gas reserves has led to rapid industrialization and urban development in the region. This development has significant impact on the environment and particularly in the vegetation cover in and around the urbanized areas. The analysis is based on 15 years (2000-2014) of high-resolution (250 m) Moderate Resolution Imaging Spectroradiometer (MODIS) data acquired for summer months (June through August) over the entire arctic and subarctic Western Siberian region. The analysis shows that the NDVI background trends are generally in agreement with the trends reported in previous coarse-resolution NDVI studies. Our study reveals greening over the arctic (tundra and tundra-forest) part of the region. Simultaneously, the southern (boreal taiga forest) part is browning, with the more densely vegetation areas or areas with highest NDVI, particularly along Ob River showing strong negative trend. The unexpected and interesting finding of the study is statistically robust indication of the accelerated increase of NDVI ("greening") in the older urban areas. Many Siberian cities become greener even against the decrease in the NDVI background. Moreover, interannual variations of urban NDVI are not coherent with the NDVI background variability. We also find that in tundra zones, NDVI values are higher in a 5-10 km buffer zone around the city edge than in rural areas (40 km distance from the city edge), and in taiga in a 5-10 km

  5. Effect of vegetation on rock and soil type discrimination

    NASA Technical Reports Server (NTRS)

    Siegal, B. S.; Goetz, A. F. H.

    1977-01-01

    The effect of naturally occurring vegetation on the spectral reflectance of earth materials in the wavelength region of 0.45 to 2.4 microns is determined by computer averaging of in situ acquired spectral data. The amount and type of vegetation and the spectral reflectance of the ground are considered. Low albedo materials may be altered beyond recognition with only ten per cent green vegetation cover. Dead or dry vegetation does not greatly alter the shape of the spectral reflectance curve and only changes the albedo with minimum wavelength dependency. With increasing amounts of vegetation the Landsat MSS band ratios 4/6, 4/7, 5/6, and 5/7 are significantly decreased whereas MSS ratios 4/5 and 6/7 remain entirely constant.

  6. Variation in Factors Regulating Net Greenhouse Gas Exchange Across Different Vegetation Types at Cape Bounty, Melville Island, Nunavut

    NASA Astrophysics Data System (ADS)

    Scott, N. A.; Blaser, A.; Buckley, E.; Humphreys, E.; Treitz, P.

    2015-12-01

    Global-scale climate simulations predict significant changes both in temperature and moisture regimes in the high Arctic. This could lead to changes in vegetation community distribution, as vegetation communities are distributed along moisture gradients often determined by snowfall patterns across the landscape. Furthermore, changes in soil moisture and temperature could alter fluxes of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), and the impacts of changes in these controlling factors could vary by vegetation type.We measured both spatial and temporal variation in CO2 fluxes using combinations of eddy covariance, auto-chamber, and static chamber techniques at the Cape Bounty Arctic Watershed Observatory (CBAWO). Measurements were performed in three major plant community types: polar semi-desert (PSD), mid-moisture tundra (MM) and wet sedge meadow (WS). Based on our auto-chamber data collected in all vegetation types, ecosystem respiration (ER) related positively to air temperature, and correlated more strongly with air temperature than soil temperature. Modeled ER based on eddy covariance data and air temperature over MM agreed well with measured ER in the same vegetation type. In the WS community, average net ecosystem exchange (NEE) in 2014 measured by static chambers differed in spectrally separable 'wet' and 'dry' sedge areas (-0.33 and 0.01 µmol m-2 s-1, respectively; p<0.001). Rates of ER also varied across this moisture gradient (p<0.05). Over the entire growing season and multiple years, NEE correlated poorly with air and soil temperature, suggesting that ER is not the dominant processes driving NEE. This can vary, however, over the growing season. In PSD communities measured in 2013, air temperature related positively to NEE early in the growing season, but not during the latter part of the season, when PAR (photosynthesis) became the key factor controlling NEE. Not surprisingly, NEE related strongly (0.93) to

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

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.

    2009-12-01

    Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world’s largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model (ArcVeg) to evaluate how two factors (soil organic nitrogen [SON] levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (High Arctic), D (northern Low Arctic) and E (southern Low Arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 °C caused an increase of 665 g/m2 in total biomass at the high SON site in subzone E, while only 298 g/m2 in the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g/m2 in the high SON site in contrast to 184 g/m2 in the low SON site in subzone E. When comparing low grazing to high grazing effects on soil organic nitrogen pools over time (Figure 1), higher grazing frequency led to either slower SON accumulation rates or more rapid SON depletion rates. Warming accentuated these differences caused by grazing, suggesting the interaction between grazing and warming may yield greater differences in SON levels across sites. Our results suggest that low SON and grazing may limit plant response to climate change. Interactions among bioclimate subzones, soils, grazing and warming significantly affect plant biomass and productivity in

  8. Classification of simple vegetation types using POLSAR image data

    NASA Technical Reports Server (NTRS)

    Freeman, A.

    1993-01-01

    Mapping basic vegetation or land cover types is a fairly common problem in remote sensing. Knowledge of the land cover type is a key input to algorithms which estimate geophysical parameters, such as soil moisture, surface roughness, leaf area index or biomass from remotely sensed data. In an earlier paper, an algorithm for fitting a simple three-component scattering model to POLSAR data was presented. The algorithm yielded estimates for surface scatter, double-bounce scatter and volume scatter for each pixel in a POLSAR image data set. In this paper, we show how the relative levels of each of the three components can be used as inputs to simple classifier for vegetation type. Vegetation classes include no vegetation cover (e.g. bare soil or desert), low vegetation cover (e.g. grassland), moderate vegetation cover (e.g. fully developed crops), forest and urban areas. Implementation of the approach requires estimates for the three components from all three frequencies available using the NASA/JPL AIRSAR, i.e. C-, L- and P-bands. The research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration.

  9. Effect of vegetation type on throughfall deposition and seepage flux.

    PubMed

    De Schrijver, A; Staelens, J; Wuyts, K; Van Hoydonck, G; Janssen, N; Mertens, J; Gielis, L; Geudens, G; Augusto, L; Verheyen, K

    2008-05-01

    This paper compares different vegetation types (coniferous and deciduous forest, grassed and pure heathland) in terms of input (throughfall deposition) and output (seepage flux) in a region with intermediate nitrogen load (+/-20kg Nha(-1)y(-1) via bulk precipitation) in comparable conditions in north Belgium. Coniferous forest (two plots Pinus sylvestris and two plots Pinus nigra) received significantly higher nitrogen and sulphur throughfall deposition than deciduous forest and heathland. Grassed and pure heathland had significantly highest throughfall quantities of Ca(2+) and Mg(2+), respectively. The observed differences in throughfall deposition between the different vegetation types were not univocally reflected in the ion seepage flux. Considerable seepage fluxes of NO(3)(-), SO(4)(2-), Ca(2+) and Al(III) were only found under the P. nigra plots. We discuss our hypothesis that the P. nigra forests already evolved to a situation of N saturation, while the other vegetation types did not.

  10. Transitions in High-Arctic Vegetation Growth Patterns and Ecosystem Productivity from 2000-2013 Tracked with Cameras

    NASA Astrophysics Data System (ADS)

    Westergaard-Nielsen, A.; Hansen, B. U.; Klosterman, S.; Pedersen, S. H.; Schmidt, N. M.; Abermann, J.; Lund, M.

    2015-12-01

    The changes in vegetation seasonality in high northern latitudes resulting from changes atmospheric temperatures and precipitation are still not well understood. Continued monitoring and research is therefore needed. In this study we use 13 years of time lapse camera data and climate data from high-Arctic Northeast Greenland to assess the seasonal response of a dwarf shrub heath, grassland, and fens to snow cover, soil moisture, and atmospheric and soil temperatures. Based on the camera data, we computed a greenness index which was subsequently used to analyze transition dates in vegetation seasonality. We show that snow cover and subsequent water from the melting snow pack is highly important for the seasonality. We found a significant advancement in start of growing season of 12 days but not a significant increase in growing season length. Both the timing and greenness index value of peak of growing season was significantly correlated to the available water in the pre-melt snow pack, mostly pronounced in vegetation with limited soil water. The end of growing season was likewise significantly correlated to the water equivalents in the pre-melt snowpack. Moreover, the vegetation greenness was highly correlated to GPP, and shifts in seasonality as tracked by the greenness index are thus expected to have direct influence on ecosystem productivity.

  11. ARCTIC VEGETATION AND SOIL DATABASE OF ORGANOCHLORINE PESTICIDES AND PCBS IN ALASKA AND SIBERIA

    EPA Science Inventory

    The US EPA Office of Research and Development conducted the Arctic Contaminant Research Program (Landers, D. H. et al. 1992) from 1991 to 1994 through the Corvallis, Oregon, research laboratory. The purpose of this effort was to evaluate the evidence for atmospheric contaminatio...

  12. Soil microbial properties under different vegetation types on Mountain Han.

    PubMed

    Wang, Miao; Qu, Laiye; Ma, Keming; Yuan, Xiu

    2013-06-01

    This study investigated the influence of broadleaf and conifer vegetation on soil microbial communities in a distinct vertical distribution belt in Northeast China. Soil samples were taken at 0-5, 5-10 and 10-20 cm depths from four vegetation types at different altitudes, which were characterized by poplar (Populus davidiana) (1250-1300 m), poplar (P. davidiana) mixed with birch (Betula platyphylla) (1370-1550 m), birch (B. platyphylla) (1550-1720 m), and larch (Larix principis-rupprechtii) (1840-1890 m). Microbial biomass and community structure were determined using the fumigation-extraction method and phospholipid fatty acid (PLFA) analysis, and soil fungal community level physiological profiles (CLPP) were characterized using Biolog FF Microplates. It was found that soil properties, especially soil organic carbon and water content, contributed significantly to the variations in soil microbes. With increasing soil depth, the soil microbial biomass, fungal biomass, and fungal catabolic ability diminished; however, the ratio of fungi to bacteria increased. The fungal ratio was higher under larch forests compared to that under poplar, birch, and their mixed forests, although the soil microbial biomass was lower. The direct contribution of vegetation types to the soil microbial community variation was 12%. If the indirect contribution through soil organic carbon was included, variations in the vegetation type had substantial influences on soil microbial composition and diversity.

  13. Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the aboveground vegetation.

    PubMed

    Mundra, Sunil; Halvorsen, Rune; Kauserud, Håvard; Müller, Eike; Vik, Unni; Eidesen, Pernille B

    2015-03-01

    Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3-3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation. PMID:25483568

  14. Arctic fungal communities associated with roots of Bistorta vivipara do not respond to the same fine-scale edaphic gradients as the aboveground vegetation.

    PubMed

    Mundra, Sunil; Halvorsen, Rune; Kauserud, Håvard; Müller, Eike; Vik, Unni; Eidesen, Pernille B

    2015-03-01

    Soil conditions and microclimate are important determinants of the fine-scale distribution of plant species in the Arctic, creating locally heterogeneous vegetation. We hypothesize that root-associated fungal (RAF) communities respond to the same fine-scale environmental gradients as the aboveground vegetation, creating a coherent pattern between aboveground vegetation and RAF. We explored how RAF communities of the ectomycorrhizal (ECM) plant Bistorta vivipara and aboveground vegetation structure of arctic plants were affected by biotic and abiotic variables at 0.3-3.0-m scales. RAF communities were determined using pyrosequencing. Composition and spatial structure of RAF and aboveground vegetation in relation to collected biotic and abiotic variables were analysed by ordination and semi-variance analyses. The vegetation was spatially structured along soil C and N gradients, whereas RAF lacked significant spatial structure. A weak relationship between RAF community composition and the cover of two ECM plants, B. vivipara and S. polaris, was found, and RAF richness increased with host root length and root weight. Results suggest that the fine-scale spatial structure of RAF communities of B. vivipara and the aboveground vegetation are driven by different factors. At fine spatial scales, neighbouring ECM plants may affect RAF community composition, whereas soil nutrients gradients structure the vegetation.

  15. Field method for isolation of trichostrongyle larvae from vegetation of natural pastures of Arctic ruminants.

    PubMed

    Raundrup, K; Clemmensen, S; Forchhammer, M C; Kapel, C M O

    2003-04-01

    The extent to which wild ruminant populations are exposed to infective helminth larvae on their natural pastures is relatively undetermined. In the present study, a modified method for sampling of herbage and isolation of trichostrongyle infective third-stage larvae from natural pastures was used successfully in a muskox habitat in low-Arctic Greenland. The method, a revision of the Macro-Baermann method, is particularly aimed at fieldwork under primitive conditions.

  16. Field method for isolation of trichostrongyle larvae from vegetation of natural pastures of Arctic ruminants.

    PubMed

    Raundrup, K; Clemmensen, S; Forchhammer, M C; Kapel, C M O

    2003-04-01

    The extent to which wild ruminant populations are exposed to infective helminth larvae on their natural pastures is relatively undetermined. In the present study, a modified method for sampling of herbage and isolation of trichostrongyle infective third-stage larvae from natural pastures was used successfully in a muskox habitat in low-Arctic Greenland. The method, a revision of the Macro-Baermann method, is particularly aimed at fieldwork under primitive conditions. PMID:12760673

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

    USGS Publications Warehouse

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

    2014-01-01

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

  18. How Spatial Variation in Areal Extent and Configuration of Labile Vegetation States Affect the Riparian Bird Community in Arctic Tundra

    PubMed Central

    Henden, John-André; Yoccoz, Nigel G.; Ims, Rolf A.; Langeland, Knut

    2013-01-01

    The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation of willow thickets

  19. How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra.

    PubMed

    Henden, John-André; Yoccoz, Nigel G; Ims, Rolf A; Langeland, Knut

    2013-01-01

    The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation of willow thickets

  20. A hierarchic approach to examining panArctic vegetation with a focus on the linkages between remote sensing and plot-based studies.

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Daniëls, F. J. A.; Alsos, I. G.; Bhatt, U. S.; Breen, A. L.; Buchhorn, M.; Bültmann, H.; Edwards, M. E.; Ehrich, D.; Epstein, H. E.; Gould, W. A.; Ims, R. A.; Meltofte, H.; Murray, D. F.; Raynolds, M. K.; Talbot, S. S.

    2015-12-01

    A circumpolar view of Arctic vegetation developed with the advent of satellite-derived remote-sensing products. Interpretations of what the revealed patterns mean are dependent on a foundation of in-situ plot-based observations. Despite the importance of ground-based observations, only a few areas have been intensively sampled and mapped, mainly in the vicinity of permanent Arctic observatories. Much of the information is project specific and is based on sampling protocols that are difficult to compare across sites. Here, we demonstrate a more consistent multi-level hierarchic approach for vegetation description and analysis at the Toolik Lake Field Station, Alaska. We advocate for a well-coordinated, interdisciplinary network of vegetation observation stations. Key recommendations include: (1) Complete local floras for many more areas in than presently exist. Species names should be standardized using the Pan-Arctic Flora. (2) Permanently marked and replicated vegetation monitoring plots in the full range of habitats at each station. Methods of establishing and monitoring the plots should include consistent internationally accepted standards for vegetation data collection, vegetation classification, plot markings, and standardized approaches to describe the local environment, including photo points showing the vegetation and soils up close and in landscape view. (3) Standardized approaches for collecting in-situ time-series of spectral data. Standardized methods for collecting and analyzing phytomass data are especially needed. (4) Interdisciplinary studies. Vegetation observations should be conducted in concert with observations of soils, permafrost, animals and ecosystem processes at the same plots. (5) Periodic (perhaps every 5-10 years) ground-based surveys. These should include surveys of species composition, canopy structure, biomass, leaf-area index, and NDVI, along with high-resolution satellite-based remote-sensing products at the same time.

  1. Wildfire, thermokarst and vegetation change: integrating diverse controls over carbon cycling in arctic and boreal ecosystems

    NASA Astrophysics Data System (ADS)

    Mack, M. C.; Alexander, H. D.; DeMarco, J.; Melvin, A.

    2012-12-01

    Climate is warming more rapidly in the tundra and forests of high northern latitudes than any other place on earth. Large, globally-important stocks of carbon (C) reside in these ecosystems. Characterized by cold, moist climate and frozen soils, these ecosystems have historically acted as a net sink for atmospheric C: they remove more C from the atmosphere on an annual basis than they release, resulting in the accumulation of large stocks in soils and plants. With warming climate comes the potential for fundamental changes in ecological controls over C cycling. Plant growth is limited by both low temperature and the slow regeneration of nutrients such as nitrogen (N). If warming stimulates plant growth by alleviating these limitations, than C uptake may increase. Indeed, satellite indices of greening as well as observations of shrub expansion and northern migration of the arctic treeline point towards increased plant productivity concurrent with climate warming. But as soils warm, microbial decomposition and release of C to the atmosphere, as well as disturbances such as wildfire or thermal erosion (thermokarst), are likely to increase, and it is unclear whether increased C loss may balance or even outweigh increased production, at least on the time-scale of decades to centuries. Understanding the net outcome of these two processes is important because it determines the sign of the feedback between the arctic/boreal C cycle and climate. A positive feedback, where warming increases C losses more than uptake, would amplify anthropogenic changes in climate, accelerating warming and destabilizing feedbacks between ecosystems and the atmosphere. A negative feedback, by contrast, where warming increases C uptake more than losses, would dampen the anthropogenic signal and stabilize climate. This presentation will focus on three general areas of ecological control over net ecosystem C balance in arctic and boreal ecosystems: nutrient availability, changing disturbance

  2. Vegetation of the Savannah River Site: Major community types

    SciTech Connect

    Workman, S.W.; McLeod, K.W.

    1990-01-01

    The eight major plant community types of the Savannah River Site (SRS) are distributed along topographic and moisture gradients and strongly controlled by local management practices. Communities range from sandhill communities in the xeric uplands to bottomland or swamp forests in low-lying areas subject to periodic flooding. The variety of community types and extensive land area (78,000 ha) of the SRS provides habitat for a diversity of plant species. As a National Environmental Research Park, the SRS provides an area for study of man-altered systems in relation to natural systems. A site-wide Set-Aside Areas program designates specific parcels of land representing different community types on the SRS. These areas conserve habitat for plants and wildlife, including some endangered, threatened and rare species. This document provides descriptions, including community characteristics and species composition, for the eight major vegetation communities of the SRS (old field, sandhill, upland hardwood, pinelands, bottomland, swamp, Carolina bay and fresh water). Species lists of tree, shrub, vine, herbaceous, and lower plant species of the SRS, by community type, were compiled from existing literature, herbarium information, and solicited additions from researchers familiar with SRS vegetation; these are provided in appendices. 130 refs., 19 figs.

  3. Arctic vegetation damage by winter-generated coal mining pollution released upon thawing

    SciTech Connect

    Bo Elberling; Jens Soendergaard; Louise A. Jensen; Lea B. Schmidt; Birger U. Hansen; Gert Asmund; Tonci BalicZunic; Joergen Hollesen; Susanne Hanson; Per-Erik Jansson; Thomas Friborg

    2007-04-01

    Acid mine drainage (known as AMD) is a well-known environmental problem resulting from the oxidation of sulfidic mine waste. In cold regions, AMD is often considered limited by low temperatures most of the year and observed environmental impact is related to pollution generated during the warm summer period. Here we show that heat generation within an oxidizing, sulfidic, coal-mining waste-rock pile in Svalbard (Arctic Norway) (78{sup o}N) is high enough to keep the pile warm (roughly 5{sup o}C throughout the year) despite mean annual air temperatures below -5{sup o}C. Consequently, weathering processes continue year-round within the waste-rock pile which is characterised as a mixture of coal and a siltstone-mudstone. During the winter, weathering products accumulate within the pile because of a frozen outer layer on the pile and are released as a flush within 2 weeks of soil thawing in the spring. Consequently, spring runoff water contains elevated concentrations of metals. Several of these metals are taken up and accumulated in plants where they reach phytotoxic levels, including aluminum and manganese. Laboratory experiments document that uptake of Al and Mn in native plant species is highly correlated with dissolved concentrations. Therefore, future remedial actions to control the adverse environmental impacts of cold region coal-mining need to pay more attention to winter processes including AMD generation and accumulation of weathering products. 34 refs., 3 figs., 2 tabs.

  4. Changes in Arctic Vegetation Amplify High-Latitude Warming Through Greenhouse Effect

    NASA Astrophysics Data System (ADS)

    Swann, A.; Fung, I.; Levis, S.; Bonan, G. B.; Doney, S. C.

    2009-12-01

    Changes in vegetation cover are recognized to modify climate and the energy budget of the Earth through changes in albedo in high latitudes and evapotranspiration (ET) in the tropics. In snow-covered regions, the springtime growth of leaves enhances solar absorption because surface albedo is reduced from the albedo of snow (~0.8) towards the albedo of leaves (~0.1). Leaves also play a hydrologic role, transpiring soil water to the atmosphere. It has been suggested that broad-leaf deciduous trees may invade warming tundra more effectively than boreal evergreen trees and these trees have higher rates of transpiration than needle-leaf trees. Here we use a global climate model with an interactive biosphere to investigate the effects of adding deciduous trees on bare ground at high northern latitudes. We find that the top-of-atmosphere radiative imbalance from enhanced transpiration (associated with the expanded forest cover) is 2.4 times larger than the direct forcing due to albedo change from the forest. Albedo change is considered to be the dominant mechanism by which trees directly modify climate at high-latitudes, but our findings suggest an additional mechanism through transpiration. Furthermore, the greenhouse warming by additional water vapor melts sea ice and triggers a positive feedback through changes in ocean albedo and evaporation. Vegetation feedbacks through albedo and transpiration produce a strong warming if they act in combination with sea-ice processes.

  5. Soil microbial respiration from various microhabitats in Arctic landscape: impact of soil type, environmental conditions and soil age

    NASA Astrophysics Data System (ADS)

    Biasi, Christina; Jokinen, Simo; Marushchak, Maija; Trubnikova, Tatiana; Hämäläinen, Kai; Oinonen, Markku; Martikainen, Pertti

    2014-05-01

    Soil respiration is the second largest C flux between atmosphere and terrestrial ecosystems after gross primary production. Carbon dioxide released from soils is thus a major contributor to the atmospheric CO2 concentration. Despite the global importance, soil respiration and its components (heterotrophic and autotrophic respiration) remain poorly understood and not well constrained fluxes of the terrestrial C cycle. This is particularly true for the Arctic, where huge amounts of the Earth's soil carbon is stored. Here, we report on heterotrophic soil respiration rates from various Arctic tundra microhabitats measured in situ. The study site was Seida (67°07'N, 62°57'E, 100 m a.s.l.) which is characterized by typical sub-arctic permafrost landscape which comprises raised, vegetated permafrost peat plateaus, interspersed with spots of bare peat surfaces (peat circles), and upland mineral soils. We used isotope partitioning approach based on differences in natural abundance of 14C between soil and plants to separate sources of soil-respired CO2. In addition, the tradition trenching approach was employed. Complementary laboratory incubations with homogenized soil were conducted to assess primary decomposability of the soils and to identify age of the CO2 released and thus get more information on the nature of the sources of respiration. The major aim was to link SMR rates with of soil type, land cover class, soil physic-chemical properties (e.g. water content), soil C stocks and age of soil. Results show that, despite profound differences in soil characteristics and primary decomposability of organic matter, surface CO2 fluxes derived from soil microbial respiration rates were rather similar between microhabitats. The only factor which influenced, at least to some extent, the respiration rates was total soil C (and N) stocks in surface soils. There was some evidence for reduced soil-related CO2 emissions from peatlands, though results were not consistent between the

  6. Major vegetation types, climatological data, and solar radiation calculations for Colorado's Brush Creek valley

    SciTech Connect

    Whiteman, C.D.; Lambeth, R.; Allwine, K.J.

    1987-04-01

    In this report we present information on the vegetative cover, climate, and solar radiation for the Brush Creek valley. A brief vegetative survey was made on October 3, 1984, to identify the vegetation types in the lowest 8 km of the valley; the reader is cautioned that this included only a small part of the Brush Creek valley. The intent was to identify the principal vegetation types, with no attempt to use available scientific sampling techniques to determine accurate relative frequencies of the vegetation types. Nevertheless, the site survey has allowed us to identify the major species of vegetation, and to make reasonably accurate differentiations of both major vegetation types on valley surfaces (the valley floor, two sidewalls, and ridgetops) and the relative abundance of major vegetation types on each surface.

  7. Late Pliocene and Early Pleistocene vegetation history of northeastern Russian Arctic inferred from the Lake El'gygytgyn pollen record

    NASA Astrophysics Data System (ADS)

    Andreev, A. A.; Tarasov, P. E.; Wennrich, V.; Raschke, E.; Herzschuh, U.; Nowaczyk, N. R.; Brigham-Grette, J.; Melles, M.

    2014-05-01

    The 318 m thick lacustrine sediment record from Lake El'gygytgyn, northeastern Russian Arctic cored by the international El'gygytgyn Drilling Project provides unique opportunities for the time-continuous reconstruction of the regional paleoenvironmental history for the past 3.6 Myr. Pollen studies of the lower 216 m of the lacustrine sediments demonstrate their value as an excellent archive of vegetation and climate changes during the Late Pliocene and Early Pleistocene. About 3.5-3.35 Myr BP, the vegetation at Lake El'gygytgyn, now an area of tundra was dominated by spruce-larch-fir-hemlock forests. After ca. 3.35 Myr BP dark coniferous taxa gradually disappeared. A very pronounced environmental change took place ca. 3.31-3.28 Myr BP, corresponding to the Marine Isotope Stage (MIS) M2, when treeless tundra- and steppe-like habitats became dominant in the regional vegetation. Climate conditions were similar to those of Late Pleistocene cold intervals. Numerous coprophilous fungi spores identified in the pollen samples suggest the presence of grazing animals around the lake. Following the MIS M2 event, larch-pine forests with some spruce mostly dominated the area until ca. 2.6 Myr BP, interrupted by colder and drier intervals ca. 3.043-3.025, 2.935-2.912, and 2.719-2.698 Myr BP. At the beginning of the Pleistocene, ca. 2.6 Myr BP, noticeable climatic deterioration occurred. Forested habitats changed to predominantly treeless and shrubby environments, which reflect a relatively cold and dry climate. Peaks in observed green algae colonies (Botryococcus) around 2.53, 2.45, 2.32-2.305, 2.20 and 2.16-2.15 Myr BP suggest a spread of shallow water environments. A few intervals (i.e., 2.55-2.53, ca. 2.37, and 2.35-2.32 Myr BP) with a higher presence of coniferous taxa (mostly pine and larch) document some relatively short-term climate ameliorations during Early Pleistocene glacial periods.

  8. New vegetation type map of India prepared using satellite remote sensing: Comparison with global vegetation maps and utilities

    NASA Astrophysics Data System (ADS)

    Roy, P. S.; Behera, M. D.; Murthy, M. S. R.; Roy, Arijit; Singh, Sarnam; Kushwaha, S. P. S.; Jha, C. S.; Sudhakar, S.; Joshi, P. K.; Reddy, Ch. Sudhakar; Gupta, Stutee; Pujar, Girish; Dutt, C. B. S.; Srivastava, V. K.; Porwal, M. C.; Tripathi, Poonam; Singh, J. S.; Chitale, Vishwas; Skidmore, A. K.; Rajshekhar, G.; Kushwaha, Deepak; Karnatak, Harish; Saran, Sameer; Giriraj, A.; Padalia, Hitendra; Kale, Manish; Nandy, Subrato; Jeganathan, C.; Singh, C. P.; Biradar, C. M.; Pattanaik, Chiranjibi; Singh, D. K.; Devagiri, G. M.; Talukdar, Gautam; Panigrahy, Rabindra K.; Singh, Harnam; Sharma, J. R.; Haridasan, K.; Trivedi, Shivam; Singh, K. P.; Kannan, L.; Daniel, M.; Misra, M. K.; Niphadkar, Madhura; Nagabhatla, Nidhi; Prasad, Nupoor; Tripathi, O. P.; Prasad, P. Rama Chandra; Dash, Pushpa; Qureshi, Qamer; Tripathi, S. K.; Ramesh, B. R.; Gowda, Balakrishnan; Tomar, Sanjay; Romshoo, Shakil; Giriraj, Shilpa; Ravan, Shirish A.; Behera, Soumit Kumar; Paul, Subrato; Das, Ashesh Kumar; Ranganath, B. K.; Singh, T. P.; Sahu, T. R.; Shankar, Uma; Menon, A. R. R.; Srivastava, Gaurav; Neeti; Sharma, Subrat; Mohapatra, U. B.; Peddi, Ashok; Rashid, Humayun; Salroo, Irfan; Krishna, P. Hari; Hajra, P. K.; Vergheese, A. O.; Matin, Shafique; Chaudhary, Swapnil A.; Ghosh, Sonali; Lakshmi, Udaya; Rawat, Deepshikha; Ambastha, Kalpana; Malik, Akhtar H.; Devi, B. S. S.; Gowda, Balakrishna; Sharma, K. C.; Mukharjee, Prashant; Sharma, Ajay; Davidar, Priya; Raju, R. R. Venkata; Katewa, S. S.; Kant, Shashi; Raju, Vatsavaya S.; Uniyal, B. P.; Debnath, Bijan; Rout, D. K.; Thapa, Rajesh; Joseph, Shijo; Chhetri, Pradeep; Ramachandran, Reshma M.

    2015-07-01

    A seamless vegetation type map of India (scale 1: 50,000) prepared using medium-resolution IRS LISS-III images is presented. The map was created using an on-screen visual interpretation technique and has an accuracy of 90%, as assessed using 15,565 ground control points. India has hitherto been using potential vegetation/forest type map prepared by Champion and Seth in 1968. We characterized and mapped further the vegetation type distribution in the country in terms of occurrence and distribution, area occupancy, percentage of protected area (PA) covered by each vegetation type, range of elevation, mean annual temperature and precipitation over the past 100 years. A remote sensing-amenable hierarchical classification scheme that accommodates natural and semi-natural systems was conceptualized, and the natural vegetation was classified into forests, scrub/shrub lands and grasslands on the basis of extent of vegetation cover. We discuss the distribution and potential utility of the vegetation type map in a broad range of ecological, climatic and conservation applications from global, national and local perspectives. We used 15,565 ground control points to assess the accuracy of products available globally (i.e., GlobCover, Holdridge's life zone map and potential natural vegetation (PNV) maps). Hence we recommend that the map prepared herein be used widely. This vegetation type map is the most comprehensive one developed for India so far. It was prepared using 23.5 m seasonal satellite remote sensing data, field samples and information relating to the biogeography, climate and soil. The digital map is now available through a web portal (http://bis.iirs.gov.in).

  9. Masking Vegetable Bitterness to Improve Palatability Depends on Vegetable Type and Taste Phenotype

    PubMed Central

    2013-01-01

    Consumption of dark green vegetables falls short of recommendations, in part, because of unpleasant bitterness. A laboratory-based study of 37 adults was used to determine bitter and hedonic responses to vegetables (asparagus, Brussels sprouts, kale) with bitter masking agents (1.33 M sodium acetate, 10 and 32 mM sodium chloride, and 3.2 mM aspartame) and then characterized by taste phenotype and vegetable liking. In repeated-measures ANOVA, aspartame was most effective at suppressing bitterness and improving hedonic responses for all sampled vegetables. Among the sodium salts, 32 mM sodium chloride decreased bitterness for kale and sodium acetate reduced bitterness across all vegetables with a tendency to increase liking for Brussels sprouts, as release from mixture suppression increased perceived sweetness. Participants were nearly equally divided into three 6-n-propylthiouracil (PROP) phenotype groups. Those tasting the least PROP bitterness (non-tasters) reported least vegetable bitterness, and the additives produced little change in vegetable liking. Aspartame persisted as the most effective bitter blocker for the PROP tasters (medium, supertasters), improving vegetable liking for the medium tasters but too much sweetness for supertasters. The sodium salts showed some bitter blocking for PROP tasters, particularly sodium acetate, without significant gains in vegetable liking. Via a survey, adults characterized as low vegetable likers reported greater increase in vegetable liking with the maskers than did vegetable likers. These results suggest that bitter masking agents (mainly sweeteners) can suppress bitterness to increase acceptance if they are matched to perceived vegetable bitterness or to self-reported vegetable disliking. PMID:23682306

  10. Masking Vegetable Bitterness to Improve Palatability Depends on Vegetable Type and Taste Phenotype.

    PubMed

    Sharafi, Mastaneh; Hayes, John E; Duffy, Valerie B

    2013-03-01

    Consumption of dark green vegetables falls short of recommendations, in part, because of unpleasant bitterness. A laboratory-based study of 37 adults was used to determine bitter and hedonic responses to vegetables (asparagus, Brussels sprouts, kale) with bitter masking agents (1.33 M sodium acetate, 10 and 32 mM sodium chloride, and 3.2 mM aspartame) and then characterized by taste phenotype and vegetable liking. In repeated-measures ANOVA, aspartame was most effective at suppressing bitterness and improving hedonic responses for all sampled vegetables. Among the sodium salts, 32 mM sodium chloride decreased bitterness for kale and sodium acetate reduced bitterness across all vegetables with a tendency to increase liking for Brussels sprouts, as release from mixture suppression increased perceived sweetness. Participants were nearly equally divided into three 6-n-propylthiouracil (PROP) phenotype groups. Those tasting the least PROP bitterness (non-tasters) reported least vegetable bitterness, and the additives produced little change in vegetable liking. Aspartame persisted as the most effective bitter blocker for the PROP tasters (medium, supertasters), improving vegetable liking for the medium tasters but too much sweetness for supertasters. The sodium salts showed some bitter blocking for PROP tasters, particularly sodium acetate, without significant gains in vegetable liking. Via a survey, adults characterized as low vegetable likers reported greater increase in vegetable liking with the maskers than did vegetable likers. These results suggest that bitter masking agents (mainly sweeteners) can suppress bitterness to increase acceptance if they are matched to perceived vegetable bitterness or to self-reported vegetable disliking.

  11. Improving the representation of fire disturbance in dynamic vegetation models by assimilating satellite data: a case study over the Arctic

    NASA Astrophysics Data System (ADS)

    Kantzas, E. P.; Quegan, S.; Lomas, M.

    2015-08-01

    Fire provides an impulsive and stochastic pathway for carbon from the terrestrial biosphere to enter the atmosphere. Despite fire emissions being of similar magnitude to net ecosystem exchange in many biomes, even the most complex dynamic vegetation models (DVMs) embedded in general circulation models contain poor representations of fire behaviour and dynamics, such as propagation and distribution of fire sizes. A model-independent methodology is developed which addresses this issue. Its focus is on the Arctic where fire is linked to permafrost dynamics and on occasion can release great amounts of carbon from carbon-rich organic soils. Connected-component labelling is used to identify individual fire events across Canada and Russia from daily, low-resolution burned area satellite products, and the obtained fire size probability distributions are validated against historical data. This allows the creation of a fire database holding information on area burned and temporal evolution of fires in space and time. A method of assimilating the statistical distribution of fire area into a DVM whilst maintaining its fire return interval is then described. The algorithm imposes a regional scale spatially dependent fire regime on a sub-scale spatially independent model; the fire regime is described by large-scale statistical distributions of fire intensity and spatial extent, and the temporal dynamics (fire return intervals) are determined locally. This permits DVMs to estimate many aspects of post-fire dynamics that cannot occur under their current representations of fire, as is illustrated by considering the modelled evolution of land cover, biomass and net ecosystem exchange after a fire.

  12. Spatial and temporal patterns of greenness on the Yamal Peninsula, Russia: interactions of ecological and social factors affecting the Arctic normalized difference vegetation index

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Leibman, M. O.; Epstein, H. E.; Forbes, B. C.; Bhatt, U. S.; Raynolds, M. K.; Comiso, J. C.; Gubarkov, A. A.; Khomutov, A. V.; Jia, G. J.; Kaarlejärvi, E.; Kaplan, J. O.; Kumpula, T.; Kuss, P.; Matyshak, G.; Moskalenko, N. G.; Orekhov, P.; Romanovsky, V. E.; Ukraientseva, N. G.; Yu, Q.

    2009-10-01

    The causes of a greening trend detected in the Arctic using the normalized difference vegetation index (NDVI) are still poorly understood. Changes in NDVI are a result of multiple ecological and social factors that affect tundra net primary productivity. Here we use a 25 year time series of AVHRR-derived NDVI data (AVHRR: advanced very high resolution radiometer), climate analysis, a global geographic information database and ground-based studies to examine the spatial and temporal patterns of vegetation greenness on the Yamal Peninsula, Russia. We assess the effects of climate change, gas-field development, reindeer grazing and permafrost degradation. In contrast to the case for Arctic North America, there has not been a significant trend in summer temperature or NDVI, and much of the pattern of NDVI in this region is due to disturbances. There has been a 37% change in early-summer coastal sea-ice concentration, a 4% increase in summer land temperatures and a 7% change in the average time-integrated NDVI over the length of the satellite observations. Gas-field infrastructure is not currently extensive enough to affect regional NDVI patterns. The effect of reindeer is difficult to quantitatively assess because of the lack of control areas where reindeer are excluded. Many of the greenest landscapes on the Yamal are associated with landslides and drainage networks that have resulted from ongoing rapid permafrost degradation. A warming climate and enhanced winter snow are likely to exacerbate positive feedbacks between climate and permafrost thawing. We present a diagram that summarizes the social and ecological factors that influence Arctic NDVI. The NDVI should be viewed as a powerful monitoring tool that integrates the cumulative effect of a multitude of factors affecting Arctic land-cover change.

  13. The vegetative arctic freshwater green alga Zygnema is insensitive to experimental UV exposure.

    PubMed

    Holzinger, Andreas; Roleda, Michael Y; Lütz, Cornelius

    2009-12-01

    The physiological performance and ultrastructural integrity of the vegetative freshwater green alga Zygnema sp., growing under ambient polar day solar radiation and after exposure to experimentally low radiation, but with high UVR:PAR ratio were investigated. In the laboratory, algae were exposed to low photosynthetic active radiation (PAR=P, 400-700 nm, 20 micromol m(-2) s(-1)), PAR + UV-A = PA (320-400 nm, 4.00 W m(-2) = UV-A) and PAR + UV-A + UV-B = PAB (280-320 nm, 0.42 W m(-2) = UV-B) for 24 h at 7 degrees C. Photosynthetic performance and ultrastructure of ambient solar radiation-exposed (field control) and experimentally treated Zygnema samples were assessed using chlorophyll fluorescence, and transmission electron microscopy (TEM). No significant treatment effect was observed in the photosynthesis-irradiance curve parameters. Exclusion of the UV-B spectrum in the laboratory treatment caused significantly lower effective photosynthetic quantum yield compared to samples exposed to the whole radiation spectrum. TEM revealed no obvious differences in the ultrastructure of field control and laboratory P-, PA- and PAB-exposed samples. Substantial amounts of lipid bodies, visualized by Sudan IV staining, were observed in all samples. Chloroplasts contained numerous plastoglobules. Organelles like mitochondria, Golgi bodies and the nucleus remained unaffected by the radiation exposures. Zygnema is well adapted to ambient solar radiation, enabling the alga to cope with experimental UV exposure and it is expected to persist in a scenario with enhanced UV radiation caused by stratospheric ozone depletion.

  14. Vegetation associations in a rare community type - Coastal tallgrass prairie

    USGS Publications Warehouse

    Grace, J.B.; Allain, L.; Allen, C.

    2000-01-01

    The coastal prairie ecoregion is located along the northwestern coastal plain of the Gulf of Mexico in North America. Because of agricultural and urban development, less than 1% of the original 3.4 million ha of this ecosystem type remains in native condition, making it one of the most endangered ecosystems in North America. The objective of this study was to characterize the vegetation and environmental relationships in a relatively pristine example of lowland coastal prairie in order to provide information for use in conservation and restoration. The study area was a small, isolated prairie located near the southern boundary of the coastal prairie region. Samples were taken along three parallel transects that spanned the prairie. Parameters measured included species composition, elevation, soil characteristics, indications of recent disturbance, above-ground biomass, and light penetration through the plant canopy. Fifty-four species were found in the 107 0.25-m2 plots and a total of 96 species were found at the site. Only two non-native species occurred in sample plots, both of which were uncommon. Cluster analysis was used to identify six vegetation groups, which were primarily dominated by members of the Poaceae or Asteraceae. A conspicuous, natural edaphic feature of the prairie was the presence of 'mima' mounds, which are raised areas approximately 0.5 to 1 m high and 5 to 10 m across. Indicator species analysis revealed a significant number of species that were largely restricted to mounds and these were predominately upland and colonizing species. Ordination was performed using nonmetric, multidimensional scaling. The dominant environmental influence on species composition was found to be elevation and a host of correlated factors including those associated with soil organic content. A secondary group of factors, consisting primarily of soil cations, was found to explain additional variance among plots. Overall, this prairie was found to contain plant

  15. Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro.

    PubMed

    Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

    2015-01-01

    In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866-4550 m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies.

  16. Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro.

    PubMed

    Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

    2015-01-01

    In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866-4550 m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies. PMID:26406985

  17. Vertical and Horizontal Vegetation Structure across Natural and Modified Habitat Types at Mount Kilimanjaro

    PubMed Central

    Rutten, Gemma; Ensslin, Andreas; Hemp, Andreas; Fischer, Markus

    2015-01-01

    In most habitats, vegetation provides the main structure of the environment. This complexity can facilitate biodiversity and ecosystem services. Therefore, measures of vegetation structure can serve as indicators in ecosystem management. However, many structural measures are laborious and require expert knowledge. Here, we used consistent and convenient measures to assess vegetation structure over an exceptionally broad elevation gradient of 866–4550m above sea level at Mount Kilimanjaro, Tanzania. Additionally, we compared (human)-modified habitats, including maize fields, traditionally managed home gardens, grasslands, commercial coffee farms and logged and burned forests with natural habitats along this elevation gradient. We distinguished vertical and horizontal vegetation structure to account for habitat complexity and heterogeneity. Vertical vegetation structure (assessed as number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) displayed a unimodal elevation pattern, peaking at intermediate elevations in montane forests, whereas horizontal structure (assessed as coefficient of variation of number, width and density of vegetation layers, maximum canopy height, leaf area index and vegetation cover) was lowest at intermediate altitudes. Overall, vertical structure was consistently lower in modified than in natural habitat types, whereas horizontal structure was inconsistently different in modified than in natural habitat types, depending on the specific structural measure and habitat type. Our study shows how vertical and horizontal vegetation structure can be assessed efficiently in various habitat types in tropical mountain regions, and we suggest to apply this as a tool for informing future biodiversity and ecosystem service studies. PMID:26406985

  18. The tri-soil experiment: do plants discriminate among vegetation soil types?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We tested if rooting mass and root nutrient uptake of cheatgrass (Bromus tectorum) or creeping wildrye (Leymus triticoides) were influenced by vegetation soil type. Three soil types (A horizons), similar in gross physical and chemical properties, were freshly-collected. The soils varied in the veget...

  19. Comparison of Vegetation Water Use Using the Horton Index in a Sub-arctic, Alaskan Boreal Forest Environment Using Hydrograph Analysis

    NASA Astrophysics Data System (ADS)

    Bolton, W. R.; Cable, J.

    2012-12-01

    The sub-arctic environment is in the zone of discontinuous permafrost. The extreme energy influx from winter to summer has a strong influence on water storage and release processes at the watershed scale. For example, the seven months of snow accumulation are followed by a short 2-week period of snow ablation in which approximately 1/3 of the annual precipitation is released into the system. In permafrost soils, the soils begin to thaw immediately at the conclusion of snow melt, increasing the storage capacity of the soils. The storage capacity of the soils reaches a maximum in late summer then rapidly decreases during the freeze-back period in October. In permafrost-free soils dominated by deciduous vegetation, the trees appear to have a major role in taking up and transpiring liquid precipitation to back to the atmosphere. Conversely, in permafrost soils dominated by coniferous vegetation, the trees appear to have a more minor role in the cycling of liquid water during precipitation events. The overarching goal of our research is to quantify the relative roles of vegetation water use and soil storage dynamics associated with permafrost presence/absence in determining the magnitude and timing of water pathways in the sub-Arctic boreal forest. As part of this goal, we quantified the Horton Index - a metric used to describe vegetation water use relative to available soil water - in two small sub-basins of the Caribou-Poker Creeks Research Watershed, located near Fairbanks, Alaska. The C2 (5.2 km2) and C3 (5.7km2) sub-basins are underlain by approximately 2 and 53% permafrost, and are dominated by deciduous (Betula neoalaskana and Populus tremuloides) and coniferous vegetation (Picea mariana), respectively. Catchment scale calculations of the Horton Index are made using stream flow analysis and during snow-free precipitation events over an 11-year period. In each sub-basin, the Horton Index varies with time with the greatest variation occurring in the spring and fall

  20. Effects of vegetation types on soil moisture estimation from the normalized land surface temperature versus vegetation index space

    NASA Astrophysics Data System (ADS)

    Zhang, Dianjun; Zhou, Guoqing

    2015-12-01

    Soil moisture (SM) is a key variable that has been widely used in many environmental studies. Land surface temperature versus vegetation index (LST-VI) space becomes a common way to estimate SM in optical remote sensing applications. Normalized LST-VI space is established by the normalized LST and VI to obtain the comparable SM in Zhang et al. (Validation of a practical normalized soil moisture model with in situ measurements in humid and semiarid regions [J]. International Journal of Remote Sensing, DOI: 10.1080/01431161.2015.1055610). The boundary conditions in the study were set to limit the point A (the driest bare soil) and B (the wettest bare soil) for surface energy closure. However, no limitation was installed for point D (the full vegetation cover). In this paper, many vegetation types are simulated by the land surface model - Noah LSM 3.2 to analyze the effects on soil moisture estimation, such as crop, grass and mixed forest. The locations of point D are changed with vegetation types. The normalized LST of point D for forest is much lower than crop and grass. The location of point D is basically unchanged for crop and grass.

  1. Mapping vegetation types with the multiple spectral feature mapping algorithm in both emission and absorption

    NASA Technical Reports Server (NTRS)

    Clark, Roger N.; Swayze, Gregg A.; Koch, Christopher; Ager, Cathy

    1992-01-01

    Vegetation covers a large portion of the Earth's land surface. Remotely sensing quantitative information from vegetation has proven difficult because in a broad sense, all vegetation is similar from a chemical viewpoint, and most healthy plants are green. Plant species are generally characterized by the leaf and flower or fruit morphology, not by remote sensing spectral signatures. But to the human eye, many plants show varying shades of green, so there is direct evidence for spectral differences between plant types. Quantifying these changes in a predictable manner has not been easy. The Clark spectral features mapping algorithm was applied to mapping spectral features in vegetation species.

  2. Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments

    SciTech Connect

    Oswald, W W; Anderson, P M; Brown, T A; Brubaker, L B; Hu, F S; Lozhkin, A V; Tinner, W; Kaltenrieder, P

    2006-05-29

    Dating lake sediments by accelerator mass spectrometry (AMS) {sup 14}C analysis of plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of {sup 14}C dating experiments using samples from Alaskan and Siberian lake-sediment cores. First, to test whether our analytical procedures introduced a sample-mass bias, we obtained {sup 14}C dates for different-sized pieces of single woody macrofossils. In these sample-mass experiments, sized statistically equivalent ages were found for samples as small as 0.05 mg C. Second, to assess whether macrofossil type influenced dating results, we conducted sample-type experiments in which {sup 14}C dates were obtained for different macrofossil types sieved from the same depth in the sediment. We dated materials from multiple levels in sediment cores from Upper Capsule Lake (North Slope, northern Alaska) and Grizzly Lake (Copper River Basin, southern Alaska), and from single depths in other records from northern Alaska. In several of the experiments there were significant discrepancies between dates for different plant tissues, and in most cases wood and charcoal were older than other macrofossil types, usually by several hundred years. This pattern suggests that {sup 14}C dates for woody macrofossils may misrepresent the age of the sediment by centuries, perhaps due to their longer terrestrial residence time and the potential in-built age of long-lived plants. This study identifies why some {sup 14}C dates appear to be inconsistent with the overall age-depth trend of a lake-sediment record, and it may guide the selection of {sup 14}C samples in future studies.

  3. What are the most important factors determining different vegetation types in the Chapada Diamantina, Brazil?

    PubMed

    Neves, S P S; Funch, R; Conceição, A A; Miranda, L A P; Funch, L S

    2016-06-01

    A transect was used to examine the environmental and biological descriptors of a compact vegetation mosaic in the Chapada Diamantina in northeastern Brazil, including the floristic composition, spectrum of plant life forms, rainfall, and soil properties that defined areas of cerrado (Brazilian savanna), caatinga (seasonally dry tropical forest thorny, deciduous shrub/arboreal vegetation) and cerrado-caatinga transition vegetation. The floristic survey was made monthly from April/2009 to March/2012. A dendrogram of similarity was generated using the Jaccard Index based on a matrix of the species that occurred in at least two of the vegetation types examined. The proportions of life forms in each vegetation type were compared using the chi-square test. Composite soil samples were analyzed by simple variance (ANOVA) to examine relationships between soil parameters of each vegetation type and the transition area. The monthly precipitation levels in each vegetation type were measured and compared using the chi-square test. A total of 323 species of angiosperms were collected distributed in 193 genera and 54 families. The dendrogram demonstrated strong difference between the floristic compositions of the cerrado and caatinga, sharing 2% similarity. The chi-square test did not demonstrate any significant statistical differences between the monthly values of recorded rainfall. The organic matter and clay contents of the soilsin the caatinga increased while sand decreased, and the proportions of therophyte, hemicryptophyte, and chamaephyte life forms decreased and phanerophytes increased. We can therefore conclude that the floristic composition and the spectrum of life forms combined to define the cerrado and caatinga vegetation along the transect examined, with soil being the principal conditioning factor determining the different vegetation types, independent of precipitation levels.

  4. What are the most important factors determining different vegetation types in the Chapada Diamantina, Brazil?

    PubMed

    Neves, S P S; Funch, R; Conceição, A A; Miranda, L A P; Funch, L S

    2016-06-01

    A transect was used to examine the environmental and biological descriptors of a compact vegetation mosaic in the Chapada Diamantina in northeastern Brazil, including the floristic composition, spectrum of plant life forms, rainfall, and soil properties that defined areas of cerrado (Brazilian savanna), caatinga (seasonally dry tropical forest thorny, deciduous shrub/arboreal vegetation) and cerrado-caatinga transition vegetation. The floristic survey was made monthly from April/2009 to March/2012. A dendrogram of similarity was generated using the Jaccard Index based on a matrix of the species that occurred in at least two of the vegetation types examined. The proportions of life forms in each vegetation type were compared using the chi-square test. Composite soil samples were analyzed by simple variance (ANOVA) to examine relationships between soil parameters of each vegetation type and the transition area. The monthly precipitation levels in each vegetation type were measured and compared using the chi-square test. A total of 323 species of angiosperms were collected distributed in 193 genera and 54 families. The dendrogram demonstrated strong difference between the floristic compositions of the cerrado and caatinga, sharing 2% similarity. The chi-square test did not demonstrate any significant statistical differences between the monthly values of recorded rainfall. The organic matter and clay contents of the soilsin the caatinga increased while sand decreased, and the proportions of therophyte, hemicryptophyte, and chamaephyte life forms decreased and phanerophytes increased. We can therefore conclude that the floristic composition and the spectrum of life forms combined to define the cerrado and caatinga vegetation along the transect examined, with soil being the principal conditioning factor determining the different vegetation types, independent of precipitation levels. PMID:26934155

  5. Identification of phenological stages and vegetative types for land use classification

    NASA Technical Reports Server (NTRS)

    Branton, C. I. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. A large grassland was located on the Kenai Peninsula which may be a potential grazing land. Two 1:250,000 vegetation maps were constructed from ERTS-1 scenes 1049-20505 and 1066-20453 using 70 mm MSS chips and black and white prints for an area of 3.5 million acres. Another area (464,000 acres) was mapped using digital data. The latter map is the most accurate and detailed vegetation map of that area produced to date. Areal extents of identified vegetation types were derived for the area mapped from digital data. Early spring (prior to leafing out of the deciduous trees) is suspected as being the best time for mapping Alaskan vegetation from MSS data due to the radiometrically distinctness of the vegetation communities at that time.

  6. Wave Velocity Attenuation and Sediment Retention among Different Vegetation Types in a Pacific Northwest Estuary

    NASA Astrophysics Data System (ADS)

    Lemein, T.; Cox, D. T.; Albert, D.; Blackmar, P.

    2012-12-01

    Feedbacks between vegetation, wave climate, and sedimentation create stable ecosystem states within estuaries that provide ecosystem services such as wildlife habitat, erosion control, and pollution filtration. Flume and field studies conducted with cordgrass (Spartina spp.) and sea grasses (Zostera spp., Halodule spp.) have demonstrated that the presence of vegetation reduces wave energy and increases sediment retention. Since the spatial distribution of plant species and the presence of unique plant species differ between estuaries, there is a need to understand how individual plant species, or groups of species with similar morphology, influence wave characteristics and sedimentation. Within Tillamook Bay, Oregon, three species of emergent vascular vegetation species (Carex lyngbyei, Eleocharis sp., Schoenoplectus pungens) and one species of submergent vascular vegetation species (Zostera marina) are present in the high wave energy portion of the estuary at the border of open water and the start of vegetation. These species represent three distinct growth forms (emergent reeds, emergent grasses, submergent grasses) and occur at varying densities relative to each other, as well as within the estuary. Using paired acoustic Doppler velocimeters (ADVs), we quantify the relative attenuation of wave velocity between vegetation types and densities within the estuary and compare these results with published attenuation rates from flume and field studies in different environments. The effect of decreased wave velocity on sediment retention is measured using permanent sediment markers within and outside of vegetation stands and paired with ADV data. Sediment retention is predicted to vary seasonally with seasonal vegetation composition changes and remain constant in unvegetated areas. From this experiment we expect to identify like groups of plant species whose attenuation characteristics are the same, allowing for models of wave-vegetation-sediment interaction to be

  7. Alien plant invasion in mixed-grass prairie: Effects of vegetation type and anthropogenic disturbance

    USGS Publications Warehouse

    Larson, D.L.; Anderson, P.J.; Newton, W.

    2001-01-01

    The ability of alien plant species to invade a region depends not only on attributes of the plant, but on characteristics of the habitat being invaded. Here, we examine characteristics that may influence the success of alien plant invasion in mixed-grass prairie at Theodore Roosevelt National Park, in western North Dakota, USA. The park consists of two geographically separate units with similar vegetation types and management history, which allowed us to examine the effects of native vegetation type, anthropogenic disturbance, and the separate park units on the invasion of native plant communities by alien plant species common to counties surrounding both park units. If matters of chance related to availability of propagules and transient establishment opportunities determine the success of invasion, park unit and anthropogenic disturbance should better explain the variation in alien plant frequency. If invasibility is more strongly related to biotic or physical characteristics of the native plant communities, models of alien plant occurrence should include vegetation type as an explanatory variable. We examined >1300 transects across all vegetation types in both units of the park. Akaike's Information Criterion (AIC) indicated that the fully parameterized model, including the interaction among vegetation type, disturbance, and park unit, best described the distribution of both total number of alien plants per transect and frequency of alien plants on transects where they occurred. Although all vegetation types were invaded by alien plants, mesic communities had both greater numbers and higher frequencies of alien plants than did drier communities. A strong element of stochasticity, reflected in differences in frequencies of individual species between the two park units, suggests that prediction of risk of invasion will always involve uncertainty. In addition, despite well-documented associations between anthropogenic disturbance and alien plant invasion, five of

  8. Identification of phenological stages and vegetative types for land use classification

    NASA Technical Reports Server (NTRS)

    Branton, C. I. (Principal Investigator); Mckendrick, J. D.

    1973-01-01

    The author has identified the following significant results. A large grassland was located on the Kenai Peninsula which may be a potential grazing land. Two 1:250 K vegetation maps were constructed from ERTS-1 scenes 1049-20505 and 1066-20453 using 70 mm MSS chips and black and white prints for an area of 3.5 million acres. Another area (464,000 acres) was mapped using digital data. The latter map is the most accurate and detailed vegetation map of that area produced to date. Areal extents of identified vegetation types were derived for the area mapped from digital data. Early spring (prior to leafing out of deciduous trees) is suspected as being the best time for mapping Alaskan vegetation from MSS data due to the best time for mapping Alaskan vegetation from MSS data due to the radiometrically distinctness of the vegetation communities at that time. Vegetative overlays produced at 1:250 K compare favorably with vegetative maps compiled by Lloyd A. Spetzman and assembled by the joint Federal-State Land Use Planning Commission for Alaska.

  9. Divergent Impacts of Two Cattle Types on Vegetation in Coastal Meadows: Implications for Management

    NASA Astrophysics Data System (ADS)

    Laurila, Marika; Huuskonen, Arto; Pesonen, Maiju; Kaseva, Janne; Joki-Tokola, Erkki; Hyvärinen, Marko

    2015-11-01

    The proportion of beef cattle in relation to the total number of cattle has increased in Europe, which has led to a higher contribution of beef cattle in the management of semi-natural grasslands. Changes in vegetation caused by this change in grazers are virtually unexplored so far. In the present study, the impacts of beef and dairy cattle on vegetation structure and composition were compared on Bothnian Bay coastal meadows. Vegetation parameters were measured in seven beef cattle, six dairy heifer pastures, and in six unmanaged meadows. Compared to unmanaged meadows, vegetation in grazed meadows was significantly lower in height and more frequently colonized by low-growth species. As expected, vegetation grazed by beef cattle was more open than that on dairy heifer pastures where litter cover and proportion of bare ground were in the same level as in the unmanaged meadows. However, the observed differences may have in part arisen from the higher cattle densities in coastal meadows grazed by beef cattle than by dairy heifers. The frequencies of different species groups and the species richness values of vegetation did not differ between the coastal meadows grazed by the two cattle types. One reason for this may be the relatively short management history of the studied pastures. The potential differences in grazing impacts of the two cattle types on vegetation structure can be utilized in the management of coastal meadows for species with divergent habitat requirements.

  10. Divergent Impacts of Two Cattle Types on Vegetation in Coastal Meadows: Implications for Management.

    PubMed

    Laurila, Marika; Huuskonen, Arto; Pesonen, Maiju; Kaseva, Janne; Joki-Tokola, Erkki; Hyvärinen, Marko

    2015-11-01

    The proportion of beef cattle in relation to the total number of cattle has increased in Europe, which has led to a higher contribution of beef cattle in the management of semi-natural grasslands. Changes in vegetation caused by this change in grazers are virtually unexplored so far. In the present study, the impacts of beef and dairy cattle on vegetation structure and composition were compared on Bothnian Bay coastal meadows. Vegetation parameters were measured in seven beef cattle, six dairy heifer pastures, and in six unmanaged meadows. Compared to unmanaged meadows, vegetation in grazed meadows was significantly lower in height and more frequently colonized by low-growth species. As expected, vegetation grazed by beef cattle was more open than that on dairy heifer pastures where litter cover and proportion of bare ground were in the same level as in the unmanaged meadows. However, the observed differences may have in part arisen from the higher cattle densities in coastal meadows grazed by beef cattle than by dairy heifers. The frequencies of different species groups and the species richness values of vegetation did not differ between the coastal meadows grazed by the two cattle types. One reason for this may be the relatively short management history of the studied pastures. The potential differences in grazing impacts of the two cattle types on vegetation structure can be utilized in the management of coastal meadows for species with divergent habitat requirements.

  11. Surface water types in the Western Canadian Arctic: geochemical evolution and aquatic carbon transport

    NASA Astrophysics Data System (ADS)

    Dean, Joshua F.; Billett, Mike F.; Dinsmore, Kerry J.; Lessels, Jason S.; Street, Lorna; Washbourne, Ian; Subke, Jens-Arne; Tetzlaff, Doerthe; Baxter, Robert; Wookey, Philip A.

    2015-04-01

    Arctic surface waters are a substantial conduit for terrestrial C flow as well as a potential source of GHGs to the atmosphere - a significant positive feedback to global climate warming and a key component of the net ecosystem carbon balance in permafrost regions. As temperatures rise in the Arctic, permafrost thaw deepens releasing C from the landscape into the aquatic system making streams and lakes increasingly important conduits and reactors of both allochthonous and autochthonous C. The HYDRA project ('Permafrost catchments in transition: hydrological controls on carbon cycling and greenhouse gas budgets'), aims to quantify the assimilation of C and the controls of C movement between the plant-soil-water-atmosphere continuum. The specific aspect of the project presented here considers the different aquatic pathways in warming Arctic permafrost catchments, and the potential role that they play in GHG emissions and aquatic C cycling. This study presents the surface water geochemistry of Siksik Creek, a small (

  12. Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

    NASA Astrophysics Data System (ADS)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2014-10-01

    The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005-2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

  13. Delayed responses of an Arctic ecosystem to an extremely dry summer: impacts on net ecosystem exchange and vegetation functioning

    NASA Astrophysics Data System (ADS)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2013-12-01

    The importance and mode of action of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. Summer 2007 in Barrow, Arctic Alaska, experienced unusually high air temperatures (fifth warmest over a 65 yr period) and record low precipitation (lowest over a 65 yr period). These abnormal conditions resulted in strongly reduced net Sphagnum CO2 uptake, but no effect neither on vascular plant development nor on net ecosystem exchange (NEE) from this arctic tundra ecosystem. Gross primary production (GPP) and ecosystem respiration (Reco) were both generally greater during most of this extreme summer. Cumulative ecosystem C uptake in 2007 was similar to the previous summers, showing the capacity of the ecosystem to compensate in its net ecosystem exchange (NEE) despite the impact on other functions and structure such as substantial necrosis of the Sphagnum layer. Surprisingly, the lowest ecosystem C uptake (2005-2009) was observed during the 2008 summer, i.e the year directly following the extremely summer. In 2008, cumulative C uptake was ∼70% lower than prior years. This reduction cannot solely be attributed to mosses, which typically contribute with ∼40% - of the entire ecosystem C uptake. The minimum summer cumulative C uptake in 2008 suggests that the entire ecosystem experienced difficulty readjusting to more typical weather after experiencing exceptionally warm and dry conditions. Importantly, the return to a substantial cumulative C uptake occurred two summers after the extreme event, which suggest a high resilience of this tundra ecosystem. Overall, these results show a highly complex response of the C uptake and its sub-components to atypically dry conditions. The impact of multiple extreme events still awaits further investigation.

  14. Three years exclusion of large herbivores in a high arctic mire in NE Greenland resulted in changed vegetation density and greenhouse gas emission and uptake

    NASA Astrophysics Data System (ADS)

    Falk, Julie M.; Schmidt, Niels Martin; Christensen, Torben R.; Forchhammer, Mads C.; Jackowicz-Korczynski, Marcin; Ström, Lena

    2014-05-01

    Herbivory is an important part of many ecosystems and their presence effects the ecosystems carbon balance with both direct and indirect effects. Little is known about what will happen to an arctic ecosystem that is influenced by herbivory, if the animals disappear. We hypothesized that trampling and grazing by large herbivores influence the vegetation density and composition and hereby the carbon balance. Method: In 2010 an in-situ field experiment in Zackenberg, NE Greenland, were initiated to study the effects of herbivory on the vegetation and carbon balance. Exclosures were established to exclude the muskoxen (Ovibos moschatus), which are a natural part of these ecosystems. The experiment consists of five block replicates with three treatments within each block, i.e., control, exclosure and a snow fence (the treatment area is 10x10 m and the fences are 1 m high). During the growing season we have since 2011 performed weekly measurements of CO2 and CH4fluxes, the concentration of labile substrate for CH4 formation (organic acid concentration) in pore-water and additional ecosystem properties, i.e., water table depth, active layer depth and soil temperature. In 2013 a detailed analysis of the vascular plant species composition and density within each measurement plot were performed. Furthermore biomass (including mosses) samples 20x20 cm were harvested within all treatments. Results: The third year after the initiation of the experiment we observed a clear effect of excluding muskoxen grazing from the ecosystem. The exclosures had lower uptake of CO2 and lower CH4 emission. The vegetation analysis inside the plots showed a decrease in total number of vascular tillers and of Eriophorum scheuchzeri (ES) tillers. Correspondingly, the biomass samples from the exclosures had lower number of total plant tillers, ES tillers, total green leaves and green ES leaves and the height of all vascular plants and of ES plants were higher. Finally, the dry weight of the biomass

  15. [Reproductive phenology of three vegetation types from a coastal plain of Paraguana Penninsula, Venezuela].

    PubMed

    Lemus-Jiménez, Luis José; Ramírez, Nelson

    2002-01-01

    Reproductive phenology of 51 plant species was evaluated according to life form and vegetation types in a coastal plain of the Paraguaná Peninsula, Estado Falcón, Venezuela. Plant species distribution according to three vegetation types (herbaceous littoral, herbaceous psamophil, and mangrove area) was determined. Life form frequency was different according to vegetation type. Herbaceous littoral and herbaceous psamophil vegetation were dominated by herbaceous species; woody species were mostly frequent in the mangrove vegetation. Phenological data revealed that 14 (27.5%) plant species flower and fruit year-round; 23 (45.1%) plant species flower and fruit at the beginning of the wet season; seven (13.7%) plant species flower at the end of wet season, and seven (13.7%) more flower at the beginning of the dry season. Flowsring and fruiting phenology showed similar frequency distribution during the year; reproductive phenology was independent of life forms. Flowering and fruiting peaks occurred during the rainy season and the beginning of the dry season for trees and perennial herbs, and from one to three months later for shrubs and annual herbs. The lowest proportion of flowering and fruiting occurred before rain increase for all life forms. Flowering and fruiting phenologies were similar for the three vegetation types evaluated: flowering peak occurred during the lowest value of precipitation, three to four months after precipitation peak, and fruiting peak occurred four months later from the precipitation peak. These results suggest that flowering and fruiting phenology were not affected by life form and vegetation types. The peaks of flowering and fruiting during the lowest values of precipitation may be considered as a slow and late response to the precipitation maximum, and to the proximity between maximum and minimum of precipitation.

  16. [Characteristics of soil microbial community under different vegetation types in Wuyishan National Nature Reserve, East China].

    PubMed

    Wu, Ze-yan; Lin, Wen-xiong; Chen, Zhi-fang; Fang, Chang-xun; Zhang, Zhi-xing; Wu, Lin-kun; Zhou, Ming-ming; Shen, Li-hua

    2013-08-01

    By using Biolog Ecoplate system, this paper studied the structure and functional diversity of soil microbial community under different vegetation types in Wuyishan National Nature Reserve, aimed to probe into the effects of vegetation type on the diversity of soil microbial community. The results showed that the soil chemical properties, soil enzyme activities, and average well color development (AWCD) were higher in natural forest than in planted forest, and were the lowest in abandoned field. The AWCD reflecting soil microbial activity and functional diversity was increased with increasing incubation time, but there existed significant differences among different vegetation types. The carbon sources mostly used by soil microbes were carbohydrates and carboxylic acids, followed by amino acids, phenolic acids and polymers, and amines had the lowest utilization rate. The Simpson index, Shannon index, Richness index and McIntosh index in natural forest were holistically higher than those in planted forest. Principal component analysis (PCA) identified 2 principal component factors in relation to carbon sources, explaining 56.3% and 30.2% of the variation, respectively. The carbon sources used by soil microbial community differed with vegetation types. Amino acids and amides were the two main carbon sources separating the 2 principal component factors. The results of this study could provide basis for further approaching the relationships between vegetation diversity and soil microbial community diversity.

  17. Differences in hydrological responses for different vegetation types on a steep slope on the Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Duan, Liangxia; Huang, Mingbin; Zhang, Luodan

    2016-06-01

    Extensive vegetation restoration practices have been implemented to control soil erosion on the Loess Plateau, China. However, no strict guidelines are available to determine the most suitable plant species for vegetation restoration within a given area. The objective of this study was to quantify the changes of each component (soil water storage, surface runoff, and actual evapotranspiration) of a water balance model and soil loss over time under eight different vegetation types, and to further determine the optimal vegetation type for soil and water conservation and sustainable ecological restoration on the steep slopes (>25°) on the Loess Plateau. The results indicated that vegetation type substantially affected soil water storage and that the greatest soil water storage in both the shallow (0-2 m) and the deep soil layers (2-5 m) occurred under Bothriochloa ischaemum L. (BOI). Vegetation type also affected surface runoff and soil losses. The most effective vegetation types for reducing soil erosion were BOI and Sea-buckthorn (Hippophae rhamnoides L.), while Chinese pine (Pinus tabulaeformis Carr.) and Chinese pine + Black locust (Robinia pseudoacacia L.) were the most ineffective types. Soil water dynamics and evapotranspiration varied considerably among the different vegetation types. A soil water surplus was only found under BOI, while insufficient water replenishment existed under the other seven vegetation types. The higher water consumption rates of the seven vegetation types could result in soil desiccation, which could lead to severe water stresses that would adversely affect plant growth. This study suggested that both vegetation type and its effect on controlling soil erosion should be considered when implementing vegetation restoration and that BOI should be highly recommended for vegetation restoration on the steep slopes of the Loess Plateau. A similar approach to the one used in this study could be applied to other regions of the world confronted

  18. [Fine root biomass and production of four vegetation types in Loess Plateau, China].

    PubMed

    Deng, Qiang; Li, Ting; Yuan, Zhi-You; Jiao, Feng

    2014-11-01

    Fine roots (≤ 2 mm) play a major role in biogeochemical cycling in ecosystems. By the methods of soil cores and ingrowth soil cores, we studied the biomass and annual production of fine roots in 0-40 cm soil layers of four main vegetation types, i. e. , Robinia pseudoacacia plantation, deciduous shrubs, abandoned grassland, and Artemisia desertorum community in Loess Plateau, China. The spatial patterns of fine root biomass and production were negatively associated with latitudes. The fine root biomass in the 0-40 cm soil layer was in the order of deciduous shrubs (220 g · m(-2)), R. pseudoacacia plantation (163 g · m(-2)), abandoned grassland (162 g · m(-2)) and A. desertorum community (79 g · m(-2)). The proportion of ≤ 1 mm fine root biomass (74.1%) in the 0-40 cm soil layer of abandoned grassland was significantly higher than those in the other three vegetation types. The fine root biomass of the four vegetation types was mainly distributed in the 0-10 cm soil layer and decreased with soil depth. The proportion of fine root biomass (44.1%) in the 0-10 cm soil layer of abandoned grassland was significantly higher than those in other three vegetation types. The fine root productions of four vegetation types were in the order of abandoned grassland (315 g · m(-2) · a(-1)) > deciduous shrubs (249 g · m(-2) a(-1)) > R. pseudoacacia plantation (219 g · m(-2) · a(-1)) > A. desertorum community (115 g · m(-2) · a(-1)), and mainly concentrated in the 0-10 cm top soil layer and decreased with the soil depth. The proportion of the annual production (40.4%) in the 0-10 cm soil layer was the highest in abandoned grassland. Fine roots of abandoned grassland turned over faster than those from the other three vegetation types.

  19. Mapping Arctic plant functional type distributions in the Barrow Environmental Observatory using WorldView-2 and LiDAR datasets

    DOE PAGESBeta

    Langford, Zachary; Kumar, Jitendra; Hoffman, Forrest; Norby, Richard J.; Wullschleger, Stan; Sloan, Victoria; Iversen, Colleen

    2016-09-06

    Multi-scale modeling of Arctic tundra vegetation requires characterization of the heterogeneous tundra landscape, which includes representation of distinct plant functional types (PFTs). We combined high-resolution multi-spectral remote sensing imagery from the WorldView-2 satellite with light detecting and ranging (LiDAR)-derived digital elevation models (DEM) to characterize the tundra landscape in and around the Barrow Environmental Observatory (BEO), a 3021-hectare research reserve located at the northern edge of the Alaskan Arctic Coastal Plain. Vegetation surveys were conducted during the growing season (June August) of 2012 from 48 1 m 1 m plots in the study region for estimating the percent cover ofmore » PFTs (i.e., sedges, grasses, forbs, shrubs, lichens and mosses). Statistical relationships were developed between spectral and topographic remote sensing characteristics and PFT fractions at the vegetation plots from field surveys. These derived relationships were employed to statistically upscale PFT fractions for our study region of 586 hectares at 0.25-m resolution around the sampling areas within the BEO, which was bounded by the LiDAR footprint. We employed an unsupervised clustering for stratification of this polygonal tundra landscape and used the clusters for segregating the field data for our upscaling algorithm over our study region, which was an inverse distance weighted (IDW) interpolation. We describe two versions of PFT distribution maps upscaled by IDW from WorldView-2 imagery and LiDAR: (1) a version computed from a single image in the middle of the growing season; and (2) a version computed from multiple images through the growing season. This approach allowed us to quantify the value of phenology for improving PFT distribution estimates. We also evaluated the representativeness of the field surveys by measuring the Euclidean distance between every pixel. This guided the ground-truthing campaign in late July of 2014 for addressing

  20. Characterizing the Seasonal Dynamics of Plant Community Photosynthesis Across a Range of Vegetation Types

    SciTech Connect

    Gu, Lianhong; Post, Wilfred M; Baldocchi, Dennis; Black, Andy; Suyker, A.E.,; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2009-01-01

    The seasonal cycle of plant community photosynthesis is one of the most important biotic oscillations to mankind. This study built upon previous efforts to develop a comprehensive framework to studying this cycle systematically with eddy covariance flux measurements. We proposed a new function to represent the cycle and generalized a set of phenological indices to quantify its dynamic characteristics. We suggest that the seasonal variation of plant community photosynthesis generally consists of five distinctive phases in sequence each of which results from the interaction between the inherent biological and ecological processes and the progression of climatic conditions and reflects the unique functioning of plant community at different stages of the growing season. We applied the improved methodology to seven vegetation sites ranging from evergreen and deciduous forests to crop to grasslands and covering both cool-season (vegetation active during cool months, e.g. Mediterranean climate grasslands) and warm-season (vegetation active during warm months, e.g. temperate and boreal forests) vegetation types. Our application revealed interesting phenomena that had not been reported before and pointed to new research directions. We found that for the warm-season vegetation type, the recovery of plant community photosynthesis at the beginning of the growing season was faster than the senescence at the end of the growing season while for the coolseason vegetation type, the opposite was true. Furthermore, for the warm-season vegetation type, the recovery was closely correlated with the senescence such that a faster photosynthetic recovery implied a speedier photosynthetic senescence and vice versa. There was evidence that a similar close correlation could also exist for the cool-season vegetation type, and furthermore, the recovery-senescence relationship may be invariant between the warm-season and cool-season vegetation types up to an offset in the intercept. We also

  1. Soil Respiration Responses to Variation in Temperature Treatment and Vegetation Type

    NASA Astrophysics Data System (ADS)

    Liu, S.; Pavao-zuckerman, M.

    2013-12-01

    Complex linkages exist between terrestrial vegetation, soil moisture, soil organic matter (SOM), local climate, and soil microorganisms. Thus, large-scale changes in vegetation, such as the woody plant encroachment observed in many historically semiarid and arid grasslands worldwide, could potentially alter the flux of carbon from soil reserves to the atmosphere. Mathematical models that attempt to project the long-term impact of vegetative shifts on soil fluxes largely rely on assumptions such as first-order donor control rather than incorporate the biological aspects of soil respiration such as microbial activity. To examine the impact of vegetation type on soil physicochemical properties and soil microbial respiration and provide experimental data to refine existing predictive models, we compared soil (ground basalt from northern Arizona) in mesocosms established with no vegetation, velvet mesquites (Prosopis velutina; woody shrub), or sideoats gramas (Bouteloua curtipendula; grass) for 2 years, The temperature sensitivity of soil respiration was examined by incubating soil (0-10 and 10-30 cm depth fractions) from each vegetation treatment at 10, 20, 30, and 40 °C for 24 hours. Vegetated soils contained more SOM (~0.1% for mesquite and grass mesocosms) than non-vegetated soils (~0.02%). Respiration rates were generally highest from grass-established soils, intermediate from mesquite-established soils, and lowest from non-vegetated soils. Respiration rates of samples incubated without the addition of substrate peaked at approximately 30 °C, whereas respiration rates of samples incubated with dextrose were highest at 40 °C. Further, the respiration assays suggest that while respiration rates are overall higher in grass-established soils, mesquite-established soils are more temperature sensitive which may have significant implications in the context of global warming and current fire management practices.

  2. Photosynthetic Characterization of Plant Functional Types from Coastal Tundra to Improve Representation of the Arctic in Earth System Models

    NASA Astrophysics Data System (ADS)

    Rogers, A.; Xu, C.; McDowell, N. G.; Sloan, V. L.; Norby, R. J.

    2012-12-01

    The primary goal of Earth System Models (ESMs) is to improve understanding and projection of future global change. In order to do this they must accurately represent the carbon fluxes associated with the terrestrial carbon cycle. Photosynthetic CO2 uptake is well described by the Farquhar, von Caemmerer and Berry model of photosynthesis, and most ESMs use a derivation of this model. One of the key parameters required by the Farquhar, von Caemmerer and Berry model is an estimate of the maximum rate of carboxylation by the enzyme Rubisco (Vc,max). In ESMs the parameter Vc,max is usually fixed for a given plant functional type (PFT) and often estimated from the empirical relationship between leaf N content and Vc,max. However, uncertainty in the estimation of Vc,max has been shown to account for significant variation in model estimation of gross primary production, particularly in the Arctic. As part of a new multidisciplinary project to improve the representation of the Arctic in ESMs (Next Generation Ecosystem Experiments - Arctic) we have begun to characterize photosynthetic parameters and N acquisition in the key Arctic PFTs. We measured the response of photosynthesis (A) to internal CO2 concentration (ci) in situ in two sedges (Carex aquatilis, Eriophorum angustifolium), a grass (Dupontia fisheri) and a forb (Petasites frigidus) growing on the Barrow Environmental Observatory, Barrow, AK. The values of Vc,max (normalized to 25oC) currently used to represent Arctic PFTs in ESMs are approximately half of the values we measured in these species in July, 2012, on the coastal tundra in Barrow. We hypothesize that these plants have a greater fraction of leaf N invested in Rubisco (FLNR) than is assumed by the models. The parameter Vc,max is used directly as a driver for respiration in some ESMs, and in other ESMs Vc,max is linked to leaf N content and N acquisition through FLNR. Therefore, these results have implications for ESMs beyond photosynthesis, and suggest that

  3. Does vegetation type matter? Plant-soil interactions change urban rain garden hydrology

    NASA Astrophysics Data System (ADS)

    Johnston, M. R.; Balster, N. J.

    2009-12-01

    Residential infiltration basins or rain gardens are being installed at an ever-increasing rate across the urban landscape, yet their impact on the urban hydrologic cycle remains largely untested. Specifically, because rain garden design varies considerably, we know little about how plant-soil dynamics control their hydrologic function. In a controlled field experiment with closed-system rain gardens, we tested the hydrologic response of three vegetation treatments common in rain garden design (shrubs, wet-mesic prairie, turfgrass). We used a complete, randomized block design in which each vegetative treatment was replicated three times. Each rain garden represented 17% of a contributing roof area where stormwater was collected and then applied following precipitation events. We continuously monitored stormwater input, soil water content, and soil exfiltration to assess differences in the hydrologic function of each rain garden. Overall, vegetation type significantly changed the magnitude and timing of the hydrologic response. During the months of June and July, 2009, the rain gardens planted with shrubs, prairie, and turfgrass all reduced the volume of soil exfiltration by 50%, 30%, and 17%, respectively, relative to the non-vegetated controls. Similarly, depending on storm magnitude and antecedent soil moisture, vegetation type significantly decreased the mean peak flow rate of exfiltration (p < 0.001), as well as the duration of the exfiltration response (p < 0.0001). The flashiest hydrologic responses (i.e. shortest lag time, highest peak flow rate) were observed in the turfgrass gardens. We explain these vegetative-mediated responses in hydrology relative to differences in infiltration, aboveground dry mass, root dynamics, and transpirative loss. Our data suggest that changing the vegetation type of urban rain gardens yields marked differences in the hydrologic budget via shifts in ecohydrological processes.

  4. Vegetable but not fruit consumption reduces the risk of type 2 diabetes in Chinese women.

    PubMed

    Villegas, Raquel; Shu, Xiao Ou; Gao, Yu-Tang; Yang, Gong; Elasy, Tom; Li, Honglan; Zheng, Wei

    2008-03-01

    We examined associations between fruit and vegetable intake and the incidence of type 2 diabetes (T2D) in a population-based prospective study of 64,191 women with no history of T2D or other chronic diseases at study recruitment and with valid dietary information. Dietary intake was assessed by in-person interviews using a validated FFQ. During 297,755 person-years of follow-up, 1608 new cases of T2D were documented. We used a Cox regression model to evaluate the association of fruit and vegetable intake (g/d) with the risk of T2D. Quintiles of vegetable intake and T2D were inversely associated. The relative risk for T2D for the upper quintile relative to the lower quintile of vegetable intake was 0.72 (95%CI: 0.61-0.85; P < 0.01) in multivariate analysis. Individual vegetable groups were all inversely and significantly associated with the risk of T2D. Fruit intake was not associated with the incidence of diabetes in this population. Our data suggest that vegetable consumption may protect against the development of T2D.

  5. Impacts of the Variability of Ice Types on the Decline of the Arctic Perennial Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2005-01-01

    The observed rapid decline in the Arctic perennial ice cover is one of the most remarkable signal of change in the Arctic region. Updated data now show an even higher rate of decline of 9.8% per decade than the previous report of 8.9% per decade mainly because of abnormally low values in the last 4 years. To gain insights into this decline, the variability of the second year ice, which is the relatively thin component of the perennial ice cover, and other ice types is studied. The perennial ice cover in the 1990s was observed to be highly variable which might have led to higher production of second year ice and may in part explain the observed ice thinning during the period and triggered further decline. The passive microwave signature of second year ice is also studied and results show that while the signature is different from that of the older multiyear ice, it is surprisingly more similar to that of first year ice. This in part explains why previous estimates of the area of multiyear ice during the winter period are considerably lower than the area of the perennial ice cover during the preceding summer. Four distinct clusters representing radiometrically different types have been identified using multi-channel cluster analysis of passive microwave data. Data from two of these clusters, postulated to come from second year and older multiyear ice regions are also shown to have average thicknesses of 2.4 and 4.1 m, respectively, indicating that the passive microwave data may contain some ice thickness information that can be utilized for mass balance studies. The yearly anomaly maps indicate high gains of first year ice cover in the Arctic during the last decade which means higher production of second year ice and fraction of this type in the declining perennial ice cover. While not the only cause, the rapid decline in the perennial ice cover is in part caused by the increasing fractional component of the thinner second year ice cover that is very vulnerable to

  6. Variation in Soil Respiration across Soil and Vegetation Types in an Alpine Valley

    PubMed Central

    Rubin, Aurélie

    2016-01-01

    Background and Aims Soils of mountain regions and their associated plant communities are highly diverse over short spatial scales due to the heterogeneity of geological substrates and highly dynamic geomorphic processes. The consequences of this heterogeneity for biogeochemical transfers, however, remain poorly documented. The objective of this study was to quantify the variability of soil-surface carbon dioxide efflux, known as soil respiration (Rs), across soil and vegetation types in an Alpine valley. To this aim, we measured Rs rates during the peak and late growing season (July-October) in 48 plots located in pastoral areas of a small valley of the Swiss Alps. Findings Four herbaceous vegetation types were identified, three corresponding to different stages of primary succession (Petasition paradoxi in pioneer conditions, Seslerion in more advanced stages and Poion alpinae replacing the climactic forests), as well as one (Rumicion alpinae) corresponding to eutrophic grasslands in intensively grazed areas. Soils were developed on calcareous alluvial and colluvial fan deposits and were classified into six types including three Fluvisols grades and three Cambisols grades. Plant and soil types had a high level of co-occurrence. The strongest predictor of Rs was soil temperature, yet we detected additional explanatory power of sampling month, showing that temporal variation was not entirely reducible to variations in temperature. Vegetation and soil types were also major determinants of Rs. During the warmest month (August), Rs rates varied by over a factor three between soil and vegetation types, ranging from 2.5 μmol m-2 s-1 in pioneer environments (Petasition on Very Young Fluvisols) to 8.5 μmol m-2 s-1 in differentiated soils supporting nitrophilous species (Rumicion on Calcaric Cambisols). Conclusions Overall, this study provides quantitative estimates of spatial and temporal variability in Rs in the mountain environment, and demonstrates that estimations of

  7. Vegetation associated with different walking track types in the Kosciuszko alpine area, Australia.

    PubMed

    Hill, Wendy; Pickering, Catherine Marina

    2006-01-01

    Tourism infrastructure such as walking tracks can have negative effects on vegetation including in mountain regions. In the alpine area around continental Australia's highest mountain, Mt Kosciuszko (2228 m), there is a range of walking tracks (paved, gravel and raised steel mesh surfaces) in addition to an extensive network of informal/non-hardened tracks. Vegetation characteristics were compared between track types on/under tracks, on the track verge, and in the adjacent native vegetation. For a raised steel mesh walkway there was no difference in vegetation under the walkway, on the verge, and 3m away. In contrast, for a non-hardened track there was 35% bare ground on the track surface but no other detectable impacts. Gravel and paved tracks had distinct verges largely comprising bare ground and exotic species. For non-hardened tracks there was an estimated 270 m2 of disturbance per km of track. For wide gravel tracks the combined area of bare ground, exotic plants and gravel was estimated as 4290 m2 per km, while for narrow gravel tracks it was estimated as 2940 m2 per km. For paved tracks there was around 2680 m2 per km of damage. In contrast, there was no detectable effect of raised steel mesh walkway on vegetation highlighting some of the benefits of this surface over other track types.

  8. Distribution of the common tick, Ixodes ricinus (Acari: Ixodidae), in different vegetation types in southern Sweden.

    PubMed

    Lindström, Anders; Jaenson, Thomas G T

    2003-07-01

    The aim of this study was to investigate whether differences in Ixodes ricinus (L.) nymphal relative density exist among different vegetation types in southern Sweden. Nymphal I. ricinus were sampled in southeastern Scania in southern Sweden during June-August 1997. A total of 110-180 25-m2 samples were taken by blanket-dragging from each of nine different vegetation types. There was a highly significant difference in nymphal abundance between the open areas as one group and the forested areas as another group (P < 0.0001). Vegetation types that differed significantly in median nymphal abundance from all other vegetation types were pine forest (16 nymphs/100 m2) and beech forest (40 nymphs/100 m2). No significant differences in median nymphal density were revealed among mixed deciduous forest, alder forest, oak forest, and hazel forest (28-32 nymphs/100 m2), or among dry meadow, meadow, and heath (0 nymphs/100 m2). Forestation of open areas is likely to lead to increased I. ricinus abundance and disease risk.

  9. [Fine root biomass of four main vegetation types in Daluo Mountain of Ningxia, Northwest China].

    PubMed

    Su, Ji-Shuai; Cheng, Ji-Min; Gao, Yang; Qiu, Zhi-Hu; Cao, Huai-qing

    2013-03-01

    By the method of soil core sampling, this paper studied the fine root biomass, soil water content, and soil bulk density in 0-40 cm soil layer of four main vegetation types (Picea crassifolia forest, Pinus tabulaeformis forest, deciduous shrubs, and desert grassland) in Daluo Mountain of Ningxia, and the fine root biomass in the 0-40 cm soil layer of P. crassifolia forests with the ages of 50-, 70-, and 100 a. The fine root biomass of the four vegetation types was mainly distributed in 0-20 cm soil layer, with the rank of P. tabulaeformis forest > P. crassifolia forest > deciduous shrubs > desert grassland, and the fine root biomass of P. tabulaeformis forest was significantly higher than that of the other three vegetation types. The fine root biomass of the P. crassifolia forests with different ages was 70 a > 100 a > 50 a, and there were no significant differences in the live fine root biomass ratio and dead fine root biomass ratio among the three P. crassifolia forests. The soil water content in the 0-40 cm soil layer of the four vegetation types was P. crassifolia forest > P. tabulaeformis forest > deciduous shrubs > desert grassland, while the soil bulk density followed an opposite pattern, and was significantly negatively correlated with the fine root biomass.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  11. Peat initiation, soil carbon accumulation, fire, and vegetation changes in north-central Canadian arctic lowland forest peatlands during the Holocene

    NASA Astrophysics Data System (ADS)

    Camill, P.; Umbanhowar, C. E., Jr.; Edlund, M. B.; Geiss, C. E.

    2015-12-01

    Peat-forming regions are significant components of the earth system in terms of carbon exchange between the atmosphere and biosphere. While attention has been given to processes controlling carbon accumulation in major peatland/lowland regions at high latitudes, less is known about the processes controlling soil carbon accumulation rates in other globally abundant peat-forming ecosystems, such as lowland arctic forests. These systems are potentially important for two reasons: (1) Many lowland forest peatlands exist at the interface between uplands and aquatic systems; the onset and rate of peat accumulation, as well as the composition of peat mosses, may therefore alter the biogeochemical properties of lakes and streams; (2) soil carbon accumulation might differ from rates observed from the larger open peatlands, offering additional insights to the vulnerability of high-latitude peat to climatic change. We collected and dated 25 peat cores from eight lake sites in an 18,000-km2 low-arctic region of Manitoba Canada and measured areal carbon accumulation rates, charcoal concentration (as a proxy for fire severity), and plant macrofossils (as a proxy for vegetation change). The distribution of basal radiocarbon dates indicates that the oldest peat initiation occurred 7,000-8,000 B.P. in post-glacial landscapes, but peak peat formation occurred < 3,000 B.P., presumably as landscape paludification rose with increased net moisture during Neoglacial cooling. In locations where peat initiation occurred before 6,000 B.P., the initial communities were variable (bog-poor fen-moderate rich fen), whereas most sites initiating after 6,000 B.P. formed (and remained) as bogs, suggesting increasing dominance of Sphagnum peatmosses as paludification progressed. Carbon accumulation rates were consistently low (10-30 gm-2y-1), with no clear correlation to fire. Also absent was rapid accumulation early in the peatland development characteristic of early successional fens. These results

  12. [Influence of three types of riparian vegetation on fluvial erosion control in Pantanos de Centla, Mexico].

    PubMed

    Sepúlveda-Lozada, Alejandra; Geissen, Violette; Ochoa-Gaona, Susana; Jarquín-Sánchez, Aarón; de la Cruz, Simón Hernández; Capetillo, Edward; Zamora-Cornelio, Luis Felipe

    2009-12-01

    Wetlands constitute very important ecological areas. The aim of this study was to quantify the soil losses due to fluvial erosion from 2006 to 2008 in two riverbanks under three types of vegetal coverage dominated by Haematoxylum campechianum, Dalbergia brownei and Brachiaria mutica, in the Pantanos de Centla Biosphere Reserve, SE Mexico. The relationship between the texture, organic matter and pH of soils and soil losses was evaluated. We used erosion sticks to estimate soil losses in 18 plots (three plots per type, three vegetation types, two riverbanks). Soil loss decreased in this order: H. campechianum>B. mutica>D. brownei indicating that D. brownei scrubland has the most potential to retain soil. The higher erosive impact within H. campechianum sites can be related with the low density of these trees in the study areas, as well as the lack of association with other types of vegetation that could reinforce the rooting of the soil profile. Furthermore, soil losses in H. campechianum sites were dependent on soil texture. The soils under this type of vegetal coverage were mainly sandy, which are more vulnerable to the erosive action in comparison with fine textured soils or soils with higher clay content, like the ones found in D. brownei and B. mutica sites. Soil losses of 100 % in the second year (B. mutica plots) can be attributed to the distribution of roots in the upper soil layer and also to livestock management along riverbanks. This study recognizes the importance of D. brownei scrublands in riverbank soil retention. Nevertheless it is necessary to consider the role of an entire vegetal community in future research. PMID:20073341

  13. Alternative diesel fuel study on four different types of vegetable oils of Turkish origin

    SciTech Connect

    Oezaktas, T.; Cigizoglu, K.B.; Karaosmanoglu, F.

    1997-02-01

    Four different types of vegetable oils of Turkish origin (sunflower, corn, soybean, and olive oil) were blended with grade 2-D diesel fuel at a ratio of 20/80 (v/v). Blends were investigated in a diesel engine with a precombustion chamber at speeds between 1,200 and 2,100 rpm. Vegetable oils, diesel fuel, and fuel blends were characterized according to standard test methods. It was found that for short-term use, the fuel blends have engine characteristics similar to the baseline diesel fuel. Fuel blends also display less smoke emissions than diesel fuel.

  14. The Dependence of Peat Soil Hydraulic Conductivity on Dominant Vegetation Type in Mountain Fens

    NASA Astrophysics Data System (ADS)

    Crockett, A. C.; Ronayne, M. J.; Cooper, D. J.

    2014-12-01

    The peat soil within fen wetlands provides water storage that can substantially influence the hydrology of mountain watersheds. In this study, we investigated the relationship between hydraulic conductivity and vegetation type for fens occurring in Rocky Mountain National Park (RMNP), Colorado, USA. Vegetation in RMNP fens can be dominated by woody plants and shrubs, such as willows; by mosses; or by herbaceous plants such as sedges. Fens dominated by each vegetation type were selected for study. Six fens were investigated, all of which are in the Colorado River watershed on the west side of RMNP. For each site, soil hydraulic conductivity was measured at multiple locations using a single-ring infiltrometer. As a result of the shallow water table in these fens (the water table was always within 10 cm of the surface), horizontal hydraulic gradients were produced during the field tests. The measured infiltration rates were analyzed using the numerical model HYDRUS. In order to determine the hydraulic conductivity, a parameter estimation problem was solved using HYDRUS as the forward simulator. Horizontal flow was explicitly accounted for in the model. This approach produced more accurate estimates of hydraulic conductivity than would be obtained using an analytical solution that assumes strictly vertical flow. Significant differences in hydraulic properties between fens appear to result at least in part from the effects of different dominant vegetation types on peat soil formation.

  15. An approach for detecting five typical vegetation types on the Chinese Loess Plateau using Landsat TM data.

    PubMed

    Wang, Zhi-Jie; Jiao, Ju-Ying; Lei, Bo; Su, Yuan

    2015-09-01

    Remote sensing can provide large-scale spatial data for the detection of vegetation types. In this study, two shortwave infrared spectral bands (TM5 and TM7) and one visible spectral band (TM3) of Landsat 5 TM data were used to detect five typical vegetation types (communities dominated by Bothriochloa ischaemum, Artemisia gmelinii, Hippophae rhamnoides, Robinia pseudoacacia, and Quercus liaotungensis) using 270 field survey data in the Yanhe watershed on the Loess Plateau. The relationships between 200 field data points and their corresponding radiance reflectance were analyzed, and the equation termed the vegetation type index (VTI) was generated. The VTI values of five vegetation types were calculated, and the accuracy was tested using the remaining 70 field data points. The applicability of VTI was also tested by the distribution of vegetation type of two small watersheds in the Yanhe watershed and field sample data collected from other regions (Ziwuling Region, Huangling County, and Luochuan County) on the Loess Plateau. The results showed that the VTI can effectively detect the five vegetation types with an average accuracy exceeding 80 % and a representativeness above 85 %. As a new approach for monitoring vegetation types using remote sensing at a larger regional scale, VTI can play an important role in the assessment of vegetation restoration and in the investigation of the spatial distribution and community diversity of vegetation on the Loess Plateau.

  16. [CHARACTERISTICS OF COMBINED ANESTHESIA WITH EPIDURAL COMPONENTE DEPENDING ON VEGETATIVE NERVOUS SYSTEM TYPE].

    PubMed

    Hasanov, F J; Aslanov, A A; Muradov, N F; Namazova, K N

    2016-01-01

    The research objective was to study the characteristics of combined anesthesia with epidural componente (CAEC) depending on vegetative nervous system type (VNS) in patients who underwent large scale traumatic surgical operations on abdominal cavity organs. The scientific research was conducted in Anaesthesiology--Reanimation Department of the Scientific Surgical Centre named after acad. MA. Topchubashev, the Ministry of Health of the Azerbaijan Republic. The research objects were 69 patients who underwent operations in conditions of CAEC due to different serious surgical pathologies of abdominal cavity organs. VNS type was identified based on electroencephalogram, Cerdo Vegetative Index (CVI), Hildebrandt coefficient (HC) and single neurophysiological tests. The patients were divided into three groups depending on VNS type: I--normotonics--17 patients (24.7%), II--sympathatonics--25 patients (36.2%), and III--vagotonics--27 patients (39.1%). Blood adrenocorticotropic hormone (ACTH) and cortisol concentration were studied in 3 stages: I -preoperative, II--operation traumatic stage, III--the 1st postoperative days. The other indicators (heart rate, systolic blood pressure--SBP, dyastolic blood pressure--DBR average blood pressure--BP ave., pulse oximetry SpO₂, ECG, gases in blood and acid-base balance, electrolytes, blood glucose level, myocardium oxygen demand--MOD) were registered after 20 minutes and the 2nd day after operation besides the above stages. The research results indicated that it is possible to define the vegetative nervous system type superiority based on complex of single tests data, EEG, ECG, Cerdo Vegetative Index, Hildebrandt coefficient. CAEC can be considered optimun alternative of general anesthesia ensuring neurohumoral and hemodynamic stability in large scale, traumatic operations on abdominal cavity organs. Clinical course of CAEC is characterized by firmer hemodynamic and humoral stability in patients with functional balance of

  17. Impact of climate and vegetation type on evapotranspiration from green roofs

    NASA Astrophysics Data System (ADS)

    Sia, M. E.; Robinson, C. E.; O'Carroll, D. M.; Voogt, J. A.; Smart, C. C.; Way, D. A.

    2015-12-01

    Green roofs are an increasingly popular low impact development tool used to mitigate the adverse effects of urbanization and the loss of vegetated spaces. The benefits of green roofs include reducing stormwater volume and peak flows, reducing building energy loads, and mitigating the urban heat island effect. Evapotranspiration (ET) is a key process fundamental to hydrologic and thermal performance of green roofs. For example, ET governs the water storage volume available in the soil medium and thus the ability of the green roof to retain and attenuate stormwater. Green roof design considerations such as soil medium depth and plant type impact ET rates. Additionally, climate has a strong impact on ET rates. To date, the influence between climate and green roof design factors (e.g. vegetation type and soil medium depth) on ET rates have not been well quantified. We performed a field study to evaluate the impact of climate, vegetation type, and soil medium depth on ET rates from extensive modular green roofs over prolonged drying periods. Three Canadian cities with distinct climates were chosen as field sites: London, ON, Calgary, AB, and Halifax, NS. At each site, daily module weights were recorded from May to August in 2013 and 2014 for approximately 40 green roof modules. These modules were divided into four vegetation treatments (three single species and one mixed species), and each treatment was divided into two groups of soil medium depth (10 cm or 15 cm). Daily ET rates and seasonal moisture loss were calculated and compared for the modules to determine which treatment provided the highest ET rates. The root depth profile, leaf area index, and stomatal resistance were also measured. On average, daily ET rates among the vegetation treatments did not vary greatly, however, observations on plant survival indicate which plant types are best suited for each site. In all three sites, mixed species in 15 cm of soil medium had higher seasonal moisture loss compared to

  18. Long-Term Arctic Peatland Dynamics, Vegetation and Climate History of the Pur-Taz Region, Western Siberia

    NASA Technical Reports Server (NTRS)

    Peteet, Dorothy; Andreev, Andrei; Bardeen, William; Mistretta, Francesca

    1998-01-01

    Stratigraphic analyses of peat composition, LOI, pollen, spores, macrofossils, charcoal, and AMS ages are used to reconstruct the peatland, vegetation and climatic dynamics in the Pur-Taz region of western Siberia over 5000 years (9300 - 4500 BP). Section stratigraphy shows many changes from shallow lake sediment to different combinations of forested or open sedge, moss, and Equisetum fen and peatland environments. Macrofossil and pollen data indicate that Larix sibirica and Betula pubescens trees were first to arrive, followed by Picea obovata. The dominance of Picea macrofossils 6000-5000 BP in the Pur-Taz peatland along with regional Picea pollen maxima indicate warmer conditions and movement of the spruce treeline northward at this time. The decline of pollen and macrofossils from all of these tree species in uppermost peats suggests a change in the environment less favorable for their growth, perhaps cooler temperatures and/or less moisture. Of major significance is the evidence for old ages of the uppermost peats in this area of Siberia, suggesting a real lack of peat accumulation in recent millennia or recent oxidation of uppermost peat.

  19. Effect of grassland vegetation type on the responses of hydrological processes to seasonal precipitation patterns

    NASA Astrophysics Data System (ADS)

    Salve, Rohit; Sudderth, Erika A.; St. Clair, Samuel B.; Torn, Margaret S.

    2011-11-01

    SummaryUnder future climate scenarios, rainfall patterns and species composition in California grasslands are predicted to change, potentially impacting soil-moisture dynamics and ecosystem function. The primary objective of this study was to assess the impact of altered rainfall on soil-moisture dynamics in three annual grassland vegetation types. We monitored seasonal changes in soil moisture under three different rainfall regimes in mesocosms planted with: (1) a mixed forb-grass community, (2) an Avena barbata monoculture, and (3) an Erodium botrys monoculture. We applied watering treatments in pulses, followed by dry periods that are representative of natural rainfall patterns in California annual grasslands. While rainfall was the dominant treatment, its impact on hydrological processes varied over the growing season. Surprisingly, there were only small differences in the hydrologic response among the three vegetation types. We found significant temporal variability in evapotranspiration, seepage, and soil-moisture content. Both Water Use Efficiency (WUE) and Rain Use Efficiency (RUE) decreased as annual precipitation totals increased. Results from this investigation suggest that both precipitation and vegetation have a significant interactive effect on soil-moisture dynamics. When combined, seasonal precipitation and grassland vegetation influence near-surface hydrology in ways that cannot be predicted from manipulation of a single variable.

  20. Assessing climate refugia from a terrestrial vegetation vulnerability assessment for 29 types in California.

    NASA Astrophysics Data System (ADS)

    Thorne, J. H.; Bjorkman, J.; Boynton, R.; Stewart, J.; Holguin, A.; Schwartz, M.; Albright, W.

    2015-12-01

    We assessed the climate vulnerability of 29 terrestrial macrogroup vegetation types in the National Vegetation Classification Scheme covering 99% of California. Using a 2015 landcover map, we defined current and future climate exposure of each type by assessing conditions at all known locations. This approach identifies both areas of expected high stress and of climate refugia. Species distribution models of the vegetation types proved to over-predict the extent of occupied lands, compared to their mapped extents. Trait based components of the vulnerability assessment were far less influential on level of vulnerability than climate projection. Various cutoffs can be selected to describe refugia. Here we classed refugia as the 20% of climate conditions most frequently occupied by a type. Under CNRM CM5 RCP 4.5, of 70,143 km2 that are the most climate-insulated locations, 46,420 km2 move to higher levels of climate exposure. At the other extreme of climate projections tested, MIROC ESM RCP 8.5, 59,137 km2 are lost. Four macrogroups lose their refugia under CNRM 4.5: Pacific Northwest Conifer Forests, Mountain Riparian Scrub and Wet Meadow, Salt Marsh, and Great Basin Upland Scrub. Under MIROC 8.5 and additional 8 macrogroups lose the most commonly experienced climate: Subalpine Aspen Forests & Pine Woodlands, Non-Native Forest and Woodlands, North Coast Deciduous Scrub and Terrace Prairie, Coastal Dune and Bluff Scrub, Freshwater Marsh, Wet Mountain Meadow, Big Sagebrush Scrub, and Alpine Vegetation. These results raise interesting questions regarding the definition of refugia. We review the results and ask how appropriate they are for different ecosystem types.

  1. Effects of neighboring vascular plants on the abundance of bryophytes in different vegetation types

    NASA Astrophysics Data System (ADS)

    Jägerbrand, Annika K.; Kudo, Gaku; Alatalo, Juha M.; Molau, Ulf

    2012-07-01

    Due to the climate change, vegetation of tundra ecosystems is predicted to shift toward shrub and tree dominance, and this change may influence bryophytes. To estimate how changes in growing environment and the dominance of vascular plants influence bryophyte abundance, we compared the relationship of occurrence of bryophytes among other plant types in a five-year experiment of warming (T), fertilization (F) and T + F in two vegetation types, heath and meadow, in a subarctic-alpine ecosystem. We compared individual leaf area among shrub species to confirm that deciduous shrubs might cause severe shading effect. Effects of neighboring functional types on the performance of Hylocomium splendens was also analyzed. Results show that F and T + F treatments significantly influenced bryophyte abundance negatively. Under natural conditions, bryophytes in the heath site were negatively related to the abundance of shrubs and lichens and the relationship between lichens and bryophytes strengthened after the experimental period. After five years of experimental treatments in the meadow, a positive abundance relationship emerged between bryophytes and deciduous shrubs, evergreen shrubs and forbs. This relationship was not found in the heath site. Our study therefore shows that the abundance relationships between bryophytes and plants in two vegetation types within the same area can be different. Deciduous shrubs had larger leaf area than evergreen shrubs but did not show any shading effect on H. splendens.

  2. Molecular characterization of tol, a mediator of mating-type-associated vegetative incompatibility in Neurospora crassa.

    PubMed Central

    Shiu, P K; Glass, N L

    1999-01-01

    The mating-type locus in the haploid filamentous fungus, Neurospora crassa, controls mating and sexual development. The fusion of reproductive structures of opposite mating type, A and a, is required to initiate sexual reproduction. However, the fusion of hyphae of opposite mating type during vegetative growth results in growth inhibition and cell death, a process that is mediated by the tol locus. Mutations in tol are recessive and suppress mating-type-associated heterokaryon incompatibility. In this study, we describe the cloning and characterization of tol. The tol gene encodes a putative 1011-amino-acid polypeptide with a coiled-coil domain and a leucine-rich repeat. Both regions are required for tol activity. Repeat-induced point mutations in tol result in mutants that are wild type during vegetative growth and sexual reproduction, but that allow opposite mating-type individuals to form a vigorous heterokaryon. Transcript analyses show that tol mRNA is present during vegetative growth but absent during a cross. These data suggest that tol transcription is repressed to allow the coexistence of opposite mating-type nuclei during the sexual reproductive phase. tol is expressed in a mat A, mat a, A/a partial diploid and in a mating-type deletion strain, indicating that MAT A-1 and MAT a-1 are not absolutely required for transcription or repression of tol. These data suggest that TOL may rather interact with MAT A-1 and/or MAT a-1 (or downstream products) to form a death-triggering complex. PMID:9927450

  3. Fossil hyrax dung and evidence of Late Pleistocene and Holocene vegetation types in the Namib Desert

    NASA Astrophysics Data System (ADS)

    Scott, Louis; Marais, Eugene; Brook, George A.

    2004-12-01

    Pollen was derived from fossil dung of herbivorous hyraxes, deposited in a rock shelter on the highest mountain in Namibia, Dâures or Brandberg, situated on the Namib Desert margin. Radiocarbon dating ranging in age between modern times and 30 000 yr BP showed it represents the first empirical pollen evidence of continental palaeovegetation during the Late Pleistocene along the western escarpment of southern Africa. The initial results indicate Last Glacial Maximum vegetation differed totally from the current pattern as vegetation types were dominated by small Asteraceae shrubs, in contrast to those of the Holocene and modern times which show more succulents, grass and woody elements (arboreal pollen). The results suggest that Cape floral communities did not reach into the tropics along the western escarpment of Africa, despite such pollen types occurring in marine cores. Copyright

  4. Effect of vegetative filter strips on herbicide runoff under various types of rainfall.

    PubMed

    Otto, Stefan; Cardinali, Alessandra; Marotta, Ester; Paradisi, Cristina; Zanin, Giuseppe

    2012-06-01

    Narrow vegetative filter strips proved to effectively reduce herbicide runoff from cultivated fields mainly due to the ability of vegetation to delay surface runoff, promote infiltration and adsorb herbicides. A field trial was conducted from 2007 to 2009 in north-east Italy in order to evaluate the effectiveness of various types of vegetative filter strips to reduce spring-summer runoff of the herbicides mesotrione, metolachlor and terbuthylazine, widely used in maize, and to evaluate the effect of the rainfall characteristics on the runoff volume and concentration. Results show that without vegetative filter strip the herbicide load that reaches the surface water is about 5-6 g ha(-1)year(-1) for metolachlor and terbuthylazine (i.e. 0.5-0.9% of the applied rate), confirming that runoff from flat fields as in the Po Valley can have a minor effect on the water quality, and that most of the risk is posed by a few, or even just one extreme rainfall event with a return period of about 25-27 years, causing runoff with a maximum concentration of 64-77 μg L(-1). Mesotrione instead showed rapid soil disappearance and was observed at a concentration of 1.0-3.8 μg L(-1) only after one extreme (artificial) rainfall. Vegetative filter strips of any type are generally effective and can reduce herbicide runoff by 80-88%. Their effectiveness is steady even under severe rainfall conditions, and this supports their implementation in an environmental regulatory scheme at a catchment or regional scale.

  5. Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid-Holocene, and present

    USGS Publications Warehouse

    Bigelow, N.H.; Brubaker, L.B.; Edwards, M.E.; Harrison, S.P.; Prentice, I.C.; Anderson, P.M.; Andreev, A.A.; Bartlein, P.J.; Christensen, T.R.; Cramer, W.; Kaplan, J.O.; Lozhkin, A.V.; Matveyeva, N.V.; Murray, D.F.; McGuire, A.D.; Razzhivin, V.Y.; Ritchie, J.C.; Smith, B.; Walker, D. A.; Gajewski, K.; Wolf, V.; Holmqvist, B.H.; Igarashi, Y.; Kremenetskii, K.; Paus, A.; Pisaric, M.F.J.; Volkova, V.S.

    2003-01-01

    A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55??N at the last glacial maximum (LGM) and mid-Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (???200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (???200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.

  6. Fruit and vegetable intake and incidence of type 2 diabetes mellitus: systematic review and meta-analysis

    PubMed Central

    Gray, Laura J; Troughton, Jacqui; Khunti, Kamlesh; Davies, Melanie J

    2010-01-01

    Objective To investigate the independent effects of intake of fruit and vegetables on incidence of type 2 diabetes. Design Systematic review and meta-analysis. Data sources Medline, Embase, CINAHL, British Nursing Index (BNI), and the Cochrane library were searched for medical subject headings and keywords on diabetes, prediabetes, fruit, and vegetables. Expert opinions were sought and reference lists of relevant articles checked. Study selection Prospective cohort studies with an independent measure of intake of fruit, vegetables, or fruit and vegetables and data on incidence of type 2 diabetes. Results Six studies met the inclusion criteria; four of these studies also provided separate information on the consumption of green leafy vegetables. Summary estimates showed that greater intake of green leafy vegetables was associated with a 14% (hazard ratio 0.86, 95% confidence interval 0.77 to 0.97) reduction in risk of type 2 diabetes (P=0.01). The summary estimates showed no significant benefits of increasing the consumption of vegetables, fruit, or fruit and vegetables combined. Conclusion Increasing daily intake of green leafy vegetables could significantly reduce the risk of type 2 diabetes and should be investigated further. PMID:20724400

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  8. A Bohemian-type Silurian (Wenlockian) pelecypod faunule from Arctic Canada.

    USGS Publications Warehouse

    Pojeta, J., Jr.; Norford, B.S.

    1987-01-01

    The pelecypod genera Slava and Rhombopteria are reported for the first time from Canada, where they occur in a limestone concretion within the Cape Phillips Formation, Cornwallis Island, Arctic Archipelago. These genera are characteristic of Silurian rocks in Bohemia, Czechoslovakia. Graptolites from the same concretion indicate the Monograptus ludensis Zone (uppermost Wenlockian); this age is substantiated by associated conodonts, trilobites, vertebrates, and pelecypods but with less precision. It is difficult to explain the occurrence of Slava and Rhombopteria in the middle of Laurentia on the basis of some map reconstructions of the Wenlockian world. The Canadian material of Slava novaterra n. sp. and Rhombopteria cf. R. mira (Barrande) is described. Leptodesma (Leptodesma) sp. A and an indeterminate grammysiid pelecypod from the same concretion are illustrated. Information is provided to show that Newsomella Foerste, from Wenlockian-Ludlovian rocks of Illinois, Wisconsin, and Tennessee, is not a subgenus of Rhombopteria Jackson. -Authors

  9. Effect of non-crop vegetation types on conservation biological control of pests in olive groves.

    PubMed

    Paredes, Daniel; Cayuela, Luis; Gurr, Geoff M; Campos, Mercedes

    2013-01-01

    Conservation biological control (CBC) is an environmentally sound potential alternative to the use of chemical insecticides. It involves modifications of the environment to promote natural enemy activity on pests. Despite many CBC studies increasing abundance of natural enemies, there are far fewer demonstrations of reduced pest density and very little work has been conducted in olive crops. In this study we investigated the effects of four forms of non-crop vegetation on the abundance of two important pests: the olive psyllid (Euphyllura olivina) and the olive moth (Prays oleae). Areas of herbaceous vegetation and areas of woody vegetation near olive crops, and smaller patches of woody vegetation within olive groves, decreased pest abundance in the crop. Inter-row ground covers that are known to increase the abundance of some predators and parasitoids had no effect on the pests, possibly as a result of lack of synchrony between pests and natural enemies, lack of specificity or intra-guild predation. This study identifies examples of the right types of diversity for use in conservation biological control in olive production systems. PMID:23904994

  10. Effect of non-crop vegetation types on conservation biological control of pests in olive groves

    PubMed Central

    Cayuela, Luis; Gurr, Geoff M.; Campos, Mercedes

    2013-01-01

    Conservation biological control (CBC) is an environmentally sound potential alternative to the use of chemical insecticides. It involves modifications of the environment to promote natural enemy activity on pests. Despite many CBC studies increasing abundance of natural enemies, there are far fewer demonstrations of reduced pest density and very little work has been conducted in olive crops. In this study we investigated the effects of four forms of non-crop vegetation on the abundance of two important pests: the olive psyllid (Euphyllura olivina) and the olive moth (Prays oleae). Areas of herbaceous vegetation and areas of woody vegetation near olive crops, and smaller patches of woody vegetation within olive groves, decreased pest abundance in the crop. Inter-row ground covers that are known to increase the abundance of some predators and parasitoids had no effect on the pests, possibly as a result of lack of synchrony between pests and natural enemies, lack of specificity or intra-guild predation. This study identifies examples of the right types of diversity for use in conservation biological control in olive production systems. PMID:23904994

  11. Arctic plant diversity in the Early Eocene greenhouse

    PubMed Central

    Harrington, Guy J.; Eberle, Jaelyn; Le-Page, Ben A.; Dawson, Mary; Hutchison, J. Howard

    2012-01-01

    For the majority of the Early Caenozoic, a remarkable expanse of humid, mesothermal to temperate forests spread across Northern Polar regions that now contain specialized plant and animal communities adapted to life in extreme environments. Little is known on the taxonomic diversity of Arctic floras during greenhouse periods of the Caenozoic. We show for the first time that plant richness in the globally warm Early Eocene (approx. 55–52 Myr) in the Canadian High Arctic (76° N) is comparable with that approximately 3500 km further south at mid-latitudes in the US western interior (44–47° N). Arctic Eocene pollen floras are most comparable in richness with today's forests in the southeastern United States, some 5000 km further south of the Arctic. Nearly half of the Eocene, Arctic plant taxa are endemic and the richness of pollen floras implies significant patchiness to the vegetation type and clear regional richness of angiosperms. The reduced latitudinal diversity gradient in Early Eocene North American plant species demonstrates that extreme photoperiod in the Arctic did not limit taxonomic diversity of plants. PMID:22072610

  12. Regional vegetation die-off in response to global-change-type drought

    PubMed Central

    Breshears, David D.; Cobb, Neil S.; Rich, Paul M.; Price, Kevin P.; Allen, Craig D.; Balice, Randy G.; Romme, William H.; Kastens, Jude H.; Floyd, M. Lisa; Belnap, Jayne; Anderson, Jesse J.; Myers, Orrin B.; Meyer, Clifton W.

    2005-01-01

    Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a piñon) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions. PMID:16217022

  13. Role of vegetation type on hydraulic conductivity in urban rain gardens

    NASA Astrophysics Data System (ADS)

    Schott, K.; Balster, N. J.; Johnston, M. R.

    2009-12-01

    Although case studies report improved control of urban stormwater within residential rain gardens, the extent to which vegetation type (shrub, turf, prairie) affects the saturated hydraulic conductivity (Ksat) of these depressions has yet to be investigated in a controlled experiment. We hypothesized that there would be significant differences in hydraulic conductivity by vegetation type due to differences in soil physical characteristics and rooting dynamics such that Ksat of shrub gardens would exceed that of prairie, followed by turf. To test this hypothesis, we measured changes in Ksat relative to the above vegetation types as well as non-vegetative controls, each of which were replicated three times for a total of 12 rain gardens. Ksat was calculated using a published method for curve-fitting to single-ring infiltration with a two-head approach where the shape factor is independent of ponding depth. Constant-head infiltration rates were measured at two alternating ponding depths within each garden twice over the growing season. Root core samples were also taken to qualify belowground characteristics including soil bulk density and rooting dynamics relative to differences in Ksat. We found the control and shrub gardens had the lowest mean Ksat of 3.56 (SE = 0.96) and 3.73 (1.22) cm3 hr-1, respectively. Prairie gardens had the next highest mean Ksat of 12.18 (2.26) cm3 hr-1, and turf had the highest mean value of 23.63 (1.81) cm3 hr-1. These data suggest that a denser rooting network near the soil surface may influence saturated hydraulic conductivity. We applied our observed flow rates to a Glover solution model for 3-dimensional flow, which revealed considerably larger discrepancies in turf gardens than beneath prairie or shrub. This indicated that lateral flow conditions in the turf plots could be the explanation for our observed infiltration rates.

  14. Regional vegetation die-off in response to global-change-type drought

    USGS Publications Warehouse

    Breshears, D.D.; Cobb, N.S.; Rich, P.M.; Price, K.P.; Allen, C.D.; Balice, R.G.; Romme, W.H.; Kastens, J.H.; Floyd, M. Lisa; Belnap, J.; Anderson, J.J.; Myers, O.B.; Meyer, Clifton W.

    2005-01-01

    Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a pin??on) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions. ?? 2005 by The National Academy of Sciences of the USA.

  15. The effect of abrupt permafrost thaw on the water table, vegetation and carbon feedback: results from a sub-arctic peatland

    NASA Astrophysics Data System (ADS)

    Malhotra, A.; Roulet, N. T.

    2015-12-01

    Uncertainty in estimating the carbon loss from thawing ice-rich permafrost is attributed, in part, to the abrupt changes in ecosystem structure and function after thaw. In a thawing peat plateau in the discontinuous permafrost zone (Stordalen, Mire, Sweden; ST), we tested for the occurrence of abrupt changes in hydrology and the effects of these changes on the water table and vegetation feedback. Using a chronosequence approach along three transects that capture several transitional thaw stages, we found abrupt hydrological changes following thaw, wherein adjacent areas (1 m apart) had unrelated water table depth (WTD) fluctuations. Despite these abrupt changes, surprisingly, the same Gaussian model of plant abundance explained by WTD could be applied to data from both ST and an undisturbed ombrotrophic peatland (Mer Bleue Bog, Canada; MB). However, the Gaussian model fit was better at MB than at ST. Furthermore, explanatory power of the model at ST decreased with increasing permafrost thaw. While water table and vegetation feedback in a thawing landscape is similar to that of a peatland without transitional land cover types, the vegetation and carbon feedback is complicated by non-linear shifts in the partitioning of gaseous effluxes between CO2 and CH4. These results will be presented along with key implications for modeling carbon loss from thawing landscapes.

  16. Range vegetation type mapping and above-ground green biomass estimations using multispectral imagery. [Wyoming

    NASA Technical Reports Server (NTRS)

    Houston, R. S. (Principal Investigator); Gordon, R. C.

    1974-01-01

    The author has identified the following significant results. Range vegetation types have been successfully mapped on a portion of the 68,000 acre study site located west of Baggs, Wyoming, using ERTS-1 imagery. These types have been ascertained from field transects over a five year period. Comparable studies will be made with EREP imagery. Above-ground biomass estimation studies are being conducted utilizing double sampling techniques on two similar study sites. Information obtained will be correlated with percent relative reflectance measurements obtained on the ground which will be related to image brightness levels. This will provide an estimate of above-ground green biomass with multispectral imagery.

  17. Cloud radiative forcing sensitivity to Arctic synoptic regimes, surface type, cloud phase and cloud properties during the Fall 2014 Arctic Radiation, IceBridge and Sea-Ice Experiment (ARISE)

    NASA Astrophysics Data System (ADS)

    Segal-Rosenheimer, Michal; Redemann, Jens; Shinozuka, Yohei; Flynn, Connor; LeBanc, Samuel; Schmidt, Sebastian; Song, Shi; Bucholtz, Anthony; Reid, Elizabeth; Anderson, Bruce; Corr, Chelsea; Smith, William L.; Kato, Seiji; Spangenberg, Douglas A.; Hofton, Michelle; Moore, Richard; Winstead, Edward; Thornhill, Lee K.

    2015-04-01

    Surface cloud radiative forcing (CRF) estimates in the Arctic cover a wide range of values when comparing various datasets (e.g. MERRA, CERES), and show high bias when compared to in-situ ground-based flux measurement stations (e.g. in Greenland) [Wenshan and Zender, 2014]. These high variations and biases result from an intricate relationship between the prevailing synoptic regimes, surface types (open ocean versus sea-ice), and cloud properties [e.g. Barton et al., 2012; Bennartz et al., 2013]. To date, analyses are focused on large-scale or inter-annual comparisons [e.g. Barton et al., 2012; Taylor et al., 2014], or on several specific ground-based sites [Shupe et al., 2004; Sedlar et al., 2012]. Nevertheless, smaller scale CRF variations related to the sharp changes in sea-ice cover, cloud type and synoptic regimes in autumn are still not well understood. Here, we are focusing on assessing the CRF sensitivity to a composite variable matrix of atmospheric stability regimes, cloud profiles and properties and surface type changes during the NASA ARISE campaign conducted in the Fall of 2014 during the Arctic sea-ice minimum in the Beaufort Sea. We are interested in answering the following questions: (1) what are the combinations of distinct synoptic regimes, surface types, and cloud properties that result in the lowest or highest simulated CRF values over the Arctic Beaufort Sea during the autumn 2014 sea-ice growth period?, and (2) can we relate these simulated extremes to the observations made during the ARISE campaign? We are using the libRadtran radiative transfer modeling package to calculate the CRF sensitivity matrix, with daily gridded atmospheric profiles input from MERRA re-analysis, cloud fields and properties from CALIPSO, MODIS, AVHRR, daily variations in sea-ice margins from AMSR-2, and complementary airborne measurements collected on the C-130 during the campaign. In performing sensitivity analysis, we examine CRF extremes sorted by atmospheric

  18. Temporal variations in soil moisture for three typical vegetation types in inner Mongolia, northern China.

    PubMed

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area. PMID:25781333

  19. Temporal variations in soil moisture for three typical vegetation types in inner Mongolia, northern China.

    PubMed

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area.

  20. Temporal Variations in Soil Moisture for Three Typical Vegetation Types in Inner Mongolia, Northern China

    PubMed Central

    Zheng, Hao; Gao, Jixi; Teng, Yanguo; Feng, Chaoyang; Tian, Meirong

    2015-01-01

    Drought and shortages of soil water are becoming extremely severe due to global climate change. A better understanding of the relationship between vegetation type and soil-moisture conditions is crucial for conserving soil water in forests and for maintaining a favorable hydrological balance in semiarid areas, such as the Saihanwula National Nature Reserve in Inner Mongolia, China. We investigated the temporal dynamics of soil moisture in this reserve to a depth of 40 cm under three types of vegetation during a period of rainwater recharge. Rainwater from most rainfalls recharged the soil water poorly below 40 cm, and the rainfall threshold for increasing the moisture content of surface soil for the three vegetations was in the order: artificial Larix spp. (AL) > Quercus mongolica (QM) > unused grassland (UG). QM had the highest mean soil moisture content (21.13%) during the monitoring period, followed by UG (16.52%) and AL (14.55%); and the lowest coefficient of variation (CV 9.6-12.5%), followed by UG (CV 10.9-18.7%) and AL (CV 13.9-21.0%). QM soil had a higher nutrient content and higher soil porosities, which were likely responsible for the higher ability of this cover to retain soil water. The relatively smaller QM trees were able to maintain soil moisture better in the study area. PMID:25781333

  1. Improving the representation of Arctic photosynthesis in Earth system models

    NASA Astrophysics Data System (ADS)

    Rogers, A.; Serbin, S.; Ely, K.; Sloan, V. L.; Wyatt, R. A.; Kubien, D. S.; Ali, A. A.; Xu, C.; Wullschleger, S. D.

    2015-12-01

    The primary goal of Earth System Models (ESMs) is to improve understanding and projection of future global change. In order to do this they must accurately represent the carbon fluxes associated with the terrestrial carbon cycle. Although Arctic carbon fluxes are small - relative to global carbon fluxes - uncertainty is large. As part of a multidisciplinary project to improve the representation of the Arctic in ESMs (Next Generation Ecosystem Experiments - Arctic) we are examining the photosynthetic parameterization of the Arctic plant functional type (PFT) in ESMs. Photosynthetic CO2 uptake is well described by the Farquhar, von Caemmerer and Berry (FvCB) model of photosynthesis. Most ESMs use a derivation of the FvCB model to calculate gross primary productivity. Two key parameters required by the FvCB model are an estimate of the maximum rate of carboxylation by the enzyme Rubisco (Vc,max) and the maximum rate of electron transport (Jmax). In ESMs the parameter Vc,max is usually fixed for a given PFT. Only four ESMs currently have an explicit Arctic PFT and the data used to derive Vc,max for the Arctic PFT in these models relies on small data sets and unjustified assumptions. We examined the derivation of Vc,max and Jmax in current Arctic PFTs and estimated Vc,max and Jmax for 7 species representing both dominant vegetation and key Arctic PFTs growing on the Barrow Environmental Observatory, Barrow, AK. The values of Vc,max currently used to represent Arctic PFTs in ESMs are 70% lower than the values we measured in these species. Examination of the derivation of Vc,max in ESMs identified that the cause of the relatively low Vc,max value was the result of underestimating both the leaf N content and the investment of that N in Rubisco. Contemporary temperature response functions for Vc,max also appear to underestimate Vc,max at low temperature. ESMs typically use a single multiplier (JVratio) to convert Vc,max to Jmax for all PFTs. We found that the JVratio of

  2. A Broad Approach to Abrupt Boundaries: Looking Beyond the Boundary at Soil Attributes within and Across Tropical Vegetation Types

    PubMed Central

    Warman, Laura; Bradford, Matt G.; Moles, Angela T.

    2013-01-01

    Most research on boundaries between vegetation types emphasizes the contrasts and similarities between conditions on either side of a boundary, but does not compare boundary to non-boundary vegetation. That is, most previous studies lack suitable controls, and may therefore overlook underlying aspects of landscape variability at a regional scale and underestimate the effects that the vegetation itself has on the soil. We compared 25 soil chemistry variables in rainforest, sclerophyll vegetation and across rainforest-sclerophyll boundaries in north-eastern Queensland, Australia. Like previous studies, we did find some contrasts in soil chemistry across vegetation boundaries. However we did not find greater variation in chemical parameters across boundary transects than in transects set in either rainforest or woodland. We also found that soil on both sides of the boundary is more similar to “rainforest soil” than to “woodland soil”. Transects in wet sclerophyll forests with increasing degrees of rainforest invasion showed that as rainforest invades wet sclerophyll forest, the soil beneath wet sclerophyll forest becomes increasingly similar to rainforest soil. Our results have implications for understanding regional vegetation dynamics. Considering soil-vegetation feedbacks and the differences between soil at boundaries and in non-boundary sites may hold clues to some of the processes that occur across and between vegetation types in a wide range of ecosystems. Finally, we suggest that including appropriate controls should become standard practice for studies of vegetation boundaries and edge effects worldwide. PMID:23593312

  3. Stable Isotopes Indicate Nitrogen Sources in Pinguicula vulgaris Across Contrasting Habitat Types in Sub-Arctic Sweden

    NASA Astrophysics Data System (ADS)

    Ackerman, D.; Hobbie, E. A.; Varner, R. K.; Steele, K.

    2012-12-01

    Like most carnivorous plant species, Pinguicula vulgaris (common butterwort) obtains nitrogen from both soil pools and insect prey. Prior studies have estimated percent prey-derived nitrogen (%PDN) for the entire plant, but it may be expected that %PDN varies between plant parts. By measuring stable isotopic ratios in the soil, plants, and naturally captured prey, this study estimated %PDN in both foliage and roots. Plants, soil and insects were collected during July 2012 in sub-arctic Sweden across two habitat types: dry heath and moist sphagnum. Insect samples were homogenized for each site, and all samples were cleaned, dried, and measured for δ15N in an isotope ratio mass spectrometer. Roots showed consistent %PDN in both habitat types, whereas foliage in moist sphagnum sites had significantly greater %PDN than foliage in dry heath sites. Amount of captured prey did not differ significantly between habitat types. These results provide the framework for a rough model of the differential distribution of prey- and soil-derived nitrogen in P. vulgaris, where root nitrogen is split approximately evenly between the two sources, and foliar nitrogen varies by site, possibly dependent on the accessibility of nitrogen in the soil pool.

  4. Relation of MODIS EVI and LAI across time, vegetation types and hydrological regimes

    NASA Astrophysics Data System (ADS)

    Alexandridis, Thomas; Ovakoglou, George

    2015-04-01

    Estimation of the Leaf Area Index (LAI) of a landscape is considered important to describe the ecosystems activity and is used as an important input parameter in hydrological and biogeochemical models related to water and carbon cycle, desertification risk, etc. The measurement of LAI in the field is a laborious and costly process and is mainly done by indirect methods, such as hemispherical photographs that are processed by specialized software. For this reason there have been several attempts to estimate LAI with multispectral satellite images, using theoretical biomass development models, or empirical equations using vegetation indices and land cover maps. The aim of this work is to study the relation of MODIS EVI and LAI across time, vegetation type, and hydrological regime. This was achieved by studying 120 maps of EVI and LAI which cover a hydrological year and five hydrologically diverse areas: river Nestos in Greece, Queimados catchment in Brazil, Rijnland catchment in The Netherlands, river Tamega in Portugal, and river Umbeluzi in Mozambique. The following Terra MODIS composite datasets were downloaded for the hydrological year 2012-2013: MOD13A2 "Vegetation Indices" and MCD15A2 "LAI and FPAR", as well as the equivalent quality information layers (QA). All the pixels that fall in a vegetation land cover (according to the MERIS GLOBCOVER map) were sampled for the analysis, with the exception of those that fell at the border between two vegetation or other land cover categories, to avoid the influence of mixed pixels. Using linear regression analysis, the relationship between EVI and LAI was identified per date, vegetation type and study area. Results show that vegetation type has the highest influence in the variation of the relationship between EVI and LAI in each study area. The coefficient of determination (R2) is high and statistically significant (ranging from 0.41 to 0.83 in 90% of the cases). When plotting the EVI factor from the regression equation

  5. River flooding as a driver of polygon dynamics: modern vegetation data and a millennial peat record from the Anabar River lowlands (Arctic Siberia)

    NASA Astrophysics Data System (ADS)

    Zibulski, R.; Herzschuh, U.; Pestryakova, L. A.; Wolter, J.; Müller, S.; Schilling, N.; Wetterich, S.; Schirrmeister, L.; Tian, F.

    2013-08-01

    The spatial and temporal variability of a low-centred polygon on the eastern floodplain area of the lower Anabar River (72.070° N, 113.921° E; northern Yakutia, Siberia) has been investigated using a multi-method approach. The present-day vegetation in each square metre was analysed, revealing a community of Larix, shrubby Betula, and Salix on the polygon rim, a dominance of Carex and Andromeda polifolia in the rim-to-pond transition zone, and a predominantly monospecific Scorpidium scorpioides coverage within the pond. The total organic carbon (TOC) content, TOC / TN (total nitrogen) ratio, grain size, vascular plant macrofossils, moss remains, diatoms, and pollen were analysed for two vertical sections and a sediment core from a transect across the polygon. Radiocarbon dating indicates that the formation of the polygon started at least 1500 yr ago; the general positions of the pond and rim have not changed since that time. Two types of pond vegetation were identified, indicating two contrasting development stages of the polygon. The first was a well-established moss association, dominated by submerged or floating Scorpidium scorpioides and/or Drepanocladus spp. and overgrown by epiphytic diatoms such as Tabellaria flocculosa and Eunotia taxa. This stage coincides temporally with a period in which the polygon was only drained by lateral subsurface water flow, as indicated by mixed grain sizes. A different moss association occurred during times of repeated river flooding (indicated by homogeneous medium-grained sand that probably accumulated during the annual spring snowmelt), characterized by an abundance of Meesia triquetra and a dominance of benthic diatoms (e.g. Navicula vulpina), indicative of a relatively high pH and a high tolerance of disturbance. A comparison of the local polygon vegetation (inferred from moss and macrofossil spectra) with the regional vegetation (inferred from pollen spectra) indicated that the moss association with Scorpidium

  6. River flooding as a driver of polygon dynamics: modern vegetation data and a millennial peat record from the Anabar River lowlands (Arctic Siberia)

    NASA Astrophysics Data System (ADS)

    Zibulski, R.; Herzschuh, U.; Pestryakova, L. A.; Wolter, J.; Müller, S.; Schilling, N.; Wetterich, S.; Schirrmeister, L.; Tian, F.

    2013-03-01

    The spatial and temporal variability of a low-centred polygon on the eastern floodplain area of the lower Anabar River (72.070° N, 113.921° E, northern Yakutia, Siberia) has been investigated using a multi-method approach. The present-day vegetation in each square metre was analysed revealing a community of Larix shrubby Betula and Salix on the polygon rim, a dominance of Carex and Andromeda polifolia in the rim-to-pond transition zone, and a predominantly monospecific Scorpidium scorpioides coverage within the pond. The TOC content, TOC/TN ratio, grain-size, vascular plant macrofossils, moss remains, diatoms, and pollen were analysed for two vertical sections and a sediment core from a transect across the polygon. Radiocarbon dating indicates that the formation of the polygon started at least 1500 yr ago; the general positions of the pond and rim have not changed since that time. Two types of pond vegetation were identified, indicating two contrasting development stages of the polygon. The first was a well-established moss association dominated by submerged or floating Scorpidium scorpioides and/or Drepanocladus spp. and overgrown by epiphytic diatoms such as Tabellaria flocculosa and Eunotia taxa. This stage coincides temporally with a period in which the polygon was only drained by lateral subsurface water flow, as indicated by mixed grain sizes. A different moss association occurred during times of repeated river flooding (indicated by homogeneous medium-grained sand that probably accumulated during the annual spring snow melt), characterized by an abundance of Meesia triquetra and a dominance of benthic diatoms (e.g. Navicula vulpina), indicative of a relatively high pH and a high tolerance of disturbance. A comparison of the local polygon vegetation (inferred from moss and macrofossil spectra) with the regional vegetation (inferred from pollen spectra) indicated that the moss association with Scorpidium scorpioides became established during relatively

  7. Interactions between soil moisture and Atmospheric Boundary Layer at the Brazilian savana-type vegetation Cerrado

    NASA Astrophysics Data System (ADS)

    Pinheiro, L. R.; Siqueira, M. B.

    2013-05-01

    Before the large people influx and development of the central part of Brazil in the sixties, due to new capital Brasília, Cerrado, a typical Brazilian savanna-type vegetation, used to occupy about 2 million km2, going all the way from the Amazon tropical forest, in the north of the country, to the edges of what used to be of the Atlantic forest in the southeast. Today, somewhat 50% of this area has given place to agriculture, pasture and managed forests. It is forecasted that, at the current rate of this vegetation displacement, Cerrado will be gone by 2030. Understanding how Cerrado interacts with the atmosphere and how this interaction will be modified with this land-use change is a crucial step towards improving predictions of future climate-change scenarios. Cerrado is a vegetation adapted to a climate characterized by two very distinct seasons, a wet season (Nov-Mar) and dry season (May-Ago), with April and October being transitions between seasons. Typically, based on measurements in a weather station located in Brasilia, 75% of precipitation happens in the wet-season months and only 5% during dry-season. Under these circumstances, it is clear that the vegetation will have to cope with long periods of water stress. In this work we studied using numerical simulations, the interactions between soil-moisture, responsible for the water stress, with the Atmospheric Boundary Layer (ABL). The numerical model comprises of a Soil-Vegetation-Atmosphere model where the biophysical processes are represented with a big-leaf approach. Soil water is estimated with a simple logistic model and with water-stress effects on stomatal conductance are parameterized from local measurements of simultaneous latent-heat fluxes and soil moisture. ABL evolution is calculate with a slab model that considers independently surface and entrainment fluxes of sensible- and latent- heat. Temperature tropospheric lapse-rate is taken from soundings at local airport. Simulations of 30-day dry

  8. [Characteristics of soil salinity profiles and their electromagnetic response under various vegetation types in coastal saline area].

    PubMed

    Yang, Jing-Song; Yao, Rong-Jiang; Zou, Ping; Liu, Guang-Ming

    2008-10-01

    Aiming at the intrinsic relationships between vegetation type and soil salinity in coastal saline area, and by using electromagnetic induction EM38 and field sampling method, the characteristics of soil salinity profiles under various vegetation types in typical coastal saline region of the Yellow River Delta were analyzed, and the electromagnetic response characters of the salinity profiles were compared. The results showed that across the study area, soil salinity exhibited the characteristics of top enrichment and strong spatial variation. The horizontal electromagnetic conductivity EM(h) responded well to soil salinity at upper layers, and the response of vertical electromagnetic conductivity EM(v) to soil salinity at deeper layers was superior to that of EM(h). Soil salinity profiles were classified into inverted, normal, and uniform types. The vegetation types of inverted salinity profiles were mainly bare land and Suaeda salsa, while those of normal and uniform salinity profiles were cotton and weed, respectively. The sequence of top enrichment intensity was bare land > S. salsa land > weed land > cotton land. With the change of vegetation type of cotton-weed-S. salsa-bare land, the EM(v)/EM(h) value of salinity profiles decreased gradually. Nonparametric test results showed that there was a significant correlation between vegetation type and electromagnetic response characters, and the distribution characters of EM(v)/EM(h) under various vegetation types varied significantly.

  9. Wood-inhabiting fungi in southern Italy forest stands: morphogroups, vegetation types and decay classes.

    PubMed

    Granito, Vito Mario; Lunghini, Dario; Maggi, Oriana; Persiani, Anna Maria

    2015-01-01

    The authors conducted an ecological study of forests subjected to varying management. The aim of the study was to extend and integrate, within a multivariate context, knowledge of how saproxylic fungal communities behave along altitudinal/vegetational gradients in response to the varying features and quality of coarse woody debris (CWD). The intra-annual seasonal monitoring of saproxylic fungi, based on sporocarp inventories, was used to investigate saproxylic fungi in relation to vegetation types and management categories. We analyzed fungal species occurrence, recorded according to the presence/absence and frequency of sporocarps, on the basis of the harvest season, of coarse woody debris decay classes as well as other environmental and ecological variables. Two-way cluster analysis, DCA and Spearman's rank correlations, for indirect gradient analysis, were performed to identify any patterns of seasonality and decay. Most of the species were found on CWD in an intermediate decay stage. The first DCA axis revealed the vegetational/microclimate gradient as the main driver of fungal community composition, while the second axis corresponded to a strong gradient of CWD decay classes.

  10. Using vegetation cover type to predict and scale peatland methane dynamics.

    NASA Astrophysics Data System (ADS)

    McArthur, K. J.; McCalley, C. K.; Palace, M. W.; Varner, R. K.; Herrick, C.; DelGreco, J. L.

    2015-12-01

    Permafrost ecosystems contain about 50% of the global soil carbon. As these northern ecosystems experience warmer temperature, permafrost thaws and may result in an increase in atmospheric methane. We examined a thawing and discontinuous permafrost boundary at Stordalen Mire, in Northern Sweden, in an effort to better understand methane emissions. Stable isotope analysis of methane in peatland porewater can give insights into the pathway of methane production. By measuring δ13CH4 we can predict whether a system is dominated by either hydrogenotrophic or acetaclastic methane production. Currently, it is a challenge to scale these isotopic patterns, thus, atmospheric inversion models simply assume that acetoclastic production dominates. We analyzed porewater samples collected across a range of vegetation cover types for δ13CH4 using a QCL (Quantum Cascade Laser Spectrometer) in conjunction with highly accurate GPS (3-10cm) measurements and high-resolution UAV imaging. We found δ13CH4 values ranging from -88‰ to -41‰, with averages based on cover type and other vegetation features showing differences of up to -15‰. We then used a computer neural network to predict cover types across Stordalen Mire from UAV imagery based on field-based plot measurements and training samples.. This prediction map was used to scale methane flux and isotope measurements. Our results suggest that the current values used in atmospheric inversion studies may oversimplify the relationship between plant and microbial communities in complex permafrost landscapes. As we gain a deeper understanding of how vegetation relates to methanogenic communities, understanding the spatial component of ecosystem methane metabolism and distribution will be increasingly valuable.

  11. [Soil infiltration characteristics under main vegetation types in Anji County of Zhejiang Province].

    PubMed

    Liu, Dao-Ping; Chen, San-Xiong; Zhang, Jin-Chi; Xie, Li; Jiang, Jiang

    2007-03-01

    The study on the soil infiltration under different main vegetation types in Anji County of Zhejiang Province showed that the characteristics of soil infiltration differed significantly with land use type, and the test eight vegetation types could be classified into four groups, based on soil infiltration capability. The first group, deciduous broadleaved forest, had the strongest soil infiltration capability, and the second group with a stronger soil infiltration capability was composed of grass, pine forest, shrub community and tea bush. Bamboo and evergreen broadleaved forest were classified into the third group with a relatively strong soil infiltration capability, while bare land belonged to the fourth group because of the bad soil structure and poorest soil infiltration capability. The comprehensive parameters of soil infiltration (alpha) and root (beta) were obtained by principal component analysis, and the regression model of alpha and beta could be described as alpha = 0. 1708ebeta -0. 3122. Soil infiltration capability was greatly affected by soil physical and chemical characteristics and root system. Fine roots (< or = 1 mm in diameter) played effective roles on the improvement of soil physical and chemical properties, and the increase of soil infiltration capability was closely related to the amount of the fine roots.

  12. Types of fruits and vegetables used in commercial baby foods and their contribution to sugar content.

    PubMed

    Garcia, Ada Lizbeth; McLean, Kimberley; Wright, Charlotte M

    2016-10-01

    Fruits and vegetables (F&V) are often featured in names of commercial baby foods (CBFs). We aimed to survey all available CBFs in the UK market with F&V included in the food name in order to describe the amount and types of F&V used in CBF and their contribution to total sugar content. Food labels were used to identify F&V and total sugar content. Fruits were more common than vegetables in names of the 329 CBFs identified. The six most common F&V in the names were all relatively sweet: apple, banana, tomato, mango, carrot and sweet potato. The percentage of F&V in the foods ranged from a median of 94% for sweet-spoonable to 13% for dry-savoury products. Fruit content of sweet foods (n = 177) was higher than vegetable content of savoury foods (n = 152) with a median (IQR) of 64.0 g/100 g (33.0-100.0) vs. 46.0 g/100 g (33-56.7). Fruit juice was added to 18% of products. The proportion of F&V in CBF correlated significantly with sugar content for all the food types except dry-savoury food (sweet-spoonable r = 0.24, P = 0.006; savoury-spoonable r = 0.65, P < 0.001; sweet-dry r = 0.81, P < 0.001; savoury-dry r = 0.51, P = 0.06) and explained up to two-thirds of the variation in sugar content. The F&V content of CBFs mainly consists of fruits and relatively sweet vegetables which are unlikely to encourage preferences for bitter-tasting vegetables or other non-sweet foods. F&V contribute significantly to the total sugar content, particularly of savoury foods.

  13. Identification of phenological stages and vegetative types for land use classification

    NASA Technical Reports Server (NTRS)

    Mckendrick, J. D. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Classification of digital data for mapping Alaskan vegetation has been compared to ground truth data and found to have accuracies as high as 90%. These classifications are broad scale types as are currently being used on the Major Ecosystems of Alaska map prepared by the Joint Federal-State Land Use Planning Commission for Alaska. Cost estimates for several options using the ERTS-1 digital data to map the Alaskan land mass at the 1:250,000 scale ranged between $2.17 to $1.49 per square mile.

  14. The response of vegetation dynamics of the different alpine grassland types to temperature and precipitation on the Tibetan Plateau.

    PubMed

    Sun, Jian; Qin, Xiaojing; Yang, Jun

    2016-01-01

    The spatiotemporal variability of the Normalized Difference Vegetation Index (NDVI) of three vegetation types (alpine steppe, alpine meadow, and alpine desert steppe) across the Tibetan Plateau was analyzed from 1982 to 2013. In addition, the annual mean temperature (MAT) and annual mean precipitation (MAP) trends were quantified to define the spatiotemporal climate patterns. Meanwhile, the relationships between climate factors and NDVI were analyzed in order to understand the impact of climate change on vegetation dynamics. The results indicate that the maximum of NDVI increased by 0.3 and 0.2 % per 10 years in the entire regions of alpine steppe and alpine meadow, respectively. However, no significant change in the NDVI of the alpine desert steppe has been observed since 1982. A negative relationship between NDVI and MAT was found in all these alpine grassland types, while MAP positively impacted the vegetation dynamics of all grasslands. Also, the effects of temperature and precipitation on different vegetation types differed, and the correlation coefficient for MAP and NDVI in alpine meadow is larger than that for other vegetation types. We also explored the percentages of precipitation and temperature influence on NDVI variation, using redundancy analysis at the observation point scale. The results show that precipitation is a primary limiting factor for alpine vegetation dynamic, rather than temperature. Most importantly, the results can serve as a tool for grassland ecosystem management.

  15. Live from the Arctic

    NASA Astrophysics Data System (ADS)

    Warnick, W. K.; Haines-Stiles, G.; Warburton, J.; Sunwood, K.

    2003-12-01

    residents speak in eloquent terms of the changes they see around them, manifested in new patterns of vegetation, the melting of permafrost and the absence of game species that used to be abundant. Meanwhile, new satellites and more sophisticated sensors on the ground and in the ice, add scientific testimony that seems to support and even extend native perceptions. Live from the Arctic will unify both perspectives, and use todays most powerful and effective communications media to connect young people and general audiences all across America to researchers and communities living and working in the Arctic. During IPY there will be a level of interest in the Polar regions unprecedented in a generation. Live from the Arctic offers unique resources to satisfy that curiosity, and encourage active participation and engagement in understanding some of Earths most significant peoples, places and rapidly changing conditions.

  16. Selection of vegetation types and density of bison in an arid ecosystem

    USGS Publications Warehouse

    Schoenecker, Kathryn A.; Zeigenfuss, Linda C.; Nielsen, Scott E.; Pague, Chris

    2015-01-01

    Understanding species habitat selection and factors that drive selection are key components for conservation. We report the first resource selection functions (RSFs) for bison inhabiting an arid ecosystem and use them with density estimates of bison to estimate the number of bison that could be supported if the bison range were expanded to federal lands in the San Luis Valley of Colorado. We derived RSFs for vegetation types using locations of plains bison collected weekly over 3 years from 2005 to 2007. Bison selected for wet or mesic grassland habitats in all seasons. Wetland selection by bison was predicted to be 18 times greater than that of rabbitbrush vegetation, the reference category, and selection of meadows was predicted to be 11 times greater than that of the rabbitbrush type. Willow-dominated plant communities were strongly avoided. Cottonwood communities were also avoided, with the exception of some moderate levels of selection in fall. The willow and cottonwood communities have an understory with low biomass of herbaceous species and low productivity in this arid system. Based on the RSFs we predicted that in the San Luis Valley of Colorado up to 2,379 bison could be supported in similar habitats under Fish and Wildlife Service (FWS) jurisdiction, and up to 759 bison could be supported on adjacent National Park Service (NPS) land. This modeling framework provides a conservation tool for the restoration of bison to their historical habitats, and has utility for application to other terrestrial species where assumptions are met. 

  17. Vegetation type conversion in Los Peñasquitos Lagoon, California: an examination of the role of watershed urbanization.

    PubMed

    Greer, Keith; Stow, Douglas

    2003-04-01

    The objective of this study was to examine the role that watershed urbanization has played in changes to the vegetation types within Los Peñasquitos Lagoon, San Diego, California. Aerial photographs taken between 1928 and 1999 were used to examine changes in vegetation types. The aerial photographs were scanned into digital format and incorporated into a geographic information system (GIS). A combination of image classification techniques was used to differentiate the vegetation types. Land use/cover of the Carmel Valley watershed of the Los Peñasquitos Lagoon was mapped for the same dates as the aerial photographs. A temporal geographic analysis was conducted on the conversion of areal extent of lagoon vegetation types compared to areal extent of urban development in the watershed. Soil salinity and dry season (June-September) stream discharge were measured. The results show that approximately 80.3% of the vegetation in the study area has changed types between 1928 and 1999. Increases in the areal extent of urban development within the watershed show a strong positive relationship compared to the areal extent of brackish marsh and riparian vegetation, and a strong negative relationship to the areal extent of salt panne and mudflats. There was no significant relationship between urban development and salt marsh vegetation.Dry season stream discharge has increased by an order of magnitude. The increase in stream discharge supports the hypothesis that increased freshwater has lowered soil salinity, allowing for invasion by glycophytic species. Hydrology and soil salinity appear to be significant factors for maintaining the distribution of the lagoon vegetation types and the biotic communities that rely upon them.

  18. Variations of deep soil moisture under different vegetation types and influencing factors in a watershed of the Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Fang, Xuening; Zhao, Wenwu; Wang, Lixin; Feng, Qiang; Ding, Jingyi; Liu, Yuanxin; Zhang, Xiao

    2016-08-01

    Soil moisture in deep soil layers is a relatively stable water resource for vegetation growth in the semi-arid Loess Plateau of China. Characterizing the variations in deep soil moisture and its influencing factors at a moderate watershed scale is important to ensure the sustainability of vegetation restoration efforts. In this study, we focus on analyzing the variations and factors that influence the deep soil moisture (DSM) in 80-500 cm soil layers based on a soil moisture survey of the Ansai watershed in Yan'an in Shanxi Province. Our results can be divided into four main findings. (1) At the watershed scale, higher variations in the DSM occurred at 120-140 and 480-500 cm in the vertical direction. At the comparable depths, the variation in the DSM under native vegetation was much lower than that in human-managed vegetation and introduced vegetation. (2) The DSM in native vegetation and human-managed vegetation was significantly higher than that in introduced vegetation, and different degrees of soil desiccation occurred under all the introduced vegetation types. Caragana korshinskii and black locust caused the most serious desiccation. (3) Taking the DSM conditions of native vegetation as a reference, the DSM in this watershed could be divided into three layers: (i) a rainfall transpiration layer (80-220 cm); (ii) a transition layer (220-400 cm); and (iii) a stable layer (400-500 cm). (4) The factors influencing DSM at the watershed scale varied with vegetation types. The main local controls of the DSM variations were the soil particle composition and mean annual rainfall; human agricultural management measures can alter the soil bulk density, which contributes to higher DSM in farmland and apple orchards. The plant growth conditions, planting density, and litter water holding capacity of introduced vegetation showed significant relationships with the DSM. The results of this study are of practical significance for vegetation restoration strategies, especially

  19. Effects of Vegetable Oil Type and Lipophilic Emulsifiers on the Induction Period of Fat Crystallization.

    PubMed

    Miyagawa, Yayoi; Ogawa, Takenobu; Nakagawa, Kyuya; Adachi, Shuji

    2015-01-01

    The induction period of crystallization, which is defined as the time required for oil to start to crystallize, is useful indicator of the freeze-thaw stability of food emulsions such as mayonnaise. We investigated the induction period of vegetable oils with low melting points, such as rapeseed and soybean oils, which are commonly employed for mayonnaise production. The induction period was measured by monitoring the temperature of a specimen during storage at low temperature. The induction period depended on the type of oil and lipophilic emulsifier, emulsifier concentration, and storage temperature. The effect of the oil type on the induction period depended on the composition of the oil. Differential scanning calorimetry (DSC) analyses of the lipophilic emulsifiers suggested that the melting trend of the emulsifier is strongly related to the induction period.

  20. The effect of vegetation type and fire on permafrost thaw: An empirical test of a process based model

    NASA Astrophysics Data System (ADS)

    Thierry, Aaron; Estop-Aragones, Cristian; Fisher, James; Hartley, Iain; Murton, Julian; Phoenix, Gareth; Street, Lorna; Williams, Mathew

    2015-04-01

    As conditions become more favourable for plant growth in the high latitudes, most models predict that these areas will take up more carbon during the 21st century. However, vast stores of carbon are frozen in boreal and arctic permafrost, and warming may result in some of this carbon being released to the atmosphere. The recent inclusion of permafrost thaw in large-scale model simulations has suggested that the permafrost feedback could potentially substantially reduce the predicted global net uptake of carbon by terrestrial ecosystems, with major implications for the rate of climate change. However, large uncertainties remain in predicting rates of permafrost thaw and in determining the impacts of thaw in contrasting ecosystems, with many of the key processes missing from carbon-climate models. The role that different plant communities play in insulating soils and protecting permafrost is poorly quantified, with key groups such as mosses absent in many models. But it is thought that they may play a key role in determining permafrost resilience. In order to test the importance of these ecological processes we use a new specially acquired dataset from sites in the Canadian arctic to develop, parameterise and evaluate a detailed process-based model of vegetation-soil-permafrost interactions which includes an insulating moss understory. We tested the sensitivity of modelled active layer depth to a series of factors linked to fire disturbance, which is common in boreal permafrost areas. We show how simulations of active layer depth (ALD) respond to removals of (i) vascular vegetation, (ii) moss cover, and (iii) organic soil layers. We compare model responses to observed patterns from Canada. We also describe the sensitivity of our modelled ALD to changes in temperature and precipitation. We found that four parameters controlled most of the sensitivity in the modelled ALD, linked to conductivity of organic soils and mosses.

  1. Comprehensive Study of Carbonaceous Species in Arctic Snow: from Snow Type to Carbon Sources and Sinks in the Snowpack

    NASA Astrophysics Data System (ADS)

    Voisin, D.; Cozic, J.; Houdier, S.; Barret, M.; Jaffrezo, J. L.; King, M. D.; Beine, H. J.; Domine, F.

    2012-04-01

    Carbonaceous species play critical roles in the interaction of snow with the overlying atmosphere. Elemental or Black Carbon strongly increases solar energy uptake and snow melt, therefore influencing the snow-climate feedback loop. Carbonyls and complex organic molecules such as Humic Like Substances also absorb UV and visible light, therefore influencing photochemistry and light penetration depths in the snowpack. It has been proposed that some of those complex organic molecules, acting as electron donors in photochemical reactions might change the photolysis paths of nitric acid from NO / NO2 to HONO. Yet, comprehensive investigations of the organic matter in arctic snowpack are scarce, and often limited to a few specific species. Such a comprehensive representation of carbonaceous species in Arctic snow is the focus of the present work, lead during the OASIS field campaign in Barrow and focuses on major classes of carbonaceous species, defined operationally: Elemental Carbon (EC), which is close to BC; Water Insoluble Organic Carbon (WInOC); Dissolved Organic Carbon (DOC), which altogether represent the Total Carbon Content (TCC) of the snowpack. Among DOC species, we will more particularly focus on HUmic LIke Substances (HULIS), C2 - C5 dicarboxylic acids and short chain aldehydes, as these compounds are most particularly involved in snow photochemistry, especially HULIS, whose optical properties (UV-Vis absorbance) are measured and discussed. In order to link observed concentrations to physico-chemical processes in the snow pack, we use snow type as a morphological marker of those processes and of the snowpack's history. Similarly, as the different classes of compounds measured are differently affected by the physical processes that lead the transformation of the snowpack, they can be used to probe into those processes. This strategy enables us to discuss in a common framework physical and chemical processes affecting carbonaceous species and the snowpack

  2. Poles Apart: Arctic and Antarctic Octadecabacter strains Share High Genome Plasticity and a New Type of Xanthorhodopsin

    PubMed Central

    Vollmers, John; Voget, Sonja; Dietrich, Sascha; Gollnow, Kathleen; Smits, Maike; Meyer, Katja; Brinkhoff, Thorsten; Simon, Meinhard; Daniel, Rolf

    2013-01-01

    The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps. PMID:23671678

  3. Poles apart: Arctic and Antarctic Octadecabacter strains share high genome plasticity and a new type of xanthorhodopsin.

    PubMed

    Vollmers, John; Voget, Sonja; Dietrich, Sascha; Gollnow, Kathleen; Smits, Maike; Meyer, Katja; Brinkhoff, Thorsten; Simon, Meinhard; Daniel, Rolf

    2013-01-01

    The genus Octadecabacter is a member of the ubiquitous marine Roseobacter clade. The two described species of this genus, Octadecabacter arcticus and Octadecabacter antarcticus, are psychrophilic and display a bipolar distribution. Here we provide the manually annotated and finished genome sequences of the type strains O. arcticus 238 and O. antarcticus 307, isolated from sea ice of the Arctic and Antarctic, respectively. Both genomes exhibit a high genome plasticity caused by an unusually high density and diversity of transposable elements. This could explain the discrepancy between the low genome synteny and high 16S rRNA gene sequence similarity between both strains. Numerous characteristic features were identified in the Octadecabacter genomes, which show indications of horizontal gene transfer and may represent specific adaptations to the habitats of the strains. These include a gene cluster encoding the synthesis and degradation of cyanophycin in O. arcticus 238, which is absent in O. antarcticus 307 and unique among the Roseobacter clade. Furthermore, genes representing a new subgroup of xanthorhodopsins as an adaptation to icy environments are present in both Octadecabacter strains. This new xanthorhodopsin subgroup differs from the previously characterized xanthorhodopsins of Salinibacter ruber and Gloeobacter violaceus in phylogeny, biogeography and the potential to bind 4-keto-carotenoids. Biochemical characterization of the Octadecabacter xanthorhodopsins revealed that they function as light-driven proton pumps. PMID:23671678

  4. Inhibition of NMDA Type Glutamate Receptors Induces Arousal from Torpor in Hibernating Arctic Ground Squirrels (Urocitellus parryii)

    PubMed Central

    Jinka, Tulasi R.; Rasley, Brian T.; Drew, Kelly L.

    2012-01-01

    Hibernation is an adaptation to overcome periods of resource limitation often associated with extreme climatic conditions. The hibernation season consists of prolonged bouts of torpor that are interrupted by brief interbout arousals. Physiological mechanisms regulating spontaneous arousals are poorly understood, but may be related to a need for gluconeogenesis or elimination of metabolic wastes. Glutamate is derived from glutamine through the glutamate-glutamine cycle and from glucose via the pyruvate carboxylase pathway when nitrogen balance favors formation of glutamine. The present study tests the hypothesis that activation of NMDA type glutamate receptors (NMDAR) maintains torpor in arctic ground squirrel (AGS; Urocitellus parryii).Administration of NMDAR antagonists MK-801 (5mg/kg,ip) that crosses blood-brain barrier and AP5 (5mg/kg,ip) that does not cross the blood brain barrier induced arousal in AGS. Central administration of MK-801 (0.2, 2, 20 or 200 μg; icv) to hibernating AGS failed to induce arousal. Results suggest that activation of NMDAR at a peripheral or circumventricular site is necessary to maintain prolonged torpor and that a decrease in glutamate at these sites may contribute to spontaneous arousal in AGS. PMID:22697356

  5. Distinguishing Bark Beetle-infested Vegetation by Tree Species Types and Stress Levels using Landsat Data

    NASA Astrophysics Data System (ADS)

    Sivanpillai, R.; Ewers, B. E.; Speckman, H. N.; Miller, S. N.

    2015-12-01

    In the Western United States, more than 3 million hectares of lodgepole pine forests have been impacted by the Mountain pine beetle outbreak, while another 166,000 hectares of spruce-fir forests have been attacked by Spruce beetle. Following the beetle attack, the trees lose their hydraulic conductivity thus altering their carbon and water fluxes. These trees go through various stages of stress until mortality, described by color changes in their needles prior to losing them. Modeling the impact of these vegetation types require thematically precise land cover data that distinguishes lodgepole pine and spruce-fir forests along with the stage of impact since the ecosystem fluxes are different for these two systems. However, the national and regional-scale land cover datasets derived from remotely sensed data do not have this required thematic precision. We evaluated the feasibility of multispectral data collected by Landsat 8 to distinguish lodgepole pine and spruce fir, and subsequently model the different stages of attack using field data collected in Medicine Bow National Forest (Wyoming, USA). Operational Land Imager, onboard Landsat 8 has more spectral bands and higher radiometric resolution (12 bit) in comparison to sensors onboard earlier Landsat missions which could improve the ability to distinguish these vegetation types and their stress conditions. In addition to these characteristics, its repeat coverage, rigorous radiometric calibration, wide swath width, and no-cost data provide unique advantages to Landsat data for mapping large geographic areas. Initial results from this study highlight the importance of SWIR bands for distinguishing different levels of stress, and the need for ancillary data for distinguishing species types. Insights gained from this study could lead to the generation of land cover maps with higher thematic precision, and improve the ability to model various ecosystem processes as a result of these infestations.

  6. Observing Arctic Ecology using Networked Infomechanical Systems

    NASA Astrophysics Data System (ADS)

    Healey, N. C.; Oberbauer, S. F.; Hollister, R. D.; Tweedie, C. E.; Welker, J. M.; Gould, W. A.

    2012-12-01

    Understanding ecological dynamics is important for investigation into the potential impacts of climate change in the Arctic. Established in the early 1990's, the International Tundra Experiment (ITEX) began observational inquiry of plant phenology, plant growth, community composition, and ecosystem properties as part of a greater effort to study changes across the Arctic. Unfortunately, these observations are labor intensive and time consuming, greatly limiting their frequency and spatial coverage. We have expanded the capability of ITEX to analyze ecological phenomenon with improved spatial and temporal resolution through the use of Networked Infomechanical Systems (NIMS) as part of the Arctic Observing Network (AON) program. The systems exhibit customizable infrastructure that supports a high level of versatility in sensor arrays in combination with information technology that allows for adaptable configurations to numerous environmental observation applications. We observe stereo and static time-lapse photography, air and surface temperature, incoming and outgoing long and short wave radiation, net radiation, and hyperspectral reflectance that provides critical information to understanding how vegetation in the Arctic is responding to ambient climate conditions. These measurements are conducted concurrent with ongoing manual measurements using ITEX protocols. Our NIMS travels at a rate of three centimeters per second while suspended on steel cables that are ~1 m from the surface spanning transects ~50 m in length. The transects are located to span soil moisture gradients across a variety of land cover types including dry heath, moist acidic tussock tundra, shrub tundra, wet meadows, dry meadows, and water tracks. We have deployed NIMS at four locations on the North Slope of Alaska, USA associated with 1 km2 ARCSS vegetation study grids including Barrow, Atqasuk, Toolik Lake, and Imnavait Creek. A fifth system has been deployed in Thule, Greenland beginning in

  7. A Methodology for Soil Moisture Retrieval from Land Surface Temperature, Vegetation Index, Topography and Soil Type

    NASA Astrophysics Data System (ADS)

    Pradhan, N. R.

    2015-12-01

    Soil moisture conditions have an impact upon hydrological processes, biological and biogeochemical processes, eco-hydrology, floods and droughts due to changing climate, near-surface atmospheric conditions and the partition of incoming solar and long-wave radiation between sensible and latent heat fluxes. Hence, soil moisture conditions virtually effect on all aspects of engineering / military engineering activities such as operational mobility, detection of landmines and unexploded ordinance, natural material penetration/excavation, peaking factor analysis in dam design etc. Like other natural systems, soil moisture pattern can vary from completely disorganized (disordered, random) to highly organized. To understand this varying soil moisture pattern, this research utilized topographic wetness index from digital elevation models (DEM) along with vegetation index from remotely sensed measurements in red and near-infrared bands, as well as land surface temperature (LST) in the thermal infrared bands. This research developed a methodology to relate a combined index from DEM, LST and vegetation index with the physical soil moisture properties of soil types and the degree of saturation. The advantage in using this relationship is twofold: first it retrieves soil moisture content at the scale of soil data resolution even though the derived indexes are in a coarse resolution, and secondly the derived soil moisture distribution represents both organized and disorganized patterns of actual soil moisture. The derived soil moisture is used in driving the hydrological model simulations of runoff, sediment and nutrients.

  8. Vegetation types alter soil respiration and its temperature sensitivity at the field scale in an estuary wetland.

    PubMed

    Han, Guangxuan; Xing, Qinghui; Luo, Yiqi; Rafique, Rashad; Yu, Junbao; Mikle, Nate

    2014-01-01

    Vegetation type plays an important role in regulating the temporal and spatial variation of soil respiration. Therefore, vegetation patchiness may cause high uncertainties in the estimates of soil respiration for scaling field measurements to ecosystem level. Few studies provide insights regarding the influence of vegetation types on soil respiration and its temperature sensitivity in an estuary wetland. In order to enhance the understanding of this issue, we focused on the growing season and investigated how the soil respiration and its temperature sensitivity are affected by the different vegetation (Phragmites australis, Suaeda salsa and bare soil) in the Yellow River Estuary. During the growing season, there were significant linear relationships between soil respiration rates and shoot and root biomass, respectively. On the diurnal timescale, daytime soil respiration was more dependent on net photosynthesis. A positive correlation between soil respiration and net photosynthesis at the Phragmites australis site was found. There were exponential correlations between soil respiration and soil temperature, and the fitted Q10 values varied among different vegetation types (1.81, 2.15 and 3.43 for Phragmites australis, Suaeda salsa and bare soil sites, respectively). During the growing season, the mean soil respiration was consistently higher at the Phragmites australis site (1.11 µmol CO2 m(-2) s(-1)), followed by the Suaeda salsa site (0.77 µmol CO2 m(-2) s(-1)) and the bare soil site (0.41 µmol CO2 m(-2) s(-1)). The mean monthly soil respiration was positively correlated with shoot and root biomass, total C, and total N among the three vegetation patches. Our results suggest that vegetation patchiness at a field scale might have a large impact on ecosystem-scale soil respiration. Therefore, it is necessary to consider the differences in vegetation types when using models to evaluate soil respiration in an estuary wetland.

  9. Usefulness of Skylab color photography and ERTS-1 multispectral imagery for mapping range vegetation types in southwestern Wyoming

    NASA Technical Reports Server (NTRS)

    Gordon, R. C. (Principal Investigator)

    1974-01-01

    The author has identified the following significant results. Aerial photography at scales of 1:43,400 and 1:104,500 was used to evaluate the usefulness of Skylab color photography (scales of 1:477,979 and 1:712,917) and ERTS-1 multispectral imagery (scale 1:1,000,000) for mapping range vegetation types. The project was successful in producing a range vegetation map of the 68,000 acres of salt desert shrub type in southwestern Wyoming. Techniques for estimation of above-ground green biomass have not yet been confirmed due to the mechanical failure of the photometer used in obtaining relative reflectance measurement. However, graphs of log transmittance versus above-ground green biomass indicate that production estimates may be made for some vegetation types from ERTS imagery. Other vegetation types not suitable for direct ERTS estimation of green biomass may possibly be related to those vegetation types whose production has been estimated from the multispectral imagery.

  10. Burn Severities, Fire Intensities, and Impacts to Major Vegetation Types from the Cerro Grande Fire

    SciTech Connect

    Balice, Randy G.; Bennett, Kathryn D.; Wright, Marjorie A.

    2004-12-15

    The Cerro Grande Fire resulted in major impacts and changes to the ecosystems that were burned. To partially document these effects, we estimated the acreage of major vegetation types that were burned at selected burn severity levels and fire intensity levels. To accomplish this, we adopted independently developed burn severity and fire intensity maps, in combination with a land cover map developed for habitat management purposes, as a basis for the analysis. To provide a measure of confidence in the acreage estimates, the accuracies of these maps were also assessed. In addition, two other maps of comparable quality were assessed for accuracy: one that was developed for mapping fuel risk and a second map that resulted from a preliminary application of an evolutionary computation software system, called GENIE.

  11. Wildfires alter rodent community structure across four vegetation types in southern California, USA

    USGS Publications Warehouse

    Brehme, Cheryl S.; Clark, Denise R.; Rochester, Carlton J.; Fisher, Robert N.

    2011-01-01

    We surveyed burned and unburned plots across four habitat reserves in San Diego County, California, USA, in 2005 and 2006, to assess the effects of the 2003 wildfires on the community structure and relative abundance of rodent species. The reserves each contained multiple vegetation types (coastal sage scrub, chaparral, woodland, and grassland) and spanned from 250 m to 1078 m in elevation. Multivariate analyses revealed a more simplified rodent community structure in all burned habitats in comparison to unburned habitats. Reduction in shrub and tree cover was highly predictive of changes in post-fire rodent community structure in the burned coastal sage scrub and chaparral habitats. Reduction in cover was not predictive for the less substantially burned woodlands and grasslands, for which we hypothesized that interspecific competition played a greater role in post-fire community structure. Across vegetation types, generalists and open habitat specialists typically increased in relative abundance, whereas closed habitat specialists decreased. We documented significant increases in relative abundance of the deer mouse (Peromyscus maniculatus Wagner) and Dulzura kangaroo rat (Dipodomys simulans Merriam). In contrast, we found significant decreases in relative abundance for the California mouse (Peromyscus californicus Gambel), San Diego pocket mouse (Chaetodipus fallax Merriam), desert woodrat (Neotoma lepida Thomas), and brush mouse (Peromyscus boylii Baird). Currently, our research program involves assessment of whether habitat conservation plans (HCPs) in southern California provide long-term protection to HCP covered species, as well as preserve ecosystem function. The scenario of increased wildfires needs to be incorporated into this assessment. We discuss our results in relation to management and conservation planning under a future scenario of larger and more frequent wildfires in southern California.

  12. Impacts of grassland types and vegetation cover changes on surface air temperature in the regions of temperate grassland of China

    NASA Astrophysics Data System (ADS)

    Shen, Xiangjin; Liu, Binhui; Li, Guangdi; Yu, Pujia; Zhou, Daowei

    2016-10-01

    The sensitivity of surface air temperature response to different grassland types and vegetation cover changes in the regions of temperate grassland of China was analyzed by observation minus reanalysis (OMR) method. The basis of the OMR approach is that reanalysis data are insensitive to local surface properties, so the temperature differences between surface observations and reanalysis can be attributed to land effects. Results showed that growing-season air temperature increased by 0.592 °C/decade in the regions of temperate grassland of China, with about 31 % of observed warming associated with the effects of grassland types and vegetation cover changes. For different grassland types, the growing-season OMR trend was the strongest for temperate desert steppe (0.259 °C/decade) and the weakest for temperate meadow (0.114 °C/decade). Our results suggest that the stronger intraseasonal changes of grassland vegetation are present, the more sensitive the OMR trend responds to the intraseasonal vegetation cover changes. In August and September, the OMR of temperate meadow showed a weak cooling trend. For temperate meadow, about 72.2 and 72.6 % of surface cooling were explained by both grassland type and increase of vegetation cover for August and September, respectively. For temperate steppe and temperate desert steppe, due to the limited soil moisture and little evaporative cooling feedback, the vegetation changes have no significant effect on the surface air temperature. These results indicate that the impact of grassland types and vegetation cover changes should be considered when projecting further climate change in the temperate grassland region of China.

  13. High diversity and potential origins of T4-type bacteriophages on the surface of Arctic glaciers.

    PubMed

    Bellas, Christopher M; Anesio, Alexandre M

    2013-09-01

    Tailed bacteriophages are the most abundant viruses in the biosphere. Here we examined the T4-type bacteriophage community inhabiting the surface of two glaciers in Svalbard. We used a molecular approach to target g23, the major capsid protein gene, to demonstrate that in the extreme cryoconite hole habitats the T4-type phages are surprisingly diverse. Phylogenetic analysis revealed that cryoconite hole sediments harbour a mixed phage community spanning multiple T4-type phage subgroups. The majority (71 %) of phage sequences clustered into three novel phylogenetically distinct groups, whilst the remainder clustered with known marine and soil derived phage sequences. The meltwater in cryoconite holes also contained a further distinct phage community which was related to previously detected marine phage variants. The ability of phages to move between marine and glacial habitats was tested in a transplantation experiment. Phages from the nearby marine fjord were found to be capable of initiating infection of supraglacial bacteria, suggesting suitable hosts could be found by non-native phages. Together this evidence suggests that the surface of glaciers contain both novel and cosmopolitan phages, some of which may have arrived in the cryosphere from other biomes.

  14. Assessing onset and length of greening period in six vegetation types in Oaxaca, Mexico, using NDVI-precipitation relationships.

    PubMed

    Gómez-Mendoza, L; Galicia, L; Cuevas-Fernández, M L; Magaña, V; Gómez, G; Palacio-Prieto, J L

    2008-07-01

    Variations in the normalized vegetation index (NDVI) for the state of Oaxaca, in southern Mexico, were analyzed in terms of precipitation anomalies for the period 1997-2003. Using 10-day averages in NDVI data, obtained from AVHRR satellite information, the response of six types of vegetation to intra-annual and inter-annual fluctuations in precipitation were examined. The onset and temporal evolution of the greening period were studied in terms of precipitation variations through spectral analysis (coherence and phase). The results indicate that extremely dry periods, such as those observed in 1997 and 2001, resulted in low values of NDVI for much of Oaxaca, while good precipitation periods produced a rapid response (20-30 days of delay) from a stressed to a non-stressed condition in most vegetation types. One of these rapid changes occurred during the transition from dry to wet conditions during the summer of 1998. As in many parts of the tropics and subtropics, the NDVI reflects low frequency variations in precipitation on several spatial scales. Even after long dry periods (2001-2002), the various regional vegetation types are capable of recovering when a good rainy season takes place, indicating that vegetation types such as the evergreen forests in the high parts of Oaxaca respond better to rainfall characteristics (timing, amount) than to temperature changes, as is the case in most mid-latitudes. This finding may be relevant to prepare climate change scenarios for forests, where increases in surface temperature and precipitation anomalies are expected.

  15. Frost flowers on young Arctic sea ice: The climatic, chemical, and microbial significance of an emerging ice type

    NASA Astrophysics Data System (ADS)

    Barber, D. G.; Ehn, J. K.; Pućko, M.; Rysgaard, S.; Deming, J. W.; Bowman, J. S.; Papakyriakou, T.; Galley, R. J.; Søgaard, D. H.

    2014-10-01

    Ongoing changes in Arctic sea ice are increasing the spatial and temporal range of young sea ice types over which frost flowers can occur, yet the significance of frost flowers to ocean-sea ice-atmosphere exchange processes remains poorly understood. Frost flowers form when moisture from seawater becomes available to a cold atmosphere and surface winds are low, allowing for supersaturation of the near-surface boundary layer. Ice grown in a pond cut in young ice at the mouth of Young Sound, NE Greenland, in March 2012, showed that expanding frost flower clusters began forming as soon as the ice formed. The new ice and frost flowers dramatically changed the radiative and thermal environment. The frost flowers were about 5°C colder than the brine surface, with an approximately linear temperature gradient from their base to their upper tips. Salinity and δ18O values indicated that frost flowers primarily originated from the surface brine skim. Ikaite crystals were observed to form within an hour in both frost flowers and the thin pond ice. Average ikaite concentrations were 1013 µmol kg-1 in frost flowers and 1061 µmol kg-1 in the surface slush layer. Chamber flux measurements confirmed an efflux of CO2 at the brine-wetted sea ice surface, in line with expectations from the brine chemistry. Bacteria concentrations generally increased with salinity in frost flowers and the surface slush layer. Bacterial densities and taxa indicated that a selective process occurred at the ice surface and confirmed the general pattern of primary oceanic origin versus negligible atmospheric deposition.

  16. The diversity changes of soil microbial communities stimulated by climate, soil type and vegetation type analyzed via a functional gene array.

    PubMed

    Chen, Fu; Tan, Min; Yang, Yongjun; Ma, Jing; Zhang, Shaoliang; Li, Gang

    2015-11-01

    The aim of this study was to analyze the changes of soil microbial communities stimulated by climate, soil type and vegetation type using a functional gene array. The dataset GSE51592 was obtained from Gene Expression Omnibus, including 54 soil samples. Genetic diversity variation of samples under different sites, soil and vegetation types was examined by calculating the percentage of specific gene number in each sample. Furthermore, gene functional categories and microorganism species in samples under different environmental factors were respectively divided. Gene number in samples with cropping was higher than in samples without cropping. When site, soil type and vegetation type were as the sole variable, respectively, the percentage of specific genes in samples from Yingtan, in phaeozem samples and in samples with cropping was higher. Furthermore, the percentage of gene number in organic remediation for phaeozem and cambisol samples was significant at p < 0.05, comparing with that for acrisol samples. At superkingdom level of microorganisms, for the same category, there was no significant difference (p < 0.05) between the samples. At phylum level, for the categories of Bacteroidetes and Cyanobacteria, the percentage of gene number in cambisol samples was significantly higher (p < 0.05). Conversely, in the category of Proteobacteria, the percentage of gene number in phaeozem and acrisol samples was markedly higher (p < 0.05). Microbial diversity of soil was cooperatively driven by climate, soil type and vegetation type.

  17. Structural complexity and land-surface energy exchange along a gradient from arctic tundra to boreal forest

    USGS Publications Warehouse

    Thompson, C.; Beringer, J.; Chapin, F. S.; McGuire, A.D.

    2004-01-01

    Question: Current climate changes in the Alaskan Arctic, which are characterized by increases in temperature and length of growing season, could alter vegetation structure, especially through increases in shrub cover or the movement of treeline. These changes in vegetation structure have consequences for the climate system. What is the relationship between structural complexity and partitioning of surface energy along a gradient from tundra through shrub tundra to closed canopy forest? Location: Arctic tundra-boreal forest transition in the Alaskan Arctic. Methods: Along this gradient of increasing canopy complexity, we measured key vegetation characteristics, including community composition, biomass, cover, height, leaf area index and stem area index. We relate these vegetation characteristics to albedo and the partitioning of net radiation into ground, latent, and sensible heating fluxes. Results: Canopy complexity increased along the sequence from tundra to forest due to the addition of new plant functional types. This led to non-linear changes in biomass, cover, and height in the understory. The increased canopy complexity resulted in reduced ground heat fluxes, relatively conserved latent heat fluxes and increased sensible heat fluxes. The localized warming associated with increased sensible heating over more complex canopies may amplify regional warming, causing further vegetation change in the Alaskan Arctic.

  18. Arctic Refuge

    Atmospheric Science Data Center

    2014-05-15

    article title:  Summer in the Arctic National Wildlife Refuge     View Larger Image This colorful image of the Arctic National Wildlife Refuge and the Beaufort Sea was acquired by the Multi-angle Imaging SpectroRadiometer (MISR) nadir ...

  19. Recent studies of halogen activation in the Arctic and the role of sea ice types (Invited)

    NASA Astrophysics Data System (ADS)

    Shepson, P. B.

    2009-12-01

    It has long been known that chemical processes occur at sea ice surfaces that lead to the emission of photolabile halogen species such as Br2 and BrCl, and that subsequent photolysis of those species starts a halogen atom chain reaction that can lead to near-total destruction of ozone and elemental mercury in the lower atmosphere, in springtime. These processes have been observed through satellite remote sensing via the OMI, GOME and SCIAMACHY satellite instruments. While there are numerous hypotheses about the types of surfaces that are important (e.g. first year sea ice, frost flowers, salt-laden snowpacks, sea salt aerosol) to the initiation of this process, there is to date little information that points to any one of these as being dominant. In recent years there has been a significant change in the nature of sea ice cover, with relatively much more seasonal ice, and much less multi-year ice. These changes, along with the satellite data, present an opportunity, and the need, to investigate these questions. Here I discuss recent field measurements, and how they compare to satellite observations, and review what we know and yet need to learn.

  20. Ecological recovery in an Arctic delta following widespread saline incursion.

    PubMed

    Lantz, Trevor C; Kokelj, Steve V; Fraser, Robert H

    2015-01-01

    Arctic ecosystems are vulnerable to the combined effects of climate change and a range of other anthropogenic perturbations. Predicting the cumulative impact of these stressors requires an improved understanding of the factors affecting ecological resilience. In September of 1999, a severe storm surge in the Mackenzie Delta flooded alluvial surfaces up to 30 km inland from the coast with saline waters, driving environmental impacts unprecedented in the last millennium. In this study we combined field monitoring of permanent sampling plots with an analysis of the Landsat archive (1986-2011) to explore the factors affecting the recovery of ecosystems to this disturbance. Soil salinization following the 1999 storm caused the abrupt dieback of more than 30,000 ha of tundra vegetation. Vegetation cover and soil chemistry show that recovery is occurring, but the rate and spatial extent are strongly dependent on vegetation type, with graminoid- and upright shrub-dominated areas showing recovery after a decade, but dwarf shrub tundra exhibiting little to no recovery over this period. Our analyses suggest that recovery from salinization has been strongly influenced by vegetation type and the frequency of freshwater flooding following the storm. With increased ocean storm activity, rising sea levels, and reduced sea ice cover, Arctic coastal ecosystems will be more likely to experience similar disturbances in the future, highlighting the importance of combining field sampling with regional-scale remote sensing in efforts to detect, understand, and anticipate environmental change.

  1. Ecological recovery in an Arctic delta following widespread saline incursion.

    PubMed

    Lantz, Trevor C; Kokelj, Steve V; Fraser, Robert H

    2015-01-01

    Arctic ecosystems are vulnerable to the combined effects of climate change and a range of other anthropogenic perturbations. Predicting the cumulative impact of these stressors requires an improved understanding of the factors affecting ecological resilience. In September of 1999, a severe storm surge in the Mackenzie Delta flooded alluvial surfaces up to 30 km inland from the coast with saline waters, driving environmental impacts unprecedented in the last millennium. In this study we combined field monitoring of permanent sampling plots with an analysis of the Landsat archive (1986-2011) to explore the factors affecting the recovery of ecosystems to this disturbance. Soil salinization following the 1999 storm caused the abrupt dieback of more than 30,000 ha of tundra vegetation. Vegetation cover and soil chemistry show that recovery is occurring, but the rate and spatial extent are strongly dependent on vegetation type, with graminoid- and upright shrub-dominated areas showing recovery after a decade, but dwarf shrub tundra exhibiting little to no recovery over this period. Our analyses suggest that recovery from salinization has been strongly influenced by vegetation type and the frequency of freshwater flooding following the storm. With increased ocean storm activity, rising sea levels, and reduced sea ice cover, Arctic coastal ecosystems will be more likely to experience similar disturbances in the future, highlighting the importance of combining field sampling with regional-scale remote sensing in efforts to detect, understand, and anticipate environmental change. PMID:26255366

  2. Effects of different vegetation types on the shear strength of root-permeated soils

    NASA Astrophysics Data System (ADS)

    Yildiz, Anil; Graf, Frank; Rickli, Christian; Springman, Sarah M.

    2016-04-01

    The effects of vegetation and, in particular, of forests on the stability of slopes are well recognized and have been widely studied in recent decades. However, there is still a lack of understanding of the underlying processes that occur prior to triggering superficial failures in root-permeated soil. Thus, appropriate quantification of the vegetation effects on the shear strength of soil is crucial in order to be able to evaluate the stability of a vegetated slope. Direct shear testing is widely employed to determine the shearing response of root-permeated soil. However, mechanical aspects of direct shear apparatuses may affect the shear strength parameters derived, which often remains unnoticed and hampers direct comparison between different studies. A robust Inclinable Large-scale Direct Shear Apparatus (ILDSA), with dimensions of 500x500x400 mm, was built in order to shear root-permeated soil specimens and to analyse the influence of the machine setup on the results, too. Two different sets of planted specimens were prepared using moraine (SP-SM) from a recent landslide area in Central Switzerland: a first set consisting of Alnus incana, Trifolium pratense, Poa pratensis and a second set, consisting of these three species complemented with Salix appendiculata, Achillea millefolium, Anthyllis vulneraria. Direct shear tests were conducted on specimens planted with the different vegetation types, at a constant rate of horizontal displacement of 1 mm/min up to a maximum horizontal displacement of 190 mm, and under three different applied normal stresses: 6 kPa, 11 kPa and 16 kPa. Artificial rainfall was applied at a constant intensity (100 mm/h) prior to shearing. Tensiometers had been installed close to the shear surface and were monitored continuously to obtain the matric suction during the saturation process. Suctions were reduced as close to 0 kPa as possible, in order to simulate the loss of strength after a heavy period of rainfall. The analyses of the above

  3. Arctic Climate and Terrestrial Vegetation Responses During the Middle to Late Eocene and Early Oligocene: Colder Winters Preceded Cool-Down.

    NASA Astrophysics Data System (ADS)

    Greenwood, D. R.; Eldrett, J.

    2006-12-01

    The late Eocene to early Oligocene is recognized as an interval of substantial change in the global climate, with isotopic proxies of climate indicating a significant drop in sea surface temperatures. Other studies have shown, however that at middle latitudes that terrestrial mean annual temperature did not change significantly over this interval, and that the major change was likely a shift towards a greater range of seasonal temperatures; colder winters and warmer summers. Previous analyses of high latitude (Arctic) middle Eocene climate using both leaf physiognomic analysis and qualitative analysis of identified nearest living relatives of terrestrial floras indicated upper microthermal environments (mean annual temp. or MAT ca 10°C but perhaps as high as 15°C, coldest month mean temp. or CMMT ca 0°C) for Axel Heiberg Island in the Arctic Archipelago, but did not address precipitation nor provide data on the Eocene-Oligocene transition in the Arctic. Presented here are new estimates of temperature and precipitation (annual and season amounts) for the Arctic based on NLR analysis of terrestrial plant palynomorphs (spores and pollen) from the ODP 913B and 985 cores from near Greenland. The record of climate for the Greenland cores show a similar climate in the middle Eocene to that previously estimated for Axel Heiberg Island further to the west, with MAT 10- 15°C but with CMMT >5°C. Precipitation was high (mean annual precip. or MAP >180 cm/yr), although with large uncertainties attached to the estimate. The climate proxy record for the late Eocene to early Oligocene shows a lack of change in MAT and MAP over the time interval. Consistent with other published records at middle latitudes, however, winter temperatures (as CMMT) show greater variability leading up to the E-O boundary, and consistently cooler values in the early Oligocene (CMMT <5°C) than recorded for most of the middle to late Eocene record (CMMT >5°C). Plant groups sensitive to freezing such

  4. Effect of Replacing Pork Fat with Vegetable Oils on Quality Properties of Emulsion-type Pork Sausages.

    PubMed

    Lee, Hyun-Jin; Jung, Eun-Hee; Lee, Sang-Hwa; Kim, Jong-Hee; Lee, Jae-Joon; Choi, Yang-Ii

    2015-01-01

    This study was conducted to evaluate the quality properties of emulsion-type pork sausages when pork fat is replaced with vegetable oil mixtures during processing. Pork sausages were processed under six treatment conditions: T1 (20% pork fat), T2 (10% pork fat + 2% grape seed oil + 4% olive oil + 4% canola oil), T3 (4% grape seed oil + 16% canola oil), T4 (4% grape seed oil + 4% olive oil + 12% canola oil), T5 (4% grape seed oil + 8% olive oil + 8% canola oil), and T6 (4% grape seed oil + 12% olive oil + 4% canola oil). Proximate analysis showed significant (p<0.05) differences in the moisture, protein, and fat content among the emulsion-type pork sausages. Furthermore, replacement with vegetable oil mixtures significantly decreased the ash content (p<0.05), increased water-holding capacity in emulsion-type pork sausages. Also, cholesterol content in T6 was significantly lower than T2 (p<0.05). In the texture profile analysis, hardness and chewiness of emulsion-type pork sausages were significantly (p<0.05) decreased by vegetable oil mixtures replacement. On the contrary, cohesiveness and springiness in the T4 group were similar to those of group T1. The unsaturated fatty acid content in emulsion-type pork sausages was increased by vegetable oil mixtures replacement. Replacement of pork fat with mixed vegetable oils had no negative effects on the quality properties of emulsion-type pork sausages, and due to its reduced saturated fatty acid composition, the product had the quality characteristics of the healthy meat products desired by consumers.

  5. Effect of Replacing Pork Fat with Vegetable Oils on Quality Properties of Emulsion-type Pork Sausages

    PubMed Central

    Lee, Hyun-Jin; Jung, Eun-Hee; Lee, Sang-Hwa; Kim, Jong-Hee; Lee, Jae-Joon; Choi, Yang-II

    2015-01-01

    This study was conducted to evaluate the quality properties of emulsion-type pork sausages when pork fat is replaced with vegetable oil mixtures during processing. Pork sausages were processed under six treatment conditions: T1 (20% pork fat), T2 (10% pork fat + 2% grape seed oil + 4% olive oil + 4% canola oil), T3 (4% grape seed oil + 16% canola oil), T4 (4% grape seed oil + 4% olive oil + 12% canola oil), T5 (4% grape seed oil + 8% olive oil + 8% canola oil), and T6 (4% grape seed oil + 12% olive oil + 4% canola oil). Proximate analysis showed significant (p<0.05) differences in the moisture, protein, and fat content among the emulsion-type pork sausages. Furthermore, replacement with vegetable oil mixtures significantly decreased the ash content (p<0.05), increased water-holding capacity in emulsion-type pork sausages. Also, cholesterol content in T6 was significantly lower than T2 (p<0.05). In the texture profile analysis, hardness and chewiness of emulsion-type pork sausages were significantly (p<0.05) decreased by vegetable oil mixtures replacement. On the contrary, cohesiveness and springiness in the T4 group were similar to those of group T1. The unsaturated fatty acid content in emulsion-type pork sausages was increased by vegetable oil mixtures replacement. Replacement of pork fat with mixed vegetable oils had no negative effects on the quality properties of emulsion-type pork sausages, and due to its reduced saturated fatty acid composition, the product had the quality characteristics of the healthy meat products desired by consumers. PMID:26761810

  6. Effect of Replacing Pork Fat with Vegetable Oils on Quality Properties of Emulsion-type Pork Sausages.

    PubMed

    Lee, Hyun-Jin; Jung, Eun-Hee; Lee, Sang-Hwa; Kim, Jong-Hee; Lee, Jae-Joon; Choi, Yang-Ii

    2015-01-01

    This study was conducted to evaluate the quality properties of emulsion-type pork sausages when pork fat is replaced with vegetable oil mixtures during processing. Pork sausages were processed under six treatment conditions: T1 (20% pork fat), T2 (10% pork fat + 2% grape seed oil + 4% olive oil + 4% canola oil), T3 (4% grape seed oil + 16% canola oil), T4 (4% grape seed oil + 4% olive oil + 12% canola oil), T5 (4% grape seed oil + 8% olive oil + 8% canola oil), and T6 (4% grape seed oil + 12% olive oil + 4% canola oil). Proximate analysis showed significant (p<0.05) differences in the moisture, protein, and fat content among the emulsion-type pork sausages. Furthermore, replacement with vegetable oil mixtures significantly decreased the ash content (p<0.05), increased water-holding capacity in emulsion-type pork sausages. Also, cholesterol content in T6 was significantly lower than T2 (p<0.05). In the texture profile analysis, hardness and chewiness of emulsion-type pork sausages were significantly (p<0.05) decreased by vegetable oil mixtures replacement. On the contrary, cohesiveness and springiness in the T4 group were similar to those of group T1. The unsaturated fatty acid content in emulsion-type pork sausages was increased by vegetable oil mixtures replacement. Replacement of pork fat with mixed vegetable oils had no negative effects on the quality properties of emulsion-type pork sausages, and due to its reduced saturated fatty acid composition, the product had the quality characteristics of the healthy meat products desired by consumers. PMID:26761810

  7. Arctic Watch

    NASA Astrophysics Data System (ADS)

    Orcutt, John; Baggeroer, Arthur; Mikhalevsky, Peter; Munk, Walter; Sagen, Hanne; Vernon, Frank; Worcester, Peter

    2015-04-01

    The dramatic reduction of sea ice in the Arctic Ocean will increase human activities in the coming years. This will be driven by increased demand for energy and the marine resources of an Arctic Ocean more accessible to ships. Oil and gas exploration, fisheries, mineral extraction, marine transportation, research and development, tourism and search and rescue will increase the pressure on the vulnerable Arctic environment. Synoptic in-situ year-round observational technologies are needed to monitor and forecast changes in the Arctic atmosphere-ice-ocean system at daily, seasonal, annual and decadal scales to inform and enable sustainable development and enforcement of international Arctic agreements and treaties, while protecting this critical environment. This paper will discuss multipurpose acoustic networks, including subsea cable components, in the Arctic. These networks provide communication, power, underwater and under-ice navigation, passive monitoring of ambient sound (ice, seismic, biologic and anthropogenic), and acoustic remote sensing (tomography and thermometry), supporting and complementing data collection from platforms, moorings and autonomous vehicles. This paper supports the development and implementation of regional to basin-wide acoustic networks as an integral component of a multidisciplinary, in situ Arctic Ocean Observatory.

  8. Biodiesel classification by base stock type (vegetable oil) using near infrared spectroscopy data.

    PubMed

    Balabin, Roman M; Safieva, Ravilya Z

    2011-03-18

    The use of biofuels, such as bioethanol or biodiesel, has rapidly increased in the last few years. Near infrared (near-IR, NIR, or NIRS) spectroscopy (>4000cm(-1)) has previously been reported as a cheap and fast alternative for biodiesel quality control when compared with infrared, Raman, or nuclear magnetic resonance (NMR) methods; in addition, NIR can easily be done in real time (on-line). In this proof-of-principle paper, we attempt to find a correlation between the near infrared spectrum of a biodiesel sample and its base stock. This correlation is used to classify fuel samples into 10 groups according to their origin (vegetable oil): sunflower, coconut, palm, soy/soya, cottonseed, castor, Jatropha, etc. Principal component analysis (PCA) is used for outlier detection and dimensionality reduction of the NIR spectral data. Four different multivariate data analysis techniques are used to solve the classification problem, including regularized discriminant analysis (RDA), partial least squares method/projection on latent structures (PLS-DA), K-nearest neighbors (KNN) technique, and support vector machines (SVMs). Classifying biodiesel by feedstock (base stock) type can be successfully solved with modern machine learning techniques and NIR spectroscopy data. KNN and SVM methods were found to be highly effective for biodiesel classification by feedstock oil type. A classification error (E) of less than 5% can be reached using an SVM-based approach. If computational time is an important consideration, the KNN technique (E=6.2%) can be recommended for practical (industrial) implementation. Comparison with gasoline and motor oil data shows the relative simplicity of this methodology for biodiesel classification. PMID:21397073

  9. A comparative analysis of MODIS based spectral indices for drought monitoring over fire prone vegetation types

    NASA Astrophysics Data System (ADS)

    Caccamo, G.; Chisholm, L. A.; Bradstock, R.; Puotinen, M. L.

    2010-12-01

    Drought is a complex natural hazard with severe impacts on ecosystems. Several studies have highlighted links between drought spatio-temporal patterns and wildfire behaviour. Recent research showed drought can affect the development of catastrophic fires through influence on the spatial connectivity of dry fuel patches. Wildfires that are initiated at isolated ignition points (‘within patch scale’) can propagate non-linearly across landscapes (“among-patches”) if fuels are sufficiently dry and connected. Consequently, accurate mapping of drought at fine spatial resolution represents a priority to monitor “among-patches” continuity of flammable fuels in fire prone regions. Traditional methods of drought monitoring are based on meteorological indices (MI) calculated from weather stations data. The network of weather stations is often sparse and inadequate to produce fine spatial resolution surfaces of MI especially across remote forested areas. Spectral indices (SI) based on satellite data provide sound and cost-effective alternatives to MI, offering spatially dense information regularly recorded over large areas across a wide range of wavelengths. Since a considerable number of SI have been proposed as drought monitoring tool, the selection of the most appropriate index for a specific region represents an essential operation to ensure efficiency in drought mapping. In this study we propose a comprehensive analysis to evaluate the performance of a wide range of Vis, NIR and SWIR based SI towards drought condition monitoring over fire prone vegetation types, using the Sydney Basin bioregion (Australia) as case study. All spectral indices were derived from reflectance data sets obtained from MODIS Terra time series (2000-2009). The relationships between SI and drought conditions were analysed using a meteorological index (Standardized Precipitation Index, SPI) as rainfall deficiency indicator. The spatial and temporal co-variability between SPI and spectral

  10. [Ecological stoichiometric characteristics in leaf and litter under different vegetation types of Zhifanggou watershed on the Loess Plateau, China].

    PubMed

    Li, Xin; Zeng, Ouan-chao; An, Shao-Shan; Dong, Yang-Hong; Li, Ya-Yun

    2015-03-01

    The purpose was to characterize the effects of vegetation types on plant leaf and litter carbon (C), nitrogen (N), phosphorus (P), potassium (K) and C: N: P: K ecological stoichiometric characteristics in seven dominant plant species, including Robinia pseudoacacia, Syringa, Sophora viciifolia, Hippophae rhamnoides, Rosa xanthina, Artemisia sacrorum, Artemisia giraldii, of Zhifanggou Watershed on the Loess Plateau, China. This paper indicated the differences between the contents of C, N, P and K and the characteristics of ecological stoichiometric in the different vegetation types, including forest type, shrub type and grass type. Concentrations of C, N, P and K were measured, and C: N: P: K was estimated for different vegetation types. There were no significant differences in leaf C, N and P concentrations among the three vegetation types. But significant differences in leaf K concentration existed, and the K concentration in leaf was the highest in grass type, and the lowest in shrub type. The contents of C, N, P and K in leaf were much higher than those in litter, especially in shrub and grass types. The resorption efficiencies of C, N, P and K were different, and their ranges varied 6.16%-22.84%, 24.38%-65.18%, 22.38%-77.16% and 60.99%- 89.35%, respectively. Grass type had the highest C, P and K resorption efficiencies, and the lowest N resorption efficiency. Values of the N: P ratio in leaf varied in the range of 12.14-19.17, and varied in the range of 12.84-30.67 in litter. Values of the N: P ratio in leaf were the highest in shrub type (19. 17), and the lowest in grass (12. 14), indicating that the growth of shrub plants was limited by P, while the growth of grass plants was limited by N. The K concentration in leaf was significantly negatively correlated with values of the N: P ratio in leaf, and the K concentration in litter was significantly negatively correlated with values of the C: P ratio in leaf. Findings in this study highlighted the characteristics

  11. Soil permeability as a function of vegetation type and soil water content.

    PubMed

    Morris, R C; Fraley, L

    1994-06-01

    Soil permeability is important for estimating the rate of mass transport of 222Rn through soils and into basements (Nazaroff 1992). We measured permeability and soil water content on a set of nine plots consisting of three plots vegetated with common barley (Hordeum vulgare), three plots vegetated with Russian thistle (Salsola kali), and three bare plots. Soil moisture was consistently highest on the bare plots and lowest on the Russian thistle plots. Plots with vegetation had lower soil water content during the growing season. Permeability was consistently higher on Russian thistle plots. ANOVA showed that both soil water content and presence of Russian thistle had a significant impact on permeability but that presence of barley did not. The effect of vegetation and moisture on permeability may have significant effects on 222Rn transport in soils.

  12. Soil permeability as a function of vegetation type and soil water content

    SciTech Connect

    Morris, R.C.; Fraley, L. Jr.

    1994-06-01

    Soil permeability is important for estimating the rate of mass transport of {sup 222}Rn through soils and into basements. We measured permeability and soil water content on a set of nine plots consisting of three plots vegetated with common barley (Hordeum vulgare), three plots vegetated with Russian thistle (Salsola kali), and three bare plots. Soil moisture was consistently highest on the bare plots and lowest on the Russian thistle plots. Plots with vegetation had lower soil water content during the growing season. Permeability was consistently higher on Russian thistle plots. ANOVA showed that both soil water content and presence of Russian thistle had a significant impact on permeability but that presence of barley did not. The effect of vegetation and moisture on permeability may have significant effects on {sup 222}Rn transport in soils. 18 refs., 8 figs., 1 tab.

  13. VEGETATION TYPE AND THE INTERTIDAL MACROINVERTEBRATE FAUNA OF A BRACKISH MARSH: PHRAGMITES VS. SPARTINA

    EPA Science Inventory

    The responses of tidal marsh macroinvertebrate assemblages to the conversion of Spartina alterniflora marshes to marshes dominated by the invasive reed, Phragmites australis, are poorly understood. Changes in edaphic, vegetative, hydrological, and detrital conditions that attend ...

  14. [Characteristics of soil nematode communities in coastal wetlands with different vegetation types].

    PubMed

    Liu, Bei-Bei; Ye, Cheng-Long; Yu, Li; Jiao, Jia-Guo; Liu, Man-Qiang; Hu, Feng; Li, Hui-Xin

    2012-11-01

    An investigation was conducted on the characteristics of soil nematode communities in different vegetation belts (Spartina alterniflora belt, Sa; Suaeda glauca belt, Sg; bare land, B1; Phragmites australis belt, Pa; and wheat land, Wl) of Yancheng Wetland Reserve, Jiangsu Province of East China. A total of 39 genera and 20 families of soil nematodes were identified, and the individuals of dominant genera and common genera occupied more than 90% of the total. The total number of the nematodes differed remarkably with vegetation belts, ranged from 79 to 449 individuals per 100 grams of dry soil. Wheat land had the highest number of soil nematodes, while bare land had the lowest one. The nematode ecological indices responded differently to the vegetation belts. The Shannon index (H) and evenness index (J) decreased in the order of Pa > Sg > Wl > Sa > Bl, and the dominance index (lambda) was in the order of Bl > Sa > Wl > Sg > Pa, suggesting that the diversity and stability of the nematode community in bare land were lower than those in the other vegetation belts, and the nematode community in the bare land tended to be simplified. The maturity index (MI) was higher in uncultivated vegetation belts than in wheat land, suggesting that the wheat land was disturbed obviously. The nematode community structure differed significantly with vegetation belts, and the main contributing species in different vegetation belts also differed. There existed significant correlations between the soil physical and chemical characteristics and the nematode numbers, trophic groups, and ecological indices. Our results demonstrated that the changes of soil nematode community structure could be used as an indicator well reflecting the diversity of vegetation belt habitat, and an important bio-indicator of coastal wetland ecosystem.

  15. Vegetation types and climate conditions reflected by the modern phytolith assemblages in the subalpine Dalaoling Forest Reserve, central China

    NASA Astrophysics Data System (ADS)

    Traoré, Djakanibé Désiré; Gu, Yansheng; Liu, Humei; Shemsanga, Ceven; Ge, Jiwen

    2015-06-01

    This research describes modern phytolith records and distributions from subalpine surface soils in the Dalaoling Forest Reserve, and reveals its implications for local climate conditions with respect to the altitude gradient. Well-preserved phytolith morpho-types, assemblages, and climatic indices were used to study the relationship between local vegetation and climate conditions. The phytolith classification system is mainly based on the characteristics of detailed morpho-types described for anatomical terms, which are divided into seven groups: long cells, short cells, bulliform cells, hair cells, pteridophyte type, broad-leaved type, and gymnosperm type. Phytoliths originating from the Poaceae are composed of Pooideae (rondel and trapeziform), Panicoideae (bilobate, cross, and polylobate), Chloridoideae (short/square saddle), and Bambusoideae (oblong concave saddle). Based on the altitudinal distribution of the phytolith assemblages and the indices of aridity (Iph), climate (Ic), and tree cover density (D/P), five phytolith assemblage zones have revealed the five types of climatic conditions ranging from 1,169 m to 2,005 m in turn: warm-wet, warm-xeric to warm-mesic, warm-xeric to cool-mesic, cool-xeric, and cool-mesic to cool-xeric. The Bambusoideae, Panicoideae, and Chloridoideae are the dominant vegetation at the lower-middle of the mountains, while Pooideae is mainly distributed in the higher mountains. The close relationship between phytolith assembleages and changes of altitude gradient suggest that vegetation distribution patterns and plant ecology in the Dalaoling mountains are controlled by temperature and humidity conditions. Our results highlight the importance of phytolith records as reliable ecoclimatic indicators for vegetation ecology in subtropical regions.

  16. Increasing children's consumption of fruit and vegetables: does the type of exposure matter?

    PubMed

    Osborne, Chelsea L; Forestell, Catherine A

    2012-06-01

    This study sought to determine how eight days of home exposure to information about healthful foods and eating behaviors in the form of children's books and a variety of fruit and vegetables interacted to affect 4- to 8-year-old children's (N=59) consumption of fruit and vegetables. Before and after the home exposure, children participated in a task in which their consumption of a variety of fruit and vegetables that ranged in familiarity was measured. Results indicated that exposure to food and books were both effective at increasing consumption of fruit, but not vegetables. Additionally, children who were exposed to books consumed more of an infrequently consumed fruit presented during the post-test, but only if they had not been exposed to food during the home exposure. Overall, children's fruit consumption increased more if their mothers did not pressure them to eat, and those who were less neophobic were more likely to try a novel fruit or vegetable during the post-test. These findings suggest that information and food variety both can be effective for increasing acceptance of fruit, and highlight the need for more research that investigates the efficacy of intervention strategies that promote vegetable consumption in young children.

  17. [Effect of vegetation types on soil respiration characteristics on a smaller scale].

    PubMed

    Yan, Jun-Xia; Li, Hong-Jian; Tang, Yi; Zhang, Yi-Hui

    2009-11-01

    Soil respiration was measured from April 2005 to December 2007 using a LICOR-6400-09 chamber connecting a LiCor-6400 portable photosynthesis system at 3 sites with same elevation and soil texture but different vegetation types. The results indicated that seasonal trend of soil respiration showed a distinct temporal change with the higher values in summer and autumn months and the lower values in winter and spring. Annual means (March to December) of soil respiration for 3 the sampling sites were(3.58 +/- 2.50), (3.82 +/- 2.75) and (4.42 +/- 3.38) micromol x (m2 x s)(-1) (p > 0.05), respectively. Released annual amount (March to December) of CO2 efflux from 3 sites was from 854.9 to 1 297.2 g x (m2 x a)(-1) and the amount was no difference between sites and among years. The fitted exponential equations of soil respiration and soil temperature for 3 sites were all significant with the R2 from 0.61 to 0.81, and the Q10 and R10 calculated from fitted parameters of the equations ranged from 2.60 to 4.50, and from 1.70 to 3.02 micromol x (m2 x s)(-1). The relationships between soil respiration and soil water content were not significant for all 3 sites with a maximum R2 of the regression equations only 0.12 (p > 0.05). However, when the soil temperature was above 10 degrees C, the relationships between soil respiration and soil water content was significant (p < 0.05). Four combined regression equations including soil temperature and soil water content could be used to model relationships between soil respiration and both soil temperature and soil water content together, with the R2 most above 0.7, and maximum of 0.91. PMID:20063717

  18. Grazing effects on species composition in different vegetation types (La Palma, Canary Islands)

    NASA Astrophysics Data System (ADS)

    Arévalo, J. R.; de Nascimento, L.; Fernández-Lugo, S.; Mata, J.; Bermejo, L.

    2011-05-01

    Grazing management is probably one of the most extensive land uses, but its effects on plant communities have in many cases been revealed to be contradictory. Some authors have related these contradictions to the stochastic character of grazing systems. Because of that, it is necessary to implement specific analyses of grazing effects on each community, especially in natural protected areas, in order to provide the best information to managers. We studied the effects of grazing on the species composition of the main vegetation types where it takes place (grasslands, shrublands and pine forests) on the island of La Palma, Canary Islands. We used the point-quadrat intersect method to study the species composition of grazed and ungrazed areas, which also were characterized by their altitude, distance to farms, distance to settlements, year of sampling, herbaceous aboveground biomass and soil organic matter. The variables organic matter, productivity and species richness were not significantly affected by grazing. The species composition of the analyzed plant communities was affected more by variables such as altitude or distance to farms than by extensive grazing that has been traditionally carried out on the island of La Palma involving certain practices such as continuous monitoring of animals by goat keepers, medium stocking rates adjusted to the availability of natural pastures, supplementation during the dry season using local forage shrubs or mown pastures and rotating animals within grazing areas Although some studies have shown a negative effect of grazing on endangered plant species, these results cannot be freely extrapolated to the traditional grazing systems that exert a low pressure on plant communities (as has been found in this study). We consider extensive grazing as a viable way of ensuring sustainable management of the studied ecosystems.

  19. Late Pleistocene paleoecology of arctic ground squirrel ( Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA

    NASA Astrophysics Data System (ADS)

    Gaglioti, Benjamin V.; Barnes, Brian M.; Zazula, Grant D.; Beaudoin, Alwynne B.; Wooller, Matthew J.

    2011-11-01

    Botanical analyses of fossil and modern arctic ground squirrel ( Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identified Calamagrostis canadensis, Koeleria sp. and Carex albonigra as being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C 3 photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene.

  20. Seasonal Changes in Arctic Dissolved Organic Matter

    NASA Astrophysics Data System (ADS)

    Boot, C. M.; Wallenstein, M. D.; Schimel, J.

    2011-12-01

    The Arctic is a landscape in flux. Temperatures are shifting upward and plant communities are transitioning from tussock to shrub tundra in some regions. Decomposition processes sensitive to temperature, moisture, and plant inputs are controls on the source/sink dynamics of the Arctic C pool. The response of decomposition to warming will, in part, determine if the Arctic C pool feeds back positively or negatively to climate change. The portion of the C pool immediately available to decomposers is dissolved organic matter (DOM). The aim of this is study is to examine the molecular composition of DOM to determine which components vary seasonally in soil pore water among three vegetation types at Toolik Field Station in Alaska. Vegetation types include wet sedge (Carex aquatilis and Eriophorum angustifolium), moist acidic tussock (E. vaginatum) and shrub tundra (Betula nana and Salix sp.). These sites were sampled during winter/summer transitions in 2010 in order to capture both growing season and winter dynamics. We expected the chemical composition of DOM in pore water to be distinct among plant communities due to differences in root exudates, litter chemistry and microbial community; and vary seasonally due to shifting temperature and water availability and their impacts on decomposition of DOM. Soil pore water was isolated through centrifugation and is being characterized with ultra high performance liquid chromatography (UPLC) in line with a quadrupole time of flight mass spectrometer (QTOF-MS) as well as with specific UV absorbance at 254 nm (SUVA), and excitation emission matrices (EEMs) generated by fluorescence spectroscopy. The DOM concentrations across vegetation types show consistent seasonal patterns, spiking at thaw, and declining through late summer. As soils freeze these patterns diverge-in tussock soils DOM concentration decreases slightly, while in shrub and wet sedge sites it increases. SUVA values (indicator of aromaticity) were consistent among

  1. Iron and humic-type fluorescent dissolved organic matter in the Chukchi Sea and Canada Basin of the western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Nakayama, Yuta; Fujita, Satoshi; Kuma, Kenshi; Shimada, Koji

    2011-07-01

    The concentrations of dissolved Fe ([D-Fe]), total dissolvable Fe ([T-Fe]), humic-type fluorescence intensity (humic F intensity) as humic-type fluorescent dissolved organic matter, and nutrients were vertically determined in the shelf, slope, and basin regions (Chukchi Sea and Canada Basin) of the western Arctic Ocean during 1-27 September 2008. In all stations, the remarkably high [D-Fe] and humic F intensity were found at depths between 25 and 200 m with the subsurface maxima of [D-Fe] (1.0-3.2 nM) and humic F intensity (4-5 quinine sulfate units) in the upper halocline layer (upper HL), being associated with a prominent nutrient maximum. The high [D-Fe] and humic F intensity within the upper HL are probably attributed to the Fe(III) complexation with natural organic ligands, such as marine dissolved humic substances, resulting from main processes of the brine rejection during sea ice formation and interactions with sediments on the shelves. However, subsurface maxima (10-50 nM) of [T-Fe] were found in the lower halocline layer, beneath the upper HL, of all slope and basin regions and are mainly attributed to the resuspension of sedimentary particles in the shelf region. The finding of subsurface iron maxima in the halocline water of all regions may be the first confirmation for the lateral iron transport into the halocline layer from the shelves to the Arctic Basin.

  2. What are the patterns of carbon allocation in Arctic shrub tundra: do species differ?

    NASA Astrophysics Data System (ADS)

    Street, Lorna; Subke, Jens-Arne; Baxter, Robert; Billett, Mike; Dinsmore, Kerry; Lessels, Jason; Wookey, Philip

    2014-05-01

    Arctic "greening" is now a well-accepted phenomenon; multiple lines of evidence suggest that plant productivity has increased, driven by increases in shrub abundance. There is very little understanding, however, of how this "shrubification" will impact biogeochemical cycling, including the allocation and turnover of carbon. Recent research has shown, for example, that greater plant productivity is not necessary associated with greater ecosystem C storage. Proliferation of a number of shrub species has been observed in different regions; for example increased willow growth in Arctic Russia, as opposed to primarily alder expansion in NW Canada, where stem density increased 68 % between 1968 and 2004. The degree to which shrub type will determine the impacts of shrub expansion on the carbon cycle is unknown. We use 13C pulse-labelling to trace the fate of recently photosynthesised carbon in vegetation dominated by two common Arctic shrubs, Betula nana (dwarf birch) and Alnus viridis (green alder) just above the Arctic treeline in NW Canada. We quantify the amount of 13C assimilated, and the proportion of assimilate returned to the atmosphere via respiration versus that allocated to plant tissues. This enables an analysis of the contrasting carbon-use-efficiencies and aboveground versus belowground allocation patterns in the two vegetation types. We use these novel field data to address the hypothesis that belowground C allocation in A. viridis (a symbiotic nitrogen fixing species) is a smaller proportion of total C assimilation, as this species supports less extensive ectomycorrhizal networks compared to B. nana. This is the first tracer study of carbon allocation in N-fixing and non-N-fixing vegetation types in a natural system and provides crucial data for predictive modelling of the Arctic carbon cycle.

  3. Trophodynamics of current use pesticides and ecological relationships in the Bathurst region vegetation-caribou-wolf food chain of the Canadian Arctic.

    PubMed

    Morris, Adam D; Muir, Derek C G; Solomon, Keith R; Teixeira, Camilla; Duric, Mark; Wang, Xiaowa

    2014-09-01

    The bioaccumulation of current use pesticides (CUPs) and stable isotopes of carbon and nitrogen were investigated in vegetation-caribou-wolf food chain in the Bathurst region (Nunavut, Canada). Volumetric bioconcentration factors (BCF(v)) in vegetation were generally greatest for dacthal (10-12) ≥ endosulfan sulfate (10-11) > ß-endosulfan (>9.0-9.7) ≥ pentachloronitrobenzene (PCNB; 8.4-9.6) > α-endosulfan (8.3-9.3) > chlorpyrifos (8.0-8.7) >chlorothalonil (7.6-8.3). The BCF(v) values in vegetation were significantly correlated with the logarithm of the octanol-air partition coefficients (log K(OA)) of CUPs (r(2)  = 0.90, p = 0.0040), although dacthal was an outlier and not included in this relationship. Most biomagnification factors (BMFs) for CUPs in caribou:diet comparisons were significantly less than 1. Similarly, the majority of wolf:caribou BMFs were either significantly less than 1 or were not statistically greater than 1. Significant trophic magnification factors (TMFs) were all less than 1, indicating that these CUPs exhibit trophic dilution through this terrestrial food chain. The log K(OA) reasonably predicted bioconcentration in vegetation for most CUPs but was not correlated with BMFs or TMFs in mammals. Our results, along with those of metabolic studies, suggest that mammals actively metabolize these CUPs, limiting their biomagnification potential despite entry into the food chain through effective bioconcentration in vegetation.

  4. Impact of vegetation types on soil organic carbon stocks SOC-S in Mediterranean natural areas

    NASA Astrophysics Data System (ADS)

    Parras-Alcántara, Luis; Lozano-García, Beatriz; Cantudo-Pérez, Marta

    2015-04-01

    Soils play a key role in the carbon geochemical cycle because they can either emit large quantities of CO2 or on the contrary they can act as a store for carbon. Agriculture and forestry are the only activities that can achieve this effect through photosynthesis and the carbon incorporation into carbohydrates (Parras-Alcántara et al., 2013). The Mediterranean evergreen oak Woodland (MEOW - dehesa) is a type of pasture with scattered evergreen and deciduous oak stands in which cereals are often grown under the tree cover. It is a system dedicated to the combined production of Iberian swine, sheep, fuel wood, coal and cork as well as to hunting. These semi-natural areas still preserve some of the primitive vegetation of the Mediterranean oak forests. The dehesa is a pasture where the herbaceous layer is comprised of either cultivated cereals such as oat, barley and wheat or native vegetation dominated by annual species, which are used as grazing resources. These Iberian open woodland rangelands (dehesas) have been studied from different points of view: hydrologically, with respect to soil organic matter content, as well as in relation to gully erosion, topographical thresholds, soil erosion and runoff production, soil degradation and management practices…etc, among others. The soil organic carbon stock capacity depends not only on abiotic factors such as the mineralogical composition and the climate, but also on soil use and management (Parras et al., 2014 and 2015). In Spanish soils, climate, use and management strongly affect the carbon variability, mainly in soils in dry Mediterranean climates characterized by low organic carbon content, weak structure and readily degradable soils. Hontoria et al. (2004) emphasized that the climate and soil use are two factors that greatly influence carbon content in the Mediterranean climate. This research sought to analyze the SOC stock (SOCS) variability in MEOW - dehesa with cereals, olive grove and Mediterranean oak forest

  5. Vegetable peptones increase production of type I collagen in human fibroblasts by inducing the RSK-CCAAT/enhancer binding protein-β phosphorylation pathway.

    PubMed

    Jung, Eunsun; Cho, Jae Youl; Park, Deokhoon; Kim, Min Hee; Park, Beomseok; Lee, Sang Yeol; Lee, Jongsung

    2015-02-01

    Skin aging appears to be principally attributed to a decrease in type I collagen level and the regeneration ability of dermal fibroblasts. We hypothesized that vegetable peptones promote cell proliferation and production of type I collagen in human dermal fibroblasts. Therefore, we investigated the effects of vegetable peptones on cell proliferation and type I collagen production and their possible mechanisms in human dermal fibroblasts. Vegetable peptones significantly promoted cell proliferation in a concentration-dependent manner. In addition, the human luciferase type I collagen α2 promoter and type I procollagen synthesis assays showed that the vegetable peptones induced type I procollagen production by activating the type I collagen α2 promoter. Moreover, the vegetable peptones activated p90 ribosomal s6 kinase, which was mediated by activating the Raf-p44/42 mitogen-activated protein kinase signaling pathway. Furthermore, the vegetable peptone-induced increase in cell proliferation and type I collagen production decreased upon treatment with the ERK inhibitor PD98059. Taken together, these findings suggest that increased proliferation of human dermal fibroblasts and enhanced production of type I collagen by vegetable peptones occur primarily by inducing the p90 ribosomal s6 kinase-CCAAT/enhancer binding protein β phosphorylation pathway, which is mediated by activating Raf-ERK signaling.

  6. [Efficiency of the vegetative tea in diet therapy for patients with obesity associated with diabetes mellitus type 2].

    PubMed

    Khrushcheva, Iu V; Mal'tsev, G Iu; Popova, Iu L; Vasil'ev, A V

    2003-01-01

    The dynamic of glycemia, insulin, C-peptide, glycosylated hemoglobin, fructosamine, thyroid hormones, parameters of serum lipids, lipid peroxidation and system of antioxidant defense in 81 hospital patients and out-patients with obesity associated with diabetes mellitus type II was studied of influence of hypocaloric diet 9. Universal normalizing influence of hypocaloric diet 9 with vegetation tea was discovered on parameters of carbohydrate, lipid and oxidative metabolism and of patients clinical state of pateni. The additional criteria of evaluation of efficacy of food dietary supplements in complex treatment of patients with obesity associated with diabetes mellitus type II was offered on basis of study of influence vegetation tea on mechanisms of metabolic disorders in these patients. PMID:12968297

  7. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition

    PubMed Central

    He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer. PMID:27070782

  8. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition.

    PubMed

    Qian, Yu-Qi; He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer.

  9. Seasonality, Rather than Nutrient Addition or Vegetation Types, Influenced Short-Term Temperature Sensitivity of Soil Organic Carbon Decomposition.

    PubMed

    Qian, Yu-Qi; He, Feng-Peng; Wang, Wei

    2016-01-01

    The response of microbial respiration from soil organic carbon (SOC) decomposition to environmental changes plays a key role in predicting future trends of atmospheric CO2 concentration. However, it remains uncertain whether there is a universal trend in the response of microbial respiration to increased temperature and nutrient addition among different vegetation types. In this study, soils were sampled in spring, summer, autumn and winter from five dominant vegetation types, including pine, larch and birch forest, shrubland, and grassland, in the Saihanba area of northern China. Soil samples from each season were incubated at 1, 10, and 20°C for 5 to 7 days. Nitrogen (N; 0.035 mM as NH4NO3) and phosphorus (P; 0.03 mM as P2O5) were added to soil samples, and the responses of soil microbial respiration to increased temperature and nutrient addition were determined. We found a universal trend that soil microbial respiration increased with increased temperature regardless of sampling season or vegetation type. The temperature sensitivity (indicated by Q10, the increase in respiration rate with a 10°C increase in temperature) of microbial respiration was higher in spring and autumn than in summer and winter, irrespective of vegetation type. The Q10 was significantly positively correlated with microbial biomass and the fungal: bacterial ratio. Microbial respiration (or Q10) did not significantly respond to N or P addition. Our results suggest that short-term nutrient input might not change the SOC decomposition rate or its temperature sensitivity, whereas increased temperature might significantly enhance SOC decomposition in spring and autumn, compared with winter and summer. PMID:27070782

  10. Terminal Restriction Fragment Length Polymorphism Analysis of Soil Bacterial Communities under Different Vegetation Types in Subtropical Area.

    PubMed

    Wu, Zeyan; Lin, Wenxiong; Li, Bailian; Wu, Linkun; Fang, Changxun; Zhang, Zhixing

    2015-01-01

    Soil microbes are active players in energy flow and material exchange of the forest ecosystems, but the research on the relationship between the microbial diversity and the vegetation types is less conducted, especially in the subtropical area of China. In this present study, the rhizosphere soils of evergreen broad-leaf forest (EBF), coniferous forest (CF), subalpine dwarf forest (SDF) and alpine meadow (AM) were chosen as test sites. Terminal-restriction fragment length polymorphisms (T-RFLP) analysis was used to detect the composition and diversity of soil bacterial communities under different vegetation types in the National Natural Reserve of Wuyi Mountains. Our results revealed distinct differences in soil microbial composition under different vegetation types. Total 73 microbes were identified in soil samples of the four vegetation types, and 56, 49, 46 and 36 clones were obtained from the soils of EBF, CF, SDF and AM, respectively, and subsequently sequenced. The Actinobacteria, Fusobacterium, Bacteroidetes and Proteobacteria were the most predominant in all soil samples. The order of Shannon-Wiener index (H) of all soil samples was in the order of EBF>CF>SDF>AM, whereas bacterial species richness as estimated by four restriction enzymes indicated no significant difference. Principal component analysis (PCA) revealed that the soil bacterial communities' structures of EBF, CF, SDF and AM were clearly separated along the first and second principal components, which explained 62.17% and 31.58% of the total variance, respectively. The soil physical-chemical properties such as total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) were positively correlated with the diversity of bacterial communities.

  11. Terminal Restriction Fragment Length Polymorphism Analysis of Soil Bacterial Communities under Different Vegetation Types in Subtropical Area

    PubMed Central

    Wu, Zeyan; Lin, Wenxiong; Li, Bailian; Wu, Linkun; Fang, Changxun; Zhang, Zhixing

    2015-01-01

    Soil microbes are active players in energy flow and material exchange of the forest ecosystems, but the research on the relationship between the microbial diversity and the vegetation types is less conducted, especially in the subtropical area of China. In this present study, the rhizosphere soils of evergreen broad-leaf forest (EBF), coniferous forest (CF), subalpine dwarf forest (SDF) and alpine meadow (AM) were chosen as test sites. Terminal-restriction fragment length polymorphisms (T-RFLP) analysis was used to detect the composition and diversity of soil bacterial communities under different vegetation types in the National Natural Reserve of Wuyi Mountains. Our results revealed distinct differences in soil microbial composition under different vegetation types. Total 73 microbes were identified in soil samples of the four vegetation types, and 56, 49, 46 and 36 clones were obtained from the soils of EBF, CF, SDF and AM, respectively, and subsequently sequenced. The Actinobacteria, Fusobacterium, Bacteroidetes and Proteobacteria were the most predominant in all soil samples. The order of Shannon-Wiener index (H) of all soil samples was in the order of EBF>CF>SDF>AM, whereas bacterial species richness as estimated by four restriction enzymes indicated no significant difference. Principal component analysis (PCA) revealed that the soil bacterial communities’ structures of EBF, CF, SDF and AM were clearly separated along the first and second principal components, which explained 62.17% and 31.58% of the total variance, respectively. The soil physical-chemical properties such as total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) were positively correlated with the diversity of bacterial communities. PMID:26098851

  12. Landscape scale vegetation-type conversion and fire hazard in the San Francisco bay area open spaces

    USGS Publications Warehouse

    Russell, W.H.; McBride, J.R.

    2003-01-01

    Successional pressures resulting from fire suppression and reduced grazing have resulted in vegetation-type conversion in the open spaces surrounding the urbanized areas of the San Francisco bay area. Coverage of various vegetation types were sampled on seven sites using a chronosequence of remote images in order to measure change over time. Results suggest a significant conversion of grassland to shrubland dominated by Baccharis pilularison five of the seven sites sampled. An increase in Pseudotsuga menziesii coverage was also measured on the sites where it was present. Increases fuel and fire hazard were determined through field sampling and use of the FARSITE fire area simulator. A significant increase in biomass resulting from succession of grass-dominated to shrub-dominated communities was evident. In addition, results from the FARSITE simulations indicated significantly higher fire-line intensity, and flame length associated with shrublands over all other vegetation types sampled. These results indicate that the replacement of grass dominated with shrub-dominated landscapes has increased the probability of high intensity fires. ?? 2003 Elsevier Science B.V. All rights reserved.

  13. Energy partitioning and environmental influence factors in different vegetation types in the GEWEX Asian Monsoon Experiment

    NASA Astrophysics Data System (ADS)

    Liu, Fengshan; Tao, Fulu; Li, Shenggong; Zhang, Shuai; Xiao, Dengpan; Wang, Meng

    2014-12-01

    Environmental influences upon energy balance in areas of different vegetation types (i.e., forest at Kog-Ma in Thailand and at Yakutsk in Russia, grassland at Amdo in Chinese Tibet and at Arvaikheer in Mongolia, and mixed farmland at Tak in Thailand) in the GEWEX Asian Monsoon Experiment were investigated. The sites we investigated are geographically and climatologically different; and consequently had quite large variations in temperature ( T), water vapor pressure deficit (VPD), soil moisture (SM), and precipitation (PPT). During May-October, the net radiation flux ( R n) (in W·m-2) was 406.21 at Tak, 365.57 at Kog-Ma, 390.97 at Amdo, 316.65 at Arvaikheer, and 287.10 at Yakutsk. During the growing period, the R n partitioned into latent heat flux ( λE/ R n) was greater than that partitioned into sensible heat flux ( H/ R n) at Tak and at Kog-Ma. In contrast, λE/ R n was lower than H/ R n at Arvaikheer, H/ R n was less than λE/ R n between DOY 149 and DOY 270 at Amdo, and between DOY 165 and DOY 235 at Yakutsk. The R n partitioned into ground heat flux was generally less than 0.15. The short-wave albedo was 0.12, 0.18, and 0.20 at the forest, mixed land, and grass sites, respectively. At an hourly scale, energy partitions had no correlation with environmental factors, based on average summer halfhourly values. At a seasonal scale energy partitions were linearly correlated (usually p<0.05) with T, VPD, and SM. The λE/ R n increased with increases in SM, T, and VPD at forest areas. At mixed farmlands, λE/ R n generally had positive correlations with SM, T, and VPD, but was restrained at extremely high values of VPD and T. At grasslands, λE/ R n was enhanced with increases of SM and T, but was decreased with VPD.

  14. Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region.

    PubMed

    Liang, Yueming; Pan, Fujing; He, Xunyang; Chen, Xiangbi; Su, Yirong

    2016-09-01

    Arbuscular mycorrhizal (AM) fungi and nitrogen-fixing bacteria play important roles in plant growth and recovery in degraded ecosystems. The desertification in karst regions has become more severe in recent decades. Evaluation of the fungal and bacterial diversity of such regions during vegetation restoration is required for effective protection and restoration in these regions. Therefore, we analyzed relationships among AM fungi and nitrogen-fixing bacteria abundances, plant species diversity, and soil properties in four typical ecosystems of vegetation restoration (tussock (TK), shrub (SB), secondary forest (SF), and primary forest (PF)) in a karst region of southwest China. Abundance of AM fungi and nitrogen-fixing bacteria, plant species diversity, and soil nutrient levels increased from the tussock to the primary forest. The AM fungus, nitrogen-fixing bacterium, and plant community composition differed significantly between vegetation types (p < 0.05). Plant richness and pH were linked to the community composition of fungi and nitrogen-fixing bacteria, respectively. Available phosphorus, total nitrogen, and soil organic carbon levels and plant richness were positively correlated with the abundance of AM fungi and nitrogen-fixing bacteria (p < 0.05). The results suggested that abundance of AM fungi and nitrogen-fixing bacteria increased from the tussock to the primary forest and highlight the essentiality of these communities for vegetation restoration.

  15. Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region.

    PubMed

    Liang, Yueming; Pan, Fujing; He, Xunyang; Chen, Xiangbi; Su, Yirong

    2016-09-01

    Arbuscular mycorrhizal (AM) fungi and nitrogen-fixing bacteria play important roles in plant growth and recovery in degraded ecosystems. The desertification in karst regions has become more severe in recent decades. Evaluation of the fungal and bacterial diversity of such regions during vegetation restoration is required for effective protection and restoration in these regions. Therefore, we analyzed relationships among AM fungi and nitrogen-fixing bacteria abundances, plant species diversity, and soil properties in four typical ecosystems of vegetation restoration (tussock (TK), shrub (SB), secondary forest (SF), and primary forest (PF)) in a karst region of southwest China. Abundance of AM fungi and nitrogen-fixing bacteria, plant species diversity, and soil nutrient levels increased from the tussock to the primary forest. The AM fungus, nitrogen-fixing bacterium, and plant community composition differed significantly between vegetation types (p < 0.05). Plant richness and pH were linked to the community composition of fungi and nitrogen-fixing bacteria, respectively. Available phosphorus, total nitrogen, and soil organic carbon levels and plant richness were positively correlated with the abundance of AM fungi and nitrogen-fixing bacteria (p < 0.05). The results suggested that abundance of AM fungi and nitrogen-fixing bacteria increased from the tussock to the primary forest and highlight the essentiality of these communities for vegetation restoration. PMID:27287492

  16. Impact of soil type on vegetation response to prairie dog herbivory

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Prairie dogs and their impact on vegetation have been the focus of numerous research projects. However, the effect of soil from this interaction has been less thoroughly documented. We evaluated prairie dog colonies (on-colony) and nearby sites without prairie dogs (off-colony) on Wayden, Cabba an...

  17. Predictors of College-Student Food Security and Fruit and Vegetable Intake Differ by Housing Type

    ERIC Educational Resources Information Center

    Mirabitur, Erica; Peterson, Karen E.; Rathz, Colleen; Matlen, Stacey; Kasper, Nicole

    2016-01-01

    Objective: We assessed whether college-student characteristics associate with food security and fruit and vegetable (FV) intake and whether these associations differ in students in housing with and without food provision. Participants: 514 randomly-sampled students from a large, Midwestern, public university in 2012 and 2013 Methods: Ordered…

  18. Identification of phenological stages and vegetative types for land use classification

    NASA Technical Reports Server (NTRS)

    Mckendrick, J. D. (Principal Investigator)

    1973-01-01

    The author had identified the following significant results. Digital signatures derived from the CDU are comparable to those taken from the printouts. Therefore, using the CDU to derive signatures should be more efficient, since there is considerable time required in turn around with the computer and time required locating vegetation stands on the printout.

  19. Floodplain restoration leads to wetter and more diverse soil water regimes and vegetation types: Insight from an integrated hydroecological model

    NASA Astrophysics Data System (ADS)

    Booth, E. G.; Loheide, S. P.

    2011-12-01

    Soil moisture availability in the root zone is one of the most important factors affecting plant species composition by creating stress on vegetation both when it is lacking (water stress) and when it is excessive (oxygen stress). Plant species have individual tolerance ranges along a gradient of available soil moisture that can be described as a hydrological niche. Combining a hydrological model and a habitat niche model can provide spatially-extensive predictions of vegetation composition, which would be useful for land management decision-making under changing environmental conditions. Floodplain ecosystem restoration provides an example of the utility of such a predictive tool as a site is hydrologically altered to create a wetter environment. We developed an integrated hydroecological model that links a quasi-3D, variably-saturated, groundwater flow model that simulates soil moisture with several plant habitat niche models. The focus of this research is a floodplain in southwestern Wisconsin where post-settlement alluvium was removed with the expectation of increasing regionally-threatened wetland plant species. Hydrological niche models were created based on simultaneous observations of vegetation composition and surface effective saturation. These models were then used to predict probability of presence for two dominant plant species (Carex vulpinoidea and Elymus canadensis) and composite wetland indicator score based on simulated surface effective saturation across the study site. The model predicts the site to be more wetland-species dominant overall following restoration. However, the soil moisture regime and vegetation types are slightly drier following restoration in zones where a silt-clay confining layer is present that inhibits vertical groundwater flow from a basal gravel aquifer to the near-surface soil zone. This differential response to restoration leads to a mosaic of soil water regimes across the site, which is reflected in a wider distribution

  20. Hydroecological model predictions indicate wetter and more diverse soil water regimes and vegetation types following floodplain restoration

    NASA Astrophysics Data System (ADS)

    Booth, Eric G.; Loheide, Steven P., II

    2012-06-01

    Transitions between aquatic and terrestrial ecosystems represent zones where soil moisture is a dominant factor influencing vegetation composition. Niche models based on hydrological and vegetation observations can be powerful tools for guiding management of these zones, especially when they are linked with physically based hydrological models. Floodplain restoration represents a unique opportunity to utilize such a predictive vegetation tool when a site's hydrology is altered to create a wetter environment. A variably saturated groundwater flow model was developed and used to simulate the soil moisture regime across a floodplain in Wisconsin where post-settlement alluvium was removed with the intent of increasing regionally threatened wetland plant species. Hydrological niche models based on simultaneous observations of vegetation composition and surface effective saturation were used to predict probability of presence for two plant species (Carex vulpinoidea (fox sedge) and Elymus canadensis(Canada wildrye)) and wetland indicator score (a composite indicator of relative frequency of species in five habitat categories) based on simulated surface effective saturation. The vegetation predictions following restoration are more wetland-species dominant overall. However, zones of the study site where a confining layer is present that decouples groundwater from the near-surface soil zone tend to be drier following restoration due to restricted upward groundwater flow and less soil water storage above the confining layer. As reflected by an increase in the interquartile range in the predicted wetland indicator score, this restoration technique may increase the site-scale spatial diversity of plant community types while simultaneously accomplishing the goal of increasing wetland plant species occurrence.

  1. [Comparison of soil fertility among open-pit mine reclaimed lands in Antaibao regenerated with different vegetation types].

    PubMed

    Wang, Xiang; Li, Jin-chuan; Yue, Jian-ying; Zhou, Xiao-mei; Guo, Chun-yan; Lu, Ning; Wang, Yu-hong; Yang, Sheng-quan

    2013-09-01

    Re-vegetation is mainly applied into regeneration in opencast mine to improve the soil quality. It is very important to choose feasible vegetation types for soil restoration. In this study, three typical forest restoration types were studied at Antaibao mine, namely, Medicago sativa, mixed forests Pinus taebelaefolius-Robinia pseudoacacia-Caragana korshinskii and Elaeagnus angustifolia-Robinia pseudoacacia-Caragana korshinskii-Hipophae rhamnoides, to determine the nutrient contents and enzyme activities in different soil layers. The results showed that re-vegetation markedly increased soil nutrient contents and the enzyme activities during the restoration process. The nutrient content of soil in the P. taebelaefolius-R. pseudoacacia-C. korshinskii mixed forest field was significantly higher than those in other plots. It was found that the soil of the P. taebelaefolius-R. pseudoacacia-C. korshinskii mixed forest had the highest integrated fertility index values. In conclusion, the restoration effects of the P. zaebelaefolius-R. pseudoacacia-C. Korshinskii mixed forest was better than that of E. angustifolia-R. pseudoacacia-C. korshinskii-H. rhamnoides, while M. sativa grassland had the least effect.

  2. Analysis of fern spore banks from the soil of three vegetation types in the central region of Mexico.

    PubMed

    Ramírez-Trejo, María Del Rosario; Pérez-García, Blanca; Orozco-Segovia, Alma

    2004-05-01

    The vertical structure of fern spore banks was studied in a xerophilous shrubland, montane rain forest, and pine-oak forest in Hidalgo, Mexico, using the emergence method. Soil samples were collected in April 1999 at depths of 0-10, 10-20, and 20-30 cm. Viable spores decreased significantly with depth in all vegetation types, and the highest number of prothallia and sporophytes was found in the uppermost layer. The montane rain forest and the xerophilous shrubland had the largest and the richest banks, respectively. Twenty-three fern taxa were registered in the aboveground vegetation, 12 in the soil banks, and 43.5% were in both. Aboveground and in the soil bank, the xerophilous shrubland, the montane rain forest, and the pine-oak forest had, 17 and 7, 1 and 6, and 7 and 3 taxa, respectively. These were distributed differentially in relation to depth. The Sørensen index indicated a similarity of 61.5% between the xerophilous shrubland and the montane rain forest, and the Czeckanovsky index indicated 19.75%. The presence of viable spores in the soil of all vegetation types confirmed the existence of natural spore banks. Long-distance dispersal was an important factor determining the specific composition of the xerophilous shrubland and the pine-oak forest.

  3. Millennial-scale vegetation changes in the north-eastern Russian Arctic during the Pliocene/Pleistocene transition (2.7-2.5 Ma) inferred from the pollen record of Lake El'gygytgyn

    NASA Astrophysics Data System (ADS)

    Andreev, Andrei A.; Tarasov, Pavel E.; Wennrich, Volker; Melles, Martin

    2016-09-01

    The sediment record of Lake El'gygytgyn (67°30‧N, 172°05‧E) spans the past 3.6 Ma and provides unique opportunities for qualitative and quantitative reconstructions of the regional paleoenvironmental history of the terrestrial Arctic. Millennial-scale pollen studies of the sediments that accumulated during the Late Pliocene and Early Pleistocene (ca. 2.7 to 2.5 Ma) demonstrate orbitally-driven vegetation and climate changes during this transitional interval. Pollen spectra show a significant vegetation shift at the Pliocene/Pleistocene boundary that is, however, delayed by a few thousand years compared to lacustrine response. About 2.70-2.68 Ma the vegetation at Lake El'gygytgyn, currently a tundra area was mostly dominated by larch forests with some shrub pine, shrub alder and dwarf birch in understory. During the marine isotope stages G3 and G1, ca. 2.665-2.647 and 2.625-2.617 Ma, some spruce trees grew in the local larch-pine forests, pointing to relatively warm climate conditions. At the beginning of the Pleistocene, around 2.588 Ma, a prominent climatic deterioration led to a change from larch-dominated forests to predominantly treeless steppe- and tundra-like habitats. Between ca. 2.56-2.53 Ma some climate amelioration is reflected by the higher presence of coniferous taxa (mostly pine and larch, but probably also spruce) in the area. After 2.53 Ma a relatively cold and dry climate became dominant again, leading to open steppe-like and shrubby environments followed by climate amelioration between ca. 2.510 and 2.495 Ma, when pollen assemblages show that larch forests with dwarf birch and shrub alder still grew in the lake's vicinity. Increased contents of green algae colonies (Botryococcus) remains and Zygnema cysts around 2.691-2.689, 2.679-2.677, 2.601-2.594, 2.564-2.545, and 2.532-2.510 Ma suggest a spread of shallow-water environments most likely due to a lake-level lowering. These events occurred simultaneously with dry climate conditions inferred

  4. Wild fire effects on floristic diversity in three thermo-Mediterranean vegetation types in a small islet of eastern Aegean sea

    NASA Astrophysics Data System (ADS)

    Abraham, Eleni; Kyriazopoulos, Apostolos; Korakis, George; Parissi, Zoi; Chouvardas, Dimitrios

    2014-05-01

    Sclerophyllus scrub formations, the main vegetation type in many islands of the Aegean area, are characterized by their high biodiversity. Dominant shrub species of sclerophyllus formations are well adapted to dry season conditions by various anatomical and physiological mechanisms. As a result, their biomass acts as very flammable fine fuel, and consequently wild fires are very common in these ecosystems. Wildfire effects on vegetation and biodiversity in the Mediterranean basin have been studied and the results are diverse depending mainly on vegetation type and frequency of fire. The aim of this study was to evaluate the effects of wildfire on floristic diversity and species composition in three thermo-Mediterranean vegetation types 1) Sacropoterium spinosum phrygana, 2) low formations of Cistus creticus and 3) low formations of Cistus creticus in abandoned terraces. The research was conducted in Enoussa islet, which is located northeastern of Chios Island, in May 2013 (one year after the fire). Vegetation sampling was performed along five transects placed in recently burned and in adjacent unburned sites of each vegetation type. The plant cover and the floristic composition were measured, while diversity, evenness and dominance indices were determined for the vegetation data. Vegetation cover and the floristic diversity were significant lower and higher respectively in burned areas in comparison to the unburned. The woody species followed by the annual grasses and the annual forbs dominated in both burned and unburned areas. However, the woody species were significantly decreased in the burned areas in all vegetation types, while the annual grasses only in the burned areas of Sacropoterium spinosum phrygana and Cistus creticus in abandoned terraces. Inversely, the annual forbs significantly increased in the burned sites of Cistus creticus formations. The highest value of Morisita-Horn Index of similarity between burned and unburned sites (beta diversity) was

  5. Arctic Clouds

    Atmospheric Science Data Center

    2013-04-19

    ...   View Larger Image Stratus clouds are common in the Arctic during the summer months, and are important modulators of ... from MISR's two most obliquely forward-viewing cameras. The cold, stable air causes the clouds to persist in stratified layers, and this ...

  6. Type utilization of baked-smashed sweet potato and vegetables on patisserie product

    NASA Astrophysics Data System (ADS)

    Ana; Subekti, S.; Sudewi; Perdani, E. N.; Hanum, F.; Suciani, T.; Tania, V.

    2016-04-01

    The research was an experimental study in Green Skill Patisserie Course using Project-Based Learning model. It aims to complete the project development of pie named guramnis rainbow pie. Several experiments were carried out to produce a pie dough crust mixed with baked-smashed sweet potato and added with vegetables extract as the food coloring. The experiment method in order to make a better appearance or an attractive shape and to have more nutrition. In addition, the pie was filled with a mixture of sweet and sour gurame as Indonesian traditional food. By applying an organoleptic test to 10 respondents, the result shows that pie dough recipe using flour substituted by baked-smashed sweet potato with 2:1 of a ratio. Coloring pie dough adding extract vegetables (carrots, beets and celery) as color. We found that pie dough has more interesting pie color (90%) and the texture of the pie with a quite level of crispness (60%). Moreover, the pie taste is fairly (70%) and tasty (70%). Nutritional analysis results show that per size, serving guramnis rainbow pie contains energy as much as 81.72 calories, carbohydrates 12.5 grams, fat 2.32 grams and 2.77 grams of protein. The main findings are the pie appearance and taste was different compared to the previous pies because of the pie was served with gurame asam manis as the filling and had flour and cilembu sweet potato as the basic ingredients. The color of guramnis rainbow pie was resulted not only from food coloring but also from vegetables extract namely carrot (orange), bit (red), and salary (green). Thus, it had many benefits for health and adds the nutrition. The researchers recommend a further study in order to make pie dough with baked sweet potato and vegetables extract having an optimal level of crispness.

  7. Arctic hydroclimatology

    NASA Astrophysics Data System (ADS)

    Cherry, Jessica Ellen

    Arctic air temperature, precipitation, ground temperature, river runoff, clouds, and radiation are all changing quickly in a warming climate. Interactions and feedbacks between these features are not well understood. In particular, the relative role of local climate processes and large-scale ocean-atmosphere dynamics in driving observed Arctic changes is difficult to ascertain because of the sparsity of observations, inaccuracy of those that do exist, biases in global circulation models and analyses, and fundamental physics of the Arctic region. Four studies of Arctic hydroclimatology herein attempt to overcome these challenges. The first study, analysis of the Lena river basin hydroclimatology, shows canonical acceleration of the hydrologic cycle and amplification of global warming. Winter and spring are warming and increased frozen precipitation is contributing to permafrost melting by increasing soil insulation. Increasing runoff and soil moisture is leading to increasing evapotranspiration and changes in clouds. Changes in clouds are cooling summer days but warming summer nights, melting additional permafrost. Model simulations suggests that a deepening active layer will lead to an increasingly wet Arctic. The second two studies describe the development of the Pan-Arctic Snowfall Reconstruction (PASR). This product addresses the problem of cold season precipitation gauge biases for 1940-1999. The NASA Interannual-to-Seasonal Prediction Project Catchment-based Land Surface Model is used to reconstruct solid precipitation from observed snow depth and surface air temperatures. Error estimation is done via controlled simulations at Reynolds Creek Experimental Watershed, in Idaho. The method is then applied to stations in the pan-Arctic hydrological catchment. Comparison with existing products suggests that the PASR is a better estimate of actual snowfall for hydroclimatological studies. The final chapter is a case study on hydroclimatological variability driven by

  8. Remote sensing-based characterization, 2-m, Plant Functional Type Distributions, Barrow Environmental Observatory, 2010

    DOE Data Explorer

    Zachary Langford; Forrest Hoffman; Jitendra Kumar

    2014-01-01

    Arctic ecosystems have been observed to be warming faster than the global average and are predicted to experience accelerated changes in climate due to global warming. Arctic vegetation is particularly sensitive to warming conditions and likely to exhibit shifts in species composition, phenology and productivity under changing climate. Mapping and monitoring of changes in vegetation is essential to understand the effect of climate change on the ecosystem functions. Vegetation exhibits unique spectral characteristics which can be harnessed to discriminate plant types and develop quantitative vegetation indices. We have combined high resolution multi-spectral remote sensing from the WorldView 2 satellite with LIDAR-derived digital elevation models to characterize the tundra landscape on the North Slope of Alaska. Classification of landscape using spectral and topographic characteristics yields spatial regions with expectedly similar vegetation characteristics. A field campaign was conducted during peak growing season to collect vegetation harvests from a number of 1m x 1m plots in the study region, which were then analyzed for distribution of vegetation types in the plots. Statistical relationships were developed between spectral and topographic characteristics and vegetation type distributions at the vegetation plots. These derived relationships were employed to statistically upscale the vegetation distributions for the landscape based on spectral characteristics. Vegetation distributions developed are being used to provide Plant Functional Type (PFT) maps for use in the Community Land Model (CLM).

  9. The future of soil invertebrate communities in polar regions: different climate change responses in the Arctic and Antarctic?

    PubMed

    Nielsen, Uffe N; Wall, Diana H

    2013-03-01

    The polar regions are experiencing rapid climate change with implications for terrestrial ecosystems. Here, despite limited knowledge, we make some early predictions on soil invertebrate community responses to predicted twenty-first century climate change. Geographic and environmental differences suggest that climate change responses will differ between the Arctic and Antarctic. We predict significant, but different, belowground community changes in both regions. This change will be driven mainly by vegetation type changes in the Arctic, while communities in Antarctica will respond to climate amelioration directly and indirectly through changes in microbial community composition and activity, and the development of, and/or changes in, plant communities. Climate amelioration is likely to allow a greater influx of non-native species into both the Arctic and Antarctic promoting landscape scale biodiversity change. Non-native competitive species could, however, have negative effects on local biodiversity particularly in the Arctic where the communities are already species rich. Species ranges will shift in both areas as the climate changes potentially posing a problem for endemic species in the Arctic where options for northward migration are limited. Greater soil biotic activity may move the Arctic towards a trajectory of being a substantial carbon source, while Antarctica could become a carbon sink.

  10. Calcium concrements in the pineal gland of the Arctic fox (Vulpes lagopus) and their relationship to pinealocytes, glial cells and type I and III collagen fibers.

    PubMed

    Bulc, M; Lewczuk, B; Prusik, M; Gugołek, A; Przybylska-Gornowicz, B

    2010-01-01

    The aim of the present study was to analyze the presence and morphology of the pineal concretions in the Arctic fox and their relationship to pinealocytes, glial cells and collagen fibers. Pineals collected from 7-8 month-old and 3-4 year-old foxes (6 in each age-group) were investigated. Sections of the glands were stained with HE, Mallory's method and alizarin red S as well as subjected to a combined procedure involving immunofluorescent staining with antibodies against antigen S, glial fibril acid protein (GFAP), type I and III collagen and histochemical staining with alizarin red S. The pineal concretions were found in 2 of 6 investigated Arctic foxes aged 3 years and they were not observed in animals aged 7-8 months. The acervuli were present in the parenchyma and the connective tissue septa. They were more numerous in the distal part than in the proximal part of the gland. The acervuli stained with alizarin red S revealed an intensive red fluorescence, what enabled the use of this compound in a combined histochemical-immunofluorescent procedure. A majority of cells in the fox pineal showed positive staining with antibodies against antigen S, a marker of pinealocytes. GFAP-positive cells were especially numerous in the proximal part of the gland. Both antigen S- and GFAP-positive cells were frequently observed close to the concrements. Collagen fibers of type I and III were found in the capsule, connective tissue septa and vessels. Immunoreactive fibers did not form any capsules or basket-like structures surrounding the concrements. PMID:20731181

  11. Effects on the function of Arctic ecosystems in the short- and long-term perspectives.

    PubMed

    Callaghan, Terry V; Björn, Lars Olof; Chernov, Yuri; Chapin, Terry; Christensen, Torben R; Huntley, Brian; Ims, Rolf A; Johansson, Margareta; Jolly, Dyanna; Jonasson, Sven; Matveyeva, Nadya; Panikov, Nicolai; Oechel, Walter; Shaver, Gus

    2004-11-01

    Historically, the function of Arctic ecosystems in terms of cycles of nutrients and carbon has led to low levels of primary production and exchanges of energy, water and greenhouse gases have led to low local and regional cooling. Sequestration of carbon from atmospheric CO2, in extensive, cold organic soils and the high albedo from low, snow-covered vegetation have had impacts on regional climate. However, many aspects of the functioning of Arctic ecosystems are sensitive to changes in climate and its impacts on biodiversity. The current Arctic climate results in slow rates of organic matter decomposition. Arctic ecosystems therefore tend to accumulate organic matter and elements despite low inputs. As a result, soil-available elements like nitrogen and phosphorus are key limitations to increases in carbon fixation and further biomass and organic matter accumulation. Climate warming is expected to increase carbon and element turnover, particularly in soils, which may lead to initial losses of elements but eventual, slow recovery. Individual species and species diversity have clear impacts on element inputs and retention in Arctic ecosystems. Effects of increased CO2 and UV-B on whole ecosystems, on the other hand, are likely to be small although effects on plant tissue chemisty, decomposition and nitrogen fixation may become important in the long-term. Cycling of carbon in trace gas form is mainly as CO2 and CH4. Most carbon loss is in the form of CO2, produced by both plants and soil biota. Carbon emissions as methane from wet and moist tundra ecosystems are about 5% of emissions as CO2 and are responsive to warming in the absence of any other changes. Winter processes and vegetation type also affect CH4 emissions as well as exchanges of energy between biosphere and atmosphere. Arctic ecosystems exhibit the largest seasonal changes in energy exchange of any terrestrial ecosystem because of the large changes in albedo from late winter, when snow reflects most

  12. Strategic metal deposits of the Arctic Zone

    NASA Astrophysics Data System (ADS)

    Bortnikov, N. S.; Lobanov, K. V.; Volkov, A. V.; Galyamov, A. L.; Vikent'ev, I. V.; Tarasov, N. N.; Distler, V. V.; Lalomov, A. V.; Aristov, V. V.; Murashov, K. Yu.; Chizhova, I. A.; Chefranov, R. M.

    2015-11-01

    Mineral commodities rank high in the economies of Arctic countries, and the status of mineral resources and the dynamics of their development are of great importance. The growing tendency to develop strategic metal resources in the Circumarctic Zone is outlined in a global perspective. The Russian Arctic Zone is the leading purveyor of these metals to domestic and foreign markets. The comparative analysis of tendencies in development of strategic metal resources of the Arctic Zone in Russia and other countries is crucial for the elaboration of trends of geological exploration and research engineering. This paper provides insight into the development of Arctic strategic metal resources in global perspective. It is shown that the mineral resource potential of the Arctic circumpolar metallogenic belt is primarily controlled by large and unique deposits of nonferrous, noble, and rare metals. The prospective types of economic strategic metal deposits in the Russian Arctic Zone are shown.

  13. Community Structure of Skipper Butterflies (Lepidoptera, Hesperiidae) along Elevational Gradients in Brazilian Atlantic Forest Reflects Vegetation Type Rather than Altitude

    PubMed Central

    Carneiro, Eduardo; Mielke, Olaf Hermann Hendrik; Casagrande, Mirna Martins; Fiedler, Konrad

    2014-01-01

    Species turnover across elevational gradients has matured into an important paradigm of community ecology. Here, we tested whether ecological and phylogenetic structure of skipper butterfly assemblages is more strongly structured according to altitude or vegetation type along three elevation gradients of moderate extent in Serra do Mar, Southern Brazil. Skippers were surveyed along three different mountain transects, and data on altitude and vegetation type of every collection site were recorded. NMDS ordination plots were used to assess community turnover and the influence of phylogenetic distance between species on apparent community patterns. Ordinations based on ecological similarity (Bray-Curtis index) were compared to those based on phylogenetic distance measures (MPD and MNTD) derived from a supertree. In the absence of a well-resolved phylogeny, various branch length transformation methods were applied together with four different null models, aiming to assess if results were confounded by low-resolution trees. Species composition as well as phylogenetic community structure of skipper butterflies were more prominently related to vegetation type instead of altitude per se. Phylogenetic distances reflected spatial community patterns less clearly than species composition, but revealed a more distinct fauna of monocot feeders associated with grassland habitats, implying that historical factors have played a fundamental role in shaping species composition across elevation gradients. Phylogenetic structure of community turned out to be a relevant additional tool which was even superior to identify faunal contrasts between forest and grassland habitats related to deep evolutionary splits. Since endemic skippers tend to occur in grassland habitats in the Serra do Mar, inclusion of phylogenetic diversity may also be important for conservation decisions. PMID:25272004

  14. The influence of slope and peatland vegetation type on riverine dissolved organic carbon and water colour at different scales.

    PubMed

    Parry, L E; Chapman, P J; Palmer, S M; Wallage, Z E; Wynne, H; Holden, J

    2015-09-15

    Peatlands are important sources of fluvial carbon. Previous research has shown that riverine dissolved organic carbon (DOC) concentrations are largely controlled by soil type. However, there has been little work to establish the controls of riverine DOC within blanket peatlands that have not undergone major disturbance from drainage or burning. A total of 119 peatland catchments were sampled for riverine DOC and water colour across three drainage basins during six repeated sampling campaigns. The topographic characteristics of each catchment were determined from digital elevation models. The dominant vegetation cover was mapped using 0.5m resolution colour infrared aerial images, with ground-truthed validation revealing 82% accuracy. Forward and backward stepwise regression modelling showed that mean slope was a strong (and negative) determinant of DOC and water colour in blanket peatland river waters. There was a weak role for plant functional type in determining DOC and water colour. At the basin scale, there were major differences between the models depending on the basin. The dominance of topographic predictors of DOC found in our study, combined with a weaker role of vegetation type, paves the way for developing improved planning tools for water companies operating in peatland catchments. Using topographic data and aerial imagery it will be possible to predict which tributaries will typically yield lower DOC concentrations and which are therefore more suitable and cost-effective as raw water intakes. PMID:26003614

  15. Identification of phenological stages and vegetative types for land use classification

    NASA Technical Reports Server (NTRS)

    Branton, C. I. (Principal Investigator)

    1972-01-01

    The author has identified the following significant results. Two procedures for examining ERTS-1 imagery were investigated in cooperation with the photographic services section. Positive, 10X enlargements were produced of spectral bands 4, 6, and 7, for a portion of photo 1033-21020. Adequate detail remained to recognize physical features such as streams, glaciers, ice, and snow. Also the entire image was studied using transparencies produced by the 3M color-key process. A combination of three complementary color combinations produced visually recognizable shades apparently indicating vegetation differences. Also lakes and glacial streams of sufficient size, ice and snow, and drainage patterns can be recognized. A need is indicated for oblique low level color aerial photography in the vicinity of identifiable terrain features to assist in the positive location of vegetative communities appearing in the analysis process. In the primary areas of concern to this project identifiable manmade features are conspicuous by their absence. In image 1049-20505 band 7 produced distinct tonal differences on a mountain slope to river bottom gradient.

  16. Impacts of the variability of second-year ice types on the decline of the Arctic perennial sea-ice cover

    NASA Astrophysics Data System (ADS)

    Comiso, Josefino C.

    The observed rapid decline in the Arctic perennial ice cover is one of the most remarkable signals of change in the Arctic region. Updated data now show an even higher rate of decline of 9.8% decade -1 (1978-2005) than the previous report of 8.9% decade -1 (1978-2000). To gain insights into this decline, the variability of the second-year ice, which is the relatively thin component of the perennial ice cover, is studied. The perennial ice cover in the 1990s was observed to be highly variable, leading to relatively high production of second-year ice that may in part explain the observed ice thinning during the period and have triggered further decline. The microwave signature of second-year ice is shown to be different from that of the older multi-year ice types and, surprisingly, more similar to that of first-year ice. This in part explains why previous estimates of the area of multi-year ice during the winter period are considerably lower than the area of the perennial ice cover during the preceding summer. Analysis of multichannel cluster maps in conjunction with submarine ice-draft data indicates ability to detect regions covered primarily by second-year ice and hence to infer ice-thickness information from the microwave data. The periodic increase of second-year ice in the 1990s was apparently followed by continuous decline due in part to anomolously warm temperatures during the latter period that shortened the ice season and kept first-year ice from getting thick enough to survive the summer and become second year ice.

  17. Arctic Ocean

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.; Zukor, Dorothy J. (Technical Monitor)

    2000-01-01

    The Arctic Ocean is the smallest of the Earth's four major oceans, covering 14x10(exp 6) sq km located entirely within the Arctic Circle (66 deg 33 min N). It is a major player in the climate of the north polar region and has a variable sea ice cover that tends to increase its sensitivity to climate change. Its temperature, salinity, and ice cover have all undergone changes in the past several decades, although it is uncertain whether these predominantly reflect long-term trends, oscillations within the system, or natural variability. Major changes include a warming and expansion of the Atlantic layer, at depths of 200-900 m, a warming of the upper ocean in the Beaufort Sea, a considerable thinning (perhaps as high as 40%) of the sea ice cover, a lesser and uneven retreat of the ice cover (averaging approximately 3% per decade), and a mixed pattern of salinity increases and decreases.

  18. An expert system shell for inferring vegetation characteristics: Changes to the historical cover type database (Task F)

    NASA Technical Reports Server (NTRS)

    1993-01-01

    All the options in the NASA VEGetation Workbench (VEG) make use of a database of historical cover types. This database contains results from experiments by scientists on a wide variety of different cover types. The learning system uses the database to provide positive and negative training examples of classes that enable it to learn distinguishing features between classes of vegetation. All the other VEG options use the database to estimate the error bounds involved in the results obtained when various analysis techniques are applied to the sample of cover type data that is being studied. In the previous version of VEG, the historical cover type database was stored as part of the VEG knowledge base. This database was removed from the knowledge base. It is now stored as a series of flat files that are external to VEG. An interface between VEG and these files was provided. The interface allows the user to select which files of historical data to use. The files are then read, and the data are stored in Knowledge Engineering Environment (KEE) units using the same organization of units as in the previous version of VEG. The interface also allows the user to delete some or all of the historical database units from VEG and load new historical data from a file. This report summarizes the use of the historical cover type database in VEG. It then describes the new interface to the files containing the historical data. It describes minor changes that were made to VEG to enable the externally stored database to be used. Test runs to test the operation of the new interface and also to test the operation of VEG using historical data loaded from external files are described. Task F was completed. A Sun cartridge tape containing the KEE and Common Lisp code for the new interface and the modified version of the VEG knowledge base was delivered to the NASA GSFC technical representative.

  19. Topsoil and Deep Soil Organic Carbon Concentration and Stability Vary with Aggregate Size and Vegetation Type in Subtropical China.

    PubMed

    Fang, Xiang-Min; Chen, Fu-Sheng; Wan, Song-Ze; Yang, Qing-Pei; Shi, Jian-Min

    2015-01-01

    The impact of reforestation on soil organic carbon (OC), especially in deep layer, is poorly understood and deep soil OC stabilization in relation with aggregation and vegetation type in afforested area is unknown. Here, we collected topsoil (0-15 cm) and deep soil (30-45 cm) from six paired coniferous forests (CF) and broad-leaved forests (BF) reforested in the early 1990s in subtropical China. Soil aggregates were separated by size by dry sieving and OC stability was measured by closed-jar alkali-absorption in 71 incubation days. Soil OC concentration and mean weight diameter were higher in BF than CF. The cumulative carbon mineralization (Cmin, mg CO2-C kg-1 soil) varied with aggregate size in BF and CF topsoils, and in deep soil, it was higher in larger aggregates than in smaller aggregates in BF, but not CF. The percentage of soil OC mineralized (SOCmin, % SOC) was in general higher in larger aggregates than in smaller aggregates. Meanwhile, SOCmin was greater in CF than in BF at topsoil and deep soil aggregates. In comparison to topsoil, deep soil aggregates generally exhibited a lower Cmin, and higher SOCmin. Total nitrogen (N) and the ratio of carbon to phosphorus (C/P) were generally higher in BF than in CF in topsoil and deep soil aggregates, while the same trend of N/P was only found in deep soil aggregates. Moreover, the SOCmin negatively correlated with OC, total N, C/P and N/P. This work suggests that reforested vegetation type might play an important role in soil OC storage through internal nutrient cycling. Soil depth and aggregate size influenced OC stability, and deep soil OC stability could be altered by vegetation reforested about 20 years.

  20. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China

    PubMed Central

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-01-01

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure. PMID:26633458

  1. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China.

    PubMed

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-12-03

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure.

  2. Fractal Characteristics of Soil Retention Curve and Particle Size Distribution with Different Vegetation Types in Mountain Areas of Northern China.

    PubMed

    Niu, Xiang; Gao, Peng; Wang, Bing; Liu, Yu

    2015-12-01

    Based on fractal theory, the fractal characteristics of soil particle size distribution (PSD) and soil water retention curve (WRC) under the five vegetation types were studied in the mountainous land of Northern China. Results showed that: (1) the fractal parameters of soil PSD and soil WRC varied greatly under each different vegetation type, with Quercus acutissima Carr. and Robina pseudoacacia Linn. mixed plantation (QRM) > Pinus thunbergii Parl. and Pistacia chinensis Bunge mixed plantation (PPM) > Pinus thunbergii Parl. (PTP) > Juglans rigia Linn. (JRL) > abandoned grassland (ABG); (2) the soil fractal dimensions of woodlands (QRM, PPM, PTP and JRL) were significantly higher than that in ABG, and mixed forests (QRM and PPM) were higher than that in pure forests (PTP and JRL); (3) the fractal dimension of soil was positively correlated with the silt and clay content but negatively correlated with the sand content; and (4) the fractal dimension of soil PSD was positively correlated with the soil WRC. These indicated that the fractal parameters of soil PSD and soil WRC could act as quantitative indices to reflect the physical properties of the soil, and could be used to describe the influences of the Return Farmland to Forests Projects on soil structure. PMID:26633458

  3. Remote sensing to inform Plant Functional Type (PFT) distributions in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Kumar, J.; Langford, Z.; Yuan, F.; Hoffman, F. M.

    2014-12-01

    Sensitive Arctic ecosystems are vulnerable to change as warming climate impacts the hydrological, thermal, biogeochemical and plant physiological processes on the landscape, leading to geomorphic, biophysical and biogeochemical changes. In particular, Arctic vegetation is expected to exhibit significant shifts in community composition, phenology, distribution and productivity under a changing climate. Modeling of vegetation communities, often represented as Plant Functional Types (PFTs) in Earth System Models (ESMs), requires accurate characterization of their distributions on the landscape as input to ESMs. The unique spectral characteristics exhibited by vegetation can be sensed by remote sensing platforms and used to characterize and distinguish different vegetation types. In this study we employ multi-spectral remote sensing from WorldView--2 and LIDAR--derived digital elevation models to characterize the Arctic tundra vegetation communities near Barrow, Alaska. Using field vegetation surveys at a number of sites, we derived statistical relationships between vegetation distributions and spectral data, which were then employed to estimate the distributions of evergreen shrub, deciduous shrub, grass, sedge, forb, moss and lichen PFTs for the Barrow Environmental Observatory. Plant physiological parameters for these tundra-specific PFTs were implemented in the Community Land Model (CLM). We will present CLM results from simulations employing different distributions of these new PFTs, created using different subsets of remote sensing and in situ vegetation data, to test the sensitivity of the model to a range of predicted distributions.

  4. Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling.

    PubMed

    Trondman, A-K; Gaillard, M-J; Mazier, F; Sugita, S; Fyfe, R; Nielsen, A B; Twiddle, C; Barratt, P; Birks, H J B; Bjune, A E; Björkman, L; Broström, A; Caseldine, C; David, R; Dodson, J; Dörfler, W; Fischer, E; van Geel, B; Giesecke, T; Hultberg, T; Kalnina, L; Kangur, M; van der Knaap, P; Koff, T; Kuneš, P; Lagerås, P; Latałowa, M; Lechterbeck, J; Leroyer, C; Leydet, M; Lindbladh, M; Marquer, L; Mitchell, F J G; Odgaard, B V; Peglar, S M; Persson, T; Poska, A; Rösch, M; Seppä, H; Veski, S; Wick, L

    2015-02-01

    We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1° × 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources. PMID:25204435

  5. Arctic Social Sciences: Opportunities in Arctic Research.

    ERIC Educational Resources Information Center

    Arctic Research Consortium of the United States, Fairbanks, AK.

    The U.S. Congress passed the Arctic Research and Policy Act in 1984 and designated the National Science Foundation (NSF) the lead agency in implementing arctic research policy. In 1989, the parameters of arctic social science research were outlined, emphasizing three themes: human-environment interactions, community viability, and rapid social…

  6. Evaluation of sensor types and environmental controls on mapping biomass of coastal marsh emergent vegetation

    USGS Publications Warehouse

    Byrd, Kristin B.; O'Connell, Jessica L.; Di Tommaso, Stefania; Kelly, Maggi

    2014-01-01

    There is a need to quantify large-scale plant productivity in coastal marshes to understand marsh resilience to sea level rise, to help define eligibility for carbon offset credits, and to monitor impacts from land use, eutrophication and contamination. Remote monitoring of aboveground biomass of emergent wetland vegetation will help address this need. Differences in sensor spatial resolution, bandwidth, temporal frequency and cost constrain the accuracy of biomass maps produced for management applications. In addition the use of vegetation indices to map biomass may not be effective in wetlands due to confounding effects of water inundation on spectral reflectance. To address these challenges, we used partial least squares regression to select optimal spectral features in situ and with satellite reflectance data to develop predictive models of aboveground biomass for common emergent freshwater marsh species, Typha spp. and Schoenoplectus acutus, at two restored marshes in the Sacramento–San Joaquin River Delta, California, USA. We used field spectrometer data to test model errors associated with hyperspectral narrowbands and multispectral broadbands, the influence of water inundation on prediction accuracy, and the ability to develop species specific models. We used Hyperion data, Digital Globe World View-2 (WV-2) data, and Landsat 7 data to scale up the best statistical models of biomass. Field spectrometer-based models of the full dataset showed that narrowband reflectance data predicted biomass somewhat, though not significantly better than broadband reflectance data [R2 = 0.46 and percent normalized RMSE (%RMSE) = 16% for narrowband models]. However hyperspectral first derivative reflectance spectra best predicted biomass for plots where water levels were less than 15 cm (R2 = 0.69, %RMSE = 12.6%). In species-specific models, error rates differed by species (Typha spp.: %RMSE = 18.5%; S. acutus: %RMSE = 24.9%), likely due to the more vertical structure and

  7. Arctic Languages: An Awakening.

    ERIC Educational Resources Information Center

    Collis, Dermid R. F., Ed.

    This work is a study of Arctic languages written in an interdisciplinary manner. Part of the Unesco Arctic project aimed at safeguarding the linguistic heritage of Arctic peoples, the book is the outcome of three Unesco meetings at which conceptual approaches to and practical plans for the study of Arctic cultures and languages were worked out.…

  8. Tidal saline wetland regeneration of sentinel vegetation types in the Northern Gulf of Mexico: An overview

    USGS Publications Warehouse

    Jones, Scott F; Stagg, Camille L.; Krauss, Ken W.; Hester, Mark W.

    2016-01-01

    Tidal saline wetlands in the Northern Gulf of Mexico (NGoM) are dynamic and frequently disturbed systems that provide myriad ecosystem services. For these services to be sustained, dominant macrophytes must continuously recolonize and establish after disturbance. Macrophytes accomplish this regeneration through combinations of vegetative propagation and sexual reproduction, the relative importance of which varies by species. Concurrently, tidal saline wetland systems experience both anthropogenic and natural hydrologic alterations, such as levee construction, sea-level rise, storm impacts, and restoration activities. These hydrologic alterations can affect the success of plant regeneration, leading to large-scale, variable changes in ecosystem structure and function. This review describes the specific regeneration requirements of four dominant coastal wetland macrophytes along the NGoM (Spartina alterniflora, Avicennia germinans, Juncus roemerianus, and Batis maritima) and compares them with current hydrologic alterations to provide insights into potential future changes in dominant ecosystem structure and function and to highlight knowledge gaps in the current literature that need to be addressed.

  9. Tidal saline wetland regeneration of sentinel vegetation types in the Northern Gulf of Mexico: An overview

    NASA Astrophysics Data System (ADS)

    Jones, Scott F.; Stagg, Camille L.; Krauss, Ken W.; Hester, Mark W.

    2016-06-01

    Tidal saline wetlands in the Northern Gulf of Mexico (NGoM) are dynamic and frequently disturbed systems that provide myriad ecosystem services. For these services to be sustained, dominant macrophytes must continuously recolonize and establish after disturbance. Macrophytes accomplish this regeneration through combinations of vegetative propagation and sexual reproduction, the relative importance of which varies by species. Concurrently, tidal saline wetland systems experience both anthropogenic and natural hydrologic alterations, such as levee construction, sea-level rise, storm impacts, and restoration activities. These hydrologic alterations can affect the success of plant regeneration, leading to large-scale, variable changes in ecosystem structure and function. This review describes the specific regeneration requirements of four dominant coastal wetland macrophytes along the NGoM (Spartina alterniflora, Avicennia germinans, Juncus roemerianus, and Batis maritima) and compares them with current hydrologic alterations to provide insights into potential future changes in dominant ecosystem structure and function and to highlight knowledge gaps in the current literature that need to be addressed.

  10. Arctic Change Information for a Broad Audience

    NASA Astrophysics Data System (ADS)

    Soreide, N. N.; Overland, J. E.; Calder, J.

    2002-12-01

    Demonstrable environmental changes have occurred in the Arctic over the past three decades. NOAA's Arctic Theme Page is a rich resource web site focused on high latitude studies and the Arctic, with links to widely distributed data and information focused on the Arctic. Included is a collection of essays on relevant topics by experts in Arctic research. The website has proven useful to a wide audience, including scientists, students, teachers, decision makers and the general public, as indicated through recognition by USA Today, Science magazine, etc. (http://www.arctic.noaa.gov) Working jointly with NSF and the University of Washington's Polar Science Center as part of the Study of Environmental Arctic Change (SEARCH) program, NOAA has developed a website for access to pan-Arctic time series spanning diverse data types including climate indices, atmospheric, oceanic, sea ice, terrestrial, biological and fisheries. Modest analysis functions and more detailed analysis results are provided. (http://www.unaami.noaa.gov/). This paper will describe development of an Artic Change Detection status website to provide a direct and comprehensive view of previous and ongoing change in the Arctic for a broad climate community. For example, composite metrics are developed using principal component analysis based on 86 multivariate pan-Arctic time series for seven data types. Two of these metrics can be interpreted as a regime change/trend component and an interdecadal component. Changes can also be visually observed through tracking of 28 separate biophysical indicators. Results will be presented in the form of a web site with relevant, easily understood, value-added knowledge backed by peer review from Arctic scientists and scientific journals.

  11. The impact of greenhouse vegetable farming duration and soil types on phytoavailability of heavy metals and their health risk in eastern China.

    PubMed

    Yang, Lanqin; Huang, Biao; Hu, Wenyou; Chen, Yong; Mao, Mingcui; Yao, Lipeng

    2014-05-01

    Heavy metal contamination in vegetables from greenhouse vegetable production (GVP) in China requires major attention. For GVP sustainability at a large regional level, 441 surface GVP soil and 132 corresponding greenhouse vegetable samples were collected from six typical GVP bases in eastern China to systematically evaluate the impact of GVP duration and soil types (Anthrosols and Cambosols) on phytoavailability of four major metals, Cd, Cu, Zn, and Pb, and their health risk. The results revealed high Cd accumulation in leaf vegetables grown in Anthrosols, which might pose potential health risk. Regardless of soil types in the study region, greenhouse farming lowered soil pH and enhanced metal availability with rising GVP duration, which might exacerbate Cd phytoavailability and vegetable Cd contamination as well as potential health risk. Also, increased GVP soil organic matter contents over time, found in some locations, affected crop-depending Cu and Zn uptakes. Furthermore, due to GVP, the annual decrease rate of soil pH and increase rates of soil available metal concentrations were generally much greater in Anthrosols than those in Cambosols, which contributed a lot to high Cd uptake by leaf vegetables grown in Anthrosols and their potential health risk. From sustainable GVP perspective, fertilization strategy with reduced frequency and rate is especially important and effective for abating soil and vegetable contamination by heavy metals under greenhouse farming.

  12. Natural vegetation inventory

    NASA Technical Reports Server (NTRS)

    Schrumpf, B. J.

    1973-01-01

    Unique characteristics of ERTS imagery can be used to inventory natural vegetation. While satellite images can seldom be interpreted and identified directly in terms of vegetation types, such types can be inferred by interpretation of physical terrain features and through an understanding of the ecology of the vegetation.

  13. In situ burning of oil in coastal marshes. 1. Vegetation recovery and soil temperature as a function of water depth, oil type, and marsh type.

    PubMed

    Lin, Qianxin; Mendelssohn, Irving A; Bryner, Nelson P; Walton, William D

    2005-03-15

    In-situ burning of oiled wetlands potentially provides a cleanup technique that is generally consistent with present wetland management procedures. The effects of water depth (+10, +2, and -2 cm), oil type (crude and diesel), and oil penetration of sediment before the burn on the relationship between vegetation recovery and soil temperature for three coastal marsh types were investigated. The water depth over the soil surface during in-situ burning was a key factor controlling marsh plant recovery. Both the 10- and 2-cm water depths were sufficient to protect marsh vegetation from burning impacts, with surface soil temperatures of <35 and 48 degrees C, respectively. Plant survival rate and growth responses at these water depth burns were not significantly different from the unburned control. In contrast, a water table 2 cm below the soil surface during the burn resulted in high soil temperatures, with 90-200 degrees C at 0-0.5 cm soil depth and 55-75 degrees C at 1-2 cm soil depth. The 2-cm soil exposure to fire significantly impeded the post-burn recovery of Spartina alterniflora and Sagittaria lancifolia but did not detrimentally affect the recovery of Spartina patens and Distichlis spicata. Oil type (crude vs diesel) and oil applied to the marsh soil surface (0.5 L x m(-2)) before the burn did not significantly affect plant recovery. Thus, recovery is species-specific when no surface water exists. Even water at the soil surface will most likely protect wetland plants from burning impact.

  14. CONVERGING PATTERNS OF UPTAKE AND HYDRAULIC REDISTRIBUTION OF SOIL WATER IN CONTRASTING WOODY VEGETATION TYPES

    EPA Science Inventory

    We used concurrent measurements of soil water content and soil water potential (Ysoil) to assess the effects of Ysoil on uptake and hydraulic redistribution (HR) of soil water by roots during seasonal drought cycles in six sites characterized by different types and amounts of woo...

  15. Comparison between two vegetation indices for measuring different types of forest damage in the north-eastern United States

    NASA Technical Reports Server (NTRS)

    Vogelmann, J. E.

    1990-01-01

    The relative effectiveness of the Landsat TM-derived normalized difference vegetative index (NDVI) and the short-wave IR to NIR ratio (SWIR/NIR) index was examined in measurements of different types of damage in several forest communities. The forests examined included a site with well-defined fir waves in New Hampshire, a site undergoing well-documented coniferous forest decline in Vermont, and predominantly deciduous regions in Vermont and northwestern Massachusetts seriously impacted by pear thrips. Both NDVI and SWIR/NIR images were produced for each area. Results demonstrated that the SWIR/NIR index was superior to NDVI in distinguishing between high and low conifer damage at both fir-wave and forest decline sites; high and low deciduous-forest damage sites were easily separable using either NDVI or SWIR/NIR, but the NDVI was superior in separation between medium and low deciduous damage.

  16. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  17. [Characteristics of soil pH and exchangeable acidity in red soil profile under different vegetation types].

    PubMed

    Ji, Gang; Xu, Ming-gang; Wen, Shi-lin; Wang, Bo-ren; Zhang, Lu; Liu, Li-sheng

    2015-09-01

    The characteristics of soil pH and exchangeable acidity in soil profile under different vegetation types were studied in hilly red soil regions of southern Hunan Province, China. The soil samples from red soil profiles within 0-100 cm depth at fertilized plots and unfertilized plots were collected and analyzed to understand the profile distribution of soil pH and exchangeable acidity. The results showed that, pH in 0-60 cm soil from the fertilized plots decreased as the following sequence: citrus orchard > Arachis hypogaea field > tea garden. As for exchangeable acidity content, the sequence was A. hypogaea field ≤ citrus orchard < tea garden. After tea tree and A. hypogaea were planted for long time, acidification occurred in surface soil (0-40 cm), compared with the deep soil (60-100 cm), and soil pH decreased by 0.55 and 0.17 respectively, but such changes did not occur in citrus orchard. Soil pH in 0-40 cm soil from the natural recovery vegetation unfertilized plots decreased as the following sequence: Imperata cylindrica land > Castanea mollissima garden > Pinus elliottii forest ≥ Loropetalum chinensis forest. As for exchangeable acidity content, the sequence was L cylindrica land < C. mollissima garden < L. chinensis forest ≤ P. elliottii forest. Soil pH in surface soil (0-20 cm) from natural forest plots, secondary forest and Camellia oleifera forest were significantly lower than that from P. massoniana forest, decreased by 0.34 and 0.20 respectively. For exchangeable acidity content in 0-20 cm soil from natural forest plot, P. massoniana forest and secondary forest were significantly lower than C. oleifera forest. Compared with bare land, surface soil acidification in unfertilized plots except I. cylindrica land had been accelerated, and the natural secondary forest was the most serious among them, with surface soil pH decreasing by 0.52. However, the pH increased in deep soils from unfertilized plots except natural secondary forest, and I. cylindrica

  18. A Comparison of Sea Ice Type, Sea Ice Temperature, and Snow Thickness Distributions in the Arctic Seasonal Ice Zones with the DMSP SSM/I

    NASA Technical Reports Server (NTRS)

    St.Germain, Karen; Cavalieri, Donald J.; Markus, Thorsten

    1997-01-01

    Global climate studies have shown that sea ice is a critical component in the global climate system through its effect on the ocean and atmosphere, and on the earth's radiation balance. Polar energy studies have further shown that the distribution of thin ice and open water largely controls the distribution of surface heat exchange between the ocean and atmosphere within the winter Arctic ice pack. The thickness of the ice, the depth of snow on the ice, and the temperature profile of the snow/ice composite are all important parameters in calculating surface heat fluxes. In recent years, researchers have used various combinations of DMSP SSMI channels to independently estimate the thin ice type (which is related to ice thickness), the thin ice temperature, and the depth of snow on the ice. In each case validation efforts provided encouraging results, but taken individually each algorithm gives only one piece of the information necessary to compute the energy fluxes through the ice and snow. In this paper we present a comparison of the results from each of these algorithms to provide a more comprehensive picture of the seasonal ice zone using passive microwave observations.

  19. Latent heat exchange in the boreal and arctic biomes.

    PubMed

    Kasurinen, Ville; Alfredsen, Knut; Kolari, Pasi; Mammarella, Ivan; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Bernier, Pierre; Boike, Julia; Langer, Moritz; Belelli Marchesini, Luca; van Huissteden, Ko; Dolman, Han; Sachs, Torsten; Ohta, Takeshi; Varlagin, Andrej; Rocha, Adrian; Arain, Altaf; Oechel, Walter; Lund, Magnus; Grelle, Achim; Lindroth, Anders; Black, Andy; Aurela, Mika; Laurila, Tuomas; Lohila, Annalea; Berninger, Frank

    2014-11-01

    In this study latent heat flux (λE) measurements made at 65 boreal and arctic eddy-covariance (EC) sites were analyses by using the Penman-Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman-Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control λE in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman-Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated λE of different ecosystem types under meteorological conditions at one site. Values of λE varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that λE is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of λE as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need

  20. Remote Sensing of the Arctic Seas.

    ERIC Educational Resources Information Center

    Weeks, W. F.; And Others

    1986-01-01

    Examines remote sensing of the arctic seas by discussing: (1) passive microwave sensors; (2) active microwave sensors; (3) other types of sensors; (4) the future deployment of sensors; (5) data buoys; and (6) future endeavors. (JN)

  1. High resolution Arctic snow observations: SnowNet (Invited)

    NASA Astrophysics Data System (ADS)

    Hiemstra, C. A.; Sturm, M.; Gelvin, A. B.; Berezovskaya, S.; Saari, S. P.; Finnegan, D. C.; Liston, G. E.

    2009-12-01

    Snow’s importance has become especially prominent in the terrestrial Arctic, where snow dominates the landscape most of the year and changes in snow arrival, depth, and melt have substantial energy budget and biotic consequences. Yet, the Arctic presents formidable challenges to accurate snow measurements because snow depths can vary greatly over relatively short distances (< 10 m). Snow distribution patterns in windy environments, such as the Arctic, arise from interactions among wind, snow, vegetation, and topography. In this environment, snow is transported easily and is retained in topographic depressions, near taller vegetation, and deposited on the lee sides of hills. Reliable observations of where snow exists in the Arctic landscape can be difficult to obtain, and estimates vary depending on where snow is sampled. Measurements tend to be widely distributed and sparse. In addition, observed changes in Arctic vegetation (e.g., increasing shrubs) and land surfaces (e.g., thermokarst) complicate matters further. In response to this critical shortcoming in Arctic snow measurements, we have developed a prototype observational network (SnowNet) that employs standard meteorological observations and high resolution topographic and vegetation data in concert with a comprehensive spatially-intensive snow measurement program. Our sites at Barrow (started 2007) and Imnavait Creek (started 2008), Alaska, feature frequent site visits and intensive spatial sampling of snow depths and densities and snow-surface topography. Both sites have high resolution (~20 cm) topographic and vegetation data layers generated from remote sensing and ground surveys. Further, we have been incorporating extremely high-resolution (< 10 cm) ground-based LiDAR snow and vegetation datasets that allow us to identify relationships among topography, vegetation, and snow in Arctic environments. In addition, we have collected tens of thousands of manual snow depths across our research sites. This

  2. [Consumption of nuts and vegetal oil in people with type 1 diabetes mellitus].

    PubMed

    Ferrer-García, Juan Carlos; Granell Vidal, Lina; Muñoz Izquierdo, Amparo; Sánchez Juan, Carlos

    2015-06-01

    Introducción: estudios recientes han demostrado los beneficios cardiovasculares de la dieta mediterránea enriquecida con aceite de oliva y frutos secos. Las personas con diabetes, que tienen un mayor riesgo de complicaciones cardiovasculares, podrían beneficiarse en gran medida de seguir ese tipo de patrón alimentario. Objetivos: análisis de la ingesta de grasas vegetales procedentes de frutos secos y aceites vegetales en pacientes con diabetes mellitus tipo 1 (DM1). Métodos: estudio transversal descriptivo que compara 60 personas con DM1 y 60 sujetos sanos. Se recoge la frecuencia de consumo de aceites vegetales y de frutos secos y se calcula el aporte procedente de estos alimentos en ácidos grasos mono y poliinsaturados (ácido oleico, linoleico y -linolénico). Se utilizó un cuestionario de frecuencia de consumo diseñado de forma específica. Se recogen variables antropométricas, factores de riesgo cardiovascular y variables relacionadas con la diabetes. Resultados: el consumo total de grasa vegetal procedente de aceites vegetales fue similar en los pacientes con DM1 frente a los sujetos control (3,02 ± 1,14 vs. 3,07 ± 1,27 Raciones (R)/día, P = 0,822) y de frutos secos (1,35 ± 2,24 vs. 1,60 ± 2,44 R/semana, P = 0,560). El grupo DM1 consumió menos aceite de oliva que el grupo control (2,55 ± 1,17 vs. 3,02 ± 1,34 R/día, P = 0,046). Se detectó un menor consumo de ácido -linolénico respecto al grupo control (1,13 ± 2,06 vs. 2,64 ± 4,37 g/día, P = 0,018), mientras que no hubo diferencias en el resto de ácidos grasos (oleico 28,30 ± 18,13 vs. 29,53 ± 16,90 g/día, P = 0,703; linoleico 13,70 ± 16,80 vs. 15,45 ± 19,90 g/día, P = 0,605). En los DM1 no se demostró una influencia del consumo de las grasas vegetales procedentes de aceites y frutos secos en los parámetros antropométricos, metabólicos y variables específicas de la diabetes. Conclusiones: en las personas con DM1 el consumo total de aceites vegetales y frutos secos no

  3. Arctic technology and policy

    SciTech Connect

    Dyer, I.; Chryssostomidis, C.

    1984-01-01

    Topics covered include: legal regime of the arctic, including national and international legal frameworks that govern arctic resource development; environmental policy and socio-economic issues, focusing on the political and economic considerations of LNG transport in icebound waterways; risk and safety assessment for arctic offshore projects, drilling systems for the arctic; arctic offshore technology, including island, steel, and concrete structures; icebreaking technology, focusing on the current state of the art and indicating future research areas; arctic oceanography, summarizing characteristics of ice from field experiments pertaining to the design of structures, ships, and pipelines; arctic seismic exploration, detailing signal processes for underwater communication in the context of arctic geology and geophysics; ice morphology, providing information about ice shapes, particularly critical to the determination of overall strength of ice masses; remote sensing; modeling of arctic ice fields, including information about the design and construction of offshore facilities in polar areas; and engineering properties of ice, providing theoretical and experimental studies.

  4. [Canopy interception characteristics of main vegetation types in Liupan Mountains of China].

    PubMed

    Xu, Li-hong; Shi, Zhong-jie; Wang, Yan-hui; Xiong, Wei; Yu, Peng-tao

    2010-10-01

    Based on field observation and modeling analysis, this paper studied the canopy interception, interception capacity, and some parameters for interception modeling of main forest types in Liupan Mountains of China. For the test main forest types, the ratio of their canopy interception to precipitation ranged from 8.59% to 17.94%, throughfall was more than 80%, and stemflow ranged from 0.23% to 3.10%. The canopy interception capacity was 0.78-1.88 mm, among which, leaf interception capacity was 0.62-1.63 mm, and stem interception capacity was 0.13-0.29 mm. Conifer forest had a higher canopy interception capacity than broad-leaved forest. The modified model considering the change of leaf area index, which was used in this paper, had a higher simulating precision than the interception model used before. The simulation results for Betula albo-sinensis forest, Pinus armandii forest, Prunus shrub, and Quercus liaotungensis-Tilia paucicostata forest were good, but those for Quercus liaotungensis forest, Pinus tabulaeformis forest, and Acer tetramerum and Euonymus sanguineus shrub were bad, which might be related to the differences in canopy structure, leaf area index, and precipitation characteristics.

  5. Impact of elevated CO2, water table, and temperature changes on CO2 and CH4 fluxes from arctic tundra soils

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Haynes, Katherine; Deutschman, Douglas; Bryant, Emma; McEwing, Katherine; Davidson, Scott; Oechel, Walter

    2015-04-01

    Large uncertainties still exist on the response of tundra C emissions to future climate due, in part, to the lack of understanding of the interactive effects of potentially controlling variables on C emissions from Arctic ecosystems. In this study we subjected 48 soil cores (without active vegetation) from dominant arctic wetland vegetation types, to a laboratory manipulation of elevated atmospheric CO2, elevated temperature, and altered water table, representing current and future conditions in the Arctic for two growing seasons. To our knowledge this experiment comprised the most extensively replicated manipulation of intact soil cores in the Arctic. The hydrological status of the soil was the most dominant control on both soil CO2 and CH4 emissions. Despite higher soil CO2 emission occurring in the drier plots, substantial CO2 respiration occurred under flooded conditions, suggesting significant anaerobic respirations in these arctic tundra ecosystems. Importantly, a critical control on soil CO2 and CH4 fluxes was the original vascular plant cover. The dissolved organic carbon (DOC) concentration was correlated with cumulative CH4 emissions but not with cumulative CO2 suggesting C quality influenced CH4 production but not soil CO2 emissions. An interactive effect between increased temperature and elevated CO2 on soil CO2 emissions suggested a potential shift of the soils microbial community towards more efficient soil organic matter degraders with warming and elevated CO2. Methane emissions did not decrease over the course of the experiment, even with no input from vegetation. This result indicated that CH4 emissions are not carbon limited in these C rich soils. Overall CH4 emissions represented about 49% of the sum of total C (C-CO2 + C-CH4) emission in the wet treatments, and 15% in the dry treatments, representing a dominant component of the overall C balance from arctic soils.

  6. Use of a 600-kHz Acoustic Doppler Current Profiler to measure estuarine bottom type, relative abundance of submerged aquatic vegetation, and eelgrass canopy height

    NASA Astrophysics Data System (ADS)

    Warren, Joseph D.; Peterson, Bradley J.

    2007-03-01

    The acoustic backscatter intensity signal from a high-frequency (600 kHz) Acoustic Doppler Current Profiler (ADCP) was used to categorize four different types of bottom habitat (sand, mud, sparse and dense vegetation) in a shallow-water estuary (Shinnecock Bay, NY, USA). A diver survey of the bay measured sediment and bottom vegetation characteristics at 85 sites within the bay. These data were used to groundtruth the acoustic data. Acoustic data were collected at four sites with known bottom types and used to develop an algorithm that could categorize the bottom type. The slope of the echo intensity profile close to the bottom was used to determine the bottom type and the relative numerical density (sparse or dense) of Submerged Aquatic Vegetation (SAV). In areas where eelgrass ( Zostera marina) was the dominant SAV species, the intensity profile data were analyzed to measure the height of the vegetation canopy. An acoustic survey which categorized the bottom type of the bay was conducted from a small vessel. The percentage of sampled sites categorized as each bottom habitat type from the acoustic survey was similar to those obtained by the diver survey. These methods may provide a means to rapidly survey estuarine habitats and measure spatial and temporal variations in SAV populations, as well as changes in the height of the eelgrass canopy.

  7. Vegetation type modifies the cycling and aromaticity of DOC and N in small-scale urban stormwater basins

    NASA Astrophysics Data System (ADS)

    Nocco, M. A.; Dolliver, H.; Balster, N. J.

    2012-12-01

    Urban land use can cause ecological degradation of surface waters through stormwater inputs of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). Green infrastructure practices such as small-scale (m2) vegetated stormwater basins (e.g. bioretention basins, rain gardens, bioswales) have been implemented for the past 20 years to reduce stormwater quantity and improve water quality in urban ecosystems. Although the efficacy of these practices rests on an ecological assumption that plant-soil interactions will alter the C and N cycles relative to surrounding urban infrastructure, the impact of vegetation type on the biogeochemistry of urban stormwater basins is not well understood. We hypothesized that the two most prevalent types of vegetation planted in stormwater basins in the Midwestern United States, native prairie and woody shrubs, differ in their cycling and export of C and N due to differences in relative woody and parenchymatic tissue inputs to soil organic matter, root morphology, and root exudation. We tested this hypothesis in an open-air field laboratory consisting of 9 vegetated mesocosms (3 native prairie, 3 woody shrub, 3 bare soil) designed in 2005 according to WI-DNR specifications for residential stormwater basin construction. During precipitation events in July-October 2011, we collected stormwater runoff from an adjacent tin roof (417 m2) and conducted 9 runoff applications that mimicked the rate and intensity of runoff that would be received by a small-scale (5.9 m2) stormwater basin in the urban environment during a 2.54 cm rain event. We instrumented each mesocosm to quantify (1) first flush and peak flow concentration of DOC and TDN during gravitational soil water flux (2) DOC and TDN concentration in soil pore space after gravitational water flux ceased, and (3) SUVA254 as an optical proxy for aromaticity in the first flush and peak flow of gravitational soil water flux. Results show significant differences (p<0.05) in both DOC

  8. Projected Impacts of 21st Century Climate Change on Potential Habitat for Vegetation and Forest Types in Russia

    NASA Astrophysics Data System (ADS)

    Soja, A. J.; Tchebakova, N. M.; Parfenova, E. I.; Cantin, A.; Conard, S. G.

    2015-12-01

    Global GCMs have demonstrated profound potential for projections to affect the distribution of terrestrial ecosystems and individual species at all hierarchical levels. We modeled progression of potential Russian ecotones and forest-forming species as the climate changes. Large-scale bioclimatic models were developed to predict Russian zonal vegetation (RuBCliM) and forest types (ForCliM) from three bioclimatic indices (1) growing degree-days above 5 degrees C; (2) negative degree-days below 0 C ; and (3) an annual moisture index (ratio of growing degree days to annual precipitation). The presence or absence of continuous permafrost was explicitly included in the models as limiting the forests and tree species distribution. All simulations to predict vegetation change across Russia were run by coupling our bioclimatic models with bioclimatic indices and the permafrost distribution for the baseline period and for the future 2020, 2050 and 2100 simulated by 3 GCMs (CGCM3.1, HadCM3 and IPSLCM4) and 3 climate change scenarios (A1B, A2 and B1). Under these climate scenarios, it is projected the zonobiomes will shift far northward to reach equilibrium with the change in climate. Under the warmer and drier projected future climate, about half of Russia would be suitable for the forest-steppe ecotone and grasslands, rather than for forests. Water stress tolerant light-needled taiga would have an increased advantage over water-loving dark-needled taiga. Permafrost-tolerant L. dahurica taiga would remain the dominant forest across permafrost. Increases in severe fire weather would lead to increases in large, high-severity fires, especially at boundaries between forest ecotones, which can be expected to facilitate a more rapid progression of vegetation towards a new equilibrium with the climate. Adaptation to climate change may be facilitated by: assisting migration of forests by seed transfers to establish genotypes that may be more ecologically suited as climate changes

  9. Effect of prescribed fire on soil properties and N transformation in two vegetation types in South China.

    PubMed

    Wang, Faming; Li, Jian; Zou, Bi; Xu, Xin; Li, Zhian

    2013-06-01

    Prescribed fire is a common site preparation practice in forest management in southern China. However, the effect of fire on soil properties and N transformations is still poorly understood in this region. In this study, soil properties and N transformations in burned and unburned site of two vegetation types (Eucalyptus plantation and shrubland) were compared in rainy and dry seasons after 2 years' prescribed fire. Soil pH and soil NH4-N were all higher in the burned site compared to the unburned control. Furthermore, burned sites had 30-40 % lower of soil total phosphorus than conspecific unburned sites. There was no difference in soil organic matter, total N, soil exchangeable cations, available P or NO3-N. Nitrogen mineralization rate of 0-5 cm soil in the unburned site ranged from 8.24 to 11.6 mg N kg(-1) soil month(-1) in the rainy season, compared to a lower level of 4.82-5.25 mg N kg(-1) soil month(-1) in the burned sites. In contrast, 0-5 cm layer nitrification rate was overall 2.47 mg N kg(-1) soil month(-1) in the rainy season, and was not significantly affected by burning. The reduced understory vegetation coverage after burning may be responsible for the higher soil NH4-N in the burned site. This study highlights that a better understanding the effect of prescribed burning on soil nutrients cycling would provide a critical foundation for management decision and be beneficial to afforestation in southern China. PMID:23609305

  10. Spatial-seasonal variation of soil denitrification under three riparian vegetation types around the Dianchi Lake in Yunnan, China.

    PubMed

    Wang, Shaojun; Cao, Zilin; Li, Xiaoying; Liao, Zhouyu; Hu, Binghui; Ni, Jie; Ruan, Honghua

    2013-05-01

    Outbreaks of nuisance cyanobacterial bloom are predicted to occur frequently under the effect of severe eutrophication in the water body of Lake Dianchi since the 1990s. Riparian buffers are now well recognized for their roles in the removal of inorganic nitrogen mainly via denitrification. Little is known, however, about the mechanisms of nitrate removal in the riparian buffers of Lake Dianchi. We investigated the wet and dry seasonal dynamics of denitrification rate (DNR) in the soil profiles along the topographic gradient in three riparian buffers with different vegetation types (i.e. forest, open forest, and grass). A strong vertical pattern was observed in soil organic C and N concentrations (i.e. total N, DON, NO3-N, and NH4-N) along the soil layers. We also found significantly higher in situ denitrification activity in the upper horizon along each topohydrosequence while the activities of soil denitrification could be detected down to deeper soil horizons (0.1 to 0.8 mg N per kg dry soil per day), which may contribute significantly to the reduction of the ground water nitrate. Meanwhile, the DNR in the zones near the lake was significantly higher than that in zones near the border with the upland terrace, and also in the wet seasons than in dry seasons. Denitrification rates in the forest, open forest and grass sites were significantly different only in wet seasons. Especially, we found soil organic C had a strong correlation with denitrification in all sites, despite the large intersite variability of soil and vegetation. Our data suggested spatial heterogeneity of substrate availability along a hydrologic and topographic gradient can be the primary control on spatial-seasonal patterns of denitrification in riparian buffers.

  11. Vegetation modeling in Yakutia, northeastern Siberia: connecting to palaeovegetation simulation and model-data comparison

    NASA Astrophysics Data System (ADS)

    Ni, J.; Herzschuh, U.

    2009-04-01

    Vegetation model is a useful tool to understand the impacts of climate change on ecosystems in the present, past and future. Simulation of the palaeovegetation can link the geographical pattern of vegetation in the past to pollen proxy and then test the palaeoclimate modeling. In this study we used an equilibrium vegetation model (BIOME4) and a dynamic vegetation model (LPJ) to predict the present-day vegetation pattern and their dynamic changes from 1901-2002 in Yakutia, an Arctic and sub-Arctic region in eastern Siberia, where is sensitive to climate change. Both the models characterized the basic features of regional vegetation pattern, function and their changes through time. The BIOME4 simulated a reasonable pattern of present biome distribution compared to the regional vegetation maps, the deciduous taiga-montane forests in the southern and central Yakutia, evergreen taiga-montane forests in the southwestern mountainous region and in the eastern coast, shrub tundra and dwarf shrub tundra in the northwest and northeast mixed with temperate xerophytic shrubland. In the NW Yakutia the LPJ demonstrated a dynamic change of local vegetation during the past 102 years responding to the changed climates. Forest and shrub covered the large area from the beginning to the 1950s of the 20th Century. Tundra extended from the west to the east during 1960s to 1970s. The woody plants extended in 1980s and in late 1990s to early 21st Century and grasses extended in 1990s. The performance of global vegetation models in regional study is well, but problems still existed. More plant functional types especially the shrubs and grasses and climatic constraints to them should be taken into account when improving the models. Soil water-related parameters should be redefined. The modules of permafrost, snow, and fire should be added or modified. Regional input data of climates, vegetation and soils at finer resolutions will be obtained from the regional and local studies.

  12. [Effects of arbuscular mycorrhizal fungi on the vegetation restoration of different types of coal mine spoil banks].

    PubMed

    Zhao, Ren-Xin; Guo, Wei; Fu, Rui-Ying; Zhao, Wen-Jing; Guo, Jiang-Yuan; Bi, Na; Zhang, Jun

    2013-11-01

    A greenhouse pot experiment was conducted to investigate the influence of arbuscular mycorrhizal (AM) fungi Glomus etunicatum (GE) and Glomus versiforme (GV) on the plant growth, nutrient uptake, C: N: P stoichiometric, uptake of heavy metals by maize (Zea mays L.) grown in three types of coal mine spoil banks. The aim was to provide a technical basis for the revegetation of coal mine spoil banks in grassland ecosystem. The results indicated that the symbiotic associations were successfully established between two isolates and maize grown in the three substrates, with an average mycorrhizal colonization rate ranging from 36% to 54%. The colonization of two AM fungi significantly increased the dry weight of maize grown in recent discharged and weathered coal mine spoils and GE increased those grown in weathered coal mine spoil. Inoculation with AM fungi promoted the uptake of N, P and K by maize to varying degrees. In addition, inoculation with GE and GV also decreased C: N: P ratios, supporting the growth rate hypothesis, and had significantly differences on concentrations of Cu, Fe, Mn and Zn in shoots and roots of maize. The results indicated that GE and GV had different mycorrhizal effects on maize in the three types of substrates. GV was more suitable for the revegetation of recent discharged coal mine spoil and weathered coal mine spoil, while GE was more suitable for the revegetation of spontaneous combusted coal mine spoil. The experiment demonstrates that AM fungi have a potential role for maize to enhance the ability to adapt the composite adversity of different types of coal mine spoil and play a positive role in the revegetation of different coal mine spoil banks. Further field experiments should be conducted to evaluate the practical effects of AM fungi on the vegetation restoration of different types of coal mine spoil under field conditions.

  13. Soil respiration at mean annual temperature predicts annual total across vegetation types and biomes

    PubMed Central

    Bahn, M.; Reichstein, M.; Davidson, E. A.; Grünzweig, J.; Jung, M.; Carbone, M. S.; Epron, D.; Misson, L.; Nouvellon, Y.; Roupsard, O.; Savage, K.; Trumbore, S. E.; Gimeno, C.; Yuste, J. Curiel; Tang, J.; Vargas, R.; Janssens, I. A.

    2011-01-01

    Soil respiration (SR) constitutes the largest flux of CO2 from terrestrial ecosystems to the atmosphere. However, there still exist considerable uncertainties as to its actual magnitude, as well as its spatial and interannual variability. Based on a reanalysis and synthesis of 80 site-years for 57 forests, plantations, savannas, shrublands and grasslands from boreal to tropical climates we present evidence that total annual SR is closely related to SR at mean annual soil temperature (SRMAT), irrespective of the type of ecosystem and biome. This is theoretically expected for non water-limited ecosystems within most of the globally occurring range of annual temperature variability and sensitivity (Q10). We further show that for seasonally dry sites where annual precipitation (P) is lower than potential evapotranspiration (PET), annual SR can be predicted from wet season SRMAT corrected for a factor related to P/PET. Our finding indicates that it can be sufficient to measure SRMAT for obtaining a well constrained estimate of its annual total. This should substantially increase our capacity for assessing the spatial distribution of soil CO2 emissions across ecosystems, landscapes and regions, and thereby contribute to improving the spatial resolution of a major component of the global carbon cycle. PMID:23293656

  14. Effects of vegetation type on habitat use by crop-raiding Japanese macaques during a food-scarce season.

    PubMed

    Yamada, Aya; Muroyama, Yasuyuki

    2010-04-01

    Habitat use by crop-raiding Japanese macaques (Macaca fuscata) was studied in western Japan from December 2005 to February 2006, a food-scarce season. To examine how different vegetation types affect habitat use by monkeys, two crop-raiding troops were compared: the first troop inhabited a habitat involving more wild food resources; the second troop inhabited a habitat providing fewer wild food resources. It was hypothesized that monkeys living in the habitat with fewer wild food resources are more likely to utilize human settlements and areas around them (i.e. adjacent zones), with a dependence on crop foods. Comparisons of observed and expected habitat use frequencies showed that the first troop selected evergreen broad-leaved forests and conifer plantations, and avoided adjacent zones, rice fields, and golf courses. The second troop selected adjacent zones and avoided conifer plantations, pine forests, and deciduous broad-leaved forests. Both troops moved rapidly in avoided habitat types. These results suggest that monkeys living in the habitat with fewer wild food resources are more likely to utilize areas around human settlements during a food-scarce season.

  15. On the influence of the height of expanding shrub vegetation on boreal climate

    NASA Astrophysics Data System (ADS)

    Bonfils, C.; Phillips, T. J.; Riley, W. J.; Post, W. M.; Cameron-Smith, P. J.; Torn, M. S.

    2010-12-01

    Rapid changes in arctic vegetation are in progress in response to many factors including global warming, changing permafrost and snow and nutrient regimes. These land-cover changes include a redistribution of local vegetation types as well as northward migration of lower-latitude species and a greater cover of plants. Among others, multiple lines of evidence show that the abundance of arctic shrubs has already increased, and a northward shift of shrub-dominated tundra (as predicted using global dynamical vegetation models) may contribute further to future warming. As participants in the U.S. Department of Energy IMPACTS Project, we are investigating the potential for abrupt arctic climatic change resulting from such variations in vegetation, among other mechanisms. In a previous study, we estimated the relative magnitudes of effects to be expected from an extension of arctic shrub vegetation, in conducting several numerical experiments with the Community Climate System Model (CCSM). These experiments included 1) A “present-day-climate” control experiment with current atmospheric greenhouse-gas concentrations and with “standard” CLM plant functional types (PFTs) specified, and 2) An “expanded-shrub-type" run, in which bare ground is replaced by CLM arctic shrubs northward of their current locations. These runs allowed us to investigate the possibility of strong positive feedbacks through increased transpiration and decreased albedo, but also highlighted the possibility of the importance of height of shrubs in the strengths of those feedbacks. For this study, we performed an additional experiment, in which bare ground is replaced, this time by higher shrubs. This should allow us to confirm the importance of shrub height. These runs should help to justify the augmentation of CCSM "standard" PFTs by additional, more realistic circumarctic PFTs, which is a main aspect of this IMPACTs Project. We will report on the atmospheric climate and land-surface feedbacks

  16. Nutrient release from combustion residues of two contrasting herbaceous vegetation types.

    PubMed

    Hogue, Benjamin A; Inglett, Patrick W

    2012-08-01

    Fire is a critical regulator of biogeochemical cycles in approximately 40% of the earth's land surface. However, little is known about nutrient release from combustion residues (ash and char) from herbaceous or grassland fires of varying intensity. Much of our knowledge in this area is derived from muffle furnace temperature gradient experiments. Therefore, we used two approaches (muffle and flame burning) to combust herbaceous biomass from contrasting nutrient level sites to estimate the forms and availability of nutrients after fire. Clear differences were measured in total and extractable nutrient concentrations in combustion residues of different plant types, with most carbon (C) and nitrogen (N) being volatilized (>99%), while P remained in high concentrations in the residues. Different combustion methods yielded contrasting results, where temperatures greatly affected nutrient quantity and form in muffle furnace residues, while relatively similar residues resulted from flame combustion at varying intensities. It was also found that only 5% of N and 50% of P remaining in flame combustion residues were extractable. Flame residues appeared to be composed of mixtures of materials (ash and char) created at low (<350 °C) muffle temperatures (extractable P forms), and high (>450 °C) muffle temperatures (pH, extractable potassium (K), and extractable NH(4)-N). We attribute dissimilar results of the combustion methods to heterogeneity of combustion (zones of low oxygen availability) and short duration (<300 s) of combustion characterizing natural fires in herbaceous, grassland systems. These results can be adapted to ecosystem level models to better predict nutrient changes that may occur after a fire event. PMID:22664533

  17. A pollen-based biome reconstruction over the last 3.562 million years in the Far East Russian Arctic - new insights into climate-vegetation relationships at the regional scale

    NASA Astrophysics Data System (ADS)

    Tarasov, P. E.; Andreev, A. A.; Anderson, P. M.; Lozhkin, A. V.; Leipe, C.; Haltia, E.; Nowaczyk, N. R.; Wennrich, V.; Brigham-Grette, J.; Melles, M.

    2013-12-01

    The recent and fossil pollen data obtained under the frame of the multi-disciplinary international El'gygytgyn Drilling Project represent a unique archive, which allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could be potentially present in this region during the past. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) long phases of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals in the study region within the past million years. During the late Pliocene-early Pleistocene interval (i.e., ~3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation from generally warmer/wetter environments of the earlier (i.e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction indicates that the taxon-rich cool mixed and cool conifer forest biomes are mostly characteristic of the time prior to MIS G16, whereas the tundra biome becomes a prominent feature starting from MIS G6. These results

  18. Measurement-based upscaling of Pan Arctic Net Ecosystem Exchange: the PANEEx project

    NASA Astrophysics Data System (ADS)

    Njuabe Mbufong, Herbert; Kusbach, Antonin; Lund, Magnus; Persson, Andreas; Christensen, Torben R.; Tamstorf, Mikkel P.; Connolly, John

    2016-04-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) can be attributed to the high spatial heterogeneity of Arctic tundra due to the complex topography. Current models of C exchange handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple pan Arctic NEE (PANEEx) model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide (CO2) data from 12 Arctic tundra sites. The model input parameters (Fcsat, Rd and α) were estimated as a function of air temperature (AirT) and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship, including the saturation flux, dark respiration and initial light use efficiency, respectively. LAI and air temperature were respectively estimated from empirical relationships with remotely sensed normalized difference vegetation index (NDVI) and land surface temperature (LST). These are available as MODIS Terra product MOD13Q1 and MOD11A1 respectively. Therefore, no specific knowledge of the vegetation type is required. The PANEEx model captures the spatial heterogeneity of the Arctic tundra and was effective in simulating 77% of the measured fluxes (r2 = 0.72, p < 0.001) at the 12 sites used in the calibration of the model. Further, the model effectively estimates NEE in three disparate Alaskan ecosystems (heath, tussock and fen) with an estimation ranging between 10 - 36% of the measured fluxes. We suggest that the poor agreement between the measured and modeled NEE may result from the disparity between ground-based measured LAI (used in model calibration) and remotely sensed LAI (estimated from NDVI and used in NEE estimation). Moreover, our results suggests that using simple linear regressions may be inadequate as parameters estimated

  19. Underestimation of mid-Holocene Arctic warming in PMIP simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Qiong; Muschitiello, Francesco

    2016-04-01

    Due to the orbital forcing, Arctic is warmer during mid-Holocene (~ 6 kyr BP) in summer because the region received more insolation and also warmer in winter because of strong feedbacks, leads to an annual mean temperature warming. Existing proxy reconstructions show that the Arctic can be two degrees warmer than pre-industrial. However, not all the climate models can capture the warming, and the amplitude is about 0.5 degree less than that seen from proxy data. One possible reason is that these simulations did not take into account a fact of 'Green Sahara', where the large area of Sahara region is covered by vegetation instead of desert as it is today. By using a fully coupled climate model EC-Earth with about 100 km resolution, we have run a series of sensitivity experiments by changing the surface type, as well as accompanied change in dust emission over the northern Sahara. The results show that a green sahara not only results in local climate response such as the northward extension and strengthening of African monsoon, but also affect the large scale circulation and corresponding meridional heat transport. The combination of green sahara and reduced dust entails a general strengthening of the mid-latitude Westerlies, results in a change to more positive North Atlantic Oscillation-like conditions, and more heat transport from lower latitudes to high latitudes both in atmosphere and ocean, eventually leads to a shift towards warmer conditions over the North Atlantic and Arctic regions. This mechanism would explain the sign of rapid hydro-climatic perturbations recorded in several reconstructions from high northern latitudes after the termination of the African Humid Period around 5.5 - 5.0 kyr BP, suggesting that these regions are sensitive to changes in Saharan land cover during the present interglacial. This is central in the debate surrounding Arctic climate amplification and future projections for subtropical precipitation changes and related surface type

  20. Differences in Fine-Root Biomass of Trees and Understory Vegetation among Stand Types in Subtropical Forests.

    PubMed

    Fu, Xiaoli; Wang, Jianlei; Di, Yuebao; Wang, Huimin

    2015-01-01

    Variation of total fine-root biomass among types of tree stands has previously been attributed to the characteristics of the stand layers. The effects of the understory vegetation on total fine-root biomass are less well studied. We examined the variation of total fine-root biomass in subtropical tree stands at two sites of Datian and Huitong in China. The two sites have similar humid monsoon climate but different soil organic carbon. One examination compared two categories of basal areas (high vs. low basal area) in stands of single species. A second examination compared single-species and mixed stands with comparable basal areas. Low basal area did not correlate with low total fine-root biomass in the single-species stands. The increase in seedling density but decrease in stem density for the low basal area stands at Datian and the quite similar stand structures for the basal-area contrast at Huitong helped in the lack of association between basal area and total fine-root biomass at the two sites, respectively. The mixed stands also did not yield higher total fine-root biomasses. In addition to the lack of niche complementarity between tree species, the differences in stem and seedling densities and the belowground competition between the tree and non-tree species also contributed to the similarity of the total fine-root biomasses in the mixed and single-species stands. Across stand types, the more fertile site Datian yielded higher tree, non-tree and total fine-root biomasses than Huitong. However, the contribution of non-tree fine-root biomass to the total fine-root biomass was higher at Huitong (29.4%) than that at Datian (16.7%). This study suggests that the variation of total fine-root biomass across stand types not only was associated with the characteristics of trees, but also may be highly dependent on the understory layer.

  1. Growth potential of Salmonella spp. and Listeria monocytogenes in nine types of ready-to-eat vegetables stored at variable temperature conditions during shelf-life.

    PubMed

    Sant'Ana, Anderson S; Barbosa, Matheus S; Destro, Maria Teresa; Landgraf, Mariza; Franco, Bernadette D G M

    2012-06-15

    Growth potential (δ) is defined as the difference between the population of a microorganism at the end of shelf-life of specific food and its initial population. The determination of δ of Salmonella and Listeria monocytogenes in RTE vegetables can be very useful to determine likely threats to food safety. However, little is known on the behavior of these microorganisms in several RTE vegetables. Therefore, the aim of this study was to determine the δ of both pathogens in nine different types of RTE vegetables (escarole, collard green, spinach, watercress, arugula, grated carrot, green salad, and mix for yakisoba) stored at refrigeration (7°C) and abuse temperature (15°C). The population of aerobic microorganisms and lactic acid bacteria, including those showing antimicrobial activity has been also determined. Results indicated that L. monocytogenes was able to grow (δ≥0.5 log(10)) in more storage conditions and vegetables than Salmonella. Both microorganisms were inhibited in carrots, although a more pronounced effect has been observed against L. monocytogenes. The highest δ values were obtained when the RTE vegetables were stored 15°C/6days in collard greens (δ=3.3) and arugula (δ=3.2) (L. monocytogenes) and arugula (δ=4.1) and escarole (δ=2.8) (Salmonella). In most vegetables and storage conditions studied, the counts of total aerobic microorganisms raised significantly independent of the temperature of storage (p<0.05). Counts of lactic acid bacteria were higher in vegetables partially or fully stored at abuse temperature with recovery of isolates showing antimicrobial activity. In conclusion, the results of this study show that Salmonella and L. monocytogenes may grow and reach high populations in RTE vegetables depending on storage conditions and the definition of effective intervention strategies are needed to control their growth in these products.

  2. A high-performance ground-based prototype of horn-type sequential vegetable production facility for life support system in space

    NASA Astrophysics Data System (ADS)

    Fu, Yuming; Liu, Hui; Shao, Lingzhi; Wang, Minjuan; Berkovich, Yu A.; Erokhin, A. N.; Liu, Hong

    2013-07-01

    Vegetable cultivation plays a crucial role in dietary supplements and psychosocial benefits of the crew during manned space flight. Here we developed a ground-based prototype of horn-type sequential vegetable production facility, named Horn-type Producer (HTP), which was capable of simulating the microgravity effect and the continuous cultivation of leaf-vegetables on root modules. The growth chamber of the facility had a volume of 0.12 m3, characterized by a three-stage space expansion with plant growth. The planting surface of 0.154 m2 was comprised of six ring-shaped root modules with a fibrous ion-exchange resin substrate. Root modules were fastened to a central porous tube supplying water, and moved forward with plant growth. The total illuminated crop area of 0.567 m2 was provided by a combination of red and white light emitting diodes on the internal surfaces. In tests with a 24-h photoperiod, the productivity of the HTP at 0.3 kW for lettuce achieved 254.3 g eatable biomass per week. Long-term operation of the HTP did not alter vegetable nutrition composition to any great extent. Furthermore, the efficiency of the HTP, based on the Q-criterion, was 7 × 10-4 g2 m-3 J-1. These results show that the HTP exhibited high productivity, stable quality, and good efficiency in the process of planting lettuce, indicative of an interesting design for space vegetable production.

  3. The soil carbon/nitrogen ratio and moisture affect microbial community structures in alkaline permafrost-affected soils with different vegetation types on the Tibetan plateau.

    PubMed

    Zhang, Xinfang; Xu, Shijian; Li, Changming; Zhao, Lin; Feng, Huyuan; Yue, Guangyang; Ren, Zhengwei; Cheng, Guogdong

    2014-01-01

    In the Tibetan permafrost region, vegetation types and soil properties have been affected by permafrost degradation, but little is known about the corresponding patterns of their soil microbial communities. Thus, we analyzed the effects of vegetation types and their covariant soil properties on bacterial and fungal community structure and membership and bacterial community-level physiological patterns. Pyrosequencing and Biolog EcoPlates were used to analyze 19 permafrost-affected soil samples from four principal vegetation types: swamp meadow (SM), meadow (M), steppe (S) and desert steppe (DS). Proteobacteria, Acidobacteria, Bacteroidetes and Actinobacteria dominated bacterial communities and the main fungal phyla were Ascomycota, Basidiomycota and Mucoromycotina. The ratios of Proteobacteria/Acidobacteria decreased in the order: SM>M>S>DS, whereas the Ascomycota/Basidiomycota ratios increased. The distributions of carbon and nitrogen cycling bacterial genera detected were related to soil properties. The bacterial communities in SM/M soils degraded amines/amino acids very rapidly, while polymers were degraded rapidly by S/DS communities. UniFrac analysis of bacterial communities detected differences among vegetation types. The fungal UniFrac community patterns of SM differed from the others. Redundancy analysis showed that the carbon/nitrogen ratio had the main effect on bacteria community structures and their diversity in alkaline soil, whereas soil moisture was mainly responsible for structuring fungal communities. Thus, microbial communities and their functioning are probably affected by soil environmental change in response to permafrost degradation.

  4. SOIL EMISSIONS OF N2O, NO AND CO2 IN BRAZILIAN SAVANNAS: EFFECTS OF VEGETATION TYPE, SEASONALITY, AND PRESCRIBED FIRES

    EPA Science Inventory

    Using closed chamber techniques, soil fluxes of NO, N20 and C02 were measured from September 1999 through October 2000 in savanna areas in central Brazil (Cerrado) subjected to prescribed fires. Our studies focused on two vegetation types, cerrado stricto sensu (20-50% canopy cov...

  5. Comparing vegetation types and anthropic disturbance levels in the Atlantic forest: how do Pentatomoidea (Hemiptera: Heteroptera) assemblages respond?

    PubMed

    Bianchi, F M; Mendonça, M S; Campos, L A

    2014-12-01

    The Atlantic Forest (AF) is considered the most fragmented and endangered Brazilian biome. The diversity of phytophagous insects increases after disturbances in forests, and it was hypothesized the Pentatomidae can furnish ecologically reliable information in terms of diversity in response to the changes occurring in AF. Our aim was to quantify the response of assemblages of Pentatomoidea to gradient of human disturbance in two vegetation types of the AF-dense ombrophilous forest (DOF) and mixed ombrophilous forest (MOF). Twelve transects were grouped into environmental classes, namely open, intermediate, and closed. Overall, 1,017 pentatomoids were sampled, representing 64 species. The open environment was more abundant than closed environment, though it is expected that Pentatomoidea respond with increasing abundance when under light or moderate disturbance. The MOF was more abundant than DOF, and the composition differed between both of them. Given the differences in composition between MOF and DOF, abiotic variables are important factors acting as environmental filters for Pentatomoidea, not just directly on the insects, but probably also on the nutritional support of their host plants. PMID:25369568

  6. Effect of oil type and fatty acid composition on dynamic and steady shear rheology of vegetable oils.

    PubMed

    Yalcin, Hasan; Toker, Omer Said; Dogan, Mahmut

    2012-01-01

    In this study, effect of fatty acid composition on dynamic and steady shear rheology of oils was studied. For this aim, different types of vegetable oils (soybean, sunflower, olive, hazelnut, cottonseed and canola), were used. Rheological properties of oil samples were identified by rheometer (Thermo-Haake) at 25°C and fatty acid composition of oils was determined by GC (Agilent 6890). Steady shear rheological properties of oil samples were measured at shear rate range of 0.1-100 s⁻¹. Viscosity of olive, hazelnut, cottonseed, canola, soybean and sunflower was 61.2 mPa.s, 59.7 mPa.s, 57.3 mPa.s, 53.5 mPa.s, 48.7 mPa.s and 48.2 mPa.s, respectively. There was a significant difference between viscosity of oils except soybean and sunflower. As a result it was seen that there was a correlation between viscosity and monounsaturated (R=0.89), polyunsaturated (R=-0.97) fatty acid composition of oils, separately. Equation was found to predict viscosity of the oils based on mono and polyunsaturation composition of oils. In addition the dynamic rheological properties of oils were also examined. G', G'' and tan δ (G''/G') values were measured at 0.3 Pa (in viscoelastic region) and 0.1-1 Hz. As a result of multiple regression analysis another equations were found between tan δ, viscosity and polyunsaturated fatty acids.

  7. Biodegradation of 2,4-dichlorophenol in the presence of volatile organic compounds in soils under different vegetation types.

    PubMed

    Rhodes, Angela H; Owen, Susan M; Semple, Kirk T

    2007-04-01

    It has been suggested that monoterpenes emitted within the soil profile, either by roots or by decaying biomass, may enhance the biodegradation of organic pollutants. The aim of this study was to evaluate the effect of biogenic volatile organic compounds (VOCs) on the catabolism of 2,4-dichlorophenol in soils. Soils were collected from areas surrounding monoterpene (woodland) and nonmonoterpene (grassland)-emitting vegetation types. Soils were spiked with [UL-14C] 2,4-dichlorophenol at 10 mg kg(-1) and amended with alpha-pinene, p-cymene or a mix of monoterpenes (alpha-pinene, limonene and p-cymene in 1:1:1 ratio). The effects of monoterpene addition on the catabolism of [UL-14C] 2,4-dichlorophenol to 14CO2 by indigenous soil microbial communities were assessed in freshly spiked and 4-week-aged soils. It was found that aged woodland soils exhibited a higher level of [UL-14C] 2,4-dichlorophenol degradation, which was subsequently enhanced by the addition of monoterpenes (P<0.001), with the VOC mix and alpha-pinene amendments showing increased [UL-14C] 2,4-dichlorophenol catabolism. This study supports claims that the addition of biogenic VOCs to soils enhances the degradation of xenobiotic contaminants. PMID:17391503

  8. The biome reconstruction approach as a tool for interpretation of past vegetation and climate changes: application to modern and fossil pollen data from Lake El'gygytgyn, Far East Russian Arctic

    NASA Astrophysics Data System (ADS)

    Tarasov, P. E.; Andreev, A. A.; Anderson, P. M.; Lozhkin, A. V.; Haltia, E.; Nowaczyk, N. R.; Wennrich, V.; Brigham-Grette, J.; Melles, M.

    2013-06-01

    The modern and fossil pollen data obtained under the framework of the multi-disciplinary international "El'gygytgyn Drilling Project" represent a unique archive that allows the testing of a range of pollen-based reconstruction approaches and the deciphering of changes in the regional vegetation and climate since ~3.58 Ma. In the current study we provide details of the biome reconstruction method applied to the late Pliocene and Quaternary pollen records from Lake El'gygytgyn. All terrestrial pollen taxa identified in the spectra from Lake El'gygytgyn were assigned to major vegetation types (biomes), which today occur near the lake and in the broader region of eastern and northern Asia and, thus, could potentially have been present in this region during the past. When applied to the modern surface pollen spectra from the lake, the method shows a dominance of the tundra biome that currently characterizes the Lake El'gygytgyn area. When applied to the pollen spectra from the middle Pleistocene to present, the method suggests (1) a predominance of tundra during the Holocene, (2) a short interval during the marine isotope stage (MIS) 5.5 interglacial distinguished by cold deciduous forest, and (3) a long phase of taiga dominance during MIS 31 and, particularly, MIS 11.3. These two latter interglacials seem to be some of the longest and warmest intervals within the past million years. During the late Pliocene-early Pleistocene interval (i.e., ~3.562-2.200 Ma), there is good correspondence between the millennial-scale vegetation changes documented in the Lake El'gygytgyn record and the alternation of cold and warm marine isotope stages, which reflect changes in the global ice volume and sea level. The biome reconstruction demonstrates changes in the regional vegetation which suggest a step-like transition from generally warmer/wetter environments of the earlier (i.e., Pliocene) interval towards colder/drier environments of the Pleistocene. The reconstruction of most of

  9. Microtopographic controls on ecosystem functioning in the Arctic Coastal Plain

    NASA Astrophysics Data System (ADS)

    Zona, D.; Lipson, D. A.; Zulueta, R. C.; Oberbauer, S. F.; Oechel, W. C.

    2011-12-01

    The investigation of the microtopographic controls on thermal and hydrologic conditions of the soil and consequently the carbon dynamics from Arctic regions is of major importance. Ecosystem respiration (ER) between microsites of the same tundra type could differ more than ER in different tundra types even at different latitudes. In this study we investigated the microtopographic effect on soil temperature, thaw depth, pH, oxidation reduction potential (ORP), electrical conductivity (EC), dissolved CO2, vegetation types, and ER rates from different features forming the low-center polygon structure. Most of these environmental variables significantly differ particularly between areas with higher elevation (polygon rims) and with lower elevation (low-center polygons). Polygon rims presented the lowest water table and showed the lowest thaw depth and the highest ER (a seasonal average of 1 μmol CO2 m-2 s-1), almost double than the ER in the low-center polygons (a seasonal average of 0.6 μmol CO2 m-2 s-1). The microtopographic gradient from polygon rims to low-centers led to a very consistent pattern in pH, EC, ORP and dissolved CO2, with low-centers presenting the highest pH, the highest EC, the highest dissolved CO2, and the lowest ORP. Based on vegetation measurements, we also showed that microtopography controls the lateral flow of organic matter, and that vascular plant material accumulates as litter in the lower elevation areas, possibly contributing to the higher dissolved CO2 in the low-center polygons. Microtopography, and the ramifications discussed here, should be considered when evaluating landscape scale environmental controls on carbon dynamics in the Arctic.

  10. Expanding the Range of Plant Functional Diversity Represented in Global Vegetation Models: Towards Lineage-based Plant Functional Types

    NASA Astrophysics Data System (ADS)

    Still, C. J.; Griffith, D.; Edwards, E.; Forrestel, E.; Lehmann, C.; Anderson, M.; Craine, J.; Pau, S.; Osborne, C.

    2014-12-01

    Variation in plant species traits, such as photosynthetic and hydraulic properties, can indicate vulnerability or resilience to climate change, and feed back to broad-scale spatial and temporal patterns in biogeochemistry, demographics, and biogeography. Yet, predicting how vegetation will respond to future environmental changes is severely limited by the inability of our models to represent species-level trait variation in processes and properties, as current generation process-based models are mostly based on the generalized and abstracted concept of plant functional types (PFTs) which were originally developed for hydrological modeling. For example, there are close to 11,000 grass species, but most vegetation models have only a single C4 grass and one or two C3 grass PFTs. However, while species trait databases are expanding rapidly, they have been produced mostly from unstructured research, with a focus on easily researched traits that are not necessarily the most important for determining plant function. Additionally, implementing realistic species-level trait variation in models is challenging. Combining related and ecologically similar species in these models might ameliorate this limitation. Here we argue for an intermediate, lineage-based approach to PFTs, which draws upon recent advances in gene sequencing and phylogenetic modeling, and where trait complex variations and anatomical features are constrained by a shared evolutionary history. We provide an example of this approach with grass lineages that vary in photosynthetic pathway (C3 or C4) and other functional and structural traits. We use machine learning approaches and geospatial databases to infer the most important environmental controls and climate niche variation for the distribution of grass lineages, and utilize a rapidly expanding grass trait database to demonstrate examples of lineage-based grass PFTs. For example, grasses in the Andropogoneae are typically tall species that dominate wet and

  11. Collembola populations under sclerophyllous coppices in Provence (France): comparison between two types of vegetation, Quercus ilex L. and Quercus coccifera L.

    NASA Astrophysics Data System (ADS)

    Cortet, Jérôme; Poinsot-Balaguer, Nicole

    1998-10-01

    A comparative analysis of soil Collembola using two types of sclerophyllous vegetation ( Quercus ilex and Quercus coccifera) was performed at a calcareous site in Provence (France). Collembola populations were examined over a one-year period (11 successive months) in three different soil layers. Although no statistically significant differences could be observed for Collembola abundance and diversity, multivariate analyses (FCA) differentiated the two coppices. Phenologies of some species showed specific responses to the microclimate induced by edaphic conditions. Even though the two coppices were sclerophyllous, the structure of each vegetation, the quantity and quality of litter, which were different, could influence environmental conditions and thus the dynamics of collembolan populations.

  12. Vegetation dynamics using AVHRR/NDVI: Regional climate, carbon dioxide fertilization and crop yield relations

    NASA Astrophysics Data System (ADS)

    Lim, Chai Kyung

    Vegetation development is closely related to climate factors, and, therefore, it is important to understand how it responds to global climate changes. For the last two decades it has been possible to monitor vegetation development at continental or global scales utilizing remote sensing Normalized Difference Vegetation Index (NDVI) data. We have developed a frequency analysis method to investigate land's vegetation greenness change and its response to the El Nino Southern Oscillation (ENSO). We found an ENSO influence on a tropical forest, southern semi-deciduous forest and a northeastern mixed forest. Our analysis shows the annual trends in vegetation greenness respond more sensitively than averaging methods. Atmospheric CO2 increase is another concern for climate change, for which fertilization effect on land vegetation has been suggested. Atmospheric CO2 and NDVI have a seasonal pattern of negative correlation, which makes it difficult to discern any positive influence of CO2 on vegetation. We adopted the concept of the rate of change in atmospheric CO2 concentration and NDVI to overcome this set pattern, and to reveal undergoing fluctuations. We found evidence that suggests a CO2 fertilization effect in some arctic and sub arctic regions and northern and inland parts of the eastern humid temperate zones in North America. Although NDVI reveals the vegetation greenness only at a fixed time and location, we have transformed NDVI effectively to describe the vegetation growth dynamics in the form of a new index, Normalized Growth Index (NGI). Utilizing NGI, we found the vegetation growth during the growing season is highly negatively correlated with the initial minimum vegetation greenness. One needs to be careful when comparing Net Primary Production (NPP) using NDVI between different types of vegetation, because the same NDVI value can imply the existence of different biomass due to different Leaf Area Index (LAI). To overcome this difficulty we have developed

  13. Arctic climate tipping points.

    PubMed

    Lenton, Timothy M

    2012-02-01

    There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points.

  14. Quaternary geology of the Duck Hawk Bluffs, southwest Banks Island, Arctic Canada: a re-investigation of a critical terrestrial type locality for glacial and interglacial events bordering the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Evans, David J. A.; England, John H.; La Farge, Catherine; Coulthard, Roy D.; Lakeman, Thomas R.; Vaughan, Jessica M.

    2014-05-01

    Duck Hawk Bluffs, southwest Banks Island, is a primary section (8 km long and 60 m high) in the western Canadian Arctic Archipelago exposing a long record of Quaternary sedimentation adjacent to the Arctic Ocean. A reinvestigation of Duck Hawk Bluffs demonstrates that it is a previously unrecognized thrust-block moraine emplaced from the northeast by Laurentide ice. Previous stratigraphic models of Duck Hawk Bluffs reported a basal unit of preglacial fluvial sand and gravel (Beaufort Fm, forested Arctic), overlain by a succession of three glaciations and at least two interglacials. Our observations dismiss the occurrence of preglacial sediments and amalgamate the entire record into three glacial intervals and one prominent interglacial. The first glacigenic sedimentation is recorded by an ice-contact sandur containing redeposited allochthonous organics previously assigned to the Beaufort Fm. This is overlain by fine-grained sediments with ice wedge pseudomorphs and well-preserved bryophyte assemblages corresponding to an interglacial environment similar to modern. The second glacial interval is recorded by ice-proximal mass flows and marine rhythmites that were glacitectonized when Laurentide ice overrode the site from Amundsen Gulf to the south. Sediments of this interval have been reported to be magnetically reversed (>780 ka). The third interval of glacigenic sedimentation includes glacifluvial sand and gravel recording the arrival of Laurentide ice that overrode the site from the northeast (island interior) depositing a glacitectonite and constructing the thrust block moraine that comprises Duck Hawk Bluffs. Sediments of this interval have been reported to be magnetically normal (<780 ka). The glacitectonite contains a highly deformed melange of pre-existing sediments that were previously assigned to several formally named, marine and interglacial deposits resting in an undeformed sequence. In contrast, the tectonism associated with the thrust block moraine

  15. Global Analysis of Type Three Secretion System and Quorum Sensing Inhibition of Pseudomonas savastanoi by Polyphenols Extracts from Vegetable Residues

    PubMed Central

    Campo, Margherita; Scardigli, Arianna; Romani, Annalisa

    2016-01-01

    Protection of plants against bacterial diseases still mainly relies on the use of chemical pesticides, which in Europe correspond essentially to copper-based compounds. However, recently plant diseases control is oriented towards a rational use of molecules and extracts, generally with natural origin, with lower intrinsic toxicity and a reduced negative environmental impact. In this work, polyphenolic extracts from vegetable no food/feed residues of typical Mediterranean crops, as Olea europaea, Cynara scolymus, and Vitis vinifera were obtained and their inhibitory activity on the Type Three Secretion System (TTSS) and the Quorum Sensing (QS) of the Gram-negative phytopathogenic bacterium Pseudomonas savastanoi pv. nerii strain Psn23 was assessed. Extract from green tea (Camellia sinensis) was used as a positive control. Collectively, the data obtained through gfp-promoter fusion system and real-time PCR show that all the polyphenolic extracts here studied have a high inhibitory activity on both the TTSS and QS of Psn23, without any depressing effect on bacterial viability. Extracts from green tea and grape seeds were shown to be the most active. Such activity was confirmed in planta by a strong reduction in the ability of Psn23 to develop hyperplastic galls on explants from adult oleander plants, as well as to elicit hypersensitive response on tobacco. By using a newly developed Congo red assay and an ELISA test, we demonstrated that the TTSS-targeted activity of these polyphenolic extracts also affects the TTSS pilus assembly. In consideration of the potential application of polyphenolic extracts in plant protection, the absence of any toxicity of these polyphenolic compounds was also assessed. A widely and evolutionary conserved molecular target such as Ca2+-ATPase, essential for the survival of any living organism, was used for the toxicity assessment. PMID:27668874

  16. Fuel Consumption and Fire Emissions Estimates in Siberia: Impact of Vegetation Types, Meteorological Conditions, Forestry Practices and Fire Regimes

    NASA Astrophysics Data System (ADS)

    Kukavskaya, Elena; Conard, Susan; Ivanova, Galina; Buryak, Ludmila; Soja, Amber; Zhila, Sergey

    2015-04-01

    Boreal forests play a crucial role in carbon budgets with Siberian carbon fluxes and pools making a major contribution to the regional and global carbon cycle. Wildfire is the main ecological disturbance in Siberia that leads to changes in forest species composition and structure and in carbon storage, as well as direct emissions of greenhouse gases and aerosols to the atmosphere. At present, the global scientific community is highly interested in quantitative and accurate estimates of fire emissions. Little research on wildland fuel consumption and carbon emission estimates has been carried out in Russia until recently. From 2000 to 2007 we conducted a series of experimental fires of varying fireline intensity in light-coniferous forest of central Siberia to obtain quantitative and qualitative data on fire behavior and carbon emissions due to fires of known behavior. From 2009 to 2013 we examined a number of burned logged areas to assess the potential impact of forest practices on fire emissions. In 2013-2014 burned areas in dark-coniferous and deciduous forests were examined to determine fuel consumption and carbon emissions. We have combined and analyzed the scarce data available in the literature with data obtained in the course of our long-term research to determine the impact of various factors on fuel consumption and to develop models of carbon emissions for different ecosystems of Siberia. Carbon emissions varied drastically (from 0.5 to 40.9 tC/ha) as a function of vegetation type, weather conditions, anthropogenic effects and fire behavior characteristics and periodicity. Our study provides a basis for better understanding of the feedbacks between wildland fire emissions and changing anthropogenic disturbance patterns and climate. The data obtained could be used by air quality agencies to calculate local emissions and by managers to develop strategies to mitigate negative smoke impacts on the environmentand human health.

  17. High Arctic wetlands: Their occurrence, hydrological characteristics and sustainability

    NASA Astrophysics Data System (ADS)

    Woo, Ming-ko; Young, Kathy L.

    2006-04-01

    High Arctic wetlands, though limited in occurrence, are an important ecological niche, providing the major vegetated areas in an arid and cold polar desert environment. These wetlands are often found as patches in the barren landscape. At a few locales which may be ice-wedge polygonal grounds, glacial terrain and zones of recent coastal uplift, wetland occurrence can become extensive, forming a mosaic that comprises patches of different wetland types. Reliable water supply during the thawed season is a deciding factor in wetland sustainability. The sources include meltwater from late-lying snowbanks, localized ground water discharge, streamflow, inundation by lakes and the sea, and for some ice-wedge wetlands, ground-ice melt. Different types of wetlands have their own characteristics, and peat accumulation or diatom depositions are common. The peat cover insulates the wetland from summer heating and encourages permafrost aggradation, with the feedback that a shallow frost table reduces the moisture storage capacity in a thinly thawed layer, which becomes easily saturated. All the wetlands studied have high calcium content since they are formed on carbonate terrain. Coastal wetlands have high salt concentration while snowmelt and ground-ice melt provides dilution. The sustainability of High Arctic wetlands is predicated upon water supply exceeding the losses to evaporation and lateral drainage. Disturbances due to natural causes such as climatic variations, geomorphic changes, or human-induced drainage, can reduce inundation opportunities or increase outflow. Then, the water table drops, the vegetation changes and the peat degrades, leading to the detriment of the wetlands.

  18. Holocene planform change in broad valleys in the Southern Rocky Mountains: the role of vegetation type and beaver in shaping long-term channel complexity

    NASA Astrophysics Data System (ADS)

    Polvi-Pilgrim, L. E.; Wohl, E.

    2012-04-01

    Over the past decade, researchers have shown the importance of streambank vegetation in forming meandering channels. Recent work has also showed the importance of beaver in creating a more heterogeneous landscape, in terms of channel planform and complexity, sedimentation, and riparian vegetation. Streambank vegetation and beavers interact as ecosystem engineers to determine long-term channel planform, floodplain processes, and complexity. We use studies of Holocene beaver aggradation and effects on channel complexity, in addition to measurements of added bank strength by various riparian vegetation types, to predict Holocene planform change in broad (>200 m, disconnected from hillslopes), high-elevation (>2300 m) valleys of the Colorado Front Range in the Southern Rocky Mountains. Sediment core analyses and shallow subsurface geophysical measurements indicate that post-glacial beaver-related aggradation is significant. Additionally, historical and field evidence from the last century, when the beaver population steadily declined, shows that beaver contribute to the formation of a complex, multi-thread channel network. Streambank vegetation in the Colorado Front Range can be categorized based on its ability to provide added strength to the streambank, where riparian or rhizomatous shrubs and trees provide more strength than xeric trees or non-rhizomatous graminoids and herbs, depending on the bank texture and hydrologic conditions. Assuming a snowmelt-dominated flow regime in a gravel-bed channel system, four planform regimes are identified based on beaver populations and the abundance and presence of xeric or riparian vegetation. Following deglaciation, without beaver or bank-stabilizing vegetation, (1) a braided channel formed. The introduction of riparian vegetation and a more stable flow regime triggered a transition to (2) a meandering channel, which in turn provided habitat for beaver, allowing the formation of (3) a complex multi-thread channel system. The

  19. Reconstructing Past Vegetation Types During the Late Holocene Using Stable Carbon Isotopes of Leporids from Archaeological Sites in the American Southwest

    NASA Astrophysics Data System (ADS)

    Mauldin, R. P.; Munoz, C.; Kemp, L.; Hard, R.

    2012-12-01

    Stable carbon isotopes (δ13C) from bone collagen in leporids provide high-resolution vegetation reconstruction. Leporids [e.g., cottontails (Sylvilagus sp.), jackrabbits (Lepus sp.)] die young (ca. 2 years) and use small home ranges (< 1 km2). They consume a variety of vegetation, including plants that use both C3 and C4/CAM photosynthetic pathways. Leporids appear to focus on new growth as it becomes available throughout the year, perhaps as a function of water content. Their diet, and their bone collagen, provides a high-resolution view of the carbon isotopic values present in their local plant community. Here we provide an example of the use of leporid bone collagen for reconstruction of past vegetation types using data from several archaeological sites as well as modern collections. All samples are from a basin and range setting within the Chihuahuan Desert in far west Texas and southern New Mexico, USA. The sites span a period back to roughly 1350 BP. Isotopic patterns in leporid collagen show clear evidence of change in vegetation from around 775 BP to the modern period, with a dramatic shift of 4.2‰ in median δ13C values over this period in jackrabbit collagen and a 7.3‰ decrease in median carbon isotopic values in cottontail rabbits. These data suggest a significant increase in C3 plants in leporid diet, and by extension a relative increase in these plant types in the local environment sampled by leporids. This shift is consistent with historic accounts of more C3 mesquite, possibly because of historic land use and ranching practices in the 1800s. However, while this shift may have been accelerated by historic land use changes, our data suggest that the vegetation shift began several hundred years earlier during the prehistoric period. The prehistoric collagen isotopic record also shows increased sample variability through time in both species, suggesting that year-to-year variability in vegetation may have increased late in that sequence. Our results

  20. Is climate change affecting wolf populations in the high Arctic?

    USGS Publications Warehouse

    Mech, L.D.

    2004-01-01

    Global climate change may affect wolves in Canada's High Arctic (80DG N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.

  1. Is climate change affecting wolf populations in the high Arctic?

    USGS Publications Warehouse

    Mech, L.D.

    2004-01-01

    Gobal climate change may affect wolves in Canada's High Arctic (80?? N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena. ?? 2004 Kluwer Academic Publishers.

  2. Pleistocene graminoid-dominated ecosystems in the Arctic

    NASA Astrophysics Data System (ADS)

    Blinnikov, Mikhail S.; Gaglioti, Benjamin V.; Walker, Donald A.; Wooller, Matthew J.; Zazula, Grant D.

    2011-10-01

    We review evidence obtained from analyses of multiple proxies (floristics, mammal remains, paleoinsects, pollen, macrofossils, plant cuticles, phytoliths, stable isotopes, and modeling) that elucidate the composition and character of the graminoid-dominated ecosystems of the Pleistocene Arctic. The past thirty years have seen a renewed interest in this now-extinct biome, sometimes referred to as "tundra-steppe" (steppe-tundra in North American sources). While many questions remain, converging evidence from many new terrestrial records and proxies coupled with better understanding of paleoclimate dynamics point to the predominance of xeric and cold adapted grassland as the key former vegetation type in the Arctic confirming earlier conjectures completed in the 1960s-1980s. A variety of still existing species of grasses and forbs played key roles in the species assemblages of the time, but their mixtures were not analogous to the tundras of today. Local mosaics based on topography, proximity to the ice sheets and coasts, soil heterogeneity, animal disturbance, and fire regimes were undoubtedly present. However, inadequate coverage of terrestrial proxies exist to resolve this spatial heterogeneity. These past ecosystems were maintained by a combination of dry and cold climate and grazing pressure/disturbance by large (e.g., mammoth and horse) and small (e.g., ground squirrels) mammals. Some recent studies from Eastern Beringia (Alaska) suggest that more progress will be possible when analyses of many proxies are combined at local scales.

  3. Shrub expansion and climate feedbacks in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Goetz, Scott J.

    2012-03-01

    covered by the snowpack for part of the year. These results support evidence that shrub expansion in Arctic tundra will feed back positively to ongoing climate warming but, perhaps more importantly, illustrate the significance of shrub height in dictating the feedback strength. While differences in albedo associated with vegetation stature have been previously documented in these ecosystems (Loranty et al 2011, Sturm et al 2005a), the magnitudes of the feedbacks on regional climate were unknown. These findings highlight a pressing need to understand the rate and spatial extent at which shrub expansion is occurring. While increases in vegetation productivity inferred from satellite data have been observed across the Arctic (Bunn and Goetz 2006, Goetz et al 2005, Walker et al 2009), recent analyses suggest that the observed trends are a result of general increases in productivity across all vegetation types (Beck and Goetz 2011). Another important finding reported by Bonfils et al (2012) is the positive correlation between shrub height and modeled active layer depth (i.e. permafrost thaw). Results from a field study (Blok et al 2010) showed that the shading effects of shrub canopies reduce ground heat flux, which in turn leads to a decrease in active layer depth. Bonfils et al's (2012) results indicate that regional warming as a consequence of albedo and ET feedbacks will offset the local cooling effects of increased shrub cover, thus the net climate feedback associated with shrub expansion could be greater than reported (owing to biogeochemical processes and related feedbacks). A similar study by Lawrence and Swenson (2011) found that snow redistribution to shrub covered areas (Sturm et al 2005b) simultaneously reduced the albedo feedback by covering shrubs with snow and introduced a soil warming feedback through insulation provided by additional snow cover, with a net result of increased active layer depth under shrubs. When shrub cover (1 m tall canopy) was increased by

  4. Arctic science input wanted

    NASA Astrophysics Data System (ADS)

    The Arctic Research and Policy Act (Eos, June 26, 1984, p. 412) was signed into law by President Ronald Reagan this past July. One of its objectives is to develop a 5-year research plan for the Arctic. A request for input to this plan is being issued this week to nearly 500 people in science, engineering, and industry.To promote Arctic research and to recommend research policy in the Arctic, the new law establishes a five-member Arctic Research Commission, to be appointed by the President, and establishes an Interagency Arctic Research Policy Committee, to be composed of representatives from nearly a dozen agencies having interests in the region. The commission will make policy recommendations, and the interagency committee will implement those recommendations. The National Science Foundation (NSF) has been designated as the lead agency of the interagency committee.

  5. Decadal changes of phenological patterns over Arctic tundra biome

    NASA Astrophysics Data System (ADS)

    Jia, G. J.; Epstein, H. E.; Walker, D. A.; Wang, H.

    2008-12-01

    The northern high latitudes have experienced a continuous and accelerated trend of warming during the past 30 years, with most recent decade ranks the warmest years since 1850. Warmer springs are especially evident throughout the Arctic. Meanwhile, Arctic sea ice declined rapidly to unprecedented low extents in all months, with late summer experiences the most significant declining. Warming in the north is also evident from observations of early melting of snow and reducing snow cover. Now a key question is: in the warmth limited northern biome, what will happen to the phenological patterns of tundra vegetation as the global climate warms and seasonality of air temperature, sea ice, and snow cover shift? To answer the question we examined the onset of vegetation greenness, senescence of greenness, length of growing season, and dates of peak greenness along Arctic bioclimate gradients (subzones) to see how they change over years. Here, we combine multi-scale sub-pixel analysis and remote sensing time-series analysis to investigate recent decadal changes in vegetation phenology along spatial gradients of summer temperature and vegetation in the Arctic. The datasets used here are AVHRR 15-day 8 km time series, AVHRR 8-day 1 km dataset, and MODIS 8-day 500m Collection 5 dataset. There were detectable changes in phenological pattern over tundra biome in past two decades. Increases of vegetation greenness were observed in most of the summer periods in low arctic and mid-summer in high arctic. Peak greenness appeared earlier in high arctic and declined slower after peak in low arctic. Generally, tundra plants were having longer and stronger photosynthesis activities, and therefore increased annual vegetation productivities. Field studies have observed early growth and enhanced peak growth of many deciduous shrub species in tundra plant communities. These changes in seasonality are very likely to alter surface albedo and heat budget, modify plant photosynthesis

  6. The identification of selected vegetation types in Arizona through the photointerpretation of intermediate scale aerial photography. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Ross, G. F. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Nine photography interpretation tests were performed with a total of 19 different interpreters. Three tests were conducted with black and white intermediate scale photography and six tests with color infrared intermediate scale photography. The black and white test results show that the interpretation of vegetation mapped at the association level of classification is reliable for all the classes used at 61%. The color infrared tests indicate that the association level of mapping is unsatisfactory for vegetation interpretation of classes 1 and 6. Students' t-test indicated that intermediate scale black and white photography is significantly better than this particular color infrared photography for the interpretation of southeastern Arizona vegetation mapped at the association level.

  7. Remote sensing for monitoring of wildlife habitat: Lesser snow geese and sub-Arctic coastal marshes

    NASA Astrophysics Data System (ADS)

    Gadallah, Fawziah L.

    Human environmental impact has occurred on a global scale. Effective management of problems occurring over broad regions requires monitoring and intervention over large extents of space and time. Remote sensing provides an attractive data source, particularly as satellite data have been consistently collected over both space and time and present a readily available, inexpensive archive. At best, however, remote sensing provides proxy data for the underlying variables of interest. Here remotely sensed data are used to measure habitat degradation at a lesser snow goose colony. An increase in goose numbers has led to a loss of forage vegetation in the arctic and sub-arctic marshes where the geese nest and raise their young. In particular, isostatic rebound has generated extensive coastal marshes along the west coast of Hudson Bay, and lesser snow geese colonized such a marsh at La Perouse Bay in the late 1950's. This well-studied colony is used to assess the feasibility of mapping decadal change with Landsat imagery. A baseline map is developed using satellite data, aerial photography, and a knowledge of vegetation dynamics at the site. Calibration equations, relating the quantity of above-ground vegetation and its reflectance, are developed using cross-validation and goodness-of-prediction measures for field data collected on-site. To detect changes in vegetation state, tree-classification and cross-validation were applied to ground data. Using satellite imagery, changes in vegetation quantity and type could be detected against a background of mineral soil, but not against a background of mosses. Even in this site with low topographic variability, few species and few strong driving forces (i.e. isostatic rebound and herbivory), multiple change trajectories are possible. As different trajectories have different influences on both the reflectance of the surface and the expected behaviour and functioning of the system, each must be accounted for separately. Failure to

  8. Study on regional responses of pan-Arctic terrestrial ecosystems to recent climate variability using satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Ke

    I applied a satellite remote sensing based production efficiency model (PEM) using an integrated AVHRR and MODIS FPAR/LAI time series with a regionally corrected NCEP/NCAR reanalysis surface meteorology and NASA/GEWEX shortwave solar radiation inputs to assess annual terrestrial net primary productivity (NPP) for the pan-Arctic basin and Alaska from 1983 to 2005. I developed a satellite remote sensing based evapotranspiration (ET) algorithm using GIMMS NDVI with the above meteorology inputs to assess spatial patterns and temporal trends in ET over the pan-Arctic region. I then analyzed associated changes in the regional water balance defined as the difference between precipitation (P) and ET. I finally analyzed the effects of regional climate oscillations on vegetation productivity and the regional water balance. The results show that low temperature constraints on Boreal-Arctic NPP are decreasing by 0.43% per year (P < 0.001), whereas a positive trend in vegetation moisture constraints of 0.49% per year ( P = 0.04) are offsetting the potential benefits of longer growing seasons and contributing to recent drought related disturbances in NPP. The PEM simulations of NPP seasonality, annual anomalies and trends are similar to stand inventory network measurements of boreal aspen stem growth ( r = 0.56; P = 0.007) and atmospheric CO2 measurement based estimates of the timing of growing season onset ( r = 0.78; P < 0.001). The simulated monthly ET results agree well (RMSE=8.3 mm month-1; R2=0.89) with tower measurements for regionally dominant land cover types. Generally positive trends in ET, precipitation and available river discharge measurements imply that the pan-Arctic terrestrial water cycle is intensifying. Increasing water deficits occurred in some boreal and temperate grassland regions, which agree with regional drought records and recent satellite observations of vegetation browning and productivity decreases. Climate oscillations including Arctic Oscillation

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. White Arctic vs. Blue Arctic: Making Choices

    NASA Astrophysics Data System (ADS)

    Pfirman, S. L.; Newton, R.; Schlosser, P.; Pomerance, R.; Tremblay, B.; Murray, M. S.; Gerrard, M.

    2015-12-01

    As the Arctic warms and shifts from icy white to watery blue and resource-rich, tension is arising between the desire to restore and sustain an ice-covered Arctic and stakeholder communities that hope to benefit from an open Arctic Ocean. If emissions of greenhouse gases to the atmosphere continue on their present trend, most of the summer sea ice cover is projected to be gone by mid-century, i.e., by the time that few if any interventions could be in place to restore it. There are many local as well as global reasons for ice restoration, including for example, preserving the Arctic's reflectivity, sustaining critical habitat, and maintaining cultural traditions. However, due to challenges in implementing interventions, it may take decades before summer sea ice would begin to return. This means that future generations would be faced with bringing sea ice back into regions where they have not experienced it before. While there is likely to be interest in taking action to restore ice for the local, regional, and global services it provides, there is also interest in the economic advancement that open access brings. Dealing with these emerging issues and new combinations of stakeholders needs new approaches - yet environmental change in the Arctic is proceeding quickly and will force the issues sooner rather than later. In this contribution we examine challenges, opportunities, and responsibilities related to exploring options for restoring Arctic sea ice and potential pathways for their implementation. Negotiating responses involves international strategic considerations including security and governance, meaning that along with local communities, state decision-makers, and commercial interests, national governments will have to play central roles. While these issues are currently playing out in the Arctic, similar tensions are also emerging in other regions.

  11. Long-term recovery patterns of arctic tundra after winter seismic exploration.

    PubMed

    Jorgenson, Janet C; Ver Hoef, Jay M; Jorgenson, M T

    2010-01-01

    In response to the increasing global demand for energy, oil exploration and development are expanding into frontier areas of the Arctic, where slow-growing tundra vegetation and the underlying permafrost soils are very sensitive to disturbance. The creation of vehicle trails on the tundra from seismic exploration for oil has accelerated in the past decade, and the cumulative impact represents a geographic footprint that covers a greater extent of Alaska's North Slope tundra than all other direct human impacts combined. Seismic exploration for oil and gas was conducted on the coastal plain of the Arctic National Wildlife Refuge, Alaska, USA, in the winters of 1984 and 1985. This study documents recovery of vegetation and permafrost soils over a two-decade period after vehicle traffic on snow-covered tundra. Paired permanent vegetation plots (disturbed vs. reference) were monitored six times from 1984 to 2002. Data were collected on percent vegetative cover by plant species and on soil and ground ice characteristics. We developed Bayesian hierarchical models, with temporally and spatially autocorrelated errors, to analyze the effects of vegetation type and initial disturbance levels on recovery patterns of the different plant growth forms as well as soil thaw depth. Plant community composition was altered on the trails by species-specific responses to initial disturbance and subsequent changes in substrate. Long-term changes included increased cover of graminoids and decreased cover of evergreen shrubs and mosses. Trails with low levels of initial disturbance usually improved well over time, whereas those with medium to high levels of initial disturbance recovered slowly. Trails on ice-poor, gravel substrates of riparian areas recovered better than those on ice-rich loamy soils of the uplands, even after severe initial damage. Recovery to pre-disturbance communities was not possible where trail subsidence occurred due to thawing of ground ice. Previous studies of

  12. Long-term recovery patterns of arctic tundra after winter seismic exploration.

    PubMed

    Jorgenson, Janet C; Ver Hoef, Jay M; Jorgenson, M T

    2010-01-01

    In response to the increasing global demand for energy, oil exploration and development are expanding into frontier areas of the Arctic, where slow-growing tundra vegetation and the underlying permafrost soils are very sensitive to disturbance. The creation of vehicle trails on the tundra from seismic exploration for oil has accelerated in the past decade, and the cumulative impact represents a geographic footprint that covers a greater extent of Alaska's North Slope tundra than all other direct human impacts combined. Seismic exploration for oil and gas was conducted on the coastal plain of the Arctic National Wildlife Refuge, Alaska, USA, in the winters of 1984 and 1985. This study documents recovery of vegetation and permafrost soils over a two-decade period after vehicle traffic on snow-covered tundra. Paired permanent vegetation plots (disturbed vs. reference) were monitored six times from 1984 to 2002. Data were collected on percent vegetative cover by plant species and on soil and ground ice characteristics. We developed Bayesian hierarchical models, with temporally and spatially autocorrelated errors, to analyze the effects of vegetation type and initial disturbance levels on recovery patterns of the different plant growth forms as well as soil thaw depth. Plant community composition was altered on the trails by species-specific responses to initial disturbance and subsequent changes in substrate. Long-term changes included increased cover of graminoids and decreased cover of evergreen shrubs and mosses. Trails with low levels of initial disturbance usually improved well over time, whereas those with medium to high levels of initial disturbance recovered slowly. Trails on ice-poor, gravel substrates of riparian areas recovered better than those on ice-rich loamy soils of the uplands, even after severe initial damage. Recovery to pre-disturbance communities was not possible where trail subsidence occurred due to thawing of ground ice. Previous studies of

  13. Plant functional types in Earth system models: past experiences and future directions for application of dynamic vegetation models in high-latitude ecosystems

    PubMed Central

    Wullschleger, Stan D.; Epstein, Howard E.; Box, Elgene O.; Euskirchen, Eugénie S.; Goswami, Santonu; Iversen, Colleen M.; Kattge, Jens; Norby, Richard J.; van Bodegom, Peter M.; Xu, Xiaofeng

    2014-01-01

    Background Earth system models describe the physical, chemical and biological processes that govern our global climate. While it is difficult to single out one component as being more important than another in these sophisticated models, terrestrial vegetation is a critical player in the biogeochemical and biophysical dynamics of the Earth system. There is much debate, however, as to how plant diversity and function should be represented in these models. Scope Plant functional types (PFTs) have been adopted by modellers to represent broad groupings of plant species that share similar characteristics (e.g. growth form) and roles (e.g. photosynthetic pathway) in ecosystem function. In this review, the PFT concept is traced from its origin in the early 1800s to its current use in regional and global dynamic vegetation models (DVMs). Special attention is given to the representation and parameterization of PFTs and to validation and benchmarking of predicted patterns of vegetation distribution in high-latitude ecosystems. These ecosystems are sensitive to changing climate and thus provide a useful test case for model-based simulations of past, current and future distribution of vegetation. Conclusions Models that incorporate the PFT concept predict many of the emerging patterns of vegetation change in tundra and boreal forests, given known processes of tree mortality, treeline migration and shrub expansion. However, representation of above- and especially below-ground traits for specific PFTs continues to be problematic. Potential solutions include developing trait databases and replacing fixed parameters for PFTs with formulations based on trait co-variance and empirical trait–environment relationships. Surprisingly, despite being important to land–atmosphere interactions of carbon, water and energy, PFTs such as moss and lichen are largely absent from DVMs. Close collaboration among those involved in modelling with the disciplines of taxonomy, biogeography

  14. Analysis of Trends of the Types of Pesticide Used, Residues and Related Factors among Farmers in the Largest Vegetable Producing Area in the Philippines

    PubMed Central

    Lu, Jinky Leilanie

    2010-01-01

    The objective of study is to provide an analysis of data trends on the type of pesticide used, exposure factors, and the pesticide-related concerns among the farmers from 2005 to 2010 in one of the largest vegetable producing areas in the Philippines. This is to determine and analyze changes that have occurred for the last five years in order to provide necessary basis in promoting safe usage of pesticides. It is shown in the studies that the most commonly used type of pesticide was Tamaron (methamidophos) which is an organophosphate. The top five pesticide-related symptoms confirm findings in other studies. The risk factors to pesticide exposure were also identified in the reviewed studies such as improper mixing and loading of pesticides, and re-entering previously sprayed area. Pesticide residues were also found in vegetables, soil and water samples. This points to environmental contamination due to pesticide. It is suggested that government agencies implement programs on monitoring, surveillance, information dissemination, and training on proper use of pesticides, and seek alternative farming such as organically grown vegetables, or use of integrated pest management as well as good agricultural practices. PMID:25649105

  15. The effect of storm sequence, catchment structure, vegetation type and antecedent moisture conditions on nutrient loading and stream discharge for a small Catskill mountain watershed

    NASA Astrophysics Data System (ADS)

    Randolph, A.; Schneiderman, E. M.; Pierson, D. C.; Zion, M. S.; Band, L. E.

    2013-12-01

    Research suggests that among the possible consequences of climate change could be a change in the spatio-temporal pattern of precipitation within and across years. In particular, it is suggested that changes in inter-storm period, storm depth and the partitioning of precipitation between rain and snow events could occur. A complex interaction exists between precipitation, topographic controls, catchment structure and vegetation type and status. Collectively, they define a spatial pattern of antecedent moisture conditions across the landscape prior to each precipitation event, which in turn significantly impacts stream flow characteristics such as base flow, storm flow and nutrient loading. In the present study, we use a spatially distributed hydro-ecological model (RHESSys) to model the change in the relative contribution of stream flow and nutrient loading from sub-catchments within Biscuit Brook (Catskill mountains, New York, USA) as a function of precipitation pattern and vegetation cover. Specifically, we investigate how the spatial pattern of antecedent moisture conditions within each sub-catchment varies as a function of modeled vegetation type and precipitation pattern, and how the aggregate response of the catchment changes in terms of base flow, storm flow and nutrient loading. Implications for water quality and water quality management are assessed and discussed. Key words: climate change, RHESSys, stream discharge, nutrient loading, watershed modeling, ecological modeling, water quality

  16. Relationships among depth to frozen soil, soil wetness, and vegetation type and biomass in Tundra near Bethel, Alaska, U. S. A

    SciTech Connect

    Gross, M.F. ); Hardisky, M.A. ); Doolittle, J.A. ); Klemas, V. )

    1990-08-01

    Vegetation was sampled in three types of tundra habitat (upland, wet meadow, and lake) in southwestern Alaska. Aboveground and belowground biomass were measured by harvesting, and the depth to frozen soil was measured using ground-penetrating radar. Live and dead aboveground biomass increased, and dead belowground biomass decreased, as habitat wetness and depth to frozen soil increased. The proportion of live aerial biomass that was graminoid increased as habitat wetness and depth to frozen soil increased, whereas the proportion that was woody shrub biomass decreased with increases in habitat wetness and depth to frozen soil. The results indicate that information pertaining to either vegetation type/biomass, habitat wetness, or depth to frozen soil, could be used to infer information about the other two variables. Vegetation and frozen soil depth could be monitored remotely for large areas using tools such as satellite images and radar. Since the cycling of carbon is related to carbon storage (biomass) and depth of the biologically active (thawed) layer, it should be possible to study carbon cycles in tundra remotely, based on the relationships stated above.

  17. Snow Depth Mapping at a Basin-Wide Scale in the Western Arctic Using UAS Technology

    NASA Astrophysics Data System (ADS)

    de Jong, T.; Marsh, P.; Mann, P.; Walker, B.

    2015-12-01

    Assessing snow depths across the Arctic has proven to be extremely difficult due to the variability of snow depths at scales from metres to 100's of metres. New Unmanned Aerial Systems (UAS) technology provides the possibility to obtain centimeter level resolution imagery (~3cm), and to create Digital Surface Models (DSM) based on the Structure from Motion method. However, there is an ongoing need to quantify the accuracy of this method over different terrain and vegetation types across the Arctic. In this study, we used a small UAS equipped with a high resolution RGB camera to create DSMs over a 1 km2 watershed in the western Canadian Arctic during snow (end of winter) and snow-free periods. To improve the image georeferencing, 15 Ground Control Points were marked across the watershed and incorporated into the DSM processing. The summer DSM was subtracted from the snowcovered DSM to deliver snow depth measurements across the entire watershed. These snow depth measurements were validated by over 2000 snow depth measurements. This technique has the potential to improve larger scale snow depth mapping across watersheds by providing snow depth measurements at a ~3 cm . The ability of mapping both shallow snow (less than 75cm) covering much of the basin and snow patches (up to 5 m in depth) that cover less than 10% of the basin, but contain a significant portion of total basin snowcover, is important for both water resource applications, as well as for testing snow models.

  18. Arctic circulation regimes.

    PubMed

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  19. Arctic circulation regimes

    PubMed Central

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

    2015-01-01

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  20. Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

    NASA Astrophysics Data System (ADS)

    Kaplan, J. O.; Bigelow, N. H.; Prentice, I. C.; Harrison, S. P.; Bartlein, P. J.; Christensen, T. R.; Cramer, W.; Matveyeva, N. V.; McGuire, A. D.; Murray, D. F.; Razzhivin, V. Y.; Smith, B.; Walker, D. A.; Anderson, P. M.; Andreev, A. A.; Brubaker, L. B.; Edwards, M. E.; Lozhkin, A. V.

    2003-10-01

    Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55°N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to >700 ppm) at high latitudes were slight compared with the effects of the change in climate.

  1. Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

    USGS Publications Warehouse

    Kaplan, J.O.; Bigelow, N.H.; Prentice, I.C.; Harrison, S.P.; Bartlein, P.J.; Christensen, T.R.; Cramer, W.; Matveyeva, N.V.; McGuire, A.D.; Murray, D.F.; Razzhivin, V.Y.; Smith, B.; Walker, D. A.; Anderson, P.M.; Andreev, A.A.; Brubaker, L.B.; Edwards, M.E.; Lozhkin, A.V.

    2003-01-01

    Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55??N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to > 700 ppm) at high latitudes were slight compared with the effects of the change in climate.

  2. PAST Gateways (Palaeo-Arctic Spatial and Temporal Gateways): Introduction and overview

    NASA Astrophysics Data System (ADS)

    Ó Cofaigh, Colm; Briner, Jason P.; Kirchner, Nina; Lucchi, Renata G.; Meyer, Hanno; Kaufman, Darrell S.

    2016-09-01

    This special issue relates to the Second International Conference of the PAST Gateways (Palaeo-Arctic Spatial and Temporal Gateways) network which was held in Trieste, Italy in 2014. Twenty five papers are included and they address topics under four main themes: (1) The growth and decay of Arctic ice sheets; (2) Arctic sea ice and palaeoceanography; (3) Terrestrial Arctic environments and permafrost change; and (4) Holocene Arctic environmental change. Geographically the focus is circum-Arctic; the special issue includes detailed regional studies from Greenland, Scandinavia, Russia, and Arctic North America and the adjoining seas, as well as a series of synthesis-type, review papers on Fennoscandian Ice Sheet deglaciation and Holocene Arctic palaeo-climate change. The methodologies employed are diverse and include marine sediment core and geophysical investigations, terrestrial glacial geology and geomorphology, isotopic analysis of ground ice, palaeo-ecological analysis of lacustrine and terrestrial sedimentary archives, geochronology and numerical ice sheet modeling.

  3. Arctic Haze Analysis

    NASA Astrophysics Data System (ADS)

    Mei, Linlu; Xue, Yong

    2013-04-01

    The Arctic atmosphere is perturbed by nature/anthropogenic aerosol sources known as the Arctic haze, was firstly observed in 1956 by J. Murray Mitchell in Alaska (Mitchell, 1956). Pacyna and Shaw (1992) summarized that Arctic haze is a mixture of anthropogenic and natural pollutants from a variety of sources in different geographical areas at altitudes from 2 to 4 or 5 km while the source for layers of polluted air at altitudes below 2.5 km mainly comes from episodic transportation of anthropogenic sources situated closer to the Arctic. Arctic haze of low troposphere was found to be of a very strong seasonal variation characterized by a summer minimum and a winter maximum in Alaskan (Barrie, 1986; Shaw, 1995) and other Arctic region (Xie and Hopke, 1999). An anthropogenic factor dominated by together with metallic species like Pb, Zn, V, As, Sb, In, etc. and nature source such as sea salt factor consisting mainly of Cl, Na, and K (Xie and Hopke, 1999), dust containing Fe, Al and so on (Rahn et al.,1977). Black carbon and soot can also be included during summer time because of the mix of smoke from wildfires. The Arctic air mass is a unique meteorological feature of the troposphere characterized by sub-zero temperatures, little precipitation, stable stratification that prevents strong vertical mixing and low levels of solar radiations (Barrie, 1986), causing less pollutants was scavenged, the major revival pathway for particulates from the atmosphere in Arctic (Shaw, 1981, 1995; Heintzenberg and Larssen, 1983). Due to the special meteorological condition mentioned above, we can conclude that Eurasian is the main contributor of the Arctic pollutants and the strong transport into the Arctic from Eurasia during winter caused by the high pressure of the climatologically persistent Siberian high pressure region (Barrie, 1986). The paper intends to address the atmospheric characteristics of Arctic haze by comparing the clear day and haze day using different dataset

  4. Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model.

    PubMed

    Euskirchen, Eugénie S; Carman, Tobey B; McGuire, A David

    2014-03-01

    The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970-2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared with simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions. PMID:24105949

  5. Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model.

    PubMed

    Euskirchen, Eugénie S; Carman, Tobey B; McGuire, A David

    2014-03-01

    The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970-2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared with simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions.

  6. Changes in the structure and function of northern Alaskan ecosystems when considering variable leaf-out times across groupings of species in a dynamic vegetation model

    USGS Publications Warehouse

    Euskirchen, E.S.; Carman, T.B.; McGuire, Anthony David

    2013-01-01

    The phenology of arctic ecosystems is driven primarily by abiotic forces, with temperature acting as the main determinant of growing season onset and leaf budburst in the spring. However, while the plant species in arctic ecosystems require differing amounts of accumulated heat for leaf-out, dynamic vegetation models simulated over regional to global scales typically assume some average leaf-out for all of the species within an ecosystem. Here, we make use of air temperature records and observations of spring leaf phenology collected across dominant groupings of species (dwarf birch shrubs, willow shrubs, other deciduous shrubs, grasses, sedges, and forbs) in arctic and boreal ecosystems in Alaska. We then parameterize a dynamic vegetation model based on these data for four types of tundra ecosystems (heath tundra, shrub tundra, wet sedge tundra, and tussock tundra), as well as ecotonal boreal white spruce forest, and perform model simulations for the years 1970 -2100. Over the course of the model simulations, we found changes in ecosystem composition under this new phenology algorithm compared to simulations with the previous phenology algorithm. These changes were the result of the differential timing of leaf-out, as well as the ability for the groupings of species to compete for nitrogen and light availability. Regionally, there were differences in the trends of the carbon pools and fluxes between the new phenology algorithm and the previous phenology algorithm, although these differences depended on the future climate scenario. These findings indicate the importance of leaf phenology data collection by species and across the various ecosystem types within the highly heterogeneous Arctic landscape, and that dynamic vegetation models should consider variation in leaf-out by groupings of species within these ecosystems to make more accurate projections of future plant distributions and carbon cycling in Arctic regions.

  7. Ice-Free Arctic Ocean?

    ERIC Educational Resources Information Center

    Science Teacher, 2005

    2005-01-01

    The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years, according to a new report. The melting is accelerating, and researchers were unable to identify any natural processes that might slow the deicing of the Arctic. "What really makes the Arctic different from…

  8. Arctic Economics Model

    1995-03-01

    AEM (Arctic Economics Model) for oil and gas was developed to provide an analytic framework for understanding the arctic area resources. It provides the capacity for integrating the resource and technology information gathered by the arctic research and development (R&D) program, measuring the benefits of alternaive R&D programs, and providing updated estimates of the future oil and gas potential from arctic areas. AEM enables the user to examine field or basin-level oil and gas recovery,more » costs, and economics. It provides a standard set of selected basin-specified input values or allows the user to input their own values. AEM consists of five integrated submodels: geologic/resource submodel, which distributes the arctic resource into 15 master regions, consisting of nine arctic offshore regions, three arctic onshore regions, and three souhtern Alaska (non-arctic) regions; technology submodel, which selects the most appropriate exploration and production structure (platform) for each arctic basin and water depth; oil and gas production submodel, which contains the relationship of per well recovery as a function of field size, production decline curves, and production decline curves by product; engineering costing and field development submodel, which develops the capital and operating costs associated with arctic oil and gas development; and the economics submodel, which captures the engineering costs and development timing and links these to oil and gas prices, corporate taxes and tax credits, depreciation, and timing of investment. AEM provides measures of producible oil and gas, costs, and ecomonic viability under alternative technology or financial conditions.« less

  9. The sensitivity of simulated competition between different plant functional types to subgrid-scale representation of vegetation in a land surface model

    NASA Astrophysics Data System (ADS)

    Shrestha, R. K.; Arora, V. K.; Melton, J. R.

    2016-03-01

    The Canadian Land Surface Scheme coupled to the Canadian Terrestrial Ecosystem Model is used to simulate competition between the model's seven non-crop plant functional types (PFTs) for available space. Our objective is to assess if the model is successfully able to reproduce the observed mix of PFTs and their fractional coverages and to what extent the simulated competition is affected by the manner in which the subgrid-scale variability of vegetation is represented. The model can be run either in a composite (single tile) configuration, where structural vegetation attributes of PFTs are aggregated for use in grid-averaged energy and water balance calculations, or a mosaic (multiple tiles) configuration, where separate energy and water balance calculations are performed for each PFT. The model realistically simulates the fractional coverages of trees, grasses, and bare ground, as well as that of individual tree and grass PFTs and their succession patterns. Our results show that the model is not overly sensitive to the manner in which subgrid-scale variability of vegetation is represented. Of the seven sites chosen across the globe to illustrate the difference between the two configurations, the simulated fractional coverage of PFTs are generally very similar (root-mean-square difference, RMSD, < 5%) between the composite and mosaic configurations at locations characterized by low heterogeneity (e.g., Amazonia, Vancouver Island, and the Tibetan Plateau), whereas at locations characterized by high heterogeneity (e.g., India, South Sudan and California), the two configurations yield somewhat different results (RMSD > 5%).

  10. Arctic Climate Systems Analysis

    SciTech Connect

    Ivey, Mark D.; Robinson, David G.; Boslough, Mark B.; Backus, George A.; Peterson, Kara J.; van Bloemen Waanders, Bart G.; Swiler, Laura Painton; Desilets, Darin Maurice; Reinert, Rhonda Karen

    2015-03-01

    This study began with a challenge from program area managers at Sandia National Laboratories to technical staff in the energy, climate, and infrastructure security areas: apply a systems-level perspective to existing science and technology program areas in order to determine technology gaps, identify new technical capabilities at Sandia that could be applied to these areas, and identify opportunities for innovation. The Arctic was selected as one of these areas for systems level analyses, and this report documents the results. In this study, an emphasis was placed on the arctic atmosphere since Sandia has been active in atmospheric research in the Arctic since 1997. This study begins with a discussion of the challenges and benefits of analyzing the Arctic as a system. It goes on to discuss current and future needs of the defense, scientific, energy, and intelligence communities for more comprehensive data products related to the Arctic; assess the current state of atmospheric measurement resources available for the Arctic; and explain how the capabilities at Sandia National Laboratories can be used to address the identified technological, data, and modeling needs of the defense, scientific, energy, and intelligence communities for Arctic support.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    Vegetation changes, such as shrub encroachment and wetland expansion, have been observed in many Arctic tundra regions. These changes feed back to permafrost and climate. Permafrost can be protected by soil shading through vegetation as it reduces the amount of solar energy available for thawing. Regional climate can be affected by a reduction in surface albedo as more energy is available for atmospheric and soil heating. Here, we compared the shortwave radiation budget of two common Arctic tundra vegetation types dominated by dwarf shrubs (Betula nana) and wet sedges (Eriophorum angustifolium) in North-East Siberia. We measured time series of the shortwave and longwave radiation budget above the canopy and transmitted radiation below the canopy. Additionally, we quantified soil temperature and heat flux as well as active layer thickness. The mean growing season albedo of dwarf shrubs was 0.15 ± 0.01, for sedges it was higher (0.17 ± 0.02). Dwarf shrub transmittance was 0.36 ± 0.07 on average, and sedge transmittance was 0.28 ± 0.08. The standing dead leaves contributed strongly to the soil shading of wet sedges. Despite a lower albedo and less soil shading, the soil below dwarf shrubs conducted less heat resulting in a 17 cm shallower active layer as compared to sedges. This result was supported by additional, spatially distributed measurements of both vegetation types. Clouds were a major influencing factor for albedo and transmittance, particularly in sedge vegetation. Cloud cover reduced the albedo by 0.01 in dwarf shrubs and by 0.03 in sedges, while transmittance was increased by 0.08 and 0.10 in dwarf shrubs and sedges, respectively. Our results suggest that the observed deeper active layer below wet sedges is not primarily a result of the summer canopy radiation budget. Soil properties, such as soil albedo, moisture, and thermal conductivity, may be more influential, at least in our comparison between dwarf shrub vegetation on relatively dry patches and

  12. Description and validation of an automated methodology for mapping mineralogy, vegetation, and hydrothermal alteration type from ASTER satellite imagery with examples from the San Juan Mountains, Colorado

    USGS Publications Warehouse

    Rockwell, Barnaby W.

    2012-01-01

    The efficacy of airborne spectroscopic, or "hyperspectral," remote sensing for geoenvironmental watershed evaluations and deposit-scale mapping of exposed mineral deposits has been demonstrated. However, the acquisition, processing, and analysis of such airborne data at regional and national scales can be time and cost prohibitive. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor carried by the NASA Earth Observing System Terra satellite was designed for mineral mapping and the acquired data can be efficiently used to generate uniform mineral maps over very large areas. Multispectral remote sensing data acquired by the ASTER sensor were analyzed to identify and map minerals, mineral groups, hydrothermal alteration types, and vegetation groups in the western San Juan Mountains, Colorado, including the Silverton and Lake City calderas. This mapping was performed in support of multidisciplinary studies involving the predictive modeling of surface water geochemistry at watershed and regional scales. Detailed maps of minerals, vegetation groups, and water were produced from an ASTER scene using spectroscopic, expert system-based analysis techniques which have been previously described. New methodologies are presented for the modeling of hydrothermal alteration type based on the Boolean combination of the detailed mineral maps, and for the entirely automated mapping of alteration types, mineral groups, and green vegetation. Results of these methodologies are compared with the more detailed maps and with previously published mineral mapping results derived from analysis of high-resolution spectroscopic data acquired by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) sensor. Such comparisons are also presented for other mineralized and (or) altered areas including the Goldfield and Cuprite mining districts, Nevada and the central Marysvale volcanic field, Wah Wah Mountains, and San Francisco Mountains, Utah. The automated

  13. On the potential of long wavelength imaging radars for mapping vegetation types and woody biomass in tropical rain forests

    NASA Technical Reports Server (NTRS)

    Rignot, Eric J.; Zimmermann, Reiner; Oren, Ram

    1995-01-01

    In the tropical rain forests of Manu, in Peru, where forest biomass ranges from 4 kg/sq m in young forest succession up to 100 kg/sq m in old, undisturbed floodplain stands, the P-band polarimetric radar data gathered in June of 1993 by the AIRSAR (Airborne Synthetic Aperture Radar) instrument separate most major vegetation formations and also perform better than expected in estimating woody biomass. The worldwide need for large scale, updated biomass estimates, achieved with a uniformly applied method, as well as reliable maps of land cover, justifies a more in-depth exploration of long wavelength imaging radar applications for tropical forests inventories.

  14. Five Years of Land Surface Phenology in a Large Scale Hydrological Manipulation Experiment in an Arctic Tundra Landscape

    NASA Astrophysics Data System (ADS)

    Goswami, S.; Gamon, J. A.; Tweedie, C. E.

    2010-12-01

    Climate change appears to be most pronounced at high northern latitudes. Many of the observed and modeled climate change responses in arctic tundra ecosystems have profound effects on surface energy budgets, land-atmosphere carbon exchange, plant phenology, and geomorphic processes. Detecting biotic responses to a changing environment is essential for understanding the consequences of global change. Plants can work as very effective indicators of changing conditions and, depending on the nature of the change, respond by increasing or decreasing amounts of green-leaf biomass, chlorophyll, and water content. Shifts in the composition and abundance of plant species have important effects on ecosystem processes such as net primary production and nutrient cycling. Vegetation is expected to be responsive to arctic warming, although there is some uncertainty as to how the interplay between geomorphic, hydrologic, climatic and other biotic will manifest over a range of spatial scales. The NSF-supported Biocomplexity project in Barrow, Alaska, involves experimental manipulation of water table (drained, flooded, and control treatments) in a vegetated arctic thaw lake basin to investigate the effects of altered hydrology on land-atmosphere carbon balance. In each experimental treatment, hyperspectral reflectance data were collected in the visible and near IR range of the spectrum using a robotic tram system that operated along a 300m tramline during the snow free growing period between June and August 2005-09. Water table depths and soil volumetric water content was also collected along these transects. The years 2005-2007 were control or unmanipulated experimental years and 2008 and 2009 were experimental years where water table was raised (+10cm) and lowered (-10cm) in flooding and draining experiments respectively. This presentation will document the change in phenology (NDVI) between years, treatments, and land cover types. Findings from this research have implications

  15. How does climate change influence Arctic mercury?

    PubMed

    Stern, Gary A; Macdonald, Robie W; Outridge, Peter M; Wilson, Simon; Chételat, John; Cole, Amanda; Hintelmann, Holger; Loseto, Lisa L; Steffen, Alexandra; Wang, Feiyue; Zdanowicz, Christian

    2012-01-01

    Recent studies have shown that climate change is already having significant impacts on many aspects of transport pathways, speciation and cycling of mercury within Arctic ecosystems. For example, the extensive loss of sea-ice in the Arctic Ocean and the concurrent shift from greater proportions of perennial to annual types have been shown to promote changes in primary productivity, shift foodweb structures, alter mercury methylation and demethylation rates, and influence mercury distribution and transport across the ocean-sea-ice-atmosphere interface (bottom-up processes). In addition, changes in animal social behavior associated with changing sea-ice regimes can affect dietary exposure to mercury (top-down processes). In this review, we address these and other possible ramifications of climate variability on mercury cycling, processes and exposure by applying recent literature to the following nine questions; 1) What impact has climate change had on Arctic physical characteristics and processes? 2) How do rising temperatures affect atmospheric mercury chemistry? 3) Will a decrease in sea-ice coverage have an impact on the amount of atmospheric mercury deposited to or emitted from the Arctic Ocean, and if so, how? 4) Does climate affect air-surface mercury flux, and riverine mercury fluxes, in Arctic freshwater and terrestrial systems, and if so, how? 5) How does climate change affect mercury methylation/demethylation in different compartments in the Arctic Ocean and freshwater systems? 6) How will climate change alter the structure and dynamics of freshwater food webs, and thereby affect the bioaccumulation of mercury? 7) How will climate change alter the structure and dynamics of marine food webs, and thereby affect the bioaccumulation of marine mercury? 8) What are the likely mercury emissions from melting glaciers and thawing permafrost under climate change scenarios? and 9) What can be learned from current mass balance inventories of mercury in the Arctic? The

  16. Vegetation cover and relationships of habitat-type with elevation on the Mississippi-Alabama Barrier Islands in the initial six years after Hurricane Katrina

    NASA Astrophysics Data System (ADS)

    Funderburk, W.; Carter, G. A.; Anderson, C. P.; Jeter, G. W., Jr.; Otvos, E. G.; Lucas, K. L.; Hopper, N. L.

    2015-12-01

    Quantifying change in vegetation and geomorphic features which occur during and after storm impact is necessary toward understanding barrier island habitat resiliency under continued climate warming and sea level rise. In August, 2005, the Mississippi-Alabama barrier islands, including, from west-to-east, Cat, West Ship, East Ship, Horn, Petit Bois and Dauphin islands, were completely inundated by the tidal surge of Hurricane Katrina. Overwash, scouring, burial under sand, and mechanical damage combined with saltwater flooding and post-storm drought resulted in immediate and long-term vegetation loss. Remotely-sensed data acquired before (2004-2005) and after (2005-2011) Katrina were compared via image classification to determine immediate storm impacts and assess natural re-growth of land area and vegetation. By 2008, merely three years after the storm, total land area of Cat, West Ship, East Ship, Horn, Petit Bois and West Dauphin had recovered to 92, 90, 33, 99, 93 and 91 percent, and total vegetated land area to 85, 101, 85, 94, 83 and 102 percent of pre-Katrina values, respectively. Habitat-type maps developed from field survey, SPOT-5 and radar data were compared with LIDAR-derived elevation models to assess 2010 habitat-type distribution with respect to ground elevation. Although median MSL elevations associated with habitat classes ranged only from 0.5 m to 1.4 m, habitat-type changed distinctively with decimeter-scale changes in elevation. Low marsh, high marsh, estuarine shrubland, slash pine woodland, beach dune, bare sand and beach dune herbland were associated with median elevations of 0.5, 0.9, 1.0, 1.1, 1.2, 1.3 and 1.4 m ± 0.1 m, respectively. The anticipated increases in sea level and tropical storm energy under a continually warming climate will likely inhibit the reformation of higher-elevation habitat-types, such as shrublands and woodlands, in the 21st century.

  17. Central Arctic Atmospheric SO2 pollution from smelters: Airborne detection and Arctic Haze formation

    NASA Astrophysics Data System (ADS)

    Arnold, F.; Nau, R.; Jurkat, T.; Schlager, H.; Minikin, A.; Dörnbrack, A.; Pirjola, L.; Stohl, A.

    2009-04-01

    Arctic Haze represents a dramatic manifestation of anthropogenic pollution of a remote and previously pristine atmospheric environment, which presently experiences faster climate warming than any other region on the planet. Arctic haze influences visibility, ecosystems, and may contribute to Arctic climate warming. In spring, Arctic Haze occupies large parts of the Arctic lower troposphere, the so called Arctic Dome. The most abundant Arctic Haze component is sulphate, which was previously thought to stem preferably from Extra-Arctic anthropogenic pollution sources. However, recent model simulations suggest that sulphate particle transport into the Arctic Dome is severely hindered. During the recent POLAR YEAR 2007/2008, in 2007, we have made the first Central Arctic SO2 measurements with high vertical and horizontal resolution and detected SO2 rich pollution plumes in the entire troposphere height range up to 9000 m. Below 2000 m, inside the Arctic Dome, these plumes were most pronounced and stemmed preferably from a giant Ni-Cu smelter complex, located in the Siberian sector of the Arctic Dome, near the city Norilsk, at a distance of 2100 km from our measurement region. Our measurements and accompanying model simulations indicate that SO2 emitted by that smelter complex represents a mayor if not the dominant precursor of Arctic Dome cloud condensation nuclei and haze particles. Along with SO2, were measured aerosol particles and additional trace gases including also gas-phase NOy (sum of reactive nitrogen gases). Importantly, the abundance ratio R=SO2/NOy is quite different for different SO2 source types (about 1-2 for fossil fuel combustion, <0.1 for bio mass burning, and about 40 for Ni/Cu smelting) and therefore serves as an SO2-source marker. In addition to our air craft measurements, we have made accompanying model simulations of pollutant transport and aerosol formation and growth. Our air craft measurements were part of the ASTAR 2007 (ASTAR=Arctic Study

  18. The effects of dust on vegetation--a review.

    PubMed

    Farmer, A M

    1993-01-01

    An increase in quarrying, open-cast mining and road traffic suggest that dust deposition onto vegetation may be increasing. This review describes the physical and chemical characters of a range of dust types. The effects of dust on crops, grasslands, heathlands, trees and woodlands, arctic bryophyte and lichen communities are identified. Dust may affect photosynthesis, respiration, transpiration and allow the penetration of phytotoxic gaseous pollutants. Visible injury symptoms may occur and generally there is decreased productivity. Most of the plant communities are affected by dust deposition so that community structure is altered. Epiphytic lichen and Sphagnum dominated communities are the most sensitive of those studied. However, there have been very few detailed studies on natural and semi-natural systems and some dust types are also very understudied. Recommendations for future research are made in order to overcome this deficiency. PMID:15091915

  19. The effects of dust on vegetation--a review.

    PubMed

    Farmer, A M

    1993-01-01

    An increase in quarrying, open-cast mining and road traffic suggest that dust deposition onto vegetation may be increasing. This review describes the physical and chemical characters of a range of dust types. The effects of dust on crops, grasslands, heathlands, trees and woodlands, arctic bryophyte and lichen communities are identified. Dust may affect photosynthesis, respiration, transpiration and allow the penetration of phytotoxic gaseous pollutants. Visible injury symptoms may occur and generally there is decreased productivity. Most of the plant communities are affected by dust deposition so that community structure is altered. Epiphytic lichen and Sphagnum dominated communities are the most sensitive of those studied. However, there have been very few detailed studies on natural and semi-natural systems and some dust types are also very understudied. Recommendations for future research are made in order to overcome this deficiency.

  20. Arctic Hydrology and the role of feedbacks in the climate system (Invited)

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.

    2009-12-01

    The effects of a warming climate on the terrestrial regions of the Arctic are already quite apparent and impacts to the hydrologic system are also quite evident. The broadest impacts to the terrestrial arctic regions will result through consequent effects of changing permafrost structure and extent. As the climate differentially warms in summer and winter, the permafrost will become warmer, the active layer (the layer of soil above the permafrost that annually experiences freeze and thaw) will become thicker, the lower boundary of permafrost will become shallower and permafrost extent will decrease in area. These simple structural changes will affect every aspect of the surface water and energy balances and local ecology. Surface moisture and surface temperature are the main driving variables in local terrestrial and atmospheric linkages. Surface temperature is the linchpin in energy fluxes since it links atmospheric thermal gradients, forcing convective heat transfer, with the subsurface thermal gradients, driving conductive heat transfer. Soil moisture exerts a strong influence upon energy fluxes through controls on evaporative heat flux, phase change in thawing of permafrost, and indirect effects on thermal conductivity. In order to understand and predict ecosystem responses to a changing climate and the resultant feedbacks, it is critical to quantify the dynamic interactions of soil moisture and temperature with changes in permafrost as a function of climatic processes, landscape type, and vegetation. In future climate scenarios, the Arctic is expected to be warmer, and experience greater precipitation. With the lengthening of the summer season, however, more of this precipitation will occur as rain. The periods of potential evaporation, and transpiration will also increase. Oddly enough, even now, the Arctic may be considered a desert. The vast wetlands that cover large portions of Alaska, Canada and Siberia exist because permafrost prevents soil moisture and

  1. Arctic Ocean outflow shelves in the changing Arctic: A review and perspectives

    NASA Astrophysics Data System (ADS)

    Michel, Christine; Hamilton, Jim; Hansen, Edmond; Barber, David; Reigstad, Marit; Iacozza, John; Seuthe, Lena; Niemi, Andrea

    2015-12-01

    Over the past decade or so, international research efforts, many of which were part of the International Polar Year, have accrued our understanding of the Arctic outflow shelves. The Arctic outflow shelves, namely the East Greenland Shelf (EGS) and the Canadian Arctic Archipelago (CAA), serve as conduits through which Arctic sea ice and waters and their properties are exported to the North Atlantic. These shelves play an important role in thermohaline circulation and global circulation patterns, while being influenced by basin-scale and regional changes taking place in the Arctic. Here, we synthesize the current knowledge on key forcings of primary production and ecosystem processes on the outflow shelves, as they influence their structure and functionalities and, consequently their role in Arctic Ocean productivity and global biogeochemical cycles. For the CAA, a fresh outlook on interannual and decadal physical and biological time-series reveals recent changes in productivity patterns, while an extensive analysis of sea ice conditions over the past 33 years (1980-2012) demonstrates significant declines in multi-year ice and a redistribution of ice types. For the EGS, our analysis shows that sea ice export strongly contributes to structuring spatially diverse productivity regimes. Despite the large heterogeneity in physical and biological processes within and between the outflow shelves, a conceptual model of productivity regimes is proposed, helping identify general productivity patterns and key forcings. The different productivity regimes are expected to respond differently to current and future Arctic change, providing a useful basis upon which to develop predictive scenarios of future productivity states. Current primary production estimates for both outflow shelves very likely underestimate their contribution to total Arctic production.

  2. Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland.

    PubMed

    Shao, Xuexin; Yang, Wenying; Wu, Ming

    2015-01-01

    Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81 mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands.

  3. Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

    PubMed Central

    Shao, Xuexin; Yang, Wenying; Wu, Ming

    2015-01-01

    Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands. PMID:26560310

  4. Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland.

    PubMed

    Shao, Xuexin; Yang, Wenying; Wu, Ming

    2015-01-01

    Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81 mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands. PMID:26560310

  5. Relative roles of different-sized herbivores and plant-plant interactions in tall shrub tundra vegetation

    NASA Astrophysics Data System (ADS)

    Ravolainen, Virve; Ims, Rolf; Bårdsen, Bård-Jørgen; Stien, Audun; Kollstrøm, Julie; Lægreid, Eiliv; Bråthen, Kari Anne

    2013-04-01

    Tall shrubs play important roles in the ecology of Arctic tundra ecosystems, including support of high shrub-associated biodiversity and regulation of a range of ecosystem processes. Tall shrub patches and herbaceous vegetation surrounding them often form a two-state vegetation mosaic. Such tall shrub tundra vegetation is an important locus for current vegetation changes in the Arctic. Both abiotic and biotic drivers are known to influence the shrub component. However, although expansion of the shrub state has received much focus lately, relative strengths of the multiple drivers of vegetation state are currently not fully understood. We investigated the role of herbivory relative to temperature and relative to plant-plant interactions, conducting a field survey and experimental studies at large spatial scales in riparian tall shrub tundra in Norway. We found both summer temperatures and summer grazing by reindeer (Rangifer tarandus) to affect tall shrub distribution and expansion potential. Furthermore, we found strong and rapid shrub growth change in response to abundance of key arctic herbivores; small rodents. Finally, we quantified the relative importance of neighboring plants and both herbivore types to recruiting tall shrubs. The previously unforeseen rate at which tall shrub tundra responded to altered herbivore pressures further exemplifies its central role in the tundra ecosystems, promoting tall shrub tundra as a bell-whether of change with respect to both abiotic and biotic drivers. While many of the results clearly relate to herbivory, neighboring plants or climate as drivers, some variation remains unexplained warranting future research focus on this highly dynamic part of the tundra ecosystem. Our results suggest that spatially variable biotic interactions are likely to modify forcing by climate, calling for an ecosystem approach when studying change in tundra ecosystems.

  6. Improvement of boreal vegetation modelling and climate interactions through the introduction of new bryophyte and artic-shrub plant functional types in a land surface model.

    NASA Astrophysics Data System (ADS)

    Druel, Arsène; Krinner, Gerhard; Peylin, Philippe; Ciais, Philippe; Viovy, Nicolas; Peregon, Anna

    2016-04-01

    Boreal and tundra vegetation, which represents 22% of the global land area, has had a significant impact on climate through changes of albedo, snow cover, soil thermal dynamics, etc. However, it is frequently poorly represented in earth system models used for climate predictions. We improved the description of high-latitude vegetation and its interactions with the environment in the ORCHIDEE land surface model by creating new plant functional types with specific biogeochemical and biophysical properties: boreal shrubs, bryophytes (mosses and lichens) and boreal C3 grasses. The introduction of shrub specificities allows for an intermediate stratum between trees and grasses, with a new carbon allometry within the plant, inducing new interactions between wooden species and their environment, especially the complex snow-shrubs interaction. Similarly, the introduction of non-vascular plants (i.e. bryophytes) involves numerous changes both in physical and biological processes, such as the response of photosynthesis to surface humidity, the decomposition of carbon and the soil thermal conductivity. These changes in turn lead to new processes and interactions between vegetation and moisture (soil and air), carbon cycle, energy balance, etc. For the boreal C3 grasses we did not include new processes compared to the generic C3 grass PFT, but improved the realism of the carbon and water budgets with new boreal adjusted parameters. We assess the performance of the modified ORCHIDEE land surface model and in particular its ability to represent the new plant types (their phenology etc.), and evaluate the effects of these new PFTs on the simulated energy, water and carbon balances of boreal ecosystems. The potential impact of these refinements on future climate simulations will be discussed.

  7. NASA's Arctic Voyage 2010

    NASA Video Gallery

    NASA's first oceanographic research expedition left Alaska on June 15, 2010. The ICESCAPE mission will head into the Arctic to study sea ice and the changing ocean ecosystem. Listen to the scientis...

  8. Arctic hydrology and meteorology

    SciTech Connect

    Kane, D.L.

    1989-01-01

    To date, five years of hydrologic and meteorologic data have been collected at Imnavait Creek near Toolik Lake, Alaska. This is the most complete set of field data of this type collected in the Arctic of North America. These data have been used in process-oriented research to increase our understanding of atmosphere/hydrosphere/biosphere/lithosphere interactions. Basically, we are monitoring heat and mass transfer between various spheres to quantify rates. These could be rates of mass movement such as hillslope flow or rates of heat transfer for active layer thawing or combined heat and mass processes such as evapotranspiration. We have utilized a conceptual model to predict hydrologic processes. To test the success of this model, we are comparing our predicted rates of runoff and snowmelt to measured valves. We have also used a surface energy model to simulate active layer temperatures. The final step in this modeling effort to date was to predict what impact climatic warming would have on active layer thicknesses and how this will influence the hydrology of our research watershed by examining several streambeds.

  9. Influence of the type of vegetable oil on the drug release profile from lipid-core nanocapsules and in vivo genotoxicity study.

    PubMed

    Rigo, Lucas Almeida; Frescura, Viviane; Fiel, Luana; Coradini, Karine; Ourique, Aline Ferreira; Emanuelli, Tatiana; Quatrin, Andréia; Tedesco, Solange; Silva, Cristiane B da; Guterres, Silvia Staniçuaski; Pohlmann, Adriana Raffin; Beck, Ruy Carlos Ruver

    2014-11-01

    The use of rice bran (RB), soybean (SB) or sunflower seed (SF) oils to prepare lipid-core nanocapsules (LNCs) as controlled drug delivery systems was investigated. LNCs were prepared by interfacial deposition using the preformed polymer method. All formulations showed negative zeta potential and adequate nanotechnological characteristics (particle size 220-230  nm, polydispersity index < 0.20). The environmental safety was evaluated through an in vivo protocol (Allium cepa test) and LNCs containing RB, SB or SF oils did not present genotoxic potential. Clobetasol propionate (CP) was selected as a model drug to evaluate the influence of the type of vegetable oil on the control of the drug release from LNCs. Biphasic drug release profiles were observed for all formulations. After 168  h, the concentration of drug released from the formulation containing SF oil was lower (0.36  mg/mL) than from formulations containing SB (0.40  mg/mL) or RB oil (0.45  mg/mL). Good correlations between the consistency indices for the LNC cores and the burst and sustained drug release rate constants were obtained. Therefore, the type of the vegetal oil was shown as an important factor governing the control of drug release from LNCs.

  10. USGS Arctic science strategy

    USGS Publications Warehouse

    Shasby, Mark; Smith, Durelle

    2015-07-17

    The United States is one of eight Arctic nations responsible for the stewardship of a polar region undergoing dramatic environmental, social, and economic changes. Although warming and cooling cycles have occurred over millennia in the Arctic region, the current warming trend is unlike anything recorded previously and is affecting the region faster than any other place on Earth, bringing dramatic reductions in sea ice extent, altered weather, and thawing permafrost. Implications of these changes include rapid coastal erosion threatening villages and critical infrastructure, potentially significant effects on subsistence activities and cultural resources, changes to wildlife habitat, increased greenhouse-gas emissions from thawing permafrost, threat of invasive species, and opening of the Arctic Ocean to oil and gas exploration and increased shipping. The Arctic science portfolio of the U.S. Geological Survey (USGS) and its response to climate-related changes focuses on landscapescale ecosystem and natural resource issues and provides scientific underpinning for understanding the physical processes that shape the Arctic. The science conducted by the USGS informs the Nation's resource management policies and improves the stewardship of the Arctic Region.

  11. Arctic freshwater synthesis: Introduction

    NASA Astrophysics Data System (ADS)

    Prowse, T.; Bring, A.; Mârd, J.; Carmack, E.

    2015-11-01

    In response to a joint request from the World Climate Research Program's Climate and Cryosphere Project, the International Arctic Science Committee, and the Arctic Council's Arctic Monitoring and Assessment Program, an updated scientific assessment has been conducted of the Arctic Freshwater System (AFS), entitled the Arctic Freshwater Synthesis (AFSΣ). The major reason for joint request was an increasing concern that changes to the AFS have produced, and could produce even greater, changes to biogeophysical and socioeconomic systems of special importance to northern residents and also produce extra-Arctic climatic effects that will have global consequences. Hence, the key objective of the AFSΣ was to produce an updated, comprehensive, and integrated review of the structure and function of the entire AFS. The AFSΣ was organized around six key thematic areas: atmosphere, oceans, terrestrial hydrology, terrestrial ecology, resources and modeling, and the review of each coauthored by an international group of scientists and published as separate manuscripts in this special issue of Journal of Geophysical Research-Biogeosciences. This AFSΣ—Introduction reviews the motivations for, and foci of, previous studies of the AFS, discusses criteria used to define the domain of the AFS, and details key characteristics of the definition adopted for the AFSΣ.

  12. Laboratory testing of dispersants under Arctic conditions

    SciTech Connect

    Brandvik, P.J.; Knudsen, O.O; Moldestad, M.O.; Daling, P.S.

    1995-06-01

    The effectiveness of relevant dispersants for use under Arctic conditions has been tested with the IFP dilution test. Arctic conditions in this context are defined as low temperature (0 C) and water salinities varying between 0.5% and 3.5%. The study was performed in three steps with a screening activity first, where 14 dispersants were tested on water-in-oil (w/o) emulsions from two weathered oil types. In the next step five dispersants were tested on both weathered water free oils and w/o emulsions from four different oil types. As a third step, dispersant effectiveness as a function of salinity (0.5 to 3.5%) was tested with the most effective dispersants at high and low salinity. The results from this study shows that many of the most used dispersants which previously have shown an excellent effectiveness at high sea water salinity (3.5%) may give a very low effectiveness at low salinity (0.5%). Recently developed products especially designed for low salinity use (e.g. Inipol IPF) are very effective at low salinities, but suffer from a rather poor effectiveness at higher salinities. This is of significant operational importance in Arctic oil spill combat operations since the salinity of the surface water may vary due to ice melting. This study of dispersant`s effectiveness under Arctic conditions shows the need for development of dispersants with high effectiveness both at low temperature (0 C) and over a wide range of salinities (3.5% to 0.5%). Dispersant development has been a limited but important activity at IKU for the last five years and one of the objectives for an ongoing Arctic program at IKU is to develop such new dispersants for use under Arctic conditions.

  13. Greening of the Arctic: Partitioning Warming Versus Reindeer Herbivory for Willow Populations on Yamal Peninsula, Northwest Siberia

    NASA Astrophysics Data System (ADS)

    Forbes, B. C.; Macias-Fauria, M.; Zetterberg, P.; Kumpula, T.

    2012-12-01

    Arctic warming has been linked to observed increases in tundra shrub cover and growth in recent decades on the basis of significant relationships between deciduous shrub growth/biomass and temperature. These vegetation trends have been linked to Arctic sea-ice decline and thus to the sea-ice/albedo feedback known as Arctic amplification. However, the interactions between climate, sea ice, tundra vegetation and herbivores remain poorly understood. Recently we revealed a 50-year growth response over a >100,000 km2 area to a rise in summer temperature for willow (Salix lanata), one the most abundant shrub genera at and north of the continental treeline and an important source of reindeer forage in spring, summer and autumn. We demonstrated that whereas plant productivity is related to sea ice in late spring, the growing season peak responds to persistent synoptic-scale air masses over West Siberia associated with Fennoscandian weather systems through the Rossby wave train. Substrate was important for biomass accumulation, yet a strong correlation between growth and temperature encompasses all observed soil types. Vegetation was especially responsive to temperature in early summer. However, the role of herbivory was not addressed. The present data set explores the relationship between long-term herbivory and growth trends of shrubs experiencing warming in recent decades. Semi-domestic reindeer managed by indigenous Nenets nomads occur at high densities in summer on exposed ridge tops and graze heavily on prostrate and low erect willows. A few meters away in moderately sloped landslides tall willows remain virtually ungrazed as their canopies have grown above the browse line of ca. 180 cm. Here we detail the responses of neighboring shrub populations with and without intensive herbivory yet subject to the same decadal warming trend.

  14. Electronic atlas of the Russian Arctic coastal zone

    NASA Astrophysics Data System (ADS)

    Drozdov, D. S.; Rivkin, F. M.; Rachold, V.; Ananjeva-Malkova, G. V.; Ivanova, N. V.; Chehina, I. V.; Koreisha, M. M.; Korostelev, Yu. V.; Melnikov, E. S.

    2005-06-01

    A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000 1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country.

  15. Arctic Late Cretaceous and Paleocene Plant Community Succession

    NASA Astrophysics Data System (ADS)

    Herman, Alexei; Spicer, Robert; Daly, Robert; Jolley, David; Ahlberg, Anders; Moiseeva, Maria

    2010-05-01

    The Arctic abounds with Late Cretaceous and Paleocene plant fossils attesting to a thriving, diverse, but now extinct polar ecosystem that sequestered vast amounts of carbon. Through detailed examination of plant remains and their distributions in time and space with respect to their entombing sedimentary facies, it has been possible to reconstruct changes in Arctic vegetation composition and dynamics through the Late Cretaceous and into the Paleocene. Based on over 10,000 leaf remains, fossil wood and palynomorph assemblages from northeastern Russia and northern Alaska and palynological data from elsewhere in the Arctic we identify a number of successional plant communities (SPCs) representing seral development from early (pioneer), through middle to late SPCs and climax vegetation. We recognise that (1) Equisetites and some ferns (typically Birisia, but after the beginning of the Maastrichtian, Onoclea) were obligatory components of the early SPCs; (2) first rare angiosperms (e.g. the dicot Vitiphyllum multifidum) appeared in the middle SPCs of the Arctic in the Early - Middle Albian; (3) from late Albian times onwards angiosperms became abundant in the middle SPCs of the Arctic, but were still rare in the earlier and later SPCs; (4) monocots appeared in the Maastrichtian early SPCs; (5) all Arctic Cretaceous late SPCs (and climax vegetation) were dominated by conifers; (6) Arctic SPCs were more numerous and diverse under warm climates than cold; (7) during the Albian and late Cretaceous, advanced (Cenophytic, angiosperm-dominated) plant communities coexisted with those of a more relictual (Mesophytic, dominated by ferns and gymnosperms) aspect, and plants composing these communities did not mix; (8) coal-forming environments (mires) remained conifer, fern and bryophyte dominated throughout the late Cretaceous and Paleocene with little penetration of woody angiosperm components and thus are conservative and predominantly Mesophytic in character; (9) bryophytes

  16. The Arctic Visiting Speakers Program

    NASA Astrophysics Data System (ADS)

    Wiggins, H. V.; Fahnestock, J.

    2013-12-01

    The Arctic Visiting Speakers Program (AVS) is a program of the Arctic Research Consortium of the U.S. (ARCUS) and funded by the National Science Foundation. AVS provides small grants to researchers and other Arctic experts to travel and share their knowledge in communities where they might not otherwise connect. The program aims to: initiate and encourage arctic science education in communities with little exposure to arctic research; increase collaboration among the arctic research community; nurture communication between arctic researchers and community residents; and foster arctic science education at the local level. Individuals, community organizations, and academic organizations can apply to host a speaker. Speakers cover a wide range of arctic topics and can address a variety of audiences including K-12 students, graduate and undergraduate students, and the general public. Preference is given to tours that reach broad and varied audiences, especially those targeted to underserved populations. Between October 2000 and July 2013, AVS supported 114 tours spanning 9 different countries, including tours in 23 U.S. states. Tours over the past three and a half years have connected Arctic experts with over 6,600 audience members. Post-tour evaluations show that AVS consistently rates high for broadening interest and understanding of arctic issues. AVS provides a case study for how face-to-face interactions between arctic scientists and general audiences can produce high-impact results. Further information can be found at: http://www.arcus.org/arctic-visiting-speakers.

  17. Trajectory of the Arctic as an integrated system.

    PubMed

    Hinzman, Larry D; Deal, Clara J; McGuire, A David; Mernild, Sebastian H; Polyakov, Igor V; Walsh, John E

    2013-12-01

    Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic system and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.

  18. Trajectory of the Arctic as an integrated system.

    PubMed

    Hinzman, Larry D; Deal, Clara J; McGuire, A David; Mernild, Sebastian H; Polyakov, Igor V; Walsh, John E

    2013-12-01

    Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic system and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content. PMID:24555312

  19. Trajectory of the arctic as an integrated system

    USGS Publications Warehouse

    Hinzman, Larry; Deal, Clara; McGuire, Anthony David; Mernild, Sebastian H.; Polyakov, Igor V.; Walsh, John E.

    2013-01-01

    Although much remains to be learned about the Arctic and its component processes, many of the most urgent scientific, engineering, and social questions can only be approached through a broader system perspective. Here, we address interactions between components of the Arctic System and assess feedbacks and the extent to which feedbacks (1) are now underway in the Arctic; and (2) will shape the future trajectory of the Arctic system. We examine interdependent connections among atmospheric processes, oceanic processes, sea-ice dynamics, marine and terrestrial ecosystems, land surface stocks of carbon and water, glaciers and ice caps, and the Greenland ice sheet. Our emphasis on the interactions between components, both historical and anticipated, is targeted on the feedbacks, pathways, and processes that link these different components of the Arctic system. We present evidence that the physical components of the Arctic climate system are currently in extreme states, and that there is no indication that the system will deviate from this anomalous trajectory in the foreseeable future. The feedback for which the evidence of ongoing changes is most compelling is the surface albedo-temperature feedback, which is amplifying temperature changes over land (primarily in spring) and ocean (primarily in autumn-winter). Other feedbacks likely to emerge are those in which key processes include surface fluxes of trace gases, changes in the distribution of vegetation, changes in surface soil moisture, changes in atmospheric water vapor arising from higher temperatures and greater areas of open ocean, impacts of Arctic freshwater fluxes on the meridional overturning circulation of the ocean, and changes in Arctic clouds resulting from changes in water vapor content.

  20. Shoot versus Root Signal Involvement in Nodulation and Vegetative Growth in Wild-Type and Hypernodulating Soybean Genotypes.

    PubMed Central

    Sheng, C.; Harper, J. E.

    1997-01-01

    Grafting studies involving Williams 82 (normally nodulating) and NOD1-3 (hypernodulating) soybean (Glycine max [L.] Merr.) lines and Lablab purpureus were used to evaluate the effect of shoot and root on nodulation control and plant growth. A single- or double-wedge graft technique, with superimposed partial defoliation, was used to separate signal control from a photosynthate supply effect. Grafting of hypernodulated soybean shoots to roots of Williams 82 or L. purpureus resulted in increased nodule numbers. Grafting of two shoots to one root enhanced root growth in both soybean genotypes, whereas the nodule number was a function of shoot genotype but not of the photosynthetic area. In double-shoot, single-root-grafted plants, removing trifoliolate leaves from either Williams 82 or NOD1-3 shoots decreased root and shoot dry matter, attributable to decreased photosynthetic source. Concurrently, Williams 82 shoot defoliation increased the nodule number, whereas NOD1-3 shoot defoliation decreased the nodule number on both soybean and L. purpureus roots. It was concluded that (a) soybean leaves are the dominant site of autoregulatory signal production, which controls the nodule number; (b) soybean and L. purpureus have a common, translocatable, autoregulatory control signal; (c) seedling vegetative growth and nodule number are independently controlled; and (d) two signals, inhibitor and promoter, may be involved in controlling legume nodule numbers. PMID:12223646

  1. The Sensitivity of Simulated Competition Between Different Plant Functional Types to Subgrid Scale Representation of Vegetation in a Land Surface Model

    NASA Astrophysics Data System (ADS)

    Shrestha, R. K.; Arora, V.; Melton, J. R.

    2014-12-01

    Vegetation is a dynamic component of the earth system that affects weather and climate at hourly to centennial time scales. However, most current dynamic vegetation models do not explicitly simulate competition among Plant Functional Types (PFTs). Here we use the coupled CLASS-CTEM model (Canadian Land Surface Scheme coupled to Canadian Terrestrial Ecosystem Model) to explicitly simulate competition between nine PFTs for available space using a modified version of Lotka - Volterra (LV) predator-prey equations. The nine PFTs include evergreen and deciduous needleleaf trees, evergreen and cold and drought deciduous broadleaf trees and C3 and C4 crops and grasses. The CLASS-CTEM model can be configured either in the composite (single tile) or the mosaic (multiple tiles) mode. Our results show that the model is sensitive to the chosen mode. The simulated fractional coverage of PFTs are similar between two approaches at some locations whereas at the other locations the two approaches yield different results. The simulated fractional coverage of PFTs are also compared with the available observations-based estimates. Simulated results at selected locations across the globe show that the model is able to realistically simulate the fractional coverage of tree and grass PFTs and the bare fraction, as well as the fractional coverage of individual tree and grass PFTs. Along with the observed patterns of vegetation distribution the CLASS-CTEM modelling framework is also able to simulate realistic succession patterns. Some differences remain and these are attributed to the coarse spatial resolution of the model (~3.75°) and the limited number of PFTs represented in the model.

  2. High-latitude steppe vegetation and the mineral nutrition of Pleistocene herbivores

    NASA Astrophysics Data System (ADS)

    Davydov, S. P.; Davydova, A.; Makarevich, R.; Loranty, M. M.; Boeskorov, G.

    2014-12-01

    High-latitude steppes were widespread and zonal in the Late Pleistocene and formed a landscape basis for the Mammoth Biome. Now the patches of these steppes survived on steep slopes under southern aspects. These steppes serve as unique information sources about the Late Pleistocene "Mammoth" steppe. Numerous data obtained by palynological, carpological, and DNA analysis of plant remains from feces and stomach contents of Pleistocene herbivore mummies, as well as from buried soils and enclosing deposits show that they are similar to modern steppe plant assemblage in taxa composition. Plant's nutrient concentrations are of fundamental importance across Pleistocene grass-rich ecosystems because of their role in the support of large herbivores. The average weight of an adult mammoth skeleton (about 0.5 tons) and of a woolly rhinoceros (about 0.2 tons) clearly suggests this. Detailed studies on fossil bone remains showed mineral deficiency in large Pleistocene herbivores. A three-year study of ash and mineral contents of two types of relict steppe vegetation at the Kolyma Lowland, Arctic Siberia has been carried out. Nowadays refugia of similar vegetation are located not far (1 - 15km) from the Yedoma permafrost outcrops were abundant fossil remains are found. Dominant species of the steppe vegetation were sampled. Preliminary studies indicate that the ash-content varied 1.5-2 times in speceies of steppe herbs. The Ca, P, Mg, K element contents was higher for most steppe species than in the local herbaceous vegetation, especially in Ca and P. One of the most important elements of the mineral nutrition, the phosphorus, was always found in higher concentrations in the steppe vegetation than in plants of recently dominant landscapes of the study area. It should be noted that the mineral nutrient content of the modern steppe vegetation of Siberian Arctic is comparable to that of the recent zonal steppe of Transbaikal Region. This study supports the hypothesis that

  3. Arctic Rabies – A Review

    PubMed Central

    Mørk, Torill; Prestrud, Pål

    2004-01-01

    Rabies seems to persist throughout most arctic regions, and the northern parts of Norway, Sweden and Finland, is the only part of the Arctic where rabies has not been diagnosed in recent time. The arctic fox is the main host, and the same arctic virus variant seems to infect the arctic fox throughout the range of this species. The epidemiology of rabies seems to have certain common characteristics in arctic regions, but main questions such as the maintenance and spread of the disease remains largely unknown. The virus has spread and initiated new epidemics also in other species such as the red fox and the racoon dog. Large land areas and cold climate complicate the control of the disease, but experimental oral vaccination of arctic foxes has been successful. This article summarises the current knowledge and the typical characteristics of arctic rabies including its distribution and epidemiology. PMID:15535081

  4. Arctic Sea Ice Maximum 2011

    NASA Video Gallery

    AMSR-E Arctic Sea Ice: September 2010 to March 2011: Scientists tracking the annual maximum extent of Arctic sea ice said that 2011 was among the lowest ice extents measured since satellites began ...

  5. Atmospheric heat transfer to the Arctic under main synoptic processes

    NASA Astrophysics Data System (ADS)

    Yurova, Alla; Gnatiuk, Natalia; Bobylev, Leonid; Zhu, Yali

    2016-04-01

    Arctic - mid-latitude teleconnections are operating in both ways and behind them are potentially some causes of the enhanced Arctic warming (e.g., through heat transfer from lower to higher latitudes) and the feedbacks from the Arctic climate to the mid-latitude weather patterns. In order to explain the variability of the surface air temperature in the Arctic, we aim to analyse the typical synoptic situations that, we hypothesize, are characterized by a specific patterns of heat exchange between the Arctic and mid-latitudes. According to classification of synoptic processes in the Arctic developed at the Arctic and Antarctic Research Institute (AARI) in St. Petersburg major typical groups of synoptic situations in the Arctic are few (six). They correspond to position and intensity of low- and high-pressure centres. Therefore, the whole data sample for the winter period for the entire period of instrumental observations (archive exists back to 1939) can be split into six groups that sub-sample each of six groups/types of synoptic situations. Then heat transfer to the Arctic can be estimated as the divergence of the horizontal (advective) heat flux (the product of wind speed and temperature gradient) within each vertical atmospheric layer, which is calculated based on the ERA Interim Reanalysis data for the winter season (1979-now). Mapping heat divergence fields will reveal the main mid-latitude sources of heat transported to the Arctic, average for the whole data sample and for each of the six main groups of synoptic situations. This work was supported by RFBR grants 16-55-53031

  6. Interactions Among Livestock Grazing, Vegetation Type, and Fire Behavior in the Murphy Wildland Fire Complex in Idaho and Nevada, July 2007

    USGS Publications Warehouse

    Launchbaugh, Karen; Brammer, Bob; Brooks, Matthew L.; Bunting, Stephen C.; Clark, Patrick; Davison, Jay; Fleming, Mark; Kay, Ron; Pellant, Mike; Pyke, David A.

    2008-01-01

    A series of wildland fires were ignited by lightning in sagebrush and grassland communities near the Idaho-Nevada border southwest of Twin Falls, Idaho in July 2007. The fires burned for over two weeks and encompassed more than 650,000 acres. A team of scientists, habitat specialists, and land managers was called together by Tom Dyer, Idaho BLM State Director, to examine initial information from the Murphy Wildland Fire Complex in relation to plant communities and patterns of livestock grazing. Three approaches were used to examine this topic: (1) identify potential for livestock grazing to modify fuel loads and affect fire behavior using fire models applied to various vegetation types, fuel loads, and fire conditions; (2) compare levels of fuel consumed within and among major vegetation types; and (3) examine several observed lines of difference and discontinuity in fuel consumed to determine what factors created these contrasts. The team found that much of the Murphy Wildland Fire Complex burned under extreme fuel and weather conditions that likely overshadowed livestock grazing as a factor influencing fire extent and fuel consumption in many areas where these fires burned. Differences and abrupt contrast lines in the level of fuels consumed were affected mostly by the plant communities that existed on a site before fire. A few abrupt contrasts in burn severity coincided with apparent differences in grazing patterns of livestock, observed as fence-line contrasts. Fire modeling revealed that grazing in grassland vegetation can reduce surface rate of spread and fire-line intensity to a greater extent than in shrubland types. Under extreme fire conditions (low fuel moisture, high temperatures, and gusty winds), grazing applied at moderate utilization levels has limited or negligible effects on fire behavior. However, when weather and fuel-moisture conditions are less extreme, grazing may reduce the rate of spread and intensity of fires allowing for patchy burns with

  7. Climate of the Arctic marine environment.

    PubMed

    Walsh, John E

    2008-03-01

    The climate of the Arctic marine environment is characterized by strong seasonality in the incoming solar radiation and by tremendous spatial variations arising from a variety of surface types, including open ocean, sea ice, large islands, and proximity to major landmasses. Interannual and decadal-scale variations are prominent features of Arctic climate, complicating the distinction between natural and anthropogenically driven variations. Nevertheless, climate models consistently indicate that the Arctic is the most climatically sensitive region of the Northern Hemisphere, especially near the sea ice margins. The Arctic marine environment has shown changes over the past several decades, and these changes are part of a broader global warming that exceeds the range of natural variability over the past 1000 years. Record minima of sea ice coverage during the past few summers and increased melt from Greenland have important implications for the hydrographic regime of the Arctic marine environment. The recent changes in the atmosphere (temperature, precipitation, pressure), sea ice, and ocean appear to be a coordinated response to systematic variations of the large-scale atmospheric circulation, superimposed on a general warming that is likely associated with increasing greenhouse gases. The changes have been sufficiently large in some sectors (e.g., the Bering/Chukchi Seas) that consequences for marine ecosystems appear to be underway. Global climate models indicate an additional warming of several degrees Celsius in much of the Arctic marine environment by 2050. However, the warming is seasonal (largest in autumn and winter), spatially variable, and closely associated with further retreat of sea ice. Additional changes predicted for 2050 are a general decrease of sea level pressure (largest in the Bering sector) and an increase of precipitation. While predictions of changes in storminess cannot be made with confidence, the predicted reduction of sea ice cover will

  8. Applicability of a carbamate insecticide multiresidue method for determining additional types of pesticides in fruits and vegetables.

    PubMed

    Krause, R T; August, E M

    1983-03-01

    Several fruits and vegetables were fortified at a low (0.02-0.5 ppm) and at a high (0.1-5 ppm) level with pesticides and with a synergist, and recoveries were determined. Analyses were performed by using 3 steps of a multiresidue method for determining N-methylcarbamates in crops: methanol extraction followed by removal of plant co-extractives by solvent partitioning and chromatography with a charcoal-silanized Celite column. Eleven compounds were determined by using a high performance liquid chromatograph equipped with a reverse phase column and a fluorescence detector. Twelve additional compounds were determined by using a gas-liquid chromatograph equipped with a nonpolar packed column and an electron capture or flame photometric detector. Recoveries of 10 pesticides (azinphos ethyl, azinphos methyl, azinphos methyl oxygen analog, carbaryl, carbofuran, naphthalene acetamide, naphthalene acetic acid methyl ester, napropamide, phosalone, and phosalone oxygen analog) and the synergist piperonyl butoxide, which were determined by high performance liquid chromatography, averaged 100% (range 86-117) at the low fortification level and 102% (range 93-115) at the high fortification level. Quantitative recovery of naphthalene acetamide through the method required that an additional portion of eluting solution be passed through the charcoal column. Recoveries of 7 additional pesticides (dimethoate, malathion, methyl parathion, mevinphos, parathion, phorate oxygen analog, and pronamide), which were determined by gas-liquid chromatography (GLC), averaged 108% (range 100-120) at the low fortification level and 107% (range 99-122) at the high fortification level. DDT, diazinon, dieldrin, phorate, and pirimiphos ethyl, which were determined by GLC, were not quantitatively recovered. PMID:6853408

  9. More Arctic research needed

    NASA Astrophysics Data System (ADS)

    Bush, Susan

    The desire to achieve a balance between Arctic and Antarctic study was the message of the Senate Committee on Commerce, Science, and Transportation, which heard testimony on the need for more Arctic research on April 24. Ted Stevens (R-Alaska) noted that since 1986, study in the area has not increased as the National Science Foundation has claimed, but rather, owing to inflation, has merely kept pace. Robert Correll, assistant director of geosciences at NSF and chair of the Interagency Arctic Oceans Working Group, gave several reasons why the Arctic is an important area for study by the scientific community. Its unique environment, he said, makes it a natural laboratory. And due to its environmental sensitivity, it may provide one of the earliest indicators of global climate change. Also, its geographic location makes it a “window on space,” some of the world's largest mineral and petroleum resources are in the Arctic, and the region has great strategic and military importance.

  10. FIRE Arctic Clouds Experiment

    NASA Technical Reports Server (NTRS)

    Curry, J. A.; Hobbs, P. V.; King, M. D.; Randall, D. A.; Minnis, P.; Issac, G. A.; Pinto, J. O.; Uttal, T.; Bucholtz, A.; Cripe, D. G.; Gerber, H.; Fairall, C. W.; Garrett, T. J.; Hudson, J.; Intrieri, J. M.; Jakob, C.; Jensen, T.; Lawson, P.; Marcotte, D.; Nguyen, L.

    1998-01-01

    An overview is given of the First ISCCP Regional Experiment (FIRE) Arctic Clouds Experiment that was conducted in the Arctic during April through July, 1998. The principal goal of the field experiment was to gather the data needed to examine the impact of arctic clouds on the radiation exchange between the surface, atmosphere, and space, and to study how the surface influences the evolution of boundary layer clouds. The observations will be used to evaluate and improve climate model parameterizations of cloud and radiation processes, satellite remote sensing of cloud and surface characteristics, and understanding of cloud-radiation feedbacks in the Arctic. The experiment utilized four research aircraft that flew over surface-based observational sites in the Arctic Ocean and Barrow, Alaska. In this paper we describe the programmatic and science objectives of the project, the experimental design (including research platforms and instrumentation), conditions that were encountered during the field experiment, and some highlights of preliminary observations, modelling, and satellite remote sensing studies.

  11. Thermo-erosion gullies boost the transition from wet to mesic tundra vegetation

    NASA Astrophysics Data System (ADS)

    Perreault, Naïm; Lévesque, Esther; Fortier, Daniel; Lamarque, Laurent J.

    2016-03-01

    Continuous permafrost zones with well-developed polygonal ice-wedge networks are particularly vulnerable to climate change. Thermo-mechanical erosion can initiate the development of gullies that lead to substantial drainage of adjacent wet habitats. How vegetation responds to this particular disturbance is currently unknown but has the potential to significantly disrupt function and structure of Arctic ecosystems. Focusing on three major gullies of Bylot Island, Nunavut, we estimated the impacts of thermo-erosion processes on plant community changes. We explored over 2 years the influence of environmental factors on plant species richness, abundance and biomass in 62 low-centered wet polygons, 87 low-centered disturbed polygons and 48 mesic environment sites. Gullying decreased soil moisture by 40 % and thaw-front depth by 10 cm in the center of breached polygons within less than 5 years after the inception of ice wedge degradation, entailing a gradual yet marked vegetation shift from wet to mesic plant communities within 5 to 10 years. This transition was accompanied by a five times decrease in graminoid above-ground biomass. Soil moisture and thaw-front depth changed almost immediately following gullying initiation as they were of similar magnitude between older (> 5 years) and recently (< 5 years) disturbed polygons. In contrast, there was a lag-time in vegetation response to the altered physical environment with plant species richness and biomass differing between the two types of disturbed polygons. To date (10 years after disturbance), the stable state of the mesic environment cover has not been fully reached yet. Our results illustrate that wetlands are highly vulnerable to thermo-erosion processes, which drive landscape transformation on a relative short period of time for High Arctic perennial plant communities (5 to 10 years). Such succession towards mesic plant communities can have substantial consequences on the food availability for herbivores and

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

    PubMed

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

    2015-04-01

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

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

    PubMed

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

    2015-04-01

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

  14. Biocomplexity of Arctic Patterned-Ground Ecosystems

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Daanen, R.; Epstein, H.; Gould, W.; Gonzalez, G.; Kade, A.; Kelley, A.; Krantz, W.; Kuss, P.; Michaelson, G.; Munger, C.; Nickolsky, D.; Peterson, R.; Ping, C.; Raynolds, M.; Romanovsky, V.; Tarnocai, C.; Vonlanthan, C.

    2006-12-01

    Small-scale patterned-ground features, including non-sorted circles and small non-sorted polygons, are important features of most arctic landscapes. The size, abundance and morphology of these features are affected by complex interactions between cryological processes, soil properties, and biological processes. We examined the interactions between frost-heave, contraction cracking, soil properties, and vegetation along an 1800-km transect through 10 degrees of latitude and approximately 11 degrees C of mean July temperature. We established permanent monitoring sites at 11 locations in the 5 bioclimate subzones of the Arctic (Subzone A is the coldest; E is warmest). Patterned-ground morphology on zonal sites changes in predictable ways with differences in climate, soil-moisture, soil-texture, and the structure of the vegetation. Large well- vegetated earth hummocks 2-3 m in diameter are prevalent in forested areas and in tussock tundra areas of Subzone E. Partially vegetated and barren 1-2-m diameter non-sorted circles are dominant in the more open vegetation of subzones D and southern parts of subzone C, and small barren non-sorted polygons and turf hummocks 10-30 cm in diameter are related to small-scale contraction cracking in subzones C, B and A. Strong thermal, physical, and chemical gradients develop within frost-heave features that help to maintain the position of these features in the same locality over long time periods. Many of these gradients are related to the contrast in the vegetation mat on and between these features. This results in much warmer soil conditions within the heave features in summer and much colder conditions during the winter. Strong thermal differences drive the movement of water and the development of frost heave. Cryoturbation of organic material from the margins of frost-heave features to the permafrost table, combined with aggrading permafrost tables, acts to sequester large amounts of carbon within the permafrost of these

  15. Exposure of trees to drought-induced die-off is defined by a common climatic threshold across different vegetation types

    PubMed Central

    Mitchell, Patrick J; O'Grady, Anthony P; Hayes, Keith R; Pinkard, Elizabeth A

    2014-01-01

    Increases in drought and temperature stress in forest and woodland ecosystems are thought to be responsible for the rise in episodic mortality events observed globally. However, key climatic drivers common to mortality events and the impacts of future extreme droughts on tree survival have not been evaluated. Here, we characterize climatic drivers associated with documented tree die-off events across Australia using standardized climatic indices to represent the key dimensions of drought stress for a range of vegetation types. We identify a common probabilistic threshold associated with an increased risk of die-off across all the sites that we examined. We show that observed die-off events occur when water deficits and maximum temperatures are high and exist outside 98% of the observed range in drought intensity; this threshold was evident at all sites regardless of vegetation type and climate. The observed die-off events also coincided with at least one heat wave (three consecutive days above the 90th percentile for maximum temperature), emphasizing a pivotal role of heat stress in amplifying tree die-off and mortality processes. The joint drought intensity and maximum temperature distributions were modeled for each site to describe the co-occurrence of both hot and dry conditions and evaluate future shifts in climatic thresholds associated with the die-off events. Under a relatively dry and moderate warming scenario, the frequency of droughts capable of inducing significant tree die-off across Australia could increase from 1 in 24 years to 1 in 15 years by 2050, accompanied by a doubling in the occurrence of associated heat waves. By defining commonalities in drought conditions capable of inducing tree die-off, we show a strong interactive effect of water and high temperature stress and provide a consistent approach for assessing changes in the exposure of ecosystems to extreme drought events. PMID:24772285

  16. Exposure of trees to drought-induced die-off is defined by a common climatic threshold across different vegetation types.

    PubMed

    Mitchell, Patrick J; O'Grady, Anthony P; Hayes, Keith R; Pinkard, Elizabeth A

    2014-04-01

    Increases in drought and temperature stress in forest and woodland ecosystems are thought to be responsible for the rise in episodic mortality events observed globally. However, key climatic drivers common to mortality events and the impacts of future extreme droughts on tree survival have not been evaluated. Here, we characterize climatic drivers associated with documented tree die-off events across Australia using standardized climatic indices to represent the key dimensions of drought stress for a range of vegetation types. We identify a common probabilistic threshold associated with an increased risk of die-off across all the sites that we examined. We show that observed die-off events occur when water deficits and maximum temperatures are high and exist outside 98% of the observed range in drought intensity; this threshold was evident at all sites regardless of vegetation type and climate. The observed die-off events also coincided with at least one heat wave (three consecutive days above the 90th percentile for maximum temperature), emphasizing a pivotal role of heat stress in amplifying tree die-off and mortality processes. The joint drought intensity and maximum temperature distributions were modeled for each site to describe the co-occurrence of both hot and dry conditions and evaluate future shifts in climatic thresholds associated with the die-off events. Under a relatively dry and moderate warming scenario, the frequency of droughts capable of inducing significant tree die-off across Australia could increase from 1 in 24 years to 1 in 15 years by 2050, accompanied by a doubling in the occurrence of associated heat waves. By defining commonalities in drought conditions capable of inducing tree die-off, we show a strong interactive effect of water and high temperature stress and provide a consistent approach for assessing changes in the exposure of ecosystems to extreme drought events.

  17. Dissolved inorganic nitrogen pools and surface flux under different brackish marsh vegetation types, common reed (Phragmites australis) and salt hay (Spartina patens)

    USGS Publications Warehouse

    Windham-Myers, L.

    2005-01-01

    The current expansion of Phragmites australis into the high marsh shortgrass (Spartina patens, Distichlis spicata) communities of eastern U.S. salt marshes provided an opportunity to identify the influence of vegetation types on pools and fluxes of dissolved inorganic nitrogen (DIN). Two brackish tidal marshes of the National Estuarine Research Reserve system were examined, Piermont Marsh of the Hudson River NERR in New York and Hog Island in the Jacques Coustaeu NERR of New Jersey. Pools of DIN in porewater and rates of DIN surface flux were compared in replicated pairs of recently-expanded P. australis and neighboring S. patens-dominated patches on the high marsh surface. Both marshes generally imported nitrate (NO3-) and exported ammonium (NH4+), such that overall DIN was exported. No differences in surface exchange of NO3- or NH4+ were observed between vegetation types. Depth-averaged porewater NH4+ concentrations over the entire growing season were 56% lower under P. australis than under S. patens (average 1.4 vs. 3.2 mg NH4+ L-1) with the most profound differences in November. Porewater profiles showed an accumulation of NH4+ at depth in S. patens and constant low concentrations in P. australis from the soil surface to 50 cm depth, with no significant differences in porewater salinity. Despite these profound differences in porewater, NH 4+ diffusion from soils of P. australis and S. patens were not measurably different, were similar to other published rates, and were well below estimated rates based on passive diffusion alone. Rapid adsorption and uptake by litter and microbes in surface soils of both communities may buffer NH4+ loss to flooding tides in both communities, thereby reducing the impact of P. australis invasion on NH4+ flux to flooding waters. ?? Springer 2005.

  18. Habitat use of bonobos (Pan paniscus) at Wamba: Selection of vegetation types for ranging, feeding, and night-sleeping.

    PubMed

    Terada, Saeko; Nackoney, Janet; Sakamaki, Tetsuya; Mulavwa, Mbangi Norbert; Yumoto, Takakazu; Furuichi, Takeshi

    2015-06-01

    Understanding the habitat requirements of great apes is essential for effective conservation strategies. We examined annual habitat use of a bonobo group in the Wamba field site within the Luo Scientific Reserve, Democratic Republic of the Congo. Using satellite imagery, we categorized the group's ranging area into three forest types: (1) primary and old secondary forest (P/OS), (2) young secondary forest and agriculture (YS/Ag), and (3) swamp forest (Sw). We tracked the group for 1 year (2007-2008) and compared usage of the three forest types for ranging, feeding, and night-sleeping. We also recorded what the bonobos ate and monitored monthly fruit availability in each forest type. The group ranged and fed more often in P/OS and less often in YS/Ag and Sw than expected based on habitat availability. Also, the group slept mostly in P/OS (94% of nights monitored), but also in YS/Ag (1%), and Sw (5%). Fruit availability in P/OS had no significant effect on habitat selection, but the group fed in YS/Ag most often during the two months when fruits in P/OS were least abundant. In June, when fruit of Uapaca spp. (selectively eaten by bonobos) was generally abundant in Sw, the group mostly ranged and slept there. The bonobos fed most often on herbaceous plants in all three forest types. In Sw, the bonobos frequently ate mushrooms. Our results show that semi-open forest with abundant herbaceous plants such as YS/Ag could be an important feeding habitat and may provide fallback food for bonobos when fruits are scarce. Furthermore, Sw can serve seasonally as a main habitat to complement P/OS if adequate food resources and tree nesting opportunities are available. We conclude that bonobos use diverse habitats depending on their needs and we highlight the importance of minor-use habitats for sustaining populations of target species in conservation planning. PMID:25809523

  19. Habitat use of bonobos (Pan paniscus) at Wamba: Selection of vegetation types for ranging, feeding, and night-sleeping.

    PubMed

    Terada, Saeko; Nackoney, Janet; Sakamaki, Tetsuya; Mulavwa, Mbangi Norbert; Yumoto, Takakazu; Furuichi, Takeshi

    2015-06-01

    Understanding the habitat requirements of great apes is essential for effective conservation strategies. We examined annual habitat use of a bonobo group in the Wamba field site within the Luo Scientific Reserve, Democratic Republic of the Congo. Using satellite imagery, we categorized the group's ranging area into three forest types: (1) primary and old secondary forest (P/OS), (2) young secondary forest and agriculture (YS/Ag), and (3) swamp forest (Sw). We tracked the group for 1 year (2007-2008) and compared usage of the three forest types for ranging, feeding, and night-sleeping. We also recorded what the bonobos ate and monitored monthly fruit availability in each forest type. The group ranged and fed more often in P/OS and less often in YS/Ag and Sw than expected based on habitat availability. Also, the group slept mostly in P/OS (94% of nights monitored), but also in YS/Ag (1%), and Sw (5%). Fruit availability in P/OS had no significant effect on habitat selection, but the group fed in YS/Ag most often during the two months when fruits in P/OS were least abundant. In June, when fruit of Uapaca spp. (selectively eaten by bonobos) was generally abundant in Sw, the group mostly ranged and slept there. The bonobos fed most often on herbaceous plants in all three forest types. In Sw, the bonobos frequently ate mushrooms. Our results show that semi-open forest with abundant herbaceous plants such as YS/Ag could be an important feeding habitat and may provide fallback food for bonobos when fruits are scarce. Furthermore, Sw can serve seasonally as a main habitat to complement P/OS if adequate food resources and tree nesting opportunities are available. We conclude that bonobos use diverse habitats depending on their needs and we highlight the importance of minor-use habitats for sustaining populations of target species in conservation planning.

  20. Effects of arctic shrub expansion on biophysical vs. biogeochemical drivers of litter decomposition.

    PubMed

    DeMarco, Jennie; Mack, Michelle C; Bret-Harte, M Syndonia

    2014-07-01

    Climate warming in arctic tundra may shift dominant vegetation from graminoids to deciduous shrubs, whose functional traits could, in turn, alter biotic and abiotic controls over biogeochemical cycling of carbon (C) and nitrogen (N). We investigated whether shrub-induced changes in microclimate have stronger effects on litter decomposition and nutrient release than changes in litter quality and quantity. In arctic tundra near Toolik Lake, Alaska, USA, we incubated a common substrate in a snow-addition experiment to test whether snow accumulation around arctic deciduous shrubs altered the environment enough to increase litter decomposition rates. We compared the influence of litter quality on the rate of litter and N loss by decomposing litter from four different plant functional types in a common site. We used aboveground net primary production values and estimated decay constant (k) values from our decomposition experiments to calculate community-weighted mass loss for each site. Snow addition had no effect on decomposition of the common substrate, and the site with the highest abundance of shrubs had the lowest decomposition rates. Species varied in their decomposition rates, with species from the same functional type not always following similar patterns. Community-weighted mass loss was 1.5 times greater in the high shrub site, and only slightly decreased when adjusted for soil environment, suggesting that litter quality and quantity are the primary drivers of community decomposition. Our findings suggest that on a short time scale, the changes in soil environment associated with snow trapping by shrubs are unlikely to influence litter nutrient turnover enough to drive positive snow-shrub feedbacks. The mechanisms driving shrub expansion are more likely to do with shrub-litter feedbacks, where the higher growth rates and N uptake by shrubs allows them to produce more leaves, resulting in a larger litter N pool and faster internal cycling of nutrients. PMID

  1. Effects of arctic shrub expansion on biophysical vs. biogeochemical drivers of litter decomposition.

    PubMed

    DeMarco, Jennie; Mack, Michelle C; Bret-Harte, M Syndonia

    2014-07-01

    Climate warming in arctic tundra may shift dominant vegetation from graminoids to deciduous shrubs, whose functional traits could, in turn, alter biotic and abiotic controls over biogeochemical cycling of carbon (C) and nitrogen (N). We investigated whether shrub-induced changes in microclimate have stronger effects on litter decomposition and nutrient release than changes in litter quality and quantity. In arctic tundra near Toolik Lake, Alaska, USA, we incubated a common substrate in a snow-addition experiment to test whether snow accumulation around arctic deciduous shrubs altered the environment enough to increase litter decomposition rates. We compared the influence of litter quality on the rate of litter and N loss by decomposing litter from four different plant functional types in a common site. We used aboveground net primary production values and estimated decay constant (k) values from our decomposition experiments to calculate community-weighted mass loss for each site. Snow addition had no effect on decomposition of the common substrate, and the site with the highest abundance of shrubs had the lowest decomposition rates. Species varied in their decomposition rates, with species from the same functional type not always following similar patterns. Community-weighted mass loss was 1.5 times greater in the high shrub site, and only slightly decreased when adjusted for soil environment, suggesting that litter quality and quantity are the primary drivers of community decomposition. Our findings suggest that on a short time scale, the changes in soil environment associated with snow trapping by shrubs are unlikely to influence litter nutrient turnover enough to drive positive snow-shrub feedbacks. The mechanisms driving shrub expansion are more likely to do with shrub-litter feedbacks, where the higher growth rates and N uptake by shrubs allows them to produce more leaves, resulting in a larger litter N pool and faster internal cycling of nutrients.

  2. Use of ERTS data for mapping Arctic sea ice

    NASA Technical Reports Server (NTRS)

    Barnes, J. C.; Bowley, C. J.

    1973-01-01

    This investigation is to evaluate the application of ERTS data for detecting and mapping Arctic sea ice. The specific objectives are to determine the spectral bands most suitable for detecting ice, to measure the scale and types of ice features that can be detected, and to develop interpretive techniques for differentiating ice from clouds and for mapping ice concentrations. The ERTS data are being analyzed primarily for three Arctic areas, the eastern Beaufort Sea, Baffin Bay, and the Greenland Sea.

  3. Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils

    USGS Publications Warehouse

    Neff, J.C.; Hooper, D.U.

    2002-01-01

    Climatic change may influence decomposition dynamics in arctic and boreal ecosystems, affecting both atmospheric CO2 levels, and the flux of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to aquatic systems. In this study, we investigated landscape-scale controls on potential production of these compounds using a one-year laboratory incubation at two temperatures (10?? and 30??C). We measured the release of CO2, DOC and DON from tundra soils collected from a variety of vegetation types and climatic regimes: tussock tundra at four sites along a latitudinal gradient from the interior to the north slope of Alaska, and soils from additional vegetation types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO2 and DOC release at the high incubation temperature occurred in the soils of shrub tundra communities. Tussock tundra soils exhibited the next highest DOC fluxes followed by spruce and wet sedge tundra soils, respectively. Of the fluxes, CO2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed by DOC. DON fluxes were less variable. Total CO2 and total DOC release were positively correlated, with DOC fluxes approximately 10% of total CO2 fluxes. The ratio of CO2 production to DOC release varied significantly across vegetation types with Tussock soils producing an average of four times as much CO2 per unit DOC released compared to Spruce soils from the Fairbanks site. Sites in this study released 80-370 mg CO2-C g soil C-1 and 5-46 mg DOC g soil C-1 at high temperatures. The magnitude of these fluxes indicates that arctic carbon pools contain a large proportion of labile carbon that could be easily decomposed given optimal conditions. The size of this labile pool ranged between 9 and 41% of soil carbon on a g soil C basis, with most variation related to vegetation type rather than

  4. Arctic ozone loss

    SciTech Connect

    Zurer, P.S.

    1989-03-06

    Scientists have returned from the first comprehensive probe of the Arctic stratosphere with unexpectedly dire results: The winter atmosphere in the north polar region is loaded with the same destructive chlorine compounds that cause the Antarctic ozone hole. Atmospheric researchers who only a few weeks ago were comforted by the thought that the warmer Northern Hemisphere is strongly protected from the processes that lead to massive losses of ozone during spring in Antarctica now see very little standing in the way of an Arctic ozone hole.

  5. Mercury mobilisation from soils and ashes after a wildfire and rainfall events: effects of vegetation type and fire severity

    NASA Astrophysics Data System (ADS)

    Campos, Isabel; Abrantes, Nelson; Keizer, Jan Jacob; Vale, Carlos; Serpa, Dalila; Pereira, Patrícia

    2016-04-01

    Wildfire is a major disturbance of forests worldwide, with huge environmental impacts. The number of catastrophic wildfires is increasing over the past few decades mainly due to a combined effect of climate change and poor land-use management. Interestingly, wildfires have an important role in contaminants production and mobilization and, thus, on their biogeochemical cycles. For instance, trace elements could be mobilized during a wildfire from burnt vegetation and ashes and may eventually achieve the aquatic systems upon a rainfall period. In this regard, wildfires represent a relevant diffuse source of trace elements to aquatic systems that has, so far, been poorly investigated. The current study aims to mitigate such lack of knowledge for mercury, a well-recognized persistent toxicant with potential harmful impacts on the environment and on human health. Thus, a field study was conducted in two Portuguese forests (Ermida and S. Pedro do Sul, North-centre of Portugal) with distinct fire severity. Fire was classified as moderate in Ermida and moderate to high severity in S. Pedro do Sul. In Ermida, soil samples and ashes were collected in the seven hillslopes (three burnt eucalypt, three burnt pine and one unburnt eucalypt) immediately and 4 months after the fire, the latter following an episode of intense rainfall. In S. Pedro do Sul, sampling took place immediately after the fire in four hillslopes (one burnt eucalypt and three burnt pine). Mercury analysis was performed in an Hg analyser in which samples were thermally decomposed by controlled heating. The final decomposition products were passed through an Hg amalgamator heated to 700 °C and Hg(0) was released and detected by absorption spectrometry at 254 nm. Burnt soil samples showed significantly lower levels of mercury than non-burnt soil, confirming the potential of a forest fire to release accumulated mercury in soil prior to the burning. Such process could be particularly relevant for this element due

  6. Operating requirements for and historical operations of Arctic offshore drilling systems in the United States

    SciTech Connect

    Regg, J.; Breitmeier, J.; Walker, J.

    1995-12-31

    Many of the floating and bottom-founded drilling structures used for oil and gas exploration in the US Arctic have recently been proposed for use in the Russian Arctic offshore. This paper describes the US Arctic environmental conditions in terms of operation capabilities for the various types of drilling systems. A brief description of the various types of drilling systems used to date in the US Arctic is provided as background information. Also presented are the special regulatory requirements and contingency plans which have been developed for offshore Arctic drilling-system operations. The paper will summarize information on the operating experiences of the various drilling systems used in the US Arctic Outer Continental Shelf (OCS) to date.

  7. Interactions of Multiple Factors in Creating Small Patterned-Ground Features Across the Arctic Bioclimate Gradient

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Epstein, H. E.; Kuss, P.; Michaelson, G. J.; Ping, C. L.; Raynolds, M. K.; Romanovsky, V. E.; Tarnocai, C. T.

    2004-12-01

    Small patterned-ground landforms are described along a bioclimate gradient in northern Canada and Alaska and summarized in tables and figures showing strength of influence of contraction cracking, differential frost heave, and vegetation - within five bioclimate subzones and four major soil texture classes. In the coldest parts of the Arctic (bioclimate subzones A and B), contraction cracking at small scales (10-30 cm between cracks) is the dominant process and contributes to the formation of hummocky terrain; differential frost heave has a small role here except in course rocky terrain where sorted circles are common. The presence of contraction cracks on all surfaces, wet and dry, and on all soil types indicate that the majority of the contraction cracks are caused by thermal processes and not desiccation. Larger mounds, apparently the result of differential frost heave, occur in some areas of Subzone B where there is more vegetation and peat. In the Middle Arctic (bioclimate subzone C), both small turf hummocks and well-developed non-sorted circles occur. Turf hummocks are dominant on hill slopes; erosion of the inter-hummock areas and accumulation of eolian material on the hummock tops creates taller hummocks. Non-sorted stripes occur on many slopes. In the northern Low Arctic (Subzone D), non-sorted circles are the most common features; and turf hummocks are restricted to small areas - generally steep snow beds. The centers of most frost boils are barren or partially vegetated in Subzone D. In the sourthern Low Arctic (Subzone E), the vegetation is very active and able to colonize and totally cover frost boils. Large vegetated mounds are apparently the remnants of once active frost boils. In areas with more clayey soils of subzones D and E, well-developed tightly packed mounds are common, and frost boils often occur on the tops of the mounds. The spacing of the mound centers is often 2-3 m. Mounds are also common south of treeline. Soil texture affects frost

  8. Enhancing Nutraceutical Bioavailability from Raw and Cooked Vegetables Using Excipient Emulsions: Influence of Lipid Type on Carotenoid Bioaccessibility from Carrots.

    PubMed

    Zhang, Ruojie; Zhang, Zipei; Zou, Liqiang; Xiao, Hang; Zhang, Guodong; Decker, Eric Andrew; McClements, David Julian

    2015-12-01

    The influence of the nature of the lipid phase in excipient emulsions on the bioaccessibility and transformation of carotenoid from carrots was investigated using a gastrointestinal tract (GIT) model. Excipient emulsions were fabricated using whey protein as an emulsifier and medium-chain triglycerides (MCT), fish oil, or corn oil as the oil phase. Changes in particle size, charge, and microstructure were measured as the carrot-emulsion mixtures were passed through simulated mouth, stomach, and small intestine regions. Carotenoid bioaccessibility depended on the type of lipids used to form the excipient emulsions (corn oil > fish oil ≫ MCT), which was attributed to differences in the solubilization capacity of mixed micelles formed from different lipid digestion products. The transformation of carotenoids was greater for fish oil and corn oil than for MCT, which may have been due to greater oxidation or isomerization. The bioaccessibility of the carotenoids was higher from boiled than raw carrots, which was attributed to greater disruption of the plant tissue facilitating carotenoid release. In conclusion, excipient emulsions are highly effective at increasing carotenoid bioaccessibility from carrots, but lipid type must be optimized to ensure high efficacy.

  9. Airborne Spectral BRDF of Various Surface Types (Ocean, Vegetation, Snow, Desert, Wetlands, Cloud Decks, Smoke Layers) for Remote Sensing Applications

    NASA Technical Reports Server (NTRS)

    Gatebe, Charles K.; King, Michael D.

    2016-01-01

    In this paper we describe measurements of the bidirectional reflectance-distribution function (BRDF) acquired over a 30-year period (1984-2014) by the National Aeronautics and Space Administration's (NASA's) Cloud Absorption Radiometer (CAR). Our BRDF database encompasses various natural surfaces that are representative of many land cover or ecosystem types found throughout the world. CAR's unique measurement geometry allows a comparison of measurements acquired from different satellite instruments with various geometrical configurations, none of which are capable of obtaining such a complete and nearly instantaneous BRDF. This database is therefore of great value in validating many satellite sensors and assessing corrections of reflectances for angular effects. These data can also be used to evaluate the ability of analytical models to reproduce the observed directional signatures, to develop BRDF models that are suitable for sub-kilometer-scale satellite observations over both homogeneous and heterogeneous landscape types, and to test future spaceborne sensors. All of these BRDF data are publicly available and accessible in hierarchical data format (http:car.gsfc.nasa.gov/).

  10. Enhancing Nutraceutical Bioavailability from Raw and Cooked Vegetables Using Excipient Emulsions: Influence of Lipid Type on Carotenoid Bioaccessibility from Carrots.

    PubMed

    Zhang, Ruojie; Zhang, Zipei; Zou, Liqiang; Xiao, Hang; Zhang, Guodong; Decker, Eric Andrew; McClements, David Julian

    2015-12-01

    The influence of the nature of the lipid phase in excipient emulsions on the bioaccessibility and transformation of carotenoid from carrots was investigated using a gastrointestinal tract (GIT) model. Excipient emulsions were fabricated using whey protein as an emulsifier and medium-chain triglycerides (MCT), fish oil, or corn oil as the oil phase. Changes in particle size, charge, and microstructure were measured as the carrot-emulsion mixtures were passed through simulated mouth, stomach, and small intestine regions. Carotenoid bioaccessibility depended on the type of lipids used to form the excipient emulsions (corn oil > fish oil ≫ MCT), which was attributed to differences in the solubilization capacity of mixed micelles formed from different lipid digestion products. The transformation of carotenoids was greater for fish oil and corn oil than for MCT, which may have been due to greater oxidation or isomerization. The bioaccessibility of the carotenoids was higher from boiled than raw carrots, which was attributed to greater disruption of the plant tissue facilitating carotenoid release. In conclusion, excipient emulsions are highly effective at increasing carotenoid bioaccessibility from carrots, but lipid type must be optimized to ensure high efficacy. PMID:26585671

  11. Trophic matches in Northern Alaska: Existing synchrony among climate, vegetation, arthropods and migratory songbirds

    NASA Astrophysics Data System (ADS)

    Boelman, N.; Gough, L.; Wingfield, J. C.; Team Bird

    2011-12-01

    Climate change in the Arctic is altering patterns of seasonality while also altering the composition and structure of vegetation. In contrast to plants, energy balance, and carbon and nitrogen cycling, the responses of animal populations to these changes have been drastically understudied in the Alaskan interior and much of the Arctic. Investigations are therefore needed to better understand trophic dynamics involving vertebrates under current conditions, and to predict how this group may be impacted by both the direct and indirect effects of changing seasonality and vegetation cover. This is particularly important for migratory animals that breed annually on the arctic tundra because they provide a direct connection between the rapidly changing arctic environment and their more southern staging and over-wintering habitats. In a five year observational study, we are exploring how both shifts towards earlier spring snow melt and the ongoing increase in regional deciduous shrub dominance may affect migratory songbird communities that depend on the tundra for food and shelter during their breeding season. Here we present early results from sites in northern Alaska that differ in shrub height and abundance that reveal: (1) strong existing synchrony among the timing of spring snow melt, spring air temperatures, vegetation phenology, arthropod phenology and the timing of breeding stages of migratory songbirds, and; (2) significant differences in the types and abundance of vegetative and arthropod food sources, as well as environmental and biophysical micro-habitat conditions, between non-shrub dominated tundra plots and deciduous shrub dominated tundra. The arrival time of migratory songbirds on the tundra, and thus the onset of their breeding cycle, is cued by day length, while snow melt, plant growth and arthropod emergence are temperature sensitive. We therefore hypothesize that warmer spring time temperatures could cause a mismatch between the arrival time and onset

  12. Climate change effects on vegetation in Northeastern Siberian tundra - How does shrub growth relate to local climate and what are potential effects of shrub expansion on permafrost thawing?

    NASA Astrophysics Data System (ADS)

    Blok, Daan; Schaepman-Strub, Gabriela; Heijmans, Monique; Sass-Klaassen, Ute; Bartholomeus, Harm; Knyazikhin, Yuri; Berendse, Frank

    2010-05-01

    The Siberian tundra is one of the key permafrost regions in the Arctic because of its large spatial extent and carbon-rich yedoma soils. Changes in permafrost thaw and concomitant carbon losses to the atmosphere can have large impacts on the global climate. Permafrost thaw is believed to strongly increase this century as a result of predicted increasing air temperature. At the same time, Arctic vegetation growth and composition is predicted to respond to future climate change. Deciduous shrubs are expected to benefit most from climate warming by increasing growth and expanding their range to higher latitudes. Evidence for recent increases in deciduous shrub cover in the Arctic region is limited thus far to small areas in Alaska. We examined if deciduous shrubs at our research site in the Indigirka lowlands, Northeastern Siberia, show a growth response to the main climate variables, temperature and precipitation. We constructed tree-ring width chronologies for two key Arctic deciduous shrub species, Betula nana and Salix pulchra, dating back roughly 60 years. The ring widths records are compared to summer-warmth index and summer-precipitation data from the closest climate station, approximately 30 km from our site in order to detect the climate factor that mainly determines shrub growth. On a larger scale, recent increases in Arctic productivity, measured as Arctic greenness (Normalized Difference Vegetation Index, NDVI), suggest that shrubs may have expanded during the 80ies and 90ies of the last century. Spectral reflectance data of varying vegetation composition measured at the tundra site were reduced to NDVI to link up with long-term NDVI data. We used a multiple regression analysis to estimate how variation in NDVI is explained by plant fractional cover of different plant functional types (graminoids, deciduous shrubs, evergreen shrubs, forbs, mosses and lichens). Deciduous shrub cover was the only significant explanatory parameter in the model after parameter

  13. BRDF characteristics of tundra vegetation communities in Yamal, Western Siberia

    NASA Astrophysics Data System (ADS)

    Buchhorn, Marcel; Heim, Birgit; Walker, Donald A. Skip; Epstein, Howard; Leibman, Marina

    2013-04-01

    (NASA Yamal-LCLUC) transects and réleves at Laboravaya (southern Yamal) and Vaskiny Dachi (central Yamal), and at the Circumpolar Active Layer Monitoring (CALM) site in Vaskiny Dachi. The LCLUC plots are Greening of the Arctic (GOA) sites established in 2007 by Walker et al. (2009). The Circumpolar Active Layer Monitoring (CALM) site was established by M. Leibman (ECI) in 1993. BRDF processing for the tundra test sites demonstrate the mirror asymmetry in relative azimuth with respect to the principal plane. It also showed that the maximum scattering appears in the backward direction, but that there is no minimal forward scattering. Instead, the forward scattering is characterized by similar to higher reflectance values compared to the nadir position. Moreover, the analysis of the anisotropic behaviour of moss-dominated tundra types with 10 to 15% vascular plant cover show that the BRDF influence on vegetation indices (VI) of low-growing arctic vegetation communities can be up to 15% of the nadir value. The low sun elevation at the arctic latitudes prevents hotspot-effects, but a BRDF normalization still should be taken into account for the development of tundra-adapted vegetation indices. Walker, D.A. et al. (2009): Data Report of the 2007 and 2008 Yamal Expeditions. AGC Data Report. 133.

  14. Fire-mediated disruptive selection can explain the reseeder-resprouter dichotomy in Mediterranean-type vegetation.

    PubMed

    Altwegg, Res; De Klerk, Helen M; Midgley, Guy F

    2015-02-01

    Crown fire is a key selective pressure in Mediterranean-type plant communities. Adaptive responses to fire regimes involve trade-offs between investment for persistence (fire survival and resprouting) and reproduction (fire mortality, fast growth to reproductive maturity, and reseeding) as investments that enhance adult survival lower growth and reproductive rates. Southern hemisphere Mediterranean-type ecosystems are dominated by species with either endogenous regeneration from adult resprouting or fire-triggered seedling recruitment. Specifically, on nutrient-poor soils, these are either resprouting or reseeding life histories, with few intermediate forms, despite the fact that the transition between strategies is evolutionarily labile. How did this strong dichotomy evolve? We address this question by developing a stochastic demographic model to assess determinants of relative fitness of reseeders, resprouters and hypothetical intermediate forms. The model was parameterised using published demographic data from South African protea species and run over various relevant fire regime parameters facets. At intermediate fire return intervals, trade-offs between investment in growth versus fire resilience can cause fitness to peak at either of the extremes of the reseeder-resprouter continuum, especially when assuming realistic non-linear shapes for these trade-offs. Under these circumstances, the fitness landscape exhibits a saddle which could lead to disruptive selection. The fitness gradient between the peaks was shallow, which may explain why this life-history trait is phylogenetically labile. Resprouters had maximum fitness at shorter fire-return intervals than reseeders. The model suggests that a strong dichotomy in fire survival strategy depends on a non-linear trade-off between growth and fire persistence traits.

  15. Arctic tree rings as recorders of variations in light availability

    PubMed Central

    Stine, A. R.; Huybers, P.

    2014-01-01

    Annual growth ring variations in Arctic trees are often used to reconstruct surface temperature. In general, however, the growth of Arctic vegetation is limited both by temperature and light availability, suggesting that variations in atmospheric transmissivity may also influence tree-ring characteristics. Here we show that Arctic tree-ring density is sensitive to changes in light availability across two distinct phenomena: explosive volcanic eruptions (P<0.01) and the recent epoch of global dimming (P<0.01). In each case, the greatest response is found in the most light-limited regions of the Arctic. Essentially no late 20th century decline in tree-ring density relative to temperature is seen in the least light-limited regions of the Arctic. Consistent results follow from analysis of tree-ring width and from individually analysing each of seven tree species. Light availability thus appears an important control, opening the possibility for using tree rings to reconstruct historical changes in surface light intensity. PMID:24805143

  16. Turnover of recently assimilated carbon in arctic bryophytes.

    PubMed

    Street, L E; Subke, J A; Sommerkorn, M; Heinemeyer, A; Williams, M

    2011-10-01

    Carbon (C) allocation and turnover in arctic bryophytes is largely unknown, but their response to climatic change has potentially significant impacts on arctic ecosystem C budgets. Using a combination of pulse-chase experiments and a newly developed model of C turnover in bryophytes, we show significant differences in C turnover between two contrasting arctic moss species (Polytrichum piliferum and Sphagnum fuscum). (13)C abundance in moss tissues (measured up to 1 year) and respired CO(2) (traced over 5 days) were used to parameterise the bryophyte C model with four pools representing labile and structural C in photosynthetic and stem tissue. The model was optimised using an Ensemble Kalman Filter to ensure a focus on estimating the confidence intervals (CI) on model parameters and outputs. The ratio of aboveground NPP:GPP in Polytrichum piliferum was 23% (CI 9-35%), with an average turnover time of 1.7 days (CI 1.1-2.5 days). The aboveground NPP:GPP ratio in Sphagnum fuscum was 43% (CI 19-65%) with an average turnover time of 3.1 days (CI 1.6-6.1 days). These results are the first to show differences in C partitioning between arctic bryophyte species in situ and highlight the importance of modelling C dynamics of this group separately from vascular plants for a realistic representation of vegetation in arctic C models.

  17. Arctic lithosphere - A review

    NASA Astrophysics Data System (ADS)

    Pease, V.; Drachev, S.; Stephenson, R.; Zhang, X.

    2014-07-01

    This article reviews the characteristics of Arctic lithosphere and the principal tectonic events which have shaped it. The current state-of-knowledge associated with the crust, crustal-scale discontinuities, and their ages, as well as knowledge of the lithosphere as a whole from geophysical data, permits the division of Arctic lithosphere into discrete domains. Arctic continental lithosphere is diverse in age, composition, and structure. It has been affected by at least two periods of thermal overprinting associated with large volumes of magmatism, once in the Permo-Triassic and again in the Aptian. In addition, it was attenuated as the result of at least five phases of rifting (in the late Devonian-early Carboniferous, Permo-Triassic, Jurassic, Early Cretaceous, and Late Cretaceous-Cenozoic). Older phases of consolidation are associated with continental lithosphere and occurred through a series of continent-continent collisions in the Paleozoic. Jurassic and Cretaceous extensional phases are related to the dismembering of Pangea and Eurasia, and were concentrated in the Norway-Greenland and Canadian-Alaskan Arctic regions. Large areas of submarine, hyperextended continental (?) lithosphere developed in parts of the Amerasia Basin. After continental breakup and the accretion of new oceanic lithosphere, the Eurasia and Canada basins were formed.

  18. Community Land Model (CLM) Assessment on Simulating and Analyzing Water, Carbon and Nitrogen Cycles in Arctic Coastal Tundra at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Yuan, F.; Thornton, P. E.; King, A. W.; Ricciuto, D. M.; Post, W. M.

    2012-12-01

    Recent climate warming has been widely hypothesized to be one of primary contributors to shifting both biophysical and biological conditions of Arctic tundra ecosystem and thus water, carbon and nitrogen cycles. Both constrains on integrating multiple-scale observations scattered in various sources and comprehensive process-based model assessments on those may hinder our further and/or deepen understanding of climate impacts on Arctic tundra and their feedbacks. This preliminary study is to assess and improve, as needed, the Community Land Model (CLM-CN mode) on simulating soil water, temperature, nitrogen nutrient and other factors and their effects on soil-plant C stocks and/or fluxes in Arctic tundra at Barrow, Alaska. The model assessment is carried out by exploring and using data compiled from various researches, e.g., AmeriFlux, US/IBP, ITEX and others during past few decades in the area. We add a simple N emission subroutine in the current released CLM4 (in CESM1.0.4) and modify soil water drainage boundary conditions so that model can partially capture the landscape position effects of hydrological process on thermal and biogeochemical processes. We initially parameterize and initialize the model for Arctic tundra at Barrow, AK with 4 new plant functional types (PFTs): mosses, forbs, graminoids, and shrubs, based on literature study. It shows strong inter-annual variance of C fluxes, which tightly coupled with water, temperature and N nutrient dynamics. We then conduct a factory model experiments with drainage classes and varying PFT compositions in order to understand possible water, C and N cycle variations if vegetation changes over landscape. This preliminary analysis is of importance to apply for CLM model in this highly heterogeneous coastal Arctic tundra region under historical and projected climate changes.

  19. The Arctic Circle

    NASA Astrophysics Data System (ADS)

    McDonald, Siobhan

    2016-04-01

    My name is Siobhan McDonald. I am a visual artist living and working in Dublin. My studio is based in The School of Science at University College Dublin where I was Artist in Residence 2013-2015. A fascination with time and the changeable nature of landmass has led to ongoing conversations with scientists and research institutions across the interweaving disciplines of botany, biology and geology. I am developing a body of work following a recent research trip to the North Pole where I studied the disappearing landscape of the Arctic. Prompted by my experience of the Arctic shelf receding, this new work addresses issues of the instability of the earth's materiality. The work is grounded in an investigation of material processes, exploring the dynamic forces that transform matter and energy. This project combines art and science in a fascinating exploration of one of the Earth's last relatively untouched wilderness areas - the High Arctic to bring audiences on journeys to both real and artistically re-imagined Arctic spaces. CRYSTALLINE'S pivotal process is collaboration: with The European Space Agency; curator Helen Carey; palaeontologist Prof. Jenny McElwain, UCD; and with composer Irene Buckley. CRYSTALLINE explores our desire to make corporeal contact with geological phenomena in Polar Regions. From January 2016, in my collaboration with Jenny McElwain, I will focus on the study of plants and atmospheres from the Arctic regions as far back as 400 million years ago, to explore the essential 'nature' that, invisible to the eye, acts as imaginary portholes into other times. This work will be informed by my arctic tracings of sounds and images recorded in the glaciers of this disappearing frozen landscape. In doing so, the urgencies around the tipping of natural balances in this fragile region will be revealed. The final work will emerge from my forthcoming residency at the ESA in spring 2016. Here I will conduct a series of workshops in ESA Madrid to work with

  20. Climate-Driven Effects of Fire on Winter Habitat for Caribou in the Alaskan-Yukon Arctic

    PubMed Central

    Gustine, David D.; Brinkman, Todd J.; Lindgren, Michael A.; Schmidt, Jennifer I.; Rupp, T. Scott; Adams, Layne G.

    2014-01-01

    Climatic warming has direct implications for fire-dominated disturbance patterns in northern ecosystems. A transforming wildfire regime is altering plant composition and successional patterns, thus affecting the distribution and potentially the abundance of large herbivores. Caribou (Rangifer tarandus) are an important subsistence resource for communities throughout the north and a species that depends on terrestrial lichen in late-successional forests and tundra systems. Projected increases in area burned and reductions in stand ages may reduce lichen availability within caribou winter ranges. Sufficient reductions in lichen abundance could alter the capacity of these areas to support caribou populations. To assess the potential role of a changing fire regime on winter habitat for caribou, we used a simulation modeling platform, two global circulation models (GCMs), and a moderate emissions scenario to