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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 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

  5. Identifying nitrogen limitations to organic sediments accumulation in various vegetation types of arctic tundra (Hornsund, Svalbard)

    NASA Astrophysics Data System (ADS)

    Skrzypek, G.; Wojtuń, B.; Hua, Q.; Richter, D.; Jakubas, D.; Wojczulanis-Jakubas, K.; Samecka-Cymerman, A.

    2015-12-01

    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types in the Fuglebekken catchment (Hornsund Fjord, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds' feces (colonially breeding, planktivorous Alle alle), 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 N2-fixation. The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced substantial negative environmental pressure associated with climate change, it would adversely influence the tundra N-budget [1]. The growth rates and the sediment thickness (<15 cm) in different tundra types varied considerably but the tundra age was similar, <450 cal BP. The only exception was Ornithocoprophilous tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds' contribution to the tundra N-pool. [1] Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis-Jakubas K, Samecka-Cymerman A, 2015. Diversification of nitrogen sources in various tundra vegetation types in the high Arctic. PLoS ONE

  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. 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.

  9. New views on changing Arctic vegetation

    NASA Astrophysics Data System (ADS)

    Kennedy, Robert E.

    2012-03-01

    As climate changes, how will terrestrial vegetation respond? Because the fates of many biogeochemical, hydrological and economic cycles depend on vegetation, this question is fundamental to climate change science but extremely challenging to address. This is particularly true in the Arctic, where temperature change has been most acute globally (IPCC 2007) and where potential feedbacks to carbon, energy and hydrological cycles have important implications for the rest of the Earth system (Chapin et al 2000). It is well known that vegetation is tightly coupled to precipitation and temperature (Whittaker 1975), but predicting the response of vegetation to changes in climate involves much more than invoking the limitations of climate envelopes (Thuiller et al 2008). Models must also consider efficacy of dispersal, soil constraints, ecological interactions, possible CO2 fertilization impacts and the changing impact of other, more proximal anthropogenic effects such as pollution, disturbance, etc (Coops and Waring 2011, Lenihan et al 2008, Scheller and Mladenoff 2005). Given this complexity, a key test will be whether models can match empirical observations of changes that have already occurred. The challenge is finding empirical observations of change that are appropriate to test hypothesized impacts of climate change. As climate gradually changes across broad bioclimatic gradients, vegetation condition may change gradually as well. To capture these gradual trends, observations need at least three characteristics: (1) they must quantify a vegetation attribute that is expected to change, (2) they must measure that attribute in exactly the same way over long periods of time, and (3) they must sample diverse communities at geographic scales commensurate with the scale of expected climatic shifts. Observation networks meeting all three criteria are rare anywhere on the globe, but particularly so in remote areas. For this reason, satellite images have long been used as a

  10. Mediation of Fire-Climate Linkages by Vegetation Types in Alaskan Arctic Tundra Ecosystems: Impacts of Model Uncertainty on GCM-Based Forecasts of Future Fire Activity

    NASA Astrophysics Data System (ADS)

    Duffy, P.; Higuera, P. E.; Young, A. M.; Hu, F.; Dietze, M.

    2014-12-01

    Fire is a powerful landscape scale disturbance agent in tundra ecosystems. Impacts on biophysical properties (e.g. albedo) and biogeochemical function (e.g. carbon flux) underscore the need to better quantify fire-climate linkages in tundra ecosystems as climate change accelerates at northern high latitudes. In this context, a critical question is "How does the functional linkage between climate and fire vary across spatial domains dominated by different vegetation types?" We address this question with BLM-Alaska Fire Service area burned data (http://fire.ak.blm.gov/predsvcs/maps.php) used in conjunction with downscaled historical climate data from the Scenarios Network for Alaska Planning (http://www.snap.uaf.edu/data.php) to develop gradient boosting models of annual area burned in Alaska tundra ecosystems. The sparse historical fire records in the Arctic necessitate explicit quantification of model uncertainty associated with the development of statistical analyses. In this work, model uncertainty is depicted through the construction of separate models depicting fire-climate relationships for regions defined by the graminoid, shrub, and wetland tundra vegetation classes (Circumpolar Arctic Vegetation Map: http://www.geobotany.uaf.edu/cavm/). Non-linear relationships between annual area burned and climate variables are depicted with partial dependence functions. Our results show that vegetation-specific models result in different non-linear relationships between climate and fire. Precipitation variables generally had higher relative influence scores than temperature; however, differences between the magnitude of the scores were greater when models were built with monthly (versus seasonal) explanatory variables. Key threshold values for climate variables are identified. The impact of model uncertainty on forecasts of future fire activity was quantified using output from five different AR5/CMIP5 General Circulation Models. Model uncertainty corresponding to

  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. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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

  19. 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.

  20. The Hydrologic Cycle Response to Rapid Arctic Vegetation Change

    NASA Astrophysics Data System (ADS)

    Snyder, P. K.

    2008-12-01

    Over the last fifty years, the Northern Hemisphere high latitude land areas have warmed at rates well in excess of what can be explained by the atmospheric rise in greenhouse gases alone. Changes in the albedo of the ocean and land, whether from the loss of Arctic Ocean sea ice, changes in land cover, or changes in winter precipitation patterns account for much of the amplified warming. Although the loss of sea ice is directly related to greenhouse gas warming and low-level winds, changes in the discharge of freshwater from Arctic river basins are also responsible. While changes in river discharge can be related to precipitation, snow and ice melt, and human modification of the landscape, natural vegetation changes due to warming may also be altering the land surface hydrologic cycle and contributing to changes in the flux of freshwater to the Arctic Ocean. Satellite imagery has shown that the Arctic is becoming greener, which not only affects the surface and lower-tropospheric energy budget, but also modifies the hydrologic cycle through altering the partitioning of transpiration and plant-soil evaporation. This leads to changes in precipitation recycling and runoff, which can ultimately affect the discharge of freshwater. To illustrate this mechanism, results of a land cover change and precipitation-recycling analysis using North American Regional Reanalysis data will be presented for the Mackenzie Basin in North America. Additionally, results from a dynamic global vegetation model will be presented to evaluate the potential consequences of continued extreme warming and land cover changes to the discharge of freshwater to the Arctic Ocean.

  1. Energy fluxes retrieval on an Alaskan Arctic and Sub-Arctic vegetation by means MODIS imagery and the DTD method

    NASA Astrophysics Data System (ADS)

    Cristobal, J.; Prakash, A.; Starkenburg, D. P.; Fochesatto, G. J.; Anderson, M. C.; Gens, R.; Kane, D. L.; Kustas, W.; Alfieri, J. G.

    2012-12-01

    Evapotranspiration (ET) plays a significant role in the hydrologic cycle of Arctic and Sub-Arctic basins. Surface-atmosphere exchanges due to ET are estimated from water balance computations to be about 74% of summer precipitation or 50% of annual precipitation. Even though ET is a significant component of the hydrologic cycle in this region, the bulk estimates don't accurately account for spatial and temporal variability due to vegetation type, topography, etc. (Kane and Yang, 2004). Nowadays, remote sensing is the only technology capable of providing the necessary radiometric measurements for the calculation of the ET at global scales and in a feasible economic way, especially in Arctic and Sub-Arctic Alaskan basins with a very sparse network of both meteorological and flux towers. In this work we present the implementation and validation of the Dual-Time-Difference model (Kustas et al., 2001) to retrieve energy fluxes (ET, sensible heat flux, net radiation and soil heat flux) in tundra vegetation in Arctic conditions and in a black spruce (Picea mariana) forest in Sub-Arctic conditions. In order to validate the model in tundra vegetation we used a flux tower from the Imnavait Creek sites of the Arctic Observatory Network (Euskirchen et al. 2012). In the case of the black spruce forest, on September 2011 we installed a flux tower in the University of Alaska Fairbanks north campus that includes an eddy-covariance system as well a net radiometer, air temperature probes, soil heat flux plates, soil moisture sensors and thermistors to fully estimate energy fluxes in the field (see http://www.et.alaska.edu/ for further details). Additionally, in order to upscale energy fluxes into MODIS spatial resolution, a scintillometer was also installed covering 1.2 km across the flux tower. DTD model mainly requires meteorological inputs as well as land surface temperature (LST) and leaf area index (LAI) data, both coming from satellite imagery, at two different times: after

  2. 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.

  3. Use of a cable-based system for observing the heterogeneity of vegetation communities in arctic tundra

    NASA Astrophysics Data System (ADS)

    Ahrends, H. E.; Oberbauer, S. F.; Tweedie, C.; Hollister, R. D.

    2010-12-01

    Knowledge of changing tundra vegetation and its response to climate variability is critical for understanding the land-atmosphere-interactions for the Arctic and the global system. However, vegetation characteristics, such as phenology, structure and species composition, are characterized by an extreme heterogeneity at a small scale. Manual observations of these variables are highly time-consuming, labor intensive, subjective, and disturbing to the vegetation. In contrast, recently developed robotic systems (networked infomechanical systems, NIMS) allow for performing non-intrusive spatially integrated measurements of vegetation communities. Within the ITEX (International Tundra Experiment) AON (Arctic Observation Network) project we installed a cable-based sensor system, running over a transect of approximately 50 m length and 2 m width, at two long-term arctic research sites in Alaska. The trolley was initially equipped with instruments recording the distance to vegetation canopy, up- and downwelling short- and longwave radiation, air and surface temperature and spectral reflection. We aim to study the thermal and spectral response of the vegetation communities over a wide range of ecosystem types. We expect that automated observations, covering the spatial heterogeneity of vegetation and surface characteristics, can give a deeper insight in ecosystem functioning and vegetation response to climate. The data can be used for scaling up vegetation characteristics derived from manual measurements and for linking them to aircraft and satellite data and to carbon, water and surface energy budgets measured at the ecosystem scale. Sampling errors due to cable sag are correctable and effects of wind-driven movements can be offset by repeat measurements. First hand-pulled test measurements during summer 2010 show strong heterogeneity of the observation parameters and a variable spectral and thermal response of the plants within the transects. Differences support the

  4. 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

  5. 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

  6. Regional-Scale Vegetation Dynamics in Patterned-Ground Ecosystems of Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Kelley, A. M.; Walker, D. A.; Jia, G. J.; Raynolds, M. K.

    2006-12-01

    Regional-scale patterns of vegetation have been analyzed along a number of climate gradients throughout the world; these spatial dynamics provide important insights into the controlling factors of vegetation and the potential plant responses to environmental change. Only a few studies to date have collectively examined the vegetation biomass and production of arctic tundra ecosystems and their relationships to broadly ranging climate variables. No prior study has taken a systematic and consistent approach to examining vegetation biomass patterns along the full temperature gradient of the arctic biome. An additional complicating factor for studying vegetation of arctic tundra is the high spatial variability associated with small patterned-ground features (e.g. non-sorted circles and small non-sorted polygons), resulting from intense freeze-thaw processes. In this study, we sampled and analyzed the aboveground plant biomass components of patterned-ground ecosystems in the Arctic of northern Alaska and Canada along an 1800-km north-south gradient that spans approximately 11 degrees C of mean July temperatures. At each of ten locations along the regional temperature gradient, we ran several 50-m transects and harvested the aboveground biomass of three 20 x 50 cm plots for each transect. Vegetation biomass was dried, sorted by plant functional groups and tissue types, weighed, and analyzed as functions of the summer warmth index (SWI sum of mean monthly temperatures > 0). The absolute biomass (g/m2) of shrubs and graminoids increased exponentially with SWI, whereas forb and lichen biomass showed no change along the gradient. Moss biomass increased linearly with SWI, but with greater variabiliy than the other types. Relative aboveground biomass (% of total) of shrubs and graminoids increased with SWI, whereas percent lichen biomass decreased, and forbs again exhibited no significant change. Percentage of moss biomass was a parabolic function of SWI, with high relative

  7. 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

  8. Environment, vegetation and greenness (NDVI) along the North America and Eurasia Arctic transects

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Epstein, H. E.; Raynolds, M. K.; Kuss, P.; Kopecky, M. A.; Frost, G. V.; Daniëls, F. J. A.; Leibman, M. O.; Moskalenko, N. G.; Matyshak, G. V.; Khitun, O. V.; Khomutov, A. V.; Forbes, B. C.; Bhatt, U. S.; Kade, A. N.; Vonlanthen, C. M.; Tichý, L.

    2012-03-01

    Satellite-based measurements of the normalized difference vegetation index (NDVI; an index of vegetation greenness and photosynthetic capacity) indicate that tundra environments are generally greening and becoming more productive as climates warm in the Arctic. The greening, however, varies and is even negative in some parts of the Arctic. To help interpret the space-based observations, the International Polar Year (IPY) Greening of the Arctic project conducted ground-based surveys along two >1500 km transects that span all five Arctic bioclimate subzones. Here we summarize the climate, soil, vegetation, biomass, and spectral information collected from the North America Arctic transect (NAAT), which has a more continental climate, and the Eurasia Arctic transect (EAT), which has a more oceanic climate. The transects have broadly similar summer temperature regimes and overall vegetation physiognomy, but strong differences in precipitation, especially winter precipitation, soil texture and pH, disturbance regimes, and plant species composition and structure. The results indicate that summer warmth and NDVI increased more strongly along the more continental transect.

  9. 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

  10. 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

  11. Effects of Disturbances on Vegetation Composition and Permafrost Thaw in Boreal Forests and Tundra Ecosystems of the Siberian Arctic

    NASA Astrophysics Data System (ADS)

    Ramos, E.; Alexander, H. D.; Natali, S.

    2014-12-01

    In Arctic ecosystems, climate-driven changes to the thermal regime of permafrost soils have the potential to create surface disturbances that influence vegetation dynamics and underlying soil properties. Disturbance-mediated changes in vegetation are important because vegetation and the accumulation of soil organic matter drive ecosystem carbon (C) dynamics and contribute to the insulation of soils and protection of permafrost from thaw. We examined the effect of two disturbance types—thermokarsts and frost boils—to determine disturbance effects on the vegetation community and soil properties in northeast Siberia. In summer 2014, we measured vegetation cover, soil moisture, soil temperature, and thaw depth in two thermokarst sites within boreal forests, two frost boil sites in tundra, and in adjacent undisturbed sites within both ecosystems. Both thermokarst and frost boils resulted in decreased vegetation cover and greater exposure of mineral soils (10-40% bare soils vs. 0% in undisturbed), and consequently, 2-3 times higher soil temperature and deeper thaw depth. Compared to undisturbed areas, soil moisture was 3-4 times higher in thermokarst areas but 1.2-2 times lower in frost boil areas, which reflected differences in microtopography between these two disturbance types. In both thermokarst and frost boil disturbed areas, deciduous and evergreen shrubs covered only 5 and 10%, respectively, compared to approximately 10 and 20%, respectively, in undisturbed areas. In general, graminoids were substantially more abundant (2-20 times) in disturbed areas than in those undisturbed. These results highlight important linkages between disturbances, vegetation communities, and permafrost soils, and contribute to our understanding of how changes in arctic vegetation dynamics as direct and/or indirect consequences of climate change have the potential to impact permafrost C pools.

  12. Circumpolar Dynamics of Arctic Tundra Vegetation in Relation to Temperature Trends

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Bhatt, U. S.; Raynolds, M. K.; Walker, D. A.; Reichle, L.

    2015-12-01

    Arctic tundra vegetation has generally exhibited a "greening" trend for at least the past three decades. However, these temporal trends in tundra vegetation are highly heterogeneous in space across different arctic regions, as well as showing variability over time. The factors controlling this variability are likely numerous with complex interactions, however, a first approach is to examine how vegetation dynamics relate to trends in temperature. We used a 32-year record (1982-2013) of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperatures from Advanced Very High Resolution Radiometer (AVHRR) sensors onboard NOAA satellites (GIMMS 3g dataset) to analyze observed changes in both aboveground tundra vegetation and surface temperatures. We divided the circumpolar dataset into two continental regions (North America and Eurasia), as well as by tundra subzone (A-E) sensu the Circumpolar Arctic Vegetation Map (CAVM). We 1) compared temporal trends in both MaxNDVI (peak values) and TI-NDVI (seasonally integrated values) with those of the Summer Warmth Index (SWI - sum of mean monthly temperatures > 0 °C); 2) assessed how the detrended interannual variabilities in NDVI compared to those of SWI; and 3) analyzed current and prior year SWI, as well as prior year NDVI, as controls on current year NDVI. Interannual coefficients of variation for SWI were 2.0 - 2.5 times greater than those for NDVI, and the temporal trendlines for NDVI were much "tighter" with greater r² values than those for SWI. Interannual variability in NDVI was greatest in the "Mid-Low" Arctic, whereas interannual variability in SWI was greatest in the most southern Arctic. Surprisingly, the observed relative rates of change in NDVI were greater than those of SWI for the warmer subzones for both North America and Eurasia. Finally, the change in NDVI from one year to the next was only weakly correlated with current year SWI. These results suggest that 1) there are clearly factors

  13. 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

  14. 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.

  15. Recent and Predicted Changes in Pan-Arctic Vegetation Properties and Their Climate Feedback Implications

    NASA Astrophysics Data System (ADS)

    Goetz, S. J.

    2014-12-01

    Arctic surface air temperatures have risen at approximately twice the global rate, generating a range of ecosystem responses and associated climate feedbacks. Well-documented examples include changes in vegetation productivity, fire disturbance, the expansion of woody shrubs into tundra, and associated changes in surface albedo and net surface shortwave radiative forcing. I will briefly review these and other changes across the pan-Arctic domain using a combination of field measurements and satellite remote sensing observations. I will examine the evidence for change that has already occurred and also discuss predictions of likely future ecosystem responses under different climate change scenarios. I will identify research and data needs that would help to resolve discrepancies and disparities that have been reported. In particular I will address the current potential and limitations of vegetation distribution models and the data sets that inform them. Notably, model predictions indicate rapid shifts to larger woody growth-forms, rapid colonization due to long-distance dispersal, and favorable conditions for recruitment following disturbances like tundra fire and permafrost degradation. Future albedo, evapotranspiration and aboveground biomass will change with the redistribution of Arctic vegetation, and the climate feedbacks of these ecosystem changes can be significant. Albedo and net surface shortwave radiation changes will dominate the influence on climate, largely due to the snow masking effects of taller vegetation. The carbon implications of ecosystem change will likely be dominated by processes that influence permafrost thaw vulnerability, but predictions also indicate that vegetation in the Arctic will affect climate primarily as a biophysical medium (i.e. via albedo change). As with thawing permafrost, predicted vegetation changes would exacerbate currently amplified rates of warming. New research efforts focused on the Arctic will address the research

  16. 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.

  17. Understanding Pan-Arctic Tundra Vegetation Change Through Long-term Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The goal of this paper is to present an analysis of the seasonality of tundra vegetation variability and change using long-term remotely sensed data as well as ground based measurements and reanalyses. An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI). Coherent variability between NDVI, springtime coastal sea ice (passive microwave) and land surface temperatures (AVHRR) has also been established. Satellite based snow and cloud cover data sets are being incorporated into this analysis. The Arctic tundra is divided into domains based on Treshnikov divisions that are modified based on floristic provinces. There is notable heterogeneity in Pan-Arctic vegetation and climate trends, which necessitates a regional analysis. This study uses remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2010. The GIMMS NDVI3g data has been corrected for biases during the spring and fall, with special focus on the Arctic. Trends of Maximum NDVI (MaxNDVI), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), and open water area are calculated for the Pan Arctic. Remotely sensed snow data trends suggest varying patterns throughout the Arctic and may in part explain the heterogeneous MaxNDVI trends. Standard climate data (station, reanalysis, and model data) and ground observations are used in the analysis to provide additional support for hypothesized mechanisms. Overall, we find that trends over the 30-year record are changing as evidenced by the following examples from recent years. The sea ice decline has increased in Eurasia and slowed in North America. The weekly AVHRR landsurface temperatures reveal that there has been summer cooling over Eurasia and that the warming over North America has slowed. The MaxNDVI rates of change have diverged between N. America and Eurasia

  18. Severity of climate change dictates the direction of biophysical feedbacks of vegetation change to Arctic climate

    NASA Astrophysics Data System (ADS)

    Zhang, Wenxin; Jansson, Christer; Miller, Paul; Smith, Ben; Samuelsson, Patrick

    2014-05-01

    Vegetation-climate feedbacks induced by vegetation dynamics under climate change alter biophysical properties of the land surface that regulate energy and water exchange with the atmosphere. Simulations with Earth System Models applied at global scale suggest that the current warming in the Arctic has been amplified, with large contributions from positive feedbacks, dominated by the effect of reduced surface albedo as an increased distribution, cover and taller stature of trees and shrubs mask underlying snow, darkening the surface. However, these models generally employ simplified representation of vegetation dynamics and structure and a coarse grid resolution, overlooking local or regional scale details determined by diverse vegetation composition and landscape heterogeneity. In this study, we perform simulations using an advanced regional coupled vegetation-climate model (RCA-GUESS) applied at high resolution (0.44×0.44° ) over the Arctic Coordinated Regional Climate Downscaling Experiment (CORDEX-Arctic) domain. The climate component (RCA4) is forced with lateral boundary conditions from EC-EARTH CMIP5 simulations for three representative concentration pathways (RCP 2.6, 4.5, 8.5). Vegetation-climate response is simulated by the individual-based dynamic vegetation model (LPJ-GUESS), accounting for phenology, physiology, demography and resource competition of individual-based vegetation, and feeding variations of leaf area index and vegetative cover fraction back to the climate component, thereby adjusting surface properties and surface energy fluxes. The simulated 2m air temperature, precipitation, vegetation distribution and carbon budget for the present period has been evaluated in another paper. The purpose of this study is to elucidate the spatial and temporal characteristics of the biophysical feedbacks arising from vegetation shifts in response to different CO2 concentration pathways and their associated climate change. Our results indicate that the

  19. Vegetation-Soil-Active Layer Relationships Along a Low-Arctic Bioclimate Gradient, Alaska

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Jia, G. J.; Epstein, H. E.; Shiklomanov, N.; Nelson, F.; Hinzman, L. D.; Romanovsky, V. E.

    2002-12-01

    Northern Alaska has three of five Arctic bioclimate subzones, which are representative of the circumpolar Low Arctic. This portion of the Arctic has more or less continuous tundra plant cover and well-developed moss canopies. We examined the biomass and remotely sensed spectral properties of the vegetation canopy, active-layer thickness, and the soil properties at 21 sites on the Arctic Slope and Seward Peninsula of Alaska. The sites were grouped into three bioclimate subzones according the summer warmth at the sites. The summer warmth index (SWI) is the sum of the mean monthly temperatures greater than 0 degrees C. Subzone C, the coldest subzone, occurs in a narrow strip along the northern coast of the Alaska. Subzone D covers most of the Arctic Coastal Plain and the northwest portion of the Seward Peninsula, and Subzone E covers most of the Foothills and most of the unforested portion of the Seward Peninsula. The SWIs in Subzones C, D, and E are generally less than 10-15 degrees C, 15-25 degrees C, and 25-35 degrees C respectively. The average active layer depths were 44, 55, and 47 cm respectively The shallow active layer in Subzone E is to a large degree a response to the denser vegetation canopies in Subzone E. Total plant biomass in Subzone C, D, and E averaged 421 g m-2, 503 g m-2, and 1178 g m-2 respectively. The much higher biomass in Subzone E was due primarily to woody shrubs (40 g m-2 in Subzone C, 51 g m-2 in Subzone D, and 730 g m-2 in Subzone E). The normalized difference vegetation index (NDVI) is one measure of greenness. Highest NDVI values were obtained from acidic tundra regions in Subzone E, and the lowest NDVI values were obtained in the nonacidic areas of Subzone C. In summary, the insulative properties of the vegetation play a very important role controlling the thickness of the active layer, and the amount of vegetation biomass differs according to summer warmth and soil properties. Acidic soils in the warmest parts of the Arctic (Subzone E

  20. 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

  1. Modeling the Response of Arctic Vegetation to Increasing Atmospheric Carbon Dioxide and Climate Change

    NASA Astrophysics Data System (ADS)

    Cassidy, E. S.; Snyder, P. K.

    2009-12-01

    An increase in atmospheric carbon dioxide is contributing to planetary warming that is strongest over high latitude land areas of the Northern Hemisphere. Elevated levels of atmospheric carbon dioxide and strong warming have led to changes in vegetation distribution, permafrost depth, and snow cover, which significantly affect the interactions between the terrestrial ecosystem and the climate through biophysical and biogeochemical processes. With a continued rise in greenhouse gas emissions and additional warming in the high latitudes, uncertainty exists as to how the Arctic biosphere will respond in the coming decades and whether Arctic ecosystems will remain a carbon sink or instead become a source of carbon to the atmosphere. Elevated carbon dioxide and climate change can affect vegetation growth through changing the assimilation of carbon dioxide and the respiration of carbon from the vegetation and soil. Using a dynamic global vegetation model, the Integrated BIosphere Simulator Model (IBIS), potential changes in both the biophysical and biogeochemical processes of Arctic vegetation were analyzed to determine how future climate change and elevated atmospheric carbon dioxide may alter their functioning and ability to store carbon. High latitude regions were modeled using a variety of temperature, precipitation, and carbon dioxide scenarios. Changes in gross and net primary production, net ecosystem exchange, soil carbon, soil respiration, leaf area index, and biomass content were analyzed. Under high levels of carbon dioxide, net primary production increased at a greater rate than high levels of warming. Soil carbon decreased dramatically with high levels of warming as soil respiration increased, but soil carbon increased with higher levels of atmospheric carbon dioxide as the vegetation fixed more carbon. Net primary production also increased in scenarios with elevated precipitation. The results from the combined scenarios of climate and atmospheric carbon

  2. 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

  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. 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

  5. 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.

  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. PMID:20080628

  7. 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

  8. 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.

  9. [Effects of road construction on regional vegetation types].

    PubMed

    Liu, Shi-Liang; Liu, Qi; Wang, Cong; Yang, Jue-Jie; Deng, Li

    2013-05-01

    As a regional artificial disturbance component, road exerts great effects on vegetation types, and plays a substantial role in defining vegetation distribution to a certain extent. Aiming at the tropical rainforest degradation and artificial forest expansion in Yunnan Province of Southwest China, this paper analyzed the effects of road network extension on regional vegetation types. In the Province, different classes of roads had different effects on the vegetation types, but no obvious regularity was observed in the effects on the patch areas of different vegetation types due to the great variations of road length and affected distance. However, the vegetation patch number was more affected by lower class roads because of their wide distribution. As for different vegetation types, the vegetations on cultivated land were most affected by roads, followed by Castanopsis hystrix and Schima wallichii forests. Road network formation contributed most to the vegetation fragmentation, and there existed significant correlations between the human disturbance factors including village- and road distributions. PMID:24015533

  10. Camera derived vegetation greenness index as proxy for gross primary production in a low Arctic wetland area

    NASA Astrophysics Data System (ADS)

    Westergaard-Nielsen, Andreas; Lund, Magnus; Hansen, Birger Ulf; Tamstorf, Mikkel Peter

    2013-12-01

    The Arctic is experiencing disproportionate warming relative to the global average, and the Arctic ecosystems are as a result undergoing considerable changes. Continued monitoring of ecosystem productivity and phenology across temporal and spatial scales is a central part of assessing the magnitude of these changes. This study investigates the ability to use automatic digital camera images (DCIs) as proxy data for gross primary production (GPP) in a complex low Arctic wetland site. Vegetation greenness computed from DCIs was found to correlate significantly (R2 = 0.62, p < 0.001) with a normalized difference vegetation index (NDVI) product derived from the WorldView-2 satellite. An object-based classification based on a bi-temporal image composite was used to classify the study area into heath, copse, fen, and bedrock. Temporal evolution of vegetation greenness was evaluated and modeled with double sigmoid functions for each plant community. GPP at light saturation modeled from eddy covariance (EC) flux measurements were found to correlate significantly with vegetation greenness for all plant communities in the studied year (i.e., 2010), and the highest correlation was found between modeled fen greenness and GPP (R2 = 0.85, p < 0.001). Finally, greenness computed within modeled EC footprints were used to evaluate the influence of individual plant communities on the flux measurements. The study concludes that digital cameras may be used as a cost-effective proxy for potential GPP in remote Arctic regions.

  11. Vegetation Feedbacks Explain Recent High-latitude Summer Warming in Alaskan Arctic and Boreal Ecosystems

    NASA Astrophysics Data System (ADS)

    Chapin, F. S.; Beringer, J.; Copass, C.; Epstein, H.; Lloyd, A.; Lynch, A.; McGuire, A. D.; Sturm, M.

    2002-12-01

    Although General Circulation Models predict the observed winter and spring warming at high latitudes, there is no obvious physical mechanism in the climate system that can account for the significant increase in summer temperatures that has occurred at high latitudes during the past 30 years. We demonstrate that vegetation-induced feedbacks in snow properties and summer energy exchange with the atmosphere explain this recent summer warming. A combination of stand-age reconstructions, repeat photography, and satellite measures of vegetation greenness demonstrate an expansion of the distribution and an infilling of shrubs in moist tundra and of trees in forest tundra. These vegetation changes increase the depth and thermal resistance of the snow pack, causing a 3oC increase in winter soil temperature and an increase in winter decomposition and nutrient mineralization, which enhance plant growth. These vegetation changes also increase summer heat transport to the atmosphere by increasing radiation absorption (lower albedo) and the proportion of absorbed energy that is transferred to the atmosphere as sensible heat. The resulting increase in atmospheric heating, on a unit-area basis, is similar to effects of a doubling of atmospheric carbon dioxide or a 2% change in solar constant, such as occurred at the last glacial-interglacial boundary. Simulations with the regional climate model ARCSyM indicate that a change from shrubless tundra to shrub-dominated tundra on the North Slope of Alaska would increase July mean temperature by 1.5 to 3.5 degrees C, with the warming effects extending south into the boreal forest of interior Alaska. If these vegetation feedbacks to regional warming are widespread, as suggested by indigenous knowledge and the satellite record, they are of sufficient magnitude to explain the summer warming that has recently been observed in northern Alaska and other regions of the circumpolar Arctic.

  12. Rapid responses of permafrost and vegetation to experimentally increased snow cover in sub-arctic Sweden

    NASA Astrophysics Data System (ADS)

    Johansson, Margareta; Callaghan, Terry V.; Bosiö, Julia; Åkerman, H. Jonas; Jackowicz-Korczynski, Marcin; Christensen, Torben R.

    2013-09-01

    Increased snow depth already observed, and that predicted for the future are of critical importance to many geophysical and biological processes as well as human activities. The future characteristics of sub-arctic landscapes where permafrost is particularly vulnerable will depend on complex interactions between snow cover, vegetation and permafrost. An experimental manipulation was, therefore, set up on a lowland peat plateau with permafrost, in northernmost Sweden, to simulate projected future increases in winter precipitation and to study their effects on permafrost and vegetation. After seven years of treatment, statistically significant differences between manipulated and control plots were found in mean winter ground temperatures, which were 1.5 ° C higher in manipulated plots. During the winter, a difference in minimum temperatures of up to 9 ° C higher could be found in individual manipulated plots compared with control plots. Active layer thicknesses increased at the manipulated plots by almost 20% compared with the control plots and a mean surface subsidence of 24 cm was recorded in the manipulated plots compared to 5 cm in the control plots. The graminoid Eriophorum vaginatum has expanded in the manipulated plots and the vegetation remained green longer in the season.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  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. The role of seasonality and large-scale climate drivers in recent Pan-Arctic tundra vegetation variability and change

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI) and a coherent variability between NDVI, springtime coastal sea ice and land surface temperatures has been shown. The goal of this paper is to understand the forcing factors of this change and variability better through an analysis of the seasonality of these remotely sensed variables as well as long-term climate data sets. This study uses remotely sensed submonthly 25-km sea ice concentration, surface temperature, and NDVI from 1982 to 2010. The NDVI3g data has been corrected for biases in the spring and fall. Standard climate data (station, reanalysis, and model data) and ground observations are also examined. For overall trends, we find that summer time open water area has increased most in the Beaufort, and Siberian Seas. The seasonality of SWI trends display distinct heterogeneity across the Arctic, with maximum warming in August for most regions (Figure 1). The monthly time integrated NDVI trends display the largest positive values for most of the Arctic in July, with the exception of the E. Bering and Kara regions, which show declines during most months (Figure 2). The largest magnitude increases in Max-NDVI tend to be in subzones that are inland, particularly in the Beaufort and Chukchi regions. NDVI has increased more during spring in Eurasia and more during peak vegetation activity (July) over North America. The analysis suggests that local atmospheric circulation as well as other local factors likely plays an important role in vegetation productivity.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. EnMAP Specific BRDF Measurements and Vegetation Indices for Low-Growing Biomes in the Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Buchhorn, M.; Heim, B.; van der Linden, S.

    2011-12-01

    Global warming is highest in the Arctic where the tundra regions are expected to undergo pronounced changes. Remote sensing can provide spatial and temporal data on variables linked to vegetation and ecosystem processes on global scale. Specifically, hyperspectral remote sensing data can relate to Vegetation Indices (VIs), Leaf Area Index (LAI) and the fraction of Photosynthetically active Radiation (fPAR). Currently, spaceborne hyperspectral imaging data is provided by the CHRIS/PROBA and the Hyperion programs. The Environmental Mapping and Analysis Program (EnMAP), a German hyperspectral mission, is the next step in this line and will provide high spectral resolution observations with a ground sampling distance of 30 meter. The continuous spectral sampling provided by imaging spectroscopy offers the possibility to develop robust algorithms for vegetation indices in low-growing tundra biomes. Since the EnMAP sensor has pointing capabilities, both spectral and directional reflection characteristics need to be taken into account. In order to examine the influence of the bidirectional reflectance distribution function (BRDF) on spectral variables such as the Vegetation Indices, LAI and fPAR, we developed the EnMAP specific field goniospectrometer, EyeSight. We took part at the summer field campaign of the Earth Cryosphere Institute (RU) in 2011 on the Yamal Peninsula, Western Siberia, Russia. Field spectroscopy, vegetation and biomass analysis, and field goniometer measurements under varying sun zenith angles and moisture conditions have been conducted. The spectral measurements and BRDF measurements of the low-growing tundra are presented and discussed.

  8. 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

  9. 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

  10. Continuous Measurement of CO2 concentration in Arctic Soil by Small Open-path Type CO2 Sensors

    NASA Astrophysics Data System (ADS)

    Nakamoto, K.; Oechel, W. C.; Lipson, D.

    2006-12-01

    Permafrost and seasonally thawed Arctic soils in high northern latitudes hold approximately 25 percent of the world's soil organic carbon. The predicted warming of the Arctic, coupled with regional drying, could release much of the carbon now stored in the Arctic soils. Understanding the mechanisms controlling the release of soil organic carbon as CO2 is critical to predicting sensitive Arctic soils will respond to and influence global climate change. However, there are only a few reports of soil respiration, and very few that report continuous respiration rates. The results of chamber measurements give the overall efflux from the surface and emphasize biological and chemical processes and controls. However, they do not measure soil CO2 concentrations. To our knowledge, continuous measurements of soil CO2 concentration has not been previously conducted in the Arctic, and gas diffusivity of Arctic soils that thaw and freeze are poorly known. To obtain a better understanding of the patterns and controls on carbon release from Arctic soils, long-term measurements of soil respiration and an investigation of the underlying processes were undertaken. In this study, continuous measurements of soil CO2 concentration by small open path type infrared gas analyzers in a revegetated Arctic drained lake basin at Barrow Alaska was undertaken. Measurements were conducted from the beginning of soil thaw in summer through the following winter and summer. Changes in soil CO2 concentration during freezing and thawing processes proved especially interesting. Soil CO2 concentration in the organic layer of the drained lake basin was much higher than that of Typic Psamomoturbals soil from heath vegetation cover in Greenland (Elberling and Brandt 2003) throughout the thawing season. Soil CO2 increased with increasing soil temperature and thaw depth reflecting CO2 production in the soil. Soil CO2 concentration was greater in relatively wet soil than in dry soil. Soil CO2 concentration

  11. MERCURY IN VEGETATION AND LAKE SEDIMENTS FROM THE U.S. ARCTIC

    EPA Science Inventory

    Global atmospheric concentrations of mercury (Hg) appear to be increasing and with it the potential for ecosystem exposure and ecological effects. rom 1990 to 1993 the authors examined U.S. arctic ecosystems over a broad spatial scale to develop baseline information on current co...

  12. 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...

  13. 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

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

    USGS Publications Warehouse

    Bryant, John P.; Joly, Kyle; Chapin, F. Stuart, III; 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.

  15. Late Weichselian (Valdaian) and Holocene vegetation and environmental history of the northern Timan Ridge, European Arctic Russia

    NASA Astrophysics Data System (ADS)

    Paus, Aage; Svendsen, John Inge; Matiouchkov, Alexei

    2003-11-01

    Lake and peat deposits from the Timan Ridge, Arctic Russia, were pollen analysed, reconstructing the vegetation history and paleoenvironment since the Last Glacial Maximum (LGM) 20-18,000 years ago. The sites studied are located inside the margins of a large paleolake of about 20 km2, by us named Lake Timan. This lake developed in the Late Weichselian, more than 30,000 years after the deglaciation of this region, and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment. The lake was drained during the early Holocene when the outlet rivers eroded the spillways. A new generation of much smaller lakes formed during the Holocene when the last remnants of buried glacier ice melted away causing the exposed floor of Lake Timan to subside. Since deglaciation, the following regional vegetation development has been recorded: (1) During the initial stage of Lake Timan, the dominant vegetation was discontinuous steppe/tundra, with patches of snow bed vegetation. (2) A dwarf-shrub tundra established during the Late Weichselian interstadial (Aller ød), probably reflecting warmer and moister conditions. (3) The Younger Dryas cooling is recognised by a reversal to steppe/tundra and snowbeds on unstable mineral-soils, and higher palynological richness. (4) Soon after the transition into the Holocene, a birch-forest established on the Timan Ridge. (5) A cooling starting around 8200 cal. years BP initiated the deforestation of the exposed hills. In the most protected sites, birch trees persisted until later than 4000 years ago, reflecting a gradual development into the present treeless dwarf-shrub tundra.

  16. 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.

  17. Vegetation and climate history in the Laptev Sea region (Arctic Siberia) during Late Quaternary inferred from pollen records

    NASA Astrophysics Data System (ADS)

    Andreev, Andrei A.; Schirrmeister, Lutz; Tarasov, Pavel E.; Ganopolski, Andrey; Brovkin, Viktor; Siegert, Christine; Wetterich, Sebastian; Hubberten, Hans-Wolfgang

    2011-08-01

    Paleoenvironmental records from a number of permafrost sections and lacustrine cores from the Laptev Sea region dated by several methods ( 14C-AMS, TL, IRSL, OSL and 230Th/U) were analyzed for pollen and palynomorphs. The records reveal the environmental history for the last ca 200 kyr. For interglacial pollen spectra, quantitative temperature values were estimated using the best modern analogue method. Sparse grass-sedge vegetation indicating arctic desert environmental conditions existed prior to 200 kyr ago. Dense, wet grass-sedge tundra habitats dominated during an interstadial ca 200-190 kyr ago, reflecting warmer and wetter summers than before. Sparser vegetation communities point to much more severe stadial conditions ca 190-130 kyr ago. Open grass and Artemisia communities with shrub stands ( Alnus fruticosa, Salix, Betula nana) in more protected and moister places characterized the beginning of the Last Interglacial indicate climate conditions similar to present. Shrub tundra ( Alnus fruticosa and Betula nana) dominated during the middle Eemian climatic optimum, when summer temperatures were 4-5 °C higher than today. Early-Weichselian sparse grass-sedge dominated vegetation indicates climate conditions colder and dryer than in the previous interval. Middle Weichselian Interstadial records indicate moister and warmer climate conditions, for example, in the interval 40-32 kyr BP Salix was present within dense, grass-sedge dominated vegetation. Sedge-grass- Artemisia-communities indicate that climate became cooler and drier after 30 kyr BP, and cold, dry conditions characterized the Late Weichselian, ca 26-16 kyr BP, when grass-dominated communities with Caryophyllaceae, Asteraceae, Cichoriaceae, Selaginella rupestris were present. From 16 to 12 kyr BP, grass-sedge communities with Caryophyllaceae, Asteraceae, and Cichoriaceae indicate climate was significantly warmer and moister than during the previous interval. The presence of Salix and Betula reflect

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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).

  4. Emergent Dead Vegetation and Paired Cosmogenic Isotope Constraints on Ice Cap Activity, Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Pendleton, S.; Miller, G. H.

    2014-12-01

    Recent summer warming has now raised the equilibrium line above almost all ice caps on Baffin Island, resulting in surface lowering and marginal recession everywhere. As cold-based ice recedes it frequently exposes in situ tundra plants that were living at the time ice expanded across the site. Radiocarbon dates for each plant records when cold summers dropped regional snowline below the site, killing the plants, and snowline remained below the site until the collection date. The kill dates also represent the last time that the climate was warm enough to expose the sampling location. Seventy-six vegetation samples collected in 2013 from the Penny Ice Cap region have been dated, with significant age populations at ~0.5, 1.8, 2.3, and 3.6 ka. The absence of ages around ~1, 2, 3, 4.5, and 5.5 ka suggest periods of either no snowline depression or stability. Sixteen vegetation samples returned ages of >45 ka (2 revisited sites from 2010, 14 new). It is postulated that these radiocarbon dead samples were last exposed during the last interglaciation (~120 ka), the last time climate was as warm as present. In addition to plant collections, bedrock exposures at the ice margins were sampled for 26Al/10Be cosmogenic nuclide dating. Seven samples from and around the Penny Ice cap have returned maximum exposure ages from ~ 0.6-0.9 ma and total histories of ~0.6-1.5 ma. In general, samples from the larger Penny Ice Cap exhibited lower amounts of exposure (~20% of total history) than those samples from smaller, localized ice caps (~55%). Radiocarbon dead sites north of the Penny Ice cap experienced significantly more exposure over their lifetimes than their counterparts east of the Penny Ice cap, suggesting significant differences in local and regional land ice fluctuations over the last 2 million years. Utilizing both the method of in situ moss and 26Al/10Be dating provides new insight into both the recent activity and long-term evolution of ice on Baffin Island. In particular

  5. 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.

  6. 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

  7. 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.

  8. Mapping and characterizing the vegetation types of the Democratic Republic of Congo using SPOT VEGETATION time series

    NASA Astrophysics Data System (ADS)

    Vancutsem, C.; Pekel, J.-F.; Evrard, C.; Malaisse, F.; Defourny, P.

    2009-02-01

    The need for quantitative and accurate information to characterize the state and evolution of vegetation types at a national scale is widely recognized. This type of information is crucial for the Democratic Republic of Congo, which contains the majority of the tropical forest cover of Central Africa and a large diversity of habitats. In spite of recent progress in earth observation capabilities, vegetation mapping and seasonality analysis in equatorial areas still represent an outstanding challenge owing to high cloud coverage and the extent and limited accessibility of the territory. On one hand, the use of coarse-resolution optical data is constrained by performance in the presence of cloud screening and by noise arising from the compositing process, which limits the spatial consistency of the composite and the temporal resolution. On the other hand, the use of high-resolution data suffers from heterogeneity of acquisition dates, images and interpretation from one scene to another. The objective of the present study was to propose and demonstrate a semi-automatic processing method for vegetation mapping and seasonality characterization based on temporal and spectral information from SPOT VEGETATION time series. A land cover map with 18 vegetation classes was produced using the proposed method that was fed by ecological knowledge gathered from botanists and reference documents. The floristic composition and physiognomy of each vegetation type are described using the Land Cover Classification System developed by the FAO. Moreover, the seasonality of each class is characterized on a monthly basis and the variation in different vegetation indicators is discussed from a phenological point of view. This mapping exercise delivers the first area estimates of seven different forest types, five different savannas characterized by specific seasonality behavior and two aquatic vegetation types. Finally, the result is compared to two recent land cover maps derived from

  9. Spatial variation in landscape-level CO2 and CH4 fluxes from arctic coastal tundra: influence from vegetation, wetness, and the thaw lake cycle.

    PubMed

    Sturtevant, Cove S; Oechel, Walter C

    2013-09-01

    Regional quantification of arctic CO2 and CH4 fluxes remains difficult due to high landscape heterogeneity coupled with a sparse measurement network. Most of the arctic coastal tundra near Barrow, Alaska is part of the thaw lake cycle, which includes current thaw lakes and a 5500-year chronosequence of vegetated thaw lake basins. However, spatial variability in carbon fluxes from these features remains grossly understudied. Here, we present an analysis of whole-ecosystem CO2 and CH4 fluxes from 20 thaw lake cycle features during the 2011 growing season. We found that the thaw lake cycle was largely responsible for spatial variation in CO2 flux, mostly due to its control on gross primary productivity (GPP). Current lakes were significant CO2 sources that varied little. Vegetated basins showed declining GPP and CO2 sink with age (R(2) = 67% and 57%, respectively). CH4 fluxes measured from a subset of 12 vegetated basins showed no relationship with age or CO2 flux components. Instead, higher CH4 fluxes were related to greater landscape wetness (R(2) = 57%) and thaw depth (additional R(2) = 28%). Spatial variation in CO2 and CH4 fluxes had good satellite remote sensing indicators, and we estimated the region to be a small CO2 sink of -4.9 ± 2.4 (SE) g C m(-2) between 11 June and 25 August, which was countered by a CH4 source of 2.1 ± 0.2 (SE) g C m(-2) . Results from our scaling exercise showed that developing or validating regional estimates based on single tower sites can result in significant bias, on average by a factor 4 for CO2 flux and 30% for CH4 flux. Although our results are specific to the Arctic Coastal Plain of Alaska, the degree of landscape-scale variability, large-scale controls on carbon exchange, and implications for regional estimation seen here likely have wide relevance to other arctic landscapes. PMID:23649775

  10. 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

  11. 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

  12. 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...

  13. 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.

  14. 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.

  15. Changes versus homeostasis in alpine and sub-alpine vegetation over three decades in the sub-arctic.

    PubMed

    Hedenås, Henrik; Carlsson, Bengt A; Emanuelsson, Urban; Headley, Alistair D; Jonasson, Christer; Svensson, Brita M; Callaghan, Terry V

    2012-01-01

    Plant species distributions are expected to shift and diversity is expected to decline as a result of global climate change, particularly in the Arctic where climate warming is amplified. We have recorded the changes in richness and abundance of vascular plants at Abisko, sub-Arctic Sweden, by re-sampling five studies consisting of seven datasets; one in the mountain birch forest and six at open sites. The oldest study was initiated in 1977-1979 and the latest in 1992. Total species number increased at all sites except for the birch forest site where richness decreased. We found no general pattern in how composition of vascular plants has changed over time. Three species, Calamagrostis lapponica, Carex vaginata and Salix reticulata, showed an overall increase in cover/frequency, while two Equisetum taxa decreased. Instead, we showed that the magnitude and direction of changes in species richness and composition differ among sites. PMID:22864693

  16. 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.

  17. 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

  18. Floristic Relationships Among Vegetation Types of New Zealand and the Southern Andes: Similarities and Biogeographic Implications

    PubMed Central

    Ezcurra, Cecilia; Baccalá, Nora; Wardle, Peter

    2008-01-01

    Background and Aims Similarities between the floras of geographically comparable regions of New Zealand (NZ) and the southern Andes (SA) have interested biologists for over 150 years. The present work selects vegetation types that are physiognomically similar between the two regions, compares their floristic composition, assesses the environmental factors that characterize these matching vegetation types, and determines whether phylogenetic groups of ancestral versus modern origin are represented in different proportions in their floras, in the context of their biogeographic history. Methods Floristic relationships based on 369 genera of ten vegetation types present in both regions were investigated with correspondence analysis (CA) and ascending hierarchical clustering (AHC). The resulting ordination and classification were related to the environmental characteristics of the different vegetation types. The proportions of different phylogenetic groups between the regions (NZ, SA) were also compared, and between forest and non-forest communities. Key Results Floristic similarities between NZ and SA tend to increase from forest to non-forest vegetation, and are highest in coastal vegetation and bog. The floras of NZ and SA also differ in their phylogenetic origin, NZ being characterized by an ‘excess’ of genera of basal origin, especially in forests. Conclusions The relatively low similarities between forests of SA and NZ are related to the former being largely of in situ South American and Gondwanan origin, whereas the latter have been mostly reconstituted though transoceanic dispersal of propagules since the Oligocene. The greater similarities among non-forest plant communities of the two regions result from varied dispersal routes, including relatively recent transoceanic dispersal for coastal vegetation, possible dispersal via a still-vegetated Antarctica especially for bog plants, and independent immigration from Northern Hemisphere sources for many genera

  19. 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.

  20. 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

  1. 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

  2. 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.

  3. 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. PMID:26141223

  4. 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.

  5. Satellite Remote Sensing of Pan-arctic Vegetation Productivity, Soil Respiration and net CO2 Exchange Using MODIS and AMSR-E Data

    NASA Astrophysics Data System (ADS)

    Nirala, M. L.; Heinsch, F. A.; Kimball, J. S.; Zhao, M.; Running, S.; Oechel, W.; McDonald, K.; Njoku, E.

    2005-05-01

    We have developed an approach for regional assessment and monitoring of land-atmosphere carbon dioxide (CO2) exchange, soil heterotrophic respiration (Rh) and vegetation productivity for arctic tundra using global satellite remote sensing at optical and microwave wavelengths. We use C- and X-band brightness temperatures from AMSR-E to extract surface wetness and temperature, and MODIS data to derive land cover, Leaf Area Index (LAI) and Net Primary Production (NPP) information. Calibration and validation activities involve comparisons between satellite remote sensing and tundra CO2 eddy flux tower and biophysical measurement networks and hydro-ecological process model simulations. We analyze spatial and temporal anomalies and environmental drivers of land-atmosphere net CO2 exchange at weekly and annual time steps. Surface soil moisture status and temperature as detected from satellite remote sensing observations are found to be major drivers spatial and temporal patterns of tundra net CO2 exchange and photosynthetic and respiration processes. We also find that satellite microwave measurements are capable of capturing seasonal variations and regional patterns in tundra soil heterotrophic respiration and CO2 exchange, while our ability to extract spatial patterns at the scale of surface heterogeneity is limited by the coarse spatial scale of the satellite remote sensing footprint. Our results also indicate that carbon cycle response to climate change is non-linear and strongly coupled to arctic surface hydrology. This work was performed at The University of Montana and Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  6. 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

  7. 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.

  8. [Relationship between main vegetation types and climatic factors in Inner Mongolia].

    PubMed

    Niu, J

    2000-02-01

    The relationship between main vegetation types and climate factors in Inner Mongolia was analyzed by using up-to-date vegetation map, statistics, modeling and spatial simulation of regional climatic factors under the support of GIS. The feasible climatic range of spatial distribution of plant communities was derived from overlaying vegetation map and climate maps. The results showed that the vegetation distribution was obviously in accordance with climate. On the one hand, all the types, not only zonal vegetation, but also mountain, sandy land and low land communities changed gradually from east to west due to the distance to oceans, with a zonal differentiation, Precipitation played an important role in determining this regulation. On the other hand, latitudinal replacement of plant communities occurred with the change of temperature from north to south. In addition, temperature was also the key factor controlling the spatial distribution of vegetation types, such as meadow, steppe, shrub and low land communities on the east and west sides of Daxinganling Mountains. PMID:11766587

  9. Habitat choice by juvenile cod ( Gadus morhua L.) on sandy soft bottoms with different vegetation types

    NASA Astrophysics Data System (ADS)

    Borg, Å.; Pihl, L.; Wennhage, H.

    1997-08-01

    Habitat choice by juvenile cod ( Gadus morhua L.) on sandy bottoms with different vegetation types was studied in laboratory. The experiment was conducted day and night in flow-through tanks on two different size-classes of cod (7-13 and 17-28 cm TL). Four habitats, typical of shallow soft bottoms on the Swedish west coast: Fucus vesiculosus, Zostera marina, Cladophora sp. and bare sand, were set up pair-wise in six combinations. The main difference between habitats in this study was vegetation structure, since all parameters except vegetation type was considered equal for both sides of the experimental tanks and natural prey was eliminated. The results showed a difference in habitat utilization by juvenile cod between day (light) and night (dark). During day time the fishes showed a significant preference for vegetation, while nocturnally no significant choice of habitat was made. Both size-classes preferred Fucus, considered the most complex habitat in this study, when this was available. The smaller size-class seemed to be able to utilize the other vegetation types as well, always preferring vegetation over sand. Larger juvenile cod, on the other hand, appeared to be restricted to Fucus. This difference in habitat choice by the two size-classes might be due to a greater dependence on shelter from predation by the smaller juveniles, causing them to associate more strongly with vegetation. The larger juveniles avoided Cladophora, since they might have difficulties in entering the compact structure of this filamentous algae. Availability of vegetation at day time, as a predation refuge, as well as of open sandy areas for feeding during night, thus seems to be important for juvenile cod. It is concluded that eutrophication-induced changes in habitat structure, such as increased dominance by filamentous algae, could alter the availability of predation refuges and foraging habitats for juvenile cod.

  10. 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

  11. 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

  12. Crop Type Classification Using Vegetation Indices of RapidEye Imagery

    NASA Astrophysics Data System (ADS)

    Ustuner, M.; Sanli, F. B.; Abdikan, S.; Esetlili, M. T.; Kurucu, Y.

    2014-09-01

    Cutting-edge remote sensing technology has a significant role for managing the natural resources as well as the any other applications about the earth observation. Crop monitoring is the one of these applications since remote sensing provides us accurate, up-to-date and cost-effective information about the crop types at the different temporal and spatial resolution. In this study, the potential use of three different vegetation indices of RapidEye imagery on crop type classification as well as the effect of each indices on classification accuracy were investigated. The Normalized Difference Vegetation Index (NDVI), the Green Normalized Difference Vegetation Index (GNDVI), and the Normalized Difference Red Edge Index (NDRE) are the three vegetation indices used in this study since all of these incorporated the near-infrared (NIR) band. RapidEye imagery is highly demanded and preferred for agricultural and forestry applications since it has red-edge and NIR bands. The study area is located in Aegean region of Turkey. Radial Basis Function (RBF) kernel was used here for the Support Vector Machines (SVMs) classification. Original bands of RapidEye imagery were excluded and classification was performed with only three vegetation indices. The contribution of each indices on image classification accuracy was also tested with single band classification. Highest classification accuracy of 87, 46 % was obtained using three vegetation indices. This obtained classification accuracy is higher than the classification accuracy of any dual-combination of these vegetation indices. Results demonstrate that NDRE has the highest contribution on classification accuracy compared to the other vegetation indices and the RapidEye imagery can get satisfactory results of classification accuracy without original bands.

  13. 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.

  14. Vegetation and climate history in the Laptev Sea region (arctic Siberia) during Late Quaternary inferred from pollen records

    NASA Astrophysics Data System (ADS)

    Andreev, A.; Schirrmeister, L.; Tarasov, P.

    2009-04-01

    A number of permafrost sections dated by 14C, TL, IRSL, and 230U/Th were analysed for pollen. Pollen spectra suggest that wet grass-sedge tundra habitats dominated during an interstadial c. 200-170 ka ago. The climate was rather wet and cold. The pollen spectra reflect sparser grass-sedge vegetation cover during the Late Saalian stadial, c. 170-130 ka BP. Environmental conditions were much more severe compared with the previous interstadial. Open Poaceae and Artemisia communities dominated at the beginning of the Last Interglacial. Some shrubs (Alnus fruticosa, Salix, Betula nana) grew in more protected and wetter places. Climate was rather warm (similar to modern conditions)during this time. Shrub tundra with Alnus fruticosa and Betula nana s.l. dominated in the area during the Eemian climatic optimum, when summer temperatures were 4-5°C higher than today. Early Weichselian pollen records reflect harsh environmental conditions; sparser vegetation (mostly grass and sedge communities) during this time. Middle Weichselian (Karginsky) Interstadial records with dominance of Cyperaceae and Poaceae with some Artemisia and Salix reflects tundra- and steppe-like associations with willow shrubs dominated the area. The climate was relatively moist and warm. A rather high content of algae colonies in the sediments indicates shallow water habitats (e.g. centres of ice wedge polygons). Dominance of Poaceae, Cyperaceae, Artemisia, and Caryophyllaceae pollen with some other herbs is typical for the 40-32 ka BP (climatic optimum) old sediments when open herb dominated the area. High pollen concentrations reflect that dense grass-sedge dominated vegetation; presence of Salix is also characteristic. The records point to climate amelioration during the Middle Weichselian compared to the Early Weichselian. Climate conditions became colder and drier c. 30-26 ka BP. Pollen spectra reflect that sedge-grass-Artemisia with some Caryophyllaceae and Asteraceae dominated the vegetation

  15. 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

  16. Estimation of vegetation LAI from hyperspectral reflectance data: Effects of soil type and plant architecture

    NASA Astrophysics Data System (ADS)

    Darvishzadeh, Roshanak; Skidmore, Andrew; Atzberger, Clement; van Wieren, Sip

    2008-09-01

    The retrieval of canopy biophysical variables is known to be affected by confounding factors such as plant type and background reflectance. The effects of soil type and plant architecture on the retrieval of vegetation leaf area index (LAI) from hyperspectral data were assessed in this study. In situ measurements of LAI were related to reflectances in the red and near-infrared and also to five widely used spectral vegetation indices (VIs). The study confirmed that the spectral contrast between leaves and soil background determines the strength of the LAI-reflectance relationship. It was shown that within a given vegetation species, the optimum spectral regions for LAI estimation were similar across the investigated VIs, indicating that the various VIs are basically summarizing the same spectral information for a given vegetation species. Cross-validated results revealed that, narrow-band PVI was less influenced by soil background effects (0.15 ≤ RMSE cv ≤ 0.56). The results suggest that, when using remote sensing VIs for LAI estimation, not only is the choice of VI of importance but also prior knowledge of plant architecture and soil background. Hence, some kind of landscape stratification is required before using hyperspectral imagery for large-scale mapping of vegetation biophysical variables.

  17. Population of Humic Acid Degrading Microorganisms in Andosols under Different Vegetation Types and Grassland Management Regimens.

    PubMed

    Yanagi, Yukiko; Yoda, Kaori; Ogura, Kazuhiko; Fujitake, Nobuhide

    2008-01-01

    To examine the effect of vegetation type and grassland management regimen on the distribution of humus-degrading microorganisms, populations of humic acid-degrading (HAD) bacteria and fungi at three Andosol sites were investigated using the dilution plate method. Each site had three different vegetation types (Eulalia grassland, bamboo grassland, and coniferous plantations). Among the six grassland sites, two were maintained by burning and the others by cutting. HAD microorganisms were found in all soil samples. Low densities and small percentages of HAD bacteria were detected with no significant differences in the number of bacteria found between different vegetation types and grasslands managed in different ways. In contrast, the densities and percentages of HAD fungi differed according to vegetation type and management regimen. Specifically, the percentages of HAD fungi were significantly higher for burned grasslands. At burned sites, the numbers and percentages of HAD bacteria remained at a consistently low level, and no distinct seasonal changes were observed. In contrast, marked seasonal fluctuations in HAD fungi were detected. The percentages of these fungi remained relatively high between April and December. These fluctuations are likely due to the effects of burning on soil microorganisms. PMID:21558687

  18. [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

  19. Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Epstein, H. E.; Jia, G. J.; Balser, A.; Copass, C.; Edwards, E. J.; Gould, W. A.; Hollingsworth, J.; Knudson, J.; Maier, H. A.; Moody, A.; Raynolds, M. K.

    2003-01-01

    We examined the effects of summer warmth on leaf area index (LAI), total aboveground phytomass (TAP), and normalized difference vegetation index (NDVI) across the Arctic bioclimate zone in Alaska and extrapolated our results to the circumpolar Arctic. Phytomass, LAI, and within homogeneous areas of vegetation on acidic and nonacidic soils were regressed against the total summer warmth index (SWI) at 12 climate stations in northern Alaska (SWI = sum of mean monthly temperatures greater than 0°C). SWI varies from 9°C at Barrow to 37°C at Happy Valley. A 5°C increase in the SWI is correlated with about a 120 g m-2 increase in the aboveground phytomass for zonal vegetation on acidic sites and about 60 g m-2 on nonacidic sites. Shrubs account for most of the increase on acidic substrates, whereas mosses account for most of the increase on nonacidic soils. LAI is positively correlated with SWI on acidic sites but not on nonacidic sites. The NDVI is positively correlated with SWI on both acidic and nonacidic soils, but the NDVI on nonacidic parent material is consistently lower than the NDVI on acidic substrates. Extrapolation to the whole Arctic using a five-subzone zonation approach to stratify the circumpolar NDVI and phytomass data showed that 60% of the aboveground phytomass is concentrated in the low-shrub tundra (subzone 5), whereas the high Arctic (subzones 1-3) has only 9% of the total. Estimated phytomass densities in subzones 1-5 are 47, 256, 102, 454, and 791 g m-2, respectively. Climate warming will likely result in increased phytomass, LAI, and NDVI on zonal sites. These changes will be most noticeable in acidic areas with abundant shrub phytomass.

  20. 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.

  1. 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.

  2. Calculations of relative optical air masses for various aerosol types and minor gases in Arctic and Antarctic atmospheres

    NASA Astrophysics Data System (ADS)

    Tomasi, Claudio; Petkov, Boyan H.

    2014-02-01

    The dependence functions of relative optical air mass on apparent solar zenith angle θ have been calculated over the θ < 87° range for the vertical profiles of wet-air molecular number density in the Arctic and Antarctic atmospheres, extinction coefficients of different aerosol types, and molecular number density of water vapor, ozone, nitrogen dioxide, and oxygen dimer. The calculations were made using as weight functions the seasonal average vertical profiles of (i) pressure and temperature derived from multiyear sets of radiosounding measurements performed at Ny-Ålesund, Alert, Mario Zucchelli, and Neumayer stations; (ii) volume extinction coefficients of background summer aerosol, Arctic haze, and Kasatochi and Pinatubo volcanic aerosol measured with lidars or balloon-borne samplings; and (iii) molecular number concentrations of the above minor gases, derived from radiosonde, ozonesonde, and satellite-based observations. The air mass values were determined using a formula based on a realistic atmospheric air-refraction model. They were systematically checked by comparing their mutual differences with the uncertainties arising from the seasonal and daily variations in pressure and temperature conditions within the various ranges, where aerosol and gases attenuate the solar radiation most efficiently. The results provide evidence that secant-approximated and midlatitude air mass values are inappropriate for analyzing the Sun photometer measurements performed at polar sites. They indicate that the present evaluations can be reliably used to estimate the aerosol optical depth from the Arctic and Antarctic measurements of total optical depth, after appropriate corrections for the Rayleigh scattering and gaseous absorption optical depths.

  3. [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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. 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. PMID:22463948

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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

  4. The ecohydrological interaction of snow and vegetation type along a climate gradient in the Alps

    NASA Astrophysics Data System (ADS)

    Fatichi, S.; Ivanov, V. Y.; Rimkus, S.; Caporali, E.; Burlando, P.

    2011-12-01

    Few studies have investigated the questions of sensitivity of snowpack dynamics, energy, or carbon fluxes with respect to different plant functional types (PFT) in a mountain ecosystem. They are hampered by the sharp microclimate gradients that occur across altitudinal zones and in conditions of complex topography. A mechanistic ecohydrological model, Tethys-Chloris, is used to elucidate patterns of carbon and water fluxes across gradients of microclimates and PFTs (grass, deciduous and evergreen trees) typical of an Alpine system. The ecohydrological model is validated to reproduce snowpack dynamics for forested and open sites worldwide using the Snowmip-2 dataset. The model has also been confirmed to reproduce vegetation productivity and energy fluxes for several locations in an Alpine climate or similar conditions (Fluxnet dataset). Two synthetic climate gradients are used. One is representative of a dry alpine internal valley and the other one of a wet exposed mountain side. Synthetic climate gradients are constructed to represent variability of conditions with elevation using ground observations of the Meteo-Swiss network and an hourly weather generator, AWE-GEN. Specifically, observed data permit the parameterization of the weather generator and the simulation of co-variation among the principal climate drivers, i.e., precipitation, air temperature, relative humidity, wind speed, solar radiation, and atmospheric pressure for elevation bands from 500 up to 3500 m a.s.l. Forced with different climate conditions, the three PFTs are allowed to evolve across the elevation gradient and for dry and wet conditions. The sensitivity of hydrological and carbon fluxes to the gradients of climate and vegetation types are addressed by simulating 30 years of ecohydrological dynamics. The representation of within canopy wind profile has been found of paramount importance in providing reliable results of vegetation-snow interaction. The approach allows one to infer

  5. The Influence of Vegetation Type on the Surface Water and Energy Balance in Semiarid Ecosystems

    NASA Astrophysics Data System (ADS)

    Kurc, S. A.; Small, E. E.

    2001-12-01

    The transition from semiarid grassland to shrubland occurs over a distance of ~1 km in the Sevilleta Wildlife Refuge in New Mexico. The spatial variability of precipitation, incident shortwave radiation, and other factors is minimal across the ecotone because the transition zone spans such a short distance. Therefore, we assume that the type of vegetation is the primary factor controlling the spatial variations of water and energy cycling at this location. We examine fluxes in the grassland, shrubland, and the intermediate mixed environment to isolate the influence of vegetation type on the exchange of water and energy between the land surface and the atmosphere. Three micrometeorology sites span this shrub-grass ecotone. The Bowen Ratio-Energy Balance method is used at two of the sites and an eddy covariance system is used at the third site. We have intercompared the Bowen ratio and eddy covariance methods at each site. The differences introduced by using these two different methods are negligible compared to the observed spatial and temporal variability. We present data from two summer monsoon seasons. The response to precipitation events is dramatic and similar at all three sites across the vegetation gradient. The latent heat flux at midday changes from nearly 0 when the soil is dry to greater than 250 W m-2 for several days following rainfall. These temporal fluctuations are much greater than the spatial differences associated with vegetation cover observed under either wet or dry conditions. However, the drydown following rainfall, and the attendant variations in water and energy fluxes, is different across the ecotone. In the shrubland, soil moisture and evapotranspiration decrease more quickly than in the grassland.

  6. 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

  7. 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

  8. 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 ... formats available at JPL August 23, 2000 - Stratus clouds help modulate the arctic climate. project:  ...

  9. 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

  10. 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.

  11. 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

  12. 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

  13. [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. PMID:19123343

  14. Occurrence of polycyclic aromatic hydrocarbons in artisanal Palmero cheese smoked with two types of vegetable matter.

    PubMed

    Guillén, M D; Palencia, G; Sopelana, P; Ibargoitia, M L

    2007-06-01

    Palmero cheese is a fresh smoked cheese from the Isle of Palma (Canary Islands), manufactured with goat's milk. To guarantee its safety, the occurrence of polycyclic aromatic hydrocarbons (PAH) in artisanal Palmero cheese smoked with 2 types of vegetable matter (almond shells and dry prickly pear) was studied. The determination of PAH includes extraction and clean-up steps, followed by separation, identification, and quantification of PAH by gas chromatography-mass spectrometry in selected ion-monitoring mode. The most abundant PAH are those with 2 and 3 aromatic rings. Although the highest total PAH concentrations corresponded to the cheeses smoked with almond shells, the degree of PAH contamination of the cheeses studied was lower than that found in other cheeses smoked in the traditional way. The nature of the vegetable material used for smoking seemed to have an influence on the type of PAH formed, especially on alkylderivatives and some light PAH. However, despite the artisanal, and consequently variable, production process of these cheeses, many similarities have been found among their PAH profiles. In fact, relatively constant relationships are observed between the concentrations of certain pairs of PAH. Benzo(a)pyrene was only present in 2 samples, and in much lower concentrations than the maximum allowed legal limits. Therefore, according to the results obtained, it appears that it is possible to obtain a safe product without renouncing the artisanal character or the sensory properties of this type of cheese. PMID:17517711

  15. [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. PMID:17552181

  16. 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.

  17. 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. PMID:26661956

  18. 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.

  19. 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. 

  20. Invertebrate availability and vegetation characteristics explain use of nonnesting cover types by mature-forest songbirds during the postfledging period

    USGS Publications Warehouse

    Streby, Henry M.; Peterson, Sean M.; Andersen, D.E.

    2011-01-01

    Some species of mature-forest-nesting songbirds use regenerating clearcuts and forested wetlands during the postfledging period (between nesting and migration). Relatively dense vegetation structure and abundant food resources in non-mature-forest cover types have been hypothesized to explain this phenomenon. We examined the relative importance of vegetation structure and invertebrate availability on use of nonnesting cover types by adult and hatch-year Ovenbirds (Seiurus aurocapilla) and American Redstarts (Setophaga ruticilla) during the postfledging period of 2009 in northern Minnesota. We used mist nets to sample bird use of forested wetlands and regenerating clearcuts of three age groups: 1-6, 7-12, and 16-19 yr after harvest. We modeled captures of birds using vegetation characteristics and invertebrate availability sampled around nets as explanatory variables. For all birds studied, captures were best explained by food availability and secondarily by vegetation characteristics including litter depth and woody debris for Ovenbirds and canopy height for American Redstarts. Shrub-level invertebrate availability received a cumulative weight of 0.74-0.99 in Akaike's information criterion corrected ranked models for adult and hatch-year birds of both species. Vegetation density and variation in vegetation density explained almost no variation in captures of either species. We conclude that both invertebrate availability and some vegetation characteristics influence use of nonnesting cover types by Ovenbirds and American Redstarts during the postfledging period, but that invertebrate availability is generally the stronger predictor of that use. ?? 2011 Association of Field Ornithologists.

  1. 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

  2. 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.

  3. 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

  4. 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

  5. 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

  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. 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.

  8. 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.

  9. Vegetation Types Alter Soil Respiration and Its Temperature Sensitivity at the Field Scale in an Estuary Wetland

    PubMed Central

    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. PMID:24608636

  10. Suitability of the vegetation types in Mexico's Tamaulipas state for the siting of hazardous waste treatment plants.

    PubMed

    Cram, Silke; Sommer, Irene; Morales, Luis-Miguel; Oropeza, Oralia; Carmona, Estela; González-Medrano, Francisco

    2006-07-01

    A land suitability study was carried out by applying a multiple-criteria technique to 12 different vegetation types in Mexico's Tamaulipas state to help select potentially suitable sites for hazardous waste treatment plants. Species richness, spatial distribution, and uniqueness were selected as the criteria for estimating a vegetation type's suitability. Using the analytical hierarchy process, we ranked and mapped vegetation types, then compared the results with rankings of the same vegetation types based only on their number of endemic species. The suitabilities of the various vegetation types were ordered in more or less the same way by both methods, except in two cases for which the results were very different. The method proved to be a useful tool despite the availability of only partial (mostly qualitative) information; under such circumstances, expert experience can be incorporated in the evaluation process to a limited degree. The technique described in this paper has a high potential to aid decisions when many opinions and options must be considered simultaneously. PMID:16364535

  11. 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.

  12. Support vector machines for recognition of semi-arid vegetation types using MISR multi-angle imagery

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mapping accurately community types is one of the main challenges for monitoring arid and semi-arid grasslands with remote sensing. The multi-angle approach has been proven useful for mapping vegetation types in desert grassland. The Multi-angle Imaging Spectro-Radiometer (MISR) provides 4 spectral b...

  13. 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.

  14. Reflectance properties of selected arctic-boreal land cover types: field measurements and their application in remote sensing

    NASA Astrophysics Data System (ADS)

    Peltoniemi, J. I.; Suomalainen, J.; Puttonen, E.; Näränen, J.; Rautiainen, M.

    2008-03-01

    We developed a mobile remote sensing measurement facility for spectral and anisotropic reflectance measurements. We measured reflection properties (BRF) of over 100 samples from most common land cover types in boreal and subarctic regions. This extensive data set serves as a unique reference opportunity for developing interpretation algorithms for remotely sensed materials as well as for modelling climatic effects in the boreal and subarctic zones. Our goniometric measurements show that the reflectances of the most common land cover types in the boreal and subarctic region can differ from each other by a factor of 100. Some types are strong forward scatterers, some backward scatterers, some reflect specularly, some have strong colours, some are bright in visual, some in infrared. We noted that spatial variations in reflectance, even among the same type of vegetation, can be well over 20%, diurnal variations of the same order and seasonal variation often over a factor of 10. This has significant consequences on the interpretation of satellite and airborne images and on the development of radiation regime models in both optical remote sensing and climate change research. We propose that the accuracy of optical remote sensing can be improved by an order of magnitude, if better physical reflectance models can be introduced. Further improvements can be reached by more optimised design of sensors and orbits/flight lines, by the effective combining of several data sources and better processing of atmospheric effects. We conclude that more extensive and systematic laboratory experiments and field measurements are needed, with more modelling effort.

  15. 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., III; 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.

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  2. Seasat synthetic aperture radar ( SAR) response to lowland vegetation types in eastern Maryland and Virginia.

    USGS Publications Warehouse

    Krohn, M.D.; Milton, N.M.; Segal, D.B.

    1983-01-01

    Examination of Seasat SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the 30-digital number (DN) increase observed in the digital Seasat data. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.-from Authors

  3. Comparing the impacts of hiking, skiing and horse riding on trail and vegetation in different types of forest.

    PubMed

    Törn, A; Tolvanen, A; Norokorpi, Y; Tervo, R; Siikamäki, P

    2009-03-01

    Nature-based tourism in protected areas has increased and diversified dramatically during the last decades. Different recreational activities have a range of impacts on natural environments. This paper reports results from a comparison of the impacts of hiking, cross-country skiing and horse riding on trail characteristics and vegetation in northern Finland. Widths and depths of existing trails, and vegetation on trails and in the neighbouring forests were monitored in two research sites during 2001 and 2002. Trail characteristics and vegetation were clearly related to the recreational activity, research site and forest type. Horse trails were as deep as hiking trails, even though the annual number of users was 150-fold higher on the hiking trails. Simultaneously, cross-country skiing had the least effect on trails due to the protective snow cover during winter. Hiking trail plots had little or no vegetation cover, horse riding trail plots had lower vegetation cover than forest plots, while skiing had no impact on total vegetation cover. On the other hand, on horse riding trails there were more forbs and grasses, many of which did not grow naturally in the forest. These species that were limited to riding trails may change the structure of adjacent plant communities in the long run. Therefore, the type of activities undertaken and the sensitivity of habitats to these activities should be a major consideration in the planning and management of nature-based tourism. Establishment of artificial structures, such as stairs, duckboards and trail cover, or complete closure of the site, may be the only way to protect the most sensitive or deteriorated sites. PMID:18930578

  4. Comparison of interception and initial retention of wet-deposited contaminants on leaves of different vegetation types

    NASA Astrophysics Data System (ADS)

    Owen Hoffman, F.; Thiessen, Kathleen M.; Rael, Rolando M.

    Simulated rain containing both soluble radionuclides and insoluble particles labeled with a radionuclide was manually applied to several kinds of vegetation, including a conifer, a broad-leafed tree, and several herbaceous species. The fraction of each radioactive material intercepted and initially retained by the vegetation was determined for each plant type. This fraction was determined both as the mass interception factor, r/Y, and the leaf area interception fraction, LAIF. Mean values of r/Y ranged from 0.16 to 2.9 m 2 kg -1 and of the LAIF, from 0.011 to 0.16. There was a greater range in mean retention values among radionuclide types than among plant species; the range among plant types tended to be less with the LAIF than the r/Y. Significantly less interception and initial retention was measured for anions than for cations or the insoluble particles.

  5. 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.

  6. 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.

  7. 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.

  8. 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. PMID:24975230

  9. 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.

  10. [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

  11. 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.

  12. 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.

  13. 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

  14. Nutritional differences and leaf acclimation of climbing plants and the associated vegetation in different types of an Andean montane rainforest.

    PubMed

    Salzer, J; Matezki, S; Kazda, M

    2006-03-01

    Climbing plants are known to play an important role in tropical forest systems, but key features for their distribution are only partly understood. Investigation was carried out to find if climbers differ from self-supporting vegetation in their adjustment of leaf parameters over a wide variety of light regimes in different forest types along an altitudinal gradient. Relative photon flux density (PFDrel) was assessed above 75 pairs of strictly linked climbers and supporting vegetation on seven plots between 2,020 and 2,700 m a.s.l. along a mountain range in South-Ecuador up to the Páramo vegetation. Leaf samples from both growth forms were analyzed for leaf area (LA), specific leaf mass (LMA), mass and area-based carbon and nitrogen concentration (C, Carea, N, and Narea) and concentrations of P, K, Ca, Mg, Mn and Al. Leaf size of climbers was independent of general light condition, whereas the leaf size of the self-supporting vegetation increased in shade. LMA increased as expected with altitude and irradiance for both growth forms, but climbers generally built smaller leaves with lower LMA. N, P, and K concentrations were higher in the leaves of climbers than in their supporters. Relationships of LMA and Narea to the light conditions were more pronounced within the climbers than within their supporters. Slope for the regression between climber's Narea and LMA was twice as steep as for the supporter leaves. Al accumulators were only found within the self-supporting vegetation. The investigated traits indicate improved adjustment towards light supply within climbers compared to self-supporting vegetation. Thus climbing plants seem to have a higher potential trade off in resource-use efficiency regarding irradiance and nutrients. PMID:16341891

  15. The hydrological responses of different land cover types in a re-vegetation catchment area of the Loess Plateau, China

    NASA Astrophysics Data System (ADS)

    Wang, S.; Fu, B. J.; Gao, G. Y.; Zhou, J.

    2012-05-01

    The impact of re-vegetation on soil moisture dynamics was investigated by comparing five land cover types. Soil moisture and temperature variations under grass (Andropogon), subshrub (Artemisia scoparia), shrub (Spiraea pubescens), tree (Robinia pseudoacacia), and crop (Zea mays) vegetation were monitored in an experiment performed during the growing season of 2011. There were more than 10 soil moisture pulses during the period of data collection, and the surface soil moisture of all of the land cover types showed an increasing trend. Corn cover was associated with consistently higher soil moisture readings than the other surfaces. Grass and subshrubs showed an intermediate moisture level, with that of grass being slightly higher than that of subshrub most of the time. Shrubs and trees were characterized by lower soil moisture readings, with the shrub levels consistently being slightly higher than those of the trees. With the exception of the corn land cover type, the average soil temperature showed the same regime as the average moisture content, but exhibiting a downward trend throughout the observation period. Three typical decreasing periods were chosen to compare the differences in water losses. In periods of both relatively lower and higher water soil moisture contents, subshrubs lost the largest amount of water. The daily water loss associated with corn was most variable. The tree and shrub sites presented an intermediate level, with that of tree being slightly higher compared to shrub; the daily water loss trends of these two land cover types were similar and were more stable than those of the other types. The amount of water loss related to the grass land cover type is determined by the initial moisture content. Soil under subshrubs acquired and retained soil moisture resources more efficiently than the other cover types, representing an adaptive vegetation type in this area.

  16. Seasat synthetic aperture radar /SAR/ response to lowland vegetation types in eastern Maryland and Virginia

    NASA Technical Reports Server (NTRS)

    Krohn, M. D.; Milton, N. M.; Segal, D. B.

    1983-01-01

    Examination of Seasat SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the 30-digital number (DN) increase observed in the digital Seasat data. The brightest areas in the Chickahominy, Virginia, drainage, containing P. virginica about 0.4 m high, contrast with the brightest areas in the Blackwater, Maryland, marshes, which contain mature loblolly pine in standing water. The darkest vegetated area in the Chickahominy drainage contains a forest of Nyssa aquatica (water tupelo) about 18 m high, while the darkest vegetated area in the Blackwater marshes contains the marsh plant Spartina alterniflora, 0.3 m high. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. 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...

  3. Phosphorus Uptake During Four Years by Different Vegetative Cover Types in a Riparian Buffer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vegetative buffers have been shown to reduce nutrient loss associated with the transport of detached soil particles and may through plant uptake offer a means to capture dissolved nutrients moving to surface waters through the soil solution. The objective of this 4-year study was to evaluate change...

  4. Estimating Pan Arctic Net Ecosystem Exchange using Functional Relationships with Air temperature, Leaf Area Index and Photosynthetic Active Radiation

    NASA Astrophysics Data System (ADS)

    Mbufong, H.; Kusbach, A.; Lund, M.; Persson, A.; Christensen, T. R.; Tamstorf, M. P.; Connolly, J.

    2015-12-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) is often attributed to the high spatial heterogeneity of Arctic tundra. Current models of carbon exchange thus 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 NEE 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 data from 12 Arctic tundra sites. The model input parameters (fcsat, Rd and α) were estimated as a function of air temperature and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship. They describe the saturation flux, dark respiration and initial light use efficiency, respectively. While remotely sensed LAI is readily available as a MODIS Terra product (MCD15A3), air temperature was estimated from a direct relationship with MODIS land surface temperature (MOD11A2, LST). Therefore, no specific knowledge of the vegetation type is required. Preliminary results show the model captures the spatial heterogeneity of the Arctic tundra but so far, overestimates NEE on all 17 test sites which include heaths, bogs, fens, and tussock tundra vegetation. The final updated results and error assessment will be presented at the conference in December.

  5. 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. PMID:21653423

  6. 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

  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. 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.

  10. Enhancing NASA's Contribution to Arctic Terrestrial Hydrology and the Study of Polar Change

    NASA Astrophysics Data System (ADS)

    Walsh, J. E.; Elfring, C.; Vorosmarty, C. J.; McGuire, A. D.

    2001-12-01

    In a recent report by the National Academies, an interdisciplinary committee assessed NASA's polar geophysical datasets in the context of the science questions driving the Earth Science Enterprise (ESE) and other avenues of polar research. The report examines data sets in terms of the major ESE themes: ongoing changes in polar climate and the biosphere, forcings of the polar climate system, responses and feedbacks to the forcing, consequences of change in the polar regions, and prediction of such changes. It includes a matrix of science needs and available data sets and, from that, identifies high-priority measurement needs, many of which are directly relevant to Arctic hydrology. The greatest needs are improved measurements of polar precipitation, surface albedo, freshwater discharge from terrestrial regions, surface temperatures and turbulent fluxes, permafrost extent and dynamics, ocean salinity, ice sheet mass flux, land surface (especially vegetative) characteristics, and sea ice thickness. For Arctic hydrological studies, key needs include surface radiation parameters (albedo, roughness), especially with regard to the timing of ice-out in rivers and lakes, the associated pulse of freshwater discharge, biogeochemical fluxes, and aquatic biology. There is a particular need for pan-Arctic datasets of vegetative characteristics such as leaf area index, structural composition, canopy density, albedo, disturbance characteristics, wetland extent, and nitrogen deposition. Pan-Arctic information of this type will require novel efforts in the synthesis of different products, often from different sensors. Such information, as well as high-resolution surface elevation and topography, is needed for Arctic land system models that include hydrology and ecosystem dynamics. Key changes to be anticipated or predicted by these models include changes in water supplies from snow and snow-fed rivers, effects of physical environmental change on terrestrial productivity and

  11. Vegetation types, dominant compositions, woody plant diversity and stand structure in Trishna Wildlife Sanctuary of Northeast India.

    PubMed

    Majumdar, Koushik; Datta, B K

    2015-03-01

    Present study was carried out to assess the vegetation types, diversity and phytosociological status of woody plants in Trishna Wildlife Sanctuary of Tripura, Northeast India. Vegetation data was derived by 25 line transects (10 m wide and 500 m length, each 0.5 ha size). All woody species at >10 cm gbh (Girth at Breast Height) within each plots were measured and counted. A total of six forest types were classified by cluster analysis using Importance Value Index (IVI) of 289 woody species. Species diversity, forest structure and woody community associations were evaluated and discussed. One way ANOVA revealed significant differences in all species diversity measures and stand structure along the forest types. Distribution of stem density at ten different gbh classes showed reverse J-shaped curves. Population status of woody plants was also examined through grouping of all individuals into four population age stages viz. sapling (<30 cm gbh), adult (> or = 30 - <120 cm gbh), mature (>120 - 210 cm gbh) and old (> or =210 cm). To observe dominant composition and species population trend, IVI of top ten dominant species from all forest types were tabulated. The present study suggested that Trishna Wildlife Sanctuary is an important habitat in Tripura from floristic point of view and it should be conserved on priority basis for remaining wildlife endurances and monitor for forest livelihoods products for sustainable biodiversity conservation in this region. PMID:25895264

  12. 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

  13. 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.

  14. 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

  15. 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

  16. Landscape object-based analysis of wetland plant functional types: the effects of spatial scale, vegetation classes and classifier methods

    NASA Astrophysics Data System (ADS)

    Dronova, I.; Gong, P.; Wang, L.; Clinton, N.; Fu, W.; Qi, S.

    2011-12-01

    Remote sensing-based vegetation classifications representing plant function such as photosynthesis and productivity are challenging in wetlands with complex cover and difficult field access. Recent advances in object-based image analysis (OBIA) and machine-learning algorithms offer new classification tools; however, few comparisons of different algorithms and spatial scales have been discussed to date. We applied OBIA to delineate wetland plant functional types (PFTs) for Poyang Lake, the largest freshwater lake in China and Ramsar wetland conservation site, from 30-m Landsat TM scene at the peak of spring growing season. We targeted major PFTs (C3 grasses, C3 forbs and different types of C4 grasses and aquatic vegetation) that are both key players in system's biogeochemical cycles and critical providers of waterbird habitat. Classification results were compared among: a) several object segmentation scales (with average object sizes 900-9000 m2); b) several families of statistical classifiers (including Bayesian, Logistic, Neural Network, Decision Trees and Support Vector Machines) and c) two hierarchical levels of vegetation classification, a generalized 3-class set and more detailed 6-class set. We found that classification benefited from object-based approach which allowed including object shape, texture and context descriptors in classification. While a number of classifiers achieved high accuracy at the finest pixel-equivalent segmentation scale, the highest accuracies and best agreement among algorithms occurred at coarser object scales. No single classifier was consistently superior across all scales, although selected algorithms of Neural Network, Logistic and K-Nearest Neighbors families frequently provided the best discrimination of classes at different scales. The choice of vegetation categories also affected classification accuracy. The 6-class set allowed for higher individual class accuracies but lower overall accuracies than the 3-class set because

  17. Untangling the role of elevation, aspect, and vegetation type on ecohydrological dynamics along a climate gradient in the Alps

    NASA Astrophysics Data System (ADS)

    Fatichi, S.; Ivanov, V. Y.; Rimkus, S.; Caporali, E.; Burlando, P.

    2012-04-01

    Vegetation dynamics and performance are strongly influenced by environmental conditions. Specifically, light, precipitation, and air temperature exert a predominant role. These climatic variables covariate with elevation and aspect in areas of complex terrain. Quantification of specific elevation and aspect effects on vegetation productivity and mass and energy fluxes can lead to a better understating of environment-driven distribution of vegetation and parsimonious up-scaling parameterizations useful in hydrological applications. A detailed characterization of climatic differences with elevation is however a daunting task. In this study, two synthetic climate gradients, constructed using hourly meteorological data and a stochastic weather generator, AWE-GEN, are used to force a mechanistic ecohydrological model, Tethys-Chloris, and quantify energy, carbon, and water fluxes for three generic Plant Functional Types (PFTs). One gradient is representative of a dry, sheltered alpine valley (Valais), whereas the other one characterizes a wet, exposed mountain side (Bernese Oberland). Thirty year long time series of cross-correlated precipitation, air temperature, relative humidity, wind speed, solar radiation, and atmospheric pressure for elevation bands from 500 up to 3500 m a.s.l. are generated to represent the climatic differences. The incoming radiation is successively recalculated for different combinations of aspect and slope. Under these specific climatic forcing conditions, the response of deciduous and evergreen trees, and grass typical of the Alpine system is investigated. The parameterization of the ecohydrological model was tested to reproduce vegetation productivity and energy fluxes for several locations in an Alpine climate or similar conditions (Fluxnet dataset) and to correctly simulate snowpack dynamics for forested and open sites worldwide (Snowmip-2 dataset). The three PFTs evolve at different elevations and aspects for dry and wet conditions

  18. 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.

  19. 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.

  20. 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.

  1. 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. PMID:26418563

  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. 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

  4. 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.

  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. 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

  7. Watershed-Scale Crop Type Classification using Seasonal Trends in Remote Sensing-Derived Vegetation Indices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Analysis and simulation of watershed-scale processes requires spatial characterization of land use, including differentiation among crop types. If this crop type information could be obtained accurately from remote sensing data, the effort required would be significantly reduced, especially for larg...

  8. 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.…

  9. 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

  10. 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.

  11. 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.

  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. Human Papillomavirus Type 31b E1 and E2 Transcript Expression Correlates with Vegetative Viral Genome Amplification

    PubMed Central

    Ozbun, Michelle A.; Meyers, Craig

    2013-01-01

    Human papillomavirus (HPV) genome replication is dependent on the expression of E1 and E2 proteins. The organotypic (raft) culture system was used to investigate changes in viral early gene expression and vegetative genome replication during the complete life cycle of HPV type 31b (HPV31b). We have previously shown the synthesis of HPV31b viral particles as early as 10 days of growth of CIN-612 9E raft tissues (Ozbun, M. A., and Meyers, C (1997) J. Virol. 71, 5161–5172). In the present study, we investigated the structures and temporal expression levels of HPV31b G1 and E2 transcripts, as well as the replication of the viral genome during the viral life cycle. The amplification state of the HPV31b genome was maximal at 10 days of raft tissue growth. Furthermore, the expression levels of E1 and E2 RNAs correlated with vegetative viral DNA replication. Levels of E1- and E2-specific transcripts were dissimilar throughout the viral life cycle. E2 RNA levels remained relatively constant, whereas E1 RNA levels were upregulated during the maximal amplification of viral genomes and the biosynthesis of virions. These data indicate that E1 may be the major regulator of viral genome amplification in preparation for DNA packaging and virion morphogenesis. PMID:9721231

  14. An atmosphere-ocean GCM modelling study of the climate response to changing Arctic seaways in the early Cenozoic.

    NASA Astrophysics Data System (ADS)

    Roberts, C. D.; Legrande, A. N.; Tripati, A. K.

    2008-12-01

    The report of fossil Azolla (a freshwater aquatic fern) in sediments from the Lomonosov Ridge suggests low salinity conditions occurred in the Arctic Ocean in the early Eocene. Restricted passages between the Arctic Ocean and the surrounding oceans are hypothesized to have caused this Arctic freshening. We investigate this scenario using a water-isotope enabled atmosphere-ocean general circulation model with Eocene boundary conditions including 4xCO2, 7xCH4, altered bathymetry and topography, and an estimated distribution of Eocene vegetational types. In one experiment, oceanic exchange between the Arctic Ocean and other ocean basins was restricted to two shallow (~250 m) seaways, one in the North Atlantic, the Greenland-Norwegian seaway, and the second connecting the Arctic Ocean with the Tethys Ocean, the Turgai Straits. In the restricted configuration, the Greenland-Norwegian seaway was closed and exchange through the Turgai Straits was limited to a depth of ~60 m. The simulations suggest that the severe restriction of Arctic seaways in the early Eocene may have been sufficient to freshen Arctic Ocean surface waters, conducive to Azolla blooms. When exchange with the Arctic Ocean is limited, salinities in the upper several hundred meters of the water column decrease by ~10 psu. In some regions, surface salinity is within 2-3 psu of the reported maximum modern conditions tolerated by Azolla (~5 psu). In the restricted scenario, salt is stored preferentially in the North Atlantic and Tethys oceans, resulting in enhanced meridional overturning, increased poleward heat transport in the North Atlantic western boundary current, and warming of surface and intermediate waters in the North Atlantic by several degrees. Increased sensible and latent heat fluxes from the North Atlantic Ocean, combined with a reduction in cloud albedo, also lead to an increase in surface air temperature of over much of North America, Greenland and Eurasia. Our work is consistent with

  15. WASHOUT CONDITION OF CLUMP-TYPE GRASS CONSIDERING THE CHANGE OF THE REFERENCE VELOCITY AND SHEAR STRESS IN THE VEGETATED AREA

    NASA Astrophysics Data System (ADS)

    Hara, Tatsuaki; Tanaka, Norio

    Threshold shear stress for removing grasses by flood is important but is not well understood quantitatively for clump-type vegetation, Eragrostis curvula. New model for calculating the velocities in the vegetated layer and the surface layer was proposed and the model was validated with flume experiments. The bed shear stress in vegetation was calculated by the momentum balance in the vegetated layer, and was applied for evaluating the wash-out conditions of the grass. The threshold value for removing the clump-type vegetation was evaluated as a rate of shear stress of d90, grain diameter at which 90% volume passed through the sieve, and the critical shear stress of d90, WOI. The critical WOI for removing the grass is 1.9-2.1, and 1.8-1.9 for one layer analysis, and two layer analysis, respectively. The critical shear stress inside the vegetated region does not decrease much because there is bare land between each clump-type grass, and the flow is accelerated in the region by the momentum exchange.

  16. RECOGNITION OF SEMI-ARID VEGETATION TYPES BASED ON MISR MULTI-ANGULAR OBSERVATIONS AND SURFACE ANISOTROPY PATTERNS INVERSED BY BIDIRECTIONAL REFLECTANCE MODELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mapping accurately community type is one of main challenges for monitoring semi-arid grasslands with remote sensing. Multi-angle approach has been proved useful for mapping vegetation types in desert. Multi-angle Imaging Spectro-Radiometer (MISR) provides 4 spectral bands and 9 angular observations....

  17. 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...

  18. 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.

  19. [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

  20. 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

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. 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

  7. Russian Arctic

    Atmospheric Science Data Center

    2013-04-16

    ... cameras, displayed as red, green and blue, respectively. Water appears blue in this image because sun glint makes smooth, wet surfaces ... cameras, providing information about the distribution and density of trees and shrubs in this area. Creating accurate maps of vegetation ...

  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. 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

  11. 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

  12. Estimations of moisture content in the active layer in an Arctic ecosystem by using ground-penetrating radar profiling

    NASA Astrophysics Data System (ADS)

    Gacitúa, Guisella; Tamstorf, Mikkel Peter; Kristiansen, Søren Munch; Uribe, José Andrés

    2012-04-01

    We applied high-frequency GPR at a study site in the high arctic ecosystem of Northeast Greenland to evaluate its usefulness in assessing depth of, and water content in, the active layer at Zackenberg Valley (74°N; 20°W) to evaluate its usefulness in the high arctic ecosystems. The study site includes different vegetation types, and it well represents of the entire valley, for which we aimed to determine the conditions and characteristics that influence the GPR performance in the active layer. The spatial distribution of moisture content along the transect studied was estimated using GPR data (400 MHz antenna), depth to permafrost, soil samples and vegetation observations. Vertical distribution of the water content in the unfrozen soil bulk was predicted for several points on the transect by combining data that influence the behavior of the radar waves with that of capacitive moisture probes. The statistical models resulted to be highly significant, thus assuming common conditions of the soil to the classified vegetation, we can obtain from the GPR data, truthful estimations of water content, and, moreover, we can predict the distribution to the bottom of the active layer. Hence, we conclude that GPR is a viable option for improving active layer spatial quantification of water contents that can be used to assess changes in the active layer in arctic regions.

  13. 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

  14. Vegetation and Climate history of Franz Jozef Land Archipelago in the Late Holocene according pollen data

    NASA Astrophysics Data System (ADS)

    Nosevich, Ekaterina; Anisimov, Michail; Sapelko, Tatyana

    2015-04-01

    The archipelago Franz-Josef Land is situated in the Arctic Ocean (80°40' N, 54°50'E). It is one of the important areas for arctic research due to organization of Russian Arctic National Park there. Therefore, an interest to the environmental history of this territory grows up and any new data might have a high value. However, geographical remoteness of the archipelago is the reason why there are not much work has been done up to date. .A focus of our researches is vegetation and climate reconstruction during the Late Holocene history according pollen data. In frame of studying of the Franz Josef Land during complex expedition of Russian Arctic National Park on the islands geomorphological and botanical researches was occurred. Nowadays the typical island of archipelago presents the ice cap and glacier-free marine terraces of 35 m high at maximum, where solifluction and permafrost are developed. The archipelago has a maritime Arctic climate. Vegetation of archipelago Franz-Josef Land presents the northern type of Polar Desert. It includes 57 species of vascular plants (Poaceae, Juncaceae, Caryophyllaceae, Brassicaceae, Saxifragaceae etc). We studied the peat core from the southern part of Majbel Island, in the archipelago Franz Josef Land. More than a half of the island is covered by glacier. The core was sampled at the inner margin of ice-free high marine terrace, near the southern slope of bedrock hill. We received preliminary pollen data and radiocarbon data 3010±80 C14 y.a. at the bottom. The pollen concentration is low, but we manage to make some reconstructions of vegetation and climate. For correct interpretation of our results, we used surface samples from different islands of archipelago (Jackson, Hooker, Greely, Alexsandra land, Yeva-Liv, Appolonov, Georg land, Kane, Bell). Subrecent spectra include species presented in flora of region, but also those which are not founded at this region in this time.

  15. 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

  16. 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

  17. Differences in Fine-Root Biomass of Trees and Understory Vegetation among Stand Types in Subtropical Forests

    PubMed Central

    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. PMID:26047358

  18. 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. PMID:22561064

  19. 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.

  20. 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...

  1. NuukBasic - Climate effects monitoring in low arctic Greenland

    NASA Astrophysics Data System (ADS)

    Aastrup, P.; Nymand, J.; Raundrup, K.; Tamstorf, M. P.; Forchhammer, M. C.; Schmidt, N. M.; Lauridsen, T. L.

    2009-12-01

    The climate effects research program in Zackenberg in high arctic Greenland got a counterpart in Nuuk in low arctic West Greenland in 2007. The programme NuukBasic is described and, for the first time, results will presented from several of the monitoring components (Table 1). In particular, we focus on changes in plant phenology, vegetation greenness, graded effects of UVB radiation and lake ecology. Results are compared and contrasted concurrent changes at the high arctic site Zackenberg in Northeast Greenland.Biological Monitoring elements in NuukBasis

  2. Arctic Climate during Eocene Hyperthermals: Wet Summers on Ellesmere Island?

    NASA Astrophysics Data System (ADS)

    Greenwood, D. R.; West, C. K.; Basinger, J. F.

    2012-12-01

    Previous work has shown that during the late Paleocene to middle Eocene, mesothermal conditions (i.e., MAT ~12-15° C) and high precipitation (MAP > 150cm/yr) characterized Arctic climates - an Arctic rain forest. Recent analyses of Arctic Eocene wood stable isotope chemistry are consistent with the annual and seasonal temperature estimates from leaf physiognomy and nearest living relative analogy from fossil plants, including the lack of freezing winters, but is interpreted as showing that there was a summer peak in precipitation - modern analogs are best sought on the summer-wet east coasts (e.g., China, Japan, South Korea) not the winter-wet west coasts of present-day northern temperate continents (e.g., Pacific northwest of North America). Highly seasonal 'monsoon-type' summer-wet precipitation regimes (i.e., summer precip./winter precip. > 3.0) seem to characterize Eocene hyperthermal conditions in several regions of the earth, including the Arctic and Antarctic, based on both climate model sensitivity experiments and the paleoclimate proxy evidence. The leaf physiognomy proxy previously applied to estimate Arctic Paleogene precipitation was leaf area analysis (LAA), a correlation between mean leaf size in woody dicot vegetation and annual precipitation. New data from modern monsoonal sites, however demonstrates that for deciduous-dicot dominated vegetation, summer precipitation determines mean leaf size, not annual totals, and therefore that under markedly seasonal precipitation and/or light regimes that summer precipitation is being estimated using LAA. Presented here is a new analysis of a leaf macrofloras from 3 separate florules of the Margaret Formation (Split Lake, Stenkul Fiord and Strathcona Fiord) from Ellesmere Island that are placed stratigraphically as early Eocene, and likely fall within Eocene thermal maximum 1 (ETM1; = the 'PETM') or ETM2. These floras are each characterized by a mix of large-leafed and small-leafed dicot taxa, with overall

  3. 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

  4. 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

  5. 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. PMID:22270703

  6. 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

  7. The Greening of the Arctic IPY Project

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Bhatt, U. S.; Epstein, H. E.

    2008-12-01

    In 2007, Arctic sea ice extent declined to the lowest level in recorded history, 24 percent lower than the previous record in 2005. If the Arctic continues to warm over the next few decades as predicted by most arctic scientists, large changes in vegetation biomass will occur and will have important consequences to many components of the Arctic system including status of the permafrost, hydrological cycles, wildlife, and human occupation. There will also be important feedbacks to climate through changes in albedo and carbon fluxes. Changes in biomass are already happening. In Arctic Alaska from 1981 to 2001, the greenness of the landscapes as measured by satellite-derived values of the normalized difference vegetation index (NDVI) increased by 17 percent. It is uncertain what this remarkable change in greenness means with respect to plant biomass, but current NDVI-biomass relationships suggest that an average of over 100 g m-2 have been added to the tundra of northern Alaska within the past twenty years. Other studies have shown a major increase of shrub cover across northern Alaska during the past 50 years. If the Arctic Ocean becomes ice- free during the summer, some of the largest percentage increases could occur in the coldest parts of the Arctic. The three major objectives of this project are: (1) establish baseline ground observations along two transects in North American and Eurasia that traverse the entire Arctic bioclimate gradient; (2) use remote sensing and climate change analysis to determine how changes in sea ice concentrations affect land-surface temperature and the NDVI, (3) use vegetation-change models to predict how vegetation will change in the future. Strong correlations exist between sea-ice concentrations, land-surface temperatures, and the maximum and integrated NDVI). The changes in greening have been strongest in the Beaufort Sea region. Between 1982 and 2007, sea ice in the 50-km coastal strip of Beaufort Sea area during the period 18 June

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. How the insulating properties of snow affect soil carbon distribution in the continental pan-Arctic area

    NASA Astrophysics Data System (ADS)

    Gouttevin, I.; Menegoz, M.; Dominé, F.; Krinner, G.; Koven, C.; Ciais, P.; Tarnocai, C.; Boike, J.

    2012-06-01

    We demonstrate the effect of an ecosystem differentiated insulation by snow on the soil thermal regime and on the terrestrial soil carbon distribution in the pan-Arctic area. This is done by means of a sensitivity study performed with the land surface model ORCHIDEE, which furthermore provides a first quantification of this effect. Based on field campaigns reporting higher thermal conductivities and densities for the tundra snowpack than for taiga snow, two distributions of near-equilibrium soil carbon stocks are computed, one relying on uniform snow thermal properties and the other using ecosystem-differentiated snow thermal properties. Those modeled distributions strongly depend on soil temperature through decomposition processes. Considering higher insulation by snow in taiga areas induces warmer soil temperatures by up to 12 K in winter at 50 cm depth. This warmer soil signal persists over summer with a temperature difference of up to 4 K at 50 cm depth, especially in areas exhibiting a thick, enduring snow cover. These thermal changes have implications on the modeled soil carbon stocks, which are reduced by 8% in the pan-Arctic continental area when the vegetation-induced variations of snow thermal properties are accounted for. This is the result of diverse and spatially heterogeneous ecosystem processes: where higher soil temperatures lift nitrogen limitation on plant productivity, tree plant functional types thrive whereas light limitation and enhanced water stress are the new constrains on lower vegetation, resulting in a reduced net productivity at the pan-Arctic scale. Concomitantly, higher soil temperatures yield increased respiration rates (+22% over the study area) and result in reduced permafrost extent and deeper active layers which expose greater volumes of soil to microbial decomposition. The three effects combine to produce lower soil carbon stocks in the pan-Arctic terrestrial area. Our study highlights the role of snow in combination with

  14. 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

  15. 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.

  16. 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.

  17. Glasnost in the Arctic

    NASA Astrophysics Data System (ADS)

    Roederer, Juan

    The question of establishing an international body to coordinate research activities in the Arctic is an old one. Proposals have been formulated on several occasions during the last 3 decades, but they have never been implemented.At present, a few adhoc or semiprivate bodies are engaged in cooperative ventures of arctic research, and there are several bilateral programs between Arctic countries. Yet there is no northern equivalent to the Scientific Committee on Antarctic Research (SCAR) o f the International Council of Scientific Unions (ICSU). The politically and strategically sensitive nature of the Arctic regions has been a seemingly insurmountable obstacle. Recently, however, an international initiative spearheaded by the U.S. Arctic Research Commission led to promising developments regarding international scientific cooperation in the Arctic.

  18. Nutrient Limitations Constrain the Feedback Capacity of Landscapes in the High Arctic: Nonlinearities and Synergism

    NASA Astrophysics Data System (ADS)

    Arens, S. J.; Sullivan, P. F.; Welker, J. M.; Rogers, M. C.; Holland, K.; Schimel, J.; Persson, K.

    2006-12-01

    Nutrient availability appears to be a controlling factor in the structure and function of High Arctic terrestrial systems as depicted by biological hot spots such as bird cliffs which are found throughout the arctic. Understanding the processes by which nutrients control plant production, canopy structure, and ecosystem carbon cycling have been well studied in the Low Arctic, where fertilization experiments have been employed for decades. Few studies have examined how the amount and type of nutrient augmentations (fertilization) affects the magnitude and pattern of CO2 exchange, species composition and optical properties of prostrate dwarf-shrub, herb tundra, the largest ecosystem in the High Arctic. In this study, amendments of three levels of nitrogen (N) (0.5 g/m2, 1.0 g/m2 and 5.0 g/m2) phosphorus (P) (2.5 g/m2) were initiated in prostrate dwarf- shrub, herb tundra near Pituffik (Thule), Greenland (76¢ªN, 68¢ªW). Species composition, net ecosystem CO2 exchange (NEE), gross primary photosynthesis (GPP), ecosystem respiration (ER) and plot-level normalized difference vegetation index (NDVI) were used to quantify changes in ecosystem structure and function. Non- linear responses to the addition of different levels of N were observed. CO2 gas exchange and NDVI showed indicated the strongest response at middle levels of N addition (1.0 g/m2). Strong and synergystic responses to the combined addition of nitrogen and phosphorus were observed. Increases in vegetation density and a shift in species composition were observed when N and P were added to these systems, partially explaining the near doubling of NDVI values from 0.3 to 0.6. Rates of NEE, GPP and ER were significantly higher when N and P were combined compared to independent additions of each or when compared to non-fertilized areas. Our results indicate that feedback processes such as CO2 exchange, optical properties and vegetation composition and structure are co-limited by N and P and that the addition

  19. 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.

  20. 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

  1. High Arctic Biogenic Volatile Organic Compound emissions

    NASA Astrophysics Data System (ADS)

    Schollert, Michelle; Buchard, Sebrina; Faubert, Patrick; Michelsen, Anders; Rinnan, Riikka

    2013-04-01

    Biogenic volatile organic compounds (BVOCs) emitted from terrestrial vegetation participate in oxidative reactions, affecting the tropospheric ozone concentration and the lifetimes of greenhouse gasses such as methane. Also, they affect the formation of secondary organic aerosols. BVOCs thus provide a strong link between the terrestrial biosphere, the atmosphere and the climate. Global models of BVOC emissions have assumed minimal emissions from the high latitudes due to low temperatures, short growing seasons and sparse vegetation cover. However, measurements from this region of the world are lacking and emissions from the High Arctic have not been published yet. The aim of this study was to obtain the first estimates for BVOC emissions from the High Arctic. Hereby, we wish to add new knowledge to the understanding of global BVOC emissions. Measurements were conducted in NE Greenland (74°30' N, 20°30' W) in four vegetation communities in the study area. These four vegetation communities were dominated by Cassiope tetragona, Salix arctica, Vaccinium uliginosum and Kobresia myosuroides/Dryas octopetela/Salix arctica, respectively. Emissions were measured by enclosure technique and collection of volatiles into adsorbent cartridges in August 2009. The volatiles were analyzed by gas chromatography-mass spectrometry following thermal desorption. Isoprene showed highest emissions in S. arctica-dominated heath, where it was the dominant single BVOC. However, isoprene emission decreased below detection limit in the end of August when the temperature was at or below 10°C. According to a principal component analysis, monoterpene and sesquiterpene emissions were especially associated with C. tetragona-dominated heath. Especially S. arctica and C. tetragona dominated heaths showed distinct patterns of emitted BVOCs. Emissions of BVOC from the studied high arctic heaths were clearly lower than the emissions observed previously in subarctic heaths with more dense vegetation

  2. Field Evidence for Differences in Post-Fire Aeolian Transport Related to Vegetation Type in Semi-Arid Grasslands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Disturbances such as wildfires, which cause a temporary reduction in vegetation cover, can greatly accelerate soil erosion by wind and promote dust emissions. Enhanced erosion leads to a reduction in soil fertility and the post-fire mobilization of soil and associated emissions of dust represent a s...

  3. 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

  4. 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.

  5. Functional convergence of tundra vegetation simplifies the interpretation of flux observations at larger spatial scales

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Williams, M.; Evans, J. G.; Lloyd, C. R.; Prieto-Blanco, A.; Disney, M.; Street, L. E.; Shaver, G. R.

    2007-12-01

    A central challenge in terrestrial carbon cycle research is upscaling measurements of vegetation function to larger spatial and temporal scales. A solution is required to, for example, make chamber-based measurements relevant at larger spatial scales and to make eddy covariance measurements applicable to leaf or chamber- based studies. Here we demonstrate that a simple model for photosynthesis and ecosystem respiration parameterized using pan-arctic chamber flux measurements closely matches eddy covariance flux observations in a tundra ecosystem near Abisko, Sweden. The agreement holds when using a generic parameter set that does not account for vegetation type or measurement location. Inverting the model to predict leaf area using eddy covariance-measured net ecosystem exchange closely approximates tower-based LAI estimates across seasons and during periods of drought stress. Thus, recent findings documenting functional convergence of arctic vegetation holds at multiple spatial as well as temporal scales using both chamber and tower measurements. After validating the model using the eddy covariance measurements, we integrate the model with meteorological and LAI observations using a simple data assimilation scheme. The reduction of error achieved via data assimilation is compared to standard techniques of estimating eddy covariance error. Our analysis demonstrates that accurate estimates of C flux at multiple spatial scales across the tundra biome are possible given accurate estimates of photosynthetically active radiation, temperature, and leaf area index given the observed functional convergence of tundra vegetation.

  6. 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

  7. Biocomplexity in the High Arctic: Linearity's, interactions and hidden secrets in surface processes

    NASA Astrophysics Data System (ADS)

    Welker, J. M.; Sletten, R.; Hallet, B.; Schimel, J.; Hagedorn, B.; Sullivan, P.; Steltzer, H.; Holland, K.; Horwath, J.; Arens, S.; Rogers, M.; Garnes, D.; Perrson, K.

    2006-12-01

    We have explored the physical-chemical-biological interactions and their controls on surface carbon and water dynamics in the High Arctic landscapes of NW Greenland. Our studies have been conducted across a series of scales from the landscape patterns of vegetation to plot-level studies of carbon and water. To address these issues we have: a) established a multi-level heating experiment to test the linearity of plant and soil responses to warming and included a watering regime to examine the complexity of temperature-water interactions, b) established a snow augmentation study in polar semi-desert and polar desert landscapes to investigate whether landscape type regulates shifts in winter soil temperatures, soil water chemistry, soil microbial processes, plant growth, vegetation processes and trace gas exchanges and c) articulated the linearity and complexity in surface processes changes (vegetation, trace gas flux and microbial dynamics) associated with increasing soil fertility using three-levels of N additions, with and without P supplements. Observational and inventory studies have been implemented to complement our experimental studies with the: a) quantification of soil carbon pools across the landscape using landscape NDVI classes derived from ASTER satellite images, b) excavation of a polar stripe site to provide the first 3- dimensional depiction and analysis of non-sorted polar strips and cryoturbation effects on buried carbon, c) ice sheet, terrestrial-marine linkages with watershed studies of stream water geochemistry and d) identifying ecophysiological plant processes including soil water sources and leaf gas exchange along natural gradients of soil water and temperature. We have discovered four main secrets of high arctic systems: 1) non-linearity is the rule rather than the norm in these extreme systems, 2) the surface traits of the high arctic do not represent the true features of soil carbon pools and sequestration, 3) ice sheet melt water is

  8. Projected impacts of 21st century climate change on the distribution of potential habitat for vegetation, forest types and major conifer species across Russia.

    NASA Astrophysics Data System (ADS)

    Tchebakova, Nadezda; Parfenova, Elena; Cantin, Alan; Shvetsov, Eugene; Soja, Amber; Conard, Susane

    2013-04-01

    Global simulations have demonstrated the potential for profound effects of GCM-projected climate change on the distribution of terrestrial ecosystems and individual species at all hierarchical levels. We modeled progressions of potential vegetation cover, forest cover and forest types in Russia in the warming climate during the 21st century. We used large-scale bioclimatic models to predict zonal vegetation (RuBCliM), and forest cover (ForCliM) and forest types. A forest type was defined as a combination of a dominant tree conifer and a ground layer. Distributions of vegetation zones (zonobiomes), conifer species and forest types were simulated based on three bioclimatic indices (1) growing degree-days above 5oC ; (2) negative degree-days below 0oC; and (3) an annual moisture index (ratio of growing degree days to annual precipitation). Additionally, the presence/absence of continuous permafrost, identified by active layer depth of 2 m, was explicitly included in the models as limiting the forests and tree species distribution in Siberia. 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 1971-2000 and for the future decades of 2011-2020, 2041-2050 and 2091-2100. To provide a range of warming we used three global climate models (CGCM3.1, HadCM3 and IPSLCM4) and three climate change scenarios (A1B, A2 and B1). The CGCM model and the B1 scenario projected the smallest temperature increases, and the IPSL model and the A2 scenario projected the greatest temperature increases. We compared the modeled vegetation and the modeled tree species distributions in the contemporary climate to actual vegetation and forest maps using Kappa (K) statistics. RuBioCliM models of Russian zonal vegetation were fairly accurate (K= 0.40). Contemporary major conifer species (Pinus sibirica, Pinus sylvestris, Larix spp., Abies sibirica and Picea obovata

  9. Emissions from International Shipping in the Arctic

    NASA Astrophysics Data System (ADS)

    Corbett, J. J.; Winebrake, J. J.; Gold, M.; Harder, S.

    2008-12-01

    Studies assessing the potential impacts of international shipping on climate and air pollution demonstrate that ships contribute significantly to global climate change and health impacts through emission of GHGs and raised the potential for disproportionate impacts from shipping in the Arctic region. We present an activity- based model inventory of emissions of CO2, BC, NOx, SOx, PM, and CO for shipping in the Arctic. We estimate emissions for a particular "vessel-trip" or "voyage" based on Arctic shipping data collected by the Arctic Marine Shipping Assessment for 2004. The detailed voyage data provided for our inventory effort included some 3800 ship trips, represent some 2.6 million km of ship voyages (range 2.0 to 3.9 million km, or 1.1 to 2.1 million nautical miles), and nearly 15,000 voyage days for 2004; this is equivalent to less than 500 transoceanic voyages, compared to many tens of thousands transoceanic voyages per year to major ports around the world. In 2004, the top five vessel types, bulk carrier, general cargo, fishing, government vessels, and containerships, account for nearly 80 percent of total emissions. Preliminary results show CO2 emissions from shipping in the Arctic to be approximately 2.3 Tg CO2 per yr. Given that total CO2 emissions from international shipping globally are about 1000 Tg CO2 per yr, Arctic contributions would amount to less than 0.25 percent of total ship emissions. Relative to total CO2 emissions from all sources, the contributions of Arctic shipping are on the order of one-hundredth of one percent (0.006-0.008 percent). BC emissions from Arctic shipping, on a mass basis alone (estimated here to be ~600 tonnes /year), may have limited independent impact on global climate change compared to other sources, but could have significant regional impacts. More concerning may be micro-scale emissions (e.g., at harbor or in port) which could affect local air pollution or ecosystems, depending on regional conditions. Pollutants

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. [Communities of Actynomicetes fungy in three vegetation types of the Colombian Amazon: abundance, morphotypes and the 16s rDNA gene].

    PubMed

    Cardona, Gladys Inés; Peña-Venegas, Clara Patricia; Ruiz-García, Manuel

    2009-12-01

    Among soil microorganisms, Actinomycetes play an important role in the sustainability of natural and agricultural systems: decomposition of organic matter; degradation of recalcitrant compounds like lignin; nitrogen fixation; degradation of agricultural chemicals and biological control in plants and animals. We evaluated their diversity in soils under three different vegetation covers (pasture, tropical primary forest and stubble) at two depths in the Southern Colombian Amazon border. We collected five replicates per vegetation type (in each, three samples at 0-20cm and three at 20-30cm; for a total of 30 samples). Abundance and phenotypic diversity were determined by plate counting. Genomic DNA was extracted from the isolates: the 16s rDNA gene was amplified with specific primers, and its genetic diversity was estimated by means of an amplified restriction analysis (ARDRA). Actynomicetes abundance varied with vegetation and depth, possibly reflecting presence of earthworms, macro-fauna and physico-chemical characteristics associated to fertility, as well as organic matter, total bases, and optimal capacity to cationic interchange. Primary forests had the highest diversity. Sixteen morpho-types (six genera) were identified; Streptomyces was the most abundant everywhere. The heterogeneity ofARDRA patterns prevented species identification because of the intra-species variability in sequences of 16s rDNA operons. This community is a biological indicator of landscape alteration and could include new bio-active compounds of pharmaceutical interest. PMID:20073339

  15. 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

  16. 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

  17. 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

  18. Observation Platforms and Data Streams of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic)

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.; Wullschleger, S. D.; Graham, D. E.; Hubbard, S. S.; Norby, R. J.; Rogers, A.; Torn, M. S.; Wilson, C. J.

    2013-12-01

    The goal of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic) is to deliver a process-rich ecosystem model, extending from bedrock to the top of the vegetative canopy, in which the evolution of Arctic ecosystems in a changing climate can be modeled at the scale of a high resolution Earth System Model grid cell. Increasing our confidence in climate projections for high-latitude regions of the world requires a coordinated set of observation platforms that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. Initial research has focused upon the highly dynamic landscapes of the North Slope (Barrow, Alaska) where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. This vision includes mechanistic studies in the field and in the laboratory; modeling of critical and interrelated water, nitrogen, carbon, and energy dynamics; and characterization of important interactions from molecular to landscape scales that drive feedbacks to the climate system. To complete these investigations, an integrated program of field monitoring has been initiated. These include observations of meteorological, hydrological, ecological and geophysical processes. These data streams are intended to supplement and extend existing polar data sets to advance our understanding of the Arctic environment and its response to a rapidly changing climate.

  19. 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.

  20. Refinement of microwave vegetation indices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous investigations have established the basis for a new type of vegetation index based on passive microwave satellite observations. These microwave vegetation indices (MVIs) have been qualitatively evaluated by examining global spatial and seasonal temporal features. Limited quantitative studie...

  1. 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

  2. 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.

  3. 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…

  4. Arctic Coastal Dynamics (ACD)

    NASA Astrophysics Data System (ADS)

    Rachold, V.; Boike, J.

    2003-04-01

    Coastal dynamics directly reflecting the complicated land-ocean interactions play an important role in the balance of sediments, organic carbon and nutrients in the Arctic basin. Recent studies indicate that sediment input to the Arctic shelves resulting from erosion of ice-rich, permafrost-dominated coasts may be equal to or greater than input from river discharge. Thus, the understanding and quantification of coastal processes is critical for interpreting the geological history of the Arctic shelves. The predictions of future behavior of these coasts in response to climatic and sea level changes is an important issue because most of the human activity that occurs at high latitudes concentrates on the Arctic coastlines. As an initiative of the International Permafrost Association (IPA) the multi-disciplinary, multi-national forum Arctic Coastal Dynamics (ACD), which was recently accepted as a project of the International Arctic Sciences Committee (IASC), had been developed. The overall objective of ACD is to improve our understanding of circum-Arctic coastal dynamics as a function of environmental forcing, coastal geology and cryology and morphodynamic behavior. In particular, the project aims to: - establish the rates and magnitudes of erosion and accumulation of Arctic coasts; - develop a network of long-term monitoring sites including local community-based observational sites; - identify and undertake focused research on critical processes; - estimate the amount of sediments and organic carbon derived from coastal erosion; - refine and apply an Arctic coastal classification (includes ground-ice, permafrost, geology etc.) in digital form (GIS format); - extract and utilize existing information on relevant environmental forcing parameters (e.g. wind speed, sea level, fetch, sea ice etc.); - produce a series of thematic and derived maps (e.g. coastal classification, ground-ice, sensitivity etc.); - develop empirical models to assess the sensitivity of Arctic

  5. Arctic Economics Model

    Energy Science and Technology Software Center (ESTSC)

    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

  6. Development of a Polar Stratospheric Cloud Model within the Community Earth System Model using constraints on Type I PSCs from the 2010-2011 Arctic winter

    NASA Astrophysics Data System (ADS)

    Zhu, Yunqian; Toon, Owen B.; Lambert, Alyn; Kinnison, Douglas E.; Brakebusch, Matthias; Bardeen, Charles G.; Mills, Michael J.; English, Jason M.

    2015-06-01

    Polar stratospheric clouds (PSCs) are critical elements of Arctic and Antarctic ozone depletion. We establish a PSC microphysics model using coupled chemistry, climate, and microphysics models driven by specific dynamics. We explore the microphysical formation and evolution of STS (Supercooled Ternary Solution) and NAT (Nitric Acid Trihydrate). Characteristics of STS particles dominated by thermodynamics compare well with observations. For example, the mass of STS is close to the thermodynamic equilibrium assumption when the particle surface area is >4 µm2/cm3. We derive a new nucleation rate equation for NAT based on observed denitrification in the 2010-2011 Arctic winter. The homogeneous nucleation scheme leads to supermicron NAT particles as observed. We also find that as the number density of NAT particles increases, the denitrification also increases. Simulations of the PSC lidar backscatter, denitrification, and gas phase species are generally within error bars of the observations. However, the simulations are very sensitive to temperature, which limits our ability to fully constrain some parameters (e.g., denitrification, ozone amount) based on observations.

  7. 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

  8. Using Ecosystem Functional Types in land-surface modeling to characterize and monitor the spatial and inter-annual variability of vegetation dynamics

    NASA Astrophysics Data System (ADS)

    Alcaraz-Segura, D.; Paruelo, J.; Epstein, H. E.; Berbery, E. H.; Kalnay, E.; Cabello, J.; Jobbagy, E. G.

    2009-12-01

    Including the inter-annual variability of vegetation dynamics into land-surface models is necessary to account for land use/cover change effects on Global Climate Models. However, land-surface models use land-cover classifications dictated by structural attributes of vegetation that have little sensitivity to environmental change and are difficult to update and result in a delayed response. This rigid representation of vegetation reduces the ability of models to represent rapid changes including land-use shifts, fires, floods, droughts, and insect outbreaks. Functional attributes of vegetation describing its energy and matter exchange with the atmosphere, have a shorter response to environmental changes and are relatively easy to monitor with satellite data. We applied the concept of Ecosystem Functional Types (EFTs; patches of the land-surface with similar carbon gain dynamics) to characterize the spatial and inter-annual variability of vegetation dynamics across natural and agricultural systems in the La Plata Basin of South America. Three descriptors of carbon gain dynamics were derived from seasonal curves of Normalized Difference Vegetation Index (NDVI) and used to identify EFTs based on annual mean (surrogate of primary production), seasonal coefficient of variation (indicator of seasonality), and date of maximum NDVI (descriptor of phenology). Results from two NDVI datasets were compared (AVHRR-LTDR version 2, 1982-1999, 15-day and 5 km resolution; and MOD13A2 MODIS, 2000-2006, 16-day and 1 km resolution). Both datasets showed greater spatial and inter-annual variability of the EFT composition in agricultural areas compared to natural areas. During 1982-1999, the percentage of the La Plata Basin occupied by EFTs with low productivity, high seasonality, and spring and fall NDVI maxima tended to decrease, while EFTs with high productivity, low seasonality, and summer maxima tended to increase. We speculate that these trends may be due to a positive trend in

  9. 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.

  10. 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%).

  11. 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

  12. 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.

  13. 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

  14. Satellite monitoring of impact Arctic regions

    NASA Astrophysics Data System (ADS)

    Bondur, V. G.; Vorobev, V. E.

    2015-12-01

    The results of satellite monitoring of the environmental state of impact Arctic regions subjected to heavy anthropogenic influence are given. We analyze arrays of vegetation indices and complex spectral transformations derived from processed long-term (1973-2013) satellite data for areas around the cities of Arkhangelsk and Zapolyarny (Murmansk oblast). These data have been used to evaluate the changes in the state of the environment and reveal areas of peak anthropogenic impacts causing significant morphologic changes in all kinds of geosystems and strongly affecting the Arctic natural ecosystems. We have identified the impact regions that are subjected to peak anthropogenic impact and found that these areas are associated with specific industrial facilities.

  15. 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

  16. Effects of vegetable type, package atmosphere and storage temperature on growth and survival of Escherichia coli O157:H7 and Listeria monocytogenes.

    PubMed

    Francis, G A; O'Beirne, D

    2001-08-01

    The survival and growth of Escherichia coli O157:H7 (ATCC 43888 and NCTC 12900) and Listeria monocytogenes (ATCC 19114 and NCTC 11994) during storage (4 and 8 degrees C) on ready-to-use (RTU) packaged vegetables (lettuce, swedes (rutabaga), dry coleslaw mix, soybean sprouts) were studied. The vegetables were sealed within oriented polypropylene packaging film, and modified atmospheres developed in packs during storage due to produce respiration. Survival and growth patterns were dependent on vegetable type, package atmosphere, storage temperature and bacterial strain. Populations of L. monocytogenes and E. coli O157:H7 increased (P<0.05, by 1.5 to 2.5 log cycles, depending on strain) during a 12-day storage period on shredded lettuce (8 degrees C). L. monocytogenes populations also increased (by approximately 1 log cycle) on packaged swedes, did not change significantly (P>0.05) in packages of soybean sprouts and decreased by approximately 1.5 log cycles (P<0.05) on coleslaw mix (8 degrees C). E. coli O157:H7 populations on packaged coleslaw and soybean sprouts increased (by 1.5 to 2.5 log cycles) up to day 5, but declined during subsequent storage (8 degrees C). On packaged swedes (8 degrees C), populations of E. coli O157:H7 strain ATCC 43888 increased (by approximately 1 log cycle) during storage, whereas populations of strain 12900 increased between days 2 and 5, and declined during subsequent storage. Reducing the storage temperature from 8 to 4 degrees C reduced the growth of L. monocytogenes and E. coli O157:H7 on packaged RTU vegetables. However, viable populations remained at the end of the storage period at 4 degrees C. PMID:11641769

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. 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...

  2. 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

  3. Parameter Sensitivity of the Arctic BIOME BGC model for Estimating Evapotranspiration

    NASA Astrophysics Data System (ADS)

    Engstrom, R. N.; Hope, A.

    2005-12-01

    Modeling evapotranspiration (ET) in Arctic coastal plain ecosystems is challenging due to the unique environmental conditions, including non-vascular vegetation, permafrost, and a large standing dead vegetation component. In a previous study, the commonly used ecosystem process model, BIOME BGC, was modified to include representations of these unique Arctic conditions. The modifications resulted in a new model, Arctic BIOME BGC that significantly reduced the random and systematic errors when compared to eddy flux tower measurements. However, the modifications made in Arctic BIOME BGC added complexity and a number of new parameters. In this study the generalized sensitivity analysis methodology was used to examine the Arctic BIOME BGC model sensitivity to the thirteen parameters in the application of estimating daily ET over a four year time period in the Arctic coastal plain. The thirteen parameters investigated represented those which most directly impact model ET estimates and include all of the new ones added in the development of Arctic BIOME BGC. Results indicate that the model was highly sensitive to eight of the thirteen parameters. This suggests that the new process representations added in Arctic BIOME BGC were important for modeling ET in these ecosystems. Two parameters, standing dead leaf area index and snow absorptivity, had unique, identifiable values that corresponded well to observed data. Overall, there were many physically realistic parameter sets that were able to produce acceptable model predictions indicating that parameter equifinality is present within the model.

  4. 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.

  5. 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.

  6. 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. PMID:23978050

  7. 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.

  8. USGS Arctic science strategy

    USGS Publications Warehouse

    Shasby, Mark; Smith, Durelle

    2015-01-01

    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.

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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 ...

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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.

  2. 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

  3. On Prediction and Predictability of the Arctic Climate System

    NASA Astrophysics Data System (ADS)

    Maslowski, W.; Clement Kinney, J.; Roberts, A.; Higgins, M.; Osinski, R.; Cassano, J. J.; Craig, A.; Gutowski, W. J.; Lettenmaier, D. P.; Lipscomb, W. H.; Tulaczyk, S. M.; Zeng, X.

    2012-12-01

    Arctic sea ice is a key indicator of the state of Earth's climate because of both its sensitivity to warming and its role in amplifying climate change. However, the current system-level understanding and representation of critical arctic processes and feedbacks in state-of-the-art Earth System Models (EaSMs) is still inadequate. This becomes increasingly critical as the perennial and total summer sea ice cover continues its accelerated decline that started in the late 1990s. Growing evidence suggests that the shrinking Arctic ice pack affects pan-Arctic atmospheric and oceanic circulation, snow cover, the Greenland ice sheet, permafrost and vegetation. Such changes could have significant ramifications for global sea level, the global surface energy and moisture budget, atmospheric and oceanic circulations, geosphere-biosphere feedbacks, as well as affecting native coastal communities, and international commerce. We evaluate available results from CMIP5 models against limited observations for their skill in representing recent decadal variability of Arctic sea ice area, thickness, drift and export. We also intercompare results from CMIP5 models with selected CMIP3 models and a hierarchy of regional ice-ocean and fully coupled climate models to demonstrate possible gains or outstanding limitations in representing past and present climate variability in the Arctic. Some of the limitations we have diagnosed in the CMIP3 family of models include: northward oceanic heat fluxes and their interface with the atmosphere, distribution of sea ice area and thickness, variability of sea ice volume in the Arctic Ocean, and freshwater (both solid and liquid) export into the North Atlantic. We argue that the ability of global models to realistically reproduce the above processes affecting recent warming and sea ice melt in the Arctic Ocean distorts predictability of EaSMs and limits the accuracy of their future arctic and global climate predictions. To better understand the past

  4. 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

  5. Tundra Rehabilitation in Alaska's Arctic

    NASA Astrophysics Data System (ADS)

    Lynn, L. A.

    2012-12-01

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

  6. Patterns and controls of winter carbon dioxide emissions and microbial biomass C and N, in two arctic ecosystem types under varying snow regimes

    NASA Astrophysics Data System (ADS)

    Larsen, K. S.

    2003-04-01

    In a manipulative study, snow fences were put up in sub arctic birch forest and dry heath areas near Abisko, Northern Sweden, increasing the natural snow-cover by 5-35 cm. In early March, CO2 fluxes were 77% and 157% higher in the snow-fenced areas (birch and heath, respectively) and in the snowmelt period from April to May there was a tendency to higher effluxes of CO2 in patches with increased snow-cover. This indicates that small increases in winter snowfall have the potential to increase the CO2 loss substantially from these ecosystems during the off-season. CO2 fluxes integrated over 22 days in April-May at the heath site constituted 8% of growing season net primary production at a nearby heath site, showing that a substantial part of annual CO2 loss may take place during the early spring. In a second study, measurements of CO2 emissions from birch and heath ecosystems situated across a natural snow-cover gradient were performed. The results of this study corroborates with the findings in the snow fence study, showing consistently higher fluxes from sites with higher snow depths. The microbial biomass N and P were determined in both studies and were consistently high in the sub nivean soils compared to summer estimates, indicating that microbes provide a significant buffer limiting the export of mineral nutrients in the snowmelt period. A significant decrease in microbial biomass was observed as plots became snow free at the heath site. Although such decreases have been suggested to be caused by freeze-thaw cycles, this cannot fully explain the observation in this study. The first spring thaw and the transition from constant, sub-zero temperatures and a constant water regime to more variable conditions, and possibly increased grazing by nematodes and protozoans, may also play and important role controlling the microbial population during and after snowmelt.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. Dissolved organic matter sources in large Arctic rivers

    NASA Astrophysics Data System (ADS)

    Amon, Rainer; Walker, Sally; Prokushkin, Anatoly; Guggenberger, Georg

    2013-04-01

    The composition of dissolved organic carbon (DOC) of the six largest Arctic rivers was studied between 2003 and 2007 as part of the PARTNERS Project. Samples were collected over seasonal cycles relatively close to the river mouths. Here we report the lignin phenol and p-hydroxybenzene composition along with optical properties of Arctic river DOC in order to identify major sources of carbon. Arctic river DOC represents an important carbon conduit linking the large pools of organic carbon in the Arctic/Subarctic watersheds to the Arctic Ocean. Most of the annual lignin discharge (>75%) occurs during the two month of spring freshet with extremely high lignin concentrations and a lignin phenol composition indicative of fresh vegetation from boreal forests. The three large Siberian rivers, Lena, Yenisei, and Ob, which also have the highest proportion of forests within their watersheds, contribute about 90% of the total lignin discharge to the Arctic Ocean. The composition of river DOC is also characterized by elevated levels of p-hydroxybenzenes, particularly during the low flow season, which indicates a larger contribution from mosses and peat bogs. The lignin composition was strongly related to the average 14C-age of DOC supporting the abundance of young, boreal-vegetation-derived leachates during spring flood, and older, soil-, peat-, and wetland-derived DOC during groundwater dominated low flow conditions, particularly in the Ob and Yukon Rivers. We observed significant differences in DOC concentration and composition between the rivers over the seasonal cycles with the Mackenzie River being the most unique, the Lena River being similar to the Yenisei, and the Yukon being most similar to the Ob. The observed relationship between the lignin phenol composition and watershed characteristics suggests that DOC discharge from these rivers could increase in a warmer climate under otherwise undisturbed conditions.

  12. 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

  13. Improved Sampling Strategy for Arctic Snow Distribution

    NASA Astrophysics Data System (ADS)

    Homan, J. W.; Kane, D. L.

    2012-12-01

    Watershed scale hydrologic models require good estimates of the spatially distributed snow water equivalent (SWE) at winter's end. Snow on the ground in treeless Arctic environments is susceptible to significant wind redistribution, which results in very heterogeneous snowpacks, with greater quantities of snow collection in depressions, valley bottoms and leeward sides of ridges. In the Arctic, precipitation and snow gauges are very poor indicators of the actual spatial snowpack distribution, particularly at winter's end when ablation occurs. Snow distribution patterns are similar from year to year because they are largely controlled by the interaction of topography, vegetation, and consistent weather patterns. From one year to the next, none of these controls radically change. Consequently, shallow and deep areas of snow tend to be spatially predetermined, resulting in depth (or SWE) differences that may vary as a whole, but not relative to each other, from year to year. This work attempts to identify snowpack distribution patterns at a watershed scale in the Arctic. Snow patterns are intended to be established by numerous field survey points from past end-of-winter field campaigns. All measured SWE values represent a certain percentage of a given watershed. Some may represent small-scale anomalies (local scale), while others might represent a large-scale area (regional scale). Since we are interested in identifying snowpack distribution patterns at a watershed scale, we aim to develop an improved point-source sampling strategy that only surveys regional representative areas. This will only be possible if the extreme high and low SWE measurements that represent local-scale snow conditions are removed in the sampled data set. The integration of these pattern identification methods will produce a hybrid approach to identifying snowpack distribution patterns. Improvement in our estimates of the snowpack distribution will aid in the forecasting of snowmelt runoff

  14. 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.

  15. Role of Mediterranean diet, tropical vegetables rich in antioxidants, and sunlight exposure in blindness, cataract and glaucoma among African type 2 diabetics

    PubMed Central

    Moïse, Mvitu Muaka; Benjamin, Longo-Mbenza; Doris, Tulomba Mona; Dalida, Kibokela Ndembe; Augustin, Nge Okwe

    2012-01-01

    AIM To assess whether regular Mediterranean diet and regular intake of vegetables may reduce the risk of blindness, cataract, and glaucoma in these type 2 diabetics. METHODS A cross-sectional design was carried out among known black diabetics admitted at the diabetic clinics of Kinshasa, between October 2008 and March 2009. The Mediterranean-style dietary score (MSDPS) was used to characterize a Mediterranean-style dietary pattern in the study population using the Harvard semi quantitative FFQ adapted for Africa. RESULTS Five hundred Type 2 diabetic patients were included in this study (48% of males; 40% aged ≥60 years). There was a significant association between blindness, cataract and aging; between blindness (P<0.05), cataract (P<0.05), glaucoma (P<0.05), and physical inactivity; between blindness (P<0.05), cataract (P<0.0001), glaucoma (P<0.01) and high SES, and a very significant association between blindness (P<0.0001), cataract (P<0.0001), glaucoma (P<0.0001) and exposure to sunlight. There was also a significant association between blindness, glaucoma, and male sex. Regular intake of Mediterranean diet, Brassica Rapa, beans, Abelmoschus, Musa acuminata reduced significantly the risk of blindness, cataract and glaucoma. CONCLUSION Regular intake of Mediterranean diet, Brassica Rapa, beans, Abelmoschus, and Musa acuminata may significantly reduce the risk of blindness or its major causes among type 2 diabetes mellitus in Africa. PMID:22762057

  16. 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

  17. 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

  18. 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.

  19. 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

  20. 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/).

  1. 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

  2. Modeling evapotranspiration in Arctic coastal plain ecosystems using a modified BIOME-BGC model

    NASA Astrophysics Data System (ADS)

    Engstrom, Ryan; Hope, Allen; Kwon, Hyojung; Harazono, Yoshinobu; Mano, Masayoshi; Oechel, Walter

    2006-06-01

    Modeling evapotranspiration (ET) in Arctic coastal plain ecosystems is challenging owing to the unique conditions present in this environment, including permafrost, nonvascular vegetation, and a large standing dead vegetation component. In this study the ecosystem process model, BIOME-BGC, was adapted to represent these unique conditions in Arctic ecosystems by including a new water storage and evaporation routine that accounts for nonvascular vegetation and the effects of permafrost, adding ground heat flux as an input, and representing ground shading by dead vegetation. The new Arctic version and the original BIOME-BGC models are compared to observed ET from two eddy flux towers in Barrow, Alaska over four summer seasons (1999-2002). The two towers are located less than 1 km apart, yet represent contrasting moisture conditions. One is located in a drained thaw lake, marsh area, while the other is located in a drier, upland area characterized by mesic tundra. Results indicate that the original BIOME-BGC model substantially underestimated ET, while the Arctic version slightly overestimated ET at both sites. The new Arctic model version worked particularly well at the wet tower because the model was able to capture energy limitations better than water limitations. Errors in the simulation of snowmelt date led to errors in the ET estimates at both sites. Finally, the substantial differences in soil moisture led to substantially different ET rates between the sites that were difficult to simulate and indicates that soil moisture heterogeneity is a strong controller on ET in these ecosystems.

  3. Quantifying the effects of nutrient addition on community diversity of serpentine vegetation using parametric entropy of type α

    NASA Astrophysics Data System (ADS)

    Ricotta, Carlo; Chiarucci, Alessandro; Avena, Giancarlo

    2004-03-01

    A desirable property of a diversity index is the so-called sum property. For a diversity index that possesses the sum property, such as species richness N, Shannon's entropy H or Simpson's index 1/ D, the community diversity is decomposable into species-level patterns and the sum of single species diversities gives the pooled diversity of the species collection. In this paper, parametric diversity of type α is used to quantify how fertilizer applied to soil affects the relative contribution of species endemic or preferential to serpentine soils within a garigue plant community in Tuscany (Italy). Soil fertilizer significantly improved the biomass production of the original species pool without any significant colonization by alien species. However, the major biomass increments were experienced by species that are not exclusive to serpentine soils. In this view, the reduced abundance of species endemic or preferential to serpentine soils can be interpreted as a loss of 'ecological quality' of the analyzed community.

  4. 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. PMID:25348575

  5. 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.

  6. Communicating Arctic Change (Invited)

    NASA Astrophysics Data System (ADS)

    Serreze, M.

    2009-12-01

    Nowhere on the planet are emerging signals of climate change more visible than in the Arctic. Rapid warming, a quickly shrinking summer sea ice cover, and thawing permafrost, will have impacts that extend beyond the Arctic and may reverberate around the globe. The National Snow and Ice Data Center (NSIDC) of the University of Colorado has taken a leading role in trying to effectively communicate the science and importance of Arctic change. Our popular “Sea Ice News and Analysis” web site tracks the Arctic’s shrinking ice cover and provides scientific analysis with language that is accurate yet accessible to a wide audience. Our Education Center provides accessible information on all components of the Earth’s cryosphere, the changes being seen, and how scientists conduct research. A challenge faced by NSIDC is countering the increasing level of confusion and misinformation regarding Arctic and global change, a complex problem that reflects the low level of scientific literacy by much of the public, the difficulties many scientists face in communicating their findings in accurate but understandable terms, and efforts by some groups to deliberately misrepresent and distort climate change science. This talk will outline through examples ways in which NSIDC has been successful in science communication and education, as well as lessons learned from failures.

  7. Evidence and Implications of Recent Climate Change in Terrestrial Regions of the Arctic

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.; Bettez, N.; Chapin, F. S.; Dyurgerov, M.; Fastie, C.; Griffith, D. B.; Hope, A.; Huntington, H. P.; Jensen, A.; Kane, D. L.; Kofinas, G.; Lynch, A.; Lloyd, A.; McGuire, A. D.; Nelson, F. E.; Osterkamp, T.; Oechel, W. C.; Racine, C.; Romanovsky, V. E.; Schimel, J.; Stow, D.; Sturm, M.; Tweedie, C. E.; Vourlitis, G.; Walker, M.; Webber, P. J.; Welker, J.; Winker, K.; Yoshikawa, K.

    2002-12-01

    Are changes occurring in the polar terrestrial regime? Is the distribution of permafrost and Arctic region freeze and thaw changing? Is the hydrology of Arctic terrestrial regions changing? Are significant changes occurring in the distribution and productivity of high-latitude vegetation? If one examines any individual scientific discipline, evidence of climate change in arctic regions offers only pieces of the puzzle. Here we present a broad array of evidence to provide a convincing case of change in the arctic climate and a system-wide response of terrestrial processes. The thermal regime of the Arctic holds unique characteristics and consequently will display marked changes in response to climate warming. In many cases, threshold changes will occur in physical systems proceeding from permanently frozen to periodically thawed. Dramatic changes also accompany biological systems adapting to an evolving environment. In the last 25 to 400 years a wide range of changes in the Arctic have been detected. In many cases, these changes started, or accelerated, in the mid-1970s. Some of the changes, like later freeze-up and earlier break-up of arctic rivers and lakes, mirror arctic-wide and even global increases in air temperature. Others document more subtle or complex responses of the arctic system as it adapts to current and longer-term trends in climate. Since the arctic system is particularly sensitive to changes in rain- and snowfall, timing of freeze-up and break-up, and the intensity of storm activity, it is likely that much of what has been documented to date, and will be observed in the future, arises from changes in these forcing fields. Unfortunately, compared with temperature, they are poorly known. Regardless of the driving forces, however, the combined observations and documentation offer diffuse but substantial evidence that the arctic system may be entering a state not seen before in recent history.

  8. 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.

  9. Canopy Spectral Imaging (NDVI) As A Proxy For Shrub Biomass And Ecosystem Carbon Fluxes Across Arctic Tundra Habitats

    NASA Astrophysics Data System (ADS)

    Flower, C. E.; Welker, J. M.; Gonzalez-Meler, M. A.

    2015-12-01

    There is widespread consensus that climate change is contributing to rapid vegetation shifts in the ecologically sensitive Arctic tundra. These tussock grass dominated systems are shifting to tussock/woody shrub communities leading to likely alterations in carbon (C) sequestration and ecosystem productivity, which in turn can manifest in "greening" and changes in normalized difference vegetation index values (NDVI). While the expansion of woody vegetation is well established, our understanding of the ecosystem dynamics associated with this new habitat remain largely unknown. To untangle how the Arctic tundra may be impacted by these vegetation shifts we paired vegetation measurements (i.e. shrub biomass, leaf area, and shrub canopy area) and ecosystem C fluxes (e.g. net ecosystem exchange, NEE, and ecosystem respiration) with ground-level measurements of NDVI. Measurements were conducted at the Toolik Field Station in dry heath and moist acidic tundra habitats which are two primary habitat types on the North Slope of Alaska. We found strong positive relationships between shrub leaf area and biomass as well as shrub canopy area and biomass, relationships that were corroborated with NDVI measurements. This lends support for the use of NDVI as a proxy measurement of leaf area and shrub biomass. Additionally, NDVI was negatively correlated with ecosystem respiration across habitats, with respiratory fluxes consistently higher in the moist acidic relative to the dry heath tundra. Finally, we observed a significant positive nonlinear relationship between NEE and NDVI (R2~0.8; P<0.01). Shrub removal revealed that NEE was strongly controlled by woody shrubs. The positive relationship between NDVI and NEE highlights the potential shifts in the C balance of the Arctic tundra associated with woody encroachment. This increased plant productivity may offset greenhouse gas losses from permafrost degradation contributing some resilience to this system otherwise considered a

  10. 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

  11. 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 project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old) across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (−21%) than the Central Arctic herd that wintered primarily in the arctic tundra (−11%). Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas. PMID

  12. Climate-driven effects of fire on winter habitat for caribou in the Alaskan-Yukon Arctic

    USGS Publications Warehouse

    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 project annual fire characteristics and the resulting abundance of lichen-producing vegetation types (i.e., spruce forests and tundra >60 years old) across a modeling domain that encompassed the winter ranges of the Central Arctic and Porcupine caribou herds in the Alaskan-Yukon Arctic. Fires were less numerous and smaller in tundra compared to spruce habitats throughout the 90-year projection for both GCMs. Given the more likely climate trajectory, we projected that the Porcupine caribou herd, which winters primarily in the boreal forest, could be expected to experience a greater reduction in lichen-producing winter habitats (−21%) than the Central Arctic herd that wintered primarily in the arctic tundra (−11%). Our results suggest that caribou herds wintering in boreal forest will undergo fire-driven reductions in lichen-producing habitats that will, at a minimum, alter their distribution. Range shifts of caribou resulting from fire-driven changes to winter habitat may diminish access to caribou for rural communities that reside in fire-prone areas.

  13. Contemporary Changes in Vegetation of Polar Regions

    NASA Astrophysics Data System (ADS)

    Olech, Maria; Węgrzyn, Michał; Lisowska, Maja; Słaby, Agnieszka; Angiel, Piotr

    2011-01-01

    Rapid climate changes which have been observed over the recent years in both polar regions of the Earth, directly or indirectly affect vegetation dynamics. This article presents the main directions of the changes taking place in the recent years in tundra communities of both polar regions, based on original research carried out in the Arctic in Spitsbergen and in the maritime Antarctic on King George Island.

  14. High arctic snow avalanche observations and modeling in Svalbard 2007-2009

    NASA Astrophysics Data System (ADS)

    Eckerstorfer, Markus; Christiansen, Hanne H.; Humlum, Ole

    2010-05-01

    Systematic snow avalanche observations, carried out by the Norklima CRYOSLOPE Svalbard research project 2007-2009, represent the first comprehensive study of periglacial slope processes and especially snow avalanches in a high arctic maritime landscape. The main focus is on snow avalanche types, their spatial distribution, timing and associated controlling meteorological and snow pack conditions. Another focus is on the classification of the snow pack in central Svalbard in terms of thickness, hardness, stratigraphy and most persistent weak layers that cause avalanching. As a result of increasing population and tourism, snow mobile transportation and other recreational use of the steep terrain has increased, especially during the last 10-15 years in Svalbard. Such winter activity takes place in a high relief, almost vegetation free landscape, affected by snow avalanches. We present results from the 3 years project period, as well as the methods used to collect observations on snow avalanches, the snow pack and the meteorological data along the most intensively used 70 km snow mobile tracks around Svalbard's main settlement Longyearbyen. This enables us to identify the main factors controlling snow avalanches. We have recorded the amount of traffic along the main snow mobile tracks in our snow avalanche affected study area by use of radar, for avalanche risk evaluation. We also exemplify the high arctic maritime snow climate as an important additional type of snow climate, and emphasize its characteristics. Along with the field work, numerical modeling of avalanche activity has been developed and tested during the winter 2008-2009, on a weekly basis. The modeling includes topography, geomorphology and vegetation as input data, along with daily meteorological observations on air temperature, wind, cloud cover and precipitation from two meteorological stations at different altitudes. Examples from this modeling experiment will be presented together with the collected

  15. Arctic ice islands

    SciTech Connect

    Sackinger, W.M.; Jeffries, M.O.; Lu, M.C.; Li, F.C.

    1988-01-01

    The development of offshore oil and gas resources in the Arctic waters of Alaska requires offshore structures which successfully resist the lateral forces due to moving, drifting ice. Ice islands are floating, a tabular icebergs, up to 60 meters thick, of solid ice throughout their thickness. The ice islands are thus regarded as the strongest ice features in the Arctic; fixed offshore structures which can directly withstand the impact of ice islands are possible but in some locations may be so expensive as to make oilfield development uneconomic. The resolution of the ice island problem requires two research steps: (1) calculation of the probability of interaction between an ice island and an offshore structure in a given region; and (2) if the probability if sufficiently large, then the study of possible interactions between ice island and structure, to discover mitigative measures to deal with the moving ice island. The ice island research conducted during the 1983-1988 interval, which is summarized in this report, was concerned with the first step. Monte Carlo simulations of ice island generation and movement suggest that ice island lifetimes range from 0 to 70 years, and that 85% of the lifetimes are less then 35 years. The simulation shows a mean value of 18 ice islands present at any time in the Arctic Ocean, with a 90% probability of less than 30 ice islands. At this time, approximately 34 ice islands are known, from observations, to exist in the Arctic Ocean, not including the 10-meter thick class of ice islands. Return interval plots from the simulation show that coastal zones of the Beaufort and Chukchi Seas, already leased for oil development, have ice island recurrences of 10 to 100 years. This implies that the ice island hazard must be considered thoroughly, and appropriate safety measures adopted, when offshore oil production plans are formulated for the Alaskan Arctic offshore. 132 refs., 161 figs., 17 tabs.

  16. Arctic ecosystem functional zones: identification and quantification using an above and below ground monitoring strategy

    NASA Astrophysics Data System (ADS)

    Hubbard, Susan S.; Ajo-Franklin, Jonathan B.; Dafflon, Baptiste; Dou, Shan; Kneafsey, Tim J.; Peterson, John E.; Tas, Neslihan; Torn, Margaret S.; Phuong Tran, Anh; Ulrich, Craig; Wainwright, Haruko; Wu, Yuxin; Wullschleger, Stan

    2015-04-01

    to characterize and monitor ecosystem functioning - within and across permafrost, active layer and land-surface compartments and as a function of geomorphology and seasonal dynamics (thaw, growing season, freeze-up, and winter seasons). The second construct uses statistical approaches with the rich datasets to identify Arctic functional zones. Functional zones are regions in the landscape that have unique assemblages of above- and below-ground properties relevant to ecosystem functioning. Results demonstrate the strong co-variation of above and below ground properties in this Arctic ecosystem, particularly highlighting the critical influence of soil moisture on vegetation dynamics and redox-based active-layer biogeochemistry important for carbon cycling. The results also indicate that polygon types (low centered, high centered) have more power to explain the variations in properties than polygon features (trough, rim, center). This finding allows delineation of functional zones through grouping contiguous, similar types of polygons using remote sensing and surface geophysical datasets. Applied to the tundra NGEE study site, the functional zone approach permitted aggregation of critical properties associated with ~1350 polygons and their individual features, which vary over centimeter-to-meter length scales, into a few functional zones having suites of co-varying properties that were tractably defined over ~hundred meter length scales. The developed above-and-below ground monitoring strategy and functional zone approach are proving to be extremely valuable for gaining new insights about a complex Arctic ecosystem and for characterizing the system properties at high resolution and yet with spatial extents relevant for informing models focused on simulating ecosystem-climate feedbacks.

  17. Atmospheric aspects of Arctic change

    NASA Astrophysics Data System (ADS)

    Overland, J. E.

    2011-12-01

    Three important features of recent Arctic change are the rather uniform pattern of Arctic temperature amplification in response to greenhouse gas forcing, the modification of atmospheric temperature and wind patterns over newly sea-ice-free regions, and the possible increased linkage between Arctic climate and sub-arctic weather. An important argument for anthropogenic forcing of recent Arctic change is the model predicted rather uniform increases in Arctic temperatures, in contrast to more regional temperature maximums associated with intrinsic climate variability patterns such as those which occurred during the 1930s Arctic warming. Sea-ice-free areas at the end of summer are allowing: added heat and moisture transport into the troposphere as documented during the recent Japanese vessel Mirai cruises, decreased boundary layer stratification, and modification of wind flow through thermal wind processes. Winter 2009-2010 and December 2010 showed a unique connectivity between the Arctic and more southern weather when the typical polar vortex was replaced by high geopotential heights over the central Arctic and low heights over mid-latitudes that resulted in record snow and low temperatures, a Warm Arctic-Cold Continents pattern. A major challenge of Arctic meteorology is to understand the interaction of forced changes such as loss of sea ice and land impacts with intrinsic climate patterns such as the North Atlantic Oscillation and Pacific North American climate patterns. Could persistent shifts in Arctic climate be triggered by a combination of a gradual upward trend in temperature, an extreme event e.g. fortuitous timing in the natural variability of the atmospheric or ocean general circulation, and Arctic specific feedbacks? Scientific progress on both issues requires sustained decadal observations.

  18. Modeled changes in terrestrial C storage on the Arctic coastal plain of Alaska suggest a mid-century 21st shift from C sink to source.

    NASA Astrophysics Data System (ADS)

    Tucker, C.; Euskirchen, E. S.; Genet, H.; McGuire, A. D.; Rupp, S. T.; Breen, A. L.; Kurkowski, T. A.; Bennett, A.; Kofinas, G.

    2014-12-01

    Arctic tundra contains significant carbon (C) stocks, which are likely to change in response to climate change, depending on the balance of plant production and decomposition responses to warming and thawing permafrost. We modeled terrestrial C over the period 1901-2100 in a 67,000 km2 region of the eastern Arctic Coastal Plain of Alaska with four dominant vegetation types: wet sedge, tussock, shrub and heath tundra. The Terrestrial Ecosystem Model (TEM) is a biogeochemical model that simulates the C and N dynamics of vegetation and soils in response to climatic drivers. The version of TEM used here includes a dynamic organic soil module that allows the size of the organic soil layer to change through time. We model historical (1900-2010) and future (2010-2100) dynamics for low, intermediate and high CO2 emissions scenarios. During the period 2000-2010, modeled net primary productivity and vegetation C were significantly positively correlated with the MODIS derived normalized difference vegetation index, as were the start and end of the growing season, and the duration of the snow-covered season. Between 1900 and 2100, C storage in vegetation increased most in shrub and tussock tundra (52 % and 43 %, respectively) and somewhat less in wet sedge and heath tundra (15 % and 21 %, respectively), consistent with observed expansion of shrubby biomass across the region. Simulated terrestrial C storage for the study region changed from 40.5 kg C m-2 (soil=39.6, vegetation=1.0) in 1901 to 42.2 kg C m-2 (soil=40.9, vegetation=1.2) in 2010. In the intermediate warming scenario, by 2050, the total terrestrial C storage in the study region increased by 0.5 kg C m-2 but by 2100, 60% of this new C storage was lost, indicating a shift from net C uptake to net C loss in the study region toward the end of the century, driven by a shift in the relative magnitudes of C inputs from litter and losses from heterotrophic respiration. These changes were correlated with a 21 day increase in

  19. The Sub-Arctic Carbon Cycle: Assimilating Multi-Scale Chamber, Tower and Aircraft Flux Observations into Ecological Models

    NASA Astrophysics Data System (ADS)

    Hill, T. C.; Stoy, P. C.; Baxter, R.; Clement, R.; Disney, M.; Evans, J.; Fletcher, B.; Gornall, J.; Harding, R.; Hartley, I. P.; Ineson, P.; Moncrieff, J.; Phoenix, G.; Sloan, V.; Poyatos, R.; Prieto-Blanco, A.; Subke, J.; Street, L.; Wade, T. J.; Wayolle, A.; Wookey, P.; Williams, M. D.

    2009-12-01

    The Arctic has already warmed significantly, and warming of 4-7 °C is expected over the next century. However, linkages between climate, the carbon cycle, the energy balance, and hydrology mean that the response of arctic ecosystems to these changes remains poorly understood. The release by warming of considerable but poorly quantified carbon stores from high latitude soils could accelerate the build-up of atmospheric CO2. The Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS) project, part of International Polar Year, was designed to improve predictions of the response of the Arctic terrestrial biosphere to climate change. The project operated at two sites (Abisko, Sweden and Kevo, Finland) over multiple years, utilising roving flux chambers (CO2/CH4), five flux towers (CO2/CH4/H2O) and a research aircraft equipped for fluxes (CO2/H2O) to directly measure multi-scale exchanges in-conjunction with other observations (both plot level and satellite). We show how these data can be combined using data assimilation approaches to address the question “what controls the temporal and spatial variability of carbon exchange by sub-Arctic ecosystems?” Eddy covariance measurements of mire methane exchanges agreed with chamber estimates, indicating that mires were strong summer sources, while birch woodland was a weak sink. However, remote sensing of mire extent was limited at resolutions > 30 m, and variations in sink/source activity suggested that upscaling CH4 exchanges (from chamber, to tower, to landscape) required higher resolution (ideally <10 m) landcover data in heterogeneous Arctic landscapes. Chamber and eddy covariance measurements of CO2 exchange recorded similar seasonal timing over a range of vegetation types. Birch woodlands had the greatest range of CO2 exchanges compared to tundra and mires. The challenge of measuring continuous fluxes across the full annual cycle, and inherent uncertainties in the methods, complicates the determination of

  20. Modeling the summertime Arctic cloudy boundary layer

    SciTech Connect

    Curry, J.A.; Pinto, J.O.; McInnes, K.L.

    1996-04-01

    Global climate models have particular difficulty in simulating the low-level clouds during the Arctic summer. Model problems are exacerbated in the polar regions by the complicated vertical structure of the Arctic boundary layer. The presence of multiple cloud layers, a humidity inversion above cloud top, and vertical fluxes in the cloud that are decoupled from the surface fluxes, identified in Curry et al. (1988), suggest that models containing sophisticated physical parameterizations would be required to accurately model this region. Accurate modeling of the vertical structure of multiple cloud layers in climate models is important for determination of the surface radiative fluxes. This study focuses on the problem of modeling the layered structure of the Arctic summertime boundary-layer clouds and in particular, the representation of the more complex boundary layer type consisting of a stable foggy surface layer surmounted by a cloud-topped mixed layer. A hierarchical modeling/diagnosis approach is used. A case study from the summertime Arctic Stratus Experiment is examined. A high-resolution, one-dimensional model of turbulence and radiation is tested against the observations and is then used in sensitivity studies to infer the optimal conditions for maintaining two separate layers in the Arctic summertime boundary layer. A three-dimensional mesoscale atmospheric model is then used to simulate the interaction of this cloud deck with the large-scale atmospheric dynamics. An assessment of the improvements needed to the parameterizations of the boundary layer, cloud microphysics, and radiation in the 3-D model is made.

  1. Radar and infrared remote sensing of terrain, water resources, arctic sea ice, and agriculture

    NASA Technical Reports Server (NTRS)

    Biggs, A. W.

    1983-01-01

    Radar range measurements, basic waveforms of radar systems, and radar displays are initially described. These are followed by backscatter from several types of terrain and vegetation as a function of frequency and grazing angle. Analytical models for this backscatter include the facet models of radar return, with range-angle, velocity-range, velocity-angle, range, velocity, and angular only discriminations. Several side-looking airborne radar geometries are presented. Radar images of Arctic sea ice, fresh water lake ice, cloud-covered terrain, and related areas are presented to identify applications of radar imagery. Volume scatter models are applied to radar imagery from alpine snowfields. Short pulse ice thickness radar for subsurface probes is discussed in fresh-water ice and sea ice detection. Infrared scanners, including multispectral, are described. Diffusion of cold water into a river, Arctic sea ice, power plant discharges, volcanic heat, and related areas are presented in thermal imagery. Multispectral radar and infrared imagery are discussed, with comparisons of photographic, infrared, and radar imagery of the same terrain or subjects.

  2. Marine Records of Paleoclimate and Paleoenvironments Vs Anthropological Archives in Arctic-Subarctic Regions: Missing Links

    NASA Astrophysics Data System (ADS)

    de Vernal, A.

    2014-12-01

    Climatic changes are recorded by biogenic remains fossilized in marine sediment. These remains and their chemical and isotopic properties allow the establishment of times series of ocean/climate parameters (temperature, sea ice cover, salinity, productivity), as well as of inland vegetation (from pollen grains in continental margin sediments). Such "paleoclimate" studies provide a comprehensive picture of Holocene climate changes at low to mid latitudes but Arctic-subarctic regions remain poorly documented. The rarity of representative records is mostly due to their remote and difficult access, as well as to the generally low biogenic content of marine sediment because of low productivity and/or poor preservation of biominerals (carbonates and opal). Moreover, when available, time series from Arctic-subarctic often suffer poor time resolution and chronological control. Nevertheless, a few paleoclimate records are available. Some of the best-resolved time series are from the Canadian Arctic (eastern and northern Baffin bay, Hudson Strait). They show large amplitude changes during the glacial/interglacial transition in relation with meltwater discharge rates and sea-level changes, and point to the inception of full "postglacial conditions" some 7000 years ago only. Since then, they also recorded millennial type oscillations of smaller amplitude, but out of phase in the western vs eastern subpolar North Atlantic. Paleoclimate reconstructions from marine cores often provide a picture of a "mean" decadal to centennial state of the environment because of the time span represented by sediment samples adding to smoothing effect of sea-floor sediment mixing by benthic organisms. In contradistinction, humane occupation and mobility might be more directly influenced by climate instabilities and extreme events, whose documentation from sedimentary archives represents a real challenge for the geoscience community.

  3. Measuring diurnal cycles of plant transpiration fluxes in the Arctic with an automated clear chamber

    NASA Astrophysics Data System (ADS)

    Cohen, L. R.; Raz Yaseef, N.; Curtis, J. B.; Rahn, T. A.; Young, J. M.; Newman, B. D.

    2013-12-01

    Evapotranspiration is an important greenhouse gas and a major component of the hydrological cycle, but methodological challenges still limit our knowledge of this flux. Measuring evapotranspiration is even more difficult when aiming to partition plant transpiration and soil evaporation. Information on this process for arctic systems is very limited. In order to decrease this gap, our objective was to directly measure plant transpiration in Barrow, Alaska (71.3°N 156.7°W). A commercial system allows measuring carbon soil respiration fluxes with an automated clear chamber connected to an infrared gas-analyzer (Licor 8100), and while it simultaneously measures water concentrations, it is not calibrated to measure vapor fluxes. We calibrated the clear chamber against a previously established method based on a Licor 6400 soil chamber, and we developed a code to calculate fluxes. We performed laboratory comparisons in New Mexico and field comparisons in the Arctic, suggesting that this is a valid tool for a large range of climates. In the field we found a strong correlation between the two instruments with R2 of 0.79. Even with 24 hours of daylight in the Arctic, the system captures a clear diurnal transpiration flux, peaking at 0.9 mmol m-2 s-1 and showing no flux at the lowest points. This new method should be a powerful approach for long term measurements of specific vegetation types or surface features. Such Data can also be used to help understand controls on larger scale eddy covariance tower measurements of evapotranspiration.

  4. Annual arctic wolf pack size related to arctic hare numbers

    USGS Publications Warehouse

    Mech, L.D.

    2007-01-01

    During the summers of 2000 through 2006, I counted arctic wolf (Canis lupus arctos) pups and adults in a pack, arctic hares (Lepus arcticus) along a 9 km index route in the area, and muskoxen (Ovibos moschatus) in a 250 km2 part of the area near Eureka (80?? N, 86?? W), Ellesmere Island, Nunavut, Canada. Adult wolf numbers did not correlate with muskox numbers, but they were positively related (r2 = 0.89; p < 0.01) to an arctic hare index. This is the first report relating wolf numbers to non-ungulate prey. ?? The Arctic Institute of North America.

  5. Challenges in Modeling Disturbance Regimes and Their Impacts in Arctic and Boreal Ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    McGuire, A. D.; Rupp, T. S.; Kurz, W.

    2013-12-01

    Disturbances in arctic and boreal terrestrial ecosystems influence services provided by these ecosystems to society. In particular, changes in disturbance regimes in northern latitudes have uncertain consequences for the climate system. A major challenge for the scientific community is to develop the capability to predict how the frequency, severity and resultant impacts of disturbance regimes will change in response to future changes in climate projected for northern high latitudes. Here we compare what is known about drivers and impacts of wildfire, phytophagous insect pests, and thermokarst disturbance to illustrate the complexities in predicting future changes in disturbance regimes and their impacts in arctic and boreal regions. Much of the research on predicting fire has relied on the use of drivers related to fire weather. However, changes in vegetation, such as increases in broadleaf species, associated with intensified fire regimes have the potential to influence future fire regimes through negative feedbacks associated with reduced flammability. Phytophagous insect outbreaks have affected substantial portions of the boreal region in the past, but frequently the range of the tree host is larger than the range of the insect. There is evidence that a number of insect species are expanding their range in response to climate change. Major challenges to predicting outbreaks of phytophagous insects include modeling the effects of climate change on insect growth and maturation, winter mortality, plant host health, the synchrony of insect life stages and plant host phenology, and changes in the ranges of insect pests. Moreover, Earth System Models often simplify the representation of vegetation characteristics, e.g. the use of plant functional types, providing insufficient detail to link to insect population models. Thermokarst disturbance occurs when the thawing of ice-rich permafrost results in substantial ground subsidence. In the boreal forest, thermokarst can

  6. Improving understanding of controls on spatial variability in methane fluxes in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Davidson, Scott J.; Sloan, Victoria; Phoenix, Gareth; Wagner, Robert; Oechel, Walter; Zona, Donatella

    2015-04-01

    The Arctic is experiencing rapid climate change relative to the rest of the globe, and this increase in temperature has feedback effects across hydrological and thermal regimes, plant community distribution and carbon stocks within tundra soils. Arctic wetlands account for a significant amount of methane emissions from natural ecosystems to the atmosphere and with further permafrost degradation under a warming climate, these emissions are expected to increase. Methane (CH4) is an extremely important component of the global carbon cycle with a global warming potential 28.5 times greater than carbon dioxide over a 100 year time scale (IPCC, 2013). In order to validate carbon cycle models, modelling methane at broader landscape scales is needed. To date direct measurements of methane have been sporadic in time and space which, while capturing some key controls on the spatial heterogeneity, make it difficult to accurately upscale methane emissions to the landscape and regional scales. This study investigates what is controlling the spatial heterogeneity of methane fluxes across Arctic tundra. We combined over 300 portable chamber observations from 13 micro-topographic positions (with multiple vegetation types) across three locations spanning a 300km latitudinal gradient in Northern Alaska from Barrow to Ivotuk with synchronous measurements of environmental (soil temperature, soil moisture, water table, active layer thaw depth, pH) and vegetation (plant community composition, height, sedge tiller counts) variables to evaluate key controls on methane fluxes. To assess the diurnal variation in CH4 fluxes, we also performed automated chamber measurements in one study site (Barrow) location. Multiple statistical approaches (regression tree and multiple linear regression) were used to identify key controlling variables and their interactions. Methane emissions across all sites ranged from -0.08 to 15.3 mg C-CH4 m-2 hr-1. As expected, soil moisture was the main control

  7. Microbial Analysis of Arctic Snow and Frost Flowers: What Next Generation Sequencing Method Can Reveal

    NASA Astrophysics Data System (ADS)

    Mortazavi, R.; Attiya, S.; Ariya, P. A.

    2014-12-01

    We herein examined and identified the population of the microbial communities of Arctic snow types and frost flower during the spring 2009 campaign of the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) program in Barrow, Alaska, USA. In addition to conventional microbial identification techniques (culture-isolation-PCR amplification-sequencing) we deployed a state-of-the-art genomic Next Generation Sequencing (NGS) technique to examine the true bacterial communities in Arctic samples. Our results have indicated that diverse community of microbial exists in Arctic with many originating from distinct ecological environment. The alterations observed in the texture of Arctic samples by microbial has further signified their importance in ecosystem.

  8. Arctic River organic matter transport

    NASA Astrophysics Data System (ADS)

    Raymond, Peter; Gustafsson, Orjan; Vonk, Jorien; Spencer, Robert; McClelland, Jim

    2016-04-01

    Arctic Rivers have unique hydrology and biogeochemistry. They also have a large impact on the Arctic Ocean due to the large amount of riverine inflow and small ocean volume. With respect to organic matter, their influence is magnified by the large stores of soil carbon and distinct soil hydrology. Here we present a recap of what is known of Arctic River organic matter transport. We will present a summary of what is known of the ages and sources of Arctic River dissolved and particulate organic matter. We will also discuss the current status of what is known about changes in riverine organic matter export due to global change.

  9. Arctic thermal design

    SciTech Connect

    Lunardini, V.J.

    1985-05-01

    Arctic engineering theories and techniques are discussed. The problems associated with ameliorating cold-climate effects is examined. External accumulation of ice on solid surfaces, floating ice sheets, icebergs, multiyear ice, and ice ridges are discussed, and the problems associated with these hazards are analyzed. The author believes that it is possible to deal rationally with these problems if the engineer is aware of them, and that ignorance can cause spectacular failures in the cold regions.

  10. Arctic offshore platform

    SciTech Connect

    Bhula, D.N.

    1984-01-24

    An offshore structure is disclosed for use in drilling and producing wells in arctic regions having a conical shaped lower portion that extends above the surface of the water and a cylindrical upper section. The conical portion is provided with a controlled stiffness outer surface for withstanding the loads produced by ice striking the structure. The stiffness properties of the outer shell and flexible members are designed to distribute the load and avoid high local loads on the inner parts of the structure.

  11. Index of streamflow and water quality records to September 30, 1978, Arctic Slope, Alaska

    USGS Publications Warehouse

    Still, Patsy J.

    1980-01-01

    This report, which is one of a series of reports for Alaska, lists stations in Arctic Slope, Alaska, at which streamflow and water quality data have been collected by the U.S. Geological Survey. Included are a hydrologic subregion map of Arctic Slope, Alaska, and a table listing the types of data collected and periods of record. (USGS)

  12. Changes to freshwater systems affecting Arctic infrastructure and natural resources

    NASA Astrophysics Data System (ADS)

    Instanes, Arne; Kokorev, Vasily; Janowicz, Richard; Bruland, Oddbjørn; Sand, Knut; Prowse, Terry

    2016-03-01

    The resources component of the Arctic Freshwater Synthesis focuses on the potential impact of future climate and change on water resources in the Arctic and how Arctic infrastructure and exploration and production of natural resources are affected. Freshwater availability may increase in the Arctic in the future in response to an increase in middle- and high-latitude annual precipitation. Changes in type of precipitation, its seasonal distribution, timing, and rate of snowmelt represent a challenge to municipalities and transportation networks subjected to flooding and droughts and to current industries and future industrial development. A reliable well-distributed water source is essential for all infrastructures, industrial development, and other sectorial uses in the Arctic. Fluctuations in water supply and seasonal precipitation and temperature may represent not only opportunities but also threats to water quantity and quality for Arctic communities and industrial use. The impact of future climate change is varying depending on the geographical area and the current state of infrastructure and industrial development. This paper provides a summary of our current knowledge related to the system function and key physical processes affecting northern water resources, industry, and other sectorial infrastructure.

  13. Geolocating Russian sources for Arctic black carbon

    NASA Astrophysics Data System (ADS)

    Cheng, Meng-Dawn

    2014-08-01

    To design and implement an effective emission control strategy for black carbon (BC), the locations and strength of BC sources must be identified. Lack of accurate source information from the Russian Federation has created difficulty for a range of research and policy activities in the Arctic because Russia occupies the largest landmass in the Arctic Circle. A project was initiated to resolve emission sources of BC in the Russian Federation by using the Potential Source Contribution Function (PSCF). It used atmospheric BC data from two Arctic sampling stations at Alert Nunavut, Canada, and Tiksi Bay, Russia. The geographical regions of BC emission sources in Russia were identified and summarized as follows: (1) a region surrounding Moscow, (2) regions in Eurasia stretching along the Ural Mountains from the White Sea to the Black Sea, and (3) a number of scattered areas from western Siberia to the Russian Far East. Particulate potassium ions, non-marine sulfate, and vanadium were used to assist in resolving the source types: forest fire/biomass burning, coal-fired power plant, and oil combustion. Correlating these maps with the BC map helped to resolve source regions of BC emissions and connect them to their corresponding source types. The results imply that a region south of Moscow and another north of the Ural Mountains could be significant BC sources, but none of the grid cells in these regions could be linked to forest fires, oil combustion, or coal-fired power plants based on these three markers.

  14. Volatile organic compound emission profiles of four common arctic plants

    NASA Astrophysics Data System (ADS)

    Vedel-Petersen, Ida; Schollert, Michelle; Nymand, Josephine; Rinnan, Riikka

    2015-11-01

    The biogenic volatile organic compound (BVOC) emissions from plants impact atmosphere and climate. The species-specific emissions, and thereby the atmospheric impact, of many plant species are still unknown. Knowledge of BVOC emission from arctic plants is particularly limited. The vast area and relatively high leaf temperature give the Arctic potential for emissions that cannot be neglected. This field study aimed to elucidate the BVOC emission profiles for four common arctic plant species in their natural environment during the growing season. BVOCs were sampled from aboveground parts of Empetrum hermaphroditum, Salix glauca, Salix arctophila and Betula nana using the dynamic enclosure technique and collection of volatiles in adsorbent cartridges, analyzed by gas chromatography-mass spectrometry. Sampling occurred three times: in late June/early July, in mid-July and in early August. E. hermaphroditum emitted the least BVOCs, dominated by sesquiterpenes (SQTs) and non-isoprenoid BVOCs. The Salix spp. emitted the most, dominated by isoprene. The emissions of B. nana were composed of about two-thirds non-isoprenoid BVOCs, with moderate amounts of monoterpenes (MTs) and SQTs. The total B. nana emissions and the MT and SQT emissions standardized to 30 °C were highest in the first measurement in early July, while the other species had the highest emissions in the last measurement in early August. As climate change is expected to increase plant biomass and change vegetation composition in the Arctic, the BVOC emissions from arctic ecosystems will also change. Our results suggest that if the abundance of deciduous shrubs like Betula and Salix spp. increases at the expense of slower growing evergreens like E. hermaphroditum, there is the potential for increased emissions of isoprene, MTs and non-isoprenoid BVOCs in the Arctic.

  15. The relationship between phytomass, NDVI and vegetation communities on Svalbard

    NASA Astrophysics Data System (ADS)

    Johansen, Bernt; Tømmervik, Hans

    2014-04-01

    Several studies have shown a close relationship between vegetation fertility and different vegetation indices extracted from satellite data. The vegetation fertility in Arctic is at overall scales highly related to temperature. At lower scales surface material, snow cover, hydrology and anthropogenic effects (geese, reindeer) are determinant in constituting the different vegetation communities. The extent and occurrence of different vegetation communities are expressed in vegetation maps. On Svalbard a vegetation map covering the entire archipelago has recently been developed. The map is differentiated into 18 map units showing large areas of non- and sparsely vegetated ground. The most favorable vegetation is seen as productive marshes and moss tundra communities in the lowland. Various mathematical combinations of spectral channels in satellite images have been applied as sensitive indicators of the presence and condition of green vegetation. Today the normalized difference vegetation index (NDVI) is mostly used to display this information. NDVI is an indicator of the density of chlorophyll in leaf tissue calculated from the red and near infrared bands: NDVI = (NIR - RED)/(NIR + RED). NDVI gives values between -1 and +1 where vegetated areas in general yield high positive values, while non-vegetated ground is found on the negative side.

  16. Determination of total antioxidant activity in three types of local vegetables shoots and the cytotoxic effect of their ethanolic extracts against different cancer cell lines.

    PubMed

    Rahmat, Asmah; Kumar, Vijay; Fong, Loo Mei; Endrini, Susi; Sani, Huzaimah Abdullah

    2003-01-01

    Antioxidants play an important role in inhibiting and scavenging radicals, thus providing protection to humans against infections and degenerative diseases. Literature shows that the antioxidant activity is high on herbal and vegetable plants. Realizing the fact, this research was carried out to determine total antioxidant activity and the potential anticancer properties in three types of selected local vegetable shoots such as Diplazium esculentum (paku shoot), Manihot utillissima (tapioca shoot) and Sauropous androgynus (cekur manis). The research was also done to determine the effect of boiling, on total antioxidant activity whereby samples of fresh shoots are compared with samples of boiled shoots. In every case, antioxidant activity is compared to alpha-tocopherol and two methods of extraction used are the organic and the aqueous methods. Besides that, two research methods used were the ferric thiocyanate (FTC) and thiobarbituric acid (TBA) with absorbance of 500 nm and 532 nm respectively. Oneway ANOVA test at P <0.05 determines significant differences between various samples. In the cytotoxic study, the ethanolic extract and several cell lines i.e. breast cancer (MDA-MB-231 and MCF-7), colon cancer (Caco-2), liver cancer (HepG2) and normal liver (Chang liver) were used. The IC50-value was determined by using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The antioxidant study found that all the samples in both aqueous and organic extraction were significantly different. The total antioxidant activity values of aqueous extract in descending order are as follows : M. utilissima (fresh)> D. esculentum (fresh) > S.androgynus (fresh) > M.utilissima (boiled) > D. esculentum (boiled) > S.androgynus (boiled). It also was found that S.androgynus shoots ethanolic extract was able to inhibit the viability of the breast cancer cell lines, MDA-MB-231 with the IC subset 50 value of 53.33 microg/ml. However, S.androgynus shoots and D

  17. Impacts of a Warming Arctic - Arctic Climate Impact Assessment

    NASA Astrophysics Data System (ADS)

    Arctic Climate Impact Assessment

    2004-12-01

    The Arctic is now experiencing some of the most rapid and severe climate change on earth. Over the next 100 years, climate change is expected to accelerate, contributing to major physical, ecological, social, and economic changes, many of which have already begun. Changes in arctic climate will also affect the rest of the world through increased global warming and rising sea levels. Impacts of a Warming Arctic is a plain language synthesis of the key findings of the Arctic Climate Impact Assessment (ACIA), designed to be accessible to policymakers and the broader public. The ACIA is a comprehensively researched, fully referenced, and independently reviewed evaluation of arctic climate change. It has involved an international effort by hundreds of scientists. This report provides vital information to society as it contemplates its responses to one of the greatest challenges of our time. It is illustrated in full color throughout.

  18. Uncertainty analysis of vegetation distribution in the northern high latitudes during the 21st century with a dynamic vegetation model.

    PubMed

    Jiang, Yueyang; Zhuang, Qianlai; Schaphoff, Sibyll; Sitch, Stephen; Sokolov, Andrei; Kicklighter, David; Melillo, Jerry

    2012-03-01

    This study aims to assess how high-latitude vegetation may respond under various climate scenarios during the 21st century with a focus on analyzing model parameters induced uncertainty and how this uncertainty compares to the uncertainty induced by various climates. The analysis was based on a set of 10,000 Monte Carlo ensemble Lund-Potsdam-Jena (LPJ) simulations for the northern high latitudes (45(o)N and polewards) for the period 1900-2100. The LPJ Dynamic Global Vegetation Model (LPJ-DGVM) was run under contemporary and future climates from four Special Report Emission Scenarios (SRES), A1FI, A2, B1, and B2, based on the Hadley Centre General Circulation Model (GCM), and six climate scenarios, X901M, X902L, X903H, X904M, X905L, and X906H from the Integrated Global System Model (IGSM) at the Massachusetts Institute of Technology (MIT). In the current dynamic vegetation model, some parameters are more important than others in determining the vegetation distribution. Parameters that control plant carbon uptake and light-use efficiency have the predominant influence on the vegetation distribution of both woody and herbaceous plant functional types. The relative importance of different parameters varies temporally and spatially and is influenced by climate inputs. In addition to climate, these parameters play an important role in determining the vegetation distribution in the region. The parameter-based uncertainties contribute most to the total uncertainty. The current warming conditions lead to a complexity of vegetation responses in the region. Temperate trees will be more sensitive to climate variability, compared with boreal forest trees and C3 perennial grasses. This sensitivity would result in a unanimous northward greenness migration due to anomalous warming in the northern high latitudes. Temporally, boreal needleleaved evergreen plants are projected to decline considerably, and a large portion of C3 perennial grass is projected to disappear by the end of

  19. Uncertainty analysis of vegetation distribution in the northern high latitudes during the 21st century with a dynamic vegetation model

    PubMed Central

    Jiang, Yueyang; Zhuang, Qianlai; Schaphoff, Sibyll; Sitch, Stephen; Sokolov, Andrei; Kicklighter, David; Melillo, Jerry

    2012-01-01

    This study aims to assess how high-latitude vegetation may respond under various climate scenarios during the 21st century with a focus on analyzing model parameters induced uncertainty and how this uncertainty compares to the uncertainty induced by various climates. The analysis was based on a set of 10,000 Monte Carlo ensemble Lund-Potsdam-Jena (LPJ) simulations for the northern high latitudes (45oN and polewards) for the period 1900–2100. The LPJ Dynamic Global Vegetation Model (LPJ-DGVM) was run under contemporary and future climates from four Special Report Emission Scenarios (SRES), A1FI, A2, B1, and B2, based on the Hadley Centre General Circulation Model (GCM), and six climate scenarios, X901M, X902L, X903H, X904M, X905L, and X906H from the Integrated Global System Model (IGSM) at the Massachusetts Institute of Technology (MIT). In the current dynamic vegetation model, some parameters are more important than others in determining the vegetation distribution. Parameters that control plant carbon uptake and light-use efficiency have the predominant influence on the vegetation distribution of both woody and herbaceous plant functional types. The relative importance of different parameters varies temporally and spatially and is influenced by climate inputs. In addition to climate, these parameters play an important role in determining the vegetation distribution in the region. The parameter-based uncertainties contribute most to the total uncertainty. The current warming conditions lead to a complexity of vegetation responses in the region. Temperate trees will be more sensitive to climate variability, compared with boreal forest trees and C3 perennial grasses. This sensitivity would result in a unanimous northward greenness migration due to anomalous warming in the northern high latitudes. Temporally, boreal needleleaved evergreen plants are projected to decline considerably, and a large portion of C3 perennial grass is projected to disappear by the end of

  20. Changing Seasonality in the Arctic and its Influences on Biogeochemical Processing in Tundra River Networks

    NASA Astrophysics Data System (ADS)

    Bowden, W. B.; Gooseff, M. N.; Wollheim, W. M.; Herstand, M. R.; Treat, C. C.; Whittinghill, K. A.; Wlostowski, A. N.

    2011-12-01

    One of the primary expressions of climate change in the arctic is a change in "seasonality"; i.e., changes in the timing, duration, and characteristics of the traditional arctic seasons. These changes are most likely to affect temperature and precipitation patterns but will have relatively little effect on the annual light regime. Temperature, precipitation, and light are crucial drivers in any ecosystem and so the potential that the relationships between these three master environmental variables will change in the future has important consequences. Our research addresses how river networks process critical nutrients (C, N, and P) delivered from land as they are transported to coastal zones. We are currently focusing on land-water interactions in headwater streams. As in any ecosystem, temperature strongly influences microbial processing in soils and thus net mineralization of organic nutrients. Nutrients made available by microbial processing in the soil will be used by vegetation as long as the vegetation actively grows. However, active growth by vegetation is highly dependent on the annual light regime, which is not changing substantially. Thus, as arctic seasonality changes there is a growing asynchrony developing between production of nutrients by soil microbes and the demand for nutrients by vegetation, with greater production of nutrients by temperature-dependent microbes than demand by light-dependent vegetation. It is reasonable to expect that the "excess" nutrients produced in this way will migrate to streams and we hypothesize that this seasonal subsidy may strongly influence the structure and function of arctic stream ecosystems. Previous stream research in the arctic largely ignored the spring and fall tail seasons. Preliminary findings indicate that the seasonal asynchrony has profound influences on nutrient concentrations and autotrophic biomass in arctic streams. We expect this to have important influences on key processes such as primary

  1. A History of Coastal Research in the Arctic (Invited)

    NASA Astrophysics Data System (ADS)

    Walker, H. J.; McGraw, M.

    2009-12-01

    Laboratory in 1947. Although these organizations were broad based, they occasionally had research projects devoted to arctic shorelines. In the USSR, research by Felix Are on shore retreat in the Arctic set the pattern for detail. Because the concentration of people (native as well as non-native) in the Arctic tends to be along the coast(such as Barrow, Alaska and Tuktoyaktuk, Canada) or rivers, some of the earliest research dealt with erosion that threatened settlements. In the process, consideration was given to such factors as sea ice, ground ice and permafrost, sediment type, long-shore drift, tides, wave action, and river discharge. Although there were scattered relevant projects, it was not until the last quarter of the 20th century that teamwork on arctic coastal research began to make its mark. Especially notable are the Russian-German cooperative study of the Lena Delta in 1998 and the International Arctic Science Committee's project on Arctic Coastal Dynamics. The number of detailed studies from such initiatives has increased during the last two decades.

  2. Summer in the Arctic National Wildlife Refuge

    NASA Technical Reports Server (NTRS)

    2001-01-01

    -60 kilometers, arctic tundra dominates the coastal plain, until reaching the foothills of the Brooks Mountain Range. Beneath the tundra, a layer of permafrost reaches an average depth of 600 meters, restricting water drainage through the soil, and increasing the sensitivity of tundra vegetation to disturbance. Precipitation is scarce (less than 16 centimeters per year) and the small amount of melt water or rain that soaks into the tundra remains near the surface. This is why the coastal plain can be classified as a wetland.

    The western boundary of the Refuge is marked by the Canning River, about halfway between the center and left-hand side of the image, and the eastern boundary is near the right-hand edge at the US/Canadian border. The two permanent human settlements within the image area are Kaktovic near the tip of the large rounded peninsula, and Arctic Village south of the Brooks Range near the southern Refuge boundary. The area represented by the image is approximately 380 kilometers x 540 kilometers.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  3. Fermented Vegetables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter is organized into several sections. The first has information on the history of vegetable fermentation research in the US, dating back to the late 1880s. A overview of commercial cucumber and sauerkraut fermentation practices follows, focusing on the US market, although there is some me...

  4. Fermented Vegetables

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The wide variety of fermented foods of the world can be classified by the materials obtained from the fermentation, such as alcohol (beer, wine), organic acid such as lactic acid and acetic acid (vegetables, dairy), carbon dioxide (bread), and amino acids or peptides from protein (fish fermentations...

  5. The Arctic Circumpolar Boundary Current

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Ivanov, Vladimir V.; Nurser, A. J. George; Bacon, Sheldon; Polyakov, Igor V.; Coward, Andrew C.; Naveira-Garabato, Alberto C.; Beszczynska-Moeller, Agnieszka

    2011-09-01

    We present high-resolution simulations and observational data as evidence of a fast current flowing along the shelf break of the Siberian and Alaskan shelves in the Arctic Ocean. Thus far, the Arctic Circumpolar Boundary Current (ACBC) has been seen as comprising two branches: the Fram Strait and Barents Sea Branches (FSB and BSB, respectively). Here we describe a new third branch, the Arctic Shelf Break Branch (ASBB). We show that the forcing mechanism for the ASBB is a combination of buoyancy loss and non-local wind, creating high pressure upstream in the Barents Sea. The potential vorticity influx through the St. Anna Trough dictates the cyclonic direction of flow of the ASBB, which is the most energetic large-scale circulation structure in the Arctic Ocean. It plays a substantial role in transporting Arctic halocline waters and exhibits a robust seasonal cycle with a summer minimum and winter maximum. The simulations show the continuity of the FSB all the way around the Arctic shelves and the uninterrupted ASBB between the St. Anna Trough and the western Fram Strait. The BSB flows continuously along the Siberian shelf as far as the Chukchi Plateau, where it partly diverges from the continental slope into the ocean interior. The Alaskan Shelf break Current (ASC) is the analog of the ASBB in the Canadian Arctic. The ASC is forced by the local winds and high upstream pressure in Bering Strait, caused by the drop in sea surface height between the Pacific and Arctic Oceans.

  6. Offshore outlook: the American Arctic

    SciTech Connect

    Jahns, M.O.

    1985-05-01

    Offshore areas in the American Arctic are highlighted and the development of the area is compared with other offshore areas where the required technology is more readily available. Principal areas are shown in which new concepts are being put to practice. Canada's east coast is examined. Several technological trends are reviewed to help operators accelerate the discovery and development of arctic petroleum reserves.

  7. Quantifying the Arctic methane budget

    NASA Astrophysics Data System (ADS)

    Warwick, Nicola; Cain, Michelle; Pyle, John

    2014-05-01

    The Arctic is a major source of atmospheric methane, containing climate-sensitive emissions from natural wetlands and gas hydrates, as well as the fossil fuel industry. Both wetland and gas hydrate methane emissions from the Arctic may increase with increasing temperature, resulting in a positive feedback leading to enhancement of climate warming. It is important that these poorly-constrained sources are quantified by location and strength and their vulnerability to change be assessed. The MAMM project (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling') addresses these issues as part of the UK NERC Arctic Programme. A global chemistry transport model has been used, along with MAMM and other long term observations, to assess our understanding of the different source and sink terms in the Arctic methane budget. Simulations including methane coloured by source and latitude are used to distinguish between Arctic seasonal variability arising from transport and that arising from changes in Arctic sources and sinks. Methane isotopologue tracers provide a further constraint on modelled methane variability, distinguishing between isotopically light and heavy sources (e.g. wetlands and gas fields). We focus on quantifying the magnitude and seasonal variability of Arctic wetland emissions.

  8. The soil microbial community composition and soil microbial carbon uptake are more affected by soil type than by different vegetation types (C3 and C4 plants) and seasonal changes

    NASA Astrophysics Data System (ADS)

    Griselle Mellado Vazquez, Perla; Lange, Markus; Gleixner, Gerd

    2016-04-01

    This study investigates the influence of different vegetation types (C3 and C4 plants), soil type and seasonal changes on the soil microbial biomass, soil microbial community composition and soil microbial carbon (C) uptake. We collected soil samples in winter (non-growing season) and summer (growing season) in 2012 from an experimental site cropping C3 and C4 plants for 6 years on two different soil types (sandy and clayey). The amount of phospholipid fatty acids (PLFAs) and their compound-specific δ13C values were used to determined microbial biomass and the flow of C from plants to soil microorganisms, respectively. Higher microbial biomass was found in the growing season. The microbial community composition was mainly explained by soil type. Higher amounts of SOC were driving the predominance of G+ bacteria, actinobacteria and cyclic G- bacteria in sandy soils, whereas root biomass was significantly related to the increased proportions of G- bacteria in clayey soils. Plant-derived C in G- bacteria increased significantly in clayey soils in the growing season. This increase was positively and significantly driven by root biomass. Moreover, changes in plant-derived C among microbial groups pointed to specific capabilities of different microbial groups to decompose distinct sources of C. We concluded that soil texture and favorable growth conditions driven by rhizosphere interactions are the most important factors controlling the soil microbial community. Our results demonstrate that a change of C3 plants vs. C4 plants has only a minor effect on the soil microbial community. Thus, such experiments are well suited to investigate soil organic matter dynamics as they allow to trace the C flow from plants into the soil microbial community without changing the community abundance and composition.

  9. Viral hepatitis in the Arctic. A review from a Circumpolar Workshop on Viral hepatitis, ICCH13.

    PubMed

    Tulisov, Andrei; McMahon, Brian J; Koch, Anders; Minuk, Gerald; Chulanov, Vladimir; Bruce, Michael G; Uhanova, Julia; Børresen, Malene; Williams, James; Osiowy, Carla; Gelvan, Allan; Alexeeva, Marfa; Larke, Bryce; Watt, Kymberly

    2007-01-01

    This article is a review of the viral hepatitis workshop, held during the 13th International Congress of the Circumpolar Health consists of a review of data on viral hepatitis in the Arctic territories of four countries: Canada, Greenland, Russia and United States (Alaska). The main purpose of the workshop was to exchange knowledge on viral hepatitis in the Arctic and identify further needs for collaborative hepatitis research, which is planned to be implemented through the established Viral Hepatitis Working Group in the Arctic. The review is based on the available published research results, surveillance data and professional opinions of the authors. The information is presented by Arctic country. Viral hepatitis constitutes an important problem among Aboriginal peoples of the Arctic; the incidence of most types of viral hepatitis is higher among indigenous populations than in the general public. However, due to differences in the available information from each of the four Arctic countries, it is difficult to compare differences in types of disease in them. The main areas for future research are: HBV genotypes distribution, relations between different types of HBV, HCV and disease outcomes, HBV mutation rate and specific substitutions in the HBV genome over time in the Arctic, and occurrence of active liver disease in HBsAg carriers living in the Arctic, as well as further research in viral hepatitis A, C, D and E. PMID:17929632

  10. Two-source energy balance model implementation in the Alaska Arctic tundra

    NASA Astrophysics Data System (ADS)

    Cristóbal-Rosselló, J.; Prakash, A.; Anderson, M. C.; Kustas, W. P.; Kane, D. L.

    2014-12-01

    Evaporation and transpiration are the two main processes involved in water transfer from vegetated and non-vegetated areas to the atmosphere. Evapotranspiration (ET) from the Earth's vegetation constitutes 88% of the total terrestrial ET, and returns more than 50% of terrestrial precipitation to the atmosphere (Oki and Kane, 2006); therefore it plays a key role in both the hydrological cycle and the energy balance of the land surface. In Arctic regions, surface-atmosphere exchanges due to ET are estimated from water balance computations to be about 74% of summer precipitation or 50% of annual precipitation. Even though ET is a significant component of the hydrologic cycle in this region, these bulk estimates do not accurately account for spatial and temporal variability due to vegetation type, topography, etc. (Kane and Yang, 2004). In this work we present the implementation of the Two-Source Energy Balance method, TSEB (Norman et al., 1995), in two Alaska Arctic tundra settings, as a base-line to retrieve energy fluxes at the regional scale from remote sensing imagery. In order to calibrate and validate the model, four flux towers located at the Imanvait Creek and the Anaktuvuk river were used. The TSEB model mainly requires meteorological inputs as well as land surface temperature (LST) and leaf area index (LAI) data. In this study, TSEB was run from late May to early September from 2008 to 2011 in all sky conditions using half hour intervals of meteorological data from the flux tower, and the LST derived from the four component net radiation instrument. TERRA/AQUA MODIS LAI daily product (MOD15/MYD15) was used as LAI input data. Results show an acceptable agreement between the TSEB model and flux tower data. RMSE obtained in the case of net radiation, latent heat, sensible heat and soil heat fluxes was 12, 51, 60 and 27 W/m2. Further efforts will be focused on the daily energy flux integration through implementation of the DTD model (Norman et al., 2000).

  11. Influence of vegetation type and site-to-site variability on soil carbonate clumped isotope records, Andean piedmont of Central Argentina (32-34°S)

    NASA Astrophysics Data System (ADS)

    Ringham, Mallory C.; Hoke, Gregory D.; Huntington, Katharine W.; Aranibar, Julieta N.

    2016-04-01

    The clumped isotope geothermometer estimates the formation temperature (T (Δ47)) of carbonates and has great potential to enhance the extraction of environmental data from pedogenic (soil) carbonate in the geologic record. However, the influence of vegetation type and site-specific conditions on carbonate formation processes and T (Δ47) records remains poorly understood. This study examines the potential for variability in T (Δ47) data between nearby, same elevation sites with different C3/C4 biomass. Pedogenic carbonates (undercoatings and nodules) were collected from five modern soil pits in the semi-arid eastern Andean piedmont of Argentina under a summer precipitation regime. Three pits were instrumented with temperature and moisture sensors to 1 m depth, and a fourth was instrumented with additional soil CO2 and atmospheric (temperature, relative humidity, insolation, and rainfall) sensors. T (Δ47) values (mean: 30 ± 6 °C (±1SE)) are invariant with depth and are statistically indistinguishable between the four instrumented sites, though a 10 °C difference between our T (Δ47) values and those of a nearby Peters et al. (2013, EPSL) study suggests the potential for significant site-to-site variability, likely due to local soil hydrology. The results of this study suggest that deeper (≥40 cm) T (Δ47) values are consistent with carbonate formation during the early part of soil drying immediately after large mid-summer rainstorms. Carbonate formation ≤ 40 cm depth may be biased to soil drying after small, frequent precipitation events occurring throughout the spring, summer, and fall months, averaging to shallow summer T (Δ47) values and resulting in a near-isothermal T (Δ47) profile.

  12. Are tree ontogenetic structure and allometric relationship independent of vegetation formation type? A case study with Cordia oncocalyx in the Brazilian caatinga

    NASA Astrophysics Data System (ADS)

    Silveira, Andréa P.; Martins, Fernando R.; Araújo, Francisca S.

    2012-08-01

    In temperate and tropical rainforests, ontogenetic structure and allometry during tree ontogeny are often associated with light gradients. Light is not considered a limiting resource in deciduous thorny woodland (DTW), but establishment and growth occur during a short rainy period, when the canopy is fully leaved and light in the understory may be modified. Our aim was to investigate whether the light gradient in DTW and the biomechanical limitations of tree growth would be enough to produce an ontogenetic structure and allometric growth similar to rainforest canopy trees. We investigated the ontogenetic stages and diameter-height relationship of Cordia oncocalyx (Boraginaceae), a dominant canopy tree of the DTW of semiarid northeastern Brazil. We tagged, measured and classified the ontogenetic stages of 2.895 individuals in a 1 ha area (5°6'58.1″S and 40°52'19.4″W). In the rainy season only 4.7% of the light falling on the canopy reached the ground. Initial ontogenetic stages, mainly infant (50.9%) and seedling (42.1%), were predominant in the population, with the remaining 7% distributed among juvenile, immature, virginile and reproductive. The ontogenetic structure was similar to that of rainforest tree species, but the population formed both permanent seed and infant banks in response to long dry periods and erratic rainy spells. Like many other Boraginaceae tree species in tropical rainforests, C. oncocalyx has a Prévost architectural model, but allometric growth was quite different from rainforest trees. C. oncocalyx invested slightly more in diameter at first, then in height and finally invested greatly in diameter and attained an asymptotic height. The continued high investment in diameter growth at late stages and the asymptotic height point to low tree density and more frequent xylem embolism as the main drivers of tree allometric shape in DTW. This indicates that tree ontogenetic structure and allometric relationships depend on vegetation

  13. Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

    PubMed Central

    Morgado, Luis N; Semenova, Tatiana A; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-01-01

    Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage. PMID:25156129

  14. Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska.

    PubMed

    Morgado, Luis N; Semenova, Tatiana A; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-02-01

    Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage. PMID:25156129

  15. Arctic Submarine Slope Stability

    NASA Astrophysics Data System (ADS)

    Winkelmann, D.; Geissler, W.

    2010-12-01

    Submarine landsliding represents aside submarine earthquakes major natural hazard to coastal and sea-floor infrastructure as well as to coastal communities due to their ability to generate large-scale tsunamis with their socio-economic consequences. The investigation of submarine landslides, their conditions and trigger mechanisms, recurrence rates and potential impact remains an important task for the evaluation of risks in coastal management and offshore industrial activities. In the light of a changing globe with warming oceans and rising sea-level accompanied by increasing human population along coasts and enhanced near- and offshore activities, slope stability issues gain more importance than ever before. The Arctic exhibits the most rapid and drastic changes and is predicted to change even faster. Aside rising air temperatures, enhanced inflow of less cooled Atlantic water into the Arctic Ocean reduces sea-ice cover and warms the surroundings. Slope stability is challenged considering large areas of permafrost and hydrates. The Hinlopen/Yermak Megaslide (HYM) north of Svalbard is the first and so far only reported large-scale submarine landslide in the Arctic Ocean. The HYM exhibits the highest headwalls that have been found on siliciclastic margins. With more than 10.000 square kilometer areal extent and app. 2.400 cubic kilometer of involved sedimentary material, it is one of the largest exposed submarine slides worldwide. Geometry and age put this slide in a special position in discussing submarine slope stability on glaciated continental margins. The HYM occurred 30 ka ago, when the global sea-level dropped by app. 50 m within less than one millennium due to rapid onset of global glaciation. It probably caused a tsunami with circum-Arctic impact and wave heights exceeding 130 meters. The HYM affected the slope stability field in its neighbourhood by removal of support. Post-megaslide slope instability as expressed in creeping and smaller-scaled slides are

  16. a New Japanese Project for Arctic Climate Change Research - Grene Arctic - (Invited)

    NASA Astrophysics Data System (ADS)

    Enomoto, H.

    2013-12-01

    A new Arctic Climate Change Research Project 'Rapid Change of the Arctic Climate System and its Global Influences' has started in 2011 for a five years project. GRENE-Arctic project is an initiative of Arctic study by more than 30 Japanese universities and institutes as the flame work of GRENE (Green Network of Excellence) of MEXT (Ministry of Education, Culture, Sports, Science and Technology, Japan). The GRENE-Arctic project set four strategic research targets: 1. Understanding the mechanism of warming amplification in the Arctic 2. Understanding the Arctic system for global climate and future change 3. Evaluation of the effects of Arctic change on weather in Japan, marine ecosystems and fisheries 4. Prediction of sea Ice distribution and Arctic sea routes This project aims to realize the strategic research targets by executing following studies: -Improvement of coupled general circulation models based on validations of the Arctic climate reproducibility and on mechanism analyses of the Arctic climate change and variability -The role of Arctic cryosphere in the global change -Change in terrestrial ecosystem of pan-Arctic and its effect on climate -Studies on greenhouse gas cycles in the Arctic and their responses to climate change -Atmospheric studies on Arctic change and its global impacts -Ecosystem studies of the Arctic ocean declining Sea ice -Projection of Arctic Sea ice responding to availability of Arctic sea route (* ** ***) *Changes in the Arctic ocean and mechanisms on catastrophic reduction of Arctic sea ice cover **Coordinated observational and modeling studies on the basic structure and variability of the Arctic sea ice-ocean system ***Sea ice prediction and construction of ice navigation support system for the Arctic sea route. Although GRENE Arctic project aims to product scientific contribution in a concentrated program during 2011-2016, Japanese Arctic research community established Japan Consortium for Arctic Environmental Research (JCAR) in May

  17. Arctic Summer Ice Processes

    NASA Technical Reports Server (NTRS)

    Holt, Benjamin

    1999-01-01

    The primary objective of this study is to estimate the flux of heat and freshwater resulting from sea ice melt in the polar seas. The approach taken is to examine the decay of sea ice in the summer months primarily through the use of spaceborne Synthetic Aperture Radar (SAR) imagery. The improved understanding of the dynamics of the melt process can be usefully combined with ice thermodynamic and upper ocean models to form more complete models of ice melt. Models indicate that more heat is absorbed in the upper ocean when the ice cover is composed of smaller rather than larger floes and when there is more open water. Over the course of the summer, floes disintegrate by physical forcing and heating, melting into smaller and smaller sizes. By measuring the change in distribution of floes together with open water over a summer period, we can make estimates of the amount of heating by region and time. In a climatic sense, these studies are intended to improve the understanding of the Arctic heat budget which can then be eventually incorporated into improved global climate models. This work has two focus areas. The first is examining the detailed effect of storms on floe size and open water. A strong Arctic low pressure storm has been shown to loosen up the pack ice, increase the open water concentration well into the pack ice, and change the distribution of floes toward fewer and smaller floes. This suggests episodic melting and the increased importance of horizontal (lateral) melt during storms. The second focus area is related to an extensive ship-based experiment that recently took place in the Arctic called Surface Heat Budget of the Arctic (SHEBA). An icebreaker was placed purposely into the older pack ice north of Alaska in September 1997. The ship served as the base for experimenters who deployed extensive instrumentation to measure the atmosphere, ocean, and ice during a one-year period. My experiment will be to derive similar measurements (floe size, open

  18. Arctic hydrology and meteorology

    SciTech Connect

    Kane, D.L.

    1990-01-01

    During 1990, we have continued our meteorological and hydrologic data collection in support of our process-oriented research. The six years of data collected to data is unique in its scope and continuity in a North Hemisphere Arctic setting. This valuable data base has allowed us to further our understanding of the interconnections and interactions between the atmosphere/hydrosphere/biosphere/lithosphere. The increased understanding of the heat and mass transfer processes has allowed us to increase our model-oriented research efforts.

  19. Long-range transport of air pollution into the Arctic

    NASA Astrophysics Data System (ADS)

    Stohl, A.; Berg, T.; Breivik, K.; Burkhart, J. F.; Eckhardt, S.; Fjæraa, A.; Forster, C.; Herber, A.; Lunder, C.; McMillan, W. W.; None, N.; Manø, S.; Oltmans, S.; Shiobara, M.; Stebel, K.; Hirdman, D.; Stroem, J.; Tørseth, K.; Treffeisen, R.; Virkkunen, K.; Yttri, K. E.; Andrews, E.; Kowal, D.; Mefford, T.; Ogren, J. A.; Sharma, S.; Spichtinger, N.; Stone, R.; Hoch, S.; Wehrli, C.

    2007-12-01

    This paper presents an overview of air pollution transport into the Arctic. The major transport processes will be highlighted, as well as their seasonal, interannual, and spatial variability. The source regions of Arctic air pollution will be discussed, with a focus on black carbon (BC) sources, as BC can produce significant radiative forcing in the Arctic. It is found that Europe is the main source region for BC in winter, whereas boreal forest fires are the strongest source in summer, especially in years of strong burning. Two case studies of recent extreme Arctic air pollution events will be presented. In summer 2004, boreal forest fires in Alaska and Canada caused pan-Arctic enhancements of black carbon. The BC concentrations measured at Barrow (Alaska), Alert (Canada), Summit (Greenland) and Zeppelin (Spitsbergen) were all episodically elevated, as a result of the long-range transport of the biomass burning emissions. Aerosol optical depth was also episodically elevated at these stations, with an almost continuous elevation over more than a month at Summit. During the second episode in spring 2006, new records were set for all measured air pollutant species at the Zeppelin station (Spitsbergen) as well as for ozone in Iceland. At Zeppelin, BC, AOD, aerosol mass, ozone, carbon monoxide and other compounds all reached new record levels, compared to the long-term monitoring record. The episode was caused by transport of polluted air masses from Eastern Europe deep into the Arctic, a consequence of the unusual warmth in the European Arctic during the episode. While fossil fuel combustion sources certainly contributed to this episode, smoke from agricultural fires in Eastern Europe was the dominant pollution component. We also suggest a new revolatilization mechanism for persistent organic pollutants (POPs) stored in soils and vegetation by fires, as POPs were strongly elevated during both episodes. All this suggests a considerable influence of biomass burning on

  20. Mapping the Surficial Geology of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Mosher, D. C.; Jakobsson, M.; Gebhardt, C.; Mayer, L. A.

    2014-12-01

    Surficial geologic mapping of the Arctic Ocean was undertaken to provide a basis for understanding different geologic environments in this polar setting. Mapping was based on data acquired from numerous icebreaker and submarine missions to the polar region. The intent was to create a geologic layer overlying the International Bathymetric Chart of the Arctic Ocean. Analysis of subbottom profiler and multibeam bathymetric data in conjunction with sediment cores and the regional morphology rendered from the IBCAO data were used to map different surficial geologic units. For a relatively small ocean basin, the Arctic Ocean reveals a plethora of margin and basin types reflecting both the complex tectonic origins of the basin and its diverse sedimentation history. Broad and narrow shelves were subjected to a complex ice-margin history in the Quaternary, and bear the sediment types and morphological features as a result. Some shelfal areas are heavily influenced by rivers. Extensive deep water ridges and plateaus are isolated from coastal input and have a long history of hemipelagic deposition. An active spreading ridge and regions of recent volcanism have volcani-clastic and heavily altered sediments. Some regions of the Arctic Ocean are proposed to have been influenced by bolide impact. The flanks of the basins demonstrate complex sedimentation patterns resulting from mass failures and ice-margin outflow. The deep basins of the Arctic Ocean are filled with turbidites resulting from these mass-flows and are interbedded with hemiplegic deposits.

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