Landscape and Environmental Effects on Organic Carbon in Tundra Soils, Est Greenland PDF Download
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Author: Julia I. Bradley-Cook
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Book Description
"Arctic soils in the permafrost region store substantially more carbon than is contained in the atmosphere, and are undergoing rapid change associated with anthropogenic climate change. Soil decomposition is an important component of ecosystem carbon flux that creates a biological feedback with the potential to accelerate climate change. In this research, I investigated controls on soil carbon storage and respiration to evaluate sensitivities of soil carbon processes to key drivers of change, and their interactions, and tested metabolic theories that predict the thermal response of soil decomposition. To assess the controls of landscape age and climate on carbon storage, respiration potential and organic matter quality, I conducted long-term incubations of soils collected from four study areas across western Greenland. I found that soil carbon storage and organic matter quality varied with landscape age, but the nonlinear patterns across the gradient point to the importance of interactions with other controls on soil carbon. To test the carbon quality temperature hypothesis and measure temperature and moisture controls on microbial decomposition in shrub and graminoid soils, I conducted an incubation experiment on tundra mineral soils. In contrast to the theoretical predictions, I found that temperature sensitivity was significantly higher in graminoid soils than shrub soils. These results indicate that the large stocks of carbon in graminoid soils should be more susceptible to carbon mineralization in a warming Arctic than shrub soils. To evaluate landscape variation in carbon storage and respiration, I measured soil carbon stocks, in-situ soil respiration, and abiotic variables associated with functional vegetation types at nine study sites near Kangerlussuaq, Greenland. Results from this study provide further evidence that graminoid soils with high moisture content are "hot spots" for soil carbon accumulation and turnover within this tundra landscape. I linked estimates of soil carbon stocks to a high-resolution land cover classification map to create an inventory of tundra soil carbon stocks and estimate soil carbon losses under shrub expansion scenarios."
Author: Julia I. Bradley-Cook
Publisher:
ISBN:
Category :
Languages : en
Pages : 314
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Book Description
"Arctic soils in the permafrost region store substantially more carbon than is contained in the atmosphere, and are undergoing rapid change associated with anthropogenic climate change. Soil decomposition is an important component of ecosystem carbon flux that creates a biological feedback with the potential to accelerate climate change. In this research, I investigated controls on soil carbon storage and respiration to evaluate sensitivities of soil carbon processes to key drivers of change, and their interactions, and tested metabolic theories that predict the thermal response of soil decomposition. To assess the controls of landscape age and climate on carbon storage, respiration potential and organic matter quality, I conducted long-term incubations of soils collected from four study areas across western Greenland. I found that soil carbon storage and organic matter quality varied with landscape age, but the nonlinear patterns across the gradient point to the importance of interactions with other controls on soil carbon. To test the carbon quality temperature hypothesis and measure temperature and moisture controls on microbial decomposition in shrub and graminoid soils, I conducted an incubation experiment on tundra mineral soils. In contrast to the theoretical predictions, I found that temperature sensitivity was significantly higher in graminoid soils than shrub soils. These results indicate that the large stocks of carbon in graminoid soils should be more susceptible to carbon mineralization in a warming Arctic than shrub soils. To evaluate landscape variation in carbon storage and respiration, I measured soil carbon stocks, in-situ soil respiration, and abiotic variables associated with functional vegetation types at nine study sites near Kangerlussuaq, Greenland. Results from this study provide further evidence that graminoid soils with high moisture content are "hot spots" for soil carbon accumulation and turnover within this tundra landscape. I linked estimates of soil carbon stocks to a high-resolution land cover classification map to create an inventory of tundra soil carbon stocks and estimate soil carbon losses under shrub expansion scenarios."
Author: Philipp Gries
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Soils of the northern circumpolar region are a key organic carbon storage strained by global warming. Thawing of permafrost-affected soils from global warming increases greenhouse-gas emissions whose quantification is limited by sparse, uncertain and spatially diverse data of soil organic carbon stocks (SOCS) across the Arctic region, especially in Greenland. The accurate assessment of the effects of global warming requires better understanding of environmental interactions and feedbacks on SOCS which, however, vary spatially and across scales in Arctic environments. Therefore, different scales were selected to identify scale-dependent effects of environmental factors and processes on the SOCS distribution in permafrost-affected soils in Arctic environments, exemplified by two study areas in West Greenland. Three controlling factors (vegetation, landscape, aspect) were used as representation of spatial varying environmental conditions to investigate the spatial SOCS distribution over short distances separately in both areas on the local scale and over a long distance between both areas on the regional scale. Further, the spatial SOCS distribution was analyzed using a set of multi-scale terrain and spatial features representing environmental processes acting parallel but differing in their intensity on the moraine, valley and catchment scale. The soil data set comprises of SOCS from 140 locations distributed over a study area at the coast and at the ice margin of West Greenland being characterized by oceanic and continental climate. On the local scale, the SOCS distribution was best explained by vegetation and aspect as both reflect the importance of wind and solar radiation in both areas. Furthermore, aspect and curvature best mapped the SOCS distribution shaped by water-driven relocation processes on the moraine and valley scale in SISI and wind-induced processes acting parallel on the moraine, valley and catchment scale in RUSS. On the regional scale, differences in the SOCS distribution result from contrasting climate conditions between the coast and the ice margin which both are reflected by differences in the importance of relevant terrain features and scales and vegetation units between both study areas. Consequently, it is recommended to apply multi-scale terrain features in combination with vegetation to address scale-dependent soil-landscape interrelations being essential for spatial analysis of SOCS in West Greenland.
Author:
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 149
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The Arctic is rapidly changing as a result of climate forcing induced by rising greenhouse gas concentrations. Given the large soil organic carbon pools of this biome, understanding how potential changes to arctic ecosystems will affect the Arctic's net carbon balance is imperative for improving predictions of future global climate. However, complicating this understanding is the large heterogeneity of arctic landscapes. There is currently the need for more wholeecosystem studies not only to improve regional flux estimates but also to determine how smallscale variability integrates to form the whole-ecosystem response to climate-induced changes in tundra conditions. This dissertation addresses this research need with a combination of regionalscale observations and whole-ecosystem moisture experimentation in the arctic coastal tundra near Barrow, Alaska. Regional-scale variability in cumulative growing season net CO2 exchange (NEE) was very large and was strongly tied to declining productivity associated with ecosystem development across the dominant landscape unit: thaw lakes and an age sequence of drained thaw lake basins. Contrary to many previous small-scale studies, moisture (aside from lakes) was not a dominant factor controlling regional-scale variability in NEE. However, this result was supported by a study of whole-ecosystem NEE and ecosystem respiration (ER) in a large-scale moisture manipulation experiment. This study confirmed what the few previous large-scale experiments have found: that increased wetness does not necessarily reduce ER and increase carbon storage. Furthermore, the release to the atmosphere of respired CO2 in moist and wet conditions was strongly enhanced by increased wind speed. This effect was shown to be largely missed by small-scale chamber measurements and is currently inadequately considered in commonly used models to partition ER from NEE determined by eddy covariance. Landscapescale variability in CH4 emissions was also large, but was mostly controlled by ecosystem moisture status and had very little relation to ecosystem development or productivity, identifying contrasting patterns and controls on fluxes of CO2 and CH4. The large control of CH4 flux variability by soil moisture was confirmed by the large-scale moisture manipulation experiment in which an experimentally raised water table resulted in higher CH4 emission. This experiment identified further control of moisture on autumn CH4 emissions, linking the decline in autumn CH4 emissions to the decline in liquid moisture during soil freezing. A higher water table slowed the soil freezing process, prolonging higher CH4 emissions later into the autumn and early winter. Combined, these results indicate that the variability in CO2 and CH4 emissions is large but can be explained and predicted in order to improve and validate regional flux models. Taken together, these results suggest that increased soil moisture in arctic areas may increase both CO2 and CH4 emissions, while increased lake drainage could turn strong CO2 source areas into large CO2 sinks as vegetation develops and soil organic matter accumulates.
Author: James F. Reynolds
Publisher: Springer
ISBN: 9783662011478
Category : Science
Languages : en
Pages : 440
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Following the discovery of large petroleum reserves in northern Alaska, the US Department of Energy implemented an integrated field and modeling study to help define potential impacts of energy-related disturbances on tundra ecosystems. This volume presents the major findings from this study, ranging from ecosystem physiology and biogeochemistry to landscape models that quantify the impact of road-building. An important resource for researchers and students interested in arctic ecology, as well as for environmental managers concerned with practical issues of disturbances.
Author: James F. Reynolds
Publisher: Springer
ISBN: 9783540592631
Category : Science
Languages : en
Pages : 0
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Book Description
Following the discovery of large petroleum reserves in northern Alaska, the US Department of Energy implemented an integrated field and modeling study to help define potential impacts of energy-related disturbances on tundra ecosystems. This volume presents the major findings from this study, ranging from ecosystem physiology and biogeochemistry to landscape models that quantify the impact of road-building. An important resource for researchers and students interested in arctic ecology, as well as for environmental managers concerned with practical issues of disturbances.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, and low-molecular-weight (LMW) organic acids were analyzed during incubation at either -2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO2 and CH4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO2 and CH4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO2 and CH4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.
Author: Marc T. Mayes
Publisher:
ISBN:
Category :
Languages : en
Pages : 352
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Author: Anna Foster
Publisher:
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Category :
Languages : en
Pages : 0
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Author: Audrey A. J. Wayolle
Publisher:
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Category :
Languages : en
Pages :
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In recent years, concern has grown over the consequences of global warming. The arctic region is thought to be particularly vulnerable to increasing temperatures, and warming is occurring here substantially more rapidly than at lower latitudes. Consequently, assessments of the state of the Arctic are a focus of international efforts. For the terrestrial Arctic, large datasets are generated by remote sensing of above-ground variables, with an emphasis on vegetation properties, and, by association, carbon fluxes. However, the terrestrial component of the carbon (C) cycle remains poorly quantified and the below-ground distribution and stocks of soil C can not be quantified directly by remote sensing. Large areas of the Arctic are also difficult to access, limiting field surveys. The scientific community does know, however, that this region stores a massive proportion (although poorly quantified, soil C stocks for tundra soils vary from 96 to 192 Gt C) of the global reservoir of soil carbon, much of it in permafrost (900 Gt C), and these stocks may be very vulnerable to increased rates of decomposition due to rising temperatures. The consequences of this could be increasing source strength of the radiatively forcing gases carbon dioxide (CO2) and methane (CH4). The principal objective of this project is to provide a critical evaluation of methods used to link soil C stocks and fluxes at the usual scales spanned by the field surveys (centimetre to kilometre) and remote sensing surveys (kilometre to hundreds of kilometres). The soil C distribution of two sub-arctic sites in contrasting climatic, landscape/geomorphologic and vegetation settings has been described and analysed. The transition between birch forest and tundra heath in the Abisko (Swedish Lapland) field site, and the transition between mire and birch forest in the Kevo (Finnish Lapland) field site span several vegetation categories and landscape contexts. The natural variability of below-ground C stocks (excluding coarse roots > 2 mm diameter), at scales from the centimetre to the kilometre scale, is high: 0.01 to 18.8 kg C m-2 for the 0 - 4 cm depth in a 2.5 km2 area of Abisko. The depths of the soil profiles and the soil C stocks are not directly linked to either vegetation categories or Leaf Area Index (LAI), thus vegetation properties are not a straightforward proxy for soil C distribution. When mapping soil or vegetation categories over large areas, it is usually necessary to aggregate several vegetation or soil categories to simplify the output (both for mapping and for modelling). Using this approach, an average value of 2.3 kg C m-2 was derived both for soils beneath treeless areas and forest understorey. This aggregated value is potentially misleading, however, because there is significant skew resulting from the inclusion of exposed ridges (with very low soil C stocks) in the 'treeless' category. Furthermore, if birch trees colonise tundra heath and other 'open' plant communities in the coming decades, there will likely be substantial shifts in soil C stocks. This will be both due to direct climate effects on decomposition, but also due to changes in above- and below-ground C inputs (both in quantity and quality) and possibly changes in so-called root 'priming' effects on the decomposition of existing organic matter. A model of soil respiration using parameters from field surveys shows that soils of the birch forest are more sensitive to increases in mean annual temperature than soils under tundra heath. The heterogeneity of soil properties, moisture and temperature regimes and vegetation cover in ecotone areas means that responses to climate change will differ across these landscapes. Any exercise in upscaling results from field surveys has to indicate the heterogeneity of vegetation and soil categories to guide soil sampling and modelling of C cycle processes in the Arctic.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 32
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Northern ecosystems contain up to 455 Gt of C in the soil active layer and upper permafrost, which is equivalent to approximately 60% of the carbon currently in the atmosphere as CO2. Much of this carbon is stored in the soil as dead organic matter. Its fate is subject to the net effects of global change on the plant and soil systems of northern ecosystems. The arctic alone contains about 60 Gt C, 90% of which is present in the soil active layer and upper permafrost, and is assumed to have been a sink for CO2 during the historic and recent geologic past. Depending on the nature, rate, and magnitude of global environmental change, the arctic may have a positive or negative feedback on global change. Results from the DOE- funded research efforts of 1990 and 1991 indicate that the arctic has become a source of CO2 to the atmosphere. Measurements made in the Barrow, Alaska region during 1992 support these results. This change coincides with recent climatic variation in the arctic, and suggests a positive feedback of arctic ecosystems on atmospheric CO2 and global change. There are obvious potential errors in scaling plot level measurements to landscape, mesoscale, and global spatial scales. In light of the results from the recent DOE-funded research, and the remaining uncertainties regarding the change in arctic ecosystem function due to high latitude warming, a revised set of research goals is proposed for the 1993--94 year. The research proposed in this application has four principal aspects: (A) Long- term response of arctic plants and ecosystems to elevated atmospheric CO2. (B) Circumpolar patterns of net ecosystem CO2 flux. (C) In situ controls by temperature and moisture on net ecosystem CO2 flux. (D) Scaling of CO2 flux from plot, to landscape, to regional scales.
