Soil organic carbon and nitrogen pools in thermokarst-affected permafrost terrain
Permafrost soils are widespread in the Northern Hemisphere and contain high amounts of carbon (C) and nitrogen (N). Due to the changing climate, permafrost thaws and makes previously frozen C and N available for the active C and N cycles. While additional N might increase plant growth in the nutrien...
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| Format: | Thesis |
| Language: | unknown |
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2019
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| Online Access: | https://epic.awi.de/id/eprint/51514/ https://hdl.handle.net/10013/epic.393b95ff-1d0f-4659-9376-ef084d27741a |
| Summary: | Permafrost soils are widespread in the Northern Hemisphere and contain high amounts of carbon (C) and nitrogen (N). Due to the changing climate, permafrost thaws and makes previously frozen C and N available for the active C and N cycles. While additional N might increase plant growth in the nutrient limited tundra, additional C will be decomposed by microbial activity and released through respiration as CO2 or CH4 into the atmosphere. This, in turn, increases the amount of C in the atmosphere, which triggers climate warming and is thus considered a positive feedback loop to climate warming termed the “permafrost-carbon-climate feedback”. The focus of this dissertation is on deep, ice-rich permafrost deposits, which are prone to rapid degradation through thermokarst processes. Thermokarst involves the thawing of ice-rich permafrost and leads to surface subsidence, lake formation but also lake drainage. Therefore, once thaw is initiated, irreversible changes occur on the landscape and affect C and N that have been freeze-locked for millennia. However, thermokarst processes in permafrost environments are not yet implemented in global permafrost-carbon and climate models, even though they have the potential to degrade and change the surface of a landscape and to mobilize C and N within short time scales. In this dissertation, I investigated different, rapidly changing permafrost environments in terms of their C and N contents in the top two meters of soil. This includes the yedoma-dominated study sites on Sobo-Sise Island and Bykovsky Peninsula in the north of east Siberia, the thermokarst lake landscape north of Teshekpuk Lake on the Arctic Coastal Plain of northern Alaska, and five different Arctic river deltas in the north and west of Alaska. For this analysis, a total of 77 permafrost soil cores were collected and more than 1,000 samples analyzed for their C and N contents. With a combination of field, laboratory, and remote sensing methods, landscape soil organic C and soil N was characterized. A coherent, ... |
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