Subarctic ecosystem responses to climate, catchment and permafrost dynamics in the Holocene
This thesis assesses aspects of the wetland development, permafrost dynamics and associated changes in carbon and nutrient cycling of the Stordalen Mire in northern Sweden. Various ecological and biogeochemical analyses of one peat and two lake sediment sequences were conducted, including analyses o...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Department of Geology, Lund University
2009
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| Online Access: | https://lup.lub.lu.se/record/1304185 https://portal.research.lu.se/files/4066937/3162733.pdf |
| Summary: | This thesis assesses aspects of the wetland development, permafrost dynamics and associated changes in carbon and nutrient cycling of the Stordalen Mire in northern Sweden. Various ecological and biogeochemical analyses of one peat and two lake sediment sequences were conducted, including analyses of organic matter and carbonate content, mosses, diatoms, testate amoebae, pigments, carbon and nitrogen and their stable isotopes, near infrared spectroscopy and biogenic silica. Results revealed that the structural development of the mire occurred during the later part of the Holocene. Peat inception was dated at 4700 cal BP and onset of organic sedimentation in two adjacent lake basins occurred at 3400 and 2650 cal BP. Fen peat accumulated until minimum 2800 cal BP, and after c.2650 cal BP an early permafrost aggradation phase likely caused frost heave and significant changes in the wetland structure and hydrology. Peat is largely missing in the examined core between 2800 and 1350 cal BP, reflecting either environmental stress causing a decrease/cease of peat accumulation and/or erosion of previously formed peat. An increased content of redeposited peat in one of the lakes after c.2100 cal BP, points to mire erosion caused by permafrost decay. A high nutrient/productivity layer in the other lake between 1900 and 1800 cal BP may have been related to the same event in the mire. Sedge peat accumulated from 1350 cal BP. Renewed permafrost aggradation is indicated indirectly around 700 cal BP and directly 120 cal BP from changes in peat building vegetation. Fen peat and transitions between dominating mire vegetation communities were characterized by frequent diatoms and high nutrient concentrations. Permafrost phases were associated with poor fen and bog formation, and thus considerably more acidic conditions in the mire as compared to pH conditions when richer fen communities dominated. This development resulted in more acidic runoff to adjacent lakes and affected carbonate precipitation there. Further, poor catchment ... |
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