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Effect of historical land-use on lake-water carbon and geochemistry:: A multi-proxy study of two lake sediment profiles in Dalarna throughout the Holocene
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Paleolimnologi)
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
Abstract [en]

This study examines changes in lake-water total organic carbon (LW-TOC) and lake sediment geochemistry in two lakes, Stångtjärnen and Holtjärnen in (Dalarna, Sweden), during the Holocene and the role of the historic forest grazing and farming (fäbod-system). The aims of the study were to: 1. Discern the effects of natural processes on the lake’s biogeochemistry in different position in the landscape. 2. Identify the effects and differences in intensity of historic land-use on the lakes. A multi-proxy study was conducted encompassing multi-element (15) geochemistry, biogenic silica, LW-TOC, chlorophyll a and published pollen records. The first lake, Stångtjärnen, is shaped and influenced by surrounding mires, which developed shortly after deglaciation and stabilized the LW-TOC at 19 mg L-1 throughout most of the Holocene, while Holtjärnen, a small upland lake, changed from a productive lake (BSi: 35 %), low humic (LW-TOC: 8 mg L-1) to a less productive (BSi: 4 %) more humic lake (LW-TOC: 12 mg L-1) in 7300 BP. The intensification of agricultural land-use (e.g. hay-making) in Stångtjärnen reduced the concentrations of organic associated elements (Br, Cl) and LW-TOC and increased lithogenic elements (K, Ti), while Holtjärnen showed less anthropogenic influence. The comparison between the two lakes displayed the intensive influence of land-use on the Stångtjärnen catchment, showcased by changes in the sediment geochemistry, vegetation composition and the extent of the forest-grazing system in a landscape perspective. In response to the changes of the Holocene, Stångtjärnen’s mires became the main influence, while Holtjärnen was more sensitive to changes. 

Place, publisher, year, edition, pages
2016. , 62 p.
Keyword [en]
lake-water TOC, summer farming, forest grazing, sediment geochemistry
National Category
Other Earth and Related Environmental Sciences
URN: urn:nbn:se:umu:diva-121525OAI: diva2:933085
Subject / course
Examensarbete i Geovetenskap/naturgeografi avseende masterexamen
Educational program
Master's Programme in Geoecology
2016-05-30, NC 230, Umeå, 13:00 (English)
Available from: 2016-08-29 Created: 2016-06-03 Last updated: 2016-08-29Bibliographically approved

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