Climate change, especially global warming caused by greenhouse gas emissions, is affecting all parts of the society. In addition to the direct emissions of greenhouse gases, changes in land use have an impact on the carbon cycle and potentially large impact on the climate. The growing awareness of organic matter transportation between terrestrial and aquatic ecosystems in response to land use is needed for analysis and prediction of the human impact on organic carbon cycling which is fundamental for the development environmental management strategies. Long-term records of environmental variation in centennial to millennial scale are essential for the assessment of ecosystem dynamics in response to early and recent anthropogenic. Lake sediments chronologically deposited with materials originating from both within the lake (e.g., organic matter from macrophytes) and the catchment area (e.g., pollen from vascular plants and minerogenic material), and record the changes in the water body and the watershed. Hence, lake sediments can be used to reconstruct the environment changes on lakes and their catchment areas with multiple proxies.
In my PhD project, I will study two lakes (Skottenesjön and Lyngsjön) in southern Sweden with different settings, one is located in forest catchment, and the other is dominated by agricultural land. The topmost sections covering the past 1000 years of both records will be analysed with multiple proxies focusing on the human impact on terrestrial and aquatic ecosystems. Catchment-scale vegetation changes will be reconstructed quantitatively using pollen analysis and the Landscape Reconstruction Algorithm (LRA). Bulk geochemical and mineral magnetic analyses in combination with organic geochemistry including lignin phenols and lipid biomarkers are used to identify the sources of organic matter derived from the catchment. We will analyse potential relations between land-use changes (forestry, agriculture, drainage patterns) and changes in the delivery of organic and mineral matter from the catchment to the aquatic system by comparing the reconstructed vegetation with the geochemical and mineral magnetic results.
Supervisors: Dan Hammarlund, Karl Ljung, Anne Birgitte Nielsen