Stratigraphy and dating of a lake sediment record from Lyngsjön, eastern Scania : human impact and aeolian sand deposition during the last millennium

Sammanfattning: A small lake in north-eastern Scania, southern Sweden, Lake Lyngsjön, reveals a long history of aeolian sand drift based on a 3 meter long sediment sequence covering the last approximately 1400 years. Human impact, primarily through intensified land use and decreased forest cover, has periodically led to increased aeolian sand drift both locally and regionally. Elevated C/N ratios suggest a period of increased forest cover close to the lake as seen primarily through elevated pine pollen frequencies during the 10th century and later during the 18th century. Agricultural changes such as the 19th century land amalgamation, which would have led to enhanced wind erosion of fields, was simultaneously countered through the plantation of trees, which hampered transportation of aeolian sand into the lake. The continuation of intensified agricultural activity after the implementation of land amalgamation successively led to increased deposition of aeolian sand during the onset of the 20th century. Organic and carbonate contents of the sediments are generally anti-correlated for the majority of the succession although changes in land use during the past 100 years, with substantial input of aeolian sand around the 1920s, seem to have had a major impact on the total inorganic carbon (TIC) signal; possibly by a reduction in carbonate producing algae. Later agricultural changes during the 1940s did not have any major effects on the lake since the plantation of pine and spruce in proximity of the lake acted as a shelter for aeolian sand drift. Correlations between the reconstructed aeolian sand content within the more recent part of the succession and documented historical events have been used to explain earlier aeolian sand deposition events during the 10th and 12th century. A continuous record of cultivated pollen points towards an uninterrupted human influence having an effect on the lake sediments during the past millennium. Maps from the 17th century and onwards reveal a close relationship between past aeolian sand deposition and changes in forest extent on a local to regional scale.