Lake Sediments Used to Quantify the Erosional Response to Land Use Change in Southern Sweden

Abstract

1. A multi-disciplinary approach within the framework of the lake catchment ecosystem provides a basis for studying environmental processes through time. 2. Using magnetic susceptibility measurements, it is possible to correlate a large number of sediment cores economically and rapidly, and hence to calculate sediment volumes and masses, and chemical flux. A combination of radiometric (210Pb and 137Cs) and palaeomagnetic dating methods allows influx data to be placed on an absolute timescale. 3. Linking the sediment influx records to a landscape history derived from pollen, diatom and land use records suggests that sediment yield from the catchment has been most affected by anthropogenic activity. In particular, early deforestation accelerated sediment loss from ca. 0.25 t ha -1 yr-1 yr to 0.86-2.5 t ha-1 yr -1 within a period of 1000 yr. The period AD 1300-1550 witnessed a drop in sediment yield to 0.5-1.5 ha -1 yr -1, perhaps related to the agrarian depression, and recent expansion of the cultivated area has led to a 1.5 fold increase in sediment yield. 4. Reconstructions of P flux in present and AD 1682 catchments suggests that in contrast to the highly subsidised present system, the earlier system ran at a net loss with losses of P at a rate of 1.5 kg ha-1 yr-1. 5. Close calibration of sediment and enviromental records may form the basis for reconstructing environmental processes and for quantifying environmental thresholds, time-lags, response and recovery rates. This represents an important extension to contemporary process studies based on monitoring over short timescales.