ABSTRACT:
Soil erosion in agricultural watersheds consists of a natural (geologic) component and an accelerated (human-induced) component. There is little information available, particularly in developing countries, on the accelerated component of soil and nutrient erosion, or its effect on agricultural sustainability. Lakes and watersheds are physically linked ecosystems, and lake sediments preserve historical records of material export from watersheds. We used paleolimnological methods to calculate sediment accumulation rates for four lakes in Yunnan Province, China. We estimated trap efficiencies of three of the lake basins, calculated recent erosion rates for their watersheds, and calculated low-disturbance rates that approximate natural erosion. Human activities in recent centuries caused a 15-fold increase relative to natural erosion rates of non-carbonate, clastic materials from two small [350 km2 (135 mi2)] watersheds. Phosphorus export from these watersheds increased approximately 19 fold. The degree of human influence appeared to differ between the two larger [2700 km2 (1042 mi2)] watersheds. Accelerated soil and nutrient erosion rates from Yunnan watersheds are high, and may ultimately destabilize agricultural productivity and the agrarian economy.
Footnotes
Thomas J. Whitmore and Mark Brenner are Research Associates in the Department of Fisheries and Aquatic Sciences, University of Florida, Gainesville 32606. Daniel R. Engstrom is Adjunct Professor in the Department of Geology and Geophysics, University of Minnesota, Minneapolis 55455. Song Xueliang is Senior Engineer and Director of the Paleontological Department, Yunnan Institute of Geological Sciences, Baita Road, Kunming, Yunnan Province, P.R.C. This paper is Journal Series No. R-02843 of the Florida Agricultural Experiment Station. Research was supported by NSF grant INT 8802793. We thank Allen M. Moore, Michael W. Binford and Yunnan Institute of Geological Sciences personnel for field assistance. Radiocarbon dates for Qilu Hu were kindly provided by Robert Stuckenrath.
- Copyright 1994 by the Soil and Water Conservation Society
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