科研之友
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摘要
Soils deliver a range of ecosystem services and underpin conventional global food production which must increase to feed the projected growth in human population. Although soil erosion by water and subsequent sediment delivery to rivers are natural processes, anthropogenic pressures, including modem farming practices and management, have accelerated soil erosion rates on both arable and grassland. A range of approaches can be used to assess and document soil erosion rates and, in the case of the UK, these mainly comprise the Cs-137-based approach, conventional surveys using volumetric measurements, integration of information on suspended sediment flux, fine sediment source apportionment and landscape sediment retention and traditional bounded hydrological monitoring at edge-of-field using experimental platforms. We compare the erosion rates for arable and grassland in lowland England assessed by these different techniques. Rates assessed by volumetric measurements are similar to those generated by integrating information on suspended sediment flux, sources and landscape retention, but are much less than those estimated by the Cs-137-based approach; of the order of one magnitude less for arable land. The Cs-137 approach assumes an initial distribution of Cs-137 uniformly spread across the landscape and relates the sampled distribution to erosion, but other (transport) processes are also involved and their representation in the calibration procedures remains problematic. We suggest that the Cs-137 technique needs to be validated more rigorously and conversion models re-calibrated. As things stand, rates of erosion based on the distribution of Cs-137 may well overstate the severity of the problem in lowland Britain and, therefore, are not a reliable indicator of water erosion rates.
- 出版日期2017-10
