Influence of Topsoil Aggregate Stability on Runoff and Erosion

摘要

Estimating runoff and water erosion is expensive and time-consuming, but several authors have reported that these phenomena are linked to soil aggregate stability, whose determination is far easier. As this link had generally been deduced from rainfall simulations on sieved soil samples, our aim was to test its validity through field investigations. We determined susceptibility to runoff and erosion at three levels: through measurement of runoff and soil losses from 1m~2 microplots under simulated rainfall (Mediterranean highlands) and from 100 to 800m~2 runoff plots under natural rainfall (tropical areas), and finally, through semi-quantitative assessment of erosion feature frequency (Mediterranean hillsides). In each case, aggregate stability was determined by immersion in water and wet-sieving of 2mm sieved, air-dried 0 to 10cm soil samples. Runoff depths and soil losses from microplots and runoff plots, as well as the frequency index of erosion features on hillsides, were negatively correlated with topsoil stable macroaggregate (> 0.2 mm) content. As it greatly influences particle detachment by rainfall and seal formation, topsoil aggregate stability may thus be considered as an important determinant (and as a relevant indicator) of soil susceptibility to runoff and erosion, especially in Mediterranean and tropical areas, which undergo intense rainfall.