Climate effects on soil erodibility

Soil erodibility data, calculated using measured soil loss from standard runoff plots, collected over at least one year and applying the standard requirements for calculating the soil erodibility factor (K) of the Universal Soil Loss Equation (USLE), have been analysed to investigate whether climate affects the susceptibility of soils to water erosion. In total, more than 300 K-values extracted from the literature have been analysed. Due to the limited availability of data related to the characteristics of the soil and the location of the measuring sites, all the analysis has been carried out using only soil textural characteristics, organic matter content, rock fragment content and the some general characteristics of the climatic zone where the plots were located. The first evidence of a strong climate effect on soil erodibility is shown by the seasonal variation of mean monthly soil erodibility (K-m). Using data collected in the USA and Italy an effect of mean monthly air temperature on K-m could be identified. Data collected in Indonesia (where mean monthly air temperature remains fairly constant throughout the year) showed comparable variations of monthly soil erodibility. However, it was impossible to explain these variations in K-m as no other data than mean monthly air temperature were available. Mean annual soil erodibility shows a clear climate effect. Soil erodibilities can be subdivided into two large groups, one corresponding to soils in cool climates (Df and Cf climate according to the Koppen-Geiger climate classification) and another to soils located in warm climates (tropical Af and Aw climates). Erodibilities of Mediterranean soils (found under Cs climate) plot among the soils found in Af and Aw climates. These subdivisions can be made for both stony and non-stony soils. Limited data suggest that soil aggregate stability is a good predictor for explaining soil erodibility variations between different climate zones. Copyright (C) 2007 John Wiley & Sons, Ltd.