1082 M. P. Salvador Sanchis et al. Copyright © 2007 John Wiley & Sons, Ltd. Earth Surf. Process. Landforms 33, 1082–1097 (2008) DOI: 10.1002/esp Earth Surface Processes and Landforms Earth Surf. Process. Landforms 33, 1082–1097 (2008) Published online 28 September 2007 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1002/esp.1604 Climate effects on soil erodibility M. P . Salvador Sanchis, 1 * D. Torri, 1 L. Borselli 1 and J. Poesen 2 1 Research Institute for Hydrogeological Protection (CNR), Firenze, Italy 2 Physical and Regional Geography Research Group, K. U. Leuven, Heverlee, Belgium Abstract Soil erodibility data, calculated using measured soil loss from standard runoff plots, col- lected 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 sub- divided into two large groups, one corresponding to soils in cool climates (Df and Cf climate according to the Köppen–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 © 2007 John Wiley & Sons, Ltd. Keywords: water erosion; soil erodibility; climate; climatic change; air temperature; aggre- gate stability; soil texture; stoniness; soil organic matter content *Correspondence to: M. P. Salvador Sanchis, Research Institute for Hydrogeological Protection (CNR) – Via Madonna del Piano 10,50019 Sesto Fiorentino, Italy. E-mail: salvador@irpi.cnr.it Received 29 June 2006; Revised 28 April 2007; Accepted 12 July 2007 Introduction Erodibility represents the soil’s response to rainfall and runoff erosivity. Using such a definition, soil erodibility is not a measurable single parameter because it includes all the soil characteristics (both static and dynamic ones) that control a range of sub-processes affecting soil erosion. Hence, the soil characteristics that control the soil’s behaviour with respect to soil–water interaction (i.e. infiltration rate, permeability, water retention forces, porosity, exchangeable ions, primary particle sizes and mineralogy, aggregate size and stability, soil organic matter) are all important, as they interact, directly and indirectly, with rainfall to produce ponding water in soil surface depressions and surface runoff. Raindrop impact causes detachment, transport and deposition of soil particles, contributing to erosion and interacting with overland flow (e.g. sealing of the soil surface, decreasing soil infiltration rate, increasing overland flow turbu- lence). At the same time, the water layer standing or running over the soil surface reduces the effectiveness of raindrop impact, while overland flow, possibly aided by the added turbulence due to the impacting drops, detaches, entrains and transports soil particles and aggregates.