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The hydrological response of Mediterranean hillslopes depends on the type of soil surface components (SSC) which is controlled by the strongly climate. Along a Mediterranean climatic gradient, the type of soil surface component is modified as the aridity increases: biotic ones (annual plants, litter, moss and lichens) used to be more significant under humid climatic conditions, whereas abiotic ones (crusts, rock fragments and outcrops), under semiarid conditions. The aim of the study is to analyse the hydrological behaviour of different types of SSC in three field sites under different Mediterranean climatic conditions to (1) confirm whether the pluviometric gradient factor affects their hydrological response, and (2) whether, in each field site, SSC play the same role as controlling factors of infiltration processes. The method is based on grouping explanatory variables (related to precipitations, topography, vegetal cover, soil moisture and some soil physical, chemical and hydrological properties) through factorial analysis being applied for both regional and local approaches. The results confirm that the type of soil surface component acts as regulator of soil hydrological processes along the pluviometric gradient as well as at every field site, and show that the role played by the type of soil surface component is a much more significant key-factor for the hydrological response of soils under dry-Mediterranean climatic conditions. Copyright (C) 2010 John Wiley & Sons, Ltd.