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Effects of exposure, scrub position, and soil surface components on the hydrological response in small plots in southern Spain



Rangelands are a major component of the Mediterranean landscape. These environments are commonly affected by grazing, which reduces vegetation cover. Consequently, patchy vegetation patterns occur on Mediterranean hillslopes, where the bare soil is characterized by a number of surface components that are controlled by climatic conditions and exposure. The aim of this study was to assess at a fine scale the effects of exposure, scrub, and soil surface components on the hydrological response under various Mediterranean climatic conditions. A set of closed plots (each of area 1·3 m2) were established in each of three Mediterranean rangeland environments that differ in climatic conditions (humid, dry, and semiarid), but were not affected by intensive grazing. Rainfall was recorded at a meteorological station installed at each field site, and topsoil moisture was measured after every rainfall event, when run-off was collected. The results showed that (i) run-off was generated when topsoil moisture was close to saturation in the case of humid sites, and close to the wilting point at dry and semi-arid sites; (ii) run-off did not follow the same trends as rainfall and topsoil moisture along the climatic gradient because of the effects of soil surface components; (iii) the hydrological response in the plots was not clearly controlled by exposure and the location of scrub, especially at the semi-arid site; and (iv) the differences between field sites were small because of the influence of grazing on vegetation cover and the effects of soil water repellency, both of which require further investigation. Copyright © 2010 John Wiley & Sons, Ltd.