El impacto de la ganadería y la agricultura en los ecosistemas terrestres.-Grazing and soil erosion in dehesas of SW Spain

Abstract

ABSTRACT Water erosion and its relation to livestock grazing in semi-arid to dry subhumid Mediterranean rangelands with a disperse tree cover is analyzed, based on a variety of studies carried out since 1990 in Extremadura, Spain. The dominant factors of sheetwash are rainfall intensity and soil surface cover, the latter being controlled by rainfall amounts and livestock density. The discontinuous valley bottom gullies present a complex relationship with catchment hydrology. Giving the high temporal variability of sediment losses, the influence of livestock on gully erosion is difficult to determine with short-term studies. Analysis of aerial photographs (1945–2006) of the Parapuños study catchment point to an enhanced gully activity during the last decade as a consequence of increased livestock numbers.