Relaciones agua-suelo-vegetación.-Incidencia del stress hídrico en las relaciones suelo-agua-planta a lo largo de un gradiente pluviométrico en el sur de España

Abstract

ABSTRACT The Andalusian Mediterranean Watershed, in the South of the Iberian Peninsula, shows a climatic gradient from the Straits of Gibraltar (1,600 mm year-1) to the Cabo de Gata (150 mm year-1). Climate conditions differences are translating into variations in the elements of the eco-geomorphological system at hillslope scale. In this study has been analysed the immediate consequences of a period of two years drought (2004-06) on several elements of the Mediterranean eco-geomorphological system at three hillslopes (sub-humid, dry Mediterranean and semi-arid). The soil water content, the pattern of vegetation and some soil properties (organic matter content, aggregate stability and permeability) were analysed before (Nov-2003) and during (Nov-2005) the drought period. Final results have shown: i) reduction in soil water content which reached in the wet seasons values below wilting point, affecting negatively to the water available for vegetation and especially in the wettest sites; ii) reduction in vegetation cover and in the number of plants, especially at semi-arid field site; iii) changes in the organic matter content which aggravates the loss of stability of soil aggregates, a process seen more clearly under more arid conditions; and iv) reduction of soil permeability in all situations in the climate gradient studied, which supposes a priori an increase in erosive processes due to surface runoff. These results indicate increased vulnerability of the eco-geomorphological system because of the rainfall drought situation.