CAMBIOS EN LA CUBIERTA VEGETAL EN EL PIRINEO ARAGONÉS EN LOS ÚLTIMOS 50 AÑOS

Changes of vegetal cover in the Aragonese western Pyrenees are shown throughout the last 50 years. The evolution is characterized by a generalised revegetation process with an advance of shrubs and forests. The medium and low slo- pes show the most intense revegetation as a consequence of the agricultural aban- donment and the decrease of the livestock pressure. Nevertheless, few vegetation changes are recorded in cultivated lands and the pastures located above timberline. In the analysed period, the most important changes were recorded in the decades of 1960 and 1970 whereas in the decades of 1980 and 1990 the rate of vegetation growth has decreased noticeably. The socioeconomic factors (agricultural abandon- ment, livestock extensification and reforestations) affect the spatial and temporal pat- terns of revegetation. Also the relief has a noticeable influence, mainly elevation and aspect.