Factors on the spatial variability of the plant cover changes in the Pyrenees

Abstract

Mediterranean mountain areas show during the twentieth century intense revegetation processes, mainly characterised by the advance of forests and shrubs. This is explained by land abandonment and the noticeable decrease of the livestock pressure on the pastures. This paper analyses the influence of some physical and human factors on the intensity and spatial patterns of the revegetation processes in the Borau valley (Central Spanish Pyrenees) between 1957 and 2000. About 45% of the study area showed important modifications in the vegetation cover. The succession processes toward more mature vegetation stages are dominant (41.5%). On the contrary, the retreat toward less mature vegetation stages affects small sectors (3.5%). Low and middle slopes covered by abandoned fields were the areas in which the main changes were observed. Nevertheless, the advance towards more mature vegetation stages was moderate, since the 25.8% of the area only advanced one stage, the 14.3% showed an advance of two stages and only the 1,4% of the territory showed an advance of more than two stages. Livestock pressure and terrain exposure, which determine the solar incoming radiation, were the most important factors to explain the spatial differences in the land cover change. On the contrary, other topographic variables play a secondary role, although other studies have shown their important influence at more detailed spatial scales.