Uso do solo em ambientes semiáridos: efeitos sobre a estrutura da vegetação e interação entre plantas em uma floresta tropical seca

Abstract

Land use is the main driver of vegetation changes worldwide and its long-lasting effect is critical in arid and semi-arid systems. Brazilian Caatinga is one of the species-richest semiarid biomes of the world and is threatened by strong land use pressure and poor protection. Land use in Caatinga mainly comprises grazing by cattle, donkeys, goats or horses, and wood extraction for construction work and charcoal production. In this study, we investigate the effects of past and present land use on plant community richness and structure. We used LANDSAT and GEOEYE satellite information to identify Caatinga forest areas with and without past vegetation clearing. We also quantified current land use, measured as the degree of grazing and wood extraction. We then assessed current vegetation structure, in particular vegetation cover, height, basal area for shrubs and trees, and seedling recruitment. The association between past vegetation clearing and strong present grazing showed a compelling negative effect on vegetation structure, increasing the proportion of bare ground. We suggest that land use planning projects in semi-arid systems should avoid grazing in areas that suffered past clear-cut. This simple land use technique should help to prevent processes of land impoverishment and desertification in semi-arid systems.