Diversity and floristic patterns of mediterranean grasslands: the relative influence of environmental and land management factors

Managed grasslands are normally ecosystems with high species diversity. They are associated with traditional extensive livestock grazing. Land-use changes, in particular gradual abandonment or grazing intensification, lead to major changes in floristic patterns of these grasslands, some included in priority habitats of the EU Habitats Directive. In order to analyse these patterns of change, Mediterranean grasslands of eastern areas of mainland Portugal were studied aiming to: (1) establish ecological gradients underlying their floristic patterns; (2) examine the relative importance of both environmental and land-use factors on their floristic composition; (3) assess how floristic composition and species richness are affected by land-use factors. Vegetation sampling was carried out from 2008 to 2009 following phytosociological procedures. Canonical Correspondence Analysis was applied. Variation partitioning was used to assess the relative influence of land-use variables. Richness, legumes cover, endemic species and bryophytes cover were compared in four land-management regimes: unmanaged; extensive grazing by sheep; extensive grazing by cattle and sheep; frequent soil tillage. Significant differences were found in floristic and diversity patterns, revealing the importance of grazing as a management tool for maintaining or improving floristic diversity. From our findings slight extensive grazing can contribute to both maintenance of species diversity and to the increase in legumes cover and thus to palatability and economic value of studied grasslands. Interactions between herbivores and grasslands, considering also their influences on soil properties, have an important role in the equilibrium states which promote biodiversity and conservation of the services of these ecosystems.