Effect of land abandonment on the vegetation of upland semi-natural grasslands in the Western Balkan Mts., Bulgaria

The area of semi-natural grasslands in Bulgaria has decreased tremendously in the past century due to agricultural intensification or abandonment. As these grasslands host valuable biodiversity, conservation measures are needed for their sustainable maintenance. We studied the effect of pastureland abandonment on plant communities at the Ponor Mt., a part of the Balkan Mts., Bulgaria. Data on floristic composition, vegetation structure and several abiotic parameters were collected in 137 randomly located 16-m(2) plots in 2008. Canonical correspondence analysis (CCA) was used to analyse how species composition is related to abiotic and land use factors. Analyses of covariance (ANCOVAs) were used to test for the effects of sheep grazing vs. abandonment on vegetation structure and composition. The main environmental factors explaining the compositional variation were related to the altitude, sheep grazing and soil depth. Pastureland abandonment led to an increase in vegetation height and of the richness of mesophytes and leafy plants, and red-list species. Grazed plots had higher total species richness, more xerophytes, rosette forming and spring-flowering species. To ensure the persistence of the species of both the open grasslands and mid-successional grassland communities, the management should be carried out in an extensive way and with a zonation regime.