Effects of grazing on vegetation of abandoned arable fields in a sub- humid Mediterranean environment

Arable land abandonment is a major land use change in the Mediterranean region. Plant colonization and vegetation succession in these areas depend on local climatic conditions, soil quality and, especially, on management practices. Livestock grazing can modify or alter the process of succession by facilitating the colonization of certain species at the expense of others. The aim of this study was to investigate the effects of grazing on vegetation of old fields. The research was conducted in the Taxiarchis village located in the Holomontas mountain of Chalkidiki, northern Greece, with a sub-humid Mediterranean climate. Plant cover and biomass were measured in adjacent moderately to heavily grazed mainly by goats and protected plots of an old field abandoned for 20 years. Species richness and abundance were also recorded and the Shannon –Wiener and equitability diversity indices were calculated. Total plant cover was significantly decreased due to grazing, but herbaceous cover was not significantly affected. Woody species did not appear in the grazed plots, while in the protected ones they covered 12.8% of the ground. Current year’s and total herbage biomass was significantly decreased due to grazing. Total biomass (herbage and woody) was dominated by the herbaceous component and differed significantly between the two treatments. Shannon – Weiner index and equitability were significantly higher in the grazed plots, due to the significant increase of species numbers and abundance. Τhe results indicate that moderate to heavy grazing can control woody species invasion and enhance plant species diversity in old fields of sub-humid Mediterranean environments.