Dry Grassland Vegetation in the Transition Zone Between two Biogeographic Regions

The geographic position of Bulgaria results in a variety of climatic and biogeographic influences on the country’s vegetation. We aim to describe the plant diversity of dry grasslands distributed in the transitional belt between the south-eastern European and Mediterranean biogeographic regions in SE Bulgaria, and to reveal if there are any obvious differences in soil properties, presence of life forms and chorotypes between syntaxa. The data set consists of 349 releves of vascular plants and bryophytes sampled in different semi-natural herbaceous vegetation types. By applying TWINSPAN, we classified 176 releves of dry grasslands to eight associations and one unranked community. One association and two subassociations are described here for the first time. Data on soil depth, soil moisture, soil pH, humus and total N content, numbers of different life forms and chorotypes were analysed statistically. The dry grasslands in SE Bulgaria were classified into different vegetation classes sharing the same territory: their communities present similarities in species composition and they have similar ratios of hemicryptophytes/therophytes and Euro-Asiatic/Mediterranean species. Dry grassland vegetation occupies mostly shallow and dry soils that vary slightly in pH, humus content and soil moisture between associations.