SPECIES RICHNESS AND VEGETATION STRUCTURE IN A LIMESTONE GRASSLAND AFTER 15 YEARS MANAGEMENT WITH 6 BIOMASS REMOVAL REGIMES

Species richness, species composition and standing crop were studied i n a limestone grassland in northern Switzerland after 13 and 15 years of experimental management with 6 management regimes differing in form , time and frequency of biomass removal. The management regimes with a cut at least every 2nd year had a higher species number per 40 m(2) a nd 1 m(2) than those cut less frequently, abandoned or annually burned . Annual burning and a cut every 5th year lead to a similar decrease i n species richness as abandonment. Differences in species richness bet ween different regimes increased with increasing spatial resolution of observation. Many species occurred in a plot during only one of the t wo sample years. This turnover of species was the highest in plots wit h the lowest species numbers, and increased with increasing spatial re solution. Standing crop was highest in plots burned annually (290 g m( -2)) and lowest in plots cut annually in July (189 g m(-2)). Standing crop and litter increased with decreasing frequency of cutting.