SPECIES ABUNDANCE PATTERNS OF PLANTS IN SWEDISH SEMINATURAL PASTURES

This investigation is based on a species inventory in semi-natural pastures, remnants of an ''old'' traditional landscape, in Sweden. The aim was to examine relationships between species richness and pasture area, neighbour pasture area, distance to nearest pasture, pasture heterogeneity and fertilization. Species occurrences were also investigated individually for the same parameters. Pasture area, neighbour pasture area and distance to nearest pasture were not found to influence species richness. Habitat heterogeneity and indications that pastures had been influenced by fertilization were however associated with both species richness and species occurrences. Heterogeneity had only positive effects whereas the effects of fertilization were only negative. Species regional abundance pattern tended to be bimodal, as predicted by the core-satellite hypothesis. No correlation between abundance and plant height, or seed size was found, as would have been expected if competitive dominance effects determined species regional abundance. There was a close to significant tendency that pasture area was positively associated with occurrences of species with features favouring a high seed dispersal capacity. We suggest that the previous history of pasture distribution and management may be of vital importance for present day species abundance pattern, even though this remains obscure in the recent landscape.