Plant species richness and persistence of rare plants in abandoned semi-natural grasslands in northern Europe

The effects of land-use history on plant species richness were studied in mesic semi-natural grasslands in SW Finland. Using generalized additive models, we studied the total number of species, number of species of dry and mesic grasslands and number of rare species of dry and mesic grasslands of 162 grazed or abandoned grassland patches. We studied only grasslands that had remained totally or mostly treeless despite of abandonment. Increase of solar radiation was positively correlated with all three richness variables. Increasing cover of trees had a negative effect on the total species richness and that of rare grassland species. Total species richness and richness of grassland species declined with increasing time after abandonment, but richness of rare species did not show a similar response. The results emphasize the importance of high solar radiation, grazing and tow cover of trees for plant species richness in mesic semi-natural grasslands in northern Europe. According to our results the increase in the cover of trees after the end of grazing may be more detrimental to grassland plants than the lack of grazing per se. (c) 2004 Elsevier GmbH. All rights reserved.