Land-use impact on plant communities in semi-natural sub-alpine grasslandsof Budalen, central Norway

Sub-alpine, semi-natural grasslands induced by mountain summer farming in B udalen, central Norway, can be divided into two main habitats: small enclos ures at each summer farm site, and the pastures surrounding them. Enclosure s are exposed to different land-use regimes including grazing, mowing, fert ilisation and soil disturbance. Pastures have never been fertilised or plou ghed and the current grazing pressure is moderate. All investigated pasture s are former haymaking areas. Higher conservation values of pastures compar ed to enclosures is reflected both in patterns of species richness and the occurrence of vulnerable species. Higher species richness in pastures is re lated to lower nutrient levels, lower loss of ignition in the soil, and hig her levels of pH. Vulnerable species are concentrated in species-rich pastu res, and have tow local abundance and regional distribution. Enclosures ref lect a complexity in land-use, were the effects of mowing, fertilising and ploughing on plant community patterns could not be separated. Tree and shru b species are common in both habitats, and indicate a successional invasion of woody species. Maintenance of land-uses that have created semi-natural grasslands in the long term perspective (grazing, cutting of trees and shru bs, and mowing) is necessary to prevent forest succession, and a prerequisi te for future conservation of sub-alpine, semi-natural grasslands. (C) 1998 Elsevier Science Ltd. All rights reserved.