Plant species richness, composition and habitat specificity in a Norwegian agricultural landscape

In this study the variation in species richness, species composition and habitat specificity is examined among all land patches in a 43-ha landscape in W Norway, created by traditional agricultural management practices, with particular focus on the distribution of semi-natural grassland species, i.e. species known to be typical of species-rich semi-natural grasslands. In 2002 about one half of the study area was intensively managed for agricultural purposes, 19.3% was woodland and 14.4% was semi-natural grassland. The main vegetation gradient in the area reflected long-term management (land-use) intensity. Both species richness and habitat specificity decreased with increasing management intensity. Semi-natural grassland species occurred throughout the landscape, although with some concentration to semi-natural grasslands. The two measures of habitat specificity both peaked in semi-natural grasslands. Comparison of the present patterns of vascular plant distributions with information on past land-use derived from a map from 1865, indicate that species typical of semi-natural grasslands persist long after land use activities have come to an end and that there is an extinction debt in the vascular flora. The significant positive relationship between patches with high richness of species typical of semi-natural grasslands, remnant semi-natural grassland patches and man-made structures with long continuity, shows that restoring formerly open semi-natural grassland ‘hot spots’ in a agricultural landscapes is advantageous both for conservation of cultural and biological values.