MANAGEMENT OF ROADSIDE VERGES: VEGETATION CHANGES AND SPECIES DIVERSITY

The effects of different management regimes on roadside vegetation is investigated in different experiments in Sweden. The studied management practices included different cutting regimes, together with leaving or removing the hay after cutting, prescribed burning of roadside vegetation. Studies of two typical "roadside species" (Anthriscus sylvestris and Plantago lanceolata), where their response to different cutting regimes in relation to nutrient availability, also carried out. Species diversity (measured as Shannon index) is favoured by cutting, but the increase is only significant when cutting is followed by hay removal. In the absence of cutting the diversity decreases. Cutting followed by hay removal decreases the abundance of several dominant species, e.g. Elymus repens. At the same time other characteristically low-growing species increase. The soil seed bank does not seem to influence species composition in the vegetation very much. However, the seed bank contains several species valuable from a conservation point of view. Burning of roadside vegetation lead to an increase in abundance of Genista pilosa, a species whose distribution today is more or less confined to roadsides. A more conservation-oriented mowing regime on the about 250 000 hectares of roadside vegetation in Sweden, will lead to a general improvement in diversity and provide many grassland species with better opportunities to survive in the future. The present management regime of cutting the vegetation and not removing it may in the long run increase the abundance of certain tall and fast-growing species. This would cause a decrease in species richness, and hence in biological diversity.