Butterflies in semi-natural pastures and power-line corridors – effects of flower richness, management, and structural vegetation characteristics
* The aim of this study was to compare the butterfly assemblages in semi-natural pastures and power-line corridors and to analyse the effects of vegetation height, occurrence of trees and shrubs and different flowering vascular plant groups on butterfly diversity and abundance. * Twelve of 26 analysed butterfly species were more abundant in power-line corridors than in semi-natural pastures. Only one species preferred semi-natural pastures. * In semi-natural pastures butterflies were most common in segments with tall vegetation, whereas butterflies in power-line corridors were most common in segments with vegetation of short or intermediate height. Short vegetation was sparser in power-line corridors (mean cover 4%) than in semi-natural pastures (33%), whereas tall vegetation was more common in power-line corridors (59%) than in semi-natural pastures (35%). * The amount of flowers was the factor that affected the abundance of most species. Twenty-one of the 26 species showed positive associations with numbers of flowers of different families. * Flowers of the plant families Apiaceae, Caryophyllaceae, Primulaceae, Rubiaceae, Scrophulariaceae, and Violaceae showed positive associations with the abundance of several butterfly species. * Vegetation height seems to be a limiting factor in semi-natural pastures, and less intensive management (division of pastures into grazing pens, late season grazing, grazing every second year, or reduced grazing pressure) would benefit butterflies. In power-line corridors (dominated by tall vegetation) the opposite would be beneficial for butterflies, for example more frequent clearing of vegetation along the power-line trails combined with mowing of selected areas.