Optimal timing of power line rights-of-ways management for the conservation of butterflies

1. Habitat loss, fragmentation, and degradation are the main threats to biodiversity. Human activities also create new habitat types that might fulfil ecological requirements for a variety of species. 2. This study investigates whether the vegetation clearing (=shrub and tree cutting) on drained mire patches on power line rights-of-ways (ROWs) keep plant communities in an early successional stage and thus provide habitats for mire specialist and non-mire butterflies. It was further studied what would be the optimal clearing interval in terms of butterfly species richness and abundance. 3. The results show that tree height, especially the height of birch, increases linearly over the 7-year period following vegetation clearing. The average birch height had a significant negative relationship with the species richness of mire and non-mire butterflies. 4. The clearing interval had a significant curvilinear relationship with the abundance of both mire and non-mire butterflies, such that the highest abundances were documented two to four growing seasons after the clearing, which would hence be the ecologically optimal vegetation clearing cycle. 5. In general, vegetation management on power line ROWs enhance favourable conditions for butterflies and may maintain habitats for mire-dependent butterflies, even on drained mires.