Epsilon Archive for Student Projects

Abstract

Over the past century, semi-natural grassland areas have been lost at alarming rates throughout Western Europe, leading to reduced populations and diversity of plants and butterflies, particularly grassland specialists. In this context, powerline corridors have emerged as alternative habitats, harbouring a relatively high level of plant and butterfly diversity, owing to regular clearings that promote disturbance-tolerant plants and create habitats suitable for many butterflies.
In Sweden, powerline corridors are typically cleared every eight years. In contrast to semi-natural pastures, butterfly diversity has been found to be negatively affected by increased vegetation height in these corridors. Recent studies suggest that more frequent clearing regimes can enhance both plant and butterfly species richness and abundance in powerline corridors, and that the removal of cleared residuals may further benefit plant and butterfly diversity.
This thesis investigates the impact of an altered management regime, consisting of more frequent clearings and removal of all cleared residuals, on general plant and butterfly diversity, as well as grassland-specific plant and butterfly diversity. A before-after control-impact study design was used, in which diversity metrics were compared between the altered and conventional management regimes over two years (2018 and 2024). The diversity metrics assessed were species richness, abundance/cover-abundance, and the Shannon diversity index.
No significant effects of the altered management regime were identified for any of the diversity metrics analysed. Some possible explanations include that more time is needed for the potential effects of the altered management to appear, and that butterfly diversity tends to be low during the first year after clearance, as is the case for the follow-up counts conducted in 2024.
Further research should evaluate the effects of the altered management regime after at least one, but ideally several, complete management cycles. Additionally, annual counts should increase the accuracy of future studies and analyses at the species level could provide useful grassland-specific plant and butterfly conservation implications.