Evaluating forest clear-cuts as alternative grassland habitats for plants and butterflies

Abstract

Temperate semi-natural grasslands in Europe and East Asia have been rapidly declining and their conservation is urgently required. Although recent studies have indicated the importance of clear-cuts as alternative habitats for grassland butterflies, there is paucity of studies that directly compare biodiversity and habitat quality between grasslands and clear-cuts using multiple taxa. In this study, we compared the plant and butterfly richness between grasslands and clear-cuts, with a focus on the distribution of butterfly resources (nectaring flowers and host plants) and endangered plant and butterfly species, in a cool temperate area of central Japan. We established three or six transects in five grassland and five clear-cut sites, and measured the richness of plants and butterflies and environmental variables such as vegetation height and coverage at both transect and site levels. At the site level, there were no differences in the richness of all plants, butterflies, and butterfly host plants, but there were significant or marginal differences in the richness of endangered plants, butterflies, and butterfly host plants. Almost all endangered plants and butterflies were found in the overall grasslands, but only half of the endangered butterfly species were observed in the overall clear-cuts. At the transect level, species richness of endangered plants and butterflies peaked at an intermediate vegetation height. Our results indicate the primary importance of existing semi-natural grasslands and the necessity of management when the vegetation becomes too high. We recommend active creation of clear-cuts near or between the existing grasslands, so that clear-cuts can provide source or backup populations and act as stepping stones to connect the isolated grassland populations.