Fostering deadwood enrichment in managed forests – The importance of tree species and sun exposure for saproxylic species

Abstract

Central European forests have been shaped by more than 2000 years of human exploitation. During this time, the increasing requirement of timber led to significant structural changes within the ecosystem. Because of declining deadwood amounts, numerous saproxylic species become extinct or threatened. Yet, various strategies of deadwood enrichment have been developed since the 1990th mainly focused on a quantitative increase. As recently shown, also microclimate and tree species are important drivers of saproxylic communities. However, it remains unclear how active forest management can increase deadwood most efficiently. For this study, we exposed a total of 108 logs of six common tree species (Abies alba, Carpinus betulus, Fagus sylvatica, Pinus sylvestris, Populus tremula, Quercus sp.) under three different treatments of sun exposure (sun exposed on a forest meadow, shaded by forest canopy, experimentally shaded). Analaysing two years of sampling, we tested the influence of tree species and sun exposure on a-, ß-, and y-diversity of saproxylic beetles, spiders, and wood-inhabiting fungi. Diversity of saproxylic beetles and wood-inhabiting fungi was determined by both, tree species and sun exposure. However, diversity of spiders was determined by sun exposure only. The results of our study indicate that conservation strategies for deadwood-dependent organisms should not only focus on the amount, but more strongly on providing a high diversity of deadwood.