Authors: Heinrichs, Steffi; Leidinger, Jan;Weisser, Wolfgang W.;Schall, Peter;

Diversifying forests is regarded beneficial for productivity, stability, and biodiversity. In Central Europe, mixed forests with the naturally dominating European beech are currently promoted. However, effects of tree species diversity can vary among species groups and can lead to shifts in species composition challenging natural communities. By combining 41 mature forest stands of pure beech, beech/oak, beech/spruce and beech/pine, we investigated the effect of distinct combinations of these forest types on gamma-diversity of 12 species groups ranging from vertebrates to belowground fungi. Using a resampling approach, we searched for landscapes that integrate overall multidiversity and the diversity of beech forest specialists.
Besides tree species identity effects, we found that highest gamma-multidiversity was reached in virtual landscapes exclusively composed of the three mixed stand types, while landscapes of pure beech forests were least diverse. The diversity of rare species followed this pattern. Pure beech forests, however, best conserve beech forest specialists of different fungi groups that were most sensitive to admixing other tree species to pure beech forests. Thus, landscapes favoring multidiversity and rare species may not be able to conserve the natural species composition of beech forests to the same degree, indicating trade-offs when it comes to defining conservation priorities.