Moving in three dimensions: effects of structural complexity on occurrence and activity of insectivorous bats in managed forest stands

1. Forest management determines to a large degree the three‐dimensional arrangement of the vegetation in production forest systems and hence has an essential influence on habitat quality for wildlife. We investigated the effects of forest structure on occurrence, activity and species composition of European bats, an ecologically important group of vertebrates known to be affected by the physical clutter of vegetation. 2. Species composition and activity of bats were assessed with acoustic monitoring on 50 one‐hectare experimental plots in a biosphere reserve in Germany. Three‐dimensional forest structure was assessed by Light Detection and Ranging (LiDAR), and a set of 20 mathematically derived and fine‐grained structural parameters with a minimum of collinearity was used for a quantitative description of the vegetation structure. 3. Occurrence and activity of bats were positively associated with the structural parameters canopy height, standard deviation of the canopy surface roughness and edge fraction, indicating older forest stands with patches of different vegetation heights. In addition, species composition in differently managed forest stands was significantly influenced by the relative proportion of structural parameters. Species of one functional group, sharing similar adaptations in wing morphology and foraging strategy, showed similar associations with three‐dimensional structural parameters. In addition, we found species‐specific structural parameter associations explaining the occurrence and activity levels of individual species in differently managed production forest types. 4. Synthesis and applications. High‐resolution LiDAR data are an important tool to assess structural habitat suitability for bat species. Our data revealed that bat occurrence and activity increases with structural heterogeneity in managed forest stands. Given, that bats provide an essential ecosystem service through top‐down control of herbivorous insects, increasing stand structural heterogeneity through management practices (e.g. selective harvesting) is a very effective strategy to assure vital ecosystem functioning in production forest systems.