Effect of forest management on temperate ant communities

Abstract

Abstract Human management of ecosystems can have direct or indirect effects on species communities. How species communities are affected by management is a key question in ecology and nature conservation. As keystone taxon, changes in ant communities can have sustained consequences for entire ecosystems. In forests, management has been shown to have an overall negative effect on ant communities in tropical and a positive effect in boreal forests. However, in temperate forests, it is unclear what components of forest management affect ant communities and how. This study explores the direct and indirect effects of forest management on the taxonomic and functional diversity of ant communities in 150 temperate forest stands in three regions in Germany. Using a multi‐model inference approach and structural equation models, we analyzed the effects of 18 variables, including variables of forest management, forest structure, arthropod diversity, and biomass, as well as abiotic factors, on ant species richness, abundance, and functional trait diversity (Rao's Q ) based on morphological ( FD M ) and life‐history traits ( FD LH ). In total, we found 28 ant species occurring on 120 plots. Main direct effects of forest management on ant abundance and species richness were caused by tree species selection, measured as dominant tree species. The main positive indirect effect was mediated by a reduced canopy cover with an increasing proportion of oak and pine, resulting in a higher temperature amplitude. Due to the low number of species in two regions, we analyzed functional diversity for the most ant species diverse region only. FD LH was affected positively by tree harvesting and negatively by structural complexity. FD M showed no response to forest management, potentially due to the low morphological diversity of temperate forest ants. Our results show that forest management practices in temperate forests strongly impact ant community structure. This can be beneficial for ants if management reduces the canopy cover, either by tree harvesting or by changing the tree species composition toward shade‐intolerant tree species. To promote ant diversity as key taxon for maintaining ecosystem processes in forest ecosystems, we suggest to integrate forest stands with more open and warmer conditions in future management strategies.