Leaf litter arthropods show little response to structural retention in a Central European forest

Decomposition of leaf litter is a central process of energy and nutrient cycling in forests, in which arthropods hold important roles. Thus, safeguarding the diversity of organisms including arthropods is increasingly being considered in contemporary forestry, not least to facilitate continued ecosystem functioning. Retention forestry tries to achieve biodiversity conservation by preservation of tree structural elements such as deadwood and tree microhabitats to provide more heterogeneous habitat. Leaf litter arthropods are, however, only indirectly connected with tree structure, which raises the question if and how the currently practised retention forestry influences the leaf litter arthropod community. As the leaf litter arthropod community includes a very diverse range of taxa that is challenging to identify morphologically, we sampled environmental DNA from leaf litter on 66 plots in the Black Forest in southern Germany that were distributed over gradients of forest and landscape features and differed in forest management intensity. We found that the richness of operational taxonomic units, a surrogate for species, was not related to forest structure but tended to increase with recent harvest intensity (which did not exceed a medium harvest intensity on our plots). Community composition was related to the share of coniferous trees present on a plot, and to a lesser extend to elevation and leaf litter coverage. Our results indicate that the leaf litter arthropod community is not responsive towards different degrees of forest structural changes introduced by management as long as the forest type is retained.