Metabarcoding reveals time after tree death as main driver of diversity and composition of invertebrate communities in deadwood

Increasing the availability of deadwood habitats to protect saproxylic biodiversity is a key objective of forest nature conservation. However, most knowledge about which factors affect invertebrate biodiversity is limited to beetles, while for other taxa, little is known about how deadwood object and forest stand scale characteristics affect communities. We analysed invertebrate samples from closed emergence traps taken 2, 4, 6, and 8 years after placing logs of 13 different tree species in nine forest stands using metabarcoding. Across all years, we found more than 4000 unique invertebrate Barcode Index Numbers (BINs), which can be used as proxy for species, excluding those of beetles and true bugs. We found a significant influence of time after tree death for BIN richness of 14 out of 15 selected groups. Increased forest stand conifer share and angiosperm deadwood at the object scale were positively related to BIN richness of five groups. Variation partitioning emphasized the importance of time after tree death for community composition of most groups. Conifer share affected mainly communities of species living at the deadwood-ground interface and spatial distance between stands affected weak dispersers with specific habitat requirements. Deadwood tree species did not explain community composition for any group. Our results highlight the importance of diverse deadwood habitats for invertebrate biodiversity even beyond beetles. Species conservation efforts aimed at promoting saproxylic biodiversity across scales should therefore foster a supply of deadwood at various decay stages to provide high diversity of habitats and food resources.