Influence of Deadwood, Tree-Related Microhabitats, and Forest Structural Features on Saproxylic Arthropod Diversity

Forest composition and structural diversity play a key role in shaping habitat availability and biodiversity, particularly influencing the occurrence of saproxylic species associated with tree-related microhabitats (TreMs). TreMs and deadwood are essential features of forest ecosystems, offering critical habitats for saproxylic arthropods that contribute to decomposition, nutrient cycling, and overall forest resilience. Understanding the complex interactions between forest structures, TreMs, and arthropod communities is crucial for biodiversity conservation and sustainable forest management. This study examines how forest composition, deadwood characteristics, and TreMs influence saproxylic arthropods' diversity in the Black Forest, Germany. Using environmental DNA (eDNA) metabarcoding, we assessed arthropod communities across 135 forest plots with varying degrees of retention. Our findings reveal that specific TreMs, such as cavities, mosses, and insect galleries, were associated with arthropod richness patterns, particularly for Collembola, Hemiptera, and Arachnida. Canopy closure emerged as the most consistent predictor of arthropod richness, while tree-related microhabitats, lying deadwood volume, snag volume, and forest management intensity showed additional taxon-specific associations. These findings reveal that species richness is associated with multiple ecological factors, highlighting the complexity of forest ecosystems. They underscore the need for forest management strategies that preserve deadwood and TreMs, enhance structural heterogeneity, and consider broader indicators of forest naturalness to effectively support arthropod biodiversity.