Urbanization Effects on the Community Structure of Saproxylic Arthropods in Warm‐Temperate Japan

Saproxylic arthropods play a key role in forests by decomposing wood and cycling nutrients within detritus food chains. While urbanization generally causes declines in biodiversity and abundance, its effects on saproxylic arthropods remain poorly understood. We examined saproxylic arthropod communities across various forests, ranging from fragmented urban forests to large forests in woodland areas and from secondary deciduous coppice forests to evergreen broadleaf old‐growth forests. Diversity and abundance were analyzed for the entire community, functional types, and individual species. The results indicated that urbanization was an important factor, whereas local factors such as evergreen tree dominance and deadwood accumulation were not. The responses of diversity and abundance to urbanization varied depending on the metrics used, such as ground area, deadwood volume, or cumulative number of individuals. Overall, when analyzed by ground area (i.e., plots), urban communities were characterized by a high number of individuals concentrated in a few species, mainly facultatively saproxylic species. Rarefaction curves based on the cumulative number of individuals revealed that forests in woodland landscapes supported significantly higher species richness than those in urban landscapes. However, surprisingly, when analyzed per unit of deadwood volume, urbanization generally increased both the abundance and species richness of saproxylic arthropods.