Forest structural changes after tree dieback affect dung beetle communities and dung removal rates

Forest ecosystems are currently experiencing the consequences of climate change, particularly increasing tree damage and mortality due to higher temperatures and longer droughts. This leads to changes in forest structure, with consequences for the abundance, diversity, and composition of organisms, as well as their provision of ecosystem functions. However, relatively little is known about how dung beetles, which are important for decomposition, respond to recent changes in forest characteristics and tree dieback. We monitored dung beetles and dung decomposition in 67 forest plots in Darmstadt, Germany. The structure of these plots varied considerably due to tree mortality caused by several years of drought and heatwaves, as well as former forest management practices in the study region. The total biomass, diversity, and species composition of dung beetles were strongly related to changes in forest structure, such as mean canopy openness, mean diameter at breast height, and forest ground cover. However, they were less related to within-plot structural heterogeneity. Higher dung beetle biomass was related to a higher dung decomposition rate, but changes in dung beetle diversity and community composition did not correlate with dung decomposition. Our results suggest that changes in forest structure result in changes in the biomass, diversity, and composition of dung beetle communities. The relationships between dung beetles and structural heterogeneity were not particularly pronounced. This indicates that the effects of tree mortality on dung beetles and subsequent changes in dung decomposition are mediated by directed shifts in mean forest structure rather than structural heterogeneity.