Forest structural changes affect dung beetle communities and dung removal rates.

Abstract

Forest ecosystems are shaped by the consequences of management activities, as well as through an increase in tree damage and mortality caused by climate change. These drivers lead to alterations in forest structure, affecting 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 ecosystem functioning, respond to recent changes in forest characteristics. 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 strongly corresponded to changes in forest structure, such as mean canopy openness, mean tree diameter at breast height, and forest ground cover. However, they were less related to within-plot environmental 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 forest management and tree mortality on dung beetles and subsequent changes in dung decomposition are mediated by directed shifts in mean forest structure rather than structural heterogeneity.