Forests provide a wide variety of ecosystem services such as timber production, biodiversity conservation, carbon sequestration, pollination, and recreation. Therefore, it is important to understand how and whether all components of the forest community are resilient to environmental change. Small-to-medium scale disturbances, such as the canopy gaps associated with even- and uneven-aged silviculture, may enhance the resilience of a forest at larger spatial scales by increasing functional diversity, even if small-scale functional diversity is reduced in the short term. We compared the effects of even- and uneven-aged silviculture on the taxonomic and functional diversities of moths (macromoths), longhorned beetles, and birds. These taxa were sampled for three years before, and up to six years after, a replicated forest management experiment in south-central Indiana (the Hardwood Ecosystem Experiment). We computed the species richness, species evenness, Shannon diversity, functional richness, functional evenness, and functional divergence of each taxon (except birds, where the data were limited to species presence/absence) in each management replicate and year, as well as each individual forest stand and year. We expected diversity to decrease in harvested stands while increasing across the managed forest landscape.
Results/Conclusions
We recorded a total of 378 moth species, 121 longhorned beetle species, and 73 bird species over multiple seasons of sampling. The effects of forest management on diversity varied by taxon, management system, and time since harvest. Moths declined in taxonomic diversity, but not in terms of functional diversity. However, functional groups that typically occur in open areas were captured in the forest matrix, especially in the uneven-aged compartments. Longhorned beetles exhibited a short-term increase in species richness after harvest. Birds increased in both species and functional richness after harvest, although the increase in functional richness was only significant at the management compartment scale. Although each taxon differed in its response to disturbance, and some species were lost from the area, it is notable that functional diversity was either not affected or increased. This suggests that these taxa are resilient to disturbance when disturbance is viewed through the lens of functional diversity. To enhance multi-functional resilience, forest managers should seek to create a landscape mosaic that includes both early-successional and mature forest habitats.