Stability in forest lepidopteran communities: how sensitive are pest species to experimental forest management?

We tested how abundance shifts in lepidopteran species might impact two different aspects of moth community structure within managed forest stands of Morgan-Monroe State Forest, Indiana. Significant changes in species abundance and species richness were observed post-harvest. Sudden eruptions in abundance, however, were not observed at the scale of the regional forest moth metacommunity. The form of the species-abundance distribution within most forest stands did not deviate from the best-fit log-normal model across all three sampling years. Abundance shifts thus appeared to be spatially extensive, low density events. Frequency of stands occupied by early seral moths increased significantly post-harvest. Several species with larvae known to be row crop or forage pests were widespread throughout Morgan-Monroe State Forest (Ostrinia nubilialis, Hypsopygia costalis, Noctua pronuba, Helicoverpa zea) 2years post-logging. Potential canopy defoliators were negatively affected by time since harvest even in unmanaged stands suggesting that outbreaks may not be expected as a consequence of harvest disturbance. This suggests that pre-harvest abundance is not a good predictor of a species' resilience to forest management. Importantly, weather-related stochastic changes in abundance might obscure forestry effects.