Managing for all of the parts - what have we learned from studies of larval and adult Lepidoptera in harvested oak-hickory forests?

by

Keith S. Summerville and Robert J. Marquis

Professor (KSS), Department of Environmental Science and Policy, Drake University, 2507 University Ave, Des Moines, Iowa 50311; Professor (RJM), Department of Biology and the Whitney R. Harris World Ecology Center, University of Missouri-St. Louis, St. Louis, Missouri 63121.

Abstract – Lepidoptera (moths and butterflies) are important components of forest ecosystems: they affect tree growth as caterpillars, provide food for higher trophic levels as caterpillars and adults, and are pollinators as adults. Here, we report on the results of two long-term studies of the effects of logging on Lepidoptera in oak hickory forests. In one study, the Missouri Forest Ecosystem Project (MOFEP), caterpillars were used as response taxa and sampling was focused on two dominant tree species, white and black oaks; a second, the Hardwood Ecosystem Experiment of Indiana (HEE) examined the response of adults to alternative harvest levels by sampling with blacklighting. Caterpillar sampling in MOFEP and in an associated chronosequence revealed that clearcutting decreases numbers and diversity of Lepidoptera, landscape effects are subtle but measurable after a single harvest, and that species richness continues to increase even after 300 years following harvest. The impacts were both insect species-specific and host plant species-specific. When using adult moths as response taxa, species composition was resilient to timber harvest under shelterwood management, recovering to the near original condition three years post logging. Richness of pollinator species was largely unaffected by timber management, the herbaceous feeding guild actually gained species under group selection, and dietary specialists decreased in logged stands. Together, these results demonstrate that Lepidoptera communities in oak-history forests respond immediately to logging due to changes in host plant availability, but may also be impacted many years subsequent due to seral changes in forest structure and composition.