Comparing the responses of larval and adult lepidopteran communities to timber harvest using long-term, landscape-scale studies in oak-hickory forests

Lepidoptera (moths and butterflies) are important components of forest ecosystems; they affect tree growth and influence nutrient cycling as caterpillars, provide food for higher trophic levels as caterpillars and adults, and are pollinators as adults. Here, we report on and compare the results of two long-term studies of the effects of logging on Lepidoptera in oak hickory forests. In one study, the Missouri Ozark Forest Ecosystem Project (MOFEP), caterpillars were used as response taxa. Sampling via observation without removal focused on larvae found on leaves of two dominant tree species, Quercus alba and Q. velutina, in alternative harvest regimes. In a second, the Hardwood Ecosystem Experiment of Indiana (HEE), we 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, year effects were as important in influencing caterpillar assemblages as the harvest per se, and that species richness of caterpillars continued to increase each year post-harvest. 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 treatment. Communities in patch cut or clear cut stands were slower to recover, and appeared to develop novel communities relative to their pre-harvest condition. A late spring frost decreased abundance and species richness of caterpillars, while a severe drought impacted adult lepidopterans, depressing species richness in patch cut stands to a greater degree than in control or shelterwood cut 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 stochastic year effects and seral changes in forest structure and composition.