Macromoth community structure along a 95‐year post‐harvest chronosequence in managed forests of northwest Washington State (U.S.A.), with comparison to old growth forest communities

Abstract

The effects of timber harvest in the moist coniferous forests of western North America are not well documented for ecologically important arthropods such as moths. We assessed the response of macromoth community structure (abundance, sample size‐corrected estimates of species richness and diversity, and overall community composition) to time since deforestation at 20 previously logged sites (1–95 years post‐harvest), and compared the macromoth communities at these stands to four old growth stands. As stand age increased following timber harvest, the number of macromoths captured in ultraviolet light traps increased and the relative abundance of dietary generalists declined, but sample size‐corrected estimates of species richness and diversity did not vary. Macromoth community composition of the youngest stands (<10 years post‐harvest) differed markedly from each other but converged soon thereafter. Macromoth communities at old growth sites featured higher capture rates, lower dominance by dietary generalists, and higher sample size‐corrected estimates of species richness and diversity than at previously logged sites. Community composition profiles for old growth sites differed from all previously logged sites, but the differences were subtle except in comparison to the youngest logged sites. None of the 188 species we sampled were old growth specialists. Our results reveal dramatic initial impacts of deforestation on macromoth communities in moist coniferous forests of western North America. Such effects are largely reversed within two decades post‐harvest but some effects persist for at least 95‐years following logging.