Comparison of Arthropods Emerging in the Spring from Douglas-fir Litter Between a Mature Stand and a Seed Orchard in Western Oregon

Abstract

The abundances of phytophagous arthropods emerging in the spring from Douglas-fir litter were compared between a 50-year-old, second-growth stand and an adjacent intensively managed seed orchard in western Oregon. Undisturbed litter in the mature stand had higher densities of emergent arthropods, especially Douglas-fir needle gall midges ( Contarinia spp.), other Cecidomyiidae, Formicidae, parasitic Hymenoptera, and oribatid mites than had seed orchard litter. Results of this study indicate that densities of phytophagous arthropods overwintering in litter are normally low relative to densities of microarthropods and that densities of overwintering phytophages may be influenced by litter structure or disturbance, or both.