Arboreal invertebrate responses to varying levels and patterns of green-tree retention in northwestern forests

Canopy arthropods play an important role in forest ecosystems and are sensi tive to anthropogenic disturbances. The DEMO (Demonstration of Ecosystem Ma nagement Options) study investigates the influence of varying levels and pa tterns of green-tree retention on diverse elements of northwestern forest e cosystems. In this paper we review the literature on forest management effe cts on canopy arthropods and describe research in progress on the response of arboreal arthropod communities to retention harvests in the Pacific Nort hwest. Pre-treatment foliage was pruned and canopy arthropods collected fro m dominant overstory and understory vegetation within six treatment units i n eight experimental blocks in western Oregon and Washington. Significant p re-treatment differences in abundance were found among blocks and treatment s for several taxa in the overstory. Block-level differences reflect natura l variation in the geographic distribution of arthropod taxa. Differences a mong treatment units may reflect the influence of local variation. Followin g harvest treatments, we expect to see changes in arthropod richness, abund ance and functional group organization in dominant overstory and understory canopies reflecting the influence of magnitude and pattern of green-tree r etention.