An experiment for assessing vertebrate response to varying levels and patterns of green-tree retention

The emphasis of forest management in the Pacific Northwest has shifted recently from the production of timber resources to the maintenance or restoration of biological diversity and ecosystem functioning. New standards and guidelines for management emphasize the retention of forest structures (live trees, logs, and snags) to reduce logging impacts, to enrich reestablished stands with important structural features, and to enhance connectivity across forest landscapes. However, little is known about the effects on wildlife of varying the level and spatial distribution of retained structures in forests of western Oregon and Washington. Replicated and controlled experiments within the Demonstration of Ecosystem Management Options (DEMO) study are beginning to quantify the effects of varying the level and spatial aggregation of green-tree retention during forest harvest on a variety of ecosystem components (e.g., vertebrates, invertebrates, vegetation, fungi), as well as snow hydrology and social perceptions of these types of regeneration harvests. Eight replicate blocks of six experimental treatments have been established on the Umpqua National Forest in Oregon, and on the Gifford Pinchot National Forest and Capitol State Forest in Washington. The objectives of the wildlife studies are to quantify patterns of species richness, evenness, and relative abundance of birds, small mammals, bats, and amphibians before and after harvest to examine short-term treatment responses. Pre-treatment sampling has been completed on all sites, harvest treatments are in progress, and post-treatment sampling has begun. In this paper, we present an overview of our hypotheses and methods, and document the occurrence and relative abundance of species prior to harvest of the study blocks. Long-term studies of vertebrate response, habitat associations, and trophic interactions are planned. Results will inform managers on the consequences of alternative forest management strategies.