COS 95-6: Projected avian population responses to 100 years of forest management
Joshua J. Lawler, University of Washington, Nathan H. Schumaker, US EPA, Brad McRae, University of California, Santa Barbara, and Thomas A. Spies, USDA Forest Service Pacific Northwest Research Station.
Animals respond to patterns in their environments at multiple spatial and temporal scales. Even within a single forest, differences in management practices can produce a mosaic of patterns within stands and across the landscape. Although we have begun to understand the effects of the structure and composition of vegetation on some animals at different spatial scales, we know far less about how populations respond to dynamic landscapes. Here, we explored the potential effects of alternative forest-management practices across a variety of land-ownerships in the Umpqua watershed of Coast Range in Oregon over a 100-year period. Using a spatially explicit population model, we simulated populations of Western Bluebirds, Willow Flycatchers, Olive-sided Flycatchers, and Pileated Woodpeckers from 1996 to 2096. We examined the effects of three alternative management policies including federal management as specified in the Northwest Forest Plan, no thinning on federal lands, and increased green-tree retention rates in logged areas. Western Bluebirds, Olive-sided Flycatchers, and Pileated Woodpeckers all responded as expected to the management practices. For example, bluebirds and woodpeckers which rely on larger trees for nesting, benefited from the increased green-tree retention policy. However, the response of Willow Flycatchers to the modeled habitat changes was unpredicted. Despite increases in habitat quality, Willow Flycatcher populations were unable to track the rate of landscape change and declined steadily. Our results emphasize the importance of both the spatial and temporal patterns of landscape change for animal populations.