An Analysis of Late‐Seral Forest Connectivity in Western Oregon, U.S.A.

Abstract

Abstract: Habitat loss and fragmentation due to timber harvest in western Oregon has put wildlife species reliant on late‐seral forest under demographic pressure as available habitat shrinks and local populations become isolated. Few studies have examined the effects of habitat removal and fragmentation on the ability of wildlife to disperse over large areas. We used a spatially explicit population model to examine the effects of landscape patterns on the dispersal success of territorial wildlife species with different dispersal capabilities and home‐range sizes. Simulations of dispersal were conducted on 8.3 million ha of forested landscape in western Oregon, based on forest conditions derived from satellite imagery. We compared dispersal success for baseline conditions of land cover with two alternative landscape patterns: late‐seral forest habitat systematically converted to a younger forest class based on (1) public ownership and (2) the Northwest Forest Plan reserve system. Dispersal success increased with larger dispersal distances and with smaller home ranges ( p < 0.01). Results indicate that the reserve system will not maintain habitat connectivity throughout the landscape for species with relatively short dispersal distances. Patches showing the greatest decrease in dispersal activity following the systematic removal of late‐seral forest habitat were identified as important areas of connectivity.