Leave islands as refugia for low-mobility species in managed forest mosaics

Abstract

In recent years, forest management in the Pacifi c Northwest has shifted from one based largely on resource extraction to one based on ecosystem management principles. Forest management based on these principles involves simultaneously balancing and sustaining multiple forest resource values, including silvicultural, social, economic, and ecological objectives. Leave islands, or green-tree retention clusters, have been proposed as an alternative silvicultural strategy designed to sustain the ecological integrity and biological diversity within intensively managed forests. However, pertinent questions regarding the relationship of the physical structure of leave islands to their associated microclimates, fl ora, and fauna remain largely unanswered. We evaluated the effectiveness of three sizes of leave islands (0.1-, 0.2-, and 0.4-ha) within a thinned forest matrix relative to thinned and unthinned forest in providing refugia for low-mobility, ecologically sensitive species one to fi ve years following forest thinning. Specifi cally, we examined differences in microhabitat and amphibian, mollusk, arthropod, and vascular plant abundance and diversity with respect to the size of leave islands in managed forests. By determining habitat correlates of species and functional group occurrence, we envision that this study will provide vital information regarding aggregated green-tree retention in managed forest landscapes. Our results indicate that there are treatment eff ects of forest thinning and leave islands relative to microclimate and some aspects of amphibian and arthropod density, and vascular plant diversity and ground cover. Th ese results suggest that leave islands may represent an effective sustainable forest management strategy by providing shortterm refugia for some species in managed forests of the Pacific Northwest, U.S.A.

Parent Publication

• Density management in the 21st century: west side story

Citation

Wessell-Kelly, Stephanie J.; Olson, Deanna H. 2013. Leave islands as refugia for low-mobility species in managed forest mosaics. In: Anderson, P.D.; Ronnenberg, K.L., eds. Density management in the 21st century: west side story. Gen. Tech. Rep. PNW-GTR-880. Portland, OR: US Department of Agriculture, Forest Service, Pacific Northwest Research Station: 123-123.