Management strategies to increase stand structural diversity and enhance biodiversity in coastal rainforests of Alaska Robert L. Deal* USDA Forest Service, Pacific Northwest Research Station, 620 SW Main Street, Suite 400, Portland, OR 97205, USA ARTICLE INFO Article history: Received 9 January 2007 Accepted 12 March 2007 Available online 3 May 2007 Keywords: Biodiversity Forest management Old-growth forests Stand structure Partial cutting Red alder Southeast Alaska Sitka spruce Western hemlock ABSTRACT Coastal rainforests of southeast Alaska have relatively simple species composition but complex structures with high diversity of tree ages, sizes and forest canopy layers, and an abundant understory plant community. Wildlife and fisheries resources also play an important role in the ecological functioning of forest and aquatic systems. Clearcutting has greatly altered these forest ecosystems with significant decreases in structural diver- sity of forest stands and greatly reduced wildlife habitat. This paper synthesizes informa- tion on management options in older forests that have never been actively managed, and in younger forests to increase diversity of stand structures and their associated effects on biodiversity. Light to moderate levels of partial cutting in old-growth forests can maintain the original diversity of overstory stand structures and understory plant communities. In younger forests that develop after clearcutting, mixed alder-conifer stands provide more heterogeneous structures and significantly higher understory biomass than in pure conifer forests. Research has shown that red alder increases diversity and abundance of under- story plants, and provides forage for deer and small mammals. Results also show a clear linkage between alder and improved invertebrate diversity in aquatic systems. A combina- tion of light partial cutting in older forests along with inclusion of red alder in conifer-dom- inated forests could provide the greatest amount of diversity and maintain the complex stand structures that are an important component of these forest ecosystems. Ó 2007 Elsevier Ltd. All rights reserved. 0. Introduction Southeast Alaska is a coastal temperate rainforest region with steeply rising coastal mountains and densely forested islands. This region contains large areas of old-growth for- ests and these forests are renowned for their scenic quality, fish and wildlife-habitat and timber resources. The Tongass National Forest encompasses most of this region with nearly 7 million hectares and is the largest national forest in the United States. The Tongass recently completed a more than decade long management planning effort that identified five focus issues including wildlife viability, fish habitat, alterna- tives to clearcutting, socio economic considerations and karst and cave resources (TLMP, 1997). Thus, forest managers in the region have been working to develop management strategies that will provide wood resources to the local econ- omy without compromising scenic quality, or aquatic and wildlife habitat. Forest managers are interested in developing silvicultural solutions to enhance options for multiple resource management. Forest practices that could maintain or increase biological diversity are crucial for forest management. 0006-3207/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2007.03.014 * Tel.: +1 503 808 2015; fax: +1 503 808 2020. E-mail address: rdeal@fs.fed.us BIOLOGICAL CONSERVATION 137 (2007) 520 – 532 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/biocon