Managing to sustain vertebrate richness in forests of the Pacific Northwest: relationships within stands

Abstract

Many regions confront potentially competing goals: sustaining biological diversity and extracting wood products from forests rich in biological diversity. Forests of the Pacific Northwest are particularly rich in vertebrates. Because little is known of many species, management tactics to sustain vertebrate richness must employ interim surrogates that credibly reflect responses of groups of vertebrates. These tactics should focus on elements of the forest, commonly altered by forest practices, to which groups of species are closely linked. We identify five such elements for forests of the Pacific Northwest: dead and dying trees, downed wood, shrubs, hardwoods (broadleaved, deciduoustrees), and riparian areas. Most forest-dwelling vertebrates in the Pacific Northwest, including those designated "at risk", require one or more of these forest elements. Late-successional forests represent particular mixes of these elements. Each element can be altered in ways that benefit or harm specific groups of species. Any management decision, including taking no action at all, favours some species while disadvantaging others. We report the proportions of the vertebrate fauna associated with the five forest elements, plus early- and late-successional stages for a range of forest types. The nature of relationships with each forest element is quantified by biologically appropriate measurements (e.g., decay state, tree species, snag density, and tree size for cavity sites). Impacts of current practices are summarized and tactics appropriate for maintaining vertebrates are described. Responses of organisms other than vertebrates are noted. Key words: forest practices, Pacific Northwest, vertebrate richness.