Ecological foundations of biodiversity: Lessons from natural and managed forests of the Pacific northwest

Fifteen years of research on old-growth and managed coniferous forests have provided sufficient understanding of biodiversity to suggest a basis for ecosystem management. First, natural old forests have a metaphysics-values associated with their existence and function can never be addressed fully with the scientific method alone; we cannot recreate old growth. Second, five processes underly forest development: crown-class differentiation, decadence, canopy stratification, understory development, and development of habitat breadth. Habitat breadth results from fine-scale spatial heterogeneity that produces structural and compositional diversity-tree species diversity, foliage-height diversity, and variety of recurring vegetation site-types. Third, the processes shape trophic pathways, lead to niche diversification, and help to structure fungal, invertebrate, and vertebrate communities. The contribution of each process to niche diversification differs in strength from its contribution to variance in forest structure and composition. Decadence seems the most fundamental, unpredictable, and intractable of the processes. Theoretically, ecosystem management based on these processes can produce landscapes that provide habitat for wildlife associated with late-seral forests, sustainable production of timber and alternative forest products, ecological services such as carbon assimilation and sequestration, economic activity that sustains rural communities, and win-win solutions with good cultural fit to conflicts over land use. Fourth, substantial uncertainty exists in every aspect of ecosystem management. Thus, achieving diverse benefits from forests requires active, intentional, adaptive ecosystem management.