The Ecology and Management of Wood in World Rivers

Influence of Wood on Aquatic Biodiversity

Steven M. Wondzell and Peter A. Bisson


Abstract.—We review published literature examining the role of wood in mediating biodiversity in aquatic ecosystems, identifying the components of biodiversity, taxonomic groups, and scales that have been studied, and highlight gaps in existing knowledge. The components of biodiversity most frequently studied include species diversity (or richness) of macroinvertebrates and fishes, structural complexity within habitat units, and the diversity of habitats found in a stream reach. Many of these studies show that large wood increases biodiversity by providing stable, hard substrates for colonization by periphyton and macroinvertebrates; by increasing microhabitat complexity; and by shaping channel morphology by controlling patterns of erosion and deposition in stream reaches. The abundance of wood in channels, as well as its functional role, varies greatly in longitudinal, lateral, and vertical dimensions along the river corridor. The influence of wood on community structure and ecosystem processes also varies across these dimensions and from stream headwaters to river mouths and nearshore marine environments. Thus, wood can influence biodiversity at all of these scales. Numerous studies, however, have failed to show an effect of wood on biodiversity. These conflicting results illustrate that wood abundance, its functional role in streams, and its influence on biodiversity depend on a variety of factors, and it is the total effect of all these factors, not simply the presence of large wood, that determines patterns of biodiversity.