Trends in Using Wood to Restore Aquatic Habitats and Fish Communities in Western North American Rivers

摘要

Advances in understanding wood dynamics in rivers of western North America have led to several important management trends. First, there is a trend away from using "hard" engineering approaches to anchoring wood in streams toward using "soft" placement techniques that allow some wood movement. Second, wood is being placed in locations where channel form and hydraulics favor stability and where wood is likely to accumulate. Third, there is an increased emphasis on passive recruitment of wood from natural source areas (instead of active placement) where the likelihood that it will enter streams through channel migration, windthrow, and landslides is high. Fourth, restoration targets for wood loads are incorporating landscape-scale objectives; thus, managing wood to emulate the spatial and temporal variability produced by natural disturbances is replacing fixed prescriptions for wood in individual reaches. Predicting the effects of wood restoration on individual fish populations in western North America is problematic because local biophysical conditions generate so much experimental noise that it is rarely possible to partition the effects of wood restoration from other sources of variation. Development of appropriate monitoring techniques, combined with a regional network of experimental catchments that include restored and unrestored streams, would help track changes in population status and gauge the effectiveness of wood restoration efforts.