Response of In‐Stream Wood to Riparian Timber Harvesting: Field Observations and Long‐Term Projections

Abstract

AbstractIn‐stream large wood (LW) is a prominent feature of forested aquatic ecosystems worldwide, yet many questions remain regarding the response of LW patterns to riparian timber harvesting. This paper proposes a conceptual model of wood storage response to harvesting and combines a unique 45 year record of LW with output from a wood budget model to examine changes in LW characteristics and long‐term impacts from riparian logging. The wood budget model is used to predict the timing of minimum storage and assess storage recovery time scales under three scenarios representing different spatial harvest patterns and harvest severity. The impact of harvesting is reflected in the field data: Reductions in wood volume and the loss of large logjams were apparent in channel areas adjacent to logged zones, but wood volume changed less where a riparian buffer was retained. Results from the budget model indicate that impacts from timber harvesting are projected to continue beyond 150 years while riparian forests recover. Minimum modeled LW loads are projected to be nearly 50% lower than preharvest conditions, and minimums occur 50 to 80 years postharvest, depending on the influence of LW transport and proximity to harvesting. In evaluating the conceptual model, harvesting configuration and severity are not found to greatly impact time to minimum storage and recovery, but do impact the magnitude of LW losses. Similar to other studies, these findings indicate that riparian harvesting has an impact beyond the century scale, with major implications for stream channel functionality and aquatic habitat.