Long-Term Trends in Fish Habitat and Effectiveness of Buffer Strips in Southeast Alaska

The riparian buffer strip provisions for private timberlands in Southeast Alaska are intended to protect fish habitat, maintain ecological functions, and facilitate the sustained yield of forest products. Although scientific knowledge informed the development of these best management practices (BMP), there is continuing debate about the effectiveness of modern management schemes to protect and sustain ecological values over the long-term. To address this concern, the timber industry and state agencies in Alaska implemented (began 1994) long-term effectiveness monitoring of 17 watersheds which have only been managed for timber harvest under modern forest practice rules.  Our findings indicate the response to logging is variable and is probably related to a number of factors, including time since timber harvest, natural variability in physical conditions among sites, and the timing of monitoring relative to the occurrence of storm disturbance events. For example, at many sites there is a pulse in large wood (LW) recruitment within several years after timber harvest that is followed by a decade long decline in recruitment rate.  In some cases this increase in LW supply correlates with an increase in pool frequency shortly after timber harvest that continues on an increasing trend more than a decade after logging. We found that only a small proportion of the post-harvest LW recruits are functioning to form habitat during the first decade after logging, therefore we predict the observed habitat trends will probably continue for several decades. These findings suggest that buffer strips similar to those in this study have not prevented logging related changes; rather they functionally augment natural riparian processes that form new habitat and are likely to sustain the ecological values intended by the BMPs.