Timber harvest is the primary disturbance to streams of Southeast Alaska. Timber management pre-1980 occurred with few rules restricting harvest near streams, leading to degraded habitat in streams near harvested areas. In response, regulations were established in the late 1970's to protect both terrestrial and aquatic resources. Initial best management practices (BMPs) restricted use of heavy equipment and regulated harvest practices, though did not define how close harvest could occur near streams. Trees would be taken directly up to banks, potentially decreasing future sources of large wood and increasing bank erosion. Further, both historical and current harvest through watersheds can have additional effects on streams, including altering catchment hydrology and increasing streambed sedimentation. Understanding how current and historical timber harvest may affect the region's streams is critical for their successful management. In this study, I characterize current condition of streams harvested under the initial BMPs and explore relationships between natural and timber harvest-related landscape factors at local and catchment scales, with results indicating relationships between landscape factors and stream habitat at both scales. Local channel morphology and riparian characteristics were strongly associated with habitat, with smaller median particle sizes detected in streams with harvested vs. unharvested riparian zones. At the catchment scale, timber harvest factors explained more variation than natural landscape factors in measures of large wood abundance and distribution. Results from this work will aid managers of both timber and fisheries industries in protecting and restoring streams and forests of the region.
Read
