Impacts of timber harvest on adjacent stands of old-growth coast redwood (Sequoia sempervirens) forests

Data collected on nine sites within the Redwood National and State Parks management area were used to determine the depth of influence of conditions created by clear-cut timber harvest on adjacent old-growth stands of Sequoia sempervirens (coast redwood). Results indicate that factors related to stand structure and species distribution, species richness and eveness, and damage to trees by Ursus americanus (California black-bears), were significantly correlated to distance from the timber harvest boundary. Results were applied to the core area model to determine the effective size of old-growth forest preserves, and to make recommendations on the size and function of buffer zones.; Forest structure within old-growth stands adjacent to timber harvest boundaries was altered in several ways by the influence of the induced edge. The height and canopy cover of forest canopy layers, the density of various size classes of trees, and observed crown dieback, exhibited correlations to distance from the timber harvest boundary. Similar correlations were found for several aspects of species distribution including: density of individual species, dominance of major tree species, and the frequency distribution of individuals species. Species richness and habitat heterogeneity (Shannon diversity) were both higher within the old-growth portions of the study sites. Significant reductions in both measures of diversity were found in uncut stands in proximity to the timber harvest boundary. The density of trees damaged by California black bears was also shown to be correlated to distance from the timber harvest boundary, as well as time since harvest, the density of poles sized trees, and the dominance of Sequoia sempervirens.; The depth of influence for variables correlated to distance from the timber harvest boundary ranged from 40 to greater than 200 meters (>3 × tree height). In addition, sites that experienced the longest period of regeneration (∼50 years) still exhibited significant structural and compositional effects related to the timber harvest boundary within adjacent uncut stands. Significant reduction in the effective size of old-growth redwood preserves, as a result of edge effects, was found for all of the study sites sampled.