Group Selection Edge Effects on the Vascular Plant Community of a Sierra Nevada Old-growth Forest

For an old-growth forest edge in the Sierra Nevada, we quantified the extent of edge effects from a group selection harvest. Across transects from the interior of the old-growth forest through the group selection opening, we quantified changes in resource availability (light, soil moisture, and seedbed) and vegetation composition (cover, richness). We found a steep change in light availability and community composition from the intact old-growth to the group selection. Both parametric and non-parametric multivariate analyses indicated two distinct plant associations, old-growth and group selection, with little indication of an edge association. Understory plant species richness normalized to a total area sampled of 0.25 ha was significantly greater in the group selection (74 species) than in the old-growth (55 species). Chimaphila umbellata and Carex brainerdii were the most abundant species in the old-growth and group selection respectively. Tragopogon dubius was the most abundant of six exotic species found in the group selection while there were no nonnative species found in the old-growth forest.