A chronosequence of vegetation change following timber harvest in naturally recovering coast redwood (Sequoia sempervirens) forests
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The management of second-growth coast redwood (Sequoia sempervirens) forests for the purpose of restoration and ecological conservation is a growing trend. However, little is known about the long-term regenerative potential of this forest type in the absence of postharvest management techniques such as thinning and planting. Data were collected on a chronosequence of second-growth sites (18 to 127 years) and three old-growth reference sites in order to characterize changes in stand structure and composition over time. A total of 360 plots on 18 sites with minimal post-harvest treatment were sampled in the central range of the coast redwood forest in California in order to compare stand conditions between post-harvest age groups.
One-way ANOVA with Bonferroni post-hoc analyses indicated that stand density, canopy cover, and species richness approached old-growth conditions within 40 to 80 years. Total basal area and the mean maximum diameter of S. sempervirens stems continued to increase up to 127 years. Cover of non-native species declined with stand age to the extent that no nonnative species were recorded in stands older than 60 years. The cover of old-growth associated understory species was highest on the oldest second-growth stands and in some cases reached levels statistically equivalent to the old-growth references sites between 40 and 100 years. Results suggest that coast redwood forests are highly resilient to human disturbance and will recover naturally over time in the absence of post harvest management.