Publication Date

Spring 2020

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


William Russell

Subject Areas

Environmental studies


Restoration of late seral features in second-growth Sequoia sempervirens forests is an important management concern, as so little of the original old-growth remains. The abundance of herbaceous species provides a metric for assessing recovery in these forests where associated understory plants are adapted to closed canopy conditions. Data were collected using a stratified random sampling design across three treatments: mechanically thinned second-growth, un-thinned second-growth, and old-growth reference stands. Pairwise PerMANOVA indicated greater abundance and diversity of native herbs in old-growth and un-thinned second-growth compared to thinned stands, as well as higher measures of canopy cover, basal area, and dominance of S. sempervirens. Thinned plots exhibited lower stand density than un-thinned stands but also higher abundance of non-native herbs. Non-metric multidimensional scaling suggested that un-thinned sites were more similar to old-growth than thinned sites in regard to understory composition and abundance, and indicator species analysis returned a suite of indicator species shared between un-thinned plots and old-growth plots while thinned plots shared one indicator with old-growth. In addition, both old-growth and un-thinned second growth sites were dominated by residual species, while thinned plots were dominated by invader species. These results suggest that while mechanical thinning of second-growth S. sempervirens stands may provide temporary effects to stand structure and composition, these treatments do not support the recovery of late seral understory species.