Abstract
Assessment of forest recovery following disturbance is enhanced by the use of biological indicators. One such indicator, the abundance of understory species, was examined in coast redwood (Sequoia sempervirens) forests using non-metric multiple dimensional scaling (NMDS) and indicator species analysis (ISA). Randomly distributed 10 m diameter circular plots were employed to record the abundance of all understory species across three treatments: actively managed (0 - 45 years since harvest); mature second-growth (~80 - 120 years since harvest); and unharvested old-growth stands. NMDS with perMANOVA analysis signified separation between treatments with the shade tolerant herbaceous species Trillium ovatum, Viola sempervirens, and Oxalis oregana positively correlated with mature second-growth and old-growth treatments. ISA supported the inclusion of T. ovatum, with the addition of Prosartes hookerii, as indicators of mature second-growth and old-growth. Both NMDS and ISA specified associations for Ceanothus thyrsiflorus and Stachys bullata with actively-managed stands. Occurrence of non-natives was low across treatments, though significantly higher on actively managed stands, with the shade intolerant invasive plants, Cortaderia sp. and Myosotis latifolia, occurring exclusively in actively-managed sites.
Highlights
Reestablishment of herbaceous plants may provide an effective indicator of recovery following logging in coast redwood (Sequoia sempervirens) forests, where understory species are dependent on low levels of disturbance and closed canopy conditions (Runkle, 1982)
The objective of this study was to analyze the abundance of individual understory species in response to logging history, with the hypothesis that shade tolerant herbaceous species would be more abundant in old-growth and mature second-growth compared to actively managed stands
The cover of T. ovatum, V. sempervirens, and O. oregana were all positively correlated along the horizontal axis NMDS1 in the direction of the mature second growth and old-growth clusters
Summary
Russell turbance in a variety of ecosystems (Andersen & Sparling, 1997; Coelho et al, 2009; Egli, 2011; Pander & Geist, 2013) Such indicators are identified based on their association with a specific forest type, and dependence on inherent habitat conditions (Mcclelland & Mcclelland, 1999; Drever et al, 2008; Egli, 2011). Reestablishment of herbaceous plants may provide an effective indicator of recovery following logging in coast redwood (Sequoia sempervirens) forests, where understory species are dependent on low levels of disturbance and closed canopy conditions (Runkle, 1982). The canopy of coast redwood forests is rarely disturbed by natural stand-replacing events, and provides the conditions necessary for dependent herbaceous species to thrive (Van Pelt & Franklin, 2000). The use of herbaceous understory species as indicators is an attractive option, as much of the plant diversity in coast redwood forests is found in the understory, and many of these species are known to be sensitive to logging (Gilliam, 2007; Loya & Jules, 2008; Russell & Michels, 2010)
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