Data from: The 15-year post-treatment response of a mixed-conifer understory plant community to thinning and burning treatments

Disturbance is central to maintaining diversity in forest ecosystems. In
the dry forests of the western United States, over a century of fire
exclusion has altered the fire regimes of these forests, resulting in high
fuel loads and a loss of plant diversity. Mechanical thinning and
prescribed fire are widely used to restore structural complexity and
species diversity in many western U.S. forests. While studies have shown
that the reintroduction of fire into these forests initially promotes
plant diversity, there is limited information on the persistence of this
effect. We evaluated the effects of thinning and burning treatments on the
understory plant community fifteen years after treatment in an old-growth,
Sierran mixed-conifer forest. Using a full-factorial design, including
three levels of thinning and two levels of burning, we found mechanical
thinning and prescribed fire reduced litter depths and increased the
availability of bare ground, resulting in an initial increase in herb
cover. However, fifteen years after treatment, litter depths and shrub
cover increased, resulting in a more homogenous understory community and a
loss of herb cover. Overall, our results suggest that while thinning and
burning treatments initially promote herbaceous plant cover, these effects
are short lived in the absence of a second disturbance.