Data from: Increases in understory plant cover and richness persist following restoration treatments in Pinus ponderosa forests

A combination of forest thinning followed by prescribed burning is widely
applied in the western US to increase ecosystem resistance and resilience
to disturbances. Understory plant community responses may be driven both
by management treatments and climatic factors. Thus, responses to
treatments during a 20-year megadrought have implications for the role of
management in fostering adaptive capacity to climate change. We used a
network of five sites (600 plots) spanning an environmental gradient in
ponderosa pine (Pinus ponderosa) forests of the American Southwest, an
ecosystem that is broadly distributed and actively managed throughout the
western US.  We used repeated long-term monitoring data to
quantify plant community responses to treatment 1-5, 6-10, and >10
years post-implementation. Specifically, we focused on the effects of
treatment and abiotic conditions on native and nonnative plant cover and
species richness, and on the proportion of native species with northern
(cool-mesic) biogeographic affinities. Overall, thinning and prescribed
burning nearly doubled native cover and increased native species richness
by about 50% relative to untreated controls. These effects persisted for
over a decade after treatment, even under the influence of significant and
persistent drought. Cover and richness were also greater on intermediate
to wet sites. Finally, native species with northern biogeographic
affinities were reduced for up to five years after treatment relative to
those with southern (warm-xeric) affinities, and in dry years, indicating
that both management and interannual climate variability may foster shifts
in plant communities that are more resilient to a warming climate.
Synthesis and applications: In ponderosa pine forests of the American
Southwest, tree thinning followed by prescribed burning will generally
promote restoration goals of increasing resilience to climate change by
enhancing the diversity and abundance of native understory plant species,
even during a persistent 20-year megadrought.