Data from: A trait-based approach to assessing resistance and resilience to wildfire in two iconic North American conifers

Ongoing changes in fire activity have the potential to drive widespread
shifts in Earth’s vegetation. Plant traits and vital rates can be
indicators of the ability of individuals to survive fire (resistance) and
populations to persist (resilience) following fire and provide a
method to assess vulnerability to fire-driven vegetation shifts.
In 15 study sites spanning climatic gradients in the southern Rocky
Mountains, U.S.A., we quantified variation in key traits and vital rates
of two co-occurring, widely-distributed conifers (Pinus ponderosa Douglas
ex. P. Lawson & C. Lawson and Pseudotsuga menziesii (Mirb.)
Franco). We used mixed models to explain inter- and intraspecific
variation in tree growth, survival, bark thickness, and seed cone
production, as a function of species, tree life stage (i.e., diameter,
height, and age), average climate, local competition, and site conditions.
P. ponderosa was predicted to survive low-severity fire at a 23% earlier
age than P. menziesii. P. ponderosa had thicker bark and more rapid
juvenile height growth, traits conferring greater fire resistance. In
contrast, P. menziesii was predicted to produce seed cones at a 28%
earlier age than P. ponderosa. For both species, larger individuals were
more likely to survive fire and to produce cones. For P. ponderosa, cone
production increased where average actual evapotranspiration (AET) was
higher and local competition was lower. More frequent cone production on
productive sites with higher AET is an important and underappreciated
mechanism that may help to explain greater resilience to fire in these
areas. Synthesis:  Our analyses indicated that many plant traits
and vital rates related to fire differed between P. ponderosa and P.
menziesii, with trade-offs between investment in traits that promote
individual defence to fire and those that promote recolonization of
disturbed sites. Future changes in fire activity will act as a filter
throughout North American forests, with our findings providing insight
into which individuals and populations of two iconic species are most
vulnerable to future change and offering a framework for future inquiry in
other forests facing an uncertain future.