Data from: Warming, soil moisture, and loss of snow increase Bromus tectorum's population growth rate

Climate change threatens to exacerbate the impacts of invasive species. In
temperate ecosystems, direct effects of warming may be compounded by
dramatic reductions in winter snow cover. Cheatgrass (Bromus tectorum) is
arguably the most destructive biological invader in basins of the North
American Intermountain West, and warming could increase its performance
through direct effects on demographic rates or through indirect effects
mediated by loss of snow. We conducted a two-year experimental
manipulation of temperature and snow pack to test whether 1) warming
increases cheatgrass population growth rate and 2) reduced snow cover
contributes to cheatgrass' positive response to warming. We used
infrared heaters operating continuously to create the warming treatment,
but turned heaters on only during snowfalls for the snowmelt treatment. We
monitored cheatgrass population growth rate and the vital rates that
determine it: emergence, survival and fecundity. Growth rate increased in
both warming and snowmelt treatments. The largest increases occurred in
warming plots during the wettest year, indicating that the magnitude of
response to warming depends on moisture availability. Warming increased
both fecundity and survival, especially in the wet year, while snowmelt
contributed to the positive effects of warming by increasing survival. Our
results indicate that increasing temperature will exacerbate cheatgrass
impacts, especially where warming causes large reductions in the depth and
duration of snow cover.