Climate is more influential to vegetation green-up than factors that contribute to erosion following high-severity wildfire

<p>Background</p> <p>In the southwestern United States, post-fire vegetation recovery is increasingly variable in forest burned at high-severity. Many factors, including temperature, drought, and erosion, can reduce post-fire vegetation recovery rates. Here, we examined how post-fire precipitation variability, topography, and soils influenced post-fire vegetation recovery in the southwestern United States as measured by greenness. We modeled relationships between post-fire vegetation and these predictors using Random Forest and examined changes in post-fire normalized burn ratio across fires in Arizona and New Mexico. We incorporated growing season climate to determine if year-of-fire effects were persistent during the subsequent five years or if temperature, water deficit, and precipitation in the years following fire were more influential for vegetation greenness.</p> <p>Results</p> <p>We found reductions in post-fire greenness in areas burned at high-severity when heavy and intense precipitation fell on more erodible soils immediately post-fire. In <a>highly erodible</a> scenarios, when accounting for growing season climate, coefficient of variation for year-of-fire precipitation, total precipitation, and soil erodibility decreased greenness in the fifth year. While the effects of year-of-fire factors related to erosion were significant, they were small, and the variability explained by growing season vapor pressure deficit and growing season precipitation were significantly greater.</p> <p>Conclusions</p> <p>Our results suggest that while the factors that contribute to post-fire erosion and its effects on vegetation recovery are important, at a regional scale, the majority of the variability in post-fire greenness in high-severity burned areas in southwestern forests is due to climatic drivers such as growing season precipitation and vapor pressure deficit. Given the scale of area burned at high-severity, the likelihood that high-severity burned area will continue to increase, and the potential for more post-fire erosion that can result in different vegetation trajectories, quantifying how these factors alter the trajectory of greenness and what that means in terms of ecosystem development is central to understanding how different ecosystem types will be distributed across these landscapes with additional climate change.</p>