Assistant professor University of Colorado-Boulder Boulder, Colorado, United States
Abstract: Climate change and decades of fire suppression have increased wildfire activity in the western United States, impacting ecosystem composition and functioning, as well as human well-being. Fire regimes, local climates, and land management practices influence post-fire forest recovery trajectories. In recent decades, increases in the spatial extent of high-severity fires have interacted with hotter and drier conditions to facilitate shifts in post-fire vegetation communities in forests of the western US. These new ecological communities may have different distributions of functional traits. In some circumstances, post-fire forest communities may be better adapted to climate change conditions, as measured by an increase in functional trait values related to drought tolerance (e.g., leaf thickness and root depth) or resistance to and recovery from wildfires (e.g., bark thickness and resprouting ability). However, post-fire shifts in forest composition and species functional traits also have implications for ecosystem functions and services such as aboveground biomass and timber yield.
We use data from the United States Forest Service’s Forest Inventory and Analysis program and a novel database of species-level functional traits for more than 100 tree species in the western US to assess the effect of fire severity, local climatic factors, and forest management regimes on post-fire tree functional traits. We compare forest functional traits related to climate change resistance and ecosystem service provisioning before and after wildfires on land managed by different ownership types for different objectives. We find that forest plots that burned tended to experience shifts in the distribution of their tree functional traits when compared to plots that did not burn: post-fire communities had, on average, higher wood density, lower specific leaf area, and increased resprouting ability. Our results provide new insight into how land management interacts with changing fire regimes to impact forest composition and function across the western United States, informing management that seeks to maintain forest functions and ecosystem services in the context of rapid environmental change.
