Evaluating the impact of multiple stressors on vegetation succession after wildfire

Abstract

Succession has been studied since the early days of ecology, yet it is uncertain how the properties of succession are affected by stressors such as climate change, human activity, and increasingly severe disturbance events. In this study, I examined post-fire vegetation succession in Waterton Lakes National Park (WLNP), located in the southern Canadian Rocky Mountains, to ask how climate change, human disturbance and distance to seed sources affect the rate and trajectory of succession. I compared succession in burned sites with unburned sites to determine how the properties and drivers of succession after fire differed. To characterize the shifts in community types affected by fire and determine the persistence of those shifts, I described 12 community types and compared tree seedling densities between burned and unburned sites of those community types. I did not find strong evidence that climate change, human disturbance or increased distance to seed sources affected the rate or trajectory of vegetation succession post-fire. The trajectory of succession in burned plant communities tended to be consistent with a return to their pre-fire state, while in unburned communities the trajectory generally diverged from pre-fire composition. Burned areas shifted away from forested community types, and towards two new shrub dominated community types which were not present in WLNP prior to the fire. Most burned forested community types had regeneration of their dominant tree species, indicating a likely return of the pre-fire community type over time. My study shows that post-fire plant community succession in WLNP is largely resilient to modern stressors.