Factors Driving Vegetation Trajectories of Post-Wildfire Landscapes in the Interior of British Columbia, Canada

Background: Globally, shifting fire regimes which have increased in frequency and severity-- driven by climate change, land use changes, and fire suppression-- are altering vegetation dynamics. Little is known about the impacts of this new era of wildfire on seedbank dynamics, and native and non-native plants. Given constrained resources and the expanding extent of wildfire-affected areas, there is a pressing need to understand the factors influencing post-fire vegetation dynamics data to prioritize and guide landscape-level recovery interventions. The 46,000 ha McKay Creek Wildfire in the interior of British Columbia, Canada, provided a unique opportunity to assess how factors such as topography, burn severity, and pre-fire invasive plant presence drive post-wildfire vegetation trajectories due to its diverse ecosystems, representation of all burn severities, and extensive baseline data on the presence of invasive species. We hypothesized that both prior presence of non-native plants and high burn severity would result in increased presence of non-native plant populations on post-wildfire landscapes. Results: Foliar cover was recorded by species and grouped by native status (native or non-native), life cycle (annual, biennial, perennial), and life form (e.g., forb, grass, shrub) on 80 plots stratified by burn severity and pre-fire presence of invasive plants. Our findings showed that bare ground accounted for the greatest proportion of cover across all plots, remaining near or above 50% across all stratifications. Native cover ranged from just over 25% to 41%, varying with burn severity and prior invasive plant presence. Non-native cover remained below 5% across all conditions. Topography, particularly elevation and aspect, was the strongest driver of post-fire vegetation patterns with the proportion of native plant cover highest at higher elevations and on west-facing slopes. Plant lifecycle was an influential factor on non-native plants, with annuals most prevalent in high severity burns and at lower elevations, and perennials most abundant at higher elevations. Burn severity had limited influence on total non-native cover. Conclusions: At a time when wildfire is increasing in size, frequency and intensity, and resources are limited for recovery efforts, our study may contribute critical insights for land managers to prioritize and plan post-fire restoration activities such as monitoring, prevention and management of invasive species, and interventions such as planting.