Factors influencing early post-wildfire vegetation and implications for invasive plant management in the interior of British Columbia, Canada.

Abstract

Background: Wildfire activity is increasingly characterized by larger fire events and a greater prevalence of high-severity burns, driven by climate change, land-use change, and prolonged fire suppression. These shifts are altering post-fire vegetation dynamics, yet uncertainty remains regarding how early post-fire plant responses vary with burn severity and pre-fire occurrence of invasive plants under contemporary fire conditions. Given limited capacity for post-fire monitoring and restoration across increasingly large fire-affected landscapes, identifying factors associated with early post-fire vegetation responses is critical for prioritizing surveillance and supporting invasive plant management through early detection and rapid response (EDRR) programs. The 46,000 ha McKay Creek Wildfire in interior British Columbia, Canada, provided an opportunity to examine how burn severity, topography, and pre-fire occurrence of invasive plants (based on mapped infestation extent) influence early post-fire vegetation composition across diverse ecosystems. We predicted that both high burn severity and pre-fire occurrence of invasive plants would be associated with increased non-native plant cover following wildfire.

Results: Vegetation cover was recorded by species and grouped by native status (native or non-native), and life cycle (annual, biennial, perennial), on 80 plots stratified by burn severity and pre-fire occurrence of invasive plants. Two years post-fire, vegetation cover was dominated by bare ground across all plots, while native plant cover exceeded non-native cover under all conditions. At the broad status-group level (native vs. non-native), post-fire vegetation cover did not differ meaningfully across burn severity classes or between areas with and without documented pre-fire occurrence of invasive plants. Instead, elevation was the strongest driver of early post-fire vegetation patterns, with native cover increasing and non-native cover and bare ground decreasing at higher elevations. When vegetation was disaggregated by status and life cycle, non-native annual cover was higher in high-severity burns and at lower elevations, and non-native perennial cover increased with elevation.

Conclusions: At a time when wildfires are increasing in size, frequency, and intensity, and resources for recovery are limited, this study provides region-specific insights to support prioritization of early post-fire restoration activities such as monitoring, prevention and management of invasive plants, and planting of native species.