Fire severity and plant productivity recovery in a mixed grass prairie wildfire driven by extreme winds

Abstract

Background Wildfire on rangelands in the mixed grassland can severely disrupt livestock operations. Understanding how fire severity impacts post-fire production recovery is important for grazing management. Aims We examined how topography and other environmental factors influence wildfire severity, or the consumption of biomass and exposure of soil, under extreme (>120 km h−1) wind conditions in native mixed grass prairie in western Canada. We also examined how variation in fire severity impacts grassland production recovery. Methods Fire severity and production recovery were measured using the bare soil index (BSI) and normalised difference vegetation index (NDVI). Impacts of topography, wind exposure, and site capability on fire severity and production recovery were assessed using generalised additive models. Key results Fire severity varied as a function of slope, wind exposure and fuel load. Severity peaked at NDVI between 0 and 0.4, values associated with high litter content and minimal green vegetation. Interactions between slope and aspect with respect to dominant wind direction generated very high fire severity on slopes greater than 15° that faced into the wind. Production recovery increased moderately with higher fire severity and recovery was generally higher on sites with lower potential productivity. Implications Post-fire production recovery was rapid; fire severity and site capability had only modest impacts on recovery rates demonstrating the resilience of grassland ecosystems to even severe wildfire.