The effect of severe wildfire on microhabitat structure varies over fine-scale distances away from amphibian breeding ponds in southwestern Alberta

Abstract

Abstract Small-scale features of the environment create localized climatic conditions, influence the resources available to different organisms, and are key to diverse and resilient forests. Wildfire may alter critical microhabitat for sensitive taxa, yet studies directly quantifying these effects are limited. Here, we present a rare before-after-control-impact assessment of the impacts of severe wildfire on microhabitat structure around amphibian breeding ponds. Using 462 photoquadrats sampled eight years before and three years after the 2017 Kenow wildfire in Waterton Lakes National Park (Alberta, Canada), we quantified changes in 14 microhabitat features at three different distances (0, 3, and 10 m) away from burned and unburned amphibian breeding ponds. Non-parametric multivariate analysis of variance suggested distance from pond edge was a significant predictor of microhabitat composition before the wildfire, with the proportion of soil (bare ground) decreasing and the proportion of shrubs and forbs increasing away from pond edges. We detected a significant interaction between distance, burn status, and time, suggesting that the relationship between microhabitat and distance depended on the joint effects of burn status and time. This result was driven by changes 10 m away from pond edges in the burn zone, where sites experienced an increase in the proportion of forbs, soil, gravel, and rocks, and the loss of moss cover following the fire. Microhabitat change was more pronounced at high-elevation sites, although power to statistically isolate the effect of elevation was limited. Our results demonstrate fine-scale gradients in the impacts of wildfire on microhabitats around small wetlands, with areas immediately adjacent to pond edges being less impacted than sites further away. These findings advance our understanding of how wetland edges respond to wildfire and we discuss potential implications for amphibian movement, persistence, and recovery following severe wildfire.