Changes in microhabitat structure around amphibian breeding ponds in the northern Rocky Mountains following severe wildfire

Microhabitats promote diverse and resilient forests. Wildfire may alter critical microhabitat, yet studies directly quantifying these effects are limited. Here, we use a rare before-after-control-impact dataset to assess the impacts of severe wildfire on fine-scale gradients in microhabitat structure associated with amphibian breeding ponds in the Rocky Mountains. Using 462 photoquadrats sampled eight years before and two years after the 2017 Kenow wildfire in Waterton Lakes National Park, we quantified changes in 14 microhabitat features at three different distances (0, 3, and 10 m) away from burned and unburned ponds. Non-parametric multivariate analysis of variance suggested distance from pond edge was a significant predictor of microhabitat composition prior to the wildfire, with the proportion of soil (bare ground) decreasing and the proportion of shrubs and forbs increasing away from pond edges. A significant interaction between distance, burn status, and time was observed, 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 test the effect of elevation was limited. Our study demonstrates heterogeneity in the impacts of wildfire on microhabitats along fine-scale gradients. We discuss implications of these findings for the management of amphibians using these sites.