Population-level effects of prescribed fires on terrestrial salamanders

Abstract

Prescribed fires are widely used for oak (Quercus) regeneration in hardwood forests, but the reported effects on terrestrial salamanders are variable, with some authors describing little to no effect of prescribed fire on salamanders and others reporting negative results. Factors such as variable fire intensity, sampling methodology, and imperfect salamander detection, which vary by study, may influence the effects of prescribed fires on salamanders. We examined the response of red-backed (Plethodon cinereus) and zig-zag (Plethodon dorsalis) salamanders to prescribed fire in forests of the Midwest U.S., accounting for changes in salamander behavior and detection by accounting for capture probability, and considering the influence of local fire intensity. We also explored the effects of fire on environmental variables (leaf litter depth, soil moisture, soil temperature, and soil pH) to identify possible mechanisms driving fire’s influence on salamanders. From spring 2019 through fall 2022, a total of 4922 salamander captures were recorded, representing 1939 individually marked salamanders at six coverboard grids in southern Indiana. Occurrence of fire affected survival and temporary emigration of salamanders, likely indicating that salamanders retreated underground, on two of the four grids. Fire occurrence and intensity did not significantly affect environmental variables except for leaf litter depth, which was negatively affected. However, soil moisture had a stronger influence on salamander capture probability than leaf litter. Overall, effects of prescribed fires on salamander populations in this study were inconsistent. In contrast, environmental factors had strong impacts on salamanders, but themselves exhibited either no relationship or a short-term relationship to prescribed fire variables. Notably, large salamander populations may be better able to tolerate prescribed fires. Such populations will be important to support during prescribed fire management to protect the species, especially as the effects of repeated prescribed fires and compounding effects are unknown. Understanding the interplay between forest management practices and wildlife habitat features such as soil moisture and leaf litter will be critical to identifying best practices for supporting wildlife populations reliant on such features during prescribed fires.