Prescribed fire and timber harvest effects on terrestrial salamander abundance, detectability, and microhabitat use

Abstract

Prescribed fire and timber harvest are anthropogenic disturbances that modify resource availability and ecosystem structure, and can affect wildlife both directly and indirectly. Terrestrial salamanders are effective indicators of forest health due to their high abundance and sensitivity to microclimatic conditions. Given their ecological importance, it is critical to understand how forest salamanders respond to management-related disturbances. We predicted that timber harvest and prescribed fire would decrease salamander abundance and availability, and increase salamander cover object use. We surveyed for southern red-backed salamanders (Plethodon serratus) over 9 sampling periods from 2010 to 2014 in a Missouri Ozark (USA) forest, and used binomial mixture models to estimate abundance and detectability in a large-scale Before-After, Control-Impact (BACI) experiment. Five replicate 5-ha units were randomly assigned to each treatment (prescribed burn, shelterwood harvest, midstory herbicide) and control. We compared abundance, surface activity, detectability, and microhabitat use among treatments. Abundance and surface activity decreased post-treatment in shelterwood, midstory, and burn units. Abundance estimates in midstory and burn units rebounded in the second post-treatment year but declined further in shelterwood harvest units. Overall, treatments had stronger effects on salamander availability than on actual abundance. We also found a higher proportion of salamanders under cover objects after prescribed fire, further illustrating the importance of accounting for imperfect detectability. Our findings foster a more robust understanding of the mechanisms underlying population-level responses to management practices, ultimately increasing our ability to manage terrestrial salamanders effectively.