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. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Long‐term herpetofaunal response to repeated fuel reduction treatments

“…This could be due to higher activity levels associated with decreased litter depth or cover and associated changes in microclimate, changes in prey availability, or expanded foraging areas (Homyack et al 2011). In contrast, other studies reported short‐term decreased surface activity and abundance, and increased use of cover objects after 1 (O'Donnell et al , 2016) or 2 (Ford et al ) low‐intensity dormant‐season prescribed burns in upland hardwood forest, based on diurnal plot searches or coverboard methods.…”

“…Subsequent results following a second burn in burn‐only and mechanical + burn (2006–2007) showed no difference in plethodontid salamanders in 2006 but fewer in mechanical + burn than burn‐only or control in 2007 (Matthews et al ). Several other studies showed that 1 or 2 low‐intensity, dormant‐season burns do not adversely affect terrestrial salamanders (Ford et al , O'Donnell et al , Raybuck et al , Seiboldt , Greenberg et al ). Importantly, the long‐term results from this study indicate that, despite some variability among some treatments within individual years (Matthews et al ), terrestrial salamander abundance did not decline overall, even after 4 repeated burns in burn‐only and mechanical + burn, and further canopy cover reduction in mechanical + burn.…”

“…Perceived changes in reptile and amphibian capture rates are potentially confounded by behavioral changes following disturbances, weather, and sampling methods. For example, salamanders may retreat belowground or under cover objects (Grover , O'Donnell and Semlitsch 2015, O'Donnell et al ), American toads may increase their use of coarse woody debris (Pitt et al ), and lizards may increase surface activity in response to reduced leaf litter or warmer temperatures (Fouts et al ) following burns or other forest disturbances. Snapshot survey methods, including coverboards (Hocking et al , Pough et al ) or active searches (O'Donnell et al ), can provide insight into behavioral shifts, or changes in microdistribution by herpetofauna in response to disturbances (Marsh and Goicochea ) but may not accurately measure overall surface activity, a metric of relative abundance, within a longer activity window.…”

“…Heavy research focus on terrestrial salamanders as indicators of forest health (Ash , Harpole and Haas , Homyack and Haas , Ford et al , O'Donnell et al ) is partly because they are abundant, and easily captured using visual searches or coverboards (O'Donnell and Semlitsch ) compared to many other amphibian or reptile species (Moorman et al ). In contrast, drift fences with pitfall traps sample multiple, surface‐active reptile, and amphibian species, providing a broader overview of community‐level response to disturbances, and allowing for assessment of various species with different life‐history requirements, as potential indicators of forest conditions.…”

“…Wildlife response to fuel reduction treatments, especially when repeated, may vary over time. Several short‐term studies indicated that low‐intensity dormant‐season prescribed burns in upland hardwood forest had a minimal and transient effect on forest structure or wildlife (O'Donnell et al , Raybuck et al , Seiboldt , Greenberg et al ). However, repeated burning could have additive effects on habitat attributes, such as canopy cover, shrub density, or leaf litter depth, and associated changes in forest floor microclimate, food, and cover resources that might alter habitat suitability for various taxa over the long‐term.…”