Importance of forestry practices relative to microhabitat and microclimate changes for juvenile pond-breeding amphibians

Abstract

Balancing the goals of forest management and species conservation is a major challenge. Forestry practices could be refined with greater understanding of the importance of large-scale forestry practices versus smaller-scale microhabitat and microclimate variables in driving demographic vital rates for species of conservation concern. We examined the relative importance of forestry practices, microhabitat, and microclimate on juvenile anuran survival and growth. To do so, we examined three different species: wood frogs (Lithobates sylvaticus), American toads (Anaxyrus americanus), and southern leopard frogs (Lithobates sphenocephalus), in three different years using terrestrial enclosures. Terrestrial enclosures were placed in forestry treatment plots with unharvested forest, partial cut forest, early successional forest (ESF; i.e. 4–6year old clearcut) with downed wood removed, and ESF with downed wood retained in central Missouri, USA. We ranked models using an information-theoretic approach to determine whether forestry treatment, microhabitat (logs, canopy cover, leaf litter depth), or microclimate (temperature and soil moisture) best predicted juvenile survival and growth. We found that microhabitat and microclimate, but not forestry practices, were important for survival and growth. However, small sample sizes may have limited our ability to detect forestry treatment effects. Most associations with growth and survival involved microclimate variables. Effects of microhabitat showed positive associations of survival with canopy cover and downed wood and of growth with leaf litter depth. All effects varied by species/year and season, as is common for studies on the effects of forestry practices on amphibians, indicating that it would be useful to maintain a variety of different microhabitats and microclimates to support a diverse anuran community. Because juvenile survival is a population-regulating parameter for many amphibians, it may be prudent to focus on creating favorable microhabitats and microclimates within areas under active forest management. However, it would be useful to repeat this type of study in different eco-regions with different species to determine the generalizability of these results.