Habitat trees and salamanders: Conservation and management implications in temperate forests

Abstract

Among vertebrates the concept of “habitat tree” in temperate forests, involving tree size and microhabitat occurrence, has been investigated mainly for birds and mammals. However, trees are also used by many amphibian species or sometimes by whole amphibian families that have evolved adaptations for living on trees. While there is a self-evident link between arboreal amphibians, which occur mainly in tropical forests, and trees, the relationship between trees and forest ground-dwelling amphibians is less widely studied and more difficult to understand. As a consequence, the effect of forestry practices on amphibian communities are commonly considered at the landscape scale, identifying habitat alteration and loss as major threats. We provide the first evidence that the combination of forestry practices and species conservation strategies may act at a smaller scale than those traditionally adopted: the single-tree scale. Our study focused on the Italian endemic spectacled salamander (Salamandrina perspicillata). In a hectare forest stand in central Italy we marked nearly 400 trees individually and for each we measured the DBH, the number of buttresses in the stump (BUT) and the number of cavities between soil and stump (HOL). Salamanders were sampled and individually marked at each tree in eleven sampling occasions, during 2013 and 2014. We discovered that the concept of “habitat tree” may also hold for salamanders, and that DBH and HOL are the best predictors of tree suitability for salamanders. Moreover, using the number of captures for the same individuals on the same tree, occurring in different years, we were able to distinguish between trees that act as permanent or temporary shelters for salamanders. Permanent shelters were not only used by the same individuals in different years, but also hosted a larger number of salamanders, and were characterized by a larger number of HOL. Our findings may be considered of importance for drawing up forest management plans and achieving conservation objectives. During forest harvest operations, for the purpose of salamander conservation we suggest retaining trees with a larger DBH (>30cm) and a high number of HOL. Finally, since BUT is highly correlated with HOL but is less sensitive to variations during time, we suggest this parameter be used as a proxy of HOL.