Habitat Correlates of the Southern Torrent Salamander, Rhyacotriton variegatus (Caudata: Rhyacotritonidae), in Northwestern California

Abstract

Asystematic stratified sampling design was used to quantify the habitat relationships of the southern torrent salamander, Rhyacotriton variegatus, in northwestern California. We sampled 53 first to third order streams, each surrounded by at least 5-7 ha of relatively homogeneous forest or harvested forest habitat. Measurements of 121 attributes of the forest and stream environment were recorded in conjunction with area-constrained aquatic sampling for salamanders. A subset of 68 variables, grouped into 11 ecological components including attributes at the landscape, macrohabitat, and microhabitat scales, was used in a hierarchical analysis of habitat associations. Results from discriminant and regression analyses indicated that this species occurs within a relatively narrow range of physical and microclimatic conditions and is associated with cold, clear headwater to low-order streams with loose, coarse substrates (low sedimentation), in humid forest habitats with large conifers, abundant moss, and HO% canopy closure. Thus, the southern torrent salamander demonstrates an ecological dependence on conditions of microcli- mate and habitat structure that are typically best created, stabilized, and maintained within late seral forests in northwestern California.