EFFECTS OF FOREST ROADS ON THE ABUNDANCE AND ACTIVITY OF TERRESTRIAL SALAMANDERS

Abstract

One of the major effects of deforestation is the creation of numerous edge zones where remaining forest meets nonforest habitat. At this interface, edge effects on forest habitats can include altered abiotic conditions, changes in rates of competition and predation, and altered community structure. While the edge effects resulting from clear- cuts and other open habitats are well-studied, little is known about the comparative edge effects of forest roads. We studied the effects of forest roads on the abundance, surface activity, and body condition of red-backed salamanders (Plethodon cinereus) and slimy salamanders (P. glutinosus and P. cylindraceus) in the Southern Appalachians of Virginia. We conducted surveys for salamanders at 21 sites where gravel roads bisected mature forest. These sites were divided into three data sets based on region and year of survey. We also carried out an enclosure experiment to determine whether road edges influenced the surface activity and detectability of red-backed salamanders. We found fewer red-backed salaman- ders near roads in all three data sets. These edge effects extended ,20 m into the forest in two of the three data sets but increased linearly out to 80 m in the data set collected during an unusually dry period. In contrast, slimy salamanders showed no clear responses to forest-road edges and had significantly different responses than those of red-backed salamanders. Within our experimental enclosures, red-backed salamander detectability did not differ between edge and interior habitats, suggesting that the patterns we observed were not simply due to changes in salamander activity patterns. Like red-backed salamander counts, soil moisture and cover object area also tended to decrease near roads. The steepness of the gradient in soil moisture was a significant predictor of the steepness of the decline in salamander counts, while there was no significant relationship between the decreases in cover object area and decreases in salamander counts. Collectively, these results show that edge effects from forest roads may be comparable to edge effects from clear-cuts or other types of silvicultural edges. Additionally, they suggest that, for terrestrial salamanders, variation in the magnitude of edge effects may be related to variation in soil moisture. Management approaches that minimize soil desiccation associated with road building and maintenance may reduce the impacts of roads on amphibian populations in adjacent forest.