Residual effects of thinning and high white-tailed deer densities on northern redback salamanders in southern New England oak forests

摘要

Research has demonstrated that even-aged regeneration harvests, especially clearcutting, can have a major and long-lasting detrimental effect on forest amphibians, but the effects of less intensive silvicultural treatments have not been well documented. Additionally, the chronic overabundance of white-tailed deer (Odocoileus virginianus) has become a problem in many parts of North America, with associated effects on vegetation composition and structure and on other wildlife. The effects of crown thinning and deer overabundance on the relative abundance of forest-floor salamanders were assessed in 1995-97 in a southern New England (Massachusetts) mixed oak-broadleaved forest with some pine. Salamanders were surveyed by using cover boards in 16 forest stands with thinned or unthinned treatments and with histories of low (3-6 deer/km2) or high (10-17 deer/km2) deer densities. Surveys were conducted 5 times a year for 3 years. Northern redback salamanders (Plethodon cinereus) were the dominate species in all surveys and in all treatment classes. Redbacks were most abundant in spring and fall surveys and in the second and third year of the study. Neither thinning nor white-tailed deer density had a significant effect on the number of redback observations: stands with high numbers of redbacks occurred in all treatment classes. At the stand level, numbers of redback observations were positively correlated with the number of pieces and area of coarse woody debris and with the density of tall (>=1 m) woody stems. The study suggests that a stand disturbance, where a large percentage of the canopy is retained and that results in an increase in cover of understorey vegetation, would result in no long-term effect on forest-floor salamanders.