Date of Award
Environmental and Forest Biology
Salamanders, Soil acidity
Acidic deposition resulting from emissions of sulfur and nitrogen has negatively impacted the hardwood forests of the northeastern United States, causing depletion of key nutrients such as calcium and chronic acidification of forest soil habitats. Strongly acidic habitats (pH < 3.5) have long been considered lethal to eastern red-backed salamanders (Plethodon cinereus), but recent studies found that P. cinereus were abundant in hardwood forests with soil pH as low as 2.7 – a condition resulting from anthropogenic acid inputs. Although abundance of P. cinereus does not appear to be constrained by soil pH, I hypothesized that very acidic habitats would negatively impact the demographics of P. cinereus populations, including age distribution, growth rates, and age at sexual maturity. I analyzed demographic parameters of extant P. cinereus populations that were sampled in 2012 at four hardwood forests in NH and VT (USA) that ranged in soil/forest floor pH from 2.7 – 3.7. I determined the age of each P. cinereus using skeletochronology techniques to estimate population age structure, estimated growth curves for each population using the von Bertalanffy equation and Chapman’s method, and evaluated mean age at sexual maturity for each population. Overall, soil pH did not appear to strongly affect P. cinereus populations. However, the most acidic site (pH 2.7) had a greater proportion of juveniles to adults, suggesting that fewer juveniles survive to adulthood at soil pH < 3.0. The mean age of sexually mature individuals was significantly higher at the most acidic site compared to least acidic site, but was not significantly different from the sites with intermediate pH sites. My results suggest that it is possible that P. cinereus populations have locally adapted to very acidic soils, but that demographic differences may reveal sensitivity of populations to this stressor. Further study of habitat pH and P. cinereus is warranted because these salamanders comprise a large portion of forest faunal biomass and play an key ecological role in nutrient cycling
Cappelli, Laura R., "The effects of soil acidity on the age structure and age at sexual maturity of eastern red-backed salamanders (Plethodon cinereus) in hardwood forests of New Hampshire and Vermont" (2016). Honors Theses. 84.