Response of Red-Backed Salamanders (Plethodon Cinereus) to Changes in Hemlock Forest Soil Driven by Invasive Hemlock Woolly Adelgid (Adelges Tsugae)

Abstract

Hemlock forests of the northeastern United States are declining due to the invasive hemlock woolly adelgid (HWA) (Adelges tsugae). Hardwood species replace these forests, which affects soil properties that may influence other communities, such as red-backed salamanders (red-backs) (Plethodon cinereus). This study examined the effects of HWA invasion on soil properties and how this affects red-backs at the Hemlock Removal Experiment at Harvard Forest, which consists of eight 0.8 ha plots treated with girdling to simulate HWA invasion, logging to simulate common management practices, or hemlock-or hardwood-dominated controls. Coverboard surveys were used to determine the relative abundance of red-backs between plots during June and July 2014 and soil cores were collected from which the bulk density, moisture, pH, temperature, leaf litter, and carbon-nitrogen ratio were measured. Ordination provided a soil quality index based on temperature, pH, and carbon-to-nitrogen ratio, which was significantly different between plot treatments (p < 0.05) and showed a significant negative correlation with the red-back relative abundance (p < 0.05). The findings support the hypothesis that red-backs are affected by soil quality, which is affected by plot treatment and thus HWA invasion. Further studies should explore how salamanders react in the long term towards changing environments and consider the use of red-backs as indicator species.

Eastern red-backed salamanders: A comprehensive review of an undervalued model in evolution, ecology, & behavior

“…In recently harvested forests in West Virginia, P. cinereus expends more energy on body maintenance, although there were no consistent patterns related to body condition or invertebrate abundance (Homyack et al, 2011). In New York, Beier et al (2012) found a positive relationship between P. cinereus abundance and a well-defined calcium gradient, while in Massachusetts, Ochs & Siddig (2017) found P. cinereus was more prevalent in forests with lower soil pH, lower carbon to nitrogen (C:N) ratios, and lower temperatures. The authors note that the first two characteristics, low soil pH and low C:N ratios, are characteristic of hemlock stands, which used to be much more common within the range of P. cinereus prior to the arrival of hemlock wooly adelgid (Siddig et al, 2019).…”

“…Another line of investigation has made connections between ecosystem changes or elemental gradients to P. cinereus populations or energetics (Homyack, Haas, & Hopkins, 2011;Beier et al, 2012;Ochs & Siddig, 2017). In recently harvested forests in West Virginia, P. cinereus expends more energy on body maintenance, although there were no consistent patterns related to body condition or invertebrate abundance (Homyack et al, 2011).…”

“…The loss of hemlocks and other massive ecosystem changes as a result of invasive species who affect fundamental environmental properties relied on by forest floor inhabitants (e.g. soil chemistry, temperature), may also influence P. cinereus (e.g., Caceres-Charneco & Ransom, 2010;Ochs & Siddig, 2017). Continental invasions of earthworms undoubtedly influence P. cinereus in many ways, but especially by changing soil properties and P. cinereus behavior, which likely influence the role of salamanders in shaping North American forest ecosystems (Caceres-Charneco & Ransom, 2010; see also Community Ecology section above).…”

Logging response alters trajectories of reorganization after loss of a foundation tree species

“…Girdling and logging both resulted in a transformation from a deeply shaded evergreen coniferous forest with a sparse understory, to a deciduous hardwood forest with greater understory species abundance and richness (Orwig et al, 2013). This regime shift had cascading effects on salamanders (Ochs & Siddig, 2017;Siddig et al, 2016), moose and deer (Faison et al, 2016), small mammals (Degrassi, 2016), ants (Record et al, 2018), and macroarthropods (Sackett et al, 2011). Soil carbon storage and soil CO 2 efflux changed surprisingly little after hemlock loss (Finzi et al, 2014;Raymer et al, 2013), in contrast with findings of lower soil CO 2 efflux in the southern Appalachians after T A B L E 2 Summary of differences in the rate, magnitude, and persistence of change between the girdled and logged plots over 15 years.…”