Can groundwater fluxes mitigate changing thermal habitat in southern Appalachian fens?

Abstract:

Fens, groundwater-fed alkaline wetlands, provide many ecosystem services such as improving water quality, reducing flooding, and creating a unique habitat for endangered species such as the federally threatened bog turtle. Bog turtles have historically relied on fen soils that are thermally-buffered by seeps, springs, and streams to thermoregulate during hot summers and cold winters. However, the long-term suitability of fen thermal refugia in a changing climate is uncertain; shifting groundwater fluxes may serve to either mitigate or compound the impacts of climate change. In this study, we quantify soil temperatures on daily and seasonal timescales for two southern Appalachian fens in North Carolina, USA to develop a baseline understanding of the effects of groundwater fluxes on fen thermal refugia.

We record soil temperatures at 2.5, 5.0, and 10.0 cm below ground level in eight locations across an Ashe County, N.C. fen (elevation: 1,573 m, area: 9,338 m2), and ten locations across a Wilkes County, N.C. fen (elevation: 563 m, area: 18,500 m2). As expected, preliminary results confirm that fen soils are thermally buffered from air temperatures. At the Ashe county fen in December 2018, the average daily air temperature was 3.0°C with a minimum temperature of -0.5°C, while the average daily 2.5 cm soil temperature was 3.3°C with a warmer minimum temperature of 0.9°C. In June 2019, the average daily air temperature was 17.5°C with a maximum of 26.0°C, but the average daily 2.5 cm soil temperature was 17.7°C with a colder maximum temperature of 23.4°C. Forthcoming results will demonstrate how fen soil temperatures vary with proximity to groundwater fluxes and energy balance components.