MEASURING THE IMPACT OF GROUNDWATER ON BOG TURTLE THERMAL HABITAT IN SOUTHERN APPALACHIAN FENS

Wetlands provide many ecosystem services such as improving water quality, helping to reduce flooding, and providing a habitat for many endangered species such as the federally threatened bog turtle. The bog turtle is a palm-sized, semi-aquatic turtle that is primarily found in fens, groundwater-fed alkaline wetlands. Since water has a higher specific heat than air, we hypothesize that the presence of groundwater in fens creates saturated soils that provides habitat for turtles to stay cool in the summer and warm during hibernation in the winter. Climate change may alter the thermal regime of fens, making it necessary to quantify baseline fen soil temperatures on seasonal timescales and understand thermal variability within fens so that we may anticipate future adverse impacts to the fen thermal habitat.

In this study we assess soil water temperatures for two fens in the Appalachian Highlands of North Carolina, United States from August 2018 through November 2019. We record soil water temperature at 2.5, 5.0, and 10.0 cm below ground level including eight locations in an Ashe County fen (elevation: 1,573 m, area: 9,338 m²), and ten locations in a Wilkes County fen (elevation: 563 m, area: 18,500 m²). Preliminary results from the Ashe County fen confirm our hypothesis that soil water provides an important thermal buffer. In December 2018, the average daily air temperature was 3.0°C and the average daily magnitude (maximum-minimum) of air temperature was 9.3°C. At 2.5 cm below ground level, the average daily temperature was similar to the air temperature (2.5°C), but the average daily magnitude was only 1.6°C, suggesting that the soil was insulated from freezing temperatures. In June 2019, the average daily air temperature was 17.5±8.5°C. At 2.5 cm below ground level, the average daily temperature was 18.6±5.7°C, indicating that the soil was buffered from hotter summer temperatures. Forthcoming results will demonstrate how soil water temperatures vary within and between fens which will help enact more effective conservation strategies to protect bog turtle thermal habitats.