Testing Functional Variation in Thermal Properties for Antarctic Mosses

Abstract

As the maritime Antarctic ecosystem continues to warm, glacial retreat will further expose subterranean permafrost to warmer conditions. One of the most visible changes in the ecosystem is the colonization of the new ice-free areas by bryophytes, particularly mosses. These bryophytes are having important effects on terrestrial thermal properties, but little is known about differences among Antarctic moss species in their thermal properties. Here, I measured the thermal conductivity, specific heat capacity, and the water content of moss species on King George Island to understand the insulation ability of Antarctic mosses, Polytrichastrum alpinum, Sanionia georgicouncinata, Chorisodontium aciphyllum, Andreaea gainii, and Syntrichia filaris. I found that C. aciphyllum consistently showed the highest thermal conductivity with little drop off as plants dried over time. S. georgicouncinata and S. filaris both showed a mid-level thermal conductivity with a greater drop off over time than C. aciphyllum, while P. alpinum and A. gainii both had a significantly lower thermal conductivity. These data mirror what was found in the percent water content remaining over time. Morphologically, plants in low nitrogen sites were less thick and dense than in high nitrogen sites, yet this resulted in higher rather than lower thermal conductivity. In low nitrogen sites, I found that plants had higher thermal conductivity and lower overall relative water content but retained that water longer. These data suggest that Antarctic mosses fall into functional groups based largely on their canopy morphology and thermal properties, and that elevated nitrogen has a significant enough effect on their canopy morphology to impact their thermal properties and water content. This study investigates how species composition, functional grouping, and changing nutrient dynamics affect the role bryophytes play in the temperature dynamics of the maritime Antarctic system. This understanding will aid in making educated predictions regarding the future of the permafrost layer and ecosystem structure under continued warming.