Seasonal changes in methane and carbon dioxide flux in wood ant (Formica aquilonia) nests and the surrounding forest soil

We investigated the seasonal fluxes of CH4 and CO2 in wood ant (Formica aquilonia) nest mounds and in the surrounding temperate forest soil because temperate forest soils are important sinks of CH4 and sources of CO2. Gas fluxes were measured eight times (at 1- to 2-month intervals) from July 2013 to May 2014 using a static chamber method in a spruce forest in the Czech Republic. Nest and air temperatures were recorded using dataloggers. Averaged across the 11-month sampling period, CH4 flux was less negative in ant nest mounds (−16 ± 19 μg CH4 m−2 h−1) than in the forest soil (−44 ± 18 μg CH4 m−2 h−1). CH4 flux did not show a strong seasonal pattern and was negative in ant nest mounds and forest soil, even in winter when the surfaces of ant nest mounds and forest soil were frozen. The only exception occurred in ant nest mounds in summer, when CH4 fluxes tended to be less negative. Averaged across the 11-month sampling period, CO2 flux was higher in ant nest mounds (189 ± 204 μg CO2 m−2 h−1) than in the forest soil (105 ± 80 μg CO2 m−2 h−1). The biggest difference in CO2 flux occurred in July when it was almost six times higher in the ant nest mounds than in the forest soil. CO2 flux was greater in summer than in winter in both ant nest mounds and the forest soil. In conclusion, ant nest mounds oxidize less CH4 and produce more CO2 than the surrounding forest soil.