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

Abstract

Abstract We investigated the seasonal fluxes of CH 4 and CO 2 in wood ant ( Formica aquilonia ) nest mounds and in the surrounding temperate forest soil because temperate forest soils are important sinks of CH 4 and sources of CO 2 . 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, CH 4 flux was less negative in ant nest mounds (−16 ± 19 μg CH 4 m −2 h −1 ) than in the forest soil (−44 ± 18 μg CH 4 m −2 h −1 ). CH 4 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 CH 4 fluxes tended to be less negative. Averaged across the 11-month sampling period, CO 2 flux was higher in ant nest mounds (189 ± 204 μg CO 2 m −2 h −1 ) than in the forest soil (105 ± 80 μg CO 2 m −2 h −1 ). The biggest difference in CO 2 flux occurred in July when it was almost six times higher in the ant nest mounds than in the forest soil. CO 2 flux was greater in summer than in winter in both ant nest mounds and the forest soil. In conclusion, ant nest mounds oxidize less CH 4 and produce more CO 2 than the surrounding forest soil.