Rethinking Termite Methane Emissions: Does the Mound Environment Matter?

Abstract

Termites are important decomposers in tropical ecosystems and emit methane (CH 4 ) as they digest plant material. Global estimates of termite‐derived CH 4 are calculated using termite emission factors (TEF, measured from individuals) and estimated biomass. However, this approach overlooks how the termite mound, via internal and external factors, may influence emissions to the atmosphere. Termite feeding habits, mound methanotrophs and mound structure (internal environment), as well as temperature and season (external environment) can influence net CH 4 emission but remain unparameterized. We investigated how these factors shaped CH 4 emissions from three dominant mound‐building termite species (Coptotermes acinaciformis , Nasutitermes magnus , and Amitermes laurensis ) in a northern Australian savanna across four seasons. We compared species‐level TEFs and emissions at the mound‐ and landscape‐scales to evaluate relative species contributions, both with and without accounting for the internal and external environment. We hypothesized that larger, thinner‐walled mounds would emit greater CH 4 , and that emissions would be higher at high temperatures and during wet seasons. We expected greater emissions with lower abundances of methanotrophs and pmoA gene copies (involved in CH 4 oxidation) in mound material. Coptotermes acinaciformis individuals had the highest TEFs (1.07 μg CH 4 g −1 termite h −1 ), N. magnus mounds emitted the most CH 4 (3426 μg CH 4 h −1 m −2 ) and A. laurensis had the highest emissions at the landscape scale (1.04 × 10 −9 Tg CH 4 ha −1 year −1 ). CH 4 emissions increased with temperature and were highest in the wet‐to‐dry transition season. Mound structure, bacterial methanotroph communities, and pmoA abundance had no effect on CH 4 emissions. Our results highlight the limitations of relying solely on TEFs to estimate contributions of termites to global CH 4 emissions and emphasize the importance of incorporating external environmental conditions, while further exploring internal mound processes. This information allows more accurate parameterization of termite CH 4 contributions to savanna carbon and global CH 4 budgets.

Bibliographic Information