The relationships between termite mound CH 4/CO 2 emissions and internal concentration ratios are species specific
We investigated the relative importance of CH 4 and CO 2 fluxes from soil and termite mounds at four different sites in the tropical savannas of northern Australia near Darwin and assessed different methods to indirectly predict CH 4 fluxes based on CO 2 fluxes and internal gas concentrations. The annual flux from termite mounds and surrounding soil was dominated by CO 2 with large variations among sites. On a carbon dioxide equivalent (CO 2-e) basis, annual CH 4 flux estimates from termite mounds were 5- to 46-fold smaller than the concurrent annual CO 2 flux estimates. Differences between annual soil CO 2 and soil CH 4 (CO 2-e) fluxes were even greater, soil CO 2 fluxes being almost three orders of magnitude greater than soil CH 4 (CO 2-e) fluxes at site. The contribution of CH 4 and CO 2 emissions from termite mounds to the total CH 4 and CO 2 emissions from termite mounds and soil in CO 2-e was less than 1%. There were significant relationships between mound CH 4 flux and mound CO 2 flux, enabling the prediction of CH 4 flux from measured CO 2 flux; however, these relationships were clearly termite species specific. We also observed significant relationships between mound flux and gas concentration inside mound, for both CH 4 and CO 2, and for all termite species, thereby enabling the prediction of flux from measured mound internal gas concentration. However, these relationships were also termite species specific. Using the relationship between mound internal gas concentration and flux from one species to predict mound fluxes from other termite species (as has been done in the past) would result in errors of more than 5-fold for mound CH 4 flux and 3-fold for mound CO 2 flux. This study highlights that CO 2 fluxes from termite mounds are generally more than one order of magnitude greater than CH 4 fluxes. There are species-specific relationships between CH 4 and CO 2 fluxes from a mound, and between the inside mound concentration of a gas and the mound flux emission of the same gas, but these relationships vary greatly among termite species. Thus, there is no generic relationship that will allow for the accurate prediction of CH 4 fluxes from termite mounds of all species, but given the data limitations, the above methods may still be used with caution.