The relationships between termite mound CH4/CO2 emissions and internal concentration ratios are species specific

[摘要] We investigated the relative importance of CH₄ and CO₂ fluxes fromsoil and termite mounds at four different sites in the tropical savannas ofnorthern Australia near Darwin and assessed different methods to indirectlypredict CH₄ fluxes based on CO₂ fluxes and internal gasconcentrations.The annual flux from termite mounds and surrounding soil was dominated byCO₂ with large variations among sites. On a carbon dioxide equivalent (CO₂-e)basis, annualCH₄ flux estimates from termite mounds were 5- to 46-fold smaller thanthe concurrent annual CO₂ flux estimates. Differences between annualsoil CO₂ and soil CH₄ (CO₂-e) fluxes were even greater, soilCO₂ fluxes being almost three orders of magnitude greater than soilCH₄ (CO₂-e) fluxes at site. The contribution of CH₄ andCO₂ emissions from termite mounds to the total CH₄ and CO₂emissions from termite mounds and soil in CO₂-e was less than 1%.There were significant relationships between mound CH₄ flux and moundCO₂ flux, enabling the prediction of CH₄ flux from measuredCO₂ flux; however, these relationships were clearly termite speciesspecific.We also observed significant relationships between mound flux and gasconcentration inside mound, for both CH₄ and CO₂, and for alltermite species, thereby enabling the prediction of flux from measured moundinternal gas concentration. However, these relationships were also termitespecies specific. Using the relationship between mound internal gasconcentration and flux from one species to predict mound fluxes from othertermite species (as has been done in the past) would result in errors of morethan 5-fold for mound CH₄ flux and 3-fold for mound CO₂ flux.This study highlights that CO₂ fluxes from termite mounds are generallymore than one order of magnitude greater than CH₄ fluxes. There arespecies-specific relationships between CH₄ and CO₂ fluxes from amound, and between the inside mound concentration of a gas and the moundflux emission of the same gas, but these relationships vary greatly amongtermite species. Thus, there is no generic relationship that willallow for the accurate prediction of CH₄ fluxes from termite mounds ofall species, but given the data limitations, the above methods may still be used with caution.

[学科分类] 地球化学与岩石