Abstract
Abstract. We investigated the relative importance of CH4 and CO2 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 CH4 fluxes based on CO2 fluxes and internal gas concentrations. The annual flux from termite mounds and surrounding soil was dominated by CO2 with large variations among sites. On a carbon dioxide equivalent (CO2-e) basis, annual CH4 flux estimates from termite mounds were 5- to 46-fold smaller than the concurrent annual CO2 flux estimates. Differences between annual soil CO2 and soil CH4 (CO2-e) fluxes were even greater, soil CO2 fluxes being almost three orders of magnitude greater than soil CH4 (CO2-e) fluxes at site. The contribution of CH4 and CO2 emissions from termite mounds to the total CH4 and CO2 emissions from termite mounds and soil in CO2-e was less than 1%. There were significant relationships between mound CH4 flux and mound CO2 flux, enabling the prediction of CH4 flux from measured CO2 flux; however, these relationships were clearly termite species specific. We also observed significant relationships between mound flux and gas concentration inside mound, for both CH4 and CO2, 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 CH4 flux and 3-fold for mound CO2 flux. This study highlights that CO2 fluxes from termite mounds are generally more than one order of magnitude greater than CH4 fluxes. There are species-specific relationships between CH4 and CO2 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 CH4 fluxes from termite mounds of all species, but given the data limitations, the above methods may still be used with caution.
Highlights
Introduction mite mounds and soil inCO2-e was less than 1 %
Mound CH4 fluxes were greater in the wet season when compared to the dry season for all species except T. hastilis, which did not show an obvious seasonal pattern in flux (Fig. 1)
Mean mound CO2 fluxes were similar for M. nervosus and T. pastinator, ranging between 76 ± 2 and 731 ± 237 mg CO2-C m−2 h−1, and were more than 2-fold greater than that measured for T. hastilis and A. meridionalis (Fig. 1)
Summary
Introduction mite mounds and soil inCO2-e was less than 1 %. We observed significant relationships between mound flux and gas concentration inside mound, for both CH4 and CO2, and for all termite species, thereby enabling the prediction of flux from measured mound internal gas concentration. 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 Savannas cover 20 % of theSgololibdal Elaandrthsurface and are recognized for producing almost 30 % of global net primary production (Grace et al, 2006; Hutley and Setterfield, 2008), playing an important role in the global carbon cycle. Soil-derived CH4 fluxes are the net product of soil CH4 oxidation (Livesley et al, 2011) by methanotrophic bacteria under aerobic soil conditions and soil CH4 production by methanogenic bacteria under anaerobic soil conditions and from termite gut bacteria (Jamali et al, 2011a)
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