The Importance of Termites to the CH4 Balance of a Tropical Savanna Woodland of Northern Australia

Termites produce methane (CH4) as a by-product of microbial metabolism of food in their hindguts, and are one of the most uncertain components of the regional and global CH4 exchange estimates. This study was conducted at Howard Springs near Darwin, and presents the first estimate of CH4 emissions from termites based on replicated in situ seasonal flux measurements in Australian savannas. Using measured fluxes of CH4 between termite mounds and the atmosphere, and between soil and the atmosphere across seasons we determined net CH4 flux within a tropical savanna woodland of northern Australia. By accounting for both mound-building and subterranean termite colony types, and estimating the contribution from tree-dwelling colonies it was calculated that termites were a CH4 source of +0.24 kg CH4-C ha-1 y-1 and soils were a CH4 sink of -1.14 kg CH4-C ha-1 y-1. Termites offset 21% of CH4 consumed by soil resulting in net sink strength of -0.90 kg CH4-C ha-1 y-1 for these savannas. For Microcerotermes nervosus (Hill), the most abundant mound-building termite species at this site, mound basal area explained 48% of the variation in mound CH4 flux. CH4 emissions from termites offset 0.1% of the net biome productivity (NBP) and CH4 consumption by soil adds 0.5% to the NBP of these tropical savannas at Howard Springs.