ABSTRACT
The last 20 years have seen growing interest in the terrestrial carbon cycle in the context of global change. The consequent attempts to fully quantify it, over the whole land surface of the earth, have seen special attention given to greenhouse gas emissions. Social insects have high visibility in many terrestrial biomes, reflecting their large abundance and biomass, with important consequent impacts on ecosystem processes (Hölldobler and Wilson, 2009). Of the social insects, ants and termites clearly outnumber not only bees and wasps, but quite commonly the remaining macroarthropods as well (for example Billen, 1992; Stork and Brendell, 1993). In their classic, but still highly relevant study of central Amazonian rainforest, Fittkau and Klinge (1973) showed that ants and termites together made up more than 15 per cent of all animal biomass. Subsequent work suggests that this dominance is general in the humid tropics and improvements in sampling methods (especially for the more cryptic termites, see Moreira et al, 2008) indicate that the greater contribution is in fact made by termites, which can in exceptional cases reach biomass densities of more than 100g m–2, an impact which could only be matched or exceeded by earthworms (for reviews see Wood and Sands, 1978; Lavelle et al, 1997; Watt et al, 1997; Bignell and Eggleton, 2000; Bignell, 2006). Termite colonies are known to produce a range of trace gases that potentially affect atmospheric chemistry and/or the geological emissions are a significant global source of earth’s radiative balance. The gases are CO2, CH4, N2O, H2, CO and chloroform (CHCl3), but only CO2 and CH4 are generated in sufficient quantity to make termites of interest in global budgets (Khalil et al, 1990). Of these, CH4 emissions attract most attention, as this gas has 25 times the radiative forcing potential of CO2 over a 100-year time horizon. As a consequence, there have been several quantitative studies of termite assemblages, often accompanied by attempts to estimate their contribution of CH4 fluxes to the atmosphere.
