ARS | Publication request: The significance of termites as decomposers in contrasting grassland communities of semi-arid eastern Australia

Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2008
Publication Date: January 1, 2009
Citation: Noble, J.C., Muller, W.J., Whitford, W.G., Pfitzner, G.H. 2009. The significance of termites as decomposers in contrasting grassland communities of semi-arid eastern Australia. Journal of Arid Environments. 73:113-119.

Interpretive Summary: An important process in deserts around the world is the eventual decomposition, or decay, of all biomass, or organic matter produced. The limited nutrients available in deserts for primary production, such as plant growth, are dependant upon this decay process to recycle nutrients back into the soil. These studies in the Australian desert examined the role of termites in this decay process. Around the world termites are a major decomposer. This study, however, illustrated that decay of biomass has 2 distinct stages in deserts, a fragmentation phase and a mineralization phase. The fragmentation phase can be influenced by organisms such as termites, but can also be driven by weathering processes, such as those driven by sunlight and freezing temperatures. The mineralization phase, though, is certainly influenced by organisms such as termites. As with most biological processes and systems, decay in deserts is influenced by several factors, both biological and non-biological.

Technical Abstract: Decomposition of various litter forms including dead tussocks of two native perennial grasses, woollybutt (Eragrostis eriopoda) and mulga mitchell (Thyridolepis mitchelliana), as well as roots of woollybutt, dung of sheep and kangaroo, and bleached toilet rolls, was studied in contrasting grazing exclosures, half of which had termites excluded by biocide (termiticide) treatment. Dead mulga mitchell tussocks decayed more rapidly than woollybutt tussocks during the first 17 months post mortem. Thereafter, rate of decay differed little between species. After 3 years, only small amounts of tussock residues of either species remained and only then did the impact of biocide treatment become significant. Decomposition of kangaroo pellets was typically bimodal with significantly higher decomposition recorded in the controls (no biocide) up to 40 months after treatment, and many intact pellets remaining in the biocide-treated plots. While decomposition of sheep pellets showed similar bimodality, decomposition remained significantly lower in the biocide treatments for the entire duration of the experiment. Results suggest that abiotic processes, including those induced by UV radiation, may be dominant influences mediating decomposition of litter in these semi-arid ecosystems, especially following high rainfall seasons when abundant grass biomass has been generated providing a surfeit of potential forage for harvester termites.