Decomposition of elephant dung in an arid, tropical environment

Carbon dioxide evolution from elephant dung and bare soil was measured in relation to the chemical composition of the decomposing organic material, temperature and moisture. Carbon mineralisation from the dung was extremely rapid during the first 48 hours after deposition but micro-organism activity became progressively more limited by moisture after this initial period, and was at a comparatively low rate after two weeks when the dung was dry. Under high moisture-controlled conditions CO2 evolution from the dung was primarily temperature limited, but a decrease in the carbon mineralisation rate and the temperature response over the 14 day experimental period suggested that the availability of carbon and nutrient resources also became limiting to micro-organism activity. Carbon dioxide evolution from the soil was negligible under normal conditions but both the soil and dry dung showed a rapid increase in CO2 evolution rates following the addition of water. The implication of these results for the dynamics of soil organic matter during the wet and dry seasons and for the ecology of dung beetles is discussed.