EFFECT OF SUBSTRATE LOCATION IN SOIL AND SOIL PORE-WATER REGIME ON CARBON TURNOVER

Introduction of C-14-labelled glucose into soil pores of two different size classes (<6 and 6-30 mum neck dia) of a Vertisol, and subsequent comparison of C-14 flow at two matric potentials (-50 and -10 kPa), enabled an evaluation of the effects of substrate location and pore-water regime on carbon turnover. Based on (CO2)-C-14 evolution and biomass C-14 concentrations in soil, turnover of added substrate carbon during a 4-week incubation was found to be greater when substrate was located in the larger pores, and particularly when such amended soil was held at the lower soil water matric potential. Observed differences in carbon turnover highlighted the importance of spatial compartmentalization of substrates and decomposers (primary and secondary) in soil due to both pore size exclusion (microhabitats) and the degree to which pores are water-filled.