Interaction effects of elevated CO2 and temperature on microbial biomass and enzyme activities in tropical rice soils

Abstract

The impacts of elevated CO₂ and temperature on microbial biomass and soil enzyme activities in four physicochemically different types of tropical rice soils (Aeric Endoaquept, Aeric Tropoaquept, Ultic Haplustalf and Udic Rhodostalf) were investigated in a laboratory incubation study. Soil samples were incubated under 400, 500 and 600 μmol mol^− 1 CO₂ concentration at 25°C, 35°C and 45°C for 2 months. Elevated CO₂ significantly increased the mean microbial biomass carbon (MBC) content, across the soils, over control by 6.2%, 38.0% and 49.2% at 400, 500 and 600 μmol mol^− 1 CO₂ concentration, respectively. Soil enzyme activities (fluorescein diacetate hydrolase, dehydrogenase, β-glucosidase, urease, alkaline and acid phosphatases) also increased significantly ranging from 1.3% (urease) to 53.2% (alkaline phosphatase) under high CO₂ in the soils studied. Both MBC and soil enzyme activities were further stimulated at high temperatures suggesting elevated CO₂ and high temperature interaction accelerated the general turnover of the organic C fractions of the soil and through increase in microbially mediated processes.