Temperature sensitivity of anaerobic labile soil organic carbon decomposition in brackish marsh

The global warming has a potential for acceleration of labile soil organic carbon decomposition. Arrhenius equation is one of the useful equation for predicting temperature sensitivity of carbon decomposition, with the activation energy of rate constant being a key factor. The purpose of this study is the evaluation of temperature sensitivity of labile soil organic carbon decomposition under anaerobic condition in wetland soil using the activation energy of rate constant among different vegetation types. The soil samples were incubated at three different temperatures (10, 20, and 30°C) under anaerobic condition and carbon decomposition rates (sum of CO₂ and CH₄ production) were measured by gas chromatography. The first-order kinetic model with Arrhenius equation was used for approximate of anaerobic carbon decomposition. For determination of activation energy of rate constant, non-linear least-squares method was conducted between observed carbon decomposition rate and predicted carbon decomposition rate which calculated by Arrhenius equation. The activation energy of rate constant of anaerobic labile soil organic carbon decomposition was different among vegetation types. We successfully determined the activation energy of rate constant of CO2 or CH4 production from Phragites, Juncus, and Miscanthus+Cirsium-dominated vegetation soil with Arrhenius equation. Hence, this study suggests that Arrhenius equation was useful for evaluation of temperature sensitivity of labile soil organic carbon decomposition not only aerobic condition, but also anaerobic condition among several vegetation types in the wetland ecosystem. Moreover, gaseous carbon production from soil under Juncus yocoscensis dominated soil appeared higher activation energy and temperature sensitivity than that from soil under other vegetation types.