2.4 Soil respiration measurement
The subset of air-dried soil samples was then pre-incubated for 14 days at 25°C under flooded conditions. For each measurement of respiration rate, approximately 20 g (equivalent dry weight) of each soil sample was incubated in a 500-mL container at 25°C for 24 h. At the end of this period, CO2 concentrations in the headspace were measured using an Agilent-7890a gas chromatograph equipped with a flame ionization detector (Agilent Technologies, Inc.). Soil respiration rates were calculated from the net accumulation of CO2 over time. The soil metabolic quotient (qCO2) was calculated by dividing the soil respiration rate by the MBC content (Plaza et al., 2004).