*2.3. Microbial Respiration*

Soil microbial respiration was measured according to Isermeyer [22]. Twenty-five-gram soil samples were incubated in closed glass jars under dark conditions at field capacity and 30 ◦C. The CO2 evolved was trapped by 0.2 N NaOH and measured by titration of the excess NaOH with 0.2 N HCl. The jars without soil maintained at the same way served as a CO2 blank. The difference of consumed volume of HCl between the samples and the blank in titration was considered to estimate the amount of CO2 evolution by soil microorganisms. Cumulated microbial respiration (CSR) is the respiration

rate during 25 days of incubation period in mg CO2–C kg−<sup>1</sup> soil. Basal respiration rate (BSR) is the respiration at the last day of incubation (The 25th day) expressed in mg CO2–C kg<sup>−</sup><sup>1</sup> soil d<sup>−</sup>1.

The microbial metabolic quotient (qCO2) indicates the amount of CO2–C produced per unit MBC and was calculated from BSR per unit MBC in mg CO2–C 10<sup>−</sup><sup>2</sup> h−<sup>1</sup> mg MBC−<sup>1</sup> [23]. The mineralization quotient (qM) is expressed in% and calculated as the ratio of the CSR to SOC. The qM represents the efficiency of microflora to metabolize the soil organic carbon [24]. The efficiency of microbes to decompose organic carbon (CUE) was estimated as the ratio of microbial biomass carbon to soil organic carbon [25].
