Soil microbial biomass and respiration measurements
We measured soil microbial biomass (Cmic) and respiration using 5 g of
fresh soil on an automated O2-micro-compensation
apparatus (Scheu 1992). Soil microbial respiration was measured first,
as the oxygen consumption per hour per dry weight of soil in µl
(respiration given in µl O2 g-1 dry
weight h-1). This reflects the active part of the soil
microbial community at the sampling time. Afterwards, the microbial
biomass (given in µg microbial carbon g-1 dry weight)
was measured by adding glucose (8 mg per gram of dry soil) to the
samples (substrate-induced respiration [SIR] method). This
measurement represents the total metabolically active biomass of soil
microorganisms of the sample.