Samples were incubated in
incubation vessels containing water to prevent desiccation of the
samples in climate chambers at three different temperatures: 5 C,
15 C or 25 C. One subset of the samples was incubated for four
weeks and a further one was incubated for eight weeks. The CO2
evolution was monitored by continuous
flushing of the headspace
of each vessel with varying amounts of fresh air, depending on the
expected and already measured CO2 emissions, and subsequent
chromatographic measurement of the CO2 concentration in the
exhaust air (Loftfield et al., 1997). Depending on the total number
of vessels connected to the gas chromatograph, one measurement
took place at least every six hours. After
finishing the incubation
experiment, the two subsamples of 75 g each were combined and
sieved to pass 10 mm. An aliquot of the material was then dried at
40 C for aggregate fractionation, while a second aliquot was sieved
to pass 2 mm and used for the determination of microbial C.