Tomeasure the sediment C pool, the depth of sedimentary organic C
was measured by gradually forcing a metal probe into the sediment
stratum. The sediment depths from all plots were determined to be
N4 m. In each sampling plot, a sediment core (250 cm in depth) was
drilled using a Russian peat borer (52 mm in diameter) for minimizing
the sediment disturbance during the drilling process. Immediately following
collection, sediment cores were placed in PVC tubes, sealed in
the aluminum foils in order to minimize the gas exchange, then placed
in a cooler, and processed within 24 h after collection. Laboratory processing
started with first removing the outer layer (~0.5 cm in thickness)
of the sediment cores, then slicing into 5, 10, and 15 cm
intervals for the core depths of 0–50, 50–100, and 100–250 cm, respectively.
The sediment samples were packed in labeled polyethylene bags
for further analysis. Subsamples of all sediment slices were also placed
in plastic cubes (1 cm3) for determining bulk sediment density. All sediment
samples weremaintained on ice in coolers and transported to the
laboratory where they were frozen at −20 °C until further processing
and analysis.