To measure 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.