Components of organic carbon pool and profile distribution of δ13C values in typical stagnic anthrosols from Hangzhou-Jiaxing-Huzhou Plain.

Three typical stagnic anthrosols,including silty-clayey yellow mottled paddy soil on fluvialmarine,blue clayey paddy soil,and gleyed blue clayey paddy soil,were collected from the Hangzhou-Jiaxing-Huzhou Plain to characterize vertical distribution of total organic C,particulate organic C,black C and δ13C values in the soil profile,and distribution of organic C and black C in different sizes of water-stable aggregates.The results showed that total organic C pool in 1-m soil profile was lower in silty-clayey yellow mottled paddy soil on fluvialmarine than those of blue clayey paddy soil and gleyed blue clayey paddy soil.Particulate organic C,accounted for 10.6%-29.3% of the total soil organic carbon,decreased with increasing profile depth.Black C,accounted for 4.2%-24.6% of the total soil organic carbon,decreased with increasing depth for silty-clayey yellow mottled paddy soil on fluvialmarine and blue clayey paddy soil,and was even for gleyed blue clayey paddy soil.Contents of total organic C and particulate organic C increased with increasing size of water-stable aggregates,but content of black C in aggregates was not related to the size of aggregates.However,black C tended to be richened in clay component.The size of black C decreased with increasing profile depth.The δ13C values decreased in the order of black C total organic C particulate organic C,and increased with profile depth.