中文摘要：

采集杭州湾南岸围垦农田土壤样品（0—10，10-20，20-30，30-40，40～50cm），分析不同围垦时期（10，40，60，120a以上）农田土壤有机碳、水溶性有机碳、易氧化碳和轻组有机质的变化特征。结果表明：各有机碳活性组分变化规律总体上与土壤有机碳相近但亦有不同之处。随围垦时间增加，土壤有机碳及其活性组分呈增加趋势，但围垦40a以上，其含量均趋于相对稳定水平；其中0—10cm土层，土壤有机碳、水溶性有机碳、易氧化碳和轻组有机质含量增幅依次为40．43％，14．23％，25．47％，13．68％。土壤有机碳及其活性组分含量主要分布在0—20cm土层，但水溶性有机碳略有差别。水溶性有机碳分配比例随围垦年限增加而减小，易氧化碳则相反。土壤有机碳与其活性组分之间均显著正相关，各组分与土壤全氮、土壤含水量呈显著正相关。综上表明，随围垦年限延长土壤有机碳含量增加但其稳定性有所下降，有机碳活性组分能够敏感地反映土壤有机碳动态特征。

英文摘要：

This research was carried out to investigate the South Coast of the Hangzhou Bay and collect reclaimed soil samples （0- 10,10- 20,20- 30,30- 40,40- 50 cm）, to analyze the change characteristics of soil organic carbon, dissolved organic carbon, readily oxidized carbon and light fraction organic matter of farmland during different recla- mation period （10,40,60,120 a）. The results indicated that： The variations of organic carbon active fractions were similar to soil organic carbon substantially and it still existed differences. Soil organic carbon and its active frac- tions showed an increasing trend with increasing reclamation time, but the increase was diminished after 40 a and their contents tended to be relative stable afterwards. As to 0--10 cm soil layer, soil organic carbon, dis- solved organic carbon, readily oxidized carbon and light fraction organic matter increased by 40. 43%, 14.23% ,25.47%,13. 68%, respectively. Soil organic carbon and its active fractions content mainly distribu- ted in 0--20 cm soil layer, but dissolved organic carbon presented slightly difference. The ratio of dissolved organic carbon to soil organic carbon reduced with increasing reclamation time, however, the proportions of readily oxidized carbon increased. Soil organic carbon was significantly positive related to its active fractions and they all showed significantly positive correlated with soil total nitrogen, soil moisture content. In sum- mary, with increasing reclamation period, soil organic carbon content increased but its stability declined and the labile organic carbon could sensitively indicate soil organic carbon dynamics in Hangzhou Bay.