中文摘要：

大量研究证明稻田土壤比旱地土壤更具固碳潜力,但至今对稻田土壤固碳机制的认识尚不甚清楚。本研究于2007年利用两个开垦年代相似,近20多年分别一直种植双季稻和双季玉米的长期定位试验,来比较不同种植模式下土壤有机碳及其组分的差异。结果表明,水田土壤总有机碳和总氮的浓度分别是旱地的2.2倍和2.5倍。与试验前相比,水稻种植显著提高了土壤有机碳的含量,增幅达到30.8%,而旱地的前后差异不显著。在所有团聚体粒径水平上,水田有机碳的浓度均显著高于旱地。其中53～250μm微团聚体相差最大,水田是旱地的近3倍。水田微团聚体保护碳（iPOM_m）在土壤中的浓度是旱地的4.2倍,微团聚体保护碳在总有机碳中的比重也显著高于旱地,达到25.5%,是旱地的2倍。水田和旱地iPOM_m组分碳的差异能够解释其总有机碳差异的42.8%。上述结果可以增强我们对稻田土壤固碳机制的了解,为稻田土壤碳管理提供理论依据。

英文摘要：

Although increasing evidences have shown that paddy field soils owned a greater potential for carbon sequestration than that in upland soils, the underlying mechanisms have not been recognized clearly. The objective of this stud）, was to identify the differences in soil organic carbon（SOC ）and its fractions between long-term double rice cropping and double corn cropping fields with similar cropping histories. Our results showed that the concentrations of total organic carhon （TOC）and total nitrogen（TN ）in the paddy field soil were 2.2 and 2.5 times higher than those in the upland soil, respectively. Compared with the initial level of SOC, long-term rice cuhivation increased the concentration of SOC by 30.8%, while no significant effects were found in the upland soil after more than 20 years corn clopping. Furthermore, concentrations of aggregate-associated SOC in the paddy soil were significantly higher than that in the corn field soil. The most difference in aggregate-associated SOC was up to 3 times in the 53-250 μm microaggregates. Concentrations of microaggregate protected C（ iPOM_m）on a whole soil basis were 4.2 folds higher in the paddy field than that in the corn field. The proportion of iPOM_m in TOC reached 25.5% in the paddy soil with 2 times higher than that in the upland soil. Moreover, the difference in microaggregate protected C between the paddy field and the upland field could explain 42.8% of the difference in TOC. Hence, it is concluded that above resuhs could enhance the understanding of SOC sequestration in paddy fields, and be beneficial to soil carbon management in paddy soils.