中文摘要：

通过选取亚热带5种不同母质发育的稻田土壤（黄泥田I、黄泥田II、麻砂泥、红黄泥、河沙泥），按土壤发生层次采集剖面样品，研究土壤溶解性有机碳（DOC）的剖面分布特征及其与土壤有机碳（SOC）的关系，并探讨DOC的剖面迁移规律及影响因素。结果表明：稻田土壤剖面DOC含量介于13.61～90.34 mg·kg^-1，以耕作层（A/A-a和A-p）最高，平均达到69.40 mg·kg^-1，耕作层以下相对较低。除河沙泥外，其余4种稻田土壤剖面DOC含量并未随土层深度的增加而逐渐降低，而是在渗育层（P）及以下的某些土层（如We/W2层、C层）出现DOC含量较上一层次升高的现象。这可能与稻田土壤剖面特殊的DOC淋溶和淀积、生物降解、矿物相吸附和氧化还原状况有关。DOC/SOC的比例介于0.21%～1.31%，以耕作层土壤最低，表下层土壤相对较高，反映稻田表下层土壤SOC的活性较耕作层明显增强，在人为干扰（如翻耕）下，表下层土壤SOC可能更容易损失。相关分析表明，DOC与SOC呈显著正相关，剖面SOC含量对DOC的剖面分布具有决定作用。从维持土壤质量和固碳减排的角度看，应针对不同类型稻田土壤采取不同的耕作和管理措施。

英文摘要：

Five subtropical paddy soils developed from different parent materials （reddish yellow clayey soil I, reddish yellow clayey soil II, granitic sandy soil, red clay soil, and alluvial sandy soil） were chosen, and samples were collected according to soil genetic horizons, aimed to investigate the profile distribution characteristics of dissolved organic carbon （DOC） in subtropical paddy soils, and to approach the profile shift patterns of DOC and related affecting factors. In the test soils, the DOC content in the profiles ranged from 13.61 to 90.34 mg·kg^-1. Plough layer had the highest DOC content （72.33 mg·kg^-1 on average）, whereas the below layers showed relatively lower DOC content. Except for alluvial sandy soil, the DOC content in the other four soils did not decrease gradually with increasing depth, while had a higher distribution in some horizons （e.g., percogenic horizon, waterloggogenic horizon, and parent rock horizon） than in upper horizon, which could be related to the special leaching and deposition processes of DOC, its biological degradation, mineral phase adsorption, and the regimes of redox throughout the whole profile. The percentage of DOC to soil organic carbon （SOC） （DOC/SOC） in the whole profiles ranged from 0.21% to 1.31%, with the lowest value in plough layer and relatively higher values in below layers. It was suggested that the SOC in below layers could be more active and more sensitive to human disturbances （e.g., ploughup） than that in plough layer. Correlation analysis showed that there was a significant positive correlation between DOC and SOC, suggesting the decisive effect of SOC level in the profiles on the profile distribution of DOC. From the viewpoints of maintaining soil quality, sequestrating soil C, and mitigating soil CO2 emission, it would be necessary to take different cultivation and management modes for different kinds of subtropical paddy soils.