The objective of this study was to investigate the impact of land use change, from rice paddy to natural wetland, on soil organic matter dynamics 12 years after the former was abandoned. Cold water extracted organic carbon (CWEOC) and hot water extracted organic carbon (HWEOC) obtained from surface and subsurface soil layers were measured as important indexes, reflecting organic matter dynamics. The quality of CWEOC and HWEOC was characterized by UV absorbance and parallel factor analysis (PARAFAC) modeling of fluorescence excitation-emission matrices (FEEMs). The results showed the land use change didn’t significantly alter the quantity of SOC in all layer, but decrease the concentrations of CWEOC and HWEOC whereas the δ¹³C values appeared to increase. It suggested the carbon input into soil induced the change of DOC. The SUVA254 results showed aromatic content of DOC was less abundant in rice paddy, indicating DOC from paddy soil is more labile. The FEEM analysis suggested extracts from the rice paddy surface and wetland subsurface layers contain more humic-like fluorophores, while higher abundances of the tryptophan-like fluorophore were found in rice paddy subsurface and wetland surface layers. Overall, converting rice paddy to wetland didn’t alter the stock of SOC; however, it significantly decreased the stock and stability of dissolved organic carbon.

这项研究的目的是调查从稻田到自然湿地的土地利用变化对土壤有机质动力学的影响，在废弃土壤有机质后12年。测量从表层和地下土壤层获得的冷水提取的有机碳（CWEOC）和热水提取的有机碳（HWEOC）作为重要指标，反映了有机质的动态。CWEOC和HWEOC的质量通过紫外吸收和荧光激发-发射矩阵（FEEM）的平行因子分析（PARAFAC）模型来表征。结果表明，土地利用变化没有改变显著SOC的数量在所有层，但减少CWEOC和HWEOC的浓度，而δ ¹³C值似乎增加。这表明碳输入土壤引起DOC的变化。SUVA254结果表明稻田中DOC的芳香含量较低，表明稻田中的DOC较不稳定。FEEM分析表明，来自稻田表层和湿地表层的提取物含有更多的腐殖质类荧光团，而在稻田表层和湿地表层中发现的色氨酸类荧光团含量更高。总体而言，将稻田改成湿地并没有改变SOC的存量。但是，它大大降低了溶解有机碳的储量和稳定性。