Liao Yu-Qin, Long Juan, Mu Zhi-Jian, Wen Shou-Xin, Li Cui-Lian, Yang Zhi-Min, Zhao Xiu-Lan
College of Resources and Environment, Southwest University, Chongqing 400716, China.
Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China.
Huan Jing Ke Xue. 2022 Jun 8;43(6):3348-3356. doi: 10.13227/j.hjkx.202109090.
Soil was sampled from 182 profiles in typical farmlands of Chongqing and analyzed for the stable carbon isotope composition of organic matter (C). The results showed that the values of C for each soil profile were gradually increasing with increasing soil depth, and the mean values were (-23.63±1.53)‰, (-22.43±1.59)‰, and (-21.42±1.90)‰ for surface, middle, and bottom layers, respectively. The C values in the northeastern region of Chongqing tended to be more negative, whereas those in central Chongqing were less negative. Paddy fields showed the most negative values of C, followed by rice-upland rotating fields and upland fields, with the average being (-25.32±0.93)‰, (-23.17±1.37)‰, and (-24.75±1.28)‰ for the surface layers, respectively. For different soil types, the C values in the surface layers were in the order of paddy soil<alluvial soil<purplish soil<calcareous soil<yellow soil. According to the regression-tree analysis, the crop types predominantly influenced the variation in C in surface soils, and soil types mainly affected that in the middle- and bottom-layer soils. Other factors, such as soil properties (TN, SOC, and pH) and meteorological conditions (precipitation and air temperature) played only minor roles in the variation of C. In short, the stable isotope composition of organic carbon in the surface soils was primarily controlled by the input carbon source, whereas that in the deeper layers was closely linked with carbon cycling processes within the soils.
从重庆典型农田的182个土壤剖面采集土壤样本，分析土壤有机质（C）的稳定碳同位素组成。结果表明，各土壤剖面的C值随土壤深度增加而逐渐升高，表层、中层和底层的平均值分别为（-23.63±1.53）‰、（-22.43±1.59）‰和（-21.42±1.90）‰。重庆东北部地区的C值趋于更负，而重庆中部地区的C值则没那么负。稻田的C值最负，其次是水旱轮作田和旱地，表层的平均值分别为（-25.32±0.93）‰、（-23.17±1.37）‰和（-24.75±1.28）‰。对于不同土壤类型，表层的C值顺序为水稻土<冲积土<紫色土<石灰土<黄壤。根据回归树分析，作物类型主要影响表层土壤中C的变化，而土壤类型主要影响中层和底层土壤中C的变化。其他因素，如土壤性质（总氮、土壤有机碳和pH值）和气象条件（降水量和气温）在C的变化中仅起次要作用。简而言之，表层土壤中有机碳的稳定同位素组成主要受输入碳源控制，而深层土壤中的稳定同位素组成则与土壤内部的碳循环过程密切相关。
