Chen Xuan, Li Yu-E, Wan Yun-Fan, Gao Qing-Zhu, Wang Bin, Qin Xiao-Bo
Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences/Key Laboratory for Agro-Environment, Ministry of Agriculture and Rural Affairs, Beijing 100081, China.
Ying Yong Sheng Tai Xue Bao. 2021 Jun;32(6):1998-2006. doi: 10.13287/j.1001-9332.202106.030.
Losses of organic matter in agricultural watersheds result in eutrophication and land degra-dation, which not only threaten water quality and food security, but also lead to environmental problems such as the greenhouse gases emission. We used C, N and C/N as fingerprint markers to trace the sources of sedimentary organic matter at the outlet in the Nanyue small watershed. We analyzed the spatial distribution in watershed sedimentary organic matter and soils of typical land use types, including forest, paddy field, and vegetable fields. The Bayesian stable isotope mixing model was used to quantitatively estimate the contribution of different sources. The results showed that there was significant spatial variation of δC. The δC of sediment organic matter (-22.6‰±0.53‰) and forest soil (-23.13‰±1.71‰) was significantly higher than that of paddy soil (-25.24‰±1.4‰). The differences of δN among the sources were not significant, with sediment having the maximum (4.37±0.83)‰ and forest soil having the minimum (2.38±1.97)‰. Forest soil had the highest C/N of 16.66±7.18, while paddy soil had the lowest C/N of 11.95±0.92. The results of the Bayesian stable isotope mixture model showed that the contribution rates of forest land, paddy fields and vegetable fields to the organic matter deposited at the outlet in the watershed were 19.6%, 15.7%, and 64.7%, respectively. Paddy filed and vegetable field had a combined contribution rate of 80.4%. It was concluded that, soils of agricultural land were the main sources of organic matter deposited in the Nanyue small watershed, and that nutrient loss in the watershed would be effectively controlled by optimizing farmland management.
农业流域中的有机物质流失会导致富营养化和土地退化，这不仅威胁水质和粮食安全，还会引发温室气体排放等环境问题。我们使用碳、氮和碳氮比作为指纹标记来追踪南岳小流域出口处沉积有机物质的来源。我们分析了流域内典型土地利用类型（包括森林、稻田和菜地）的沉积有机物质和土壤的空间分布。利用贝叶斯稳定同位素混合模型定量估算不同来源的贡献。结果表明，δC存在显著的空间变异。沉积物有机质（-22.6‰±0.53‰）和森林土壤（-23.13‰±1.71‰）的δC显著高于稻田土壤（-25.24‰±1.4‰）。各来源之间的δN差异不显著，沉积物的δN最高（4.37±0.83）‰，森林土壤的δN最低（2.38±1.97）‰。森林土壤的碳氮比最高，为16.66±7.18，而稻田土壤的碳氮比最低，为11.95±0.92。贝叶斯稳定同位素混合模型的结果表明，林地、稻田和菜地对流域出口处沉积有机质的贡献率分别为19.6%、15.7%和64.7%。稻田和菜地的综合贡献率为80.4%。研究得出结论，农业用地土壤是南岳小流域沉积有机质的主要来源，通过优化农田管理可以有效控制流域内的养分流失。
