内蒙古河套灌区盐碱土壤CH4吸收和N2O排放特征及其驱动机制研究

Greenhouse gas causes global warming is the focus global environmental problem. Agriculture management change is an important strategy of greenhouse gas (GHG) mitigation. The Hetao irrigation district in inner Mongolia is one of three irrigation district in China and the important production basis of food supplies. Saline-alkali soils are widely distributed in the irrigation district in Inner Mongolia. Saline-alkali soil acreage was known as increased. Furthermore, in this area, fertilizer utilization rate was lower than the other areas, therefore, we conducted a study in the irrigation district in inner Mongolia to investigate the effects of saline-alkali soils on atmospheric CH4 uptake and N2O emission by field experiment and incubation experiment. Flux measurements were obtained using a closed-chamber method, and carried out continuously during the periods of in 2014,2015,2016 and 2017. The relationships between CH4 uptake, N2O emission capacity and soils' salinization were studied in incubation experiments. The objectives (i) were to investigate the impact of different mode of agricultural production ( fertilizer , irrigation and crop species) and the levels of different salinity on greenhouse gas uptake and emission in saline-alkali soils, and assess the spatial and temporal variability of net CH4 and N2O fluxes from different agriculture production mode in saline-alkali soils, and (ii) to indicate soil carbon and nitrogen cycle and the mechanisms in saline-alkali soils, and (iii) to explain the variability in CH4 and N2O fluxes by differences of soil properties and soil microbiology in saline-alkali soils. These findings suggest a basis for policymakers to find economical greenhouse gas (GHG) mitigation strategies in consideration of land use management and provide a scientific basis and data support for evaluation of greenhouse gas emission.

大气温室气体浓度升高和全球变暖是全球关注的热点问题。不同农业生产方式减缓农田温室气体排放潜力是当前各国政府和科学家关注焦点。本项目针对内蒙古河套灌区土壤盐碱程度严重，氮肥施用过量利用率低和黄河水漫灌三大特点，以河套灌区乌拉特前旗灌域盐碱土壤粮食作物-蔬菜复种模式农田和裸地为研究对象，通过水肥耦合、盐碱程度和复种模式土壤碳氮过程， CH4 吸收和N2O 排放通量原位观测研究，完成：1.比较盐碱土壤不同盐碱程度和不同农业生产方式温室气体CH4吸收和N2O排放强度和特征，盐碱土壤温室气体减排潜力评估；2.揭示盐碱土壤不同盐碱程度和不同农业生产方式土壤碳氮迁移转化时空变化规律，土壤功能变化动态特征和驱动机制；3.阐明盐碱土壤温室气体CH4吸收和N2O排放同土壤碳氮迁移转化过程关联的微生物学机制。研究结果将有助于降低我国温室气体排放总量估算的不确定性，为制定温室气体减排策略提供科学依据和数据支撑。

本研究针对全球变暖倍受关注的CH4和N2O两种重要的温室气体，研究内蒙古河套灌区不同盐碱程度土壤CH4吸收和N2O排放强度和过程及其微生物学机制。采取野外原位观测和室内机制相结合的研究方法，阐释不同盐碱程度土壤CH4吸收和N2O排放规律。(1)盐化土壤修复是减缓温室气体排放的重要措施。轻度盐碱土壤CH4累积吸收量在2014~2016年3个生长季分别为150.0 mg/m2，119.6 mg/m2，99.9 mg/m2，重度盐碱土壤CH4累积吸收量比轻度盐碱土壤分别降低27%，28%和19%；盐化土壤CH4累积吸收量比轻度盐碱土壤分别降低35%，35%和53%。(2)盐分含量是不同盐碱程度土壤N2O排放的驱动因子。N2O排放取决于不同盐碱程度土壤培养前后NH4+-N含量差值，加入外源盐后，N2O累积排放变化量的94.6％由土壤NH4+-N含量差值解释（R2＝0.95，p＜0.01）。(3)土壤甲烷氧化菌比活性是不同盐碱程度土壤CH4吸收潜力的根本驱动力。CH4浓度4.10×104 µg•kg-1盐碱土壤CH4累积吸收量大于大气外源CH4浓度6.85 µg•kg-1 CH4累积吸收量，不同盐碱程度土壤甲烷氧化菌比活性越高，CH4累积吸收量越大；盐碱土壤甲烷氧化菌比活性变化量越大，CH4累积吸收变化量越高。(4)轻度盐碱土壤减缓温室效应的潜力巨大。轻度盐碱土壤N2O累积排放量分别为180.6 mg/m2, 167.6 mg/m2, 118.2 mg/m2;强度盐碱土壤N2O累积排放量比轻度盐碱土壤分别增加19%, 26%和45%。轻度盐碱土壤CH4累积吸收量分别为150.0 mg/m2, 119.6 mg/m2, 99.9 mg/m2;强度盐碱土壤CH4累积吸收量比轻度盐碱土壤分别降低27%, 28%和19%。(5)土壤w (EC)、pH值、w (SOC)、w (TP)是土壤细菌群落结构多样性的显著影响因子。本研究的实施不仅有助于提供调控不同盐碱程度土壤CH4吸收和N2O排放的科学依据，也为脆弱农业生态环境改善提供数据支撑。