氮沉降升高下天山高寒草原N2O排放与土壤氮转化及氮去向研究

Emissions of Anthropogenic reactive nitrogen have greatly accelerated atmospheric deposition by reactive N species worldwide and resulted in the alternation of nitrogen cycle of grassland ecosystem. This project was conducted in the alpine grassland of Tianshan Mountains. Monitoring atmospheric N deposition, N addition experiments, 15N tracer technique combined with the static incubation method were conducted to research on the following aspects: Response of N2O emission to various N depositions and its annual and seasonal characters; Effect of soil N mineralization and growing season on the N2O emission; Nitrogen use efficiency and loss rate for N fertilization and the rate of N2O emission to N loss in alpine grassland ecosystem. This project will deepen our understanding of N cycle and help us manage grassland ecosystem.

人类活动加快了大气活性氮的释放, 导致全球氮沉降持续升高, 并且显著影响着草原生态系统的氮循环。本项目拟以新疆天山高寒草原为研究对象,通过大气氮沉降监测、外源氮添加、野外定位观测、室内模拟分析与15N示踪相结合的方法,揭示不同氮沉降水平下, N2O排放的季节变化特点；阐明土壤氮矿化、无机氮变化、关键生长阶段对N2O排放的影响机理；解析氮在高寒草原植物-土壤-大气系统的去向及其对N2O排放的影响；本研究对于深入理解草原生态系统的氮循环具有重要意义，有助于草原生态系统的健康管理和永续发展。

本研究以新疆天山巴音布鲁克高寒草原生态系统为对象，探讨氧化亚氮排放对氮素输入的响应，阐明土壤氮矿化和氮去向对其排放的影响。研究表明：天山高寒草原生态系统的气态HNO3、NH3和NO2的年沉降通量分别为1.47、0. 68 和0.13 kg N ha-1，颗粒物中铵态氮和硝态氮的年通量分别为0.23和0.25 kg N ha-1，降水中铵态氮和硝态氮的年沉降通量分别为2.47和1.59 kg N ha-1，研究区的无机氮沉降通量为6.82 kg N ha-1；春季融化阶段的土壤硝态氮浓度变化为27.43-70.47 mg Kg-1，土壤铵态氮无显著变化，净氮矿化在春季融化阶段表现为抑制效应。氮添加促进了生长旺季的净硝化速率，硝化速率与氧化亚氮排放表现为显著正相关；铵态氮和硝态氮在植物地上部分和根系的回收率没有显著变化，氨态氮和硝态氮的损失率约为50%，氧化亚氮的年排放通量约占氮肥输入量的0.2%-1.6%。