全球变暖和氮格局的改变对生态系统碳通量的变化具有深远的影响，长期的模拟增温和氮沉降实验对预测21世纪全球气候变化下草地生态系统生产力和碳匮缺的响应有着至关重要的意义。在中国东北松嫩草地开展4年的增温和施氮实验，通过测定羊草草地光合特性，试图揭示全球变化对羊草草地的碳、水通量产生的影响。试验采用一个封闭的光合测定系统（LI-6400）测定草地的碳、水通量变化，通过计算CO2的变化量确定净生态系统CO2交换量。结果表明，增温降低了净生态系统CO2交换量（NEE），净生态系统生产力（GEP）和生态系统蒸腾作用（ET），升高了生态系统呼吸（ER）和水分利用效率（WUE）；施氮处理刺激了NEE、ER、GEP和WUE；增温加施氮处理，氮素的添加缓解了因增温对生态系统产生的负效应。碳、水通量对全球变化的响应是通过改变生物群落中优势物种羊草的数量实现的，全球变化能在短期内迅速改变松嫩草地的碳通量。这些结果都有助于理解未来生态系统碳循环对全球气候变化的反馈。
The global warming and a changing nitrogen regime could have a profound impact on ecosystem's carbon flux, therefore, a good understanding of carbon flux responses to changing environmental conditions is critical for predicting the productivity and carbon sequestration potential of grass ecosystems during the 21st century. Measurements of photosynthetic characteristics were made in Yangcao (Leymus chinensis) grassland under a warming and nitrogen deposition soil during the period from 2006 to 2009. In situ diurnal Net Ecosystem CO2 Exchange (NEE) was measured by determining the rise in CO2 in IRGA. Analysis of CO2 fluxes during 4 years shows that the climate warming reduces NEE, Gross Ecosystem Productivity (GEP) and Evapotranspiration (ET), while increases Ecosystem Respiration (ER) and ecosystem Water-Use Efficiency (WUE). The increased N stimulates the NEE, ER, GEP and WUE. Under conditions of warming plus nitrogen, the nitrogen ameliorates the negative impacts of climatic warming on ecosystem carbon fluxes. Carbon flux responses to global change were driven overwhelmingly by gains and losses by Leymus chinensis, as the native plants in the Songnen grassland. Climate change could rapidly alter carbon fluxes in the Songnen grassland. These results provide an understanding of the future impact of the terrestrial carbon-cycle feedback on the global climate change.
