我国草原下垫面碳水交换过程的年际变化特征及其控制因子

The response sensitivities of the grassland ecosystems in different climatic zones to climate variability have significant differences. Understanding of the underlying causes of variations in exchange of carbon and water vapor fluxes over grassland land surfaces is crucial for accurate estimates of regional carbon and water budgets, and for predicting the impact of climate change on grasslands and the carbon budget of grasslands. The obtained eddy covariance measurement data over four grassland land surfaces, including the Lijiang alpine meadow, the Bange alpine steppe in Tibet, the degraded grassland in the semiarid area of northeast China and the typical steppe in Inner Mongolia, will be used, and the project will carry out additional observations. The seasonal and interannual variations in carbon dioxide flux (gross primary production and ecosystem respiration) and actual evapotranspiration (canopy transpiration and soil evaporation) will be analyzed. The climatic and biological controlling factors of carbon and water fluxes in space and time over the grassland land surfaces in different climatic zones will be investigated. The other aims of this project are to establish the non-linear relationships between carbon and water fluxes and satellite remote sensing data; study the impact of carbon and water vapor fluxes measurements over grasslands on regional carbon and water budgets; and discuss the effects of inhomogeneities within the flux footprint on the site-scale flux measurements and the regional carbon and water fluxes. This study can provide scientific basis for the protection and sustainable development of the grassland ecosystems in China.

不同气候带的草原生态系统对气候变率的响应敏感度存在显著差异。研究草原下垫面碳水通量交换的控制因子，是精确估算区域尺度碳水收支的基础，对于预测气候变化对草原的影响及估算草原生态系统碳收支有重要意义。本项目拟利用丽江高山草甸、西藏班戈高寒草地、东北半干旱区退化草地和内蒙古典型草原已取得的涡动相关观测资料，同时开展补充观测；分析二氧化碳通量（总初级生产力和生态系统呼吸）和实际蒸散（植被蒸腾和土壤蒸发）的季节和年际变化特征，揭示不同气候带的草原下垫面碳水通量时空变化的气象和生物控制因子；建立碳水通量与卫星遥感资料的非线性关系，研究草原碳水通量观测对区域碳水收支的影响；讨论非均匀下垫面对通量观测和区域尺度上碳水通量的影响。本研究可以为我国草原生态系统的保护及其可持续发展提供科学依据。