植被物候对半干旱区草地生态系统碳交换过程的影响及数值模拟

The grassland ecosystem located in semiarid area is vulnerable to climate variability and human activities. Large annual variability of net ecosystem exchange (NEE) over this area has been observed. Plant phenology plays an important role in regulating annual variability of NEE. One promising avenue for better modeling of interannual variability of carbon exchange process is improved simulation of plant phenology. Based on long-term and continuous carbon fluxes measurement and remote sensing data, we investigate the effect of plant phenology.on interannual variability of carbon exchange process over grassland in semiarid area. The plant phenology variability and its controlling factors will be pointed out. Different land surface models which describe plant phenology with different schemes will be selected to simulate carbon exchange process over grassland ecosystem. The uncertainty of interannual variability of carbon fluxes caused by simulated plant phenology will be assessed. Plant phenology parameterized schemes will be improved based on further understanding of drivers on plant phenology. The feedbacks of carbon cycling on future climate change over grassland ecosystems will be discussed.

半干旱区草地生态系统受气候变化和人类活动影响敏感，其生态系统净碳交换过程存在较大的年际波动。植被物候对生态系统净碳交换的年际变化有重要的调节作用，改进植被物候的模拟可减少净碳交换年际变化模拟的不确定性。本项目拟利用已取得的多年连续的涡动观测资料，结合遥感资料，分析我国半干旱区草地生态系统植被物候对碳交换过程年际变化的影响，揭示植被物候的变化特征及主要的控制因子。选取包含不同物候参数化方案的陆面模式，模拟草地生态系统的碳交换过程，评估植被物候模拟对净碳交换年际变化的不确定性。结合植被物候主要控制因子的分析，尝试改进植被物候模拟的参数化方案，探讨草地生态系统碳循环过程对未来气候变化的可能响应。

半干旱区草地生态系统受气候变化和人类活动影响敏感，其生态系统净碳交换过程存在较大的年际波动。植被物候对生态系统净碳交换的年际变化有重要的调节作用，改进植被物候的模拟可减少净碳交换年际变化模拟的不确定性。本项目拟利用已取得的多年连续的涡动观测资料，结合遥感资料，分析了我国半干旱区草地生态系统植被物候对碳交换过程年际变化的影响，揭示植被物候的变化特征及主要的控制因子。选取包含不同物候参数化方案的陆面模式，模拟草地生态系统的碳交换过程，评估了植被物候模拟对该地区的适用性。结果表明，半干旱区的植被物候表现出显著的年际变异。最大净碳交换速率年际变异是影响净碳收支年际变异最显著的影响因子。生长季长度的年际异常对于净碳交换总量也有显著影响。SiBcrop模拟的总初级生产力达到峰值的日期以及累积净碳交换总量由负值转变为正值的日期等与观测更为接近。SiBcrop模拟的净碳吸收开始的日期优于净碳吸收结束的日期，且模拟的生长季净碳交换总量优于非生长季。本项目的研究结果为半干旱区应对气候变化提供了决策依据。