青藏高原典型生态系统碳氮水循环过程及其气候效应

The geographical and topographical characteristics of the Qinghai-Tibetan Plateau, the highest plateau in the world with an extensive area, play a critical role in the regional and global climate systems. The climatic influences of the plateau are highly dependent on the carbon, nitrogen and water cycles in the plateau ecosystems, because these cycles contribute to not only the global warming potential but also the climatic system through changes in land surface processes. We will focus on these key ecosystem processes of the major vegetation at three ecological observatory platforms at Dangxiong, Haibei and Gangcha. We are to clarify the metabolism process of carbon, nitrogen and water in major plant functional types, and to characterize these processes in major ecosystems, through the long-term observation, manipulation experiments including the warming experiment through down-ward mini-ecosystem transplantation at Dangxiong and Haibei along altitudinal gradient, and the OTC warming experiment at the Gangcha permafrost. Using the data obtained from these approaches and from other resources, we will improve three current models, by including plants trait into a process based model, adding attitudinal effects into a physiological model (P-model) and combining soil processes to the VISIT model, to simulate the carbon, nitrogen and water cycles, and to make projections using climatic scenarios provided by IPCC 2013, to assess the effects of the ecosystem processes on the global warming potential.

青藏高原海拔高、面积辽阔，其独特的地理地形特征对区域环境和气候变化具有极为重要的影响，其影响的程度主要取决于高原生态系统的碳氮水循环过程，这不仅因为碳氮水对全球温室气体潜能具有很大贡献，同时也因为植被覆盖的变化会影响高原能量平衡，进而影响局部甚至全球气候。本研究以青藏高原典型生态系统为对象，聚焦最关键的生态系统过程，即碳氮水循环过程。我们将利用当雄和海北建立的高海拔和大海拔跨度研究平台以及在刚察建立的多时期热融冻土系列的研究平台，通过长期观测、移植或开放圆顶箱式增温、放牧围封控制实验、并利用以植物功能性状为核心的过程模型和以光合作用蒸腾作用的海拔效应为关键的机理模型，阐明青藏高原不同功能性植物的碳氮水代谢和典型生态系统的碳氮水循环过程，模拟这些过程在不同气候变化情景下的动态，预测碳氮水循环以及温室气体潜能，为探讨青藏高原生态系统过程的气候效应提供科学依据。

本项目的目的是，以青藏高原典型生态系统为对象，整合不同时空尺度的证据，阐明碳氮水循环的关键过程及其机理，模拟并预测这些过程在不同气候变化情景下的变化动态。项目的主要成果如下：在叶片和个体水平上, 对影响碳氮水代谢的生理生化与形态结构等关键性状进行野外观测、实验和模型分析，发现关键叶性状如叶大小、光学特性、碳水代谢等关键特性与海拔的变化规律、以及这些变化规律与气候要素的关系；在样地、区域以及生态系统水平上，通过大量的野外调查、实验观察、遥感与模型分析，阐释了高寒草地碳氮水循环关键参数的时空格局及驱动因素，特别就高寒草地碳氮循环关键过程对冻土融化的响应进行了系统而深入的研究，同时分析了多重气候要素影响植被生长的作用机理，评估了植被变化对青藏高原生态系统碳水通量的反馈影响。这些研究成果为理解和预测在全球变化背景下青藏高原碳氮水循环提供了新的证据、概念和理论基础。本项目培养了一批优秀的生态学研究人才。