山地生态系统水碳耦合的带谱分异规律及其对水循环的影响

To identify the mechanisms of variations, causes of ecosystems water cycle and their impacts on watershed hydrological processes is a grant challenge in modern hydrology improvement. It is the bottleneck for developing the hydrological model and for meeting the important practical needs of the upper reaches of the Yangtze River water resource management to accurately express the highly heterogeneous eco-hydrological processes. By the use of the rich vertical vegetation zones and perfect altitudinal observation systems for water, soil, air, and organisms in Mt. Gongga, we are able to construct nested synchronous observation network in multi-vegetation zones for water and carbon coupling cycle process and its impacts on hydrological process of watershed. Based on ecosystem water cycle and carbon cycle and their coupling relationship, the present study intend to explore the internal mechanism of the interaction among water, vegetation and climate under different climatic zones, to reveal the relationship of water-carbon coupling, the patterns of spatio-temporal variation, and formation mechanism in different vegetation zones, and its impacts on hydrological process of watershed, to identify the eco-carbon process of key water cycle, to proceed the eco-hydrological model of watershed based on the coupling mechanism of ecosystem water-carbon. This study will be contribute to deepen the substantial recognition in water cycle pattern and variation process under the heterogeneous conditions of mountain vegetation zones, and to provide the crucial scientific basis for enriching and developing eco-hydrological model, accurately analyzing and forecasting the hydrological dynamics and water resource evolution in the reaches of Yangtze River.

不同生态系统水循环的差异性、成因及其影响流域水文过程的机理认知是现代水文科学发展的最大挑战，山地高度异质性的生态水文过程的准确刻画是解决流域水文模型发展瓶颈和长江上游水资源问题的重要现实需求。利用长江上游贡嘎山丰富的垂直植被带谱和完善的梯带水、土、气、生观测试验体系，构建山地生态系统水碳耦合循环过程及其对流域水文过程影响的多带谱嵌套式同步观测试验研究网络。以生态系统水循环与碳循环及其耦合关系为基础，探索山地不同气候带谱下的水、植被与气候相互作用的内在机制，揭示山地不同生态带谱水碳耦合关系、时空分异规律、形成机理及其对流域水文过程的影响，建立关键水循环过程的生态碳过程识别方法，发展流域尺度基于生态系统水碳耦合机理的生态水文模型。有助于深化对山地多带谱异质生态条件下的水循环规律与变化过程的本质认识，为丰富和发展生态水文模式、准确分析和预测长江上游水文动态与水资源演化提供关键科学依据。

陆地生态系统碳循环和水循环是陆地表层系统物质能量循环的核心，也是陆地生态系统相互耦合的2个重要生态学过程，更是全球变化科学研究的核心问题。然而，山地带谱的水碳平衡关系及其对水循环影响的认识还十分有限。基于贡嘎山海拔2800~3700m的暗针叶林生态系统为研究对象，发现：1）水分利用效率具有显著的时空变异格局，原因是碳获取和水分损耗对环境因子和生理因子响应差异所致；2）GPP和NPP的月变化和海拔梯度变化受温度和水分控制，而年际变化主要受辐射的控制；3）自养呼吸和异氧呼吸的季节变化和海拔梯度变化受温度影响显著，非生长季，生态系统呼吸变化与GPP变化一致，而生长季，生态系统呼吸变化受GPP和环境因子共同制约；4）季节尺度上，生态系统呼吸和蒸散发并没有显著相关关系，海拔梯度上，碳利用效率和蒸散发具有负相关关系。该研究揭示了山地暗针叶林生态系统水碳关系时空格局及影响机制，为未来继续探索山地生态系统碳循环对水循环过程的影响提供了科学基础。