CO2浓度升高和气候变化对陆地生态系统碳水循环影响的不确定性分析

Significant changes of carbon and water cycles in terrestrial ecosystem are highlighted due to elevated atmospheric CO2 concentrations. One hand, owing to changes in climatic factors e.g. temperature and precipitation, terrestrial ecosystem carbon and water cycles have been modified. On the other hand, an increase of atmospheric CO2 concentration causes a growth in carbon input of terrestrial ecosystem, changes in vegetation structure and mechanism of vegetation stomatal regulation, then leading to changes in carbon and water cycles of ecosystem. However, lack of knowledge about climatic and physiological effects produced by increased CO2 concentration is a major factor resulting in great uncertainties of these models. Based on multiple coupled models in CMIP5, this study is intended to calculate the response indexes of the different variables of carbon and water cycles in response to elevated CO2 and climate change. Then their affecting strength and region are assessed quantitatively in global and Afro-Asian monsoon region at different spatial scales, as well as their relative contribution. The mechanism of the inherent uncertainty in simulated variables of carbon and water cycles among these models will be explored. In addition, using our atmosphere-ocean-land coupled model (FGOALS-AVIM), the feedbacks of vegetation structure and stomatal regulation on carbon and water cycles will be estimated quantitatively accompanied by elevated CO2, as well as their mechanism differences.

大气CO2浓度快速增加背景下，陆地生态系统碳循环和水循环发生了显著变化。一方面，由于气温和降水等气候因子的变化引起了陆地生态系统碳水循环的变化；另一方面，由于CO2浓度的变化直接改变了陆地生态系统的碳输入、植被形态和植被气孔调节机制，导致陆地生态系统碳水循环的变化。由于对CO2浓度变化引起的气候效应和生理效应认识上的不足，使得气候模式对陆地生态碳水循环模拟存在很大的不确定性。本申请拟基于CMIP5多模式集合，计算碳水循环不同变量对CO2浓度升高和气候变化的响应指数，定量评估全球和亚非季风区不同空间尺度的CO2浓度升高和气候变化对碳水循环影响的强度和范围，以及二者相对贡献的大小，探讨模式模拟碳水循环变量不确定性的机理。并利用我国海陆气耦合模式FGOALS-AVIM，定量研究CO2浓度升高背景下植被形态和植被气孔调节对碳水循环的反馈以及二者的机制差异。

CO2浓度快速增加背景下，基于CMIP5多模式集合数据，分析了陆地生态系统碳-水通量，包括陆地生态系统的净初级生产力 (NPP)、土壤呼吸 (RH)、净生态系统生产力 (NEP)和降水 (PR) 、蒸散 (ET) 、径流 (RUNOFF)）等变量，对大气CO2浓度升高和气候变化响应指数时空格局和历史演变过程以及不同模式模拟这些变量的不确定性。其中以亚马逊、北亚和东亚季风区为例，探讨CO2浓度升高和气候变化对典型区域的碳水循环动态影响以及驱动机制。基于耦合模式FGOALS-AVIM，包含了植被和土壤的碳循环过程以及与气候变化相互作用，研究CO2浓度快速增加情景下，降水是调节全球和东亚区域NPP、NEP变化的主要驱动力，若是降水减少，LAI降低，植被气孔导度减少，而气孔阻力增加。项目启动至今发表论文和论著共6篇，其中SCI文章3篇。