亚热带常绿阔叶林叶绿素荧光角度均一化校正及对总初级生产力估算精度的影响

Chlorophyll fluorescence is directly related to the photosynthesis of plants, so it is an important monitoring index of vegetation growth status and ecological functions. Sun-induced chlorophyll fluorescence (SIF) has become a new trend in the development of simultaneous observation of carbon flux and hyperspectral observations. However, considerable uncertainties in gross primary productivity (GPP) estimation using remotely sensed SIF exist due to variations in the sun-target-view observation geometry that could induce unwanted variations in SIF observation. In this study, we will carry out multi-angle observations of SIF in a subtropical evergreen broad-leaved forest in Dinghushan, to analyze the dynamic changes of GPP of the forest. Besides, the angular normalization of SIF model will be improved, to elucidate the effects of the sun-target-view observation geometry for SIF observation. We hope to reveal the association mechanism of SIF and GPP in subtropical evergreen broad-leaved forests, thus providing important technical methods and theories for monitoring the response and feedback of subtropical forest vegetation to climate change.

叶绿素荧光（SIF）与植物光合作用直接相关，是植被生长状况和生态功能的重要监测指标，成为当前碳通量与高光谱同步观测研究发展的新趋势。然而，观测几何（太阳–传感器–目标角度）变化对SIF和植被总初级生产力（GPP）之间关系的影响尚不清晰。本研究以鼎湖山亚热带常绿阔叶林为研究对象，开展日光诱导叶绿素荧光的多角度观测，分析亚热带常绿阔叶林林冠多角度SIF的动态变化特征，优化和改进荧光角度订正模型，阐明太阳–传感器–目标角度变化对SIF和GPP之间关系的影响，揭示亚热带常绿阔叶林植被荧光与GPP的关联机制，从而为监测亚热带森林植被对气候变化的响应和反馈提供重要的技术方法和理论支持。

本项目按照计划执行，在亚热带常绿阔叶林开展冠层 SIF 和GPP 的同步连续观测，通过连续 2 个生长季的季节变化观测，模型模拟，统计方法等研究叶片生理生化参数、冠层结构参数、荧光动力学参数以及冠层光化学反射率指数和太阳诱导荧光的日间和季节变化规律。项目重点开展了以下几个方面的研究：.· 通过多角度叶绿素荧光数据明晰观测几何（太阳-传感器-目标角度）对SIF-GPP之间关系的影响以及阳叶和阴叶对冠层SIF 的贡献并建立其估算模型；冠层SIF 估算GPP的误差随观测几何变化的特征，优化基于SIF 的GPP 估算模型.· 通过对叶片色素（叶绿素，类胡萝卜素和叶黄素等）以及叶片最大羧化速率的观测，分析叶片生理生化参数的季节变化规律，探讨叶片色素与叶片光合能力之间的关系；.· 通过对叶片光谱反射率的观测，分析叶片光谱反射率的日间和季节变化规律，并探讨叶片光化学反射率指数与叶片色素含量的组合与叶片光合能力的关系；.· 通过将叶绿素与叶片最大羧化速率的关系加入到生态系统过程模型中，改进叶片SIF和PRI对 GPP 季节变化的模拟效果