SAMBA – Solar-induced chlorophyll fluorescence (SIF) in the AMazon BAsin

通过光合作用的初级生产总值(GPP)是大气中最大的二氧化碳吸收机制，因此决定了大气中人为二氧化碳排放量的变异性。大量的碳在热带雨林中循环，占全球光合作用吸收二氧化碳的34%左右。然而，由于传统测量方法的巨大偏差，人们对热带雨林中的GPP仍然知之甚少。为了解决这一关键的知识差距，亚马逊盆地Samba-Solar诱导的叶绿素荧光(SIF)项目旨在量化热带雨林的碳吸收和光合作用，并分析它们与环境条件的关系。我们建议利用一种新的观测方法来检测太阳诱导的叶绿素荧光(SIF)，它是光合作用活性的指示器，并提供GPP的估计。在光合作用过程中，被叶绿素吸收的部分太阳辐射被光合作用有效辐射(PAR)吸收后在更长的波长(650-850 nm)处重新发射，即所谓的SIF，在红光(~685 nm)和远红光(~740 nm)光谱区有两个发射峰。然而，需要将现场叶片数据与SIF遥感全球尺度数据联系起来的冠层观测是稀疏的。拟议的工作将以申请者的经验为基础，使用最近开发的下一代冠层SIF仪器--PhotoSpec--进行空间分辨率的同步红色和远红SIF和植被指数观测。将在加州大学洛杉矶分校2015至2018年间开发的原始PhotoSpec设计的基础上建造PhotoSpec仪器，包括针对热带雨林部署进行调整的修改。该仪器将部署在巴西的亚马逊雨林进行数据收集，以获得对SIF和生态系统GPP的持续估计。我们建议利用现有的一组碳循环观测和土壤-树冠模型来利用这一综合数据集来研究季节物候、二氧化碳通量的变化，并最终研究热带雨林大气中二氧化碳的命运。这些活动的数据将改善基于过程的关于SIF和总二氧化碳通量的知识，这是更好地约束光合作用过程和碳通量的模型模拟所迫切需要的。这些活动将推动大气、生物和环境科学交叉领域的基础研究，并为评估气候变化的预测反馈提供关键信息。

Gross Primary Production (GPP) through photosynthesis is the single largest uptake mechanism of atmospheric CO2 and thus drives the variability of the airborne fraction of anthropogenic CO2 emissions. A significant amount of carbon is cycled through tropical rainforests, globally accounting for about 34% of CO2 uptake by photosynthesis, or GPP. However, GPP in tropical rainforests remains poorly understood due to large biases of traditional measurement methods. To address this critical knowledge gap, the project ‚SAMBA – Solarinduced chlorophyll fluorescence (SIF) in the Amazon Basin‘ aims to quantify the carbon uptake and photosynthesis of tropical rainforests and to analyze how they are linked to environmental conditions. We propose to make use of a new observation method to detect solarinduced chlorophyll fluorescence (SIF), which is an indicator for photosynthetic activity and provides an estimation of GPP. During photosynthesis, parts of the solar radiation absorbed by chlorophyll are re-emitted at longer wavelengths (650 – 850 nm) after absorption of photosynthetically active radiation (PAR), so-called SIF with two emission peaks in the red (~685 nm) and the far-red (~740 nm) spectral region. However, canopy observations, which are needed to link in-situ leaf data with remotely-sensed global scale data of SIF, are sparse. The proposed work will build on the applicant‘s experiences using the recently developed next- generation canopy SIF instrument - PhotoSpec - to perform spatially resolved simultaneous red and far-red SIF and vegetation index observations. A PhotoSpec instrument will be build based on the original PhotoSpec design developed at UCLA between 2015 and 2018, including modifications adjusted for tropical rainforests deployments. The instrument will be deployed in the Amazon rainforest of Brasil for data collection to obtain continuous estimates of SIF and ecosystem GPP. We propose to exploit this comprehensive data set with an existing set of carbon cycle observations and soil-canopy models to investigate changes in seasonal phenology, CO2 fluxes, and ultimately the fate of atmospheric CO2 from tropical rainforests. Data from the activities will improve the process-based knowledge on SIF and gross CO2 fluxes that is urgently needed to better constrain model simulations of photosynthetic processes and carbon fluxes. These activities will advance fundamental research at the intersection of atmospheric, biological and environmental sciences, and provide critical information to evaluate the predicted feedbacks of climate change.