MSA: Dynamics of Chlorophyll Fluorescence and Its Relationship with Photosynthesis from Leaf to Continent: Theory Meets Data

光合作用是植物利用太阳能将二氧化碳（CO2）和水转化为糖和氧气的过程。光合作用可以直接在单个叶片中观察到，但不能在整个植物、地区、大陆或地球仪中观察到。这种能力阻碍了对未来粮食生产和地球气候变化的预测。太阳诱导叶绿素荧光（Solar-Induced Chlorophyll Fluorescence，SIF）测量是近年来卫星和地基观测技术的一个突破。SIF可以让我们在更大的尺度上估计光合作用。该项目将研究如何将SIF测量的光合作用从叶片应用到大陆水平。研究结果将使利用叶片光合作用的知识，以支持陆地生态系统的光合CO2吸收的未来能力的预测。SIF测量已经从正在进行和即将进行的卫星任务中进行。这些测量可以更好地估计碳源和汇，这可以为减缓和适应气候变化提供信息，并有助于预测未来的粮食生产。本研究的总体目标是建立在光合作用光反应的机械模型基础上的跨尺度分析框架。为了实现这一目标，将执行三项任务：1）通过建立具有关键植物生物物理和生化参数（例如，非光化学猝灭;（2）将理论光反应模型与冠层辐射传输模型相结合，以了解国家生态观测网络（氖）在广泛生态区的SIF-光合动力学的驱动因素; 3）使用国家大气研究中心（NCAR）社区土地模型（CLM）中实施的分析框架，限制美国相邻地区的光合作用估计和变化。所开发的数据库将在该项目结束后永久储存，并可供广大科学界使用和扩展。开发的理论模型将首次分解隐藏在传统使用的光利用效率概念中的复杂性。该项目将充分利用氖的机载观测平台数据集，以澄清叶黄素循环如何影响SIF，这还没有与SIF一起探索之前。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Photosynthesis is the process by which plants use the sun's energy to convert carbon dioxide (CO2) and water into sugar and oxygen. Photosynthesis can be directly observed in single leaves but not for whole plants, regions, continents, or the globe. This inability hinders the prediction of future food production and how Earth's climate may change. Measurement of Solar-Induced chlorophyll Fluorescence (SIF) is a recent breakthrough in satellite and ground-based observation. SIF may allow us to estimate photosynthesis for larger scales. This project will study how photosynthesis measured by SIF can be applied from the leaf to continental levels. The results will enable using knowledge of leaf-level photosynthesis to support prediction of the future capacity of photosynthetic CO2 uptake by terrestrial ecosystems. SIF measurements are already underway from ongoing and upcoming satellite missions. These measurements may allow better estimates of carbon sources and sinks, which can inform climate change mitigation and adaptation and help predict future food production.The overall goal of this research is to develop a cross-scale analytical framework, built upon the mechanistic models of light reactions of photosynthesis. To achieve this goal, three tasks will be performed: 1) develop and validate a leaf-level theoretical modeling framework for SIF and photosynthesis by building a database with key plant biophysical and biochemical parameters (e.g., non-photochemical quenching; fraction of open photosystem II reaction centers) of light reactions across a wide range of species and environmental conditions at Cornell Botanic Garden and Musgrave Research Farm; 2) integrate theoretical light reaction models with canopy radiative transfer models to understand the driving factors for SIF-photosynthetic dynamics across the National Ecological Observatory Network (NEON) sites across wide ecoregions; 3) constrain photosynthesis estimates and variability across conterminous US using the analytical framework implemented into the National Center for Atmospheric Research (NCAR) Community Land Model (CLM). The database developed will be permanently stored beyond the lifespan of this project and accessible and expandable by the science community at large. The theoretical models developed will, for the first time, decompose the complexities hidden in the traditionally used Light Use Efficiency concept. This project will fully utilize NEON's Airborne Observation Platform datasets to clarify how the xanthophyll cycle affects SIF, which has not yet been explored in conjunction with SIF before.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.