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

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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.