Seminar: Jennifer E. Johnson

Tuesday, April 6, 2021 - 12:00pm

Jennifer E. Johnson

Research Associate, Carnegie Institution for Science

A new quantitative framework for understanding the responses of photosynthesis to the environment

The capture of incoming solar radiation by photosynthesis is one of the most critical inputs to the Earth system and one of the most difficult to monitor and predict accurately. Traditionally, the challenge has been that large-scale estimates of gross primary production have been based on measurements of carbon dioxide and there is no direct way to differentiate between the photosynthetic capture and the respiratory release of this trace gas. Against this background, the emerging space-based observations of solar-induced chlorophyll fluorescence have the potential to enable a major breakthrough because they provide the first large-scale measurement that is uniquely linked to photosynthesis. In order to take full advantage of this, we need an improved understanding of the processes that link photosynthetic light capture, carbon dioxide fixation, and fluorescence emission. In this talk, I will present experiments that provide a new perspective on the limits and regulation of steady-state photosynthesis in higher plants. Then, I will describe how I have translated these experimental results into a quantitative model that relates photosynthetic gas-exchange to chlorophyll fluorescence. Finally, I will outline a vision for how this model can be developed and applied in a data assimilation framework to advance understanding and management of the global carbon cycle.

Dr. Jennifer E. Johnson is a Research Associate in the Department of Global Ecology at the Carnegie Institution for Science. She received her PhD in Ecology and Evolutionary Biology from Stanford University, where she was a National Science Foundation Graduate Research Fellow and a Bing-Mooney Fellow in Environmental Science and Conservation. Her research has been recognized with the Dwight Billings Award for Physiological Ecology from the Ecological Society of America. Dr. Johnson’s interests center on understanding the state of the global carbon cycle, diagnosing the poise of carbon-climate feedbacks, and forecasting the future dynamics of terrestrial ecosystems and the atmosphere. Her current work focuses on developing a new quantitative model of photosynthesis that relates gas-exchange to chlorophyll fluorescence.

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