CO<sub>2</sub> fertilization of terrestrial photosynthesis inferred from site to global scales.

Chen, Chi; Riley, William J; Prentice, I Colin; Keenan, Trevor F · Proc Natl Acad Sci U S A · 2022

basic_science · Level V

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Abstract

SignificanceThe magnitude of the CO<sub>2</sub> fertilization effect on terrestrial photosynthesis is uncertain because it is not directly observed and is subject to confounding effects of climatic variability. We apply three well-established eco-evolutionary optimality theories of gas exchange and photosynthesis, constraining the main processes of CO<sub>2</sub> fertilization using measurable variables. Using this framework, we provide robust observationally inferred evidence that a strong CO<sub>2</sub> fertilization effect is detectable in globally distributed eddy covariance networks. Applying our method to upscale photosynthesis globally, we find that the magnitude of the CO<sub>2</sub> fertilization effect is comparable to its in situ counterpart but highlight the potential for substantial underestimation of this effect in tropical forests for many reflectance-based satellite photosynthesis products.