DOE OSTI ยท 3384897
Atmospheric Feedbacks Reverse the Sensitivity of Modeled Photosynthesis to Stomatal Function
Abstract
Stomata mediate fluxes of carbon and water between terrestrial plants and the atmosphere. These fluxes are governed by stomatal function and can be modulated in many Earth system models by an empirical parameter within the calculation of stomatal conductance, the stomatal slope (๐ 1โข๐ ). Intuitively, ๐ 1โข๐ represents the marginal water cost of carbon, relating it to the emergent plant property of water use efficiency. Observations show that ๐ 1โข๐ can range widely across and within plant types in varying environments, and this distribution of ๐ 1โข๐ is not captured within Earth system models which represent each plant type with a single ๐ 1โข๐ value. Here we examine how ๐ 1โข๐ influences photosynthesis using coupled Earth system model simulations by perturbing ๐ 1โข๐ to observed 5โขtโขh and 95โขtโขh percentiles for each plant type. We find that high ๐ 1โข๐ reduces photosynthesis nearly everywhere, while low ๐ 1โข๐ has regionally dependent responses. Under fixed atmospheric conditions, low ๐ 1โข๐ increases photosynthesis in the Amazon and central North America but decreases photosynthesis in boreal Canada. These responses reverse when the atmosphere responds interactively due to spatially differing sensitivity to increases in temperature and vapor pressure deficit. Choice of ๐ 1โข๐ also influences photosynthetic response to changes in atmospheric carbon dioxide (CO 2 ), with lower and higher ๐1โข๐ modifying total global response to elevated 2x preindustrial CO 2 by +6.4% and โ9.6%, respectively. Our work demonstrates that atmospheric feedbacks are critical for determining the photosynthetic response to ๐ 1โข๐ assumptions and some regions are particularly sensitive to choice of ๐ 1โข๐ .
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Liu, Amy X. [University of Washington, Seattle, WA (United States)] (ORCID:0000000207250227), Zarakas, Claire M. [University of Washington, Seattle, WA (United States)] (ORCID:0000000199923785), Buchovecky, Benjamin G. [University of Washington, Seattle, WA (United States)] (ORCID:0009000630224488), Hawkins, Linnia R. [Columbia University, New York, NY (United States)] (ORCID:0000000166784248), Cordak, Alana S. [University of Georgia, Athens, GA (United States)] (ORCID:000900047403805X), Cornish, Ashley E. [University of Georgia, Athens, GA (United States)] (ORCID:000900068300434X), Haagsma, Marja [Oregon State University, Corvallis, OR (United States)] (ORCID:0000000217777284), Kooperman, Gabriel J. [University of Georgia, Athens, GA (United States)] (ORCID:0000000231744913), Still, Chris J. [Oregon State University, Corvallis, OR (United States)] (ORCID:0000000282954494), Koven, Charles D. [Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)] (ORCID:0000000233670065), Turner, Alexander J. [University of Washington, Seattle, WA (United States)] (ORCID:0000000314067372), Battisti, David S. [University of Washington, Seattle, WA (United States)] (ORCID:0000000348711293), Randerson, James T. [University of California, Irvine, CA (United States)] (ORCID:0000000165597387), Hoffman, Forrest M. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000158024134), Swann, Abigail L. S. [University of Washington, Seattle, WA (United States)] (ORCID:0000000185131074). 2025-11-17. Atmospheric Feedbacks Reverse the Sensitivity of Modeled Photosynthesis to Stomatal Function. https://doi.org/10.1029/2025ms005177
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