Mesophyll conductance in land surface models: effects on photosynthesis and transpiration

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Knauer, Juergen; Zaehle, Soenke; de Kauwe, Martin; Haverd, Vanessa; Reichstein, Markus; Sun, Ying


2019-10-28


Journal Article


Plant Journal


101


4


858-873


858-873


The CO2 transfer conductance within plant leaves (mesophyll conductance, gm) is currently not considered explicitly in most land surface models (LSMs), but instead treated implicitly as an intrinsic property of the photosynthetic machinery. Here, we review approaches to overcome this model deficiency by explicitly accounting for gm, which comprises the re-adjustment of photosynthetic parameters and a model describing the variation of gm in dependence of environmental conditions. An explicit representation of gm causes changes in the response of photosynthesis to environmental factors, foremost leaf temperature, and ambient CO2 concentration, which are most pronounced when gm is small. These changes in leaf-level photosynthesis translate into a stronger climate and CO2 response of gross primary productivity (GPP) and transpiration at the global scale. The results from two independent studies show consistent latitudinal patterns of these effects with biggest differences in GPP in the boreal zone (up to ~15%). Transpiration and evapotranspiration show spatially similar, but attenuated, changes compared with GPP. These changes are indirect effects of gm caused by the assumed strong coupling between stomatal conductance and photosynthesis in current LSMs. Key uncertainties in these simulations are the variation of gm with light and the robustness of its temperature response across plant types and growth conditions. Future research activities focusing on the response of gm to environmental factors and its relation to other plant traits have the potential to improve the representation of photosynthesis in LSMs and to better understand its present and future role in the Earth system.


Wiley-Blackwell


Environmental Sciences not elsewhere classified


https://doi.org/10.1111/tpj.14587


Link to Publisher's Version


EP196454


Journal article - Refereed


English


Knauer, Juergen; Zaehle, Soenke; de Kauwe, Martin; Haverd, Vanessa; Reichstein, Markus; Sun, Ying. Mesophyll conductance in land surface models: effects on photosynthesis and transpiration. Plant Journal. 2019; 101(4 858-873):858-873. https://doi.org/10.1111/tpj.14587



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