By Wang Han
The model paper on our Pmodel was published in Geoscientific Model Development this week (https://doi.org/10.5194/gmd-13-1545-2020). Different from the theory paper of Pmodel (Wang et al., 2017), this model paper is aiming to archive and clarify the technical details of Pmodel, and evaluate Pmodel more thoroughly against a larger GPP dataset derived from a globally distributed network of ecosystem flux measurements.
Different from the earlier Pmodel version proposed by Wang et al. (2017), this new version includes improvements as below: (1) considering the temperature dependence of the intrinsic quantum yield based on experimental studies by the Bernacchi et al. (2003), (2) including an empirical constrain of soil moisture on GPP, (3) re-estimating the parameter value of β in the prediction of the leaf-internal to -ambient CO2 concentration, (4) re-calibrating the parameter of intrinsic quantum yield. Those improvements allow Pmodel to represent the impact of drought stress on GPP, seeing Stocker et al. (2019). Although this effect is implemented in an empirical way, the group has been working on developing new theory to improve the implementation. Hopefully, this empirical relationship could be eventually replaced by some theoretical function.
LPICEA people have also been working on improving and extending Pmodel. Han Wang has extended Pmodel to predict the thermal acclimation of leaf dark respiration (Wang et al., 2020). She is now working on the diurnal cycle of photosynthesis, trying to explain the sub-optimal vertical gradient of photosynthesis. She has also been working on developing a theoretical model of LMA, which has been shown as a key trait determining LAI and therefore the Pmodel prediction on GPP. Tan Shen is now applying Pmodel to predict evapotranspiration via the coupled linkage between photosynthesis and transpiration. Shengchao Qiao has extended Pmodel into a crop model to predict wheat yield in China (Qiao et al., 2020), and is now applying the new model at a global scale to diagnose the various impacts on global wheat yield. After testing the predictability of Pmodel on key photosynthetic traits variation along the Gongga elevation transect, Huiying Xu is now focusing on the coordination between hydraulic and photosynthetic traits, trying to develop new theory on the hydraulic constrains on carbon assimilation. Ziqi Zhu, Shen Tan, Shengchao Qiao and Han Wang are working together on understanding the environmental control on LAI from first-principles at the global scale.
Other relevant blog from the NextGen vegetation modelling group: https://research.reading.ac.uk/palaeoclimate/p-model-v1-0/
References
Bernacchi, C. J., Pimentel, C., and Long, S. P.: In vivo tem- perature response functions of parameters required to model RuBP-limited photosynthesis, Plant Cell Environ., 26, 1419– 1430, 2003
Qiao, S.C., Wang, H., Prentice, I. C. and Harrison, S.P.: Extending a first-principles primary production model to predict wheat yields, Agricultural and Forest Meteorology., 287, 107932, 2020
Stocker, B. D., Zscheischler, J., Keenan, T. F., Prentice, I. C., Seneviratne, S. I., and Peñuelas, J.: Drought impacts on terrestrial primary production underestimated by satellite monitoring, Nature Geoscience, 12, 264–270, 2019
Wang, H., Atkin, O. K., Keenan, T. F., Smith, N. G., Wright, I. J., Bloomfield, K. J., Kattge, J. Reich, P. and Prentice, I. C.: Acclimation of leaf respiration consistent with optimal photosynthetic capacity. 26(4), 2573-2583, 2020
Wang, H., Prentice, I. C., Keenan, T. F., Davis, T. W., Wright, I. J., Cornwell, W. K., Evans, B. J., and Peng, C.: Towards a universal model for carbon dioxide uptake by plants, Nat. Plants, 3, 734– 741, 2017