Accurate representation of photosynthesis in terrestrial biosphere models (TBMs) is essential for robust projections of global change. However, according to Alistair Rogers from Brookhaven National laboratory and his international colleagues, current representations of photosynthesis vary markedly between TBMs, contributing uncertainty to projections of global carbon fluxes. In an article recently published in New Phytologist, Rogers et al. compared the representation of photosynthesis in seven TBMs by examining leaf and canopy level responses of photosynthetic CO₂ assimilation (A) to key environmental variables: light, temperature, CO₂ concentration, vapor pressure deficit, and soil water content. These researchers identified areas where limited process knowledge prevents inclusion of physiological phenomena in current TBMs and research areas where data are urgently needed for model parameterization or evaluation. As a guide to help others, they provide a roadmap for new science needed to improve the representation of photosynthesis in the next generation of terrestrial biosphere and Earth system models. Rogers and his colleagues feel that the roadmap provides a useful template for meaningful collaboration between empiricists and modelers and that including the physiological outputs recommended as readily available diagnostic features will be a highly valuable addition in new TBMs.

Reference:

Alistair R, BE Medlyn, JS Dukes, G Bonan, S von Caemmerer, MC Dietze, J Kattge, ADB. Leakey, LM Mercado, U Niinemets, IC Prentice, SP Serbin, S Sitch, DA Way, and S Zaehle. 2017. A roadmap for improving the representation of photosynthesis in Earth system models. New Phytologist 213: 22-42. http://dx.doi.org/10.1111/nph.14283

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Figure 5. Summary of the main areas of scientific activity required to advance representation of photosynthesis in Earth system models. Blue boxes show areas where fundamental research is required to advance understanding before incorporation into models. Yellow boxes show areas where model refinement or development is required to improve process representation. Green boxes highlight areas where data are needed to parameterize models or are required to evaluate alternative approaches. The numbers in the boxes are keyed to our recommendations in the text.