Estimates of the optimized value (for the entire dataset and by PFT) of leaf photosynthetic traits (Jfac, k3 and SLA).

The squared difference between measured Na and predicted Nac values were minimized by Newton’s method. A) The optimization was done with one trait at a time without changing the values of the two other traits. The optimized values are ordered by PFT (i.e. the first value corresponds to PFT1). B) The optimized values by PFT were compared to mean per PFT in the dataset by using a linear regression model. Abbreviations: PFT1, temperate broadleaved and coniferous evergreen trees; PFT2, temperate broadleaved deciduous trees; PFT3, deciduous shrubs and herbs; PFT4, perennial C3 grasses and forbs; PFT5, C3 crops (wheat); PFT6, N-fixing trees.