## Abstract

Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate (V_{cmax}). Estimating this parameter using A-C_{i} curves (net photosynthesis, A, vs intercellular CO_{2} concentration, C_{i}) is laborious, which limits availability of V_{cmax} data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO_{2} concentration (A_{sat}) measurements, from which V_{cmax} can be extracted using a 'one-point method'. We used a global dataset of A-C_{i} curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate V_{cmax} from A_{sat} via this 'one-point method'. If leaf respiration during the day (R_{day}) is known exactly, V_{cmax} can be estimated with an r^{2} value of 0.98 and a root-mean-squared error (RMSE) of 8.19 μmol m^{-2} s^{-1}. However, R_{day} typically must be estimated. Estimating R_{day} as 1.5% of V_{cmax,} we found that V_{cmax} could be estimated with an r^{2} of 0.95 and an RMSE of 17.1 μmol m^{-2} s^{-1}. The one-point method provides a robust means to expand current databases of field-measured V_{cmax}, giving new potential to improve vegetation models and quantify the environmental drivers of V_{cmax} variation.

Original language | English |
---|---|

Journal | New Phytologist |

Early online date | 31 Dec 2015 |

DOIs | |

Publication status | Published - 2015 |

## Keywords

- A-C curve
- Leaf respiration during the day (R)
- Maximum carboxylation rate (V)
- Net photosynthetic rate at saturating irradiance and at ambient atmospheric CO concentration (A)