Abstract:
Photosynthetic response to light and temperature was modeled using data from a small red alder (Alnus rubra B. ) community growing in a controlled environment chamber linked to the computer. This new system controls air temperature, root temperature, and vapor pressure over a wide range, and both light intensity and spectral quality are comparable with natural sunlight. Net photosynthetic rates are measured by continuously monitoring atmospheric CO in the gas-tight environment chamber. Photosynthetic measurements were taken
between 0.06 ly/min and 0.68 ly/min (total short-wave radiation) at temperatures from 6° to 30°C. A stepwise multiple linear regression analysis accounted for 98% of the variation in steady-state net photosynthesis using light and temperature plus two interaction terms as independent variables.
Non-linear models were constructed based on the known light curve for photosynthesis of single plants. The weighted average deviation of the data from the best non-linear model was + 3.7%. Extrapolation of
predicted photosynthetic response appears reliable except for an inconsistency at light energies below 5% full sunlight for temperatures less than 6°C.
