© 2000 Heron Publishing—Victoria, Canada
Modeling the influence of temperature on monthly gross primary
productivity of sugar maple stands
Frédéric Raulier (1), Pierre Y. Bernier (1) and Chhun-Huor Ung (1)
1. Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 3800, Sainte-Foy,
Quebec, G1V 4C7, Canada / Received October 22, 1999
Summary
A bottom-up and a top-down model were used to estimate the effect of temperature on monthly gross primary productivity (GPP)
of sugar maple (Acer saccharum Marsh.). The bottom-up model computed canopy photosynthesis at an hourly time step from detailed physiological sub-models
of leaf photosynthesis and stomatal conductance. Leaf mass per area was used as a covariable to integrate photosynthesis through
the canopy. The top-down model used a radiation-use efficiency coefficient to relate canopy gross photosynthesis to absorbed
photosynthetically active radiation at a monthly time step. The parameters of the top-down model were estimated from simulations
with the bottom-up model. Forty single-year simulations were made using records of daily maximum and minimum temperatures
from weather stations selected within the natural range of sugar maple in the province of Québec, Canada. Leaf area index
was randomly varied between 4 and 10. Within a broad range of values, temperature had a minor effect on predicted monthly
canopy-level GPP and its contribution to explaining the variability of GPP was low, both through its direct effect on photosynthetic
processes (1.1%), and indirectly through the effect of relative humidity on stomatal conductance (4.0%). This result was unchanged
when key parameters relating photosynthesis to temperature and stomatal conductance to atmospheric humidity were changed in
the bottom-up model. An increase in time step from hourly to monthly resulted in a downward shift in the optimum temperature
range for photosynthesis, from 30 °C for a leaf at saturating irradiance to 22 °C for the canopy at a monthly time scale.
Keywords:
Acer saccharum, canopy photosynthesis, gross primary productivity, leaf mass per area, radiation use efficiency, temperature.
