Simulated carbon dioxide exchange of leaves of barley scaled to the canopy and compared to measured fluxes

Information on the exchange of carbon dioxide between the earth's surface and the atmosphere is critical for successful prediction of future climate. In the present study a model of leaf photosynthesis and stomatal conductance was parameterised based on field measurements of leaf photosynthesis and stomatal conductance. The simulated leaf gas exchange was scaled to the canopy level using the big leaf approach based on estimated radiation capture by the canopy and coupled to calculations of atmospheric resistance and soil carbon dioxide efflux to simulate the fluxes of carbon dioxide over a barley field. The model was found to be applicable for the conditions and simulated values agree well with canopy fluxes measured using the eddy covariance technique for a four-week period during the second field campaign of the Northern Hemisphere Climate processes Land-surface Experiment (NOPEX) in the region around Uppsala, Sweden, during June and July 1995. The rate of canopy development was high during the period and the leaf area index (LAI) changed from 0.7 to 3.5. Evaluation of the sensitivity of the model to driving variables and key canopy parameters showed high sensitivity to information on development and physiological characteristics of the canopy. (C) 1999 Elsevier Science B.V. All rights reserved.