Multi-layer model of CO2 exchange in a plant community coupled with the water budget of leaf surfaces

In order to examine the impact of a rainfall event on the CO2 flux above a plant community, a multi-layer model for CO2 and H2O exchange was coupled with the processes of rainfall interception and the water budget of leaves. The performance of the CO2 gas and water exchange model was investigated under conditions of intense short wave radiation during and following a rainfall event. The model could simulate how leaves become wet within a canopy during a rainfall event and how leaves dry afterwards, as well as the water and energy budgets in the canopy. The simulated CO2 flux over a plant community was compared with and without rainfall, and showed that wet leaves caused more net CO2 absorption by the canopy during and after a rainfall event for the set of parameters used. Simulated transpiration, leaf temperature, and stomatal conductance were investigated in canopy layers, and it was found that evaporation from leaves decreases leaf temperature and changes stomatal conductance, and that both changes affect the net assimilation rate within the canopy. This study suggests that the both changes in stomatal conductance and leaf temperature caused by evaporation from wet leaves can influence the net CO2 exchange between a plant community and the atmosphere. (C) 2002 Elsevier Science B.V. All rights reserved.