Evaluating the models of stomatal conductance response to humidity in a tropical rain forest of Xishuangbanna, southwest China

The ecosystem-level fluxes of water vapour and carbon dioxide were measured from 2003 to 2006 at a tropical rain forest in Xishuangbanna, southwest China, using the eddy covariance (EC) technique. These flux measurements allowed the canopy-level evaluation of stomatal conductance (g) response to humidity models. The results showed that both the BWB model and the Leuning model discussed here underestimated g at high humidity and overestimated g at the mid-to-low range of humidity. In contrast, the Wang models discussed here (model-h_a and model-D_a) perfectly described the relationship of g response to humidity. The model comparison results also demonstrated high consistency over all the observation years. The good performance of the Wang model-h_a and model-D_a indicated that stomatal conductance responds more sensitively to humidity deficit or water vapour pressure deficit than to relative humidity itself at canopy level.