Modelling forest transpiration and CO2 fluxes—response to soil moisture stress

The effects of soil drought on the leaf gas exchange variables of a stomatal conductance model are assessed in the case of woody plants, based on a meta-analysis of data sets available from the literature. For the first stage, 32 data sets obtained in well-watered conditions are analysed. For the second stage, we analyse four data sets including a soil drying cycle under present and doubled atmospheric CO2 concentration (350 and 700 μmol mol−1, respectively) for two tree species, maritime pine and sessile oak. Interesting relationships emerge, which suggest that woody plants may adopt one or two strategies when facing drought. A simple parameterisation of the effects of soil drought is proposed to account for the two types of drought responses which are: drought-avoiding (maritime pine) and drought-tolerant (sessile oak).