Abstract: Stomata are accesses of moisture and CO₂, and gateways for moisture evaporating and gas exchanging. Modeling has been the most effective and appropriate method for discussing the relationship between stomata and the environmental factors, when lacking the understanding of the stomata mechanism to environmental responses. Based on a Li-6400 portable apparatus, this article used two commonly used stomatal conductance models, Jarvis and BWB, to simulate the leaf stomatal conductance of Populus euphratica Oliv. on the basis of the measured data from June to September during the growing season in 2014. Results show that:the determination coefficient of the Jarvis model was 0.665, with RMSE, RE and MAE being 0.047, 0.011 and 0.002, respectively. The determination coefficient of the BWB model was 0.365, with RMSE, RE and MAE being 0.075, 0.447 and 0.061, respectively. This indicated that for the young and middle aged Populus euphratica Oliv. forest in arid and semi-arid regions, the simulation accuracy of the Jarvis model was better than that of the BWB model, and the simulated values based on the Jarvis model were closer to those observed by the Li-6400 portable apparatus. Possible reason was that the soil moisture content and temperature together determined the open or close of the stomata which would then confine the assimilation rate of CO₂, this was inconsistent with the premise of the BWB model.

Key words: Ejin oasis, extreme dry condition, Populus euphratica, stomatal conductance