Abstract:

Research on stomatal behavior characteristics， influence on water use and response to environmental factors at blade scale， and stomatal conductance of the simulation， to understand the regional mechanism of vegetation and the ecological system to adapt to the environment and water resources management is of great significance. In this study， the photosynthetic physiological characteristics of Tamarix chinensis were observed by the LI-COR 6400 photosynthesis measurement system in the field， and the characteristics， influence， and response to environmental factors of stomatal conductance （G_s） of Tamarix chinensis leaves were analyzed. The results showed that： （1） Atmospheric relative humidity （h_s）， photosynthetically active radiation （PAR） and air temperature （T_a） had significant effects on G_s， and the correlation between the three environmental factors and leaves G_s was ranked as h_s （0.662） >PAR （0.613） >T_a （0.601） in descending order. （2） The diurnal variation trend of leaf G_s of Tamarix chinensis increased at first and then decreased. At 06:00， G_s increased with PAR enhancement and T_a increase， then PAR weakened and T_a decreased， then G_s decreased. Due to the high midday T_a in June and July， stomatal closure of leaves was caused， and the maximum G_s value appeared at around 10:00 in June and July， and around 14:00 in August and September. （3） At the end of the growing season， Tamarix chinensis could adapt to the arid environment by increasing WUE by regulating G_s to achieve efficient water use. （4） By using three different models： an experience model （Jarvis）， a semi-empirical model （BWB）， and the mechanism of stomatal conductance model （USO） to simulate G_s， the determination coefficient （R²）， the modified efficiency coefficient （MEC） and the root mean square error （RMSE） of the simulation results were （0.713， 0.409， 0.024）， （0.482， 0.309， 0.158） and （0.260， 0.135， 0.255）， respectively. Among the three models， the results of the Jarvis model simulation were obtained with the highest R² and MEC values and the lowest RMSE value， indicating that its simulation accuracy was the highest.

Key words: Tamarix chinensis, stomatal conductance, Jarvis model, BWB model, USO model