The Simulation of Leaf Stomatal Conductance of Populus euphratica in Desert Riparian Forest in Ejin

The response of photosynthesis of Populus euphratica Oliv.to changes of photosynthetically active radiation (PAR) and the relationship between leaf stomatal conductance and photosynthesis were studied using Li-6400 in Ejin oasis,based on the long-term leaf gas-exchange observations during May to September in 2005.The results showed that:(1)Net photosynthetic rate increases with increasing stomatal conductance (gs) initially,but when gs exceeds a certain value,it will decrease with increasing gs,which was attributed to non-stomatal factors;(2)The relationship between photosynthesis and PAR could be described by a non-rectangular hyperbola;(3)The B-B model could perfectly describe the relationship between the stomatal conductance and photosynthesis (R2=0.92).However,the simulated values of stomatal conductance by coupling a B-B model and a non-rectangular hyperbolic photosynthesis model are slightly greater than the observed values.Thus,it was necessary to consider the influence of water stress on the stomatal conductance in arid zone,and the future research should focus on the mechanism of physiological ecology based on the relationship among water and carbon cycles in terrestrial ecosystem,and try to develop a new water-carbon coupling cycle in arid terrestrial ecosystem.