Relationships among the net photosynthesis ( Pn ), light intensity ( L ),air temperature( T ),relative humidity ( RH ) of Quercus glauca at the levels of different leaf types, seasons, and the whole year were analyzed. Results showed that Pn was a positively bound to the L. The L determined Pn when T <25℃. But when T >25℃, it had a negative effect on Pn , and the effect became stronger as T rising. Low soil moisture made a strongly negative effect of T on Pn ....