A Li-6400 portable photosynthesis system was used to measure a few of photosynthetic physiology parameters of Pinus tabulaeformis growing under different soil water contents(SWC)on the sunny slope in southern foothill of Daqing Mountains.In order to determine the range of suitable SWC of the tree species growth,the response processes of net photosynthesis rate(Pn),carboxylation efficiency(Ce),transpiration rate(Tr),water use efficiency(WUE)to different SWC were studied,and the rule of its photosynthesis und...