Abstract: Authors investigated the effect of artificial flooding on physiological charactersitics of 16 poplar clones from the following three avenues; (1) effects of artificial flooding water level on physiological reponses among the clones; (2) effects of artificial flooding duration on physiological charac- terisitics; (3) clonal variation on resistance to flooding. Measured indicators include variable chlorophyll a fluorescence Fv. , leaf diffusion resistancere re, leaf transpiration rate Tr, leaf water potential . The results revealed that there existed significant differences among the clones in physiological values and there were remarkable effects of artificial flooding on both flooding duration and water level. Multivariate analyses showed that the clones were classified into three types of tolerance to flooding.