Abstract: The floristic equilibrium point and its biogeographic significance are important for understanding the floristic origin, distribution , and spatial patterns of plant diversity . Based on field surveys, documented data and related case studies, the relationship between altitude and latitude at floristic equilibrium points , and its biogeographic significance are examined. The results showed a floristic equilibrium point at 2 050m elevation on Mt . Yao , northeastern Yunnan, China. The elevation of the floristic equilibrium point decreases with an increase in latitude .Mean annual temperature at different floristic
equilibrium points shows high consistency around 12 . 96±0 . 28℃ , which hints that the floristic equilibrium point reflects certain energy requirements . Below the floristic equilibrium point , the majority of the flora contains tropical and subtropical elements; above that point temperate elements are dominant. According to the relationship between altitude and latitude at the floristic equilibrium point, the theoretical north-south dividing line between the vegetation in eastern China is around 36°N . According to the mean annual temperature at the floristic equilibrium point and spatial patterns of the isotherm in eastern China, the north-south boundary of vegetation is between 34 and 35°N, on the northern slope of the Qinling Mountains, which is consistent with previous case studies .

Key words: Floristic equilibrium point