The article taking the representative natural vegetation(Populus euphratica)in the lower reaches of Tarim River as the test vegetation,the air temperature,net solar radiation,atmospheric humidity,wind speed on the canopy top edge,groundwater level and cross sectional area of the P.euphratica,as initial influence factors of model based on the field test.Multiple linear regression model,nonlinear regression model and complete quadratic regression model were established based on the least square method;transpi...