Abstract: The thermal dissipation sap flow probe and the automatic weather station were applied to measure the sap flow of the artificial Populus and environmental factor for long-term in the dunes-meadow ecotone of Horqin Sandy Land. The results showed that the diurnal variation of sap flow velocity and meteorological factors varied significantly under different weather conditions, and each factor had obvious fluctuation characteristics of day and night in sunny days, and fluctuation extents were small in rainy days, and cloudy days were between the sunny day and rainy day; The main meteorological factors affecting the sap flow rate were different under different weather conditions, and the sap flow velocity was predominantly affected by net radiation in sunny days (partial correlation coefficient was 0.72), and affected by air temperature in cloudy days (partial correlation coefficient was 0.69); The average daily sap flow velocity of typical sunny day approximately obeyed quadratic curve in the whole growing season, and the summer was larger than the spring and the fall, and diurnal variation of sap flow velocity had significant differences in peak value, start time and peak time of sap flow in different months; Forest land had adequate water supply, and there were no significant differences in sap flow velocity after persistent drought and rain, and water required for transpiration of Populus was mainly from groundwater, and the groundwater table decreased significantly in 09:00-17:00, and the larger the sap flow velocity, the lower the groundwater table; For different diameter at breast height, the time lag of sap flow velocity to each meteorological factors was same, but for different months, the time lag of sap flow velocity to each meteorological factors varied obviously.

Key words: Populus, thermal dissipation probe, sapflow, environmental factors, season change