Abstract: Sap flow in Artemisia ordosica, together with environmental variables, were continuously measured in situ from July to October 2012. Results showed that weather conditions exerted a strong control over the diurnal pattern of sap flow. The daily maximum sap flow rates were 107.81, 79.40, and 4.34 g·cm^-2·h^-1 on sunny, cloudy and rainy days, respectively. Sap flow showed pronounced seasonal variations, with the maximum occurring in July and the minimum in October. During drought periods, daily sap flow rate increased with soil water content, with that measured at 30 cm depth having the highest explanatory power. Under higher soil water conditions, daily sap flow rate showed a strong correlation with micrometeorological factors. Based on correlation analyses, these factors were ranked as follows in terms of the magnitude of their effects on sap flow: vapor pressure deficit > solar radiation > average air temperature > relative humidity.

Key words: shelterbelt, Populus simonii, growth characteristics, Pinus tabuliformis., Ulmus pumila