[Transpiration of Hedysarum scoparium in arid desert region of Shiyang River basin, Gansu Province].

By using heat pulse technique, an investigation on the transpiration of Hedysarum scoparium was conducted in the arid desert region of Shiyang River basin, Gansu Province. The results indicated that with increasing inserted depth of probe, the sap flow velocity in H. scoparium xylem had a trend from high to low. In the taproot with smaller diameter, the average sap flow velocity at different positions was faster, and the change range was bigger. Among the taproots with different diameters, there existed a larger difference in the magnitude of sap flux, but the change trend was similar, i. e., smaller at nighttime and larger at daytime, and showing a multi-peak curve. A linear correlation was observed between the diurnal sap flux and the reference crop evapotranspiration, and the transpiration mainly occurred during the period from June to September, occupying 79.04% of the total annual transpiration. The diurnal sap flux of H. scoparium at its later growth period had significant correlation with the moisture content in 0-50 cm sand layer, but no correlations with that in other sand layers. The effects of main meteorological factors on the sap flux of H. scoparium were in the sequence of air temperature > vapor pressure difference > wind speed.