Abstract: In this study, Dynamax sap flow measuring system and automatic meteorological station were used to estimate stem sap flow of Hippophae rhamnoides L. subsp. sinensis Rousi and its relationships with environmental factors during fruit stage in Ulan Buh Desert. The results showed that the stem sap flow of H. rthamnoides fluctuated significantly, with a singlepeak curve from day to night. The sap flow started at 8:00. The peak value of the sap flow appeared at about 10:00, being 227.94-307.86 g·h^-1. The minimum value of the sap flow appeared at about 21:30, being 11.04-26.29 g·h^-1. The sap flow was closely related to environmental factors. The sap flow rate and variation on clear days were generally higher than on cloudy and rainy days. Total radiation, air relative humidity, air temperature and wind speed were the major factors affecting the stem sap flow rate of H. rthamnoides. Moreover, the diurnal variation characteristics of transpiration rate was similar to the sap flow rate, but the peak value of the transpiration rate lagged about 3 hours compared to that of the sap flow.

Key words: soil organic carbon, reversion of desertification, carbon sequestration, soil particle