干旱区生态环境知识资源中心

Stem sap flow variations of Populus euphratica in the Ejina oasis at the lower reach of the Heihe River and their relations to the environmental factors were observed using the heat pulse velocity recorder (HPVR), test data recorder(TDR) and ICT automatic weather station in one-year period. The results showed that the daily variations of sap flow of Populus enphratica exhibited an unimodal character and occurred a lower value in the morning and night time due to the effects of root pressure; the sap flow at different points showed a similar variation tendency but increased with increasing depth. The sap flow reached a maximum value at the depth of 15mm and them decreased. In the orientation, the sap flow rate was much higher on the southern side( south, west) than on the northern side( north, east). Under the condition of water stress the stem sap flow fluctuated largely. The quantitative relation between the stem sap flow and meteorological factors can give a better prediction to the water consumption through the stem transpiration.