Characteristics of Sap Flow in Eucalyptus urophylla Plantations on the Leizhou Peninsula

Heat pulse method was applied to study sap flux density (SFD) of single tree in 4-year-old Eucalyptus urophylla plantation from September 1999 to September 2000 on Leizhou Peninsula, southern China. The results indicated that SFD of outer sapwood moved faster than the inner; the daily SFD of trees with different diameter followed similar pattern, the bigger trees had faster SFD than smaller trees due to size of root system. To prove the accuracy of heat pulse method, water use of a 2-year-old young tree with height of 6 m was measured by the heat pulse method and a cut-stem method at the same time.It was showed that the estimated water use differed by 3.4% only. Among meteorological factors, solar radiation and VPD were the main factors affecting the sap flow. The heat pulse method was proved to be a accurate way to measure water transpiration by eucalypt tree plantations and recommended for wider application in water balance studies of plantations.