The Granier-type thermal dissipation probes(TDP) were applied to a naturally-growing Quercus liaotungensis tree in the semiarid loess plateau region to measure the long-term dynamics and azimuthal variations of sap flow on xylem trunk.Air temperature,relative air humidity,and solar radiation were monitored at the same time.In this paper,the correlations among sap flux densities at four different azimuthal directions,effects of different data source on the estimates of whole-tree sap flow and transpiration,a...