[Influence of measurement position on calculating pear tree stem sap flow]

By the method of heat pulse, this paper studied the influence of different measurement positions on calculating the stem sap flow velocity and quantity of pear trees. The results showed that at definite depths, the directional variation of the volume fraction of water and wood was lower than the seasonal change of wood physical parameters. The directional and seasonal variation of the volumetric water and wood was 0.01 - 0.03 and 0 - 0.02, and 0.02 - 0.09 and 0.02 -0.08, respectively. The sap flow velocity at definite depth, which was calculated by different depths wood physical parameters measured at the same time, had no significant difference, but that calculated by the same depth wood parameters measured at different time was significantly different. The sap flow quantity measured at the inner two points and four points was underestimated 1.5 and 4.9 times of that measured at the outer corresponding measurement positions, relative to the estimation obtained from a multi-point measurement. The sap flow quantity measured by four-point at the position of 0 - 0.6 from the cambium could represent the water consumption of whole tree.