Spatial variations in sap flow rates in mature tree stems before and after drilling treatment

The dye uptake and heat transfer methods are used to understand sap movement in mature tree stems, but correlation of results between both methods is weak. The circumferential variation of sap movement is detected generally in the heated transfer method. On the other hand, the tangential movement such as helical ascent is tracked in dye uptake method. It is still unclear whether the circumferential and the tangential movements in both methods mean same and/or related phenomenon. In this study, we monitored sap flux density (Fd) on the east and west sides in intact stems of Betula ermanii Cham. using the thermal-dissipation method to identify Fd response to the creation of artificial flows through severed vessels by drill treatments. We then tracked sap flow by injecting dye solution. The Fd values in east side tended to be higher than that in west side before drilling treatment. Similar Fd values in both sides were detected after drilling treatments, and dye heights were similar to Fd values after drilling in any sides. Simple comparison of water ascent using both methods can lead to errors, because water ascent from severed vessels may differ from water ascent via roots.