Diurnal sap-flow relationship between stem and root 1 and within the measured positions in root 1. SFD recorded by the lower point of the sap-flow sensor (SFD_lower) versus SFD_stem (A), sap-flux density recorded by the upper point of the sap-flow sensor (SFD_upper) versus SFD_stem (B), and SFD_lower versus SFD_upper (C). Symbols of different colors represent different days: blue (August 17, 2018 when SWC at the depth close to root 1 was 0.18 cm³ cm⁻³), green (July 21, 2018 when SWC was 0.12 cm³ cm⁻³), yellow (August 12, 2018 when SWC was 0.07 cm³ cm⁻³). Filled symbols are 0:00–12:00, and open symbols are 12:00–24:00. The shaded area indicates positive sap flow, and the white area indicates reverse sap flow