Plan view of measured roots and their cross-sections at measured positions. Roots in NI treatment in 2018 (A) and 2019 (D), CI treatment in 2018 (B), and FI treatment in 2018 (C) and 2019 (E). Sap flow sensor positions in roots are marked by red points and blue lines are drip tubes with the emitters (A–E). Positions of the upper and lower sap-flow measured points in each root’s cross-section (F). The root piths are represented by black points and the vertical diameter of the root cross-sections are shown in brackets (F)