Chin J Plant Ecol ›› 2023, Vol. 47 ›› Issue (1): 123-133.DOI: 10.17521/cjpe.2021.0492

• Research Articles • Previous Articles     Next Articles

Root sap flow and hydraulic redistribution of Populus tomentosa

LIU Yang1, MA Xu2, DI Nan3, ZENG Zi-Hang4, FU Hai-Man5, LI Xin6, XI Ben-Ye1,**()   

  1. 1Ministry of Education Key Laboratory of Silviculture and Conservation, Beijing Forestry University, Beijing 100083, China
    2Chinese Society of Forestry, Beijing 100091, China
    3School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
    4School of Landscape and Architecture, Beijing Forestry University, Beijing 100083, China
    5Planning and Design Institute of Forest Products Industry, National Forestry and Grassland Administration, Beijing 100010, China
    6Sinton Technology Ltd., Beijing 100193, China
  • Received:2021-12-27 Accepted:2022-02-17 Online:2023-01-20 Published:2022-04-11
  • Contact: **XI Ben-Ye,ORCID:0000-0003-4730-6384(
  • About author:*Contributed equally to this work
  • Supported by:
    National Natural Science Foundation of China(31872702);National Natural Science Foundation of China(32171763);National Natural Science Foundation of China(32001304)


Aims To determine whether there is hydraulic redistribution in the root system of Populus tomentosa, and to explore its characteristics and influencing factors.
Methods The heat ratio method was used to monitor the long-term sap flow of 7 lateral roots (R1-R7) of four-year P. tomentosa trees, and the soil moisture and meteorological factors were measured simultaneously.
Important findings This study showed two patterns of hydraulic redistribution of P. tomentosa, namely, drought-induced hydraulic lift and rainfall-induced hydraulic descent. The occurrence and characteristic of hydraulic redistribution were affected by the distribution depth and diameter size of the lateral roots. In general, the magnitude of hydraulic redistribution was relatively low. In the growing season, the amount of water redistributed by P. tomentosa roots was low; however, under extreme drought conditions, the amount of water redistributed by the lateral roots could reach 64.6% of its total daily sap flow, indicating that hydraulic redistribution would provide plenty of water for dry lateral roots. This study showed that the root water uptake was significantly related to the meteorology-soil coupling factors (solar radiation (Rs) × soil water content (SWC), vapor pressure deficit (VPD) × SWC, reference evapotranspiration (ETo) × SWC), but not to the hydraulic redistribution. In addition, this study found a unique daytime reverse sap flow occurred in shallow lateral roots. The reverse sap flow could account for up to 79.2% (R1) and 90.7% (R2) of the total daily sap flow, which could play an essential role in the drought resistance of shallow roots.

Key words: Populus tomentosa, root sap flow, hydraulic redistribution, hydraulic lift