Chin J Plant Ecol ›› 2024, Vol. 48 ›› Issue (4): 496-507.DOI: 10.17521/cjpe.2023.0043

• Research Articles • Previous Articles     Next Articles

Comparison of methods for dividing nighttime sap flow components in Populus tomentosa trees

YANG Shang-Jin1,2,3,*, FAN Yun-Xiang2,3,*, ZHANG Yu-Wen2,3, HAN Qiao-Ling1, ZHAO Yue1, DUAN Jie2,3, DI Nan4,**(), XI Ben-Ye2,3   

  1. 1School of Technology, Beijing Forestry University, Beijing 100083, China
    2Ministry of Education Key Laboratory of Silviculture and Conservation, Beijing Forestry University, Beijing 100083, China
    3Laboratory for Silviculture and Forest Ecosystem in Arid- and Semi-Arid Region of State Forestry and Grassland Administration, Beijing 100083, China
    4School of Ecology and Environment, Inner Mongolia University, Hohhot 010021, China
  • Received:2023-02-16 Accepted:2023-06-15 Online:2024-04-20 Published:2024-05-11
  • Contact: ** (dinan1225@163.com)
  • Supported by:
    National Natural Science Foundation of China(32001304);National Natural Science Foundation of China(32171763);Natural Science Foundation of Nei Mongol(2020BS03002)

Abstract:

Aims Nighttime sap flow can be lost through the leave stomata as nocturnal transpiration or stored in the stem as nocturnal refilling. Distinguishing transpiration and refilling from nighttime sap flow has been a challenging and pressing problem that needs to be addressed. Although the water-refilling forecasting method is widely used due to its convenience, its accuracy is highly questionable.
Methods To systematically analyze the accuracy and applicability of four water-refilling forecasting methods for the division of nighttime sap flow components, we conducted a study using Populus tomentosa as the test material. The thermal dissipation probe (TDP) were utilized to measure the nighttime sap flow. By combining the accuracy advantage of the height difference method in stem water-refilling with that of the water-refilling forecasting method in nighttime transpiration, we compared and analyzed the estimation effects of the four commonly used water-refilling forecasting methods in this study.
Important findings In terms of estimating the amount of the nocturnal transpiration using the four methods based on sap flow at different heights, only the linear decay model method (Line Method) showed no significant difference, while the other methods exhibited large deviations. When comparing the estimated stem water refilling using the four water-refilling forecasting methods with the results calculated by the height difference method, only the prediction method based on transpiration inversion (Et method) showed a significant difference, while the other methods did not. Additionally, among the four water-refilling forecasting methods, the Line method had the smallest deviation. Thereby, we propose using the sap flow height difference method for water-refilling forecasting to divide nighttime sap flow into three components, namely stem water-refilling, canopy water-refilling, and nocturnal transpiration. This method improves the estimation accuracy of stem water-refilling below the canopy by applying the height difference method. Furthermore, it enhances the accuracy in differentiating canopy water-refilling and nocturnal transpiration through the Line method with the smallest error. Using the new method, the calculated amount of nocturnal refilling was approximately 76.5%, which was 19.8%-26.5% higher than the findings of existing studies. The responses of the divided nighttime sap flow components to environmental factors indicated that vapor pressure deficit (VPD) and shallow soil water content were the main factors influencing nocturnal refilling. The proportion of nocturnal transpiration in nighttime sap flow exhibited a negative and nonlinear correlation with VPD.

Key words: comparison of methods, nighttime sap flow, nocturnal transpiration, nocturnal refilling, component division, poplar plantation, thermal dissipation probe