Sap flow sensor integration for precision irrigation management in Christmas trees - a scoping review

Abstract

Smart agriculture is increasingly used to optimize irrigation management and improve water use efficiency. Sap flow measurement is a potentially effective technique for estimating plant water use and evaluating crop water demand, particularly in conifer species grown for commercial purposes such as Christmas tree production. Conifers possess unique xylem structures and hydraulic architectures that strongly influence water transport, transpiration dynamics, stomatal regulation, and physiological responses to drought stress. Several sap flow quantification techniques have been developed to measure sap velocity and estimate transpiration rates. However, measurement accuracy can be affected by factors such as sensor design, installation methods, location, environmental conditions, species-specific wood anatomy and soil-plant-water status. Consequently, calibration procedures and species-specific adjustments are necessary to improve the reliability of sap flow measurements in conifer species. This paper reviews current advances in sap flow measurement techniques and their application in irrigation management of conifers. It highlights the implications of conifer hydraulic traits for interpreting sap flow data and discusses the importance of calibration and methodological considerations. In addition, key research gaps and future directions are identified, emphasizing the need for improved measurement approaches and integration of sap flow technology into precision irrigation strategies to enhance water use efficiency.