A double-ratio method to measure fast, slow and reverse sap flows.

Area of Science:

• Plant Physiology
• Hydrology
• Biophysics

Background:

• Sap velocity measurement is crucial for understanding plant water transport and hydrological processes.
• Existing heat-pulse methods struggle to accurately quantify sap flow across diverse velocity ranges, including very low or negative (reverse) flow.
• A robust method is needed to overcome these limitations in sap velocity measurement.

Purpose of the Study:

• To introduce and validate a novel method, the double-ratio method (DRM), for measuring sap velocity.
• To demonstrate the DRM's capability to measure sap velocity across an unprecedented range, including high, low, and reverse flow.
• To assess the DRM's ability to provide real-time estimates of wood thermal diffusivity.

Main Methods:

• The double-ratio method (DRM) utilizes one proximal and two distal temperature sensors relative to a heat source.
• Heat-pulse techniques are employed to quantify sap velocity based on temperature dissipation patterns.
• The DRM was validated using whole-tree lysimetry in Eucalyptus cypellocarpa.

Main Results:

• The DRM demonstrated robustness across a wide spectrum of sap velocities.
• The method showed strong agreement with lysimetry data, confirming its accuracy.
• Real-time estimation of wood thermal diffusivity was achieved.

Conclusions:

• The DRM offers a significant advancement in sap velocity measurement technology.
• This method overcomes limitations of previous techniques, enabling more comprehensive hydrological and plant water relation studies.
• The DRM's ability to measure reverse flow and provide real-time diffusivity is particularly valuable.