A double-ratio method to measure fast, slow and reverse sap flows. (7th June 2021)

• Record Type: Journal Article
• Authors: Deng, Zijuan; Vice, Heather K; Gilbert, Matthew E; Adams, Mark A; Buckley, Thomas N
• Editors: Steppe, Kathy
• Is Part Of: Tree physiology. Volume 41:Number 12(2021)
• Page Start: 2438
• Page End: 2453
• Publication Date: 2021-06-07
• Subjects: double-ratio method -- Eucalyptus cypellocarpa -- heat-pulse-based technique -- sap flow -- sap flux -- sap velocity -- thermal diffusivity; Trees -- Physiology -- Periodicals; 582.16
• DOI: 10.1093/treephys/tpab081
• Languages: English
• ISSNs: 0829-318X

Abstract

Abstract: Sap velocity measurements are useful in fields ranging from plant water relations to hydrology at a variety of scales. Techniques based on pulses of heat are among the most common methods to measure sap velocity, but most lack ability to measure velocities across a wide range, including very high, very low and negative velocities (reverse flow). We propose a new method, the double-ratio method (DRM), which is robust across an unprecedented range of sap velocities and provides real-time estimates of the thermal diffusivity of wood. The DRM employs one temperature sensor upstream (proximal) and two sensors downstream (distal) to the source of heat. This facilitates several theoretical, heat-based approaches to quantifying sap velocity. We tested the DRM using whole-tree lysimetry in Eucalyptus cypellocarpa L.A.S. Johnson and found strong agreement across a wide range of velocities.