Sap-flux density measurement methods: working principles and applicability
Maurits W. Vandegehuchte A B and Kathy Steppe A
+ Author Affiliations
- Author Affiliations
A Laboratory of Plant Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Gent, Belgium.
B Corresponding author. Email: maurits.vandegehuchte@ugent.be
Functional Plant Biology 40(3) 213-223 https://doi.org/10.1071/FP12233
Submitted: 3 August 2012 Accepted: 17 December 2012 Published: 11 February 2013
Abstract
Sap-flow measurements have become increasingly important in plant science. Since the early experiments with dyes, many methods have been developed. Most of these are based on the application of heat in the sapwood which is transported by the moving sap. By measuring changes in the temperature field around the heater, sap flow can be derived. Although these methods all have the same basis, their working principles vary widely. A first distinction can be made between those measuring the sap-flow rate (g h–1) such as the stem heat balance and trunk sector heat balance method and those measuring sap-flux density (cm3 cm–2 h–1). Within the latter, the thermal dissipation and heat field deformation methods are based on continuous heating, whereas the compensation heat pulse velocity, Tmax, heat ratio, calibrated average gradient and Sapflow+ methods are based on the application of heat pulses. Each of these methods has its advantages and limitations. Although the sap-flow rate methods have been adequately described in previous reviews, recent developments in sap-flux density methods prompted a synthesis of the existing but scattered literature. This paper reviews sap-flux density methods to enable users to make a well founded choice, whether for practical applications or fundamental research questions, and to encourage further improvement in sap-flux density measurement techniques.
Additional keywords: heat pulse, heat balance, transpiration, plant water relations, review, sensor.
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