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Transient thermal dissipation method for xylem sap flow measurement: implementation with a single probe
F C Do1, S Isarangkool Na Ayutthaya, A Rocheteau
1IRD, UMR Eco&Sols, Campus SupAgro-INRA, F-34060 Montpellier, France. frederic.do@ird.fr
Tree Physiology
|April 19, 2011
Summary
The transient thermal dissipation (TTD) method for measuring tree water relations can now use a single probe, simplifying xylem sap flow measurements. This low-cost, single-probe approach accurately estimates sap flux density, making it the simplest available technique.
Area of Science:
- Plant Physiology
- Environmental Science
- Forestry
Background:
- Accurate measurement of xylem sap flow is crucial for understanding tree water relations across various conditions.
- Existing methods like the constant thermal dissipation (CTD) and transient thermal dissipation (TTD) methods offer valuable data but can be complex or energy-intensive.
- Simplifying these measurements can increase accessibility and applicability in diverse research settings.
Purpose of the Study:
- To evaluate the applicability of the transient thermal dissipation (TTD) method using a single probe without a reference sensor.
- To assess if a simplified TTD method with a single probe maintains accuracy in estimating xylem sap flow rates.
- To determine if a previously established multi-species calibration is suitable for the single-probe TTD method.
Main Methods:
- Comparison of dual-probe and single-probe TTD responses in a laboratory hydraulic column using sawdust.
- Field validation of the single-probe TTD method by comparing diurnal sap flow kinetics in a young tree over five days.
- Analysis of thermal index and sap flux density estimations under varying flux densities and sapwood temperatures.
Main Results:
- Laboratory tests showed single-probe and dual-probe TTD methods yielded comparable temperature signals and thermal indices across a wide range of sap flux densities.
- In trees, interpolated cooled probe temperatures accurately reflected reference temperature changes, and single-probe sap flux density estimates matched dual-probe results.
- The thermal index from the single-probe method fell within the variability of the established multi-species calibration, supporting its non-species-specific application.
Conclusions:
- The transient thermal dissipation (TTD) method is effective and accurate when implemented with a single probe, eliminating the need for a reference sensor.
- This simplified single-probe TTD method offers a low-cost, user-friendly, and potentially the simplest technique for measuring xylem sap flow.
- The findings support the use of a non-species-specific calibration for diffuse porous trees, enhancing the method's broad applicability.
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