Hydraulic conductivity-induced systematic parameter variation in a widely used thermal dissipation sap-flow technique
Ya-Jun Chen1,2,3, Phisamai Maenpuen1,2,4, Masatoshi Katabuchi1,2
1Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, 666303, China.
The New Phytologist
|August 26, 2025
Summary
Accurate sap-flow estimation using the thermal-dissipation method requires species-specific calibration coefficients. Recalibrated coefficients improve transpiration estimates, especially for species with high hydraulic conductivity, and account for scaling uncertainties.
Area of Science:
- Plant physiology
- Forestry science
- Hydrology
Background:
- The Granier-type thermal-dissipation method (TDM) is a widely used sap-flow technique.
- Original TDM calibration coefficients often underestimate high sap-flow rates, limiting their applicability across diverse species and wood properties.
Purpose of the Study:
- To derive and validate species-specific TDM coefficients for a broad range of plant types.
- To investigate factors influencing TDM coefficient accuracy and explore interspecific variations.
- To assess the impact of calibration and scaling uncertainties on transpiration estimates.
Main Methods:
- Derived new TDM coefficients (scaling factors and exponents) for 31 species (diffuse-porous, ring-porous, palms, lianas).
- Compiled 119 published coefficients for 88 additional species across seven xylem types.
- Analyzed factors influencing coefficients, including wood properties, statistical models, and calibration pressures.
- Investigated the role of vessel-lumen area fraction and hydraulic conductivity.
- Applied original and recalibrated coefficients to a rubber plantation for comparison.
Main Results:
- Recalibrated coefficients differed substantially from original values, particularly for ring-porous and liana species.
- Vessel-lumen area fraction and hydraulic conductivity explained interspecific variation in coefficients.
- Original coefficients yielded underestimated transpiration in a rubber plantation, while recalibrated ones provided reasonable estimates.
- Scaling uncertainties (sapwood area, radial/azimuth effects) significantly contributed to total estimation uncertainty.
Conclusions:
- Species-specific calibration is crucial for accurate TDM sap-flow measurements, especially for species with high hydraulic conductivity.
- Interspecific variation in coefficients is linked to wood anatomical and hydraulic traits.
- Addressing both calibration and scaling uncertainties is essential for reliable transpiration estimation.
Keywords:
evapotranspirationrubber plantationssap flowtranspirationtropical rainforestwater budgetwhole‐plant water usexylem typesMore Related Videos
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