16 Sep 2022
16 Sep 2022
Status: this preprint is currently under review for the journal HESS.

Technical note: Validation of Aleppo pine transpiration rate measurements using the heat ratio method under laboratory conditions

Ana M. Sabater1,2, José Antonio Valiente3, Juan Bellot2,4, and Alberto Vilagrosa1,2 Ana M. Sabater et al.
  • 1Mediterranean Centre for Environmental Studies (Fundación CEAM), Joint Research Unit University of Alicante–CEAM, PO Box 99, C. San Vicente del Raspeig, s/n,03080 Alicante, Spain
  • 2Department of Ecology, University of Alicante, C. San Vicente del Raspeig, s/n, 03080 Alicante, Spain
  • 3Mediterranean Centre for Environmental Studies (Fundación CEAM), C. Charles R. Darwin 14, Parque Tecnológico, 46980 Paterna, Valencia, Spain
  • 4The Multidisciplinary Institute for Environmental Studies (IMEM), University of Alicante, C. San Vicente del Raspeig, s/n, 03080 Alicante, Spain

Abstract. Tree transpiration considerably contributes to evaporative fluxes to the atmosphere in terrestrial ecosystems. Accurate transpiration quantification promotes the knowledge of water consumption by forests and could favour an adaptive forest management, especially in a global change context. Tree transpiration can be measured by a wide range of methods, and one of the valued ones is sap flow measurements. However, species-specific validations of techniques are required. Hence the objectives of this study were to validate transpiration rate measurements by the heat ratio method (HRM) in juvenile Aleppo pine trees (Pinus halepensis Mill.) by using the probe misalignment correction proposed by Larsen et al. (2020). This study simultaneously recorded the transpiration rate by tree sap flow following the HRM technique (THRM) and tree water losses by load cells (TOBS). These measurements were taken in combination with the environmental variables that control this process such as different vapour pressure deficit (VPD) ranges of air and the soil relative extractable water (REW). The results showed an accurate linear correspondence between TOBS and the transpiration rate measurements both without and with probe misalignment correction, THRM and THRM MIS, respectively, but interestingly underestimations at high transpiration rates were observed. However, underestimations were removed when applying probe misalignment correction. THRM MIS showed a good relation between the VPDxREW interaction. This study supports the notion that HRM offers accurate low values under a wide range of abiotic conditions, and is useful in isohydric species with low transpirations rates like Aleppo pine. To conclude, our results support the validation of both transpiration rate measurements by the THRM and probe misalignment correction in Aleppo pine under different environmental laboratory conditions.

Ana M. Sabater et al.

Status: open (until 11 Nov 2022)

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Ana M. Sabater et al.

Ana M. Sabater et al.


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Short summary
This paper is focused on the improvement of the quantifications of Aleppo pine water consumption using a sap flow method and the use of a correction recently proposed to increase the accuracy of these measurements. The validation protocol ensures a high-quality quantification of water consumption with applications to Mediterranean pine forests. These results have potential implications in forest adaptative management studies and may help to improve the forests health in the face of global change