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Influence of stem temperature changes on heat pulse sap flux density measurements

(2015) TREE PHYSIOLOGY. 35(4). p.346-353
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Abstract
While natural spatial temperature gradients between measurement needles have been thoroughly investigated for continuous heat-based sap flow methods, little attention has been given to how natural changes in stem temperature impact heat pulse-based methods through temporal rather than spatial effects. By modelling the theoretical equation for both an ideal instantaneous pulse and a step pulse and applying a finite element model which included actual needle dimensions and wound effects, the influence of a varying stem temperature on heat pulse-based methods was investigated. It was shown that the heat ratio (HR) method was influenced, while for the compensation heat pulse and T-max methods changes in stem temperatures of up to 0.002 degrees C s(-1) did not lead to significantly different results. For the HR method, rising stem temperatures during measurements led to lower heat pulse velocity values, while decreasing stem temperatures led to both higher and lower heat pulse velocities, and to imaginary results for high flows. These errors of up to 40% can easily be prevented by including a temperature correction in the data analysis procedure, calculating the slope of the natural temperature change based on the measured temperatures before application of the heat pulse. Results of a greenhouse and outdoor experiment on Pinus pinea L. show the influence of this correction on low and average sap flux densities.
Keywords
WATER RELATIONS, NUMERICAL-ANALYSIS, BALANCE METHOD, WOODY-PLANTS, FLOW, TREES, GRADIENTS, TRANSPIRATION, transpiration, sensor, heat dissipation, sap flow, THERMAL-DIFFUSIVITY, DISSIPATION METHOD

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Citation

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Chicago
Vandegehuchte, Maurits, Stephen SO Burgess, Alec Downey, and Kathy Steppe. 2015. “Influence of Stem Temperature Changes on Heat Pulse Sap Flux Density Measurements.” Tree Physiology 35 (4): 346–353.
APA
Vandegehuchte, Maurits, Burgess, S. S., Downey, A., & Steppe, K. (2015). Influence of stem temperature changes on heat pulse sap flux density measurements. TREE PHYSIOLOGY, 35(4), 346–353.
Vancouver
1.
Vandegehuchte M, Burgess SS, Downey A, Steppe K. Influence of stem temperature changes on heat pulse sap flux density measurements. TREE PHYSIOLOGY. 2015;35(4):346–53.
MLA
Vandegehuchte, Maurits, Stephen SO Burgess, Alec Downey, et al. “Influence of Stem Temperature Changes on Heat Pulse Sap Flux Density Measurements.” TREE PHYSIOLOGY 35.4 (2015): 346–353. Print.
@article{8033007,
  abstract     = {While natural spatial temperature gradients between measurement needles have been thoroughly investigated for continuous heat-based sap flow methods, little attention has been given to how natural changes in stem temperature impact heat pulse-based methods through temporal rather than spatial effects. By modelling the theoretical equation for both an ideal instantaneous pulse and a step pulse and applying a finite element model which included actual needle dimensions and wound effects, the influence of a varying stem temperature on heat pulse-based methods was investigated. It was shown that the heat ratio (HR) method was influenced, while for the compensation heat pulse and T-max methods changes in stem temperatures of up to 0.002 degrees C s(-1) did not lead to significantly different results. For the HR method, rising stem temperatures during measurements led to lower heat pulse velocity values, while decreasing stem temperatures led to both higher and lower heat pulse velocities, and to imaginary results for high flows. These errors of up to 40\% can easily be prevented by including a temperature correction in the data analysis procedure, calculating the slope of the natural temperature change based on the measured temperatures before application of the heat pulse. Results of a greenhouse and outdoor experiment on Pinus pinea L. show the influence of this correction on low and average sap flux densities.},
  author       = {Vandegehuchte, Maurits and Burgess, Stephen SO and Downey, Alec and Steppe, Kathy},
  issn         = {0829-318X},
  journal      = {TREE PHYSIOLOGY},
  language     = {eng},
  number       = {4},
  pages        = {346--353},
  title        = {Influence of stem temperature changes on heat pulse sap flux density measurements},
  url          = {http://dx.doi.org/10.1093/treephys/tpu068},
  volume       = {35},
  year         = {2015},
}

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