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Changes in stem water content influence sap flux density measurements with thermal dissipation probes

(2014) TREES-STRUCTURE AND FUNCTION. 28(3). p.949-955
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Abstract
There is increasing evidence of diel variation in water content of stems of living trees as a result of changes in internal water reserves. The interplay between dynamic water storage and sap flow is of current interest, but the accuracy of measurement of both variables has come into question. Fluctuations in stem water content may induce inaccuracy in thermal-based measurements of sap flux density because wood thermal properties are dependent on water content. The most widely used thermal method for measuring sap flux density is the thermal dissipation probe (TDP) with continuous heating, which measures the influence of moving sap on the temperature difference between a heated needle and a reference needle vertically separated in the flow stream. The objective of our study was to investigate how diel fluctuations in water content could influence TDP measurements of sap flux density. We analysed the influence of water content on the zero-flow maximum temperature difference, dTm, which is used as the reference for calculating sap flux density, and present results of a dehydration experiment on cut branch segments of American sycamore (Platanus occidentalis L.). We demonstrate both theoretically and experimentally that dTm increases when stem water content declines. Because dTm is measured at night when water content is high, this phenomenon could result in underestimations of sap flux density during the day when water content is lower. We conclude that diel dynamics in water content should be considered when TDP is used to measure sap flow.
Keywords
HEAT PULSE METHOD, CONDUCTIVITY, STORAGE, TREE TRUNKS, STOMATAL CONDUCTANCE, XYLEM EMBOLISM, FLOW MEASUREMENT, EMBOLISM FORMATION, LEAF HYDRAULIC CONDUCTANCE, Sap flow sensor, Wood thermal characteristics, Granier equation, NATURAL TEMPERATURE-GRADIENTS, Error analysis, Dynamic water content

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Citation

Please use this url to cite or link to this publication:

Chicago
Vergeynst, Lidewei, Maurits Vandegehuchte, Mary Anne McGuire, Robert O Teskey, and Kathy Steppe. 2014. “Changes in Stem Water Content Influence Sap Flux Density Measurements with Thermal Dissipation Probes.” Trees-structure and Function 28 (3): 949–955.
APA
Vergeynst, Lidewei, Vandegehuchte, M., McGuire, M. A., Teskey, R. O., & Steppe, K. (2014). Changes in stem water content influence sap flux density measurements with thermal dissipation probes. TREES-STRUCTURE AND FUNCTION, 28(3), 949–955.
Vancouver
1.
Vergeynst L, Vandegehuchte M, McGuire MA, Teskey RO, Steppe K. Changes in stem water content influence sap flux density measurements with thermal dissipation probes. TREES-STRUCTURE AND FUNCTION. 2014;28(3):949–55.
MLA
Vergeynst, Lidewei, Maurits Vandegehuchte, Mary Anne McGuire, et al. “Changes in Stem Water Content Influence Sap Flux Density Measurements with Thermal Dissipation Probes.” TREES-STRUCTURE AND FUNCTION 28.3 (2014): 949–955. Print.
@article{4413429,
  abstract     = {There is increasing evidence of diel variation in water content of stems of living trees as a result of changes in internal water reserves. The interplay between dynamic water storage and sap flow is of current interest, but the accuracy of measurement of both variables has come into question. Fluctuations in stem water content may induce inaccuracy in thermal-based measurements of sap flux density because wood thermal properties are dependent on water content. The most widely used thermal method for measuring sap flux density is the thermal dissipation probe (TDP) with continuous heating, which measures the influence of moving sap on the temperature difference between a heated needle and a reference needle vertically separated in the flow stream. The objective of our study was to investigate how diel fluctuations in water content could influence TDP measurements of sap flux density. We analysed the influence of water content on the zero-flow maximum temperature difference, dTm, which is used as the reference for calculating sap flux density, and present results of a dehydration experiment on cut branch segments of American sycamore (Platanus occidentalis L.). We demonstrate both theoretically and experimentally that dTm increases when stem water content declines. Because dTm is measured at night when water content is high, this phenomenon could result in underestimations of sap flux density during the day when water content is lower. We conclude that diel dynamics in water content should be considered when TDP is used to measure sap flow.},
  author       = {Vergeynst, Lidewei and Vandegehuchte, Maurits and McGuire, Mary Anne and Teskey, Robert O and Steppe, Kathy},
  issn         = {0931-1890},
  journal      = {TREES-STRUCTURE AND FUNCTION},
  language     = {eng},
  number       = {3},
  pages        = {949--955},
  title        = {Changes in stem water content influence sap flux density measurements with thermal dissipation probes},
  url          = {http://dx.doi.org/10.1007/s00468-014-0989-y},
  volume       = {28},
  year         = {2014},
}

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