Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates?

Hikaru Komatsu, Yoshinori Shinohara, Tomonori Kume, Kenji Tsuruta, Kyoichi Otsuki

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Stand transpiration (E) estimated using the sap-flux method includes uncertainty induced by variations in sap flux (F) within a tree (i.e. radial and azimuthal variations) and those between trees. Unlike radial variations, azimuthal variations are not particularly systematic (i.e. higher/lower F is not always recorded for a specific direction). Here, we present a theoretical framework to address the question on how to allocate a limited number of sensors to minimize uncertainty in E estimates. Specifically, we compare uncertainty in E estimates for two cases: (1) measuring F for two or more directions to cover azimuthal variations in F and (2) measuring F for one direction to cover between-tree variations in F. The framework formulates the variation in the probability density function for E (σE) based on F recorded in m different azimuthal directions (e.g. north, east, south and west). This formula allows us to determine the m value that minimizes σE. This study applied the framework to F data recorded for a 55-year-old Cryptomeria japonica stand. σEfor m = 1 was found to be less than the values for m = 2, 3 and 4. Our results suggest that measuring F for one azimuthal direction provides more reliable E estimates than measuring F for two or more azimuthal directions for this stand, given a limited number of sensors. Application of this framework to other datasets helps us decide how to allocate sensors most effectively.

Original languageEnglish
Pages (from-to)2129-2137
Number of pages9
JournalHydrological Processes
Volume30
Issue number13
DOIs
Publication statusPublished - Jun 30 2016

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transpiration
sensor
probability density function
measuring

All Science Journal Classification (ASJC) codes

  • Water Science and Technology

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Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates? / Komatsu, Hikaru; Shinohara, Yoshinori; Kume, Tomonori; Tsuruta, Kenji; Otsuki, Kyoichi.

In: Hydrological Processes, Vol. 30, No. 13, 30.06.2016, p. 2129-2137.

Research output: Contribution to journalArticle

Komatsu, Hikaru ; Shinohara, Yoshinori ; Kume, Tomonori ; Tsuruta, Kenji ; Otsuki, Kyoichi. / Does measuring azimuthal variations in sap flux lead to more reliable stand transpiration estimates?. In: Hydrological Processes. 2016 ; Vol. 30, No. 13. pp. 2129-2137.
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