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| Titel |
Determining Accuracy of Thermal Dissipation Methods-based Sap Flux in Japanese Cedar Trees |
| VerfasserIn |
Man-Ping Su, Yoshinori Shinohara, Sophie Laplace, Song-Jin Lin, Tomonori Kume |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137695
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| Publikation (Nr.) |
 EGU/EGU2017-490.pdf |
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| Zusammenfassung |
| Thermal dissipation method, one kind of sap flux measurement method that can estimate
individual tree transpiration, have been widely used because of its low cost and
uncomplicated operation. Although thermal dissipation method is widespread, the accuracy
of this method is doubted recently because some tree species materials in previous studies
were not suitable for its empirical formula from Granier due to difference of wood
characteristics. In Taiwan, Cryptomeria japonica (Japanese cedar) is one of the dominant
species in mountainous area, quantifying the transpiration of Japanese cedar trees is
indispensable to understand water cycling there. However, no one have tested the accuracy of
thermal dissipation methods-based sap flux for Japanese cedar trees in Taiwan. Thus, in this
study we conducted calibration experiment using twelve Japanese cedar stem segments from
six trees to investigate the accuracy of thermal dissipation methods-based sap flux in Japanese
cedar trees in Taiwan.
By pumping water from segment bottom to top and inserting probes into segments to
collect data simultaneously, we compared sap flux densities calculated from real water
uptakes (Fd_actual) and empirical formula (Fd_Granier). Exact sapwood area and
sapwood depth of each sample were obtained from dying segment with safranin stain
solution.
Our results showed that Fd_Granier underestimated 39 % of Fd_actual across sap flux
densities ranging from 10 to 150 (cm3m−2s−1); while applying sapwood depth corrected
formula from Clearwater, Fd_Granier became accurately that only underestimated 0.01 % of
Fd_actual. However, when sap flux densities ranging from 10 to 50 (cm3m−2s−1)which is
similar with the field data of Japanese cedar trees in a mountainous area of Taiwan,
Fd_Granier underestimated 51 % of Fd_actual, and underestimated 26 % with applying
Clearwater sapwood depth corrected formula.
These results suggested sapwood depth significantly impacted on the accuracy of thermal
dissipation method; hence, careful determination of sapwood depth is the key for the accurate
transpiration estimates. This study also apply the derived results to long-term field data in the
mountainous area in Taiwan. |
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