Sap flow measurements in grapevines (Vitis vinifera L.) 2. Granier measurements |
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Authors: | Braun P Schmid J |
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Institution: | 1.Institut für Obstbau und Gemüsebau, Universit?t Bonn, Auf dem Hügel 6, D-53121, Bonn, Germany ;2.Forschungsanstalt Geisenheim, Fachgebiet Rebenzüchtung und -veredlung, Von Lade Str. 1, D-65366, Geisenheim, Germany ; |
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Abstract: | The Granier-system, a relatively simple and continuous method for measuring sap flux density, has been adapted and evaluated
for its use in older, mature grapevines. The original calibration of Granier (1985, Annales Sciences Forestieres, 42, 193-200)
could be extended to a sap flux density of up to 400 10-6 m3 m-2 s-1 with only little error at high flux densities. A time lag of around 20 min was apparent between transpiration and calculated
sap flow which was attributed to the thermal mass of the sensors themselves. The time lag and the consequently dampened response
of the system caused a very low accuracy over short time periods thus reducing the value for detailed plant physiological
investigations. However, when integrating over longer time intervals, much of the error cancelled out. For daily values the
maximum error was within ±10% and after a period of 89 days only 1.5% error remained. This method is thus best suited for
long term measurements of total water use.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | Huber value Granier method modelling sap flux density Vitis water use xylem flow |
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