Journal Article

A comparison of daily water use estimates derived from constant-heat sap-flow probe values and gravimetric measurements in pot-grown saplings

Katherine A. McCulloh, Klaus Winter, Frederick C. Meinzer, Milton Garcia, Jorge Aranda and Barbara Lachenbruch

in Tree Physiology

Volume 27, issue 9, pages 1355-1360
Published in print September 2007 | ISSN: 0829-318X
Published online September 2007 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/27.9.1355
A comparison of daily water use estimates derived from constant-heat sap-flow probe values and gravimetric measurements in pot-grown saplings

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Use of Granier-style heat dissipation sensors to measure sap flow is common in plant physiology, ecology and hydrology. There has been concern that any change to the original Granier design invalidates the empirical relationship between sap flux density and the temperature difference between the probes. Here, we compared daily water use estimates from gravimetric measurements with values from variable length heat dissipation sensors, which are a relatively new design. Values recorded during a one-week period were compared for three large pot-grown saplings of each of the tropical trees Pseudobombax septenatum (Jacq.) Dugand and Calophyllum longifolium Willd. For five of the six individuals, P values from paired t-tests comparing the two methods ranged from 0.12 to 0.43 and differences in estimates of total daily water use over the week of the experiment averaged < 3%. In one P. septenatum sapling, the sap flow sensors underestimated water use relative to the gravimetric measurements. This discrepancy could have been associated with naturally occurring gradients in temperature that reduced the difference in temperature between the probes, which would have caused the sensor method to underestimate water use. Our results indicate that substitution of variable length heat dissipation probes for probes of the original Granier design did not invalidate the empirical relationship determined by Granier between sap flux density and the temperature difference between probes.

Keywords: Calophyllum longifolium; Granier sensors; Pseudobombax septenatum; variable length probes; validation

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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