Articles
Flexible external heat-pulse sap flow sensor for bi-directional measurement of sap flow in small-diameter stems
Article number
1419_21
Pages
169 – 180
Language
English
Abstract
At present, most sap flow sensors are probe-based and therefore inappropriate with small diameter trees, where large comparative amounts of cross-sectional xylem will be disrupted by the probes and heat produced.
While external non-invasive sap flow sensors can measure bi-directional flow in trees with diameters less than 10 mm, they are based on the heat ratio method derived from a line heat source.
This presents the potential to create localized heating around the heat source, disrupting the natural flow of sap within the tree.
Therefore, in this study, we propose a non-invasive sap flow sensor consisting of a ring heat source heating the circumference of the stem along with a modified heat ratio method.
Calibration of the measured heat pulse velocity ( ) was conducted by gravimetric measurement of an imposed flow through sections of stem.
Two species were examined: white poplar (Populus alba) and paper birch (Betula papyrifera). Preliminary results of the sap flow sensor show linear agreement of both species with their imposed flow, ranging between -20 to 20 g h‑1.
While external non-invasive sap flow sensors can measure bi-directional flow in trees with diameters less than 10 mm, they are based on the heat ratio method derived from a line heat source.
This presents the potential to create localized heating around the heat source, disrupting the natural flow of sap within the tree.
Therefore, in this study, we propose a non-invasive sap flow sensor consisting of a ring heat source heating the circumference of the stem along with a modified heat ratio method.
Calibration of the measured heat pulse velocity ( ) was conducted by gravimetric measurement of an imposed flow through sections of stem.
Two species were examined: white poplar (Populus alba) and paper birch (Betula papyrifera). Preliminary results of the sap flow sensor show linear agreement of both species with their imposed flow, ranging between -20 to 20 g h‑1.
Publication
Authors
M. Rennie, J. Morgenroth, M.J. Watson
Keywords
bi-directional sap flow, heat ratio method, sap flow sensor, white poplar (Populus alba), paper birch (Betula papyrifera)
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