Abstract
Repeatable field measurements of water use by single trees or entire stands are of great interest to forest ecologists. Heat has been widely used as a means to evaluate sap flow rates for over 70 years; however the techniques used are intrusive and intrinsically disrupt the flow of sap to be measured. The only truly non-intrusive system developed to date is magnetic resonance imaging (MRI), but this is clearly not suitable for use in the field. We have therefore developed a non-invasive approach using a fibre-delivered, near-infrared laser source (λ=812 nm) for the pulsed heating of a small portion of the stem and an IR camera for monitoring the surface temperature in the region surrounding the point of heating. Heat flow occurs by a combination of forced convection (sap flow) and conduction, and so analysis of this changing temperature field can provide a measure of sap flow velocity.
© 2007 IEEE
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