The Maple Sap Season in
Underhill Ctr., Vermont: Spring 2008
Proctor Maple Research Center - University of Vermont  

Open For The Spring Season

Temperature measurements (updated on the graph every 15 min.) are
made with thermocouples (extremely accurate temperature measuring
probes) inside or adjacent to several large sugar maple trees located
in the woods 600' SE of our laboratory. Air temperatures are measured
at 4.5' and 54' above the ground, and branch temperature is from the
center of a 1" branch located 54'. Trunk temperatures are measured in
a 22" diameter tree, at the depths indicated and at a height of 4.5'.

Sap pressure measurements are made by connecting small pressure sensors to 5/16" tapholes drilled 2" into the trunk on the north and south side a tree. Pressure measurements are from the same tree as the temperature measurements. Positive pressure, shown on the graph as pounds per square inch, is the pressure generated by thawing of frozen twigs, which causes sap to flow from wounds.  Negative pressure occurs when the temperature is below freezing, causing the tree to take up soil water. 

Sapflow shown on the graph is from a single taphole on either side of a large tree nearby. The lines on the graph represent cumulative flow; the flow rate can be estimated by the slope of the lines (periodically the sap totals are reset to zero so that the line will not go off the graph). Simultaneous flow and pressure measurements on the same tree are not used because the presence of an open taphole reduces sap pressure in the immediate vicinity of the wound and would yield misleading data.

After the data are generated, images are automatically created, and transferred to the UVM webserver at 30 min intervals through a fiber-optic network connection.

Questions or Comments about TreeMet, please e-mail Timothy Wilmot.

This document was created by T.R. Wilmot & T.D. Perkins, Proctor Maple Research Center. 03/09/04, revised 11/02/07.