Institution: Proctor Maple Research Center

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Drivers of Sap Flow in Maple

Sap now in maple trees has been described many times. Milburn and O’Malley (1984) provided the first well-accepted modern description,which was later modified and improved by Tyree (1984), then further by Cirelliet al. (2008). Stem pressure and now in maple were then mathematically modelled in detail by Graf et al. (2015) with additional refinements and comparison with field-derived measurements by Zarrinderakhta et al. (2024). While these articles provide extensive detail into the anatomy and physiology of the science of the sap now mechanism, they are somewhat unavailable to most people. A good general description of the sap now mechanism is described in more modest detail in the Third Edition of North American Maple Syrup Producers Manual (Perkins et al. 2022), so won’t be discussed at length here. Rather, this article is aimed at describing pressure gradients and the sources and magnitude of those pressures as they related to sap exudation from maple tapholes.

Publication:
Maple Syrup Digest
Date:
December 15, 2024

Why Does the Sap Stop Running After a Few Days if it Doesn’t Freeze Again?

Without a freeze, the flow of sap will continue to slow and eventually stop because there is no longer a difference between the pressure inside and outside of the tree. However, producers often observe an uptick in sap flow during the daytime over a few days. Why does this occur? Where did the extra sap come from? Typically, these short bursts of increased sap flow happen when the temperature warms over the next few days. The warm temperature causes gas bubbles in the wood fibers to expand and squeeze more water from the wood tissues, where it flows into the vessels and out through the taphole. This might occur for a couple of days, and eventually turn into slow weeping flows before ceasing entirely.

Publication:
Maple Syrup Digest
Date:
March 27, 2023

North American Maple Syrup Producers Manual, 3rd Ed.

Since 1958 the North American Maple Syrup Producers Manual has served as a basic reference source for the production of pure maple products. This 2022 edition provides up-to-date, science-based information and recommendations relating to all aspects of the industry. The guidelines presented will help users ranging from the hobby and beginning producer level to those well-established in the industry. In addition, the information herein will benefit foresters, land managers, Extension and outreach personnel, and others aiming to provide assistance to those in the maple industry. Numerous photographs, tables, a glossary and hyperlinks to selected source materials are included.

This publication is also available in print, at www.mapleresearch.org/ordermanual.

Date:
July 19, 2022

Yields from Early Tapping and Taphole “Rejuvenation” Strategies

Because the impacts on yields of early tapping strategies, with or without subsequent rejuvenation, are likely to be affected by weather conditions which can vary widely from year to year, controlled experiments over multiple years are required in order to more fully assess whether any of these strategies result in greater yields than tapholes made during the standard spring sap flow period, or whether any increases in yield would be sufficient to compensate for the increased costs associated with implementing them. Thus, we conducted a multi-year, controlled experiment to assess the yields of several early tapping strategies, with and without subsequent rejuvenation, relative to the yields of standard spring tapholes.

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Date:
November 20, 2021

Climate Change & Maple

Dr. Tim Perkins (Director-University of Vermont Proctor Maple Research Center) discusses the intimate relationship between weather and maple sap flow, changing climatic conditions have the potential to affect the maple industry in a variety of ways. This presentation describes research that has been conducted on climate change and maple as well as new ongoing work, and describe some possible effects of changing climate on the future of the industry in the northeast.

Date:
April 11, 2018