The sugar concentrations and the volume yields of Acer saccharum Marsh. sap from trees with single tapholes both show large variations from year to year and during sap flow seasons. Daily measurements of sugar concentration and volume yield from 29 trees for 18 years show consistent patterns. High sugar concentrations and high volume yields are characteristic of some trees; lower sugar concentrations and smaller volume yields are characteristic of other trees. A regression analysis shows a highly significant relationship between sugar concentration and volume yield in individual trees.
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More then a decade ago there was a renewed realization that microbial contamination of maple sap collection systems was having a significant detrimental impact on sap yields. Several research studies to investigate ways to improve sap yields from tubing systems were undertaken at both the University of Vermont Proctor Maple Research Center (Underhill, VT) and at the Cornell University Arnot Forest (Van Etten, NY) starting at about the same time and proceeded both as independent and joint projects from 2009-2018. The results of many of these studies have been reported in the past in numerous individual publications and presentations. This article seeks to combine and present this extensive body of work into a single, comprehensive, but concise summary of our results.
The current ‘traditional’ tap hole number guidelines involve adding a tap for each 5 inch dbh above 10 inches dbh. ‘Conservative’ guidelines involve placing one tap in trees 12 inch dbh and a second tap in trees more than 18 inches dbh. The reasons behind the traditional guidelines are not stated in the North American Maple Syrup Producers Manual, but the conservative guidelines are suggested when there is concern for tree health. The purpose of this article is discover where these guidelines came from and to re-establish the reasons why they exist.
The initial application of plastic tubing for gathering maple sap in the 1950s was indisputably one of the most significant technological developments of the maple industry in the twentieth century. However, the first viable tubing system was introduced over forty years earlier as a gravity drawn system made completely of metal.
Sap exudation refers to the process whereby sugar maple trees (Acer saccharum) are capable of generating significant stem pressure in a leafless state, something that occurs to a lesser extent in only a few other related species such as birch and walnut. This exudation pressure is what causes maple sap to flow from a taphole in sufficient quantities to be harvested and processed into syrup. Exudation has been studied for well over 100 years and has been the subject of many scientific studies, but there is as yet no definitive explanation for how such large pressures can be generated in the absence of transpiration (i.e., when no photosynthesis occurs to drive the flow of sap).
This article is intended to accompany the Tapping Zone Model available to download at the University of Vermont Proctor Maple Research Center (UVM-PMRC) website. It provides a general explanation of the model and how it can be used. The model can be used to estimate the chances of hitting conductive and nonconductive wood when tapping, and this can be used to assess the sustainability of current or planned tapping practices.
A model that calculates the proportions of conductive and nonconductive wood in the tapping zone of a tree over time given user-input values for tree diameter and tapping practices.
A new method of gathering sap from sugar maple saplings is being tested.
Research conducted at the University of Vermont Proctor Maple Research Center over several years to explore a variety of methods to potentially increase sap yields from tubing systems through modifications of the lateral/dropline portion of the sap collection system.
Maple sap is a complex nutrient matrix collected during spring to produce maple syrup. The characteristics of sap change over the production period and its composition directly impacts syrup quality. This variability could in part be attributed to changes in tree metabolism following dormancy release, but little is known about these changes in deciduous trees. Therefore, understanding the variation in sap composition associated with dormancy release could help pinpoint the causes of some defects in maple syrup. In particular, a defect known as ÒbuddyÓ, is an increasing concern for the industry. This off-flavor appears around the time of bud break, hence its name. To investigate sap variation related to bud break and the buddy defect, we monitored sap variation with respect to a dormancy release index (Sbb) and syrup quality. First, we looked at variation in amino acid content during this period. We observed a shift in amino acid relative proportions associated with dormancy release and found that most of them increase rapidly near the point of bud break, correlating with changes in syrup quality. Second, we identified biological processes that respond to variation in maple sap by performing a competition assay using the barcoded Saccharomyces cerevisiae prototroph deletion collection. This untargeted approach revealed that the organic sulfur content may be responsible for the development of the buddy off-flavor, and that dormancy release is necessary for the appearance of the defect, but other factors such as microbial activity may also be contributing.