Source: UNIVERSITY OF VERMONT submitted to
LONG-TERM EFFECTS OF SAP EXTRACTION ON SUGAR MAPLE GROWTH AND HEALTH
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
REVISED
Funding Source
HATCH
Reporting Frequency
Annual
Accession No.
1000464
Grant No.
(N/A)
Project No.
VT-H-02008
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Oct 1, 2013
Project End Date
Sep 30, 2018
Grant Year
(N/A)
Project Director
Perkins, T.
Recipient Organization
UNIVERSITY OF VERMONT
(N/A)
BURLINGTON,VT 05405
Performing Department
Plant Biology
Non Technical Summary
Maple syrup production is based on the premise that tapping trees to collect sap has no substantive detrimental effects on the overall health of the trees, and thus is a longterm, sustainable agricultural activity. While there is copious evidence from historical and contemporary maple sugaring practice that tapping trees over a long-time frame (100+ years) does not significantly impact mortality when conservative tapping guidelines are used, there is relatively little scientific evidence examining the effects of sap extraction on tree health and productivity. An essential piece of information to assess this assumption is the growth rates of trees tapped for maple syrup production compared to those of untapped trees under the same growth conditions. The proposed work will examine the health and growth of tapped and untapped maple trees as part of an ongoing multi-faceted assessment of sustainable tapping guidelines.
Animal Health Component
0%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
20520991020100%
Knowledge Area
205 - Plant Management Systems;

Subject Of Investigation
2099 - Sugar crops, general/other;

Field Of Science
1020 - Physiology;
Goals / Objectives
The objectives of the proposed work are to determine whether tapping trees for maple production significantly impacts long-term tree growth and health, and whether tapping with modern, high-yield sap collection practices impacts tree growth to a significantly greater degree than tapping with traditional (gravity) collection practices. This will allow a more complete examination of the assertion that tapping trees for sap collection, whether with traditional or more modern practices, is a sustainable practice. To meet this objective we will test the following null hypotheses: 1. There is no difference in stem diameter growth, basal area increment, twig growth or tree health (dieback and crown transparency) between tapped and untapped trees. 2. Level of carbohydrate extraction has no effect on stem diameter growth, basal area increment, twig growth or tree health (dieback and crown transparency).
Project Methods
A single maple stand with uniform conditions (management history, tree age, etc.)at UVM PMRC be located. One hundred and twenty trees will be selected, with 40 trees assigned randomly to each of 3 experimental treatments: 1) Control - No Sap Collection (untapped), 2) Traditional Sap Collection (tapped, gravity collection = low carbohydrate extraction), and3) High-Yield Sap Collection (tapped, vacuum ≥ 25"Hg collection, high carbohydrate extraction) Care will be taken to ensure trees within the treatment groups have equivalent distributions of health (crown size and condition), size (diameter), and other factors that might influence radial growth. Beginning in spring 2014, trees will be tapped (Traditional and High-Yield treatments), or left untapped (Control). Each tapped tree will be connected to a sap collection canister via a new spout and short section of maple tubing. Vacuum will be supplied to each collection canister of the High-Yield treatment trees using a liquid-ring pump. Trees will be checked weekly during the sap flow season to ensure that sap collection is proceeding nominally. Average vacuum level will be verified using data loggers. Sap volume and sugar content from each canister will be measured at the end of the sap flow season and used to calculate the total yield for each tree and the average total yield for each treatment. The circumference at a marked location on each tree will be measured in the autumn before treatments begin, and each year thereafter in order to quantify tree diameter growth and to calculate basal area increment (BAI). These data will be used to calculate the average growth rates and average BAI of trees in each treatment group. Sap collection and growth measurements will be repeated annually for five years. During the summer after the fifth sap season, branches will be harvested from the upper 1/3 of the crown of each tree, and internode length (shoot growth) measured with a ruler. In addition, estimates of tree vigor will be made at the same time using standard techniques. Analysis of variance will be used to determine if measured parameters differ significantly between treatments. This will enable us to determine if stem growth, shoot growth, or tree vigor between trees tapped for maple production differ significantly from those of untapped trees, and whether growth rates differ between trees tapped with high-yield and traditional (gravity) sap collection methods. Regression analysis will be used to determine the relationship between sugar extraction rates and tree growth rates. The analysis of growth rate data will be performed annually; however the results after five years of the experiment will enable us to assess any long-term effects of tapping on tree growth.

Progress 10/01/16 to 09/30/17

Outputs
Target Audience:This research is aimed at informing maple producers how sap collectioncan affect long-term tree health and growth. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest?Interim progress reports were made to several maple producer groups as part of an update on research activities. What do you plan to do during the next reporting period to accomplish the goals?Sap collection will be conducted for the study treatments during the 2018 sugaring season. During the fall, stem and twig growth will be assessed for all study trees and the effect of treatments (various levels of sap extraction) on tree growth and health evaluated.

Impacts
What was accomplished under these goals? Study tree growth was measured in the fall of 2016 and again in 2017. Sap collection from the three treatments was made during the spring sugaring season of 2017.

Publications


    Progress 10/01/15 to 09/30/16

    Outputs
    Target Audience:Maple researchers, producers, and industry professionals are interested in understanding the impacts that maple sap collection practices have on the health and growth of their crop trees. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals?We will measure sap yields and sap sugar content over the 2017 sugaring season. At the end of the 2017 growing season we will measure diameter growth and taphole closure of the experimental trees.

    Impacts
    What was accomplished under these goals? We collected sap yields and sugar contents over the 2016 maple sap season for the experimental treatments. At the end of the growing season, we measured taphole closure and stem diameter growth.

    Publications


      Progress 10/01/14 to 09/30/15

      Outputs
      Target Audience:Maple producers in Vermont and surrounding areas were presented with information during maple conferences regarding the impacts of tapping and sap extraction from maple stems. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?This project helps to advance our understanding of how collection of maple sap from trees with different practices affects the growth and health of trees. How have the results been disseminated to communities of interest?Maple producers have been informed of the preliminary results of this project through presentations at maple conferences and meetings, and through interaction with producers on maple industry community forums. What do you plan to do during the next reporting period to accomplish the goals?Sap will be collected from trees with gravity and vacuum during the spring of 2016. Diameter growth will be measured at the end of the 2016 growing season.

      Impacts
      What was accomplished under these goals? Sap was collected from trees under gravity and vacuum conditions.Similar tothe results inyear one, twice as much sap was collected from trees with vacuum as from trees with gravity. Measurements of tree diameter revealed no significant differences in growth due to treatment (no tapping, gravity sap collection, vacuum sap collection).

      Publications


        Progress 10/01/13 to 09/30/14

        Outputs
        Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Sap collection experiments will be repeated, and diameters of study trees will be measured.

        Impacts
        What was accomplished under these goals? This project examines whether removal of sap though the maple sugaring process effects the health and growth of trees. By comparing trees that have not been tapped with those that have been tapped with either gravity or vacuum collection methods, we can determine the impact of carbohydrate removal on trees. In this first year of study, 90 mature maple trees that had never been tapped were selected and randomly assigned to one of the three treatment groups. Sap collection was conducted during the spring sugaring season. Sap volume in the "gravity" treatment was approximately half that of the "vacuum" treatment.

        Publications