We had two objectives in the study of sugar maples which showed signs of decline and stress on a roadside where deicing salt was used in the winter. One goal was to determine if tree stress is related to the levels offsodium and chloride in their sap and in the groundwater and soil around their roots; and, if so, to develop methodology approved by the Association of Official Analytical Chemists (AOAC) that would allow any laboratory to use a standard method to assess maple tree decline due to sodium and chloride effect. The second goal was to evaluate the quality of the syrup processed from sap aseptically collected from maples in decline. We are updating here the later objective of the project that is of interest to the sugar maple producers.
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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.
Higher and wider discoloration, compartmentalisation and decay in maple wood by the use of the PFA pellet restricts the healthy sapwood areas and diminishes translocation of sap and nutrients. Furthermore, technological advances for better sanitation in sap collection and storage presently in use by the maple industry, tested by research to be safe for maple tree health and syrup quality, have made the use of the PFA pellet unnecessary.
The total area and number of xylem rays and vessels from tangential and cross sections of twigs of 12 sugar maples (Acer saccharum Marsh.) were determined by the use of an image-analyzing computer. A nested analysis of variance indicated that xylem rays of trees of high sap and sugar yield are more numerous and larger than the rays of other sugar maples. The total area and number of xylem vessels were about the same in all 12 trees.
We initiated a controlled test of the effect of in-line UV light on the microorganisms in free-flowing sugar maple sap that had not been treated by PFA pellets at the taphole. We also wanted to test the effect of temperature-controlled sap storage for five intervals up to 7 days (167 h) prior to processing to syrup.