Vigor and Nutrition vs. Sap Sugar Concentration in Sugar Maples

Abstract Although maple dieback has received considerable recent attention in the Northeast, little has been reported about the relationship between sap sugar yield and crown health or crown nutrition. We measured sap sugar concentration (sweetness) in six northern Vermont maple stands in the springs of 1990-1992, and sap volume yield from tapholes at one stand in 1991. The stands differed in average crown dieback, canopy transparency, density, and mean dbh, as well as cation exchange capacity (CEC) of upper soil horizons. Sweetness of individual trees was correlated with sweetness measured the previous year (r > 0.72, P 0.45, P < 0.001), but correlations between sweetness and crown dieback or canopy transparency were low (r < 0.14). Sap volume was negatively correlated with crown dieback (r = -0.51, P = < 0.001). Possible explanations for these findings are discussed. Foliar nutrient status of trees was not well correlated with sap sweetness (r < 0.30). Affects of soil amendments, primarily cations, on sap sugar concentration were studied at three stands with low CEC. There were no treatment-dependent changes in sap sweetness 2 yr after the first fertilizer application. North. J. Appl. For. 12(4):156-162.