Yields in maple sugaring are a function of the sap's mean sugar content and the sap volume extracted each season. Sugar content and volume are correlated among trees and increase with trees size (Rademacher et al., 2023). The average residence time of the soluble sugars in sap, i.e., almost exclusively succrose (Gregory and Hawley, 1983), is about 4 years (Muhr et al., ), indicating that nonstructural carbon reserves that enable the use of carbohydrates over multiple years play a pivotal role for maple sugaring. The level of nonstructural carbon reserves has also been suggested to be a proxy of tree vigor (Trumbore et al., 2015). Another proxy of tree vigor is radial growth (Dobbertin et al., 2005). Consequently, it has been hypothesised and shown among young maples that tree growth and sap sugar content are correlated (Liang and Howward, 1990). Both radial growth and sap sugar concentrations are known to vary from year to year. However, until today nobody has investigated whether interannual variations in radial growth are related to interannual variations in sap sugar content and/or volume.
We have collected radial growth data as well as data on sap sugar content and volume for individual trees for multiple sites over the past three years. In addition, we propose to use the existing sap flow data from Harvard Forest and growth data to further investigate this relationship. Sap flow data including sap sugar content and volume has been collected at for a selection of red and sugar maples at Harvard Forest since 2011 (HF285). We propose to core the maple trees, that has been tapped for over a decade to add them to our data set and analyse relationships of growth and sap sugar content and volume.