Maple sap and syrup production is an economically and culturally important industry in the northeastern U.S., with commercial harvest of the temperature-sensitive sap having occurred for several centuries. Since 1960, a significant decline in maple syrup yield has been associated with warming spring temperatures during the critical sugaring period and increases in summer drought frequencies, but how this current decline compares within the natural range of variability expected for many agricultural products, including maple syrup, is unknown. Holistic studies integrating climatology, tree physiology, forest ecology, and dendrochronology to investigate and quantify the environmental variables associated with maple syrup production are lacking. Few sugar maple tree-ring chronologies from the northeastern U.S. exist, yet preliminary work with sugar maple tree-ring data indicates this species can be easily cross-dated and that variations in tree-ring widths are significantly correlated with maple syrup yield. This doctoral dissertation research project will incorporate dendrochronological techniques to develop yield reconstructions as well as predict yield up to several months prior to the sugaring season. The use of tree-ring data will allow for the forecasting of maple syrup production under different climate conditions. This project will extend the historical record of maple syrup yield by over 100 years using tree-ring data and thus place the current decline in a larger historical perspective than currently exists. The tree-ring data will be used to test the viability of developing an accurate forecast several months prior to the sugaring season, because no predictive metric currently exists to forecast maple syrup yield.
This project will help determine the effectiveness of using sugar maple tree-ring data to predict and reconstruct maple syrup yields during the past two centuries. It will model climatological and meteorological variables that have affected syrup yields and tree-ring growth since the early 1900s; and it will explore the possible causes for the post-1950s decline in syrup production. The project will help promote the effectiveness of using tree-ring data to predict agricultural yields, which will ultimately provide farmers additional information about crop-yield cycles, and this knowledge will help determine appropriate management methods for sugarbush operators during less-favorable climatological conditions. The data from this research will be published in peer-reviewed journals and shared with the U.S. Department of Agriculture, the North American Maple Syrup Council, the New York State Maple Producers Associations, Inc., the Cornell Sugar Maple Research and Extension Program, and the International Tree-Ring Data Bank. High-quality, long-term crop yield data are scarce for many species, and the use of tree-ring data to reconstruct yield may be a viable method for extending historical records to examine annual-to-decadal harvest fluctuations. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.
This project examined whether maple syrup yield in New York State could be predicted and reconstructed based on variations in tree-ring widths of sugar maple trees. Tree-ring data from six sites were collected at the principal syrup-producing regions in the state. Annual statewide maple syrup yield-per-tap was then compared to the tree-ring data to determine if variations in ring-widths were significantly associated with yield. Questions addressed were whether declines in syrup production beginning in the latter half of the 20th century could be placed in a historical context, what the growth-climate relationships were for sugar maple, what meteorological variables affected growth and syrup yield, and the feasibility of using tree-ring data for predicting yield. Key findings were that relationships between sugar maple tree-ring growth and maple syrup yield are likely to produce information with finer-scale spatio-temporal resolution than statewide maple syrup yield data provide. Both local topoedaphic conditions (i.e., soils, aspect, and slope) and microclimate may be the principal factors affecting syrup production. The concept of terroir, which includes the combined effects of soil, climate and other site-specific environmental characteristics as it affects viticulture and wine production, may be equally applicable to the causes of interannual variability in maple syrup yield. Radial growth of sugar maple is weakly associated with climate-division scale climatic variables, suggesting the interannual variability in growth is more controlled by microsite-level conditions, which may explain the lack of association between radial growth and state-wide maple syrup data. It may be possible to predict and reconstruct maple syrup yield if more fine-scaled data are used. As sugar maple trees can exceed 200 years age, successfully reconstructing past yields may allow maple syrup producers to examine if natural cycles exist and place boom or bust cycles/years in a multi-century historical context. Additionally, the results showed that factors affecting sap production are influenced by several variables over multiple years prior to harvest.
