UMass ecologist leads 1st study of climate change impact on sugar maples

AMHERST — As maple sugaring season approaches, plant ecologist Kristina Stinson at the University of Massachusetts recently received a two-year, $149,800 grant to study the impact of climate change on the quantity and quality of sugar maple sap, including its chemical composition.

The researchers believe this is the first study to look at the effect of climate change on sap quality, its sugar content and chemistry as opposed to flow and volume, and the first to investigate how red maple compares to sugar maple as a source for sap.

Stinson and colleagues hope to predict maple syrup quality under future climate conditions and explore a variety of management strategies.

Maple sap is mainly sugar and water, Stinson explains, but compounds called phytochemicals that occur naturally in plants give maple sap its signature flavor. Any sap containing sugar could be boiled down to syrup, but maple does have a unique flavor. People sometimes do tap birch, walnut or hickory, for example, but these syrups have a different flavor and take more time and energy because of lower sugar content.

Stinson notes, “Phytochemicals are what give sap from the different species their particular flavors.” Phyto is Greek for plant; phytochemicals give blueberries their deep blue color, for example, and garlic its distinctive smell and flavor. This so-called “secondary plant chemistry” can also offer advantages, she notes, such as protection against insect pests or frost.

Sap quality has two components, sugar content and secondary chemistry. Sap sugar content determines how much syrup can be made from a given volume of sap; all syrup sold commercially has a consistent density of sugar, about 66 to 68 percent.

Stinson says another goal of this study, which will use historical as well as ecological data, is to “get a handle on how much variation there is in this secondary chemistry, the different concentrations of phytochemicals and the relationship to syrup quality in sugar and red maples across the landscape.”

At present, the researchers have enlisted students and volunteers who sample 15 to 20 trees per site at six locations, one at Harvard Forest in Petersham , one near Dartmouth in New Hampshire, two managed by a scientist at the University of Virginia’s College at Wise, one led by a researcher at the University of Québec Chicoutimi and one at Indiana Dunes National Lakeshore.

Over the decades, the tapping season has started earlier and earlier, Stinson says. Estimates are that it may now start two weeks earlier than the traditional date.

She hopes the number of sampling sites will eventually reach 30, representing a variety of eco-zones. Each will be managed by scientists at colleges and universities, or by state, federal and industry technicians, or citizen scientists in sugaring families. They will also assess overall tree health.

UMass reseasrchers hope their work has the potential to help inform producers about how they might be able to adapt their business and other plans to climate change.”

Many people aren’t aware that producing maple sugar had a very patriotic role to play for the North during the Civil War, Stinson says, as an alternative to sugar cane harvested by slaves in the Caribbean. “It is part of our cultural heritage.” Native Americans have been tapping trees for centuries, and some tribes’ origin stories include tapping maple trees for sap.

Stinson, an assistant professor of environmental conservation, and co-investigator Toni Lyn Morelli, a research ecologist at the U.S. Geological Survey, with UMass Amherst postdoctoral researcher Joshua Rapp, received the grant from the Northeast Climate Science Center at UMass Amherst to study sap quality and plant chemistry in maples from Virginia to Quebec and from Massachusetts to Indiana.

Author: Going Green

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