Maple Minus Forest

Abby Van den Berg and Tim Perkins with a topless maple. Photo courtesy of UVM.

Until the 1940s, most Christmas trees were cut from forests. Now they’re harvested from tree plantations. The maple sugarbush may soon be making a similar move from forest to field.

In 2009, Tim Perkins and Abby van den Berg cut the top off a maple tree. As researchers at the University of Vermont’s Proctor Maple Research Center, they simply wanted to learn more about sap flow. Instead, they discovered an entirely new way to make maple syrup.

Imagine a tightly-spaced plantation of two-inch-diameter sugar maple saplings. The stems are each cut chest high, and then covered with a sealed plastic bag. Inside the bag, the sap flows out of the stump under vacuum pressure and into a tube. The result: huge quantities of sap.

Typically, a sugarbush produces about 40 gallons of maple syrup per acre of forest by tapping, perhaps, 80 mature trees. With this new method, the researchers estimate that producers could get more than 400 gallons of syrup per acre, drawing from about 6,000 orderly saplings. In other words, these plantations would allow maple syrup to be produced like a traditional agricultural row crop.

“We didn’t set out to develop this system,” said van den Berg. “We were looking at ways to improve vacuum systems.” But, during a spring thaw, the crown-less sapling they were experimenting on just kept yielding sap under vacuum pressure. And more sap and more sap.

“We got to the point where we should have exhausted any water that was in the tree, but the moisture didn’t drop,” said Perkins. “The only explanation was that we were pulling water out of the ground, right up through and out the stem.” In other words, the cut tree worked like a sugar-filled straw stuck in the ground.

Theoretically, a plantation-style sugarmaker could cut and recut a single-stemmed maple sapling for around five years before they’d have to give it four to seven years off to regrow. (Juvenile trees are physiologically different than mature trees, so they have a higher tolerance for pruning .) “The better approach,” said Perkins, “would be to coppice the tree early to form multiple stems. Then you would cut and harvest from only one stem per individual [tree] each year, which would give adequate time for the stem to recover and the process could continue almost indefinitely.”

The researchers estimate that the cost of production would be roughly the same as with current methods. “I think you’re going to find sugarmakers who are doing both,” said Perkins, “standard sugarbush and plantation.”

With climate change, this dual approach may offer improved chances for success in the face of warmer temperatures. “If this region is going to warm more, then with a plantation we don’t have to rely as much on strong freeze/thaw cycles” to get sap flowing,” Perkins said, “because these smaller trees freeze faster and thaw faster.”

Any form of maple syrup production relies on freezing temperatures to transform starch in the wood into sugar. But in larger trees, it’s much more important to generate sap pressure from a freeze/thaw cycle, van den Berg explains. In a plantation system, small trees can rely predominately on vacuum-assisted flow.

Jacques Couture, a maple syrup producer in Vermont’s Northeast Kingdom, and chair of the Vermont Maple Sugarmakers Association, sees how this new technique might help producers be more nimble. “One of the really interesting aspects [of the plantation approach] is the possibility to establish some maple syrup production in a much shorter time span than is the current norm,” he notes.

“If we had a natural disaster, such as a widespread hurricane or some insect pest that would wipe out a large percentage of the maple stands,” he said, “this might appeal to some who were affected as an alternative way of getting back into production sooner than the normal 40-plus years for trees to grow to tappable size, as we know it today.” Plantation saplings could be ready in seven years – and not just maple: birch, walnut, and other syrup-producing trees work with this technique too.

Much remains unknown about the implications of this research. “It’s too early to make any predictions,” said Eric Sorkin, a producer of organic maple syrup from Cambridge, Vermont, who was briefed on the new research. But he believes it could lead to a fundamental shift in the way we make maple syrup. “If this leads maple syrup from a semi-wild crop to something farmed, plantation-style, I think that would be tremendously sad,” he said.

Van den Berg foresees how this new technique could have positive implications for long-time maple producers and landowners. “If you are using ten acres of abandoned farmland that you already own, this technique makes a lot of sense,” she said. With lower start-up costs, and quicker expansion (or contraction) of one’s business, “it’s another way to help us maintain the traditional working landscape.”

The new equipment needed to produce syrup this way is not yet on the market. “We are just beginning discussions with some maple equipment manufacturers,” Perkins said, “so it is possible we’ll have prototypes to test for 2015.”

  1. Cynthia Hughes → in Vermont
    Mar 24, 2014

    I have to wonder about the wisdom of this approach. I can see why it would be appealing to farmers, but what about the health of the forests? Would people begin clear cutting so that they could grow these plantations instead of maintaining the health of the forest for the entire ecosystem and not just our human needs?

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