Sugar Maples To Get Doses of Calcium To Stay Healthy

Newswise — As autumn spreads its warm colors across the Northern Forest, nearly all eyes gaze upward.

But scientists studying how to improve the health of the forest focus in the opposite direction " they suspect that soil calcium deficiencies are at the root of widespread problems caused by acid rain.

Now University of Vermont scientists are tackling the issue in a new way.

At the International Maple Producers Conference Oct. 17-19 in Lake George, N.Y., Timothy Perkins will discuss and offer the first copies of his co-authored booklet, "Fertilizing A Sugarbush" recommending that sugarmakers add calcium to their woodlands to increase maple production. This is the first time maple producers are advised to amend soil to improve the crop.

The publication, funded by the University of Vermont Agricultural Research Station, is the culmination of Perkins and Timothy Wilmot's seven-year, $285,000 study that ended in 2003 and was funded by the Freeman Foundation.

"If your site is deficient in some nutrient " not just calcium " you may be able to fertilize your trees and increase production. However, calcium is the number one deficiency in soils throughout the Northeast," says Perkins, who is the director of UVM's Proctor Maple Research Center in Underhill, Vt., not far from the campus in Burlington.

Perkins, a research associate professor of botany, recommends that forest owners perform a soil test or look at other plants at the site that indicate whether soil is alkaline or acidic before considering adding amendments.

Sugarmaker Arthur Krueger did just that. And when the soil test on a 10-acre stand near the southern Vermont town of Cuttingsville, showed an acidic pH of 4.5 (on a scale where 7 is neutral), he decided to experiment.

A local business offered him free calcium carbonate (commonly called lime). He took 10 tons.

That's a little harder to swallow than the recommended daily calcium requirement for most adults over age 50: 1200 milligrams. Krueger says he doesn't take calcium himself. "I drink milk in my coffee."

Perhaps it's a stretch to say that just as humans need calcium for strong bones, trees need calcium for strong trunks and branches, however, UVM researchers do liken the effects of calcium deficiency in trees to a weakened immune system that makes trees vulnerable to a host of stresses: storms, insects and drought among them.

"Sugarbush" " as stands of sugar maples are called "and forests in general, grow densely and often are without roads. Terrain may be hilly. So the recommendation is not as easy as the more common practices of gardeners liming the lilac bed or farmers fertilizing a cornfield before planting.

Acting on preliminary findings of Perkins' and Wilmot's work, Krueger plans to add one ton per acre as time allows and at various times of year.

No small task.

"In order to get the lime in where the trees are I use a pony, a cart and a shovel for a couple reasons: one, you do a lot less damage to the roots than you do with a vehicle and two, I guess I should've been born an Amish man," Krueger says, half joking.

"It takes three horse hours and five man hours to spread a ton of lime," he adds. "Already it looks like I'm doing some good " trees are greener, there's more life and slower decline on the top. But I'm like the story of the little Dutch boy with his finger in the dyke. I can lime a small portion of my woods but the problem is with all the forests.

"Fertilizing and liming are not panaceas," Perkins stresses. "If the stand is not thinned or if the soil is already fertile, it won't help."

"While adding calcium to is intended to aid maple production and not fall color, calcium is the link between the overall health of maple trees and the damage caused by acid rain. Acid rain leaches calcium out of soil, and from leaves as acidic particles and gases landing on leaves and increases the availability of aluminum which further limits calcium uptake.

"There's not yet conclusive evidence that there's a link between acid rain damage and fall leaf coloration. Data indicates that calcium is an important trigger in the production of the pigments (anthocyanins) that produce red color in leaves," says Paul Schaberg, a UVM adjunct faculty member and U.S. Forest Service scientist. "But how that plays out in the landscape, we don't know. We don't even have the data on it.

"Theoretically, by depleting calcium, acid rain could mute the production of red leaf pigments. However, by acting as a stress itseld, acid rain could also temporarily trigger greater stress response, including red color production. Whatever happens with leaf color, the more important issue is the influence of calcium depletion on the overall productivity and health of forests," Schaberg adds. "We know that red spruce and sugar maples are especially sensitive to calcium loss, and if we lose them it affects the whole ecosystem." Speaking as a member of the UVM research team of Don DeHayes and Gary Hawley who have published on the topic in several journals, Schaberg says, "we actually suspect that red spruce and sugar maples may be the canaries in the coal mine," early indicators of problems that will affect many tree species.

Just as gardeners amend some soils with limestone to bring the pH closer too neutral, some wildlife managers add lime to stream water to reduce acidity and restore fish production. Likewise researchers experimented with adding calcium to soils in a section of forest at the Hubbard Brook Experimental Forest in Durham, N.H., in 2003 with positive results. However Schaberg is quick to point out that this exercise "cost a million dollars for one watershed on one side of one mountain.

"Growing evidence indicates that at least some forests benefit from calcium addition to replace the calcium lost by acid rain. However, this raises an important question " what is the most cost effective method of combating acid rain-induced calcium loss?," he says. "It would be an extremely expensive, Herculean chore to add calcium back to all the forests that are being depleted by acid rain. Perhaps if we would just appropriately reduce pollution then nature would take care of this on its own?

Or as sugarmaker Arthur Krueger aptly put it, "An ounce of prevention is worth 10 tons of lime."

For a link to the Proctor Maple Research Center: http://www.uvm.edu/~pmrc/For a web version of this article: http://www.uvm.edu/theview/article.php?id=1390