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State of Adirondack maple is debatable

November 18, 2015
By SHAUN KITTLE - Outdoors Writer ( , Lake Placid News

The state of sugar maples in the Adirondacks is up for debate.

A recently released study by SUNY College of Environmental Science and Forestry graduate student Daniel Bishop found that most of the 242 trees his team sampled on sites west of the central Adirondacks were experiencing decreased growth rates.

The decline has been documented across central and northern portions of the tree's range, including in New York, Vermont, Pennsylvania and eastern Canada, with discolored foliage, branch dieback and increased death rates cited in other studies as evidence of the problem.

Article Photos

A sugar maple along the Bloomingdale Bog Trail in Saranac Lake shows off its colors last fall.
News photo — Shaun Kittle

The introduction to Bishop's paper, "Regional growth decline of sugar maple and its potential causes," suggests acid rain and climate change could be the cause of the decline, but Uihlein Forest Director Mike Farrell, who runs Cornell University's Sugar Maple Research and Extension Field Station, said there isn't enough evidence to draw those conclusions.

Bishop said he started the research to learn if there was a correlation between the growth rate of sugar maples and a changing climate or acid rain deposition, and the data does show that something is happening to the trees.

"We were surprised to see a large number of the sugar maple trees experienced a declining growth rate," Bishop said. "To be clear, we weren't expecting that at all. In contrast, only a small percentage experienced either non-changing or positive trends."

To determine the growth rate of the trees, Bishop measured the width of each tree ring and the diameter of the trunk they came from, and then he used those numbers to calculate the area of new wood the tree gained each year. The tree rings can easily be seen by taking a core sample from the tree. Each ring marks a year's worth of growth.

Bishop said the growing conditions for sugar maples have actually improved for the species as average temperatures have risen over the years.

"The region has experienced increased warming and wetting over the past 30 to 40 years, so there's been an increase in precipitation and an increase in temperature, which in theory should be beneficial to the tree species," Bishop said. "Alternatively, we also know that the Clean Air Act also came into affect around that time, and we would also expect reductions in acidic deposition in the region, which should have also benefited sugar maple growth."

The team sampled the soil chemistry at each site, but Bishop said they didn't go as far as to draw conclusions on how that related to sugar maple growth. He said the focus of the paper was to look at growth rates, and he expects further research to delve into what is affecting that.

Bishop also wasn't sure what declining growth rates means for the trees themselves. Buds, roots, twig extension, leaves and sap production all need to be maintained by one energy store, but how trees allocate their energy to each of those functions isn't clear.

"A decline in stem growth could indicate less energy in the system; however, resource allocation is way more complicated than a simple, predictable one-to-one relationship," Bishop said. "It may be that growth is declining and everything else remains unchanged."

Farrell said a demonstrable decline in the growth rate of any tree species could be cause for concern, especially one as economically important as sugar maples, but more research needs to be done to understand what's going on. He said it's important to note that there are some areas in the Park where sugar maple is doing well.

In general, sugar maples don't live too long in unmanaged settings in the Adirondacks because the soils here are poor and the conditions are typically harsher than in areas south of the Park. Areas with good, rich, fertile soil tend to nurture maple growth, whereas areas that are nutrient deficient or too wet or dry can reduce maple health.

Considering those factors, sugar maple success tends to be site specific, but that also means factors like acid rain could make a good site bad.

"That (acid rain) can certainly be part of the impact, but without further research you can't make a direct connection," Farrell said.

Farrell had a number of questions after reading the study, like what was happening to the growth rates of other tree species on the sites they sampled - things like cherry, ash, beech and birch - which often grow in the vicinity of sugar maples.

"That would lead to a different conclusion, that it's not just maples in decline, that in this forest type trees are starting to slow down," Farrell said.

Farrell added that considering the forest management of each site is also important because crowded trees experience slowed growth rates and can die if enough nutrients aren't available.

"I don't discount that we have concern with maples growing in certain places in the Adirondacks," Farrell said. "Our sugar bush here in Lake Placid is a prime example, where we've seen large declines in the old trees, which are only 90 to 100 years old. According to some people's estimation, that's a young tree. They can live 300 years."

The fate of sugar maples in the Park could have a lasting effect on the economy and ecology of the region. Economically, the trees are used for lumber and for the production of maple syrup. They also display some of the boldest reds, oranges and yellows, which draw leaf peepers to the area every fall.

Ecologically, the species produces a seed crop every several years, an occurrence called a mast year, which provides an important food surge for animals.

The tree itself is also a food source for many animals. White-tailed deer, moose, snowshoe hare, flying squirrels and aphids eat sugar maple seeds, buds, twigs and leaves, and porcupines eat the bark. The species isn't just food - songbirds and woodpeckers also like to nest in them.



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