“Though a tree grows so high, the falling leaves return to the root.”
– Malay proverb
A couple of weeks ago we reported on the threat to Michigan Eastern Black Walnut trees from Thousand Cankers Disease, but apparently they’re not the only significant Michigan tree in peril. Now the Wall Street Journal is reporting that scientists are warning that acid rain will damage Great Lakes maples in the coming decades:
Sugar maple abundance already has dropped in parts of the northeastern U.S. and southeastern Canada over the past 40 years, primarily because of high acid levels in soils. The upper Great Lakes have mostly escaped the damage because the area’s soils are rich in calcium, which provides a buffer against acid.
But in an article published this month in the Journal of Applied Ecology, scientists said they had discovered another way that acid rain harms sugar maple seedlings in upper Great Lakes forests.
It causes excessive nitrogen buildups that prevent dead maple leaves from decaying after falling to the ground, hampering growth of new trees, said Donald Zak, a professor of ecology and evolutionary biology at the University of Michigan.
“The thickening of the forest floor has become a physical barrier for seedlings to reach mineral soil or to emerge from the extra litter,” Zak said. “What we’ve uncovered is a totally different and indirect mechanism by which atmospheric nitrogen deposition can negatively impact sugar maples.”
If you’re into plant biology, you might enjoy Simulated N deposition negatively impacts sugar maple regeneration in a northern hardwood ecosystem from the Journal of Applied Ecology. If you’re into fall color or maple syrup, you might enjoy encouraging your elected representatives to take action to protect the future of these glorious trees.
More beautiful maples can be found in our fall wallpaper archives.