Striped maple offers food and shelter in the understory – Waterbury Roundabout
Beneath the canopy, or upper tier, of towering trees is a second layer of vegetation known as the lower tier.
It is made up of shrubs, saplings, and understory trees that grow in the dappled shade of the upper story. An understory specialist is the striped maple, a small tree that rarely grows more than 20 feet tall and 8 inches in circumference. Despite its moderate stature, the striped maple plays an important ecological role in the forest, providing shelter and food for a variety of wildlife.
Striped maples (Acer pensylvanicum) are easily identifiable in all seasons by their greenish bark vertically striped with white or mottled with black, and their smooth, green twigs. The winter red buds and the large terminal bud (nearly ½ inch long) are also good identifying features.
These buds grow even larger as they swell in the spring. The leaves that unfold after bud burst are large, three-lobed and finely toothed. At five to six inches long and nearly as wide, striped maple leaves are the largest of the native northeast maples.
Due to the shape of its leaves, this tree is also known as goosefoot. Other names for it include moose antler and moose maple, since moose consume the buds, leaves, and bark of trees. Striped maple is sometimes confused with mountain maple, another common understory tree that has smaller, coarsely toothed leaves and brownish bark.
Drooping chains of bell-shaped, yellow-green flowers emerge on striped maple at about the same time the leaves unfurl. These flowers develop in clusters of samaras – the paired winged seeds produced by all species of maple – which ripen in the fall and disperse on late fall winds.
A striped maple may produce only female flowers, only male flowers, or both sexes in one year. Some striped maples have even been found to change sex from year to year in response to stressors such as injury and changing environmental conditions.
Widely distributed in the northeastern United States and southeastern Canada, striped maple grows as far west as Minnesota and Ontario and south through the Appalachians to Georgia. It prefers acidic, well-drained soils on cool, high sites in northern deciduous, coniferous, and mixed forests. In our area, striped maple grows best at elevations between 1,800 feet and 2,600 feet. Protected from the wind by the overstory, this maple does not need deep roots and its roots tend to be shallow and spreading. It is well adapted to surviving in deep understory shade, but grows very slowly unless a nearby tree falls or the forest is thinned, allowing more sunlight to enter. the canopy. Striped maple trees over 100 years old have been found in clearings.
Striped maple and other understory plants help create vertical diversity in a forest. Multiple layers of vegetation provide a greater variety of food and microhabitats for insects and other animals, improving the overall biodiversity of the forest. Vegetation layers are particularly important for birds, as different species prefer to feed and nest at different heights. The black-throated blue warbler, for example, often nests in understory shrubs or small trees like striped maple.
Some Native Americans traditionally used the wood of the striped maple for arrows and the bark to make a drink and for medicinal purposes. Colonial farmers fed striped maple leaves to their horses and cattle and allowed their cattle to go into the woods to graze on the spring shoots of the tree.
In addition to its ecological value as an understory tree, striped maple is an important food source for a variety of wildlife. Bees feed on nectar from striped maple flowers. Moose, deer and snowshoe hare browse on the twigs and buds in winter and moose eat the leaves in summer.
I have often seen striped maples in the Green Mountains with rows of long vertical grooves on their trunks, where moose scratched the bark in early spring, using an upward motion of their lower incisors, likely to get sap minerals. Porcupines and beavers eat the bark. Ruffed grouse eat the buds, and grouse, squirrels and chipmunks feast on the seeds.
The next time you take a walk in the forest, keep your eyes peeled for this often overlooked, yet treasured, understory tree.
Susan Shea is a Vermont-based naturalist, writer, and conservationist. The Outside Story is attributed to and edited by Northern Woodlands magazine and sponsored by the Wellborn Ecology Fund of the New Hampshire Charitable Foundation.