Ecological Importance of White Birch Trees
White birches (Betula papyrifera) are also sometimes known as paper birches. Both the Latin species name papyrifera and the common name paper birch are derived from the fact that the creamy white, mature bark of the species sloughs off in papery strips. In addition to the light-colored bark, white birches are distinguished by oval to wedge-shaped leaves and catkin-like flowers.The leaves assume a bright yellow color in the fall. White birches are native to arboreal forest clearings in northern North America.They play an important role in the ecology of their native habitats.
Birch and Fungus
Some birches have beneficial relationships with various types of fungi, including edible species like the chaga or Inonofus obliquus and the birch polypore or Piptoferus betulinus. Preparations made from these fungi have long been used in traditional herbal medicines. Like other birches, Betula papyrifera also coexists with fungi in "micorrhizal" relationships. The term "micorrhizal" comes from the Greek words for fungus and roots. In micorrhizal relationships, the roots and fungi supply each other with nutrients. Fungi also grow on dead birches, breaking down the trees' cellulose to provide nutrients for other species.
Birches are shade intolerant and are often among the first trees to colonize areas that have been decimated by fire or clear cutting. They grow quickly, providing shade and habitat for wildlife. The trees improve soil, as the roots draw nutrients from far below the surface and then restore the nutrients to topsoil when the leaves drop and degrade. As cleared areas begin to regenerate, white birches are often joined by balsam fir, spruces, jack pine and aspen. These trees eventually out-compete the short lived, sun loving, white birches.
Birches provide food, cover and nesting space for an array of wildlife. Moose, deer and snowshoe hare eat leaves or saplings of white birch. The mature trees also provide cover for these animals. Beaver and porcupine eat the bark, while voles and shrews eat the buds and seeds. Woodpeckers, chickadees, nuthatches and swallows nest in cavities in the trees. Sapsuckers bore into the bark in search of the sweet sap. They are often followed by hummingbirds and squirrels who consume the sweet liquid that pools by the holes. White birch is also the larval host to northern tiger and Canadian swallowtails, white admiral and mourning cloak butterflies.
Supporting Other Plants
Birches, which are deciduous, are often found in association with spring flowering woodland plants, which leaf out and bloom before the birch leaves appear. They are also associated with ferns as well as plants like jewelweed and asters that bloom later in the growing season. The dappled shade provided by birches is beneficial for many shrubby understory plants, including some gooseberries and hazels, as well as members of the vaccinium (blueberry and cranberry family) and raspberry families.
Though white birches survive under a wide variety of conditions in the wild, they thrive best in sunny locations with well drained soil. The trees are shallow rooted, so provide supplemental moisture until they become established. Young trees or saplings are available from nurseries. Look for varieties that are resistant to the bronze birch borer, a serious threat to birch trees. White birches can also be grown from seed or cuttings. A tree that has been cut down will also grow scores of new shoots from the base of the trunk or the roots.
- Trees for Life: Birches
- United States Department of Agriculture: Forest Service: Some Edible Fungi Growing on Trees in Northeast Woodlots
- The University of Kentucky College of Agriculture: How to Make Butterfly Gardens
- "Manual of Woody Landscape Plants"; Michael A. Dirr; 1998.