The hardwood deciduous forests of the White Mountains are home to a variety of trees, each with its own unique addition to the landscape and history of the area. Maples are renowned for their vernal sap and autumnal colors. But don’t over look the slightly smaller birch and beech trees of these forests! I often admire the old yellow leaves of the American Beech or the copper sheen of the Yellow Birch giving a dab of color to winter’s colorless landscape. And though you might not suspect it, these trees have more in common than meets the eye.
Yellow Birch (left) and American Beech (right)
The White Mountain National Forest is a host to three different types of birch trees- White (or Paper) Birch, Yellow Birch, and Grey Birch and are most easily distinguished by their peeling outer bark. This unique characteristic allows birch trees to shed epiphytes such as lichen and fungi that cling to their bark. American Beech trees are also easily identified by their bark, but instead of a rough peel, the bark of the beech tree is gray and very smooth, thus lacking traction for fungus or lichen to lay a foundation and grasp the tree. Surprisingly, these two organisms have different adaptations to solve the same problem!
Polypore fungus on a dead Yellow Birch trunk (above)
So you might be wondering why it is so important for these trees to shrug off epiphytes looking for a home. There are several answers to this question. Epiphytic decomposers such as fungus will suck resources from the tree. (Next time you see some polypore fungus on a birch tree, take a look at the higher branches- the tree is likely dead or on its last limb!) Lichens cover and darken the bark of these trees which can prevent early spring photosynthesis in the bark. The ability to do photosynthesis in early spring gives birch and beech trees a head start before the canopy thickens, shading out younger trees. Additionally, in the case of the birch tree, darkening of the bark makes it less reflective against the sun and more susceptible to a freeze/thaw cycle on a cold but sunny winter day. These rapid changes in temperature can lead to cracking of the trunk, critically damaging vital tissues of the tree.
So next time you are in the woods, take some time to appreciate the variety of adaptations Mother Nature has used for survival. It seems she might be sending us a message- there is more than one way to get things done!