By: Katie Finch, Senior Nature Educator
Leaves are probably the most common feature used to identify trees. But in winter, when so many trees have dropped their leaves, combinations of other features are needed. The bark, along with the pattern and shape of buds on branches can be used to determine species. The bare branches of deciduous trees provide a good opportunity to better see the shape of trees.
The shape of trees, in part, is caused by genetics. A Red Maple has a different shape and structure than an American Elm tree because their cells contain a different set of genes passed down from the parent tree. Red Maples inherit an oval-like shape, with their branches spreading widest in the middle of the crown. Elm trees inherit a vase-like shape. Their branches grow up, spreading wider into the crown, then spill over and drape down. This shape is so distinctive, once recognized, it can be seen while driving 65 miles per hour through Salamanca on the side of I-86.
Why are there so many different shapes of trees? For some shapes, the function is evident. Evergreen trees, like hemlock, fir, and spruce maintain triangular shapes. This helps them shed snow and reduce wind resistance, both tree-damaging features in the colder climates in which they evolved. In a triangle shape, from top to bottom, each layer of branches sticks out a little farther, so they are not shaded. This allows their leaves more opportunities to capture sunlight.
But what is the function of a round tree verses a vase-like tree? I’m not sure we know yet. With both shapes, the trees can collect the resources they need to grow and reproduce, while providing food and shelter to other creatures. Both shapes work. Sometimes there’s more than one solution to a problem.
The environment also has a huge impact on the shape of a tree. Trees are driven by the need to capture sunlight with their leaves. This light energy breaks apart carbon dioxide and water and rearranges it into sugar and oxygen. So, trees grow toward the sun.
The same species of tree can have a completely different shape depending on where it is growing. If a White Oak is growing in a forest, surrounded by other trees, it will grow up rather than out. Its branches will be more vertical, trying to reach the sun before the other trees around it.
But in an open field or yard, without competition, the branches spread wide, almost parallel to the ground. These open-grown oak trees also stand out from a distance. Their spreading shape seems to call out for someone to climb in its branches or picnic in its vast shade.
In a forest, there is still room for unique shapes. Look for trees with crooked trunks or lopsided shapes. Chances are, they are leaning toward an opening to get more sun. Trees are shaped by what and who else is around them.
Wind, snow, insects, fungus, browsing animals, or too much or too few water or nutrients in the soil also affect how a tree grows. There are so many things outside of a tree’s control – even where the seed lands and puts down roots.
A tree is not in control of where it starts its life. An acorn stashed by a squirrel may be in a location with perfect light, soil, and water conditions to grow into a model specimen of an oak. Or not. And it grows anyway with what it has and becomes wind-shaped, stunted, or deer-browsed.
Some trees seem to excel, despite their tough start. Yellow Birch seeds, blown by the wind, can land anywhere. This birch survives on the sunny ground of a forest, but also in soil-filled crevices of a rock or on a fallen tree stump. And where it starts affects the shape of their roots. Some exposed yellow birch roots are longer than I am tall as they reach from the elevated perch to the soil. The rock formations that dot our region’s landscape are a great place to find such reaching roots.
Trees are shaped by both what they are but also where they are. It is both their nature and their nurture that affects what they become. Tree shapes, especially in the winter, are just another element of our fascinating natural world to observe.
Audubon Community Nature Center builds and nurtures connections between people and nature. ACNC is located just east of Route 62 between Warren and Jamestown. The trails are open from dawn to dusk and birds of prey can be viewed anytime the trails are open. The Nature Center is open from 10:00 a.m. until 4:30 p.m. daily except Sunday when it opens at 1:00 p.m. More information can be found online at auduboncnc.org or by calling (716) 569-2345.
Featured image: The shape of deciduous trees is revealed when their leaves drop. Photo by Katie Finch
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