The structure of a tree is a remarkable engineering feat. Why don’t trees fall over more often? When tree crowns catch the full force of the wind, their trunks acts as a lever, transferring that force to root systems that anchor the tree in the soil. If the tree has a tap root, it’s unlikely to blow over in a wind-storm.
The local environment shapes the way that trees allocate resources to their roots. A tree grown in the open tends to produce a more extensive root system than a member of the same species growing in a dense forest. That creates a problem for landscape managers.
If you build a road or a house in an area that once supported a dense forest, a certain amount of “edge” is produced, where trees that did not grow up exposed to the full brunt of wind are now subject to it. For the first few years after construction, there is often substantial wind-fall of trees along this newly created edge.
I saw this firsthand in my neighborhood. Property owners removed some well-established trees from their yards, only to find that those that remained were unaccustomed to full wind exposure. As a result, in inclement weather, these yards have experienced a large number of fallen trees. I imagine this is the opposite of what they hoped to achieve.
So the next time you watch trees in a windstorm, note how well the trees in a forest survive, compared to newly isolated trees that are left along edges and in manicured lawns. And be careful when well-intentioned preventative cuts leave trees on the edge more vulnerable.
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Photo, taken on June 8, 2004, courtesy of Rebecca Partington via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio. Support for Earth Wise comes from the Cary Institute of Ecosystem Studies in Millbrook, NY, with partial support from the Field Day Foundation.