By David Hawke -- “If a tree falls in the forest, and there is no one there to hear it, does it make a sound?” was the question introduced by George Berkeley in 1710. Surprisingly, this was in the context of perception, not forest management. Nowadays I suppose the question is, “If a tree falls on a power line, and no one has electricity, how do you call Hydro One?”
Early this month, a twister of great force touched down in several wooded areas around the village of Washago, just north of Orillia. And yes, trees were falling, right, left and centre. Big white pines and old red oaks, large but weak poplars, and half dead basswood all came crashing down in horrific piles of broken branches and shredded leaves. The swath of devastation was marked mainly by a series of uprooted trees, although a smattering of broken tops also added to the heap.
Viewing a forest after such a dynamic event is quite revealing in regards to forest growth, geography, physics and gut-wrenching emotions.
Washago is located at the northern tip of Lake Couchiching, which is where the limestone bedrock stops and the granite Canadian Shield begins. Just south of the town can be found farm fields and an ever-growing residential presence; the soil is deep, the land is flat, and access is easy. However, once on the Shield, the land is rugged, with only a thin layer of soil atop the granite rock base.
It is this shallow soil layer that is the downfall of many a big tree. By the time a white pine or red oak reaches some level of maturity at age 60 or so, it should have a root network that stretches both deep and wide. The deep roots seek water and provide anchorage, the wide spreading shallow roots seek nutrients from the upper soil layer.
When the winds blow strongly, the large, exposed, branchy side of the tree catches the air mass like the sail of a ship, and a push me-pull you war is waged between dense wood fiber and invisible yet formidable moving air. By holding on with its roots, a tree often bends and deflects the wind, getting by with just a wild wobble. But when the roots can't run deep and hold tight… something’s got to give.
Most of the blow-down trees I found were intact, just now positioned horizontal rather than vertical, their roots exposed as a giant semi-circle of loose soil above bare rock. The broken tops of nearby trees were the result of those caught in the path of the thick limbs of the falling giant.
An event like this is a good thing, speaking from a healthy woodlot point of view. Admittedly, an event like this is not such a good thing when your house, car or power lines are under said tangle of fallen trees. But let’s look at the natural forest and the results of what just happened.
A healthy forest has a mix of tree species and a mix of young, mature and old trees. As a forest grows, the species of trees within it changes from those which require lots of sunlight (sumac, birch, butternut and poplar) to eventually become a forest comprised of trees that are shade tolerant (sugar maple, red oak). Each community of trees replaces the one before in a successional manner, the final result being called a climax forest, one that no longer changes but rather replaces itself with saplings of its own self growing in the shade below.
But Nature knows that a forest comprised solely of the same old-same old will not be nearly as healthy as a forest comprised of a variety of trees. To be a healthy and dynamic forest there needs to be diversity. So, tornados were invented by Ma Nature to fix the problem.
As a large, sunlight-hogging mature tree is knocked aside, there is a hole left in the above canopy. This opening provides opportunity for light to reach the forest floor, and that light stimulates the growth of seedlings and wildflowers long forgotten. Diversity happens, a shift occurs in the list of what lives and grows here, and life goes on within the woodlot.
That fallen tree is not yet done with its service to the forest… it may take decades, but as the mosses, wildflowers and fungi that use the rotting trunk as their own home, the nutrients that were bound up in that rotting wood will slowly, eventually, be released to become the soil of the next forest floor. Salamanders and beetles will find shelter beneath the damp wood. Bears will tear the ancient log apart in search of ants and grubs. The cycle of nutrients will continue. Fallen trees are essential for forest health.
Not that I’m wishing for devastating storms to roar through here with regularity, but when one does, it is a great time to see how nature functions within its own rules.
Dave’s Notebook: With this nice weather upon us, find time to get out and about, whether with yard work or a wander through a forest of many colours.
© 2020 David J. Hawke