This year's fall leaves have been the most colorful showing that we have seen in recent years.
For the first time in quite a few years, I watched as a maple tree shed all of its leaves in just a matter of minutes. There only was a slight breeze, not enough to move the leaves that fell on the ground under the tree.
Leaves dropping all at once through quiet air betrays an active process of self-amputation. Each leaf fell from the weight of the leaf itself without any help from even the slightest breeze.
To find the reason for this, we need to go back to July when the tree had finished growing for the year, and its energy turned to growing buds for next year's leaves.
By the first of September, the tree was finished growing the buds, which remain dormant throughout the winter months. After warm sunlight and plenty of water arrive in the spring, the buds will burst open.
As the bud unfolds, we can see how the leaf is folded inside and surely marvel at how a leaf can be compressed so tightly inside the tiny bud.
As the leaf unfolds, it does so without a crease or muss. This manner of folding is called venation.
During the spring and summer months, the leaves are used to make glucose through the process of photosynthesis. Chlorophyll is the actual molecule in which the light, water and hydrogen reaction takes place.
Auxin is a key ingredient in the formation of buds and also an overall growth hormone that is found in every leaf. Leaves do not just grow on a tree in a random way. On most plants, leaves, which are the tree's solar collectors, are arranged so that each will receive the greatest possible exposure to the direct rays of the sun. Leaves on some trees will shade out leaves on smaller trees; however, a tree's leaves will not shade out the other leaves on the same tree.
In the fall, as the days grow shorter and colder, these changes trigger the leaves to lose their ability to create auxin, which causes the balance of auxin and a chemical called abscisin to become unfavorable, and a layer of corky cells (abscission cells) develops on every leaf where it joins the twig.
The word abscission is Latin, meaning "to cut" - hence, our word scissor.
The resulting abscission layer consists of a band of cells that separate easily from each other. At this point, the leaf is cut off from the tree and cannot transfer sugar that thickens the sap.
The manufacture of chlorophyll ceases altogether, and now the colors of the leaves, which were hidden by the green chlorophyll, are shown.
Other factors, such as wind, species of tree, elevation, temperature, humidity and even the length of daylight, all have input in the tree's shedding of its leaves. Of these, the wind plays the most important part.
Have you ever wondered why trees shed their leaves? Leaves, which are thin and full of water, would freeze during the winter. If a tree kept its leaves, freezing temperatures and high winds soon would snap the leaves from the tree, leaving the tree to face winter with thousands of open and hollow wounds.
Under these conditions, water would enter the wounds, with freezing and thawing occurring that could split the branch ends, leaving the tree in a vulnerable shape.
However, when a tree sheds its leaves a layer of cork cells form, which quickly seal the wounds.
Many birds and animals make use of leaves. For example:
Deer will feed upon dead leaves;
A squirrel's nest, called a drey, is made with leaves;
A female turkey's back is covered with dead leaves while she sits on her eggs and when she stands up, the leaves will fall off to conceal the eggs; and
Beavers use leaves to help plug holes in their dams and lodges.
Many animals line their nests with dry leaves. Countless insects, bugs and bacteria live in and continually feed upon the dead leaves on the forest floor. These creatures are plentiful, with ten billion microscopic organisms in just 60 cubic inches of soil.
The leaves that fell off the trees this past fall will lay on the ground for about two years before the "cleanup crew" will be able to eat, digest and expel them as nutrients. Of course, this helps trees to grow taller with more leaves.
Nature sure is amazing.
Bower retired after 34 years as a wildlife conservation officer for the state Game Commission. He has published several books about his experiences. Questions and comments may be sent to him at 153 Redington Ave., Troy PA 16947.
