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Did you know that the state of Maine is the most heavily forested state in the union? It's true. Over 90 percent of the sates land mass is devoted to growing trees. That's 17 million acres! In addition, we have a wide variety of trees, with over 50 native species, and many more ornamental trees in various neighborhoods. With such an abundance of trees, it is no wonder that we have such a breathtaking season.
Every autumn, magic transformations begin as trees begin to prepare for winter. In certain regions, such as our own, the shedding of leaves is preceded by a spectacular color show. Formerly green leaves turn to brilliant shades of yellow, orange, and red. These color changes are the result of transformations in leaf pigments.
All during the spring and summer, leaves serve as factories where most of the foods necessary for the trees' growth are manufactured. This food-making process takes place inside the leaf in numerous cells that contain the pigment chlorophyll, which actually masks the true color of the leaf by absorbing all other light colors and reflecting only the green light spectrum--thus the leaves appear to our eyes as green.
The energy of the light absorbed by chlorophyll is converted into chemical energy stored in carbohydrates (sugars and starches). By the plant absorbing water and nutrients through its roots, and absorbing carbon dioxide from the air, the chemical process of photosynthesis takes place. This chemical change drives the biochemical reactions that cause plants to grow, flower, and produce seed.
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Chlorophyll is not a very stable compound; bright sunlight causes it to decompose. To maintain the amount of chlorophyll in their leaves, plants continuously synthesize it. The synthesis of chlorophyll in plants requires sunlight and warm temperatures. During the summer months, chlorophyll is continuously broken down and regenerated in the leaves of the trees.
The shortening of the days, and the cooler temperatures at night trigger several changes within the tree. One of these changes is the growth of a corky membrane between the branch and the leaf stem. This membrane interferes with the flow of nutrients into the leaf. As this nutrient flow is interrupted, the production of chlorophyll in the leaf declines, and the green color begins to fade.
The different chemical components that are always present inside the structure of the individual leaf will determine its fleeting brilliant color in the fall. But weather also plays a factor in determining color. The degree of color may vary from tree to tree. For example, leaves directly exposed to the sun may turn red, while those on the shady side of the same tree, may appear yellow or orange. Also, the colors on the same tree may vary from year to year, depend
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ing upon the combination of weather conditions.
According to the tree experts at several universities including North Carolina State and the US Department of Agriculture, and the US Forestry Service, the most vivid colors appear after a warm, dry summer and early autumn rains which will help prevent early leaf fall. Long periods of wet weather in late fall will produce a rather drab coloration. Droughts favor the chemical formation of anthocyanin which is the chemical that is most responsible for the brilliant reds and purples. Drought conditions, especially in late summer, also favor red pigment formation due to the reduction of nitrate absorption through the tree's roots.
Just as rainfall, or lack of rainfall plays a significant role in the brilliance of the autumn colors, temperature also plays a part. The best colors seem to be displayed when relative warm and sunny days are followed by cold nights through early October. Light frost will enhance the colors, but a hard, killing frost will hasten the actual fall of the leaves from the trees. The right combination of temperature, rainfall, and sunshine can prolong the autumn foliage brilliance by as much as two weeks.
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