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ruleNEW ENGLAND FALL FOLIAGE: HOW COLORS CHANGE AND IN WHICH ORDERrule

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THE FASCINATINATING STORY OF HOW LEAVES CHANGE COLOR

My wife and I have considered fall our favorite season for 31 years, whether the colors are brilliant and mesmerizing or muted and dull. We've tried repeatedly to find the reason, but can't quite pin one down. Probably because there are so many fond factors involved.

That we first met in the fall is probably the best reason (my wife made me write that). But there's something else, too. Perhaps it's the fragrance of smoke wafting from chimneys and mixing with the heady scent of the last cutting, the harvest, and fresh, chilly air.

Or maybe it's the promise of snows to come (another family favorite) and the coziness of a down comforter on a cold, autumn night. Or maybe it's the awe-inspiring, majestic colors. Fall foliage color changes, though always the same process year after year, do have different results. The leaves can be varied and gorgeous, deeply colored spectacles that take your breath away.

Looking at all of those features makes me think it's all of the above and that the absence of any one would deprive us of the awesomeness we've come to expect.

Regardless, it never occurred to either of us to question what motivates trees and their leaves to form a strong synergy during the spring and a "leaf-be-gone" strategy in the fall.

Through the process of photosynthesis, the leaves, at least in part, helped to make the tree's food, only to have trees deprive the leaves of chlorophyll (what makes them green and helps the tree produce glucose), force them to produce stark, luscious Fall Foliage colors, break away and become the next layer of soil on the forest floor.

As we know, the leaf color change is a phenomenon unique to deciduous forests, a healthy mix of maple, birch, poplar, redbud, elm, sugar maple, evergreens, sumac, oak, dogwood, hickory, sweet gum, black gum, sourwood and ash trees.

WHICH TREE LEAVES TURN WHAT COLOR?

Leaf color changes in New England fall foliage color changes are determined by the tree's species. For instance, the evergreens, spruce, fir trees and rhododendrons and laurel, among others, are called evergreens for a reason. Even though some species will change the color of their leaves, what remains at season's end stays green.

Birch, elm, poplar, redbud and hickory trees give us the gold and yellow hues that seem to dominate as the backdrop for the reds in autumn's color scheme.

Red oak, hickory, ash, sugar maple, sweet gum, black gum, sourwood, red maple, as well as dogwoods give us the stunning red, deep magenta and purple colors, although they can produce yellow leaves. We get maroon from sumac.

WHY AND HOW DO LEAVES CHANGE COLOR?

Knowing which tree produces which color is one thing. The big and growing question over the years has been why and how they change? The most popular belief in scientific circles holds that as there are more summer days behind than there are ahead, and as the days grow shorter and the nights longer and cooler, the leaf color change is triggered within the trees.

The process begins with the severance of chlorophyll to the leaves and clothing them in their inherited colors before they fall off and glide to nature's woodland carpets.

As with all things scientific (or botany-related in this case), theories conceived by the specialists exist as slightly different spins on the phenomenon that visits New England and other parts of the country each year.

THE FALL FOLIAGE COLOR CHANGE PROCESS

Without plants, trees in particular, I wouldn't be keyboarding this story now. They are nature's carbon dioxide scrubbers and oxygen providers. As we inhale, we're breathing IN oxygen produced by plants and trees. Our blood is oxygenated in our lungs and it then carries the oxygen to our tissues. What gets exhaled in that process is carbon dioxide.

If that builds up to certain levels, it can be fatal in humans, so trees feed us the life-nurturing gas we need to breath and protect us from harmful gases that would imperil our lives.

Water is taken from the soil by the tree's roots, and carbon dioxide from the air by the leaves. Sunlight then converts both water and carbon dioxide into glucose, a natural sugar, which becomes food for trees.

The catalyst for all this is chlorophyll. Under the green in the leaves of trees that produce yellow leaf color lays xanthophyll, one of the yellow pigments that gives the leaves their yellow, gold and orange colors.

Some scientists conclude that the whole leaf isn't completely yellow under the green, but rather exists in small patches that spread in the fall. Others maintain that what we see in autumn is just as prevalent in July, but lies hidden under summer's green tints.

During the summer, some of the tree's food (glucose), is stored for winter reserves. When summer ebbs, the trees are able to decrease or cease food production and stop the flow of chlorophyll to the leaves. That eliminates the green color.

In contrast, the leaves that give us the deep red and magenta colors appear only in the fall when the temperature ranges between freezing and 45 degrees and the trees have plenty of sun. They aren't "under" the green in the leaves as is the case with the yellow species. Instead, some of the glucose produced when the tree manufactured its food is trapped in the leaves and when the chlorophyll disappears, the glucose reddens because it contains anthrocyanin, a red pigment. It's the same tincture that makes roses and geraniums red.

Finally, oak leaves contain waste from the tree, so they turn brown before falling to the forest floor.

While leaf color is determined by tree type, color saturation, or how bright the hues become, is affected by how cool and sunny fall days are. The cooler and sunnier, the brighter the colors. But summer weather can play a role as well. If there's too much or too little rain, for instance, the colors may not be as bright during the peak period.

WHAT ROLE DOES WEATHER PLAY IN COLOR SATURATION?

The biggest determinants of how deep the hues will become are water and air temperature.

Frosty nights that stay above freezing, and sunny, warm fall days are responsible for color depth. Leaves turn much brighter under those conditions.

In the case of trees that yield yellow leaves, ever present are carotenoids and carotene. These form the yellow tints that lie beneath the green and emerge as all yellow, orange or gold in the fall. In the case of red leaves, this ideal weather produces anthocyanin tinctures. They produce radiant reds, magenta and sometimes purple leaves.

How moist the soil is as it relates to the temperatures can produce a spectacular color array or one that's dull and flat. Ideally, if the preceding spring produced a good deal of rain and summer weather was "normal," neither too hot, nor too cold, not too wet, nor too dry, the best autumn colors are produced.

A summer drought will likely delay peak foliage. Too much summer rain can have a similar effect. In other words, if everything is not in optimum balance, the colors can be delayed and when the leaves change color, they appear muted.

WHAT MAKES LEAVES FALL?

In early autumn, in response to the shortening days and declining intensity of sunlight, trees begin the processes leading up to their baldness (no PC emails; I'm follicly challenged myself). The veins that carry fluids into and out of the leaf gradually close off as a layer of cells forms at the base of each leaf. These clogged veins trap sugars in the leaf and promote production of anthocyanins. Once this separation layer is complete and the connecting tissues are sealed off, the leaf is ready to fall.

As autumn begins to yield to winter, the colors fade and the stems binding leaf to tree branch begin to weaken. Before long, the leaves are literally hanging by threads--the tiny arteries that brought them water and glucose during the summer. Fall's winds, leaf pickers, wild animals, almost anything that brushes up against them snap them off the tree.

Fortunately, the colors remain after the leaves have dropped, but only for a day or so, so if you want to collect and press them, you can take them off the trees yourself, or if you see one you really like on the ground, you can collect that and press it, but do it quickly. Once they dry out, they get very fragile and break easily.

Eventually, all of the leaves are rendered brown by the presence of tannin; it's the same substance that gives tea leaves their brown color after they're harvested.

We have very carefully selected and picked from red-leaf-colored trees the highest quality red leaves we can find and my wife has mastered the art of folding them into what appears to be a rose.

CONCLUSION

While summer is the busiest tourist season in some New England states, fall is a very close second. There's nothing quite like this time of year, nor is there any end to the ways you can view the powerfully colored canopy.

In the other segments of the NewEnglandTimes.Com Fall Foliage Section, we'll tell you where to find the best tour routes, show off some of our fall photos, help you decide when to come on up to chase the peak, where to stay and provide you with a range of attractions. You'll find something of interest in each and every one.


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