When the leaves fall off - part 2 - includes related articles

American Forests, Sept-Oct, 1994 by Lester A. DeCoster

On the ground lie the lungs of the planet. Here are eight things to do with the and lots of other neat autumn stuff.

WHAT BETTER NAME than "fall" for a season when trillions of leaves fall from billions of trees? On the parts of the planet tilted now away from the sun we see less daylight. The weather cools. Leaves that moved and transformed tons of water, air, and nutrients with power from the summer sun now sputter and stall in weak fall sunlight--some "flame out" in beautiful colors.

We go leaf-looking in hardwood regions: admiring the fall colors, supporting th highway fund, and encouraging country inns to stay open just a little longer. But bright foliage soon turns to drifts of dead organic matter. Here lie the lungs of the planet: leaves turning brown and shriveling as if they had smoked pack a day for far too long. Even with evergreens, older leaves (needles) are dying and dropping to the ground, forming layer upon layer of tree debris.

Fall looks like an ending. But it is neither ending nor beginning--just another stage in the constant maintenance and renewal of living things. Now is an excellent time to assess tree conditions and plan your season's projects. You can see things in the fall that are obscured by the summer leaves that cover every live twig and branch. Also, there are mountains of dead leaves to be deal with.

Walk with me out into fall's aromatic old-attic (dry) or clothes-hamper (damp) smell--the smell of a monumental organic recycling project. Dead leaves are decaying and venting a musty brew into the air. It gets in your nose and tweaks your sneeze reflex. There's lots of rustling from crinkled, dry leaves lying on every flat surface. A breeze, a step, a scampering squirrel, even the light touch of a falling twig sets off a cascade of rustling.

We'll probably hear another fall sound--a whining roar--that in recent years ha spread across North America. Combine the bugling of an elk with the sound of a very large vacuum cleaner, and you have it--the sound of the leaf blower. Repeated at intervals from place to place, the noise resembles territorial animal calls. It does involve territorial animals--us. Blasting away with leaf blowers, we move leaves from our territory onto someone else's.

In fall we work very hard to make sure fallen leaves don't stay in the one plac they belong--on the ground. We regard dead leaves as trash. And since we've bee trained that trash must be disposed of out of sight of civilized folks, we wave our wind wands and blow those leaves into piles, into bags, into trucks. We blo them into the streets to be washed down drains and beaten into mush by the constant tread of traffic. We sneak them over to the next-door neighbors; they blow them to their neighbors, who blow them on . . . and on until dunes of leaves are lodged in uncared-for sections.

Dead leaves are worn-out tree engines, but they're still full of fuel. Kick a few worn-out tree engines around with me. A 60-year-old maple, doing its fall thing, has dumped around 200,000 leaves (about 120 pounds). A 30-year-old, mixed-species forest has dropped 10 million leaves (weighing about 3,000 pounds per acre. But there's more going on here than colorful scenes and falling leaves.

SOIL MOISTURE IS INCREASING. On a hot summer day, a large tree like our 60-year-old maple will move 7,500 pounds of water from the ground out through its leaves into the air. That's equivalent to the cooling power of six room-siz air conditioners. No wonder it's cooler around growing trees. No wonder the soi gets damp in the fall.

THE DEAD LEAVES WE ARE WALKING ON BUILT THEIR OWN REPLACEMENTS BEFORE FALLING OFF THE TREE. Working leaves fuel tree maintenance and growth, seed production, and creation of a replacement leaf behind each working leaf. By the end of summer, each small new leaf is rolled and wrapped in an insulating bud. Warmer weather and longer days next spring will quickly pop these new leaves out of their coverings, ready to go to work.

TREES HAVE STOPPED PRODUCING OXYGEN. Summer leaves use sun power to combine carbon dioxide and water, making tree fuel (sugars) and oxygen. The process is called photosynthesis (meaning, appropriately, "putting together with light"). Working leaf exhaust is oxygen, exhaled into the air (lucky for us since we nee it to breathe). Now that trees are dormant, oxygen is used and carbon dioxide i released from tree respiration and decaying or burning leaves and other organic matter.

But we are not going to gasp for oxygen or feel greenhouse warming from this process, because most of the carbon from carbon dioxide taken in through the summer is still held in tree branches and stems. Oceans and growing plants in those parts of the planet now coming into summer are taking in carbon dioxide and giving off oxygen.

DEAD LEAVES ARE BECOMING FERTILIZER AND HUMUS. A one-acre, 30-year-old forest will pull about 350 pounds of nutrients from the soil annually--240 pounds of this falls back to the soil in leaves and twigs. Key elements in leaves in orde of quantity are: calcium, nitrogen, and potassium, followed by small amounts of magnesium, sulfur, and phosphorous. Layers of leaves also slow rainwater/snowmelt runoff, intercepting and absorbing water, and improve soil aeration and water retention by adding humus. If you let the trash truck haul your leaves away, you are throwing away mulch and nutrients.