The burning branches pop and scatter onto the forest floor. Fire spreads to dry twigs and needles. Flames dance over dead logs and leap up nearby tree trunks. Soon the forest crackles and snaps in a red-orange light (see photo).
This is the end of the forest, right? Actually, the answer is bigger than that. A fire can be just another step in the forest's ongoing natural cycle.
STEP ONE: BEGINNING THE CYCLE
The forest-fire cycle has been happening over and over for thousands of years. Fire may seem to be terribly destructive, but many forests depend on it to stay healthy. Here's how it works in a western pine forest:
When the forest burns, the fire acts sort of like a giant gardener. It clears, trims, weeds--and even spreads seeds! Fire cleans up old leaves, needles, and dried-out logs and limbs heaped all over the ground. As this stuff burns, it turns into powdery ashes full of minerals. The minerals help new trees grow.
But where do the new trees come from? In a pine forest, they come from the seeds that grow in pine cones high up on branches. These cones are sealed in a sappy wrapping. When they get heated by fire, the sap melts and the cones burst open like popcorn. The seeds sail out in all directions, and some may land in ash-covered soil where the fire has already passed.
Forest fires usually start during the summer and may continue burning for several months before going out. A fire naturally goes out in one of two ways. It can run out of fuel (fallen wood and standing trees). Or it can be put out by rain or snow.
STEP TWO: NEW GROWTH
Once the fire is out, the next step in the cycle begins. When spring comes, rainwater and melted snow help seeds sprout. Green grasses peep out of the black earth. In early summer, golden glacier lilies may pop up. Little pine seedlings sprout long, soft needles. And in late summer, fields of pink fireweed blossoms may spread throughout the area.
During this step of the cycle, animals may also benefit from the fire's work. Although some have lost their homes and hiding places, many animals can find new ones in burned-out tree trunks. They also can chow down on scorched bark and the new green growth that starts cropping up all around.
Newcomers Settle In
After a fire, lots of newcomers venture onto the scene. New trees and shrubs shoot up fast because more sunlight reaches the forest floor than before. Beetles chew into fallen trees and blackened logs. Woodpeckers and other birds build nests in burned- out tree holes.
The birds eat berries and leaves from newly grown woody plants. They also eat grasshoppers, ants, beetles, and caterpillars that find new homes in the burned woods.
A fire may destroy the usual nesting places of birds and other animals. But after a fire the forest is full of new nest sites to choose from. A pair of owls, for example, may pick a newly burned- out tree trunk to make a home for their owlets.
STEP THREE: FULL OF LIFE
The third step in the fire cycle is a healthy forest--filled with lots of different kinds of plants and animals. Seedlings grow into adult pines. During this time, many generations of animals are born, find mates, raise families, and die in the forest community.
FINAL STEP: OLD AGE
If a fire doesn't happen sooner, a pine forest may survive for 200 to 300 years. But time begins to catch up with a forest that old. Some of the huge, aging pines begin to die. One wobbles and leans on the next. Another creaks, cracks, and crashes to the ground. Soon, many old giants lie scattered on the forest floor.
Then, on another summer day, black clouds darken the sky. Boom-- zap! The fire cycle starts all over again. . . .
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|Title Annotation:||environmental aspects of forest fires|
|Date:||Oct 1, 1995|
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