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Case Study
Yellowstone Forest Fires
Forest Fires
I. How They Work
II. Fire Management
I. Map of Yellowstone
II. Yellowstone Fire
III. One Year After
IV. Six Years After

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Yellowstone Fire Analysis
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How They Work: Nature's Tinderbox

Tinderbox: a metal box for holding readily combustible material, such as dry twigs, used to kindle fires. Our pioneer forefathers would protect their tinderboxes from the damp and wet, literally with their lives.

One sunny afternoon, a father and his daughter were hiking in a forest. When they finished sharing a bottle of lemonade, they stood up and forgot the bottle lying on the ground. The bottle lay there. Leaves and pine needles fell on it, soil dirtied it, snow covered it, rain washed it off. Eventually, only a small part of the bottle glistened above the leaves

Several years later, the summer proved to be particularly hot and dry. Leaves crackled, needles crunched, and twigs snapped when hikers stepped on them; even the leaves on the trees were turning brown. For a month there was no rain, and the humidity was particularly low. The forest became a tinderbox. A sliver of sunlight pierced the forest canopy, reached the edge of the bottle, and the glass magnified the heat of the light onto the pine needles that lay beneath it. The heat caused the needles to burst into flame. The air and fuel were so dry, and the debris on the ground so loosely packed, that the air, smoke, and gases rising out of the flames spread rapidly. They leapt up to the parched branches and leaves on the trees, and leap-frogged from one tree to the next. The brisk wind carried the flames with it. A forest fire had come to life.

Fires are what they eat.
Forest fires spread in three different ways, depending on where most of the forest's fuel is located. Surface fires burn the low-lying plants and shrubs (more or less up to the height of an adult's waist) and the litter and debris that accumulate on the ground. Crown fires move through the tops of trees, leaping from treetop to treetop. Crown fires are sprinters, the fastest spreading and most dramatic of all forest fires. When winds are strong, they can burn their way across the tops of forests at speeds of 16 km. per hour or more! (Note: The world's top sprinters can run over 34 km. per hour. The world's top marathoners average around 21 km. per hour.) Ground fires are plodders. They creep beneath the surface litter, consuming dead and decomposing organic materials in a slow-moving, unspectacular fashion. They are known to begin in campfires and burn through the root systems of dead trees, springing up in many places at once. They are extremely destructive and perhaps the most difficult to track and bring under control. Of course, most wildfires are blends of all three types, and they travel in often unpredictable patterns and directions until the weather changes or their fuel supply runs out.

What goes around...like a carousel or wheel of fate.
The forest where the girl and her father hiked that hot, dry summer was destroyed by the wildfire. People came to the edge of the forest and looked. The ground was the color of ash, and the trees were blackened stumps. They saw no plants, no flowers, no green leaves, no birds, nor did they slap any pesky mosquitoes. The people looked and shook their heads, and some even cried. "The forest has died," they decided, and they walked away, looking for another place to enjoy nature.

The people couldn't see the tumult of life beneath the charred surface. The forest hadn't died. The soil was still there, and all the burned materials were making it richer still. Within a month after the fire, grasses and plants began to poke above the ashes, and birds and other small animals found food and building materials in the debris. Seeds sheltered from the fire inside cones or deep in the soil came to life. The rains returned and watered them. With the tall trees gone, sunlight was able to reach the ground, giving life to hundreds of thousands of seedlings that wouldn't have survived in the deep shadows of the old forest. A variety of fast-growing, light-hungry tree species and fruit-bearing bushes, such as whortleberry and huckleberry bushes, luxuriated in the new conditions; while the slower-growing shade trees common to the old forest were scarcely to be seen. Over the years, the seedlings became saplings, young trees grew to the height of humans. People began to return to the forest. The saplings grew into tall trees with lush leafy canopies or thick coats of pine needles. Once again, the ground was in shade. The plants and trees that preferred shade finally had their turn to grow. Over the decades, they grew to dominate the forest, for the light-hungry trees could not tolerate the new conditions. People who hiked along the shady paths thought of the forest as ancient.

Then, one sunny, spring afternoon, a father and his daughter were hiking in the forest. When they finished sharing a bottle of lemonade, they left the bottle on the ground, beside the rock that had warmed them as they rested.

Review Questions

  1. Describe the 3 different ways in which forest fires spread.
  2. A forest fire has just occurred. Draw a circular diagram to describe what will likely happen before the next fire.
  3. What conditions might be present in a forest immediately before a fire?