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Reading passage for Sample correction
Wilderness management has advanced greatly over the last century, due in part to such practices as the suppression of forest fires and limitations on the clear-cutting of trees. Monitoring forests for small brushfires is easier with aircraft, as is the use of large amounts of water sophisticated chemical fire extinguishers to prevent fires from spreading.
The goals of decreasing the amount of destruction by fires and cutting are wide-ranging. One is simply the longer lives and improved health of trees. In some areas of hickory and oak forest on the Eastern Seaboard, fire suppression has allowed the maturation of so many trees that the treetops form a continuous canopy.
There is evidence of the healthful effects of fire suppression closer to the ground as well. Vines and low bushes that would be burned out in a forest fire can flourish when fires are suppressed, of course, but there is a more indirect way fires harm plant life. Chemical tests on areas that have recently experienced forest fires demonstrate that burning decreases the overall amount of nutrients in the soil. Suppressing fires prevents such a decrease. Ferns, wildflowers, and herbs grow without disturbance.
Finally, wildlife can benefit. In the eastern hickory and oak forests, the suppression of fires has meant that forest animals-ranging from small insects and birds to large deer and bears-are not burned to death. Deer populations, in particular, have increased notably.
Listening passage for Sample correction
For years, forest fires were regarded as uniformly destructive, and forest managers put a lot of effort into preventing them. But it turns out that fire suppression may have destructive long-term effects on the forests it’s supposed to protect.
For instance, mature oaks have grown so thickly in some places that little light reaches the forest floor. But young oak trees need light in order to grow properly. The lack of light has meant that new oaks aren’t maturing rapidly enough to replace the older oaks. It also means that other tree species that don’t need so much light, such as maples, are invading oak and hickory forests and competing for resources.
There are competition problems at ground level too. What forest fires, both natural and artificial, used to do is burn off some of the plants on the forest floor before they could glow into huge thickets. Now they run wild over the ground-and again, that meant it’s hard for young trees and other native plants to grow.
Then there’s the increase in the deer population-this partially results from the lack of forest fires and partially from limitations on hunting-but the thing is, deer like to eat the leaves off oak saplings. So if one of those seedlings somehow does manage to get a good start, despite the shade and all the other plants competing for nutrients, it’s likely to be killed by having its leaves eaten.
Oh, and one other thing: Scientists are now finding that forest fires release nutrients from the plants and animals that are burned. That means that, even though the total amount of nutrients is decreased, there can actually be more nutrients available on the soil surface for plants that are trying to grow back afterward. |
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