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1、 全国免费咨询电话：400-0123-267 托福写作：普林斯顿练习写作8 小马过河为大家准备了“托福写作：普林斯顿练习写作8”，供各位备考托福的考生们参考使用，来提高自己的托福成绩！免费咨询电话：400-0123-267 Reading 8 Wilderness management has advanced greatly over the last century,due in part to such practices as the suppression of forest fired and limitations on the clear-cutting of trees.Mo
2、nitoring forests for small brushfires is easier with aircraft,as is the use of large amounts of water and sophisticated chemical fire extinguishers to prevent fires from spreading.The goals decreasing the amount of destruction by fires and cutting are wide-ranging.One is simply the longer lives and
3、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 b
4、ushes 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.S
5、uppressing fires prevents such a decrease.Ferns,wildflowers and herbs grow without disturbance.Finally,wildlife can benefit.In the eastern hickory and oak forest,the suppression of fires has meant that forest animals ranging from small insects and birds to large deer and bears are not burned to deat
6、h.Deer populations,in particular,have increased notably.Listening 8 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 suppressions may have destructive long-term effects on the forests its supposed to
7、 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 arent maturing rapidly enough to replace the older oaks.It also means that other tree s
8、pecies that dont need so much light,such as maples,are invading oak and hickory forests and competing for resource.全国免费咨询电话：400-0123-267 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 befo
9、re they could grow into huge thickets.Now they run wild over the groundand again,that means its hard for young trees and other native plants to grow.Then th eres the increase in the deer populationthis partially results from the lack of forest fires and partially from limitations on huntingbut the t
10、hing is,deer like to eat the leaves of oak saplings.So if one of those oak seedlings somehow does manage to get a good start,despite the shade and all the other plants competing for nutrients,its 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 thought 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.来源于：小马过河 小马过河资料下载频道，欢迎您来下载！