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托福综合写作优秀作文练习题：黄杉数量正在减少

2015-04-06 09:16:00来源：网络

　　托福综合写作听力材料：

　　Unfortunately，we still do not knowwhat is killing the yellow cedar. None of the explanations discussed in thereading is adequate.

　　很遗憾，我们还是不知道是什么导致了黄杉的死亡。阅读部分没有一个假说可以解释其数量减少。

　　First, the cedar bark beetle. Well, theproblem with this explanation is these healthy yellow cedars are generally muchmore resistant to insect infection than other tree species. For example, thebark and leaves of the yellow cedars are concentrated with powerful chemicalsthat are poisonous to insects. So, healthy cedars are unlikely to suffer fromthe insect damage. So, how can we explain those dead cedars that were infectedwith beetles? In those cases, the beetles attacked trees that were alreadydamaged or sick and what probably dead any way. So, the beetles are not the fundamentalcause responsible for the decline of the yellow cedars.

　　首先是杉皮甲虫假说。这个解释的问题在于黄杉相对于其他树种来说其实有更强的抵御害虫侵袭的能力。比如，黄杉的树皮和叶子上聚集着一些对于昆虫来说有毒的的强力化学物质。所以，健康的黄杉是不会受到害虫损害的。那么，我们该如何解释那些因为甲虫侵袭而死亡的黄杉呢?这种情况是因为甲虫侵袭的是已经受损或者患病的黄杉，这些黄杉没有甲虫也会死去。所以，甲虫的入侵不是黄杉数量下降的重要因素。

　　Second, although bears damage some trees, theyare not the cause of the overall population decline. Yellow cedars population hasbeen declining all across the northwestern coast of North America, both on themainland and on the islands just off the coast. There are no bears on the islands,yet the islands cedars are still in decline. Since the decline occurs with andwithout bears, the bears cannot be responsible.

　　第二，虽然熊破坏一些树木，但是他们却不是整个黄杉种群数量下降的原因。在北美西北部整个海岸线上的黄杉数量都在下降，不管是在大陆还是在离岸的岛屿上。而在那些岛屿上是没有熊的，而黄杉的数量却依然减少。因为无论有无熊黄杉数量都在减少，所以熊不回事数量减少的原因。

　　And finally, the theory about rootsuffering from frozen damage. Well, the reading passage forgot to take one factinto account. Many more treesare dying in the lower elevations where it is warmerthan in the higher elevations where it is cold. If freezing damage wereresponsible for the decline, we would expect to see more trees die in the coldweather of the high elevations. Instead, more trees die in the relative warm ofthe low elevations. So, although the climate change may have made the cedarroots more sensitive than they used to be, this is not what killed them.

　　最后是根系因低温损害假说。恩，阅读部分忘掉了一个事实，那就是在温暖的海拔低处，黄杉死亡数量比相对寒冷的高海拔地区要多。如果低温损害是数量减少的原因，那么我们可以推理在寒冷的高海拔地区树木死亡的要多。然而事实相反，温暖的低海拔地区死亡的数量更多。所以，虽然气候的改变让黄杉根系变得比过去更加铭感，但是这不是他们死亡的原因。

本文关键字: 托福综合写作 托福写作 托福作文

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