托福tpo23综合写作及原文材料

托福tpo23综合写作范文及原文材料

　　从1880年开始的一个多世纪以来，黄杉的数量在逐渐减少。科学家提出了几个假说来解释黄杉数量的下降。下面是小编分享的关于黄杉的托福tpo23综合写作材料和范文，希望能对大家有所帮助!

托福tpo23综合写作范文

　　

　　In the lecture, the professor points out that the hypothesis made by the reading passage is not adequate to explain why the population of Yellow Cedar is on the

　　decline. He points out several weaknesses of the statements made by the reading passage.

　　On one hand, the professor claims that insect parasite may not be the fundamental cause of the decline. In fact, he argues that healthy yellow cedar can secrete chemicals which can kill the cedar bark beetles so that they are unlikely to suffer from insect parasite. The trees that suffers insect parasite have already been sick or on the edge of death.

　　On the other hand, the professor asserts that brown bears cannot cause overall decline in yellow cedar population. There is decline both on the mainland of North America and islands along the coast. However, there is no brown bear on the islands at all.

　　What’s more, the professor doubts the hypothesis that the change of climate is to blame for the declination. He admits that the climate has changed rapidly recently. And, if the climate change is the real cause, the number of trees died on the higher elevation should be larger than that on a lower elevation. The fact is, however, on the opposite.

　　托福tpo23综合写作阅读材料：

　　Populations of the yellow cedar, a species of tree that is common in northwestern North America, have been steadily declining for more than a century now, since about 1880. Scientists have advanced several hypotheses to explain this decline.

　　黄杉是北美西北部常见的树木。但是从 1880 年开始的一个多世纪以来，黄杉的

　　数量在逐渐减少。目前，科学家提出了几个假说来解释黄杉数量的下降。

　　One hypothesis is that the yellow cedar decline may be caused by insect parasites, specifically the cedar bark beetle. This beetle is known to attack cedar trees; the beetle larvae eat the wood. There have been recorded instances of sustained beetle attacks overwhelming and killing yellow cedars, so this insect is a good candidate for the cause of the tree’s decline.

　　其中一个假说认为黄杉数量下降是由以衫皮甲虫为代表的寄生害虫导致。这种甲 虫据了解是以杉树皮为食，而其幼虫则以木质部分为食。史上不乏对于甲虫侵蚀 和导致黄杉大量死亡的记录。因为，这种甲虫很可能是黄杉数量减少的原因。

　　A second hypothesis attributes the decline to brown bears. Bears sometimes claw at the cedars in order to eat the tree bark, which has a high sugar content. In fact, the cedar bark can contain as much sugar as the wild berries that are a staple of the bears’ diet. Although the bears’ clawing is unlikely to destroy trees by itself, their aggressive feeding habits may critically weaken enough trees to be responsible for the decline.

　　第二种假说认为是棕熊导致了黄杉数量的减少。熊有时会扒下黄杉的树皮用以食 用，因为黄杉树皮还有很高的糖分。事实上，黄杉树皮的含糖量同棕熊主要使用 的野生浆果相差无几。虽然棕熊扒树皮的行为不会直接导致黄杉的死亡，但是它 们这种破坏性的.觅食行为却因为降低了树木的生命力，而间接导致黄杉数量的减 少。

　　The third hypothesis states that gradual changes of climate may be to blame. Over the last hundred years, the patterns of seasonal as well as day-­‐to-­‐day temperatures have changed in northwestern North America. These changes have

　　affected the root systems of the yellow cedar trees: the fine surface roots now start growing in the late winter rather than in the early spring. The change in the timing of root growth may have significant consequences. Growing roots are sensitive and are therefore likely to suffer damage from partial freezing on cold winter nights. This frozen root damage may be capable of undermining the health of the whole tree, eventually killing it.

　　第三个假说是气候的缓慢变化导致了黄杉数量的减少。在过去的一百年里，在北 美西北部，无论是季节性的气候更替还是每天的气温调节都发生了变化。这些变 化对黄杉根系产生了影响。以前，黄杉的表面细根是初春开始生长的;而现在却 在晚冬就开始生长。根系生长时间的变化可能会造成非常严重的后果。新生的根 系都非常敏感，因而非常容易因为冬季夜晚部分结冰的温度受到损害。这种根系 冻伤现象可能会导致整个树木健康状况下降，并逐渐导致死亡。

　　托福tpo23综合写作听力材料：

　　Unfortunately， we still do not know what is killing the yellow cedar. None of the explanations discussed in the reading 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, the problem with this explanation is these healthy yellow cedars are generally much more resistant to insect infection than other tree species. For example, the bark and leaves of the yellow cedars are concentrated with powerful chemicals that are poisonous to insects. So, healthy cedars are unlikely to suffer from the insect damage. So, how can we explain those dead cedars that were infected with beetles? In those cases, the beetles attacked trees that were already damaged or sick and what probably dead any way. So, the beetles are not the fundamental cause 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, they are not the cause of the over all population decline. Yellow cedars population has been declining all across the northwestern coast of North America, both on the mainland 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 and without bears, the bears can not 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 root suffering from frozen damage. Well, the reading passage forgot to take one fact into account. Many more trees are dying in the lower elevations where it is warmer than in the higher elevations where it is cold. If freezing damage were responsible for the decline, we would expect to see more trees die in the cold weather of the high elevations. Instead, more trees die in the relative warm of the low elevations. So, although the climate change may have made the cedar roots more sensitive then 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。

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