託福tpo23綜合寫作範文及原文材料

從1880年開始的一個多世紀以來，黃杉的數量在逐漸減少。科學家提出了幾個假説來解釋黃杉數量的下降。下面是小編分享的關於黃杉的託福tpo23綜合寫作材料和範文，希望能對大家有所幫助!

託福tpo23綜合寫作範文　　

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.

　　託福tpo23綜合寫作閲讀材料：

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.

黃杉是北美西北部常見的樹木。但是從 1880 年開始的一個多世紀以來，黃杉的

數量在逐漸減少。目前，科學家提出了幾個假説來解釋黃杉數量的下降。

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.

其中一個假説認為黃杉數量下降是由以衫皮甲蟲為代表的寄生害蟲導致。這種甲 蟲據瞭解是以杉樹皮為食，而其幼蟲則以木質部分為食。史上不乏對於甲蟲侵蝕 和導致黃杉大量死亡的記錄。因為，這種甲蟲很可能是黃杉數量減少的原因。

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.

第二種假説認為是棕熊導致了黃杉數量的減少。熊有時會扒下黃杉的樹皮用以食 用，因為黃杉樹皮還有很高的糖分。事實上，黃杉樹皮的含糖量同棕熊主要使用 的野生漿果相差無幾。雖然棕熊扒樹皮的行為不會直接導致黃杉的死亡，但是它 們這種破壞性的覓食行為卻因為降低了樹木的生命力，而間接導致黃杉數量的.減 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.

第三個假説是氣候的緩慢變化導致了黃杉數量的減少。在過去的一百年裏，在北 美西北部，無論是季節性的氣候更替還是每天的氣温調節都發生了變化。這些變 化對黃杉根系產生了影響。以前，黃杉的表面細根是初春開始生長的;而現在卻 在晚冬就開始生長。根系生長時間的變化可能會造成非常嚴重的後果。新生的根 系都非常敏感，因而非常容易因為冬季夜晚部分結冰的温度受到損害。這種根系 凍傷現象可能會導致整個樹木健康狀況下降，並逐漸導致死亡。

　　託福tpo23綜合寫作聽力材料：

Unfortunately， we still do not know what is killing the yellow cedar. None of the explanations discussed in the reading is adequate.

很遺憾，我們還是不知道是什麼導致了黃杉的死亡。閲讀部分沒有一個假説可以 解釋其數量減少。

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.

首先是杉皮甲蟲假説。這個解釋的問題在於黃杉相對於其他樹種來説其實有更強 的抵禦害蟲侵襲的能力。比如，黃杉的樹皮和葉子上聚集着一些對於昆蟲來説有 毒的的強力化學物質。所以，健康的黃杉是不會受到害蟲損害的。那麼，我們該 如何解釋那些因為甲蟲侵襲而死亡的黃杉呢?這種情況是因為甲蟲侵襲的是已 經受損或者患病的黃杉，這些黃杉沒有甲蟲也會死去。所以，甲蟲的入侵不是黃 杉數量下降的重要因素。

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，雖然熊破壞一些樹木，但是他們卻不是整個黃杉種羣數量下降的原因。在 北美西北部整個海岸線上的黃杉數量都在下降，不管是在大陸還是在離岸的島嶼 上。而在那些島嶼上是沒有熊的，而黃杉的數量卻依然減少。因為無論有無熊黃杉數量都在減少，所以熊不回事數量減少的原因。

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.

最後是根系因低温損害假説。恩，閲讀部分忘掉了一個事實，那就是在温暖的海拔低處，黃杉死亡數量比相對寒冷的高海拔地區要多。如果低温損害是數量減少 的原因，那麼我們可以推理在寒冷的高海拔地區樹木死亡的要多。然而事實相反， 温暖的低海拔地區死亡的數量更多。所以，雖然氣候的改變讓黃杉根系變得比過 去更加銘感，但是這不是他們死亡的原因。