Integrated writingPopulations 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 decl

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Integrated writing
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.

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.

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.

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.

The speaker refuted the three hypotheses stated in the passage about why the number of yellow cedar decline, mainly with three counter points to the three hypotheses.

First, even though that the beetle larvae eat the wood and may let yellow cedar die, the hypothesis is worthy of doubt. In fact, healthy yellow cedar produces some kind of chemical material that is a poison to the insects. As a result, healthy yellow cedar should be more resistant to the insects, and the hypothesis might be wrong, with the fact presented.

Second, despite bears sometimes claw at the cedars and could probably make the cedars damaged and dead, it could not be the exact reason of the decline of population. The speaker provided another
evidence that the decline is a general trend across the northwestern North America, no matter on the mainland or on the island. Actually, there are no bears on the island, and, as a consequence, bears could not be the cause, which worsen the second hypothesis.

Third, while the gradual changes of climate do let the roots more sensitive and vulnerable, it is still not the right one with the existence of the other evidence. In fact, the diminish of number of yellow cedar mainly occurs at low elevation areas, which is warmer, not colder. If the hypothesis were right, the most damaged areas should be the coldest ones, not as those in the record. Therefore, the given clue weaken the third hypothesis. And, as a result, the cause of the decline is still unknown.

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Category: Excellent Excellent
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No. of Words: 257 250
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No. of Different Words: 133 150
Fourth Root of Number of Words: 4.004 4.7
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Avg. Sentence Length: 21.417 21.0
Sentence Length SD: 6.171 7.5
Use of Discourse Markers (%): 0.833 0.12
Sentence-Text Coherence: 0.361 0.35
Sentence-Para Coherence: 0.602 0.50
Sentence-Sentence Coherence: 0.065 0.07
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