tpo23. Summarize the point in the lecture which disapproves those of reading.

Recently, there has been a lot of debate about what are the causes of the yellow cedar declining in population. One group represented by the professor thinks that the cause is still unknown. However, others like the author prefers to take one of several hypotheses that explains the causes of declining number of the yellow cedar.

First, the professor explains that in regard for the “beetle insect’s hypothesis" that those insect only attacks sick and damaged trees, that eventually are going to die anyway. He added that researchers found that healthy trees carries powerful chemicals that consider poisonous to the beetles, and since both healthy and beetle’s attacked yellow cedar trees are both declining in population that only mean that the beetles have nothing to do with the overall declining in yellow cedar. However, the text explains that the beetle attacks cedar in order for their larva to eat cedar's wood, which made the beetle a good candidate for the declining cause.

Second, the professor refers to the "bear’s hypothesis" that there are no bears on island, and yet both island and mainland yellow cedar are declining in population that means bears are not the cause of the declining. However, the text goes further to explains why the bears attacks the cedar, because cedar bark contains a lot of sugar which consider a staple for bear's diet.

Finally, the professor states that the reading forgot to mention a pivotal fact that many of the yellow cedar trees how lives on high attitude where it is cold are dyeing beside the trees how lives at warmer lower attitude. He added that although the climate causes a noticeable changes in cedar's root sensitivity, but it is not the main cause of the declining number of the yellow cedar. However, the text averse that gradual climate changes had a significant role in the increased sensitivity of cedar's root causing them to freeze in cold winter’s night.