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

The article is about declining population of yellow cedar trees and three hypotheses for declination. The author is giving three reasons of support. However, The professor explains that nobody knows what is the main cause of reducing yellow cedars and refutes each of the author's reason.

First, the article states that yellow cedar trees are attacked by bark beetle. The professor refutes this point by saying healthy yellow cedar trees are resistant to beetle. He adds that barks and leaves of cedar tree are poisonous. The attacked trees were already damaged and they were about to die.

Second, the reading posits that may be brown bear damaged the trees, because of the sugar content bark which tastes like wild berries. According to the professor, population of trees is declining everywhere in northwest of North America, even on islands. There are no bears on the islands. Even though, some trees may damaged by bears but not all of them.

Third, the reading claims that gradual changes in climate may be to blame for declination of trees. Due to change in seasons, roots are growing in late winter rather than early spring. Growing roots are getting exposed to cold weather and partial freezing of roots killing the trees. The author opposes this point by saying that tree population is declining on the lower elevation than high elevation. Research has prove that warm temperature cedars dying than cold weather. So third reason is also impossible.