TPO 23 Integrated task

The reading and the lecture are both talking about the decrease in the population of the yellow cedar. The article provides three hypotheses regarding why the population of this kind of tree has been declining. In contrast, the lecturer states that they do not know exactly what causes this drop in the population, and none of the hypotheses presented in the reading are adequate. Afterward, he mentions three reasons to support his assertion.

First, it is claimed in the passage that insect parasites can be a reason why the yellow cedars have been declined. The lecturer refutes this claim and notes that the healthy yellow cedars are strongly resistant to insects. In fact, these trees have some chemical compounds which are poisonous to insects. Therefore, it is unlikely for them to suffer from insect parasites. In addition , insects only attack the trees which are not healthy, and they are already dead.

Secondly, the article mentions brown bears and their aggressive feeding habits as another reason of declining the yellow cedars. The professor disagrees with this statement, and asserts that although bears can damage the trees, they are not responsible for the decreasing of the population of these trees. He goes on saying that in some areas such as Main Island and Long Island, despite the population drop of the trees, no brown bears are existed . In fact, the population is getting lower with or without the brown bears, which proves that bears are not responsible for this lost .

Finally, the author of the reading claims that gradual climate changes is another cause of the decrease in yellow cedars population. The growing roots are sensitive to partial freezing on cold winter nights and by changing the growing time from spring to winter, the trees will not be healthy and eventually, they will die. In contrast, the lecturer refuses this hypothesis and mentions that lots of trees are destroyed in the high temperatures in comparison to low temperatures. He alleges that the cold can damage the trees and this freezing damage can cause trees to die; however, more trees are dead because of the heat. As a result, the cold and freezing is not the reason that kills the trees.