Both author and lecturer offer two opposing views on the hypotheses of explanation for the yellow cedar decrement.

Both author and lecturer offer two opposing views on the hypotheses of explanation for the yellow cedar decrement. While the reading passage lists some factors as the plausible reason for the phenomenon, the professor counters these specific points, and presents clues to call in the question for the information in the text. First of all, the article mentions to the surmise of insect parasites, especially the cedar bark beetle is one of the possible factors of this event. However, the instructor refutes this surmise. As he asserts, the healthy cedar releases a specific substance which is toxic; in addition, it attacks the insects. As a result, whenever, the yellow cedar is defeated by the insects, the insects will be contaminated by this substance, and they will die. That is how the lecturer casts doubt the truth of this surmise. Next, meanwhile, the passage names the brown bears and their eating habits as another feasible hypothesis, the professor casts doubt on the accuracy of this claim. As he states, although the eating habit of brown bear can damage the trees, it cannot lead to this huge population decreasing. Moreover, inasmuch as the decline occurs in the both mainland and island; however, the island is not the habitat of the brown bears. Consequently, the brown bear does not lead to this decrement. Finally, the text posits the gradual alteration of climate, which makes the roots of the trees be sensitive. On the other hand, the lecturer challenges the validity of this presumes. Based on his evidence, even though the change of weather makes them sensitive, as she points out the decrease of trees in the hot, lower elevation is more than the cold, high spots. Hence, if the cold weather leads to this phenomenon, the majority of decrement should happen in the high elevation; however, the actual records are contradicted with this assumption.