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

According to the lecturer and the reading, there are several positive points has been discussed about yellow cedars and several negative point about yellow cedar. The lecturer explains that the three hypothesis about yellow cedar decline that mentioned in the reading is not accurate. However, the reading passage contends that Scientists have advanced several hypotheses to explain this decline.

The first point the lecturer makes it that we don't know the exact reasons of decline. According to the professor cedar bark beetle more resistance that other trees, it's saturated with powerful chemicals. if the trees attacked by parasite so maybe those trees was already sick. This point from the lecturer contrasts with the reading because the reading only says that yellow cedar decline caused by insect parasites.

Another point that the lecturer uses to cast doubt on the reading is there is no brown beers in northwestern North America. The lecturer claims that since that the decline occurs with or without bear so the bear is not
responsible. However, the reading only states that Bears sometimes claw at the cedars in order to eat the tree bark, which has a high sugar content

finally the professor stated that, on the contrary of the reading, cedar trees primarily die at lower elevation where it is warmer than higher elevation where it is colder. In other words, if cold was the main cause of death so all the trees could be dead. This contradicts the final idea of the reading passage because it only says that Growing roots are sensitive and are therefore likely to suffer damage from partial freezing on clod winter nights. This frozen root damage may be capable of undermining the health of the whole tree, eventually killing it.