Answers to Figure Legend Questions
FIGURE 17.2 The most destruction occurred immediately below the mountain, where a huge magma-filled bulge exploded and released rock and mud down the north side of the mountain. An area later known as the Pumice Plain, formed by the hot, pelting pumice rock, experienced the most destruction.
The massive wave of debris from the explosion was funneled down the North Fork Toutle River, removing most life along the way. Spirit Lake was also completely destroyed because of its location within the path of the avalanche. Other areas, such as the south side of the mountain and the locations farther from the explosion (mudflow zone and blowdown zone), experienced blowdown of all trees, but some life remained, especially underground. Finally, the least destruction occurred in the scorch zone, where trees were denuded but remained standing.FIGURE 17.4 Whether a disturbance is intense or frequent will depend on the susceptibility of the organisms involved and their ability to respond to the disturbance. The intensity and frequency of disturbance for an insect population will be quantitatively different from that for an elephant population. The same disturbance—let's say, a tree falling in a forest—could cause major destruction for the insect population living on that tree while having little effect on the elephant population, even if an elephant were struck by the tree. Of course, the insect population would recover much faster than an elephant population might.
FIGURE 17.9 The oldest communities are located in the areas that have been exposed the longest since glacial retreat, such as the mouth of the bay. Here, succession has been able to proceed for over 200 years and has allowed the formation of mature spruce forests. As the glacial retreat becomes more recent, the communities become younger, such that the youngest, pioneer community is located closest to the glacier.
FIGURE 17.17 The fish preferred to eat the tunicate Styela, because when the tiles were protected from fish predation, it was the species that dominated. When fish predation was allowed, the bryozoan Schizoporella dominated, suggesting that it was unpalatable to the fish. This experiment suggests that Styela is the dominant competitor over Schizoporella in the absence of predation.