GEOG 2500 Lecture Notes - Lecture 3: Dutch Elm Disease, Nitrogen Fixation, Parasitism
Document Summary
Symbiotic nitrogen fixation is a very important process: mutualisms are very tightly evolved relationships. Symbiosis: facilitation, it benefits one species more than the other, parasitism, benefits one species at the expense of another. Example: strangler figs have small seeds that get dispersed. These seeds land in the branch of the canopy, and then germinate. Parasites are not a big control on the population of the species, because this is usually an evolved relationship. If parasites kill all the members of the species, they will have to recondition the relationship, and these parasites will go extinct. It came from asia and was imported on logs that didn"t have bark on them. It was a native disease to chestnuts in area, but it did affect n a. It is a type of fungus, and it has replaced the elm population with red elms and slippery elms that are not as large-growing.
