Laboratory 8

Forest Ecology - FOR 3213

When two species which consume the same resources for survival are grown together with a limited amount of resources in an experiment, eventually one species will disappear and the other will dominate. This finding led to the concept of the competitive exclusion principle; when two species compete for the same resources they cannot coexist indefinitely. Organisms can coexist when they do not utilize the same resources or when the resources are much more abundant than needed to sustain both populations.

Experiment: Tomatoes and bush beans were grown together for 2 months and harvested to determine the average weight per plant. The treatments were: 100% tomato, 75% tomato-25% bean, 50% tomato and bean, 25% tomato-75% bean and 0% tomato-100% bean. There were four plants per pot. Determine the biomass per plant and plot this value against density of the competitor for each species.

Report: The report should include a graph of the relation between biomass per plant and density of the competitor. Discuss the results in regard to the effects of competition on vigor or size. Your report should include the answer to the following questions: