Wasps of this genus are used to control citrus scale insects in California. Evidence of Competition among Trees in Removal Experiments Growth rates of some trees increase after removal of other species. This provides direct evidence of competition for light, water, and nutrients. The researchers suggested that lower competition for belowground resources could account for the observed results. This is primarily competition for water and nutrients.
Belowground competition is called root competition .
This is primarily competition for light. Figure 22-8 illustrates how these types of competition can be arranged in a greenhouse setting. Figure 22- 9 illustrates results of root and shoot competition between white clover, Trifolium repens , and the perennial ryegrass, Lolium perenne . The ryegrass was the superior competitor in both types of competition. It is likely that the outcome of competition will differ between two competing species.