Important as a control over  population growth, diversity in communities, invasibility of non-native plants

definition: the use of a resource by one organism that results in reduced availability of that resource for another organism and limts its potential growth and reproduction.

resource must be limiting; for plants includes light, water, nutrients, pollinators, and seed dispersers

competition operates at the level of the individual, but has implications at the population and community levels

Intraspecific competition = competition within the same species
Interspecific competition = competition between different species
interspecific competition is often asymmetric, i.e. one species is a better competitor than another species

Eventual outcome of asymmetric interspecific competition is competitive exclusion- one species population will eventually go extinct (locally)

Apparent competition- increase in abundance of one species results in a decrease in another as a result of increase in herbivore populations problematic to both species

Mechanisms of Competition
1) Exploitation competition- rate of resource capture determines competitive success (e.g. amount of light or nutrient capture)

traits influencing competitive ability depend on the limiting resource- e.g. transpiration rate, plant growth rate

2) Interference competition- allelopathy, chemical interference; problems with allelopathy: autotoxicity, concentrations, microbial degredation

Detecting Influence of Competition

experimental approach (greenhouse and field)
>  removals and additions
>  plant “target “ and neighbor plants at different densities

Measures of outcome of competition:
competitive effect- influence of a species on its neighbors, and competitive response- how a plant responds to a neighbor

Resource "need" may be predictive of competitive outcome
R*= the minimum resource supply that a species population needs to sustain itself (l = 1)

Is competition more intense in productive areas? (The Grime-Tilman Debate)

Grime: competition is more intense in productive areas because there are more neighbors to compete with.
Stress tolerance becomes important in less productive areas.  Trade-off between stress tolerant and competitive traits (growth rates, resource use)

Tilman: competition is important at all levels of productivity.
What changes is the resources plants compete for: light in productive environments and soil resources in unproductive environments.
Predicts a trade-off in shoot and root competition

Support exists for both sides-  although recent review of literature failed to support general trend of increasing competition with increasing productivity
 
 
 

rev 10/23/05