Competition among grasses

Plant responses to competition may be dictated by the levels of resources available. The objective of this study was to examine whether the amount of water influences the intensity of competition among plants. Competition and watering were manipulated in a crossed-design garden experiment in Texas. The experimental species, Schizachyrium scoparium (Poaceae), was planted in three rows that were not watered, but received only natural precipitation, and three rows that were supplemented with additional water. Six target plants in each row were randomly assigned to competition treatments and received either four conspecific neigbors or no neighbors.

Competition was shown to be strong, and was demonstrated by a strong negative effect of neighbors on target plants. There was an indication of enhanced plant growth in the watered treatments and a trend for competition to be stronger in the watered treatments. We conclude that the intensity of competition is greater at the higher resource levels of water.