An experimental study of competition among fugitive prairie plants.
Abstract
Competition was assessed among 5 wind-dispersed perennial fugitive plant species which constitute a guild on small open sites on the Cayler Prairie Preserve, NW Iowa. When immigrations were separated by more than one growing season, preemptive competition occurred: initial colonists were not affected, but most later arrivals died during the first growing season, and none survived to maturity. When multiple immigrations occurred within a single year, exploitative competition depressed growth and propagule production of co-occurring species in inverse proportion to their propagule size. For individuals of each species the competition threshold was that immigration rate above which reproductive success was lowered due to the combined effects of preemptive and exploitative competition. When immigration and competition are directly related (as with competition for sites or resources within sites), competition increases with the density of the limiting resource and will have greatest effect on plants at high densities of the limiting resource. Intra- and interspecific competition are also likely to influence reproductive success within local populations of these fugitive species. -from Authors