Competitive relations among species from pastures of different ages

Abstract

All possible pairs of Dactylis glomerate, Holcus lanatus, Lolium perenne, Poa compressa, and Trifolium repens were collected where the species pairs occurred in close proximity in pastures that were 2, 21, and 40 years old. Each clone was grown with its natural neighbouring clone in experimental field plots for a period of 1 year. Differences in competitive relations between two species from pastures of different ages were measured by total mixture yield and component yield quotient, i.e., the yield quotient of the lowest and highest yielding components. Results show that the relative competitive abilities of particular species differ markedly depending on the age of the pasture from which the plants were collected. Very little support is given for the traditional view that selection pressures from competition usually result in the evolution of niche differentiation in the component species of a community. Alternative evolutionary consequences of competition permitting coexistence are discussed.