Shading, defoliation, temperature, growth stage, and residual fertility ef~fects on competition betweenrumex acetosella, trifolium repens, and lolium (multiflorum×perenne)

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Abstract
Competitive suppression of Rumex acetosella by Lolium sp. in undefoliated swards was increased by shading, but Trifolium repens dominated R. acetosella most strongly when not shaded. Intense defoliation early in the development of the swards reduced the suppression of R. acetosella. These effects were related to the prostrate rosette habit of R. acetosella, the species ability to regenerate shoots from roots, and seed characteristics which avoid germination under stands of existing vegetation. Residual pH, nitrogen, and fertility responses were related to competition for nutrients by R. acetosella, Lolium, and T. repens. Growth of R. acetosella markedly affected pH, a change of this effect being associated with flowering. The competitive power of R. acetosella was reduced relative to Lolium but increased relative to T. repens in a lower temperature regime. A population from a relatively closed lowland grassland community suppressed a population from a relatively open sub-alpine community, and this was related to differences in plant elevation and leaf form. Practical implications of these results are mainly related to the mid-altitude grasslands of the South Island, New Zealand, where R. acetosella is frequently an abundant component of newly sown pastures.