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Citation. Wilson, S. D. 1994. Initial size and the competitive responses of two grasses at two levels of soil nitrogen: a field experiment. Canadian Journal of Botany 72:1349-1354.   [1212  LTER]

Abstract. I tested whether initial size influenced the ability of grasses to compete against established perennial vegetation in an old field, both in plots with little competition for light and in plots with intense light competition. Seedlings of Schizachyrium scoparium (a perennial) and Setaria viridis (an annual) were assigned to three classes of initial size; small seedlings had about half the initial mass of medium seedlings, which had about half the mass of large seedlings. Seedlings were transplanted into subplots with neighbours either present or absent, within 10 plots that received either NH4NO3 or no additional nitrogen. Transplant final mass (roots and shoots) was significantly lower in the presence of neighbours and increased significantly with initial size. There was no significant interaction between competition and initial size, however, indicating that competition suppressed seedlings of all sizes to about the same extent. Further, there was no significant three-way interaction, suggesting that size did not influence competitive response more in environments where light was limiting. These results differ from pot experiments and monocultures by suggesting that initial size does not influence the ability of a plant to compete against neighbours on either nutrient-rich or nutrient-poor soils.

Keywords. competition, competitive response, competitive ability, size, removal experiments, nitrogen

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