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The Role of Germination Date, Spatial Arrangement, and Neighbourhood Effects in Competitive Interactions in Linum

N. L. Fowler
Journal of Ecology
Vol. 72, No. 1 (Mar., 1984), pp. 307-318
DOI: 10.2307/2260023
Stable URL: http://www.jstor.org/stable/2260023
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
The Role of Germination Date, Spatial Arrangement, and Neighbourhood Effects in Competitive Interactions in Linum
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Abstract

(1) The simultaneous effects of density, spatial pattern, and date of germination upon plant growth and reproduction were examined in Linum grandiflorum var. rubrum grown in a bench filled with soil. Newly germinated seedlings were planted on two dates at three densities; spatial pattern was created by varying the sizes of the patches containing plants of a single planting date. (2) Density, germination date, and spatial pattern all had significant effects upon plant weight and the number of flowers per plant. The three factors interacted in their effects in a complex fashion; the effect of each pattern was dependent upon the density, and the effect of a pattern-density combination was dependent upon germination date. (3) The competition experienced by an individual plant is due to its immediate neighbours. Therefore, the correlations between the weight of individuals and the weight of the neighbouring plants within 7.1 cm were calculated; no pattern of correlations was evident. Correlations between plant biomass and the biomass of all neighbours within 7.1 cm, weighted by their distance away, were negative, but low. These results were evidently due to individuals experiencing interference from a relatively large number of neighbouring individuals, and so, as well as the expected negative correlations, positive correlations occurred among neighbours due to suppression by a third individual. (4) The substitution of a function of a function of the sizes of neighbouring individuals for overall density in the prediction and explanation of competitive effects thus presents some major problems in those cases in which individuals compete with many neighbours. (5) The `failure' of nearest neighbour analysis to detect clearcut negative correlations between the sizes of neighbouring plants should not necessarily be interpreted as evidence for the absence of competition; it may be the result of competition among many neighbouring individuals.

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