A Quantitative Evaluation of the Bray‐Curtis Ordination

The Bray—Curtis ordination provides position values (x) along an ordination axis and distances (e) from the axis for samples of communities. Upon ordination, samples are displaced from their true positions on the coenocline axis into an arch the height of which increases as beta (between—habitat) diversity increases. The cause of this displacement is the fact that the similarity measure is not a linear estimator of ecological separation. The shape of this arch and the consequent effects on the x and e values are shown for various beta diversities. Refinements are suggested for the Bray—Curtis ordination.

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