Kenneth A. Kershaw, Quantitative and Dynamic Ecology, American Elsevier, 1964

POSITIVE CORRELATIONS BETWEEN PLANT SPECIES IN GRASSLAND, FORMING A CONSTELLATION

The three groups in fact reflect the initial and secondary stages of two lines of succession. DeVries (1953) examined a large number of grassland sites in Holland and estimated the percentage frequency of the species in each of the sample sites. Correlation coefficients were calculated and the data presented in the form of a two-dimensional diagram based on positive correlations similar to the Juncus effusus example above. Again a number of groupings are present, all of them inter-related yet forming fairly distinct ecological groupings.