Multivariate Methods in Plant Ecology: IV. Nodal Analysis

Abstract

Nodal analysis is a method by which concentrates of vegetational information can be extracted from a matrix of species/site records by examining the coincidences between the results of normal and inverse association-analysis (already described separately in previous communications). The "vegetation-units" extracted can be defined and characterized by reference to both plants and habitat, and can be ranked in importance according to the precision of the statistical definition. The operation of the method is demonstrated on two natural populations, one consisting of "stand" data from heathland, and the other of transect data from fenland. The results of both analyses are assessed and found to be ecologically meaningful. The nature of the vegetation-units extracted by nodal analysis is considered in relation to certain current vegetational concepts; and the general place of statistical analysis in vegetational studies is briefly discussed.