Catenation: Quantitative methods for the definition of coenoclines

Abstract

Catenation is defined as the ordering of elements in continuous sequences that best accounts for local similarities without assuming linear relations. It is thus a non-linear relative of ordination. When applied to phytosociological data it is equivalent to the detection and definition of coenoclines. Several mathematical methods of catenation are available and potentially useful in phytosociology. One such method, continuity analysis (parametric mapping) has been tested on a variety of simulated and real vegetation data. Despite some computation problems, it usually succeeded in accurately recovering simulated coenoclines which were strongly curved in Euclidean vegetation space. In data from Wisconsin vegetation it defined a first catena which was similar to the ‘continuum’ defined by the leading dominants method; but in one case indicated some modifications and the existence of a second dimension. When applied to other sets of real data, the method detected between one and three catenae or nonlinear dimensions, which were usually closely related to environmental gradients. The relationships of species (or communities) to these catenae tended to be of a bell-shaped form, even though such a form is not explicitly assumed in the method.