Date of Award
Doctor of Philosophy
Vegetation analysis is, as a rule, comparative. Based on community components, which are plant populations, the analysis is necessarily taxonomy dependent. The fact that alternative taxonomies may, depending on the defining character set and the degree of fuzziness inherent in grouping plant individuals, lead to different perceptions has been notoriously unobserved by the dominant ecological tradition.;In the presence of choice, the question arises: which taxonomy? My main theses in the dissertation are concerned with how to answer this question. Specifically, I argue that: (1) Different taxonomic systems have conceptual justification and practical utility in vegetation studies. (2) The utility of taxonomies arising from different systems and character sets can be assessed. (3) The optimality of a taxonomic scheme is dependent on context, and its definition requires the notions of ecological relevance, structural convergence, structural divergence, and parsimony as guiding principles. (4) The perception of community components as crisp or fuzzy entities matters. A fuzzy view reduces analytical indeterminacy and alleviates the problem of character order. (5) The methodology constrained by these concepts is capable of revealing information hitherto unobtainable by the ecologist.;Character-based community analysis is not new, but in its recent state it lacks a coherent theory and appropriate analytical tools. I attempted to develop both theory and tools from a base available to me through L. Orloci's. I accepted his character-based hierarchical model, and the idea of focusing on alternative taxonomic systems and order related problems. The result is a new comprehensive approach and a complex algorithm for its implementation. Specifically, I review past work, and present original propositions regarding: community resemblance measures, structural evaluation functions, character ranking, randomization-based probabilistic assessments, fuzziness of population taxa in community studies, and the application of eigenordination. I also describe a comprehensive program in C to perform the analyses, and give examples suggesting areas of utility for the approach. The interpretation of compositional structures in terms of environmental conditions and plant character patterns, and a quantitative assessment of structural convergence in geographically distant communities that do not share a common flora stand out as typical areas of application.
Pillar, Valerio De, "The Theory Of Character-based Community Analysis" (1991). Digitized Theses. 2102.