Date of Award:

5-1-1977

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Life Sciences:Biology

Committee Chair(s)

James A. MacMahon

Committee

James A. MacMahon

Committee

Ronald Canfield

Committee

Neil West

Abstract

Recent studies suggest problems resulting from using essentially linear ordination techniques on non-linear ecological data. A new non-linear method, termed polynomial ordination, was developed in response to these problems. Its effectiveness was compared to that of two standard techniques, Bray-Curtis ordination and principal components analysis, by testing with both simulated and field data. The original species axes are resolved into their principal components. If significant curvilinear relationships between principal components are present, new axes are defined along these curves. The positions of the sample points along the axes are then coordinatized. Using simulated data, the coordinates of the sample points on the first axis were compared to their coordinates on the original simulated gradient. Two statistics were used to evaluate how well the gradient was recovered. Of the methods tested, polynomial ordination best placed the samples in the correct order; principal components analysis best recovered their absolute positions. Ordinations of vegetation samples along a Sonoran Desert bajada by all three methods, suggested that soil particle size is a major environmental gradient affecting the species composition of the vegetation.

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