Phytograph: Useful Tool or Decorative Doodle?
1968
McCormick, Jack | Harcombe, Paul A.
The phytograph is a quadriaxial polygonal graph used to present data on species performance in vegetation. The area of the quadrilateral formed by connecting plotted points on adjacent axes is considered to portray the ₘass effect of the four axial values. This mass effect is an expression of the relative importance of the species. Since Lutz (1930) introduced the phytograph, it has been used in at least 34 original studies of North American forest vegetation. Lutz's original phytograph employed relative, semi—relative, and non—relative bases on different axes. Subsequent users have introduced many modifications in parameters and form, but every published phytograph has included at least one non—relative parameter. A major defect in the phytograph previously has been undetected. The area of the quadrilateral negatively distorts the graphic representation of relative importance. The value of the phytograph depends on the legitimacy of expressing parameter values in relative terms and of combining three or more terms to describe the relative importance of a species. If phytographs are used, their accuracy and information content can be increase by adopting several modifications, such as rescaling the axes by a square—root percentage method and using relative values on all axes.
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