Nearest-Neighbour Relationships of Overlapping Circles and the Dispersion Pattern of Desert Shrubs

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Abstract
(1) Most techniques for analyzing the dispersion of plant individuals in populations assume that the objects in question are points. When applied to populations of desert shrubs, these techniques often indicate significantly uniform dispersion. (2) The growth patterns of some plants may result in the overlap and fusion of separate individuals to form a clump that cannot be distinguished from that produced by a single individual. This inability to distinguish intimately fused individuals creates a bias toward perceiving uniformity as the techniques of dispersion analysis are based on theory relating to the dispersion of dimensionless points. (3) Simberloff''s technique of analysis of nearest-neighbour relationships of non-overlapping circles can be adapted to overlapping circles that become indistinguishable at some critical minimum separation distance and thus provides a technique for pattern analysis under these circumstances. (4) Analysis of the dispersion of Larrea tridentata in the Colorado Desert of California [UK] demonstrates that its clumped growth pattern creates a strong bias toward the perception of uniformity with techniques based on the point-dispersion theory.