SCALES OF SEGREGATION AND AGGREGATION OF PLANTS OF DIFFERENT KINDS

This paper introduces a method for examining the scales of segregation or aggregation of two kinds of plants. It uses the mapped positions of plants but is based on methods originally designed for contiguous quadrat data and may be referred to as two-dimensional local quadrat covariance. A complementary randomization procedure makes it possible to test whether observed aggregation is merely the result of overall patchiness. These methods are applied to analyze the spatial pattern of Solidago canadensis L. plants in an old hayfield, with and without insect galls. In many of the 12 plots sampled, the galled and nongalled plants were found to be aggregated at scales around 0.7m. The randomization test showed, however, that this apparent aggregation was often due to the overall patchiness of the plants' dispersion, and that in some cases, within the patchiness the two kinds of plants were actually segregated at a similar scare.