The use of point-to-plant distances in the study of the pattern of plant populations
Document Type: Journal Article
Author(s): E. C. Pielou
Publication Year: 1959

Cataloging Information

  • Balsamorhiza sagittata
  • Bigelowia groveolens
  • British Columbia
  • Canada
  • distribution
  • pine forests
  • Pinus contorta
  • plant communities
  • plant growth
  • population density
  • sampling
  • statistical analysis
Record Maintained By:
Record Last Modified: June 1, 2018
FRAMES Record Number: 30389
Tall Timbers Record Number: 4374
TTRS Location Status: In-file
TTRS Call Number: Journals-J
TTRS Abstract Status: Okay, Fair use, Reproduced by permission

This bibliographic record was either created or modified by the Tall Timbers Research Station and Land Conservancy and is provided without charge to promote research and education in Fire Ecology. The E.V. Komarek Fire Ecology Database is the intellectual property of the Tall Timbers Research Station and Land Conservancy.


From the text...SUMMARY: '1. The most straightforward method of assessing the degree of non-randomness, if any, of a plant population is to collect a sample of distances from random points to the plant individuals nearest them. A knowledge of the density of the individuals, independently determined, is also necessary. 2. As an index of non-randomness a = pDw is suggested, where D is density and w is the mean of the squares of the point-to-plant distances. a is equal to, less than or greater than (n-1)/n according as the population is random, regular or aggregated. The significance of a departure of a from this value is easily found since 2na is distributed like x² with 2n degrees of freedom. Observed values of a from two non-random populations may be compared by a t-test. 3. The advantage of using this index is that it will reveal all the non-randomness present and not merely the smallest scale of non-randomness as an index based on plant-to-plant distances would. Also no distances need be measured from randomly chosen plants; the selection of truly random plants is exceedingly laborious and a biased sample is useless as it is likely to give most misleading results. 4. Owing to the fact that point-to-plant distances may sometimes have the same frequency distribution in random, regular or aggregated populations, the observed distribution of this variate will not necessarily, by itself, reveal non-randomness. The writer is at present investigating the distribution of point-to-plant distances in regular populations.'

Online Link(s):
Pielou, E. C. 1959. The use of point-to-plant distances in the study of the pattern of plant populations. Journal of Ecology, v. 47, p. 607-613.