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Analysis of Local Variation in Plant Size
Author(s) -
Mitchell-Olds Thomas
Publication year - 1987
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1938807
Subject(s) - statistics , variation (astronomy) , competition (biology) , econometrics , path analysis (statistics) , statistical analysis , statistical hypothesis testing , ecology , biology , mathematics , physics , astrophysics
Attempts to quantify local competitive interactions by examining size and growth of neighboring plants may suffer from several statistical difficulties: (1) when individuals are analyzed both as focal plants and as neighbors of other individuals, observations are not independent and tests of statistical significance may be invalid, (2) effects of competition and local site quality may be confounded. The techniques of path analysis and randomization tests are described; use of these procedures may permit more accurate estimation and testing of influences on individual plant growth. Analysis of results of field and greenhouse experiments with Impatiens capensis showed that conventional statistical tests may yield serious errors in estimates of significance, and that these errors are of unpredictable magnitude and direction. The results demonstrate that it is essential to measure or estimate the effects of site quality on variation in plant size.