Mathematical and Biological Considerations on Yield- and Competition-Density Effects in Self-thinning Plant Populations

概要

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A mathematical model for describing the density effect occurring in self-thinningpopulations is developed on the basis of the following three basic assumptions: (1)the growth of yield follows the general logistic equation; (2) final yield becomesconstant irrespective of initial density; and (3) there exists a functional relationshipbetween actual and initial densities. The resultant equation takes the same reciprocal form as the reciprocal equation derived from Shinozaki-Kira's theory, i.e., thelogistic theory of the C-D effect, which deals with the density effect occurring in nonself-thinning populations. It is, however, recognized that one of the two coefficients is quite different in mathematical interpretation between the two reciprocalequations based on the present theory and the logistic theory of the C-D effect, respectively. The present conclusion is consistent with the empirical facts that the reciprocal relationship between yield (or mean phytomass) and density is discerniblein not only nonself-thinning populations, but also self-thinning populations. Thepresent model is expected to systematically interpret underlying mechanisms between the density effect, which is observed at a time constant among populationsvarying in initial density, and self-thinning, which is observed along a time continuum in any given population.
琉球大学理学部の論文
1998-09-00