A dynamic model for growth and mortality of individual plants in a stand is developed, based on the process of canopy photosynthesis, and assuming an allometric relationship between plant height and weight, i.e. an allocation-growth pattern of plant height and stem diameter. The following were shown by simulation: (i) competition between individuals in a crowded stand is never completely one-sided but always asymmetrically two-sided, even though competition is only for light; (ii) plants of the ‘height-growth’ type exhibit a greater asymmetry in competition than plants of the ‘diameter-growth’ type; (iii) the competition mode between plants of the ‘height-growth’ type becomes more asymmetric with increasing photosynthetic ability than with plants of the ‘diameter-growth’ type. These results can explain recent empirical results obtained from several natural plant communities.
