Interspecific competition among three canopy-tree species in a mixed-species even-aged forest of central Japan

We investigated causes and consequences of interspecific competition among canopy-tree species with different shade-tolerance. The shading effects caused by neighbors were determined fur three tree species, shade-tolerant Fagus crenata, and intermediate tolerant Quercus crispula and Magnolia obovata, in six even-aged stands containing different proportions of each species. The competitive attributes (sensitivity to suppression and intensity of shading) varied considerably among species. Shade-tolerant F. crenata caused most intensive shading effects probably because of its deeper crown depth. Less-tolerant Q. crispula decreased its stem growth and crown depth markedly in association with the presence of shade-tolerant F. crenata. In contrast, F. crenata and M. obovata were less influenced by their neighbors; it may be due to its own higher shade-tolerance in the case of F. crenata and larger initial growth rates in ill. obovata. We suppose that differences in initial species composition may lead a species to have different dominance in stand development. When shade-tolerant species are absent in mixture, less shade-tolerant species could maintain their dominance for a long period. In contrast, mixture with tolerant species would reduce the dominance of less-tolerant species, unless they had growth advantage in early stage in development. (C) 2000 Elsevier Science B.V. All rights reserved.