Abstract: With Hegyi's competition index model, the intraspecific and interspecific competitive intensity and the population and individual competitive disturbance of canopy populations in Pometia tomentosa community, one of the tropical seasonal rain forests in Xishuangbanna, were analyzed. The interspecific competition is more intensive than the intraspecific competition. Acanopy population competes with many of other canopy populations. Most tree populations in canopy layer are interfered by and with other populations. The competition intensity of individuals decreases with increasing height of objective trees. Most individuals in lower layers are suppressed. None of tree populations is superior in competition. The mature individuals are only superior in competition. The populations whose seedlings and juveniles are alive under the suppressed condition may maintain their stability in the community over a long period of time.

Key words: Tropical rain forest, Competition, Competitive index, pollen, abiotic stress, floret sterility, rice