Abstract: According to field investigation data,the intraspecific competition and interspecific competition of Pinus koraiensis in broad-leaved Korean pine mixed forest in Changbai Mountains were studied by using Hegyi's competition index model for individual tree.The results showed that intraspecific competition intensity of Pinus koraiensis reduced with increase of diameter scale of trees.The order of competition intensity is:Pinus koraiensis-Fraxinus mandshurica>Pinus koraiensis-Quercus mongolica>Pinus koraiensis-Pinus koraiensis>Pinus koraiensis-Tilia amurensis>Pinus koraiensis-Acer mono>Pinus koraiensis-Tilia mandshurica>Pinus koraiensis-Acer mandshurica.The relationship between competition intensity and individual size of objective tree follows closely the equation CI =AD-B.Based on the relationship,competition intensity in the forest is simulated.At the same time,some conclusions and suggestions are proposed.It is proved that Hegyi′s competition model for individual tree can provide quantitative index for study on intraspecific and interspecific relationship in plant population ecology.

Key words: Quercus wutaishanica, seed coat, sowing depth, seed germination, seedling growth.