Abstract: Based on the investigation data of 3 sample plots in Muling Forestry Bureau, the effective competitive trees were identified by using the concept of dynamic radius in competition zone. The intraspecific and interspecific competition intensities for natural Korean pine(Pinus koraiensis) forests were quantitatively analyzed based on Hegyi competition index. The results showed that intraspecific and interspecific competition intensities of Korean pine were 18%, 82% of total competition intensity, respectively. Hence, competition pressure of Korean pine mainly came from interspecies rather than intraspecies. Some species, such as Acer mono, Picea koraiensis and Abies nephrolepis, which were in a dominant position because of their big size and large quantity, gave a high competition pressure to Korean pine. The relationship between DBH and CI for competitive trees of Korean pine was negative power function and the competitive intensity decreased gradually as DBH increasing. When DBH of Korean pine is smaller than 25 cm, it is under higher competition; on the other hand, that above 25 cm was under lower and steady competition.

Key words: natural Korean pine forest, intraspecific competition, interspecific competition, Hegyi&rsquo, s index