Study on intraspecific and interspecific competition of Pinus taiwanensis

Pinus taiwanensis is a common species,and it is one of the dominant species in subtropical area. The intraspecific and interspecific competitions of P.taiwanensis were analyzed quantitatively by using the improved competition index. The results show that with the increase of the size of objective tree and the distance between plants,the intraspecific competition intensity decreases,because of the population density regulation during self-thinning. In the community,there are many other species,but their diameter at breast height is less than that of P.taiwanensis,as a result,the competition intensity of intraspecific was more excessive than that of interspecific. The order of competition intensity is P.taiwanensis—P.taiwanensisCunninghamia lanceolata—P.taiwanensisQuercus glandulifera—P.taiwanensisother species—P.taiwanensis. The relation between competition intensity and individual growth of objective tree follows closely the following equation CI=AD-B,and the changing of competition intensity is very small when the diameter of the objective tree grows to 20 cm. The model can simulate and predict the intraspecific and interspecific competition efficiently. The study provides a new approach to measure the competition intensity and to ascertain the neighborhood zone on studying the plant competition.