Abstract: By using Hegyi's singletree competition index model, the intra and interspecific competition intensities of endemic and endangered plant  Magnol ia zenii from Baohuashan National Forest Park in Zhenjiang City of Jiangsu Province were quantitatively analyzed, with the methods suitable for treating the surveyed data of clonal ramet discussed. The main competitive stress to the M. zenii population came from interspecific competition, which accounted for 907% of the total. The competition intensity of interspecific competition with M. zenii followed the order of Phoebe sheareri>Acer henryi>Juglans cathayensis>M. zenii>Phyllostachys heterocycla>Platycarya strobilacea>Liquidambar formosana>Gleditsia sinensis>Celtis sinensis. The relationship of the competition intensity between competitive trees and objective trees in the whole forest with the DBH of objective trees nearly conformed to power function, while that between other competitive and objective trees with the DBH of objective trees conformed to logarithm function. There was a significant negative correlation between the whole forest competition intensity and the DBH of objective trees. The predicated results showed that when the DBH of M. zenii reached 30 cm, the change in competition intensity was very small. As for clonal ramet, it was suggested that the method of taking the summation of basal areas at breast height of a species’clonal ramet cluster as the equal area of single tree of the same species was more reasonable.

Key words: Bacteria, Antibiotics, Biological control