The density effect of rare and endangered Tsuga longibracteata population was analyzed by the theoretical model describing the whole density change process of plant population, i.e. N =exp( a ln 2S+b ln S+c) , where N and S represent population density and mean basal area of T.longibracteata at breast height respectively, and a, b, c are parameters. Then, the authors proposed a density effect model considering the effect of different site and associated species on density regulation of T.longibracteata, which was described as N= exp (-0 42426H 0 55323 ln 2S-5 60238H 0 25191 ln S-6 75209H 0 10815 )+ exp (0 20437 ln 2S′-0 095858 ln S′-0 14548), where H and S′ represented mean height of dominant trees and mean basal area of associated species at breast height. The simulated result showed that the model fitted well observed data from T. longibracteata population. Therefore it is very useful in practice, which will provide a scientific basis for density management of T. longibracteata population.
