Study on Intraspecific and Interspecific Competition of Picea crassifolia in Liancheng National Nature Reserve of Gansu

Using Hegyi's competition index model for individual tree,we analyse the intraspecific and interspecific competition of Picea crassifolia in Liancheng National Nature Reserve of Gansu.The re- sults show that intraspecific competition intensity of Picea crassifolia reduced with increase in diameter scale of the trees.The intraspecific competition is more bigger than interspecific competition.The order of competition intensity(CI)is:Picea crassifoliaPicea wilsoniiAcer tetramerum var.betulifoliumPopulus davidianaBetula albo-sinensisSalix sp.The relationship between competition intensity and individual growth of objecttive tree follows closely the equation CI=AD~(-B).When the diameter scale reaches 45 cm,there is little change of competition intensity.The CI of Picea crassifolia has plus correlation with altitude and crown density.