Relationship between the forest density and competition of the main trees in Daqing Mountains

On the basis of investigated samples of forest at Daqing Mountain,the formula d=r/(r: individual diameter breast height,:mean diameter at breast height) was used to class the stems to Ⅰ-Ⅴ levels with relative diameter at breast height,and it was used to analyze the density influences on forest structure,the class of stem and the competition of Pinus tabulaeformis,Larix principis-rupprechtii and Betula platyphlla.The results indicate that the proper density of pinus tabulaeformis is less than 3200 stand·hm2,and the competition of Larix principis-rupprechtii is not serious with 1700 stand ·hm2 of the density.The Betula platyphlla is influenced by origin and ages,the density influence is not notable.