Abstract: Based on the biomass of average tree and the forest inventory data,determination was made on above and under ground biomass of a single tree from Ulmus glaucescens of Helan Mountains,and through the method of recession analysis,a study was conducted on the relation among each organ biomass and tree height(H),diameter at breast height(D),diameter at 1/2 total height(D_1/2)and D₂H.The result showed that the biomass distribution ratio of each part of Ulmus glaucescens of Helan Mountains was in the order of trunk > root > branch > bark > leaf.Trunk,branch and leaf biomass recession models were well fitted;root and bark biomass recession models were fitted not as well as the other models.Any independent variable number and biomass fitting prediction equation applicability are preferable.

Key words: biomass, recession models, Ulmus glaucescens, Helan Mountains