Abstract: Taking the most important coniferous species of Beijing,Populus,as the studying object,and using the mensuration volume data of 1678 sample trees,the authors developed the compatible two-and one-variable (diameter at breast height-dbh,and diameter at root collar-drc)tree volume equations,height-dbh regression models,and drc-dbh regression models for three species,i.e.,P.tomentosa,P.× euramericana and P.× canadensis,through employing dummy variable model and error-in-variable simultaneous equations approach,and analyzed the differences between the models of three species.The results showed that the mean prediction errors (MPE’s)of two-variable tree volume equations were all less than 2%,and the MPE’s of one-variable equations based on dbh and drc were almost less than 3%,which could meet the need of precision for developing tree volume tables.The tree volume equations constructed in this paper could be applied for volume estimation of poplar forests in Beijing.

Key words: volume equation, height-dbh model, drc-dbh model, dummy variable, error-in-variable, simultaneous equations, Populus