Establisment of Single-tree Biomass Equations for Betula alnoides

In this paper,based on the biomass of 157 sample trees of Betula alnoides collected and measured in Yunnan Province from 2019 to 2020 (including 106 above-ground biomass(AGB) and 51 whole tree biomass).The one-variable and two-variable above-ground and below-ground single-tree independent biomass equations as W=a×D^b、W=a×D^b×H^C,the stem,branches,leaves biomass equations compatible with above-ground biomass equations were established.Finally a root-shoot ratio model was build up,which could be used to estimate below-ground biomass together with above-ground biomass equations.The results showed that:for one-way and binary equations of the above-ground and below-ground biomass,the weight functions W=1/(D²),W=1/(D²H),W=1/(D^0.5) and W=1/(D²H) are selected respectively and weighted regression was carried out to solve the model parameters, which significantly reduced the influence of heteroscedasticity and improved the stability of the model.The compatible biomass equations solved the problem that the sum of the sub-biomass of single-tree branches, leaves, stem was inconsistent with the total above-ground biomass.The prediction precision of above-ground biomass and stem more than 94%,and were more than 92% for branches,leaves biomass estimation respectively,the prediction precision of below-ground biomass model was more than 87%,all models were recommended to be applied to biomass estimation of Betula alnoides.