Allometric Relationships for Aboveground Woody Biomass Differ Among Hybrid Poplar Genomic Groups and Clones in the North-Central USA.

Allometric biomass equations were developed based on harvests of 198 trees from 15 field sites in the north-central USA, with the trees representing 4 hybrid poplar genomic groups and a total of 11 clones within these groups. Specifically, equations were developed to describe woody (branch + stem) total dry weight (TDW) as a function of diameter at breast height (DBH), along with hypothesis tests of differences among genomic groups and clones for equation intercepts and slopes. Inclusion of groups or clones improved model fit (r² = 0.90 or 0.91, respectively) compared to the generic model consisting of only DBH (r² = 0.85). Differences in equation parameters translated into significant differences among groups and clones for estimated TDW when compared at mean DBH (20 cm). Equations were also developed to describe branch-to-stem weight ratio (BSR) as a function of TDW and tree height (H), also with hypothesis tests of differences in intercepts and slopes among genomic groups and clones. Inclusion of genomic groups somewhat improved model fit (r² = 0.57) compared to the generic model consisting of only TDW and H (r² = 0.53), whereas model fit improved more markedly with the inclusion of clones (r² = 0.75). Our results indicate that group- and clone-specific equations (rather than generic ones) are warranted for hybrid poplars, and that group-specific equations are adequate for estimating TDW whereas clone-specific equations are more appropriate for estimating BSR. [ABSTRACT FROM AUTHOR]