Additive Tree Biomass Equations for Midrotation Loblolly Pine Plantations

Abstract

Biomass estimation is a prerequisite for calculating biomass energy, carbon storage, and sequestration of forests and for examining forest productivity and nutrient cycling. With destructive biomass sampling data from 456 sampled trees on 114 plots of loblolly pine culture and density studies at ages 12, 15, and 16, two systems of nonlinear additive tree biomass equations were developed. One was based on DBH, tree height, live crown length and width, and diameter at live crown base, and the other was based on DBH and tree height only. The systems guarantee additivity in biomass equations. The nonlinear seemingly unrelated regressions (NSUR) approach was used to account for the inherent correlation among the biomass equations, and heteroscedasticity was addressed by having a unique weighting function for each equation. 1 Both systems of biomass equations were compared with previously published equations and the new ones provided more accurate predictions, especially with respect to branch and foliage biomass. The new systems can be used to accurately estimate tree component or total tree aboveground biomass of midrotation loblolly pine plantations in the southeastern United States.