Biomass Estimates of Small Diameter Planted and Natural-Origin Loblolly Pines Show Major Departures from the National Biomass Estimator Equations

Abstract

As southern pine forests (both planted and naturally regenerated) are more heavily used to provide biomass for the developing energy sectors and carbon sequestration, a better understanding of models used to characterize regional biomass estimates is needed. We harvested loblolly pines (Pinus taeda L.) between 0.5 and 15 cm dbh from several plantations and naturally regenerated stands in southeastern Arkansas to evaluate allometric relationships based on stand origin. In this process, each pine was separated into stemwood, branches ϩ foliage, and taproot biomass components. Although the differences changed with dbh, loblolly pines from planted stands generally had greater percentages of biomass allocated to foliage ϩ branches and taproots, whereas those from natural-origin stands had greater amounts in stemwood, aboveground, and total biomass. National Biomass Estimator (NBE) high-specific gravity pine equations predicted natural-origin aboveground biomass reasonably well. However, the same NBE model underpredicted aboveground biomass for small (Ͻ5 cm) diameter planted pine and overpredicted planted pines between 7 and 15 cm dbh. When scaled to stand-level estimates, the NBE models resulted in estimates for average stand diameters of 5, 10, and 15 cm that ranged from Ϫ18.6 to 2.1% for natural stands and from Ϫ21.9 to 62.8% for planted stands.

Biomass Functions and Carbon Content Variabilities of Natural and Planted Pinus koraiensis in Northeast China

“…Compared to the PA models, the DV models successfully reduced the estimation bias by 35.80%, 41.65%, 12.57%, and 6.35%, and for the foliage, branch, stem, and root biomass, respectively (calculated using RMSE, Equation (7)). These findings are in line with previous research by Zeng [ 9 ], Schurel et al [ 31 ], and Widagdo et al [ 24 ], which confirmed the importance of considering the origin’s effect on biomass models of Chinese fir ( Cunninghamia lanceolata ), loblolly pine ( Pinus taeda ), and larch ( Larix gmelinii ) in southern China, Arkansas, and northeast China, respectively. Better performance of origin-based biomass models might also be related to a major shift in productivity allocation (i.e., stand density or site productivity) between the planted and natural forest, leading to differences in their tree features, such as wood density [ 60 ].…”

“…As one of the most superior predictors for predicting biomass, diameter at breast height (D) has been widely applied in a large number of tree-level species’ allometric equations across regions and forest types [ 7 , 31 ]. However, researchers still put a strong effort into increasing the biomass equation’s accuracy by adding more supporting independent predictors, such as tree total height (H), crown length, crown radius, wood density, and tree/stand age [ 6 , 19 , 41 ].…”

“…Fu et al [ 30 ] used the aboveground biomass data of Pinus massoniana from planted and natural forests in southern China and concluded that involving the origin-effect with both dummy variables and mixed-effect models brought significantly better performance on model estimation compared to the population average model. Schuller et al [ 31 ] harvested small diameter natural- and planted-origin trees (0.5–15 cm) of Pinus taeda in southern Arkansas to analyze the origin’s effect on biomass allometric relationships and reported that the partitioning proportions of branches, foliage, and root biomass were found to be greater in planted Pinus taeda compared to those of naturally regenerated samples, whereas this was vice versa for stems, aboveground, and total biomass. Widagdo et al [ 24 ] utilized the above- and below-ground biomass dataset to establish Larix gmelinii origin-based individual tree biomass models in northeast China; and found that the origin-based models significantly improved the estimation of total biomass and all biomass components compared to the basic origin-free models.…”

Aboveground Biomass Equations for Small Trees of Brutian Pine in Turkey to Facilitate Harvesting and Management

“…As a result, available woody biomass and the carbon stored at early stages are often neglected. Only a few studies address the estimation of small diameter tree biomass in tropical dry forests [14,17], in temperate deciduous forest [15,18], and in temperate pine forest [19]. Ideally, the biomass equations should be developed covering all size classes without discontinuity at any tree size.…”