Allometric Equations for Estimating Compartment Biomass and Stem Volume in Mature Hybrid Poplars: General or Site-Specific?

Abstract

Abstract:We evaluated the extent to which general or site-specific allometric equations, using diameter at breast height (DBH) as a predictor, are more accurate for estimating stem volume, stem biomass, branch biomass, aboveground woody biomass, and coarse root biomass in 14 year-old plantations of Populus canadensis × Populus maximowiczii (clone DN × M-915508) located along an environmental gradient in southern Québec (eastern Canada). The effect of tree size and site on stem wood basic density, moisture content, and proportion of branch biomass was also evaluated. For stem volume, stem biomass, and aboveground biomass, site-specific and general models had comparable fit and accuracy, but lower Akaike's Information Criterion (AICc) values were observed for the general models. For the branch and coarse root biomass, higher fit and accuracy and lower AICc values were observed for the site-specific models. Allometric trajectory changes (plastic allometry) across sites were mainly observed for coarse root biomass, branch biomass, and stem volume. On the low fertility site, allocation was increased to coarse roots and decreased to stem volume. Site-specific tradeoffs between tree architecture and stem wood density explained the relatively invariant allometry for the whole aboveground woody biomass across the plantation sites. On the high fertility sites, basic wood density was the lowest and declined as tree DBH increased. At all sites, stem wood moisture content and the proportion of branch biomass increased with DBH. Overall, this study showed that biomass allometry, tree architecture, and biomass quality are a function of both tree size and plantation environment in hybrid poplar. Allometric model selection (site-specific or general) should depend on the objective pursued (evaluation of yield, nutrient budget, carbon stocks).

Assessment of load and quality of logging residues from clear-felling areas in Järvselja: a case study from Southeast Estonia

“…The strong environmental effect on the allometric relationship between diameter at breast height and compartment biomass have been observed (Forrester et al 2017). Smaller diameeter at breast height trees had lower humidity content and lower proportion of branches (Fortier et al 2017). Our results shows that from smaller average diameter at breast height stands with higher number of trees per hectare were collected higher amount of branches.…”

“…Together with the rising interest towards the resource potential of harvest residues, there is a rising need to enhance the stand residues predictive capabilities of our forest biomass models (Eastaugh et al 2013). Which general or site-specific equations are more accurate for estimating branch biomass, allometric studies could be give answer (Fortier et al 2017). The young Norway spruce trees growing on soils with higher C/N ratio are more likely to have higher branches biomass (Dutcă et al 2014).…”

Planting Density and Site Effects on Stem Dimensions, Stand Productivity, Biomass Partitioning, Carbon Stocks and Soil Nutrient Supply in Hybrid Poplar Plantations

“…For stem volume estimations after 8 years, we used a clone-specific allometric relationship that had been previously developed for clone DN×M-915508 in 8 year-old hybrid poplar plantations of the study region [7]. For estimations of stem volume, stem biomass, branch biomass and coarse root biomass after 14 years, we used site-specific allometric relationships that were developed in the studied experimental design with 14 year-old trees [48]. Site-specific relationships were chosen over generic models because allometry of clone DN×M-915508 was found to be plastic across the studied plantation environments, especially for coarse root biomass, branch biomass and stem volume [48].…”

“…For estimations of stem volume, stem biomass, branch biomass and coarse root biomass after 14 years, we used site-specific allometric relationships that were developed in the studied experimental design with 14 year-old trees [48]. Site-specific relationships were chosen over generic models because allometry of clone DN×M-915508 was found to be plastic across the studied plantation environments, especially for coarse root biomass, branch biomass and stem volume [48]. During destructive harvest procedures, subsamples from stem, branch and coarse root biomass were collected for C concentration determination in 14-year-old poplars.…”

“…Given that destructive harvest procedures were only done in the 494, 1111 and 1975 trees/ha density treatments at each site, only three samples of stem, branch and coarse root biomass were collected at each site. For each compartment, each of these subsamples consisted in a composite sample collected from two average-sized trees within the plot (see Fortier et al [48] for a complete description of stem subsamples collection). At each site, and for a given compartment (stem, branch or coarse root biomass), we used C concentration data obtained in the 494, 1111 and 1975 trees/ha treatment as an estimate of C concentration of 741, 988 and 1481 trees/ha treatments respectively.…”