Effect of tree, stand, and site variables on the allometry of Eucalyptus globulus tree biomass

Abstract

The objective of this study was to develop a system of compatible equations to estimate eucalyptus ( Eucalyptus globulus Labill.) tree aboveground biomass and biomass of tree components for forest biomass prediction across regional boundaries. Data came from 441 trees sampled on several sites (99 and 14 plots in planted and coppice regenerated stands, respectively) representative of the eucalyptus expansion area in Portugal. The system of equations, simultaneously fitted using seemingly unrelated regression, was based on the allometric model for the biomass of stem wood, stem bark, leaves, and branches. Total aboveground biomass was expressed as the sum of the biomass of the respective tree components. The study allowed the following conclusions: (i) there is a significant increase in the predictive ability of the models that include height (stem components) or crown length (crown components) as an additional predictor to diameter at 1.30 m; (ii) there is a clear effect of the stage of development of the stand on tree allometry, with a decreasing pattern of the allometric constants; (iii) no effect of stand density, site index or climate on tree allometry was found; and (iv) for practical purposes, the same system of equations can be used for planted and coppice regenerated stands.

Biomass allometry and carbon factors for a Mediterranean pine (Pinus pinea L.) in Portugal

“…The tree variables d and h had a significant effect on the allometric relationships for biomass and volume, in agreement with other authors (António et al, 2007;Calama and Montero, 2006). Some studies had tested other variables with success, namely with tree age for eucalypts in Congo (Saint-Andre et al, 2005), stand age for Pinus pinaster in Aquitaine (Porté et al, 2002), sapwood area to stem diameter for several boreal species (Bond-Lamberty et al, 2002).…”

Improving the robustness of biomass functions: from empirical to functional approaches

“…In addition, their modeling efficiencies were only slightly reduced when shifting to the validation data set. This, together with the failure to adjust any covariate model for the parameters used in the structural approach, suggests that d and h captured much of the variability associated with stem biomass, which is in agreement with many other studies (e.g., Cairns et al 2003;Chave et al 2004;Brandeis et al 2006;António et al 2007). Quite interestingly, the multiplicative model of Cienciala et al (2008) leads to estimates of parameters for d and h that were quite similar to those imposed by the structural approach, which strongly supports the latter.…”

“…In addition, when a lot of data are available, a subset can be devoted to validation in order to independently evaluate model performances (Saint-André et al 2005;Wutzler et al 2008;Genet et al 2011). The use of covariate models is another way to improve the validity range of biomass equations; this approach consists in fitting biomass equations site by site (or stand by stand) and to relate equation parameters to site/stand variables (Saint- André et al 2005;António et al 2007;Genet et al 2011). Finally, the problem of tree component additivity is now commonly solved by using joint-generalized least square regression, also called seemingly unrelated regression (Parresol 2001;Lambert et al 2005).…”

Allometries for Widely Spaced Populus ssp. and Betula ssp. in Nurse Crop Systems

“…In accordance with other studies, the additional inclusion of tree height in allometric biomass equations could reduce the standard error of estimate particularly for predictions of stem wood and aboveground woody biomass [62,69]. Apart from these examples, the major improvement was the flexibility of such models to account for changing height-to-diameter ratios between our study plots.…”