Biomass expansion factors for Eucalyptus globulus stands in Portugal

Abstract

One of several procedures for estimating carbon stocks in forests is the estimation of tree or stand biomass based on forest inventory data. The two approaches normally used to convert field measurements of trees to stand biomass values are allometric biomass equations and biomass expansion factors (BEFs). BEFs are used in published National Forest Inventory results in which biomass is not estimated or as a complement of growth models that do not include biomass predictions. In this paper, the effectiveness of BEFs for estimating total stand biomass in Portuguese Eucalyptus globulus plantations was analyzed. Here, BEF is defined as the ratio of total stand biomass (aboveground biomass plus root biomass) to stand volume with bark. To calculate total biomass, an equation was developed to estimate root biomass as a function of aboveground biomass. Changes of BEF with stand variables were analyzed. Strong relationships were observed between BEF and stand age, stand basal area, stand volume and dominant height. Consequently, an equation to predict BEF as a function of stand variables was fitted, and dominant height was selected as the predictor stand variable. Estimates of total stand biomass based on individual tree allometric equations were compared with estimates obtained with a constant BEF (0.77), used in the Portuguese National Inventory Report on Greenhouse Gases, and with estimates obtained using the dominant height-dependent BEF equation developed in this work. The BEF prediction model proposed in this work may be used to improve E. globulus Portuguese biomass estimates when tree allometric equations cannot be used.Key words: root biomass; aboveground biomass; biomass expansion factors; allometric equations. Resumen Factores de expansión de la biomasa de rodales de Eucalyptus globulus en PortugalEl objetivo es estimar las reservas de carbono en los bosques mediante la comparación de dos métodos: ecuaciones alométricas de biomasa y los factores de expansión de la biomasa (BEF). Las estimaciones de la biomasa total del rodal, basado en las ecuaciones alométricas de árboles individuales se compararon con las estimaciones obtenidas con unos factores de expansión constante de la biomasa (BEF) de 0.77, utilizados en el Informe del Inventario Nacional de Portugal de gases de efecto invernadero, y con las estimaciones obtenidas utilizando la ecuación de altura dominante de BEF desarrollada en este trabajo. En este trabajo se analizó la eficacia de la BEF para estimar la biomasa total del stand en portugués plantaciones de Eucalyptus globulus. Aquí, el BEF se define como el cociente de la biomasa total del stand (biomasa aérea más la biomasa de raíces), situándose el volumen con corteza. Para el cálculo de la biomasa total, se desarrolló una ecuación para estimar la biomasa de raíces en función de la biomasa sobre el suelo. Se analizaron los cambios de BEF con las variables del rodal. Se observó una gran relación entre el BEF y la edad del rodal, el área basal, el volumen y la altura dominante. Por lo tanto, ...

Modeling the above and belowground biomass of planted and coppiced Eucalytpus globulus stands in NW Spain

“…The range of R/S of our data, in planted trees (0.15 to 0.65), was very similar to those reported by Cairns et al (1997), for many tropical, temperate boreal species (0.1 to 0.6), and Bernardo et al (1998) (0.2 to 0.6) for several eucalypt species in Brazil. A number of authors have reported decreasing R/S values with tree size or aboveground biomass (Misra et al 1998;Levillain et al 2011;Resh et al 2003;Kuyah et al 2013) or age (Laclau et al 2000;Soares and Tomé 2012) in eucalypt. However, studies modeling the belowground biomass and R/S ratios as a function of dendrometric variables are extremely scarce in eucalypt species (Paul et al 2008;Jonson and Freudenberger 2011), and they show the same trend with diameter than in our study.…”

“…A number of studies have recently been developed to estimate E. globulus tree total aboveground biomass and its components (stem wood, bark, branches, leaves) in the Iberian Peninsula (e.g., Montero et al 2005;Ruiz-Peinado et al 2012;Soares and Tomé 2012;Herrero et al 2014) and elsewhere (O'Grady et al 2006;Zewdie et al 2009). Antonio et al (2007) carried out a comprehensive study to estimate aboveground biomass components for that species in Portugal, including tree and stand explanatory variables.…”

Eucalyptus globulus Stumpwood as a Raw Material for Pulping

“…The stands are normally exploited with three cutting cycles, and at the end of the commercial exploitation, the plantations must be re-established and the stumps removed prior to soil preparation (Barreiro and Tomé 2012;Soares and Tomé 2012).…”

Estimates of Tree Biomass, and Its Uncertainties Through Mean-of-Ratios, Ratio-of-Means, and Regression Estimators in Double Sampling: A Comparative Study of Mecrusse Woodlands

“…An example of ratio estimators in forestry is the estimate of biomass density with the aid of biomass expansion factor (BEF), where BEF is the ratio. Vegetation BEFs can be estimated either by mean-of-ratios [7][8][9] or by ratio-of-means [10][11][12][13][14].…”