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.
Highlights
The Good Practice Guidance of Land Use, LandUse Change and Forestry (GPG-LULUCF) emphasizes the importance of estimating, measuring, monitoring and reporting on carbon stock changes and greenhouse gas emissions from LULUCF activities under Articles 3, 6 and 12 of the Kyoto Protocol
Estimates of carbon stocks and stock changes in temperate and boreal forests are based on forest inventory data (Lehtonen et al, 2004)
∑2 i=1 where n is the number of observations in the fitting dataset; yi and y i are the observed and the estimated value for observation i, respectively; and y is the mean of the observed values
Summary
The Good Practice Guidance of Land Use, LandUse Change and Forestry (GPG-LULUCF) emphasizes the importance of estimating, measuring, monitoring and reporting on carbon stock changes and greenhouse gas emissions from LULUCF activities under Articles 3 (paragraphs 3 and 4), 6 and 12 of the Kyoto Protocol. To estimate carbon stock changes in living biomass, two methods have been suggested (Nabuurs et al, 2003): (a) the default method, which involves subtraction of the biomass carbon loss from the estimated biomass carbon increment for the reporting year, and (b) the stock change method, which involves biomass carbon stock inventories for a given forest area at two time points. In the latter method, biomass change is the difference between biomass at time t2 and t1, divided by the number of years between the inventories. These allometric biomass equations can be functions of diameter at breast height (Brown, 2002; Landsberg and Waring, 1997) or diameter at breast height and total height (António et al, 2007; Bartelink, 1996; Monserud and Marshal, 1999; Reed and Tomé, 1998)
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