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

Abstract

Key message: The study developed equations for predicting aboveground and belowground biomass of planted and coppicedEucalyptus globulusin NW Spain. It was the first published work considering site effects on aboveground biomass and first work for predicting root biomass, for this species in this region, where it covers about 310,000 ha. Context: Eucalyptus globulus is a species of great economic relevance, being increasingly used for bioenergy. In Galicia (NW Spain), where most of the E. globulus in the country is growing, there are scarce studies modeling aboveground biomass fractions of that species, together with a lack of information on its belowground biomass. Aims: The objective of this study was to develop new and more accurate allometries for predicting E. globulus tree aboveground biomass fractions and coarse belowground biomass in NW Spain. Methods: Aboveground biomass models were calibrated by two approaches: nonlinear seemingly unrelated regressions (NSUR), using tree and stand variables, and nonlinear mixed effects (nlme) equations adding the site factor effect. Validation was made with an independent dataset (85 trees). Belowground biomass equations were constructed for planted and coppiced trees. Results: Crown length and dominant height substantially improved the precision in leaf and branch biomass estimation (NSUR). An added value of our study was the modeling of root/shoot ratio, as a function of diameter of planted and coppiced trees, for first time in this species. Conclusion: This study confirms the importance of site and stand stage to explain aboveground biomass variability. Although different belowground biomass accumulation patterns were observed for planted and coppice trees, aboveground biomass equations were common.