A three level system for estimating the biomass of Castanea sativa Mill. coppice stands in north-west Spain María Menéndez-Miguélez a,⇑ , Elena Canga a,1 , Marcos Barrio-Anta b , Juan Majada a,b,1 , Pedro Álvarez-Álvarez b a Forest and Wood Technology Research Centre (CETEMAS)/Finca Experimental ‘‘La Mata’’ s/n, Grado, Asturias, Spain b Research Group in Atlantic Forests (GIS-Forest), Department of Organisms and Systems Biology, University of Oviedo, Escuela Politécnica de Mieres (E.P.M.), Campus Universitario de Mieres, C/Gonzalo Gutiérrez Quirós, 33600 Mieres, Spain article info Article history: Received 27 June 2012 Received in revised form 23 November 2012 Accepted 25 November 2012 Available online 12 January 2013 Keywords: Chestnut coppice Biomass Individual tree Stool Stand abstract Aboveground biomass was studied in Castanea sativa Mill. coppice stands in north-west Spain, and bio- mass equations were fitted at three levels (individual tree, stool and stand). Four systems of biomass esti- mation were developed. In two of the systems, the following individual tree variables were taken into account: standing tree variables and stump dimension variables. In the other two systems, biomass was estimated at stool and stand level, respectively. In order to represent the existing range of ages, stand densities and sites in the study area, samples of 120 trees (for the individual tree level), 45 stools (for the stool level) and 70 plots (for the stand level) were chosen for study. The trees were felled and destructively sampled to separate biomass into the fol- lowing components: wood, bark, thick branches, medium branches, thin branches and leaves. Several equations for quantifying the biomass of the different biomass components were evaluated. Heterocedas- ticity was corrected for by weighted fitting. To guarantee the additivity of the different biomass compo- nents, the equations were fitted simultaneously by nonlinear seemingly unrelated regressions (NSURs). The different biomass levels considered accounted for between 60% and 90% of the total variability, depending on the level and component evaluated. Most of the equations developed in this study were evaluated with an independent dataset, which confirmed the good performance of the biomass equations for prediction purposes. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction The edaphic, climatic and ecological conditions in northern Spain are ideal for optimal growth of sweet chestnut (Castanea sati- va Mill.) (Gandullo et al., 2004). In Spain, chestnut stands are distributed over an area of 272,400 ha (Fig. 1), of which 154,500 ha are covered by pure chest- nut stands, i.e. in which chestnut is the dominant tree species (chestnut tree cover rate, CTR P 60%). The existing types of chest- nut woodland differ widely in terms of stand structure (coppice stands and high forest) and the main productive aim (nut and wood production). In north-west Spain, coppice stands devoted to nut production have been almost totally abandoned, and most stands are now devoted to production of high quality timber and biomass. Sweet chestnut forest covers a total area of 123,549 ha in Astu- rias, mainly as coppice stands (approximately 70,000 ha are pure coppice stands) (DGCONA, 2003). The average total volume (with bark) of sweet chestnut stands harvested in Asturias in 2008 was 21,737 m 3 (the mean value for the period 2002–2008 was 40,000 m 3 )(SADEI, 2008), which represents 19.9% of the total vol- ume of this species harvested during 2008 in Spain (109,285 m 3 ) (MARM, 2008). The chestnut coppice stands currently existing north-western Spain (Fig. 1) were established as a result of the economic and cul- tural changes that occurred after the 18th century. However, dur- ing the last 30–60 years, many traditional coppices have been abandoned or the rotation time has been greatly lengthened, resulting in unstable and degraded stands. The Government of Asturias is currently working to establish a regional strategy for sustainable harvesting of forest biomass, particularly aimed at the exploitation of chestnut coppice. Several biomass management plans have been proposed for this purpose (Álvarez-Vergel et al., 2011). 0378-1127/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.foreco.2012.11.040 ⇑ Corresponding author. Present address: CETEMAS/Forest and Wood Technology Research Centre/Finca Experimental ‘‘La Mata’’ s/n, Grado, Asturias, Spain. Tel.: +34 985 75 47 25. E-mail address: mmenendez@cetemas.es (M. Menéndez-Miguélez). URL: http://www.cetemas.es (M. Menéndez-Miguélez). 1 Tel.: +34 985 75 47 25. Forest Ecology and Management 291 (2013) 417–426 Contents lists available at SciVerse ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco