Eucalyptus in agrosilvopastoral systems: An alternative for carbon sequestration and the production of roundwood and sawmill timber

Abstract

Integrated crop-livestock-forestry systems offer sustainable strategies for mitigating greenhouse gas emissions and enhancing agricultural diversification and intensification, with eucalyptus being the dominant tree component in Brazil. This study aimed to characterise wood quality and carbon stocks in two Eucalyptus genotypes in agrosilvopastoral systems in the Brazilian Cerrado. This research innovates by quantifying wood volume and carbon stock in two integrated systems, thereby providing insights into the key factors that optimize the quality of roundwood timber. Trees of Eucalyptus urograndis and E. cloeziana were monitored throughout their production cycle, and the evaluations for this study were carried out at 120 months after transplanting, prior to timber harvest. Longitudinal discs were removed from six trees per treatment at 2 %, 10 %, 30 %, 50 % and 70 % of the commercial height. We evaluated attributes such as bark content, heartwood to sapwood ratio, pith eccentricity, basic density and carbon content in the wood. To determine carbon stock, a total of 18 trees per treatment were sampled, with three trees selected from each of six diameter classes, representing the lower, middle, and upper diameter ranges, and their volumes were subsequently calculated using the Smalian method. Both genotypes showed wood quality associated with a bark content of <3.5 %, acceptable pith eccentricity below 5 %, heartwood to sapwood ratio greater than one, percentage of heartwood greater than 50 %, and a high basic density of >0.60 g/cm³, ideal indicators for using the wood in sawmills, the construction industry and rural areas. A carbon stock of 50 Mg ha⁻¹ in the stem of E. urograndis, double that E. cloeziana (25 Mg ha⁻¹) indicate a significant capacity for carbon fixation within the wood of this hybrid species in an agrosilvopastoral system in the Brazilian Cerrado biome. Our findings showed that silvicultural practices and eucalyptus genotypes adapted to edaphoclimatic conditions are the key factors for maximizing carbon sequestration and achieving high-quality wood production for construction and sawmills within agrosilvopastoral systems.