Wood energy yield for Eucalyptus clones growing under seasonal drought-stress in Brazil

Abstract

Brazil is internationally recognized for the high yield of its Eucalyptus plantation forests and the use of wood as bioenergy. The expansion of Eucalyptus forests to water-limited regions in Brazil and around the world has required the selection of superior drought-adapted clones, since this is a limiting factor for the wood yield of Eucalyptus plantations. In addition to growth, the wood quality for bioenergy must be considered when selecting these Eucalyptus genotypes growing under seasonal drought-stress. Our study focused on evaluating the energy potential based on wood energy yield from a diverse set of 20 Eucalyptus multispecies clones planted under seasonal drought-stress in Brazil. In addition, correlation and path analyses were used to indicate which wood quality and yield traits influenced energy yield the most. The experiment area is characterized as tropical with dry winter climate type (Aw), with precipitation irregularly distributed throughout the year, with 5 months of water deficit. The mean annual increment (MAI) was calculated, trees were cut and wood samples were obtained six years after installing the experiment to determine the wood basic density, higher heating value, energy density, dry matter, and energy yield. Our results indicate that there are Eucalyptus genotypes adapted to seasonal drought-stress and present a high yield. The CCL36 (E. urophylla x E. grandis) clone has the greatest energy potential as it has the largest wood energy yield (982,587 MJ ha−1 year−1), and is also the most productive with 94.99 m³ ha−1 year−1 of wood. The wood energy yield of the Eucalyptus clones is strongly related to the mean annual increment and the increment in dry matter. However, wood traits such as basic density and heating value had little influence on wood energy yield. Thus, it is concluded that there are clones with high productive potential which can increase the biomass supply for energy in tropical regions with dry winter climate types, such as areas of recent forest expansion.