Evaluation of Changes in Tree Morphology Parameters, Biomass Yield, Chemical and Energy Properties at Three Spacings of Short Rotation Energy Plantations of Gmelina arborea in Costa Rica, from 1 to 2 Years of Age

Propose: Tree diameter and height, yield and chemical and energy properties increment throughout two different ages (1- and 2-year-old) were evaluated in Gmelina arborea trees growing in short rotation woody crops at three sites and three spacings (0.5 × 1.0, 1.0 × 1.0 and 2.0 × 1.0 m). Results: The results showed great variation in parameters evaluated in relation to site, whereas for spacing the results were regular. Diameter, height and biomass yield increased in 2-year-old trees at all sites and spacings. The higher increments were observed in the 0.5 × 1.0 m spacing at sites 2 and 3. Biomass distribution in the different parts of 2-year-old trees showed increased biomass in the trunk and branches, and reduced biomass in leaves. The study of biomass properties showed increments in the specific gravity and reductions in the moisture content (MC) of trunk and branches, but MC of bark was regular. The increment in specific gravity and volatile contents was highest in the 0.5 × 1.0 m spacing, while MC of trunk, branches and bark, heat calorific value and ash content decreased. Carbon and nitrogen contents were irregular throughout spacing and sites. Conclusions: It was determined that at 2 years of age, Sites 1 and 2 presented normal behavior of Gmelina arborea in SRWC conditions, and in the Site 3 the changes produced improved the quality of biomass for energy purposes.