Eucalyptus species for biomass energy in New Zealand—I: Growth screening trials at first harvest

Abstract

Twelve species of the subgenus Symphyomyrtus and seven of the subgenus Monocalyptus were evaluated for biomass production in small plots under a short rotation forestry regime. The trees were planted at a stocking density equivalent to 2200 stems/ha, and harvested after 3 years. The growth and yield were monitored by measuring the percentage tree survival, stump diameter (mm), tree height (m), and dry weight which was used to determine the comparable biomass yields of the different species. Coppice regrowth was subsequently monitored and is reported elsewhere. The means of tree stump diameter, height and dry weight varied with species. Tree dry weights from the plots with zero mortality ranged from 18.9 kg for E. rodwayii to 21.1 kg for E. brookerana of the Symphyomyrtus subgenus, and from 13.1 kg for E. elata to 15.5 kg for E. nitida for the Monocalyptus subgenus. Biomass yields from the plots with 100% survival varied between 9.6 and 15.5 oven dry tonnes per hectare per year. Overall, species belonging to the Symphyomyrtus subgenus had relatively higher stump diameters, heights, dry weights, and consequently higher yields, than those belonging to the Monocalyptus subgenus. Although the survival rates, growth and yields of the different species showed variations after 3 years, the results were considered to be indicative only for the local region. They were inadequate for making commercial decisions on the choice of species for SRF schemes for biomass production over a wide range of soils and climates. Nevertheless the most outstanding species identified would be worthy of further consideration for any specific site with a temperate climate.