Short rotation coppice tree species selection for woody biomass production in New Zealand

Nine species of Eucalyptus were compared with one selected species of each of Salix, Acacia and Populus for woody biomass production when grown in a temperate climate under a short rotation regime. Ten clones of the promising species E. viminalis were also included in the small plot, randomised block experiment. The trees, planted at a stocking density of 5000 stems/ha, were harvested as single stems at 3 yr of age, then again as coppice regrowth following a further 3-yr rotation. Tree survival, stump diameters (mm), heights (m), and tree dry weights were measured and used to determine the above ground biomass yields. The four replicated plots, each with five trees, of E. viminalis 3680, E. botryoides, E. pseudoglobulus and S. matsudana x alba (Moutere) showed no tree mortality even after the second harvest. Most of the other species had over 80% survival rates, E. nitens being the exception at below 50%. Average heights and dry weights of the harvested coppice trees were significantly greater than when first harvested as single stems. Mean annual incremental biomass dry matter yields (tdm/ha/yr) at the single stem harvest ranged from 2.00 tdm/ha/yr for E. nitens up to 39.72 tdm/ha/yr for E. viminalis 3683. At the coppice harvest E. nitens was again the lowest yielding (2.94 tdm/ha/yr) with other species ranging up to 50.64 tdm/ha/yr for E. pseudoglobulus. On combining total biomass yields from both rotations, most Eucalyptus species produced significantly more biomass than the other genera, with E. viminalis 3678 and E. pseudoglobulus exceeding 35 tdm/ha/yr during the 6-yr period.