Growth and utilisation of 22-year-old managed Eucalyptus regnans.
E. regnans was planted in 1973 on a farm site at Esk, North Island, New Zealand, at 620 stems/ha. Herbicide was applied pre- and post-planting, and fertilizer applied at 30 g urea/tree. Some form pruning was done in 1975, butt log pruning to 6 m in 1980, and thinning to 290 and 120 stems/ha in 1980 and 1983, respectively. Grazing with sheep started in 1975 and with cattle in 1977. In 1995, a MARVL [the computer program Method for the Assessment of Recoverable Volume by Log types] inventory was carried out to determine sawlog yield by log quality class. The MARVL data showed large-diameter stems with more than half the merchantable sawlog component as pruned butt logs; the next main component was pulpwood, reflecting the 350 mm minimum sawlog diameter. Sawing and peeling studies were carried out on 15 sample trees selected across the diameter range, and felled and cross cut into an assortment of pruned peeler bolts, pruned sawlogs and large- and small-branched sawlogs. Sawn timber was air dried in summer 1995-96 and re-assessed in mid-1996. Data on the results are tabulated. The logs sawed well converting with a quarter sawn green timber grade recovery of 46% of roundwood volume. Pruning did not significantly increase clears (there were large defect cores) but increased clear board length. On drying there was minor collapse, and more severe internal checking. The bolts peeled well with a usable yield of green veneer of 60%, but this had high tangential shrinkage and showed splitting on drying. There was some decay and staining associated with pruning, and kino (gummosis) pockets were present bit these were only significant for veneer production. It is suggested that drying technology needs to be improved for satisfactory utilization of young managed E. regnans.