Forest Reseearch Institute Symposium on Prunning and Thinning

Authors: R.N. James, J.R. Tustin, W.R.J. Sutton
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1970, Issue N.Z.J.For. 15(1) 1970, pp 25-56, May 1970
Publisher: New Zealand Institute of Forestry

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Abstract: A symposium to discuss pruning and thinning was held by the Forest Research Institute, Rotorua, in March, 1970.
Future wood requirements were predicted to double from the year 1970 to 2000; during this period the proportion of sawlogs would decline from 74% to 51% of total wood production, while pulpwood would increase from 24% to 47%. It was stressed that New Zealand must consider carefully the types of forest products to be exported. To meet the range of specifications for different end products, advantage should be taken of the two extreme tree types in radiata pine — the uninodal and multinodal.
The economics of pruning are greatly affected by the timing of all operations. The result of any pruning is the production of considerable quantities of clear cutting grades.
Forest managers have often paid insufficient attention to markets in formulating production thinning prescriptions, and have frequently not defined adequately what was meant by an "economic" production thinning. The effect of thinning on main crop values should be studied in any such evaluation. Many delegates favoured production thinning on tractorable country, but there was general agreement that the difficulties of steep country thinning were best avoided by the use of a silvicultural regime which concentrated on clearfelling. Overseas trends towards complete mechanization in harvesting are expected to have only a small impact on New Zealand practice.
Basic in the determination of tending schedules are the end use objective, overall profitability, and recognition of the manipulative possibilities of initial spacing, pruning, thinning and tree morphology. For example, an optimum regime for production of boards is one with wide spacing and early heavy thinning to ensure maximum diameter growth on final crop trees with well-pruned butt logs and, where possible, uninodal second logs. It was not resolved whether satisfactory production of framing and board grades could be achieved by the same regime.
Efficient implementation of silvicultural schedules requires an objective method of programming stands for treatment, and a skilled, motivated labour force in balance with supervisory staff. Control systems should include well-defined, easily-assessed quality standards and be directed towards the achievement of overall management goals. The latter should be well thought out and clearly stated.
The symposium revealed a substantial diversity of opinion on how man-made forests of exotic conifers should be grown and tended. It did emphasize, however, that if future markets could be defined, positive pruning and thinning operations could play a major role in the achievement of quality and profitability objectives.

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