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New Zealand Journal of Forestry (1979) 24(2): 230–240
©New Zealand Institute of Forestry

Research article
The influence of tree breeding and stocking rate on tree crop quality

R.N. James

In a field trial at Rotoehu State Forest, radiata pine raised from seed orchard seed were established in a series of plots at rates ranging from 250 to 1500 stems/ha. Trees from a routine seedlot were also planted at 1500 stems/ha. The regime applied involved pruning to 6 m in three lifts with three concurrent thinnings to a final crop of 250 stems/ha. After each pruning! thinning selection the residual crop trees -were assessed and d.b.h. was measured. At the last assessment 90% of the final crop derived from seed orchard stock planted at 1500 stems/ha were good form dominants and co-dominants, but only 51% of the crop from the routine seed source established at the same stocking fitted this description. Where fust the final-crop stocking was planted using seed orchard-derived stock, only 23%o of the crop were good form dominants or co-dominants. Crop quality improved rapidly with increased initial stocking, up to 1000 stems/ha, but improvement was slower from higher stocking. This indicates that establishing as few as four times the final crop may be all that is necessary. The rate of diameter growth was lowest in crop trees derived from the routine seed source.
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