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New Zealand Journal of Forestry (1980) 25(1): 15–34
©New Zealand Institute of Forestry

Research article
Growth of radiata pine under the direct sawlog regime.

B. R. Manley and R. L. Knowles

In order to analyse the growth of radiata pine (Pinus radiata D. Don) managed under the direct sawlog regime, plots were sought which had been thinned to a final stocking of about 200 stems /ha near the time of high pruning. Data were available for a total of 43 plots at 23 locations throughout New Zealand, including 22 plots at 10 different trials in the Rotorua region.
Growth trends differed between regions, indicating the need for growth models {when based on top height) to be prepared regionally.
Estimates based on the extrapolation of straight-line regressions for each Rotorua-region trial predict a basal area in the range 39-46 m2/ha at top height 36 m. Extrapolation of an overall linear regression for the nine, planted, butt-log-pruned, Rotorua plots resulted in an estimate of 44 m2/ha basal area at top height 36 m. A similar estimate based on the six regenerated plots gave about 41 m2/ha. However, estimates for vlanted, butt-log-pruned plots at Mangatu, Gwavas, and Santoft forests tended to be between 56 and 64 m2/ha at top height 36 m. Estimates for Mohaka, Te Wera, Golden Downs, and Otago Coast forests (based on limited data) lie within or beneath the estimated range for the Rotorua region.
Results indicate that the Beekhuis yield-prediction method is inappropriate for stands in the Rotorua region which have been thinned early and heavily; for these the Kaingaroa Growth Model gives a better estimate. However, data from Mangatu, Gwavas, Santoft, and Ngaumu forests suggest that the Beekhuis method may be suitable for the direct sawlog regime on at least these forests.

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