Evaluating pruned sawlog quality and assessing sawmill recoveries in New Zealand
1994
Park, J.C.
Pruned plantation-grown timber crops, principally radiata pine, have now reached maturity and are being harvested on a large scale in New Zealand. Pruned sawlogs are being milled domestically and also exported. Due to the wide range in growing sites and silviculture applied, pruned log quality and clearwood potential is highly variable. Attempts at predicting pruned log quality from available stand records failed, and log size alone was found to provide equally poor indication. Pruned logs of similar age, size, and external appearance are shown here to vary by up to 100 percent in clearwood potential. The problems that arose with the trading and utilization of pruned logs were addressed through research assisted by sawing simulation. Methods for defining pruned sawlog quality, from measurements of both internal and external log variables, and for sampling stands, were developed. Complementary systems were also developed for assessing and improving sawmill conversions of pruned logs. A selection of three case studies is used to demonstrate how all these systems are now being successfully applied in the commercial sector. The New Zealand experience (problems and solutions reported here) is pertinent to growers of pruned crops in other countries and immediately relevant to offshore sawmillers and importers of our pruned logs. The basic philosophy also has much wider general relevance. Similar systems, defining log quality by measurable variables and benchmarking sawmill recoveries via sawing simulation, may be applied to virtually any timber crop.
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