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NZ research into radiata pine as an agricultural crop

University of Canterbury (UC) research could revolutionise New Zealand’s forest industry by treating radiata pine as an agricultural crop and screening for strength and stability at a young age. Source: Voxy NZ

The advantage of using young trees is that there is no wastage of resources on trees, which would otherwise end up in low economic gains because of low value products, UC forestry postgraduate student researcher Monika Sharma said.

Her research has helped develop techniques that can quickly and reliably screen young trees for stiffness and dimensional stability.

The project has been funded by the forestry industry and the Ministry of Business, Innovation and Employment.

The New Zealand forest industry is based on forests covering 1.8 million hectares which makes up around 6.6% of New Zealand’s land area. Pinus radiata accounts for about 90% of the total planted area.

In the last 50 years, radiata pine breeding programs focused on improving volume which has resulted in a fall in harvesting age from 35 to 45 years to just 25 to 30 years.

In radiata pine, which is 25 years old, 50% of the merchantable wood is core wood, formed in the first 10 growth rings which falls below the threshold stiffness required for structural timber. Therefore, it can only be utilised for low value products.

The approximate value of low grade timber is $220 per cubic metre whereas structural timber price is $430 per cubic metre.

There is large natural variability in the unimproved tree population. Some trees can attain the threshold stiffness in five years while others attain the same threshold in 18 years. This variability can be exploited to reduce percentage of timber below threshold by selecting trees that can attain threshold early in their life.

In comparison with agricultural breeding programs, there is not much progress in forestry breeding programs because of long breeding cycles. Preferred tree breeding selection age is around eight to 10 years and the purpose of the selection is to increase the accuracy of the prediction for merchantable volume at the end of the rotation.

Big trees provide information regarding gross volume only but nothing regarding the quality of wood.

Economic gains depend on merchantable volume and quality of wood or all of the volume ends up as low value product.

For wood quality, it is desirable to screen trees just a few year old as there is most variable and unimproved wood among trees at that age. Shorter breeding cycles should outweigh any lower accuracy in early selection said Sharma.