Merchantability of Pinus radiata in relation to previous land use

Summary

An integrated thinning operation was carried out in 21-year-old radiata pine stands in the central tablelands of New South Wales to examine the effect of previous land use and associated problems of poor tree form on recovery of merchantable timber. The areas thinned were contiguous sections of plantation which had different types of land use prior to plantation establishment; native forest, cleared grazing land (pasture) and cleared land initially grazed and subsequently cultivated and cropped (cultivated pasture). Total volumes of harvested trees (to 8 cm small end diameter) were estimated (assuming no poor tree form) from regressions relating volume to stem diameter. This estimate was compared with the actual volume of saw logs and pulp wood recovered on site and with merchantable yields predicted using a locally derived Forestry Commission equation.

On-site yields of saw logs plus pulp wood were 143 m³ ha⁻¹ from the ex-native forest site, 191 m³ ha⁻¹ from the ex-cultivated pasture site and 210 m³ ha⁻¹ from the ex-pasture site. This represented a total recovery of more than 90% of the total stem volume to 8 cm small end diameter from ex-native forest and ex-pasture trees compared with 73% from the ex-cultivated pasture trees.

Of the trees harvested, 45% from the ex-native forest site had stem defects compared with 65% from the ex-pasture site and 88% from the ex-cultivated pasture site. These defects reduced the average saw log volume per tree by at least 50% in trees greater than 35 cm DBHOB. In contrast, the yield of pulpwood was similar for deformed and non-deformed trees because some logs which did not meet saw log specifications were down-graded to pulp logs.

Keywords:

• stem deformation
• yield
• poor tree form
• multiple leaders
• stem distortion
• malformation
• volume
• thinning