An investigation into the flexural properties of sawn timber and poles of South African grown Pinus maximinoi (H.E.Moore)

Abstract

Pinus maximinoi is a species that can potentially be deployed commercially to provide structural timber and poles for the South African market. The objective of this study was to investigate the flexural properties of sawn timber and poles of P. maximinoi from young plantations of the Southern Cape. A total of 60 trees and 150 logs for the sawmill study were obtained from two research trials on the Longmore estate in the Humansdorp area (13.7 years old), and on the Kruisfontein estate close to Knysna (9.0 years old). Some 74 poles from the same compartments were removed and tested in bending. The P. maximinoi sawn timber had excellent bending properties, superior to sawn timber from other South African Pinus species, tested at similar radial positions in previous studies. Analysis of variation showed that site, log height and board radial position had a significant influence on the modulus of elasticity (MOE) of sawn timber. Multiple regression analysis showed that board MOE can be predicted using a model including tree taper, time-of-flight measured with Treesonic and wood density (model R² = 0.87). The P. maximinoi poles complied with the mean MOE national standard requirement SANS 457-2 of 9 000 MPa but not with the fifth percentile (bending strength) modulus of rupture (MOR) requirement of 34 MPa. This study and other research, however, showed that the national standard requirement for MOR of poles might be too high for current log resources in South Africa. The investigation into the bending and other properties of P. maximinoi sawn boards and poles showed extremely positive results. Based on this wood quality study of P. maximinoi, it is certainly a very promising species for deployment in the Southern Cape and potentially other regions in South Africa.