Comparative in-ground natural durability of white and black cypress pines (Callitris glaucophylla and C. endlicheri).

摘要

Stakes composed of outer heartwood of Callitris glaucophylla (white cypress pine), Callitris endlicheri (black cypress pine), Corymbia maculata (spotted gum) and Eucalyptus regnans (mountain ash) were exposed to in-ground accelerated testing for 280 weeks (5.4 y). The time for each stake to reach unserviceability (loss of 60-75% of cross-section) due to microbial attack was recorded. The time for Callitris glaucophylla was not significantly different (P>0.05) from that of Corymbia maculata. Both these Class 2 timbers were significantly different in durability from Callitris endlicheri which, in turn, was significantly different (P<0.05) from E. regnans, a less durable Class 4 timber. Calibration with long-term field test results for Callitris glaucophylla and Corymbia maculata suggested that Callitris endlicheri should remain Class 2. The sapwood of both Callitris species showed evidence of higher natural durability than that of Pinus radiata. Other comparisons demonstrated that no significant difference was found in time to unserviceability of Ca. glaucophylla from two sites (Forbes and Gilgandra, both NSW), and similarly for Ca. endlicheri. Also, no significant correlation between time to unserviceability and density was found..