Vessel and fibre property variation in Eucalyptus globulus and Eucalyptus nitens: Some preliminary results

Abstract

Vessel areas and distributions in Eucalyptus globulus and E. nitens vary in a consistent, significant and predictable way from pith to bark and within annual rings. Trends in vessel areas and distributions can be quantitled despite the presence of indistinct annual rings and false rings. There is evidence of a vessel free area in first earlywood in E. nitens in which fibre properties are predictably different. At 5% height the vessel free area in the 1991 and 1992 annual rings is 13% and 10% respectively. Individual vessel areas increase and vessel numbers decrease from pith to bark in both E. globulus and E. nitens. Total vessel area increases slowly across the disc but is markedly influenced by position within annual rings - decreasing from latewood (LW) to first earlywood (EW); increasing in midwood (MW) and then decreasing from MW to LW. Vessel morphology and fibre morphology follow an EW, MW and LW segmentation in both E. globulus and E. nitens. The transition to latewood vessels is synchronous with the transition to latewood fibres. From EW to MW vessel frequency (per mm2) significantly increases (1- to 2-fold), as does vessel percentage coverage (total vessel area/total segment area) (1.5- to 2-fold); while fibre lumen diameter and wall thickness increase and decrease respectively. Vessel frequency and percentage coverage in latewood are significantly less (50% less) than vessels in MW at 5% height, while fibre lumen diameter and wall thickness decrease and increase respectively. Changes in vessel number and area across the ring conform with changes in fibre morphology producing a synchronous partition between latewood (LW) and non-latewood in vessels and fibres in the 1993 ring for both species and in the 1994 ring in E. nitens.