Variation in microfibril angle in Eucalyptus clones

Abstract

The microfibril angle of the S 2 layer in wood fibres is an ultra-microscopical feature that influences important properties affecting the utilisation of timber. However, this characteristic is as yet little studied, and this is especially true of the genus Eucalyptus. The microfibril angle of the S 2 layer of the secondary wall was measured in fibres taken from eight-year-old trees of 11 Eucalyptus clones growing in four sites in Brazil. The overall mean microfibril angle measured was 8.88. While the angle seemed to decrease slightly from pith to bark in a non-linear fashion, this decrease was not statistically significant. The microfibril angle showed statistically significant differences between sites and between clones, although the broad sense heritability of the microfibril angel was low (h 2 s0.293). Various theories attempt to explain the microfibril orientation, but we conclude that environmental stresses play an important role in defining the angle in Eucalyptus wood.

Microfibril angle of Eucalyptus grandis wood in relation to the cambial age

“…Melo et al (2004) studying the influence of topography on the MFA in 4 two-year old E. grandis × E. urophylla clones, found that the overall average was 26º. Lima et al (2004) found an average angle of 8,8° for wood of clones of Eucalyptus grandis × Eucalyptus urophylla at eight years of age. found an average MFA equal to 10,3º for wood of 30 clones of six-year-old Eucalyptus grandis × E. uroplhylla, planted for pulp production.…”

“…The characteristics of cellulose pulps are related to MFA (Downes et al 2003). Environmental conditions play an important role in defining the microfibril angle (Hori et al 2002, Wimmer et al 2002, Lima et al 2004, Melo 2004). …”

“…Among the few published papers data for MFA of Eucalyptus clonal wood for the production of pulp has been described by Lima et al (2004), Melo (2004) and . In these studies the MFA ranged from 12º to 21º, depending on the location and the genetic material considered.…”

“…As examples of these influences, strength can be affected by microfibril angle in that smaller angles are responsible for higher resistance to compression (Mott et al 2002, Lima et al 2004, while larger angles are responsible for greater elasticity (Barnett and Bonham 2004, Chauhan et al 2006, Donaldson 2008). …”

CARACTERÍSTICAS DAS DIMENSÕES DAS FIBRAS E ANÁLISE DO ÂNGULO MICROFIBRILAR DE Toona ciliata CULTIVADA EM DIFERENTES LOCALIDADES

“…Embora os valores obtidos por Lima et al (2004), estudando a variação do ângulo microfibrilar das madeiras de 11 clones de Eucalyptus com 8 anos de idade, em quatro locais diferentes, tenham sido inferiores aos do cedro australiano, apresentaram valores que variaram de 7,4 a 10,0 graus e uma média de 8,8 graus.…”