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Characterisation of Eucalyptus nitens plantations for veneer production

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Vega Rivero, MH (2016) Characterisation of Eucalyptus nitens plantations for veneer production. PhD thesis, University of Tasmania.

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[img] PDF (Whole thesis)
Vega_Rivero_who...pdf | Document not available for request/download
Full text restricted
Available under University of Tasmania Standard License.

Abstract

Eucalyptus nitens is widely planted in temperate-cold regions around the world,
mainly for pulpwood production. However there is interest in its use for veneerbased
engineered wood products to increase the value and market opportunities
for the E. nitens plantation resource. This study examined such opportunities by
studying factors which affect veneer recovery as well as those which influence
wood properties important for veneer quality.
This thesis had four main experiments. The first experiment examined log-end
splitting with respect to log storage, steaming, plantation site and tree position.
Log-end splitting is a major defect of Eucalyptus logs which has the potential to
significantly reduce the recovery of veneer. Log-end splitting was assessed
immediately post-felling, after transport and storage and immediately prior to
veneer peeling, using upper and lower logs from each of 41 trees from three 20-22
year old plantations. The study found that log-end splitting varied across sites, was
higher in upper than lower logs, and increased with time in storage particularly in
the upper log. In the system studied, log steaming did not significantly affect the
severity of log-end splitting.
The three remaining studies dealt with the assessment of three important wood
properties: density, microfibril angle and modulus of elasticity. SilviScan was the
main approach used for assessing radial and site variation in these characteristics.
However, in the second study an attempt was made to develop more rapid and cost
effective approaches using near-infrared spectroscopy. Radial scans of breast-height
samples from 86 trees and three sites were used to successfully develop nearinfrared
calibrations of these wood properties against 1 mm resolution SilviScan
measurements. However, the capacity of these models to predict wood properties
when applied to independent sites was mixed and generally poor. SilviScan
measurements were therefore used throughout the remainder of the thesis where
comparisons across sites were the main focus.
The third study examined radial change in density, microfibril angle and modulus of
elasticity. While radial change in these veneer-critical wood properties is known to
occur, the extent to which patterns vary, both between sites and trees within sites,
is poorly understood in Eucalyptus. Radial models were developed to determine the
trends in these wood properties from pith to cambium using samples from 2.5 m
above ground level taken from forty-one 20-22 year old trees from three E. nitens
plantations. Simple linear regression models were used to model density, while
non-linear functions were used to model the radial variation of microfibril angle
(asymptotic function) and modulus of elasticity (sigmoidal function), against both
cambial age and percentage area from pith. The radial trends from pith to cambium
in density, microfibril angle and modulus of elasticity found in this study were clear
and matched the general trends in other studies of Eucalyptus. However, significant
differences were obtained in the pattern of radial variation in these wood
properties both among trees within sites as well as between sites. The radial
patterns of change were similar regardless of whether they were assessed based on
cambial age or percentage of the cross-sectional area and site rankings were the
same.
Lastly, the site variation in density, microfibril angle and modulus of elasticity across
the Tasmanian E. nitens plantation estate was modelled. This study was based on
area-weighted tree means obtained from radial SilviScan data. Three trees from
each of 46 sites were used to develop the models and those from an additional 13
sites used as a validation data set. Site-level averages for the three wood
properties were modelled using various forest, environmental and climatic variables
as explanatory variables. Stepwise backward regression was used to select the most
parsimonious linear model for each wood property. The final models included only
plantation age and annual precipitation for all three wood properties as well as
elevation for density. These models were well validated and used to map predicted
spatial variation in these veneer-critical wood properties across the Tasmanian
plantation estate to aid resource characterisation and forest management.
A key result to emerge from this thesis was the importance of site-level factors on
log traits and wood properties likely to impact the quantity and quality of veneer
from Tasmanian E. nitens plantations. This thesis was able to characterise and
predict variation in these wood properties, both within individual trees and across
the Tasmanian plantation estate. These results have direct management
implications, allowing quantification of the impact of different growing conditions
on the wood properties of harvested logs and therefore on the potential veneer
recovery. Coupled with growth and economic models, these results will assist in
optimisation of available forestry resources and future planning.

Item Type: Thesis (PhD)
Keywords: Eucalyptus nitens, veneer, growth stresses, splitting, near infrared, density, MFA, MOE
Copyright Information:

Copyright 2016 the Author

Additional Information:

Chapter 2 appears to be the equivalent of post-print version of an article published as: Vega, M., Hamilton, M.G., Blackburn, D.P. et al., (2016), Annals of Forest Science, 73(2), 257-266. The final publication is available at Springer via http://dx.doi.org/10.1007/s13595-015-0496-3

Date Deposited: 31 Oct 2016 21:57
Last Modified: 16 Nov 2016 23:53
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