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Abstract

This project investigated the effect of waterlogging on the productivity of
Eucalyptus globulus under field conditions, and the relative tolerance of the two
temperate plantation eucalypt species, E. glob ulus and E. nitens, from the
subgenus Symphyomyrtus, to waterlogging.
In eucalypt plantations across Tasmania, waterlogging is a serious threat to
productivity. It is estimated that at least 11 % of all commercial eucalypt
plantations in Tasmania are affected to some degree, by waterlogging. The losses
incurred by waterlogging during the first 2 years of plantation establishment were
found to have significant long-term effects on tree productivity at two sites across
the state.
In the field, soil indicators of long-term waterlogging, specifically the evidence of
greying, in combination with current seasonal waterlogging and development of
hypoxic soil conditions were found to be the factors closely associated with severe
reductions in tree height and growth. The use of extensive soil mapping and
assessment prior to plantation establishment are therefore effective tools in
identifying potential waterlogging problems.
Under long-term waterlogging, there was no indication of the development of
plant water stress during exposure to waterlogging. Waterlogged seedlings of
both species exhibited reduced foliar nutrient status, with significantly reduced
foliar nitrogen, phosphorus and potassium concentrations. Therefore,
waterlogging-induced nutrient deficiency is a mechanism involved in the growth
reduction of these species under waterlogged conditions.
Various methods of fertiliser application were investigated to determine the most
"effective mode in ameliorating waterlogging damage. Soil-based applications of
slow release fertilisers applied either prior to, or after, a waterlogging event, were
the most successful. Fertiliser application was associated with improved growth,
foliar nutrition and increased aerenchymatous root production.
Reduced availability of nutrients in waterlogged soils and/or reduced uptake of
these nutrients are the two possible mechanisms leading to the development of
foliar nutrient deficiency of waterlogged plants. It was found that under hypoxic
hydroponic culture, seedlings with low nutrient status were capable of an
increased uptake of nutrients when transferred to high nutrient conditions. This
result is significant as it identifies reduced availability of soil nutrients as the
primary mechanism responsible for the development of foliar nutrient deficiency
in E. globulus and E. nitens under waterlogged conditions.
The relationship between aerenchymatous root development and waterlogging
tolerance was investigated. It was determined that singular measurements of root
adaptive capacity should not be used as the sole measure of tolerance to
waterlogging in these species. The regulation of growth and maintenance of
relatively high photosynthetic rates are also useful indicators of tolerance. Using
this array of measures, it was determined that E. nitens was inherently more
waterlogging tolerant than E. globulus. Eucalyptus globulus seedlings
demonstrated a greater potential for increased waterlogging tolerance by the
application of fertiliser regimes.

Item Type:	Thesis - PhD
Authors/Creators:	Barton-Johnson, RJ
Keywords:	Eucalyptus globulus, Eucalyptus
Copyright Holders:	The Author
Copyright Information:	Copyright 2006 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (PhD)--University of Tasmania, 2006. Includes bibliographical references
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