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Nutrient distribution and redistribution of copper in Eucalyptus globulus plantations in south-western Australia

Rogers, Catherine Lesley (2002) Nutrient distribution and redistribution of copper in Eucalyptus globulus plantations in south-western Australia. PhD thesis, Murdoch University.

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Abstract

In south-western Australia, nearly 180,000 ha of short-rotation plantations of Eucalyptus globulus have been recently established on ex pasture-land with soils of low natural fertility. This thesis explores several facets of nutrient requirements for productive E. globulus plantations. Since copper (Cu) deficiency was found to be widespread in the region, the research emphasises the distribution and behaviour of Cu in E. globulus.

In a survey of 25 two-year-old E. globulus plantations in 1996, Cu deficiency occurred in 58% of plantations and was the most prevalent nutrient deficiency observed. The application of Cu-containing fertiliser at establishment of new plantations reduced the incidence of Cu deficiency by 81%.

The above and below-ground nutrient distribution and nutrient content of one. three, five and seven year-old E. globulus plantations were determined by destructively sampling trees at a site near Karridale. In one-year-old trees, the total nutrient biomass/tree was in the order: N (67 g) > K (38 g) > Ca (32 g) > Mg (9 g) > P (7 g) > S (6 g) > Mn (1080 mg) > Fe (217 mg) > Zn (96 mg) > B (90 mg) > Cu (23 mg). The total nutrient content in the tree at age 7 was in the order Ca (1486 g) > N (655 g) > K (345 g) > Mg (249 g) > P (92 g) > Mn (17 g) > Fe (3.9 g) > Zn (1.9 g) > B (1.8 g) > Cu (0.4 g). In young trees, most of the nutrient capital was located in the leaves, but by year 5 the proportion of nutrients allocated to the trunk and roots became dominant. Even with the management practice of debarking on site, nutrients would be removed if harvested at age 7 years, by the following amounts: Cu (54%) > K (43%) > P (42%) > B (34%) > N (31%) > Zn (31%) > Fe (26%) >Mg (22%) > Mn (20%) > Ca (13%).

Because of the incidence of Cu deficiency and the potential loss of Cu off-site with wood removal, the behaviour of Cu was explored. It was hypothesised that if Cu is phloem mobile the Cu reserves in foliage of short-rotation eucalypt plantations could be important for driving growth at the shoot tip. The net movement of Cu into and out of leaves was studied by sampling tagged leaves over a two-year period at two sites. Although Cu and N redistribution are closely linked in some annual species, in E. globulus Cu appears to be poorly mobile and is not retranslocated with N. For example. whereas Cu contents of the youngest fully expanded leaf increased with age, nitrogen contents were bimodal suggesting considerable retranslocation of N. At one site, a Mycosphaerella leaf spot disease outbreak resulted in the premature loss of most of the juvenile foliage, by two years of age. Nitrogen concentrations, but not Cu concentrations, in the new leaves increased markedly in time with leaf loss.

In an experiment where the lower half of the canopy was shaded, the redistribution of Cu from senescing leaves was investigated. Shading promoted the allocation of N but not Cu to young leaves. This further suggests that Cu is poorly phloem-mobile and any redistribution of Cu is not closely linked to N in young E. globulus.

It is concluded that new shoot growth in young E. globulus plantations is likely to be dependent on the external supply of Cu throughout the growing season. Furthermore, there is a need to assess potential benefits of late age fertiliser on the yield of E. globulus in south-western Australia, and for sustainable growth in successive rotations, the soil nutrient capital will need to be maintained by the addition of trace element fertilisers.

Item Type: Thesis (PhD)
Murdoch Affiliation: Division of Science and Engineering
School of Biological Sciences and Biotechnology
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: repository@murdoch.edu.au. Thank you.
Supervisor(s): Dell, Bernard
URI: http://researchrepository.murdoch.edu.au/id/eprint/52619
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