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Ecology of ectomycorrhizal fungi in eucalypt plantations in Western Australia and the Philippines

Pampolina, Nelson M. (2000) Ecology of ectomycorrhizal fungi in eucalypt plantations in Western Australia and the Philippines. PhD thesis, Murdoch University.

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Eucalypts are grown in plantations around the world because of their silvicultural characteristics, economic importance and environmental values. In Australia, the establishment of new eucalypt plantations has increased to over 30,000 ha annually, supplying hardwood fibre predominantly to the Pacific Rim countries. In the Philippines, exotic eucalypts are favoured in reforestation and industrial plantation programs, but increasingly slow-growing native species are being established in fast-growing plantations. Wood production, however, in these regions is often constrained by unproductive soil due to long periods of weathering and lateritization (Western Australia), or deforestation and succession of Imperata grasslands (Philippines). Application of phosphatic fertilizers, as well as ectomycorrhizal (ECM) fungal inoculum are practised in parts of the region. However, the ecology of ECM fungi and the consequence of P application on ECM fungi have not been explored in eucalypt plantations.

This thesis explores the potential role of ECM fungi in Eucalyptus globulus (W. Australia) and E. urophylla (Philippines) plantations and quantifies the effects of P application on ECM fungal dynamics. Commercial eucalypt plantations (a 2 and a 4-year-old E. globulus, a zero and a 19-month-old E. urophylla) were chosen to represent contrasting climates (mediterranean and tropical) and edaphic conditions. Basic studies on fine root growth in E. globulus and associated ECM fungi were undenaken. A 4-year-old E. globulus stand in Australia and a 19-month-old stand of E. urophylla in the Philippines were fertilized with three rates of P (nil = 0, low=100, high=1000 kg P ha-1) and effects on tree biomass, ECM fungi, soil hyphae, fine roots and litter were examined. Finally, to investigate the potential role of ECM fungi in mixed plantations, an indigenous dipterocarp species was introduced into a 25-monthold E. urophylla stand in the Philippines.

Growth of fine roots in E. globulus was maximum in April (0.27 kg m-3) and minimum in August (0.09 kg m-3) when soil moistures were 5.4 and 15.6%, respectively. Over 76% of the fine root biomass and 73% of the soil hyphae were concentrated in the 0-20 cm soil horizon. Fungal diversity under the E. globulus (6 genera and 9 species) was higher than under E. urophylla (3 genera and 3 species). The common genera under E. globulus were Laccaria, Pisolithus, and Scleroderma, whereas Scleroderma and Thelephora were abundant in E. urophylla. The annual basidiocarp biomass was 18 to 23 kg ha-1 under E. globulus compared to over 5.8 kg ha-1 under E. urophylla.

The application of P to E. globulus reduced the number of basidiocarps by 5 (low P) to 14 % (high P), basidiocarp and soil hyphal biomass by 26 to 40 % and 29 to 44 %, respectively, without influencing above-ground ECM fungal diversity. Whole tree biomass or litterfall was not affected, but low P increased fine root biomass in ingrowth cores at 6 months to 364 kg ha-1. Accumulation of N, P, K and Cu generally declined in fungi and litterfall with P, but P and K increased in tree biomass. The total nutrient load was in the order: above-ground tree > soil hyphae > below-ground tree > litter > fine roots > basidiocarps. By contrast, the application of P to E. urophylla had no effect on fungal diversity, fungal biomass, tree growth or litter production, but substantially reduced soil hyphal length by 31 to 52%. The nutrient content of E. urophylla aboveground was approximately equal to the sum of the nutrient load in roots, litter and ECM fungi.

In the E. urophylla plantation where Shorea contorta was introduced, there were 4 ECM fungal species above-ground and 18 ECM morphotypes (11 in 5. contorta and 7 in E. urophylla) below-ground. From RFLP analysis, it was concluded that some species of Scleroderma were able to naturally colonize roots of Shorea and Eucalyptus. Outplanted S. contorta, which were mycorrhizal, had better survival (33-48%) than non-mycorrhizal plants at 18 months.

Item Type: Thesis (PhD)
Murdoch Affiliation: Division of Science and Engineering
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Dell, Bernard and Malajczuk, Nicholas
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