- Title
- The effect of compost and microbial inoculum on spoil carbon, water stable aggregation of spoil and the growth of native plants at Mount Owen Mine
- Creator
- Newman, Kate
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The overarching hypothesis for this research was that rehabilitation of native woodland at Mount Owen Mine in the Hunter Valley, NSW (32o23’13”S 151o06’10”E) is possible in the absence of respreading topsoil. The primary objective was to determine whether the addition of microbial inoculum and municipal waste compost to the mine spoil, improves its function and capacity to support native plants from the target woodland community. The sampling and analysis approaches, plus spoil baseline characteristics, were first determined in Chapters 3 and 4. This was in order to develop an understanding of the Mount Owen field spoil system. The compost and microbial amendments were applied, and changes in spoil Carbon pools and water stable aggregation were then investigated in Chapter 5. Finally, in Chapter 6 the growth responses of native plants were examined, along with the microbial communities in, on, and around the plant roots. Spoil is the non-target waste product from mining. In order to ascertain the effects of adding ameliorants to the Mount Owen spoil, the characteristics of the spoil had to be established. However, describing the properties of spoil, relied on the application of sampling techniques and laboratory analyses which, have been developed for the study of soils. Trials demonstrated complexities associated with spatial heterogeneity, as well as similarity (autocorrelation) in designing appropriate spoil sampling regimes. Some standard soil sample preparation and laboratory analysis practices were applicable, or could be applied with modifications. However, sieving to remove > 2 mm fraction of a sample; the use of a soil chamber to measure Carbon dioxide efflux as an approximation of spoil respiration; and undertaking Dichromate oxidation to measure organic Carbon content were deemed unjustified, or inappropriate for analysis of Mount Owen spoil. The subsequently determined characteristics of the mine spoil heavily reflected parent mudstone and siltstone materials. They were indicative of a highly stressful environment for native plant growth. On average 44.2 % of the spoil sample mass consisted of particles > 2 mm in size, approximately four years after spreading. Mean spoil water potential and electrical conductivity were low, being -113 MPa and 78.6 μS/cm, respectively. The pH of the spoil was alkaline (mean pH approximately 8.6). Labile organic Carbon, essential for many functional processes in a rehabilitating ecosystem was less than one percent. Microbial DNA amplicon sequencing from spoil samples and blasting of the ITS and 16S regions assigned only 506 operational taxonomic units (OTUs). The spoil microbial community profile was generally characteristic of arid, alkaline, “young” soils being dominated by the Phyla Proteobacteria, Ascomycetes fungi and Actinobacteria. High total Carbon to Nitrogen ratios (C:N) suggested a high coal content in the spoil. This was confirmed using a model reliant on differential calculation of coal from measurements of Total Carbon, non-coal Carbonate and non-coal Organic Carbon. Coal was estimated on average to make up approximately 69.91% of the Carbon in the Mount Owen spoil samples. Values in samples ranged from 58 - 76%. Both the dominance of coal as a Carbon source, and the variation in its distribution highlight the need for quantification, despite the complexities and the current lack of a consistent, accessible approach. Municipal waste compost and microbial inoculum were added to the spoil in an experimental spoil rehabilitation site at Mount Owen, in order to improve the spoil structural and functional characteristics. Spoil aggregate stability, spoil Carbon content, and native plant growth rate conditional on survival were utilised as indicators of structure and function. The application of compost and inoculum had no discernible effect on spoil water stable aggregates, as determined by a modified wet sieving approach. Without quantification and correction, rock and coal fragments present in the Mount Owen spoil led to overestimation of water stable aggregates. The correction of samples involved differential calculation of pre- and post- disaggregation sample mass. The absence of observable treatment trends potentially related to a lack of fine colloid size particles, and/or insufficient build-up of root and microbial biomass for binding. The bulk density data indicated that the coarse spoil material appeared to be in an overriding state of degradation, 4 years after exposure at the surface and respreading. Thus, the lack of observable treatment effect on aggregate stability may also have been an artefact of the wet sieving procedure, and the unstable nature of the spoil material analysed. The microbial inoculum consisted of a mix of various plant-associating strains of ectomycorrhizal fungi, arbuscular mycorrhizal fungi, rhizobia and melanised root associating fungi. The capacity of the inoculant strains to form associations with native woodland species was investigated. The target woodland species tested were Acacia parvipinnula, Corymbia maculata, Dodonaea viscosa and Hakea sericea. Each plant species demonstrated capacity to simultaneously host multiple associations. The growth rate conditional on survival of C. maculata plants increased similarly in all treatments over time, demonstrating no treatment effect. The growth rate of surviving H. sericea plants initially decreased rapidly in the first 6 months, then stabilised. The application of compost alone, or in combination with inoculum, enabled H. sericea plants in these treatments to stabilise at a higher rate. This response may have been linked to the presence of Glomus spp. inferred by molecular analysis of root samples, and observed morphologically. The growth rate conditional on survival of D. viscosa plants was improved (though not statistically significantly) by the presence of inoculum applied alone, or in combination with compost. Molecular and morphological analyses inferred the presence of both ecto- and arbuscular mycorrhizae in roots collected beneath D. viscosa plants. The abundance of the arbuscular mycorrhizal fungus, Glomus spp. was highest in the roots sampled from inoculum treatments. Therefore, it appeared that the growth rate conditional on survival of D. viscosa plants may have been more strongly influenced by the arbuscular mycorrhizal association. Inoculation treatment similarly improved the growth rate conditional on survival of A. parvipinnula plants. Though, again the trend was not statistically significant. Morphological and molecular analysis of root samples suggested that A. parvipinnula plants associated with rhizobia, ecto- and arbuscular mycorrhizal fungi, and melanised root associating fungi. The abundance of the ectomycorrhizal fungus, Pisolithus spp. and the rhizobia, Burkholderia spp. were highest in the inoculum only treated root samples. In addition, spoil samples collected from beneath A. parvipinnula plants of this treatment, had higher active and less active Carbon content. The increased active Carbon may have related directly to the increased abundance of the Burkholderia spp. and Pisolithus spp. Increases in root biomass production may also have resulted from the associations, and contributed to Carbon pools. It is possible that the increased Carbon also resulted from fresh inputs of stable, vegetative or microbiological matter. Biodegradation of coal by Burkholderia spp., and/or Pisolithus spp., and/or other known coal degrading microbes, may also have contributed. Thus, based on this study it appears that the application of compost and inoculum to Mount Owen spoil can lead to improvements in the functional capacity of the spoil media to support the rehabilitation of local native woodlands. In previous pot trials it had been reported that combining these ameliorants led to additional improvements, compared to when they were applied individually (Daynes et al. 2013). However, no significant amplified effect from combining ameliorants was observed on growth rate conditional on survival for C. maculata, H. sericea, D. viscosa or A. parvipinnula, or on spoil Carbon status beneath A. parvipinnula plants grown in the field as part of the current study.
- Subject
- Mount Owen Mine; Hunter Valley (N.S.W.); spoil carbon; compost
- Identifier
- http://hdl.handle.net/1959.13/1395465
- Identifier
- uon:33886
- Rights
- Copyright 2018 Kate Newman
- Language
- eng
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