- Title
- Examining accelerated ecosystem development in the ecological restoration of mined land
- Creator
- Scanlon, Robert James
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Restoration of endangered flora communities is a sensitive task that typically occurs in ecosystems where only a moderate level of disturbance has occurred. Open-cut coal mining, however, is an extreme level of disturbance, after which restoration of biodiverse, endangered ecological communities has been difficult. Regardless of the difficulties, there are constant social, economic and environmental pressures to accelerate the restoration process. This thesis examines the idea that ecosystem development (flora and microbial composition, nutrient capital and ecosystem processes) can be accelerated by various treatments without compromising the creation of an endangered flora community. The research sites are active coal mines in the Hunter Valley, New South Wales, Australia, an area where a shortage of available quality topsoil is common. This study investigates how well combinations of subsoil, coarse woodchip mulch and a commercial municipal solid waste compost, Organic Growth Medium (OGM), work as ameliorants for spoil to create an endangered flora community. On set-up, the Experimental Site received seeds from 50 targeted species comprising the endangered community and ancillary species from the local area. The site was examined 4–6 years after establishment. Comparisons are made to an older (15 years) site that was rehabilitated by best practice methods (Ring Rd) and a best available reference (the Ravensworth State Forest (RSF)). The flora community showed clear distinctions between treatments with OGM and treatments with subsoil. Generally, treatments with OGM had a higher proportion of members from the Chenopodiaceae family, whereas treatments without OGM and with subsoil had higher densities of the genus Acacia. As Chenopodiaceae species were typically ancillary, treatments with subsoil have the closest composition to the references. By varying the ameliorants used, a mosaic approach to the restoration would allow the positive benefits of each treatment to be included in the project and increase diversity. Further, restoration of spoil benefits from combining multiple ameliorants (for example, Subsoil + Mulch + OGM). The microbial community composition was examined using gene sequencing with 16S and ITS primers to determine if the origin of the ameliorant had a significant effect on its community composition, and therefore the plant community composition. The study found almost no relationship between fresh OGM from the supplier and the microbial community composition on the Experimental Site. The Subsoil Mulch treatment microbial had the closest community composition to the references. However, there may be an overriding effect from dispersal into the site because the Spoil OGM treatment, although still trending differently, was much more like the rest of the Experimental Site than either the spoil or the OGM that it was produced from. A nutrient inventory was developed to determine if the restored ecosystem would have sufficient nutrient capital to match the reference ecosystem. Although nitrogen had been indicated as a major limiting nutrient in previous studies, phosphorus was found to be lacking on the Subsoil Mulch treatment. The inventory suggested that even if plants were able to access all of the phosphorus in the system, Subsoil Mulch may not have enough phosphorus in the vegetation, litter and upper 30 cm of soil to match the biotic component of the reference. This suggests that although the community developing on this treatment is currently compositionally ideal, it may in the long term not develop the desired structures of a woodland or forest. The rate of ecosystem processes was examined to determine if soil fertility accelerated the rate of decomposition, increased available nutrients and increased tree growth rates. Even though Spoil OGM had very high available nutrients compared with Subsoil Mulch, there was limited evidence for any difference in ecosystem processes. The only confirmed difference was that the negative control treatment, Spoil, performed extremely poorly. This suggests that in the short term, an unmeasured factor is having a larger effect on the functional development of the site than decomposition and soil fertility. As part of the study, the RSF reference was identified as probably being in a retrogressive state, having low phosphorus due to the length of time since catastrophic disturbance. Hypothetically, restoring a site in retrogression would require the return of low-fertility conditions. However, this study has shown risks from that approach and suggests that the flora community does not require low fertility to be restored. Overall, of the four treatments examined in depth, the two best performers both have issues: Subsoil Mulch is deficient in phosphorus while Subsoil OGM Mulch is not attaining the highest quality outcome based on the Australian federal community assessment due to higher exotic cover. The Ring Rd, therefore, has shown the advantages of industry best practice methods because it outperformed the Experimental Site with characteristics including restoration using a high species diversity seeding list featuring the correct community, applying high-quality topsoil from the local area and allowing time for development to occur. Accelerating ecosystem development as part of restoration is possible but careful management will be required to maintain the appropriate trajectory. Restoration of endangered ecological communities is still a difficult task, one that should not be attempted lightly. Given the poor restoration potential of no intervention, accelerated development is a worthy goal and, with appropriate management, many of the treatments examined in this study can provide a quality restoration outcome.
- Subject
- restoration ecology; coal mine restoration; soil restoration; flora community; soil microbial community; nutrient cycling; nutrient inventory; ecosystem retrogression
- Identifier
- http://hdl.handle.net/1959.13/1425952
- Identifier
- uon:38336
- Rights
- Copyright 2021 Robert James Scanlon
- Language
- eng
- Full Text
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