- Title
- Investigating factors affecting restoration of native grassland in ex-cropland
- Creator
- Shakir, Shakir Bahaddin
- Date
- 2019
- Type
- Text; Thesis; PhD
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/170915
- Identifier
- vital:14249
- Abstract
- Native grasslands are one of the most endangered ecosystems in Australia. Approximately 99% of native grasslands have been disturbed for agriculture and pastoralism. Today, however, many agricultural and grazing lands have been abandoned. Restoring abandoned areas to native grassland is a challenge that must be met if these systems are to persist. This thesis sought to gain a better understanding of the biotic and abiotic barriers to restoring native grasslands in ex-cropping land, and to investigate novel techniques to overcome them in degraded native grassland in the Victorian Volcanic Plains. Firstly, I compared ex-cropland to high-quality remnant grassland, and showed that excropland supports a high number of exotic weeds, a lack of native species propagules, high nutrient levels (especially phosphorus and nitrogen), and an absence of organic carbon—all barriers which must be overcome if native grassland restoration is to succeed. I conducted a replicated field experiment in ex-cropland, to investigate four restoration approaches to overcoming barriers to restoration: (i) adding urban green waste to heat and kill the exotic seed bank (ii) adding sugar and/or mulch to promote microorganism and draw down soil nitrogen, (iii) using a modified clay product called Phoslock to reduce soil phosphorus levels, and (iv) scalping of topsoil 10 cm on ex-cropland site to remove the exotic seed bank and high nutrient soil. After each treatment, native grass seed was added, and the vegetation, seed bank, soil nutrients and microbial activity were monitored over 2.5 years. The hot mulch, scalping and sugar treatments all achieved significantly greater cover of native grasses than the control treatments. The hot waste treatment also effectively eliminated the exotic weed seed bank, but the soil N levels increased dramatically, which is counterproductive to the long-term goals of grassland restoration. Scalping out-performed all other treatments with regard to reducing soil N and P. All treatments suffered from reinvasion by exotic species, suggesting that any grassland restoration technique needs to be coupled with ongoing exotic weed management. Abstract ii High soil phosphorus is a difficult barrier to restoration of native grassland. A possible way to address this is to use plants with high P uptake to help draw down soil P. Native grassland taxa from the genus Ptilotus have been shown to have high P-uptake. I conducted two studies of Ptilotus macrocephalus and Ptilotus polystachyus to investigate their potential in this role. The first of these was an examination of techniques to break their seed dormancy, and to find their optimum germination conditions. I tested their response to smoke water, heating shock, cold stratification and gibberellic acid. The highest germination rates (62% and 38% for P. microcephalus and P. polystachyus, respectively) were achieved when the seeds were pre-treated with GA500 and exposed to a temperature range of (20/18OC) and a 12h dark/12h light regime. Smoke water, heat shock and the removal of floral bracts also improved germination rates, but not at the same magnitude as GA. The second study of Ptilotus was a glasshouse trial that examined the effectiveness of the two taxa at reducing available soil phosphorus. This trial included a third high P-uptake species (Lupinus albus) for comparison, and also investigated if the addition of Phoslock® could bind soil P into insoluble forms. P. macrocephalus and P. polystachyus accumulated high amounts of soil P. Thus, several years of seeding and harvesting of these plants is anticipated to provide a useful option for soil P reduction. Phoslock® reduced soil available P, but only at high concentration of Phoslock 1500 g/m2 and at very high soil P concentrations; it was less effective at levels that typically expect in ex-cropping paddocks. The findings of this thesis have advanced our current knowledge of the restoration of excropland. The research has tested methods to overcome biotic and abiotic barriers to restoration of the Victorian Volcanic Plains grasslands, and has demonstrated some practical approaches to begin the treatment. It was suggested that many of the methods and techniques used in this study could be useful technique in broad areas of grassland restoration within Australia as well as in similar situations in temperate climate conditions across the globe.; Doctor of Philosophy
- Publisher
- Federation University Australia
- Rights
- Copyright Shakir Bahaddin Shakir
- Rights
- Open Access
- Rights
- This metadata is freely available under a CCO license
- Subject
- Grassland; Restoration; Weeds; Mulch; Phoslock; Green waste; Volcanic Plain.
- Full Text
- Thesis Supervisor
- Singarayer Florentine
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