Enhancing seed-based restoration in south-east Queensland using Australian native species Fernanda Caro Beveridge Agronomist Engineer, Pontifical University of Chile A thesis submitted for the degree of Master of Philosophy at The University of Queensland in 2019 School of Agriculture and Food Sciences Abstract Australia’s unique plant diversity is threatened by numerous pressures, such as habitat destruction, land degradation and invasive species. In extreme, but frequent cases of habitat destruction and degradation, this results in deeply eroded and damaged landscapes, making it hard for natural regeneration to take place. Land restoration using Australian native seeds (i.e. seed-based restoration) could be a feasible and effective option for restoring degraded landscapes. Using seeds to restore natural ecosystems has a greater chance of success if the seeds are ready to germinate at the time of sowing or given appropriate environmental conditions. For some species, seed characteristics such as seed fill, viability, and dormancy are critical factors that can reduce the rate and percentage of seeds germinating at any given time and are therefore fundamental to the success of seed-based restoration programs. However, these characteristics are often not known in advance, reducing the predictability and cost-effectiveness of using seeds for restoring eroded and damaged landscapes. To overcome seed germination issues and improve seed-based restoration outcomes, this thesis studies the seed ecology of ten Australian native species (four Poaceae, four Fabaceae and two Asparagaceae) that are commonly used in revegetating degraded landscapes in south-east Queensland. The aim was to understand the environmental cues needed to trigger germination, and how these requirements could be met by artificial means, such as chemical (potassium nitrate, smoke water, gibberellic acid, leaching) and/or mechanical (nicking) pre-treatments. Moreover, the use of seed-enhancing technologies (SET: priming, seed coating and seed cookies) was undertaken to study different methods of delivering the germination-enhancing chemicals (GECs) to seeds, also as a seed delivery method to the restoration site. Finally, restoration trials were undertaken in a degraded landscape by using different soil (topsoil or subsoil), site treatments (cover crop, hydrocompost or control) and seed treatment (seed cookies and control) to identify approaches that could enhance field germination, seedling emergence and establishment. The results from this study show that seed fill and/or dormancy were important factors in achieving seed germination and/or seedling emergence. Poaceae species presented low rates of seed fill (< 50%), with Themeda triandra seed fill of only 8 ± 1%. Dormancy was partly i responsible for the low germination percentages in the four Poaceae species studied. The use of SETs (seed priming and/or seed coating) with at least one GEC significantly increased emergence rates of Cymbopogon refractus, Capillipedium spicigerum and Bothriochloa bladhii, as compared to the untreated controls, when studied in greenhouse pot trials. For C. refractus and C. spicigerum, positive differences were seen between certain GECs and their controls, 1 week after sowing (P ≤ 0.0001 and P ≤ 0.001 respectively). Dormancy delayed and reduced final germination in Lomandra longifolia and Lomandra hystrix. Leaching seeds under running tap water gave significantly improved germination rates (P £ 0.05) for both species (in comparison to other treatments and the control). Germination promotion in both species was thought to be due to the removal of water-soluble germination inhibitors present in the outermost tissues of the fruit (pericarp and/or seed coat). Even so, final germination percentage for L. longifolia was < 50%, possibly due to further dormancy mechanisms present within the embryo (deep physiological dormancy). On the other hand, physical dormancy of the Fabaceae species (Kennedia rubicunda, Jacksonia scoparia, Indigofera australis and Acacia myrtifolia) was successfully overcome by scarifying the seeds for 2 minutes in hot water (95°C). Finally, field trials revealed that seed-based restoration in a deeply degraded site can be a challenging task. No significant differences (P < 0.05) were observed in seedling emergence, plant establishment or plant cover between soil types, site preparation treatments or SET treatments during a 10-month long field trial. The results suggest that environmental abiotic and biotic factors in the field (such as low soil moisture and nutrient level and the presence of weeds) need to be overcome before, during and after seed sowing occurs, so to enhance the resulting seedling performance. Results also suggest that restoration outcomes using native seed should be evaluated over a longer timescale than just 10 months. The trial in this study was sown and maintained under the same conditions as most large-scale restoration projects, with no input (irrigation, weed or herbivore control). Seedling emergence was severely affected by the poor soil quality, competition from invasive species and the lack of soil moisture. This research shows that pre-treating native seeds before sowing has the potential to enhance seed performance for seed-based restoration purposes. Treating seeds with GECs and SETs can successfully increase final germination percentage and seedling emergence ii rates. These experiments also show how the use of SET in the laboratory and greenhouse do not necessarily predict outcomes when using native seeds in the field. To realise the potential of seed-based restoration, further research is required to develop species-specific SETs and the specific effects GECs can have on seed germination. Moreover, methods of providing adequate micro-environments for seedling establishment and techniques developed according to site-specific needs should be developed to make best use of these technologies efficiently. It is critical that all technologies studied in the laboratory and greenhouse are later tested in the field, and that the research focuses on techniques that are applicable to large-scale restoration projects where hundreds of thousands of seeds are to be sown across large landscapes. iii Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, financial support and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my higher degree by research candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis and have sought permission from co- authors for any jointly authored works included in the thesis. iv Publications during candidature Conference papers and posters by the candidate relevant to the thesis but not forming part of it: Fernanda Caro, Alwyn Williams, Steve Adkins (2018) Enhancing seed-based restoration of Australian native species. National Landcare conference, Brisbane, Australia 10-12 October 2018 (poster). Fernanda Caro, Alwyn Williams, Steve Adkins (2018) Seed enhancement of Australian native species to improve seed-based restoration outcomes. 12th Australasian Plant Conservation conference, Canberra, Australia 11-15 November 2018 (poster and paper). Fernanda Caro, Alwyn Williams, Steve Adkins (2019) Seed-enhancing technologies to improve seed-based restoration using native grass species. Seed Ecology VI Conference Regensburg, Germany 29-2 August 2019 (oral presentation). Publications included in this thesis: No publications included. Submitted manuscripts included in this thesis: No submitted manuscripts included. v Contributions by others to the thesis No contributions by others. Statement of parts of the thesis submitted to qualify for the award of another degree No works submitted towards another degree have been included in this thesis. Research Involving Human or Animal Subjects No animal or human subjects were involved in this research. vi Acknowledgements This thesis was possible due to the support, guidance and assistance of many individuals who supported the author throughout this project. I would like to acknowledge the constant guidance and advice of Professor Steve Adkins, principal advisor of this thesis, who kindly provided constant advice throughout the