Abstract
Almost half of the global land surface is considered degraded, and this is expected to worsen due to ongoing land degradation and impacts of climate changes. Ecological restoration has emerged as a pivotal strategy to combat climate change and safeguard global biodiversity. Within ecological restoration, seed-based restoration is the primary method for reintroducing native plant species to degraded ecosystems at large scales. However, seed-based restoration faces numerous biotic and abiotic challenges that prevent or delay the recovery of native plant species. To address these challenges, seed enhancement technologies (SETs) have emerged as an avenue to improve the success of seed-based restoration efforts. The effectiveness of SETs is contingent on their adaptability to the specific challenges inherent in each restoration context. In this thesis, I set out to address two overarching research objectives: (i) the development of pellet SETs tailored to address the specific challenges to native species recovery in a range of contexts and (ii) maximise the emergence and establishment of native species, thereby improving seed-based restoration.
Chapter 1 explores the need for effective ecological restoration and its associated challenges. It also serves as an introduction to the three restoration contexts that will be investigated in this thesis: old fields, drought-prone areas, and fire-affected environments. The aim of this chapter is to establish the foundation for the subsequent research by offering essential context and emphasising the urgency of confronting restoration challenges within these degraded contexts.
Chapter 2 explores the application of seed coating and extruded pellet SETs with a specific focus on mitigating water limitations and depleted soil microbes. The aim of this chapter is to review the existing research landscape, assessing the effectiveness of active ingredients and SET types, and identifying key factors driving successful outcomes in the literature. The results compiled in this chapter provide insights into the combinations of SET types and active ingredients most likely to yield successful restoration under water- or microbe-limited conditions. Additionally, this chapter illuminates several knowledge gaps in the current body of literature. Addressing these gaps through further exploration holds the potential to significantly advance our understanding of how to optimise the utilisation of SETs.
Chapter 3 explores the application of pellet SETs containing fresh topsoil to enhance the emergence and growth of native species, and the soil microbial activity on a degraded agricultural site where topsoil was removed. This study seeks to test the efficacy of pellet SETs in fostering the recovery of native plant species in challenging environments characterised by soil degradation and land use change. The results obtained in this chapter provide evidence that the combined use of pellet SETs and direct seeding significantly improves the emergence of some native plant species on degraded agricultural soils.
Chapter 4 explores the potential of surfactants and superabsorbent polymers (SAPs) in pellet SETs to facilitate seedling emergence during drought conditions. Four distinct watering regimes that simulate drought scenarios were explored. Among these treatments, two encompass variations in watering frequency, while the remaining two involve modifications in watering quantities. The findings presented in this chapter demonstrate that pellet SETs containing surfactants and SAPs have the capacity to improve the emergence of native species, under ambient conditions and when watering events are larger and less frequent. However, it is important to note that these results are heavily influenced by species and the product utilised.
Chapter 5 explores the potential of pellet SETs to improve the emergence of seven native species in fire-affected soils. Fires can have detrimental effects on soil, impacting its physical, biological, and chemical properties, which in turn hinders the ability of native plant species to recover after fire. In this study, pellet SETs containing commercially available soil microbial amendments, surfactants , and a combination of both, were deployed into fire-affected soils, aiming to enhance the emergence of native species. The results here show the pellet SETs can be detrimental to the emergence and survival of native species in post-fire conditions. Nonetheless, this study also emphasises the importance of refining the formulation of pellet SETs to eliminate unintended adverse effects on seedling emergence and survival before they can be utilised effectively to aid the establishment and recovery of native species at risk of changing fire regimes.
This thesis marks a substantial contribution to developing our understanding of the application of pellet SETs for the restoration of degraded ecosystems. This research highlights multiple underlying mechanisms driving both positive and negative effects, necessitating further exploration to develop a comprehensive understanding. In summary, this research provides invaluable insights into the potential of pellet SETs as a practical and effective restoration tool for reintroducing native species across a range of degraded contexts. While acknowledging the progress made, it also emphasises the ongoing need for further exploration and refinement to enhance the applicability and success of pellet SETs in ecosystem restoration.
Chapter 1 explores the need for effective ecological restoration and its associated challenges. It also serves as an introduction to the three restoration contexts that will be investigated in this thesis: old fields, drought-prone areas, and fire-affected environments. The aim of this chapter is to establish the foundation for the subsequent research by offering essential context and emphasising the urgency of confronting restoration challenges within these degraded contexts.
Chapter 2 explores the application of seed coating and extruded pellet SETs with a specific focus on mitigating water limitations and depleted soil microbes. The aim of this chapter is to review the existing research landscape, assessing the effectiveness of active ingredients and SET types, and identifying key factors driving successful outcomes in the literature. The results compiled in this chapter provide insights into the combinations of SET types and active ingredients most likely to yield successful restoration under water- or microbe-limited conditions. Additionally, this chapter illuminates several knowledge gaps in the current body of literature. Addressing these gaps through further exploration holds the potential to significantly advance our understanding of how to optimise the utilisation of SETs.
Chapter 3 explores the application of pellet SETs containing fresh topsoil to enhance the emergence and growth of native species, and the soil microbial activity on a degraded agricultural site where topsoil was removed. This study seeks to test the efficacy of pellet SETs in fostering the recovery of native plant species in challenging environments characterised by soil degradation and land use change. The results obtained in this chapter provide evidence that the combined use of pellet SETs and direct seeding significantly improves the emergence of some native plant species on degraded agricultural soils.
Chapter 4 explores the potential of surfactants and superabsorbent polymers (SAPs) in pellet SETs to facilitate seedling emergence during drought conditions. Four distinct watering regimes that simulate drought scenarios were explored. Among these treatments, two encompass variations in watering frequency, while the remaining two involve modifications in watering quantities. The findings presented in this chapter demonstrate that pellet SETs containing surfactants and SAPs have the capacity to improve the emergence of native species, under ambient conditions and when watering events are larger and less frequent. However, it is important to note that these results are heavily influenced by species and the product utilised.
Chapter 5 explores the potential of pellet SETs to improve the emergence of seven native species in fire-affected soils. Fires can have detrimental effects on soil, impacting its physical, biological, and chemical properties, which in turn hinders the ability of native plant species to recover after fire. In this study, pellet SETs containing commercially available soil microbial amendments, surfactants , and a combination of both, were deployed into fire-affected soils, aiming to enhance the emergence of native species. The results here show the pellet SETs can be detrimental to the emergence and survival of native species in post-fire conditions. Nonetheless, this study also emphasises the importance of refining the formulation of pellet SETs to eliminate unintended adverse effects on seedling emergence and survival before they can be utilised effectively to aid the establishment and recovery of native species at risk of changing fire regimes.
This thesis marks a substantial contribution to developing our understanding of the application of pellet SETs for the restoration of degraded ecosystems. This research highlights multiple underlying mechanisms driving both positive and negative effects, necessitating further exploration to develop a comprehensive understanding. In summary, this research provides invaluable insights into the potential of pellet SETs as a practical and effective restoration tool for reintroducing native species across a range of degraded contexts. While acknowledging the progress made, it also emphasises the ongoing need for further exploration and refinement to enhance the applicability and success of pellet SETs in ecosystem restoration.
Original language | English |
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Qualification | Doctor of Philosophy |
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Place of Publication | Australia |
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Publication status | Published - 2024 |