School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemInvestigating the seed ecology, functional traits and ecological strategies of Australian annual plants to create diverse, flowering green roofs( 2022)A diverse vegetation layer on green roofs is important to achieving and maximising green roof ecosystem services. Previous green roof research has mostly examined succulents and perennial plants with less attention to annuals and few green roofs incorporate annuals in the planting designs. This is despite annual species having an important role in some natural habitats with conditions that are analogous to green roofs. Their ability to escape seasonally harsh conditions as seeds, fast and cheap establishment via sowing, rapid growth, and the biodiversity and aesthetic value of their colourful flowers are also potential advantages of using annual plants on green roofs. Australia is a continent with a diverse annual flora with colourful and attractive flowering species and high potential to be used in horticultural applications such as green roofs. Therefore, the objective of this project is to develop an attractive flowering, resilient plant palette of Australian annual species suitable for green roofs in Mediterranean-like climates. However, to achieve this, we need more knowledge regarding annual species seed germination, functional traits and ecological strategies. Seed germination capacity is one of main constraints in seed-based projects. A high proportion of wild plant species in Australia produce seeds that are dormant upon maturity and will not germinate without a suitable pre-treatment. Increasing knowledge about factors such as seed mass and climate variables that may influence or predict germination percentage is helpful if species are to be used in horticultural applications, like green roofs. To do so, we commercially sourced seeds of 58 Australian annual species from a wide range of habitats and performed germination tests using different germination stimulants and temperatures in growth chambers. Only 20 out of 58 species germinated regardless of the applied treatments and no optimal treatment was found for all species. No relationship was found between seed mass, and germination percentage and speed. Lower germination was observed in species from hotter and drier environments as well as environments with more variable rainfall. Moreover, germination speed was greater in species from drier environments and environments with lower climate variability. Finding significant relationships between climate variables and germination attributes, and no relationship between seed mass and germination, shows that climate is a better indicator of germination and could be a more useful way to select annual species for horticultural applications than seed mass. The plant functional traits of plant species growing on green roofs are major factors determining the ecosystem services green roofs provide. Moreover, flowering plants which can quickly achieve high cover, growth and biomass are desirable for aesthetic reasons and to meet green roof construction guidelines. Annual species are generally drought escapers with acquisitive strategy and ‘fast’ traits, rapid growth and flowering. However, since annuals grow successfully in different habitats and climates, it is expected that they have different strategies to live and complete their life-cycle. To quantify plant strategies of annuals and evaluate the ecosystem services they may offer on green roofs and to develop a trait-based plant palette of annuals for green roofs, I undertook a common garden experiment with 18 annual plant species (successfully germinated in the previous experiment). It explored the relationships among traits related to drought resistance and resource acquisition, competitive and reproductive ability and also aimed to determine whether differences in plant strategies would influence their growth rate, shoot biomass and flowering time. Species with higher acquisitive strategy were more competitive, fast growing and produced higher final biomass. Two opposing strategies were observed in the studied annual species in regard to their flowering time and relative growth rate. Plant species also showed a trade-off between their flowering time and specific leaf area (SLA). Fast flowering species with higher SLA were considered less drought resistance (drought escapers), as earlier flowering and higher SLA are both evolutionary responses of annual species to escape stress. Fast growing species with resource acquisitive strategy could be more desirable on green roofs as they have higher water use and therefore, stormwater mitigation ability. It is also more preferable to select species with a range of time to flowering onset and SLA to achieve a long-term flowering community with different levels of drought resistance. Finally, I created a seed mixture using 16 species which we found had higher than 50% germination in the earlier study. I then sowed them in extensive green roof modules, to assess the effects of water availability on annual plant growth and diversity. Species abundance and richness were not significantly different between irrigation levels but showed a significant reduction through the experiment. Plant cover was significantly higher when the mixes were irrigated at a higher frequency; however, > 80% plant cover was achieved in all irrigation treatments. At the community level, functional diversity was unaffected by irrigation frequency. This study showed that annual species seed mixes can have good germination and establishment on green roof substrate and attain high species and functional diversity and cover with little irrigation.
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ItemQuantification and payment for ecosystem services from community-managed forests in Nepal( 2018)Humans obtain many benefits from forests that are vital for societal well-being, such as food, timber, fibre, flood protection, clean water and climate regulation. These are known as ecosystem services (ES). The supply of ES varies across space and time and is affected by changes in land use and land cover (LULC), landscape composition and broader social and economic changes. In Nepal, community-based forestry (CBF) emerged in the 1970s against the backdrop of deforestation and widespread concerns over the ‘crisis of Himalayan degradation’ and has become the dominant national strategy for forest management. Over the last 40-years, the Nepalese model of CBF has become globally recognised. Forest area, quality and biodiversity have increased, but the focus of CBF is on the provision of ecosystem goods for local subsistence, and there has been limited analysis of the role of CBF in ES supply to communities. Nor has the potential for local community managers to receive benefits or incentives to continue to conserve watersheds, forests and biodiversity and enhance ES been explored. Most benefits are consumed by wider users who do not contribute to protect and manage the forests. Despite widespread implementation of systems of payment for ecosystem services (PES) benefits to poor people have been limited. This thesis investigated the policy, social and technical arrangements for the assessment of ES and implementation of payment mechanisms to increase environmental, economic and social equity outcomes from CBF in Nepal. The study focused on the Phewa watershed near Pokhara in western Nepal. Quantitative and qualitative approaches were used to assess and prioritise ES resulting from CBF to inform appropriate payment mechanisms. A mixed-methods approach was employed to analyse and interpret the data. Geospatial tools were used to examine the LULC transition from remotely-sensed time series data and linked to spatial distribution of ES. Community perceptions and expert opinion were sought to investigate priority ES, forest policies and PES design considerations. Findings indicated that CBF provides many ES, delivering local to global benefits as a result of forest restoration. However, Nepal’s forest policy and practices are still dominated by narrow notions of forest management that do not accommodate the holistic concept of ES. In addition, many innovative cases are emerging in CBF that demonstrate the emergence of more diverse management strategies, new forms of tenure rights and autonomy in institutional spaces that can potentially catalyse the wider adoption of the ES framework in CBF regimes. Results indicated that 23 ES were relevant to local communities and other stakeholders in the Phewa watershed. Sediment retention, recreation and ecotourism, freshwater, firewood and timber were priority ES for local benefits, while recreation and ecotourism, biodiversity maintenance, sediment retention and carbon stock are priority ES for wider benefits. Priority ES reveal critical areas of correlation and conflict between different services and stakeholder groups. While trade-offs exist between provisioning services and regulating, habitat and cultural services, synergies are identified between regulating, cultural and habitat services. Significant changes in land cover in the Phewa watershed have had positive impacts on ES. Maps showed the distribution of ES varies significantly across the watershed. Dense forests provide higher sediment retention, carbon stocks, biodiversity maintenance, and raw materials but reduced water yield. Likewise, increased aesthetic value provides opportunities for recreation and ecotourism. However, benefits relevant indicators reveal that the societal benefits of most ES are lower compared to the supply of ES. Among the19 design considerations relevant to stakeholders for PES design, only nine, livelihoods, pro-poor participation, tenure arrangements, payment structures, government policy, local institutions, PES governance, opportunity costs and transaction costs are perceived as important for pro-poor PES design. Although the effectiveness of a PES scheme is often measured economically or biologically, our results indicate the essential design considerations for stakeholders are policy, social, financial and institutional arrangements. Overall, an integrated investment strategy and institutional mechanisms should be developed to incentivise local people and continue positive externalities from CBF. This thesis is one of the first studies to undertake an integrated analysis of policy, social, biophysical and institutional arrangements for assessment and payment of ES. The simple and easily replicable process and outcomes of this study are applicable in other parts of Nepal and elsewhere in developing countries or data-poor regions.
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ItemDirect seeding onto green roof substrate supports species rich, high cover novel grassland( 2016)The vegetation of green roofs is central to their functioning and ability to provide ecosystem services. When vegetation performs well, green roofs contribute to storm water mitigation, thermally buffer buildings, improve biodiversity and provide aesthetic and recreational relief in the grey city landscape. However, poor vegetation performance is common, with a decline in both species richness and cover over time. This decline can in part be attributed to design, failing to consider community assemblage mechanisms that lead to quality vegetation performance. Direct seeding of grassland species could offer a randomness in distribution and abundance of seedlings that supports early community self-organization and co-existence. Comparatively, adult plant establishment does not provide this early opportunity. This thesis determines, the ability of a scoria based green roof substrate to support the germination and establishment of a species rich, high cover, novel grassland community, and the direct seeding sowing methods to achieve this. Additionally, species richness, and abundance were investigated as potential drivers of cover. A grassland forb only species seed mix was applied in two experiments. Experiment One (n=7), in glasshouse conditions, investigated application of seed with and without a sand bed, and depth of sowing; six treatments. Experiment Two (n=10) in green roof module conditions outside under irrigation, investigated depth of sowing and rate; four treatments. Main results showed a species rich and abundant germination on scoria based green roof substrate. Results indicated that both depth of sowing at greater than 10 mm and application in a sand bed, reduced species richness and abundance. In green roof module conditions, surface sowing indicated a slight species richness advantage and an abundance disadvantage, in comparison to sowing between 0 to 10 mm depth. Sowing rate approaching that of on ground grassland restoration rates, were shown to be as effective as a doubled sowing rate in producing a species rich, high cover. This study found; no support for species richness as a key driver of cover, however abundance is indicated as an early key driver of cover, and may not act in isolation during rapid cover development. These findings are relevant to management practices. Quality vegetation performance, achieved at sowing rates approximating on ground restoration, suggest that further investigation into lowering rate and species richness and cover response, is warranted. Long term studies investigating community dynamics, would give insight into this novel community’s ability to continue co-existence as a functional resilient system, as a predictor of ecosystem service potential.
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ItemEcosystem goods and services in production landscapes in south-eastern Australia( 2013)Ecosystem goods and services (EGS), the benefits that humans obtain from ecosystems, are vital for human well-being. As human populations increase so do demands for almost all EGS. Managing changing landscapes for multiple EGS is therefore a key challenge for resource planners and decision makers. However, in many cases the supply of different types of goods and services can conflict. For example, the enhancement of provisioning services can lead to declines in regulating and cultural services, but there are few tools available for analysing these trade-offs in a spatially-explicit way. This thesis developed approaches and tools for spatially explicit measurement and management of multiple EGS provided by production landscapes. These were used to assess the impacts of land-use change and to provide a basis for managing these trade-offs using case studies in two contrasting production landscapes in south-eastern Australia. Both landscapes have been subject to extensive clearing of native vegetation, which is now present in remnant patches. One study landscape had a concentration of commercially-valuable hardwood and softwood plantations, and the other was dominated by land traditionally focused on agricultural production that is currently being re-configured to provide for more sustainable farming practices and to increase provision of multiple ecosystem services. The study involved five components: (i) development of a novel, qualitative approach for rapid assessment of EGS in changing landscapes that was used to assess observed and potential changes in land use and land cover and their impact on the production of different EGS (Chapter 2); (ii) development and testing of an approach for assessing multiple EGS across space and time using a case study of six key EGS in a sub-catchment in Lower Glenelg Basin, south-western Victoria that demonstrated landscape-scale trade-offs between provisioning and many regulating services (Chapter 3); (iii) an economic valuation of EGS using market and non-market techniques to produce spatial economic value maps (Chapter 4); (iv) spatial assessment of the biodiversity values that underpin provision of many ecosystem services utilising a variety of readily available data and tools (Chapter 5); and (v) assessment of trade-offs and synergies among multiple EGS under current land use and realistic future land-use scenarios (Chapter 6). Results indicate that EGS can be assessed and mapped in a variety of ways depending on the availability of data, time, and funding as well as level of detail and accuracy required. A qualitative assessment can be useful for an initial investigation (Chapter 2) while quantitative and monetary assessments may be required for detailed landscape-scale planning (Chapters 3, 4). In addition, the provision of EGS by production landscapes can vary considerably depending on land use and land cover, and management choices. The study demonstrates that landscapes dedicated mostly to agricultural production have limited capacity to produce the range of ecosystem services required for human health and well-being, while landscapes with a mosaic of land uses can produce a wide range of services, although these are often subject to trade-offs between multiple EGS (Chapters 2, 3). Furthermore, the study demonstrated that spatial assessment and mapping of biodiversity value plays a vital role in identifying key areas for conservation and establishing conservation priorities to allocate limited resources (Chapter 5). There is potential for an improved balance of the multiple EGS required for human health and well-being at the landscape scale, although the economic incentive to adopt more sustainable land use practices that produce a wide range of services are compromised due to the lack of economic valuation of public ecosystem services (Chapter 6). High hopes have been placed by researchers on spatial assessment, mapping and economic valuations of ecosystem goods and services to influence policy makers for coping with the accelerating degradation of natural capital. The approaches and tools used in this thesis can potentially enhance our collective choices regarding the management of landscapes for multiple values and can help policy makers and land managers to enhance the total benefits that landscapes provide to societies through the provision of an optimal mix of goods and services.