Continued expansion of the gold and nickel mining industry in Western Australia during recent years has led to disturbance of larger areas and the generation of increasing volumes of waste rock. Mine operators are obligated to rehabilitate all disturbed surfaces and reconstructed landforms, and considerable effort and expense is now applied to the achievement of this objective. Associated with increasing rehabilitation effort is the requirement to accurately judge rehabilitation success through the development of completion criteria. Completion criteria are rehabilitation performance objectives set as conditions of approval for each stage of rehabilitation and for the project as a whole. They provide standards against which the success of rehabilitation can be measured, or more broadly the point at which responsibility for rehabilitation is complete. The current research project tackles the development of completion criteria by investigating ecosystem function within a variety of rehabilitation trials at four mine sites located in arid and semi-arid Western Australia, and also within surrounding 'natural' vegetation complexes undisturbed by mining, termed analogue sites. Six specific objectives were identified as part of the study: 1. To establish an appropriate end point land use for each mine site where field trials were established; 2. To examine long-term ecosystem development through the assessment of revegetation at a variety of rehabilitation sites; 3. To examine functional components within analogue communities and make appropriate comparisons with rehabilitation trials; 4. To record the potential reproductive capacity of revegetation progeny, and determine how this relates to ecosystem function; / 5. To provide a better understanding of ecosystem function by investigating the relationship between state factors, interactive controls, and ecosystem processes at rehabilitation and analogue sites; and 6. To develop a methodology for establishing realistic environmental completion criteria at mine sites situated in arid and semi-arid Western Australia. Field trials were established at four mine sites located within three subtly different bioclimatic zones that extend through the arid / semi-arid shrubland belt of Western Australia; Northeastern Goldfields (Granny Smith Gold Mine, Sunrise Dam Gold Mine), Eastern Goldfields (Black Swan Nickel Mine), and Northeastern Wheatbelt (Westonia Gold Mine). 1 The re-establishment of a self-sustaining vegetation cover integrated with the surrounding ecosystem, was the common end land use objective at the four mine sites selected for this study. For three sites located in the Northeastern Goldfields and Eastern Goldfields of Western Australia, sheep were grazed on surrounding rangeland; the fourth site located in the Northeastern Wheatbelt of Western Australia, and was surrounded by Crown Land. 2 To better understand ecosystem function, the dynamic behaviour and interaction of plant biodiversity parameters was monitored regularly at 19 post-mining rehabilitation sites up to 11 years after direct seeding. For functional ecosystems, plant biodiversity parameters changed rapidly during the initial five years after seeding following predictable trends, after which time they remained within a relatively stable range. / The stabilising of parameters over time was identified as a key indicator of rehabilitation success, however the point at which the parameters stabilised was influenced by numerous variables and was difficult to accurately predict. Prolific seed germination resulted in high seedling density during the initial growing season. Plant density then progressively decreased in response to competition, before stabilising within a range approximately five years after seeding. Revegetation cover was typically low during the first growing season, increasing rapidly there after before also stabilising in line with plant density. Maximum species richness was generally achieved during the first and second year when annual Atriplex species were prominent. Perennial Atriplex species established more slowly during the early stages of revegetation development, but eventually replaced the annual component as the dominant taxa. Perennial Maireana species required up to three years before germinating in the field and establishing themselves in the revegetation; in many cases they replaced perennial Atriplex as the prominent taxa. The presence or absence of cyclonic rainfall during the first growing season was a major determinant of the ecosystem trajectory, controlling revegetation structure and composition. The germination and successful establishment of hard seeded species, including Acacia and Senna, was reliant on heavy summer rainfall during the early stages of ecosystem development to break seed dormancy and extend the length of the first growing season. This provided an important competitive advantage against faster growing Atriplex species, which possessed greater drought tolerance. / The intensity of summer rainfall was also beneficial in leaching surface salts from the upper profile and hence, reducing salinity within the rooting zone. In the absence of heavy summer rainfall during the first growing season, the establishment of a low chenopod dominated vegetation cover was favoured, total species richness for the rehabilitation tended to be lower, and the variety of plant life forms was restricted to low and mid stratum shrubs. Increasing water stress resulted in progressively higher rates of local species extinction, with fewer taxa possessing the drought tolerance adaptations required to survive. For established revegetation, cyclonic rainfall increased productivity (as measured by % foliage ground cover) and stimulated the establishment of new taxa, which in many cases were brought in from adjacent unmined vegetation complexes (analogue sites). While the benefits of summer cyclonic rainfall were undoubtedly important to ari and semi-arid ecosystems, the occurrence of drought was also important in buffering the ecosystem against large-scale change by acting as a negative feedback to constrain cumulative productivity. Parent waste rock material varied considerably between rehabilitation sites, affecting the soil resource supply and associated functional components. Extreme salinity was a typical limitation of the rehabilitation medium, reducing the variety of salt tolerant species and favouring annual Atriplex during the early stages of ecosystem development. The cover of annual species present during early stages of ecosystem development contributed to decreasing salinity in the plant rooting zone, by reducing surface temperature and hence capillary rise of salts during summer months. / Annual Atriplex species were replaced by perennial Atriplex in line with decreasing surface salinity. Fundamental to successful revegetation of the post-mining rehabilitation site was the requirement that reconstruction and contouring focus on maximising water retention and reducing salinity within the upper soil profile. Once the initial vegetation community established and plant parameters became relatively stable, change continued to occur, albeit slowly. One factor contributing to this change was the immigration rate of biota from adjacent revegetation or more commonly from surrounding analogue complexes. Linking rehabilitation areas to surrounding functional ecosystems ensured the movement of plants and animals, and ultimately increased the rate of recovery. The sustainability of post-mining rehabilitation was enhanced where these links were established early, allowing for the provision of additional seed and the migration of displaced species. The life cycle pattern of keystone species in the revegetation was found to be an important determinant in long-term sustainability of the plant cover, particularly for chenopod shrublands where one species was typically dominant. The senescence and death of large numbers of a dominant revegetation species together, had the ability to significantly alter the revegetation structure and composition. The impact for rehabilitation where a number of dominant taxa co-exist was less pronounced. Thus it follows that a minimum level of species richness was important to long-term rehabilitation sustainability, as was the development of an age-class structure in the rehabilitation. / The most common disturbances encountered at the rehabilitation trial sites were drought, overgrazing and weed infestation. All three disturbances decreased the plant biodiversity parameters measured. Ecosystem recovery following disturbance was dependent on effective rainfall, but occurred rapidly with plant parameters returning to pre-disturbance levels within one to two growing seasons. The recovery of plant biodiversity parameters followed the same trends identified at functional rehabilitation sites during the initial five years following direct seeding. 3 Assessment of plant biodiversity parameters occurred at 15 analogue sites supporting native vegetation undisturbed by mining. It was anticipated that data from analogue sites could be used as a 'reference' against which to compare developing rehabilitation. However, analogue vegetation complexes were less dynamic in comparison to rehabilitation sites. Minor seasonal changes were recorded for plant biodiversity parameters, but overall annual change was minimal. Significant and sudden changes within analogue communities only occurred following disturbance, such as severe overgrazing, and recovery to pre-disturbance levels was rapid following the removal of the disturbance and return of effective rainfall. A major difference between rehabilitation and analogue sites related to their age. Rehabilitation sites were 'juvenile systems' assessed against a time frame much shorter than had been required for natural processes to achieve the developmental state represented at analogue sites. / Hence, it was important not to model one specific analogue site too closely, but instead model the desired revegetation structure and species composition on a variety of local analogue complexes occurring in parent materials 'matched' closely to those of the rehabilitation site. Data from analogue sites should be utilised extensively during rehabilitation planning, but cautiously when interpreting the rehabilitation outcome. For mine sites in arid and semi-arid Western Australia, the application of specific numeric targets for plant biodiversity parameters as a measure of rehabilitation success was not recommended. A number of factors and controls in the developing ecosystem together determined the rehabilitation outcome. These factors were site and time specific; minor changes in any number of variables led to significantly different rehabilitation outcomes, making them difficult to accurately predict. 4 Quality and germination testing confirmed progeny seed from a number of rehabilitation trials was of similar or higher viability than the maternal seed originally sown. This was further confirmed by field responses at trials in the Northeastern Goldfields one year after the 1994 drought, when elevated plant density was recorded following the return of above average rainfall. The ability of rehabilitation to show an immediate response to rainfall following a seven-month drought, and for vegetation parameters to subsequently recover to pre-disturbance levels within one to two years, provided an indication that the revegetation cover was resilient. The relationship between plant production and rainfall was dependent on a 'carryover' effect between seasons or following drought years, and 'pulses' mediated, for instance, by the amount of seed in the soil store. / The 'reserve' component in and ecosystems was responsible for both the memory of the system between pulses and for its long-term resilience. 6 The analysis of time series data collected from 19 rehabilitation trials emphasized the importance of planning and implementation of best practice techniques to subsequent rehabilitation success, and reinforced the difficulty associated with accurately predicting the final rehabilitation outcome. The large spatial heterogeneity of undisturbed vegetation complexes across the landscape of arid and semi-arid Western Australia, provided the foundation on which site-specific rehabilitation scenarios could be modelled, albeit with caution. The translation of data into useful completion criteria was dependent on the realisation that successful rehabilitation requires the implementation of best practice rehabilitation techniques, as determined by technically prescriptive (design) based standards, as much as the identification of a successful rehabilitation outcome, as determined by performance (outcome) based standards. With this in mind, completion criteria were developed as part of a robust theoretical framework incorporating the larger mine plan, and were not simply based on numbers generated as stand-alone performance standards. The broad methodology generated could be adopted by any mine site across the mining industry, however the criteria and, more specifically, the standards for each criterion should always remain site specific. / The methodology designed for developing completion criteria has been addressed in three stages: 1. Planning, 2. Operational and Monitoring, and 3. Post-Mining Hand-Over. Within each stage three parameters are addressed: 1. Criteria, 2. Process, and 3. Standard. 'Planning' is the most important stage in the development of completion criteria. It is the stage when an appropriate end land use is determined, analogue sites are assessed, a rehabilitation plan developed along with specified design standards ensuring implementation of best practice techniques, and a process of risk assessment implemented. The 'Operational Monitoring Stage' focuses on rehabilitation success during the period of ecosystem development. This stage is concerned largely with rehabilitation monitoring, from which performance standards can be developed to gauge rehabilitation success for specific periods during revegetation development. The initial task in Stage 2 is to ensure all aspects of the rehabilitation plan have been implemented as specified in Stage 1, and meet agreed design standards. The final stage of the completion criteria process, 'Post Mining Hand Over', is to ensure the rehabilitated site is safe, and able to successfully revert to the end land use. / While plant biodiversity parameters formed the focus of the current study, a variety of other functional ecosystem components may also make sound assessment criteria for determining rehabilitation success. Increasing the knowledge base for other functional components in arid and semi-arid ecosystems would further increase the ability to accurately determine rehabilitation success.

This study investigates coal discard cover soil fertility and its potential for degradation, particularly in terms of its salinisation and acidification potential. Seven rehabilitated coal discard dumps in the Witbank, Ermelo and Newcastle regions were used as study areas. All areas were rehabilitated with a cover soil layer, revegetated and annually fertilised with nitrate fertilisers, super phosphate, kraal manure and lime. Performance guideline for pH of 5.5-(6.5 i0.5)-7.5 and electrical conductivity guideline of preferably less than 200 mS.rn-' but not higher than 400 mS.m-' were set based on literature information. Soil chemical data from a three-year fertilisation programme were used to assess the fertility of the cover soil surface (0-150mm). Data collected over a three year period as well as additional electrical conductivity and pH measurements from the cover soil surface, subsoil, cover soil/coal contact zone and underlying coal itself were used to assess the occurrence of salinisation and acidification of the cover soil. The soil fertility varied significantly among dumps as well as over the three years. Results indicated an increase in ammonium acetate extractable macro elements (calcium, magnesium and potassium). With the exception of manganese, no micro-element toxicities were recorded. Iron concentrations were slightly elevated in some of the sandy cover soil layers. No increase in soluble nitrogen (nitrate and ammonium) was found and most soluble nitrogen was in the form of nitrates. In general the Bray extractable phosphate increased during the study period. It can be predicted that with the following fertiliser programme increases of exchangeable macro-elements as well as available phosphorus can be expected. The study could not indicate an increase in adsorbed or available nitrogen. Organic carbon was initially not analysed therefore no comments can be made whether organic matter increased. Four of the seven dumps surveyed had comparably similar organic carbon levels to the background samples. Overall the fertiliser programme increased the electrical conductivity and decreased the acidity of the cover soil surface. Acidity and salinity was in general not a problem at the surface of the cover soil and pH was even slightly higher in cover soil samples. The acidity and especially salinity increased at the subsoil and so did the sulphate concentrations. Calcium and magnesium sulphate were predominantly responsible for higher electrical conductivity measurements. The percentage exchangeable sodium was also predominantly less than 2% indicating that sodicity is not currently a problem in cover soil. Soil fertility was satisfactory for vegetation growth and macroelement concentrations were in the correct ratio although calcium was slightly high. An elevated sulphate concentration, in comparison to the natural grassland soils, as well as a high salinity and high acidity in the subsoil layers indicate that salinisation and acidification could deteriorate without proper management. A slightly acidic cover soil can also be attributed partially to its natural acidic pH due to the wellweathered and leach property of burrow pit. Higher than recommended salinity levels were found in subsoil samples but the occurrence of acidification of the subsoil was more dump specific. In relation to acidity and salinity guidelines only the cover soil of one dump was concerning and the larger dumps subsoil acidity and salinity were elevated. The following management strategies are proposed: a) The acidification potential, and therefore the pyrite content of the coal discard must be considered during decisions making on the rehabilitation method (clay barriers), topsoil depth, maintenance and mine closure potential. b) The occasional monitoring of the subsoil's and coal contact acidity is recommended, although not much can be done to stop acidification after cover-soil placement. c) To ensure a more sustained from of nitrogen supplementation over the long term the use of selected legumes should be investigated. Research in Europe and Australia suggested that nitrogen fixation could contribute substantially to the nitrogen for plant uptake. d) The physical properties of the topsoil (bulk density 8 soil compaction) are also being neglected and needs to be assessed occasionally and interpreted together with chemical analyses. Observations in other studies indicate that this could be the most fundamental problem for vegetation growth and not necessarily soil fertility, since soil physical properties could have a major impact on root development. Key words: Coal discard, mine rehabilitation, soil fertility, topsoil degradation, salinisation, and acidification / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.

This study investigates coal discard cover soil fertility and its potential for degradation, particularly in terms of its salinisation and acidification potential. Seven rehabilitated coal discard dumps in the Witbank, Ermelo and Newcastle regions were used as study areas. All areas were rehabilitated with a cover soil layer, revegetated and annually fertilised with nitrate fertilisers, super phosphate, kraal manure and lime. Performance guideline for pH of 5.5-(6.5 i0.5)-7.5 and electrical conductivity guideline of preferably less than 200 mS.rn-' but not higher than 400 mS.m-' were set based on literature information. Soil chemical data from a three-year fertilisation programme were used to assess the fertility of the cover soil surface (0-150mm). Data collected over a three year period as well as additional electrical conductivity and pH measurements from the cover soil surface, subsoil, cover soil/coal contact zone and underlying coal itself were used to assess the occurrence of salinisation and acidification of the cover soil. The soil fertility varied significantly among dumps as well as over the three years. Results indicated an increase in ammonium acetate extractable macro elements (calcium, magnesium and potassium). With the exception of manganese, no micro-element toxicities were recorded. Iron concentrations were slightly elevated in some of the sandy cover soil layers. No increase in soluble nitrogen (nitrate and ammonium) was found and most soluble nitrogen was in the form of nitrates. In general the Bray extractable phosphate increased during the study period. It can be predicted that with the following fertiliser programme increases of exchangeable macro-elements as well as available phosphorus can be expected. The study could not indicate an increase in adsorbed or available nitrogen. Organic carbon was initially not analysed therefore no comments can be made whether organic matter increased. Four of the seven dumps surveyed had comparably similar organic carbon levels to the background samples. Overall the fertiliser programme increased the electrical conductivity and decreased the acidity of the cover soil surface. Acidity and salinity was in general not a problem at the surface of the cover soil and pH was even slightly higher in cover soil samples. The acidity and especially salinity increased at the subsoil and so did the sulphate concentrations. Calcium and magnesium sulphate were predominantly responsible for higher electrical conductivity measurements. The percentage exchangeable sodium was also predominantly less than 2% indicating that sodicity is not currently a problem in cover soil. Soil fertility was satisfactory for vegetation growth and macroelement concentrations were in the correct ratio although calcium was slightly high. An elevated sulphate concentration, in comparison to the natural grassland soils, as well as a high salinity and high acidity in the subsoil layers indicate that salinisation and acidification could deteriorate without proper management. A slightly acidic cover soil can also be attributed partially to its natural acidic pH due to the wellweathered and leach property of burrow pit. Higher than recommended salinity levels were found in subsoil samples but the occurrence of acidification of the subsoil was more dump specific. In relation to acidity and salinity guidelines only the cover soil of one dump was concerning and the larger dumps subsoil acidity and salinity were elevated. The following management strategies are proposed: a) The acidification potential, and therefore the pyrite content of the coal discard must be considered during decisions making on the rehabilitation method (clay barriers), topsoil depth, maintenance and mine closure potential. b) The occasional monitoring of the subsoil's and coal contact acidity is recommended, although not much can be done to stop acidification after cover-soil placement. c) To ensure a more sustained from of nitrogen supplementation over the long term the use of selected legumes should be investigated. Research in Europe and Australia suggested that nitrogen fixation could contribute substantially to the nitrogen for plant uptake. d) The physical properties of the topsoil (bulk density 8 soil compaction) are also being neglected and needs to be assessed occasionally and interpreted together with chemical analyses. Observations in other studies indicate that this could be the most fundamental problem for vegetation growth and not necessarily soil fertility, since soil physical properties could have a major impact on root development. Key words: Coal discard, mine rehabilitation, soil fertility, topsoil degradation, salinisation, and acidification / Thesis (M. Environmental Management)--North-West University, Potchefstroom Campus, 2004.

Como forma temporária de uso do solo, a mineração requer planejar o futuro uso da área minerada de modo a deixar um legado positivo, por meio de engajamento com as partes interessadas e afetadas. Entretanto o processo de avaliação dos resultados da recuperação de áreas degradadas está quase sempre estritamente relacionado ao monitoramento de parâmetros biofísicos, sem avaliar o benefício social resultante. A característica integradora do conceito de serviços ecossistêmicos propicia avanços no planejamento e avaliação de resultados de programas de recuperação de áreas degradadas, ao demonstrar como a restauração das funções do ecossistema, induzida pela recuperação, pode melhorar o fornecimento de serviços, o que é refletido na qualidade de vida de seus beneficiários. O objetivo desta tese foi desenvolver um framework que permita incorporar o conceito de serviços ecossistêmicos ao processo de planejamento, implementação e monitoramento dos programas de recuperação de áreas degradadas pela mineração. Tal framework foi desenvolvido incialmente em língua inglesa e chamado de ESAR - Ecosystem Services Assessment for Rehabilitation. A metodologia geral da pesquisa é composta por quatro etapas sequenciais. A primeira foi a revisão da literatura e das boas práticas internacionais, quando foram levantadas informações para desenvolver uma versão preliminar do framework. Na segunda, o ESAR foi testado em duas minas de bauxita operadas pela empresa Alcoa, uma localizada na floresta Amazônica, Pará, Brasil e outra localizada na jarrah forest, na Austrália Ocidental. A terceira etapa objetivou realizar uma validação do ESAR segundo a perspectiva de profissionais da área de mineração. Finalmente, na quarta etapa o ESAR foi submetido à revisão de técnicos dos órgãos governamentais responsáveis pela regulação das minas de bauxita. Em síntese, os resultados dos testes de validação do ESAR demonstram que não se pode assumir que esforços de restauração ecológica automaticamente restauram a qualidade de vida da população afetada pela mineração, assim como a restauração da biodiversidade não necessariamente conduz à recuperação de benefícios sociais provenientes de um serviço ecossistêmico. Tanto os profissionais quanto os reguladores, brasileiros e australianos, acreditam que a análise de resultados requerida pelo ESAR é a etapa mais difícil de ser aplicada e não vem sendo praticada. Discute-se que o conceito de serviços ecossistêmicos facilita o envolvimento das partes interessadas e afetadas, desde que a coleta e análise de dados sejam planejadas e seus resultados sejam estruturados em um banco de dados integrado. A pesquisa leva a concluir que há valor em repensar ou reestruturar práticas de recuperação de áreas degradadas pela mineração de modo a acomodar o conceito de serviços ecossistêmicos ao longo de processos já estabelecidos, para que os benefícios sociais da recuperação sejam explicitamente demonstrados, facilitando a licença social para operar, bem como deixando um legado positivo pós-mineração. / Mining is a temporary land use hence companies are required to rehabilitate mined areas to ensure a positive legacy to society. Engaging with stakeholders is considered a good practice to support planning for post-mining land use. However, only biophysical indicators have been used to assess mine rehabilitation efforts, without an adequate evaluation of social outcomes. Ecosystem services assessment is a tool increasingly being used to understand the benefits that society obtains from ecosystems and is in many decision-making contexts. The integrative characteristic of the ecosystem services concept could advance planning and monitoring mine rehabilitation by translating biophysical outcomes into social benefits, and demonstrating how rehabilitation efforts could improve human well-being. This thesis developed a framework to incorporate the ecosystem services concept into the planning and monitoring process of mine rehabilitation. The framework was called ESAR - Ecosystem Services Assessment for Rehabilitation. The research was conducted in four phases. The first aimed at reviewing the literature and international best practices to develop the draft version of ESAR. In the second phase, ESAR was tested in two bauxite mines located in forest ecosystems, one in Brazil and another in Australia, both operated by the company Alcoa. The third phase aimed at validating ESAR by mining professionals from Brazil and Australia perspectives. In the last phase, government regulators of the two countries assessed ESAR. Overall the study demonstrates that meeting regulatory requirements for rehabilitation, as measured by ecological indicators, does not automatically correlate with acceptable social outcomes. Professionals and regulators see ESAR as an opportunity to engage stakeholders and demonstrate social benefits of mine rehabilitation. Both also affirmed that outcomes analysis of rehabilitation programmes is currently poorly done, and it is the most difficult step of ESAR. We argue that the ecosystem services concept facilitates stakeholders\' engagement and that a structured and integrated database is required to demonstrate beneficial outcomes. In conclusion, the research showed value in reframing mine rehabilitation practices to accommodate ecosystem services alongside the well-established ecological goals so as to explicitly demonstrate the social benefits of rehabilitation.

Gold mine waste poses a significant challenge for rehabilitation practitioners and can negatively impact on soil, air, surface water and groundwater quality. This, in turn, can affect the environmental quality of humans and other biota in nearby settlements and surrounding ecosystems. All mines are required to have a plan in place to impede or mitigate these environmental impacts and to ensure that all legislation is complied with to apply for closure. Site closure is the eventual goal of all mine residue complexes, as it is the stage at which a company becomes released from all legal and financial liability. The South African legislation is comprehensive and essentially requires that all latent and residual environmental impacts are addressed and that an end land-use designation is put in place that conforms to the principles of sustainable development. The Chemwes Tailings Storage Facility complex near Stilfontein was monitored to provide a strategic assessment of the state of the rehabilitation, and to provide recommendations for the successful remediation of problem sites. A combination of vegetation sampling, landscape function assessments and substrate chemical analyses were conducted to gain a predictive understanding of rehabilitation progress. The monitoring was conducted over two years across a chronosequence of rehabilitating sites from tailings dam slopes and an adjacent spillage site. An undisturbed grassland and a starter-wall served as reference sites. The data were first analysed independently and then by making use of multivariate data ordinations. This allowed for holistic investigations of the relationships between sites, substrate chemistry, vegetation composition and landscape function. The results showed that the tailings dams had a distinctly different suite of vegetation from the reference sites, but had no statistically significant differences in composition across the rehabilitating chronosequence. There were positive correlations between rehabilitation site age and landscape function indices, suggesting that some aspects of ecosystem development were occurring over time. In some sites, deterioration in the substrate quality as a growth medium was observed with increases in acidity and salinity. This was most likely caused by pyrite oxidation in the tailings and the high concentrations of free salts. The increasing acidity and salinity resulted in vegetation senescence and declines in landscape function. However, those sites that possessed higher landscape function appeared to have the ecosystem processes in place that temporarily suppressed negative chemical changes. Whilst this was encouraging,the rehabilitation chronosequence had not yet proven the self-sustainability that it would require for closure purposes. Further monitoring would be required over time. The sustainability of the rehabilitating chronosequence was brought into question by the high acid-forming potential of the tailings growth medium. Concerns were also raised over the ability of the established vegetation cover to persist under conditions of increasing stress and disturbance. Furthermore, the land-use capabilities of the sites are limited by current rehabilitation procedures and various recommendations were made to rectify this. A more streamlined monitoring framework for the tailings complex was also proposed. The contribution of this work lies in its holistic integration of monitoring techniques and the meaningful analysis of ecosystem function, an aspect largely ignored in minesite rehabilitation. / Thesis (M.Sc. (Environmental Sciences and Management))--North-West University, Potchefstroom Campus, 2009.

Gold mine waste poses a significant challenge for rehabilitation practitioners and can negatively impact on soil, air, surface water and groundwater quality. This, in turn, can affect the environmental quality of humans and other biota in nearby settlements and surrounding ecosystems. All mines are required to have a plan in place to impede or mitigate these environmental impacts and to ensure that all legislation is complied with to apply for closure. Site closure is the eventual goal of all mine residue complexes, as it is the stage at which a company becomes released from all legal and financial liability. The South African legislation is comprehensive and essentially requires that all latent and residual environmental impacts are addressed and that an end land-use designation is put in place that conforms to the principles of sustainable development. The Chemwes Tailings Storage Facility complex near Stilfontein was monitored to provide a strategic assessment of the state of the rehabilitation, and to provide recommendations for the successful remediation of problem sites. A combination of vegetation sampling, landscape function assessments and substrate chemical analyses were conducted to gain a predictive understanding of rehabilitation progress. The monitoring was conducted over two years across a chronosequence of rehabilitating sites from tailings dam slopes and an adjacent spillage site. An undisturbed grassland and a starter-wall served as reference sites. The data were first analysed independently and then by making use of multivariate data ordinations. This allowed for holistic investigations of the relationships between sites, substrate chemistry, vegetation composition and landscape function. The results showed that the tailings dams had a distinctly different suite of vegetation from the reference sites, but had no statistically significant differences in composition across the rehabilitating chronosequence. There were positive correlations between rehabilitation site age and landscape function indices, suggesting that some aspects of ecosystem development were occurring over time. In some sites, deterioration in the substrate quality as a growth medium was observed with increases in acidity and salinity. This was most likely caused by pyrite oxidation in the tailings and the high concentrations of free salts. The increasing acidity and salinity resulted in vegetation senescence and declines in landscape function. However, those sites that possessed higher landscape function appeared to have the ecosystem processes in place that temporarily suppressed negative chemical changes. Whilst this was encouraging,the rehabilitation chronosequence had not yet proven the self-sustainability that it would require for closure purposes. Further monitoring would be required over time. The sustainability of the rehabilitating chronosequence was brought into question by the high acid-forming potential of the tailings growth medium. Concerns were also raised over the ability of the established vegetation cover to persist under conditions of increasing stress and disturbance. Furthermore, the land-use capabilities of the sites are limited by current rehabilitation procedures and various recommendations were made to rectify this. A more streamlined monitoring framework for the tailings complex was also proposed. The contribution of this work lies in its holistic integration of monitoring techniques and the meaningful analysis of ecosystem function, an aspect largely ignored in minesite rehabilitation. / Thesis (M.Sc. (Environmental Sciences and Management))--North-West University, Potchefstroom Campus, 2009.

A mineração promove alterações significativas nos atributos do solo. Freqüentemente o substrato, proveniente de materiais estéreis do processo minerador, serve como meio de crescimento da vegetação das áreas em recuperação ambiental. Um procedimento para monitoramento da qualidade do substrato dessas áreas foi desenvolvido e testado. Os estudos foram conduzidos em uma mina de areia industrial situada no interior do Estado de São Paulo que apresenta cronosseqüência de medidas de restabelecimento de vegetação nativa em bacias de disposição de rejeitos de tratamento de minério, permitindo a simulação do monitoramento por um período de 14 anos. Foram analisadas as mudanças das características físico-químicas do substrato em conjunto com as mudanças na vegetação. Como resultado, verificou-se uma evolução positiva na qualidade do substrato que acompanha o desenvolvimento das espécies implantadas e conclui-se que as variáveis estudadas têm plena possibilidade de atuarem como indicadoras de desempenho da revegetação. Deste conjunto de variáveis, a densidade de solo, os teores de matéria orgânica e fósforo e o pH são os indicadores mais apropriados para avaliar o estado da revegetação, especificamente para as condições do ambiente das bacias de rejeito estudado. As áreas avaliadas encontram-se estabilizadas e contêm uma comunidade vegetal já formada. Contudo, a compactação do substrato, os baixos teores de matéria orgânica e o crescimento invasivo de Brachiaria decumbens (capim braquiária) foram identificados como fatores adversos que dificultam uma melhoria mais contundente na comunidade estabelecida. Concluiu-se que o método proposto constitui um instrumento prático para se obter parâmetros numéricos que permitam uma avaliação quantitativa e objetiva das áreas revegetadas e dos resultados das medidas de recuperação ambiental. Os indicadores podem ser utilizados em conjunto com parâmetros específicos que descrevam o estado da comunidade vegetal. Adicionalmente, podem ter aplicação em minerações de outros bens minerais, particularmente no caso de recuperação ambiental de bacias de disposição de rejeitos. / Mining is an agent of significant changes in soil properties. Successful land rehabilitation depends on restoring those characteristics in natural soils or establishing a suitable substratum for plant growth using available materials such as waste rock or mineral tailings. A process for monitoring the quality of the substratum in mine-affected areas was developed and tested. The study was carried out at an industrial sand mine located in São Paulo State, Brazil. Different plots situated in a tailings pond were restored with native species by the company for the past 14 years, allowing for 10+ years of simulated monitoring. Soil samples were collected to measure a series of physical and chemical substratum properties. Indicators of vegetation development were collected in each plot. As a result, a positive quality evolution of the substratum is observed simultaneously with the development of planted trees. In conclusion it was verified that observed substratum variables have ample possibilities to be suitable as revegetation performing indicators. From all substratum variables studied, soil density, organic matter, P contents and pH are the most appropriated indicators, specifically in the environmental conditions of the tailings pond studied. All evaluated areas feature a well established vegetal community. However substratum compaction, low contents of organic matter and intense weed growing (Brachiaria decumbens) were identified as limitative. The proposed method sets up a practical instrument to obtain quantitative parameters that allow for an objective assessment of revegetated areas and environmental rehabilitation actions. The indicators may be applied to other types of mines, specifically in case of tailing disposal sites.

A mineração promove alterações significativas nos atributos do solo. Freqüentemente o substrato, proveniente de materiais estéreis do processo minerador, serve como meio de crescimento da vegetação das áreas em recuperação ambiental. Um procedimento para monitoramento da qualidade do substrato dessas áreas foi desenvolvido e testado. Os estudos foram conduzidos em uma mina de areia industrial situada no interior do Estado de São Paulo que apresenta cronosseqüência de medidas de restabelecimento de vegetação nativa em bacias de disposição de rejeitos de tratamento de minério, permitindo a simulação do monitoramento por um período de 14 anos. Foram analisadas as mudanças das características físico-químicas do substrato em conjunto com as mudanças na vegetação. Como resultado, verificou-se uma evolução positiva na qualidade do substrato que acompanha o desenvolvimento das espécies implantadas e conclui-se que as variáveis estudadas têm plena possibilidade de atuarem como indicadoras de desempenho da revegetação. Deste conjunto de variáveis, a densidade de solo, os teores de matéria orgânica e fósforo e o pH são os indicadores mais apropriados para avaliar o estado da revegetação, especificamente para as condições do ambiente das bacias de rejeito estudado. As áreas avaliadas encontram-se estabilizadas e contêm uma comunidade vegetal já formada. Contudo, a compactação do substrato, os baixos teores de matéria orgânica e o crescimento invasivo de Brachiaria decumbens (capim braquiária) foram identificados como fatores adversos que dificultam uma melhoria mais contundente na comunidade estabelecida. Concluiu-se que o método proposto constitui um instrumento prático para se obter parâmetros numéricos que permitam uma avaliação quantitativa e objetiva das áreas revegetadas e dos resultados das medidas de recuperação ambiental. Os indicadores podem ser utilizados em conjunto com parâmetros específicos que descrevam o estado da comunidade vegetal. Adicionalmente, podem ter aplicação em minerações de outros bens minerais, particularmente no caso de recuperação ambiental de bacias de disposição de rejeitos. / Mining is an agent of significant changes in soil properties. Successful land rehabilitation depends on restoring those characteristics in natural soils or establishing a suitable substratum for plant growth using available materials such as waste rock or mineral tailings. A process for monitoring the quality of the substratum in mine-affected areas was developed and tested. The study was carried out at an industrial sand mine located in São Paulo State, Brazil. Different plots situated in a tailings pond were restored with native species by the company for the past 14 years, allowing for 10+ years of simulated monitoring. Soil samples were collected to measure a series of physical and chemical substratum properties. Indicators of vegetation development were collected in each plot. As a result, a positive quality evolution of the substratum is observed simultaneously with the development of planted trees. In conclusion it was verified that observed substratum variables have ample possibilities to be suitable as revegetation performing indicators. From all substratum variables studied, soil density, organic matter, P contents and pH are the most appropriated indicators, specifically in the environmental conditions of the tailings pond studied. All evaluated areas feature a well established vegetal community. However substratum compaction, low contents of organic matter and intense weed growing (Brachiaria decumbens) were identified as limitative. The proposed method sets up a practical instrument to obtain quantitative parameters that allow for an objective assessment of revegetated areas and environmental rehabilitation actions. The indicators may be applied to other types of mines, specifically in case of tailing disposal sites.

[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.

[Truncated abstract. Please see the pdf format for the complete text. Also, formulae and special characters can only be approximated here. Please see the pdf version for an accurate reproduction.] This thesis examines the water use, ecophysiology and hydraulic architecture of Eucalyptus marginata (jarrah) growing on bauxite mine rehabilitation sites in the jarrah forest of south-western Australia. The principal objective was to characterise the key environment and plant-based influences on tree water use, and to better understand the dynamics of water use over a range of spatial and temporal scales in this drought-prone ecosystem. A novel sap flow measurement system (based on the use of the heat pulse method) was developed so that a large number of trees could be monitored concurrently in the field. A validation experiment using potted jarrah saplings showed that rates of sap flow (transpiration) obtained using this system agreed with those obtained gravimetrically. Notably, diurnal patterns of transpiration were measured accurately and with precision using the newly developed heat ratio method. Field studies showed that water stress and water use by jarrah saplings on rehabilitation sites were strongly seasonal: being greatest in summer when it was warm and dry, and least in winter when it was cool and wet. At different times, water use was influenced by soil water availability, vapour pressure deficit (VPD) and plant hydraulic conductance. In some areas, there was evidence of a rapid decline in transpiration in response to dry soil conditions. At the end of summer, most saplings on rehabilitation sites were not water stressed, whereas water status in the forest was poor for small saplings but improved with increasing size. It has been recognised that mature jarrah trees avoid drought by having deep root systems, however, it appears that saplings on rehabilitation sites may have not yet developed functional deep roots, and as such, they may be heavily reliant on moisture stored in surface soil horizons. Simple predictive models of tree water use revealed that stand water use was 74 % of annual rainfall at a high density (leaf area index, LAI = 3.1), high rainfall (1200 mm yr-1) site, and 12 % of rainfall at a low density (LAI = 0.4), low rainfall (600 mm yr-1) site, and that water use increased with stand growth. A controlled field experiment confirmed that: (1) sapling transpiration was restricted as root-zone water availability declined, irrespective of VPD; (2) transpiration was correlated with VPD when water was abundant; and (3) transpiration was limited by soil-to-leaf hydraulic conductance when water was abundant and VPD was high (> 2 kPa). Specifically, transpiration was regulated by stomatal conductance. Large stomatal apertures could sustain high transpiration rates, but stomata were sensitive to hydraulic perturbations caused by soil water deficits and/or high evaporative demand. No other physiological mechanisms conferred immediate resistance to drought. Empirical observations were agreeably linked with a current theory suggesting that stomata regulate transpiration and plant water potential in order to prevent hydraulic dysfunction following a reduction in soil-to-leaf hydraulic conductance. Moreover, it was clear that plant hydraulic capacity determined the pattern and extent of stomatal regulation. Differences in hydraulic capacity across a gradient in water availability were a reflection of differences in root-to-leaf hydraulic conductance, and were possibly related to differences in xylem structure. Saplings on rehabilitation sites had greater hydraulic conductance (by 50 %) and greater leaf-specific rates of transpiration at the high rainfall site (1.5 kg m-2 day1) than at the low rainfall site (0.8 kg m-2 day1) under near optimal conditions. Also, rehabilitation-grown saplings had significantly greater leaf area, leaf area to sapwood area ratios and hydraulic conductance (by 30-50 %) compared to forest-grown saplings, a strong indication that soils in rehabilitation sites contained more water than soils in the forest. Results suggested that: (1) the hydraulic structure and function of saplings growing under the same climatic conditions was determined by soil water availability; (2) drought reduced stomatal conductance and transpiration by reducing whole-tree hydraulic conductance; and (3) saplings growing on open rehabilitation sites utilised more abundant water, light and nutrients than saplings growing in the forest understorey. These findings support a paradigm that trees evolve hydraulic equipment and physiological characteristics suited to the most efficient use of water from a particular spatial and temporal niche in the soil environment.