Thai Nguyen University of Agriculture and Forestry Degree Program Bachelor of Environmental Science and Management Student Name Mishel Valery Valiña Rañada Research Title “Rehabilitation
INTRODUCTION
Research Rationale
Australia holds the world’s richest iron ore reserves and is responsible for over half (55%) of the global output Moreover, 94% of the country’s total production is produced from Pilbara region alone of Western Australia In addition, Western Australia’s production had been rising annually by an average rate of 12% (Western Australia’s Iron Ore Profile 2016) The escalating industry of iron ore in Western Australia, particularly in Pilbara region, has resulted in the expansion of degraded land In addition, millions of tonnes of mine wastes are generated annually, while the source of topsoil, which is essentially used for post-mining rehabilitation, is becoming limited (Bell, 2002; Garnett, 2004; Van Vreeswyk et al., 2004; Yanez, 2014) As the mining industry expands and develops, rehabilitation becomes a global priority (Shackelford et al., 2017) Although there are studies made to test the rehabilitation potential of mine wastes in general, there are gaps in our knowledge that need thorough research specifically on the potential of iron ore coarse rejects (Lottermoser, 2011) Previous studies recommended fertilizing to replace the nutrient banks lost during vegetation removal and other mining processes (Bell, 2002) However, there is only limited knowledge with regards to the appropriate rates and application method of macro-nutrients and micro-nutrients considering the potential environmental impact, cost-effectivity and labor-efficiency (Lottermoser, 2011) For these reasons, the industry is constrained from utilizing coarse rejects and other mine waste for the revegetation of native plant species
The Pilbara region is located in the north of the State of Western Australia having a land cover of 507,896 square kilometers (Department of Regional Development, Western Australia, 2013) It is home to some of the World’s most ancient natural landscapes with rocks dating back from 2 to 3.5 billion years The region is known as the engine room of Australia for having massive mining industries of crude oil, salt, natural gas and iron ore Particularly, the extraction of iron ore is generally performed through a blasting and removal process from large open-pit mines before it is crushed, screened and blended for export or local consumption (Garnett, 2004; Department of Industry, Australia, 2011)
Coarse rejects are by-product wastes of iron ore mining Ores that are extracted from the open-pit mine are transported to processing plants These iron ores are subjected to various unit processes such us screening, air classification and dry magnetic separators to reduce impurities and increase the ore grade to a marketable product without any production of chemical pollutants (Garnett, 2004) Several authors claim that these coarse rejects have the potential to act as a surrogate topsoil for plant growth (Johnson et al., 1989; Gellert, 2012; Outback Ecology, 2012), but this potential has rarely been investigated
Rehabilitation is the principal process used to mitigate the long-term impacts of mining on the environment (Department of Industry, Tourism and Resources, Western Australia, 2006) Improvements in rehabilitation practices are crucial to cope up with the increasing land and ecosystem degradation due to growing mining industry Its success, specifically on the revegetation of native plant species, is often
5 affected by topsoil resource and management It is a significant factor in mine rehabilitation for it has the optimum characteristics for growth and establishment of plants Because iron ore is generally extracted from the open-pit mine, major concerns are the disposal of accumulating excessive mine waste and the limited source of topsoil which is not enough for a large-scale revegetation (Garnett, 2004) The remoteness of the mine sites has resulted to a limited supply of topsoil for rehabilitation use (Bell, 2002) Moreover, uplands of the Pilbara are rocky with little natural topsoil development while plains are denuded because of soil erosion causing deflated to no topsoil land surface (van Vreeswyk et al., 2004)
Although reusing of mine wastes had already been pursued before, the concept of using it for rehabilitation remained as an idea that has not been widely taken up by the industry Majority of mine wastes, particularly coarse rejects, are still placed in storage and disposal facilities regardless of the rehabilitation efforts This is mainly because of insufficient studies regarding its potential as an alternative substrate for revegetation Evaluation and research in relation to this issue are much needed to produce data on success and failure of modern rehabilitation Such studies are essential contribution in broadening the knowledge on the improvement and development of new rehabilitation practices (Lottermoser, 2011)
The removal of vegetation, disturbance of soil profile and other processes during mining, reduce the nutrient content of topsoil needed for revegetation (Daws, 2009) The use of chemical amendments on altering the chemical composition can promote vegetation establishment and survival (Lacy et al., 2004) The report from SCI3120
Natural Sciences Project by Edith Cowan University (2016) showed that among the treatment application of organic matter and inorganic fertiliser, native plant species performed best on coarse reject substrates with inorganic fertiliser amendment (“Unpublished report for SCI3120 Natural Sciences Project”, 2016) Given these results and limitations of the study, thorough research on different fertiliser rates and application method considering the cost-effectivity over a large-scale application are provided for future studies
Optimizing the fertiliser rates is a key aspect of rehabilitation Fertiliser rates need to be sufficient to support the establishment of vegetation and at the same time incorporates the cost of application Additionally, the application rates should be low enough to minimize potential negative impacts such as promotion of weed species, excessive nutrient run-off or the direct impact of high phosphorous on some proteaceous species (Daw, 2009) Moreover, excessive use of fertiliser can be toxic and can cause detrimental effects on native plant species, specifically in Australia (Sydney Environmental and Soil Laboratory, n.d.) Studies testing the effects of different fertiliser rates will be beneficial to the mining companies as it will help them avoid wasting money on unnecessary amounts of fertiliser used over large-scale rehabilitation
Experts from different countries, such as Australia, South Africa and United States, who are facing the same problem with rehabilitating mine sites, often collaborate to address the problem (Bell, 2015) Now their research team is focusing on restoring diverse native plant communities following mining and specifically on
7 how to get the seeds to germinate and establish more reliably in the degraded land at large scales (Merritt, 2015) Choosing the suitable native plant species for a particular site and purpose is essential (Department of Planning, Land and Heritage, Western Australia, 2011) This study focused on the establishment and early growth and development of three different types of Pilbara native plant species to assess the effectiveness of coarse rejects with different levels of fertiliser as a substrate Considering the natural environment of Pilbara region and for the purpose of rehabilitation, three native plant species of Eucalyptus leucophloia (tree type), Triodia pungens (grass type) and Acacia tumida (shrub type) are selected based on their outstanding characteristics, landscape dominance and suitability for rehabilitation (Erickson et al., 2016).
Research Objectives
The study aims to compare the establishment and growth performances of three native plant species in coarse reject substrates with different levels of fertiliser for the rehabilitation of iron ore mining area in Pilbara Region, Western Australia
The specific objectives of the study are:
• To compare the seed germination rates with different levels of fertiliser
• To assess the survivorship and growth performances of each of the native plant species within different levels of fertiliser.
Hypothesis
There are no significant differences among the growth performances of the three native plant species within different treatments of “coarse rejects”
There are significant differences among the growth performances of the three native plant species within different treatments of “coarse rejects”.
Limitations
Due to time and space constraints, the study was limited to the growth performances of three native plant species of Pilbara region of Western Australia, namely Eucalyptus leucophloia, Triodia pungens and Acacia tumida The research was conducted at the glasshouse of Edith Cowan University in Joondalup, Perth, Western Australia The
“coarse rejects” used was the actual samples from the iron ore mining site in Pilbara
There were several notable limitations in the research First, the time allotted on the research study was not enough to evaluate the long-term growth performances of the native plant species on different level of fertiliser treatments Therefore, the researcher limited the study on the effects of different levels of fertiliser treatments focusing on the germination, establishment and early growth and development of the native plant species
Obtaining information from the actual field site is essential However, such trials are expensive and requires more labor and time Therefore, the researcher used pot trials to conduct the study The experiment was done in the glasshouse and not in the field Despite of the efforts on manipulating the conditions in the glasshouse to the desired measures, there are still environmental factors within Pilbara region that can’t easily be replicated Thus, performing this study in the field was recommended to examine the results under the actual environmental conditions of Pilbara
The use of “coarse rejects” as a substrate for plant growth had just recently subjected for research The lack of prior studies on coarse rejects had limited the available literature and other resources In this case, the researcher gathered as many related literatures and research studies as possible to support the study Therefore, future studies about coarse rejects will be a great contribution to the literature field of rehabilitation.
Definitions
Coarse rejects The by-product wastes from iron ore extraction It is the rejected materials from the processing plant after screening and magnetic separation
Iron ore Rocks from which metallic iron can be economically extracted
Mine waste A general term to any material extracted from mining that has little or no economic value that includes coarse rejects, waste rocks, overburden and tailings
Native plant species It refers to those species that occur naturally in a particular area without human introduction or intervention
Pre-treatment It is a process used to increase the germination of seeds
Rehabilitation It involves returning the land to its natural state post mining through strict, well-researched strategies of revegetation and the regeneration of natural ecosystems
Revegetation It is the process of replanting and rebuilding the soil of disturbed land Substrate A material used as growth media for plants
Waste rocks It is the result of blasting during the extraction of ore from the mining area producing random sizes ranging from block and pebble-size down to fine sand -size particles and dust
LITERATURE REVIEW
Iron Ore Mining Industry in Pilbara, Western Australia
Australia has the world’s richest and largest reserves of iron ore Within the estimated 35 billion tonnes of iron ore reserve, 17 billion tonnes contains iron (Mining Technology, 2014) In 2016, the country was considered the largest exporter of iron ore in the world; responsible for over half (55%) of the global output amounting to US$39.5 billion (Workman, 2017) Furthermore, 94% of the country’s total production in 2015 was produced from Pilbara region alone of Western Australia From 2004 to 2015, the production of the State of Western Australia is rising annually by 12% (Western Australia Department of State and Development, 2016)
The Pilbara is one of the largest region in Western Australia that is located at the north of the State Pilbara region covers up 507,896 square kilometers of some of the World’s most ancient landscapes with rocks dating back to at least two billion years Within more than 66,000 population, the region’s economy is dominated by construction, export and mining (Department of Regional Development, Western Australia, 2013) Being home to massive mining industries of crude oil, salt, natural gas and iron ore, the region was named as the “engine room” of Australia From over 50 different minerals produced by 111 principal mining projects and hundred smaller mines of Western Australia, iron ore was the most valuable resource in 2015-16 (Department of Jobs, Tourism, Science and Innovation, Western Australia, 2016)
Geoscience Australia (2013) defined iron ore as “rocks from which metallic iron can be economically extracted” According to Jonathan Law, an expert on locating and managing mineral deposits at the CSIRO, “the ones that have made the Pilbara great are secondary enrichments of banded iron ore”, which are made of thin layers of iron oxides that have been further enriched by the actions of water by washing away waste minerals leaving concentrated bands of iron oxide (Pincock, 2010) Hematite (Fe2O3) and Magnetite (Fe3O4) are the principal iron ores Hematite is a non-metallic iron oxide mineral that contains 69.9% iron with a color variations of steel silver to reddish brown
On the other hand, magnetite is highly magnetic containing 72.4% iron that is generally black in color Though magnetite contains higher iron compared to hematite, the presence of impurities results in a lower ore grade that makes the production of concentrates more costly (Geoscience Australia, 2013) Most of Australia’s iron ore produce is direct shipping quality hematite ore However, operations that extract magnetite are attracting increasing interest (Department of Industry, Australia, 2011) Magnetite mining is an emerging industry in Australia with large deposits being developed in Pilbara (Geoscience Australia, 2013) In Pilbara, most of the iron ore mines are mostly centered around Newman and Tom Price The region hosts three of the eleven biggest iron ore companies in the world: BHP Billiton Ltd (BHP), Rio Tinto Ltd (Rio) and Fortescue Metals Group Ltd (FMG) (Mining Technology, 2014 and Australian Mines Atlas, 2015)
Finding banded iron formations are extremely easy due to their magnetic properties Deposits are mostly discovered on the surface (Law, 2010) Generally, iron
13 ore mining uses the open pit method Overburden is removed and placed at temporary location for later use Then, iron ore was extracted from large mine pits through blasting and removal process before it was subjected to a primary crushing using semi-mobile crushing units (Department of Industry, Australia, 2011) With the use of overland conveyors or haul roads, crushed ores are transported to the central processing plant(s) for screening, air classification and dry magnetic separators This is done to reduce impurities and increase ore grade to a marketable product without any production of chemical pollutants (Garnett, 2004) Afterwards, long trains, of up to 2-kilometer in length and over 250 wagons, carries about 25,000 tons of ore to port sites in each trip for further treatment and blending in preparation for export or local consumption (Geoscience Australia, 2015).
Mining Rehabilitation in Pilbara, Western Australia
The Pilbara is located in the Northwest of Australia The region is known for its unique geology, topography and vegetation associations (Erickson et al., 2016) Its landscape is variable and shaped with a number of ranges, river valleys and peneplains (Van Vreeswyk et al., 2004) Floristically, the region is divided to four subregions of
Hamersley, Fortescue, Chichester and Roebourne with regional towns that are scattered throughout the region supporting various tourism, pastoral and mining industries (Erickson et al., 2016)
This arid- tropical region has two distinct seasons, hot summer from October to April and mild winter from May to September Overall, it has a mean maximum temperature of 31.4 o C and mean minimum temperature of 17.3 o C (Bureau of Meteorology, 2014) Peak rainfalls that occur during the summer months of January to March is a climatic condition influenced by tropical cyclones and depressions entering from Northern Australian waters producing sporadic and intense thunderstorms On the other hand, smaller peak rainfall during May to June is generally a result of cold fronts moving easterly across the Western Australia which causes occasional light winter rains in Pilbara Region (Gentilli, 1972; Garnett, 2004)
The region is a mining “hot spot” wherein 92% of its land is covered with either live or pending mining tenements (ABC News Australia, 2014) According to their report, in recent years, an unprecedented growth of iron ore industry has been experienced Unfortunately, the environmental knowledge is not enough to cope up with the industry’s growth level Pilbara is a key mining region which largely drives the state’s economy therefore the state government had to ensure that the “balance approach” on both factors of economy and environment is maintained Environmental Protection Agency is now taking steps to protect the biodiversity of the region
Rehabilitation is the principal process used to mitigate the long-term impacts of mining on the environment (Department of Industry, Tourism and Resources, Western Australia, 2006) Improvements on rehabilitation practices are crucial to cope up with the
15 expanding land and ecosystem degradation due to growing mining industry There are several concerns regarding the rehabilitation process
Firstly, the success on revegetation of native plant species is often affected by topsoil resource and management Topsoil is the top 200mm to 250mm of the soil profile that is biologically active having viable seeds and organic matter content (Yanez, 2014) Before digging up the area for mining, the topsoil was stripped first for a direct utilization to a nearby rehabilitation area within 1km from the mine face Otherwise, in cases where there is no nearby area to be rehabilitated, topsoil is stockpiled with a height of no more than 2m for a short period of time (maximum of 2 years) According to the report of Fortescue Metals Group by Garnett, “minimizing the amount of time that the topsoil is stockpiled will maximize the return of the floral species from the seed resource within the topsoil” It is a significant factor in mining rehabilitation for it has the optimum characteristics for growth and establishment of plants However, the source of topsoil is becoming limited and not enough to cover up the expanding damage of mining overtime (Garnett, 2004) The Pilbara’s upland areas are rocky with little natural topsoil development On the other hand, due to soil erosion, plains are having deflated to no topsoil land surface (van Vreeswyk et al., 2004) Because mine sites are often remote, the supply of topsoil for rehabilitation is becoming limited (Bell, 2002)
In addition, because iron ore is generally extracted from open-pit mine, disposal of accumulating mine wastes and rejected materials are becoming a concern (Garnett,
2004) Normally, these mine wastes and rejects, together with the overburdens, are
16 utilized to backfill the mined areas But in the case of having limited topsoil source, rehabilitation and mining sectors are now looking to mine wastes and rejected materials’ potential to substitute topsoil
Surface materials to be used vary depending on the sources available within the site and its potential to support plant establishment (Yanez, 2014) Likewise, the remoteness of mine sites has resulted to utilization of available substrate such as coarse rejects, waste rocks and other mine wastes as cover materials (Bell, 2002) In relation, management of growth media became another issue Construction of the soil profile, including the topsoil, subsoil and benign waste, is an essential component of a successful rehabilitation and successive revegetation (Yanez, 2014) Nutrient banks are lost during vegetation removal and other mining process therefore, in most cases, fertilizing is required Careful planning based on detailed soil characterization studies and rehabilitation objectives and targets is essential to know the appropriate types and application methods of macro-nutrients and micro-nutrients (Bell, 2002)
However, majority of mine wastes, including coarse rejects, are still placed in storage and disposal facilities regardless of the rehabilitation efforts due to limited studies regarding the potential of coarse rejects for rehabilitation of mines and revegetation of native plant species (Lottermoser, 2011).
Rehabilitation Potential of Coarse Rejects
Generally, coarse rejects are by-product wastes of iron ore mining After extracting the overburdens from the open pit mine, waste rocks are removed through
17 blasting (“User Guidelines for Wastes”, 2016) Subsequently, iron ores are extracted, crushed and conveyed to processing plant for screening and other process using magnetic separators This process removes impurities and the resulting rejected materials are the
“coarse rejects” These coarse rejects typically have a size ranging from 0.5 mm to 200 mm Like any other aggregates, these wastes can be processed to a desired gradation by crushing and sizing (“User Guidelines for Wastes”, 2016) There is an approximately, 0.35 tonnes of rejects generated for every ton of screened ore processed (Garnett, 2004)
Based on the analysis for Net Acid Generation (NAC) and Net Acid Producing Potential, dry rejects are found to be not acid forming (NAF) and in fact have acid neutralizing capacity (ANC) due to the presence of carbonate materials in the samples, as confirmed by the X-ray Diffraction (XRD) (Dowling, 2013)
Furthermore, a Trial Landform (TLF) was constructed by Energy Resources of Australia Ltd (ERA) in 2009 to provide data for refinement of revegetation strategy and, at the same time, demonstrate ERA’s revegetation ability using native plant species similar in density and abundance to those existing in nearby areas The ongoing four years of monitoring, on the Ranger Project Area near Jabiru in the Northern Territory, has shown clear differences in performance between the revegetation methods and substrates
It was found out that germination and survival is higher on waste rock (Gellert, 2012)
Likewise, a ten-year research project at a Southern WA Goldfield that compared the effects of different cover treatments, such as topsoil, waste rock, road ballast and uncovered tailings on pH and EC of the cover profile, showed that the treatments
18 involving both a layer of waste rock and topsoil is likely to result in the highest vegetative cover (Outback Ecology, 2012) Soil profile reconstruction at Bottle Creek Gold Mine in WA involved 500 mm of waste rock, topsoil spread to a depth of 100 mm and deep ripping along the surface of the contour (Anderson et al., 2002)
There are previous studies which supports reusing of mine wastes, including tailings (Lacy et al., 2004), overburden (Garnet, 2004) and waste rocks (Gellert, 2012), for rehabilitation strategies However, the potential of iron ore mining “coarse rejects” on the rehabilitation of mine sites and specifically on revegetating the native plant species of Pilbara has rarely been investigated Since there are very few experimental studies carried out to evidently confirm the potential of these coarse rejects, the mining companies are constrained on utilizing the increasing piles of coarse rejects as a substitute to the declining source of topsoil Thus, the mining rehabilitation processes are slowed down.
Fertiliser Amendments on Mine Wastes
Mine wastes (mostly tailings, overburdens and waste rocks) were previously studied regarding its potential in the rehabilitation of mine sites These studies are dealing on how to improve the quality of these mine wastes for revegetation; which are mostly about the use and effects of fertilizers
A study in Darling Range, Western Australia about the jarrah forest restoration after bauxite mining by Daws (2009), which mines and restores ~800ha of forest to re- establish a self-sustaining jarrah-forest ecosystem, stated that nutrient needed for restoration and revegetation is reduced due to the removal of vegetation and disturbance
19 of soil profile during mining As the metalliferous mining industries expand worldwide, the attention to cultivate and improve mine wastes for mine rehabilitation increased as well Most of the rehabilitation practices were based on substrate amelioration using innocuous covering materials and fertiliser amendments However, before, non- indigenous species are used, and revegetation of native plant species is rarely attempted Despite the physical and chemical properties of metal mine wastes, it is still possible to meet the requirements of plant species’ restoration (Johnson et al., 1989)
Moreover, sufficient rates of fertilisers are necessary to support establishing vegetation (SER Australasia Conference 2012) It should be low enough to minimize the potential negative impacts such as excessive nutrient run-off, promotion of weed species or the direct impact of high phosphorous on some proteaceous species (Daws, 2009) In addition, excessive use of fertiliser can be toxic and can cause detrimental effects on the native plant species in Australia (Sydney Environmental and Soil Laboratory, n.d.) Studies regarding this matter will be beneficial for the mining companies to avoid wasting money on unnecessary amounts of fertiliser used over a large-scale rehabilitation
A study from Department of Planning, Land and Heritage, Western Australia
(2011) claimed that, trials using nitrogen and slow-release fertilisers have promoted growth of Spinifex sericeus in the eastern States and New Zealand Slow release fertilisers, which are available in pellet or pill form, are the best fertilisers to use Likewise, a study by Lacy et al (2004) showed that one of the approaches for tailings
20 storage facility rehabilitation includes chemical amendments wherein the physical structure or chemical composition of the tailings is altered to promote vegetation establishment and survival (e.g usage of gypsum, lime and fertilisers)
The use of chemical amendment on altering the chemical composition can promote vegetation establishment and survival (Lacy et al., 2004) However, a thorough research regarding the suitable fertiliser and appropriate application rates is essential Such study is needed to provide enough information and feasible results considering the cost-effectiveness and labor-efficiency for a large-scale application Moreover, OSMOCOTE Plus Trace Elements (Native Garden) is a controlled-release plant fertiliser specially formulated for Australian native plant species It uses prill technology (a small aggregate or granulated materials, mostly dry sphere, made from melted liquid) with high quality fertiliser encased in a permeable and biodegradable soy extract coating that contains a balanced micro dose of nutrients so a plant's response from an application is reliable and consistent It releases more nutrients when the plants are growing faster within high temperature and releases enough within cold environment when the plants are growing slower It is made safe to be used for young plants with soft leaves and tender roots It can be mixed with the soil directly at time of planting (Scotts Australia, 2017)
According to Bell (2002), the author of a chapter on ‘Remediation of Chemical Limitations’ in the book of “The Restoration and Management of Derelict Land: Modern Approaches”, there are four ways of assessing whether a soil or waste on a degraded site is deficient in nutrients for vegetation growth This includes: (1) plant symptoms, (2)
21 plant analysis, (3) small pot plant growth trials and (4) field site plant growth trials The last two methods provide the opportunity to determine the appropriate proportion of nutrients needed for maximum growth It is essential to obtain information from the actual field site trials However, such trials are expensive Therefore, small pot trials are mostly used since it’s a cost-effective way of narrowing down the number of treatments which need to be tested in the field It is preferable to delineate the major limiting factors via a pot trial program Additionally, fertiliser assessment program using pot trials can assess the response of the selected species to amended different levels of nutrient Non- nutrient factors such as temperature, water availability and aeration can also be manipulated within the glasshouse where the pot trial is conducted There are types of nutritional pot trials that include (1) nutrient omission or subtractive trial, (2) factorial and (3) rate of addition In most situations of mine rehabilitation, macronutrient deficiency limits the plant growth In order to have a more efficient design of field fertiliser trials, it is desirable to obtain a full response curve in a pot trial first before commencing on a large-scale field experiments
International research students at Edith Cowan University in Perth, Western Australia conducted pot trials on the growth performances of four native plant species (Eucalyptus leucophloia, Acacia tumida, Triodia pungens and Grevillea wickhamii) on coarse reject substrates with organic matter and inorganic fertiliser in 2016 (unpublished study) Parameters such as germination rate, plant height and dry weight were used to measure the growth of plants Among the treatments, the coarse reject substrate with a
15g of fertiliser amendment showed a significant effect on the plant’s growth (“Unpublished report for SCI3120 Natural Sciences Project”, 2016).
Revegetation of Native Plant Species
There’s a wide array of vegetation types present in Pilbara ecosystem To have a successful land restoration and conservation, a wide selection of species is essential The long-lived perennial grasses, shrubs and trees of Triodia, Eragrostis, Acacia, Senna, Tephrosia and Eucalyptus are the core elements of the region’s vegetation (Erickson et al., 2016) Within the 1800 species across the whole Pilbara, approximately 15% of it was endemic to the region (Department of Planning, Land and Heritage, Western Australia, 2011) These endemic and other local specialties are now being focused on the conservation programs Choosing the suitable native plant species for a particular site and purpose was essential Likewise, fertiliser trials should use plant species that are climatically suited to the area Ideally, selected species should include those that are previously used on pot trials or on other related studies (Bell, 2002) In addition, species selection should consider both the species diversity and structural diversity, for instance, species from various strata such as grasses and low-lying shrubs for groundcover provides landform stability and taller shrubs and trees provide fauna habitat (Yanez,
2014) Flora in arid regions, especially the seeds found throughout the Pilbara, is highly adaptive to survive the extreme seasonal fluctuations in temperature and moisture availability (Erickson et al., 2016) However, during mine rehabilitation, even the plants best adapted to the harsh environmental condition of Pilbara region is struggling to
23 establish their seeds and grow Considering the natural environment of Pilbara region and for a purpose of rehabilitation, three (3) native plant species of Eucalyptus leucophloia
(tree type), Triodia pungens (grass type) and Acacia tumida (shrub type) were selected based on: (i) the core elements of the Pilbara region’s vegetation, (ii) their outstanding characteristics to withstand natural forces of wind and water, (iii) dominance of the local landscapes and (iv) suitability on the study
Eucalyptus leucophloia subsp leucophloia, commonly known as Snappy gum, is a small tree or mallee that usually grows 2.5 to 10m high It has a powdery bark throughout, alternate pruinose leaves and small pruinose fruits with exserted valves Mallees and trees of Eucalyptus are scattered among the expansive hummock grasslands and are widely spread in Pilbara, but not extending far beyond the region (Erickson et al.,
2016) Moreover, tree steppes of Eucalyptus occur on ranges (Kendrick & McKenzie,
2001) Pre-treatment of seed is not required because this species is non-dormant with germination of 100% (Erickson et al., 2016)
Soft spinifex (Triodia pungens) is a drought-resistant perennial grass with stolons and culms measuring about 0.2 to 2.3m high There are about 22 spinifex species recognized in the region This species grows on a wide range of soils, particularly in gravelly and rocky areas, but can also be found on plains and flats (Erickson et al., 2016)
Triodia hummock grasslands dominate most of the landscapes such as the uplands, mountain chains and the more skeletal soils of the indulating plains (Kendrick & Stanley,
2001) These species are one of the most affected with the resource development projects
24 within the arid-zone Thus, these species became essential for restoration projects and management (Barrett, 2012) The species has a physiological dormancy type that requires smoke-treatment to increase its germination to 90% Smoke water is extracted from dry rice straw by burning and bubbling the smoke through water To stimulate the germination of plants, seeds are soaked in a 10% dilution of this smoke water for up to 24 hours (Chumpookam, 2012; Erickson et al., 2016)
In Australia, the secondary center of Acacia species richness and endemism is in
Pilbara There are about 122 species of Acacia within the region (Erickson et al., 2016) Acacia tumida var pilbarensis also known as Pilbara pindan wattle has hard grey glossy bark that is occasionally fissured On the other hand, A tumida as a smooth and pruinose bark when young It is a shrub that typically grows to a height of 2 -15m (Muell, n.d.) Dwarf shrub steppe of Acacia grows on the coastal and sub-coastal plains, red sandplains and dunes of the region (Kendrick & Stanley, 2001) This species has a physical dormancy type Some species have a specialized, microscopic structure within the end of the seed or fruit coat which is termed as water gap Wet heat treatment breaks the dormancy by rupturing this water gap and increases its germination to >90% Majority of
Acacia species responds well when seeds are immersed in water at 90 to 95 o C for two minutes (Erickson et al., 2016)
METHODS
Materials
All the materials and equipment are provided by Edith Cowan University, Joondalup Campus, Perth, Western Australia The research is also financially supported by the mining company (See Appendix I)
3.1.1 Pre- treatment and preparation of seeds:
• Eucalyptus leucophloia spp leucophloia (100 seeds)
• Acacia tumida var pilbarensis (100 seeds)
• Nearly boiling water about 90 o C – 95 o C (800ml)
• 120 experimental pots (9cm x 9cm x 18cm)
• Coarse rejects from iron ore mine site in Pilbara is supplied by the Fortescue Metal Group, a global iron ore company
• Scotts Osmocote® Plus Trace Elements: Native Gardens (Controlled Release Fertiliser) 2kg
- 10 preparations of 5mg for low level
- 10 preparations of 15mg for medium level
- 10 preparations of 45mg for high level
- 3 preparations of ~100g sample from raw coarse reject sample
- 3 preparations of ~100g sample from treatment 1 pots (control)
- 3 preparations of ~100g sample from treatment 2 pots (low level of fertiliser)
- 3 preparations of ~100g sample from treatment 3 pots (medium level of fertiliser)
- 3 preparations of ~100g sample from treatment 4 pots (high level of fertiliser)
3.1.4 Data recording and experimental pot labelling
• White Knight Flouro Colour Spray paint (green and red)
• Permanent markers (white, blue, black and red)
Methods
3.2.1 Time and Place of Study
The actual experiment was conducted at Edith Cowan University, Joondalup, Perth, Western Australia from April 2017 to September 2017 The study was carried out at Bldg 17, University glasshouse The experimental area had a temperature of 27 o C with a normal humidity Daily watering was running every 7am through automatic irrigation system
The research had four treatments including three different levels of fertiliser (low, medium and high amount) and control (no fertiliser) Three native plant species of
Eucalyptus leucophloia (tree type), Triodia pungens (grass type) and Acacia tumida (shrub type) were chosen based from their outstanding characteristics and fitness to the study (Erickson et al., 2016) There were 10 replications for each treatment having a total of 120 pots (4 treatments x 3 native plant species x 10 replications) The amount of fertiliser applied to the medium treatment followed the recommendations of the fertiliser manufacturer (Scotts Australia), with the ‘high’ treatment being three times this amount, and the ‘low’ treatment one-third of this amount
Table 1 Substrate contents of every experimental treatment
Treatment 2 Coarse rejects + low amount of fertiliser (5g per pot) Treatment 3 Coarse rejects + medium amount of fertiliser (15g) Treatment 4 Coarse rejects + high amount of fertiliser (45g)
Species number were assigned according to the seed size starting from the smallest to the biggest:
Species 1: Eucalyptus leucophloia spp leucophloia
Species 3: Acacia tumida var pilbarensis
Each native plant species has four treatments resulting to a total of 12 groups with
Group 7: Treatment 3 Species 2 Group 8: Treatment 4 Species 2 Group 9: Treatment 1 Species 3 Group 10: Treatment 2 Species 3 Group 11: Treatment 3 Species 3 Group 12: Treatment 4 Species 3
Completely randomized design (CRD) is used as a research design to eliminate systematic error such as biasness in allocation or in glasshouse position (Yarnes, 2013; Nokoe, n.d.; Penn State Eberly College of Science, n.d.) The pot number, with the respective treatments and species, is assigned randomly using the table of random numbers (Appendix 6) (FAO Forestry Department, n.d.) Each of the pots were labeled as (G3) T3S1 (P1), (G12) T4S3 (P2), (G9) T1S3 (P3) … (G11) T3S3 (P119) and (G10) T2S3 (P120) All the experimental pots were arranged into ascending order inside the potting shed
(G - group/ replicates, T - treatment, S – native plant species, P – pot number)
Treatment 2: low level of fertiliser
Treatment 3: medium level of fertiliser
Treatment 4: high level of fertiliser
Numbered pot arranged in ascending order
Figure 2 Actual Experimental Layout (See Appendix C)
Pre-treatment for seed germination
After the preparation and labelling of experimental pots, pre-treatment of seeds was done to break the dormancy and to maximize its germination Eucalyptus leucophloia species were non-dormant therefore pre-treatment was not required Triodia pungens has a physiological dormancy type To increase its germination to 90%, seeds were soaked in smoke water (25ml smoke solution: 250ml water) for 24 hours before sowing Acacia tumida, having a physical dormancy type, was subjected to wet heat for 2 minutes at 90-95 o C to have a >90% of germination After soaking it for 2mins, the beaker was filled with cold water to stop the heating effect on the seeds After a couple of minutes, it was sieved for sowing (Erickson et al., 2016)
Same amount of coarse rejects was prepared for all 120 pots Every pot was watered before applying the fertilisers Treatment 1 (control) was filled with coarse rejects alone without any fertiliser amendments Then, 5g of fertiliser was applied on Treatment 2 (low level), 15g on Treatment 3 (medium level) and 45g on Treatment 4 (high level) The recommended amount of 15g on the fertiliser packaging was used as the basis for the medium level (Treatment 3); 3x of it was used for high level (Treatment 4) and 1/3 was used for low level (treatment 2) (Daws, 2009 and Scotts Australia, n.d.)
For every native plant species, 10 seeds were randomly sown in each pot of every treatment, making sure that all of it were covered with enough substrates on top Ideally, seeds were sown not deeper than twice its diameter Small seeds of Eucalyptus leucophloia and Triodia pungens were sown half a centimeter depth On the other hand, Acacia tumida, having a bigger seed size, were sown at a depth of about 1cm
The area was watered every morning at 7AM by the auto-irrigation system at the University glasshouse (Bldg 17)
Seeds sown was given five weeks to germinate and establish before moving to the next phase of measuring the growth parameters (including number of leaves, plant height and dry weight) The best growing seedling was selected to remain in each pot as a main experimental plant where the data were gathered The selection of the best growing seedling was based on the comparison of plant height, number of true leaves and appearance of the plant All the excess sprouts were removed to avoid the nutrient and water competition Pots with no sprouts were transplanted with a seedling taken from the reserved seedling pots Transplanting was done as gentle as possible to prevent too much stress on the plant
For this study, plant growth was assessed using three parameters such as the number of leaves, height of plant and the plant’s dry weight (Andrew et al., 2000;
Kriedemann et al., n.d.) Specific techniques were provided to have an accurate and precise measurement of data with consideration to the characteristics of the three native plant species
Criteria were set to ensure a consistent observation of a “successful germination”
A seed was considered to have successfully germinated when two distinctly separate cotyledons (embryonic leaves) emerged This was valid for all three native plant species (First the Seed Foundation Organization, n.d)
Leaf number reflects the stages of development of the seedling Therefore, it was used as an additional parameter that was observed every week to acquire visual data for the assessment of plant development (Wood et al., 2000) In addition, the data gathered from the weekly development of leaves were compared with the weekly height of the plants Counting of leaves for each native plant species was carried out with different considerations and measures:
Paired leaves of Eucalyptus, with at least 0.5 cm size each, were counted excluding the cotyledons
Individual leaves, with a length of at least 0.5 cm, were counted
All the emerging leaf/ stem from the main plant stem (with at least 0.5cm length) were counted individually, excluding the last stem/ leaf at the top to avoid counting the phyllodes
Plant height was measured every week to provide data for plant growth (Andrew et al., 2000; Kriedemann, et al., n.d.) Specific measures with respect to the species’ differences were taken into consideration for height measurement (Heady, 1957)
Height was measured from the base of the plant at the level of the soil up to the top intersection of leaves
Plant height was measured from the base of the plant at the soil level up to the tip of the longest leaf
Height was measured from the base of the plant at the soil level up to the apical tip
At the last week of the experiment, all the experimental plants were harvested then oven-dried for 48 hours with a temperature of 95 o C to remove the water content before
36 weighing Growth is an irreversible increase in plant size and one of the parameters used to measure plant’s growth by measuring the quantitative change in biomass (weight) (Missouri Botanical Garden, 2003; Kriedemann et al., n.d.)
A prior chemical analysis on raw coarse reject samples were already provided by the mining company as a basis for any potential student project on coarse rejects rehabilitation for Pilbara mine To examine the effectiveness of the amended levels of fertiliser on the chemical/ nutrient content of the coarse rejects, chemical analysis was conducted Due to time restrictions, the chemical analysis of substrates was done halfway through the experimental process Three soil samples weighing ~100g were gathered from each of the treatments (control, low, medium and high) and the raw coarse rejects The methods used to analyze the soil chemical properties were provided in the appendix section (See Appendix F)
The statistical analyses of the data were performed using Microsoft Excel 2016 Analysis of Variance (ANOVA) single factor was carried out to determine if there was a significant difference between the growth performances of the three native plant species within different treatments of “coarse rejects” The ANOVA single factor was specifically used with the growth parameters of plant height and plant’s dry weight (biomass)
RESULTS
Seed Germination Rate
As shown in the bar graph (See Figure 3), all the species of E leucophloia, T pungens and A tumida germinated best on (T1) substrates with coarse rejects alone, having a germination of 90%, 24% and 41%, respectively Conversely, (T4) has the lowest germination for all the species, accounted to 8% in E leucophloia, 3% in T pungens and 9% in A tumida In addition, the data appeared to suggest that the germination rate, specifically on the species of E leucophloia and A tumida, were reduced as the level of fertiliser increases
Figure 3 The graph of seed germination rate of Eucalyptus leucophloia (Species 1), Triodia pungens (Species 2) and Acacia tumida (Species 3)
Number of Leaves
All the species (See Figure 4: Eucalyptus leucophloia, Figure 5: Triodia pungens and
Figure 6: Acacia tumida) showed the highest (weekly) number of leaves on (T2) substrates with 5g of fertiliser applied Moreover, it was observed that the number of leaves of the surviving plants of E leucophloia, T pungens and A tumida within (T3) and (T4) suddenly increased after week 11 While, all the species’ number of leaves in (T1) was found either slowly increasing or remains nearly the same number all throughout the weeks On the other hand, the number of leaves of E leucophloia and A tumida species in (T4) consistently declined to 0
Species 1 (EL) Species 2 (TP) Species 3 (AT)
Se ed G erm in at ion (% )
Figure 4 Weekly data for Eucalyptus leucophloia species' number of leaves
Figure 5 Weekly data for Triodia pungens species' number of leaves
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 15
Me an N u m b er o f L eav es
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 15
Me an N u m b er o f L eav es
Figure 6 Weekly data for Acacia tumida species' number of leaves
Height of Plant
The ANOVA results (See Table 2) on E leucophloia and A tumida proved that there was a significant difference among different levels of fertiliser treatments since their p- value (1.04E-09 and 7.83E-06, respectively) was less than the significance level of 0.05
On the other hand, the ANOVA result on T pungens species has a p-value of 0.85 which is greater than the significance level of 0.05 This indicates that there was not enough evidence to reject the null hypothesis
Table 2 ANOVA results of the plant height data of Eucalyptus leucophloia (Species 1), Triodia pungens (Species 2) and Acacia tumida (Species 3)
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 15
Me an N u m b er o f L eav es
SS df MS F P-value F crit
According to the mean height graph of all the species (See Figure 7), (T2) substrates with 5g of fertiliser showed the highest mean height (8.86cm, 7.34cm and 6.19cm, respectively) In addition, as the level of fertiliser increases to (T3) and (T4), it was observed that the plant height of all the species decreased
Figure7 The mean height graph of Eucalyptus leucophloia (Species 1), Triodia pungens (Species 2) and Acacia tumida (Species 3)
In terms of the weekly changes in plant height, the graph showed that the heights of all the species (See Figure 8: Eucalyptus leucophloia, Figure 9: Triodia pungens and Figure 10: Acacia tumida), were distinctly increasing in (T2) every week The surviving plants in (T3) and (T4) was also observed to increase in height after week 11 On the other hand, the weekly height of all the species in (T1) was either slowly increasing or remains nearly the same height weekly Conversely, E leucophloia and A tumida species’ height in (T4) dramatically declined to nearly 0 in the first weeks
Me an H eight o f Plan ts
Figure 8 Weekly data of Eucapyltus leucophloia species' mean plant height
Figure 9 Weekly data of Triodia pungens species' mean plant height
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 13 Week 15
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 13 Week 15
Figure10 Weekly data of Acacia tumida species' mean plant height
Dry weight (Biomass)
The ANOVA results (See Table 3) on the dry weights of E leucophloia and A tumida showed that there was a significant difference on the effects of different levels of fertiliser on plant’s dry weight Both have a p-value of 0.0001 and 0.01, respectively, which were less than the significance value of 0.05 On the other hand, T pungens has p- value of 0.20 which are greater than the significance value of 0.05, which indicates that there was no significant evidence to reject the null hypothesis
Table 3 ANOVA results on the biomass data of Eucalyptus leucophloia (Species 1), Triodia pungens (Species 2) and Acacia tumida (Species 3)
Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 13 Week 15
SS df MS F P-value F crit
Based on the graph (See Figure 11), in terms of plant’s dry weight, it was evident that all the species appeared to grow least on the substrates with coarse rejects alone (T1) Within the last few weeks of the experiment, the surviving plants in (T3) and (T4) appeared to grow well in terms of weight, which can be linked from the plant height and leaf number data results
Figure 11 The graph of mean dry weight of Eucalyptus leucophloia (Species 1), Triodia pungens
(Species 2) and Acacia tumida (Species 3)
Me an Dry W eight o f P lan ts (g)
Mean Dry Weight of Plants (Biomass)
Survivorship
Figure 12 Survivorship (%) of Eucalyptus leucophloia, Triodia pungens and Acacia tumida on different levels of fertiliser treatments (T1, T2, T3 and T4)
The generated bar graph on the survivorship percentage (See Figure 12), evidently showed that (T1) has the best survivorship having a 100% on all the native plant species
As observed in the graph, the survivorship of the species decreased as the fertiliser level increased from (T2) to (T4).
Chemical Analysis of Substrates
The results of the analysis report from the CSBP Soil and Plant Analysis Laboratory showed the chemical nutrient content of the raw coarse reject samples and each of the substrates treated with different levels of fertiliser (See Table 4)
Table 4 Summary table of chemical analysis of raw coarse rejects (CR) and the coarse reject substrates treated with different levels of fertiliser (T1, T2, T3 and T4) taken half-way through the experiment (at week 11)
Color LTGR GRBR GRBR GRBR GRBR
(SP2) Triodia pungens (SP3) Acacia tumida
Su rv iv o rs h ip (% )
Texture 1.5 (sand/ loam) 1.5 (sand/ loam)
Raw coarse rejects have a texture of 1.5, which is under the “sand/ loam” texture category with 5% gravel and a color variation of light gray As the results showed, coarse rejects have an Ammonium Nitrogen of 4.3mg/kg and a Nitrate Nitrogen of 14.3mg/kg
On the other hand, Phosphorus were found to be low having