The re-settlement of a ruined earth: Investigating the notion of “dwelling” through The design of a settlement in a post apocalyptic landscape
- Authors: Holdstock, Miranda
- Date: 2020-01
- Subjects: Landscape architecture , Restoration ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59051 , vital:60259
- Description: It is 2100 and anthropogenic climate change is well underway. Human civilisation has collapsed and those who survived the apocalypse are condemned to a life of wandering along a ruined earth; placeless; hopeless; searching for sanctuary. Our most elemental instincts will find this place, and build on it, as we always have. There, we will construct an order in the chaos of the apocalypse, by building dwelling. In an apocalyptic landscape our dependence on dwelling is only amplified. This dwelling, an evolved shelter, the beginnings of settlement, is the manifestation of its dweller’s psyche: the totality of the human mind; the conscious and unconscious; the seen and unseen. It is a chronicle of their dreamworld, memories and experiences. And, when the dweller is also the builder, the dwelling is crafted as an intricate memory-scape - which, in the climate apocalypse, is easily desecrated by the horrors of the end of the known world. Because, at our most vulnerable, when our mortality is confronted, a crisis of being occurs. Those who cannot withstand the physical and psychological suffering that the apocalypse inspires, will become non-beings: those who unconsciously long for death. To portray this, a climate refugee becomes the project’s protagonist. Through her psychological evolution, a dwelling will be built at a site to which she wandered, that represents a ruined earth, where the remains of human civilisation are left behind. Her architecture will embody principles that might facilitate survival in a hyper-harsh environment and safeguard her fragile psychology through bio-inspired and phenomenological design. The final product of this thesis will be a symbolic representation of human wandering, settling and dwelling - the origin of civilisation within chaos. Which, despite the denial of climate change, might be sooner than we think. , Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 2020
- Full Text:
- Date Issued: 2020-01
- Authors: Holdstock, Miranda
- Date: 2020-01
- Subjects: Landscape architecture , Restoration ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59051 , vital:60259
- Description: It is 2100 and anthropogenic climate change is well underway. Human civilisation has collapsed and those who survived the apocalypse are condemned to a life of wandering along a ruined earth; placeless; hopeless; searching for sanctuary. Our most elemental instincts will find this place, and build on it, as we always have. There, we will construct an order in the chaos of the apocalypse, by building dwelling. In an apocalyptic landscape our dependence on dwelling is only amplified. This dwelling, an evolved shelter, the beginnings of settlement, is the manifestation of its dweller’s psyche: the totality of the human mind; the conscious and unconscious; the seen and unseen. It is a chronicle of their dreamworld, memories and experiences. And, when the dweller is also the builder, the dwelling is crafted as an intricate memory-scape - which, in the climate apocalypse, is easily desecrated by the horrors of the end of the known world. Because, at our most vulnerable, when our mortality is confronted, a crisis of being occurs. Those who cannot withstand the physical and psychological suffering that the apocalypse inspires, will become non-beings: those who unconsciously long for death. To portray this, a climate refugee becomes the project’s protagonist. Through her psychological evolution, a dwelling will be built at a site to which she wandered, that represents a ruined earth, where the remains of human civilisation are left behind. Her architecture will embody principles that might facilitate survival in a hyper-harsh environment and safeguard her fragile psychology through bio-inspired and phenomenological design. The final product of this thesis will be a symbolic representation of human wandering, settling and dwelling - the origin of civilisation within chaos. Which, despite the denial of climate change, might be sooner than we think. , Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 2020
- Full Text:
- Date Issued: 2020-01
Factors affecting effective ecological restoration of Portulacaria afra (spekboom)-rich subtropical thicket and aboveground carbon endpoint projections
- Van der Vyver, Marius Lodewyk
- Authors: Van der Vyver, Marius Lodewyk
- Date: 2018
- Subjects: Restoration ecology , Plant conservation -- South Africa Portulacaria afra -- South Africa Shrubs -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23250 , vital:30468
- Description: Among the requirements to achieve effective ecological restoration on a landscape scale are a scientific underpinning, strong adaptive management and the setting of realistic endpoints. Efficacy and success depend on a complex interplay of factors of both local and regional influence. Biome-wide restoration experiments are rare, but valuable for evaluating efficacy of different protocols according to local context. The Thicket-wide Plot (TWP) experiment was initiated by the Subtropical Thicket Restoration Programme to inform landscape-scale ecological restoration of degraded Portulacaria afra (spekboom)-rich Subtropical Thicket. Thirteen different planting treatments of Portulacaria afra (spekboom) truncheons were planted as replicated rows on 0.25 ha fenced plots across the distribution range of spekboom-rich thicket habitat to better establish effective restoration protocols. I used a rule-based learning ensemble algorithm to evaluate 60 different predictors that potentially impact effective restoration, covering a range of climatic, topographic, edaphic, ecological and management related factors observed at 227 of these TWP plots. Percentage survivorship and aboveground biomass carbon sequestration rate (ABCsr) were taken as proxies for efficacy derived from subsequent monitoring data gathered 2 - 5 years after establishment, and a new allometric model I developed for spekboom. I found herbivory and identification of target habitat the two most important predictors of restoration efficacy, both well within the control of the practitioner. Highest survivorship and ABCsr were associated with larger truncheons planted deeper. The only exception to this pattern was found amongst the two smallest size truncheon categories. The application of external rooting hormone or watering treatment to truncheons were found of no significance to effective restoration, while all the pruned treatments were, in association with lesser planting depth, found to be significantly less effective than untreated truncheons planted deeper. When the restoration protocol is optimal (largest truncheons planted deepest in target habitats and protected from herbivory), my results show higher annual carbon sequestration rates (1.46 - 3.7 t C ha−1 yr−1 in aboveground biomass) than most older restoration sites that have been identified as benchmarks of success. In order to project ABC endpoints, I generated 40 new species-specific allometric models and used them to estimate biomass and carbon of intact and degraded stands on five sites spread out across the region. The highest AGC for stands in both intact and degraded states were estimated at 42.96 t Cha−1 and 12.98 t C ha−1 respectively, and the lowest at 26.32 t C ha−1 and 2.52 t C ha−1. Large canopy dominant (LCD) species contributed the largest AGC portion at three intact stands. The second largest portion was recorded for spekboom. The difference between paired stands on each sample site ranged between 23.8 and 32.8 t C ha−1, which provide a realistic target for biome-wide restoration that, when adopted together with current protocols, may be reached within three decades of inception.
- Full Text:
- Date Issued: 2018
- Authors: Van der Vyver, Marius Lodewyk
- Date: 2018
- Subjects: Restoration ecology , Plant conservation -- South Africa Portulacaria afra -- South Africa Shrubs -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23250 , vital:30468
- Description: Among the requirements to achieve effective ecological restoration on a landscape scale are a scientific underpinning, strong adaptive management and the setting of realistic endpoints. Efficacy and success depend on a complex interplay of factors of both local and regional influence. Biome-wide restoration experiments are rare, but valuable for evaluating efficacy of different protocols according to local context. The Thicket-wide Plot (TWP) experiment was initiated by the Subtropical Thicket Restoration Programme to inform landscape-scale ecological restoration of degraded Portulacaria afra (spekboom)-rich Subtropical Thicket. Thirteen different planting treatments of Portulacaria afra (spekboom) truncheons were planted as replicated rows on 0.25 ha fenced plots across the distribution range of spekboom-rich thicket habitat to better establish effective restoration protocols. I used a rule-based learning ensemble algorithm to evaluate 60 different predictors that potentially impact effective restoration, covering a range of climatic, topographic, edaphic, ecological and management related factors observed at 227 of these TWP plots. Percentage survivorship and aboveground biomass carbon sequestration rate (ABCsr) were taken as proxies for efficacy derived from subsequent monitoring data gathered 2 - 5 years after establishment, and a new allometric model I developed for spekboom. I found herbivory and identification of target habitat the two most important predictors of restoration efficacy, both well within the control of the practitioner. Highest survivorship and ABCsr were associated with larger truncheons planted deeper. The only exception to this pattern was found amongst the two smallest size truncheon categories. The application of external rooting hormone or watering treatment to truncheons were found of no significance to effective restoration, while all the pruned treatments were, in association with lesser planting depth, found to be significantly less effective than untreated truncheons planted deeper. When the restoration protocol is optimal (largest truncheons planted deepest in target habitats and protected from herbivory), my results show higher annual carbon sequestration rates (1.46 - 3.7 t C ha−1 yr−1 in aboveground biomass) than most older restoration sites that have been identified as benchmarks of success. In order to project ABC endpoints, I generated 40 new species-specific allometric models and used them to estimate biomass and carbon of intact and degraded stands on five sites spread out across the region. The highest AGC for stands in both intact and degraded states were estimated at 42.96 t Cha−1 and 12.98 t C ha−1 respectively, and the lowest at 26.32 t C ha−1 and 2.52 t C ha−1. Large canopy dominant (LCD) species contributed the largest AGC portion at three intact stands. The second largest portion was recorded for spekboom. The difference between paired stands on each sample site ranged between 23.8 and 32.8 t C ha−1, which provide a realistic target for biome-wide restoration that, when adopted together with current protocols, may be reached within three decades of inception.
- Full Text:
- Date Issued: 2018
A hybrid approach to beach erosion mitigation and amenity enhancement, St Francis Bay, South Africa
- Authors: Anderson, Dylan Rory
- Date: 2008
- Subjects: Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10611 , http://hdl.handle.net/10948/d1008192 , Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Description: The St Francis Bay beach has experienced chronic erosion over the past three decades. This erosion can largely be attributed to the stabilisation of a large coastal dunefield which contributed +/- 80 percent of the sand supply to St Francis Bay. Stabilisation began in 1975 initially using plant cuttings and followed by the development of the Santareme holiday suburb resulting in complete stabilisation by 1985. Effects were felt from the late 1970‟s and since then the beach has retreated at between 0.5 - 3 m.yr-1. Erosion has encroached on beachfront properties since the early 1990‟s, leading to the placement of 3-4 m high unsightly rock revetments along much of the beach. Where properly maintained these structures have proved successful in protecting the properties behind, however exacerbated erosion of areas in front and adjacent to these structures is evident. Currently no dry beach is present at high tide for most of the year, leading to a significant reduction in beach amenity value. Several technical studies to investigate remediation of this beach erosion problem have been conducted since the early 1990‟s. This study includes investigations into the processes and dynamics of the existing environment and evaluation of the effectiveness and impacts of several elements of a hybrid approach to coastal protection and amenity enhancement for St Francis Bay beach. This proposal incorporated: Multi-Purpose Reefs (MPR‟s) offshore, for coastal protection and amenity enhancement in terms of surfing; beach nourishment with sand from the Kromme Estuary and dune rehabilitation with appropriate native sand binding species. Extensive fieldwork and data collection were conducted, this included: a series of bathymetric surveys; diving surveys and a helicopter flight; sediment sampling; beach profiling and deployment of a wave/current meter. Analysis of these data provided a greater understanding of the existing environment and dynamics of St Francis Bay and provided reliable inputs for numerical modelling. Numerical and physical modelling was conducted to assess the existing processes and conduct MPR design testing. In addition calibrated hydrodynamic modelling of the Kromme Estuary was conducted in order to assess the impacts of sand extraction from the large sand banks within the mouth of the Kromme Estuary for use as beach nourishment. Comparison of bathymetric survey data collected by the author in 2005/06 with survey data collected by the South African Navy Hydrographic Office (SANHO) in 1952 suggest a major loss of sand from the bay, with a volume difference of some 8.8 X 106 m3 calculated. Greater losses were measured between 10-15 m water depths, with shallow areas of +/- 5 m water depth, remaining more stable. This can be attributed to the presence of shallow reef and rocky substrate through much of the bay at this depth range. Monthly RTK GPS survey data from September 2006 to September 2007 indicates a total loss of 40 000 m3 over this period with the greatest losses measured along the northern part of the beach. The greatest losses were measured after large long period waves from a southerly to south-easterly direction occurred in conjunction with equinox tides in mid March 2007. Sediment sampling at over 100 locations within the bay indicated a high percentage of reef (26 percent) and fairly consistent grain size in the fine to medium size class throughout much of the beach, bay and large sand bank within the estuary. While the majority of the South African Coast is exposed to the predominant south westerly winds and waves, St Francis Bay‟s orientation means that waves from a south easterly to easterly direction dominate. The results of the detailed numerical modelling of the hydrodynamics agree with previous calculations and modelling results which concluded that strong unidirectional longshore currents occur along the headland due to the oblique angle of wave incidence and the close to parallel angle of wave incidence along the beach leads to weak longshore currents of variable direction. Erosion along St Francis Bay beach is a result of cross-shore erosion due to large waves from a southerly to easterly direction. Detached breakwaters are the most effective form of coastal protection in these environments and MPR‟s offer additional benefits over traditional breakwater structures. Results of empirical calculations and numerical modelling indicate that the MPR‟s will provide effective coastal protection through the processes of wave dissipation, wave rotation, salient formation and alteration of nearshore circulation. Physical modelling results allowed the MPR design to be assessed and refined in terms of surfing amenity enhancement and construction constraints. In addition numerical modelling results indicate that impacts due to the extraction of up to 600 000 m3 of sand from the lower Kromme Estuary result in highly localised velocity reduction, mainly limited to the extraction areas. The calculated rate of sediment influx into the lower Kromme Estuary indicates that limited extraction, in the order of 20 000 – 40 000 m3 per year, should be sustainable in the long term. Sedimentation of the lower estuary over recent years has had negative recreational and ecological impacts, through reduced navigability and water exchange respectively. Therefore both the estuary and beach systems prove to benefit from this approach. Although not investigated in detail as part of this study, evidence from numerous projects worldwide indicates that foredunes help to trap wind-blown sand on the beach and form a buffer to storm erosion, therefore dune rehabilitation with native sand-binding plant species was recommended as the third element of the proposed remediation of St Francis Bay beach.
- Full Text:
- Date Issued: 2008
- Authors: Anderson, Dylan Rory
- Date: 2008
- Subjects: Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10611 , http://hdl.handle.net/10948/d1008192 , Beach erosion -- South Africa -- St Francis Bay , Shore protection -- South Africa -- St Francis Bay , Restoration ecology
- Description: The St Francis Bay beach has experienced chronic erosion over the past three decades. This erosion can largely be attributed to the stabilisation of a large coastal dunefield which contributed +/- 80 percent of the sand supply to St Francis Bay. Stabilisation began in 1975 initially using plant cuttings and followed by the development of the Santareme holiday suburb resulting in complete stabilisation by 1985. Effects were felt from the late 1970‟s and since then the beach has retreated at between 0.5 - 3 m.yr-1. Erosion has encroached on beachfront properties since the early 1990‟s, leading to the placement of 3-4 m high unsightly rock revetments along much of the beach. Where properly maintained these structures have proved successful in protecting the properties behind, however exacerbated erosion of areas in front and adjacent to these structures is evident. Currently no dry beach is present at high tide for most of the year, leading to a significant reduction in beach amenity value. Several technical studies to investigate remediation of this beach erosion problem have been conducted since the early 1990‟s. This study includes investigations into the processes and dynamics of the existing environment and evaluation of the effectiveness and impacts of several elements of a hybrid approach to coastal protection and amenity enhancement for St Francis Bay beach. This proposal incorporated: Multi-Purpose Reefs (MPR‟s) offshore, for coastal protection and amenity enhancement in terms of surfing; beach nourishment with sand from the Kromme Estuary and dune rehabilitation with appropriate native sand binding species. Extensive fieldwork and data collection were conducted, this included: a series of bathymetric surveys; diving surveys and a helicopter flight; sediment sampling; beach profiling and deployment of a wave/current meter. Analysis of these data provided a greater understanding of the existing environment and dynamics of St Francis Bay and provided reliable inputs for numerical modelling. Numerical and physical modelling was conducted to assess the existing processes and conduct MPR design testing. In addition calibrated hydrodynamic modelling of the Kromme Estuary was conducted in order to assess the impacts of sand extraction from the large sand banks within the mouth of the Kromme Estuary for use as beach nourishment. Comparison of bathymetric survey data collected by the author in 2005/06 with survey data collected by the South African Navy Hydrographic Office (SANHO) in 1952 suggest a major loss of sand from the bay, with a volume difference of some 8.8 X 106 m3 calculated. Greater losses were measured between 10-15 m water depths, with shallow areas of +/- 5 m water depth, remaining more stable. This can be attributed to the presence of shallow reef and rocky substrate through much of the bay at this depth range. Monthly RTK GPS survey data from September 2006 to September 2007 indicates a total loss of 40 000 m3 over this period with the greatest losses measured along the northern part of the beach. The greatest losses were measured after large long period waves from a southerly to south-easterly direction occurred in conjunction with equinox tides in mid March 2007. Sediment sampling at over 100 locations within the bay indicated a high percentage of reef (26 percent) and fairly consistent grain size in the fine to medium size class throughout much of the beach, bay and large sand bank within the estuary. While the majority of the South African Coast is exposed to the predominant south westerly winds and waves, St Francis Bay‟s orientation means that waves from a south easterly to easterly direction dominate. The results of the detailed numerical modelling of the hydrodynamics agree with previous calculations and modelling results which concluded that strong unidirectional longshore currents occur along the headland due to the oblique angle of wave incidence and the close to parallel angle of wave incidence along the beach leads to weak longshore currents of variable direction. Erosion along St Francis Bay beach is a result of cross-shore erosion due to large waves from a southerly to easterly direction. Detached breakwaters are the most effective form of coastal protection in these environments and MPR‟s offer additional benefits over traditional breakwater structures. Results of empirical calculations and numerical modelling indicate that the MPR‟s will provide effective coastal protection through the processes of wave dissipation, wave rotation, salient formation and alteration of nearshore circulation. Physical modelling results allowed the MPR design to be assessed and refined in terms of surfing amenity enhancement and construction constraints. In addition numerical modelling results indicate that impacts due to the extraction of up to 600 000 m3 of sand from the lower Kromme Estuary result in highly localised velocity reduction, mainly limited to the extraction areas. The calculated rate of sediment influx into the lower Kromme Estuary indicates that limited extraction, in the order of 20 000 – 40 000 m3 per year, should be sustainable in the long term. Sedimentation of the lower estuary over recent years has had negative recreational and ecological impacts, through reduced navigability and water exchange respectively. Therefore both the estuary and beach systems prove to benefit from this approach. Although not investigated in detail as part of this study, evidence from numerous projects worldwide indicates that foredunes help to trap wind-blown sand on the beach and form a buffer to storm erosion, therefore dune rehabilitation with native sand-binding plant species was recommended as the third element of the proposed remediation of St Francis Bay beach.
- Full Text:
- Date Issued: 2008
Interaction between arbuscular mycorrhizal fungi and soil microbial populations in the rhizosphere
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
- Authors: Ike-Izundu, Nnenna Esther
- Date: 2008
- Subjects: Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3962 , http://hdl.handle.net/10962/d1004021 , Mycorrhizas , Mycorrhizal fungi , Vesicular-arbuscular mycorrhizas , Soil microbiology , Rhizosphere , Revegetation , Restoration ecology
- Description: This study examined the rehabilitation potential of AM fungi with organic and inorganic fertilisers under pot and field trial conditions as well as their interaction with rhizospheric organisms and specific functional groups. In addition, the study highlighted the effects of land-use management on AM fungal populations in soil and the mycorrhizal status of some selected plants from one of the study sites. The study focussed on two sites that differ in operational activities and these included a mined area that was to be rehabilitated and a commercial farming site. A pot trial was conducted using an overburdened soil resulting from kaolin clay mining. Pots were seeded with Cynodon dactylon and treated with either Organic Tea or NPK (3:1:5) fertiliser, with or without AM fungal inoculum. The compatibility of these fertilisers with AM fungi was assessed by plant growth and percentage root colonisation. Maximum shoot height and plant biomass were observed at the 28th week with NPK (3:1:5) fertiliser supporting mycorrhizal colonisation by 80%. The result indicated the potential of AM fungi to be used in rehabilitation with minimal phosphate fertiliser. Similarly, a field trial was set-up using 17 x 17 m[superscript 2] plots in the mining site that were treated with the same organic and inorganic fertilisers as well as with AM fungal inoculum in different combinations. The interaction between AM fungi and soil microbial population was determined using culture dependent and culture independent techniques. The culture dependent technique involved the use of soil dilution and plating on general purpose and selective media. The result showed that there was no change in the total culturable bacterial number in the untreated and AM fungal treated plots, while a change in species composition was observed in the functional groups. Different functional groups identified included nitrogen fixing bacteria, pseudomonads, actinomycetes, phosphate solubilisers and the fungal counterparts. Gram-positive bacteria were observed as the predominant phenotypic type, while nitrogen fixers and actinomycetes were the predominant functional groups. Species identified from each functional group were Pseudomonas fulva, Bacillus megaterium, Streptomyces and actinomycetales bacteria. Meanwhile, fungi such as Ampelomyces, Fusarium, Penicillium, Aspergillus, Cephalosporium and Exserohilium were identified morphologically and molecularly. Furthermore, the mining site had a significantly higher bacterial number than the farming site thereby indicating the effects of land-use management on culturable bacterial numbers. The culture independent technique was carried out by cloning of the bacterial 16S rDNA and sequencing. Identified clones were Bradyrhizobium, Propionibacterium and Sporichthya. A cladogram constructed with the nucleotides sequences of identified functional species, clones and closely related nucleotide sequences from the Genbank indicated that nucleotide sequences differed in terms of the method used. The activity and establishment of the introduced AM fungal population was determined by spore enumeration, infectivity assay, percentage root colonisation and assessment of glomalin concentrations. The results indicated that the two land use types affected AM fungal populations. However, the establishment of AM fungi in the farming site was more successful than in the mining site as indicated by the higher infectivity pontential. Selected host plants, which were collected around the mine area, were observed to be mainly colonised by AM fungi and these were identified as Pentzia incana, Elytropappus rhinocerotis, Euphorbia meloformis, Selago corymbosa, Albuca canadensis and Helichrysum rosum. These plant species were able to thrive under harsh environmental conditions, thereby indicating their potential use as rehabilitation host plants. Generally, the findings of this study has provided an insight into the interaction between arbuscular mycorrhizal fungi and other soil microorganisms in two fields with differing land use management practices.
- Full Text:
- Date Issued: 2008
- «
- ‹
- 1
- ›
- »