Mining activities cause severe disturbance to the soil environment in terms of soil quality
and productivity and are of serious concern worldwide. Under South African legislation,
developers are required to ecologically rehabilitate damaged environments. The application
of agronomic approaches for the rehabilitation of coal discard sites has failed dismally in
the arid areas of southern Africa. It is obvious that compliance with mitigation and
rehabilitation requirements cannot be enforced without a thorough understanding of the
ecological principles that ensure ecological stability and subsequent sustainability of soil
ecosystems. Soil micro organisms are crucial role-players in the processes that make energy
and nutrients available for recycling in the soil ecosystem. Poor management practices and
other negative impacts on soil ecosystems affect both the physical and chemical properties
of soil, as well as the functional and structural properties of soil microbial communities.
Disturbances of soil ecosystems that impact on the normal functioning of microbial
communities are potentially detrimental to soil formation, energy transfers, nutrient
cycling, plant reestablishment and long-term stability. In this regard, an extensive overview
of soil properties and processes indicated that the use of microbiological and biochemical
soil properties, such as microbial biomass, enzymatic activity and the analysis of microbial
community structure by the quantification of specific signature lipid biomarkers are useful
as indicators of soil ecological stress or restoration properties because they are more
responsive to small changes than physical and chemical characteristics. In this study, the
relationship between the physical and chemical characteristics and different biological
indicators of soil quality in the topsoil covers of seven coal discard sites under
rehabilitation in South Africa, as well as three reference sites was investigated. Through the
assimilation of basic quantitative data and the assessment of certain physical, chemical and
biological properties of the topsoil covers obtained from the various coal discard sites as
well as the reference sites, the relative success or progress of rehabilitation and the possible
correlation between the biological indicators of soil quality and the establishment of self sustaining
vegetation covers was determined. Results from soil physical and chemical
analyses and percentage vegetation cover were correlated with the results obtained for the
functional and structural diversity of microbial communities at the various sites. All results
were investigated through statistical and multivariate analysis and the most prominent
physical and chemical parameters that influence the biological and biochemical properties
of the soil and possibly the establishment of self-sustainable vegetation cover on these
mine-tailing sites were identified. Results obtained from this study indicated no significant
difference (p>0.05) between the various discard sites based on conventional
microbiological enumeration techniques. However, significant differences (p<0.05) could
be observed between the three reference sites. All enzymatic activities assayed for the
rehabilitation sites, with the exception of urease and alkaline phosphatase displayed a
strong, positive association with the organic carbon content (%C). Ammonium
concentration had a weak association with all the enzymes studied and pH only showed a
negative association with acid phosphatase activity. A positive association was observed
between the viable microbial biomass, vegetation cover and the organic carbon content,
ammonium, nitrate and phosphorus concentrations of the soil. The various rehabilitation
and reference sites could be differentiated based on the microbial community structure as
determined by phospholipid fatty acid (PLFA) analysis. It is hypothesised that the
microbial community structure of the Hendrina site is not sustainable when classified along
an r-K gradient and that the high percentage of vegetation cover and high levels of
estimated viable microbial biomass are an artificial reflection of the current management
practices being employed at this site. Results obtained during this study, suggest that an
absence or low percentage of vegetation cover and associated lower organic matter content
of the soil have a significant negative impact on soil biochemical properties (enzymatic
activity) as well as microbial population size. Furthermore, prevailing environmental
physico-chemical and management characteristics significantly influences the vegetation
cover and subsequently the microbial community structure. The results indicate that the
microbial ecosystems in the coal discard sites could become more stable and ecologically
self-regulating, provided effective management to enhance the organic carbon content of
the soil. This could enhance nutrient cycling, resulting in changes of soil structure and
eventually an improved soil quality which could facilitate the establishment of self sustaining
vegetation cover. Results obtained during this study suggest that a polyphasic
assessment of physical and chemical properties; microbial activities by enzymatic analysis;
the characterisation of microbial community structure by analysis of phospholipid fatty
acids; and the multifactorial analysis of the data obtained can be used as complementary
assessment criteria for the evaluation of the trend of rehabilitation of mine tailings and
discard sites. Strategic management criteria are recommended based on the soil
quality environmental sustainability indices to facilitate the establishment of self sustainable
vegetation covers. The contribution of this research to soil ecology is
significant with regards to the intensive investigation and explanation of characteristics and
processes that drive ecological rehabilitation and determine the quality of the soil
environment. The multidisciplinary approach that is proposed could, furthermore, assist in
the successful rehabilitation and establishment of self-sustaining vegetation covers at
industrially disturbed areas, as well as assist in improving degraded soil quality associated
with both intensive and informal agriculture. Additionally, this approach could negate the
negative social and environmental impacts frequently associated with these activities. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2004.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/383 |
| Date | January 2003 |
| Creators | Claassens, Sarina |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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