The rehabilitation of degraded soils, such as those associated with post-mining sites, requires
knowledge of the soil ecosystem and its physical, chemical, and biological composition in order for
rehabilitation efforts to fulfil the long-term goal of reconstructing a stable ecosystem for
rehabilitated mine soil. This study addresses the need for appropriate assessment criteria to
determine the progress of rehabilitation and subsequently the success of management practices.
Significant contributions made by this investigation included the establishment of minimum
and maximum values for microbial community measurements from two case studies of
rehabilitated coal discard sites. Furthermore, it was shown that there was no relationship between
changes in microbial community function and structure and the rehabilitation age of the sites.
Following this, the considerable impact of management practices on microbial communities was
illustrated.
The first part of the study investigated the temporal changes in microbial community
function and structure in a chronosequence of rehabilitated coal discard sites aged 1 to 11 years.
The most important observation made during the investigation of the microbial communities in the
different aged soil covers of the rehabilitated coal discard sites, was that there was no relationship
between rehabilitation age and microbial activity or abundance of certain microbial groups. What
was responsible for a clear differentiation between sites and a shift in microbial community
attributes was the management practices applied.
A comparison of two chronosequences of rehabilitated coal discard sites was achieved by an
application of the 'space-for-time' hypothesis. Sites of different ages and at separate locations
('space') were identified to obtain a chronosequence of ages ('time'). The two chronosequences
included sites aged 1 to 11 years (chronosequence A) and 6 to 17 years (chronosequence B),
respectively. Sites in the same chronosequence were managed identically, while there was a
distinct difference in management practices applied to each chronosequence. The long-term effect
of the different management regimes on the soil microbial community function and structure was
investigated. Again, there was no relationship between rehabilitation age and microbial community
measurements. Fluctuations of selected microbial properties occurred in both chronosequences and
similar temporal trends existed over the rehabilitation periods. However, the less intensively
managed chronosequence (8) seemed more stable (less fluctuation occurred) over the
rehabilitation period than the more intensively managed chronosequence (A). It was therefore
concluded that the microbial communities in the less managed sites maintained their functional
and structural integrity within bounds in the absence of management inputs or disturbance. While
there was similarity in the trends over time for individual microbial community measurements, the
seemingly more stable conditions in chronosequence 6 are important in terms of the goal of
rehabilitation. / Thesis (Ph.D. (Environmental Science)--North-West University, Potchefstroom Campus, 2007
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/1295 |
| Date | January 2007 |
| Creators | Claassens, Sarina |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
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