Tatera brantsii was numerically dominant in the small mammal community on the plateaux
of the rehabilitated ash disposal sites of ESKOM's Hendrina Power Station in 1998 and 1999
(Vermaak 2000). The species seemed well adapted to exploit this environment and, through
biopedturbation, had altered the topsoil structure and chemistry. The consequences of this and
other activities also affected the rehabilitated plant community of the PFA-dam habitat.
Burrowing appeared limited to just under the topsoil layer, and seemed more extensive than
burrows of this species in natural ecosystems. The burrow system architecture was mapped
and quantified, and localised increases in nitrates, phosphorous and organic carbon in
immediately associated substrate were noted. However, this substrate enrichment was
transient, and disappeared following the abandonment, and subsequent collapse of burrow
systems, when gerbil colonies migrated away from the area. The mixing of soil horizons also
resulted in a more homogeneous substrate, which was more friable, and thus drier. The high
pH and salinity of the topsoil layer in areas undisturbed by gerbil burrowing, and
concentrations of particular elements associated with either the topsoil covering or the ash,
were reduced as a consequence of substrate mixing in disturbed areas. Gerbil impacts on the
substrate of this habitat seemed to promote pedogenesis, eliminating the sharp distinction
between the topsoil covering and the ash below, but the re-exposed ash of the burrow mounds
would become subject to erosion, and reduce the effectiveness of the rehabilitation effort.
Gerbil activities increased the number of plant species, especially ruderal forbs, comprising
the plant community of the PFA-dam habitat, but plant community diversity was not
significantly increased. However, numerical dominance by few tussock grass species was
diminished , possibly reflecting burial under mounds of excavated substrate. The biomass and
cover of some grass species were reduced in areas of gerbil impacts, and plant lifecycles
appeared to be completed sooner in areas affected by gerbil activities. These effects may be as
a result of the drier substrate produced following the collapse of the extensive network of
abandoned burrows. The succession of this plant community towards an underutilised
grassland state, the expected outcome of the rehabilitation effort, was minimally affected by
gerbil activities. The effects of T.brantsii activities in this PFA-dam habitat were not as
distinct as the effects noted by other authors studying fossorial rodent impacts in less
disturbed habitats. This could be because further disturbances in this habitat would merely
add to the currently disturbed state, whereas disturbance in more natural habitats, would show
more of a change from the initial state. / Thesis (M.Sc. (Zoology))--North-West University, Potchefstroom Campus, 2007.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/1246 |
| Date | January 2006 |
| Creators | Wright, Nevil Ian |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.002 seconds