Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The Exxaro Namakwa Sands heavy mineral sands mine at Brand-se-Baai, on the west coast of
South Africa, is an important source of income, development and job-creation in the region.
However, this comes at a great environmental cost, as strip mining causes large scale destruction
of ecosystems through the complete removal of vegetation and topsoil. This is particularly
problematic in an environment, such as Namaqualand, where the arid and windy climate, as well
as saline and nutrient-poor soils, hamper rehabilitation. These environmental constraints create
the need to develop a site-specific rehabilitation program. At Namakwa Sands the objective of
rehabilitation is to “rehabilitate and re-vegetate disturbed areas and establish a self-sustaining
Strandveld vegetation cover in order to control dust generation, control wind and water erosion, as
well as restore land capability. In general, vegetation will be rehabilitated to a minimum grazing
standard capable of supporting small stock (sheep) grazing.” In order to achieve this Namakwa
Sands conducted rehabilitation experiments with topsoil replacement, seeding of indigenous
species and translocation of mature plants.
Monitoring is an important part of the rehabilitation process as it allows rehabilitation practitioners
to evaluate success and to adapt their management strategies and rehabilitation methods, as well
as to evaluate and, if necessary, change their rehabilitation objectives. This study forms part of the
monitoring process at Namakwa Sands. It assesses the success of sites that were experimentally
rehabilitated in 2001 and a site that was rehabilitated in 2008, using current practice, in order to
identify possible management requirements on rehabilitated sites as well as improvements on
rehabilitation objectives, methods and monitoring. This study also tests the Landscape Function
Analysis (LFA) as rehabilitation monitoring tool by correlating LFA indices with traditional
measurements of biophysical variables or their surrogates. Results showed that experimental sites were not successful in returning vegetation cover and plant
species richness to the required levels, but did achieve the grazing capacity objective. These sites
will need adaptive management to achieve the vegetation cover and plant species richness
objectives. The recently rehabilitated site achieved the three-year vegetation cover and plant
species richness objectives, as well as the grazing capacity objective, within two years after
rehabilitation. Namakwa Sands should therefore continue using the current rehabilitation method.
However, rehabilitation should be done in multiple stages in future to decrease the mortality of
nursery cuttings and to facilitate the return of late successional species to rehabilitated sites. The sustainability of small stock farming on rangeland with the grazing capacity that is identified as the
minimum objective is questionable and this merits further investigation. LFA can be a useful tool to
monitor nutrient cycling and soil stability at Namakwa Sands, provided that enough replicates are
used. However, LFA cannot be used as is to assess water infiltration at Namakwa Sands, due to
assumptions in the calculation of this index that do not hold for the Namaqualand environment.
Landscape functioning should be monitored annually to complement vegetation surveys. / AFRIKAANSE OPSOMMING: Die Exxaro Namakwa Sands swaarminerale-sandmyn by Brand-se-Baai, aan die weskus van
Suid-Afrika, is ‘n belangrike bron van inkomste, ontwikkeling en werkskepping in die streek. Daar
is egter negatiewe omgewingsimpakte aan verbonde, aangesien die strookmyntegniek
grootskaalse vernietiging van ekosisteme veroorsaak deur die algehele verwydering van die
plantegroei en bogrond. Dit is veral problematies in ‘n omgewing, soos Namakwaland, waar die
droë en winderige klimaat, asook die souterige en voedingstof-arme grond, rehabilitasie belemmer.
Hierdie beperkings wat deur die omgewing veroorsaak word skep die behoefte om ‘n
rehabilitasieprogram te ontwikkel wat spesifiek is tot die terrein. Die doel van rehabilitasie by
Namakwa Sands is om te rehabiliteer en herplant op versteurde gebiede en om selfonderhoudende
Strandveld plantbedekking te vestig om sodoende stofgenerering te beheer, om
wind- en watererosie te beheer, en om grondgebruik-vermoë te herstel. In die algemeen sal
plantbedekking gerehabiliteer word tot ‘n minimum weidingskapasiteit wat kleinveeweiding
(skaapweiding) kan onderhou. Om dit te bereik het Namakwa Sands rehabilitasie-eksperimente
uitgevoer met terugplasing van bogrond, saai van inheemse spesies en oorplanting van volwasse
inheemse plante. Monitering is ‘n belangrike deel van die rehabilitasieproses, aangesien dit rehabilitasie-praktisyns
in staat stel om sukses te evalueer en om bestuurstrategieë en rehabilitasiemetodes aan te pas,
sowel as om rehabilitasiedoelwitte te evalueer en, indien nodig, aan te pas. Hierdie studie vorm
deel van die moniteringsproses by Namakwa Sands. Dit assesseer die sukses op persele wat
eksperimenteel gerehabiliteer is in 2001 en ‘n perseel wat in 2008 gerehabiliteer is, volgens die
huidige praktyk, om moontlike bestuursbehoeftes op gerehabiliteerde persele en verbeteringe aan
rehabilitasiedoelwitte, -metodes en –monitering te identifiseer. Hierdie studie toets ook die
geskiktheid van die Landscape Function Analysis (LFA) as ‘n rehabilitasie-moniteringsinstrument
deur LFA-indekse met tradisionele metings van biofisiese veranderlikes of hul surrogate te
korreleer.
Resultate dui daarop dat eksperimentele persele nie suksesvol was om plantbedekking en
plantspesies-rykdom tot die vereiste vlakke te herstel nie, maar wel die weidingskapasiteit-doelwit
bereik het. Hierdie persele benodig aanpassingsbestuur om plantbedekking- en
plantspesiesrykdom-doelwitte te bereik. Die perseel wat onlangs gerehabiliteer is, het binne twee
jaar na rehabilitasie die drie-jaar plantbedekking- en plantspesiesrykdom-doelwitte, sowel as die weidingskapasiteitdoelwit bereik. Daarom moet Namakwa Sands voortgaan om die huidige
rehabilitasiemetode te gebruik. Rehabilitasie moet egter in die toekoms in veelvoudige stadiums
gedoen word om die mortaliteit van kwekery-steggies te verminder en om die terugkeer van laatsuksessionele
spesies na gerehabiliteerde persele te fasiliteer. Die volhoubaarheid van
kleinveeboerdery op weiveld met die minimum vereiste weidingskapasiteit word betwyfel en vereis
verdere ondersoek. LFA kan ‘n bruikbare instrument wees om siklering van voedingstowwe en
grondstabiliteit te monitor by Namakwa Sands indien genoeg repliserings gebruik word. LFA kan
egter nie in die huidige vorm gebruik word om waterinfiltrasie by Namakwa Sands te assesseer
nie, aangesien daar aannames in die berekening van die indeks is wat nie juis is in die
Namakwaland omgewing nie. Landskapfunksionering behoort jaarliks gemoniteer te word om
plantopnames aan te vul.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17886 |
| Date | 12 1900 |
| Creators | Pauw, Marco Johann |
| Contributors | Esler, Karen J., Le Maitre, David, Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 116 p. : ill., maps |
| Rights | Stellenbosch University |
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