Show simple item record

dc.contributor.advisorMalan, P. J.
dc.contributor.advisorSnyman, H. A.
dc.contributor.authorMyburgh, Tjaart
dc.date.accessioned2015-11-20T13:35:34Z
dc.date.available2015-11-20T13:35:34Z
dc.date.copyright2013-01
dc.date.issued2013-01
dc.date.submitted2013-01
dc.identifier.urihttp://hdl.handle.net/11660/1712
dc.description.abstractEnglish: Up to the 1980’s marginal soils were successfully ploughed for crop production, but unfortunately those soils soon proved to be marginal. Due to high input costs, the Department of Agriculture soon implemented the “soil conversion scheme” to promote the conversion of those ploughed marginal soils to permanent pastures. It was especially the low maize prices that triggered the conversion scheme in the 1980’s. Regardless the implementation of the soil conversion scheme, many farmers unfortunately just abandoned some of these marginal fields which resulted in many hectares of unproductive previously cultivated fields, being referred to as abandoned fields. The aim of this study was to investigate a few abandoned fields at a single location in the semi-arid central Free State in an attempt to gather information on the dynamics of such disturbed ecosystems and identify their restoration potential. The study investigated the interaction between plant and soil variables to quantify the impact of different soil physical and chemical characteristics on vegetation dynamics (species composition and density). The species richness, as well as the influence of different soil characteristics were determined to identify which might have the biggest influence on the recovery potential of the disturbed area. The soil seed bank was also investigated to quantify the survival potential of climax grass species on abandoned fields, and why these species do not establish voluntarily on these disturbed areas. The main aim of the study was to quantify the influence of soil characteristics on the vegetation dynamics of abandoned fields. The results clearly showed that marginal soils, withdrawn from cash-crop cultivation, are among the most seriously degraded areas with low soil fertility (N and C content). It is creating a more favourable habitat for pioneer grass species. This study sheds more light on the poor natural rehabilitation rate of abandoned fields in the semi-arid Free State Province of South Africa. It was proven that the establishment of climax vegetation might be largely influenced by phosphorus (P), cation exchange capacity (CEC), nitrogen (N), carbon (C), soil compaction and the composition of the soil seed bank. It was note worthy that some of the abandoned fields still showed very slow progress in natural restoration after 20 years. The areas that showed least recovery needed to be cultivated and established with a cultivated pasture like Digitaria eriantha sub. eriantha. On the other hand, other areas recovered to such an extent that oversowing or the placement of Themeda triandra sheafs might improve restoration. The best recovered areas can only be upgraded in productivity by scientific management strategies which include long resting periods. Drastic human interference is an absolute necessity to speed up the process of plant succession (rehabilitation). Future investigation might include long-term trials to monitor the reaction of vegetation and soil characteristics to the introduction of organic matter as well as the seed of climax grass species.en_ZA
dc.description.abstractAfrikaans: Marginale gronde was tot en met die 1980’s ekonomies suksesvol omgeploeg vir kontantgewasproduksie, maar was kort voor lank as onekonomies (marginaal) beskou. Hoë insetkostes het veroorsaak dat die Departement van Landbou ‘n grondomskakelingskema geïmplementeer het om die omgeploegde marginale gronde weer terug te skakel na natuurlike weiding. Dit was veral die lae mieliepryse wat die omskakeling teweeg gebring het. Ongeag die implementering van die grondomskakelingskema het sekere boere steeds geen restourasie aksies op van die marginale gronde toegepas nie. Die gevolg hiervan was dat baie hektare voorheen bewerkte lande onproduktief agtergelaat is sonder om aangeplante weidings daarop te vestig. Hierdie studie het ten doel gehad om hierdie onproduktiewe oulande, wat geleë is in die sentrale Vrystaat, te bestudeer ten einde die dinamika van versteurde ekosisteme te verstaan en dan die restorasie potensiaal daarvan te identifiseer. ‘n Studie oor die interaksies tussen plant en grond veranderlikes is onderneem om sodoende die impak van die grond se fisiese en chemiese karaktereienskappe te kwantifiseer. Die plantegroei dinamika, naamlik spesie samestelling en digtheid is ook gekwantifiseer. Die spesie samestelling, asook die invloed van grondeienskappe is bepaal om sodoende die komponente te identifiseer wat die grootste invloed op die herstelpotensiaal van die versteurde area sou hê. Die saadbank is ook bestudeer om sodoende te bepaal of daar wel klimaksgrassade teenwoordig is in die oulande, asook waarom die oulande nie natuurlik herstel nie. Die hoofdoel met die studie was om die invloed van grondeienskappe op die plantegroei dinamika van die oulande te kwantifiseer. Die resultate wys duidelik dat marginale gronde, wat onttrek is van kontantgewasverbouing, ernstige gedegradeerde areas is, met ‘n lae grond vrugbaarheid (C en N inhoud). Dit skep ‘n meer gunstige habitat vir pionier grasspesies. Die studie het ook meer lig gewerp op die swak natuurlike restourasie tempo van oulande in die semi-ariede Vrystaat Provinsie van Suid Afrika. Dit is bewys dat die vestiging van klimaksgrasse grootliks beïnvloed word deur fosfor (P), katioon uitruilbare kapasiteit (KUK), stikstof (N), koolstof (C), grond kompaksie en die samestelling van die grondsaadbank. Dit was merkwaardig dat die oulande stadige vordering getoon het na ‘n tydperk van 20 jaar van bewerkingsonttrekking. Daar word aanbeveel dat die swakste herstelde areas gerestoureer word met die vestiging van ‘n aangeplante weiding soos Digitaria eriantha sub. eriantha. Aan die anderkant kan areas wat reeds gevorderde herstel toon met Themeda triandra gerwe wat daarop gepak word aangevul word om restourasie te versnel. Die beste reeds herstelde areas kan met ‘n wetenskaplik gefundeerde veldbestuurspraktyk opgradeer word wat lang rus periodes insluit. ‘n Drastiese ingryping deur die mens is van kardinale belang om die proses van plant suksessie te versnel. Toekomstige ondersoeke moet langtermyn proewe insluit ten einde die plantegroei en die grondeienskappe se reaksies op die aanvulling van organiese materiaal en saad van klimaksgrasspesies te ondersoek.af
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDissertation (M.Sc.Agric. (Animal, Wildlife and Grassland Sciences))--University of the Free State, 2013en_ZA
dc.subjectSoil dynamicsen_ZA
dc.subjectSoil mechanicsen_ZA
dc.titleVegetation dynamics and soil characteristics of abandoned cultivated fieldsen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record