A plant ecological evaluation of mechanical bush thinning in Marakele Park, Limpopo Province
| dc.contributor.advisor | Smit, G. N. | |
| dc.contributor.advisor | Du Preez, P. J. | |
| dc.contributor.author | Pienaar, Francina Christina | |
| dc.date.accessioned | 2015-11-11T06:29:28Z | |
| dc.date.available | 2015-11-11T06:29:28Z | |
| dc.date.copyright | 2006-05-31 | |
| dc.date.issued | 2008-01-19 | |
| dc.date.submitted | 2006-05-31 | |
| dc.description.abstract | English: Bush encroachment is currently of great concern in Marakele Park. The main motivation for this study, conducted during the 2003/2004 and 2004/2005 seasons, was to determine whether mechanical bush thinning, executed with a mechanical mulc her, namely the Barko Tractor, was successful in solving the bush encroachment problem in the areas where it was applied. The specific objectives of this study were to identify, describe and interpret the plant communities of a section of Marakele Park, and to establish the influences of the thinning treatments on the dynamics of the ecosystem, more specifically the regrowth and browse production of the woody plants, the species composition and dry matter (DM) yield of the herbaceous layer and the short term changes in the soil. Eight experimental plots (3 treatments, 3 controls, 2 coppice) were selected in three veld types (Acacia mellifera – Grewia flava, Combretum apiculatum – Grewia flava and Acacia erubescens – Dichrostachys cinerea), in which tree thinning was applied during 2002 and 2003. Each plot was 100 m x 200 m (20 000 m2 = 2 ha) in size. The vegetation of the plots was phytosociologically studied during the 2003/2004 season with the aid of the Braun-Blanquet vegetation sampling method. A total of 80 relevés were surveyed and upon analysis 3 major communities, 7 communities, 6 sub-communities and 3 variants were identified. The woody layer was quantified with a quantitative description technique, which is incorporated in the BECVOL-model. A step point-method and the Ecological Index Method were used to determine the species composition and veld condition of the herbaceous layer, respectively, and a harvesting method was used to determine the DM yield and the associated grazing capacity. The thinning treatments resulted in an initial decreased number of woody plants, but since no follow-up treatments were applied, a large number of new seedlings have since established and the majority of cut-plants coppiced vigorously. However, approximately three years after the thinning treatments the leaf biomass (ETTE ha-1) of the woody layer increased due to regrowth and re-encroachment to a point where negative interactions between the woody and herbaceous plants, as a result of competition for soil water and nutrients, were evident again. The species diversity of the herbaceous layer increased after the thinning treatments, but species normally associated with disturbed and overgrazed veld still dominated. It was concluded that the herbaceous layer of Marakele Park is in a poor ecological state and indications are that it is still deteriorating. The herbaceous DM yield did not respond to the thinning treatments as expected, except in areas protected from grazing herbivores. As a result, the grazing capacity of the Park was comparatively low. It is clear that Marakele Park is currently overstocked with various game species, especially of high density, selective short grass grazers. Thinning treatments will therefore not be successful unless the herbivore game numbers are reduced. Few soil variables changed significantly as a result of the thinning treatments, but in view of the fact that soil enrichment is a slow process, monitoring of the soil variables is recommended. The specific soil propertie s did, however, have a decisive influence on the vegetation type. The Combretum apiculatum – Grewia flava plots occurred on relatively shallow, gravelly soil, while the Acacia dominated plots occurred on deeper, more fertile soil. It was also concluded that the Barko Tractor, due to its size and weight, had a negative impact on the soil, mainly in the form of soil compaction. Subhabitat differentiation, rainfall and herbivory played an important role in the study area and indicated that the vegetation of Marakele Park displays both equilibrial and non-equilibrial trends. The high grazing pressure, together with the high incidence of coppice and re-encroachment of woody plants after the initial thinning treatments, as well as the lack of follow-up treatments, effectively neutralised the success of the mechanical bush thinning treatments. In order to restore these thinned areas from re-encroachment it will be necessary to cut the plants again and combine this effort with a cut-stump treatment (chemical herbicide). Due to the negative impact of the Barko Tractor, it should not be used again during any follow-up operation. | en_ZA |
| dc.description.abstract | Afrikaans: Bosverdigting is op die oomblik ‘n groot bron van kommer in Marakele Park. Die hoof motivering vir die studie, uitgevoer tydens die 2003/2004 en 2004/2005 seisoen, was die evaluering van die sukses van meganiese bosuitdunning met ‘n meganiese maler, naamlik die Barko Trekker, toegepas op verdigte areas. Die spesifieke doelwitte van die studie was die identifisering, beskrywing en interpretasie van ‘n deel van Marakele Park se plantegroei gemeenskappe. Hierbenewens is die invloed van die uitdunningsbehandelings op houtagtige plante; die spesiesamestelling en droëmateriaal (DM) produksie van die kruidlaag en die korttermyn veranderinge van die grond ook bepaal. Agt eksperimentele plotte (3 behandelings, 3 kontroles, 2 hergroei) is in drie veldtipes (Acacia mellifera – Grewia flava, Combretum apiculatum – Grewia flava en Acacia erubescens – Dichrostachys cinerea) waar boomuitdunning toegepas is tydens 2002 en 2003, geselekteer. Elke plot was 100 m x 200 m (20 000 m2 = 2 ha) in grootte. Die plantegroei van die plotte is fitososiologies bestudeer tydens die 2003/2004 seisoen met behulp van die Braun-Blanquet plantopnamemetode. ‘n Totaal van 80 relevés is ondersoek waarna 3 hoof gemeenskappe, 7 gemeenskappe, 6 subgemeenskappe en 3 variante geïdentifiseer is. Die houtagtige komponent is gekwantifiseer met ‘n kwantitatiewe beskrywingstegniek wat in die BECVOL-model geïnkorporeer is. ‘n Stappunt metode en die Ekologiese Indeks Metode is gebruik om onderskeidelik die spesiesamestelling en veld toestand van die kruidlaag te bepaal. ‘n Oestegniek is gebruik om die DM produksie en geassosieërde weidingskapasiteit te bepaal. Die uitdunningsbehandelings het tot ‘n aanvanklike verlaging in die hoeveelheid houtagtige plante gelei, maar aangesien geen opvolg behandelings toegepas is nie, het ‘n groot aantal nuwe saailinge gevestig en die meerderheid van die gesnyde plante het sterk hergroei. As gevolg van die hergroei en herverdigting was die blaar biomassa (ETTE ha-1) van die houtagtige plante ongeveer drie jaar na die aanvanklike uitdunningsbehandelings weer by ‘n punt waar die negatiewe interaksie, as gevolg van kompetisie, tussen die houtagtige and kruidagtige plante, vir grondwater en nutriënte, sigbaar was. Die spesie diversiteit van die kruidlaag het verhoog na die uitdunningsbehandelings, maar dit was steeds gedomineer deur spesies wat normaalweg met versteurde en oorbeweide veld geassosieer word. Die afleiding is gemaak dat die kruidlaag van Marakele Park in ‘n swak ekologiese toestand is en volgens alle aanduidings steeds besig is om te verswak. Die DM produksie van die kruidlaag het nie na verwagting op die uitdunningsbehandelings gereageer nie, behalwe in die areas wat teen beweiding beskerm was. Gevolglik was die weidingskapasiteit van die park vergelykend laag. Dit is duidelik dat Marakele Park oorbewei word deur ‘n verskeidenheid wildspesies – veral hoë digtheid, selektiewe grasvreters – en dat die uitdunningsbehandelings nie suksesvol sal wees tensy die herbivoor wildgetalle verminder word nie. Weinig van die grondveranderlikes het verander as gevolg van die uitdunningsbehandelings, maar omdat grondverryking ‘n stadige proses is, word monitering van grondveranderlikes aanbeveel. Die spesifieke grondeienskappe het egter ‘n betekenisvolle effek op die plantegroei tipes gehad. Die Combretum apiculatum – Grewia flava persele het op relatief vlak, klipperige grond voorgekom, terwyl die Acacia gedomineerde persele op dieper, meer vrugbare grond voorgekom het. Die gevolgtrekking is gemaak dat die Barko Trekker, as gevolg van sy grootte en gewig, ‘n negatiewe impak op die grond gehad het, veral ten opsigte van grond kompaksie. Subhabitat verskille, reënval en beweiding het ‘n belangrike rol in die studie area gespeel en aanduidings is dat die plantegroei van Marakele Park beide ekwilibriale and nie -ekwilibriale neigings toon. Die hoë weidruk, tesame met die groot mate van hergroei en herverdigting van houtagtige plante na die aanvanklike uitdunningsbehandelings, asook die gebrek aan opvolg aksies, het die sukses van die meganiese bosuitdunningsbehandelings effektief geneutraliseer. Om die uitgedunde areas van herverdigting te laat herstel, sal dit nodig wees om die plante weer the sny, gekombineerd met die spuit van die gesnyde stompe met ‘n chemiese boomdoder. As gevolg van die grootte en onselektiewe werking van die Barko Trekker, word die gebruik daarvan vir die opvolgbehandeling nie aanbeveel nie. | af |
| dc.description.sponsorship | National Research Foundation (NRF) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/1597 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Dissertation (M.Sc. (Animal, Wildlife and Grassland Sciences))--University of the Free State, 2006 | en_ZA |
| dc.subject | Savanna ecology -- South Africa -- Limpopo | en_ZA |
| dc.subject | Invasive plants -- Ecology | en_ZA |
| dc.subject | Invasive plants -- South Africa -- Limpopo | en_ZA |
| dc.subject | Bush encroachment | en_ZA |
| dc.subject | Dry matter yield | en_ZA |
| dc.subject | Herbaceous layer | en_ZA |
| dc.subject | Herbivory | en_ZA |
| dc.subject | Mechanical bush thinning | en_ZA |
| dc.subject | Soil enrichment | en_ZA |
| dc.subject | Braun-Blanquet | en_ZA |
| dc.subject | BECVOL-model | en_ZA |
| dc.subject | Barko Tractor | en_ZA |
| dc.subject | Rainfall | en_ZA |
| dc.title | A plant ecological evaluation of mechanical bush thinning in Marakele Park, Limpopo Province | en_ZA |
| dc.type | Dissertation | en_ZA |