Thesis (MSc)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Arid and semi-arid rangelands of the Nama-Karoo Biome are believed to have changed
considerably since the arrival of domestic livestock in the veld. Severe grazing pressure
is considered to be one of the prime factors responsible for the perceived degradation of
vegetation and concurrent soil degradation. To understand the process of degradation
and to make further recommendations for future veld restoration, a large-scale project
was undertaken in the Eastern Cape. This project focused on the role that landscape
heterogeneity plays in providing refuges for plant species. The key question asked in
this project was: What role do these hypothetically less grazed mesas play in the
conservation of rangelands in the Nama-Karoo of the Eastern Cape?
This study, a component of the larger project, investigated grazing and soil landscape
gradients on- and off- the three mesas (Tafelberg, Folminkskop and Buffelskop) in the
Middelburg District of the Eastern Cape, South Africa and the possible influences that
they might have on the veld. The flats surrounding the mesas were mostly used as
grazing camps in contrast to the plateaux of the mesas, which had varied levels of
accessibility.
In the absence of direct observations, the primary objective of the study was to test the
differential dung pellet abundance and impact of animals on different parts of the
landscape. As such, dung pellet counts in this study were correlated with surrogates of
soil physical properties including bare ground, trampling and litter cover. Variation in
dung pellet density was found at the different habitats (flats, slopes and plateaux) of all
mesas. The flats to the north-eastern and south-western of Tafelberg mesa were found
to be more heavily utilized by livestock and herbivores, while the plateaux and southeastern
slopes of Folminkskop and Buffelskop were also utilized by grazers. The
Tafelberg mesa was the only study site that was consistent with the hypothesis which
stated that grazers would be less concentrated on the plateau compared to the
surrounding flats due to its inaccessibility, whilst the high mean dung pellet density on
the plateaux of the smaller Folminkskop and Buffelskop mesas due to easier access
contradicted the original hypothesis. It appeared that dung pellet density did not clearly
turn out to be an indicator of habitat use in this study, but showed where slopes and
plateaux were accessible to herbivores, as in the case for the Buffelskop mesa, a higher abundance of dung pellets were found suggesting that higher intensities of habitat use
took place.
During this study a strong pattern was observed of bare soil patches on the flats
surrounding the mesas. There was a decrease in percentage of bare soil along the
gradient of the three mesas with a high percentage of bare soil on the plateaux of the
mesas. A significant correlation was found between bare soil and dung pellet density.
However, the plateaux of Folminkskop and Buffelskop had a high percentage of bare soil
compared to the plateau of Tafelberg mesa. Farmers mainly used these smaller mesas
as grazing camps for their livestock and herbivores. A positive correlation between bare
soil and litter cover of the different habitats was evident in this study. A lower
percentage of litter cover at these sites was associated with a high percentage of bare
soil. Litter is very important in a healthy vegetation community in terms of nutrient
cycling and fertile patches.
A detailed assessment of soil chemical and physical properties would reveal, firstly, if
vegetation change is better explained by soil or grazing effects and, secondly, if changes
in soil have resulted from land use. Differences in macro- and micro-site variations
between open-canopy (between shrubs) and closed-canopy (under shrubs) sites for
each habitat were determined to differentiate between local scales due to land use and
landscape scales due to geomorphology. The results suggested that carbon,
phosphorus, calcium, magnesium, copper and manganese levels in soils at landscape
scale better explain vegetation changes between habitats. At a local scale (open- and
closed-canopy sites) land use was responsible for little changes in soils. Changes in
only soil potassium, zinc and boron elements were actually a consequence of local
scales due to land use. The soil nutrient content on the slopes appeared to be
intermediate between the flats and plateaux of all three mesas. It appeared that dolerite
capped Tafelberg and Folminkskop mesas had high silt and clay content, while
Buffelskop (sandstone) mesa had a lower silt and clay content. Consequently, the
texture and parent material of the soils contributed to the variations in soil nutrient
composition between these mesas. High infiltration rate together with low nutrient
content on the flats clearly showed that these flats, surrounding the mesas were
degraded. The high infiltration rates were caused by high activity by livestock and other
indigenous animals on the flats which breaks the surface crusting of bare soil and improve infiltration. It was concluded that high levels of grazing at these sites have also
altered the textural and soil properties.
Endozoochory dispersal and the deposition of dung pellets in areas of small patch
disturbances play an important role in veld regeneration in degraded areas. Dung
pellets collected from permanent study sites on the southeastern and northwestern flats
and slopes, and all the study sites on the plateau of Tafelberg mesa, was sown in
seedling trays, watered and monitored for seedling germination. Species list were then
compared to below-ground soil seed bank data and above-ground vegetation data
collected by other researchers at the same permanent study sites. Higher seedling
percentages were recorded from dung pellets collected on the flats than on the plateau.
A total of sixteen species were found to germinate in dung pellets collected on the flats
compared to ten species germinating in dung pellets collected on the slopes and two
species on the plateau of Tafelberg mesa. The seeds that germinated represent a
variety of palatable grasses and shrub species. Aristida sp., Eragrostis bicolor,
Eragrostis ch/orome/as and Eragrostis obtusa were palatable grasses recorded for dung
pellets collected on the flats. Of the species recorded, Aristida sp., Chenopodium sp.
and Pentzia sp. were found in dung pellets but were not recorded in parallel soil seedbank
and vegetation studies.
Successful restoration of veld conditions requires strict grazing management practices.
Germination of seed in dung pellets might be considered to be a valuable means of
indicating restoration potential and rangeland conditions for the identification of both
degraded and conservation worthy areas. With appropriate land management skills and
restoration measures, these challenges can be constructively and creatively faced. / AFRIKAANSE OPSOMMING: Daar word geglo dat die ariede en sernl-arlede weivelde van die Nama-Karoo bioom
aansienlik verander het sedert die aankoms van mak lewende hawe in die veld. Swaar
weidingsdruk word beskou as een van die vernaamste faktore verantwoordelik vir die
waarneembare oorbeweiding van plantegroei en die gelyktydige grond agteruitgang
(degradasie). Ten einde die proses van degradasie beter te verstaan, en om verdere
aanbevelings te kan maak vir toekomstige veld herstel, is huidiglik 'n grootskaalse projek
in die Oos-Kaap aan die gang oor die rol wat landskap ongelyksoortigheid speel in die
voorsiening van skuiling aan plant spesies.
Hierdie studie ondersoek weiding en grondlandskap gradiënte (op en af) van die drie
mesas (Tafelberg, Folminkskop en Buffelskop) in die Middelburg streek van die Oos-
Kaap, Suid-Afrika en die moontlike invloed wat hierdie gradiënte op die veld het. Die
vlaktes was meestal gebruik vir weidingskampe in teenstelling met die kruin van die
mesas. Hierdie studie het duidelike patrone vir habitat-gebruik op die vlaktes, hange en
kruine van al die mesas aangetoon. Die vraag wat gestel was, was watter rol speel
hierdie hipoteties minder beweide mesas in die bewaring van weivelde in die Nama-
Karoo van die Oos-Kaap?
Hierdie studie toets nie direk vir mis verspreiding as 'n plaasvervanger vir dier
verspreiding in die landskap sedert werklike dier getalle nie oorweeg was nie. In die
awesigheid van direkte waarneming, die primêre doelwit was om te toets die
differensiaal misdigtheid en die impak van diere op verskillende dele van die landskap.
Mis getalle in hierdie studie was gekorreleer met plaasvervangers van fisiese
eienskappe insluitent onbedekte grond, vertrapping en droë plant material decking.
Variasie in misdigtheid was gevind by die verskillende habitate (vlaktes, hange en
kruine) van all die mesas. Die vlaktes aan die noord-oostelike en suid-westelike kante
van die Tafelberg mesa was meer hewig benut deur lewende hawe en hêrbivore, terwyl
die kruine en suid-oostelike hange van Folminkskop en Buffelskop ook gebruik was deur
weidende diere. Die Tafelberg mesa was die enigste studie area wat konsekwent was
met die hipotese, terwyl die hoë gemiddeld misdigtheid op die kruine van die kleiner
Folminkskop en Buffelskop mesas, as gevolg van makliker toegang weerspreek die
oorspronklike hipotese. Dit blyk dat misdigtheid duidelik opkom as 'n nie aanwyser
habitat-gebruik in hierdie studie, maar wys well waar hange en kruine toeganklik was vir herbivore, soos in die geval van Buffelskop mesa, oorvloed van mis was gevind wat
voorstel dat hoer intensiteit van habitat-gebruik voorgekom het.
'n Duidelike patroon is waargeneem tydens hierdie studie van onbedekte grond areas
op die vlaktes rondom mesas. Daar was 'n afname in persentasie onbedekte grond
langs die gradiënt van die drie mesas. Die kruine van Folminkskop en Buffelskop toon
hoër persentasies onbedekte grond in vergelyking met die kruin van die Tafelberg mesa.
Daar is 'n betekenisvolle korrelasie tussen onbedekte grond en misdigtheid gevind.
Boere gebruik hierdie kleiner mesas hoofsaaklik as weidingskampe vir hulle lewende
hawe en hêrbivore. In hierdie studie is daar 'n positiewe korrelasie gevind tussen
onbedekte grond en droë plant material decking van die verskillende habitatte. Droë
plantmateriaal bedekking speel 'n baie belangrik rol in 'n gesonde plant gemeenskap in
terme van voedingsirkulering en vrugbare kolle.
'n Breedvoerige skatting van grond chemise en fisiese eienskappe wou openbaar
eerstens of plantegroei verandering beter verklaar word deur grond of weiding effekte en
tweedens, of verandering in grond veroorsaak was deur land-gebruik. Verskille in
makro- en mikroterrein-wisseling tussen oop-blaredak (tussenplantruimtes) en toeblaredak
(onderplantdekking) terreine vir elke habitat was bepaal om te onderskei
tussen lokaal effek as gevolg van land-gebruik en landskap effek as gevolg van
geomorfologie. Die resultate stel voor dat koolstof, fosfor, kalsium, magnesium, koper
en mangaan vlakke in die grond by landskap effek beter plantegroei verandering tussen
habitate verduidelik. By 'n lokaal effek (oop-en toe-blaredak terreine) land-gebruik was
verantwoordelik vir min veranderinge in grond. Verandering in grond kalium, sink en
baron elemente was werklik 'n gevolg van lokaal effek as gevolg van land-gebruik. Die
nutrient inhoud van grond op die hange blyk intermediêr te wees tussen die van die
vlaktes en kruine van al drie mesas. Hierdie studie toon ook dat die geologie en
topografie van hierdie mesas die grond tekstuur en nutrient samestelling op en af van
die mesas beinvloed. Dit wil voorkom asof die dolerite bedekte Tafelberg en
Folminkskop mesas, hoë slik en klei materiaal bevat, terwyl Buffelskop (sandsteen)
mesa 'n laer slik en klei inhoud het. Gevolglik, tekstueel en ouer materiaal grond dra by
tot die variasie in grond nutrient samestelling tussen hierdie mesas. Hoë infiltrasie
tempo tesame met lae voedingstof van die vlaktes dui daarop dat die vlaktes rondom die
mesas oorbewei was. Hierdie hoë infiltrasie tempo word veroorsaak deur hoë dierlike aktiwieteite op die vlaktes deur lewende hawe en ander inheemse diere wat die
oppervlakke van onbedekte grond versteur en infiltrasie verbeter. Die gevolgtrekking
word gemaak dat die hoë weidingsvlakke van hierdie terreine ook die tekstuur en ander
grond eienskappe verander het.
Endozoochoreeuse verspreiding en die mis-afsetting in gebiede van klein areaversteurings,
speel 'n belangrike rol in veld herlewing in oorbeweide gebiede. Mis
versamel by permanente studie terreine op die SO en NW vlaktes en hange, as ook al
die studie terreine op die kruin van die Tafelberg mesa, is gesaai in saailing bakke,
besproei en gekontroleer vir saailing ontkieming. 'n Lys van spesies is vergelyk met
onder-grondse saadbank gegewens en bo-grondse plantegroei gegewens wat deur
ander navorsers by dieselfde studie terreine versamel was. Hoër saailing persentasies
is gevind vir mis wat op die vlaktes versamel is as op die kruine. 'n Totaal van sestien
geidentifiseerde spesies het uit die mis op die vlaktes ontkiem in vergelyking met die tien
spesies wat ontkiem het uit die mis van die hange en twee spesies iut die mis van die
kruin van Tafelberg mesa. Die ontkiemde saad verteenwoordig 'n verskeidenheid van
vreetbare gras en struik spesies. Aristide sp., Eragrostis bicolor, Eragrostis chloromelas
en Eragrostis obtusa is vreetbare grasse wat gevind was in die mis versamelop die
vlaktes. Die spesies opname wys dat Aristida sp., Chenopodium sp. en Pentzia sp.
Gevind was in die mis, maar nie in die parallelle grond saadbank en plantegroei studies
nie.
Die suksesvolle herstel van veldtoestande vereis "n streng weidingsbestuur toepassing.
Die ontkieming van saad in mis kan beskou word as "n bekostigbare manier om veld
herstel potentiaal te bepaal, asook weiveld toestande vir die indentifiseering van beide
degradasie en bewaring van waardevolle areas. Met gepaste veldbestuur vaardighede
en herstel maatreels, kan hierdie uitdagings konstruktief en kreatief aangespreek word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53711 |
| Date | 12 1900 |
| Creators | Hendricks, Neile Oliver |
| Contributors | Esler, K. J., Knight, R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 142 p. : ill. |
| Rights | Stellenbosch University |
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