Thesis (MSc (Conservation Ecology and Entomology))--Stellenbosch University, 2009. / ENGLISH ABSTRACT: An understanding of the interactions of herbivores, plant nutrients and soil properties is
crucial for grazing management. Of particular interest are plant palatability and herbivore
grazing preferences. These aspects, the focus of this thesis, were studied in a Swartland Shale
Renosterveld and Swartland Alluvium Fynbos mosaic in the Western Cape of South Africa.
This vegetation is classified as critically endangered due to the transformation of its landscape
in favour of agricultural production and urban settlement.
Pre-colonial herbivore vertebrates were hunted out by 1700, leading to a sparse knowledge of
the early dynamics of the vegetation. However, currently game farmers and landowners are
re-introducing selected species into the area. Thus, managers require knowledge on how to
implement practical guidelines for best-practice grazing management. This study investigates,
firstly, the relationship between plants and animals. This included seasonal assessment of seed
germination from dung of bontebok and eland; the effect of stocking rates on plant
palatability (crude protein, crude fibre, crude fat, moisture, tannin and mineral) of herbage
was studied with the aim to understand how palatability influences herbivore forage decisions.
Secondly, this study looked at how stocking rates influence soil nutrients (nitrogen,
phosphorus), and others soil properties such as pH and soil moisture.
The distribution of alien grasses was facilitated by grazers. About 58 % of grasses germinated
from the dung of eland and Bontebok were alien species. Additionally, there was significant
variation in palatability related to grazing pressure and plant maturity between sites and over
seasons. Grasses on the high grazing site had higher carbohydrate (3%-5% higher) and protein
content (1%-5% higher) than at the least grazed site. Mature grasses contained less water
(10%-20%), but no obvious variation in tannin concentration than immature grasses.
However, species such as Ficinia sp. showed variations with grazing pressure and maturity.
Ficinia sp. on the high grazing site had higher tannin concentration (5mg/ml-22mg/ml) and
crude protein (4%-9%) than at the least grazed site. When the plant ages, tannin concentration
increase (ranging from 15% to19% higher). Two types of plant were recoreded according to
their chemical response following grazing pressure. These types are 1) plants that are grazing
tolerant and which produce more carbohydrate when grazed and 2) plants that are grazing
intolerant under high grazing pressure and which produce chemical defence compounds such
as tannin to deter herbivores attacks. The results indicate that in fynbos and renosterveld, the
relationship between preference and plant chemical compounds is not consistent since no
IV
patterns emerged to explain what compounds drive preference. A combination of chemical
compounds may be the reason for the selection by the grazers; alternatively, other compounds
not included in the study may influence the forage selection by an herbivore.
The second part of the study showed that stocking rates appeared to have a significant effect
on soil properties investigated. Soil moisture was significantly affected by the stocking rate in
autumn. The high grazing intensity site had the lowest soil moisture especially in autumn
(10% lower than the control site), likely due to heavy trampling and soil compaction. pH was
the lowest at the high grazing intensity site in all seasons compared to the control site. Likely
reasons were the high deposition of nitrogen through dung and urine deposition, high removal
of basic cations and animal exportation through hunting activities. Lastly, grazing maintains
inorganic nitrogen at stable levels regardless of seasonal changes and increases the
concentration of phosphorus especially under high grazing pressure compare to less grazed
sites.
The grazing dynamics of Swartland Shale Renosterveld - Swartland Alluvium Fynbos mosaic
system are complex and multifaceted. Farmers need to pay attention to the nutritional status of
plant species grazed to know whether they meet the nutritional requirements of the game in
the area. Overstocking should be avoided in this system as it triggers the production of
tanniferous compounds that could decrease the survivorship of herbivores. Moderate grazing
0.09 LAU/ha pressure provides the best stocking rates for effective grazing management. / AFRIKAANSE OPSOMMING: Vir suksesvolle weidingsbestuur is dit noodsaaklik om die interaksie tussen herbivore,
plantvoedingstowwe en grondeienskappe te verstaan. Van besondere belang is
plantsmaaklikheid en herbivore se weidingsvoorkeure. Hierdie aspekte, wat die fokus van
hierdie tesis is, is bestudeer in ‘n Swartland Shale Renosterveld en Swartland Alluvium
Fynbos-mosaïek in die Wes-Kaap Provinsie van Suid-Afrika. Hierdie plantegroei word as
kritiek bedreigd geklassifiseer weens die transformering van sy landskap ten gunste van
landbou-aktiwiteite en stedelike vestiging.
Pre-koloniale herbivoor vertebrata is teen 1700 deur jagters uitgeroei, wat gelei het tot min
kennis oor die vroeë dinamiek van die plantegroei. Wildsboere en grondeienaars is egter besig
om geselekteerde spesies in die area te hervestig. Bestuurders moet dus weet hoe om praktiese
riglyne vir beste-praktyk weidingsbestuur te implementeer. Hierdie studie ondersoek eerstens
die verhouding tussen plante en diere. Dit sluit seisoenale evaluering van saadontkieming uit
die mis van bontebokke en elande in; die effek van veegetalle op plantsmaaklikheid
(ruproteïen, ruvesel, ru-vet, vogpeil, tannien en minerale) van die weiveld is bestudeer om vas
te stel hoe plantsmaaklikheid herbivore se weidingsbesluite beïnvloed. Tweedens het die
studie die invloed van veegetalle op grondvoedingstowwe (stikstof, fosfor) ondersoek, asook
ander grondeienskappe soos pH en grondvogpeile.
Die verspreiding van uitheemse grasse is deur weidende diere gefassiliteer. Ongeveer 58%
van alle grasse wat uit die mis van elande en bontebokke ontkiem het, was uitheemse spesies.
Verder was daar beduidende variasie in plantsmaaklikheid verwant aan beweidingsdruk en
plantvolwassenheid tussen verskillende persele en oor seisoene. Grasse op die hoogs beweide
persele het 3%-5% hoër koolhidraatinhoude en 1%-5% hoër proteïeninhoude gehad as die
minder beweide persele. Volwasse grasse het 10%-20% minder water bevat as onvolwasse
grasse, maar het nie in terme van tannienkonsentrasie van die onvolwasse grasse verskil nie.
Spesies soos Ficinia sp. het variasies getoon met beweidingsdruk en volwassenheid. Ficinia
sp. het op die hoog-beweide perseel ‘n hoër tannienkonsentrasie (5mg/ml-22mg/ml) en meer
ruproteïen (4%-9%) gehad as op die minste beweide perseel. Wanneer die plant verouder,
verhoog die toename in tannienkonsentrasie (met tussen 15% en 19%). Twee tipes plante is
aangeteken volgens hul chemiese response ná beweidingsdruk. Hierdie tipes is 1) plante wat
beweidingstolerant is en wat meer koolhidrate produseer wanneer hulle as weiding dien en 2)
plante wat onder hoë beweidingsdruk beweidingsintolerant is en wat chemiese verbindings
VI
soos tannien produseer om herbivooraanvalle af te weer. Die resultate dui aan dat die
verhouding tussen voorkeur en plante se chemiese verbindings nie konstant bly in fynbos en
renosterveld nie, aangesien geen patrone na vore getree het wat kon verklaar watter
verbindings bepalend is vir voorkeur nie. ‘n Kombinasie van chemiese verbindings mag die
rede wees waarom die herbivore sekere plante verkies; alternatiewelik mag ‘n herbivoor se
plantseleksie beïnvloed word deur chemiese verbindings anders as dié wat in hierdie studie
ondersoek is.
Die tweede deel van die studie het aangetoon dat veegetalle blyk ‘n beduidende invloed te hê
op die grondeienskappe wat ondersoek is. Grondvogpeile is in die herfs beduidend beïnvloed
deur die veegetalle. Die perseel met die hoë beweidingsintensiteit het die laagste grondvogpeil
gehad, veral in die winter (10% laer as dié van die kontrole-perseel), waarskynlik weens erge
getrappel en grondkompaktering. Vergeleke met die kontrole-perseel was pH die laagste op
die perseel met die hoë beweidingsintensiteit, in alle seisoene. Waarskynlike redes hiervoor is
die hoë neeerslag van stikstof deur mis- en uriene-neerslae, hoë verwydering van basiese
katione en dierevervoer wat deur jagaktiwiteite teweeg gebring word. Laatstens behou
weiding anorganiese stikstof teen stabiele vlakke ongeag van seisoenale veranderinge en
toenames in die konsentrasie van fosfor, veral onder hoë beweidingsdruk vergeleke met
minder beweide persele.
Die weidingsdinamiek van die Swartland Shale Renosterveld - Swartland Alluvium Fynbosmosaïeksisteem
is kompleks en veelvlakkig. Boere behoort aandag te skenk aan die
voedingstofstatus van die plantspesies wat as weiding dien, sodat hulle kan weet of die
voedingsbehoeftes van die wild in die omgewing bevredig word. Die aanhou van te veel vee
in hierdie sisteem behoort vermy te word aangesien dit as sneller dien vir die produksie van
tannienbevattende verbindings wat die oorlewingsvermoë van herbivore kan verlaag. Matige
beweidingsdruk (0.09 LAU/ha) bied vir effektiewe weidingsbestuur die beste veegetalle.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4043 |
| Date | 03 1900 |
| Creators | Mubamu Makady, Elvis |
| Contributors | Krug, Cornelia B., Esler, Karen J., Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 103 p. : ill., maps |
| Rights | Stellenbosch University |
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