Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Due to the extraordinary drought resistance of the grapevine, viticulture without irrigation in the winter rainfall coastal areas of South Africa is a feasible and commonly used practice. Wine quality is largely determined by the quality of the grapes from which it is made. Grapevine physiology is affected both directly and indirectly by water stress, which may vary according to soil type and prevailing atmospheric conditions. The water status of the grapevine can affect grape composition profoundly, either directly or indirectly, in either a positive or negative way, depending on the degree as well as the duration of water stress. There are three important factors involved in the development of water stress, namely the transpiration rate, the rate of water movement from the soil to the roots, and the relationship of soil water potential to leaf water potential. All three these factors are affected by atmospheric and/or soil conditions. In warm winelands such as South Africa (Western Cape), with a mediterranean climate which is characterised by a hot, dry summer period, the most important characteristic of soil is its ability to supply sufficient water to the grapevine during the entire growing season. Leaf water potential (Ψl) has gained wide acceptance as a fundamental measure of grapevine water status, and has been widely applied in viticultural research. Shortly before dawn, Ψl approaches equilibrium with soil water potential and reaches a maximum daily value. The study formed an integral part of a comprehensive, multi-disciplinary research project (ARC Infruitec-Nietvoorbij Project No. WW13/01) on the effect of soil and climate on wine quality, which commenced in 1993 and will be completed in 2004. This study was conducted during the 2002/03 growing season in two Sauvignon blanc vineyards situated at Helshoogte and Papegaaiberg, both in the Stellenbosch district, approximately nine kilometres apart. Two experiment plots, representing contrasting soil types in terms of soil water regime, were selected in each vineyard. At Helshoogte the two soils represented the Tukulu and Hutton forms, and the soils at Papegaaiberg were of the Avalon and Tukulu forms. The aim of this study was to determine the effect of atmospheric conditions and soil water status on the level of water stress in the grapevines for each soil at each locality, as well as the effect of grapevine water stress on yield and wine quality. This was done by determining and comparing the soil water status, soil water holding capacity of the soils and the evapotranspiration of the grapevines on the two different soils, at each of the two localities differing in mesoclimate and topography. The atmospheric conditions at the two localities during the 2002/03 season were also determined and compared to the long-term average atmospheric conditions, and the level of water stress of grapevines on each soil at each locality was measured. During the 2002/03 growing season, atmospheric conditions were relatively warm and dry in comparison to the long-term averages of previous seasons. These conditions accentuated the effects of certain soil properties that may not come forward during wetter, normal seasons. The usually wet Tukulu soil at Helshoogte was drier than expected during the 2002/03 season compared to the Hutton soil. Due to more vigorous growth on the Tukulu soil, grapevines extracted more soil water early in the season, leading to a low soil water matric potential and more water stress in the grapevines. Due to the higher vigour, resulting in more canopy shading, and more water stress, the dominant aroma in wines from the Tukulu soil was fresh vegetative. The Hutton soil maintained consistency with regards to both yield and wine quality compared to previous seasons. On the other hand the Tukulu soil supported a higher yield, but with lower than normal wine quality. The Avalon soil at Papegaaiberg maintained the highest soil water potential towards the end of the season, probably due to capillary supplementation from the sub-soil. Grapevines on the Tukulu soil at Papegaaiberg experienced much higher water stress than ones on the other three soils, especially during the later part of the season. This could be ascribed to a combination of factors, the most important being the severe soil compaction at a shallow depth, seriously limiting rooting depth and root distribution, which is detrimental to grapevine performance. Both the soil water status and atmospheric conditions played important roles in determining the amount of water stress that the grapevines experienced at different stages. The air temperature and vapour pressure deficit throughout the season were consistently lower at Helshoogte, the cooler terroir, compared to Papegaaiberg, the warmer terroir. At flowering, Ψl was lower for grapevines at Helshoogte than at Papegaaiberg, showing that diurnal grapevine water status was primarily controlled by soil water content. The difference in grapevine water status between the two terroirs gradually diminished until it was reversed during the post harvest period when Ψl in grapevines at Papegaaiberg tended to be lower compared to those at Helshoogte. The relatively low pre-dawn Ψl at Helshoogte indicated that the grapevines were subjected to excessive water stress resulting from the low soil water content. However, grapevines at Helshoogte did not suffer material water stress (i.e. Ψl < -1.20 MPa) during the warmest part of the day, suggesting that partial stomatal closure prevented the development of excessive water stress in the grapevines. This suggests that low pre-dawn Ψl values do not necessarily imply that grapevines will experience more water stress over the warmer part of the day, or visa versa. This does not rule out the possibility that side-effects of partial stomatal closure, such as reduced photosynthesis, can have negative effects on grapevine functioning in general. These results also suggest that measurement of diurnal Ψl cycles at various phenological stages is required to understand and quantify terroir effects on grapevine water status. / AFRIKAANSE OPSOMMING: Danksy die droogteweerstand van die wingerdstok is die verbouing van wingerde sonder besproeiing ‘n praktiese en algemene verskynsel in die winterreënval-areas van Suid-Afrika. Wynkwaliteit word grootliks bepaal deur die kwaliteit van die druiwe waarvan dit gemaak word. Wingerdfisiologie word direk en indirek beïnvloed deur waterstres, wat kan varieer volgens die grondtipe en die heersende atmosferiese toestande. Die waterstatus van die wingerdstok beïnvloed druifsamestelling, direk of indirek, en positief of negatief, afhangend van die graad en tydsduur van die waterstres. Daar is drie belangrike faktore betrokke by die ontwikkeling van waterstres, naamlik die transpirasietempo, die tempo van waterbeweging vanaf die grond na die wortels, en die verhouding tussen die grondwatermatrikspotensiaal tot blaarwaterpotensiaal. Al drie die faktore word beïnvloed deur die atmosferiese en/of grondtoestande. In warm wynboulande soos Suid-Afrika (Weskaap), met ‘n meditereense klimaat wat gekarakteriseer word deur ‘n warm, droë somerperiode, is die belangrikste eienskap van grond die vermoë om voldoende water aan die wingerdstok te verskaf gedurende die hele seisoen. Blaarwaterpotensiaal (Ψl) het wye aanvaarding bekom as die fundamentele meting van wingerstokwaterstatus, en word wyd toegepas in wingerdkundige navorsing. Kort voor sonsopkoms, nader Ψl ‘n ewewig met die grondwatermatrikspotensiaal en bereik ‘n maksimum daaglikse waarde. Die studie vorm ‘n integrale deel van ‘n omvattende, multi-dissiplinêre navorsingsprojek (ARC Infruitec-Nietvoorbij Projek No. WW13/01) op die effek van grond en klimaat op wynkwaliteit, wat in 1993 in aanvang geneem het en in 2004 afgehandel sal word. Hierdie studie is uitgevoer gedurende die 2002/03 seisoen in twee Sauvignon blanc wingerde geleë by Helshoogte en Papegaaiberg, beide in die Stellenbosch distrik, ongeveer nege kilometer van mekaar. Twee eksperimentele persele, elkeen verteenwoordigend van kontrasterende grondtipes in terme van grondwaterregime, is geselekteer in elke wingerd. By Helshoogte word die twee gronde verteenwoordig deur die Tukulu en Hutton grondvorms, en die gronde by Papegaaiberg is van die Avalon en Tukulu vorms. Die doel van die studie was om die effek van atmosferiese toestande en grondwaterstatus op die wingerdstok se waterstatus vir elke grond by die twee lokaliteite te bepaal, sowel as die effek van die wingerdstok se waterstatus op die opbrengs en wynkwaliteit. Dit is gedoen deur die grondwaterstatus, die grondwaterhouvermoë, sowel as die evapotranspirasie van die wingerdstokke op die twee verskillende gronde by elk van die twee lokaliteite, wat verskil in mesoklimaat en topografie, te bepaal en vergelyk. Die atmosferiese toestande by die twee lokaliteite gedurende die 2002/03 seisoen is ook bepaal en vergelyk met die langtermyn gemiddelde atmosferiese toestande. Die vlakke van waterstres in wingerdstokke op elke grond by elke lokaliteit is ook gemeet. Gedurende die 2002/03 groeiseisoen, was die atmosferiese toestande relatief warm en droog in vergelyking met die langtermyn gemiddeldes van vorige seisoene. Hierdie kondisies aksentueer die effek van sekere grondeienskappe wat nie noodwendig na vore kom gedurende normale, natter seisoene nie. Die gewoonlike nat Tukulu grond by Helshoogte was droër as verwag gedurende 2002/03 in vergelyking met die Hutton grond. As gevolg van sterker groekrag op die Tukulu grond, het wingerdstokke meer grondwater onttrek vroeg in die seisoen, wat gelei het tot ‘n lae grondwatermatrikspotensiaal en meer waterstres in die wingerdstokke. Die sterker groeikrag het meer beskaduwing van die lower asook meer waterstres veroorsaak, wat gelei het daartoe dat die dominante aroma in wyne vanaf druiwe op die Tukulu grond vars vegetatief was. Die Hutton grond het bestendig gebly in terme van opbrengs en wynkwaliteit in vergelyking met vorige seisoene. Daarteenoor het die Tukulu grond ‘n hoër opbrengs gelewer, maar met laer as gewoonlike wynkwaliteit. Die Avalon grond by Papegaaiberg het die hoogste grondwatermatrikspotensiaal behou tot die einde van die seisoen, heelwaarskynlik a.g.v. kapillêre aanvulling vanuit die ondergrond. Wingerdstokke op die Tukulu grond by Papegaaiberg het heelwat meer waterstres ondervind as op die ander drie gronde, veral later in die seisoen. Dit kan toegeskryf word aan ‘n kombinasie van faktore, die belangrikse daarvan die erge grondkompaksie vlak in die grond, wat worteldiepte en -verspreiding ernstig beperk het, wat op sy beurt nadelig is vir wingerdprestasie. Beide die grondwaterstatus en atmosferiese toestande het ‘n belangrike rol gespeel in die bepaling van die hoeveelheid waterstres wat die wingerdstok op verskillende stadiums ondervind het. Die lugtemperatuur en waterdampdruktekort was regdeur die seisoen laer by Helshoogte, die koeler terroir, as by Papegaaiberg, die warmer terroir. Gedurende blom was die Ψl laer vir wingerdstokke by Helshoogte as by Papegaaiberg, wat daarop wys dat daaglikse wingerdstok waterstatus hoofsaaklik deur die grondwaterinhoud bepaal was. Die verskil in wingerdstok waterstatus tussen die twee terroirs het geleidelik verminder totdat dit omgekeer was gedurende die na-oes periode toe Ψl in wingerdstokke by Papegaaiberg geneig het om laer te wees in vergelyking met die by Helshoogte. Die relatiewe lae voorsonop Ψl by Helshoogte het daarop gedui dat die wingerdstokke aan oormatige waterstres onderwerp was. Die wingerdstokke by Helshoogte het egter nie materiële waterstres (i.e. Ψl < -1.20 MPa) gedurende die warmste gedeelte van die dag ondervind nie, wat aandui dat gedeeltelike huidmondjiesluiting plaasgevind het om die ontwikkeling van oormatige waterstres te verhoed.Dit dui aan dat lae voorsonop Ψl waardes nie noodwendig impliseer dat wingerdstokke meer waterstres gedurende die warmste gedeelte van die dag sal ondervind nie, of visa versa. Dit sluit nie die moontlikheid uit dat negatiewe neweeffekte van gedeeltelike huidmondjiesluiting, soos ‘n vermindering in fotosintese, ‘n negatiewe effek kan hê op die wingerdstok se funksionering in die algemeen nie. Hierdie resultate stel voor dat die meting van daaglikse Ψl siklusse gedurende verskeie fenologiese stadia benodig word om die effek van terroir op die wingerdstok se waterstatus te verstaan en te kwantifiseer.

Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Mucoralean fungi are mostly saprotrophs that are frequently encountered in soil habitats. Using an isolation temperature of circa 25°C, other workers obtained these fungi from a wide diversity of geographical areas in southern Africa. However, it is known that psychrotolerant mucoralean fungi, able to grow at 25°C as well as at 5°C, occur in pristine Alti Mountain Grassland. Nothing is known about the diversity of these psychrotolerant soil fungi in other vegetation types of South Africa. Consequently, in this study, the psychrotolerant fungal taxa and numbers in soil from a vineyard and from pristine Mountain Fynbos were determined using an incubation temperature of 4°C and a complex isolation medium. The latter contained agar, malt extract, peptone, yeast extract, penicillin and streptomycin sulphate. Soil samples were analysed in late summer, autumn and mid-winter. It was found that, for the samples taken in late summer and autumn, the diversity of mucoralean species in the soil differed between fynbos and vineyard. In winter however, no significant difference was detected between the Shannon's diversity indices of mucoralean species in the soil samples taken from the two habitats. It was found that in both soil types, the percentage mucoralean fungi on the plates increased from summer to winter. In addition, the numbers of detectable Morlierella subgenus Morlierella on the plates were higher in winter than in late summer. The diversity of mucoralean species obtained during winter in fynbos and vineyard soil was significantly less than the diversity of these species in Alti Mountain Grassland soil. To determine if the Morlierella subgenus Morlierella isolates from the fynbos and vineyard soil, and those obtained from Alti Mountain Grassland, differ in the ability to grow at low temperatures, the radial growth rate on malt extract agar at 4°C and BOC was determined for each isolate. The results indicate that not only did seasonal changes occur in the taxa within Morlierella subgenus Morlierella, but that the isolates dominating the soil in different seasons also differed in the ability to grow at low temperatures. The percentage of isolates that had reached greater colony diameters after B days of incubation at 4°C, was higher for the isolates obtained in the cold wet month of July than for those obtained in the warmer dryer month of February. Similar results were obtained with the radial growth experiments conducted at BOC. The Morlierella subgenus Morlierella isolates obtained in winter from fynbos and vineyard soil showed less variation in low temperature growth rate than the isolates of this taxon obtained in winter from Alti Mountain Grassland soil during a previous study. This variation corresponds to the greater number (20) of Morlierella subgenus Morlierella species found in the grassland soil. Altogether only seven species of this subgenus was detected during the present study in the fynbos and vineyard soil samples. It was speculated that this difference in diversity between the fynbos and vineyard isolates, and the grassland isolates obtained in a previous study, might have been as a result of differences in the habitat or the enumeration methods used. The phylogenetic relationship between different psychrotolerant isolates of Morlierella subgenus Morlierella originating from the soil of the fynbos, vineyard and Alti Mountain Grassland, was subsequently determine through comparison of ITS regions, within ribosomal RNA repeats. Consequently, 45 psychrotolerant Morlierella subgenus Morlierella isolates originating from the three soil habitats was compared on the basis ITS 1 nucleotide sequence composition and radial growth rate at 4°C. Phylogenetic analyses showed that the isolates could be grouped into two clusters correlating with the ability to grow at low temperatures. Each cluster was further subdivided into two subgroups. It was found that except for one subgroup and the reference strain occurring in another subgroup, all the subgroups contain isolates originating from a single soil habitat. Therefore, the ITS 1 sequence of these fungi seems to indicate the original habitat and ability to grow at low temperatures. This correlation of the ITS sequence with the ecological habitat of a fungus has also been observed by other workers for other fungal groups. / AFRIKAANSE OPSOMMING: Mucoraliese fungi is meestal saprotrofe wat dikwels in grondhabitatte aangetref word. Deur gebruik te maak van 'n isolasietemperatuur van circa 25°C, het ander werkers dié fungi van 'n wye verskeidenheid geografiese gebiede in suidelike Afrika verkry. Dit is egter bekend dat die psigrotolerante mucoraliese fungi, wat in staat is om by 2SoC en ook by SaC te groei, in ongeskonde Alti Berg-Grasland voorkom. Niks is egter bekend oor die diversiteit van dié psigrotolerante grondfungi in ander veldtipes van suidelike Afrika nie. Die psigrotolerante fungustaksa en -getalle in grond van 'n wingerd en van ongeskonde Berg Fynbos is gevolglik in dié studie bepaal deur gebruik te maak van 'n inkubasietemperatuur van 4"C en 'n komplekse isolasiemedium. Laasgenoemde het agar, moutekstrak, peptoon, gisekstrak, penisillien en streptomisiensulfaat bevat. Grondmonsters is in die laatsomer, herfs en midwinter geanaliseer. Daar is 'n verskil gevind tussen die diversiteit van die mucoraliese spesies in die grond van fynbos en dié van wingerd in die monsters wat in die laatsomer en midwinter geneem is. In die winter is daar egter geen beduidende verskil gevind tussen die Shannon diversiteitsindekse van mucoraliese spesies in die grondmonsters wat uit die twee habitatte getrek is nie. In albei grondtipes is daar gevind dat die persentasie mucoraliese fungi op die plate toegeneem het van somer tot winter. Daarby was die aantal waarneembare Morlierella subgenus Morlierella op die plate meer in die winter as in die laatsomer. Die diversiteit van mucoraliese spesies wat in die winter uit fynbos- en wingerdgrond verkry is, was beduidend minder as die diversiteit van dié spesies in Alti Berg-Grasland grond. Om te bepaal of die Morlierella subgenus Morlierella isolate van die fynbos- en wingerdgrond en dié van Alti Berg-Grasland van mekaar verskil ten opsigte van hul vermoë om by lae temperature te groei, is die radiale groeitempo op moutekstrak by 4"C en aoc vir elke isolaat bepaal. Die resultate dui aan dat daar nie alleen seisoenale veranderinge in die taksa binne Morlierella subgenus Morlierella voorkom nie, maar dat die isolate wat tydens verskillende seisoene uit die grond verkry is, ook ten opsigte van hul groeivermoë by lae temperature van mekaar verskil. Die persentasie isolate wat groter kolonie diameters bereik het ná B dae inkubasie by 4°C, was hoër vir die isolate van die koue, nat Juliemaand as vir dié wat in die warmer en droër Februariemaand verkry is. Soortgelyke resultate is verkry met radiale groei-eksperimente wat by BOC gedoen is. Die MortierelIa subgenus MortierelIa isolate wat in die winter uit fynbos- en wingerdgrond verkry is, het In kleiner variasie in hul groeitempo by lae temperature getoon as die isolate in dié takson wat tydens 'n vorige studie in die winter uit Alti Berg-Grasland grond verkry is. Dié variasie stem ooreen met die groter aantal (20) MortierelIa subgenus MortierelIa spesies wat in die graslandgrond gevind is. Slegs sewe spesies van dié subgenus is gedurende die huidige studie in die fynbos- en wingerdgrondmonsters waargeneem. Daar is gespekuleer dat dié verskil in diversiteit tussen die fynbos- en wingerdisolate en die graslandisolate van die vorige studie die gevolg mag wees van verskille tussen die habitat of die enumerasiemetodes wat gebruik is. Die filogenetiese verwantskap tussen verskillende psigrotolerante isolate van MortierelIa subgenus MortierelIa uit die grond van die fynbos, wingerd en Alti Berg-Grasland, is vervolgens bepaal deur 'n vergelyking van interne getranskribeerde spasieerder (ITS) areas, binne ribosomale RNS herhalings. Daar is gevolglik 45 psigrotolerante MortierelIa subgenus MortierelIa isolate uit die drie grondhabitatte met mekaar vergelyk op grond van die basis ITS 1 nukleotied opeenvolgingsamestelling en radiale groeitempo by 4°C. Filogenetiese analises het die isolate in twee groepe verdeel op grond van hul vermoë om by lae temperature te groei. Elke groep is verder in twee subgroepe verdeel. Daar is gevind dat behalwe vir een subgroep en die verwysingstam wat in 'n ander subgroep voorgekom het, elkeen van die subgroepe bestaan het uit isolate wat van 'n enkele grond habitat verkry is. Dit wil dus voorkom of die ITS 1 opeenvolging van dié fungi 'n aanduiding gee van die oorspronklike habitat en die vermoë om by lae temperature te groei. Dié korrelasie tussen die ITS opeenvolging en die ekologiese habitat van 'n fungus is ook deur ander werkers vir ander fungusgroepe waargeneem.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Food demands for the ever-increasing human population is increasing the pressure on the agricultural sector to produce more food. In order to satisfy these demands, farmers are turning to chemical biocides for the control of pest species to produce greater crop yields. All pesticides must be toxic or poisonous to the target species they intend to control. Unfortunately, most pesticides are toxic or poisonous to non-target organisms as well, with detrimental effects on their health. Organic farming was developed to enhance the overall health of the farm's natural soilmicrobe- plant-animal biodiversity. No synthetic fertilisers and/or pesticides are used when farming organically. Life in the soil consists of intricate food webs and interactions between the soil dwelling invertebrates. The soil-organisms are divided into three main groups, viz., Micro-organisms (e.g. protozoa, bacteria and fungi) mesofauna (nematodes, Collembola and Acari) and macro-fauna (e.g. millipedes, isopods, insects, molluscs and earthworms). The invertebrates are very susceptible to chemical contamination by chemical biocides in natural and agro-ecosystems. The soil invertebrate communities are responsible for the decomposition of organic material in soil, thereby remineralising the soil. The decomposition processes start with comminution of the large pieces of organic material by meso- and macro-fauna and ends with the micro-fauna and microbial organisms that complete these processes by returning the nutrients in an inorganic form to the soil. The aim of this study was to investigate whether, and to what extent the soil organisms are influenced by different management practices viz., organic management practices versus conventional management practices. A vineyard on the farm Plaisir de Merle, in Simondium, Western Cape was used for the present study. One half of a one hectare vineyard was managed organically and the other half conventionally. Within each vineyard block six different treatments were performed. Three of the treatments were strictly organic and the other three were strictly conventional. Four replicates of each management treatment were performed. The bait-lamina technique was used to assess the feeding activity of the soil organisms exposed to the different management treatments. In addition to the bait-lamina trials in the vineyard itself, bait-lamina tests were performed in microcosm studies with soil from the organically and conventionally managed vineyard blocks under controlled conditions. In order to assess the impact of the various pesticides that are used in the vineyards in the conventional way, on the soil fauna, standard acute toxicity tests and behavioural tests were performed on Eisenia fetida, the compost worm. The bait-lamina tests in the vineyard revealed that the moisture content of the soil plays an important role in the biological activity of soil fauna. The different management treatments did affect the biological activity of the soil fauna, but seasonal changes also proved to be one of the important factors governing biological processes in the soil. The acute toxicity tests showed that the active ingredients (mancozeb, penconazole and trifloxystrobin) of three of the pesticides that were tested in this study, had negatively affected E. fetida at their recommended application concentrations. The remaining two pesticides' active ingredients (glyphosate and N-acetyl salicylic acid) did not affect the earthworms negatively at the recommended application concentrations. The preference behavioural trials showed that E. fetida could detect and avoid contaminated substrates at the LCso-concentrations of the different pesticides. All the earthworms were influenced positively in the preference behaviour experiments. Because of certain limitations of the bait-lamina technique, it was difficult to formulate conclusions on what happens in the soil. A possible explanation for the differences in feeding activity of soil fauna could be attributed to the migration of the soil fauna to more habitable soil horizons during the dry summer conditions, when most of the pesticides are applied. The ecological relevance of the acute toxicity tests conducted need to be investigated further. It is clear that the acute toxicity tests provided important information that should be considered, but care should be taken and the necessary safety factors be determined and considered when doing risk assessment studies. The results of the preference behaviour studies showed that for certain pesticides E. fetida can be a sensitive bioindicator of acute and/or sub-acute lethal toxicity testing but this might not necessarily be the case for other pesticides. The goal of doing laboratory studies is to gain as much information to make reliable extrapolations to field situations from laboratory data. Laboratory-to-field extrapolations are very complicated because of the physico-chemical composition of soil, the unpredictable way pesticides behave within soil and the reaction of soil organisms to the soil and to the chemical biocides that are used. Further studies need to be done in order to fully understand to what extent the soil fauna were affected by the different management practices applied to the vineyard at Plaisir de Merle. / AFRIKAANSE OPSOMMING: Voedsel aanvraag vir die toenemende menslike bevolking plaas groot druk op die landbou sektor om meer kos te produseer. Om aan die voedsel eise te voldoen, gebruik boere al meer chemiese biosiede om pesspesies te bestry. Alle pestisiede moet toksies of giftig wees vir die teiken organisme waarvoor dit bestem is. Ongelukkig is die meeste pestisiede ook toksies of giftig vir nie-teiken organismes, wat tot nadelige effekte op hul gesonheid kan lei. Organiese boerdery is ontwikkel om die algehele gesondheid van die plaas se natuurlike grond-mikrobe-plant-dier biodiversiteit te bevorder. Geen sintetiese bemestingstowwe en/of pestisiede mag gebruik word wanneer daar organies geboer word nie. Die lewe in die grond bestaan uit ingewikkelde voedselwebbe en interaksies tussen die grondlewende invertebrate. Die grond invertebrate word verdeel in drie hoof groepe, nl. mikro-organismes (bv. Protozoa, bakterieë en fungi) meso fauna (Nematoda, Collembole en Acari) en makrofauna (bv. Millipoda, Isopoda, Insecta, Mollusca en erdwurms). Die Invertebrata is die mees vatbaarste vir chemiese kontaminasie deur chemiese biosiedes in natuurlike en landbou ekosisteme. Die grond invertebraat gemeenskappe is verantwoordelik vir die afbreek van alle organiese materiaal in die grond en dus vir remineralisering van die grond. Die afbreekproses begin by die komminusie van groter stukke organiese materiaal deur die meso- en makrofauna en eindig met die mikrofauna en mikrobes wat die prosesse voltooi deur die nutriente terug te plaas in die vorm van anorganiese produkte in die grond. Die doel van hierdie studie was om te ondersoek of, en tot watter mate, grond organismes geraak word deur verskillende grondbestuurspraktyke, nl. Organiese grondbestuurspraktyke teenoor die konvensionele grondbestuurspraktyke. 'n Wingerd op die plaas Plaisir de Merle, in Simondium, Wes-Kaap, was gebruik vir die huidige studie. Een helfte van 'n een hektaar wingerd is organies bestuur en die ander helfte is op die konvensionele manier bestuur. Op elk van die twee wingerd blokke is ses verskillende behandelings toegepas. Drie van die behandelings was streng organies en die ander drie was streng konvensioneel van aard. Vier replikate van elke behandeling is toegepas op elk van die twee wingerdblokke. Die bait-lamina metode is gebruik om die voedingsaktiwiteit van die grond organismes te asses seer. As toevoeging tot die bait-lamina proewe in die wingerd self, is bait-lamina toetse ook in mikro-kosmosse in die laboratorium gedoen met grond afkomstig vanaf die twee wingerdblokke. Om die impak van die verskillende pestisiede op die grondorganismes te ondersoek, is standaard akute toksisteitstoestse en gedragstoetse uitgevoer met die komposerdwurm, Eisenia fetida. Die bait-lamina resultate in die wingerd het getoon dat die voginhoud van die grond die belangrikste rol speel wat die biologiese aktiwiteit van die grondorganismes beïnvloed. Die verskillende behandelings het die biologiese aktiwiteit van die grond fauna geaffekteer, maar seisoenale veranderings is ook uitgesonder as een van die bepalende faktore wat die biologiese prosesse in die grond stuur. Die akute toksisiteitstoetse het getoon dat die aktiewe bestandeie van drie van die pestisiede (mancozeb, penconazole en trifloxystrobin), E. fetida negatief beïnvloed het teen die aanbeveelde konsentrasies wat toegedien is. Die aktiewe bestandeie van die ander twee pestiede (glyphosate en N-asetiel sallisiel suur) het nie die erdwurms nadelig beïnvloed teen die aanbeveelde konsentrasies wat toegedien is nie. Die gedragsproewe het getoon dat E. fetida die LCso-konsentrasies van al die verskillende pestisiede kan waarneem en vermy. Al die erdwurms is positief beïnvloed in die gedragseksperimente met die verskillende pestisiede. Omdat die bait-laminametode sekere beperkings het, was dit moeilik om tot gevolgtrekkings te kom oor wat presies in die grond gebeur. 'n Moontlike verklaring vir die verskillende voedingsaktiwiteite van die grond fauna kan toegereken word aan die migrasie van die grondorganismes na meer leefbare grondhorisonne gedurende die droë somer toestande, wat toevallig met die spuit van die meeste pestisiede ooreenstem. Die ekologiese relevansie van die akute toksisiteitstoetse wat uitgevoer is, moet meer deeglik ondersoek word. Die belangrikheid van die akute toksisteitstoetse is duidelik en het waardevolle informasie gelewer, maar sorg moet geneem word, en die nodige veiligheids faktore moet bepaal word en in ag geneem word, wanneer riskobepalingstudies gedoen word. Die gedragsproewe het getoon dat vir sekere pestisiede E. fetida 'n sensitiewe bioindikator van akute en/of sub-akute letale toksisiteits toetse kan wees, maar nie noodwendig vir ander pestisiede nie. Die doel van laboratoriumstudies is om so veel as moontlik inligting te versamelom vertroubare ekstrapolasie te kan maak na situasies in die veld vanaf laboratorium data. Laboratorium-na-veld ekstrapolasies is dikwels baie gekompliseerd as gevolg van die fisies-chemiese samestelling van die grond, die onvoorspelbare manier waarop chemiese pestisiede met die grond reageer en die reaksie van die grondorganismes op chemiese biosiede in die grond. Verdere studies moet gedoen word om so deeglik maanlik die mate van die impak wat die verskillende bestuurspraktyke op die grond fauna het, te verstaan op Plaisir de Merle.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2005. / This thesis forms part of a research program that is investigated by ARC Infruitec- Nietvoorbij and the University of Stellenbosch. The aim of this program is to quantify the effect of soil and climate on wine quality and character as a basis for scientific demarcation of production regions. Natural factors are first quantified and characterised so that relative homogeneous natural terroir units (NTU) can be identified. Thereafter wines made from these different localities are assessed for similarities which permit grouping of localities into viticultural terroirs. The present study involved seven research plots in the Robertson district, making use of initial measurements by ARC Infruitec-Nietvoorbij in the 2000/01 and 2001/02 seasons together with more intensive measurements in the 2002/03 and 2003/04. The seven plots are located in two wards, Le Chasseur and Vinkrivier. Sauvignon blanc plots were marked at two localities, each with two sub-plots occurring in one block. Three Cabernet Sauvignon plots were marked out. Two plots occurred in one block in Le Chasseur and one plot in Vinkrivier. Plots within the same block were located on different soil types so that the effect of soil type on wine quality and character could be monitored. Morphological examination of soil profiles at each plot was carried out together with physical and chemical analysis of samples taken at 30cm depth intervals. Soil water content was measured at regular intervals to assess soil water tension. Vineyard performance was assessed in terms of phenology, root system studies, leafwaterpotential measurements, canopy quality assessment, leaf analysis, shoot growth, and data relating to ripening, harvest and pruning. Wines were made from each plot by ARC Infruitec- Nietvoorbij and evaluated by a tasting panel after six months and then again after eighteen months. Meteorological data were collected in each ward.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Invasive alien trees (IATs) and agriculture are rapidly altering the capacity of ecosystems to provide a variety of essential services, with decreasing habitat quality having an adverse effect on arthropod biodiversity. Although both agricultural intensification and IATs have an impact on ecosystems, it is unclear which of these two is currently the most severe. Here I compare the influences of vineyards and IATs on arthropod diversity in the Cape Floristic Region (CFR) from two perspectives. Firstly, insect diversity from four different vegetation types (native fynbos, IATs, cleared invasive alien trees (CIATs) and vineyards), and their ecotones were assessed. Secondly, soil compaction in the different vegetation types was assessed and compared to determine how soil compaction relates to arthropod species richness and abundance. Surface-active arthropods were used for these evaluations, as they were considered to be the most abundant, yet sensitive groups for these comparative assessments. Pitfall trapping, which has been widely used for such comparative studies, was the method of choice. Additionally, as a result of incidental wildfires at some of the study sites (IATs and fynbos vegetation), it was decided opportunistically to assess recovery of arthropod diversity following the impact of fire. The results categorically indicate that IATs had by far the most significant impact, in comparison with vineyards, in reducing arthropod diversity and changing assemblage composition. Both IATs and vineyards, not surprisingly, supported lower arthropod diversity compared to fynbos, while CIATs supported arthropod species richness comparable to that of fynbos. However, different invertebrate species responded differently to IAT invasion, with some species even adapted to conditions in IAT patches. Environmental factors such as leaf litter and soil compaction were strongly correlated with arthropod species richness. However, other factors, such as soil moisture content, were not correlated with species richness, despite varying significantly between different vegetation types. IATs were found to reduce soil compaction, while vineyards increased soil compaction. The ecotone between adjacent land-use types was important for sustaining high arthropod species richness, particularly for the CIATs/fynbos ecotone, followed by the interface between CIATs/vineyard and vineyard/fynbos. Some species even preferred ecotones. Surface-active invertebrate species richness declined substantially immediately after fire in both IATs and fynbos. Nevertheless, recovery was rapid, with some species recolonizing or re-establishing within three months. Indeed, both species richness and abundance were high following fire. Fire had no significant impact on arthropod assemblage within IATs, despite having a serious impact in the fynbos where a different arthropod assemblage was observed after fire. The recovery of the historic assemblages may be dependent on both the pre-fire composition of the habitat and its adjacent vegetation. Effective co-operation among conservation biologists, farmers, and landowners to actively plan the future of CFR landscape biodiversity is required. / AFRIKAANSE OPSOMMING: Indringer uitheemse bome (IUB) en landbou bedrywighede is vinnig besig om die kapasiteit van ekosisteme vir die voorsiening van „n verskeidenheid van noodsaaklike dienste, met „n afname in habitatkwaliteit en „n nadelige uitwerking op artropood biodiversiteit, te verander. Alhoewel beide, landbou intensifikasie en IUB‟s, ‟n impak op ekosisteme uitoefen, is dit onduidelik watter van hierdie twee huidig die mees ernstige een is. In hierdie studie vergelyk ek die invloed van wingerde en IUB‟s op artropood diversiteit in die Kaapse Floristiese Streek (KFS) vanuit twee perspektiewe. Eerstens, insekdiversiteit van vier verskillende vegetasietipes (natuurlike fynbos, IUB‟s, verwyderde indringer uitheemse bome (VIUB‟s) en wingerde) en hulle ekotone is bepaal. Tweedens, is grondverdigting in en van die verskillende vegetasietipes ondersoek en vergelyk om te bepaal hoe grondverdigting verband hou met artropood spesies rykheid en volopheid. Oppervlak-aktiewe artropode is vir hierdie bepalings gebruik aangesien hulle beskou word as die mees volopste, maar ook mees sensitiewe groepe vir hierdie vergelykende bepalings. Pitvalvangste, wat alom gebruik word vir sulke vergelykende studies, was die verkose werkswyse. Bykomend, as gevolg van onbeplande veldbrande in sommige studie gebiede (IUB‟s en fynbos plantegroei), is oppertunisties van die geleentheid gebruik gemaak om die herstel van artropood diversiteit na die impak van brand te bepaal. Die resultate toon duidelik aan dat IUB‟s, in vergelyking met wingerde, by verre die mees beduidende impak gehad het deur ‟n verlaging van artropood diversiteit en veranderende groeperingssamestellings. Beide, IUB‟s en wingerde, het, nie onverwags nie, in vergelyking met fynbos, laer artropood diversiteit ondersteun, terwyl VIUB‟s artropood spesies verskeidenheid, vergelykbaar met dié van fynbos, ondersteun het. Verskillende invertebrate spesies het egter verskillend gereageer op IUB indringing, en sommige spesies het selfs by toestande in IUB kolle aangepas. Omgewingsfaktore soos blaarafval en grondverdigting was sterk gekorrelleer met artropood spesies rykheid. Ander faktore, soos grondvoginhoud, was egter nie in ooreenstemming met spesies rykheid nie, ten spyte van ‟n beduidende wisseling tussen verskillende vegetasietipes. IUB‟s het grondverdigting verminder, terwyl by wingerde grondverdigting toegeneem het. Die ekotone tussen aanliggende grondgebruike was belangrik om hoë artropood spesies rykheid, veral by die VIUB‟s/fynbos ekotoon, gevolg deur die kontaksones tussen VIUB‟s/wingerd en wingerd/fynbos, te onderhou. Sommige spesies het selfs ekotone verkies. Oppervlak-aktiewe invertebraat spesies rykheid het onmiddelik na brand in beide, IUB‟s en fynbos, wesenlik afgeneem. Tog was herstel vinnig, met sekere spesies wat binne drie maande teruggekeer of hulle hervestig het. Inderdaad was beide, spesies rykheid en volopheid, hoog na ‟n brand. Brand het geen noemenswaardige invloed op artropood groeperings binne IUB‟s gehad nie, ten spyte van ‟n ernstige impak in fynbos waar ‟n verskillende artropood groepering na ‟n brand waargeneem is. Die herstel van die historiese groeperings van beide, die voor-brand samestelling van die habitat en sy aangrensende plantegroei, mag afhanklik wees. Effektiewe en aktiewe samewerking tussen bewaringsbioloë, boere, en grondeienaars om die toekoms van KFS landskap biodiversiteit te beplan, word benodig.