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The geometric tortoise (Psammobates geometricus) in a fragmented habitat along a national highway : status and mitigationEberle, Dirk 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The geometric tortoise, Psammobates geometricus, found in the Western Cape, South
Africa, is one of the world's rarest tortoises. At present, it is only known from five
isolated geographical areas, one being the Worcester-Tulbagh Valley. The primary
aims of my study were to determine the status of geometric tortoise subpopulations
along the Nl highway in the Worcester Valley, to determine the population structure
of these subpopulations and, if necessary, to provide recommendations for the
mitigation ofNI highway-induced impacts on geometric tortoise subpopulations
along the road. All Renosterveld remnants along the Nl between Du Toitskloof and
Worcester were surveyed for the presence of geometric tortoises, and tortoise density
and population structure were determined for each remnant that supports tortoises.
Two geometric tortoise subpopulations on opposite sides of the Nl were identified. In
the larger remnant of the two, females dominated both the subadult and adult classes,
whereas in the other remnant male frequency was slightly higher than female
frequency for the adult class only. In both remnants, adult females were significantly
larger than adult males in mean carapace length. Mean body mass for adult females
and males also differed significantly in both remnants. Analysis of habitat quality
showed that both remnants supporting the geometric tortoise are seriously infested by
encroaching indigenous and alien plants. The barrier effect of the Nl highway can be
mitigated by constructing underpasses, linking the two remnants on opposite sides of
the road. Furthermore, road mortality of tortoises can be avoided by erecting tortoise
proof fencing along appropriate sections of the highway in the Worcester Valley. By linking the remnants, the largest single area available to the geometric tortoise in the
Worcester Valley will also be formed. An additional aim of my study was to
investigate the correspondence of geometric tortoise density in individual habitat
remnants to the West-to-East change in vegetation composition/characteristics
occurring along the Nl in the Worcester Valley. Vegetation
composition/characteristics were thus determined in all remnants also surveyed for
tortoises. The West-to-East change in vegetation composition/characteristics of the
study area indicates that there is a transition from Renosterveld in the West to karroid
veld in the East. / AFRIKAANSE OPSOMMING: Die geometriese skilpad, Psammobates geometrieus, wat in die Wes-Kaap, Suid-
Afrika, voorkom, is een van die wêreld se skaarste skilpaaie. Vandag word hierdie
skilpad net nog in vyf geïsoleerde geografiese streke gekry, een van hulle die
Worcester-Tulbagh Vallei. Die primêre doel van my studie was om die status van
geometriese skilpad subpopulasies langs die Nl snelweg in die Worcester Vallei te
ondersoek en om die populasiestruktuur van hierdie subpopulasies te bepaal. Verder
was die doelook, om aanbevelings te maak oor hoe die impakte van die pad op die
geometriese skilpad subpopulasies langs die Nl verminder kan word. Al die
Renosterveld oorblyfsels langs die Nl tussen Du Toitskloof en Worcester, en binne
die bekende gebied van die geometriese skilpad, is deursoek vir geometriese
skilpaaie. Populasiedigtheid en populasiestruktuur van die skilpaaie is bepaal vir elke
oorblyfsel wat skilpaaie bevat. Twee geometriese skilpad subpopulasies is gekryaan
teenoorgestelde kante van die Nl. In die groter oorblyfsel, het wyfies albei die
onvolwasse en volwasse klasse gedomineer. In die ander oorblyfsel is gevind dat die
frekwensie van mannetjies ietwat hoër was as die frekwensie van wyfies, maar vir
slegs die volwasse kategorie. Binne albei oorblyfsels is gevind dat volwassse wyfies
betekenisvol groter in gemiddelde doplengte is as volwasse mannetjies. Gemiddelde
liggaamsgewig het ook betekenisvol verskil tussen volwasse wyfies en mannetjies in
albei oorblyfsels. 'n Analise van habitatkwaliteit het gewys dat beide oorblyfsels wat
die geometriese skilpad ondersteun grootliks ingeneem is deur inheemse indringers,
sowel as uitheemse plante. Die versperrings effek van die Nl snelweg kan verminder
word deur duikwege te skep wat die twee ooblyfsels, op teenoorgestelde kante van die pad, verbind. Bowendien, deur 'n ondeurdringbare heining langs passende dele
van die snelweg in die Worcester Vallei op te rig, sal skilpadmortaliteit vermy word.
Deur oorblyfsels te verbind, salook die grootste enkele area, beskibaar aan die
geometriese skilpad in die Worcester Vallei, gevorm word. 'n Addisionele doel van
hierdie studie was om veranderinge in vegetasie langs 'n wes-na-oos gradient binne
die studie area te korreleer met die teenwoordigheid van skilpaaie langs hierdie
gradient. Vegetasie samestelling/eienskappe is dus bepaal vir elke oorblyfsel wat
deursoek is vir skilpaaie. Die wes-na-oos verandering in vegetasie
samestelling/eienskappe binne die studie area wys dat daar 'n oorgang van
Renosterveld in die weste na 'n karooagtige veld in die ooste is.
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A critical analysis of the potential of urban agriculture in the Khayelitsha Mitchell’s Plain areaNel, David 03 1900 (has links)
Thesis (MDF)--Stellenbosch University, 2012. / Poverty, which was traditionally a rural phenomenon, has become one of the main drivers behind people migrating to urban areas. It is estimated that more than 50 per cent of the global population lives in cities while the current annual growth rate of cities in sub-Saharan Africa is almost double the worldwide average.
The provision of food for the growing number of poor urban citizens is a major challenge, which needs to be addressed by city authorities. As most of the urbanised poor are exposed to agriculture due to their rural backgrounds, agriculture should be viewed as a possible solution to the challenge of urban food security for the urban poor. Put differently, feeding a growing urban population living in poverty will be one of the major humanitarian and political challenges of the next century. This implies that increased pressure will be put on urban agriculture for food production inside or close to cities, especially in developing countries where poor transportation infrastructure between the cities and rural areas creates problems for food supply.
This research explores the significance of urban agriculture as one of the solutions to urban poverty. The aim of this research report is to critically analyse the concept of urban agriculture and how it can contribute to urban renewal and the alleviation of poverty for the urban poor. It focuses particularly on the scope, problems and challenges of urban agriculture in the high density settlements of Khayelitsha-Mitchell’s Plain in Cape Town where widespread poverty and high unemployment intensifies the need for low cost food production for poor households.
The research takes into account the lessons learned in the past and looks at the role government, individuals, community organisations, NGO’s and corporate South Africa can play in expanding urban agriculture. We look at the different types of urban agriculture and the various success factors and potential pitfalls in implementing strategies of urban agriculture. This research also takes a closer look at the various problems faced by those keen to utilise urban agriculture opportunities.
This research indicates that urbanisation is inevitable and has a negative impact on the poverty levels of urban citizens due to the migration of the rural poor. This is relevant to the Western Cape and in particular, to the Cape Town townships of Khayelitsha and Mitchell’s Plain, due to the accelerating migration from the rural Eastern Cape.
The City of Cape Town is doing a fair amount of work in the field of urban agriculture through the Urban Agriculture Policy it adopted in 2007. However, this research concludes that urban agriculture in Africa, including South Africa, still does not receive the necessary recognition or support when compared to the developed world.
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An evaluation of the cost-effectiveness of the introduction of an isoniazid prophylaxis treatment (IPT) register for tuberculosis contact management in children less than five years of age in a high-burden community healthcare clinic (CHC) setting in the Western Cape, South AfricaVan Soelen, Nelda 12 1900 (has links)
Thesis (MBA)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Childhood tuberculosis is an infectious disease that can cause serious illness and mortality in especially young children. Following contact with an infectious adult tuberculosis case, the disease is easily preventable through preventive isoniazid treatment, yet very few exposed and at-risk children currently access this healthcare service in most high-burden settings. Previous research pointed out the multifactorial and complex nature of the barriers to accessing preventive care. Specifically, the lack of a formalised recording and reporting tool, such as the universally used tuberculosis treatment registers, possibly contribute to the operational barriers of preventive care delivery to these children. The purpose of this research was to evaluate the cost-effectiveness of an isoniazid preventive treatment register tool used at community level.
The study utilised previously reported data from the study population and other high-burden settings to construct a decision analysis model that included varying probabilities of isoniazid preventive treatment across three high risk age groups (<1 year of age, 1 – 2 years of age, 3 – 5 years of age), coupled with disease probabilities and associated treatment costs. The scenarios simulated included 1) the routine isoniazid preventive treatment service (3% started on treatment, 17% identified as eligible); and 2) an isoniazid preventive treatment service supported by a recording register (15% (adherent to six months of treatment) and 38% (started on IPT treatment)). In addition, two hypothetical simulations were included for 76% and 100% isoniazid preventive treatment uptake; these hypothetical simulations required additional community based healthcare worker resources in addition to the register tool.
The observations from the literature indicated that more children were identified (24(17%) vs. 54(38%)) and started (4(3%, base case) vs. 54) on isoniazid preventive treatment following the implementation of the register. As expected, the mean number of tuberculosis cases prevented, increased as the proportion of eligible children that received isoniazid preventive treatment, improved; the change in the number of cases prevented per simulation showed incremental improvements which were all significantly better (p<0.01) than the base case.. The incremental cost-effectiveness ratios incurred savings for each of the scenarios simulated since the mean costs for each of the simulations were significantly less (p<0.01) than the costs associated with the base case.
The current evidence suggests that the proposed isoniazid preventive treatment register tool is a cost-effective alternative to the current standard of care in place at community level for at-risk children exposed to tuberculosis. It is therefore recommended that the tool be used incrementally on a bigger scale, until such time that sufficient evidence has been generated to support widespread implementation.
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Investigating the experiences of women principals in high schools in the Western CapeBosch, Mare 04 1900 (has links)
Thesis (MBA)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This research focused on the experiences of female principals of co-ed high schools in the Western Cape. It investigated the path that their careers followed from the decision to become a teacher to ultimately being appointed as a principal and then having to lead the school. It further investigated the personal, organisational and social factors that were influential along the way. In addition, it probed the motivation and drive behind their career choice as well as the barriers and challenges encountered along the way.
The researcher interviewed nine female principals. They were asked to tell their life story, with emphasis on their career route thus far. Key questions were asked, focusing on the motivation behind their career choice, whether they had been actively prepared for promotion and how their appointment was received.
The interviews were transcribed in order to prepare them for data analysis. Any content that recorded experiences that contributed to their growth and development in teaching was coded accordingly. This produced a spectrum of codes. The codes were then placed into a diagram and grouped together, based on their meaning and implications. Identified groups included education and training, self-belief, work-life balance, mentorship, support and the stereotyping of women. The interconnectedness of the group was considered, together with their collective impact on the individual principals’ career route.
The research findings indicated that the career route of the principals was determined by various factors on a personal level as well as on organisational and social levels. On a personal level, qualifications obtained and the influence of parents, family and own teachers played a role. This was critical in preparing the individual for the career path that was to follow. On an organisational level, opportunities taken, work ethic, mentorship and gender barriers were factors encountered. On a social level, the stereotyping of women and the changing family structure were factors that had to be contended with. Once appointed, it was found that the support from family, colleagues and learners contributed to their success.
It emerged that the potential of these women had been identified early on in their careers and that they gained confidence when they were granted opportunities to learn and grow. To become a principal was in most cases never their intention but something that developed as they went about doing their work with commitment and diligence. Throughout, it remained a priority for them to invest in the lives of learners and the greatest joy was derived from seeing learners develop into young adults who were contributing to society.
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Challenges facing small and medium enterprise contractors in delivering grade R classrooms for the Western Cape department of transport and public worksChadhliwa, Taona Quinton 04 1900 (has links)
Thesis (MDF)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The Western Cape Education Department (WCED), through the Department of Public Works (DTPW), launched the Grade R classroom programme in 2009 to increase primary school enrolment in less privileged communities. Due to the low construction contract values the programme has attracted SME contractors. These SMEs have stalled the programme by either not delivering on time or by going insolvent whilst building Grade R classrooms. This research investigated the challenges encountered by SME contractors in delivering Grade R classrooms.
The objectives of the research were achieved by means of a questionnaire administered through telephonic interviews and face-to-face interviews. Thirteen contractors have taken part in the programme since 2009. All contractors who have built the classrooms in the Cape Metropole region were contacted for a telephonic interview of which 12 agreed to participate in the telephonic interviews.
Descriptive statistics were used to collate and discuss the challenges reported by the contractors. The findings are similar to other studies of SME contractors. SME contractors that took part in the survey confirmed that financial factors, economic and external environment, management skills and expansion and growth factors have been affecting their businesses. The fifth factor, which is the project specific factor, had the most interesting data. Nine out of twelve contractors interviewed indicated that they were not satisfied with the grade R contract working environment. If it was not for scarcity of work, they would not tender for Grade R classrooms. Nine out of twelve contractors interviewed indicated that the DTPW and its agents hindered the successful delivery of Grade R projects through their actions. The main reasons given were the late handover of sites, incomplete construction information, unreasonable construction period, numerous specification changes and delays in processing information.
What emerges from the data collected is that the DTPW needs to address the challenges highlighted in this research report. Addressing the challenges will ensure the success of the Grade R programme. This will be beneficial to both the SME contractors and the DTPW. The study also makes recommendations on how to address the challenges.
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Epidemiological study of tuberculosis in Macassar CampMohammed, Ashraf, Prinsloo, F. R., Donald, P. R. 12 1900 (has links)
Thesis (MSc (Community Health))--University of Stellenbosch. 1995. / Please refer to full text for abstract
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Field biology and identification of fruit flies in the Western Cape ProvinceHobololo, Vuyisile Lanele 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Two fruit fly species, Ceratitis capitata (Wiedemann) and C. rosa (Karsch)
(Diptera: Tephritidae) are known to attack deciduous fruit in the Western Cape
Province of South Africa. The relative abundance of these two pests was studied in
different kinds of fruit throughout the year.
To facilitate field monitoring, using the immature stages, morphological
differences between larval instars of C. capitata and C. rosa were investigated.
Morphological characters of the larvae, such as the spiracles (anterior and posterior),
mouth hooks and oral ridges were used. Many of these characters are only suitable to
distinguish between the second and third instar larvae as these structures are not yet
developed in the first instar larvae. Anterior spiracles were examined in terms of the
number of tubules (papillae) and size or shape of the felt chambers. The number of
papillae in both species was similar in the second and third instar larvae, but differed
between the larvae of the two species (8-10 for C. capitata and 10-13 for C. rosa). In
both species the felt chambers of the second instar larvae were narrow and elongate
whilst those of the third instar larvae were broad and short. The major difference
between the mouthhooks of the two tephritids was the presence of a sub-apical tooth in
the third instar larva of C. rosa, being absent in the third instar of C. capitata.
For the morphometric study, both laboratory-reared and field-collected specimens
were examined. Measurements of the body dimensions (length and width) and various
parts of the cephalopharyngeal skeleton (CPS) (mandible base, mandible length and
distance between the tip and notch) were recorded in all three instars of both C.
capitata and C. rosa. The data were analysed using finite mixture analysis (FMA-N1)
and Levene's test was used to test for homogeneity of variances. The results of these analyses were used to estimate the frequency distributions of the larval measurements.
In some cases overlaps in distributions were evident and were resolved using the same
program, finite mixture analysis (FMA-N1), based on the probability of the overlapping
measurements belonging to the designated instar (i.e. the one with highest probability).
Determination of growth ratios suggested an approximate conformation to Dyar's rule
thereby disputing the possibility of any hidden instar. However, in most cases
measurements of the field samples did not conform to Dyar's rule.
For the larval instars of C. capitata and C. rosa with overlapping morphological
features, the morphometric approach as a distinguishing tool was demonstrated. In the
field survey, the relative abundance of C. rosa at all experimental sites was very low in
both orchards and adjacent vines. This suggested that this pest was either not a threat
in these sites (crops) or the monitoring procedures applied, should be revised. Trap
catches indicated high levels of infestation by C. capitata on some sites and low
infestation levels at others. On the site with the highest population levels, activity peaks
in the orchards did not co-incide with those in the adjacent vineyards. This suggested
that these vineyards could be alternative hosts for fruit fly after the fruit in the orchards
have been harvested.
Forced oviposition (in vitro) studies indicated that Colombard (grown in
Simonsvlei) was the most suitable host for survival of C. capitata. Other wine grape
cultivars such as Chardonnay were also suitable for the total larval development of C.
capitata. / AFRIKAANSE OPSOMMING: Twee spesies van die vrugtevlieg, Ceratitis capitata (Wiedemann) en C. rosa
(Karsch) (Diptera: Tephritidae), val sagtevrugte in die Wes Kaap Provinsie van Suid-
Afrika aan. Die groot hoeveelheid van hierdie twee plae op verskillende soorte vrugte is
regdeur die jaar bestudeer.
Voordat enige insekplaag gemonitor kan word, is dit belangrik dat die identiteit
van die besondere plaag, insluitend sy onvolwasse stadiums, bekend moet wees. In
hierdie studie word die morfologiese verskille tussen die larwe stadiums van C. capitata
en C. rosa ondersoek.
Kenmerke soos die spirakels (voor en agter), mondhake en mondriwwe is
gebruik. Baie van hierdie morfologiese kenmerke kan net gebruik word om te onderskei
tussen larwes in die tweede en derde stadiums omdat hierdie strukture nog nie in die
eerste stadium ontwikkel is nie. Die voorste spirakels is ondersoek in terme van die
aantal tubules (papillae) en die grootte en vorm van die vilt kamers. In beide spesies is
die aantal papillae dieselfde vir die tweede en derde larwe stadiums, maar daar was en
verskil tussen die larwes van die twee spesies (8-10 vir C. capitata en 10-13 vir C.
rosa). In altwee spesies was die viIt kamers van die twee stadium larwes sma I en
verleng, terwyl dit in die derde stadium larwes breed en kort was. Die hoof verskil
tussen die mondhake van die twee vrugtevliee was die aanwesigheid van die
subapikale tand in die derde stadium larwe van C. rosa, terwyl dit afwesig is in die
derde stadium van C. capitata.
Vir die morfometriese studie is voorbeelde van laboratorium geteelde vrugtevliee,
asook vilee wat in die veld gevind is, ondersoek. Die liggaamsafmetings (Iengte en
breedte) is gemeet asook die skelet (mandibel basis, mandibel lengte en die afstand tussen die punt en die kerf) in al drie stadiums van C. capitata en C. rosa. Die data is
ontleed deur middel van eindige mengsel analise (FMA-N1) en Levene se toets is
gebruik om vir homogeniteit en variansies te toets. Die resultate van die ontleding is
gebruik om die frekwensie verspreiding van die larwale metings te skat. In sommige
gevalle was daar oorvleueling en dit is opgelos met die gebruik van dieselfde program
FMA-N1 baseer op die moontlikheid dat die metings wat oorvleuel, aan die aangeduide
stadium (d.w.s die een met die hoogste waarskynlikheid) behoort. Die vasstelling van
groei ratios dui aan dat dit naasteby ooreenstem met Dyar se reel en dus die
moontlikheid van 'n versteekte stadium betwis. Maar in die meeste gevalle stem die
veldmonsters nie ooreen met Dyar se reel nie.
Die feit dat die morfometriese benadering die verrnoe het om larwale monsters
met oorvleuelende morfologiese kenmerke, beteken dat dit kwalifiseer as In instrument
om tussen die larwe stadiums van C. capitata en C. rosa te onderskei. Baie min C. rosa
is in vrugteboorde en in nabygelee wingerde gevind. Dit dui of dat die plaag nie 'n
bedreiging vir die vrugte inhou nie, of dat die monitor prosedures hersien moet word.
Lokvalle dui aan dat daar 'n hoe vlak van infestasie van C. capitata in sommige
gebeide is en In lae vlak in ander. Op die plek met die hoogste bevolking van
vrugtevliee het die aktiwiteit in die boorde nie ooreengestem met die aktiwiteit in die
nabygelee wingerde nie. Dit dui aan dat hierdie wingerde 'n alternatiewe blyplek bied
aan die vrugtevliee nadat die vrugte in die boorde geoes is.
Gedwonge oviposisie studies dui aan dat C. capitata die beste kan oorleef in
Colombard (gekweek te Simonsvlei). Ander wyndruif kultivars is ook geskik vir die
ontwikkeling tot by die laaste larwe stadium van C. capitata.
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Plant parasitic organisms in the rizosphere of apple trees in the Western Cape, with special reference to woolly apple aphidVan Jaarsveld, Alwyn Jacobus 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Various aspects of the biology and ecology of woolly apple aphid, Eriosoma
lanigerum, were investigated, including initial galling damage caused by E. lanigerum to
the roots of apple trees, the possible relationship between E. lanigerum and Xiphinema and
Pratylenchus nematodes and the effectiveness of Biostart 2000® and Furfural® as possible
control agents of E. lanigerum in the orchard.
Preliminary root damage by first instar E. lanigerum feeding was characterized by
the mechanical injury of endodermis and parenchyma tissues. Damage by second, third and
fourth instar E. lanigerum was similar, but the symptoms were more pronounced. Damage
caused by adults included a pronounced swelling at infected areas of the root. Cell walls
hardened until the root was radially strengthened with sclerenchyma tissue and nonconducting
xylem vessels while the cuticle expanded greatly through the growth of corklike
cambium tissue.
There was no direct relationship between the population dynamics of E.
lanigerum and those of Xiphinema and Pratylenchus nematodes. The occurrence of E.
lanigerum appeared to be seasonal while P. penetrans and Xiphinema numbers fluctuated
erratically. Undamaged root nitrogen levels seemed to correspond with the normal root
growth cycle. Nitrogen levels from galled roots were significantly lower than those of
undamaged roots, probably due to E. lanigerum feeding. Soils rich in fine sand and clay
sustained higher populations of E. lanigerum and Xiphinema than sandy soils. The number
of E. lanigerum found in soil samples correlated well with the damage index allocated to
the samples. The numbers of Xiphinema found in soil samples also correlated well with the
damage index allocated to the samples according to suspected Xiphinema damage
symptoms.
Both Biostart 2000® and Furfural® were effective as control agents of woolly apple
aphid. Furfural'Ï, a chemical waste product of the sugarcane industry, was however not as
effective as Biostart 2000®, a product that includes an activator and three bacterial species,
Bacillus laterosporus, B. chitinosporus and B. licheniformis. The bacteria in the Biostart
2000® treated pots could replicate themselves under suitable conditions while Furfural®
dilutes with each watering. Biostart 2000® is also easier to prepare than Furfural® since the
components of Biostart 2000® readily mix to form a paste easily thinned by water, whereas
Furfural® is an oily substance that does not easily disperse in water.
Root damage was initiated soon after E. lanigerum started feeding, however there
was no apparent relationship between E. lanigerum and the nematode species. The most
promising, environmentally friendly control measure was Biostart 2000®. / AFRIKAANSE OPSOMMING: Verskeie aspekte van biologie en die ekologie van die appel bloedluis, Eriosoma
lanigerum, was ondersoek insluitende aanvanklike galvorming veroorsaak deur E.
lanigerum op wortels van appelbome, die moontlike verwantskap tussen E. lanigerum en
Xiphinema en Pratylenchus nematodes en die effektiwiteit van Biostart 2000® en Furfural®
as moontlike beheeragente van E. lanigerum in die boord.
Aanvanklike wortelskade deur eerste ins tar E. lanigerum voeding was gekenmerk
deur die meganiese beskadiging van endodermale en parenchiem weefsel. Skade
veroorsaak deur tweede, derde en vierde instar E. lanigerum was soortgelyk alhoewel die
simptome meer beklemtoond was. Skade deur volwassenes het 'n meer duidelike swelsel
by geïnfekteerde wortelareas ingesluit. Selwande het verhard totdat die wortel
radiaalsgewys versterk was met skierenchiem weefsel en nie-geleidende xileemvate terwyl
die kutikula grootliks toegeneem het deur die groei van kurkagtige kambiumweefsel.
Daar was geen direkte verwantskap tussen die bevolkingsdinamika van E.
lanigerum en dié van Xiphinema en Pratylenchus nematodes nie. Die voorkoms van E.
lanigerum was seisoenaal terwyl P. penetrans en Xiphinema se getalle onvoorspelbaar
gefluktueer het. Onbeskadigde wortel stikstofvlakke het ooreengestem met die normale
wortel groeisiklus. Stikstof vlakke van galwortels was noemenswaardig laer as dié van
onbeskadigde wortels, heel waarskynlik as gevolg van voeding deur E. lanigerum. Grond
ryk aan fyn sand en klei het groter bevolkings van E. lanigerum en Xiphinema onderhou as
sanderige gronde. Die aantal E. lanigerum in grondmonsters het goed ooreengestem met
die skade indeks wat aan die monsters toegeken was. Die aantal Xiphinema in
grondmonsters het ook goed ooreengestem met die beskadigingsindeks wat aan die
monsters toegeken is weens vermoedelike Xiphinema skade simptome.
Beide Biostart 2000® en Furfural® was effektief as beheeragente van die
appelbloedluis. Furfural'", 'n afvalproduk van die suikerriet industrie, was egter minder
effektief as Biostart 2000®, 'n produk bestaande uit 'n aktiveerder en drie bakterie spesies,
Bacillus laterosporus, B. chitinosporus en B. licheniformis. Die bakterië in die Biostart
2000® behandelde potte kon vermeerder onder gunstige toestande terwyl Furfural® na elke
besproeiing verdun het. Biostart 2000® is ook makliker om aan te maak as Furfural®
aangesien die bestanddele van Biostart 2000® geredelik meng tot 'n wateroplosbare pasta,
terwyl Furfural® 'n olierige vloeistofis wat moeilik 'n waterige suspensie vorm.
Wortelskade het plaasgevind kort nadat E. lanigerum begin voed het, alhoewel daar
geen duidelike verwantskap tussen E. lanigerum en nematode spesies voorgekom het nie.
Die mees belowende omgewingsvriendelike beheermaatreël was Biostart 2000®.
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Virulence spectrum, molecular characterisation and fungicide sensitivity of the South African Rhynchosporium secalis populationRobbertse, Barbara 12 1900 (has links)
Thesis (PhDAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Barley leaf scald, caused by Rhynchosporium secalis, is the most important disease of
barley (Hordeum vulgare) in the Western Cape province of South Africa. The disease
was first reported from South Africa in 1937. The present study is the first attempt to
characterise the South African R. secalis population. Topics such as pathogenesisrelated
proteins, virulence spectra, variability of pathotypes, sources of variation, host
resistance, breeding strategies, molecular characterisation and fungicide sensitivity are
summarised in Part 1 of this dissertation. In succeeding Parts the focus is on the
characteristics of the local R. secalis population regarding virulence spectrum, DNA
polymorphisms, in vitro as well as in vivo fungicide sensitivity. These aspects are
treated as separate entities, leading to some duplication which is unavoidable.
In Part 2 the virulence spectra of 50 R. secalis isolates from a population in the.
Western Cape province were determined. Twenty-one races were detected using 17
differential barley cultivars. The two most prevalent races, namely races 4 and 7 had
three and four virulence genes respectively. Both race 4 and 7 were virulent on the
most susceptible cultivars, namely West China, Steudelli, C.I.8618 and C.I.2226.
Considering the resistance genes reported for cultivars Atlas 46, Turk, and C.I.3515
which showed no susceptible cultivar-pathogen interaction, it would appear that the Rh-
Rh3-Rh4 complex is primarily involved in conferring resistance to the local R. secalis
isolates.
A total of 20 races (47 isolates) characterised in Part 2 were selected for further
characterisation by means of DNA fingerprinting. In Part 3 an anonymous multilocus
DNA probe was used to characterise the genotypic structure of these isolates by means
of RFLP analysis. No correlation between any particular fingerprint pattern, race,
district, field or lesion was found. The two most prevalent races, 4 and 7, did not share
the same genotypes, even when isolated from the same field or lesion. The genotypic
diversity of the isolates studied was 46.5% of the theoretical maximum diversity. The
high level of genotypic variation observed in the South African R. secalis population
resembled the genotypic diversity observed in other cereal pathogens with known
sexual structures. Although no teleomorph has yet been observed, these data suggest
that sexual recombination may operate within the local population of R. secalis. In South Africa barley scald is primarily controlled by means of fungicides. The
continued use of fungicides on cereal crops results in the build-up of fungicide
resistance in the population, which could lower the efficacy of these compounds. These
aspects were investigated in Part 4, where isolates (collected during 1993 to 1995) were
evaluated in vitro for sensitivity to triadimenol, tebuconazole, flusilazole and
propiconazole. The sensitivity fluctuated but in 1995 isolates were significantly less
sensitive towards triadimenol than in the previous two years. In a second experiment,
isolates collected from two fields with a 5-6 year-history of triadimenol seed treatments
and tebuconazole applications, were evaluated for their fungicide sensitivity. A
significant positive correlation was observed between tebuconazole and triadimenol
sensitivity among,R. secalis populations from these fields. However, such a correlation
was not found within the R. secalis population collected during 1993-1995 where
shorter crop rotation patterns and a range of fungicides was applied. In a third
experiment, the fungicide sensitivity of local R. secalis isolates was evaluated towards
two new triazole fungicides, namely bromuconazole and triticonazole. Correlation
coefficients observed between these new triazoles and those previously applied in South
Africa were not significantly positive. The lack of significant cross-resistance has
important practical implications regarding the management of fungicide resistance.
In Part 5, isolates with different minimum inhibitory concentration (MIC)
towards tebuconazole in vitro (1, 3 and 10 ug/ml) were compared in vivo. The aim of
this study was to determine how MIC values would influence virulence (leaf area
affected) and sporulation. Results indicated that all isolates were equally fit to induce
lesions and sporulate in the absence of tebuconazole. Thus no fitness cost was
associated with the degree of tebuconazole sensitivity in the present study. All R.
secalis isolates were able to induce lesions on tebuconazole treated leaves, but differed
significantly with respect to the percentage leaf area affected. Isolates, least sensitive
(MIC = 10 ug/rnl) towards tebuconazole were more adapted on tebuconazole treated
leaves, being able to repeatedly cause larger lesions than sensitive R. secalis isolates
(MIC = 1 ug/rnl), Sporulation was not significantly different between isolates on
lesions of untreated or tebuconazole treated leaves. Larger leaf areas affected and
adequate sporulation suggest that a less sensitive population would result in more
disease in tebuconazole treated fields. In conclusion, this study revealed the variability associated with the South
African R. secalis population regarding virulence spectrum and genotypic structure.
The data in this study suggest that it is likely that the local population will easily adapt
to newly introduced, single gene resistance. For more durable resistance, higher levels
of quantitative resistance should be introduced. This type of resistance is, however,
more difficult to identify and incorporate than single gene resistance. Consequently,
barley scald control will remain dependent on the efficacy of fungicide applications.
Furthermore, the lack of cross-resistance and low frequency of resistant isolates
indicates a low risk for the development of fungicide resistance in the local R. secalis
population. Other factors such as current crop rotation practices and the range of
fungicides being ~pplied also contribute to this low risk level. However, the status of
these factors can change over time. The in vivo tebuconazole sensitivity study has
indicated that a resistant field population of R. secalis may be able to build-up. It is,
therefore, necessary to monitor the fungicide sensitivity of R. secalis isolates at timely
intervals with view to successful barley cultivation in the future. / AFRIKAANSE OPSOMMING: Blaarvlek op gars (Hordeum vulgare), veroorsaak deur Rhynchosporium secalis, is die
belangrikste siekte van gars in die Wes-Kaap provinsie van Suid-Afrika. Die voorkoms
van R. secalis op gars is in Suid-Afrika vir die eertse keer in 1937 gerapporteer. Hierdie
studie is die eerste poging tot karakterisering van die plaaslike R. secalis-populasie.
Aspekte soos proteïene betrokke by patogenese, virulensiespektra, variabiliteit van
patotipes, bronne van variasie, gasheerweerstand, teeltprogramme, molekulêre
karakterisering en swamdodersensitiwiteit word in Deel I van die tesis opgesom. In die
daaropvolgende gedeelte is die fokus op die karakterisering van die R. secalis-populasie
en behels DNA karakterisering, virulensiespektrum, en swamdodersensitiwiteit in vitro
asook in vivo. ..
In Deel 2 is die virulensiespektra van 50 R. secalis isolate van 'n populasie in die.
Wes-Kaap geëvalueer teenoor 17 differensiëel weerstandbiedende gars kultivars en
hieruit is 21 rasse geïdentifiseer. Die twee mees algemene rasse (rasse 4 en 7), met
onderskeidelik drie en vier virulensie gene, het virulent vertoon teenoor die mees
vatbare kultivars soos West China, Steudelli, C.I.8618 en C.I.2226. Geen vatbare
kultivar-patogeen interaksies is met kultivars Atlas 46, Turk en C.I.3515, wat al drie die
Rh-Rh3-Rh4 kompleks dra, gevind nie. Dit wil dus voorkom asof hierdie genekompleks
effektiewe gasheerweerstand teen die plaaslike R. secalis isolate kan bied.
'n Totaal van 20 rasse (47 isolate), gekarakteriseer in Deel 2, is geselekteer vir
verdere karakterisering met behulp van DNA bandpatrone. In Deel 3 is 'n anonieme
multilokus DNA peiler gebruik om deur middel van RFLP analise die genotipiese
struktuur van hierdie R. secalis-isolate te bepaal. Geen assosiasie is gevind tussen DNA
bandpatroon en ras, distrik, garsland of letsel nie. Die twee rasse (4 en 7) wat mees
algemeen voorkom, het nie dieselfde bandpatroon vertoon nie, ook nie dié afkomstig
vanuit dieselfde garsland of letsel nie. Die genotipiese diversiteit van isolate was 46.5%
van die teoretiese maksimum diversiteit. Die hoë vlak van variasie waargeneem in die
R. secalis populasie is soortgelyk aan variasie waargeneem in ander graanpatogene wat
oor 'n geslagtelike stadium in die lewenssiklus beskik. Alhoewel geen geslagtelike
stadium tot dusver geidentifiseer is nie, dui die vlak van variasie daarop dat geslagtelike
rekombinasie moontlik wel plaasvind binne die plaaslike R. secalis populasie. In Suid-Afrika word blaarvlek op gars primêr deur swamdoders beheer. Die
toenemende gebruik van swamdoders op graangewasse veroorsaak moontlik 'n opbou
van swamdoderweerstand in die populasie. Dit kan die effektiwiteit van swamdoders
verlaag. Hierdie veronderstelling is in Deel 4 ondersoek, waar die sensitiwiteit van
isolate in vitro teenoor triadimenol, tebukonasool, flusilasool en propikonasool
geëvalueer is. Die triasooi sensitiwiteit van R. secalis isolate wat gedurende die 1993-
1995 seisoen versamel is het gewissel en slegs vir triadimenol was daar 'n tendens na
meer weerstandbiedenheid. 'n Swamdoder-evaluasie is in 'n aparte eksperiment op
isolate gedoen wat versamel is vanaf twee garslande met 'n 5-6 jaar geskiedenis van
triadimenol saadbehandelings en tebukonasool bespuitings. 'n Betekenisvolle positiewe
korrelasie is waaJ~geneem tussen tebukonasool en triadimenol sensitiwiteit in R. secalis
isolate afkomstig vanaf hierdie twee garslande. 'n Soortgelyke korrelasie is egter nie
gevind in die populasie wat gedurende die 1993-1995 seisoene versamel IS me.
Laasgenoemde kan moontlik toegeskryf word aan korter wisselboupatrone en die
toediening van 'n verskeidenheid van swamdoders. In 'n derde eksperiment is die
sensitiwiteit van plaaslike R. secalis isolate teenoor twee nuwe triasole, naamlik
bromukonasool en tritikonasool getoets. Die korrelasie waargeneem tussen die twee
nuwe triasole en triasooi swamdoders reeds voorheen in gebruik in die Wes-Kaap was
me betekenisvol positief me. Die gebrek aan betekenisvolle kruisweerstandbiedendheid
het belangrike praktiese implikasies vir die bestuur van
swamdoder -weerstandbiedendheid.
In Deel 5 is isolate met wisselende minimum inhiberende konsentrasies (MIKs)
teenoor tebukonasool in vitro (1, 3 en 10 ug/ml) en in vivo vergelyk. Die doel van
hierdie studie was om te bepaal hoe wisselende MIK-waardes virulensie
(blaaroppervlakte geïnfekteer) en sporulasie sal beïnvloed. Resultate dui daarop dat alle
R. secalis isolate in hierdie studie ewe fiks was om, in die afwesigheid van
tebukonasool, letsels te induseer en te sporuleer. Die bevinding is dat die verlies in
fiksheid nie geassosieer is met die mate van tebukonasool weerstand nie. Alle R. secalis
isolate het die vermoë gehad om letsels op tebukonasool-behandelde blare te veroorsaak
maar het betekenisvol verskil ten opsigte van die blaaroppervlakte geaffekteer. Isolate
wat minder sensitief (MIK = 10 ug/rnl) teenoor tebukonasool in vitro is, het meer
aangepastheid op tebukonasool-behandelde blare getoon. Gevolglik het hierdie isolate
herhaaldelik meer letsels veroorsaak as sensitiewe isolate (MIK = 1 ug/ml), Sporulasie het nie betekenisvol verskil tussen isolate vanaf letsels op ondehandelde of tebukonsoolbehandelde
blare nie. Hierdie resultate dui egter daarop dat 'n minder sensitiewe
populasie tot meer siektevoorkoms in tebukonasool-bespuite lande kan lei.
Die studie het die veranderlike karakter van die Suid-Afrikaanse R. secalispopulasie
aangaande virulensiespektrum en genotipiese struktuur blootgelê. Dit is dus
baie moontlik dat die R. secalis-populasie maklik sal aanpas by teelmateriaal met nuwe
enkelgeen-weerstand. Vir volgehoue gasheerweerstand is dit egter nodig dat hoër
vlakke van kwantitatiewe weerstand ingeteel moet word. In die praktyk is hierdie tipe
weerstand egter baie moeiliker om te identifiseer en by nuwe teelmateriaal in te sluit as
in die geval van enkelgeen-weerstand, Dit bring mee dat blaarvlekbeheer afhanklik bly
van swamdodertoedienings as beheermaatreël. Die resultate van hierdie studie dui
daarop dat daar tans 'n lae risiko vir die ontwikkeling van swamdoderweerstand in die
plaaslike populasie is, as gevolg van die afwesigheid van kruisweerstandbiedendheid en
die lae voorkoms van weerstandbiediende isolate. Ander faktore soos die
wisselboustelsels wat toegepas word en die verskeidenheid van swamdoders toegedien
dra ook daartoe by. Ten spyte hiervan kan die status van hierdie faktore egter oor tyd
verander. Die in vivo tebukonasool studie het daarop gedui dat 'n weerstandbiedende
veldpopulasie van R. secalis die potensiaal het om te vermeerder. Gevolglik is die
tydige monitering van swamdodersenisitiwiteit van R. secalis isolate noodsaaklik om 'n
volhoubare garsproduksie te verseker.
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The riparian vegetation of the Hottentots Holland Mountains, Western Cape, South AfricaSieben, E. J. J. 12 1900 (has links)
Dissertation (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Riparian vegetation has received a lot of attention in South Africa recently, mainly
because of its importance in bank stabilization and its influence on flood regimes and
water conservation. The upper reaches have thus far received the least of this attention
because of their inaccessibility. This study mainly focuses on these reaches where
riparian vegetation is still mostly in a pristine state. The study area chosen for this
purpose is the Hottentots Holland Mountains in the Southwestern Cape, the area with
the highest rainfall in the Cape Floristic Region, which is very rich in species. Five
rivers originate in this area and the vegetation described around them covers a large
range of habitats, from high to low altitude, with different geological substrates and
different rainfall regimes.
All of these rivers are heavily disturbed in their lower reaches but are still
relatively pristine in their upper reaches. All of them are dammed in at least one place,
except for the Lourens River. An Interbasin Transfer Scheme connects the Eerste-,
Berg- and Riviersonderend Rivers. The water of this scheme is stored mainly in
Theewaterskloof Dam. Another big dam for water storage, Skuifraam Dam, will be
built on the Berg River near Franschhoek in the nearby future.
In order to study the vegetation around a river, a zonation pattern on the river
bank is described and several physical habitats are recognized. A primary distinction
is made between a Wet Bank (flooding at least once a year) and a Dry Bank (flooding
less than once a year). The Dry Bank is further subdivided into a Lower Dynamic, a
Shrub/Tree and a Back Dynamic Zone. In the lower reaches these zones are very
distinct, but in the upper reaches of a river they tend to blend into each other and some
zones can be absent or very narrow.
Vegetation has been sampled in transects across the riverbed, following the
Braun-Blanquet method. Additional vegetation samples have been recorded in the
bogs and mires at the sources of the rivers. Vegetation structure and physical habitat
has been described to contribute to the description of the vegetation types. In order to
understand the environmental processes that determine the vegetation, environmental
parameters were recorded in every vegetation sample, such as, slope, aspect,
rockiness and soil variables.
The classification of the vegetation samples resulted in the identification and
subsequent description of 26 riverine and 11 mire communities. The riverinecommunities have been subdivided into ten Community Groups, including a group of
Aquatic communities and three groups of Wet Bank communities. The main
distinction within the Wet Bank Zone is the importance of erosion or deposition as a
driving force of the ecosystem. Three groups of Fynbos communities are identified in
the Back Dynamic Zone, with Asteraceous Fynbos occurring on shales and granites,
Ericaceous Fynbos occurring on Table Mountain Group sandstones and Transitional
Fynbos on a variety of substrates. One community group is characterized by the
dominance of Cliffortia odorata, which shows affinity with some renosterveld
communities known from literature. The two final groups contain the Afromontane
Forests and Riparian Scrub communities, respectively.
Discharges are calculated from data recorded at existing gauging weirs. The
recurrence intervals, inundation levels and stream power of several flood events are
derived from these data and are extrapolated to upstream sites. It appears that most
vegetation types in the zonation pattern on the riverbank can be explained by these
flood events, except for the Afromontane Forests, which are dependent on other sitespecific
factors including protection from fire.
Constrained and unconstrained ordinations are used to relate vegetation
patterns to the environment. The vegetation is determined by three environmental
gradients, operating at different scales. The lateral gradient across the riverbed is
mainly determined by inundation frequency and stream power, which are difficult to
measure in rocky mountain situations, although variables like distance from the
water’s edge, elevation above the water level and rockiness are correlated to them.
The longitudinal gradient is the gradient along the length of the river, from high to
low altitude. This gradient has the least influence on the riparian vegetation. The
geographical gradient reflects the large-scale climatic processes across the mountain
range. This gradient accounts for the biggest part of the total explained variation.
Important variables are especially the ratio between the summer and winter rainfall
and the geological substrate. In the Fynbos Biome, where gamma diversity is
extremely high, large-scale environmental processes are important in azonal
vegetation as well. The most species-rich vegetation associated with the rivers is
found furthest from the water’s edge at intermediate altitudes.
Knowledge about the vegetation types and environmental processes in
Western Cape rivers is essential for monitoring and maintaining these special
ecosystems. Specific threats are related to possible abstraction of water from theTable Mountain Group aquifer and from climate change, which might result in an
overall drying of the ecosystem. / AFRIKAANSE OPSOMMING: Riviere se oewerplantegroei kry die laaste tyd baie aandag in Suid-Afrika,
hoofsaaklik vanweë die belang vir die beheer van vloede, stabilisasie van die oewers
en die bewaring van drinkwater. Die hoë-liggende dele van die riviere het tot dusver
die minste aandag geniet omdat hulle tot ’n groot mate ontoeganklik is weens die
onherbergsame terrein waarin hulle geleë is. In hierdie studie is daar veral na
bergstrome gekyk waar die plantegroei nog taamlik natuurlik en onversteur is. Die
studiegebied wat vir hierdie doel gekies is, is die Hottentots-Holland berge in die
Wes-Kaap. Die gebied het die hoogste reënval in die Kaapse Floristiese Ryk en is ook
baie ryk aan spesies. Vyf riviere het in hierdie gebied hulle oorsprong. Die plantegroei
wat hier voorkom sluit ‘n wye reeks habitatte in: van hoog tot laag in hoogte bo
seespieël, verskeie geologiese substrate asook verskillende reënval patrone.
Al die vyf riviere wat ondersoek is, is baie versteur in hul onderlope, maar is
nog grotendeels natuurlik in hul hoë-liggende dele. Almal is reeds opgedam deur een
of meer damme, behalwe die Lourensrivier. ’n Tussenopvanggebied-oordragskema
verbind tans die Eerste-, Berg- en Riviersonderendriviere met mekaar. Die water uit
hierdie riviere word tans hoofsaaklik in die Theewaterskloofdam opgegaar. ’n
Verdere groot opgaardam, die sogenaamde Skuifraamdam, word binnekort in die
Bergrivier te Franschhoek gebou.
Al die riviere se onderlope is tot ’n mindere of meerdere mate vervuil met
landbou- en rioolafvoerprodukte. Uitheemse indringerplante, wat die natuurlike
oewerplantegroei verdring, skep veral probleme stroomaf van plantasies en dorpe.
Om die plantegroei van die rivieroewers na te vors, te klassifiseer en te
beskryf, is variasies in die fisiese omgewing bepaal en korrelasies gesoek om die
verspreiding van die plantegroei te verklaar. Die belangrikste verdeling in die
oewerplantegroei wat gevind is, is tussen die Nat-oewersone (dit word meer as een
keer per jaar oorstroom) en die Droë-oewersone (dit word minder as een keer per jaar
oorstroom). Die Droë-oewersone word verder onderverdeel in die Laerdinamiesesone,
die Boom/Struiksone en die Agter-dinamiesesone. In die laer dele van
die rivier is hierdie soneringspatrone baie duidelik, maar in die boonste dele van die
rivier kan die onderverdelings dikwels nie van mekaar onderskei word nie omdat
hulle gemeng is, of kan die sones baie smal wees of selfs heeltemal afwesig wees.Die plantegroei is gemonster in transekte wat dwarsoor die rivierloop uitgelê
is. Die Braun-Blanquet monstertegniek is gevolg. Bykomende monsterpersele is
opgemeet in die moerasse in die boonste dele van die berg-opvanggebiede. Om die
omgewingsprosesse wat die plantegroei bepaal te verstaan, is ’n aantal
omgewingsfaktore in elke monsterperseel aangeteken, wat, onder andere, helling,
aspek en bedekking van rotse ingesluit het, terwyl die variasie in samestelling van die
bodem ook aangeteken is.
Die klassifikasie van die plantegroei het tot die beskrywing van 26
plantgemeenskappe in die riviere en 11 gemeenskappe in die moerasse gelei. Die
struktuur van die plantegroei asook kenmerke van die fisiese habitat is in die
beskrywing van die plantegroei-eenhede ingesluit. Die gemeenskappe in die riviere is
onderverdeel in tien gemeenskapsgroepe. Daar is een gemeenskapsgroep wat die
akwatiese gemeenskappe en drie wat die Nat-oewersone gemeenskappe insluit. Die
belangrikste verskille tussen die verskillende Nat-oewersone gemeenskappe word
bepaal deur die mate waartoe erosie of deposisie voorkom. Daar is ook drie
gemeenskapsgroepe van Fynbos onderskei wat in die Agter-dinamiesesone voorkom.
Dit sluit in die Aster-fynbos op die skalies en graniete, die Erica-fynbos op die
sandstene en die Oorgangs-fynbos op gemengde substrate. Een gemeenskapsgroep is
deur die dominansie van Cliffortia odorata gekenmerk. Dit toon verwantskap met
renosterveld gemeenskappe wat reeds in die literatuur beskryf is. Die laaste twee
groepe sluit die Afromontane woude en Oewerstruikbosse in.
Die waterafloop is bereken deur middel van data verkry vanaf bestaande
keerwal meetstasies. Die herhalings-intervalle, oorstromingsdiepte en vloei-sterkte
van verskillende vloedtipes word vanaf hierdie data afgelei en stroomop
geekstrapoleer. Die meeste plantegroeivariasie op die oewers kan deur die vloede
verklaar word, behalwe in die geval van die Afromontane woude, wat deur ander
omgewingsfaktore bepaal is.
Beperkte en onbeperkte ordinasie is gebruik om die verband tussen die
plantegroeipatrone en die omgewing te bepaal. Die plantegroei se verspreiding is
bepaal deur drie omgewingsgradiënte, wat op verskillende skale ‘n uitwerking het.
Die laterale gradiënt oor die rivierbedding is hoofsaaklik bepaal deur
oorstromingsfrekwensie en stroomvloeisterkte. Hierdie veranderlikes is moeilik
bepaalbaar, alhoewel ander soos, afstand vanaf die rivier, hoogte bo watervlak en
bedekking van rotse, wat hieraan gekorreleer is, wel meetbaar is. Die lengte gradiënt,dit is die gradiënt wat van oorsprong na einde langs die lengte van die rivier
teenwoordig is, het die minste invloed op die plantegroei. Die geografiese gradiënt
weerspieel die grootskaalse klimaatsveranderinge oor die bergreeks. Deur hierdie
gradiënt word die grootste deel van die totale variasie tussen die monsters verklaar.
Die belangrikste veranderlikes is die verhouding van somer- teenoor winter-reënval
en die geologiese substraat.
Soortgelyk aan die fynbos in die Fynbosbioom, waar gammadiversiteit
buitegewoon hoog is, is die grootskaalse omgewingsprosesse, ook vir asonale
oewerplantegroei, baie belangrik. Die spesierykste plantegroei rondom die rivier word
die verste van die oewer op gemiddelde hoogtes bo seespieël gevind.
Kennis oor die plantegroei en die omgewingsprosesse in die riviere in die
Wes-Kaap is belangrik vir die monitering en effektiewe beheer van hierdie besondere
ekosisteem. Spesifieke bedreigings is gekoppel aan die potensiële ontginning van
water uit die akwifer in die Tafelberggroep-sedimente asook deur grootskaalse
klimaatsveranderinge waartydens die hoeveelheid water, volgens voorspellings,
waarskynlik sal afneem in hierdie ekosisteem.
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