As the debate on the impacts of global climate change goes on at global and regional scale, climate change impacts are already being felt at local level. The thesis aims at exploring climate change as a driver of environmental and smallholder farmers’ livelihood vulnerability in Makonde District of Zimbabwe. Specifically the study seeks to: determine climate change trends and manifestations; evaluate household-level impacts of climate change and associated environmental changes on smallholder farmers’ livelihoods and lastly; to investigate the extent of household-level coping and adaptation strategies to climate change in the Makonde rural community in Zimbabwe, especially farmers in Makonde Communal Lands. Given the fact that the subject under study is multidimensional in scope, a mix of research methods was adopted in this case study. Whilst it is largely qualitative in design, the study involved some quantitative data and thus, a triangulation of different data sources and data gathering instruments was employed. The instruments used include; key informant interviews, structured observations and a household questionnaire survey. The analysis was based on a final sample of 434 out of the originally anticipated 500 households. In addition to the households’ sample, were twenty key informants and transect walk observations. The qualitative data was analyzed by means of coding, memoing, descriptions, typologies, taxonomies and visual representations, whilst quantitative data was processed through the Statistical Package for Social Sciences (SPSS) and complimented by Microsoft Excel to generate various forms of descriptive statistics. The findings suggest that climate change in the Makonde Rural District that includes the Makonde Communal Lands has been significant during the past thirty years. The climate change has contributed to significant local environmental stresses affecting local resources such as forests, fauna, water, pastures and soil among other natural assets. The local livelihoods show high levels of vulnerability to climate change due to notable low adaptive capacity. The high level of vulnerability to changing climate is exposing the study population to increased prevalence of: poverty, crop and livestock failures, food insecurity, malnutrition, disease and rural urban migration among other impacts. The study concludes that the factors creating barriers to climate change adaptation are related those contributing to poverty and holding back sustainable local development. Among the key suggestions to enhance the community’s climate change adaptation capacity, the thesis presents an establishment of a government-driven, multi-dimensional and multi-stakeholder intervention mechanism to help local communities manage their vulnerability. / Environmental Sciences / D. Litt. et Phil. (Environmental Management)

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Quality of certain Leucospermum and Leucadendron cultivars after approximately 21 days shipping has been reported to be substandard due to ‘drying out’ of leaves and, in the case of Leucadendrons, involucral leaves. The nature of the symptoms of this ‘drying out’ and the conditions under which they form, viz. long exposures to low temperatures, has led us to hypothesize that these are symptoms of chilling injury (CI). Chilling injury, as far as we are aware, has not been documented on Leucospermums or Leucadendrons. Typical CI symptomology is discussed and shown for Leucospermum ‘Gold Dust’, ‘High Gold’ and ‘Succession’ and for Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’. The nature of CI symptoms for Leucospermums and Leucadendrons was generally membranous breakdown that manifested in some cases as a ‘water soaked’ appearance which, at a more advanced stage, was generally visible as ‘dried out’ patches on the leaves. In the case of the Leucadendrons CI was also visible on the immature involucral leaves which are more sensitive to chilling conditions than mature leaves. Dark discoloration of especially immature involucral leaves is also a symptom of CI. As water uptake of shoots with chilling injury is hindered the styles of the Leucospermums wilt. As can be expected, the lower the temperature below the threshold temperature and the longer the exposure the more severe the symptoms. CI was recorded on cut flower shoots of Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ and ‘Vlam’ after 21 and 24 days storage at 1ºC. After 24 days storage the chilling injury was more severe than after 21 days storage in most cases. Each cultivar was pulsed with 5 ml per stem of a 2% (w/v) sugar solution of either lactulose, sucrose, glucose, fructose or mannose before storage. After storage, CI was recorded on day 0, 3, 7 and 10 of the vase phase. Of the cultivars tested ‘Vlam’ and especially ‘Rigoletto’ were more prone to chilling injury development. ‘High Gold’ and ‘Vlam’ shoots were pulsed with 0 (control), 1.5, 3 or 4% (w/v) solutions of either mannose or fructose. The best control of CI for both cultivars was achieved with 1.5% (w/v) solution. Lower concentrations of mannose and fructose were tested on ‘High Gold’ shoots, with a 1% (w/v) solution giving the best control for both. At high concentrations signs of toxicity became evident directly after pulsing. ‘High Gold’ shoots were pulsed with 1% (w/v) solutions of mannose and fructose and sugar analyses were performed on shoots at different stages of storage and after 10 days in the vase. A slight increase in mannose and fructose was detectable in the stems of the shoots directly after pulsing but not in the leaves or the inflorescences. This is due to the low concentrations being used. The levels of all the carbohydrates decreased during the 21 days storage and more so during the vase phase of the flowering shoots. The fact that such low concentrations were effective in controlling chilling injury suggests that the sugars may have an effect other than on the osmotic potential. Cut ‘flower’ shoots of Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ were stored for 14, 21 and 28 days, at 1º, 3º and 5ºC and CI development recorded during the subsequent 10 day vase phase. ‘Laurel Yellow’ and ‘Safari Sunset’ showed signs of chilling injury on the leaves after 28 days storage at 3ºC or lower and ‘Safari Sunset’ stored for 21 days developed chilling injury during the vase phase. Immature involucral leaves were more sensitive to chilling injury than leaves. CI increased with longer exposure times and lower storage temperatures for all three cultivars evaluated. ‘Chameleon’ was the most chilling tolerant of the cultivars up to 21 days. At 5ºC chilling injury was low irrespective of cold storage duration but longer exposures to 1º and 3ºC resulted in increased chilling injury development during the vase phase. All three cultivars were pulsed with 5 ml per stem of a 1% (w/v) solution of lactulose, sucrose, glucose, fructose or mannose and stored for 14, 21 and 28 days at 1ºC. The sugars reduced chilling injury on the leaves for ‘Safari Sunset’ when stored for 28 days and, to a lesser extent, in ‘Chameleon’. The sugars failed to reduce chilling injury of the involucral leaves of ‘Chameleon’ and ‘Laurel Yellow’ whereas there was some control especially after 28 days for ‘Safari Sunset’. In some cases the sugar pulse exacerbated chilling injury. Chilling injury generally increased rapidly after storage during the first three days in the vase and then at a lower rate for the next seven days. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ ‘cut flower’ shoots were pulsed with a 1% (w/v) glucose solution. Expressed on a dry weight basis, an increase in glucose concentration was not detected. The reduction in chilling injury of leaves by a sugar pulse is speculated, as for the Leucospermums, to be as a result of their presence in the apoplast and not the symplast and that their presence there protects the membranes against chilling conditions in some way. / AFRIKAANSE OPSOMMING: Die kwaliteit van sekere Leucospermum en Leucadendron kultivars na ongeveer 21 dae verskeping is waargeneem as substandaard as gevolg van die uitdroog van blare en, in die geval van Leucadendrons, die ‘involucral’ blare. Die aard van die simptome van hierdie uitdroging en die toestande waaronder dit plaasvind nl. lang periodes van blootstelling aan lae temperature, het ons tot die hipotese gebring dat hierdie simptome van koueskade is. Sover as wat ons bewus is, is koueskade nog nie gedokumenteer op Leucospermums of Leucadendrons nie. Tipiese koueskade simptomologie word bespreek en gewys vir Leucospermum ‘Gold Dust’, ‘High Gold’ en ‘Succession’ en vir Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’. Die koueskade simptome vir Leucospermums en Leucadendrons was oor die algemeen membraan afbraak wat ‘n water deurdrenkte voorkoms tot gevolg gehad het wat in ‘n meer gevorderde stadium sigbaar was as uitgedroogde kolle op die blare. In die geval van Leucadendrons was koueskade ook sigbaar op die onvolwasse ‘involucral’ blare wat meer sensitief is vir koue toestande as volwasse blare. Donker verkleuring van veral onvolwasse ‘involucral’ blare is ook ‘n simptoom van koueskade. Aangesien wateropname van stele met koueskade verhinder word, verwelk die ‘styles’ van die Leucospermums. Soos verwag kan word hoe laer die temperature onder die drempel temperatuur en hoe langer die blootstelling, hoe meer ernstig die simptome. Koueskade is aangeteken op gesnyde blomstele van Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ en ‘Vlam’ na 21 en 24 dae opberging by 1°C. Na 24 dae opberging was die koueskade meer ernstig as na 21 dae opberging in meeste gevalle. Elke kultivar het 5ml per steel van ‘n 2% (g/v) suiker oplossing van laktolose, sucrose, glucose, fruktose of mannose voor opberging opgeneem. Na opberging is koueskade aangeteken op dag 0, 3, 7 en 10. Van die kultivars wat getoets is, was ‘Vlam’ en veral ‘Rigoletto’ meer geneig tot koueskade ontwikkeling. ‘High Gold’ en ‘Vlam’ stele is geplaas in oplossings van 0 (kontrole), 1.5, 3 of 4 % (g/v) oplossings van mannose of fruktose. Die beste beheer van koueskade vir beide kultivars is deur die 1.5 (g/v) oplossing behaal. Laer konsentrasies van mannose en fruktose is getoets op ‘High Gold’ stele met ‘n 1% (g/v) mannose oplossing wat die beste beheer gegee het. Met hoë konsentrasies het tekens van toksisiteit sigbaar geword direk na opneem van die oplossing. ‘High Gold’ stele is geplaas in 1% (g/v) oplossings van mannose of fruktose en suiker analises is uitgevoer op stele by verskillende stadiums van opberging en na 10 dae in die vaas. ‘n Effense toename in mannose en fruktose is waargeneem in die stele van die blomme direk na opname van die oplossing, maar nie in die blare of die blomme nie. Dit is as gevolg van die lae konsentrasies wat gebruik is. Die vlakke van al die koolhidrate het afgeneem gedurende die 21 dae opberging en nog meer so gedurende die vaas periode van die blommende stele. Die feit dat sulke lae konsentrasies effektief is in die beheer van koueskade dui daarop dat die suikers ‘n effek het anders as op die osmotiese potensiaal. Snyblomme van Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ is opgeberg vir 14, 21 en 28 dae, by 1º, 3º en 5°C en koueskade ontwikkeling is aangeteken gedurende die opvolgende 10 dae vaas periode. ‘Laurel Yellow’ en ‘Safari Sunset’ het tekens gewys van koueskade op die blare na 28 dae opberging by 3°C of laer en ‘Safari Sunset’ opgeberg vir 21 dae het koueskade ontwikkel gedurende die vaas periode. Onvolwasse ‘involucral’ blare was meer sensitief vir koueskade as die blare. Koueskade het toegeneem met langer blootstellingstye en laer opbergins temperature vir al drie kultivars geëvalueer. ‘Chameleon’ was die mees koueverdraagsaam van die drie kultivars tot op 21 dae. By 5°C was laag ongeag van die koue opberging tydperk, maar langer blootstellings aan 1º en 3°C het gelei tot toename in koueskade ontwikkeling gedurende die vaas periode. Al drie kultivars is voorsien met 5ml per steel van ‘n 1% (g/v) oplossing van lactulose, sucrose, glucose, fruktose of mannose en opgeberg vir 14, 21 en 28 dae by 1°C. Die suikers het koueskade verminder op die blare van ‘Safari Sunset’ wanneer opgeberg vir 28 dae en, tot ‘n mindere mate, in ‘Chameleon’. Die suikers het egter nie koueskade verminder van die ‘involucral’ blare van ‘Chameleon’ en ‘Laurel Yellow’ nie, waar daar egter wel in ‘n mate beheer was veral na 28 dae vir ‘Safari Sunset’. In sommige gevalle het die voorsiening van suiker die koueskade vererger. Koueskade het oor die algemeen vinnig toegeneem na opberging gedurende die eerste drie dae in die vaas en dan teen ‘n laer tempo vir die volgende sewe dae. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ snyblom stele is voorsien van ‘n 1% (g/v) glukose oplossing. Uitgedruk op ‘n droëmassa basis is ‘n toename in glukose konsentrasie nie waargeneem nie. Die afname in koueskade van blare deur die voorsiening van ‘n suiker oplossing is gespekuleer vir die Leucospermums, om ‘n resultaat te wees van hulle teenwoordigheid in die apoplas en nie die simplas nie, en dat die teenwoordigheid daar die membrane op ‘n manier beskerm teen koue toestande.

As the debate on the impacts of global climate change goes on at global and regional scale, climate change impacts are already being felt at local level. The thesis aims at exploring climate change as a driver of environmental and smallholder farmers’ livelihood vulnerability in Makonde District of Zimbabwe. Specifically the study seeks to: determine climate change trends and manifestations; evaluate household-level impacts of climate change and associated environmental changes on smallholder farmers’ livelihoods and lastly; to investigate the extent of household-level coping and adaptation strategies to climate change in the Makonde rural community in Zimbabwe, especially farmers in Makonde Communal Lands. Given the fact that the subject under study is multidimensional in scope, a mix of research methods was adopted in this case study. Whilst it is largely qualitative in design, the study involved some quantitative data and thus, a triangulation of different data sources and data gathering instruments was employed. The instruments used include; key informant interviews, structured observations and a household questionnaire survey. The analysis was based on a final sample of 434 out of the originally anticipated 500 households. In addition to the households’ sample, were twenty key informants and transect walk observations. The qualitative data was analyzed by means of coding, memoing, descriptions, typologies, taxonomies and visual representations, whilst quantitative data was processed through the Statistical Package for Social Sciences (SPSS) and complimented by Microsoft Excel to generate various forms of descriptive statistics. The findings suggest that climate change in the Makonde Rural District that includes the Makonde Communal Lands has been significant during the past thirty years. The climate change has contributed to significant local environmental stresses affecting local resources such as forests, fauna, water, pastures and soil among other natural assets. The local livelihoods show high levels of vulnerability to climate change due to notable low adaptive capacity. The high level of vulnerability to changing climate is exposing the study population to increased prevalence of: poverty, crop and livestock failures, food insecurity, malnutrition, disease and rural urban migration among other impacts. The study concludes that the factors creating barriers to climate change adaptation are related those contributing to poverty and holding back sustainable local development. Among the key suggestions to enhance the community’s climate change adaptation capacity, the thesis presents an establishment of a government-driven, multi-dimensional and multi-stakeholder intervention mechanism to help local communities manage their vulnerability. / Environmental Sciences / D. Litt. et Phil. (Environmental Management)

Call number: LD2668 .T4 1979 M78 / Master of Science

Mitochondria were extracted from seedling radicles of Pima S-5 and Pima E-14 cottons and the state 3 respiration, state 4 respiration, ADP:O ratio and respiratory control (RC) ratio were measured in vitro over a range of temperatures from 6 to 18C. Mitochondria from E-14 seedlings exhibited a mean state 3 respiration rate of 13.42 μMO₂/min/gm tissue while mitochondria from S-5 seedlings showed a mean state 3 rate of 17.94 μMO₂/min/gm tissue. Mean state 4 respiration exhibited a similar trend with measurements of 73.4 μMO₂/min/gm tissue and 11.73 μMO₂/min/gm tissue for E-14 and S-5. Mitochondria from E-14 seedlings exhibited a mean ADP:O ratio of 3.73 compared to an ADP:O of 3.28 for S-5, across all assay temperatures. Mean respiratory control ratio was 1.79 for E-14 and 1.53 for S-5. These lower respiration rates of E-14 coupled with higher ADP:O ratios and RC ratios support a greater respiratory efficiency at low temperatures of this variety compared to S-5. Additionally, the E-14 mitochondrial membranes exhibited an ability to remain in a fluid state to a lower temperature than Pima S-5 mitochondrial membranes as judged by Arrhenius plots of respiration. Since mitochondrial respiration is considered to be regulated by membrane-bound enzymes, any change in membrane fluidity would conceivably affect mitochondrial enzyme activity and thus alter respiration rates. Changes in respiration rates will be reflected as a break in an Arrhenius plot. The mean break point temperature of state 3 respiration was 10.7C for E-14 and 13.4C for S-5. The mean break point temperature for state 4 respiration was 10.9C for E-14 and 13.6C for S-5. The ability of E-14 to withstand a greater degree of chilling under field conditions can be attributed, in part, to the greater fluidity of seedling mitochondrial membranes at low temperatures and concomitant conservation of respiratory energy through a lower rate of respiration. Assays of mitochondrial respiration and Arrhenius plots of mitochondrial respiration versus temperatures could be used to select cotton lines more tolerant to chilling temperatures.

This study sought to determine the effects of reselection on the adaptation of a grain sorghum (Sorghum bicolor (L.) Moench) population to heat and drought. A random-mating population, NP9BR, was subjected to selection under heat and moisture stress for nine generations to improve its resistance to drought. One hundred single plants selected from the original (C₀) and the reselected (C₉) population were grouped by maturity and evaluated for drought resistance by measuring morphological and agronomic characters under wet (normal irrigation) and dry (restricted irrigation) conditions at the University of Arizona, Marana Agricultural Center, Arizona. Eighty of the selections were grown under a sprinkler irrigation gradient system at Yuma Mesa Agricultural Center, Arizona. Selection under drought conditions reduced plant height, head exsertion, leaf width and length, and seed weight of the population. Blooming was evened out from predominantly early in C₀ to early, medium and late maturing in C₉. Moisture stress reduced grain yield by an overall 16%. The medium maturing selections suffered less yield reduction than the early and late. Although C₉ progenies showed a greater reduction in grain yield, several of them produced equal yields in wet and dry treatments. Leaf width and length were significantly correlated (p = .1%) with yield under dry conditions in all maturity groups. Most selections with very short narrow leaves had small heads and low yields. Some with medium leaf width and length out-yielded broad-leaved ones especially under dry conditions. Forty percent of the selections from C₉ had good head production characteristics under the irrigation gradient system, compared to only 20% from C₀. There were four times as many selections in C₀ unable to produce heads under the system as there were in C₉. The majority of genotypes with good head production in both populations came from the early maturing group. The highest grain yields came from C₀ selections but some C₉ selections with comparable yields were observed. This study indicates that phenotypic selection may still have potential for isolating high-yield genotypes from random-mating populations but may be inadequate for separating differences in drought tolerance among genotypes.

No description available.

Call number: LD2668 .T4 1986 T42 / Master of Science / Horticulture, Forestry, and Recreation Resources

Call number: LD2668 .T4 1986 M87 / Master of Science / Agronomy

Rangeland resources play a significant role in household production and sustainability of livelihoods among pastoral communities in Kenya. Although wildlife is one of the rangeland resources, it is viewed by pastoralists as a competitor with livestock for grazing resources rather than an economic resource. It is assumed that competition between wild herbivores and cattle may have an impact on the forage biomass in rangelands as well as on livestock production. It is from this view point of competition between wildlife and livestock for forage resources, that this study assessed effects of forage utilization by wildlife on cattle diet, plant community composition, forage biomass and level of forage utilization in semi-arid lands in Kenya. The following hypotheses were tested: there is a decline in proportion of dominant grasses due to wildlife grazing; there is a decline in forage biomass due to grazing by wildlife and there are changes in the diet of cattle (Bos indicus Lichtenstein) due to grazing by wild herbivores. Grazing experiments were conducted at the Kenya Long-term Exclosure Experiment (KLEE) on Mpala Ranch, Laikipia District, Kenya. A number of techniques were used during data collection: line transects and 1m2 quadrats to assess plant species composition, richness and diversity. Forage biomass and increment in forage weight in grazed and ungrazed exclosures were determined by use of a disc pasture meter, whereas plant species consumed by cattle and wild herbivores were assessed by observation during feeding. The dietary forage composition of herbivores was done by micro-histological analysis of faecal samples of cattle, zebra, oryx, hartebeest and Grant’s gazelle. The results indicate that there was a high (>21 %) proportion of the tall coarse grasses (Pennisetum stramineum and P. mezianum) in the exclosures grazed by cattle with wildlife in wet and dry seasons, whereas 21 % in the exclosures grazed by wild herbivores. The proportions of Themeda triandra in the exclosures grazed by cattle with wildlife in the dry season was 18 %, whereas it was more than 25 % in the exclosures grazed by cattle with wildlife in the wet season. The results also indicate that there were very highly significant (p<0.0032 and p<0.0015) differences in percentage composition of dominant and less dominant grasses between the grazed and ungrazed exclosures during the dry seasons, whereas a significant (p<0.05) difference and a highly significant (p<0.01) difference in percentage composition between the grazed and ungrazed exclosures during the wet seasons. 5 – 6 % of the total herbaceous forage biomass (0.7 % dry matter intake) was consumed in the exclosures grazed by wildlife, whereas 13 – 17 % (2.8 % dry matter intake) was consumed in the exclosures grazed by cattle. There was a large decrease of forage biomass in the pasture grazed by cattle. However, there was no significant (p<0.133) difference in forage biomass in exclosures grazed by large wildlife or grazed by elephants (mega-wildlife). There was less than 12 % utilization of dominant grass species in the exclosures grazed by wildlife, whereas over 40 % utilization of dominant grass species in the exclosures grazed by cattle. The results indicate that there is no evidence that grazing by wild herbivores decreases forage biomass in the pasture. Wildlife, therefore, should not be hunted out on communal grazing lands because it has no significant impact on the available forage biomass for livestocks. Nonetheless, stocking rates of livestock should be consistent with forage production so that wildlife conservation is integrated in pastoral production systems.