6 Records out of 22207 Records

Forest soil as sink or source of greenhouse gases : a case study of species effects on nitrous oxide and methane fluxes in Karura forest Kenya

Author: Thiong'o, Margaret Kabura

Awarding University: University of Nairobi, Kenya

Level : MA

Year: 2010

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Karura Forest, Nairobi, Kenya/Forests/Greenhouse effect/Methane/Trees/Nitric oxide/Soils ;

Abstract:

Greenhouse gas (GHG) fluxes from tropical deforestation and regrowth associated with global climate and land-use change are highly uncertain components of the contemporary carbon budget, due in part to the lack of spatially explicit and consistent information on changes in forest cover. Quantifying mass and energy exchanges within tropical forests, such Karura Forest which is contiguous with the city of Nairobi, is essential for understanding their role in the global carbon budget and how they will respond to perturbations in climate. Understanding the processes responsible for net sources and sinks of GHGs such as methane (CRt) and nitrous oxide (N20) would help in better predictions of future concentrations and the rate and extent of Climate Change. This study was carried out in Karura Forest and the objectives were (1) to asses the effect of forest type on CIiJ and N20 fluxes, (2) to evaluate the effect of seasons (wet and dry) and soil water content on the terrestrial sink and source of CH4 and N20 and (3) to determine the relationship between terrestrial N20 and CH4 fluxes, and the rates of soil net mineralization and nitrification in Karura forest. Gas fluxes were measured monthly using chamber techniques for a period of 10 months (March - December, 2008) from a natural forest stand and three different exotic plantations (Eucalyptus saligna, Cuppressus torulosa and Araucaria cunningham species). Gas analysis was done on a Shimadzu gas chromatograph (GC) fitted with an electron capture detector (ECD) for the N20 and a flame ionization detector (FID) for the CH4 detection and a 6Ft long-steel packed Porapak Q analytical column. Soil water content, inorganic N stocks and net N mineralization and nitrification rates were also determined. The forest was a net consumer (negative fluxes) of CH4 both during the wet and dry months. The CRt fluxes were significantly influenced both by the seasons (Feat = 9.44, Ftab = <0.001) and also between the species types (Feat = 4.61, Ftab =0.004). There was more uptake during the wet months compared to the dry ones. The annual uptake ofCH4 was highest in the natural forest at -4.77?0.14 while the exotics were averagely equal consumers: E. saligna (-3.75?0.14), C. torulosa (-3.61?0.13) and A. cunningham at - 3.23?0.11 Kg CRt halyr'. Most of the uptake was experienced during the wet months with the natural forest leading at -1.85?0.21 and A. cunningham the least at -1.25?0.13 mg CH4 m-2 d'. There was a net emission (positive fluxes) of N20 from the forest. The N20 fluxes were very significantly different between the seasons (Feal = 6.98, Ftab < 0.001) and also between the species type (Feal = 6.22, Ftab < 0.001). The influence of the interaction between the seasons and species type on the fluxes was also very significant (Feal = 2.47, Ftab < 0.001). The natural forest was the highest emitter of N20 at 0.37?0.03, followed by E. saligna (0.24?0.01), A. cunningham (0.20?0.02) and lowest in the C. torulosa stand at 0.18?0.01 KgN ha-1yr-l. Most of the emmisions were experienced during the wet months with the natural forest leading at 14.7 ng Ncmid' and the exotics averagely equal at 8 ng Ncm' The percent water field pore space (%WFPS) had a significant influence on the Cf4 fluxes (Feal = 2.64, = 0.112); but not on the N20 fluxes ((Feal = 0.04, Ftab = 0.85). Overall the N03 pool increased during the wet months while the NH4 pool decreased. The A. 'cunningham stand had the lowest pool of N stocks and the natural forest, the highest. The E. saligna stand had the highest pool ofN03-N both in the dry (17.9mgNlKg soil) and wet months (22mgN/Kg soil) while the natural forest stand had the highest NH4-N pool; 17.8mgN/Kg soil in the dry months but only 6.7mgN/Kg soil in the wet months. Net-N mineralization rates were not influenced by season (Feal = 0.21, Ftab = 0.644) but there was influence from the species types (Feal = 1.66, Ftab = 0.028). Net-N nitrification rates were greatly influenced b

An assessment of the contribution of Nation Media Group in enviromental conservation: the case of Karura Forest

Author: Gitonga, Elizabeth N M

Awarding University: University of Nairobi, Kenya

Level : MA

Year: 2009

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Nation Media Group ; Environmental protection ; Conservation ; Forests ; Karura Forest ;

Abstract:

There is an increasing worry about climate change globally and its threat on food security especially in the developing countries. Climate change has come about largely due to human activities that harm the environment particularly the destruction of water catchment areas. The effects are enormous - there have been more floods, shortage of food, electricity and recurrent droughts leading to serious humanitarian challenges. The environment is a very critical area in our lives today and the urgent steps we take to protect it will reap great benefits for the generations to come as well. Therefore, in addressing the reasons for the deterioration of the environment, we will be bearing in the mind the need to safeguard our future and that of generations to come. This implies that countries and corporate organisations must integrate interventions that aim at improving the lives of people through protection of the environment, alongside their business interests. The aim of this study, therefore, was to assess the contribution of Nation Media Group in environmental conservation, the case of Karura Forest. Any activities that the Nation Media Group engages in to safeguard Karura Forest and directly targeting communities living adjacent to it was the focus of this study. To achieve the objectives, the study takes a combination of both qualitative and quantitative dimension, and employing various methods of data collection namely administering a questionnaire, key informant interviews, focus group discussions and observation. The sample size for the questionnaire was 60 drawn from people living near the forest. Both purposive and stratified sampling was employed in selecting the respondents. Key informants were interviewed face-to-face. Two focus group discussions were held each comprising of eight members. Data was analysed using simple graphs, bar charts, pie charts and tables to show frequency distribution of the variables. For qualitative data, emerging topics and issues were discussed further. The major finding of the study was that to some extent Nation Media Group had succeeded in creating awareness on environmental conservation. However, other stakeholders were of great influence too.

'Donor-driven' neoliberal reform processes, 'democratization' and the production of deforestation in Kenya : the case of Karura and Oloolua forests in Nairobi.

Author: Njeru, Jeremia

Awarding University: University of Wisconsin, Milwakee, USA

Level : PhD

Year: 2008

Holding Libraries: ;

Subject Terms: Geography ; Deforestation ; Karura Forest, Nairobi, Kenya ; Oloolua Forest, Kenya ; Foreign aid ; Democracy ;

Abstract:

In sub-Saharan Africa, like most of the developing world, democratization has coincided with neoliberal economic reform. Yet, studies of democratization and neoliberalism tend to remain separate, failing to recognize their complex interconnections, both in their material and discursive dimensions. At the heart of this dissertation research is the question of how these interconnections are manifested in the environments of urban sub-Saharan Africa. The dissertation examines the role that combined processes of implementing neoliberal adjustment programs and electoral democratization in Kenya played in the deforestation of Karura and Oloolua forest reserves. The forest reserves are located in Nairobi, the nation's commercial and political capital. Both forests underwent accelerated loss of trees and land in the 1990s, a period during which state elites were grappling with early phases of neoliberal reform and electoral democratization in the country. Additionally, the dissertation examines responses from various civil society groups and individuals to the issue of deforestation. Ideas in urban political ecology, debates around relationships between the environment and both processes of democratization and neoliberal economic reform, and discussions of collective action arising from civil society and social movements inform the analysis in this dissertation. The dissertation draws from interviews and discussions conducted with state and city officials, key individuals of various civil society groups, and ordinary Nairobi residents. The dissertation also considers relevant print materials. This study concludes that the realities of electoral democracy and neoliberal economic reform in Kenya complicate simplistic views of the interactions between democratization and neoliberalism. The study argues that the pressure to satisfy donors with a neoliberal agenda, in combination with the pressure to raise funds to compete in a multiparty election, led state elites to sell and develop the public forests to reserve their power, under the pretense of privatization and reform.

Taxonomic, ecological and biodegradation studies of the Basidio-mycetions mood inhibiting fungi of Karura Forest, Kenya.

Author: Osano, Anne Adhiambo

Awarding University: University of Nairobi, Kenya

Level : PhD

Year: 1997

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Fungi ; Karura Forest, Nairobi, Kenya ; Classification ; Pathogens ;

Abstract:

Wood inhabiting basidiomycetous fungi are able to metabolise lignin, cellullose and hemicellullose components of the plant cell wall causing either a white rot when both lignin and cellullose are metabolized or a brown rot when only cellulose and hemicellulose are mineraJized. White rot fungi are the major degraders of highly lignified tissue and so play an important role in the recycling of photosythetically fixed carbon. The lignin enzyme system of the white rot fungi is extracellular, non-specific and non-hydrolytic enabling these organisms to mineralize a varierty of synthetic insecticide compounds including polycyclic aromatics and some chlorinated phenols. These fungi can therefore, be useful in bio-remediation of contaminated soils as a result of pesticide use. Some wood inhabiting fungi are responsible for biodeterioration of timber in use and electric poles while others are pathogenic on living trees. The first critical flora of East Africa only treats the very important ecological aspects of the fungi peripherally. The enzyme system of the decay fungi has been studied mainly on one species, Phanerochaete chrysosporium. Since the system can be useful not only in bioremediation but aJso in biopulping, there is need for a comprehensive study of this system in other wood inhabiting fungi. This study therefore involved taxonomic, ecological and biodegradation aspects of these fungi. The method of Ryvarden and Johansen (1980), Gilbertson and Ryvarden (1986) and Pegler (1977, 1984) were followed for taxonomic studies. The type of rot, host, rainfall, temperature, humidity and moisture were recorded when the forest was visited for a period of one year. Nitrogen and carbon were determined according to the method of Merril and Cowling, (1966). The enzyme production and assays of P. luteoalbus were done following the method of Niku- paavola et al. (1988) with modification while DDT biodegradation studies were carried out using HC scintillation counter and GC analysis. The procedure of biodeterioration of timber followed Otjen and Blanshette (1987), 54 species belonging to 35 genara were identified. Two new species of Diplomitoporus and Wo({7poria are proposed. The species Antrodie daeda/({01711is is transferred to genus Diptomitopoms from Antrodia on the basis of decay characteristics. A new genus is proposed for Trametes elegans on the same grounds, while a revision is proposed for Schizopora and Favolus. A recombination of the genera i.oweporus and Perremporia is proposed The catalytic activity of the ligninolytic enzyme released by P. lutoalbus has A pHoptimum value of 4.0 and is substrate dependent with a KM value of 0.2311 moles and Vmax ofO.357~l moles per minute. This enzyme mineralised up to 69% 14 C DDT to either 14C02 or its metabolites while Pycnoporus sanguinerius caused up to 78% weight loss in Eucalyptus sp. Wood inhabiting basidiomycetes fruited at relatively low water potential of - 20 to - 40 MPa and were affected by Carbon and Nitrogen independently but not by C: N ratio. Most fungi fruited at pH 5- 6. More fungi were added onto the East African Polypore Flora. Some species were reallocated to different genera and a new genus proposed based on decay characteristics. Pleurotus luteoalbus released enzymes comparable with those of Phanerochaete chrysosporium , The very efficient biodegradation of DDT by the above enzyme system proves the importance of these fungi in bioremediation and possibly biopuling. The decay potential of PYCflOpOruS sanguinerius is quite high and such knowledge is crucial in effective wood preservation.

A taxonomic survey of macro-fungi of Karura Forest, with particular reference to the gasteromycetes.

Author: Adungah, John Angegas

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 1993

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Karura Forest, Nairobi, Kenya ; Fungi ; Gasteromycetes ; Classification ;

Abstract:

Specimens of the macrofungi were collected at two forest types at Karura namely. mixed indigenous and' exotic forests. The spores of the collected specimens were examined bv SEM and their surface configurations described and used together with other characters for Purposes of classification. Keys for the determination of orders. families. genera and species have been prepared. Scanning Electron Microscope has been used in the study of spore and capilitial surfaces, where possible. to eliminate the ambiguity normally common when studying the structures with light microscope , The results indicate that while all the 13 species recorded are represented in the indigenous forest typesonly three are represented in the Cupressus sp. Forest type and none is represented in both Eucalyptus sp. And the Araucaria sp. Forest types.This may suggest that gasteromycete species population are threatened from existence when indigenous forest types are replaced by exotic forests. This study looks at the consequences of introducing heteroscedasticity in option pricing. The analysis shows that introducing heteroscedasticity results in a better fitting of the empirical distribution of foreign exchange rates than in the Brownian model. In the BlackScholes world the assumption is that the variance is constant, which is definitely not the case when looking at financial time series data. In this study we therefore price a European call option under a Garch model Framework using the Locally Risk Neutral Valuation Relationship. Option prices for different spot prices are calculated using simulations. We use the non-linear in mean Garch model in analyzing the Kenyan foreign exchange market.

Studies on the regeneration and growth characteristics of Brachylaena huillensis in semi-deciduous forests of Kenya.

Author: Kigomo, Bernard N

Awarding University: University of Oxford, England

Level : PhD

Year: 1989

Holding Libraries: University Microfilms International ; Kenya Forestry Research Institute Library ;

Subject Terms: Plant growth/Trees/Forestry/Brachylaena huillensis/Karura Forest, Nairobi, Kenya/Ngong Forest, Kenya/Muguga Forest, Kenya/ ;

Abstract:

Available from UMI in association with the British library. Requires signed tdf. The thesis describes investigations into the factors affecting the reproduction, especially germination, survival and growth of seedlings and adults of Brachylaena huillensis O. Hoffm, in Karura, Ngong, and Muguga forests and in the nursery. Brachylaena grows in remnants of semi-deciduous forests in the Central and Coastal areas of Kenya. Analysis of seedling, sapling and stem size distributions indicated that the tree is well represented from seedling to large diameter stems. Studies of the pattern of distribution revealed that seedlings, saplings and even adults are distributed in patches (p $<$ 0.001). The patchy distribution is a reflection of the distribution of female trees in the forest. Brachylaena is dioecious. It produces flowers and seed twice every year but flowering is influenced by the timing and amount of seasonal rainfall. Up to 80 percent of the seed is subject to pre-dispersal predation by insects. Viability of dispersed seed ranged from 0.6 to 6 percent in the laboratory but was only 2 percent on the forest floor. Loss of viability is accelerated by sunlight and, in the soil seed bank, through attack by soil organisms. Complete loss of viability of sound seed in the forest occurred within 15 weeks but seeds stored in the laboratory remained viable for 61 weeks. Germination and seedling survival are influenced by the amount and distribution of moisture. Litter reduces germination rates, and survival of germinated seedlings, but only when moisture is limiting. Growth studies in the nursery, under three light regimes, and in natural forests indicated that seedlings remained healthy in 2-14 percent of full light but grew slowly in the forest. In 40-50 percent of full light seedlings were healthy and grew fast in the nursery. Un-shaded seedlings in the nursery grew fast but had poor form. Exposure of shaded seedlings to full light resulted in damage from scorching and reduced growth. Growth rates of pole and adult trees in natural conditions are slow, ranging from 0.13 to 0.44 cm diameter per year. Low growth rates are attributed to competition and allocation of much energy to reproduction. Management under a selection system is recommended.