53 Records out of 22207 Records

The performance of selected tree species in the rehabilitation of a limestone quarry at East African Portland Cement Company land Athi River, Kenya

Author: Gathuru, Gladys

Awarding University: Kenyatta University, Kenya

Level : PhD

Year: 2011

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Athi River ; East African Portland Cement Company Limited ; Acacia xanthophloea ; Schinus molle ; Casuarina equisetifolia ; Trees ; Land reclamation ;

Abstract:

Quarrying for limestone is an economic necessity that is not only hazardous to human but also one that invariably has deleterious effect on the environment. Information on the performance of trees species is important as plants are key in the revegetation of exhausted quarries. A comparison of field performance of Acacia xanthophloea, Schinus molle, Casuarina equisetifolia and Grevillea robusta was made in an exhausted limestone quarry, backfilled with limestone mine waste, in a semi-arid area, in Athi River, Kenya, between 2005 and 2008. The aim of the study was to assess the performance of the above tree species and to determine if these tree species had an influence on the soil physical and chemical properties. The seedlings were produced in a nursery and transplanted in plots established in the exhausted quarry site using randomised complete block design. Growth performances were estimated by measuring; tree height, diameter at the stem base (BD) , and diameter at breast height (DBH) from March 2006 to March 2008. The soils physical and chemical parameters measured were: moisture content; organic matter; pH; total Nitrogen; total Phosphorus and exchangeable cations. The study revealed that the time-species interaction was significant (p<0.001), indicating continuous tree growth for all the species. The trees species performance was varied. C. equisetifolia recorded the highest growth increments for the; height (525.3 em), BD (7.42 em) and DBH (4.94 em) and the highest growth rates for; tree height (14.24 cm/month), BD (0.23 em/month) and DBH (0.l4 em/month), indicating superior performance. This was followed by A. xanthophloea and S. molle. Grevillea robusta showed poor performance and recorded the lowest growth increments for; height (231.7 em), BD (4.41 ern) and BDH (2.0 ern) and growth rate for; tree height (5.04 em/month), BD (0.084 em/month) and DBH (0.023 em/month). These results indicate that there is species-specific response that may be due to different water- and nutrient-use strategies and growth patterns. The soil had low soil moisture content which ranged from 0.67% to 2.3%; alkaline pH, ranging from 8.0 to 8.98; low soil nitrogen content ? 0.03%), related to the limited soil organic-matter content (ranging from 0.05% to 0.38%), and high to moderate exchangeable cations. All the tree species had a noticeable influence on soil chemical properties, by the end of the research period. The pH values and total Phosphorus were relatively lower in soils close to the tree row (0.5 m) and increased with distance from the trees, while the soil values for organic matter, total Nitrogen, and exchangeable cations were relatively higher close to the tree row and decreased with distance from the trees. From the study, C. equisetifolia has the best growth performance and also has a higher positive influence on the soil properties followed by A. xanthophloea. The two species are therefore recommended to be used in the rehabilitation of limestone quarries in similar semi-arid conditions.

Effects of soil physicochemical properties and genetic characteristics on distribution of acacia senegal (L) willd. varieties in the dryland areas of Kenya

Author: Githae, Eunice Wamuyu

Awarding University: University of Nairobi, Kenya

Level : PhD

Year: 2011

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Acacia senegal ; Trees ; Agroforestry ; Soils ; Arid and semi-arid regions ;

Abstract:

Acacia senegal is a dryland multipurpose tree species highly valued for gum Arabic production, agroforestry and desertification control. The aim of this study was to investigate the edaphic and genetic factors that affect distribution of the three Kenyan indigenous varieties (A. senegal var. senegal, var. kerensis and var. leiorhaehis) for the purpose of conservation of genetic resources and improvement of smallholder livelihoods in the drylands of Kenya. In the first part of research, inter-simple sequence repeat (ISSR) and chloroplast micro satellites (cpSSR) markers were used to study genetic diversity among seven Kenyan populations of A. senegal (Kajiado, Magadi, Kibwezi, Ntumburi, Ngarendare, Daaba and Kulamawe) embracing the three putative varieties. In the second part, soil physicochemical properties were assessed by collecting soil samples under the canopies of the three varieties taking into account distance from the trunks (0, 1 and 2 m) at a depth of 0 - 25 em and comparing with the soils from the open canopies. The third part estimated the potential of the three varieties to fix nitrogen in their natural ecosystems using 15N natural abundance method using two reference species namely; Balanites aegyptiaea and Commiphora africana. The study was conducted in the arid and semi arid lands of Kenya. The two molecular markers detected similar levels of Nei's gene diversity (HISSR= 0.211, HcpSSR= 0.212) among the A. senegal populations. Analysis of molecular variance (AMOV A) detected significant genetic variations within and among populations (P<O.OOl and P<O.Ol for ISSR and cpSSR, respectively), whereby the seven sites were differentiated into two regions (north and south). There were significant differences in soil 'Qa,,:{sicocaemica. 'Q'to'Qerties aro.o~ the tmee varieties (f<O.05 and P<O.Ol). Soil nutrients under the canopies were higher than in the open canopies mainly due to the effects of litter accumulation. The estimated nitrogen fixed (%Ndfa) values for the three varieties ranged from 18.20 - 32.21% with A. senegal var. senegal showing the highest values. The mean nitrogen content in leaves ranged from 2.46 - 4.0% and were higher than those of the adjacent non-fixing reference species. The results indicate that there is genetic diversity and variation among and within the three indigenous varieties of A. senegal in Kenya, which can provide raw materials for tree improvement programmes. The three A. senegal varieties have beneficial effects on soil fertility improvement and this would most likely enhance herbage productivity both in quality and quantity in the Kenyan drylands. Domestication and improvement will enhance conservation and sustainable utilization of the species, improve productivity and quality of gum and hence directly empower the drylands communities who are key collectors of gum and other forest products.

Uptake of micronutrients by acacia senegal varieties and its possible effect on gum arabic quality

Author: Lelon, Joseph Kipkosgei

Awarding University: University of Nairobi, Kenya

Level : PhD

Year: 2008

Holding Libraries: University of Nairobi Chiromo Library ;

Subject Terms: Acacia senegal ; Trees ; Plant nutrients ;

Abstract:

A study was conducted to establish the uptake of micronutrients by two Acacia senegal varieties established under arid and semi-arid conditions, and its subsequent effect on the quality of gum arabic exudates. Soil and gum arabic samples from the experimental sites at Solit, Kapkun, Kimorok and Maoi in Marigat division, Baringo district, were collected, dried and analysed to establish their baseline physical and chemical characteristics. Glasshouse pot experiments were conducted using the same soil and vermiculite media to determine uptake of copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) by Acacia senegal seedlings. A randomized, split-plot design that simulated the environmental conditions in the field was used in treatments varying from normal, low and high concentrations of the micronutrients applied. The soil types varied significantly (P < 0.05) in the level of calcium (17.3, 5.7, 6.4 and 5.0 cmol. Olkg) and magnesium (6.1, 3.3, 4.0 and 2.7 cmol. ()lkg), respectively, at the study sites. The average copper uptake (103 ppm) by Acacia senegal variety senegal in Solit on dry matter (OM) basis was significantly higher (P < 0.05) than that at Maoi (41 ppm), Kimorok (33 ppm) and Kapkun (30 ppm). Gum arabic from Acacia senegal variety senegal in Kapkun and So lit had concentrations of 45 and 40 ppm Cu, which reveal that Acacia senegal variety senegal tends to take higher Cu levels (l08 and 156 ppm) from the soils than that of Acacia senegal variety kerensis at Kimorok and Maoi (38 and 32 ppm). Iron and manganese uptake by the variety (654 and 638 ppm) at Kapkun was significantly higher (P < 0.05) than that of the variety at Kimorok (366 ppm Fe and 307 Mn), respectively. Zinc uptake by Acacia senegal variety kerensis at Kimorok (533 ppm) was significantly higher (P < 0.05) than in Maoi (233 ppm), Kapkun (224 ppm) and Solit (141 ppm). The gum arabic had ash content of 2.88%. Analysis showed that the ash content had a concentration of Zn (124 ppm) which indicated that Acacia senegal variety kerens is tend to take higher concentrations of Zn (533 ppm) from the soils than that of Acacia senegal variety senegal (141 ppm). Moisture, ash and volatile matter contents in gum arabic from Acacia senegal variety senegal were 14.9%, 3.16% and 64.24%, while Acacia senegal variety kerensis had 15.2%, 2.88% and 63.8%, respectively. Gum arabic obtained from Acacia senegal variety senegal had higher levels of copper (45 ppm), iron (1415 ppm) and manganese (109 ppm) compared to variety kerensis which by contrast had higher levels of zinc (124 ppm) and nitrogen (0.34 %), respectively. All these levels however fell within the ranges quoted in the International Standard Specifications (0.26% - 0.39% N, iron (730 - 2490 ppm), manganese (69 - 117 ppm), zinc (45 - 111 ppm), ash 2 - 4% and moisture 13 - 15%, respectively). The quality parameters of gum arabic may partly depend on soil characteristics, climate, and availability of the nutrients in the soils.

Anti-leishmanial activity of acacia mellifera (leguminosae : momosoideae) against leishmania Major

Author: Mburu, Faith Wambui

Awarding University: Kenyatta University, Kenya

Level : MSc

Year: 2007

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Acacia mellifera ; Leishmania major ; Medicinal plants ; Drug therapy ;

Abstract:

Leishmaniasis is a major group of parasitic diseases in the tropical regions. Their public health importance requires integrated measures in order to ensure effective control of the disease. Chemotherapy is the mainstay of control with pentavalent antimomal agents still widely used as the drugs of choice. However. these drugs are associated with many undesired effects, which include renal and cardiac toxicity. nlyalgia, anthralgia. pancreatitis, gastrointestinal problems. cardiac arrhythmia and sudden death. I he antimonials are also very expensive, and require a long period of administration. Subsequently. the search for compounds with possible antileishmanial activity is growing. A lot of locus is currently being given to natural products. It has long been known that plants are a rich source of compounds with potential medicinal uses. ,Acacia mellifera subsp. mellifera is a recognized medicinal plant used for conditions such as malaria pneumonia, sterility, stomach problems and primary stages of syphilis. However_ limited information is Available on its isolated metabolites. The main objective of this study was to determine whether A. mellifera has any antileisllnlanial activities. To achieve this. the stem bark and leaves of .A. mellifera were extracted using methanol and dichloromethane then extracts evaluated against Leishmania major promastigotes and alnastigotes in limo. Further fractionation on dichloromethane extracts yielded nine fractions designated as fractions I-IX. The effects of extracts as well as fractions were evaluated both in cell free media and using infected macrophages. To evaluate the immunostimulatorv activities of the extracts, production of nitric oxide in supernatants from macrophages stimulated with extracts was detected by Griess test. All tests were done in triplicate. Statistical analyses of the results obtained were done by analysis of variance. chi-square and Kluskal-Wallis test. Results revealed that extracts containing a combination of methanol and dichloromethane had the highest activity against L. major promastigotes in cell-free culture. 100%) mortality was observed on promastigotes cultured with 5mg/ml of the methanol and dichloromethane crude extracts. The methanol and dichloromethane stem bark extracts, however. did not inhibit the transformation of L. major alnastigotes into promastigotes (P>0.05). The stem bark methanol extract had the lowest infection rate of 41.35%. Infection rates of' the extracts compared to a positive control had a difference (x2 =13.89; df=9: P>0.05). The fractions of dichloromethane had a statistically significant difference in their infection rates (F=6.827: df=4.15: P<0.01). Fraction VII had the lowest infection rates of 30% at 250mg/ml and also the lowest IC50 of' 54.19pg/ml. Close in its activity were fractions Vlll and IX. Results for immunostimulatory activity among the fractions of dichloromethane indicated that there was no significant production of nitric oxide (P>0.05). These results suggest another possible mechanism of action of the fractions other than through stimulation of nitric oxide production. A comparison of the immunostimulatory effects between the methanol and dichloromethane indicated production of nitric oxide by the methanol extract. There was a difference (H4,4,4,4= 14.04: P<0.05). The results from this study demonstrate that Acacia mellifera indeed has activity against Leishmania major parasites. This is a major contribution toward attainment of the Millenium Development Goal that seeks to combat disease.

Some factors that influence the ecology of acacia xanthophloea benth. fever tree in lake Nakuru national park, Kenya

Author: Najma, Dharani

Awarding University: University of Nairobi, Kenya

Level : PhD

Year: 2006

Holding Libraries: University of Nairobi Chiromo Library ;

Subject Terms: Acacia xanthophloea ; Ecology ; Lake Nakuru National Park, Kenya ;

Abstract:

Lake Nakuru National Park is situated in Kenya's Great Rift Valley and occupies about 42 km2 at the lowest point in a wider catchment basin of approximately 1800 km'. Acacia xanthophloea (Fever tree) woodland dominates the major habitat along the park's rivers, lakeshore and flood plains. This woodland provides habitat for a range of large herbivores, mainly Rothschild's Giraffe (Gira.ffa camelopardalis rothschildi), Black Rhinoceros (Diceros bicornis), Olive Baboon (Papio anubis), Vervet Monkey (Cercopithecus pygerythrus) and several other mammals and insects. In addition the woodland also contributes to the park's aesthetic value and as a tourist attraction. Acacia xanthophloea trees have been undergoing an unexplained die back in the park due to unknown causes over the last few decades. This study investigated the environmental factors that influence the ecology of Acacia xanthophloea trees and armed at identifying the causes of the die- back. Four different sites within A. xanthophloea habitat were selected for the study structure and composition of the woodland by using rectangular plots. Within each plot, density, height, canopy cover and stem basal area of woody species were estimated. Sampling was conducted seasonally - both during the rainy and dry seasons of the year. Data were collected quarterly between May 2002 to May 2004. The study on the impacts of intense browsing pressure by large herbivores on the growth of A. xanthophloea trees was carried out using a fenced plot. This was compared with an adjacent unfenced plot. Soil, water, bark and leaf samples of A. xanthophloea trees were also collected. Vegetation profile diagrams were constructed from the transect data collected from various . woodland habitats. Results clearly indicated that the four study sites were dominated by Acacia xanthophloea trees. Other woody species include, Grewia similis, Rhus natalensis, Lantana camara, Abutilon mauritianum, May tenus heterophylla were also encountered. Significant differences were found in height growth, canopy cover and stem diameter at breast height (DBH) of Acacia trees in the fenced plots as compared with the unfenced plots both in the wet and the dry seasons. The growth in height and canopy of A. xanthophloea trees was found to be significantly higher in the fenced (un-browsed) plots than in the unfenced (browsed) plots. However, growth in DBH of Acacia trees was found to be significantly higher in the unfenced plots than in the fenced plots. Six essential and non-essential elements including nitrogen (N), copper (Cu), zinc (Zn), chromium (Cr), cadmium (Cd) and lead (Pb) in the soil, water and plant samples were analyzed using Atomic Absorption Spectrophotometry (AAS) technique for Cu, Zn, Cr, Cd and Pb, whereas N was analyzed using micro Kjeldhal method. Measurement of stable isotope composition of carbon and nitrogen in the soil and plant samples were made with the use of Isotope Ratio Mass Spectrometer (IRMS). Analysis of variance and student's t-test revealed that there was a significant (p < 0.05) seasonal trend in variation in the soil and water mean physico-chemical parameters and elemental concentrations. Also, significant (p < 0.05) differences were observed in the mean elemental concentration of the bark and leaves of A. xanthophloea trees obtained from different sites depending on a particular season. This study concluded that Lake Nakuru is becoming increasingly degraded due to the expansion of agriculture and industrialization in its environments. Its riparian and terrestrial vegetation mainly consist of Acacia xanthophloea woodland that is under threat from domestic, industrial (toxic heavy metals) and agricultural (pesticides) wastes. Pollutants enter through the sewerages, rivers, landfills, storm drainage, runoffs and underground water pollution. Therefore, its conservation requires a thorough understanding of how the lake ecosystem and its riparian and terrestrial areas function under the impact

The effects of herbivory on interactions of pollinators and flowers in Acacia spp. (Fabaceae, mimosoideae) in Laikipia

Author: Otieno Mark

Awarding University: Kenyatta University, Kenya

Level : MSc

Year: 2005

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Acacia ; Laikipia District ; Trees ; Plant reproduction ;

Abstract:

Acacia trees are among the most dominant tree species found in semi arid ecosystems with a vast geographical distribution throughout the savanna habitats. The trees are leguminous and have remarkable ability to fix nitrogen in the soil, thereby, improving fertility. About all parts of an Acacia tree are edible to different types of animals and their leaves provide the only greenery in the dry season, so are bound to be eaten. As such, they support enormous pyramids of biomass in complex food chains with super predators at the apex. Economically, they are used as basic sources of fruits, firewood, medicine and secondary products for daily human livelihoods. Owing to their important, a lot of studies have focused on their growth ecology. Herbivory and reproduction are among the most studied aspects of Acacia. However, the interactive link between these two aspects and their effect on the growth success of Acacias is poorly understood. Understanding the link between herbivory and pollination, would not only provide useful information on the interaction of plants and diversity of visitors but also information on the floral morphometry and rewards to pollinators. The general objective of this study was to determine the effects of herbivory on interactions between pollinators and flowers in Acacia spp. The study was conducted at the Mpala Research Centre in Laikipia District of Kenya (0017'N, 36053'E) on one herbivore excluded plot (70m x 50m) and in the open grazed areas adjacent to the excusion plot. Acacia trees for investigation were randomly selected. Data were recorded on floral morphometric measurements and dehiscence in different browsing levels and simulated herbivory plots. The number and type of visitors to the flowers was also recorded besides determining the species diversity of wild flora within the study site. ANOVA was used to analyze variation in different flower attributes, SNKwas used to separate means with significant differences. Generally, unbrowsed trees produed significantly (P<0.05) more flowers, florets, anthers and larger floral diameters than naturally and heaviliy browsed Acacia trees. Similarly, unbrowsed trees attracted more pollinators especially bees than naturally browsed trees. An earlier pollinator peak activity was recorded on unbrowsed trees than browsed trees. A significant shist of inflorescence dehiscence time occurred between unbrowsed and naturally browsed trees of A. nilotica, (KS=0.34, P<0.01), A. brevispica (KS=0.34, P<0.01) across the day. The unbrowsed trees attracted significantly more pollinators than naturally browsed trees probably because the unbrowsed trees had larger flowers thereby becoming more visible to pollinators from a distance than those of browsed trees. The delayed floral dehiscence of naturally browsed trees could have been caused by modification of the microclimate around the flowers making them open later in the day than unbrowsed trees. This study has shown than A. nilotica and A. brevispica vary their floral resources greatly when browsed, whereas A. etbaica tends to show compensatory floral growth. More studies therefore, need to be done on their reproductive success

The effects of Prosopis juliflora (Oc) hyne and Acacia tortilis (Forsik) trees on understorey plant species and soil properties on Njemps Flats, Baringo District Kenya.

Author: Kahi, Hemru Chore

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 2004

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Soils/Trees/Prosopis juliflora/Acacia tortilis/Njemps Flats/ ;

Abstract:

ABSTRACT NOT AVAILABLE

Evaluation of Acacia seyal and Balanites aegyptiaca as sources for nutrients for ruminants

Author: Kitilit, Jackson

Awarding University: Egerton University, Kenya

Level : MSc

Year: 2003

Holding Libraries: Egerton University Library ; World Agroforestry Centre Library ;

Subject Terms: Trees/Cattle/Feeds/Acacia seyal/Balanites aegyptica/ ;

Abstract:

ABSTRACT NOT AVAILABLE

A comparative study of soils under contrasting vegetation regimes in parts of Marigat Division Baringo District Kenya

Author: Tungani, Johnstone Odera

Awarding University: Moi University, Kenya

Level : MPhil

Year: 2002

Holding Libraries: Moi University Margaret Thatcher Library ;

Subject Terms: Baringo District/Marigat Division, Baringo District/Tugen plateau/Njemps Flats/Soils/Vegetation/Acacia mellifera/Lantana trifolia/ ;

Abstract:

There was a site in the Tugen plateau where within a stretch of less than one kilometer, a conspicuous change was observed in Acacia mellifera' s growth characteristics. A similar change was observed with respect to Lantana trifolia in the Njemp's flats site. This study was done to try and establish whether these trends in vegetation growth was due to differences in some selected soil properties across the landscape. The t statistic was used tocompare the results. In the Tugen plateau study site, there were more roots per given volume of soil in the dense vegetation than in the sparse vegetation profiles at every given depth. Roots were present in all the profile depths (down to 150 cm) in the dense vegetation region whereas in the sparse vegetation area, the presence of roots was either negligible or nil below 55 cm depth. It was also in these rootless layers that the soil factors which are known to inhibit plant survival were most prominent. The dense vegetation area had deeper profiles (over 150 cm deep) than the sparse vegetation area (average of 65 cm depth). The sparse vegetation region had higher surface and subsurface stoniness (70 % surface stoniness) than the dense vegetation area (25 % surface stoniness). The sparse vegetation soils had higher bulk densities than the dense vegetation soils. A study of the profiles showed that the dense vegetation soil profiles were more developed than those of the sparse vegetation. The mean values for pH, extractable calcium and soluble salts in the sparse vegetation soils were 7.8, 2.3 x 104 kg ha' and 1.5 x 103 kg ha' respectively while in the dense vegetation area the values were 7.4,1.7 x 104 kg ha-1 and 8.0 x 102 kg ha-1 respectively. The values of pH, extractable calcium and soluble salts in the sparse vegetation soils were well above the optimum levels for ambient plant growth. These values in the sparse vegetation soils were also higher than the corresponding values in the dense vegetation zone. It was concluded that differences in the above mentioned soil properties contributed to the differences in vegetation regimes across the Tugen site.In the Njemp's flats study site both the dense and the sparse vegetation profiles had roots present in their horizons down to 150 crn depth. However the dense vegetation profiles had more roots. There were no pronounced differences between the Njemps' sparse and the dense vegetation soils as per the factors analyzed in this study. Both vegetation zones had deep solums of more than 150 cm, had no stones on the surface or within the profile and were in similar states of profile development. The sparse vegetation zone soil surface was more crusted than the dense vegetation soil surface. The mean bulk density of the sparse vegetation soils was slightly higher than that of the dense vegetation soils that is 1.24 and 1.21 g cm-3 respectively. pH in the sparse vegetation soils was slightly higher than the mean pH of the dense vegetation soils that is 7.5 and 7.3 respectively. It was concluded that the soil properties analyzed in this study were not the contributing to the contrast in vegetation regimes observed in the Njemps' flats. Other studies ought to be done focusing on other soil and lor non-soil factors that would be causing this kind of vegetation structure.

Effects of supplemental irrigation on soil chemical properties and growth Acacia saligna in North-western Kenya.

Author: K'Otuto, G O

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 2001

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Trees/Irrigation/Acacia saligna/North Western Kenya/ ;

Abstract:

ABSTRACT NOT AVAILABLE