Theses and Dissertations

Permanent URI for this collection

https://ir.oauife.edu.ng/handle/123456789/994

Browse

Now showing 1 - 5 of 18

Open Access
Invasion of Patches of Natural Vegetation by Exotic Woody Species in Obafemi Awolowo University, Ile Ife
(2015-04-10) Akinwande, Ayomiposi Olayinka
The study investigated and determined the extent and pattern of invasion by the exotic woody species, their dispersal mechanism as well as the most successful invaders and why certain areas may be prone to invasion by exotics than others in the University Estate. This was with a view to understanding the patterns and rates of invasion of natural forest by exotic species. The study was carried out in thirteen 25 m x 25 m sample study plots in different parts of the Obafemi Awolowo University Estate, Ile-lfe using forest patches of different successional stages. In each study plot, all the woody plants that were 2 m and above in height were enumerated and identified. A tape was used to measure the girth size of each woody plant at breast height. The height was also measured using a calibrated wooden pole for the short ones and a Haga altimeter for the taller ones. The distance of each of the sample plots from the nearest built-up area and cluster of the exotic plants was recorded. The geographic location of each sample plot was determined using a Garmin global positioning system. The dispersal mechanism of each exotic species was also noted. After the field work, the densities of all enumerated woody plants, both exotic and indigenous in each sample plot were calculated. Histograms of the size class distribution of all enumerated woody plants were prepared and the sample plots compared for rate of invasion/proportion of exotics. Correlation analysis was carried out to determine the significant relationships between plot exotic density and distance from built up areas/cluster of exotics. Ordination of plots and species was also carried out to determine which plots were most prone to invasion, the most successful invaders and the plots with higher species diversity. Results showed that there were 87 woody species consisting of 12 exotic species. Five plots were characterized by young trees mostly in the 0-20 cm size class, four plots were without exotics, two plots had few exotics in the smaller size class, one plot contained only one species of exotic found in the highest size class while one plot had few exotics randomly distributed in the size classes. The six least invaded plots were mostly in their mid successional stages except one that was mature while the five most invaded were mostly early succession plots. Two plots which were in the early/mid successional stages were moderately invaded. The invaded plots were the disturbed ones that were close to the built up areas with a cluster of exotics that were deliberately planted for ornamental purposes. Distance from cluster of exotics was very strongly negatively correlated with exotic density (r = - 0.739, p = 0.01). The same applies to built up, area and exotic density (r = 0.547, p = 0.03). The most successful invaders in this study were Leuceana leucocephala, Delonix regia, Peltophorum pterocarpum, Bauhinia monandra and Azadirachta indica. Seven plots had high species diversity while six plots had low species diversity. The study concluded that most of the plots had been invaded and that disturbance, dispersal mechanism of the exotics, nearness to built up areas and cluster of exotics were major factors in the invasion of forests by exotic species in the Obafemi Awolowo University campus.
Open Access
Studies on the Productivity of Echinochloa Stagnina (Retz) P. Beauv. in the Kanji Lake Basin of Northern Nigeria.
(Obafemi Awolowo University, 1985) Obot, Emmanuel Asuquo; Sanford., W.W.
Echinochloa stagnina growing in Lake Kainji is identified, described, and separated from Echinochloa pyramidalis and Echinochloa colonaa. The grass has been recognized by cattle farmers as an important source of dry-season fodder for their stock, while the power generation authorities view it as a problem to the Lake's hydrology and optimal power generation due to its contributions to water loss from the lake through evapo-transpiration. Echinochloa stagnina which requires the annual 10 m draw-down of the lake for successful establishment and survival, shows a marked zonation and can potentially cover up to 46% of the lake's surface area. The contribution of the grass to evapotranspirational water loss from the lake accounts for the reduction of the effective lake volume by up to 17%, for example in 1979. A management strategy which demands the harvest and removal, for livestock fodder, of 5% of the total yearly standing crop (up to 120,965.4 tonnes) in order to maintain the grass as a renewable source of dry season fodder without significantly affecting power generation is presented. With such removal an estimated 3 x 106 kg of nitrogen and 4 x 105 kg phosphorus are removable from the lake ecosystem. Sources of nutrients to balance these removals are discussed. Decomposition of Echinochloa stagnina litter in Lake Kainji is rapid and does not fit the general exponential model Wt Woe`-t where Wt is the weight of litter left after time t , W0 is the original weight of litter, k is the decay coefficient and e is the base of the natural logarithm. A mathematical model, the Kainji Lake Echinochloa Model, to calculate the area colonizable by emergent vegetation any given year once the upper and lower water levels of the previous year is known, is presented and tested. A current vegetation map of the Lake is presented; the model has been used to reconstruct the vegetation cover history of the lake.
Open Access
Studies of Abscisic Acid, Cytokinins and Gibberellins in Maturing Fruits of the Oil Palm (Elaeis Guineensis Jaquin)
(Obafemi Awolowo University, 1985) Umoru, Anefi Imhonikhe; Adebona, A.C.
Maturing fruits of the oil palm (Elaeis guineensis JaCquin), were analysed for endogenous abscisic acid, cytokinin and gibberellin activities in relation to the growth rates of such fruits. Soybean callus bioassay was used to determine cytokinin activity both in n-butanol fractions, paper chromatographed and developed in n-butanol: acetic acid water solvent system and in dried, 35% ethanol eluates from LH-20 Sephadex chromatographyl Lettuce hypocotyl and lettuce germination bioassays were used to determine the respective activities of ethyl acetate-and n-butanol- soluble gibberellins and diethyl ether-soluble abscisic acid after subjecting both to thin layer chromatography on silica gel. Developing solvent system for gibberellins was isopropanol: water, while benzene: ethyl acetate: acetic acid was for abscisic acid. The results of the bioassays showed that the hormone activities occurred mainly at Rf values of 0.1-0.2, 0.4.0.5 and 0.7-0,9 for cytokinins; 0.1-0.2; 0.3-0,5 and 0,6-0,8 for gibberellins and 0.4-0.5 for abscisic acid. Co-chromatography with authentic growth substances gave Rf values at 0.7-0.8 and 0.8-0.9 for zeatin and zeatin riboside respectively; 0.7-0.8 for gibberellic acid and 0.4-0.5 for abscisic acid. The drupaceous oil palm fruits increase in growth with time and produced a sequence of gibberellins, abscisic acid and cytokinins, each with four peaks of activity, the fluctuating level of which could be linked to the accelerating, deceleration and asymptotic growth phases. Endogenous gibberellic acid and abscisic acid were tentatively identified in this study. High levels of free gibberellins occurred in the young fruits while the conjugated forms predominated in the mature ones. Four of the six isolated endogenous cytokinins were tentatively identified as zeatin, zeatin riboside, isopentenyladenine and isopentenyladonosine. Although the interconversion between ammonia- and water-soluble cytokinins presented an inconsistent pattern, yet the decrease in the free cytokinins was concomitant with an increase in the conjugated forms in the water-soluble fractions during fruit maturation.
Open Access
Some Aspects of the Ecology and Biology of Tephrosia Bracteolata Perr, & Guill (Papiliooideae - Fabaceae).
(Obafemi Awolowo University, 1986) Awodoyin, Rasheed Olufemi; Isichei, A.O.
Some aspects of the ecology and biology of Tepharosia bracteolata, a fodder plant of the Nigerian savanna often growing in association with Andropogoneae grasses, was investigated. The seeds of the plant germinated best after 20 minutes acid treatment. Some good germination was also obtained with heat and boiling water treatment. Growth rates were better in soil enriched with phosphorus than in natural soil. Since one of the aims of the experiment was to examine the feasibility or sowing rangelands with T. bracteolata, field and laboratory studies of competition between it and Andropogon tectorum were carried out. The yields of the plants were higher when grown in mixtures than in monoculutures. Values of relative yield totals for both species were in 11 test densities greater than unity indicating mutual relationship between them. Association analysis showed that the two species were randomly distributed in the field. Soil and vegetation samplings in the field show that T. bractolata does well on acid soils with low organic carbon and nitrogen contents. The crude protein of the loaf samples (12.98%-17.98%) was adequate throughout the growing season to meet the minimal 8% crude protein requirement by animals for milk production. A. tectorum can only supply adequate protein early in the season when its crude protein ranges from 7.04% to 8.21%. Nodulation was observed in T. bracteolata. The presence of leghaemoglobin at the core of the nodules indicates effectiveness in nitrogen fixation. It is suggested that T. bracteolata can be utilized in place of imported pasture species in cropping rangelands. Also, harnessing the nitrogen fixing ability of the plant to improve soil nitrogen content could save the country part of the expenditure on nitrogen fertilizer importation and could reduce environmental pollution resulting from excessive use of the fertilizers.
Open Access
Guinea Savanna Structure and Land-use in Northwestern Nigeria.
(Obafemi Awolowo University, 1985) Ero, Isaac Izogie; Sanford, W. W.
The Guinea savanna of northwestern Nigeria was characterised using parameters of climate, soil and vegetation. The scale of variability of the attributes measured in the four localities - Yelwa, Mokwa, Borgu and Jebba - was assessed and found in the case of soil and vegetation to be significant on at least a hectare to hectare scale. Density of all species, the most abundant species, size class distribution, and pattern of woody elements were estimated. Principal component analysis was employed to explore the correlation and variability of soil attributes (sand, silt, clay, organic carbon) and vegetation characteristics between plots and localities. Broad homogeneity in edaphic features was shown, while marked differences existed between plots in each location. The vegetation was heterogeneous in respect of most physiognomic/structural attributes, although considerable homogeneity was observed at Jebba and some at Mokwa. The relative physiognomic/structural heterogeneity was shown to parallel that of soil attributes and in some cases to be directly related to specific soil attributes. The stability and resilience of the sample plots were assessed. The Markovian prediction model gave varying values of weighted relative change showing that successional or maturity class differences are not mainly dependent upon differences in species composition. High diversity indices are related to stability if log-normal species distribution indicated stability, but if geometric species distribution indicates stability then stability is associated with low diversity. It is concluded that land-use and vegetation mapping must done on a local scale permitting the application of management is to delineated land units. The attributes concerning ability (functional/compositional stability) vary in relation to specific land use and should be accordingly assessed. Recommendations are made for such assessment together with listings of parameters most practical for land-use planning in the Guinea savanna.

Browse

Recent Submissions