Theses and Dissertations

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Browsing Theses and Dissertations by Author "Isichei, A. O."

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    Characterization of the Forest Types of the University of Ife Campus.
    (Obafemi Awolowo University, 1986) Chukwuka, Kanayo Stephen; Isichei, A. O.
    The rainforest in the University of Ife was characterized by species enumeration and girth measurements, and by attributes derived from these measurements in 17 sample plots. The seventeen plots were located around one of the three hills on the campus, Hill 1, a general uniformity in species composition was observed for all the plots studied with the exception of those on the hill top where Brachystegia eurycoma was found to be dominant and, at times slopes which differed in species composition. The Shannon-Weiner species diversity index for all the plots was in the range 1.88-3.36. Dominance by Manihot glaziovii and Funtumia elastics were, however, observed in two plots. Plots ordination based on species showed plots on the hill top and slopes to be floristically different from those on the flat and gentle surfaces, while the species attributes ordination based on the plots showed that species diversity index, and basal area of species were more important in characterizing the sample plots. The stem girth distribution was generally found in the 11-20cm girth class with the exception of three plots. Two of the plots have high number of big trees in the > 120cm girth class while one has the highest number of stems in the 21-30cm girth class. These observations were discussed in relation to past land use in the area. The nature of succession of these plots was assessed by a modification of Horn's (1975) Markovian change. The application of this model was, however, found not to be satisfactory in assessing the succession of the sampled plots because it showed that regrowth species such as Microdesmis puberula and Napoleons vogelii will form the next generation canopy.
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    Ecology and Biology of Piliostigma Thonningii (Schum.) Milne-Redhead in the Guinea Savanna Zone of Nigeria.
    (Obafemi Awolowo University, 1985) Mbaekwe, Ebenezer Ike; Isichei, A. O.; Sanford, W. W.
    Eighteen plots in selected sites from the Mokwa, Kainji and Yelwa areas of the Nigerian Guinea savanna were sampled systematically for vegetation attributes. Four belt transects in each plot were sampled to estimate the density of all woody individuals greater than 1m high, density of Piliostigma thonningii, total basal area of woody species, and woody plant cover. Soil samples were randomly collected from the 0-15cm depth in the plots and analysed for texture organic matter and nitrogen. The vegetation and soil data and attributes derived from them were used for ordinations using principal components analysis. The ordinations show that soil factors namely sand: clay ratio organic matter and nitrogen content were, in association with some vegetation attributes, important in determining the distribution and density of P. thonningii in the areas studied. Some aspects of the biology of the plant were also studied. Best germination results were obtained after acid treatment. The phenology of the plant and its response to perturbations were observed and these observations gave an insight into its mode of propagation. Anatomical studies showed the leaf characters as being semi-xerophytes and the stem as having growth rings. The age of the plant could be estimated from ring counts. Examination of the plant for nodules did not yield positive results but nitrogen levels in the leaves compared favourably with those of other browse plants in the same area. This identifies the plant as an important browse species in the savanna. Overall, the study has highlighted the conditions under which the plant grows and its rich potential as a source of cover and browse in the Guinea savanna.
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    Effect of Soil Texture, Nutrient Stress and Water Stress on Yield of Andropogon Gayanus Kunth and Schizachyrium Sanguineum (Retz.) Alston.
    (Obafemi Awolowo University, 1985) Oke, Samson Olajide; Isichei, A. O.
    Two grasses, Andropogon gayanus and Schizachyrium sanguineum grown to maturity in fine and coarse sand culture were subjected to nitrogen and water stresses to study how these stresses interact with soil texture in affecting growth and nitrogen accumulation in these grasses. Nutrient-stressing involved administering 200m1 of a nutrient solution containing. 35 parts per million nitrogen once in four days while for water-stressing the same volume of water was fed to the plants at the same frequency. These treatments, if administered once in two days, were considered adequate for the plants. There were two other intermediate treatments. Plants grown in fine sand produced more dry matter the highest yield was adequate nitrogen and water stressing while nutrient and water stressing gave the lowest. The biomass of the two grasses increased with increased nutrient addition to the growth medium. Nutrient stress had a more noticeable effect in reducing yield than water stress. Plants grown in coarse sand had a higher nitrogen concentration than those grown in fine sand. This is attributable to high organic matter content of fine sand the highest yield was adequate nitrogen and water stressing while nutrient and water stressing gave the lowest. The biomass of the two grasses increased with increased nutrient addition to the growth medium. Nutrient stress had a more noticeable effect in reducing yield than water stress. Plants grown in coarse sand had a higher nitrogen concentration than those grown in fine sand. This is attributable to high organic matter content of fine sand grown grasses which led to dilution of nitrogen concentration. In absolute terms, plants grown in fine sand had more nitrogen content. Increasing frequency of nitrogen addition resulted in higher nitrogen content of the grasses. As with yield, giving adequate nitrogen and water-stressing resulted in the highest nitrogen accumulation while water and nutrient stressing gave the lowest. Schizachyrium sanguineum accumulated more nitrogen than Andropogon gayanus because it is more efficient in utilizing nutrients in a low concentration medium. As for plant parts more nitrogen was accumulated in the roots than leaves or stems. The implications of these observations in relation to the natural conditions in which these grasses grow are discussed.