Browsing by Author "Sanford, W. W."

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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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    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.
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    Nitrogen Loss by Burning from Nigerian Grassland Ecosystems
    (Royal Swedish Academy of Sciences, 1980) Isichei, A. O.; Sanford, W. W.; Rosswall, T.
    Nitrogen loss by burning from natural grassland ecosystems in Western Nigeria was studied over a two-year period in three areas, including sites of Andropogon-Hyparrhenia - Schizachyrium-Brachiaria grassland in derived, Southern Guinea and Northern Guinea savanna. The production of aboveground herbaceous material and litter fall of leaves, wood and fruit/seed was estimated and the nitrogen content just prior to burning determined. Final estimates of from 12 to 15 kg ha-1 yr-1 of nitrogen lost by burning were obtained. it is suggested that such loss may be replaced to a considerable extent by rain and blue-green algal crust fixation.