Browsing by Author "Ekeleme, Friday"

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    Changes in a secondary forest in southwestern Nigeria following a ground fire
    (1986) Isichei, Augustine O.; Ekeleme, Friday; Jimoh, Bakare A.
    In January 1983, two 50 m x 50 m rain forest plots in the University of Ife campus in southwestern Nigeria were demarcated for a baseline study of species composition, litterfall and tree girth increments. By accident, a severe ground fire burnt one of the plots on 31 January, barely two weeks after litter traps had been set and species listing and fist girth measurements completed. The effect of this fire was assessed in the burnt plot after 14 months, in April 1984. The fire affected small trees especially, and there were indications that some species were more sensitive than others. Manihot glaziovii, which was present in the plot and abundant in its vicinity before the fire showed a big increase in density after the fire because it was able to germinate in the openings created by the fie. These observations were related to succession, and it is concluded that the observation by some workers that the initial composition of a regrowth forest may be partly predicted from a knowledge of the seed bank in the soil may be applicable in the present case.
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    Cover crops reduce weed seedbanks in maize-cassava systems in southwestern Nigeria
    (2003) Ekeleme, Friday; Akobundu, I. Okezie; Isichei, Augustine O.; Chikoye, David
    Weeds are a major constraint to crop production in smallholder farms in tropical Africa. The weed seedbank and annual recruitment are the main sources of weed infestation in crops. This study was carried out in Ibadan, Nigeria, to evaluate the effect on the seedbank of two types of planted fallow (alley cropping with leucaena and live mulch with tropical kudzu) and a natural bush fallow under four land-use intensities. Type of fallow was the main plot. Land-use intensities, consisting of continuous cropping of maize intercropped with cassava, I cropping yr of maize-cassava followed by 1, 2, and 3 yr of fallow, were the subplots. Averaged over a 3-yr period, the seedbank was 55% lower in the tropical kudzu plots and 43% lower in the leucaena plots compared with natural bosh. The difference in seedbanks between plots cultivated after leucaena and natural fallow was 23%. Seed density of annual broadleaf weeds was high and dominated the seedbank of both planted and natural fallow. Overall, seeds of grasses occurred at low densities in all plots cultivated after 2 to 3 yr of fallow, whereas seeds of sedges occurred more in continuously cultivated plots and plots cultivated after 1 yr of Sallow in all the fallow types. Seed density of perennial broadleaf weeds increased as land-use intensity decreased. Live mulch with tropical kudzu, especially when combined with 2 to 3 yr of fallow, lowered the seedbank more than the leucaena and traditional bush fallow systems.
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    Influence of Fallow Type and Land-Use Intensity on Weed Seed Rain in a Forest/Savanna Transition Zone
    (2000) Ekeleme, Friday; Akobundu, I. Okezie; Isichei, Augustine O; Chikoye, David
    Weed seed rain was monitored in field plots under three fallow types and four landuse intensities in Ibadan, Nigeria, in 1994 and 1995. The fallow types were natural bush, planted Leucaena leucocephala, and Pueraria phaseoloides. The land-use intensities consisted of continuous cropping, involving Zea mays/Manihot esculenta and fallowing for 1, 2, and 3 yr, with each fallow period followed by 1 yr of Z. mays/M. esculanta cultivation. In 1994, seed rain in plots cropped after P. phaseoloides fallow was significantly lower than in plots cropped after bush or L. leucocephala fallow. Pueraria phaseoloides plots had similar seed rain as bush fallow plots in 1995, and the seed rain in these plots was significantly lower than in L. leucocephala plots. Weed seed rain was significantly higher in continuously cultivated plots across all fallow types than in lots that were cultivated after one or more years of fallow. The lowest seed rain was in plots that were cropped once after a 3-yr fallow. The largest quantity of weed seed input in the plots occurred in either August or September, reflecting the life cycle of the annual weeds that dominated the vegetation. Individual species differed in pattern and duration of shedding seeds within the fallow systems and land-use intensities. Annual weeds dominated the seed rain in continuously cropped plots and seeds of perennial weeds were dominant in plots fallowed for more than 1 yr before cultivation. Weeds flowered earlier in continuously cropped plots than in plots that were cropped after 2 or 3 yr of fallow. Increased land-use intensity caused an increase in seed rain and consequently increased the soil seed bank. Pueraria phaseoloides fallow was more effective in shading weeds and probably reducing the quantity of light reaching them than the natural bush and planted L. leucocephala fallow systems, and this may have been the basis of the significantly lower seed rain in P. phaseoloides plots.
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    Mineral Nutrient Flow from an Inselberg in South-Western Nigeria
    (1990) Isichei, Augustine O.; Morton, Alan J.; Ekeleme, Friday
    In a study carried out to find out if inselbergs enrich their surroundings with nutrients via drainage, amounts of total nitrogen, nitrate-nitrogen and potassium in rainfall, drainage from bare rock patches and vegetation mats on an inselberg in South-western Nigeria were measured over one year. 43.3 kg ha-1 total nitrogen, 4.8 kg ha-1 nitrate-nitrogen and 10.7 kg ha-' potassium were recorded in rainfall for the year of study. The amount of total nitrogen in drainage from bare rock was 79% of that in rainfall whilst that in drainage from vegetation mats was 29% of the rainfall amount. The respective values for nitrate-nitrogen were 57% and 13%; for potassium they were 90% and 38%. It was assumed that the loss of nutrients as water drains through vegetation mats and over bare patches was due to absorption by plants and soil in the mats and lichens in the bare patches. It was therefore concluded that there was no net enrichment of rainwater with nutrients as it flows over inselberg slopes. There is, however, a funneling of water along with contained nutrients from the inselberg to the surrounding areas. This funneling is additional to the nutrients and rainfall incident on these surrounding areas and may account for the vegetation around inselbergs being more lush than vegetation in the same area but further away from the inselbergs. A simple modeling approach was used to assess potential nutrient outflow from inselbergs. The model shows that discharge of nutrients from the edges of inselbergs increases linearly with inselberg diameter. The model further shows that if nutrient funneling only affects an area near to the edge of the inselberg then nutrient addition is several times higher than would be expected from rainfall deposition alone.
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    Nitrogen and Potassium Leaching Off Inselberg Surface Lichens at the University of Ife.
    (Obafemi Awolowo University, 1986) Ekeleme, Friday; Isichei, A. O
    The leaching of nitrogen (nitrate-nitrogen and total nitrogen) and potassium off inselberg surface lichens by rainfall on Hill II, University of Ife campus was studied in the period between 11th March and 15th October, 1985. Rain free-fall, surface flow off lichen surfaces on the inselberg and run off from vegetation mats were collected from permanent collecting points after each shower. The nitrate-nitrogen, total-nitrogen and potassium amounts of free-fall were 1.74, 12.33 and 6.18 kgha-1yr-1 respectively. The inputs of these elements were highest in the early part of the rainy season. The concentrations of nitrate-nitrogen, total-nitrogen and potassium leached off the lichens fluctuated widely without any obvious pattern. This is discussed in relation to lichen physiology. Overall, 3.15 kgha-1yr-1 nitrate-nitrogen, 49.73kgha-1yr-1 total-nitrogen and 30.77kgha-1yr-1 potassium was leached off lichen surfaces. The highest concentration of potassium was leached in the first five showers. A comparison of both the concentrations and leaching patterns of total-nitrogen and nitrate-nitrogen off inselberg surface lichens with that leached off the vegetation mats showed that the amounts of these elements leached off the mats fluctuated as much as that leached off the lichens. The amounts of potassium leached off vegetation mats decreased as the season progressed. An estimated 2.3lkgha-1yr-1 nitrate-nitrogen, 32.73kgha-1yr-1 total-nitrogen and 25.l10kgha-1yr-1 potassium was leached off the vegetation mats. The amounts/quantities of these nutrient elements leached off the lichens were on the average higher than that leached off the mats. The estimated quantities (kgha-1yr-1) of nitrate-nitrogen, total-nitrogen and potassium charged to the environment surrounding the inselberg used for the study were 5.46, 82.46 and 55.87 respectively.