Botany-Scholarly Publications

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Browsing Botany-Scholarly Publications by Author "Adekanmbi, O.H"

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    Open Access
    PALAEOECOLOGICAL STUDIES OF QUATERNARY SEDIMENTS FROM THE UNIVERSITY OF LAGOS, NIGERIA
    (Ife Journal of Science, 2017) Adekanmbi, O.H; Alebiosu, O.S
    The knowledge of changes in past ecological conditions during the Quaternary period of Nigeria is still incipient. This necessitated a palaeoecological investigation through drilled sediments of a 45 m borehole in a swampy area at the University of Lagos, in order to ascertain possible changes in the past ecological conditions of the study area over time. Sixteen sediment samples were collected at intervals of 3 m between the depth of 0.00 m and 45.00 m and subjected to palynological, lithological, pH and salinity analyses. In the palynological study, pollen of open forest types: Alchornea cordifolia, Elaeis guineensis, Asteraceae, among others were recovered, indicating human influence over time. Pollen of Rhizophora sp., Combretaceae/Melastomataceae, Poaceae, Ceratopteris sp., Cyclosorus afer, amongst others; were also represented. Spores of Pteris sp., Nephrolepis sp. and Acrostichum sp., charred Poaceae cuticles, epidermal cells and fungal spores were also recovered. From the lithological analysis of the samples, a considerable number of lithological types were recognized, which varied in grain-size, grain sorting and grain-texture. The pH and salinity values of the sediment samples also varied considerably at different depths. However, vegetation changes during this period could be attributed to an interplay between fluctuations in the wet-dry climatic phases and anthropogenic activities. The data obtained from lithological, pH and salinity analyses reveal a mosaic of sedimentary depositional environment in which the recovered palynomorphs were preserved. Parent plants of the recovered fossil palynomorphs are still found as extant plants till today, despite the ever increasing human activities at the study area. Absolute ages were extrapolated and these revealed the period at which paleoecological changes occurred but limited to some intervals.
  • Item
    Open Access
    Palynological Analysis of Late Holocene Sediments and its Paleoenvironmental Interpretations from Lagos Coastal Environment, Southwestern Nigeria
    (Knowledgia Review, Malaysia, 2019-08) Adekanmbi, O.H; Ajikah, L.B.; Onuminya, T.O.; Ogundipe, O.T.
    Background and Objective: Information from the distribution of palynomorphs is used to infer past vegetation changes and paleo-climatic settings, characteristic of a particular environment. This palynological studies aimed to assess the distribution of palynomorphs and reconstruct the past vegetation and make inferences on the paleoclimate of a late Holocene core. Materials and Methods: Sediments samples were collected at intervals of 3 cm to a depth of 51 cm using a universal peat corer and subjected to standard palynological procedures. Prepared slides were studied with both light and scanning electron microscope. Photomicrograph of some recovered palynomorphs was imaged using Zeiss merlin scanning electron microscope. Lithological analysis and standard accelerated mass spectrometry (AMS) was also carried out to provide a calibrated accurate ratio of 14C and 13C dates. Results: Five palynoecological groups were recognized to include mangrove, freshwater swamp, riverine/lowland rainforest and fern spores suggestive of a humid climate. Absolute ages from radiocarbon dating showed the study sediments were deposited around the last 111.8±0.4 BP indicating the late Holocene. Lithology, pH and salinity analysis revealed a miscellany of sedimentary depositional environment in which the recovered palynomorphs were preserved. Conclusion: Significantly the study revealed the disappearance of mangrove vegetation notably Rhizophora sp. and Acrosticum aureum, while open vegetation dominated recovery indicating an increase in human influence on the study area.