Applications of pollen and spore studies to paleo-vegetation inferences of Iwopin, Ogun State, Nigeria

Modifications of Land Use Systems is a trigger of change in flora composition. Fossilized pollen and spore assemblages are key to unraveling past climatic and vegetation types. Eight (8) core samples recovered at three centimeters interval each were subjected to standard palynological protocols. The lithology, pH and salinity concentrations of each sample was also determined. The recovered pollen and spore assemblages revealed three distinct zones (24 – 15cm, 15-3cm and 3-0 cm) based on indicator palynomorphs. The lowest stratum in zone 1 (24-21 cm) suggests a mosaic of rainforest and open vegetation taxa. This contrasts with stratum 21-18cm, whose indicative vegetation composition was that of freshwater swamp species. Climatically, top strata are wetter than lower ones. Zone 11 was characterized by open vegetation elements such as Alchornea and Asteraceae which are indicative indices of drier period. However, occurrence of substantial amounts of fern spores at depth 9-12 cm, coinciding with appearance of fresh water elements is suggestive of interplay between terrestrial and aquatic forces. Zone 111 was characterized by representatives of fresh water swamp, open vegetation and rainforest phytoecological groups. Fresh water swamp elements and fern spores dominated this zone, indicating a very wet period. The surface sample indicates an environment purely of an open vegetation type with high distribution of Elaeis guineensis, Pteridophyte spores and fungal spores. The Pteridophytic spores indicate regular flooding, probably from the nearby lagoon. Presence of charred cuticle is presumptive of a people at ease with bush burning, an existential promoter of global warming.