Recent pollen rain analysis in Akoko environment as indicator of the vegetation of Ondo State, Nigeria

The study of Atmospheric Pollen Content (APC) in Akoko environment provides standard baseline information on environmental change, vegetation type, species composition and their utilization for sustainable development. This study was carried out in twenty randomly selected locations to examine the temporal and spatial relationship between the atmospheric pollen content and their vegetation. The palynomorphs were collected with Modified Tauber Sampler using simple random sampling technique and analyzed palynologically. Results showed 182 pollen types belonging to 76 angiospermic plant families were encountered. Three (3) were identified to family level, 57 to species level, 121 to generic level and one (1) unidentified. The predominant pollen types belong to the family Poaceae, Elaeis guineensis, Alchornea cordifolia, Aspilia africana, Casuarina equisetiifolia and Tridax procumbens. The presence of Empetrum nigrum, Linnea borealis, Stereospermum kunthianum and Vitellaria paradoxa pollen indicates evidence of long distance transport. Pollen of exotic or introduced plants was part of the atmospheric palynomorphs recorded as evidence of human impact. Airborne pollen grains were most abundant between September and January (late rainy season to early dry season). Rainfall and relative humidity had negative effect on pollen concentration. Percentage composition of pollen grains abundance showed that indicators of the Savanna taxa were the highest pollen contributors (55.74%) followed by Open Forest (22.72%), Human Impact (14.32%) and Lowland Rainforest (7.21%) taxa respectively. The various ecological indicators species identified confirmed their origin as coming from the Forest- Savanna ecological zone that is anthropogenically disturbed, which is characteristic of Akoko environment. Pollen assemblages confirmed the vegetation of the study area to be Tropical Rainforest vegetation type despite high level of anthropogenic activities on the environment.