Pedological attributes, floristic composition and profile of a coastal ecosystem in southern Nigeria

Abstract

Mangroves have important roles in the mitigation of on-going climate change as new evidence shows, and are critical natural assets for coastal  communities in the face of accelerated sea level rise. Yet, they are imperilled through unsustainable practices such as logging and crude oil mining  activities. The effect of crude oil mining and flaring of associated gas across the mangrove ecosystems within the Niger Delta region is well articulated in  literature and visibly apparent as one traverses coastal communities of the Delta. However, the abuse and devastation of this ecosystem is unabated five  decades after the discovery of oil. This devastation consequently influences the physiognomy of the mangroves, connected fauna and is likely to cascade  down the different trophic levels of this unique ecosystem. In light of their importance and current threats within the Niger Delta we assessed the floristic  structure of the Okorombokho mangrove, Eastern Obolo Local Government Area of Akwa Ibom State. Five (5) quadrats of 50 x 10 m within 5  sampling plots were used to sample vegetation and soil parameters using systematic sampling method. Results showed variations in the floristic  composition and structure of the mangrove ecosystems; with a total of 16 plant species recorded from 13 families. Bivariate correlation analysis was  employed to show significant relationships (p = 0.05; p = 0.01) between the vegetation attributes and soil factors. A prediction model using stepwise  multiple regression technique showed the responses of the vegetation attributes to soil gradients. Additionally, the profile diagrams of the study area  show a trend from mono-specific plots to mixed vegetation e.g. station 4 that was completely dominated by Rhizophora mangle; whereas other stations  (1-3) showed a mixed vegetation of Rhizophora mangle, Avicennia africana, Nypa fructicans and others. These different zones of growth are indicative of  the response of the flora to various stressors that warrants constant monitoring and management adjustments for maintenance of extant mangrove  vegetation.