MANGROVE-FRESHWATER SWAMP TRANSITION FOREST LANDSCAPE IN THE NIGER DELTA: SPECIES DOMINANCE AND DIVERSITY

Nwabueze I Igu

Abstract


Transition zones in forest ecosystems are suitable landscapes for understanding species interactions between adjacent ecosystems. This study sought to understand the biodiversity patterns and species dominance of a freshwater-mangrove transition zone in the Niger Delta and likely environmental change concerns. To achieve this, a total of 8 plots that are 1 hectare each were set up randomly across the delimited zone and used to conduct a vegetation inventory. Trees that were ≥ 10cm diameter at breast height (130cm) were identified to species levels and their results were summarized with species importance values and biodiversity indices. In all, 55 plant species within 30 families were found across the plots. More than 50% of the species were dominated by Rhizophora racemosa, Elaeis guineensis, Raphia spp, and Lannea welwitschii Engl.; with species importance values of 72.94, 64.22, 18.17 and 8.35, respectively. Species diversity ranged from 2.23 to 2.83 and the number of species varied from 29 to 42 across the plots. Though the diversity were lower than what obtains in tropical ecosystems (like lowland rain forests), they were still much higher than what the mangrove ecosystem supports. Environmental conditions in the transition zone enabled mutual species occurrence and supported community coexistence of species more than what would normally be obtainable in single ecosystems. Biodiversity conservation of the landscape is advocated as the zone serves supportive role as important refuge for species in both mangrove and freshwater landscapes currently and more importantly as the effects of environmental change become more glaring across the region.

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