Environmental Gradient: An Ecological Surrogate to Phytosociological Diversity of a Tropical Mangal-Rainforest-Ecotone in a Hydromesic Tripartite Plant Community
Edwin-Wosu, Nsirim Lucky *
Department of Plant Science and Biotechnology, Faculty of Science, University of Port Harcourt, Choba, P.M.B. 5323, Rivers State, Nigeria.
Mojuetan, Tosanyemi
Department of Plant Science and Biotechnology, Faculty of Science, University of Port Harcourt, Choba, P.M.B. 5323, Rivers State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Aim: To assess influence of edaphic environmental gradients as surrogate to phytosociological diversity in a hyromesic habitat.
Study Design: A systematic sampling approach of line-transect method was used.
Place and Duration of Study: Field sampling: tropical mangal-rainforest ecotone in parts of Asarama, Andoni, Niger-Delta, Labortory analysis: Jack Petroanalytical Laboratory, and University of Port Harcourt Ecology Laboratory, Port Harcourt, Nigeria, between September 2020 and August 2021.
Methodology: Soil sampling and analyses was based on ASTM, Stewarte and conventional methods and the data obtained was subjected to statistical analysis.
Results: Recorded 90 plant species across the sampled sites with a prevalence of 6 (65.9%) species in mangrove, 64 (70.33%) in ecotone and 55(60.44%) in rainforest sites respectively. Floristic density and life form in mangrove had 121ha-1, 3 megaphanerophytes and mesophanerophytes respectively, in ecotone 1660ha-1, 9 megaphanerophytes, 24 mesophanerophytes and 39 microphanerophytes and in rainforest 574ha-1, 13 megaphanerophytes, 18 mesophanerophytes and 24 microphanerophytes. Highest frequency of occurrence: 1 species (80%), 4 species (100%) and 1 species (80%) in mangrove, ecotone and rainforest sites, respectively. Highest abundance: mangrove (1 species), ecotone (9 species) and rainforest (3 species). Highest density: mangrove (1 species), ecotone (8 species) and rainforest (3 species). Distribution: greater in ecotone with contiguous pattern in the order: ecotone>rainforest>mangrove, among which had dissimilarity in response to significant species diversity difference in relation to significant difference in edaphic physico-chemical factors of the study sites. The mangrove site had the most acidic pH, highest salinity, moisture and electrical conductivity while rainforest and ecotone had highest organic carbon and matter. A significant negative correlation between EC & pH, and salinity & pH and positive correlation between salinity & EC as well as positive correlation between pH & OC, pH & OM, OC & OM and negative correlation between EC & OC, EC & OM were recorded.
Conclusion: This variation determined the presence, growth and abundance of the species reported in the respective study sites especially in the ecotone.
Keywords: Abundance, density, frequency, similarity index, species diversity