Asian Journal of Research in Biology

Understanding the variation in soil physicochemical properties and floristic composition is vital to sustainable forest management in tropical ecosystems. This study assessed the influence of soil attributes on species distribution and structural composition in Osomba Hill Forest, within the Oban Division of Cross River National Park, Nigeria. Systematic sampling method was used in sampling vegetation and soil of the studied location. Composite soil samples were collected at 0–15 and 15–30 cm depths and bulked together and further analyzed for their physicochemical characteristics. Fifty-two (52) tree species representing thirty-one families were identified across 20 plots. Results showed that Diospyros mespiliformis, Lophira alata, Fagara zanthoxyloides, Musanga cecropioides, and Rauwolfia vomitoria were dominant species, exhibiting the highest density and height. The soils were slightly acidic, with high organic matter content (12.94 ± 0.03%) and moderate total nitrogen (0.32 ± 0.01%), reflecting stable fertility conditions. Available phosphorus averaged 4.24 ± 0.98 mg/kg, while exchangeable bases such as calcium (5.83 ± 0.21 cmol/kg) and magnesium (2.36 ± 0.16 cmol/kg) indicated a balanced nutrient composition. The effective cation exchange capacity (9.51 ± 0.28 cmol/kg) and base saturation (90.51 ± 0.24%) further confirmed good  nutrient-holding potential despite the dominance of sand. The soils were thus characterized as sandy loam, moderately fertile and grossly favorable for supporting diverse tropical  rainforest flora. In conclusion, the significant (P<0.05) variations in vegetation attributes and soil variables including soil organic matter, total nitrogen, further reiterate the role of edaphic heterogeneity in shaping floristic composition and dynamics. These results underscore the importance of integrating soil fertility mapping and vegetation monitoring in the conservation strategy for Osomba Hill Forest.