Status of Soils in Protected Areas with Different Management Objectives in Lowland Rainforest, Southwest Nigeria

Abstract

Understanding soil properties is fundamental to sustaining the ecological integrity of protected forest ecosystems. This study examined the influence of two management categories; Strict Nature Reserve (SN) and Natural Park (NP) on soil physicochemical properties within the lowland rainforest of southwestern Nigeria. Fourteen composite soil samples, six from SN and eight from NP, were analyzed for texture, bulk density (BD), pH, organic carbon (OC), total nitrogen (TN), available phosphorus (AP), exchangeable bases (Ca²⁺, Mg²⁺, K⁺, Na⁺), and cation exchange capacity (CEC); base saturation (BS) was also determined. Both management categories exhibited sandy loam to loamy sand textures, typical of gneissic parent materials. Significant differences (p ≤ 0.05) occurred in sand, clay, BD, pH, OC, TN, AP, and CEC between management types and across soil depths. The SN recorded higher mean pH (6.6) and BS (95.68 %) than the NP (pH 4.9; BS 87.18 %), along with higher BD and CEC, reflecting a stable, organic matter–driven nutrient cycling system under minimal disturbance. The NP showed stronger pH–CEC and BD–AP correlations, indicating that moderate human activities and management interventions influence soil compaction and nutrient retention. Correlation analysis revealed stronger interrelationships among OC, TN, AP, and CEC in the SN, suggesting more efficient nutrient cycling. The SN exhibited higher ecological stability, while the NP showed management-induced variability with potential for improvement through controlled organic matter inputs. The study recommends maintaining strict protection in the SN and adopting sustainable, low-impact management in the NP to enhance soil fertility and ecosystem resilience.