Spatial Variation of Soil Physicochemical Properties with Respect to Some Selected Tree Species in the Nigerian Northern Guinea Savanna

Aim: This study was aimed to find the impact of Parkia biglobosa ( Jacq.) Benth., Daniella oliveri (Rolfe) Hutch. & Dalziel and Vitellaria paradoxa C. F. Gaertn. trees on some selected surface (0-15 cm depth) soil physicochemical properties in the Nigerian northern Guinea Savanna ecological zone.
Methodology: Soil samples were collected within the crown zones (CZs), outside CZs (2m away from the crown radii) and the open field which served as a control. The soil samples were analyzed for organic carbon (OC), total nitrogen (TN), available phosphorus (AP), exchangeable potassium (EP), pH and particle size distribution.
Results: The result indicated that these trees have significantly (α = 0.05) affected some (but not all) soil physicochemical properties within and outside their CZs. Compared with the open field, alteration of soil physicochemical properties was found to be highest within CZs in general than outside CZs and the least was the opened field.
Conclusion: The patterns of impacts of P. biglobosa, D. oliveri and V. paradoxa on different soil physicochemical properties were not the same. Each of these three different tree species has affected the soil underneath in a different way. On average, P. biglobosa has the highest impact followed by D. oliveri and the least was V. paradoxa. The soil properties that are greatly affected by the trees are OC and AP; while the least affected are pH and clay content. Such information is required for better understanding of the ecosystem and conservation of soil in particular and biodiversity in general.