Influence of geochemistry and topography on vegetation in tropical Nigeria: Geochemistry and soil thickness surpass topographic position

Abstract

The influence of lithospheric parameters on vegetation varies from one location to another, regardless of the prevailing climatic conditions. Reliable scientific information on the vegetation-environment relationship is crucial to sustainable agriculture and natural resource management. Poignantly, such information is not readily available, particularly in resource-poor countries. In this study, we assemble spatially referenced datasets on vegetation pattern, topography, soil thickness and bedrock geochemistry. We subject the datasets to global and local spatial regression analyses on GeoDa 1.18 and MGWR 2.2.1 platforms. Our intention is to examine the influence of lithospheric parameters on vegetation patterns over a climatically homogenous basin in the rainforest belt, southwestern Nigeria. The results of our study show that the variation in vegetation pattern can be explained by soil thickness, topographic curvature, and bedrock concentrations of major minerals. Bedrocks’ KO2/Fe2O3 enrichment and soil thickness are the main lithospheric parameters that influence vegetation pattern in the study area. Bedrocks’ K enrichment is relatively high and less heterogeneous while P enrichment is very low and highly heterogeneous across the study area. Fe concentration is highly heterogeneous, with the highest enrichment recorded for schist and the lowest for gneiss. While the concentration of K is discriminately high in granitic rocks, the highest concentration of P is recorded for schist. Vegetation index is averagely higher on schist than on granitic rocks. Regression models show that bedrock geochemistry and soil thickness exert the greater influence on vegetation in the study area. Based on the available data, we observe that the study area’s greenery can self-rejuvenate if left undisturbed. Our data show that the study area could support a large pool of forest carbon stocking. This potential makes the study area suitable for the UN REDD + program in Nigeria.