Land use effects on plant invasion, plant communities and soil properties in Southwestern Nigeria

Aim: The objective of this research was to analyze the association between evaluated level of species disturbance between sites as well as determine the abundance and diversity of invasive alien species and the physicochemical parameters of soil samples with the view to determining the impact of mining on the distribution of invasive species. Method: Four Land use types: active mining, abandoned mining, farmland and relatively undisturbed forest were selected as sampling sites for the study. Two 20 m by 20 m sampling plots were randomly selected in each land use types. Plants were identified to assess the floristic composition, the level of colonization of invasive species, and the diversity of the plant species. Soil chemical and physical properties in sites were analysed and plant-soil relationship was determined by means of Canonical correspondence analysis (CCA) and Principal Component Analysis (PCA). Result: Diversity analysis showed that the active mining site was the least diverse and abandoned mining site the most diverse. The characteristics of the populations of the invasive plant species in the mining sites were weeds (10%), shrubs (60%), and climbers (30%). Distribution of invasive species was influenced by the four land use types (active mining, abandoned mining, farming and relatively undisturbed forest). Solanum torvum, Panicum brevifolium, Centrosema pubescens, Commelina erecta were found to be associated with active mining site. Abandoned mining and farming sites had similar composition of invasive species. Soil analysis showed significant difference between total nitrogen, available phosphorus, organic carbon and CEC between undisturbed forest and the active mining sites. Canonical correspondence analysis showed that active mining site was associated with increasing acidity, Na+ and bulk density and characterised by plant species such as Solanum torvum, Panicum brevifolium, Centrosema pubescens, Commelina erecta while undisturbed site was associated with increasing available P, Ca2+, total N, Organic C, CEC and Mg2+ and characterised by species such as Cola hispida, Lecaniodiscus cupanoides, Bahia nitida, Mirodesmis puberula, Monodora tenuifolia. Principal component analysis identified Organic C, Total N and Ca2+ as the most important physico-chemical factors responsible for variations observed in the study. Conclusion: The study concluded that land use has significant effect on soil and is a driver for low plant diversity and introduction of invasive plant species.