Land use effects on tree species diversity and soil properties of the Awudua Forest, Ghana

Abstract

Rubber plantation establishment is a common land use that can profoundly impact plant diversity and soil properties in tropical forest ecosystems, although empirical data on such effects are scarce in tropical Africa. In this study, we examined the effects of this land use on tree species diversity and soil physicochemical properties of the Awudua Forest in Ghana. We surveyed 60 25 m × 25 m plots, 20 in each of three land uses (i.e., primary forest, secondary forest and rubber plantation) of the study area. Within each plot, we identified and enumerated all trees (≥ 10 cm diameter at breast height, dbh at 1.3 m) and collected soil samples at three depths (i.e., 0–10 cm, 10–20 cm and 20–30 cm) for the determination of soil physicochemical properties (bulk density, particle size distribution, pH, OC, TN, AP, K, Mg, Ca). Soil physicochemical properties; sand, OC, AP, K, Mg, Ca in the rubber plantation decreased by 4.4%, 24.9%, 40.0%, 16.7%, 50.0% and 20.2% respectively, whereas the primary forest recorded decreases in OC (42.2%), TN (25%), AP (71.1%), K (69%), Mg (59.6%), Ca (27%) from the surface to the sub layers. Results showed significantly lower tree species richness ( S , 12), diversity ( H', 0.37), evenness ( E , 0.43), and basal area (BA, 2.86 m 2 /ha) in the rubber plantation compared to those of the secondary forest (36, 1.10, 0.85 and 0.93 m 2 ha -1 , respectively) and the primary forest (46, 2.28, 0.97, and 3.32 m 2 ha -1 , respectively). Non-metric multidimensional scaling ordination also revealed distinct tree species composition among the land uses. Terminalia ivorensis (IVI = 7.1%), Musanga cecropoides (28.91%) and Hevea brasiliensis (72.03%) were the most dominant species in the primary forest, secondary forest and plantation respectively. Soil OC, TN, K, AP, Mg and bulk density differed among the land uses, but no differences were observed in pH and Ca. The findings confirmed the strong negative impacts of rubber plantation land use on plant diversity and soil properties, suggesting the need for mitigation measures such as afforestation and offsetting to ensure sustainable utilization and conservation of biodiversity in the reserve. • Three land uses—rubber plantation, primary forest and secondary forest—were analyzed. • Rubber plantation impacted floristic attributes more than the other land uses. • Conversion of forest to other land uses also affected soil physicochemical properties negatively.