Effects of Anthropogenic Stressors on Vegetation, Soil and Water Quality in the Upland Evergreen Tropical Forest of Atewa, Ghana

Abstract

Although tropical rain forests are rich in biodiversity and play major roles in vegetation, soil and water quality and socio-economic needs, people have imposed stress on them. The study examined vegetation, soil and water characteristics linked to anthropogenic activities— logging, mining and farming in the Atewa Range Forest Reserve (ARFR) in Ghana. The study sites were categorized into highly stressed vegetation (HSV), moderately stressed vegetation (MSV) and non-stressed vegetation (NSV). Attributes of plant species composition and structure were determined using 50 m x 50 m plots. Tree biomass and carbon stock were determined from allometric equations using tree diameter measurements. Plant diversity was estimated using Shannon Wiener and Simpson diversity indice. The intensity of anthropogenic influence between 1986 and 2016 was analysed using Normalized Differential Vegetation Index techniques. Soil organic carbon was determined using Walkley-Black method. River Birim was sampled and tested for physical, chemical and biological characteristics, as well as heavy metals. The total mean woody plant density was similar and higher for MSV and lower in HSV. Above-ground carbon stock was not significantly different among the three stress levels but below-ground carbon stocks were significantly different at the three stress levels. The forest decreased at the rate of 2 km2 per annum between 1986 and 2016. Soil pH, bulk density, moisture, organic carbon and nutrients (NPK) differed significantly. Physicochemical properties and heavy metals of the water showed significant variation at the various stress levels. Anthropogenic stressors have negatively impacted the vegetation, soil and water quality of the ARFR, therefore, there is a need for stringent management policies to control human activities.