Modelling Soil Greenhouse Gas Emissions from different Land Use types in a Semi-Deciduous Forest and its Environs in Ghana

Abstract

This study provides baseline data and analyses of the evolution of carbon dioxide emissions in the Agriculture, Forestry and Other Land Use (AFOLU) sector in Ghana, focusing on the Bobiri Forest Reserve and fringe areas. The first objective was to analyse land-use/land cover (LULC) changes from 1986 to 2022 in a semi-deciduous forest zone using intensity analysis. The results showed significant land transformations, with Croplands and mixed vegetation and non-vegetated having substantial gains, while closed forest areas decreased by over 36%. These changes were primarily driven by the increasing demand for food and population growth, highlighting the pressure on forested landscapes. The second objective assessed the impact of LULC changes and seasonal variability on soil respiration rate (SRR) across three dominant land categories; forest, fallow (open forest) and cropland (maize and rice). Seasonal variability significantly influenced SRR, with higher emissions observed during the wet season. Forests recorded the lowest SRR due to minimal disturbance and lower sunlight reaching the soil surface. In contrast, fallow and cropland areas showed higher emissions, driven by increased soil disturbance and organic matter decomposition. The model results indicated that SRR was strongly influenced by organic matter (OM), pH, soil moisture (SM) and silt content, as captured in the predictive equation: 𝑆𝑅=(3.77 𝑥10−4𝑒𝑥𝑝(0.0771𝑂𝑀))(55.94log(𝑝𝐻)−36.30)(6.36log(𝑆𝑖𝑙𝑡)+36.94)(3.23log(𝑆𝑀)+24.48) explaining up to 58% of the variability in SRR. The results highlight the role of land-use changes in altering soil carbon dynamics and SRR. The third objective projected the future evolution of soil CO2 emissions from 2022 to 2050 under a Business-as-Usual (BAU) scenario using DINAMICA EGO modelling software and a forest-based regression model in ArcGIS Pro. The projections indicated a significant increase in emissions from open forests (55 kg CO2 ha-1 d-1) compared to closed forests (50 kg CO2 ha-1 d-1) and cropland and mixed vegetation (52 kg CO2 ha-1 d-1), driven by continued deforestation and land-use conversion. The findings highlight the critical need for effective land management strategies to mitigate GHG emissions, conserve forest cover, and promote sustainable agricultural practices. Future studies should expand the scope to include methane (CH4) and nitrous oxide (N2O) emissions using advanced tools like gas chromatographs, to provide a more comprehensive assessment of emissions dynamics. Furthermore, integrating alternative land-use scenarios, alongside the BAU scenario, and comparing IPCC Tier 1 with Tier 2/3 emissions factors, will improve the accuracy of SRR projections and support more effective policy development.