Assessment of soil carbon dioxide efflux from contrasting land uses in a semi-arid savannah ecosystem, northeastern Ghana (West Africa)

Abstract

Soil respiration (SR) emits a vast amount of atmospheric carbon dioxide (CO₂) and contributes largely to the global greenhouse gas budget. The study assessed the dynamics of SR rates in the Vea catchment in northeastern Ghana, a sparsely gauged semi-arid savannah ecosystem characterized by distinct patterns of soil CO₂ efflux. Through field measurements using soil chambers, the study quantified soil CO₂ efflux rates in different land use types (woodland, cropland and grazeland), and assessed the influence of soil moisture, temperature, and soil organic carbon stocks on SR variability. The highest soil CO₂ fluxes (12.97 ± 0.89 Mg CO₂C ha⁻¹ yr⁻¹) were recorded in woodland, followed by grazeland (9.10 ± 0.42 Mg CO₂C ha⁻¹ yr⁻¹) with cropland having the lowest rate (5.61 ± 0.29 Mg CO₂C ha⁻¹ yr⁻¹). We recorded mean annual soil CO₂ flux of 9.23 ± 0.53 Mg CO₂C ha⁻¹ yr⁻¹ across the land use types and also observed significant seasonal and spatial variations in SR rates. The highest SR rate (220 mg CO₂C m⁻² h⁻¹) was recorded in the wet months (Jul-Sept and Mar-May) and the lowest rate (30 mg CO₂C m⁻² h⁻¹) in the dry months (Nov-Jan). For the wet season, the mean weekly soil CO₂ fluxes ranged between 140 and 160 mg CO₂C m⁻² hr⁻¹ as opposed to 60–75 mg CO₂C m⁻² hr⁻¹ for the dry season. Seasonal and spatial variations in SR rates were largely driven by land use type, soil moisture and the interaction of soil temperature and moisture. The results underscore the importance of understanding the emission patterns from various land uses in West African savanna ecosystems to harnessing their potential for climate change mitigation.