Soil carbon stock and emission: estimates from three land-use systems in Ghana

Background: Land-use systems that sequester carbon and reduce CO2 emissions are key in the global mitigation strategies of climate change. Greenhouse gas emission from agro-ecosystems in sub-Saharan Africa is little studied. Here, we quantified soil carbon stock (SCS) and CO2 emissions from three land-use systems viz. arable land, oil palm plantation and forestland in the semi-deciduous forest zone of Ghana. Results: Soil organic carbon concentration at the 0-15 cm layer in the forestland was 62 and 23% greater than that in the arable land and palm plantation, respectively. The SCS along the 1.0-m profile was 108.2, 99.0 and 73.5 Mg ha(-1) in the forestland, palm plantation and arable land, respectively. Arable land emitted 30-46% more CO2 than palm plantation and forestland. In the dry season, CO2 emissions were respectively 0.93, 0.63 and 0.5 kg ha(-1) h(-1) from the arable land, palm plantation and forestland. Positive relationships were observed between CO2 emissions and SCS, soil temperature, and moisture. The SCS greatly influenced CO2 emission in the dry season more than in the wet season in the relatively higher carbon-input systems (forestland and palm plantation). Soil temperature accounted for more than 55% of CO2 emissions in both seasons, which has implications in the era of rising global temperatures. Conclusions: The study provides relevant information on carbon storage abilities of the three land-use types in tropical climate and calls for drastic climate change actions to reduce degradation of forest cover and soil disturbance in agro-ecosystems in sub-Saharan Africa.