Methane uptake by a selection of soils in Ghana with different land use

Abstract

We measured the oxidation of atmospheric methane in tropical soils in Ghana covering a moisture gradient from the moist forest zone to the savanna zone at the onset of the rainy season. Land use at the sites covered undisturbed (forest and savanna) and cultivated soil, including burning. Generally, the methane oxidation rates in the tropical forest and savanna soils were low (range from 9 to 26 μg CH4 m−2 h−1) compared to, for example temperate forest soils. In the savanna soil, annual fire had decreased soil methane oxidation rates to 5 μg CH4 m−2 h−1 compared to 9 μg CH4 m−2 h−1 at a site not subjected to fire for 6 years. In paired sites of moist forest and arable soils, methane oxidation rates were lower by >60% in the arable soils. Methane oxidation rates in three arable soils in the savanna zone soils ranged from 7 to 11 μg CH4 m−2 h−1 before the first rain but increased to 23–28 μg CH4 m−2 h−1 after the rain. These rates are comparable to other reports from arable soils in tropical and temperate regions. Thus arable agriculture and, to a lesser extent, biomass burning decreased methane oxidation rates by the investigated soils.