Methane efflux from desert soils

Deserts cover ~50% of Earth’s surface but are poorly studied regarding their methane (CH ₄ ) fluxes. Current theory suggests that dry soils act as CH ₄ sinks, with higher soil carbon (C) content enhancing oxidation. To test this, we measured CH ₄ fluxes in 12 field plots with increasing C content in Israel’s Negev Desert over three summer and three winter months using automated chambers. We hypothesized that well-aerated soils would oxidize CH ₄ , and the oxidation rate will increase with more organic matter.

Contrary to our hypothesis, CH ₄ was emitted ~75% of the time, with average effluxes of 0.222 ± 0.007 nmol m ⁻² s ⁻¹ in summer and 0.081 ± 0.004 in winter. We propose that CH ₄ emissions were driven by abiotic processes related to solar radiation, not microbial activity. A shading experiment reduced CH ₄ efflux by 51%, supporting this idea.

The newly identified CH ₄ source of at least 89.8 ± 2.2 mg CH ₄ m ⁻² yr ⁻¹ equals ~30% of the modelled CH ₄ sink (~300 mg CH ₄ m ⁻² yr ⁻¹ ) for the same region.