Methane efflux from desert soils

Abstract

Deserts cover ~50% of Earths surface but are poorly studied regarding their methane (CH4) fluxes. Current theory suggests that dry soils act as CH4 sinks, with higher soil carbon (C) content enhancing oxidation. To test this, we measured CH4 fluxes in 12 field plots with increasing C content in Israels Negev Desert over three summer and three winter months using automated chambers. We hypothesized that well-aerated soils would oxidize CH4, and the oxidation rate will increase with more organic matter. Contrary to our hypothesis, CH4 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 CH4 emissions were driven by abiotic processes related to solar radiation, not microbial activity. A shading experiment reduced CH4 efflux by 51%, supporting this idea. The newly identified CH4 source of at least 89.8 {+/-} 2.2 mg CH4 m-2 yr-1 equals ~30% of the modelled CH4 sink (~300 mg CH4 m-2 yr-1) for the same region. SynopsisOur field measurements in Israels Negev Desert show that dry desert soils can emit methane, challenging current models that assume these soils consistently act as atmospheric methane sinks.