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Dryland ecosystems cover 41% of Earth's terrestrial surface while providing 60% of the world's food production, and 50% of the world's livestock. Drylands also account for 30% of global carbon while operating as a carbon sink, carbon neutral, or a carbon source depending on the season and availability of soil moisture. Within dryland soils, m ethanotrophs, methane (CH 4) consuming bacteria, are present and could aid in reducing methane from the atmosphere. However, the influence that methanotrophs have in the overall soil carbon flux of dryland soils is less known. To understand their influence, we established a soil flux experiment in a semi-arid Wyoming sagebrush (Artemesia tridentata wyomingensis Nuttall, Beetle & Young) plant community in western North America. We measured in situ CO 2 and CH 4 soil fluxes at 30-minute intervals for 16 days during the dormant season. For four days we established a soil flux baseline before adding 200-mL of cattle urine to a subset of plots to observe how cattle might influence soil carbon fluxes. We also added 200-mL of distilled water to the remaining plots as a control. We then measured all plots for an additional 12 days. We found that during the dormant season the sagebrush soils were consistently a weak CH 4 sink, while CO 2 was a weak source, and the addition of cattle urine only augmented those dynamics. We also found a diurnal pattern which coincided with increased surface air temperatures. During the nighttime, both soil CH 4 and CO 2 were carbon sinks, but between 0800 and 1600 hr soil CO 2 fluxes became a carbon source while CH 4 fluxes remained a carbon sink. These results suggest that our semi-arid Wyoming sagebrush rangelands can act as a methane sink even during the dormant season and the strength of the methane sink during the dormant season is based on soil moisture.