Automated opaque flux-chamber measurements of soil carbon dioxide (CO2) flux (soil respiration) into the atmosphere at the Amargosa Desert Research Site show seasonal and diel cycles of soil respiration that are closely linked with soil temperature and soil moisture. During 1998, soil respiration increased with soil warming through spring, reaching a maximum rate (not counting anomalously high values scattered through the record) of about 0.055 moles CO2 m-2 day-1 around Julian Day 120. Respiration rates then declined along with volumetric soil moisture content, tending to stay at or below about 0.02 moles CO2 per square meter per day (m-2 day -1) for the rest of the year, except after summer rainfalls when respiration sharply increased for short periods. The diel respiration pattern during dry spells is marked by a sharp rise in CO2 flux coincident with steeply rising soil temperatures in the morning, then dropping back to low levels about the time of maximum soil temperature. The reason for this pattern in unclear.
