Increasing carbon dioxide (CO2) concentration in the atmosphere is rapidly altering the earth’s climate. While human activities are driving this increase in atmospheric CO2, these human activities account for a small portion of the exchange of carbon (C) between the earth’s surface and the atmosphere. Soil respiration, the release of CO2 from soils through metabolic activity of soil organisms and roots, is the largest annual transfer of CO2 from land surfaces to the atmosphere. Although soil respiration is generally well balanced by plant uptake of CO2 through photosynthesis, small differences in these processes influence atmospheric CO2. Improving understanding of the controls over terrestrial C cycling is needed for accurate global C cycle models that inform climate models. Dryland (arid and semi-arid) ecosystems appear to play an important role in both total C exchange and in the year-to-year variability of C cycling. There is particular uncertainty in how dryland C cycling might change under shifting climate conditions, given lack of climate change research to date in these systems. Keywords: biogeochemistry, carbon cycle, climate change, fog desert, precipitation.