Soils constitute the largest terrestrial source of carbon dioxide to the atmosphere, and in the context of changing global temperature and moisture patterns, it is critical that we understand the climatic controls on soil respiration. We use subsurface CO2 concentrations, surface CO2 flux and detailed physical monitoring of the subsurface regime to examine physical controls on soil CO2 production. Results indicate that subsurface CO2 production is very sensitive to the subsurface thermal regime, where relationships were robust and also stable across all land use types studied. In contrast, the thermal dependence of surface CO2 flux was much weaker. We found that soil heat content, rather than soil temperature, was the most descriptive index of the biological processes contributing to soil profile CO2 production at our study sites. Soil moisture was also found to have an important influence on subsurface CO2 production, particularly because of the relationship between moisture and soil profile diffusivity. Nondiffusive profile CO2 transport also appears to be important at these sites where the subsurface controls on transport change regularly and markedly.