Soil AZD8931 and soil CO2 efflux are driven by several factors related to soil, climate and vegetation (Table 3), and consequently, variability of CO2 efflux is governed by the variability of those drivers. One of the most important control on soil respiration and soil CO2 efflux is soil temperature (e.g., Lloyd and Taylor, 1994, Vincent et al., 2006 and Terhoeven-Urselmans et al., 2009), which is confirmed by our results. The variability of soil temperature found here was overall smaller (average CV 8%) than those of CO2 efflux. Obviously, variability of soil temperature does not govern the variability of CO2 efflux, since the relationship between soil temperature and soil CO2 efflux is not strictly mono-causal. Rather, during the normal seasonal course, soil temperature increases in spring, concomitantly with the biological activity, productivity and root mass, all of which have also a strong influence on soil CO2 efflux (Kuzyakov, 2006 and Han et al., 2007).