Fig. 2. Hypothetical representation of seasonally variable CO₂ sources from different root processes contributing to total soil respiration. Root processes that generate CO₂ directly (root growth and root respiration) or indirectly (microbial respiration of root exudates) are shown to be seasonal, turning on and off depending on crop growth and phenology. A strongly seasonal pattern of total CO₂ production by roots (R_rrh) is generated, even though none of the individual process rates correlate with temperature.