correspond to p/rCO2values above 390 kJ mol−1(> 16 J cm−3CO2respired) whereas those values used in curve b of Fig. 4 correspondto p/rCO2values between 270 and 390 kJ mol−1(10–16 J cm−3CO2respired). Curve ‘a’ includes the values used to develop the calori-metric method to determine SMB by calorimetry [13]. The slopeof 0.899 ± 0.044 is intermediate between those reported for storedand fresh soil (913 and 856, respectively) [22]. By using this relationto determine the increment in SMB, X, a value of 781 ± 138 g g−1was calculated for the first peak and 522 g g−1for the second; indi-cating that calorespirometry is a very useful technique to monitormicrobial growth during the whole process.