Prolonged drought changed the microbial respiration and bacterial growth responses from pattern (i) to pattern (ii), providing an answer to our first research question. Short-term drought (4-days in our experiment) increased soil respiration rates immediately upon rewetting, with a subsequent exponential decrease. This soil respiration response coincided with a bacterial growth that increased linearly from low values, and starting immediately after rewetting.This pattern (i) was previously observed by Iovieno and Bååth (2008). The only difference between the studies was the duration (13 h in present study and 8 h in Iovieno and Bååth (2008)) until
bacterial growth reached similar levels to those in the constantly moist soil. This difference may be due to the lower incubation temperature of 17 C used in the present study instead of 22 C in the previous study, which likely slowed down the recovery of bacteria. The microbial response pattern after rewetting the 1-year dried soil closely matched pattern (ii), previously observed after rewetting soil dried for two months (Göransson et al., 2013). Rewetting soil exposed to prolonged drought increased soil respiration immediately, but this coincided with no detectable bacterial growth. This lag period for growth was followed by an exponential increase in both
respiration and bacterial growth. The calculated intrinsic growth rates based on bacterial growth data (mbact) of 0.33 h1 and respiration data (mresp) of 0.43 h1 suggest that respiration and growth increases were related during the exponential phase. Similar intrinsic growth rates were observed by Göransson et al. (2013; 0.25e 0.41 h1, with a mean of 0.34 h1; recalculated from Fig. 2 in that report). Thus, prolonged drying can change the microbial response frompattern (i) to pattern (ii), as evidenced by both bacterial growth and respiration results.