Our results confirm the suggestion that the respiration pulse after rewetting dry soil will be a C-cost for the soil microbial community (Schimel et al., 2007). Since immediately upon rewetting
the respiration rate was higher, whereas microbial growth was lower than in the moist soil, the microorganisms appeared to grow less efficiently. The size of the respiration pulse, as well as the microbial growth reduction, appeared to increase with the duration of drying. This was evidenced by the contrast between the microbial growth reduction and the large stimulation of respiration in the 1-year dried soil compared to the 4-days dried soil (Fig. 4). It has
been suggested that low nutrient availabilities (i.e. high C to nutrient ratios) can be conducive for low microbial growth efficiencies (Manzoni et al., 2012), and that rewetting dry soil can induce transient situations of nutrient limitation (Tiemann and Billings, 2011). However, in the situation of lowest microbial Cuse efficiency during the rewetting, the 1-year dried soil, the mobilized C during rewetting induced exponential microbial
growth, without any evidence of nutrient limitation. Consequently,it is unlikely that other nutrients than C explained the low microbial growth efficiency in our experiments. Irrespective, prolonged drying will affect microbial C-use efficiencies, suggesting that more extensive drought will have implications for the cycling of C in ecosystems.
Our results confirm the suggestion that the respiration pulse after rewetting dry soil will be a C-cost for the soil microbial community (Schimel et al., 2007). Since immediately upon rewettingthe respiration rate was higher, whereas microbial growth was lower than in the moist soil, the microorganisms appeared to grow less efficiently. The size of the respiration pulse, as well as the microbial growth reduction, appeared to increase with the duration of drying. This was evidenced by the contrast between the microbial growth reduction and the large stimulation of respiration in the 1-year dried soil compared to the 4-days dried soil (Fig. 4). It hasbeen suggested that low nutrient availabilities (i.e. high C to nutrient ratios) can be conducive for low microbial growth efficiencies (Manzoni et al., 2012), and that rewetting dry soil can induce transient situations of nutrient limitation (Tiemann and Billings, 2011). However, in the situation of lowest microbial Cuse efficiency during the rewetting, the 1-year dried soil, the mobilized C during rewetting induced exponential microbialgrowth, without any evidence of nutrient limitation. Consequently,it is unlikely that other nutrients than C explained the low microbial growth efficiency in our experiments. Irrespective, prolonged drying will affect microbial C-use efficiencies, suggesting that more extensive drought will have implications for the cycling of C in ecosystems.
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