3. 1. Carbon dioxide flux from rewetting
3. 2. Methane flux from rewetting
3. 3. Nitrous oxide flux from rewetting
3. 4. Nitric oxide flux from rewetting
3. 5. Ammonia flux from rewetting
Tuesday, March 29, 2011
3. A review of the effect of rewetting of dry soils on biogenic gas fluxes
Here we discuss, for each biogenic gas: a) how rewetting events influence gas fluxes in multiple ecosystems and in experimental settings; and b) the likely mechanisms and environmental controls underlying the observed patterns.
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Rousk, J., Smith, A.R., Jones, D.L., 2013. Investigating the long-term legacy of drought and warming on the soil microbial community across five European shrubland ecosystems. Global Change Biol.,DOI: 10.1111/gcb.12338
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We investigated how the legacy of warming and summer drought affected microbial communities in five different replicated long-term (>10 years) field experiments across Europe (EU-FP7 INCREASE infrastructure). To focus explicitly on legacy effects (i.e., indirect rather than direct effects of the environmental factors), we measured microbial variables under the same moisture and temperature in a brief screening, and following a pre-incubation at stable conditions. Specifically, we investigated the size and composition of the soil microbial community (PLFA) alongside measurements of bacterial (leucine incorporation) and fungal (acetate in ergosterol incorporation) growth rates, previously shown to be highly responsive to changes in environmental factors, and microbial respiration. We found no legacy effects on the microbial community size, composition, growth rates, or basal respiration rates at the effect sizes used in our experimental setup (0.6 °C, about 30% precipitation reduction). Our findings support previous reports from single short-term ecosystem studies thereby providing a clear evidence base to allow long-term, broad-scale generalizations to be made. The implication of our study is that warming and summer drought will not result in legacy effects on the microbial community and their processes within the effect sizes here studied. While legacy effects on microbial processes during perturbation cycles, such as drying–rewetting, and on tolerance to drought and warming remain to be studied, our results suggest that any effects on overall ecosystem processes will be rather limited. Thus, the legacies of warming and drought should not be prioritized factors to consider when modeling contemporary rates of biogeochemical processes in soil.
Meisner, A., Baath, E., Rousk, J., Microbial growth responses upon rewetting soil dried for four days or one year. Soil Biol. Biochem. 66, 188-192.
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A pulse of respiration is induced by rewetting dry soil. Here we study the microbial responses underlying this pulse of respiration when rewetting soil dried for 4-days or 1-year. In the 4-days dried soil, respiration increased to a maximum rate immediately upon rewetting after which it decreased exponentially. In the 1-year dried soil, respiration also increased immediately, but then remained high for 16 h, after which it increased further, exponentially, with a peak rate after 20 h. The level of bacterial growth was initially lower in rewetted than in constantly moist soil, but started to increase linearly immediately upon rewetting 4-days dried soil. In 1-year dried soil, bacterial growth started only after a 16 h lag period of zero growth, and then increased exponentially to a peak after 30 h, at rates superseding those in continually moist soil. Fungal growth started to increase immediately upon rewetting, and reached the rate of the control soil after 2 days for the 4-days dried soil, and after a week for the 1-year dried soil. Thus, prolonged drying altered the pattern of bacterial and fungal growth after rewetting. Our results suggest that both fungal and bacterial growth are uncoupled from the initial respiration pulse and that growth responses and microbial C-use efficiency can be affected by prolonged drying.