Comparing modified substrate-induced respiration with selective inhibition (SIRIN) and N2O isotope approaches to estimate fungal contribution to denitrification in three arable soils under anoxic conditions

Rohe et al.: Inhibitor and N2O isotope approaches to investigate fungal denitrification 1 Introduction difficulties of this method may be to achieve complete in- hibition of selective groups (Ladan and Jacinthe, 2016) and The greenhouse gas nitrous oxide (N2O) contributes to to avoid shifts in the structure of microbial communities as global warming and to the depletion of the ozone layer in a res. [...] In order to find mitigation strategies the linear N2O molecule; Ostrom and Ostrom, 2017) in pure for N2O emissions from arable soils, it is important to under- culture studies showed differences in N2O of bacterial and stand N2O sources and sinks and thus improve knowledge fungal denitrification (Sutka et al., 2006, 2008; Frame and about the production pathways and the microorganisms in- Casciotti. [...] To check the effectiveness SPprod = fFD ·SPFD+ fBD ·SPBD , (4) of C2H2 in blocking the N2O reduction, r15N was compared with rC2H2 , where the latter can be calculated from N2O pro- where fFD and fBD represent the fraction of N2O produced duction rates of variants −C2H2 and +C2H2: by fungi and N2O sources other than fungal denitrification, respectively, and SPFD and SPBD are the respective SP N2O−. [...] Average CO2 and N2O production rates and N2O isotopic values of N2O of the last sample collection with and without C2H2 application in the headspace (variants −C2H2 and +C2H2) of each soil (Soil 1 to 3) for treatments A without growth inhibition, B with bacterial growth inhibition, C with fungal growth inhibition, and D with bacterial and fungal growth inhibition, respectively (standard deviation. [...] Only with Soil 2 of the bility of the determined f 18 FD values based on the δ OH2O 18 variant+C2H2 were the N2O production rates of treatment D values obtained from the fitting (δ OH2O value in Table 4) significantly smaller than those of the other three treatments.