Soil microbial functional diversity changes under contrasting N2O emission events

Denitrification, the reduction of nitrogen oxides (NO3-and NO2-) to NO, N2O and, ultimately, to N2 gas in soils, is classified as a microbiologically ‘broad process’ which can be conducted by a wide array of microbes belonging to remote phylogenetic groups. Further, understanding how environmental and management factors drive denitrification is challenging because they are scale-dependent, with large scale drivers affecting denitrification fluxes both directly and through drivers working at detailed small scales.  Despite of this, we hypothesized that denitrification processes, although highly complexes due to the multiple processes and environmental conditions involved, they could present a functional convergence at the microbial community level explained by a short list of microbial groups or functions.   On the other hand, different methodological approaches to assess soil microbial diversity are currently used; among them are multiple substrate-induced respiration by MicroResp™, enzymes activities and functional genes abundance and structure by GeoChip 5S microarray. We applied all those methods to study functional diversity in 5 different soils from 5 countries: Finland, Belgium; France, Switzerland and Italy. Studied soils have a wide range of soil pH, organic Carbon and Nitrogen content, and texture. Soils were sampled at Hot Moment and Low flux emission of N2O.    The main objective of this study was to explore possible convergences in terms of functional microbial diversity in contrasting N2O emission events (low emission versus hot moments).   Result showed that MicroResp™ , enzyme activities and GeoChip 5S microarray were reliable ecological indicator to evaluate soil microbial functionality diversity. Results stressed the importance to study soil microbiome at different magnitude of N2O emission with the aim to gain a deeper knowledge of nitrifiers community. Reciprocal relationship of those methodologies, soil proprieties and magnitude of flux emission of N2O are discussed.