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International audience; Construction of Technosols through assemblage of treated soil and recycled wastes is an innovative option for the restoration of degraded lands and re-use of industrial wastes. Recent studies have evidenced that Technosols could support soil functions such as primary production but the knowledge about other ecosystemic services, such as nutrient cycling, is limited. In this work, we investigated the abundance and the activity of microbial communities involved in N-cycling in different horizons (0–15, 15–35, 35–70 cm) of two types of Technosols constructed to reclaim an industrial wasteland. The estimation by real-time PCR of the abundances of the different microbial guilds indicated a significant depth effect in both Technosols on the abundances of the total bacterial and crenarchaeal community and of the ammonia-oxidizing and denitrifying communities. Activity measurements revealed higher denitrification than nitrification rates, which were also affected by Technosol depth. Potential denitrification and nitrification were correlated with Technosol physicochemical properties but also with the abundances of the nirS denitrification gene and bacterial amoA gene, respectively. The type of Technosols influenced both the abundance and the activity of the denitrifier community but not the ammonia-oxidizers, which underlines the importance of a better understanding of microbial communities in Technosols to maximize their potential for fulfilling soil ecosystemic functions.

EA EcolDur CT3; National audience