Alarcon-Gutiérrez E. auteur aut IRD Couchaud B. auteur aut IRD Augur Christopher auteur aut IRD Calvert V. auteur aut IRD Criquet S. auteur aut IRD text journalArticle eng text/pdf born digital access The effect of available nitrogen N ((NH4)(2)SO4) amendments on various microbial variables in three different layers (OhLn, OhLv, OhLf) of a Mediterranean litter profile under an evergreen oak forest (Quercus ilex L.) were studied. Since Mediterranean litters are generally N limiting, the goal of the study was to understand how low (0.1 and 1 %) and high (5 and 10%) N amendments impact specific biological variables such as hyphal length, community-level-catabolic-profiles (CLCPs) in ECO and FF Biolog (TM) plates, basal respiration, enzymatic activities (i.e. alkaline phosphatases (AIP), laccases, peroxidases and cellulases), and laccase and cellulase isoforms from three different litter layers. Results indicated that the effects of N amendments occurred over very short incubation time (3 d), and varied depending on N concentration and litter organic matter (OM) quality (i.e. depth). Thus, it appeared that the more active layer was the intermediate (OhLv) layer, which probably contained the most labile and available C pools. As a consequence, OhLv was also the layer showing globally the more intensive microbial responses following low N amendments. Indeed, in this layer, low N supplies caused several marked increases in enzymes activities (i.e. laccases, cellulases and alkaline phosphatases), hyphal length and isoenzyme patterns, suggesting a microbial reallocation of C to biomass and enzyme production. On the contrary, high N supplies resulted in adverse effects on almost all the variables, suggesting repression or cytotoxic phenomena. specialized N limiting Resources allocation theory Zymograms Litter quality 074 068 40 7 1654-1661 2008 0038-0717 https://www.documentation.ird.fr/hor/fdi:010042688 10.1016/j.soilbio.2008.01.020 0038-0717 [F B010042688] https://www.documentation.ird.fr/hor/fdi:010042688 https://www.documentation.ird.fr/intranet/publi/2008/08/010042688.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2008-09-19 2017-08-23 fdi:010042688 fre