Variance in responses to N amendments has been documented for different AMF genera by Treseder and Allen (2002). They tested whether the initial nutrient status of an ecosystem determines how N amendments affect AMF abundance and community composition and found that the AMF biomass was increased by N additions of NH4NO3 and urea in an N-limited site, but that the N fertilization affected fungal genera differently. Our field site would undoubtedly have a larger diversity of AMF, bacteria and saprophytic fungi than the pots in our greenhouse study, due to the use of sterilized soil in the latter experiment. The idea that different mycorrhizal genera react differently to N amendments calls for more diversity in the experimental design of our greenhouse study in order to determine if the common effect of N-rich organic amendments is universal for AMF.