Long-term N-addition alters the community structure of functionally important N-cycling soil microorganisms across global grasslands

Anthropogenic nitrogen (N) input is known to alter the soil microbiome, but how N enrichment influences abundance, alpha-diversity and community structure of N-cycling functional microbial communities in grasslands remains poorly understood. Here, we collected soils from plant subjected up 9 years annual N-addition (10 g m−2 per year using urea as a N-source) unfertilized plots (control) 30 worldwide spanning large range climatic conditions. We focused on three key groups responsible for two essential processes global cycle: N2 fixation (soil diazotrophs) nitrification (AOA: ammonia-oxidizing archaea AOB: bacteria). targeted diazotrophs, AOA AOB Illumina MiSeq sequencing measured abundance (gene copy numbers) quantitative PCR. shifted diazotrophic communities, although their were not affected. responded differently N-addition. The increased, with In contrast, affected by outnumbered control under conditions low availability, whereas favoured copiotrophic AOB. Overall, showed impact diazotrophs while effects considerable. These results reveal that long-term has important ecological implications involved critical processes. Increased shifts following may change N-cycling, larger population sizes promote higher rates ammonia oxidation subsequently increase loss via gaseous N-leaching. findings bring us step closer predicting responses feedbacks microbial-mediated anthropogenic grasslands.