Anthropogenic nitrogen (N) input is known to alter the soil microbiome, but how N enrichment influences the abundance, alpha-diversity and community structure of N-cycling functional microbial communities in grass-lands remains poorly understood. Here, we collected soils from plant communities subjected to up to 9 years of annual N-addition (10 g N m− 2 per year using urea as a N-source) and from unfertilized plots (control) in 30 grasslands worldwide spanning a large range of climatic and soil conditions. We focused on three key microbial groups responsible for two essential processes of the global N cycle: N2 fixation (soil diazotrophs) and nitrification (AOA: ammonia-oxidizing archaea and AOB: ammonia-oxidizing bacteria). We targeted soil diazotrophs, AOA and AOB using Illumina MiSeq sequencing and measured the abundance (gene copy numbers) using quantitative PCR. N-addition shifted the structure of the diazotrophic communities, although their alpha-diversity and abundance were not affected. AOA and AOB responded differently to N-addition. The abundance and alpha-diversity of AOB increased, and their community structure shifted with N-addition. In contrast, AOA were not affected by N-addition. AOA abundance outnumbered AOB in control plots under conditions of low N availability, whereas N-addition favoured copiotrophic AOB. Overall, N-addition showed a low impact on soil diazotrophs and AOA while effects for AOB communities were considerable. These results reveal that long term N-addition has important ecological implications for key microbial groups involved in two critical soil N cycling processes. Increased AOB abundance and community shifts following N-addition may change soil N cycling, as larger population sizes may promote higher rates of ammonia oxidation and subsequently increase N loss via gaseous and soil N-leaching. These findings bring us a step closer to predicting the responses and feedbacks of microbial-mediated N-cycling processes to long-term anthropogenic N-addition in grasslands.
Frey, B.; Moser, B.; Tytgat, B.; Zimmermann, S.; Alberti, J.; Biederman, L.; Borer, E. T.; Broadbent, A. A. D.; Caldeira, M. C.; Davies, K. F.; Eisenhauer, N.; Eskelinen, A.; Fay, P. A.; Hagedorn, F.; Hautier, Y.; MacDougall, A. S.; McCulley, R. L.; Moore, J. L.; Nepel, M.; Power, S. A.; Seabloom, E. W.; Vázquez, E.; Virtanen, R,; Yahdjian, M. L. & Risch, A. C. (2023). Long - term N - addition alters the community structure of functionally important N - cycling soil microorganisms across global grasslands. Soil Biology and Biochemistry,176,art.108887
10.1016/j.soilbio.2022.108887
Frey, Beat,Moser, Barbara,Tytgat, Bjorn,Zimmermann, Stephan,Alberti, Juan ,Biederman, Lori, et al.. 2023. "Long - term N - addition alters the community structure of functionally important N - cycling soil microorganisms across global grasslands". Soil Biology and Biochemistry 176:art.108887.
Recuperado de http://ri.agro.uba.ar/greenstone3/library/collection/arti/document/2023frey