Long-term N-addition alters the community structure of functionally important N-cycling soil microorganisms across global grasslands. (January 2023)

• Record Type: Journal Article
• Authors: Frey, Beat; Moser, Barbara; Tytgat, Bjorn; Zimmermann, Stephan; Alberti, Juan; Biederman, Lori A.; Borer, Elizabeth T.; Broadbent, Arthur A.D.; Caldeira, Maria C.; Davies, Kendi F.; Eisenhauer, Nico; Eskelinen, Anu; Fay, Philip A.; Hagedorn, Frank; Hautier, Yann; MacDougall, Andrew S.; McCulley, Rebecca L.; Moore, Joslin L.; Nepel, Maximilian; Power, Sally A.; Seabloom, Eric W.; Vázquez, Eduardo; Virtanen, Risto; Yahdjian, Laura; Risch, Anita C.
• Is Part Of: Soil biology and biochemistry. Volume 176(2023)
• Publication Date: 2023-01
• Subjects: Ammonia oxidizer -- Biogeography -- Diazotroph -- Grassland -- N-cycling microbial community -- N-Fertilization -- N2-fixing bacteria -- nifH -- Nutrient network (NutNet) -- Urea; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2022.108887
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: 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 grasslands 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. Highlights: Ammonia-oxidizing bacteria were more sensitive than ammonia-oxidizing archaea to N-addition. Increased ammonia-oxidizing bacteria abundance and community shifts may change ammonia-oxidation. N2-fixing communities shifted with N-addition but their abundances remained unchanged. Repeated N-addition has important ecological implications for grassland productivity.