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6710313 
Journal Article 
Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity 
Maaroufi, NI; Nordin, A; Palmqvist, K; Hasselquist, NJ; Forsmark, B; Rosenstock, NP; Wallander, H; Gundale, MJ 
2019 
Yes 
Global Change Biology
ISSN: 1354-1013
EISSN: 1365-2486 
25 
9 
2900-2914 
English 
31166650 
WOS:000477200000001 
There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal forest soils. However, it is unclear how free-living saprotrophs (bacteria and fungi, SAP) and ectomycorrhizal (EM) fungi responses to N addition impact soil C dynamics. Our aim was to investigate how SAP and EM communities are impacted by N enrichment and to estimate whether these changes influence decay of litter and humus. We conducted a long-term experiment in northern Sweden, maintained since 2004, consisting of ambient, low N additions (0, 3, 6, and 12 kg N ha-1  year-1 ) simulating current N deposition rates in the boreal region, as well as a high N addition (50 kg N ha-1  year-1 ). Our data showed that long-term N enrichment impeded mass loss of litter, but not of humus, and only in response to the highest N addition treatment. Furthermore, our data showed that EM fungi reduced the mass of N and P in both substrates during the incubation period compared to when only SAP organisms were present. Low N additions had no effect on microbial community structure, while the high N addition decreased fungal and bacterial biomasses and altered EM fungi and SAP community composition. Actinomycetes were the only bacterial SAP to show increased biomass in response to the highest N addition. These results provide a mechanistic understanding of how anthropogenic N enrichment can influence soil C accumulation rates and suggest that current N deposition rates in the boreal region (≤12 kg N ha-1  year-1 ) are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter. 
carbon sequestration; ecological stoichiometry; Gadgil effect; high-throughput sequencing; ingrowth mesh bags; ITS amplicons; litter decomposition; root exclosure; soil organic matter