Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity. (10th July 2019)

• Record Type: Journal Article
• Authors: Maaroufi, Nadia I.; Nordin, Annika; Palmqvist, Kristin; Hasselquist, Niles J.; Forsmark, Benjamin; Rosenstock, Nicholas P.; Wallander, Håkan; Gundale, Michael J.
• Is Part Of: Global change biology. Volume 25:Number 9(2019)
• Page Start: 2900
• Page End: 2914
• Publication Date: 2019-07-10
• Subjects: carbon sequestration -- ecological stoichiometry -- Gadgil effect -- high‐throughput sequencing -- ingrowth mesh bags -- ITS amplicons -- litter decomposition -- root exclosure -- soil organic matter; Climatic changes -- Environmental aspects -- Periodicals; Troposphere -- Environmental aspects -- Periodicals; Biodiversity conservation -- Periodicals; Eutrophication -- Periodicals; 551.5
• DOI: 10.1111/gcb.14722
• Languages: English
• ISSNs: 1354-1013

Abstract

Abstract: 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. Abstract : There is evidence that nitrogen (N) enrichment enhances carbon (C) accumulation in boreal soils. However, it is unclear how saprotrophs (SAP) and ectomycorrhizal fungi (EMF) responses to N addition impact soil C dynamics. We show that only high N enrichment impeded litter mass loss and altered EMF and SAP communities. EMF reduced the mass of N and P in both substrates compared to when only SAP were present. Our results suggest that current N deposition rates in the boreal region are likely to have a minor impact on the soil microbial community and the decomposition of humus and litter.