Anthropogenic nitrogen enrichment enhances soil carbon accumulation by impacting saprotrophs rather than ectomycorrhizal fungal activity

Research output: Contribution to journalArticle

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.

Details

Authors
Organisations
External organisations
  • University of Bern
  • Swedish University of Agricultural Sciences, Umeå
  • Umeå University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Soil Science

Keywords

  • carbon sequestration, ecological stoichiometry, Gadgil effect, high-throughput sequencing, ingrowth mesh bags, ITS amplicons, litter decomposition, root exclosure, soil organic matter
Original languageEnglish
JournalGlobal Change Biology
Publication statusE-pub ahead of print - 2019 Jun 5
Publication categoryResearch
Peer-reviewedYes