Microbial substrate stoichiometry governs nutrient effects on nitrogen cycling in grassland soils

P. M. Schleuss, M. Widdig, L. A. Biederman, E. T. Borer, M. J. Crawley, K. P. Kirkman, E. W. Seabloom, P. D. Wragg, M. Spohn

Research output: Contribution to journalArticlepeer-review

Abstract

Human activities have increased nitrogen (N) and phosphorus (P) inputs in terrestrial ecosystems and altered carbon (C) availability, shifting the stoichiometry of microbial substrates in soils, such as the C:N:P ratios of the dissolved organic matter pool. These stoichiometric deviations between microbial biomass and its substrate may control microbial processes of N cycling. We studied the effects of this stoichiometric mismatch using a full factorial N and P addition experiment replicated in six grassland ecosystems in South Africa, the USA, and the UK. We found that N and P addition changed the dissolved organic matter C:N ratio, but not the C:N ratio of the soil microbial biomass. Compared to P addition, N addition decreased microbial N acquisition via non-symbiotic N2 fixation by −55% and increased microbial N release via net N mineralization by +134%. A possible explanation is that the dissolved elements, e.g., dissolved organic C (DOC) and dissolved total N (DN), serve as the main microbial substrate and its C:N ratio defines whether N is scarce or abundant with respect to microbial demands. If N is available in excess relative to microbial demands, net N mineralization increases. In contrast, when N is scarce, immobilization outweighs release decreasing net N mineralization. However, the activity of leucine aminopeptidases, which decompose peptides, was not affected by nutrient additions. Further, C rather than P availability may control the rates of non-symbiotic N2 fixation in the six studied grassland sites. In conclusion, globally increasing nutrient inputs change processes of microbial N acquisition and release in grassland ecosystems and these changes are largely driven by shifts in substrate stoichiometry.

Original languageEnglish (US)
Article number108168
JournalSoil Biology and Biochemistry
Volume155
DOIs
StatePublished - Apr 2021

Bibliographical note

Funding Information:
The study was funded by the German Research Foundation within the Emmy Noether program (grant SP1389/6?1). Coordination and data management of the Nutrient Network have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and Long Term Ecological Research (NSF-DEB-1234162 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13). We further thank Renate Krauss, Uwe Hell, and Karin S?llner for technical assistance, the chemical analytics (CAN) of the Bayreuth Center of Ecological and Environmental Research (BayCEER) for chemical analyses, and the Center for Stable Isotope Research and Analysis (KOSI) of the University of G?ttingen for measuring 15N isotopes.

Funding Information:
The study was funded by the German Research Foundation within the Emmy Noether program (grant SP1389/6–1). Coordination and data management of the Nutrient Network have been supported by funding to E. Borer and E. Seabloom from the National Science Foundation Research Coordination Network (NSF-DEB-1042132) and Long Term Ecological Research (NSF-DEB-1234162 to Cedar Creek LTER) programs, and the Institute on the Environment (DG-0001-13). We further thank Renate Krauss, Uwe Hell, and Karin Söllner for technical assistance, the chemical analytics (CAN) of the Bayreuth Center of Ecological and Environmental Research (BayCEER) for chemical analyses, and the Center for Stable Isotope Research and Analysis (KOSI) of the University of Göttingen for measuring 15 N isotopes.

Publisher Copyright:
© 2021 Elsevier Ltd

Keywords

  • Ecological Stoichiometry
  • Leucine aminopeptidase activity
  • Net N mineralization
  • Nitrogen release and acquisition
  • Non-symbiotic N fixation
  • Nutrient Network (NutNet)
  • Nutrient fertilization

Fingerprint Dive into the research topics of 'Microbial substrate stoichiometry governs nutrient effects on nitrogen cycling in grassland soils'. Together they form a unique fingerprint.

Cite this