Nitrogen and Phosphorus Additions Alter the Abundance of Phosphorus-Solubilizing Bacteria and Phosphatase Activity in Grassland Soils

Meike Widdig, Per M. Schleuss, Alfons R. Weig, Alexander Guhr, Lori A. Biederman, Elizabeth T. Borer, Michael J. Crawley, Kevin P. Kirkman, Eric W. Seabloom, Peter D. Wragg, Marie Spohn

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Abstract

Microorganisms mobilize phosphorus (P) in soil by solubilizing bound inorganic P from soil minerals and by mineralizing organic P via phosphatase enzymes. Nitrogen (N) inputs are predicted to increase through human activities and shift plants to be more P limited, increasing the importance of P mobilization processes for plant nutrition. We studied how the relative abundance of P-solubilizing bacteria (PSB), PSB community composition, and phosphatase activity respond to N and P addition (+N, +P, +NP) in grassland soils spanning large biogeographic gradients. The studied soils are located in South Africa, USA, and UK and part of a globally coordinated nutrient addition experiment. We show that the abundance of PSB in the topsoil was reduced by −18% in the N and by −41% in the NP treatment compared to the control. In contrast, phosphatase activity was significantly higher in the N treatment than in the control across all soils. Soil C:P ratio, sand content, pH, and water-extractable P together explained 71% of the variance of the abundance of PSB across all study sites and all treatments. Further, the community of PSB in the N and NP addition treatment differed significantly from the control. Taken together, this study shows that N addition reduced the relative abundance of PSB, altered the PSB community, and increased phosphatase activity, whereas P addition had no impact. Increasing atmospheric N deposition may therefore increase mineralization of organic P and decrease solubilization of bound inorganic P, possibly inducing a switch in the dominant P mobilization processes from P solubilization to P mineralization.

Original languageEnglish (US)
Article number185
JournalFrontiers in Environmental Science
Volume7
DOIs
StatePublished - Nov 26 2019

Bibliographical note

Funding Information:
MS thanks the German Research Foundation for funding this study through the Emmy Noether-program (grant SP1389/6-1). Coordination and data management of the Nutrient Network have been supported by funding to EB and ES 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). This publication was funded by the German Research Foundation (DFG) and the University of Bayreuth in the funding programme Open Access Publishing. We thank Anita Gössner, Uwe Hell, Renate Krauss, Ralf Mertel, and Karin Söllner for technical assistance and thank the chemical analytics (CAN) of the Bayreuth Center of Ecological and Environmental Research (BayCEER) for performing parts of the chemical analyses and the Keylab for Genomics and Bioinformatics of the BayCEER for sequencing the PSB and for the bacterial and fungal community analyses (ARISA).

Keywords

  • Nutrient Network (NutNet)
  • enzyme activity
  • nitrogen fertilization
  • phosphate solubilization
  • phosphorus cycling
  • phosphorus mineralization
  • phosphorus mobilization

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