Oecologia

, Volume 127, Issue 4, pp 540–548

A link between plant diversity, elevated CO2 and soil nitrate

  • Pascal A. Niklaus
  • E. Kandeler
  • P.W. Leadley
  • B. Schmid
  • D. Tscherko
  • C. Körner
Article

Abstract

Interactive effects of reductions in plant species diversity and increases in atmospheric CO2 were investigated in a long-term study in nutrient-poor calcareous grassland. Throughout the experiment, soil nitrate was persistently increased at low plant species diversity, and CO2 enrichment reduced soil [NO3] at all levels of plant species diversity. In our study, soil [NO3] was unrelated to root length density, microbial biomass N, community legume contents, and experimental plant communities differed only little in total N pools. However, potential nitrification revealed exactly the same treatment effects as soil [NO3], providing circumstantial evidence that nitrification rates drove the observed changes in [NO3]. One possible explanation for plant diversity effects on nitrification lies in spatial and temporal interspecific differences in plant N uptake, which would more often allow accumulation of NH4+ in part of the soil profile at low diversity than in more species-rich plant communities. Consequently, nitrification rates and soil [NO3] would increase. Elevated CO2 increased soil water contents, which may have improved NO3 diffusion to the root surface thereby reducing soil [NO3]. Higher soil moisture at elevated CO2 might also reduce nitrification rates due to less aerobic conditions. The accordance of the diversity effect on soil [NO3] with previous experiments suggests that increased soil [NO3] at low species diversity is a fairly general phenomenon, although the mechanisms causing high [NO3] may vary. In contrast, experimental evidence for effects of CO2 enrichment on soil [NO3] is ambiguous, and the antagonistic interaction of plant species reductions and elevated CO2 we have observed is thus probably less universal.

Keywords

Ammonium Nitrification Nitrogen mineralization Perennial grassland Root length density 

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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Pascal A. Niklaus
    • 1
  • E. Kandeler
    • 2
  • P.W. Leadley
    • 1
    • 3
  • B. Schmid
    • 4
  • D. Tscherko
    • 2
    • 5
  • C. Körner
    • 1
  1. 1.Institute of BotanyUniversity of BaselBaselSwitzerland
  2. 2.University of HohenheimStuttgartGermany
  3. 3.Ecologie des Populations et Communautés, URA CNRS 2154Université Paris-SudOrsay CedexFrance
  4. 4.Institut für UmweltwissenschaftenUniversity of ZürichZürichSwitzerland
  5. 5.Federal Office and Research Centre for AgricultureViennaAustria
  6. 6.Landcare ResearchPalmerston NorthNew Zealand

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