Short-term plant–soil feedback experiment fails to predict outcome of competition observed in long-term field experiment

Noelle G. Beckman, Ray Dybzinski, David Tilman

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Mounting evidence suggests that plant–soil feedbacks (PSF) may determine plant community structure. However, we still have a poor understanding of how predictions from short-term PSF experiments compare with outcomes of long-term field experiments involving competing plants. We conducted a reciprocal greenhouse experiment to examine how the growth of prairie grass species depended on the soil communities cultured by conspecific or heterospecific plant species in the field. The source soil came from monocultures in a long-term competition experiment (LTCE; Cedar Creek Ecosystem Science Reserve, MN, USA). Within the LTCE, six species of perennial prairie grasses were grown in monocultures or in eight pairwise competition plots for 12 years under conditions of low or high soil nitrogen availability. In six cases, one species clearly excluded the other; in two cases, the pair appeared to coexist. In year 15, we gathered soil from all 12 soil types (monocultures of six species by two nitrogen levels) and grew seedlings of all six species in each soil type for 7 weeks. Using biomass estimates from this greenhouse experiment, we predicted coexistence or competitive exclusion using pairwise PSFs, as derived by Bever and colleagues, and compared model predictions to observed outcomes within the LTCE. Pairwise PSFs among the species pairs ranged from negative, which is predicted to promote coexistence, to positive, which is predicted to promote competitive exclusion. However, these short-term PSF predictions bore no systematic resemblance to the actual outcomes of competition observed in the LTCE. Other forces may have more strongly influenced the competitive interactions or critical assumptions that underlie the PSF predictions may not have been met. Importantly, the pairwise PSF score derived by Bever et al. is only valid when the two species exhibit an internal equilibrium, corresponding to the Lotka–Volterra competition outcomes of stable coexistence and founder control. Predicting the other two scenarios, competitive exclusion by either species irrespective of initial conditions, requires measuring biomass in uncultured soil, which is methodologically challenging. Subject to several caveats that we discuss, our results call into question whether long-term competitive outcomes in the field can be predicted from the results of short-term PSF experiments.

Original languageEnglish (US)
Article numbere3883
JournalEcology
Volume104
Issue number2
DOIs
StatePublished - Feb 2023

Bibliographical note

Funding Information:
We thank S. Mangan for his helpful comments on the manuscript and J. Wiggins and K. George for help with the short-term PSF experiment. We thank the US National Science Foundation (DEB-0080382 and DEB-9629566) and the Andrew Mellon Foundation for funding. Noelle G. Beckman was supported by the Mathematical Biosciences Institute under the US National Science Foundation Grant DMS-0931642 and the National Socio-Environmental Synthesis Center under the US National Science Foundation Grant DBI-1052875.

Publisher Copyright:
© 2022 The Ecological Society of America.

Keywords

  • Cedar Creek
  • PSF
  • determinants of plant community diversity and structure
  • grassland
  • mechanisms of coexistence
  • prairie
  • soil community
  • soil legacies
  • soil pathogens and mutualists
  • stabilizing and destabilizing mechanisms

PubMed: MeSH publication types

  • Journal Article
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

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