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Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests

Nature Ecology & Evolution volume 7, pages 501–511 (2023)Cite this article

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An Author Correction to this article was published on 15 March 2023

This article has been updated

Abstract

A common mycorrhizal network (CMN) is formed when mycorrhizal fungal hyphae connect the roots of multiple plants of the same or different species belowground. Recently, CMNs have captured the interest of broad audiences, especially with respect to forest function and management. We are concerned, however, that recent claims in the popular media about CMNs in forests are disconnected from evidence, and that bias towards citing positive effects of CMNs has developed in the scientific literature. We first evaluated the evidence supporting three common claims. The claims that CMNs are widespread in forests and that resources are transferred through CMNs to increase seedling performance are insufficiently supported because results from field studies vary too widely, have alternative explanations or are too limited to support generalizations. The claim that mature trees preferentially send resources and defence signals to offspring through CMNs has no peer-reviewed, published evidence. We next examined how the results from CMN research are cited and found that unsupported claims have doubled in the past 25 years; a bias towards citing positive effects may obscure our understanding of the structure and function of CMNs in forests. We conclude that knowledge on CMNs is presently too sparse and unsettled to inform forest management.

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Fig. 1: Alternative explanations for the results of peer-reviewed, published field studies claiming positive effects of CMNs on interplant resource transfer or seedling performance for at least one set of environmental conditions.
Fig. 2: Methods used to evaluate CMNs in forests.
Fig. 3: Percentage of unsupported citations through time of influential studies on CMNs.

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Data availability

The datasets analysed in the current study are available from the University of Alberta Dataverse at https://doi.org/10.5683/SP3/88MZYX.

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Acknowledgements

We thank I. Mounts, S. Draud and D. Durall for participating in early discussions. I. Mounts provided the Web of Science search term and aided in screening studies for inclusion. R. Jackson formatted and cross-checked the unsupported citations for accuracy and made Supplementary Fig. 1. C. Karst designed Fig. 2.

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Authors and Affiliations

  1. Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada

    Justine Karst

  2. Department of Biology, University of British Columbia, Kelowna, British Columbia, Canada

    Melanie D. Jones

  3. Department of Biology, University of Mississippi, Oxford, MS, USA

    Jason D. Hoeksema

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  1. Justine Karst
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  2. Melanie D. Jones
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  3. Jason D. Hoeksema
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The focus of this Perspective was conceived by all of the authors and the writing was shared. J.K. led the evaluation of citations, with feedback from M.D.J. and J.D.H.

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Correspondence to Justine Karst.

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Supplementary Notes 1–4, Tables 1 and 2 and Fig, 1.

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Karst, J., Jones, M.D. & Hoeksema, J.D. Positive citation bias and overinterpreted results lead to misinformation on common mycorrhizal networks in forests. Nat Ecol Evol 7, 501–511 (2023). https://doi.org/10.1038/s41559-023-01986-1

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