Relative importance of competition and plant–soil feedback, their synergy, context dependency and implications for coexistence

• Published in: Ecology letters Vol. 21; no. 8; pp. 1268 - 1281
• Main Authors: Lekberg, Ylva, Bever, James D., Bunn, Rebecca A., Callaway, Ragan M., Hart, Miranda M., Kivlin, Stephanie N., Klironomos, John, Larkin, Beau G., Maron, John L., Reinhart, Kurt O., Remke, Michael, Putten, Wim H., Suding, Katharine
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.08.2018
• Subjects: Additive interaction; biocenosis; Biota; Coexistence; Community structure; Competition; Density; Dependence; facilitation; Feedback; Fungicides; Interspecific; interspecific competition; intraspecific competition; Meta-analysis; mutualist; pathogen; Plant species; Plants; Plants (botany); plant–soil feedback; resource gradient; Soil; soil biota; Soil Microbiology; Soil treatment; soil-plant interactions; soil biota; coexistence; mutualist; meta-analysis; resource gradient; pathogen; competition; facilitation; plant-soil feedback; Additive interaction
• ISSN: 1461-023X; 1461-0248; 1461-0248
• DOI: 10.1111/ele.13093

Plants interact simultaneously with each other and with soil biota, yet the relative importance of competition vs. plant–soil feedback (PSF) on plant performance is poorly understood. Using a meta‐analysis of 38 published studies and 150 plant species, we show that effects of interspecific competition (either growing plants with a competitor or singly, or comparing inter‐ vs. intraspecific competition) and PSF (comparing home vs. away soil, live vs. sterile soil, or control vs. fungicide‐treated soil) depended on treatments but were predominantly negative, broadly comparable in magnitude, and additive or synergistic. Stronger competitors experienced more negative PSF than weaker competitors when controlling for density (inter‐ to intraspecific competition), suggesting that PSF could prevent competitive dominance and promote coexistence. When competition was measured against plants growing singly, the strength of competition overwhelmed PSF, indicating that the relative importance of PSF may depend not only on neighbour identity but also density. We evaluate how competition and PSFs might interact across resource gradients; PSF will likely strengthen competitive interactions in high resource environments and enhance facilitative interactions in low‐resource environments. Finally, we provide a framework for filling key knowledge gaps and advancing our understanding of how these biotic interactions influence community structure.