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

Abstract

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.

Climate outweighs native vs. nonnative range‐effects for genetics and common garden performance of a cosmopolitan weed

“…Therefore, future studies should test native vs. nonnative populations’ performance under different biotic interaction scenarios, e.g., comparing the relative importance of competition and plant–soil feedback across biogeographical ranges (Lekberg et al. ).…”

Effects of soil microbes on plant competition: a perspective from modern coexistence theory

“…Indeed, variability in experimental results suggests that the relative importance of plant–soil microbe and plant–plant interactions may be highly system specific (Lekberg et al. ). Because of the context dependency of soil microbial interactions, an important question remains: what are the general conditions under which soil microbes promote plant coexistence?…”

Biotic and abiotic plant–soil feedback depends on nitrogen‐acquisition strategy and shifts during long‐term ecosystem development

“…Our third hypothesis was not fully supported by the absence of significant negative (biotic) PSF of similar magnitude in the old, severely P‐impoverished soils. However, the shift in the direction of PSF experienced by non‐N‐fixing plants, from negative in young soils to neutral in the old soils, suggests that shifts in PSF depend on environmental context in terms of soil nutrient availability (Kardol et al, ; Lekberg et al, ; Manning et al, ). Collectively, our findings illustrate the importance of soil nutrient availability and the type of plant N‐acquisition strategy in influencing the origin, strength, and direction of PSF during long‐term ecosystem development.…”

“…First, only common species from two plant functional groups (N‐fixing and non‐N‐fixing) were examined in the present study, which would only have accounted for a subset of the range of PSF present among the diverse spectrum of plant functional groups in species‐rich plant communities on these old, severely P‐impoverished soils (e.g., Lambers et al, ; Zemunik et al, ). In particular, plant functional groups associated with key below‐ground nutrient‐acquisition traits of AM, ECM, and non‐mycorrhizal cluster roots require further attention (Lekberg et al, ; Revillini et al, ; Teste et al, ; Zemunik et al, ). Second, the underlying mechanisms of how various groups of soil microorganisms (e.g., N‐fixing rhizobia, plant growth‐promoting rhizobacteria, and soil‐borne pathogens) influence PSF in this study remain something of a “black box.” Third, our chronosequence approach does not allow strong inference of the causal mechanisms between the observed shifts in PSF and soil N and P availability (Walker et al, ).…”

“…Well‐defined, long‐term soil chronosequences forming natural nutrient availability gradients provide useful model systems to explore how abiotic and biotic PSF mechanisms of plant communities respond to shifts in environmental context over a longer time‐scale (Kardol et al, ; Laliberté et al, ; Lekberg et al, ; Walker, Wardle, Bardgett, & Clarkson, ). In this study, the environmental context of interest is soil nutrient availability, particularly of N and P. The declining soil fertility and contrasting shifts in soil nutrient limitation of plant growth—from N to P limitation with soil age (Laliberté et al, ; Vitousek & Farrington, ; Walker & Syers, )—along long‐term soil chronosequences influence the relative abundance of N‐fixing and non‐N‐fixing plant species (Chapin, Walker, Fastie, & Sharman, ; Vitousek & Walker, ; Walker, ; Zemunik, Turner, Lambers, & Laliberté, ).…”