Moderate plant-soil feedbacks have small effects on the biodiversity-productivity relationship: A field experiment.

Josephine Grenzer,Anne Ebeling,Andrew Kulmatiski,Jeanette Norton,Nico Eisenhauer,Leslie Forero

doi:10.1002/ece3.7819

Abstract

Plant–soil feedback (PSF) has gained attention as a mechanism promoting plant growth and coexistence. However, most PSF research has measured monoculture growth in greenhouse conditions. Translating PSFs into effects on plant growth in field communities remains an important frontier for PSF research. Using a 4‐year, factorial field experiment in Jena, Germany, we measured the growth of nine grassland species on soils conditioned by each of the target species (i.e., 72 PSFs). Plant community models were parameterized with or without these PSF effects, and model predictions were compared to plant biomass production in diversity–productivity experiments. Plants created soils that changed subsequent plant biomass by 40%. However, because they were both positive and negative, the average PSF effect was 14% less growth on “home” than on “away” soils. Nine‐species plant communities produced 29 to 37% more biomass for polycultures than for monocultures due primarily to selection effects. With or without PSF, plant community models predicted 28%–29% more biomass for polycultures than for monocultures, again due primarily to selection effects. Synthesis: Despite causing 40% changes in plant biomass, PSFs had little effect on model predictions of plant community biomass across a range of species richness. While somewhat surprising, a lack of a PSF effect was appropriate in this site because species richness effects in this study were caused by selection effects and not complementarity effects (PSFs are a complementarity mechanism). Our plant community models helped us describe several reasons that even large PSF may not affect plant productivity. Notably, we found that dominant species demonstrated small PSF, suggesting there may be selective pressure for plants to create neutral PSF. Broadly, testing PSFs in plant communities in field conditions provided a more realistic understanding of how PSFs affect plant growth in communities in the context of other species traits.

Highlights

Plant–soil feedbacks (PSFs) have gained attention over the past 25 years as a potential mechanism of plant growth and coexistence (Bever, 1994; van der Putten et al, 2013)
It has been suggested that PSFs will intensify competitive effects in nutrient-rich conditions and strengthen facilitative effects in nutrient-poor conditions (Bever, 2003; Lekberg et al, 2018). Consistent with this idea, we found that PSFs were more negative, and competitive effects were larger in the 2014 experiment, performed at a mesic, nutrient-rich site relative to a similar recent study performed at a drier and nutrient-poor site (Forero, 2021)
While PSFs changed plant growth within plant species by 40%, this effect was smaller than differences in growth among species, and the dominant plant species demonstrated small PSFs in our experiment

Summary

Introduction

Plant–soil feedbacks (PSFs) have gained attention over the past 25 years as a potential mechanism of plant growth and coexistence (Bever, 1994; van der Putten et al, 2013). It has long been thought that the positive diversity– productivity relationship can be explained because species extract resources in different times or places (i.e., niche partitioning or complementarity; Hector et al, 1999; Loreau & Hector, 2001; Tilman et al, 1997). This mechanism can explain both species coexistence and why more diverse communities are more productive (i.e., because they more fully exploit resource space; Barry et al, 2019; Loreau et al, 2001). There has been interest in discovering additional mechanisms that contribute to diversity–productivity relationships (Eisenhauer et al, 2012; Loreau et al, 2001)

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Discussion

Conclusion