Predicting Plant-Soil Feedback in the Field: Meta-Analysis Reveals That Competition and Environmental Stress Differentially Influence PSF

Abstract

Past research on plant-soil feedbacks (PSF), largely undertaken in highly controlled greenhouse conditions, has established that plant species differentially alter abiotic and biotic soil conditions that in turn affect growth of other conspecific and heterospecific individuals in that soil. Yet, whether feedbacks under controlled greenhouse conditions reflect feedbacks in natural environments where plants are exposed to a range of abiotic and biotic pressures is still unresolved. To address how environmental context affects PSF, we conducted a meta-analysis of previously published studies that examined plant growth responses to multiple forms of competition, stress, and disturbance across various PSF methodology. We asked the following questions: (1) Can competition, stress, and disturbance alter the direction and/or strength of PSF? (2) Do particular types of competition, stress, or disturbance affect the direction and/or strength of PSF more than others? and (3) Do methods of conducting PSF research (i.e., greenhouse vs. field experiments and whether the source of soil inoculum conditioning is from the field vs. greenhouse) affect plant growth responses to PSF or competition, stress, and disturbance, or their interactions? We discovered four patterns that may be predictive of what future PSF studies conducted under more realistic conditions might reveal. First, relatively little is known about how PSF responds to environmental stress and disturbance compared to plant-plant competition. Second, specific types of competition enhanced negative effects of soil microbes on plant growth, and specific environmental stressors enhanced positive effects of soil microbes on plant growth. Third, whether PSF experiments are conducted in the field or greenhouse can change plant growth responses. And, fourth, how the soil conditioning phase is conducted can change plant growth responses. With more detail than previously shown, these results confirm that environmental context writ large can change plant growth responses in PSF Beals et al. PSF Differs With Competition, Stress experiments. These data should aid theory and predictions for conservation and restoration applications by showing the relative importance of competition, stress, and disturbance in PSF studies over time. Lastly, these data demonstrate how variation in experimental methods can alter interpretation and conclusions of PSF studies.

Disentangling nematode and arbuscular mycorrhizal fungal community effect on the growth of range-expanding Centaurea stoebe in original and new range soil

“…However, the effect of the origin of soil communities became evident in the feedback phase of Experiment II, in line with a recent experiment that demonstrated that it can take between four and six months to reveal the effect of soil microbes on plant biomass (Wang et al 2019). Moreover, the origin of soil communities determined plant biomass production under drought, being in line with a recent meta-analyses, that suggests intensified plant-soil interactions under drought (Beals et al 2020). At the same time, a recent study has reported no differences in community-level biomass of range expanders between drought and ambient conditions (Manrubia et al 2019), which suggests that in communities, neighbouring plant species might reduce the intensity of plant-soil interactions during drought.…”

Soil sample pooling generates no consistent inference bias: a meta‐analysis of 71 plant–soil feedback experiments

“…Although this viewpoint means that soil pooling may be acceptable when the scope of inference of the experiment is limited to the sampled populations, rather than a broader regional population (Gundale et␣al ., 2019), this only highlights that researchers must be explicit about the rationale and interpretation of their soil pooling methods. Plant–soil feedback research still faces multiple challenges (van der Putten et␣al ., 2013), including experimental design and interpretation (Brinkman et␣al ., 2010; this study), predicting plant–soil feedback effects (De Long et␣al ., 2019; Wandrag et␣al ., 2020), translating findings from the laboratory to the field (Heinze et␣al ., 2016; Forero et␣al ., 2019), unravelling context‐dependency along abiotic and biotic gradients (Smith‐Ramesh & Reynolds, 2017; Beals et␣al ., 2020), and linking plant–soil feedbacks to plant evolution, coexistence, and population and community dynamics (ter Horst & Zee, 2016; Chung et␣al ., 2019; Kulmatiski, 2019). Our work contributes to addressing these challenges by demonstrating that soil sample pooling may be an effective approach for large‐scale, multispecies studies that test broad hypotheses about the drivers and consequences of plant–soil feedbacks, especially when time, space or budgets are limited (Cahill et␣al ., 2017; Gundale et␣al ., 2017; Teste et␣al ., 2019).…”

Soil microbes increase switchgrass germination but not seedling growth under drought

“…Germinating in sterile conditions is common practice for many greenhouse studies (Fry et al, 2018;Naylor et al, 2017;Zolla et al, 2013), yet because root exudates are in uenced by microbial crosstalk and differ in sterile conditions (Oburger & Jones, 2018;Sasse et al, 2018), it is likely that an initial period of growth in sterile conditions could alter root exudates and, in turn, the seedlings' effect on microbial interactions after transplanting. No studies to our knowledge have evaluated how germinating in sterile conditions affects later plant-microbial interactions, but this potentially confounding effect could contribute to issues with scaling results from greenhouse (sterile germination) to eld studies (germination in live soil) (Beals et al, 2020;Forero, Grenzer, Heinze, Schittko, & Kulmatiski, 2019).…”