Plant-soil Feedback Research Articles

Plant-soil interactions alter nitrogen and phosphorus dynamics in an advancing subarctic treeline.

Treelines advance due to climate warming. The impacts of this vegetation shift on plant-soil nutrient cycling are still uncertain, yet highly relevant as nutrient availability stimulates tree growth. Here, we investigated nitrogen (N) and phosphorus (P) in plant and soil pools along two tundra-forest transects on Kola Peninsula, Russia, with a documented elevation shift of birch-dominated treeline by 70 m during the last 50 years. Results show that although total N and P stocks in the soil-plant system did not change with elevation, their distribution was significantly altered. With the transition from high-elevation tundra to low-elevation forest, P stocks in stones decreased, possibly reflecting enhanced weathering. In contrast, N and P stocks in plant biomass approximately tripled and available P and N in the soil increased fivefold toward the forest. This was paralleled by decreasing carbon (C)-to-nutrient ratios in foliage and litter, smaller C:N:P ratios in microbial biomass, and lower enzymatic activities related to N and P acquisition in forest soils. An incubation experiment further demonstrated manifold higher N and P net mineralization rates in litter and soil in forest compared to tundra, likely due to smaller C:N:P ratios in decomposing organic matter. Overall, our results show that forest expansion increases the mobilization of available nutrients through enhanced weathering and positive plant-soil feedback, with nutrient-rich forest litter releasing greater amounts of N and P upon decomposition. While the low N and P availability in tundra may retard treeline advances, its improvement toward the forest likely promotes tree growth and forest development.

Plant–mycorrhizal associations may explain the latitudinal gradient of plant community assembly

Biogeographical variation in community assembly processes forms the basis of the latitudinal gradient of biodiversity by driving β‐diversity. Classical studies on community assembly predict environmental filtering affecting β‐diversity more strongly at higher latitudes, where productivity is lower and abiotic stress is stronger. Contrary to this prediction, recent evidence indicates that plant community composition at higher latitudes exhibits more spatially clustered distributions independently of background environments, suggesting the importance of spatial processes, such as priority effects. In this study, we propose a hypothesis that resolves this paradox by considering plant–soil feedback and biogeographic variations in the dominant mycorrhizal type: we predict that the increasing prevalence of ectomycorrhizal (EcM) trees with latitude contributes to the spatially clustered distribution of plants, as EcM trees tend to exhibit positive plant–soil feedback. We analyzed a large‐scale standardized dataset of Japanese forests covering a latitudinal gradient of >10° and found that 1) the proportion of EcM trees was higher at higher latitudes, and 2) EcM tree‐rich communities exhibited more spatially clustered distributions likely due to positive plant–soil feedback. Consequently, 3) tree species composition at higher latitudes was better explained by spatial variables suggesting the importance of priority effects. Consistent with the predictions of the plant–soil feedback theory, these patterns were more pronounced in understory than in canopy communities. Taken together, our results lend support to our hypothesis that biogeographic variation in tree community assembly patterns is defined by mycorrhizal types and plant–soil feedback, thereby resolving a paradox in the latitudinal gradient of plant community assembly. Our work highlights that plant mycorrhizal type underlies the determinants of β‐diversity which is a critical component of the latitudinal gradient of diversity.

Chemically Mediated Plant-Plant Interactions: Allelopathy and Allelobiosis.

Plant-plant interactions are a central driver for plant coexistence and community assembly. Chemically mediated plant-plant interactions are represented by allelopathy and allelobiosis. Both allelopathy and allelobiosis are achieved through specialized metabolites (allelochemicals or signaling chemicals) produced and released from neighboring plants. Allelopathy exerts mostly negative effects on the establishment and growth of neighboring plants by allelochemicals, while allelobiosis provides plant neighbor detection and identity recognition mediated by signaling chemicals. Therefore, plants can chemically affect the performance of neighboring plants through the allelopathy and allelobiosis that frequently occur in plant-plant intra-specific and inter-specific interactions. Allelopathy and allelobiosis are two probably inseparable processes that occur together in plant-plant chemical interactions. Here, we comprehensively review allelopathy and allelobiosis in plant-plant interactions, including allelopathy and allelochemicals and their application for sustainable agriculture and forestry, allelobiosis and plant identity recognition, chemically mediated root-soil interactions and plant-soil feedback, and biosynthesis and the molecular mechanisms of allelochemicals and signaling chemicals. Altogether, these efforts provide the recent advancements in the wide field of allelopathy and allelobiosis, and new insights into the chemically mediated plant-plant interactions.

Chiral herbicide imazethapy influences plant-soil feedback on nitrogen metabolism by shaping rhizosphere microorganisms.

Herbicides are known to affect the soil nitrogen cycle by shaping soil microorganisms. However, it is not clear how herbicides regulate diverse transformation processes of soil nitrogen cycling by altering rhizosphere microorganisms, subsequently influencing the feedback to plant nitrogen metabolism. Here, we investigated how imazethapyr (IM) enantiomers drive plant-soil feedback on nitrogen metabolism by altering the rhizosphere microorganisms. The results indicated that (R)- and (S)-IM significantly changed the composition and structure rhizosphere microbiome with enantioselectivity and functional changes in microbial communities were associated with soil nitrogen circulation. The determination of nitrogen-cycling functional genes further supported the above findings. The results revealed that (R)- and (S)-IM could change the abundance of nitrogen-cycling functional genes by changing specific bacteria abundances, such as Bacteroidetes, Proteobacteria, and Acidobacteria, thus resulting in diverse nitrogen transformation processes. The alternation of nitrogen transformation processes indicated (R)-IM exhibited a more notable tendency to form a nitrogen cycling pattern with lower energy cost and higher nitrogen retention than (S)-IM. Sterilization experiments demonstrated changes in soil nitrogen cycling drive plant nitrogen metabolism and rhizosphere microorganisms are responsible for the above process of plant-soil feedback for nitrogen metabolism. Under IM enantiomer treatments, rhizosphere microorganisms might stimulate glutamate synthesis by promoting NH4+ uptake and glutamine-glutamate synthesis cycling in roots, thus contributing to positive feedback, with (R)-IM treatments showing more pronounced positive feedback on nitrogen metabolism than (S)-IM treatments. Our results provide theoretical support for determining the mechanism by which IM enantiomers drive plant-soil nitrogen metabolism by changing the rhizosphere microbial communities.

Distance- and density-dependent recruitment of common ragwort is not driven by plant-soil feedbacks

Janzen-Connell effects state that the accumulation of host-specific natural enemies near parent plants can negatively affect their offspring. Negative plant-soil feedbacks can produce patterns of seedling performance predicted by Janzen-Connell effects and influence plant populations, but their relevance in field conditions remains unclear. Here, using spatial point-pattern analysis, we examine the spatial distribution of Jacobaea vulgaris to assess whether distance- and density-dependent predictions of Janzen-Connell effects are evident in the field. We established 27 replicated 64 m2 plots at two grassland sites and mapped positions of rosette-bearing and flowering J. vulgaris plants within each plot. To investigate temporal distribution patterns, we tracked plant positions repeatedly in three plots during a single season. Additionally, we tested whether these patterns are soil-mediated. Soil samples were collected underneath flowering plants and at a distance of 0.5 meter, and used to compare seed germination, seedling survival, and growth under controlled conditions. Furthermore, we measured J. vulgaris growth in soil from patches with high J. vulgaris densities and in soil from areas outside these patches. The density of rosette-bearing plants was lower at close distances from flowering plants than expected from null models, suggesting negative distance-dependent plant recruitment. The degree of clustering decreased over time from rosette-bearing to flowering plants, indicating density-dependent self-thinning. Seed germination was higher in soil further away from flowering J. vulgaris plants than in soil underneath plants at one site, but soil distance was not an overall significant factor in explaining seed germination. However, seedling mortality and biomass did not differ between soils collected at the two distances, and plants produced similar biomass in soil collected from inside and outside J. vulgaris patches. Our study demonstrates conspecific distance- and density-dependent plant recruitment in J. vulgaris in the field, but we found no evidence this depends on belowground natural enemies.

Light-dark cycles may influence insitu soil bacterial networks and diurnally-sensitive taxa.

Soil bacterial taxa have important functional roles in ecosystems (e.g. nutrient cycling, soil formation, plant health). Many factors influence their assembly and regulation, with land cover types (e.g. open woodlands, grasslands), land use types (e.g. nature reserves, urban green space) and plant-soil feedbacks being well-studied factors. However, changes in soil bacterial communities insitu over light-dark cycles have received little attention, despite many plants and some bacteria having endogenous circadian rhythms that could influence soil bacterial communities. We sampled surface soils insitu across 24-h light-dark cycles (at 00:00, 06:00, 12:00, 18:00) at two land cover types (remnant vegetation vs. cleared, grassy areas) and applied 16S rRNA amplicon sequencing to investigate changes in bacterial communities. We show that land cover type strongly affected soil bacterial diversity, with soils under native vegetation expressing 15.4%-16.4% lower alpha diversity but 4.9%-10.6% greater heterogeneity than soils under cleared vegetation. In addition, we report time-dependent and site-specific changes in bacterial network complexity and between 598-922 ASVs showing significant changes in relative abundance across times. Native site node degree (bacterial interactions) at the phylum level was 16.0% higher in the early morning than in the afternoon/evening. Our results demonstrate for the first time that light-dark cycles have subtle yet important effects on soil bacterial communities insitu and that land cover influences these dynamics. We provide a new view of soil microbial ecology and suggest that future studies should consider the time of day when sampling soil bacteria.

Negative plant-soil feedback in Arabidopsis thaliana: Disentangling the effects of soil chemistry, microbiome, and extracellular self-DNA

Nutrient deficiency, natural enemies and litter autotoxicity have been proposed as possible mechanisms to explain species-specific negative plant-soil feedback (PSF). Another potential contributor to negative PSF is the plant released extracellular self-DNA during litter decay. In this study, we sought to comprehensively investigate these hypotheses by using Arabidopsis thaliana (L.) Heynh as a model plant in a feedback experiment. The experiment comprised a conditioning phase and a response phase in which the conditioned soils underwent four treatments: (i) addition of activated carbon, (ii) washing with tap water, (iii) sterilization by autoclaving, and (iv) control without any treatment. We evaluated soil chemical properties, microbiota by shotgun sequencing and the amount of A. thaliana extracellular DNA in the differently treated soils. Our results showed that washing and sterilization treatments mitigated the negative PSF effect. While shifts in soil chemical properties were not pronounced, significant changes in soil microbiota were observed, especially after sterilization. Notably, plant biomass was inversely associated with the content of plant self-DNA in the soil. Our results suggest that the negative PSF observed in the conditioned soil was associated to increased amounts of soilborne pathogens and plant self-DNA. However, fungal pathogens were not limited to negative conditions, butalso found in soils enhancing A.thaliana growth. In-depth multivariate analysis highlights that the hypothesis of negative PSF driven solely by pathogens lacks consistency. Instead, we propose a multifactorial explanation for the negative PSF buildup, in which the accumulation of self-DNA weakens the plant’s root system, making it more susceptible to pathogens.

Soil microbial communities along elevational gradients in the Madrean Sky Islands.

The Madrean Sky Islands are mountain ranges isolated by a 'desert sea'. This area is a biodiversity hotspot currently threatened by climate change. Here, we studied soil microbial communities along elevational gradients in eight Madrean Sky Islands in southeastern Arizona (USA). Our results showed that while elevational microbial richness gradients were weak and not consistent across different mountains, soil properties strongly influenced microbial community composition (overall composition and the abundance of key functional groups) along elevational gradients. In particular, warming is associated with a higher abundance of soil-borne fungal plant pathogens that concomitantly might facilitate upward elevational shifts of plant species released from negative plant-soil feedbacks. Furthermore, projected warming and drought in the area aggravated by anthropogenic nitrogen deposition on mountain tops (and thus, decreasing nitrogen limitation) can enhance a shift from ectomycorrhizal to arbuscular mycorrhizal fungi. Overall, these results indicate that climate change effects on plant-soil interactions might have profound ecosystem consequences.

Forest tree community ecology and plant–soil feedback: Theory and evidence

AbstractMounting evidence suggests that reciprocal interactions between plants and the soil microbiota can be a primary force that generates key macroscopic patterns of plant communities (coexistence, dominance, and succession) in forest ecosystems. The aim of this article is to review empirical and theoretical perspectives of plant–soil feedback research in the context of forest community ecology. I first use a simple theoretical model to get insights into an array of the dynamics generated by plant–soil feedback: negative plant–soil feedback maintains plant species diversity and reduces plant growth, while positive plant–soil feedback drives plant growth of certain species and hence their dominance. I then describe how ecologists have unveiled the enormously complex plant‐microbiota interaction (i.e., the soil conditioning experiment) and review the linkage of plant–soil feedback with three key plant community patterns: (i) dominance, (ii) spatial structure and (iii) succession. I highlight one belowground plant trait (mycorrhizal type) that can mediate these linkages: arbuscular mycorrhizal species tend to exhibit negative plant–soil feedback while ectomycorrhizal species tend to exhibit positive plant–soil feedback. Although mycorrhizal plant–soil feedback potentially explains the patterns of tree diversity from local to global scales, many questions remain. Future studies should expand plant–soil feedback theory to incorporate numerous other feedback mechanisms and test how mycorrhizal types mediate the net feedback effects that could propagate to shape large‐scale forest structures and dynamics.

Getting to the root of divergent outcomes in the modulation of plant-soil feedbacks by benzoxazinoids.

This article is a Commentary on Gfeller et al. (2024), 241: 2575–2588.

Plant–soil feedback is dependent on tree mycorrhizal types and tree species richness in a subtropical forest

Plant-soil feedback (PSF) is an important driver of plant species coexistence and diversity maintenance. However, it remains unclear how changes in PSF due to decline in tree species richness influence the performance of arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) tree species. A PSF experiment was established with eight target tree species (four AM and four EcM tree species) based on a subtropical forest Biodiversity-Ecosystem Functioning Experimental in China (BEF-China) platform, where soil inocula were collected beneath the canopy of target tree species individuals growing in monoculture and eight tree-species mixture plots. We hypothesized that the negative PSF strength of AM tree species would be stronger in monocultures than that in eight tree-species mixtures, resulting in better performance in highly diverse plant communities, whereas EcM tree species would benefit less from tree species richness. However, the results showed consistent PSFs of AM tree species regardless of tree species richness. In contrast, EcM tree species experienced a change from positive in monocultures to negative PSF in eight tree-species mixtures, influencing the performance of EcM tree seedlings. With high concern of the cascading effects of tree species richness on PSFs via modulating soil fungal communities, we revealed that the alterations in EcM fungal abundance, putatively pathogenic fungal diversity, and fungal co-occurrence network complexity mirrored those of PSF associated with EcM tree species, showing the changes from positive in monocultures to negative feedback in eight tree-species mixtures. Our findings highlight the differential PSFs exhibited by AM and EcM tree species in response to tree species richness, and provide insight into the potential role of fungal functional guilds and co-occurrence network complexity in shaping the PSFs of them.

Plant-soil feedback and plant invasion: effect of soil conditioning on native and invasive Prosopis species using the plant functional trait approach.

Invasive species have been identified as a major threat to native biodiversity and ecosystem functioning worldwide due to their superiority in spread and growth. Such superiority is explained by the invasional meltdown phenomena, which suggests that invasive species facilitate the establishment of more invasive species rather than native species by modifying the plant-soil feedback (PSF). We conducted a two-phase plant-soil feedback experiment using the native Prosopis cineraria and the invasive Prosopis juliflora in Oman. Firstly, we conditioned the soil by planting seedlings of native species, invasive species, native and invasive species "mixed", and unconditioned soil served as a control. Secondly, we tested the feedback of these four conditioned soil on the two species separately by measuring the productivity (total biomass) and the performance in the form of plant functional traits (plant height, specific leaf area (SLA), leaf nitrogen content (Nmass), leaf carbon content (Cmass) and specific root length (SRL) of native and invasive species as well as the nutrient availability in soil (soil organic carbon (SOC) and soil total nitrogen (STN)). We found that the native species produced more biomass, best performance, and higher SOC and STN when grown in soil conditioned by native species, additionally, it gave lower biomass, reduced performance, and lower SOC and STN when grown in the soil conditioned by invasive and mixed species. These results suggest negative PSF for native species and positive PSF for invasive species in the soil conditioned by invasive species, which can be considered as red flag concerning the restoration of P. cineraria as an important native species in Oman, as such positive PSF of the invasive species P. juliflora will inhibit the regeneration of P. cineraria.

Abiotic legacies mediate plant–soil feedback during early vegetation succession on rare earth element mine tailings

Abstract An increasing number of studies have shown how feedback interactions between plants and soil can influence primary and secondary succession. However, very little is known about the patterns and mechanisms of such plant–soil feedbacks on stressed mine tailings ecosystem, which can be severely contaminated by a range of toxic elements. In a two‐phase plant–soil feedback experiment based on the rare earth element (REE) mine tailing soil, we investigated biotic (changes in bacterial and fungal communities) and abiotic (changes in chemical properties) legacies of three pioneer grass species, and examined feedback effects of three grasses, two legumes and two woody plants with different root traits. Positive plant–soil feedbacks were found in Miscanthus sinensis, Paspalum thunbergii and Tephrosia candida, and neutral feedbacks were observed in the other four plants. These effects corresponded with an increase in nutrients and total organic carbon, as well as a decrease in acidity and extractable aluminium and REEs. There were less signs of biotic changes in the conditioned tailings. The correlation analysis suggested a relationship between plants' responses to soil legacies and root traits, as well as root economics spectrum. On the mine tailings, acquisitive species with higher specific root length appeared to have greater potential for positive feedback. Synthesis and application. Our study shows that early succession on contaminated rare earth element mine tailings may lead to more positive plant–soil feedback than predicted based on results of non‐contaminated soils, mainly due to the alleviation of abiotic stress in tailings. Therefore, the improvement of specific abiotic soil stress and the trait‐based selection of acquisitive plants should be preferentially considered to promote the primary restoration of degraded land.

Field to Greenhouse: How Stable Is the Soil Microbiome after Removal from the Field?

Plant-soil feedback (PSF) processes impact plant productivity and ecosystem function, but they are poorly understood because PSFs vary significantly with plant and soil type, plant growth stage, and environmental conditions. Controlled greenhouse studies are essential to unravel the mechanisms associating PSFs with plant productivity; however, successful implementation of these controlled experiments is constrained by our understanding of the persistence of the soil microbiome during the transition from field to greenhouse. This study evaluates the preservation potential of a field soil microbiome when stored in the laboratory under field temperature and moisture levels. Soil microbial diversity, taxonomic composition, and functional potential were evaluated via amplicon sequencing at the start of storage (W0), week 3 (W3), week 6 (W6), and week 9 (W9) to determine the effect of storage time on soil microbiome integrity. Though microbial richness remained stable, Shannon diversity indices decreased significantly at W6 for bacteria/archaea and W3 for fungi. Bacterial/archaeal community composition also remained stable, whereas the fungal community changed significantly during the first 3 weeks. Functional predictions revealed increased capacity for chemoheterotrophy for bacteria/archaea and decreased relative proportions of arbuscular mycorrhizal and ectomycorrhizal fungi. We show that preservation of the field soil microbiome must be a fundamental component of experimental design. Either greenhouse experiments should be initiated within 3 weeks of field soil collection, or a preliminary incubation study should be conducted to determine the time and storage conditions required to sustain the integrity of the specific field soil microbiome being studied.

Global patterns and drivers of plant-soil microbe interactions.

Plant-soil feedback (PSF) is an important mechanism determining plant community dynamics and structure. Understanding the geographic patterns and drivers of PSF is essential for understanding the mechanisms underlying geographic plant diversity patterns. We compiled a large dataset containing 5969 observations of PSF from 202 studies to demonstrate the global patterns and drivers of PSF for woody and non-woody species. Overall, PSF was negative on average and was influenced by plant attributes and environmental settings. Woody species PSFs did not vary with latitude, but non-woody PSFs were more negative at higher latitudes. PSF was consistently more positive with increasing aridity for both woody and non-woody species, likely due to increased mutualistic microbes relative to soil-borne pathogens. These findings were consistent between field and greenhouse experiments, suggesting that PSF variation can be driven by soil legacies from climates. Our findings call for caution to use PSF as an explanation of the latitudinal diversity gradient and highlight that aridity can influence plant community dynamics and structure across broad scales through mediating plant-soil microbe interactions.

Relationship between soil and species diversity in typical forest stands in Xianrendong, Liaoning Province based on plant-soil feedback.

Exploring the relationship between soil properties and species diversity in typical forest stands in Liaoning Xianrendong National Nature Reserve will help maintain the stability of forest communities in the transition zone between flora in Changbai and North China. Based on the plant-soil feedback theory, community sample data from nine typical forest stands in the study area and experimental test data from 54 soil samples, we selected indexes of soil physical and chemical properties based on the minimum data set (temperature, compactness, capillary pore space, bulk weight, capillary water holding capacity, drainage capacity, soil water storage, conductivity, pH, organic matter, Ca, Fe, K, N and P). We adopt the research method of classical statistical analysis. The soil properties of nine typical stands in Xianrendong National Nature Reserve of Liaoning Province were systematically analyzed. The relationship between soil properties and forest stands' species diversity was quantified using correlation and redundancy analyses. The Pearson correlation analysis results showed significant positive correlations between the Gleason abundance index (arbors) with conductivity, pH, organic matter, Ca, N and P; Pielou's evenness index (arbors) with bulk weight and Fe. Significant negative correlations between the Gleason abundance index (arbors) with capillary pore space, bulk weight, drainage capacity, soil water storage and capillary water holding capacity; Simpson dominance index and Shannon-Wiener diversity index with capillary water holding capacity, drainage capacity and soil water storage; Pielou's evenness index (arbors) with Ca and N. The natural moisture content and clay particles are neutral feedback. The results showed that the feedback mechanism of soil physicochemical properties on stand species diversity was complex, which was conducive to species coexistence and community stability.

Microbial Factors May Contribute to the Persistence of Australian Fairy Circles

Fairy Circles (FCs) are roughly circular, spatially periodic barren patches occurring both along the southwestern African coast, spanning the Namib Desert (NFCs), and in the Pilbara region of Western Australia (AFCs). The origin of both NFC and AFC patterns is still debatable and a subject of ongoing research. Recently, it was argued that pathogenic soil microbes may contribute to ring formation of the Triodia basedowii grass which is the same grass species that forms the AFCs. We have analyzed, under controlled laboratory conditions, soil samples taken from different parts of AFCs (center, periphery and m3atrix) for microbiological activities by Lettuce germination experiments under different manipulations. In seven different circles, out of an average of 13, root lengths of germinated seeds were strongly inhibited in the samples taken from the center, and to a lesser extent, in the samples taken from the periphery and the matrix. Quantitative analyses of the soil microbial community from the FC center found no support to the hypothesis that phytotoxic effect was caused by soil crust cyanobacteria due their low abundance. However, in soil of the FCs it identified both heterotrophic bacteria and fungi that may contribute to the phytotoxic effect. Although our study was not done with seeds of Triodia basedowii it supports the idea that microbial activities in the soil may contribute to AFC persistence by inhibiting plant germination and development in the bare soil gaps in addition to the physical soil crusts resulting from weathering. This suggests that negative plant-soil feedback can act in concert with the main driver mechanism of the AFCs, the scale-dependent plant-water feedback.

Nitrogen Deposition Amplifies the Legacy Effects of Plant Invasion.

The legacy effects of invasive plant species can hinder the recovery of native communities, especially under nitrogen deposition conditions, where invasive species show growth advantages and trigger secondary invasions in controlled areas. Therefore, it is crucial to thoroughly investigate the effects of nitrogen deposition on the legacy effects of plant invasions and their mechanisms. The hypotheses of this study are as follows: (1) Nitrogen deposition amplifies the legacy effects of plant invasion. This phenomenon was investigated by analysing four potential mechanisms covering community system structure, nitrogen metabolism, geochemical cycles, and microbial mechanisms. The results suggest that microorganisms drive plant-soil feedback processes, even regulating or limiting other factors. (2) The impact of nitrogen deposition on the legacy effects of plant invasions may be intensified primarily through enhanced nitrogen metabolism via microbial anaerobes bacteria. Essential insights into invasion ecology and ecological management have been provided by analysing how nitrogen-fixing bacteria improve nitrogen metabolism and establish sustainable methods for controlling invasive plant species. This in-depth study contributes to our better understanding of the lasting effects of plant invasions on ecosystems and provides valuable guidance for future ecological management.

Plant-soil feedback across spatiotemporal scales from immediate effects to legacy

Plants and soil biota are important ecosystem engineers interacting via plant-soil feedback on large gradient of temporal scales from immediate interactions to long term legacy, which also operate on various spatial scales. Here I emphasize three major pathways of plant-soil feedbacks: i) the biota pathway, when plants affect soil biota, such as plant symbionts or antagonists, which affect plants, ii) the soil pathway, when plants affect soil environment, which then feedbacks to plants and finally iii) the biota-soil pathway, when plants affect soil biota, which then affect soil environment, which then effect plants. Living plant roots are major driver for biota pathway, which is more important for immediate effect, while litter largely supports the biota-soil pathway important for legacy effects. Many processes that have immediate effects, produce also small but more persistent changes in soil. Legacy is produced by accumulation of this small changes over time. This is supported by soil ability to preserve and accumulate, these small changes. Legacy also alternate outcome of immediate interactions between plants, soil and soil biota. The soil property changes, caused by legacy, happen either as slow gradual changes, or relatively fast, abrupt shifting between two steady states. In both cases, soil changes can reach tipping points, altering functioning of whole plant soil system. Apart from plants, also soil conditions or soil biota can be manipulated either intentionally (e.g. by land uses change, various agriculture, forestry or ecosystem restoration practices), or non-intentionally (e.g. biological invasion), which trigger changes in plant – soil - soil biota interactions as described above and cause immediate and legacy effects. Examples, presented in this review, suggest that legacy effect is particularly important in soils in early stages of pedogenesis or during response to or recovery after disturbance. Review highlight necessity studying plant soil feedback on all relevant spatiotemporal scales.

Negative plant-soil feedbacks disproportionally affect dominant plants, facilitating coexistence in plant communities

Plant-soil feedbacks (PSFs) are suggested to be major drivers of plant species coexistence and exotic invasions in natural plant communities, where species with more positive PSFs are thought to be more abundant in communities. Most evidence for this comes from mesocosm experiments with single species, but whether the results are transposable to diverse plant communities is mostly not verified and remains debated. We performed a combined monoculture and community experiment to test whether PSFs in monocultures predict PSFs in communities, and to infer the role of PSFs in invasive plant success. We found that (1) PSFs from monocultures were poor predictors for PSFs in plant communities, (2) competitive strength of invasive species did not consistently depend on PSF, and (3) dominant species experienced a significantly stronger negative PSFs than non-dominant species when grown in community. Hence, PSFs of plant species in monocultures seem less predictive for their abundance in plant communities or for invasibility than previously assumed. Nevertheless, PSF—and particularly negative PSF—seems indeed a major driver of plant species coexistence, with a strong species-specific pathogenic effect on dominant plants facilitating the persistence of rare species.