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Range expansions, whether they are biological invasions or climate change-mediated range shifts, may have profound ecological and evolutionary consequences for plant-soil interactions. Range-expanding plants encounter soil biota with which they have a limited coevolutionary history, especially when introduced to a new continent. Past studies have found mixed results on whether plants experience positive or negative soil feedback interactions in their novel range, and these effects often change over time. One important theoretical explanation is that plants locally adapt to the soil pathogens and mutualists in their novel range. We tested this hypothesis in Dittrichia graveolens, an annual plant that is both expanding its European native range, initially coinciding with climate warming, and rapidly invading in California after human introduction. In parallel greenhouse experiments on both continents, we used plant genotypes and soils from five locations at the core and edge of each range to compare plant growth in soil inhabited by D. graveolens and nearby control microsites as a measure of plant-soil feedback. Plant-soil interactions were highly idiosyncratic across each range. On average, plant-soil feedbacks were more positive in the native range than in the exotic range. In line with the strongly heterogeneous pattern of soil responses along our biogeographic gradients, we found no evidence for evolutionary differentiation between plant genotypes from the core to edge of either range. Our results suggest that the evolution of plant-soil interactions during range expansion may be more strongly driven by local evolutionary dynamics varying across the range than by large-scale biogeographic shifts.

Background: Interactions between plants and diverse root-associated fungi are essential drivers of forest ecosystem dynamics. The symbiosis is potentially dependent on multiple ecological factors/processes such as host/symbiont specificity, background soil microbiome, inter-root dispersal of symbionts, and fungus–fungus interactions within roots. Nonetheless, it has remained a major challenge to reveal the mechanisms by which those multiple factors/processes determine the assembly of root-associated fungal communities. Based on the framework of joint species distribution modeling, we examined 1,615 root-tips samples collected in a cool-temperate forest to reveal how root-associated fungal community structure was collectively formed through filtering by host plants, associations with background soil fungi, spatial autocorrelation, and symbiont–symbiont interactions. In addition, to detect fungi that drive the assembly of the entire root-associated fungal community, we inferred networks of direct fungus–fungus associations by a statistical modeling that could account for implicit environmental effects. Results: The fine-scale community structure of root-associated fungi were best explained by the statistical model including the four ecological factors/processes. Meanwhile, among partial models, those including background soil fungal community structure and within-root fungus–fungus interactions showed the highest performance. When fine-root distributions were examined, ectomycorrhizal fungi tended to show stronger associations with background soil community structure and spatially autocorrelated patterns than other fungal guilds. In contrast, the distributions of root-endophytic fungi were inferred to depend greatly on fungus–fungus interactions. An additional statistical analysis further suggested that some endophytic fungi, such as Phialocephala and Leptodontidium, were placed at the core positions within the web of direct associations with other root-associated fungi. Conclusion: By applying emerging statistical frameworks to intensive datasets of root-associated fungal communities, we demonstrated background soil fungal community structure and fungus–fungus associations within roots, as well as filtering by host plants and spatial autocorrelation in ecological processes, could collectively drive the assembly of root-associated fungi. We also found that basic assembly rules could differ between mycorrhizal and endophytic fungi, both of which were major components of forest ecosystems. Consequently, knowledge of how multiple ecological factors/processes differentially drive the assembly of multiple fungal guilds is indispensable for comprehensively understanding the mechanisms by which terrestrial ecosystem dynamics are organized by plant–fungal symbiosis. [ABSTRACT FROM AUTHOR]

This Editorial introduces the Virtual Issue 'Chemical language of plant–microbe–microbe associations' that includes the following papers: Basak et al. (2024), Böttner et al. (2023), Brisson et al. (2023), Feng et al. (2023), Gfeller et al. (2024), Gómez‐Pérez et al. (2023), Hong et al. (2022, 2023), Hu et al. (2024), Jiang et al. (2024), Lee et al. (2024), Nakano (2024), Ökmen et al. (2023), Revillini et al. (2023), Rovenich & Thomma (2023), Simonin et al. (2022), Snelders et al. (2023), Walsh et al. (2024), Wen et al. (2023), Xia et al. (2023), Xie et al. (2023), Zhang et al. (2023, 2024), Zheng et al. (2023), Zhou et al. (2023, 2024). Access the Virtual Issue at www.newphytologist.com/virtualissues. [ABSTRACT FROM AUTHOR]

Wildfires are important natural disturbances with profound ecological impacts. However, our understanding of how to restore plant–soil microbiome interactions following wildfires remains limited, revealing a key knowledge gap in post‐wildfire ecosystem restoration. To assess the restoration of plant‐microbiome interactions in fire‐affected ecosystems, we conducted greenhouse experiments simulating wildfire effects on soil collected from Maulino Coastal Forest of central Chile, a biodiversity hotspot. We measured the plant height and photosynthesis over 90 days, and two‐year survival probability, of three common native (Aristotelia chilensis, Nothofagus glauca and N. alessandrii) and three non‐native species (Eucalyptus globulus, Pinus radiata and Genista monspessulana) planted in three soils (unburned, burned and burned soil inoculated with the native microbiome). Available nutrient concentrations (N, P and K) and activities of microbial enzymes (dehydrogenase, β‐glucosidase and urease) were also measured over 360 days. Available nutrient concentrations were consistently higher in burned and burned‐inoculated soils than in unburned soils. Enzyme activities in unburned and burned‐inoculated soils remained higher than in burned soil, indicating that the native microbiome restored microbial enzyme activities. The increase in height over 90 days was lower in burned soils compared with unburned soils for native species. However, inoculation with the native microbiome mitigated this negative effect, resulting in height increases similar to those in unburned soils. For non‐native species, burning and inoculation had negligible effects on the height increases. Similar patterns were observed for the increase in photosynthetic rate, with native species showing a reduced rate in burned soils, which was offset by microbiome inoculation, while non‐native species were unaffected by both treatments. Survival probability of native species declined in burned soil, but was the same in burned‐inoculated soil as in unburned soil. That of non‐native species was unaffected by burning or by inoculation with the native microbiome. Synthesis and applications. Native microbiomes are evidently promising tools to safeguard ecosystem functionality and mitigate species extinction risks arising from climate change and human‐induced wildfires. We advocate integrating microbiomes into future active restoration strategies for fire‐affected ecosystems. [ABSTRACT FROM AUTHOR]

The magnitude of plant–soil feedback (PSF) can depend on the time of conditioning as well as the length of feedback. Understanding the temporal variation in PSF requires insight in the response of both soil characteristics and the plant. We examined how conspecific PSF varies with the length of conditioning and the size of the response plant using Jacobaea vulgaris, a species known to experience negative conspecific PSF. Together with reanalysis of an existing microbial sequence dataset, we tested whether the temporal variation in PSF is due to size‐dependent plant sensitivity to conditioned soil or due to compositional changes in microbial communities of conditioned soil. Further, by reanalysing another existing dataset, we examined temporal dynamics of the relative growth rates (RGR) of J. vulgaris during the feedback phase. Testing varying conditioning lengths, uncovered that J. vulgaris exhibited the strongest negative PSF at 5 weeks of conditioning, after which PSF gradually attenuated. Plant sensitivity to conditioned soil decreased with increasing plant age/size of the response plant. In the feedback phase, the RGR of J. vulgaris was first higher, then lower and at the end similar in ‘away’ soil compared to ‘home’ soil. The dissimilarity in bacterial and fungal communities in ‘home’ and ‘away’ soil significantly decreased during the feedback phase. When J. vulgaris grew in ‘away’ soil, the relative abundance of 10 (out of 80) bacterial OTUs that positively correlated with plant growth decreased over time, while 5 (out of 86) OTUs that negatively correlated with plant growth the relative abundance increased over time. Additionally, only one (out of 10) fungal OTU that negatively associated with plant growth increased over time in ‘away’ soil. Synthesis. Our findings illustrate that PSF varies with the duration of soil conditioning and of the feedback phase. During the feedback phase, changes in PSF can be attributed to both the size‐dependent plant sensitivity to conditioned soil and temporal changes in the microbial community of conditioned soil. This highlights the importance of considering the reconditioning of soil microbial communities by the test plants during the feedback phase for understanding temporal variation in PSF. [ABSTRACT FROM AUTHOR]

Plant competition can be affected by plant functional traits but also by differences in fitness mediated by soil microbes. Climatic conditions such as drought further influence plant competition. Yet little is known about how soil microbes and drought interact with plant species that have distinct root traits and how this influences plant competition outcomes.We grew three plant species that co‐occur in temperate grasslands in China (Stipa krylovii, Artemisia frigida, Agropyron cristatum) in monocultures and mixtures and subjected the plant combinations to five soil inocula (root‐associated soil of S. krylovii, A. frigida, A. cristatum, an equal mixture of the three root zone soils and sterilized soil) as well as to a drought treatment. The relative change in plant biomass was used to determine plant competition outcomes.The three species exhibited clear differences in competitive abilities with A. cristatum > S. krylovii > A. frigida, and soil inocula or the drought treatment did not change the order. The relative yield (RY) of plants was affected by soil inocula, drought and plant arrangement. The strongest competitor, A. cristatum, with high total root length, root surface area and root volume experienced more negative biotic feedback, and drought enhanced the magnitude of these negative effects. On the contrary, the most inferior competitor, A. frigida, with high specific root length tended to have neutral or positive biotic feedback, and drought had no effect. Furthermore, the RY and fitness difference (reflected as the competitive ability in the mixture) of the three species were differentially influenced by root traits and plant–soil feedback. RY of A. cristatum could be predicted by the feedback effect in the mixture, and the fitness difference was mainly related to root traits. Both RY and fitness differences of A. frigida (the weakest competitor) could be predicted by root trait differences and feedback effects. Differences in root traits were the best predictors of the intermediate competitor S. krylovii.Our study shows that competition outcomes of co‐existing species depend on root traits and species‐specific PSF effects in mixture. Future work should examine the mechanisms that explain how plant competition and soil microbial heterogeneity act in conjunction with climate change in influencing plant coexistence. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Stellera chamaejasme L. is a native, widely distributed weed in steppe perennial grassland in China and countries nearby. Its spread has been attributed in part to the effect of its associated soil biota on the growth of other plants. To investigate this hypothesis, soil associated with S. chamaejasme or not was taken from grasslands in the Inner Mongolia plateau. S. chamaejasme and six co‐occurring plant species, including grasses (Leymus chinensis and Agropyron cristatum) and forbs (Allium mongolicum, Sanguisorba officinalis, Plantago asiatica, and Saussurea runcinata), were then grown with such soil or its autoclaved inocula in pot trials comparing their shoot and root growth. Fungal diversity was compared between S. chamaejasme and non‐S. chamaejasme field soils to investigate differences in functional groups associated with plant growth. The growth of S. chamaejasme, and that of the forbs tested, increased with a "live" relative to the autoclaved inoculum whilst that of the two grasses decreased. Root‐shoot ratio significantly increased for S. chamaejasme grown with its own soil biota. S. chamaejasme and non‐S. chamaejasme soil fungal communities differed, with the former having decreased relative abundance of arbuscular mycorrhizal fungi and increased abundance of plant pathogens, which might be factors promoting its spread and facilitating grassland degradation. The results improve our understanding of the role of soil biota in S. chamaejasme succession. [ABSTRACT FROM AUTHOR]

Tree lines in high latitudes and high altitudes are considered sentinels of global change. This manifests in accelerated encroachment of trees and shrubs and enhanced plant productivity, with currently unknown implications for the carbon balance of these biomes. Given the large soil organic carbon stocks in many tree line soils, we here wondered whether introducing highly productive plants would accelerate carbon cycling through rhizosphere priming effects and if certain soils would be more vulnerable to carbon loss from positive priming than others.To test this, organic and mineral soils were sampled above and below tree lines in the Swedish sub‐arctic and the Peruvian Andes. A greenhouse experiment was then performed to quantify plant‐induced changes in soil mineralisation rates (rhizosphere priming effect) and new C formation using natural abundance labelling and the C4‐species Cynodon dactylon. Several environmental, plant, soil and microbial parameter were monitored during the experiment to complement the observations on soil C cycling.Priming was predominantly positive at the beginning of the experiment, then systematically decreased in all soils during the plant growth season to be mostly negative at the end of the experiment at plant senescence. Independent of direction of priming, the magnitude of priming was always greater in organic than in corresponding mineral soils, which was best explained by the higher C contents of these soils. Integrated over the entire study period, the overall impact of priming (positive and negative) on the soil C balance was mostly negligible. Though net soil C loss was observed in organic soils from the sub‐arctic tundra in Sweden.Most notably, positive and negative priming effects were not mutually exclusive, rather omnipresent across ecosystems, depending on sampling time. The direction of priming seems to be fluctuating with plant productivity, rhizosphere carbon inputs and nutrient uptake. This highlights the need for integrative long‐term studies if we aim to understand priming effects at ecosystem scale and greenhouse and laboratory studies must be validated in situ to enable reliable ecological upscaling. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Plant–soil feedback (PSF), the reciprocal interaction between plants and their soil environment, is a fundamental ecological process that can influence coexistence and functional structure in plant communities. Current theory establishes that PSF may enhance diversity or lead to exclusion depending on whether soil conditioning disproportionately benefits heterospecific or conspecific individuals. However, a more complete picture of the impact of PSF requires understanding how PSF interacts with competition. To that end, here we propose an integrated mathematical model combining trait‐based competition and soil‐explicit PSF. Contrary to the current paradigm, we find that soil conditioning that disproportionately favours conspecific individuals can promote coexistence. Additionally, we show that priority effects are common when soil‐conditioning species differ in their edaphic preferences. These effects can allow species with large differences in competitive ability to coexist under certain soil conditions. Our results provide testable predictions tying community‐level functional patterns in plant communities to PSF and competition. [ABSTRACT FROM AUTHOR]

Trees affect the biotic and abiotic properties of the soil in which they grow. Tree species-specific effects can persist for a long time, even after the trees have been removed. We investigated to what extent such soil legacies of different tree species may impact tree seedlings in their emergence and growth. We performed a plant–soil feedback experiment, using soil that was conditioned in plots that vary in tree species composition in Białowieża Forest, Poland. Soil was taken from plots varying in proportion of birch, hornbeam, pine, and oak. In each soil, seeds of the same four target species were sown in pots. Seedling emergence and growth were monitored for one growing season. To further explore biotic implications of soil legacies, ectomycorrhizal root tip colonization of oak, a keystone forest species, was determined. We found no effect of soil legacies of tree species on the emergence measures. We, however, found a clear negative effect of pine legacies on the total biomass of all four seedling species. In addition, we found relationships between the presence of pine and soil fertility and between soil fertility and root tip colonization. Root tip colonization was positively correlated with the biomass of oak seedlings. We conclude that tree species can leave legacies that persist after that species has been removed. These legacies influence the growth of the next generation of trees likely via abiotic and biotic pathways. Thus, the choice of species in today's forest may also matter for the structure and composition of future forests. [ABSTRACT FROM AUTHOR]

Premise of research. Species-level variation in interactions with root-associated microbial communities has its evolutionary origins within species, where dissection of the mechanistic basis of plant divergence is also tractable. We use montane annual and coastal perennial populations (ecotypes) of Mimulus guttatus (yellow monkeyflower) to ask whether and how plant-microbe-soil interactions have diverged between populations with distinct life histories. Methodology. We characterized fungal communities in representative montane annual (Iron Mountain) and dune perennial (Florence dunes) habitats in Oregon, where previous reciprocal transplants revealed local adaptation. We then investigated how plant ecotype, microbial source, and soil origin affected plant performance and root-associated fungal communities in a full-factorial greenhouse experiment using plants, soils, and nested inocula (sterilized, filtered to remove arbuscular mycorrhizal fungi, and whole) from the two sites. Pivotal results. In the field, coastal perennial and montane annual monkeyflowers harbored distinct fungal communities, and perennial roots were enriched for mutualistic taxa relative to local soils. In the greenhouse common garden, microbial effects were largely negative (particularly in the annual ecotype), and there was no evidence of plant local adaptation to belowground conditions. However, the coastal perennial ecotype was more colonized by arbuscular mycorrhizal fungi than the montane annual ecotype, and it preferentially recruited local arbuscular mycorrhizal fungi taxa even when inoculated from the montane source. Conclusions. Our results suggest that population divergence in life history and related traits shapes plant responsiveness to soil microbes and the specificity of their associations with root endophytic fungi, such as arbuscular mycorrhizal fungi. Complex belowground effects on plant performance do not fit a simple pattern of local adaptation but may be by-products of other drivers of plant divergence. This work advances the study of heritable variation in plant-soil-microbe interactions in a model species for understanding the genomics of plant adaptation. [ABSTRACT FROM AUTHOR]

Abstract Background Interactions between plants and diverse root-associated fungi are essential drivers of forest ecosystem dynamics. The symbiosis is potentially dependent on multiple ecological factors/processes such as host/symbiont specificity, background soil microbiome, inter-root dispersal of symbionts, and fungus–fungus interactions within roots. Nonetheless, it has remained a major challenge to reveal the mechanisms by which those multiple factors/processes determine the assembly of root-associated fungal communities. Based on the framework of joint species distribution modeling, we examined 1,615 root-tips samples collected in a cool-temperate forest to reveal how root-associated fungal community structure was collectively formed through filtering by host plants, associations with background soil fungi, spatial autocorrelation, and symbiont–symbiont interactions. In addition, to detect fungi that drive the assembly of the entire root-associated fungal community, we inferred networks of direct fungus–fungus associations by a statistical modeling that could account for implicit environmental effects. Results The fine-scale community structure of root-associated fungi were best explained by the statistical model including the four ecological factors/processes. Meanwhile, among partial models, those including background soil fungal community structure and within-root fungus–fungus interactions showed the highest performance. When fine-root distributions were examined, ectomycorrhizal fungi tended to show stronger associations with background soil community structure and spatially autocorrelated patterns than other fungal guilds. In contrast, the distributions of root-endophytic fungi were inferred to depend greatly on fungus–fungus interactions. An additional statistical analysis further suggested that some endophytic fungi, such as Phialocephala and Leptodontidium, were placed at the core positions within the web of direct associations with other root-associated fungi. Conclusion By applying emerging statistical frameworks to intensive datasets of root-associated fungal communities, we demonstrated background soil fungal community structure and fungus–fungus associations within roots, as well as filtering by host plants and spatial autocorrelation in ecological processes, could collectively drive the assembly of root-associated fungi. We also found that basic assembly rules could differ between mycorrhizal and endophytic fungi, both of which were major components of forest ecosystems. Consequently, knowledge of how multiple ecological factors/processes differentially drive the assembly of multiple fungal guilds is indispensable for comprehensively understanding the mechanisms by which terrestrial ecosystem dynamics are organized by plant–fungal symbiosis.

Abstract Background Since the 1980s, soils in a 22-km2 area near Lake Neuchâtel in Switzerland have been recognized for their innate ability to suppress the black root rot plant disease caused by the fungal pathogen Thielaviopsis basicola. However, the efficacy of natural disease suppressive soils against insect pests has not been studied. Results We demonstrate that natural soil suppressiveness also protects plants from the leaf-feeding pest insect Oulema melanopus. Plants grown in the most suppressive soil have a reduced stress response to Oulema feeding, reflected by dampened levels of herbivore defense-related phytohormones and benzoxazinoids. Enhanced salicylate levels in insect-free plants indicate defense-priming operating in this soil. The rhizosphere microbiome of suppressive soils contained a higher proportion of plant-beneficial bacteria, coinciding with their microbiome networks being highly tolerant to the destabilizing impact of insect exposure observed in the rhizosphere of plants grown in the conducive soils. We suggest that presence of plant-beneficial bacteria in the suppressive soils along with priming, conferred plant resistance to the insect pest, manifesting also in the onset of insect microbiome dysbiosis by the displacement of the insect endosymbionts. Conclusions Our results show that an intricate soil–plant-insect feedback, relying on a stress tolerant microbiome network with the presence of plant-beneficial bacteria and plant priming, extends natural soil suppressiveness from soilborne diseases to insect pests. Video Abstract

Plant–soil feedback (PSF) plays a central role in determining plant community dynamics, yet our understanding of how different combinations of plants and microbes influence PSF remains limited. Plants of different mycorrhizal types often exhibit contrasting PSF outcomes, influencing plant recruitment and spatial structure. Generalizing across plant species based on mycorrhizal type creates the potential to examine broader effects on ecological communities. We review mechanisms contributing to different PSF outcomes between arbuscular mycorrhizal and ectomycorrhizal trees. We focus on how plant and fungal traits that differ between mycorrhizal types interact with pathogenic and saprotrophic microorganisms and nutrient and carbon cycling. Synthesis. Building on this framework, we propose several new research directions. First, mycorrhizal‐induced changes in soils can operate beyond the conspecific level, spilling over from abundant plant species onto less abundant ones. This community‐level ‘mycorrhizal spillover’ is hypothesized to affect PSF in ways that are additive and interactive with conspecific density dependence. Second, we describe how mycorrhizal effects on PSF could structure the way plant communities respond to global change. Third, we discuss how they may influence plant evolution by altering the balance of selection pressures on traits and genes related to pathogen defence and mutualism formation. [ABSTRACT FROM AUTHOR]

Summary: Mycorrhizal symbiosis, seed dispersal, and pollination are recognized as the most prominent mutualistic interactions in terrestrial ecosystems. However, it remains unclear how these symbiotic relationships have interacted to contribute to current plant diversity.We analyzed evolutionary relationships among mycorrhizal type, seed dispersal mode, and pollination mode in two global databases of 699 (database I) and 10 475 (database II) tree species. Although database II had been estimated from phylogenetic patterns and therefore had lower certainty of the mycorrhizal type than database I, whose mycorrhizal type was determined by direct observation, database II allowed analysis of many more taxa from more regions than database I.We found evidence of joint evolution of all three features in both databases. This result is robust to the effects of both sampling bias and missing taxa. Most arbuscular mycorrhizal‐associated trees had endozoochorous (biotic) seed dispersal and biotic pollination, with long dispersal distances, whereas most ectomycorrhizal‐associated trees had anemochorous (abiotic) seed dispersal and wind (abiotic) pollination mode, with shorter dispersal distances.These results provide a novel scenario in mutualistic interactions, seed dispersal, pollination, and mycorrhizal symbiosis types, which have jointly evolved and shaped current tree diversity and forest ecosystem world‐wide. See also the Commentary on this article by Sinnott‐Armstrong, 243: 1290–1292. [ABSTRACT FROM AUTHOR]

Premise: Theory predicts that mixed ploidy populations should be short‐lived due to strong fitness disadvantages for the rare ploidy. However, mixed ploidy populations are common, suggesting that the fitness costs for rare ploidies are counterbalanced by ecological benefits that emerge when rare. We investigated whether differences in ecological interactions with soil microbes help to maintain a tetraploid–hexaploid population of Larrea tridentata (creosote bush) in the Sonoran Desert, California, United States, where prior work documented ploidy‐specific root‐associated microbes. Methods: We used a plant–soil feedback (PSF) experiment to test whether host‐specific soil microbes can alter the outcomes of intraploidy vs. interploidy competition. Host‐specific soil microbes can build up over time; thus, distance from a host plant can affect the fitness of nearby plants. Results: Seedlings grown in soils from near plants of a different ploidy produced greater biomass relative to seedlings grown in soils from near plants of the same ploidy. Moreover, seedlings grown in soils from near plants of a different ploidy produced more biomass than those grown in soils that were farther from plants of a different ploidy. These results suggest that the ecological consequences of PSF may facilitate the persistence of mixed ploidy populations. Conclusions: This is the first evidence, to our knowledge, that is consistent with plant–soil microbe feedback as a viable mechanism to maintain the coexistence of multiple ploidy levels in a single population. [ABSTRACT FROM AUTHOR]

Escape from native range enemies can give invasive species a competitive edge according to the enemy‐release hypothesis. While more commonly associated with predators and herbivores, release from belowground microbial antagonists has been recently demonstrated to benefit invasive plants. Biogeographic variation in dominance and comparisons of soil communities suggest that invasive European Phragmites australis may have also benefitted from belowground enemy release in North America (NA). Here we examine the effects of native range (Europe) versus introduced range (NA) soil communities on European and North American P. australis using a reciprocal inoculation seedling growth experiment. Contrary to the enemy‐release hypothesis, we found that North American P. australis was sensitive to soil community origin in that the seedlings grown in European soil communities had higher total biomass than seedlings grown in North American soil communities. This pattern was not observed in the European P. australis seedlings which had similar biomass when grown with North American or European soil communities. Notably, North American P. australis had higher biomass than European P. australis regardless of which soil community it was grown in, suggesting a growth–defense tradeoff. Though the relative abundance of mutualists and pathogens composition did not differ between the two ranges, an indicator analysis revealed that mutualistic fungi and bacteria were key components of European soil communities but not in North American communities. Interestingly, North American soil communities had lower β diversity than European communities suggesting higher levels of community conservation among North American populations. This research represents the first evidence of growth–defense trade‐offs in North American P. australis and offers a novel mechanism in understanding the invasion of P. australis in NA. [ABSTRACT FROM AUTHOR]

Summary: In natural systems, different plant species have been shown to modulate specific nitrogen (N) cycling processes so as to meet their N demand, thereby potentially influencing their own niche. This phenomenon might go beyond plant interactions with symbiotic microorganisms and affect the much less explored plant interactions with free‐living microorganisms involved in soil N cycling, such as nitrifiers and denitrifiers.Here, we investigated variability in the modulation of soil nitrifying and denitrifying enzyme activities (NEA and DEA, respectively), and their ratio (NEA : DEA), across 193 Arabidopsis thaliana accessions. We studied the genetic and environmental determinants of such plant–soil interactions, and effects on plant biomass production in the next generation.We found that NEA, DEA, and NEA : DEA varied c. 30‐, 15‐ and 60‐fold, respectively, among A. thaliana genotypes and were related to genes linked with stress response, flowering, and nitrate nutrition, as well as to soil parameters at the geographic origin of the analysed genotypes. Moreover, plant‐mediated N cycling activities correlated with the aboveground biomass of next‐generation plants in home vs away nonautoclaved soil, suggesting a transgenerational impact of soil biotic conditioning on plant performance.Altogether, these findings suggest that nutrient‐based plant niche construction may be much more widespread than previously thought. [ABSTRACT FROM AUTHOR]

As a consequence of the tight linkages between plants, soil, and microorganisms, we hypothesized the variations in plant species would change soil and microbial stoichiometry. Here, we examined the plant leaf carbon (C):nitrogen (N):phosphorus (P) ratios of nine species coming from three plant functional groups (PFGs) in the riparian zones of Hulunbuir steppe during near-peak biomass. The soil C:N:P, microbial biomass carbon (MBC):microbial biomass nitrogen (MBN), and extracellular enzyme's C:N:P were also assessed using the soils from each species. We found that plant tissue, soil nutrient, microbial, and enzyme activity stoichiometry significantly differed among different PFGs. Plant leaf and soil nutrient ratios tended to be similar (p > 0.05) between different species within the same PFGs. The variations in leaf C:N:P significantly correlated with the changes in soil C:N:P and MBC:MBN ratios. The homeostatic coefficients (H) < 1 suggested the relationships between plants and their resources C:N:P ratios might be non-homeostatic in the examined riparian zone. By assessing plant tissue and its soil nutrient stoichiometry, this study provided a perspective to understand the linkages of plant community, soil nutrient, and microbial characteristics. [ABSTRACT FROM AUTHOR]

Background: Since the 1980s, soils in a 22-km2 area near Lake Neuchâtel in Switzerland have been recognized for their innate ability to suppress the black root rot plant disease caused by the fungal pathogen Thielaviopsis basicola. However, the efficacy of natural disease suppressive soils against insect pests has not been studied. Results: We demonstrate that natural soil suppressiveness also protects plants from the leaf-feeding pest insect Oulema melanopus. Plants grown in the most suppressive soil have a reduced stress response to Oulema feeding, reflected by dampened levels of herbivore defense-related phytohormones and benzoxazinoids. Enhanced salicylate levels in insect-free plants indicate defense-priming operating in this soil. The rhizosphere microbiome of suppressive soils contained a higher proportion of plant-beneficial bacteria, coinciding with their microbiome networks being highly tolerant to the destabilizing impact of insect exposure observed in the rhizosphere of plants grown in the conducive soils. We suggest that presence of plant-beneficial bacteria in the suppressive soils along with priming, conferred plant resistance to the insect pest, manifesting also in the onset of insect microbiome dysbiosis by the displacement of the insect endosymbionts. Conclusions: Our results show that an intricate soil–plant-insect feedback, relying on a stress tolerant microbiome network with the presence of plant-beneficial bacteria and plant priming, extends natural soil suppressiveness from soilborne diseases to insect pests. 4oEYADM9UCsv5obDEsLZQ_ Video Abstract [ABSTRACT FROM AUTHOR]

Janzen–Connell (JC) effects, hypothesized to be partially driven by negative plant–soil feedbacks (PSFs), are considered to be a key mechanism that regulates tropical forest plant diversity and coexistence. However, intraspecific variation in JC effects may weaken this mechanism, with the strength of PSFs being a potentially key variable process. We conducted a manipulated experiment with seedlings from two populations of Pometia pinnata (Sapindaceae), a tropical tree species in southwest China. We aimed to measure the intraspecific difference in PSF magnitude caused by inoculating the soil from different P. pinnata source populations and growing seedlings under differing light intensity and water availability treatments, and at varying plant densities. We found negative PSFs for both populations with the inoculum soil originating from the same sites, but PSFs differed significantly with the inoculum soil from different sites. PSF strength responded differently to biotic and abiotic drivers; PSF strength was weaker in low moisture and high light treatments than in high moisture and low light treatments. Our study documents intraspecific variation in JC effects: specifically, P. pinnata have less defenses to their natively‐sourced soil, but are more defensive to the soil feedbacks from soil sourced from other populations. Our results imply that drought and light intensity tended to weaken JC effects, which may result in loss of species diversity with climate change. [ABSTRACT FROM AUTHOR]

Plant species affect key ecosystem processes like nutrient cycling and overall ecosystem productivity through their litter. The outcome of litter effects is largely determined by its decomposability, which directly effects soil properties. If litter remains standing or unshed (i.e. marcescent), its final decomposability can be increased by photodegradation of recalcitrant structures (like lignin). If the litter is immediately shed, its decomposability largely depends on its original nutrient content. Moreover, plant species may affect soil also through other, more direct effects. It is however unknown whether marcescent and immediately shed litters affect soil, and by that plants, differently, whether direct effects of plants on soil interact with those of marcescent and shed litters, and whether these interactions are consistent under different soil conditions.We set up a pot experiment, where we tested the effects of originally marcescent and shed litters (both added on the soil surface of the pots) on three grassland species (Bromus erectus, Filipendula vulgaris and Plantago media) in contrasting soils from long‐term stable ancient grassland and grassland restored on arable land 20 years before. We also tested how litter types and plant species affect soil chemical properties and microbial community (characterised by PLFA markers).Marcescent litter contained a lower amount of nutrients, but still increased plant biomass more than shed litter, although only for F. vulgaris (likely due to mobilisation of soil nutrients).The effect of litter on soil chemical properties and microbial community was low. These were largely affected by the plant species growing in the pot. The effect of these species on the microbial community was stronger in the undisturbed soil of ancient grasslands, while plant species affected mainly chemical properties in disturbed soil of restored grasslands. B. erectus slowed down the decomposition of both litter types in restored grassland soil.The effect of marcescent litter on living plants was significant but species‐specific and depended on soil conditions. Marcescence seems to have a stronger effect on plants in disturbed soil, which indicates its importance for recovery of the ecosystem after disturbance. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Aims: Plants alter the performance of other plants by changing soil conditions. These plant-soil feedback (PSF) can be shaped by plant interactions with other organisms and may be crucial for understanding plant coexistence. Here, we analyse how specialist and generalist symbionts change the legacy left in the soil by conspecific and heterospecific plants in the absence of pathogens and litter inputs. Methods: We conducted a two-phase experiment to evaluate Trifolium repens establishment and its ability to form symbiotic associations with AMF and rhizobia in soils conditioned by Lolium multiflorum plants with contrasting levels of endophyte infection (heterospecific soils: Lm+ or Lm−) and inoculated or not with AMF (M+ or M−). We also conditioned the soils with T. repens plants inoculated with rhizobia on M+ and M− soils (conspecific soils: Tr). Results: In M- treatments, the number of established seedlings showed no difference between conspecific and heterospecific soils. In M + treatments, conditioned soils by Tr and Lm+ increased legume establishment by 64% compared to soils conditioned with Lm−. AMF colonization was higher in Tr and Lm + soils compared to Lm−. Regardless of AMF inoculation, legume biomass was higher in conspecific soils than in heterospecific ones, consistent with nodulation changes. Conclusions: We found that legume establishment depended significantly on the previous presence of heterospecific soils only when L. multiflorum was associated with Epichloë endophyte and AMF. The strength of PSF was determined by AMF inoculum, while the positive or negative nature of this effect was given by the level of endophyte infection. These findings unveil a new pathway by which these symbionts modulate the coexistence between legumes and grasses. [ABSTRACT FROM AUTHOR]

Wood decay fungi alter the abiotic and biotic properties of deadwood, which are important as nurse logs for seedling regeneration. However, the relationship between fungal decay type and seedling performance has not been evaluated experimentally. In this study, we examined the germination, growth, and survival of six arbuscular mycorrhizal (AM) and six ectomycorrhizal (ECM) tree species on three substrates (pine logs with brown and white rot and soil) by conducting seed‐sowing experiments in a mixed forest dominated by Pinus densiflora and Quercus serrata. Analysis using ribosomal DNA internal transcribed spacer 1 (rDNA ITS1) sequencing revealed that the fungal community was significantly different across three substrates. The richness of operational taxonomic units (OTUs) of AM and ECM fungi was the largest on brown rot logs and soil, respectively. The substrate significantly affected the seedling performance when comparing wood decay types, but these were not consistent across the mycorrhizal status of the seedlings. Nevertheless, seedlings of some AM trees showed better growth and enhanced mycorrhizal colonization on brown rot logs than on white rot logs. The wood decay type influenced fungal communities in the logs and the performance of some seedling species partly by different mycorrhizal colonization rates. However, the effect was seedling species dependent and showed no apparent difference between AM and ECM trees. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Dioecious plants display sexual dimorphism in functional traits, which influences sex-specific interactions. Intersexual interactions in belowground facilitation processes and mechanisms remain poorly understood, necessitating further studies. Belowground facilitation involves resource complementarity, mycorrhizal fungal networks, root exudate-mediated belowground chemical communication, and plant–soil feedback. Spatial segregation of sexes may not necessarily reflect the outcomes of sex-specific interactions, but could be associated with sex-specific reproductive strategies. Dioecious plant species exhibit sexual dimorphism in various aspects, including morphology, physiology, life history, and behavior, potentially influencing sex-specific interactions. While it is generally accepted that intersexual interactions in dioecious species are less intense compared with intrasexual interactions, the mechanisms underlying belowground facilitation in intersexual combinations remain less understood. Here, we explore these mechanisms, which encompass resource complementarity, mycorrhizal fungal networks, root exudate-mediated belowground chemical communication, as well as plant–soil feedback. We address the reason for the lack of consistency in the strength of inter- and intrasexual interactions. We also propose that a comprehensive understanding of the potential positive consequences of sex-specific interactions can contribute to maintaining ecological equilibrium, conserving biodiversity, and enhancing the productivity of agroforestry. [ABSTRACT FROM AUTHOR]

Introduced plants create lasting abiotic and biotic changes to soil that are increasingly implicated as major drivers of invasion success, yet models for investigating patterns in the impacts of these soil legacies are lacking. Here, we used Bohemian knotweed (Reynoutria × bohemica) to present a novel approach for testing whether accounting for diverse evolutionary drivers can clarify how an invader's soil legacy mediates its success. For most tested species, R. × bohemica's soil legacy did not influence seedling performance irrespective of its evolutionary history or the evolutionary novelty of species that share its soil. However, we found the relative importance of legacy effects versus other mechanisms of invader dominance depends on the life stage of the plants growing in soil conditioned by the invader. While the effects of R. × bohemica's soil legacy on seedling performance were context dependent, emergence was, on average, higher in R. × bohemica‐conditioned soils than in unconditioned soils. Thus, contrary to theory, R. × bohemica's soil legacy not only fails to impede potential competitors but may also facilitate them. Our results are particularly powerful: we detected novel insights in the face of biological complexity, even for R. × bohemica, which likely does not depend on heterospecific plant–soil feedbacks for its competitive dominance in its introduced range. Designing rigorous investigations that explore how plant species' evolutionary histories mediate an invader's soil legacy across diverse abiotic environments, as shown here, is key for producing insights in other systems. [ABSTRACT FROM AUTHOR]

Abstract Wildfires, as an environmental filter, are pivotal ecological disturbances that reshape plant communities and soil dynamics, playing a crucial role in regulating biogeographic patterns and ecosystem services. In this study, we aim to explore the effects of wildfires on forest ecosystems, specifically focusing on the plant-soil feedback mechanisms within the northeastern margin of the Qinghai-Tibet Plateau (QTP). Utilizing Partial Least Squares Path Modeling (PLS-PM), we investigated the interrelationships among soil physicochemical properties, enzyme activities, species diversity, and community stability at varying post-fire recovery stages (5, 15, and 23 years). Results indicated that in the early recovery stages, rapid changes in soil properties such as decreased pH (p

Wildfires, as an environmental filter, are pivotal ecological disturbances that reshape plant communities and soil dynamics, playing a crucial role in regulating biogeographic patterns and ecosystem services. In this study, we aim to explore the effects of wildfires on forest ecosystems, specifically focusing on the plant-soil feedback mechanisms within the northeastern margin of the Qinghai-Tibet Plateau (QTP). Utilizing Partial Least Squares Path Modeling (PLS-PM), we investigated the interrelationships among soil physicochemical properties, enzyme activities, species diversity, and community stability at varying post-fire recovery stages (5, 15, and 23 years). Results indicated that in the early recovery stages, rapid changes in soil properties such as decreased pH (p < 0.001) and increased nutrient availability facilitate the emergence of early successional species with high resource utilization traits. As the ecosystem evolved toward a climax community, the soil and vegetation exhibit increased stability. Furthermore, soil enzyme activities displayed dynamic patterns that corresponded with changes in soil nutrient content, directly influencing the regeneration and diversity of plant communities. Importantly, our study documented a transition in the influence of soil properties on community stability from direct positive effects in initial recovery phases to negative impacts in later stages, while indirect benefits accrue through increased species diversity and enzyme activity. Vegetation composition and structure changed dynamically with recovery time during community succession. Plant nutrient absorption and accumulation affected nutrient dynamics in the soil, influencing plant regeneration, distribution, and diversity. Our results underscore the complex interactions between soil and vegetation that drive the recovery dynamics post-wildfire, highlighting the resilience of forest ecosystems to fire disturbances. This study contributes to the understanding of post-fire recovery processes and offers valuable insights for the management and restoration of fire-affected forest ecosystems. [ABSTRACT FROM AUTHOR]

Background and aims: Arbuscular mycorrhizal fungi (AMF) promote uptake of nutrients by plants; inversely, soil abiotic properties determine relationships between AMF and hosts. Although multiple hypotheses have suggested the importance of AMF or soil nutrients alone for plant invasion success, few studies have examined the relative importance and synergistic effects of AMF and soil abiotic properties at the community level. Methods: Eighteen pair-wise plots with or without by Solidago canadensis invasion were surveyed and 72 rhizosphere and bulk soils were sampled to evaluate changes and the relative importance of AMF and soil abiotic properties. Assembly communities were constructed with native or invasive AMF inoculation into sterilized soils with no phosphorus (P) addition (low P), and with inorganic and organic P added to evaluate plant soil feedback-mediated synergistic effects. Results: AMF community structure and composition in the rhizosphere soils of S. canadensis differed greatly from those in the bulk and native soils. Soil abiotic properties changed synergistically with lower pH, higher conductivity, and higher P content. S. canadensis dominance was explained more by interactions between AMF and soil abiotic properties than AMF alone, but was lower than that of abiotic properties alone. In low P and added organic P conditions, synergistic changes in AMF and soil abiotic properties provided positive feedback to the invader but neutral feedback in conditions with added inorganic P. Conclusion: S. canadensis produced strong rhizosphere effects on the AMF community and soil abiotic properties, which supported its growth and competition, especially under low and organic P conditions. [ABSTRACT FROM AUTHOR]

Pairwise interactions between species can be modified by other community members, leading to emergent dynamics contingent on community composition. Despite the prevalence of such higher‐order interactions, little is known about how they are linked to the timing and order of species' arrival. We generate population dynamics from a mechanistic plant–soil feedback model, then apply a general theoretical framework to show that the modification of a pairwise interaction by a third plant depends on its germination phenology. These time‐dependent interaction modifications emerge from concurrent changes in plant and microbe populations and are strengthened by higher overlap between plants' associated microbiomes. The interaction between this overlap and the specificity of microbiomes further determines plant coexistence. Our framework is widely applicable to mechanisms in other systems from which similar time‐dependent interaction modifications can emerge, highlighting the need to integrate temporal shifts of species interactions to predict the emergent dynamics of natural communities. [ABSTRACT FROM AUTHOR]

Plant–soil feedback—feedback from plant‐induced changes in soil properties to plant fitness—is increasingly shown to drive the maintenance of local plant diversity at both interspecific and intraspecific levels. A robust understanding of the relationships between plant–soil feedback and functional plant traits, which would improve our ability to generalize plant–soil feedback results beyond specific study systems, is, however, still lacking. This is especially true at the intraspecific plant level.We assessed the relationship between plant–soil feedback and several functional traits in 13 co‐occurring grassland species, including 20 genotypes of the dominant grass, Festuca rubra. The traits encompassed various aspects of growth, root properties and root exudate variability. Combining these traits into principal gradients of functional trait variation, we also tested the potential for the conservation and collaboration gradients to explain variation in PSF.Between‐species plant–soil feedback variation was explained by differences in biomass production and exudate composition, as well as contrasting strategies along the collaboration gradient. Within‐species plant–soil feedback variation—that is between Festuca rubra genotypes—was associated with exudate variability, especially contrasting amounts of exuded phenols. Several traits had a significant effect on plant–soil feedback only via their interaction with exudate composition.Overall, PSF was associated with different traits at between‐species versus within‐species levels. Root exudate variability was, however, involved at both diversity levels. Our results put forth the role of root exudation patterns as an important driver of variation in plant–soil feedback. Better integration between research on plant–soil feedback and on root exudation would therefore improve our understanding of the processes—both ecological and evolutionary—supporting the maintenance of plant diversity within grassland communities. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Some plants, via their action on microorganisms, control soil nitrification (i.e., the transformation of ammonium into nitrate). We model how the covariation between plant control of nitrification and preference for ammonium versus nitrate impacts ecosystem properties such as productivity, nitrogen (N) losses, and overall resilience. We show that the control of nitrification can maximize productivity by minimizing total inorganic N losses. We initially predicted that plants with an ammonium preference should achieve the highest biomass when inhibiting nitrification, and conversely that plants preferring nitrate should achieve the highest biomass by stimulating nitrification. With a parametrization derived from the Lamto savanna (Ivory Coast), we find that productivity is maximal for plants that slightly prefer ammonium and inhibit nitrification. Such situations, however, lead to strong positive feedbacks that can cause abrupt shifts from a highly to a lowly productive ecosystem. The comparison with other parameter sets (Pawnee short-grass prairie [United States], intensively cultivated field, and a hypothetical parameter set in which ammonium is highly volatilized and nitrate inputs are high) shows that strategies yielding the highest biomass may be counterintuitive (i.e., preferring nitrate but inhibiting nitrification). We argue that the level of control yielding the highest productivity depends on ecosystem properties (quantity of N deposition, leaching rates, and baseline nitrification rates), not only preference. Finally, while contrasting N preferences offer, as expected, the possibility of coexistence through niche partitioning, we stress how control of nitrification can be framed as a niche construction process that adds an additional dimension to coexistence conditions. [ABSTRACT FROM AUTHOR]

Invasive plants can interact with soil microbes to enhance their own performance. Such interactive effects may persist and later affect plant performance and their population dynamics. Such 'invasive soil legacy' is the specific plant–soil feedback that can affect future invasions, while it is not clear how nitrogen deposition and interspecific competition influence invasive soil legacy. Thus, we collected field soil and conducted a greenhouse experiment to investigate the effects of soil legacy of the invasive tree Rhus typhina on the performance, functional traits and soil microbial communities of R. typhina and the native tree Ailanthus altissima under three nitrogen levels with and without interspecific competition. The experiment revealed that the outcomes of invasive soil legacies were context-specific and depended on local soil nutrient levels and species competition. Specifically, nitrogen addition changed the negative conspecific soil legacy on subsequent R. typhina to a positive effect, while it became negative in A. altissima. The invasive soil legacy promoted the transpirational rate of R. typhina and A. altissima in monoculture, but inhibited it in a mixture under nitrogen deposition. Nitrogen deposition reduced bacteria and fungi biomass of A. altissima in monocultures and mixtures. In contrast, nitrogen deposition decreased bacterial and fungal biomass of R. typhina in monocultures, but enhanced them in mixtures. Therefore, changes in plant growth, transpiration rate and soil microbial biomass might contribute to the different responses of invasive and native plants to invasive soil legacies. Nitrogen deposition and interspecific competition promote the viability of invasive plants from plant–soil feedback and indicate that ranges of subsequent plants might further expand through below-ground process under nitrogen deposition in the future. [ABSTRACT FROM AUTHOR]

Soil microorganisms play a critical role in shaping the biodiversity dynamics of plant communities. These microbial effects can arise through direct mediation of plant fitness by pathogens and mutualists, and over the past two decades, numerous studies have shined a spotlight on the role of dynamic feedbacks between plants and soil microorganisms as key determinants of plant species coexistence. Such feedbacks occur when plants modify the composition of the soil community, which in turn affects plant performance. Stimulated by a theoretical model developed in the 1990s, a bulk of the empirical evidence for microbial controls over plant coexistence comes from experiments that quantify plant growth in soil communities that were previously conditioned by conspecific or heterospecific plants. These studies have revealed that soil microbes can generate strong negative to positive frequency‐dependent dynamics among plants. Even as soil microbes have become recognized as a key player in determining plant coexistence outcomes, the past few years have seen a renewed interest in expanding the conceptual foundations of this field. New results include re‐interpretations of key metrics from classic two‐species models, extensions of plant–soil feedback theory to multispecies communities, and frameworks to integrate plant–soil feedbacks with processes like intra‐ and interspecific competition. Here, I review the implications of theoretical developments for interpreting existing empirical results and highlight proposed analyses and designs for future experiments that can enable a more complete understanding of microbial regulation of plant community dynamics. [ABSTRACT FROM AUTHOR]

Negative plant–soil feedback (PSF) arises when localized accumulations of pathogens reduce the growth of conspecifics, whereas positive PSF can occur due to the emergence of mutualists. Biochar, a carbon-rich material produced by the pyrolysis of organic matter, has been shown to modulate soil microbial communities by altering their abundance, diversity, and activity. For this reason, to assess the long-term impact of biochar on soil microbiome dynamics and subsequent plant performance, we conducted a PSF greenhouse experiment using field soil conditioned over 10 years with Vitis vinifera (L.), without (e.g., C) or with biochar at two rates (e.g., B and BB). Subsequently, the conditioned soil was employed in a response phase involving either the same plant species or different species, i.e., Medicago sativa (L.), Lolium perenne (L.), and Solanum lycopersicum (L.). We utilized next-generation sequencing to assess the abundance and diversity of fungal pathogens and arbuscular mycorrhizal fungi (AMF) within each conditioned soil. Our findings demonstrate that biochar application exerted a stimulatory effect on the growth of both conspecifics and heterospecifics. In addition, our results show that untreated soils had a higher abundance of grape-specialized fungal pathogens, mainly Ilyonectria liriodendra, with a relative abundance of 20.6% compared to 2.1% and 5.1% in B and BB, respectively. Cryptovalsa ampelina also demonstrated higher prevalence in untreated soils, accounting for 4.3% compared to 0.4% in B and 0.1% in BB. Additionally, Phaeoacremonium iranianum was exclusively present in untreated soils, comprising 12.2% of the pathogens' population. Conversely, the application of biochar reduced generalist fungal pathogens. For instance, Plenodomus biglobosus decreased from 10.5% in C to 7.1% in B and 2.3% in BB, while Ilyonectria mors-panacis declined from 5.8% in C to 0.5% in B and 0.2% in BB. Furthermore, biochar application was found to enrich the AMF community. Notably, certain species like Funneliformis geosporum exhibited increased relative abundance in biochar-treated soils, reaching 46.8% in B and 70.3% in BB, compared to 40.5% in untreated soils. Concurrently, other AMF species, namely Rhizophagus irregularis, Rhizophagus diaphanus, and Claroideoglomus drummondii, were exclusively observed in soils where biochar was applied. We propose that the alleviation of negative PSF can be attributed to the positive influence of AMF in the absence of strong inhibition by pathogens. In conclusion, our study underscores the potential of biochar application as a strategic agricultural practice for promoting sustainable soil management over the long term. [ABSTRACT FROM AUTHOR]

Although biotic and abiotic factors have been confirmed to be critical factors that affect community dynamics, their interactive effects have yet to be fully considered in grassland degradation. Herein, we tested how soil nutrients and microbes regulated plant–soil feedback (PSF) in a degraded alpine grassland. Our results indicated that soil total carbon (STC; from 17.66 to 12.55 g/kg) and total nitrogen (STN; from 3.16 to 2.74 g/kg) exhibited significant (P < 0.05) decrease from non-degraded (ND) to severely degraded (SD). Despite higher nutrients in ND soil generating significantly (P < 0.05) positive PSF (0.52) on monocots growth when the soil was sterilized, a high proportion of pathogens (36%) in ND non-sterilized soil resulted in a strong negative PSF on monocots. In contrast, the higher phenotypic plasticity of dicots coupled with a higher abundance of mutualists and saprophytes (70%) strongly promoted their survival and growth in SD with infertile soil. Our findings identified a novel mechanism that there was a functional group shift from monocots with higher vulnerability to soil pathogens in the ND fertile soil to dicots with higher dependence on nutritional mutualists in the degraded infertile soil. The emerging irreversible eco-evolutionary in PSF after degradation might cause a predicament for the restoration of degraded grassland. [ABSTRACT FROM AUTHOR]

This article is a Commentary on Gfeller et al. (2024), 241: 2575–2588. [ABSTRACT FROM AUTHOR]

Summary: Plants can suppress the growth of other plants by modifying soil properties. These negative plant–soil feedbacks are often species‐specific, suggesting that some plants possess resistance strategies. However, the underlying mechanisms remain largely unknown.Here, we investigated whether benzoxazinoids, a class of dominant secondary metabolites that are exuded into the soil by maize and other cereals, allow maize plants to cope with plant–soil feedbacks.We find that three out of five tested crop species reduce maize (Zea mays L.) performance via negative plant–soil feedbacks relative to the mean across species. This effect is partially alleviated by the capacity of maize plants to produce benzoxazinoids. Soil complementation with purified benzoxazinoids restores the protective effect for benzoxazinoid‐deficient mutants. Sterilization and reinoculation experiments suggest that benzoxazinoid‐mediated protection acts via changes in soil biota. Substantial variation of the protective effect between experiments and soil types illustrates context dependency.In conclusion, exuded plant secondary metabolites allow plants to cope with plant–soil feedbacks. These findings expand the functional repertoire of plant secondary metabolites and reveal a mechanism by which plants can resist negative effects of soil feedbacks. The uncovered phenomenon may represent a promising avenue to stabilize plant performance in crop rotations. See also the Commentary on this article by Bass, 241: 2316–2319. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: By modifying the biotic and abiotic properties of the soil, plants create soil legacies that can affect vegetation dynamics through plant–soil feedbacks (PSF). PSF are generally attributed to reciprocal effects of plants and soil biota, but these interactions can also drive changes in the identity, diversity and abundance of soil metabolites, leading to more or less persistent soil chemical legacies whose role in mediating PSF has rarely been considered. These chemical legacies may interact with microbial or nutrient legacies to affect species coexistence. Given the ecological importance of chemical interactions between plants and other organisms, a better understanding of soil chemical legacies is needed in community ecology. In this Viewpoint, we aim to: highlight the importance of belowground chemical interactions for PSF; define and integrate soil chemical legacies into PSF research by clarifying how the soil metabolome can contribute to PSF; discuss how functional traits can help predict these plant–soil interactions; propose an experimental approach to quantify plant responses to the soil solution metabolome; and describe a testable framework relying on root economics and seed dispersal traits to predict how plant species affect the soil metabolome and how they could respond to soil chemical legacies. [ABSTRACT FROM AUTHOR]

Aims: Plant-soil feedback (PSF), which may vary across spaces and time, is considered as an important mechanism in biological invasions. However, it is still unclear how PSF changes during biological invasions in different environments. Methods: To address this problems, we measured aboveground biomass and cover of the invasive plant Ageratina adenophora, richness and diversity of its co-occurring natives, PSFs for the invader, soil nutrients and fungal communities at uninvaded, recently and long invaded sites in lightly and severely disturbed habitats. Results: Invasion time and habitats influenced PSFs for the invader interactively. As invasion time increased, the positive total PSFs (response to their soil biota relative to sterilized soil) shifted to neutral, and the negative specific PSFs (response to their own soil biota relative to other species' soil biota) became more stronger in lightly disturbed habitats, but not in severely disturbed habitats. The dominance of the invader and its ecological impacts remained similar in lightly disturbed habitats, while in severely disturbed habitats, both the invader's dominance and impacts increased. The dynamics of the PSFs were associated with soil nutrients and microbes, and the former may function indirectly via affecting the lattes. Soil pathogens and AMF contributed to the dynamics of the PSFs in some cases, but not in others. Conclusions: These findings indicate that the complex spatiotemporal dynamics of PSFs may contribute to the dynamics of dominance and impact of invasive species in forests, and highlight the need to consider the effects of invasion time and environments when studying PSFs. [ABSTRACT FROM AUTHOR]

Although plant–soil feedback (PSF) is being recognized as an important driver of plant recruitment, our understanding of its role in species coexistence in natural communities remains limited by the scarcity of experimental studies on multispecies assemblages. Here, we experimentally estimated PSFs affecting seedling recruitment in 10 co‐occurring Mediterranean woody species. We estimated weak but significant species‐specific feedback. Pairwise PSFs impose similarly strong fitness differences and stabilizing‐destabilizing forces, most often impeding species coexistence. Moreover, a model of community dynamics driven exclusively by PSFs suggests that few species would coexist stably, the largest assemblage with no more than six species. Thus, PSFs alone do not suffice to explain coexistence in the studied community. A topological analysis of all subcommunities in the interaction network shows that full intransitivity (with all species involved in an intransitive loop) would be rare but it would lead to species coexistence through either stable or cyclic dynamics. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Abstract Escape from native range enemies can give invasive species a competitive edge according to the enemy‐release hypothesis. While more commonly associated with predators and herbivores, release from belowground microbial antagonists has been recently demonstrated to benefit invasive plants. Biogeographic variation in dominance and comparisons of soil communities suggest that invasive European Phragmites australis may have also benefitted from belowground enemy release in North America (NA). Here we examine the effects of native range (Europe) versus introduced range (NA) soil communities on European and North American P. australis using a reciprocal inoculation seedling growth experiment. Contrary to the enemy‐release hypothesis, we found that North American P. australis was sensitive to soil community origin in that the seedlings grown in European soil communities had higher total biomass than seedlings grown in North American soil communities. This pattern was not observed in the European P. australis seedlings which had similar biomass when grown with North American or European soil communities. Notably, North American P. australis had higher biomass than European P. australis regardless of which soil community it was grown in, suggesting a growth–defense tradeoff. Though the relative abundance of mutualists and pathogens composition did not differ between the two ranges, an indicator analysis revealed that mutualistic fungi and bacteria were key components of European soil communities but not in North American communities. Interestingly, North American soil communities had lower β diversity than European communities suggesting higher levels of community conservation among North American populations. This research represents the first evidence of growth–defense trade‐offs in North American P. australis and offers a novel mechanism in understanding the invasion of P. australis in NA.

Abstract Janzen–Connell (JC) effects, hypothesized to be partially driven by negative plant–soil feedbacks (PSFs), are considered to be a key mechanism that regulates tropical forest plant diversity and coexistence. However, intraspecific variation in JC effects may weaken this mechanism, with the strength of PSFs being a potentially key variable process. We conducted a manipulated experiment with seedlings from two populations of Pometia pinnata (Sapindaceae), a tropical tree species in southwest China. We aimed to measure the intraspecific difference in PSF magnitude caused by inoculating the soil from different P. pinnata source populations and growing seedlings under differing light intensity and water availability treatments, and at varying plant densities. We found negative PSFs for both populations with the inoculum soil originating from the same sites, but PSFs differed significantly with the inoculum soil from different sites. PSF strength responded differently to biotic and abiotic drivers; PSF strength was weaker in low moisture and high light treatments than in high moisture and low light treatments. Our study documents intraspecific variation in JC effects: specifically, P. pinnata have less defenses to their natively‐sourced soil, but are more defensive to the soil feedbacks from soil sourced from other populations. Our results imply that drought and light intensity tended to weaken JC effects, which may result in loss of species diversity with climate change.

Abstract Wood decay fungi alter the abiotic and biotic properties of deadwood, which are important as nurse logs for seedling regeneration. However, the relationship between fungal decay type and seedling performance has not been evaluated experimentally. In this study, we examined the germination, growth, and survival of six arbuscular mycorrhizal (AM) and six ectomycorrhizal (ECM) tree species on three substrates (pine logs with brown and white rot and soil) by conducting seed‐sowing experiments in a mixed forest dominated by Pinus densiflora and Quercus serrata. Analysis using ribosomal DNA internal transcribed spacer 1 (rDNA ITS1) sequencing revealed that the fungal community was significantly different across three substrates. The richness of operational taxonomic units (OTUs) of AM and ECM fungi was the largest on brown rot logs and soil, respectively. The substrate significantly affected the seedling performance when comparing wood decay types, but these were not consistent across the mycorrhizal status of the seedlings. Nevertheless, seedlings of some AM trees showed better growth and enhanced mycorrhizal colonization on brown rot logs than on white rot logs. The wood decay type influenced fungal communities in the logs and the performance of some seedling species partly by different mycorrhizal colonization rates. However, the effect was seedling species dependent and showed no apparent difference between AM and ECM trees.

Damping‐off oomycete and fungal plant pathogens reduce the germination, emergence, and survival of seedlings. In agricultural systems, this poses a significant problem as it may reduce productivity; in contrast, the impact is more subtle in natural ecosystems and may be essential for maintaining the structure and diversity of plant communities. The oomycete genus Phytophthora is frequently detected in natural plant communities causing disease in mature plants, but it is rarely assessed as a damping‐off pathogen. A pathogenicity experiment was established with five oomycete treatments, three putatively native Phytophthora species, the invasive P. cinnamomi, and Pythium irregulare, to determine the damping‐off host range in selected plant species from a hyper‐diverse Mediterranean‐type ecosystem. Additionally, plant and seed traits were analysed to determine if they were correlated with susceptibility to pre‐emergent damping‐off. Phytophthora arenaria was the only putatively native generalist damping‐off pathogen, causing 12 of 19 plant species to experience significantly reduced seedling emergence or survival relative to the control treatment. Pythium irregulare and the introduced P. cinnamomi caused significant damping‐off for 12 and 13 plant species, respectively. Plant species that were slowest to germinate and emerge were the most susceptible to pre‐emergence damping‐off caused by P. arenaria. These results suggest native and invasive Phytophthora may substantially influence the structure and diversity of natural plant communities through damping‐off. While mature plant species are the most common focus in Phytophthora research, our study indicates damping‐off should be considered to determine the full impact of these soil‐borne plant pathogens. [ABSTRACT FROM AUTHOR]