Heterospecific Soil Research Articles

Plant-Soil Feedback Effects on Germination and Growth of Native and Non-Native Species Common across Southern California

Changes in plant assemblages can influence biotic and abiotic soil conditions. These changes can cause plant–soil feedbacks that can inhibit or facilitate plant germination and growth. Here, we contribute to a growing literature examining plant–soil feedbacks in the endangered sage scrub ecosystem by examining the germination and growth of Artemisia californica, the dominant native shrub species in the ecosystem, in soil conditioned by two widespread plant invaders (Brassica nigra, Bromus madritensis ssp. rubens), and the germination and growth of these invasive species in conspecific and heterospecific soils. Our findings suggest that: (i) A. californica soils can limit establishment of some species (B. nigra) but not others (B. madritensis), (ii) A. californica soil conditions reduce growth of all plant species, and (iii) non-natives are negatively impacted by soil microbes, but in some contexts can do better in heterospecific soil. As our findings were often incongruent with other studies that examined interactions among similar species at other sites, we suggest that we are at our infancy of understanding these complex interactions, and that developing a predictive framework for understanding plant soil feedbacks in the sage scrub ecosystem involves understanding how various plant species respond in different soil contexts within the ecosystem.

Individual Plant-Soil Feedback Effects Influence Tree Growth and Rhizosphere Fungal Communities in a Temperate Forest Restoration Experiment

Plant-soil feedbacks and the soil legacy effects that create them have important implications for community composition and restoration. However, relatively few field trials test the influence of soil legacy effectsplant-soil feedbacks, especially on longer-lived species, such as trees. Here we present a field restoration experiment with 10 ectomycorrhizal fungal tree species native to eastern North America. Trees were inoculated with soils collected from conspecifics in the field or from a heterospecific: Quercus rubra. Fagus grandifolia stem elongationFollowing 16 months of growth in the field, Carya ovata diameter increase was significantly increased greater in trees receiving the by heterospecific inoculant.tion following 16 months of growth in the field, and Tthis negative plant-soil feedback is consistent with its C. ovata’s natural co-occurrence with Q. rubra. Conversely, Quercus macrocarpa diameter increase and Carya cordiformis height increase were was significantly greater when inoculated with conspecific soils, and this positive plant-soil feedback is consistent with its their numerical dominance in natural communities. We found no evidence for phylogenetic Janzen-Connell effects or conservation of soil mutualists across tree species. We also quantified differences in soil fungal community structure with next generation sequencing methods (Illumina MiSeq) following 16 months in the field. Shannon’s diversity of fungal taxa was greater in heterospecific soils of seven of our nine experimental species, consistent with a diversifying influence of heterospecific Quercus rubra soil inocula. However, only one genus, Ulmus, exhibited differences in fungal community composition derived from conspecific and heterospecific sources, suggesting a stronger effect of focal tree species than of soil inocula source. The relatedness among focal tree species also influenced fungal community composition, with tree families and genera displaying different fungal communities. We suggest that future experiments should determine whether more diverse tree and fungal communities might have enhanced ecosystem functioning in tree restoration sites.

Plant-driven changes in soil microbial communities influence seed germination through negative feedbacks.

Plant–soil feedbacks (PSFs) drive plant community diversity via interactions between plants and soil microbes. However, we know little about how frequently PSFs affect plants at the seed stage, and the compositional shifts in fungi that accompany PSFs on germination.We conducted a pairwise PSF experiment to test whether seed germination was differentially impacted by conspecific versus heterospecific soils for seven grassland species. We used metagenomics to characterize shifts in fungal community composition in soils conditioned by each plant species. To investigate whether changes in the abundance of certain fungal taxa were associated with multiple PSFs, we assigned taxonomy to soil fungi and identified putative pathogens that were significantly more abundant in soils conditioned by plant species that experienced negative or positive PSFs.We observed negative, positive, and neutral PSFs on seed germination. Although conspecific and heterospecific soils for pairs with significant PSFs contained host‐specialized soil fungal communities, soils with specialized microbial communities did not always lead to PSFs. The identity of host‐specialized pathogens, that is, taxa uniquely present or significantly more abundant in soils conditioned by plant species experiencing negative PSFs, overlapped among plant species, while putative pathogens within a single host plant species differed depending on the identity of the heterospecific plant partner. Finally, the magnitude of feedback on germination was not related to the degree of fungal community differentiation between species pairs involved in negative PSFs. Synthesis. Our findings reveal the potential importance of PSFs at the seed stage. Although plant species developed specialized fungal communities in rhizosphere soil, pathogens were not strictly host‐specific and varied not just between plant species, but according to the identity of plant partner. These results illustrate the complexity of microbe‐mediated interactions between plants at different life stages that next‐generation sequencing can begin to unravel.

Connecting plant-soil feedbacks to long-term stability in a desert grassland.

Temporal fluctuations in plant species coexistence are key to understanding ecosystem state transitions and long-term maintenance of species diversity. Although plant microbiomes can alter plant competition in short-term experiments, their relevance to natural temporal patterns in plant communities is unresolved. In a semiarid grassland, the frequency and magnitude of change in plant species composition through time varied from relatively static to highly dynamic among patches across the landscape. We field tested whether these alternative successional trajectories correlated with alternative plant-soil interactions. In temporally stable patches, we found negative plant-soil feedbacks, where plants grew worse with conspecific than heterospecific soil biota-a mechanism that maintains stability in mathematical models. In contrast, feedbacks in temporally dynamic patches were neutral to positive. Importantly, the magnitude of feedbacks depended on plant frequency, enabling plant species to increase in cover when rare, which theory predicts will promote long-term, stable coexistence. Although our study does not determine the direction of causality, our results reveal a novel link between plant-microbe interactions and temporal stability of plant species coexistence and help to explain 20+ yr of plant abundance dynamics at the patch-to-landscape scales.

Reduced water-availability lowers the strength of negative plant-soil feedbacks of two Asclepias species.

Negative plant-soil feedbacks can serve as a mechanism for plant species coexistence. Despite predicted changes in precipitation patterns due to climate change, little is known as to how the strength and direction of feedbacks change under differing soil moisture regimes. We performed a fully reciprocal greenhouse experiment where seedlings of two co-occurring Asclepias spp. (milkweed) were grown either with their own or the other species' microbial communities under high or low watering treatments. We found that seedlings of each species were smaller when exposed to conspecific relative to heterospecific soil biota, perhaps due to a build-up of specific soil pathogens. Importantly, this negative feedback diminished under reduced water-availability, and also in the absence of live soil organisms. Our findings suggest that the ability for plants to coexist may be fundamentally altered in areas that face increased drought.

Forest fire may disrupt plant\u2013microbial feedbacks

Plant–microbial feedbacks are important drivers of plant community structure and dynamics. These feedbacks are driven by the variable modification of soil microbial communities by different plant species. However, other factors besides plant species can influence soil communities and potentially interact with plant–microbial feedbacks. We tested for plant–microbial feedbacks in two Eucalyptus species, E. globulus and E. obliqua, and the influence of forest fire on these feedbacks. We collected soils from beneath mature trees of both species within native forest stands on the Forestier Peninsula, Tasmania, Australia, that had or had not been burnt by a recent forest fire. These soils were subsequently used to inoculate seedlings of both species in a glasshouse experiment. We hypothesized that (i) eucalypt seedlings would respond differently to inoculation with conspecific versus heterospecific soils (i.e., exhibit plant–microbial feedbacks) and (ii) these feedbacks would be removed by forest fire. For each species, linear mixed effects models tested for differences in seedling survival and biomass in response to inoculation with conspecific versus heterospecific soils that had been collected from either unburnt or burnt stands. Eucalyptus globulus displayed a response consistent with a positive plant–microbial feedback, where seedlings performed better when inoculated with conspecific versus heterospecific soils. However, this effect was only present when seedlings were inoculated with unburnt soils, suggesting that fire removed the positive effect of E. globulus inoculum. These findings show that external environmental factors can interact with plant–microbial feedbacks, with possible implications for plant community structure and dynamics.

Plant–soil feedback effects can be masked by aboveground herbivory under natural field conditions

For plants, herbivory and interactions with their surrounding soil ecosystem are crucial factors influencing individual performance and plant-community composition. Until now, research has mostly focused on individual effects of herbivory or plant-soil feedbacks (PSFs) on plant growth and community composition, but few studies have explicitly investigated herbivory in the context of PSFs. These few studies, however, were performed under greenhouse conditions even though PSFs and herbivory may differ between greenhouse and field conditions. Therefore, we performed a field experiment in a grassland, testing the growth responses of three grass species that consistently differ in local abundance, on soils previously conditioned by these species. We tested these PSF effects for the three species both in the presence and in the absence of aboveground herbivores. Without herbivores, the two subdominant species suffered from negative PSF effects. However, in the presence of herbivores and on heterospecific soils, the same two species experienced a significant loss of shoot biomass, whereas, in contrast, enhanced root growth was observed on conspecific soils, resulting in overall neutral PSF effects. The dominant species was not damaged by herbivores and showed overall neutral PSF effects in the field with and without herbivores. Our study provides empirical evidence that negative PSF effects that exist under natural field conditions in grasslands can be overwhelmed by aboveground herbivory. Hence, potential PSF effects might not be detected in the field, because other abiotic and biotic interactions such as aboveground herbivory have stronger effects on plant performance and might therefore mask or override these PSF effects.

Plant-soil feedbacks in declining forests: implications for species coexistence.

Plant-soil feedbacks (PSFs) play a relevant role as drivers of species abundance, coexistence, and succession in plant communities. However, the potential contribution of PSFs to community dynamics in changing forest ecosystems affected by global change drivers is still largely unexplored. We measured the direction, strength and nature (biological vs. chemical) of PSFs experienced by coexisting tree species in two types of declining Quercus suber forests of southwestern Spain (open woodland vs. closed forest) invaded by the exotic soil pathogen Phytophthora cinnamomi. To test PSFs in a realistic community context, we focused not only on individual PSFs (i.e., comparing the growth of a tree species on conspecific vs. heterospecific soil) but also calculated net-pairwise PSFs by comparing performance of coexisting tree species on their own and each other's soils. We hypothesized that the decline and death of Q.suber would alter the direction and strength of individual and net-pairwise PSFs due to the associated changes in soil nutrients and microbial communities, with implications for recruitment dynamics and species coexistence. In support of our hypothesis, we found that the decline of Q.suber translated into substantial alterations of individual and net-pairwise PSFs, which shifted from mostly neutral to significantly positive or negative, depending on the forest type. In both cases however the identified PSFs benefited other species more than Q.suber (i.e., heterospecific positive PSF in the open woodland, conspecific negative PSF in the closed forest). Our results supported PSFs driven by changes in chemical soil properties (mainly phosphorus) and arbuscular mycorrhizal fungi, but not in pathogen abundance. Overall, our study suggests that PSFs might reinforce the loss of dominance of Q.suber in declining forests invaded by P.cinnamomi by promoting the relative performance of non-declining coexisting species. More generally, our results indicate an increase in the strength of net PSFs as natural forests become disturbed by global change drivers (e.g., invasive species), suggesting an increasingly important role of PSFs in forest community dynamics in the near future.

Competition and soil resource environment alter plant-soil feedbacks for native and exotic grasses.

Feedbacks between plants and soil biota are increasingly identified as key determinants of species abundance patterns within plant communities. However, our understanding of how plant-soil feedbacks (PSFs) may contribute to invasions is limited by our understanding of how feedbacks may shift in the light of other ecological processes. Here we assess how the strength of PSFs may shift as soil microbial communities change along a gradient of soil nitrogen (N) availability and how these dynamics may be further altered by the presence of a competitor. We conducted a greenhouse experiment where we grew native Stipa pulchra and exotic Avena fatua, alone and in competition, in soils inoculated with conspecific and heterospecific soil microbial communities conditioned in low, ambient and high N environments. Stipa pulchra decreased in heterospecific soil and in the presence of a competitor, while the performance of the exotic A. fatua shifted with soil microbial communities from altered N environments. Moreover, competition and soil microbial communities from the high N environment eliminated the positive PSFs of Stipa. Our results highlight the importance of examining how individual PSFs may interact in a broader community context and contribute to the establishment, spread and dominance of invaders.

Local variation in conspecific plant density influences plant–soil feedback in a natural grassland

Several studies have argued that under field conditions plant–soil feedback may be related to the local density of a plant species, but plant–soil feedback is often studied by comparing conspecific and heterospecific soils or by using mixed soil samples collected from different locations and plant densities. We examined whether the growth of the early successional species Jacobaea vulgaris in soil collected from the field is related to the local variation in plant density of this species. In a grassland restoration site, we selected eight 8m×8m plots, four with high and four with low densities of J. vulgaris plants. In 16 subplots in each plot we recorded the density and size of J. vulgaris, and characteristics of the vegetation and the soil chemistry. Soil collected from each subplot was used in a greenhouse pot-experiment to study the growth of J. vulgaris, both in pure field soil and in sterile soil inoculated with a small part of field soil.In the field, flowering J. vulgaris plants were taller, the percentage of rosette plants was higher and seed density was larger in High- than in Low-density plots. In the pot experiment, J. vulgaris had a negative plant–soil feedback, but biomass was also lower in soil collected from High- than from Low-density plots, although only when growing in inoculated soil. Regression analyses showed that J. vulgaris biomass of plants growing in pure soil was related to soil nutrients, but also to J. vulgaris density in the field.We conclude that in the field there is local variation in the negative plant–soil feedback of J. vulgaris and that this variation can be explained by the local density of J. vulgaris, but also by other factors such as nutrient availability.

Conspecific Plant-Soil Feedbacks of Temperate Tree Species in the Southern Appalachians, USA

Many tree species have seedling recruitment patterns suggesting that they are affected by non-competitive distance-dependent sources of mortality. We conducted an experiment, with landscape-level replication, to identify cases of negative distance-dependent effects and whether variation in these effects corresponded with tree recruitment patterns in the southern Appalachian Mountains region. Specifically, soil was collected from 14 sites and used as inocula in a 62 day growth chamber experiment determining whether tree seedling growth was less when interacting with soil from conspecific (like) than heterospecific (other) tree species. Tests were performed on six tree species. Three of the tree species had been previously described as having greater recruitment around conspecifics (i.e. facilitator species group) compared to the other half (i.e. inhibitor species group). We were then able to determine whether variation in negative distance-dependent effects corresponded with recruitment patterns in the field. Across the six species, none were negatively affected by soil inocula from conspecific relative to heterospecific sources. Most species (four of six) were unaffected by soil source. Two species (Prunus serotina and Tsuga canadensis) had enhanced growth in pots inoculated with soil from conspecific trees vs. heterospecifics. Species varied in their susceptibility to soil pathogens, but trends across all species revealed that species classified as inhibitors were not more negatively affected by conspecific than heterospecific soil inocula or more susceptible to pathogenic effects than facilitators. Although plant-soil biota interactions may be important for individual species and sites, it may be difficult to scale these interactions over space or levels of ecological organization. Generalizing the importance of plant-soil feedbacks or other factors across regional scales may be especially problematic for hyperdiverse temperate forests where interactions may be spatially variable.

Weak conspecific feedbacks and exotic dominance in a species-rich savannah.

Whether dominance drives species loss can depend on the power of conspecific self-limitation as dominant populations expand; these limitations can stabilize competitive imbalances that might otherwise cause displacement. We quantify the relative strength of conspecific and heterospecific soil feedbacks in an exotic-dominated savannah, using greenhouse trials and field surveys to test whether dominants are less self-suppressed, highly suppressive of others or both. Soil feedbacks can impact plant abundance, including invasion, but their implications for coexistence in invader-dominated systems are unclear. We found that conspecific feedbacks were significantly more negative than heterospecific ones for all species including the dominant invaders; even the rarest natives performed significantly better in the soils of other species. The strength of these negative feedbacks, however, was approximately 50 per cent stronger for natives and matched their field abundance--the most self-limited natives were rare and narrowly distributed. These results suggest that exotics dominate by interacting with natives carrying heavier conspecific feedback burdens, without cultivating either negative heterospecific effects that suppress natives or positive ones that accelerate their own expansion. These feedbacks, however, could contribute to coexistence because all species were self-limited in their own soils. Although the net impact of this feedback stabilization will probably interact with other factors (e.g. herbivory), soil feedbacks may thus contribute to invader dominance without necessarily being detrimental to species richness.

The role of plant–soil feedbacks and land‐use legacies in restoration of a temperate steppe in northern China

AbstractPlant–soil feedbacks affect plant performance and plant community dynamics; however, little is known about their role in ecological restoration. Here, we studied plant–soil feedbacks in restoration of steppe vegetation after agricultural disturbance in northern China. First, we analyzed abiotic and biotic soil properties under mono‐dominant plant patches in an old‐field restoration site and in a ‘target’ steppe site. Second, we tested plant–soil feedbacks by growing plant species from these two sites on soils from con‐ and heterospecific origin. Soil properties generally did not differ between the old‐field site and steppe site, but there were significant differences among mono‐dominant plant patches within the sites. While soil species origin (i.e., the plant species beneath which the soil was collected) affected biomass of individual plant species in the feedback experiment, species‐level plant–soil feedbacks were ‘neutral’. Soil site origin (old‐field, steppe) significantly affected biomass of old‐field and steppe species. For example, old‐field species had higher biomass in old‐field soils than in steppe soils, indicating a positive land‐use legacy. However, soil site origin effects depended on the plant species beneath which the soils were collected. The predictive value of abiotic and biotic soil properties in explaining plant biomass differed between and within groups of old‐field and steppe species. We conclude that the occurrence of positive land‐use legacies for old‐field species may retard successional replacement of old‐field species by steppe species. However, high levels of idiosyncrasy in responses of old‐field and steppe plant species to con‐ and heterospecific soils indicate interspecific variation in the extent to which soil legacies and plant–soil feedbacks control successional species replacements in Chinese steppe ecosystems.

Disturbance influences the outcome of plant-soil biota interactions in the invasive Acacia longifolia and in native species

Interrelated causes of plant invasion have been gaining increasing recognition. However, research on this subject has mainly focused around conceptual models. Here we explore whether plant–soil biota feedbacks and disturbance, two major factors capable of facilitating invasive plants in introduced ranges, interact to preferentially benefit exotics compared to native plants. We investigated the influence of fire disturbance on plant–soil biota interactions for the invasive Acacia longifolia and two dominant natives (Cytisus striatus and Pinus pinaster) in Portuguese dune systems. In the first experiment, we grew exotic and native plants in soil inoculated with soil biota from unburned or recently burned soils collected in an area with small invasion intensity by A. longifolia. Soil biota effects on the exotic legume A. longifolia changed from neutral to positive after fire, whereas the opposite outcome was observed in the native legume C. striatus, and a change from negative to neutral effects after fire occurred in the native P. pinaster. Fire reduced mycorrhizal colonization in all species and rhizobial colonization in C. striatus but not in A. longifolia. In the second experiment, we grew the exotic and native plants with conspecific and heterospecific soil biota from undisturbed soils (area with low invasion intensity by A. longifolia), and from post-fire soils (area affected by a fire ∼12 years ago and currently heavily invaded by A. longifolia). The exotic benefited more from post-fire than from undisturbed soil biota, particularly from those associated with natives. Natives did not experience detrimental effects with invasive-associated soil biota. Our results show that fire disturbance affected the functional interactions between soil biota and plants that may benefit more the exotic than some native species. Disturbance may open a window of opportunity that promotes invader success by altering soil enemy and mutualistic impacts.

Conspecific and heterospecific plant–soil feedbacks influence survivorship and growth of temperate tree seedlings

Summary 1. The Janzen–Connell (J–C) Model proposes that host‐specific enemies could maintain high tree species diversity by reducing seedling performance near conspecific adults. An implicit, but untested assumption of the J–C Model is that negative conspecific feedbacks would promote replacement by heterospecific seedlings. 2. In a glasshouse experiment, we tested plant–soil feedbacks as a J–C mechanism in four temperate tree species. We assessed effects of conspecific‐ relative to heterospecific‐cultured soil extracts on seedling survival, total mass and performance for each focal species. To test the implicit assumption of replacement by heterospecific seedlings, we also compared relative performance of conspecific versus heterospecific seedlings grown with soil extract cultured by a particular tree species. We also tested whether soil microbes caused these plant–soil feedbacks and whether low irradiance increased seedling vulnerability to pathogens. 3. When grown with conspecific versus heterospecific soil extract, Acer rubrum mass decreased, Quercus rubra mass increased and Fraxinus americana increased survival. Conspecific extract reduced Acer saccharum mass in low light but increased it in high light. To integrate survival and growth, we examined seedling performance [(mean total mass × mean survival time)/(days of experiment)] at low and high light. In conspecific versus heterospecific soil extract, seedling performance was lower in two, higher in four and neutral in 18 of 24 cases, suggesting no advantage to dispersing away from conspecifics. Based on relative seedling performance within a soil extract, conspecific seedlings were disadvantaged in two, favoured in three and neutral in 19 of 24 cases relative to heterospecific seedlings. 4. Species pairwise interactions of soil modification and seedling performance were chemically mediated, occurring regardless of sterilization. Microbes lacked host specificity and reduced performance regardless of extract source. Additionally, microbial factors reduced seedling performance for Q. rubra regardless of light availability, and for A. rubrum and F. americana only in high light. 5. Synthesis. These chemical‐mediated plant–soil feedbacks probably influence community dynamics, but are inconsistent with the J–C Model. Even when a species’ seedlings responded more negatively to conspecific than heterospecific soil, heterospecific seedlings were not necessarily favoured in that species’ soil, precluding heterospecific replacement as an explanation for coexistence.

Conspecific plant–soil feedbacks reduce survivorship and growth of tropical tree seedlings

Summary 1. The Janzen–Connell (J–C) Model proposes that host‐specific enemies maintain high tree species diversity by reducing seedling performance near conspecific adults and promoting replacement by heterospecific seedlings. Support for this model often comes from decreased performance for a species at near versus far distances from conspecific adults. However, the relative success of conspecific versus heterospecific seedlings recruiting under a given tree species is a critical, but untested, component of the J–C Model. 2. In a shade‐house experiment, we tested plant–soil feedbacks as a J–C mechanism in six tropical tree species. We assessed effects of conspecific versus heterospecific cultured soil extracts on seedling performance for each species, and we compared performance of conspecific versus heterospecific seedlings grown with soil extract cultured by a particular tree species. Additionally, we tested whether soil microbes were creating these plant–soil feedbacks and whether low light increased species vulnerability to pathogens. 3. Among 30 potential comparisons of survival and mass for seedlings grown in conspecific versus heterospecific soil extracts, survival decreased in seven and increased in two, whereas mass decreased in 13 and increased in 1. To integrate survival and growth, we also examined seedling performance [(mean total mass × mean survival time)/(days of experiment)], which was lower in 16 and higher in 2 of 30 comparisons between seedlings grown with soil extract cultured by conspecific versus heterospecific individuals. Based on performance within a soil extract, conspecific seedlings were disadvantaged in 15 and favoured in 7 of 30 cases relative to heterospecific seedlings. 4. Species pairwise interactions of soil modification and seedling performance occurred regardless of sterilization, suggesting chemical mediation. Microbes lacked host‐specificity and reduced performance regardless of extract source and irradiance. 5. Synthesis. These results, along with parallel research in temperate forests, suggest that plant–soil feedbacks are an important component of seedling dynamics in both ecosystems. However, negative conspecific feedbacks were more prevalent in tropical than temperate species. Thus, negative plant–soil feedbacks appear to facilitate species coexistence via negative distance‐dependent processes in tropical but not temperate forests, but the feedbacks were mediated through chemical effects rather than through natural enemies as expected under the J–C Model.

Plant-soil feedback of native and range-expanding plant species is insensitive to temperature.

Temperature change affects many aboveground and belowground ecosystem processes. Here we investigate the effect of a 5°C temperature increase on plant–soil feedback. We compare plant species from a temperate climate region with immigrant plants that originate from warmer regions and have recently shifted their range polewards. We tested whether the magnitude of plant–soil feedback is affected by ambient temperature and whether the effect of temperature differs between these groups of plant species. Six European/Eurasian plant species that recently colonized the Netherlands (non-natives), and six related species (natives) from the Netherlands were selected. Plant–soil feedback of these species was determined by comparing performance in conspecific and heterospecific soils. In order to test the effect of temperature on these plant–soil feedback interactions, the experiments were performed at two greenhouse temperatures of 20/15°C and 25/20°C, respectively. Inoculation with unconditioned soil had the same effect on natives and non-natives. However, the effect of conspecific conditioned soil was negative compared to heterospecific soil for natives, but was positive for non-natives. In both cases, plant–soil interactions were not affected by temperature. Therefore, we conclude that the temperature component of climate change does not affect the direction, or strength of plant–soil feedback, neither for native nor for non-native plant species. However, as the non-natives have a more positive soil feedback than natives, climate warming may introduce new plant species in temperate regions that have less soil-borne control of abundance.

Negative plant-soil feedbacks may limit persistence of an invasive tree due to rapid accumulation of soil pathogens.

Soil organisms influence plant species coexistence and invasion potential. Plant-soil feedbacks occur when plants change soil community composition such that interactions with that soil community in turn may positively or negatively affect the performance of conspecifics. Theories predict and studies show that invasions may be promoted by stronger negative soil feedbacks for native compared with exotic species. We present a counter-example of a successful invader with strong negative soil feedbacks apparently caused by host-specific, pathogenic soil fungi. Using a feedback experiment in pots, we investigated whether the relative strength of plant-soil feedbacks experienced by a non-native woody invader, Sapium sebiferum, differed from several native tree species by examining their performance in soils collected near conspecifics ('home soils') or heterospecifics ('away soils') in the introduced range. Sapium seedlings, but no native seedlings, had lower survival and biomass in its home soils compared with soils of other species (negative feedback'). To investigate biotic agents potentially responsible for the observed negative feedbacks, we conducted two additional experiments designed to eliminate different soil taxa ('rescue experiments'). We found that soil sterilization (pot experiment ) or soil fungicide applications (pot and field experiments) restored Sapium performance in home soil thereby eliminating the negative feedbacks we observed in the original experiment. Such negative feedbacks apparently mediated by soil fungi could have important effects on persistence of this invader by limiting Sapium seedling success in Sapium dominated forests (home soils) though their weak effects in heterospecific (away) soils suggest a weak role in limiting initial establishment.