Search

Arbuscular mycorrhizal fungi (AMF) show wide inter- and intra-specific variability in symbiotic functioning. Despite evidence for significant consequences of such variability on plant hosts and AMF responses, there is a poor understanding regarding the effects on soil properties that can serve as soil health indicators (e.g., soil aggregate stability and nutrient leaching). This study evaluated intra- and inter-specific variability of different fungal isolates on two tree species of economic and environmental interest, Malus prunifolia and Schinus terebinthifolia. Seedlings were either inoculated or not with AMF inoculum composed of 14 (for M. prunifolia) or 16 (for Schinus terebinthifolia) individual fungal isolates from four species belonging to different families. After six months in a greenhouse, we found intra-specific and inter-specific variability among AMF isolates and species with respect to plant biomass, N and P contents, proportion of macroaggregates, aggregate mean weight diameter and soil P in the leachate. AMF intra-specific variability was more evident in symbiosis with S. terebinthifolia compared with M. prunifolia. Cohen’s d Effect Size inference was used and revealed that isolates differed when plant and soil parameters were considered and that this was host-dependent. The effect of AMF isolates in reducing soil P losses depended on the host plant and correlated weakly with the abundance of external hyphae. We conclude that intra- and inter-specific variability in AMF can have an impact both on plant parameters and soil health indicators, and this should be taken into consideration when formulating inocula for agronomic or ecological applications.

Life-history traits differ substantially among arbuscular mycorrhizal (AM) fungal families, potentially affecting hyphal nutrient acquisition efficiency, host nutrition, and thereby plant health and ecosystem function. Despite these implications, AM fungal community life-history strategies and community trait diversity effects on host nutrient acquisition are poorly understood. To address this knowledge gap, we grew Sudan grass (Sorghum sudanense) with AM fungal communities representing contrasting life-history traits and trait diversity: either 1) five species in the AM family Gigasporaceae, representing competitor traits, 2) five species in the family Glomeraceae, representing ruderal traits, or 3) a mixed-family community combining all ten AM species. After 12 weeks, we measured above and below ground plant biomass and the uptake and concentration of 12 nutrients in aboveground biomass. Overall, AM fungal colonization increased host nutrition, biomass, and foliar 15nitrogen enrichment compared to the uncolonized control. We observed the largest effects between the mixed-family community and the single-family communities for plant tissue quality, especially plant phosphorus (P), and in colonization rates. The mixed community increased plant P 1.2 and 1.3 times more than Glomeraceae and Gigasporaceae communities. However, this higher P did not translate to the greatest gains in plant biomass. Between the single-family communities, the Glomeraceae community generally outperformed the Gigasporaceae community in host nutrition and plant growth, increasing plant P concentrations 1.1 times more than the Gigasporaceae community. These findings demonstrate that AM fungal community trait composition established at the family level affects plant nutrition and that AM family diversity increases colonization and plant tissue quality.

Life-history traits differ substantially among arbuscular mycorrhizal (AM) fungal families, potentially affecting hyphal nutrient acquisition efficiency, host nutrition, and thereby plant health and ecosystem function. Despite these implications, AM fungal community life-history strategies and community trait diversity effects on host nutrient acquisition are poorly understood. To address this knowledge gap, we grew sudangrass with AM fungal communities representing contrasting life-history traits and diversity: either (1) five species in the AM family Gigasporaceae, representing competitor traits, (2) five Glomerales species, representing ruderal traits, or (3) a mixed-trait community combining all ten AM fungal species. After 12 weeks, we measured above and belowground plant biomass and aboveground nutrient uptake and concentration. Overall, AM fungal colonization increased host nutrition, biomass, and foliar δ

The increasing global demand for sustainably-produced crops has led to a renewed interest in exploiting unprocessed rocks as soil amendments and fertilizers. Carbonatite rocks are of particular relevance because of their rapid weathering rates and diverse nutrient contents. However, there are insufficient data to support or refute their efficacy and to understand their mechanism(s) of action. Here, the effects of a carbonatite on two crops were assessed and compared to those of calcitic lime. Wheat and pea were repeatedly grown under a low-nutrient regime under greenhouse conditions and their development, biomass, and shoot nutrient content were measured. The effect of the carbonatite on soil CO2 evolution was also tested for wheat. Wheat grown with carbonatite produced 40% more shoot biomass and 50% more root biomass than plants grown with lime. There was a sharp reduction in specific root length (SRL), consistent with approximately 60% increases in shoot contents of N, P, K, and Mn. These effects were smaller for pea. For wheat, CO2 from the soil was 70% greater with lime than with carbonatite. We conclude that carbonatites can provide benefits to plants beyond serving as liming agents. In addition, root architecture and SRL appear to be useful traits for predicting plant responsiveness to carbonatite addition.

PURPOSE Mycorrhizal interactions can drive plant productivity, diversity, and ecosystem function; however, gaps remain in our understanding of interactions among plants and different mycorrhizal types. Species in the Pinaceae primarily associate with ectomycorrhizal (ECM) fungi; however, some species can be colonized by arbuscular mycorrhizal (AM) fungi as rudimentary hosts. Interactions between plants and mycorrhizal fungi are expected to change along the mutualism-parasitism spectrum with changes in resource availability; however, the impacts of AM fungi on rudimentary hosts under different resource conditions are unknown. METHODS In this study, we assessed the individual and interactive effects of ECM and AM inoculation on Pinus strobus seedlings under factorial combinations of low, medium, or high nitrogen (N) and phosphorus (P) supply. RESULTS No AM colonization was observed at the end of the experiment; however, seedlings inoculated with AM fungi showed significantly reduced growth. AM inoculation also had the greatest effect on P. strobus tissue nutrient concentrations under low N fertilization including increased P and reduced Mn and N:P ratio. ECM colonization benefited P. strobus growth and P uptake, especially under low P availability, but ECM colonization rate itself was limited by low P. ECM colonization also improved seedling regulation of N:P ratio near optimum compared to uncolonized seedlings. CONCLUSION We conclude that the effects of ECM and AM inoculation on P. strobus are context dependent, which may have important implications for regeneration and early growth of P. strobus in natural and managed forests.

Soil microbiomes could play a major role in ecosystem responses to escalating anthropogenic global change. However, we currently have a poor understanding of how soil microbes will respond to interacting global change factors and if responses will be mediated by changes in plant community structure. We used a field experiment to assess changes in soil fungal and bacterial communities in response to plant invasion, experimental drought, and their combination. In addition, we evaluated the relative importance of direct versus indirect pathways of invasion and drought through changes in associated plant communities with structural equation models. We found that fungal communities were interactively structured by invasion and drought, where fungal richness was lowest with invasion under ambient conditions but highest with invasion under drought conditions. Bacterial richness was lower under drought but unaffected by invasion. Changes in the plant community, including lower plant richness and higher root biomass, moderated the direct effects of invasion on microbial richness. Fungal and bacterial functional groups, including pathogens, mutualists, and nitrogen metabolizers, were also influenced by plant community changes. In sum, plant communities mediated the effects of interacting global change drivers on soil microbial community structure, with significant potential consequences for community dynamics and ecosystem functions.

Plant–soil feedback (PSF) can be a major driver of plant performance in com- munities, and this concept can be used in selecting crop rotation sequences to maximize agricultural yields. Potential benefits of using PSF in this context include nutrient use optimization, pathogen reduction, and enhancement of mutualisms between crops and microbes. Yet the contributions of these com- bined mechanisms are poorly understood. Here we investigated the relative contributions of these mechanisms using five major crops commonly culti- vated in rotation (alfalfa, canola, maize, soybean, and wheat) under controlled conditions. We trained soil by growing each of the five crops in a “training phase,” and then reciprocally planted the five crops in the trained soils in a “feedback phase.” To tease out soil biota from nutrient effects, we established three treatments: “control” (trained unsterilized soil used in the feedback phases), “biota” (sterilized soil in the feedback phase inoculated with soil biota from the control treatment after the training phase), and “nutrient” (sterilized soils in both phases). Plant–soil feedback for each crop was calculated by com- paring the total biomass of each crop grown in soils trained by each of the four other crops (i.e., in rotation) against total biomass in self-trained soil (i.e., monocropping). We found that PSF values varied among crop combina- tions in all the treatments, but such variation was the greatest in the nutrient treatment. Overall, soil biota feedback tended to be lower, whereas nutrient feedback tended to be greater compared to the unsterilized control soil, suggesting that effects of antagonistic biota outweighed those of beneficial microbes in the biota treatment, and that plants optimized nutrient uptake when the soil microbiome was absent in the nutrient treatment. Furthermore, soils in the nutrient treatment trained by the legume crops (alfalfa and soy- bean) tended to provide the greatest positive feedback, emphasizing the impor- tant legacy of N2 fixers in crop rotation. Taken together, our data demonstrate how nutrients and soil biota can be integral to PSFs among crops, and that assessing PSFs under controlled conditions can serve as a basis to determine the most productive crop rotation sequences prior to field testing.

Since 2007, more people in the world live in urban than in rural areas. The development of urban areas has encroached into natural forest ecosystems, consequently increasing the ecological importance of parks and fragmented forest remnants. However, a major concern is that urban activities have rendered urban forests susceptible to non-native species incursions, making them central entry sites where non-native plant species can establish and spread. We have little understanding of what urban factors contribute to this process. Here we use data collected by citizen scientists to determine the differential impacts of spatial and urban factors on non-native plant introductions in urban forests. Using a model city, we mapped 18 urban forests within city limits, and identified all the native and non-native plants present at those sites. We then determined the relative contribution of spatial and socioeconomic variables on the richness and composition of native and non-native plant communities. We found that socioeconomic factors rather than spatial factors (e.g., urban forest area) were important modulators of overall or non-native species richness. Non-native species richness in urban forest fragments was primarily affected by residential layout, recent construction events, and nearby roads. This demonstrates that the proliferation of non-native species is inherent to urban activities and we propose that future studies replicate our approach in different cities to broaden our understanding of the spatial and social factors that modulate invasive species movement starting in urban areas.

Soil feedback is thought to be an important contributor to the success of invasive plants. Despite evidence that invasive plants change soil microbial diversity, the functional roles of microbes impacted by invasion are still unclear. This knowledge is a critical component of our understanding of ecological mechanisms of plant invasion. Mounting evidence suggests Alliaria petiolata can suppress arbuscular mycorrhizal fungi (AMF) to disrupt native plant communities in controlled laboratory and greenhouse experiments, though it is less clear if allelochemicals persist under natural field conditions. Alternatively, invasive plants may accumulate pathogens that are more harmful to competitors as predicted by the Enemy of my Enemy Hypothesis (EEH). We examined changes in functional groups of soil bacteria and fungi associated with ten naturally occurring populations of A. petiolata using amplicon sequences (16S and ITS rRNA). To relate soil microbial communities to impacts on co-occurring plants, we measured root infections and AMF colonization. We found no changes in the diversity and abundance of AMF in plants co-occurring with A. petiolata, suggesting that mycorrhizal suppression in the field may not be as critical to the invasion of A. petiolata as implied by more controlled experiments. Instead, we found changes in pathogen community composition and marginal evidence of increase in root lesions of plants growing with A. petiolata, lending support to the EEH. In addition to these impacts on plant health, changes in ectomycorrhiza, and other nutrient cycling microbes may be important forces underlying the invasion of A. petiolata and its impact on ecosystem function.

Root‐inhabiting fungal communities, including mutualists and antagonists, influence host plant performance, and can potentially shape plant community composition. However, there is uncertainty about how root‐inhabiting fungal communities are structured, and if fungal community characteristics are significant predictors of host plant abundance. In this study, we first assessed how root‐inhabiting fungal communities were structured in relation to the phylogeny and geographic origins (native vs. exotic) of their host plants in an old‐field community. In addition, we took into consideration the spatial arrangements (i.e. physical locations) of the individual host plants. We then tested if the relative abundances of pathogenic and beneficial arbuscular mycorrhizal (AM) fungi could predict host plant abundances. We found that host plant phylogeny was an important factor in structuring the whole fungal community, irrespective of host plant origin. Furthermore, the spatial arrangements of individual host plants were a strong predictor of AM fungal community structure. Host plant phylogeny and spatial arrangements appeared to similarly affect the structure of pathogenic fungal communities. No distinct differences were observed between native and exotic plant species in fungal community characteristics. The relative abundances of AM and pathogenic fungi were not significant predictors for observed abundances of their host plants. Synthesis. Host plant phylogeny and spatial arrangements can structure naturally occurring root‐inhabiting fungal communities. The absence of distinct differences in fungal community composition, including pathogens, in exotic and native plants suggests long residence times and the consequent naturalization of exotic species in the region, allowing for the establishment of similar plant–microbial interactions between native and exotic species.

Interactions between plants and soil biota can be major drivers of plant invasions. The ‘Enemy of my enemy’ hypothesis (EEH) predicts that native plants are more negatively impacted by enemies (e.g. pathogens) that accumulate and spillover from the invader’s rhizosphere than the invaders themselves, thereby facilitating the invasion. We tested EEH using Vincetoxicum rossicum, one of the most invasive plant species in Eastern North America, and a total of eight co-occuring native plant species. Specifically, we predicted that the native species would grow less in presence of soil biota associated with V. rossicum than that from uninvaded soils. Field soils were collected from four V. rossicum invaded and neighboring uninvaded areas for use in two experiments. In Experiment 1, V. rossicum and each of five native plant species were grown in a plant growth chamber for 3 months, either in presence or absence of soil biota from the invaded and uninvaded soils. We found that only one species (Solidago canadensis) supported EEH. In contrast, the legume Desmodium canadense more than doubled its biomass in response to V. rossicum -associated soil biota. In Experiment 2, four native legume species, including D. canadense, were examined for EEH in the same manner as in Experiment 1. Only one species (Lespedeza hirta) supported EEH and, again, V. rossicum-associated soil biota was advantageous to D. canadense. In summary, we found inconsistent support for the EEH between V. rossicum and native co-occurring species in Eastern North America. We conclude that the accumulation of rhizosphere enemies in native plants may not be a major factor in the invasive success of V. rossicum.

Prevention, early detection, rapid response, and prioritization are essential components of effective and cost-efficient invasive plant management. However, successfully implementing these strategies requires the ability to accurately predict the temporal and spatial dynamics of newly/recently detected nonnative species. Why some nonnative species become invasive and the source of variation in lag time between arrival and the onset of invasive expansion are poorly understood. One tool to fill these knowledge gaps is the “invasion curve,” which tracks nonnative species abundance (i.e., area invaded) over time after arrival in a new area. Since invasive species curves rely primarily on records from herbarium collections, we propose that these collections can be used as a springboard to develop a standardized approach to building invasion curves. This would allow researchers to compare the trajectories of nonnative species, improving risk assessment and our ability to recognize potential invasive species and factors contributing to both invasibility and invasiveness. While there have been admirable efforts to produce invasion curves, several barriers exist to their reliable production and standardization. In this paper, we explore the challenges related to the efficient production of these curves for plants using herbarium data and suggest ways in which progress could occur. It is our hope that this will better position herbaria and researchers to aid natural resource managers to prioritize needs, make effective management decisions, and develop targeted prevention and monitoring programs by taking advantage of lag times to implement timely responses.

Biofertilizers are a large part of the global agricultural economy. Recently, there has been an increase in the number of companies producing fungal inoculants. Whether these inoculants are useful is not clear; they are difficult to monitor in the field. The unintended consequences of inoculants in natural systems is not known, but if invasive, they may pose a threat to soil and plant biodiversity and ecosystem functioning. A plain language summary is available for this article.

That arbuscular mycorrhizal (AM) fungi covary with plant communities is clear, and many papers report nonrandom associations between symbiotic partners. However, these studies do not test the causal relationship, or 'codependency', whereby the composition of one guild affects the composition of the other. Here we outline underlying requirements for codependency, compare important drivers for both plant and AM fungal communities, and assess how host preference - a pre-requisite for codependency - changes across spatiotemporal scales and taxonomic resolution for both plants and AM fungi. We find few examples in the literature designed to test for codependency and those that do have been conducted within plots or mesocosms. Also, while plants and AM fungi respond similarly to coarse environmental filters, most variation remains unexplained, with host identity explaining less than 30% of the variation in AM fungal communities. These results combined question the likelihood of predictable co-occurrence, and therefore evolution of codependency, between plant and AM fungal taxa across locations. We argue that codependency is most likely to occur in homogeneous environments where specific plant - AM fungal pairings have functional consequences for the symbiosis. We end by outlining critical aspects to consider moving forward.

Legumes can interact simultaneously with multiple microbial partners in symbiosis, including arbuscular mycorrhizal fungi (AMF), N2-fixing bacteria, and nodule-associated bacteria. However, our understanding of their functional diversity and interactions remains limited. The objective of this study was to evaluate individual and combined effects of these three symbioses on the abundance and function of the symbionts, including the growth, nitrogen content, nodulation and root traits of Mimosa scabrella (Bracatinga), a common leguminous tree in South America. We grew seedlings in a growth chamber for 90 days using sterile soil inoculated with all combinations of AMF, N2 fixing and nodule-associated bacteria. We found that the tripartite symbiosis formed by host, AMF and N2 fixing bacteria increased shoot biomass 3.7x and N content 5.2x relative to non-inoculated controls. This response was 71% greater than the sum of the respective individual treatments, confirming for the first time in M. scabrella a synergistic effect of such dual inoculation. In contrast, the presence of nodule-associated bacteria in a tetrapartite symbiosis resulted in a 57.7% reduction in the number of nodules in any treatment where N2 fixing bacteria were present. Concurrently, total AM root colonization decreased by approximately 50% in the tetrapartite compared to the tripartite symbiosis. We conclude that the tripartite symbiosis formed by M. scabrella, N2 fixing bacteria, and AMF can act synergistically in promoting plant biomass and N2 fixation. However, nodule-associated bacteria can act “opportunistically”, causing a detrimental effect on the tripartite mutualism. Our findings highlight the functional complexity of multipartite symbioses and how interactions among partners can determine biological processes and outcomes.

Although arbuscular mycorrhizal (AM) fungi are obligate symbionts that can influence plant growth, the magnitude and direction of these effects are highly variable within fungal genera and even among isolates within species, as well as among plant taxa. To determine whether variability in AM fungal morphology and growth is correlated with AM fungal effects on plant growth, we established a common garden experiment with 56 AM fungal isolates comprising 17 genera and six families growing with three plant host species. Arbuscular mycorrhizal fungal morphology and growth was highly conserved among isolates of the same species and among species within a family. By contrast, plant growth response to fungal inoculation was highly variable, with the majority of variation occurring among different isolates of the same AM fungal species. Our findings show that host performance cannot be predicted from AM fungal morphology and growth traits. Divergent effects on plant growth among isolates within an AM fungal species may be caused by coevolution between co-occurring fungal and plant populations.

Summary In North America, herbicides are commonly used to control non-native invasive plants on public wildlands. Little is known about the magnitude, efficacy and financial costs of this practice, although this information is crucial for policymakers, researchers, land managers, pesticide producers and the general public. In Canada and Mexico, herbicide usage data have not been tracked by agencies. In the USA, data archiving has been implemented by federal land managing agencies. However, while area sprayed and amounts of herbicides have been documented to varying degrees, efficacy and financial costs have not been recorded in a standardized and consistent manner and data publication has been insufficient. Based on requested data, we estimate that in the USA, half a million hectares of public wildlands were sprayed with herbicides in 2010, representing 201 tonnes. Although non-selective, glyphosate was the most commonly used active ingredient. Synthesis and applications. Increasing efforts by land management agencies to collect and share herbicide usage data is a key step towards narrowing the knowledge gap on herbicide usage in invasive non-native plant management on public wildlands. Land managers and policymakers in particular would benefit from an enhanced flow of information on efficacy, costs and effects of herbicides.

Bracatinga (Mimosa scabrella Benth.) is a leguminous tree native to southern Brazil with high economic potential as a source of timber and biomass. Little is known about the diversity of bacteria in the root nodules of this species and how this diversity is associated with N2 fixation efficiency. We isolated 288 bacterial colonies from root nodules collected from M. scabrella in 61 locations across its native range. Strains were first characterized according to morphological traits and 16S rRNA sequencing and we then selected twenty-eight belonging to known nodulating genera for testing N2 fixation effectiveness. We found that M. scabrella associated with several N2 fixing and endophytic bacteria. Strains closely related to Burkholderia nodosa were the most common N2 fixing bacteria and were capable of providing all N required by the host. Cupriavidus was found nodulating M. scabrella, however, only forming non-fixing nodules. Endophytic bacteria detected in the nodules corresponded to the genera Pseudomonas, Pantoea, and, for the first time we found Paenibacillus, Brevibacillus, Serratia and Arthrobacter. Our study shows both high bacterial diversity and variability in N2 fixing effectiveness even between closely related Burkholderia strains, indicating that careful consideration of N2 fixing bacterial diversity is important to maximize the use of M. scabrella as a natural resource.

Rock fertilizers are geological resources used in agriculture for their nutrient content, but slow weathering rates hinder their effectiveness. Carbonatites are igneous rocks made mostly of carbonate minerals with a relatively high weathering rate and often containing nutrient-bearing accessory minerals (e.g., apatite and biotite). Despite evidence supporting their potential as rock fertilizers, a comprehensive review of such data is missing in the literature. Furthermore, when studies on agricultural uses of carbonatites exist, they typically centre on applied research aspects (i.e., “does it work?“) rather than on basic research aspects (i.e., “how does it work?“). Here we evaluate the applicability of carbonatites in agriculture taking into consideration the factors that affect mineral weathering and plant nutrient uptake. While there are sufficient data to conclude that carbonatites can be a source of many plant nutrients, their effectiveness depends on the interactions of many components (e.g., soils, plants, microorganisms). To develop best management practices around carbonatites used in agriculture, it is essential to understand these interactions.

Urban forests are more vulnerable to exotic species invasions than natural forests and are often a pathway for exotic invasions into natural areas. Investigating the mechanisms responsible for species coexistence in urban ecosystems is important to prevent forest invasions and conserve native biodiversity. In this experiment, we studied seedling recruitment for two exotic invasive (Acer platanoides and Rhamnus cathartica) and two native tree species (Acer saccharum and Betula papyrifera) in two urban forests. We measured the effects of distance from a mature tree on the growth of conspecific seedlings and their belowground interactions (mutualisms and pathogens). We expected that native seedlings growing in close proximity to a mature conspecific tree would more likely be damaged by co-specific pathogens than those growing further away. In contrast, considering that exotic invaders have not coevolved with the local soil pathogens, distance from the adult conspecific tree would not affect their seedlings. We collected undisturbed soil cores at five incremental distances from each adult tree and grew conspecific seeds in these cores. After three months of growth, we measured plant biomass, mycorrhizal root colonization and root lesions. We found that biomass increased with distance from the mature conspecific tree only for A. platanoides and no distance dependent signal was detected for other response variables. Our results show that distance from a conspecific mature tree may not determine exotic species invasibility in an urban forest and that, instead, this may contribute to promote native and invasive species coexistence in urban forest systems.

Non-native invasive plants can associate with and accumulate microbes in their introduced range, which may transfer to native plants and potentially exert pathogenic effects. In these cases, the invasive plant can act as a pathogen reservoir. However, little is known about this as a possible plant invasion mechanism. We isolated fungi from the roots of 32 Vincetoxicum rossicum (Apocynaceae) plants collected across Ontario, Canada, where it is highly invasive. The growth effects of known pathogenic fungi were tested on V. rossicum and two commonly co-occurring native plants, Asclepias syriaca (Apocynaceae) and Solidago canadensis (Asteraceae). We hypothesised that these fungi would reduce the growth of native plants more than that of V. rossicum. Of the18 fungal taxa isolated from V. rossicum roots, 15 were previously reported as pathogens on other plants and 16 represent new records on this plant. Four of the seven fungi tested on V. rossicum increased its total biomass and/or root-shoot ratio compared to uninoculated controls. When inoculated individually, three of these fungi had neutral growth effects on the native plants. However, when inoculated together, Cadophora sp., Ilyonectria radicicola, and Macrophomina phaseolina reduced the total biomass of S. canadensis. These results support that at least in some cases non-native invaders may benefit from associating with soil microbes that can function as pathogens on native plants. These differential functional outcomes between non-native invasive and native plants may be important for mediating plant community structure and the persistence of invasive plants.

Exotic invasive plants can show strong plantesoil feedback responses, but little is known about time scales for significant changes in soil microbial communities to occur after invasion. Previous work has suggested that plant invasions can modify arbuscular mycorrhizal (AM) fungal community structure. However, there is a lack of understanding about how long it takes for these changes to develop. To test this we investigated temporal changes in AM fungal communities colonising the invasive plant Vincetoxicum rossicum (Apocynaceae). We hypothesised that AM fungal community structure would change in a particular direction during the invasion process. We collected soil from two sites with a long history of invasion by this plant, with each site having paired invaded and uninvaded plots. Soil from these plots was used in a glasshouse experiment to characterise AM fungal community structure in the roots of V. rossicum at different times throughout a simulated growing season. AM fungal community structure differed between invaded and uninvaded plots. However, contrasting with our hypothesis, AM fungal communities colonising V. rossicum growing in soil from uninvaded plots did not change towards those in plants growing in previously invaded soil. Our data suggest that changes to AM fungal communities in the presence of V. rossicum require longer than the first growing season after establishment to develop. © 2015 Elsevier Masson SAS. All rights reserved.

Local adaptation, the differential success of genotypes in their native versus foreign environments, can influence ecological and evolutionary processes, yet its importance is difficult to estimate because it has not been widely studied, particularly in the context of interspecific interactions. Interactions between ectomycorrhizal (EM) fungi and their host plants could serve as model system for investigations of local adaptation because they are widespread and affect plant responses to both biotic and abiotic selection pressures. Furthermore, because EM fungi cycle nutrients and mediate energy flow into food webs, their local adaptation may be critical in sustaining ecological function. Despite their ecological importance and an extensive literature on their relationships with plants, the vast majority of experiments on EM symbioses fail to report critical information needed to assess local adaptation: the geographic origin of the plant, fungal inocula, and soil substrate used in the experiment. These omissions limit the utility of such studies and restrict our understanding of EM ecology and evolution. Here, we illustrate the potential importance of local adaptation in EM relationships and call for consistent reporting of the geographic origin of plant, soil, and fungi as an important step towards a better understanding of the ecology and evolution of EM symbioses.

Dog-strangling vine (Vincetoxicum rossicum, Apocynaceae) is an exotic invasive plant from Europe that is increasingly invasive in southern Ontario, Canada. The species is highly adaptive to light, soil moisture, and temperature. V. rossicum grows on calcareous soils in its native range. However, although this is currently consistent in its invaded range, its potential to spread to northern Ontario, with more acidic soils, is currently unknown. We tested the ability of V. rossicum to grow in soil from northern Ontario in comparison with southern Ontario soil. We also grew Solidago canadensis (Asteraceae), an ubiquitous and abundant native species that co-occurs with V. rossicum. We grew both species in soil collected from 26 sites in northern and southern Ontario. Soils were then used in a feedback study with both species to determine whether V. rossicum’s invasion success could be explained, at least partially, by positive plant–soil feedback. We found that biomass of V. rossicum was not significantly different between soil types but S. canadensis had lower biomass in the northern than in southern Ontario soil. Soil feedback was neutral for both species, regardless of soil type. We conclude that the spread of V. rossicum into areas of central/northern Ontario will not be limited by soil type and that plant–soil feedback may not be an important factor driving V. rossicum’s invasion.

There is an urgent need for novel agronomic improvements capable of boosting crop yields while alleviating environmental impacts. One such approach is the use of optimized crop rotations. However, a set of measurements that can serve as guiding principles for the design of crop rotations is lacking. Crop rotations take advantage of niche complementarity, enabling the optimization of nutrient use and the reduction of pests and specialist pathogen loads. However, despite the recognized importance of plant-soil microbial interactions and feedbacks for crop yield and soil health, this is ignored in the selection and management of crops for rotation systems. We review the literature and propose criteria for the design of crop rotations focusing on the roles of soil biota and feedback on crop productivity and soil health. We consider that identifying specific key organisms or consortia capable of influencing plant productivity is more important as a predictor of soil health and crop productivity than assessing the overall soil microbial diversity per se. As such, we propose that setting up soil feedback studies and applying genetic sequencing tools towards the development of soil biotic community databases has a strong potential to enable the establishment of improved soil health indicators for optimized crop rotations.

Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp. (Oleaceae), in North America. This study investigated the timing of reproductive development in female beetles and the influence of female reproductive maturity on attraction to host volatiles. Based on dissections of females of increasing age, females with access to males for mating, and thus presumed mated, developed mature eggs only after 18–24 days. In contrast, female beetles reared without access to males, and thus unmated, did not develop mature eggs at any age. Chemical analysis of cuticular hydrocarbons detected the contact sex pheromone, 9-methyl-pentacosane, in cohorts of females which were 8–9 days old and older, supporting previous research that this compound signals sexual maturity to males. Results from field-trapping bioassays demonstrated that stage of female reproductive maturity influenced their attraction to host volatiles: females caught on traps baited with foliar volatiles contained eggs and ovarioles that were significantly less developed than those on traps baited with bark sesquiterpenes. However, our results revealed that females with immature stages of ovarioles and undeveloped eggs, such as those observed in unmated females, were rarely ever caught on traps baited with either of the host volatile lures. Further research on host compounds attractive to immature females is critical for early detection and possible control of A. planipennis populations during the extended pre-oviposition period.

Little is known about the adaptive capacity of arbuscular mycorrhizal (AM) fungi to novel hosts. Here we assessed the possibility of two heterospecific AM fungal isolates to adaptively change, in terms of host biomass response, as a function of host plant identity, over the course of a growing season. First, we produced pure inocula of Rhizophagus clarus and Rhizophagus intraradices, each starting from a single spore. Second, we “trained” each isolate individually in a community with two plants, sudangrass (Sorgum bicolour subsp. drummondii) and leek (Aliium ampeloprasum var. porrum), using a dual-compartment system to allow the establishment of a common mycorrhizal network between the two hosts. Third, we conducted a greenhouse experiment to reciprocally test each “trained” clone, obtained from each compartment, either with the same (home), or the other host (away) under two contrasting phosphorus levels. Overall, results did not support adaptive responses of the AM fungi to their hosts (i.e., greater host biomass under “home” relative to “away” conditions), but the opposite (i.e., greater host biomass under “away” relative to “home” conditions) was more frequently observed. These changes in AM fungal symbiotic functioning open the possibility for relatively rapid genetic change of arbuscular mycorrhizal fungi in response to new hosts, which represents one step forward from in vitro experiments.

Mycorrhizal fungi form interconnecting plant networks in soil through which nutrients (e.g., nitrogen and phosphorus) and energy [i.e., carbon (C)] are pumped into and from plants, respectively. Mycorrhizas thus represent a direct C source from plants into the soil food web. In addition, they indirectly affect the soil food web through effects on litter quality. Preferential access to simple sugars from host plants enable mycorrhizal fungi to specialize in becoming highly competitive in nutrient acquisition relative to saprotrophic organisms that acquire energy from complex organic compounds. This results in multitrophic feedback loops that affect plant diversity, net primary productivity, and soil organic-matter decomposition. This chapter provides an overview of bottom-up and potential top-down controls of the soil food web that specifically involve mycorrhizas. We focus on the mechanisms driving feedback loops in the soil food web, highlighting the most recent advances in our understanding of such processes and pointing out the way forward.

The ecological interactions that occur in and with soil are of consequence in many ecosystems on the planet. These interactions provide numerous essential ecosystem services, and the sustainable management of soils has attracted increasing scientific and public attention. Although soil ecology emerged as an independent field of research many decades ago, and we have gained important insights into the functioning of soils, there still are fundamental aspects that need to be better understood to ensure that the ecosystem services that soils provide are not lost and that soils can be used in a sustainable way. In this perspectives paper, we highlight some of the major knowledge gaps that should be prioritized in soil ecological research. These research priorities were compiled based on an online survey of 32 editors of Pedobiologia – Journal of Soil Ecology. These editors work at universities and research centers in Europe, North America, Asia, and Australia. The questions were categorized into four themes: (1) soil biodiversity and biogeography, (2) interactions and the functioning of ecosystems, (3) global change and soil management, and (4) new directions. The respondents identified priorities that may be achievable in the near future, as well as several that are currently achievable but remain open. While some of the identified barriers to progress were technological in nature, many respondents cited a need for substantial leadership and goodwill among members of the soil ecology research community, including the need for multi-institutional partnerships, and had substantial concerns regarding the loss of taxonomic expertise. nonPeerReviewed

Background Local adaptation, the differential success of genotypes in their native versus foreign environment, arises from various evolutionary processes, but the importance of concurrent abiotic and biotic factors as drivers of local adaptation has only recently been investigated. Local adaptation to biotic interactions may be particularly important for plants, as they associate with microbial symbionts that can significantly affect their fitness and may enable rapid evolution. The arbuscular mycorrhizal (AM) symbiosis is ideal for investigations of local adaptation because it is globally widespread among most plant taxa and can significantly affect plant growth and fitness. Using meta-analysis on 1170 studies (from 139 papers), we investigated the potential for local adaptation to shape plant growth responses to arbuscular mycorrhizal inoculation. Results The magnitude and direction for mean effect size of mycorrhizal inoculation on host biomass depended on the geographic origin of the soil and symbiotic partners. Sympatric combinations of plants, AM fungi, and soil yielded large increases in host biomass compared to when all three components were allopatric. The origin of either the fungi or the plant relative to the soil was important for explaining the effect of AM inoculation on plant biomass. If plant and soil were sympatric but allopatric to the fungus, the positive effect of AM inoculation was much greater than when all three components were allopatric, suggesting potential local adaptation of the plant to the soil; however, if fungus and soil were sympatric (but allopatric to the plant) the effect of AM inoculation was indistinct from that of any allopatric combinations, indicating maladaptation of the fungus to the soil. Conclusions This study underscores the potential to detect local adaptation for mycorrhizal relationships across a broad swath of the literature. Geographic origin of plants relative to the origin of AM fungal communities and soil is important for describing the effect of mycorrhizal inoculation on plant biomass, suggesting that local adaptation represents a powerful factor for the establishment of novel combinations of fungi, plants, and soils. These results highlight the need for subsequent investigations of local adaptation in the mycorrhizal symbiosis and emphasize the importance of routinely considering the origin of plant, soil, and fungal components. Electronic supplementary material The online version of this article (doi:10.1186/s12862-016-0698-9) contains supplementary material, which is available to authorized users.

This paper reports, for the first time, a study of dioxin emissions from 10 siderurgies and metallurgies, secondary copper, aluminum and lead metallurgies, in Portugal. The study reports the emission factors and total emission amounts of PCDD/Fs, dioxin-like PCBs and hexachlorobenzene (HCB). The congener patterns were characterized and are discussed. The results showed that the total amount of PCDFs is higher than PCDDs in flue gas of each industrial unit. The toxic equivalent emission factors of pollutants emitted are 3098-3338 ngI-TEQt(-1) for PCDD/Fs and 597-659 ng I-TEQt(-1) for dioxin-like PCBs in siderurgies production (total estimated emission amounts released to atmosphere of 3.9-4.5 g I-TEQyr(-1)), 50-152 ng I-TEQt(-1) for PCDD/Fs and 24-121 ng I-TEQt(-1) for dioxin-like PCBs in ferrous foundries production (total estimated emission amounts released to atmosphere of 0.0010-0.0016 g I-TEQyr(-1)) and 5.8-5715 ng I-TEQt(-1) for PCDD/Fs and 0.49-259 ng I-TEQt(-1) for dioxin-like PCBs in non-ferrous foundries production (total estimated emission amounts released to atmosphere of 0.00014-0.12 g I-TEQyr(-1)). The HCB emission from siderurgies production is 0.94-3.2 mg t(-1) (total estimated emission amounts released 0.94-3.8 g yr(-1)), being much smaller, residual, in the emissions of the other types of plants (0.0012-0.026 mg t(-1) production and total estimated emission amounts released to atmosphere of 0.013-1.7 mg yr(-1)).

Summary The boreal forest is the world’s largest terrestrial biome, covering all continents in the northern hemisphere. Much research has focused on the effects of forest management and climate change on biodiversity and ecosystem level processes of the boreal forest. However, even though climate change and the increasing rate of resource exploitation are likely to intensify the arrival and establishment of exotic species with the potential to become invasive, the boreal forest continues to be viewed as inhospitable to incoming species and we have little understanding of its invasive species status. We reviewed the literature and compiled information on the current status of invasive species across all taxa present in the North American boreal forest. We found that an increasing number of exotic plants, insects, earthworms, slugs and pathogens are establishing in the boreal forest. Research is scarce and their ecological effects are poorly understood. However, given that some of the reported species represent a major driver of change in many ecosystems globally, we expect that this review will provide direction for invasive species research as well as preventative measures aimed at better understanding and conserving Earth’s largest terrestrial biome.

Summary 1. Arbuscular mycorrhizal fungi (AMF) have been proposed as a mechanism to reduce nutrient inputs in agriculture, thereby reducing costs and increasing environmental sustainability. However, before this can be achieved, we need to gain a better understanding of the importance of the prolonged selective pressures acting on indigenous AMF communities. 2. Much research concentrates on short-term ecological soil · plant · AMF interactions. However, we have little understanding of how long-term manipulations of abiotic conditions can be strong selection agents for AMF communities. Here, we ask how the long-term management of soil fertility and fertilizer use can influence the AM symbiosis. More specifically, we investigated whether 70 years of consistently imposed nutrient limitations affected the structure and symbiotic functioning of indigenous AMF communities. 3. Using the long-term Static Nutrient Deficiency Experiment carried out since 1937 in Thyrow, Germany, with and without nitrogen (N) and phosphorus (P) additions, we addressed the following questions: (i) Do different soil fertilizer treatments affect the overall abundance and diversity of indigenous AMF in an agricultural field; and (ii) Does the depletion of a nutrient select for an enhanced AMF ability to supply the deficient nutrient? 4. We assessed AMF spore diversity in the field and established a common garden experiment where soil nutrient treatments were calibrated against those in the long-term field experiment. For each soil nutrient treatment, we compared the growth responses of barley plants to the indigenous AMF communities isolated from the different soil fertilization treatments in the field. 5. We found that the long-term use of specific soil fertilization treatments altered the effects of the AMF symbiosis on plant and fungal growth. Consistent with the optimal foraging theory, AMF from N- or P-deficient soils grew larger but reduced plant growth more in those conditions relative to AMF isolated from non-deficient soils. This could result from both community-level changes and ⁄ or adaptations within species. 6. Thus, we propose that the ongoing agronomic management of abiotic selective pressures such as soil fertility needs to be considered as a strong determinant of AMF symbiotic functioning.

a b s t r a c t Soil environmental factors affect the structure of arbuscular mycorrhizal (AM) fungal communities present in soil. However, it is not understood to which degree management practices such as tillage lead to dissimilarities between intra- and extraradical AM fungal communities. This study aims to assess the influence of two different soil management practices (conventional tillage and no-till) on the diversity of AMF communities, both in rhizosphere soil and inside corn roots. We hypothesized that under no-till, roots are colonized as they grow through the undisturbed fungal mycelia left from the previous crop whereas under conventional tillage they are colonized by those propagules that survived disturbance and can re-establish in their new relocated and mixed environment. We predicted that the degree of similarity of AM fungal communities inside versus outside the roots would be greater under no-till than under tillage. Using terminal restriction fragment length polymorphism (T-RFLP) and denaturing gradi- ent gel electrophoresis we observed a different AM fungal community present in roots under no-till than under conventional tillage. Moreover, the communities present in the rhizosphere soil were different than in the roots of the corn plants. These results suggest that soil management does alter the diversity of AM fungal communities associated with corn roots and that plants influence the structure of the AMF community colonizing their roots. Sequencing results indicated that the majority of AMF species found in this agricultural soil was Glomus spp. However, further work is required to determine the extent to which AM fungal genotypic alterations by soil management influences competitive relationships. © 2011 Elsevier GmbH. All rights reserved.

Garlic mustard (Alliaria petiolata) is a Eurasian native that has become invasive in North America. The invasive success of A. petiolata has been partly attributed to its production of allelopathic compounds that can limit the growth of arbuscular mycorrhizal fungi (AMF). Although such effects are well known, specific effects on the richness and community composition of AMF associated with woody species have not been explored. We collected sugar maple (Acer saccharum) seedlings from eight natural forest sites in Ohio and Massachusetts, containing areas either invaded or uninvaded by A. petiolata. We measured AMF root colonization of seedlings, isolated DNA from the roots and performed PCR-TRFLP analysis to assess the richness and community composition of AMF. As expected, we found reduced AMF colonization in A. petiolata invaded patches. A. petiolata did not alter the detected TRF richness, but was associated with significant changes in the composition of AMF communities in half of the sites monitored in each region. Our results suggest that although AMF colonization was reduced in A. petiolata patches, many indigenous AMF communities include AMF that are tolerant to allelopathic effects of A. petiolata.

Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with most vascular plants including some gymnosperm species. Although species in the gymnosperm family Pinaceae normally develop ectomycorrhizal associations, AMF hyphae and vesicles, typical of members of the Suborder Glomineae, have been reported in the roots of some Pinaceae species. However, it is not known whether AMF belonging to various species and suborders are able to colonize roots of Pinaceae species and to what extent this influences the performance of Pinaceae seedlings. We tested in each of the Glomaceae, Acaulosporaceae and Gigasporineae AMF families two species for their ability to colonize and affect the growth of Pinus strobus (eastern white pine) in the presence or absence of an AMF host plant (Trifolium pretense—red clover). Glomus intraradices was the only AMF that colonized pine roots, predominantly in the presence of clover, forming intracellular hyphae and vesicles but not arbuscules. Colonization, however, did not relate to increased pine biomass and the overall presence of AMF, regardless of colonization abilities, resulted in a biomass reduction. This effect on pine seedling biomass was explained by the AMF family to which the AMF belonged, indicating that the effects of AMF on the non-host pine may be related to phylogeny. Acaulosporaceae species reduced pine biomass the most whereas, Gigasporineae species had the smallest effect on biomass. These preliminary results suggest that AMF may affect the soil microflora differently among AMF families in previously unsuspected ways with potential consequences for non-AMF host growth.

Introduced, non-native organisms are of global concern, because biological invasions can negatively affect local communities. Arbuscular mycorrhizal (AM) fungal communities have not been well studied in this context. AM fungi are abundant in most soils, forming symbiotic root-associations with many plant species. Commercial AM fungal inocula are increasingly spread worldwide, because of potentially beneficial effects on plant growth. In contrast, some invasive plant species, such as the non-mycorrhizal Alliaria petiolata, can negatively influence AM fungi. In a greenhouse study we examined changes in the structure of a local Canadian AM fungal community in response to inoculation by foreign AM fungi and the manipulated presence/absence of A. petiolata. We expected A. petiolata to have a stronger effect on the local AM fungal community than the addition of foreign AM fungal isolates. Molecular analyses indicated that inoculated foreign AM fungi successfully established and decreased molecular diversity of the local AM fungal community in host roots. A. petiolata did not affect molecular diversity, but reduced AM fungal growth in the greenhouse study and in a in vitro assay. Our findings suggest that both introduced plants and exotic AM fungi can have negative impacts on local AM fungi.

A considerable amount of phenotypic, genetic and symbiotic functional variability has been documented in arbuscular mycorrhizal fungi (AMF). However, little is known about whether distinct AMF ecotypes have evolved within their geographic range. We tested the hypothesis that AMF growing at temperatures closer to those prevalent within their origin would benefit their host and grow more than isolates distant from their native conditions. For each of six AMF species, we chose pairs of isolates that originated from distant areas with contrasting climates. Each isolate was grown in association with two grass species of different thermal optima at two temperature settings. Thus, we also tested whether AMF from different climatic origins were dependent on the thermal adaptation of the host plant species or to temperature per se. Although fungal growth was not directly affected by temperature, we found that AMF isolates originating from contrasting climates consistently and differentially altered plant growth. Our results suggest that AMF from contrasting climates have altered symbiotic function, thus linking an abiotic factor to ecotypic differentiation of putatively important symbionts.