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Whilst transgenerational effects (TGE) of abiotic conditions are becoming generally accepted in plants, those of biotic interactions remain largely unexplored. We therefore investigated the influence of TGE due to arbuscular mycorrhiza, the most widespread mutualistic interaction of plants with microorganisms, on clonal and sexual offspring of Fragaria vesca. We hypothesized that the ecological and evolutionary significance of TGE will vary between clonal and sexual offspring based on mycorrhizal status and phosphorus (P) availability experienced by the parent. In a two‐generation greenhouse experiment, parental plants were exposed to full‐factorial combinations of mycorrhizal status and high or low P availability. TGE on mycorrhiza establishment and plant performance were evaluated in their clonal and sexual offspring, which experienced the parental or all non‐parental environments. Consistently in both generations, mycorrhiza improved plant growth at low P availability, but had no or even negative effect at high P availability, concomitantly with decreased root colonization by the arbuscular mycorrhizal (AM) fungus. TGE due to mycorrhiza was generally stronger in sexually derived offspring, both on mycorrhiza formation and plant growth. In sexual offspring, parental mycorrhizal status was adaptive if the offspring's mycorrhizal status was of disadvantage: for mycorrhizal offspring growing in high P availability and for non‐mycorrhizal offspring at low P availability. Synthesis: Our results suggest that clonal and sexual reproduction are under different evolutionary pressures, leading to the development of stronger TGE mechanisms in response to mycorrhizal symbiosis in the latter. The complexity of the observed effects highlights the need for disentangling the mechanisms contributing to the TGE in clonal and sexual reproduction. Our study underlines the importance of considering reproductive strategies and the interplay between environmental factors and TGE in understanding the ecological and evolutionary dynamics of plant–symbiotic interactions. [ABSTRACT FROM AUTHOR]

Rhizosphere microbes play important roles in plant performance and ecosystem functioning. It is becoming increasingly clear that rhizosphere communities vary with soil properties and variation in root traits among plant species. However, less is known about whether and how variation in root traits within plant species influences the rhizosphere microbial communities.We evaluated the intraspecific root traits variation and explored their associations with bacterial and fungal communities in rhizosphere by focusing on an ectomycorrhizal tree species, that is Pinus massoniana, in 22 sites in subtropical China.The first dimension of the principal component analysis on root traits revealed evidence for the 'conservation' gradient of the root economics space. Overall, root traits explained more variation in fungal communities than in bacterial communities in the rhizosphere. Functional composition of rhizosphere microbial communities changed significantly along the 'conservation' gradient, with fast‐growing copiotrophic bacteria and symbiotic ectomycorrhizal fungi were significantly enriched on the 'acquisition' side, while slow‐growing oligotrophic bacteria were significantly enriched on the 'conservation' side of the gradient.Synthesis: Our study demonstrates that intraspecific variation in plant roots significantly influence rhizosphere microbial communities, which in turn can influence plant nutrition and therefore plant performance within the community. [ABSTRACT FROM AUTHOR]

The obligate plant symbionts belonging to Arbuscular Mycorrhizal Fungi (AMF), are ubiquitous in agricultural soils. Their aerobic nature makes them susceptible to the anoxic conditions prevailing in waterlogged environments, as encountered in wetland rice fields. This study utilized genotypic analysis to examine changes in AMF diversity in wetland rice cultivation compared to aerobic rice cultivation. High-throughput sequencing was employed to assess the composition of operational taxonomic units (OTUs) in both ecosystems. Our findings revealed that 88.8% of OTUs were shared between aerobic and wetland rice soils, with 6.1% and 5.1% being unique to aerobic and wetland cultivation, respectively. Various AMF families, including Glomeraceae, Paraglomeraceae, Acaulosporaceae, Geosiphonaceae, and Gigasporaceae, were prevalent in aerobic rice cultivation, whereas Claroideoglomeraceae and Diversisporaceae species dominated in wetland rice cultivation. The richness of Claroideoglomus and Diversispora species showed a strong correlation with soil phosphate and potassium concentrations. Moreover, Claroideoglomus exhibited significant positive associations with glomalin concentration, acid phosphatase, and other soil biochemical properties in wetland rice. Further co-occurrence network analysis identified Paraglomus brasilianum as the keystone species in both aerobic and wetland soil. These findings underscore the significance of species keystoneness in enhancing the ecological network of AMF in rice soils and shed light on the impact of anoxic conditions on AMF genetic drift in wetland rice cultivation. [ABSTRACT FROM AUTHOR]

The plant economics spectrum (PES) drives nutrient cycling through effects on soil decomposers. However, dead phytomass may remain standing or unshed (marcescent), hardly accessible to decomposers and be photodegraded. In arid zones, the significant part of marcescent phytomass can be decomposed without touching the ground. In temperate zones, photodegradation of marcescent phytomass is low but prompts important chemical changes, which affect its subsequent decomposability in the soil and alters the surrounding environment. It is unknown, however, how common marcescence is among different taxa and in which habitats, and how it is coordinated by PES traits.We sampled standing (marcescent) and lying (shed) dead phytomass from a broad spectrum of 127 herbaceous temperate species in a common garden experiment and related these parameters to PES traits, species ecological preferences and phylogeny.Nearly all species (97%) kept their phytomass marcescent. Tall species with a small leaf area and high leaf carbon had a high level of marcescence. Marcescent species also preferred sites affected by severe (but not necessarily frequent) disturbance. The degree of marcescence was considerably conserved in phylogeny.Synthesis. Marcescence extends PES trait effects on ecosystems, particularly in immature habitats, being a common but overlooked phenomenon of the temperate flora. [ABSTRACT FROM AUTHOR]

Livestock grazing is among the most intensive land‐use activities in grasslands, and can affect plant communities directly or indirectly via grazing‐induced soil legacies. Under climate change, grasslands are threatened globally by recurrent drought. However, the extent to which drought influences grazing‐induced soil legacy effects on plant biomass production and community composition remains largely unexplored.We grew five naturally co‐occurring plant species (three dominants and two subordinates) in mixed communities in a glasshouse experiment in live and sterilized soil that had or had not been subjected to 19 years of grazing; these plant communities were then exposed to a subsequent drought. We tested the treatment effects on plant community biomass, proportional above‐ground biomass of individual species, arbuscular mycorrhizal (AM) fungal root colonization, and soil nutrient availability.Under drought‐free conditions, soils from grazed plots produced significantly higher plant above‐ground and total community biomass compared to soils from ungrazed plots. In contrast, plant above‐ground and total community biomass were similar between grazed and ungrazed soils under drought conditions. Similarly, soils from grazed plots increased the proportional biomass of dominant species but decreased the proportion of subordinate species; however, the proportional biomass of dominant and subordinate species was similar between grazed and ungrazed soils under drought conditions. Soil NO3−‐N in grazed soil was significantly higher compared to ungrazed soil. Drought dramatically increased soil NO3−‐N in sterilized soil and had a more pronounced increase in grazed soil than in ungrazed soil. Arbuscular mycorrhizal fungal root colonization from grazed soil was lower compared to ungrazed soil. Drought significantly increased the soil available phosphorus concentration, as well as plant community AM fungal root colonization.Synthesis. Our study suggests that drought can neutralize positive grazing effects on plant community biomass production via altered plant–soil interactions. Also, we found that drought can alleviate the negative effects of grazing legacies on subordinate species by reducing competitiveness of dominant species. Our study provides new insights for understanding the underlying mechanisms of grazing effects on grassland productivity under climate change. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Identifying the primary controls of particulate (POM) and mineral‐associated organic matter (MAOM) content in soils is critical for determining future stocks of soil carbon (C) and nitrogen (N) across the globe. However, drivers of these soil organic matter fractions are likely to vary among ecosystems in response to climate, soil type and the composition of local biological communities.We tested how soil factors, climate and plant–fungal associations influenced the distribution and concentrations of C and N in MAOM and POM in seven temperate forests in the National Ecological Observatory Network (NEON) across the eastern United States. Samples of upper mineral horizon soil within each forest were collected in plots representing a gradient of dominant tree–mycorrhizal association, allowing us to test how plant and microbial communities influenced POM and MAOM across sites differing in climate and soil conditions.We found that concentrations of C and N in soil organic matter were primarily driven by soil mineralogy, but the relative abundance of MAOM versus POM C was strongly linked to plot‐level mycorrhizal dominance. Furthermore, the effect of dominant tree mycorrhizal type on the distribution of N among POM and MAOM fractions was sensitive to local climate: in cooler sites, an increasing proportion of ectomycorrhizal‐associated trees was associated with lower proportions of N in MAOM, but in warmer sites, we found the reverse. As an indicator of soil carbon age, we measured radiocarbon in the MAOM fraction but found that within and across sites, Δ14C was unrelated to mycorrhizal dominance, climate, or soil factors, suggesting that additional site‐specific factors may be primary determinants of long‐term SOM persistence.Synthesis. Our results indicate that while soil mineralogy primarily controls SOM C and N concentrations, the distribution of SOM among density fractions depends on the composition of vegetation and microbial communities, with these effects varying across sites with distinct climates. We also suggest that within biomes, the age of mineral‐associated soil carbon is not clearly linked to the factors that control concentrations of MAOM C and N. [ABSTRACT FROM AUTHOR]

Below‐ground microbiota play an important role in mediating environmental conditions with important consequences for plant performance. Micro‐organisms involved in plant–soil interactions may be associated with roots or bulk soil; however, the relative influence of these below‐ground microbial assemblages on plant performance is poorly known, particularly for marine plants.We separately manipulated the root and sediment microbial assemblages of the seagrass Zostera muelleri in a fully factorial experiment to determine how these assemblages determined plant response (e.g. growth) to nutrient enrichment, a major stressor in marine systems.Under ambient nutrient conditions, seagrass growth was maintained regardless of root microbial assemblage disruption. Under high nutrient stress, however, seagrasses with disrupted root microbiota had reduced growth, whereas growth was maintained in seagrasses with an intact root microbiota. Disruption of bulk‐sediment microbiota did not affect seagrass growth. Nutrient elevation was correlated with enhanced abundances of several putatively beneficial microbial taxa (e.g. sulphide‐oxidising Beggiatoaceae and denitrifying Geofilum rubicundum) associated with roots.Synthesis. Our results suggest that under ambient nutrient conditions micro‐organisms play a reduced role in influencing plant performance, but under more stressful conditions positive plant–root micro‐organism interactions strengthened. These results are among the first to experimentally determine that interactions between marine plants and the root‐associated microbiota are key drivers of seagrass performance under human‐induced environmental changes. This suggests that as in terrestrial systems, marine plant resilience depends on the stress‐mitigating functions of their root‐associated microbiota and disturbance to those plant–microbiota interactions can be deleterious for plant performance. Improving our understanding of these plant–micro‐organism interactions may be critical for understanding the functioning and resilience of threatened marine plants and developing more effective restoration strategies for them. [ABSTRACT FROM AUTHOR]

Litters of leaves and roots of different qualities occur naturally above‐ and below‐ground, respectively, where they decompose in contrasting abiotic and biotic environments. Therefore, ecosystem carbon (C) and nitrogen (N) dynamics can be strongly affected by the combination of litter position and quality. However, it is poorly understood how C versus N turnover of litters depend on the interplay among plant functional type (PFT), organs, traits and litter position.In a semi‐arid inland dune, soil surface and buried leaf litters and buried fine roots of 25 species across three PFTs (herbs, legume shrubs and nonlegume shrubs) were incubated for 3, 6, 9, 12, 18 and 24 months to investigate litter decomposition and C and N dynamics. Morphological and chemical (nutrient and NMR carbon) traits of initial litters of leaves and fine roots were determined.The litter decomposition rates (k values) of surface leaves and buried fine roots did not differ, but buried fine roots and buried leaf litter decomposed faster than surface leaf litter. Ratios of k values of surface leaves to buried leaves decreased with leaf C:N ratio. Herbs and legume shrubs decomposed faster than nonlegume shrubs for buried fine roots, but not for leaves. At given C loss, buried fine roots had higher N loss than leaf litters; legume shrubs with relatively higher N or lower C:N ratio had higher N loss than nonlegume shrubs. Stronger positive relationships between C and N losses were shown in leaves and legume shrubs than in fine roots and nonlegume shrubs respectively.Synthesis. The generality of faster N release of legume litters at given C release highlights the importance of legumes in N cycling in semi‐arid ecosystems where N is the limiting factor. The dynamics and coordination of C versus N release as a function of litter quality are modulated by litter position and PFT. These findings have important implications for the development of process‐based models on C and N cycles in the context of on‐going global change potentially altering the functional composition of plant communities and the relative quantities and qualities of above‐ground versus below‐ground litter. [ABSTRACT FROM AUTHOR]

Habitat divergence among close relatives is a common phenomenon. Studying the mechanisms behind habitat divergence is fundamental to understanding niche partitioning, species diversification, and other evolutionary processes. Recent studies found that soil microbes regulate the abundance and diversity of plant species. However, it remains unclear whether soil microbes can affect the habitat distributions of plants and drive habitat divergence. To fill in this knowledge gap, we investigated whether soil microbes might restrict habitat distributions of closely related oaks (Quercus spp.) in eastern North America. We performed a soil inoculum experiment using two pairs of sister species (i.e., the most closely related species) that show habitat divergence: Quercus alba (local species) vs. Q. michauxii (foreign), and Q. shumardii (local) vs. Q. acerifolia (foreign). To test whether host‐specific soil microbes are responsible for habitat restriction, we investigated the impact of local sister live soil (containing soil microbes associated with local sister species) on the survival and growth of local and foreign species. Second, to test whether habitat‐specific soil microbes are responsible for habitat restriction, we examined the effect of local habitat live soil (containing soil microbes within local sister's habitats, but not directly associated with local sister species) on the seedlings of local and foreign species. We found that local sister live soil decreased the survival and biomass of foreign species' seedlings while increasing those of local species, suggesting that host‐specific soil microbes could potentially mediate habitat exclusion. In contrast, local habitat live soil did not differentially affect the survival or biomass of the local vs. foreign species. Our study indicates that soil microbes associated with one sister species can suppress the recruitment of the other host species, contributing to the habitat partitioning of close relatives. Considering the complex interactions with soil microbes is essential for understanding the habitat distributions of closely related plants. [ABSTRACT FROM AUTHOR]

The supply of recent photosynthate from plants to soils is thought to be a critical mechanism regulating the activity and diversity of soil biota. In the Arctic, large‐scale vegetation transitions are underway in response to warming, and there is an urgent need to understand how these changes affect soil biodiversity and function.We investigated how abundance and diversity of soil fungi and invertebrates responded to a reduction in fresh below‐ground photosynthate supply in treeline birch and willow, achieved using stem girdling. We hypothesised that birch forest would support greater abundance of ectomycorrhizal (ECM) fungal species and fauna than willow shrubs, and that girdling would result in a rapid switch from ECM fungi to saprotrophs as canopy supply of C was cut, with a concomitant decline in soil fauna.Birch forest had greater fungal and faunal abundance with a large contribution of root‐associated ascomycetes (ericoid mycorrhizal fungi and root endophytes) compared to willow shrub plots, which had a higher proportion of saprotrophs and, contrary to our expectations, ECM fungi. Broad‐scale soil fungal and faunal functional group composition was not significantly changed by girdling, even in the third year of treatment. Within the ECM community, there were some changes, with genera that are believed to be particularly C‐demanding declining in girdled plots. However, it was notable how most ECM fungi remained present after 3 years of isolation of the below‐ground compartment from contemporary photosynthate supply.Synthesis. In a treeline/tundra ecosystem, distinct soil communities existed in contrasting vegetation patches within the landscape, but the structure of these communities was resistant to canopy disturbance and concomitant reduction of autotrophic C inputs. [ABSTRACT FROM AUTHOR]

Anthropogenic nitrogen (N) deposition is exposing plants and their arbuscular mycorrhizal fungi (AMFs) to elevated N availability, often leading to shifts in communities of AMF. However, physiological trade-offs among AMF taxa in their response to N enrichment vs the ability to acquire other soil nutrients could have negative effects on plant and ecosystem productivity. It follows that information on the functional traits of AMF taxa can be used to generate predictions of their potential role in mediating ecosystem responses to N enrichment. Arbuscular mycorrhizal fungi taxa that produce extensive networks of external hyphae should forage for N and phosphorus (P) more effectively, but these services incur greater carbon (C) costs to the plant. If N enrichment ameliorates plant nutrient limitation, then plants may reduce C available for AMF, which in turn could eliminate AMF taxa with large extensive external hyphae from the soil community. As a result, the remaining AMF taxa may confer less P benefit to their host plants. Using a synthesis of data from the literature, we found that the ability of a taxon to persist in the face of increasing soil N availability was particularly high in isolates from the genus Glomus, but especially low among the Gigasporaceae. Across AMF genera, our data support the prediction that AMF with a tolerance for high soil N may confer a lower P benefit to their host plant. Relationships between high N tolerance and production of external hyphae were mixed. Synthesis. If the relationship between N tolerance and plant P benefit is widespread, then shifts in arbuscular mycorrhizal fungi communities associated with N deposition could have negative consequences for the ability of plants to acquire P and possibly other nutrients via a mycorrhizal pathway. Based on this relationship, we predict that arbuscular mycorrhizal fungi responses could constrain net primary productivity in P-limited ecosystems exposed to N enrichment. This prediction could be tested in future empirical and modelling studies.

Environmental conditions experienced by parent plants can influence offspring performance through parental effects induced by DNA methylation. The offspring can also be influenced by environmental conditions experienced by their parents via soil legacy effects due to plant‐mediated changes in the composition of soil microbes. These two effects are likely to act simultaneously, but empirical evidence for combined effects is limited.We conducted a two‐phase experiment with five genotypes of a clonal plant Hydrocotyle vulgaris. In the first phase, we grew parent plants of each genotype under two light conditions (ambient vs. shade) and two DNA demethylation treatments [treated with water vs. 5‐azacytidine (5‐azaC)]. We then collected soils and clonal offspring for each genotype from each of these four treatments and measured soil (a)biotic properties. In the second phase, we grew the offspring from each of the four treatments in the four different soils, under the two light conditions.When grown under ambient light condition and in soil from ambient parents, offspring produced by ambient parents grew larger than offspring produced by shaded parents when the parents were treated with water. This difference was smaller when the parents were treated with 5‐azaC, and disappeared when the offspring were grown in soil from shaded parents. The growth difference was also observed when the offspring were grown under shaded condition and in soil from shaded parents. However, this difference was greater when the parents were treated with 5‐azaC, and disappeared when the offspring were grown in soil from ambient parents. Moreover, offspring growth was associated with fungal composition and total phosphorus of the soil in which the parents had grown.Our results show, for the first time, that light condition experienced by parents can influence offspring responses to light through both parental effects and soil legacies. The parental effects were mediated by changes in DNA methylation and the soil legacies were due to plant‐mediated changes in a combination of soil biotic and abiotic properties. These impacts may eventually influence the ecological and evolutionary trajectories of clonal plant populations. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Background Despite many studies on the importance of competition and plants' associations with mutualists and pathogens on plant performance and community organization, the joint effects of these two factors remain largely unexplored. Even less is known about how these joint effects vary through a plant's life in different environmental conditions and how they contribute to the long-term coexistence of species. Methods We investigated the role of plant–soil feedback (PSF) in intra- and interspecific competition, using two co-occurring dry grassland species as models. A two-phase PSF experiment was used. In the first phase, soil was conditioned by the two plant species. In the second, we assessed the effect of soil conditioning, competition and drought stress on seedling establishment, plant growth in the first and second vegetation season, and fruit production. We also estimated effects of different treatments on overall population growth rates and predicted the species' potential coexistence. Results Soil conditioning played a more important role in the early stages of the plants' life (seedling establishment and early growth) than competition. Specifically, we found strong negative intraspecific PSF for biomass production in the first year in both species. Although the effects of soil conditioning persisted in later stages of plant's life, competition and drought stress became more important. Surprisingly, models predicting species coexistence contrasted with the effects on individual life stages, showing that our model species benefit from their self-conditioned soil in the long run. Conclusions We provide evidence that the effects of PSF vary through plants' life stages. Our study suggests that we cannot easily predict the effects of soil conditioning on long-term coexistence of species using data only on performance at a single time as commonly done in PSF studies. We also show the importance of using as realistic environmental conditions as possible (such as drought stress experienced in dry grasslands) to draw reasonable conclusions on species coexistence. [ABSTRACT FROM AUTHOR]

Fungal communities can influence the productivity, composition and survival of trees through cycling nutrients, providing resources and altering pathogens. Thus, shifts in fungal communities could impact forests by altering interactions between trees and their environments. Fungal community composition may be shaped by stochastic and deterministic processes such as dispersal limitation, environmental filtering and partner specificity between trees and fungi. For tree species with large geographical ranges, we expect fungal assembly processes to change with environmental variation across the range of the tree partner. Due to specificity between trees and symbiotic fungi, we expect deterministic to outweigh stochastic processes in root compared with soil fungi. As some tree species have exceptional longevity, we also expected tree age to influence fungal community assembly.We surveyed fungi in four stands of Pseudotsuga menziesii with tree ages up to 800 years along an 1,800 km transect. We sampled roots and soil around 12 P. menziesii in each stand, aged the trees, and sequenced fungal rDNA to determine composition and richness from which we calculated the relative role of deterministic and stochastic assembly processes. We used null models to evaluate the relative importance of deterministic variable and homogenizing selection, and stochastic dispersal limitation, drift and homogenizing dispersal in fungal community assembly.We detected 7,280 amplicon sequence variants with 5,270 associated with soil, 3,887 with roots and 1,877 found across both roots and soils. Deterministic processes dominated root and soil fungal communities at all sites except one where stochastic processes (i.e. dispersal limitation and drift) controlled root fungi. Despite the dominance of determinism in fungal community assembly, the proportion of processes differed by site. Assembly processes did not vary with tree age.Synthesis. Taken together, we suggest that the local environment, water limitation and partner‐preference between trees and their associated fungi, influence fungal community composition across the range of P. menziesii. We conclude that while fungal communities occurring near P. menziesii are dominated by homogenizing selection, the role of neutral processes still has a minor influence on community assembly and may be important in spatially isolated communities and those with strong gradients of fungal diversity. [ABSTRACT FROM AUTHOR]

Water is the most limiting resource for plant survival and growth in arid environments, but the diversity of water‐use strategies among coexisting species in dryland communities is not well understood. There is also growing interest in assessing whether a whole‐plant coordination exists between traits related to water‐use and the leaf economic spectrum (LES).We used water stable isotopes (δ2H, δ18O) to quantify water uptake proportions from different soil depths by 24 species in a Mediterranean shrubland. Leaf traits associated with water‐use efficiency, stomatal regulation (δ13C, δ18O) and the LES (SLA, N, P, K concentrations) were also measured. We assessed potential trade‐offs between the above‐mentioned leaf traits, water uptake depth and their relationship with species abundance.We found distinct ecohydrological niche segregation among coexisting species. Bayesian models showed that our shrubland species used a median of 37% of shallow soil water (0–30 cm) and 63% of deep water (30–100 cm). Still, water source proportions varied considerably among species, as shallow soil water‐use ranged from a minimum of 6.4% to a maximum of 68%. Interspecific variability in foliar carbon investment (SLA) and nutrient concentrations was remarkably high, indicating diverse nutrient‐use strategies along the LES. Leaf δ18O, δ13C and δ15N values also differed widely among species, revealing differences in stomatal regulation, water‐use efficiency and nitrogen acquisition mechanisms. After accounting for evolutionary history effects, water uptake depth was coordinated with the LES: species using shallower soil water from fertile topsoil layers exhibited a more acquisitive carbon‐ and nutrient‐use strategy, whereas water uptake from deeper but less fertile soil layers was linked to a more conservative nutrient‐use strategy. Leaf‐level water‐use traits significantly influenced species abundance, as water‐savers with tight stomatal regulation and high water‐use efficiency were dominant.Synthesis. Greater utilisation of water stored in nutrient‐rich topsoil layers favoured a more acquisitive nutrient‐use strategy, whereas a deeper water uptake pattern appeared to constrain access to nutrients. Our findings thus suggest a largely inescapable trade‐off and coordination between soil water uptake depth and carbon‐ and nutrient‐use strategies in low‐fertility drylands. [ABSTRACT FROM AUTHOR]

Negative plant–soil feedback (PSF) has been widely considered to be a primary mechanism maintaining plant diversity. Previous studies have shown that rare species suffer stronger negative conspecific PSF than common species, but it remains unclear how rare species persist if they are more strongly self‐limited.Here, we used shade‐house and field experiments to test soil feedback effects of phylogenetically related species on seedling growth, with seven species of contrasting local abundance, in a subtropical forest, China. We quantified the PSF of conspecifics and heterospecifics and assessed the phylogenetic dependence of the feedback.Both experiments showed that although rare species suffered strong negative PSF in soils of conspecifics or phylogenetically close heterospecifics, no such feedback was found in the soils of phylogenetically distant heterospecifics. In contrast, common species had no or weak negative conspecific PSF but strong heterospecific soil PSF.Synthesis. The variation in the phylogenetically dependent PSF among rare and common species evidenced in this study ensures that rare species would grow well in the neighbourhood of phylogenetically distant heterospecifics but do poorly under their own or close relatives, while common species perform relatively well in their own neighbourhood but poorly in other's neighbourhood. This phylogenetically dependent PSF facilitates the rare–common species coexistence in communities. [ABSTRACT FROM AUTHOR]

The importance of plant–soil feedbacks (PSF) for above‐ground and below‐ground multitrophic interactions is well recognized. However, most studies only condition soil for a short time before testing the feedback response. Here we investigate the influence of time of conditioning on soil microbiome composition, plant growth and metabolomics, and plant–insect interactions. We used soil collected from large outdoor mesocosms with monocultures of six species and investigated the temporal changes in the soil over a full year.Every 2 months, we assessed the legacy effects of the soils on plant growth of one of the species (Jacobaea vulgaris) in a climate‐controlled chamber. Each time we used tissue culture plants that were genetically identical. We also measured leaf herbivore performance and leaf metabolomes, as well as the abiotic and biotic soil properties.We show that the monoculture soils harboured different microbiomes, but that these varied over time. Growth of the test plants also varied over time and plants grew consistently less well in their own soil. The soil legacy effects on the leaf metabolome were less consistent and varied strongly over time. Networking analysis showed that soil bacteria had stronger effects on the leaf metabolome than fungi early on. However, after 12 months of conditioning, only soil fungal community composition explained the metabolomic profiles of the leaves. Insect herbivory was not affected by soil conditioning, but decreased with increasing time of conditioning.Synthesis. Our results show that the biomass response of the test plants to soil conditioning remained consistent throughout the year, even though both the soil microbiome and leaf metabolomic responses to conditioned soil varied greatly over time. These soil‐induced changes in the metabolome of plants over time can be an important driver of above‐ground multitrophic interactions in nature. Our study demonstrates that the duration of conditioning has a strong impact on plant and soil properties, which highlights that temporal variation is an important aspect to consider in future studies investigating plant–soil interactions. [ABSTRACT FROM AUTHOR]

Interactions between plants and soil biota are increasingly shown to play critical roles in plant species coexistence processes. Plant species coexistence is thought to be promoted via biotic legacies that plant species leave behind in the soil after a plant disappears. These soil legacies are hypothesised to supress colonisation success when the preceding plant is of the same species, that is, when a plant species encounters its own, species‐specific soil antagonists.However, colonisation of vacant spots in plant communities is in the first place determined by the ability of plants to reach such vacant locations. We currently lack an understanding of the explicit role of soil legacy effects and their relative contribution to colonisation processes in plant communities consisting of plant species inherently differing in colonisation ability.In experimental, outdoor plant communities consisting of eight grassland species, we tested the effect of five differently conditioned soil patches on plant species colonisation success over three consecutive growing seasons. We found that colonisation success was largely determined by the species' reproductive strategy, lateral spread and growth rate, and not by the plant species that conditioned the soil patch. Fast spreading, clonal plant species reached the soil patches first and initially attained the highest biomass inside the patch. One year later, slower spreading plant species colonised the patch via seedlings. Species with intrinsically high growth rates attained the highest biomass, decreasing biomass of the initial colonisers. While subtle differences between conditioned soil patches did occur, these were not strong enough to overcome the inherent differences in colonisation ability between the various plant species.Synthesis. Our results reject the hypothesis that colonisation of vacant soil patches in plant communities is strongly affected by the legacy that is left behind by the preceding plant species. Instead, plant species life‐history strategy plays a prominent role, driving sequential plant species replacements. Based on our results and recent accounts in literature we present a conceptual model for local cyclic dynamics in grassland communities, where soil legacy plays a role in affecting the performance of established plant species rather than colonisation of vacant patches. [ABSTRACT FROM AUTHOR]

Enhanced deposition of atmospheric nitrogen (N) has profound impacts on ecosystem processes such as above-ground productivity and community structure in grasslands across the globe. But how N deposition affects below-ground processes of grasslands is less well known. Here, we evaluated the effects of chronic N amendment at a relatively low rate (20 kg ha-1 year-1) on root traits (root productivity, root biomass, root/shoot ratio) in Inner Mongolia steppes by rhizotron and ingrowth core and soil monolith techniques at levels of individual species, functional groups and ecosystem. For 8 years, N amendment suppressed above-ground net primary production (ANPP), photosynthetic rates and root biomass of forbs, but enhanced ANPP and root biomass of grasses. This led to an overall reduction in below-ground productivity of the grassland by 24-33%, while ANPP remained unchanged. Nitrogen amendment acidified soil and subsequently increased extractable soil manganese (Mn) concentration. Nitrogen amendment increased foliar Mn concentrations in forb, but not grass species, leading to a significant inhibition of photosynthetic rates in forb species. Synthesis. These findings highlight the importance of the differentiating responses of plant functional groups to long-term N deposition and the important consequences of these responses for below-ground productivity and long-term soil C sequestration.

Sphagnum mosses are keystone species in northern peatlands. Notably, they play an important role in peatland carbon (C) cycling by regulating the composition and activity of microbial communities. However, it remains unclear whether information on Sphagnum phylogeny and/or traits‐based composition (i.e. anatomical and morphological traits and metabolites) can be used to predict the structure of microbial communities and their functioning. Here we evaluated whether Sphagnum phylogeny and traits predict additional variation in peatland microbial community composition and functioning beyond what would be predicted from environmental characteristics (i.e. climatic and edaphic conditions).We collected Sphagnum and microbial data from five European peatlands distributed along a latitudinal gradient from northern Sweden to southern France. These data allowed us to assess Sphagnum anatomical and morphological traits and metabolites at different sites along changing environmental conditions. Using structural equation modelling (SEM) and phylogenetic distance analyses, we investigated the role of Sphagnum traits in shaping microbial community composition and functioning along with environmental conditions.We show that microbial community composition and traits varied independently from both Sphagnum phylogeny and the latitudinal gradient. Specifically, the addition of Sphagnum traits to climatic and edaphic variables to the SEM allowed it to explain a larger proportion of the explained variance (R2). This observation was most apparent for the biomass of decomposers (+42%) and phototrophs (+19%), as well as for growth yield microbial traits (+10%). As such, that Sphagnum metabolites were important drivers for microbial community structure and traits, while Sphagnum anatomical and morphological traits were poor predictors.Synthesis. Our results highlight that Sphagnum metabolites are more likely to influence peatland microbial food web structure and functioning than Sphagnum anatomical and morphological traits. We provide further evidence that measurements of the plant metabolome, when combined with classical functional traits, improve our understanding of how the plants interact with their associated microbiomes. [ABSTRACT FROM AUTHOR]

Purpose: Plants growing in the soils of karst forests associate with arbuscular mycorrhizae (AM) or ectomycorrhizae (ECM) to acquire nutrients. We researched how these different mycorrhizal associations affect rhizosphere soil nutrient economy in these calcareous soils. Methods: Bulk and rhizosphere soils were sampled beneath 25 AM and 9 ECM plants growing in primary forests at the Puding Karst Critical Zone Observatory. Nutrient contents and potential enzyme activities were analyzed to test the effect of different types of mycorrhizal association on rhizosphere soil nitrogen (N) and phosphorus (P) economies. Results: The contents of nitrate-N and available-P were markedly lower in the rhizospheres of ECM plants compared to AM plants. Ectomycorrhizal plants promoted relatively greater investment in N-acquisition enzymes, in contrast, AM plants caused relatively greater investment in P-acquisition enzymes. The decreased pH in the rhizospheres of AM plants likely promoted the greater P availability. Conclusion: Our results revealed how plants that form contrasting mycorrhizal associations have fundamentally different effects on rhizospheric nutrient economies in the low fertility karst soils of southwest China. Differentiation in N- and P-acquisition capacity of these plants have implications for species coexistence and the high levels of plant biodiversity observed in these forests. [ABSTRACT FROM AUTHOR]

Millions of trees are expected to be planted in forested and non‐forested ecosystems during the United Nations Decade of Restoration. Trees and soil organisms are known to interact, and are both crucial for maintaining multiple ecosystem functions. However, little is known about how the bidirectional relationships among above‐ and below‐ground diversity and ecosystem functions differ across forested and non‐forested ecosystems.We collected data from 126 sites from humid to arid areas in eastern Australia to explore bidirectional relationships among above‐ground (richness of trees and other plants) and below‐ground (richness of bacteria, fungi, invertebrate, protist) diversity and multiple ecosystem functions (multifunctionality, litter and labile carbon storage, nutrient pools, decomposition, groundstorey plant biomass production, soil stability) in forested (tree cover >10%) and non‐forested (tree cover ≤10%, open woodlands, shrublands) systems.We found that the relative importance of above‐ and below‐ground diversity differed among forested and non‐forested systems. Ecosystem functions, such as litter and labile carbon storage and soil stability, were associated mainly with tree richness in forested systems. By comparison, ecosystem functions of non‐forests were related to the richness of soil organisms. Such bidirectional biodiversity–ecosystem function relationships varied with the target function, and the relationships among ecosystem functions and the relative abundance of species varied with tree and soil taxa. The richness of other plants (i.e. all plants excluding trees) and soil organisms was positively coupled in forests only, but there were no linkages among above‐ and below‐ground diversity and ecosystem functions in non‐forests for groundstorey plant biomass production. Furthermore, increases in aridity and soil pH further weakened the biodiversity–ecosystem function relationships in forested and non‐forested systems, by suppressing above‐ground diversity and bacterial richness, respectively.Synthesis. Our study provides strong empirical evidence that the bidirectional relationships among above‐ and below‐ground diversity and ecosystem functions are highly variable across ecosystem and function types. Moreover, our study demonstrates that soil biodiversity is relatively more important than tree diversity in supporting ecosystem functions in non‐forested systems. This suggests that conservation of soil biodiversity is critical for maintaining the functioning of open woodland and shrubland systems. [ABSTRACT FROM AUTHOR]

Reallocation of nutrients from roots to shoots is essential for plant regrowth in grasslands, particularly in nutrient‐poor conditions. However, the response of root nutrient reallocation to changes in nitrogen (N) and water availability remains largely unknown.Using a novel 15N and 32P labelling technique, we quantified the contribution of N and phosphorus (P) to shoot regrowth from either root reallocation or direct soil uptake for perennial grasses exposed to high‐frequency deficit irrigation (HFDI) and N addition.Without N addition, HFDI showed no impact on uptake and reallocation of N and P, likely due to unaffected soil N availability and a greater diffusion barrier offsetting increased accumulation in plant‐available soil P. With N addition, HFDI increased plant N rather than P uptake, because of increasing soil N availability instead of P under combined HFDI and N addition. The HFDI decreased both N and P reallocation with N addition, possibly due to exhaustion of nutrient reserves in roots that were re‐allocated above‐ground. Reallocation contributed 48%–97% of N and 58%–79% of P required during the first 2 weeks of shoot regrowth.Synthesis. Our results highlight the importance of N and P reallocation from roots to buffer against changes in soil N and P availability and to maintain N:P ratio in shoot regrowth. [ABSTRACT FROM AUTHOR]

Photosynthetic carbon (C) allocated below‐ground can be shared with mycorrhizal fungi in exchange for nutrients, but also added into soil as rhizodeposits that potentially increases plant nutrient supply by supporting microbial nutrient mineralization from organic matter. How water and nitrogen (N) availability affects plant C allocation to the rhizosphere, including both arbuscular mycorrhizal fungi (AMF) symbionts and rhizodeposits, remains largely unknown.We used a 13CO2 pulse labelling experiment to assess the effects of drought and N addition on below‐ground allocation of C to soils and roots (quantified as excess 13C) and tested their relationships with AMF colonization in an Australian grassland. We also examined relationships between AMF and previously reported root respiration and decomposition of rhizodeposits in this study.We found that drought decreased the absolute amount of excess 13C allocated to both soils and roots, likely due to less photosynthetic C fixation. In contrast, proportionally more excess 13C was allocated to soils but less to root biomass with drought, suggesting that relatively more C was allocated to rhizodeposits and to AMF hyphal growth and extension. However, N addition reversed drought effects on below‐ground C allocation by retaining proportionally more excess 13C in roots and less in soils, congruent with higher soil N and phosphorus availability, root biomass and number of root tips compared to drought without N addition. This suggests that the alleviation of nutrient limitation promoted plants to expend relatively more C on root growth and root trait adjustment, but less C on rhizodeposition and mycorrhizal symbiosis.Synthesis. Mycorrhizal colonization related negatively to rhizodeposit decomposition rate but positively to both excess 13C in root biomass and root respiration, suggesting a possible trade‐off in C allocation between mycorrhizal symbiosis and rhizodeposition. We conclude that below‐ground C allocation in this grassland can be mediated by mycorrhizal colonization and is strongly affected by water and nutrient availability. [ABSTRACT FROM AUTHOR]

Plant–fungal associations strongly influence forest carbon and nitrogen cycling. The prevailing framework for understanding these relationships is through the relative abundance of arbuscular (AM) versus ectomycorrhizal (EcM) trees. Ericoid mycorrhizal (ErM) shrubs are also common in forests and interactions between co‐occurring ErM shrubs and AM and EcM trees could shift soil biogeochemical responses. Here we test hypotheses that the effects of ErM shrubs on soil carbon and nitrogen either extend or are redundant with those of EcM trees.Using regional vegetation inventory data (>3,500 plot observations) we evaluated the frequency, richness and relative abundance of ErM plants in temperate forests in the eastern United States and examined their relationship with EcM plant cover. We then used surface soil (7 cm) data from 414 plots within a single forest to analyse relationships between ErM plant cover, relative EcM tree basal area and soil carbon and nitrogen concentrations while accounting for other biogeochemical controls, such as soil moisture.At both scales, we found a positive relationship between ErM and EcM plants, and the majority of ErM plants were in the shrub layer. Within the forest site, ErM plants strongly modulated tree mycorrhizal dominance effects. We found negative relationships between EcM relative basal area and soil carbon and nitrogen concentrations, but these relationships were weak to negligible in the absence of ErM plants. Both EcM relative basal area and ErM plant cover were positively associated with the soil carbon‐to‐nitrogen ratio. However, this relationship was driven by relatively lower nitrogen for EcM trees and higher carbon for ErM plants. As such, the functional effects of ErM plants on soil biogeochemistry neither extended nor were redundant with those of EcM trees.Synthesis. We found that ErM shrubs strongly influenced the relationship between tree mycorrhizal associations and soil biogeochemistry, and the effects of ErM shrubs and EcM trees on carbon and nitrogen were functionally distinct. Our findings suggest that ErM shrubs could confound interpretation of AM versus EcM tree effects in ecosystems where they co‐occur but also bolster growing calls to consider mycorrhizal functional types as variables that strongly influence forest biogeochemistry. [ABSTRACT FROM AUTHOR]

Plant–soil feedbacks (PSF) and functional traits are two active but not well theoretically integrated areas of research. However, PSF and traits are both affected by life‐history evolution, so the two should theoretically be related.We provide a conceptual framework to link plant functional traits to two types of PSF metrics, and hypothesize that individual PSF (plant performance in conspecific vs. heterospecific soil) should be related to the fast–slow trait spectrum, whereas pairwise PSF (the sum of the individual feedbacks for two species growing in each other's soils) should be related to trait dissimilarity. We performed meta‐analyses to test these hypotheses by compiling two datasets, one dataset consisting of individual PSF values and plant trait values (specific leaf area, SLA; leaf N concentration, LNC; specific root length, SRL; fine root diameter, FRD; plant height; seed mass), and the second consisting of pairwise PSF values and trait dissimilarity.Our meta‐analyses showed that individual PSF values were more negative in faster‐growing species with greater SLA, LNC and SRL, supporting the growth–defence trade‐off hypothesis. Plant height was positively correlated with individual PSF, perhaps because large, long‐lived plants defend against pathogens better than smaller, shorter‐lived plants. We also found that larger‐seeded species had more positive or less negative PSF, likely reflecting greater tolerance of soil pathogens. The direction of relationships between trait dissimilarity and pairwise PSF varied with trait identity. Dissimilarities in SRL and FRD were negatively correlated with pairwise PSF while height dissimilarity was positively correlated with pairwise PSF. The contrasting relationships may reflect distinct links between trait dissimilarity and niche and fitness differences.Synthesis. Our results demonstrate how an integration of PSF and trait‐based approaches can advance plant community ecology. [ABSTRACT FROM AUTHOR]

Ecosystem stability is threatened by multiple global change factors such as drought and elevated nitrogen deposition. Yet, it is still poorly understood whether soil organisms can buffer against such perturbations. Here we focus on arbuscular mycorrhizal fungi (AMF), a common and widespread group of soil fungi. AMF form symbiotic associations with the majority of terrestrial land plants and promote a range of ecosystem services including plant production, diversity and nutrient cycling.We tested whether AMF have the ability to enhance the resistance and resilience of plant communities under soil moisture deficit (hereby drought) and nitrogen deposition. Grassland microcosms with 11 different plant species were established with and without AMF and exposed to elevated nitrogen levels and to an intermittent period of drought.Drought strongly reduced plant productivity and nitrogen cycling, but had limited effects on plant diversity. Nitrogen enrichment reduced plant diversity and increased nitrogen leaching and N2O emissions. The presence of AMF enhanced plant productivity, plant diversity and reduced nitrogen losses. AMF facilitated the resistance of plant productivity and nitrogen cycling to drought and the recovery of the plant community structure back to its pre drought state. Furthermore, AMF also mitigated the adverse effects of nitrogen enrichment on the resistance of multiple ecosystem functions to drought.Synthesis. Our work highlights the integral role of AMF for the stability of ecosystem functioning; AMF are not only able to promote resistance to harsh conditions of global change but also improve resilience by enabling plant communities to recover. These findings underline AMF's insurance capacity to buffer ecosystems against global change. [ABSTRACT FROM AUTHOR]

To assess the effects of global change on peatland vegetation and biogeochemistry we used a long term (21 years) in-situ plot scale manipulation experiment comprising nitrogen (N; ambient and 30 kg ha−1 yr−1), temperature (T; ambient and + 3.6 °C during growing season) and sulfur (S; ambient and 20 kg ha−1 yr−1) treatments in an oligotrophic boreal peatland. Vegetation was assessed by plant species cover estimates, while biogeochemical processes were characterized by measuring potential extracellular enzyme activity (EEA) of glucosidase, cellulase, aminopeptidase, phosphatase, and sulfatase in the peat matrix. We hypothesized that the plant communities would change in response to the N and T manipulations, and that belowground EEA would respond distinctively to the applied treatments as well as to changes in plant community. We found vascular plant cover to have strongly increased in the T treatment, whereas the Sphagnum cover collapsed in the high N treatment. Belowground we found enhanced enzymatic C and N acquisition activity in response to the N treatment, but EEA showed no response to the T treatment. No S effects were found, neither aboveground nor belowground. Contrary to our expectations, our data reveal a mismatch between above-ground vegetation patterns and belowground decomposition processes. In particular, the large increase in vascular plant cover in the warming treatment found no reflection in belowground EEA. [ABSTRACT FROM AUTHOR]

At broad spatial scales, the factors regulating litter decomposition remain ambiguous, with the understanding of these factors largely based on studies investigating site‐specific single litter species, whereas studies using multi litter species mixtures across sites are rare.We exposed in microcosms containing single species and all possible mixtures of four leaf litter species differing widely in initial chemical and physical characteristics from a temperate forest to the climatic conditions of four different forests across the Northern Hemisphere for 1 year.Calcium, magnesium and condensed tannins predicted litter mass loss of single litter species and mixtures across forest types and biomes, regardless of species richness and microarthropod presence. However, relative mixture effects differed among forest types and varied with the access to the litter by microarthropods. Access to the microcosms by microarthropods modified the decomposition of individual litter species within mixtures, which differed among forest types independent of litter species richness and composition of litter mixtures. However, soil microarthropods generally only little affected litter decomposition.Synthesis. We conclude that litter identity is the dominant driver of decomposition across different forest types and the non‐additive litter mixture effects vary among biomes despite identical leaf litter chemistry. These results suggest that across large spatial scales the environmental context of decomposing litter mixtures, including microarthropod communities, determine the decomposition of litter mixtures besides strong litter trait‐based effects. [ABSTRACT FROM AUTHOR]

1. Nutrients are a critical resource for plant growth, but the elements limiting growth in tropical forests have rarely been determined. 2. We investigated the influence of nitrogen (N), phosphorus (P), potassium (K) and micronutrients on seedling biomass and nutrient allocation in a factorial nutrient fertilization experiment in lowland tropical forest at the Barro Colorado Nature Monument, Panama. We also measured 8 years of herbivory and growth for 1800 seedlings. We sought to determine the identity of limiting elements and possible nutrient interactions. 3. The five study species were Alseis blackiana, Desmopsis panamensis, Heisteria concinna, Sorocea affinis and Tetragastris panamensis. Plants grew in deeply shaded understorey with a mean canopy openness of 4.9% (±0.7%; 1 SE). 4. Tissue N concentration increased by 11% with N addition. Tissue P concentration increased by 16% with P addition. Tissue K increased by 4% with K addition. K addition reduced root‐to‐shoot biomass ratio. There was no significant effect of fertilization on specific leaf area or leaf area ratio. 5. The proportion of leaves damaged and the mean level of damage by herbivory increased with P and K addition and showed a significant P × K interaction. 6.7ensp;Across all species and years, relative growth rate of height increased with K addition and with N and P in combination. Relative growth rate of leaf count trended 8.5% higher with K addition (P = 0.076). 7. We also added micronutrients in a parallel experiment. There was no effect of micronutrient addition on any seedling parameter. 8. Synthesis. K addition affected seedlings by enhancing tissue nutrient concentration, increasing herbivory, reducing root‐to‐shoot biomass ratio and increasing height growth. Additional effects of N or P on tissue chemistry, herbivory and growth offer support for the multiple limiting resources hypothesis. Our results suggest that seedling growth is limited by nutrients, especially K, even under highly shaded conditions in this lowland tropical forest.

Fine roots play key roles in the capacity of plants to face environmental constraints and their traits reflect adaptations to the environment, including soil structure, resource availability and climate. However, the inaccuracy of global soil and climate databases to account for the large environmental variation occurring at small spatial scale prevents accurate estimations of the linkages between environmental variables and fine‐root strategies.Here, using two global databases on fine‐root traits (Rhizopolis‐db) and species phylogenetic relatedness, and a regional database of species ecological indicator values (Baseflor), we quantified the predictive value of ecological indicator values, as an alternative to classical coarse soil and climate indicators, on the variation in four major fine‐root traits.A strong phylogenetic signal was found among species for fine‐root mean diameter, specific root length (SRL) and root tissue density (RTD), but less so for root nitrogen concentration (RNC). After accounting for this relatedness, ecological indicators still explained a large part of trait variation in our dataset for SRL, RTD and RNC. Multi‐indicators best model R2 reached.40 for SRL and RTD, and.44 for RNC, whereas it was only 0.10 for diameter. Ecological indicators of nutrient availability and soil texture were those that most strongly related to SRL, RTD and RNC. Specifically, plant fast resources use strategies characterized by high SRL, RNC and low RTD occurred more frequently in nutrient‐rich soils and in soils with light sandy textures. Additionally, light availability and atmospheric temperature were negatively related with SRL and continentality negatively influenced RNC.With respect to both nutrient and water availability ecological indicator values, opposite adaptations were observed between growth forms, particularly between woody and herbaceous species, limiting our ability to define simple, widely applicable patterns of trait–environment relationships.Synthesis. Our analysis demonstrates that species ecological indicator values are valuable predictors of plant below‐ground strategies. It provides original evidence that herbaceous species with fine‐root traits representative of fast resource use strategies typically occur in more favourable soil habitats (high nutrient and water availability); meanwhile, woody species may show the opposite trend. Other important environmental parameters concomitantly influence fine‐root trait variation in contrasting ways. [ABSTRACT FROM AUTHOR]

Increasing temperatures associated with climate change are shifting plant species to higher latitudes. Soil communities could aid the plants' shift into novel areas by harbouring fewer soil‐borne antagonists or more mutualists that influence the fitness and stress tolerance of the shifting species. Alternatively, they could contain novel antagonists or fewer mutualists. Thus, soil communities could positively or negatively affect plant range expansion, particularly if they influence plants' responses to climate, such as freeze tolerance, that feedback to affect expansion.We used the northward range expansion of the black mangrove, Avicennia germinans, into a system dominated by marsh cordgrass, Spartina alterniflora, in northern Florida, USA to study how the novel soil environment (i.e. S. alterniflora soil) affects mangrove fitness, susceptibility to cold stress and the colonization of mutualist fungi. We quantified abundance of root mutualistic fungi in mixed marsh‐mangrove habitat and conducted a laboratory experiment to test effects of steam‐sterilized and live soils from A. germinans and S. alterniflora on the growth, condition, fungal colonization and freeze tolerance of A. germinans seedlings.In the field, we found two times higher dark septate endophyte (DSE) colonization of A. germinans roots and three times higher fungal spore density in A. germinans soil compared to S. alterniflora roots and soil. In the laboratory experiment, seedlings in steamed S. alterniflora soil treatments had 50%–65% survival after freezing, compared to 0% survival in treatments with live S. alterniflora soil. A. germinans live soil mixed with S. alterniflora steamed soil yielded A. germinans roots with the highest DSE colonization and seedlings with greater shoot biomass and lower root:shoot ratios. S. alterniflora live soil lowered the freeze tolerance of A. germinans, decreased mangrove survival and depressed DSE colonization.Synthesis. S. alterniflora soil could impede A. germinans establishment in salt marsh communities. As climate warming gradually allows A. germinans to displace S. alterniflora, the rhizosphere could become increasingly hospitable to A. germinans. Our work suggests the soil community associated with resident species mediates climatic stressors to affect expansion success. [ABSTRACT FROM AUTHOR]

In response to contemporary changes in climate, many tree species are shifting upslope to find favorable habitat. In the case of obligate ectomycorrhizal species, seedling growth above upper treeline depends on fungal spore availability. In the mountain ranges of the Great Basin, a recent shift in tree species stratification has been recorded, with limber pine (LP, Pinus flexilis) leapfrogging above the ancient bristlecone pine (BCP, Pinus longaeva) forest and establishing above current treeline.We compared the ability of LP and BCP to interact with soil spore banks collected at different microhabitats (next to dead trees, young live trees or in a treeless control) above current treeline in the White Mountains of California.We found an ectomycorrhizal fungal spore bank community composed of 15 species that was dominated by an undescribed and a hitherto unsequenced species of Geopora and Rhizopogon, respectively. This represents a much richer community than was found previously in this system. While both LP and BCP were able to establish ectomycorrhiza, LP was twice as likely to do so, and when comparing only seedlings that were colonized, its root system was colonized to a three‐fold greater extent. BCP seedlings grown on soils collected under young live trees were much more likely to be colonized compared to soils from the other two microhabitats.Synthesis. These differences in ectomycorrhizal receptivity might help to explain why LP is currently establishing at higher rates above the BCP treeline. Furthermore, it is possible that LP saplings above treeline can provide ectomycorrhizal facilitation for BCP seedlings, enabling the subsequent shift of BCP above treeline. [ABSTRACT FROM AUTHOR]

Insect herbivory can have important consequences for the functioning of terrestrial ecosystems. Despite a growing recognition of the role of herbivores in above‐ground–below‐ground interactions, our current understanding is mainly restricted to studies of vertebrates in grassland and tundra ecosystems, while ecosystems with tree‐like canopies (termed forests below) and invertebrates remain understudied.Here, we assess the current state of knowledge of one key aspect of plant–herbivore interactions by conducting a meta‐analysis of the peer‐reviewed literature on the below‐ground consequences of above‐ground insect herbivory in forest ecosystems. Main results are reported as aggregated relative effect sizes (Cohen's d).We find that above‐ground insect herbivory reduced below‐ground carbon (C) allocation by plants to roots (−0.56) and root exudation (−0.85), causing shifts in root–symbiont communities, for example, a decrease (−0.67) in the abundance of ectomycorrhizal fungi. Microbial decomposer abundances showed no significant responses, while soil faunal abundances increased (0.50). C and nitrogen (N) mineralization rates (C: 0.48, N: 0.48) along with nutrient leaching (C: 0.30, N: 0.77) increased, with a stronger response to outbreak relative to background insect densities. The negative responses increased in strength in colder and dryer biomes while positive responses were reinforced in warmer and wetter biomes, thus extending previously shown effects for vertebrate herbivores to also include insect herbivory. The positive response by soil fauna to insect herbivory was the notable exception. This may be associated with the limited physical soil disturbance caused by insects compared to ungulates. Furthermore, we identified an under‐representation in the literature of large areas of boreal and tropical biomes calling for research priorities to fill these knowledge gaps. We present three recommendations for future research: addressing (a) biological drivers of biogeochemistry and response pathways, (b) knowledge gap from boreal and tropical forests, and (c) heterogeneity of herbivore disturbances.Synthesis. Insect herbivores significantly accelerate soil C and N cycling during outbreaks in forest ecosystems, but we lack knowledge on the underlying biological drivers. Overall, below‐ground responses to insect herbivory are similar to vertebrate herbivory responses, which may simplify implementing herbivory effects into ecosystem models. Nonetheless, we identify a few important differences and general knowledge gaps on which we base recommendations for future research. [ABSTRACT FROM AUTHOR]

The plant economics spectrum is increasingly recognized as a major determinant of plant species effects on terrestrial ecosystem functioning related to carbon cycling. However, the role of plant economic strategies in the effects of living root activity on soil organic carbon (SOC) dynamics through rhizodeposition remains unexplored, despite SOC being the largest terrestrial carbon pool.Using a continuous 13C‐labelling method allowing partitioning of plant and soil sources to carbon fluxes and pools, we studied here the linkages between plant economic strategies and SOC cycling processes in a 'common garden' greenhouse experiment. It includes a panel of 12 grassland species selected along a gradient of economic traits and belonging to three functionnal groups (C3 grasses, forbs and legumes).All species induced an acceleration of native SOC mineralization but this rhizosphere priming effect (RPE) substantially differed across species and varied eleven‐fold by the end of the experiment (from +26% to +295% relative to unplanted soil). Interspecific variation in RPE was primarily linked to plant photosynthetic activity associated to species economic strategies of light and CO2 resource acquisition and processing. Fast‐growing acquisitive species, such as legumes, featured large RPE, in relation with their high canopy photosynthesis coupled to high leaf photosynthetic capacity and large net primary productivity allocated above‐ground. This large RPE was further associated with high root metabolic activity, rhizodeposition and soil microbial activity. In contrast, fine‐root growth and economic traits related to soil resource foraging ability were poor predictors of RPE.The formation of new root‐derived SOC varied nine‐fold across species and was similarly positively related to the net primary productivity allocated above‐ground. Fast‐growing acquisitive species with a high photosynthetic activity induced a disproportionately large RPE relative to SOC formation.Synthesis. Overall, our study demonstrates that rhizodeposition is a major mechanism through which plant economic strategies of grassland species control soil carbon dynamics. Acquisitive versus conservative species were associated with high versus low rates of photosynthesis and rhizodeposition, in turn leading to fast versus slow SOC turnover. This emphasizes the importance of considering rhizosphere processes for understanding plant species effects on soil biogeochemistry. [ABSTRACT FROM AUTHOR]

Due to the importance of arbuscular mycorrhizal fungi (AMF) in ecosystem productivity, a key ecological question is how do their communities assemble? As plant spatial patterns constitute a mosaic of AM fungi habitats, we hypothesized that AM fungal community assembly is determined by plant community structure, both in space and time.We tested our hypothesis by sampling individuals of two host‐plant species, Brachypodium pinnatum and Elytrigia repens, from experimental communities cultivated in mesocosms, and assessed their AM fungal root colonizers by mass sequencing. We related AM fungal community structure to the distribution of neighbouring plant species at different spatio‐temporal scales.We demonstrated that AM fungal community assembly depends mostly on past plant spatial patterns at a small spatial scale (5 cm), indicating that plants growing at given locations leave a footprint on the AM fungi community. This spatial scale of response was also influenced by the host‐plant species, probably by its clonal propagation.Synthesis. Overall, we highlighted that processes involved in Arbuscular mycorrhizal (AM) fungal community assembly do not operate at the rough scale of the overall plant community mosaic but are instead locally determined, delineating the AM fungal 'eye‐view' of the host‐plant community. [ABSTRACT FROM AUTHOR]

Climate change is shifting the distribution of species, and may have a profound impact on the ecology and evolution of species interactions. However, we know little about the impact of increasing temperature and changing rainfall patterns on the interactions between plants and their beneficial and antagonistic root symbionts.Here, we used a reciprocal multifactorial growth chamber experiment with seeds and soil microbial communities from three origins to investigate the impact of temperature and soil moisture on the growth, arbuscular mycorrhizal (AM) fungal colonization and root‐associated fungal community of a perennial herb. Moreover, we tested whether plants and AM fungi performed better or worse when plants were grown with their local soil biota, for example, due to plant adaptation or changes in the genetic or species composition of the soil microbial community.Temperature and soil moisture generally increased plant growth, whereas temperature but not soil moisture increased AM fungal colonization. The strength and direction of the plants' response to temperature were dependent on soil moisture and differed among plant populations, and AM fungal colonization was further affected by the origin of the soil microbial community. The root‐associated fungal community structure was impacted by temperature, soil moisture and the soil microbial origin, with interactive effects between the microbial origin and the abiotic environment. Plant biomass was lower when plants were grown with their local soil microbes, potentially due to intraspecific negative plant–soil feedbacks.Synthesis. Our findings indicate that, beyond a relatively uniform increase of plant growth and arbuscular mycorrhizal (AM) fungal colonization with increasing temperature, plants and root‐associated fungi of different origins will vary in their response to climate change (i.e. elevated temperature and shifts in rainfall). This may create pronounced, but difficult to predict, spatial and temporal variation in the ecology and evolution of plant–microbe interactions with a changing climate. [ABSTRACT FROM AUTHOR]

Understanding the importance of biotic interactions in driving the distribution and abundance of species is a central goal of plant ecology. Early vascular plants likely colonized land occupied by biocrusts — photoautotrophic, surface‐dwelling soil communities comprised of cyanobacteria, bryophytes, lichens and fungi — suggesting biotic interactions between biocrusts and plants have been at play for some 2,000 million years. Today, biocrusts coexist with plants in dryland ecosystems worldwide, and have been shown to both facilitate or inhibit plant species performance depending on ecological context. Yet, the factors that drive the direction and magnitude of these effects remain largely unknown.We conducted a meta‐analysis of plant responses to biocrusts using a global dataset encompassing 1,004 studies from six continents.Meta‐analysis revealed there is no simple positive or negative effect of biocrusts on plants. Rather, plant responses differ by biocrust composition and plant species traits and vary across plant ontogeny. Moss‐dominated biocrusts facilitated, while lichen‐dominated biocrusts inhibited overall plant performance. Plant responses also varied among plant functional groups: C4 grasses received greater benefits from biocrusts compared to C3 grasses, and plants without N‐fixing symbionts responded more positively to biocrusts than plants with N‐fixing symbionts. Biocrusts decreased germination but facilitated growth of non‐native plant species.Synthesis. Results suggest that interspecific variation in plant responses to biocrusts, contingent on biocrust type, plant traits, and ontogeny can have strong impacts on plant species performance. These findings have important implications for understanding biocrust contributions to plant productivity and community assembly processes in ecosystems worldwide. [ABSTRACT FROM AUTHOR]

Fine roots play a key role in carbon (C) and nutrient cycling, since fine root life span drives soil organic C input and, thus, nitrogen (N) availability. The two main fungal symbioses found in temperate forest trees, ectomycorrhizae (ECM) and arbuscular mycorrhizae (AM), induce different root morphological changes upon infection, but the consequences for root life span are not clear.We explored differences in fine root life span between four AM and four ECM tree species using mini‐rhizotrons in a factorial drought experiment in large mesocosms.Median root life span of young AM and ECM trees differed fundamentally in its response to soil moisture and season of root birth; ECM root life span was reduced from 176 to 81 days in dry soil compared to moist soil, independent of season. By contrast, AM root life span was less responsive to drought, but decreased from 185 to 127 days when comparing roots produced early in the growing season versus mid‐season. In both mycorrhizal types, root life span was positively related to root diameter and negatively to the portion of lower order roots.Synthesis. While our results indicate morphological and architectural traits that predict root life span across tree species, they also indicate fundamental differences in the environmental response of root life span in young AM and ECM trees. This knowledge helps to improve global predictions of root life span. [ABSTRACT FROM AUTHOR]

Nitrogen (N) and phosphorus (P) often limit biological processes in terrestrial ecosystems. Based on previous studies mainly focusing on plants, the concept of resource limitation has evolved towards a theory of (co)limitations by multiple resources. However, this ecological framework has not been applied to analyse how soil micro‐organisms and plants concurrently respond to N and/or P addition, and whether these responses are constrained by phylogenetic relatedness.Here, we applied this framework to analyse microbial and plant responses at community and taxon levels to different fertilization treatments (four N levels without P; four P levels without N and four NP levels) in Tibetan grasslands.Total plant biomass showed serial limitation by N then P, and most plant species were limited by N only. Total archaeal abundance decreased with P addition, but diverse nutrient limitation types were observed for archaeal taxa. Closely related archaeal taxa tended to similarly respond to N, and functional similarity between distant archaeal groups was observed for response to P, possibly due to functional convergence. In contrast, total bacteria slightly increased with P addition only when plants remained N limited, whereas without N limitation, plants rather than bacteria benefited from P addition. Most bacterial taxa were limited by other resources than N and P, and no clear phylogenetic signals were observed regarding bacterial responses to N/P additions.Synthesis. We propose a novel approach for characterizing microbial response types to nutrient addition. It demonstrates that in Tibetan meadows, most dominant plant species, archaea and bacteria, respectively, depend on N, both N and P and other resources. [ABSTRACT FROM AUTHOR]

Human‐induced environmental change is occurring globally and alters ecosystem properties both directly, by changing abiotic conditions, and indirectly, by modifying community composition. The effects of changes in plant composition in determining ecosystem properties may be determined by the identity of the plants, their respective biomass in the community and also by the ability of remaining vegetation to compensate for their loss.We used the graminoid removal treatment from a long‐term (12 year) removal experiment to examine the role of graminoids in determining ecosystem properties and also the potential for biomass compensation by remaining species in a grassland in northern Canada. We conducted removals in both fertilized and non‐fertilized environments to examine context‐dependency of graminoid effects.There was full biomass compensation for graminoid removal by the remaining functional groups (i.e., total biomass was equal to no‐removal controls) after 5 years, and after 12 years fertilized plots showed overcompensation for removals.After 12 years of graminoid removals, most ecosystem properties were not affected by removals in either fertilization environment. Similarly, there were few effects on microbial biomass or function with plant removal or fertilization treatments.Comparison to earlier published responses in this experiment shows a strengthening of the responses of the plant community to graminoid removals over time while effects on ecosystem properties diminished. Full biomass compensation for removal of graminoids occurred after 5 years, and after 12 years of removals, fertilized plots had overcompensated for the loss of graminoids. In contrast, the shorter term (4 years) responses of soil available nutrients and soil moisture to removals have mainly disappeared after eight further years, likely because of the biomass compensation by the plant community.Synthesis. Comparing the effects of graminoid removals on ecosystem structure and function after 4, 7, and now 10 and 12 years of removals, we now argue that, after over a decade of graminoid removal, recovery of plant biomass is required for the maintenance of most ecosystem properties and not functional group identity, as we concluded earlier. This highlights the importance of maintaining field experiments in the long term, particularly in northern ecosystems. [ABSTRACT FROM AUTHOR]

Domesticated plants can differ from their wild counterparts in the strength and outcome of species interactions, both above‐ and belowground. Plant–soil feedbacks influence plant success, and plant‐associated soil microbial communities can influence plant interactions with herbivores and their natural enemies, yet, it remains unclear if domestication has changed these relationships.To determine the effects of domestication on plant–soil interactions, we characterized soil microbial communities associated with various cultivars of domesticated tomato and some of its wild relatives. We measured the strength and direction of plant–soil feedbacks for domesticated and wild tomatoes, and the effects of soil on plant resistance to specialist herbivory by Manduca sexta, and the attraction of a parasitoid wasp, Cotesia congregata.Domesticated tomatoes and their wild relatives had negative plant–soil feedbacks, as conspecifics cultivated soil that negatively impacted performance of subsequent plants (longer germination time, lower biomass) than if they grew in non‐tomato soils. Significant variation existed among domesticated and wild tomato varieties in the strength of these feedbacks, ranging from neutral to strongly negative. For above‐ground plant biomass, tomato wild relatives were unaffected by growing in tomato‐conditioned soil, whereas domesticated tomatoes grew smaller in tomato soil, indicating effects of plant domestication. Overall, increased microbial biomass within the rhizosphere resulted in progressively less‐negative plant–soil feedbacks.Plant cultivars had different levels of resistance to herbivory by M. sexta, but this did not depend on plant domestication or soil type. The parasitoid C. congregata was primarily attracted to herbivore damaged plants, independent of plant domestication status, and for these damaged plants, wasps preferred some cultivars over others, and wild plants grown in tomato soil over wild plants grown in non‐tomato soil.Synthesis. These results indicate that crop tomatoes are more likely to show negative plant–soil feedbacks than wild progenitors, which could partially explain their sensitivity to monocultures in agricultural soils. Furthermore, cultivar‐specific variation in the ability to generate soil microbial biomass, independent of domestication status, appears to buffer the negative consequences of sharing the same soil. Last, soil legacies were relatively absent for herbivores, but not for parasitoid wasps, suggesting trophic level specificity in soil feedbacks on plant–insect interactions. [ABSTRACT FROM AUTHOR]

Most species engage in broad interactions, in which they interact with multiple partner species. The evolutionary processes that generate such generalized interactions remain unknown, partly due to the difficulty in comparing their breadth.We argue that the interaction specificity of species involved in broad interactions evolves in three ways: (a) assemblage specialization, in which a species specializes on particular host species that contribute unique resources, yielding specialization on the entire host assemblage; (b) apparent generalism, in which a species specializes on one or few host species that contribute unique resources, but also associates with other host species that contribute functionally redundant resources; and (c) true generalism, in which a species associates with multiple hosts that overlap functionally, and that are geographically interchangeable based on opportunity for encounter, leading to frequent host switching.We performed a phylogenetically controlled analysis of data on mycorrhizal fungal associations for approximately 25% of the orchid subfamily Cypripedioideae to determine whether these plants have specialized on their mycorrhizal fungal communities, or whether they are true generalists. We also assessed the impact of environmental factors on these associations.Our results suggested strong support for apparent generalism, suggesting strong specialization on particular, dominant fungi and weak specialization on others. Large orchid clades associated with dominant fungal species, notably Tulasnella cystidiophora for genus Cypripedium, and T. cystidiophora and T. calospora for genus Paphiopedilum. Significant phylogenetic signal in fungal species richness per plant species, but not in the fungal phylogenetic diversity per plant species nor in the composition of fungal assemblages across orchid species suggested that plant phylogeny is an important determinant of fungal association. Mixed linear models showed that environment influenced specificity across plant species, and that observed differences were strongly driven by differences in sampling effort.Synthesis. We found evidence of specialization of plant species on dominant fungal species, and to a lesser extent on their close relatives. The strong dominance of particular fungal species in these associations suggests important ecological roles for them, while environmental gradients in specificity suggest strong environmental filtering of these interactions. [ABSTRACT FROM AUTHOR]

Interactions between plants and their root‐associated fungi (RAF) may influence the relative abundance of tree species and determine forest community diversity. Such plant–soil feedbacks in turn depend on the degree to which spatial distance and phylogenetic relatedness of host trees structure pathogen and mutualist communities, but research detailing these aspects of RAF communities is lacking. Here, we characterize plant–RAF associations across a diverse plant community, focusing on the degree to which RAF communities are structured by spatial distance, host phylogenetic relatedness, and host abundance. We compare results for different functional groups, including both putative mutualists and pathogens, an aspect poorly examined hitherto.We collected roots at regular intervals along ten 50 m by 2 m transects, then used DNA barcoding to identify host plants, and characterize the associated fungal community. Variance partitioning was used to measure the relative contributions of host phylogenetic relatedness and spatial distance to explaining RAF community composition. A weighted linear regression was used to measure the correlation between host abundance and RAF diversity.Phylogenetic distance among hosts was a better predictor of RAF community composition than spatial distance, but this relationship was stronger for putative pathogens than for mutualists, suggesting that pathogens show stronger host preference than mutualists. Across all functional groups, RAF showed similar levels of spatial structure. Additionally, RAF communities of locally abundant plants were less diverse than RAF communities of rare plants.Synthesis. We found that RAF communities are structured by the phylogenetic relatedness of hosts and, to a lesser extent, by spatial distance, with pathogens showing stronger host preference than mutualists. Abundant hosts had less diverse RAF communities than rare hosts, which is notable because abundant plants tend to experience weaker negative plant–soil feedback. Going forward, mechanisms underlying the host abundance‐RAF diversity relationship warrant further investigation. Additionally, the survey approach presented here could be paired with experiments linking RAF community composition to plant recruitment. [ABSTRACT FROM AUTHOR]

The occurrence of plant-associated oomycetes in natural ecosystems and particularly during long-term ecosystem development is largely unknown. Using DNA sequencing, we investigated the frequency and host relationships of plant-root-associated oomycete communities along a 120 000 y glacial chronosequence, comprising site ages with rapid compositional change ("early succession"; 5–70 y old soil); relatively stable higher-diversity sites ("mature", 280–12000 y); and ancient, nutrient-limited soils with declining plant biomass and stature ("retrogression", 60 000, 120 000 y). Plant-associated oomycetes were frequent in early successional sites, occurring in 38–65% of plant roots, but rare (mean 3%) in all older ecosystems. Oomycete OTUs occurred non-randomly with plant host species, and were more frequent on those plant species that declined most strongly in abundance between ecosystem ages. While oomycetes were common in early succession, their absence in older sites suggests a limited role in later stages of ecosystem development. [ABSTRACT FROM AUTHOR]

A major goal in microbial ecology is to understand the factors that structure bacterial communities across space and time. For microbes that are plant symbionts, community assembly processes can lead to either a positive or negative relationship between plant size or age and soil microbe diversity. Here, we evaluated the extent to which such relationships exist within a single legume species (Acacia acuminata) and their naturally occurring symbiotic nitrogen‐fixing bacteria (rhizobia).We quantified the diversity of rhizobia that associate with A. acuminata trees of variable size spanning a large environmental gradient in southwest Australia (72 trees in 24 sites spread across ~300,000 km2), using metabarcoding. We modelled rhizobia diversity using 16S exact genetic variants, in a binomial multivariate statistical framework that controlled for climate and local soil characteristics.We identified two major phylogenetic clades of rhizobia that associate with A. acuminata. Soil sampled at the base of larger Acacia trees contained a higher richness of rhizobia genetic variants. Each major clade responds differently to environmental factors (climate and soil characteristics), but the positive association between tree size and rhizobia genetic diversity was mainly driven by responses from one of the two clades. Overall tree size explained more variation than any other factor, resulting in a ~3‐fold increase in total richness and clade diversity from the smallest to the largest trees.Synthesis. Previous studies have shown that plant host species is important in structuring microbial soil communities in the rhizosphere. Our results show that host size or age within a single plant species can also structure diversity of at least one group of soil microbes. A positive relationship between plant host size and rhizobia diversity suggests that hosts may modify the niche space of their surrounding soil (niche construction hypothesis) enabling a higher richness of microbial taxa. That different rhizobial groups responded differently to host size and other ecological factors suggests that rhizobia is not an ecologically uniform group, and that entirely neutral explanations for our results are unlikely. Host plants may be analogous to "islands," where larger plant hosts may accumulate diversity over time, through migration opportunities. Previous studies have shown that plant host species is important in structuring microbial soil communities in the rhizosphere. Our results show that host size or age within a single plant species can also structure diversity of at least one group of soil microbes. A positive relationship between plant host size and rhizobia diversity suggests that hosts may modify the niche space of their surrounding soil (niche construction hypothesis) enabling a higher richness of microbial taxa. That different rhizobial groups responded differently to host size and other ecological factors suggests that rhizobia is not an ecologically uniform group, and that entirely neutral explanations for our results are unlikely. Host plants may be analogous to "islands," where larger plant hosts may accumulate diversity over time, through migration opportunities. [ABSTRACT FROM AUTHOR]

The study of coupled green and brown food webs has improved our ability to understand how nutrient cycling and plant communities respond to perturbations. Yet, it is still difficult to predict how rapidly and consistently changes in one food web propagate to the other. An area of particular uncertainty is the response of plants to the changes in leaf litter nitrogen release caused by herbivores and detritivores.We combined a field experiment and theoretical analysis to assess how herbivory, fertilization, and detritivory changed leaf litter nitrogen release and plant growth. We produced leaf litter in greenhouse cages with a factorial combination of grasshopper herbivory and additional nitrogen fertilizer. Our experiment used the resulting 15N‐labelled leaf litter to measure isopod litter consumption, litter nitrogen release, and plant nitrogen uptake in the field. We then used a dynamical systems model to distinguish whether plant growth relied (a) directly on litter nitrogen release or (b) on other nitrogen pathways so that changes in litter nitrogen release have little immediate impact.Our empirical results show that the effect of nitrogen fertilization on isopod processing of leaf litter was stronger than the effect of herbivory. Regardless, the available soil nitrogen and plant growth were independent of litter nitrogen release. Our dynamical model attributes the independence to other nitrogen sources and sinks, which buffer the plant‐available nitrogen pool. Isopods and litter with a history of herbivory reduced above‐ground plant growth when we accounted for initial field mesocosm conditions, especially the abundance of the competitively dominant goldenrods. Consequently, the impact of isopods and litter traits do propagate to influence plant growth, but do not have a large enough effect to overcome initial differences in plant biomass and community composition in one year.Synthesis. Our results indicate animals in green and brown food webs can alter plant litter nitrogen release without any significant nutrient recycling effect on plant growth. Considering the availability of external and soil‐based nitrogen sources, as well as the current plant community and microbial biomass, may be critical to determining when plant growth will respond to animal‐mediated changes in litter decomposition. Animals in green and brown food chains altered plant litter nitrogen release but not plant growth. The exchange of nitrogen with external or slow cycling pools, as captured by a diffuse cycling model, can explain why litter decomposition and plant growth were decoupled. Considering these other nitrogen pools and the current ecosystem state may help to predict animal‐mediated changes in ecosystems. [ABSTRACT FROM AUTHOR]

Plant mutualists including arbuscular mycorrhizal (AM) fungi have been postulated as being important drivers of plant community diversity and succession. Late successional plants have been shown to be more responsive to AM fungi and more sensitive to AM fungal species identity, which could generate positive feedback and potentially accelerate succession.We test the effect of AM fungi on plant diversity and on frequency dependence predicted by positive plant–AM fungi feedback across a successional gradient. We created prairie mesocosms comprised of a majority of early successional, equal abundance, and a majority of late successional plant species. We inoculated these mesocosms and a field restoration experiment with 14 different communities of AM fungi from late successional prairies that varied in levels of species richness.Overall, we found that AM fungi increased plant diversity and this was driven by the response of late successional plant species to mycorrhizae. Our results indicate that AM fungal composition is more important than AM fungal diversity per se. We found that the effect of inoculation with a single species or groups of AM fungi depended on whether those fungi benefited late successional plant species. Early successional plants consistently exhibited negative frequency‐dependent growth regardless of fungal composition, while late successional plants demonstrated positive frequency‐dependent growth in our mesocosms—but only in the presence of beneficial AM fungal species. These results are consistent with positive plant–mycorrhizal feedbacks accelerating plant community successional trajectories once late successional plants establish. Mesocosm results were mirrored with field inoculation assays where we found that beneficial AM fungi facilitated late successional plant establishment.Synthesis. Our results provide support for beneficial arbuscular mycorrhizal fungi being a primary mechanism for positive plant–soil feedback driving plant community succession, as late successional seedlings grew faster and larger when their neighbours were also late successional plant species when they were associated with beneficial arbuscular mycorrhizal fungi. We found that this positive feedback thereby accelerated succession in mesocosms and in the field. Our results provide support for beneficial arbuscular mycorrhizal fungi being a primary mechanism for positive plant–soil feedback driving plant community succession, as late successional seedlings grew faster and larger when their neighbours were also late successional plant species when they were associated with beneficial arbuscular mycorrhizal fungi. We found that this positive feedback thereby accelerated succession in mesocosms and in the field. [ABSTRACT FROM AUTHOR]