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Background and aims: Soil heterogeneity can be caused by plant-soil feedback (PSF), but little is known about how this affects plant growth and the distribution of roots. Moreover, as invasive and native plant species frequently differ in PSF and root-foraging ability, they may differ in their responses to PSF-mediated soil heterogeneity. Methods: We first conditioned soils by 16 plant species (eight confamilial pairs of invasive alien and native species). Then, we grew each species in a homogeneous treatment with unconditioned soil and in three heterogeneous treatments with four patches. In the home-soil treatment, we filled two patches with unconditioned soil and two with soil conditioned by the target species. In the foreign-soil treatment, we filled two patches with unconditioned soil and two with soil conditioned by the other species in a pair. In the home-and-foreign-soil treatment, we filled two patches with home soil and two with foreign soil. Results: Compared to the homogeneous unconditioned soil treatment, PSF negatively affected plant growth. In the heterogeneous treatment with control- and home-soil patches, biomass was reduced more strongly for the invasive species than for the native species. In the heterogeneous treatment with both home- and foreign-soil patches, root biomass of the invasive species was greater in the foreign-soil than in the home-soil patches, whereas the reverse was true for natives. Conclusion: Although invasive species suffered more from conspecific PSF, root foraging allowed them to avoid home soil. In the long term, this could help invasive species gain a competitive advantage over natives. [ABSTRACT FROM AUTHOR]

Purpose: The invasive weed common ragweed (Ambrosia artemisiifolia [L.]) has become notorious in China as a major weed in agriculture. Soil microbial communities play important roles in invasive plant growth by potentially mediating nutrient cycling in soil. However, knowledge regarding the soil microbial communities in common ragweed remains limited. Methods: In this study, a long-term field experiment was conducted to comparatively study the microbial community compositions in the rhizosphere soil of invasive common ragweed and two native plants, Chenopodium serotinum and Setaria viridis. Results: We found that the bacterial and fungal community compositions differed significantly between common ragweed and two native plants. Invasion by common ragweed selectively accumulated microorganisms, such as Exopiala, RB41, Cnuella, Dinghuibacter and Funneliformis, that can enhance carbon and nitrogen cycling and the absorption of phosphorus in the rhizosphere environment. Moreover, the relative abundances of these microorganisms were significantly related to the soil pH and ammonium contents. Furthermore, we found that microbial inoculants from rhizosphere of common ragweed promote growth of both common ragweed and S. viridis. Conclusions: Our results show that common ragweed constructs a unique rhizosphere microbial community that distinguishes it from local plants, which could contribute to its growth and expansion by providing a stronger ability to use carbon, nitrogen, and phosphorus. This study offers fundamental explanation to explain how the underground microbial community facilitate the invasion of common ragweed on an ecosystem-level. [ABSTRACT FROM AUTHOR]

Background and aims: Heavy metal (especially for potentially toxic element) contamination in soil has frequently been associated with plant invasion. However, the mechanisms underpinning plant invasion under potentially toxic element contamination remain unclear. Here we studied how differences in clonal traits of invasive and native plants affect their response strategies to stresses of potentially toxic element contamination. Methods: We manipulated clonal integration of two pairs (Alternanthera philoxeroides - A. sessilis, and Sphagneticola trilobata - S. calendulacea) of congeneric invasive and native plants by either severing stolons between ramet pair or not severing, and grew them in soils contaminated by three levels of Cd and three levels of Pb. Results: Our results show that the combination of Cd and Pb contamination decreased plant growth of recipient ramets of Alternanthera species. Under Pb stress, invasive S. trilobata is Pb-hyperaccumulation and benefits more from clonal integration than native S. calendulacea. Similarly, under Cd stress, invasive A. philoxeroides shows higher Cd risk sharing and benefits more from clonal integration than native A. sessilis. In contrast, clonal integration decreased the performance of A. sessilis under high Cd stress. Conclusion: These results suggest that invasive species such as A. philoxeroides and S. trilobata are able to alleviate the toxic effects of Cd and Pb co-contamination via clonal integration, thus becoming more invasive in contaminated environments with potentially toxic elements. [ABSTRACT FROM AUTHOR]

Aims: Environmental heterogeneity can influence biological invasions by altering the interspecific competition between native and invasive species. Soils are a key component of the abiotic environment that can vary in small scales. However, it is not clear how the mechanisms that patch size of soil heterogeneity mediates competition between native and invasive plants. Methods: We grew invasive Rhus typhina and native Rhus chinensis in intraspecific (two seedlings of the same species per pot) and interspecific competition (one seedling of each of the two species per pot) with three different soil treatments: homogeneous (Ho) and two soil heterogeneous (He1 and He2) treatments. In He1 and He2 treatments, the soil consisted of loam and peat patches but different patch sizes, and in Ho treatment, the soil was a uniform mixture of the two types of soil patches. Results: We found R. typhina had greater overall performance and belowground investment compared to R. chinensis and outcompeted R. chinensis in the interspecific competition regardless of soil heterogeneity. The strength of interspecific competition increased with increasing soil heterogeneity, such that soil heterogeneity amplified the superiority of R. typhina over R. chinensis. Moreover, R. chinensis were more plastic in phenotype than R. typhina, indicating phenotypic plasticity did not confer advantages to R. typhina over R. chinensis across various soil heterogeneity. Conclusions: Soil heterogeneity can facilitate the invasion of R. typhina by enhancing the advantages over R. chinensis and altering interspecific competition. Phenotypic divergence rather than plasticity plays an important role in mediating interspecific competition. [ABSTRACT FROM AUTHOR]

Background and aims: Invasive species represent a threat to the conservation of biological systems. Riparian ecosystems are vulnerable to plant invasions, as waterflow facilitates the dispersal of plant propagules, while invasive species may subsequently impact soil, including soil microbial communities. Downstream connectivity among disparate riverine segments is expected to cause spatial continuity of abiotic and biotic components of riparian ecosystems.We studied diversity of microbial communities in three headwater streams in Central Europe. Plant diversity, soil properties and soil microbiota were assessed on 20 sample plots per river. Soil microbial activity and community-level physiological profiling were used to study the soil microbial community.While the α-diversity of plants and soil microbiota was similar among rivers, plant communities were substantially more differentiated than microbial communities. Richness in alien and invasive plants significantly differed among rivers, which was reflected in different spatial patterns of microbial activity and diversity. A high level of spatial continuity was observed in the Kysuca river with straightened riverbed and artificial surfaces in the adjacent areas. The cover of invasive plants affects the composition of microbial functional groups of riverbed soils.The expectation of spatial continuity of riverbed soil properties including those of soil microbiota caused by connectivity between different river segments was only partially fulfilled. Spatial continuity strongly depends on the environmental setting and stream characteristics of a particular river. The presence of invasive herbs affected the functional composition of soil microbiota but had no effect on microbial activity and diversity.Methods: Invasive species represent a threat to the conservation of biological systems. Riparian ecosystems are vulnerable to plant invasions, as waterflow facilitates the dispersal of plant propagules, while invasive species may subsequently impact soil, including soil microbial communities. Downstream connectivity among disparate riverine segments is expected to cause spatial continuity of abiotic and biotic components of riparian ecosystems.We studied diversity of microbial communities in three headwater streams in Central Europe. Plant diversity, soil properties and soil microbiota were assessed on 20 sample plots per river. Soil microbial activity and community-level physiological profiling were used to study the soil microbial community.While the α-diversity of plants and soil microbiota was similar among rivers, plant communities were substantially more differentiated than microbial communities. Richness in alien and invasive plants significantly differed among rivers, which was reflected in different spatial patterns of microbial activity and diversity. A high level of spatial continuity was observed in the Kysuca river with straightened riverbed and artificial surfaces in the adjacent areas. The cover of invasive plants affects the composition of microbial functional groups of riverbed soils.The expectation of spatial continuity of riverbed soil properties including those of soil microbiota caused by connectivity between different river segments was only partially fulfilled. Spatial continuity strongly depends on the environmental setting and stream characteristics of a particular river. The presence of invasive herbs affected the functional composition of soil microbiota but had no effect on microbial activity and diversity.Results: Invasive species represent a threat to the conservation of biological systems. Riparian ecosystems are vulnerable to plant invasions, as waterflow facilitates the dispersal of plant propagules, while invasive species may subsequently impact soil, including soil microbial communities. Downstream connectivity among disparate riverine segments is expected to cause spatial continuity of abiotic and biotic components of riparian ecosystems.We studied diversity of microbial communities in three headwater streams in Central Europe. Plant diversity, soil properties and soil microbiota were assessed on 20 sample plots per river. Soil microbial activity and community-level physiological profiling were used to study the soil microbial community.While the α-diversity of plants and soil microbiota was similar among rivers, plant communities were substantially more differentiated than microbial communities. Richness in alien and invasive plants significantly differed among rivers, which was reflected in different spatial patterns of microbial activity and diversity. A high level of spatial continuity was observed in the Kysuca river with straightened riverbed and artificial surfaces in the adjacent areas. The cover of invasive plants affects the composition of microbial functional groups of riverbed soils.The expectation of spatial continuity of riverbed soil properties including those of soil microbiota caused by connectivity between different river segments was only partially fulfilled. Spatial continuity strongly depends on the environmental setting and stream characteristics of a particular river. The presence of invasive herbs affected the functional composition of soil microbiota but had no effect on microbial activity and diversity.Conclusion: Invasive species represent a threat to the conservation of biological systems. Riparian ecosystems are vulnerable to plant invasions, as waterflow facilitates the dispersal of plant propagules, while invasive species may subsequently impact soil, including soil microbial communities. Downstream connectivity among disparate riverine segments is expected to cause spatial continuity of abiotic and biotic components of riparian ecosystems.We studied diversity of microbial communities in three headwater streams in Central Europe. Plant diversity, soil properties and soil microbiota were assessed on 20 sample plots per river. Soil microbial activity and community-level physiological profiling were used to study the soil microbial community.While the α-diversity of plants and soil microbiota was similar among rivers, plant communities were substantially more differentiated than microbial communities. Richness in alien and invasive plants significantly differed among rivers, which was reflected in different spatial patterns of microbial activity and diversity. A high level of spatial continuity was observed in the Kysuca river with straightened riverbed and artificial surfaces in the adjacent areas. The cover of invasive plants affects the composition of microbial functional groups of riverbed soils.The expectation of spatial continuity of riverbed soil properties including those of soil microbiota caused by connectivity between different river segments was only partially fulfilled. Spatial continuity strongly depends on the environmental setting and stream characteristics of a particular river. The presence of invasive herbs affected the functional composition of soil microbiota but had no effect on microbial activity and diversity. [ABSTRACT FROM AUTHOR]

Purpose: Cheatgrass invasion of Intermountain sagebrush steppe in the western United States poses increasing challenges to the function and survival of this native ecosystem. The invasive success and persistence of cheatgrass has been attributed to the increasing soil total nitrogen, but mechanisms behind remain inconclusive. We hypothesized that soil microorganisms play a role in soil nitrogen associated with cheatgrass invasion. Methods: We collected soil samples from the root zone of cheatgrass, native bunchgrass, and sagebrush at two depths and from two adjacent sites in April. We examined soil chemical properties (pH, moisture content, and NH4+ and NO3− concentration) and soil microbial communities. Results: We found that cheatgrass invasion was associated with different soil microbial community composition compared to native bunchgrass and sagebrush. In particular, we observed higher relative abundances of N2 fixers and ureolytic bacteria and lower relative abundance of denitrifiers providing a potential mechanistic belowground explanation of raising soil nitrogen. Conclusions: Overall, our results indicate the importance of soil microorganisms in the dominance and persistence of invasive species. Targeted microbiome interventions should be considered to control cheatgrass invasion. [ABSTRACT FROM AUTHOR]

Aims: Understanding the ecological impacts of biological invasions is a core issue of invasion ecology. Soil microbiomes control the functioning and health of ecosystems. The aim of this study was to uncover the changes in the soil microbiome caused by invasive plant expansion. Methods: Taking the typical invasive plant Alternanthera philoxeroides as an example, the structure, diversity, co-occurrence patterns, habitat niche breadth, and assembly processes of the microbiome in invasion-present and invasion-absent soils were analyzed based on high-throughput sequencing. Results: The invasion altered the structure and composition of the soil microbiome significantly. A group of biomarkers was established using the random-forest machine-learning model to best represent the differences in the microbiome between the invasion-present and invasion-absent soils. The plant invasion decreased the beta-diversity of the soil microbiome but increased the alpha-diversity. Compared with the invasion-absent soils, the invasion-present soils had a more complex and robust network with more keystone species, fewer modules, and more co-occurring associations. The microbiome in the invasion-present soils had a wider habitat niche breadth, with a higher proportion of habitat generalists and lower proportion of habitat specialists. Finally, the importance of stochasticity in the community assembly increased in the invasion-present soils, although deterministic processes still played a dominant role. Conclusion: This study reveals the consequences to the soil microbiome of the expansion of invasive plants, which is of great significance for an in-depth understanding of the ecological impacts of plant invasion and soil-microbe ecological processes. [ABSTRACT FROM AUTHOR]

Background and aims: Several studies have shown that soil microorganisms and physicochemical properties are crucial for the successful colonisation of invasive plants. However, most researchers have focused merely on the impacts of invasive plants on soil-internal ecosystems to reveal their invasive mechanisms and ecological effectiveness. On this basis, this paper aims to investigate the role of soil physicochemical properties and microbial communities on plant invasion and the associated mechanisms.Solidago canadensis L. was used as the research object, with seed germination characteristics as the indicator of invasion capability. Comparative treatments were conducted from three dimensions: soils from invasive/native regions, sterilised/non-sterilised soil, and sterilised/non-sterilised seeds. Germination capacity was verified using seed germination experiments, and the mechanism was elucidated by 16S rRNA high-throughput sequencing of soil microorganisms and the determination of physicochemical properties.The results indicated that the seed germination characteristics of invasive soils, non-sterilised soils, and non-sterilised seed treatments were higher than those of their respective controls. The invasion of S. canadensis changed soil physicochemical properties and promoted the cycling of nitrogen and phosphorus, which affected the microbial community composition and abundance, reversing the soil to facilitate continued invasion. Soil microorganisms, including Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Basidiomycota, Chytridiomycota, and Glomeromycota, promoted S. canadensis invasion by increasing seed germination rate. Seed-borne microbial communities were beneficial to seed germination, and the sterilisation to seeds significantly reduced their germinability.This study clarified the invasion mechanism of S. canadensis regulated by soil microorganisms and physicochemical properties.Methods: Several studies have shown that soil microorganisms and physicochemical properties are crucial for the successful colonisation of invasive plants. However, most researchers have focused merely on the impacts of invasive plants on soil-internal ecosystems to reveal their invasive mechanisms and ecological effectiveness. On this basis, this paper aims to investigate the role of soil physicochemical properties and microbial communities on plant invasion and the associated mechanisms.Solidago canadensis L. was used as the research object, with seed germination characteristics as the indicator of invasion capability. Comparative treatments were conducted from three dimensions: soils from invasive/native regions, sterilised/non-sterilised soil, and sterilised/non-sterilised seeds. Germination capacity was verified using seed germination experiments, and the mechanism was elucidated by 16S rRNA high-throughput sequencing of soil microorganisms and the determination of physicochemical properties.The results indicated that the seed germination characteristics of invasive soils, non-sterilised soils, and non-sterilised seed treatments were higher than those of their respective controls. The invasion of S. canadensis changed soil physicochemical properties and promoted the cycling of nitrogen and phosphorus, which affected the microbial community composition and abundance, reversing the soil to facilitate continued invasion. Soil microorganisms, including Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Basidiomycota, Chytridiomycota, and Glomeromycota, promoted S. canadensis invasion by increasing seed germination rate. Seed-borne microbial communities were beneficial to seed germination, and the sterilisation to seeds significantly reduced their germinability.This study clarified the invasion mechanism of S. canadensis regulated by soil microorganisms and physicochemical properties.Results: Several studies have shown that soil microorganisms and physicochemical properties are crucial for the successful colonisation of invasive plants. However, most researchers have focused merely on the impacts of invasive plants on soil-internal ecosystems to reveal their invasive mechanisms and ecological effectiveness. On this basis, this paper aims to investigate the role of soil physicochemical properties and microbial communities on plant invasion and the associated mechanisms.Solidago canadensis L. was used as the research object, with seed germination characteristics as the indicator of invasion capability. Comparative treatments were conducted from three dimensions: soils from invasive/native regions, sterilised/non-sterilised soil, and sterilised/non-sterilised seeds. Germination capacity was verified using seed germination experiments, and the mechanism was elucidated by 16S rRNA high-throughput sequencing of soil microorganisms and the determination of physicochemical properties.The results indicated that the seed germination characteristics of invasive soils, non-sterilised soils, and non-sterilised seed treatments were higher than those of their respective controls. The invasion of S. canadensis changed soil physicochemical properties and promoted the cycling of nitrogen and phosphorus, which affected the microbial community composition and abundance, reversing the soil to facilitate continued invasion. Soil microorganisms, including Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Basidiomycota, Chytridiomycota, and Glomeromycota, promoted S. canadensis invasion by increasing seed germination rate. Seed-borne microbial communities were beneficial to seed germination, and the sterilisation to seeds significantly reduced their germinability.This study clarified the invasion mechanism of S. canadensis regulated by soil microorganisms and physicochemical properties.Conclusion: Several studies have shown that soil microorganisms and physicochemical properties are crucial for the successful colonisation of invasive plants. However, most researchers have focused merely on the impacts of invasive plants on soil-internal ecosystems to reveal their invasive mechanisms and ecological effectiveness. On this basis, this paper aims to investigate the role of soil physicochemical properties and microbial communities on plant invasion and the associated mechanisms.Solidago canadensis L. was used as the research object, with seed germination characteristics as the indicator of invasion capability. Comparative treatments were conducted from three dimensions: soils from invasive/native regions, sterilised/non-sterilised soil, and sterilised/non-sterilised seeds. Germination capacity was verified using seed germination experiments, and the mechanism was elucidated by 16S rRNA high-throughput sequencing of soil microorganisms and the determination of physicochemical properties.The results indicated that the seed germination characteristics of invasive soils, non-sterilised soils, and non-sterilised seed treatments were higher than those of their respective controls. The invasion of S. canadensis changed soil physicochemical properties and promoted the cycling of nitrogen and phosphorus, which affected the microbial community composition and abundance, reversing the soil to facilitate continued invasion. Soil microorganisms, including Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Basidiomycota, Chytridiomycota, and Glomeromycota, promoted S. canadensis invasion by increasing seed germination rate. Seed-borne microbial communities were beneficial to seed germination, and the sterilisation to seeds significantly reduced their germinability.This study clarified the invasion mechanism of S. canadensis regulated by soil microorganisms and physicochemical properties.Graphical abstract: Several studies have shown that soil microorganisms and physicochemical properties are crucial for the successful colonisation of invasive plants. However, most researchers have focused merely on the impacts of invasive plants on soil-internal ecosystems to reveal their invasive mechanisms and ecological effectiveness. On this basis, this paper aims to investigate the role of soil physicochemical properties and microbial communities on plant invasion and the associated mechanisms.Solidago canadensis L. was used as the research object, with seed germination characteristics as the indicator of invasion capability. Comparative treatments were conducted from three dimensions: soils from invasive/native regions, sterilised/non-sterilised soil, and sterilised/non-sterilised seeds. Germination capacity was verified using seed germination experiments, and the mechanism was elucidated by 16S rRNA high-throughput sequencing of soil microorganisms and the determination of physicochemical properties.The results indicated that the seed germination characteristics of invasive soils, non-sterilised soils, and non-sterilised seed treatments were higher than those of their respective controls. The invasion of S. canadensis changed soil physicochemical properties and promoted the cycling of nitrogen and phosphorus, which affected the microbial community composition and abundance, reversing the soil to facilitate continued invasion. Soil microorganisms, including Proteobacteria, Actinobacteriota, Acidobacteriota, Chloroflexi, Firmicutes, Basidiomycota, Chytridiomycota, and Glomeromycota, promoted S. canadensis invasion by increasing seed germination rate. Seed-borne microbial communities were beneficial to seed germination, and the sterilisation to seeds significantly reduced their germinability.This study clarified the invasion mechanism of S. canadensis regulated by soil microorganisms and physicochemical properties. [ABSTRACT FROM AUTHOR]

Purpose: Microorganisms that inhabit at microhabitat of bulk soil, rhizosphere, and root play different roles in carbon and nutrient cycling, and their changes have differential impacts on plant community dynamics. However, there is an extensive knowledge deficit regarding how plant invasion affects soil microorganisms residing at different microhabitats of plant species being invaded and even those of the invader itself. Methods: This study employed high-throughput sequencing of bacterial 16S rRNA genes and the fungal internal transcribed spacer (ITS) region to investigate the microbial community structure and function(s) of bulk soil, rhizosphere, and roots of a dominant native tree species (Cyclobalanopsis glauca) in a subtropical evergreen forest invaded and uninvaded by an invasive native species (Phyllostachys edulis, Moso bamboo), and that of the invader itself at both invaded and uninvaded forests. Moreover, we calculated the α-, β-diversity and phyla composition and predicted the function and co-occurrence network of microbes. Results: The bacterial richness rather than fungal richness in bulk soil was observed to have increased after being invaded by bamboo. Both richness and co-occurrence network of the root-associated microbiomes of C. glauca declined after being invaded by bamboo, with a more drastic change in the rhizosphere than in roots. In the case of the bamboo, it was observed that bacterial networks had strengthened after they were invaded into the ambient forest as opposed to when they were in a monoculture, with a heavier change in root than in the rhizosphere. Furthermore, the changes in the root-associated microbial composition of C. glauca were mainly relevant for nutritional cycling, particularly bacteria responsible for nitrogen (N) cycling, implying the strengthened competition of C. glauca for nutrients after being invaded by bamboo. Conclusion: This study revealed that the invasion of bamboo resulted in significant but differential changes in microbial community structure and related functions that were inhabited within the bulk soil, and at the rhizosphere, and roots of both dominant native tree species and the bamboo itself. A more profound observation was made where the invasive and non-invasive plants showed contrasting responses between rhizosphere and root after invasion or being invaded, with the rhizospheric microbes of non-invasive plants being more sensitive than that of roots, and the roots of invader were more sensitive than rhizosphere. The study findings have important implications for soil carbon and nutrients cycling and even community development of subtropical evergreen forests. [ABSTRACT FROM AUTHOR]

Aims: Invasive plants not only alter aboveground biodiversity but also belowground microbial community composition to facilitate their growth and competitiveness. However, how plant invasion affects soil microbial resource limitation and metabolic activity, and their linkages with litter and soil stoichiometries remain largely unknown. Methods: We investigated the carbon (C): nitrogen (N): phosphorus (P) stoichiometries of litter, soil, microbe and extracellular enzymes, composition of main microbial groups and substrate utilization rate in a subtropical forest invaded by Moso bamboo (Phyllostachys edulis) and those in adjacent broadleaf and mixed bamboo-broadleaf forests. Results: Bamboo invasion significantly decreased annual litter production, litter C: P and N: P ratios, and soil C:N and C:P ratios, whereas increased microbial biomass C:N and C:P ratios, resulting in decreased C:N and C:P imbalances between soil microorganisms and their resources. Bamboo invasion decreased the N and P acquiring enzymes activities, mitigated the status of microbial N and P limitation as indicated by enzymatic stoichiometry, and caused a higher C use efficiency. Soil microbial community structure was shifted towards a lower fungi: bacteria (F:B) ratio in bamboo forest. Bamboo forest soil showed a lower capacity of microbes to use N-rich resources in comparison to C-rich resources. Structural equation modeling suggested a direct and negative effect of C:N imbalance on microbial N limitation and metabolic capacity. Conclusions: This study suggests the importance of stoichiometric imbalance between decomposers and their resources in regulating soil microbial community structure and enzyme activities following plant invasion. [ABSTRACT FROM AUTHOR]

Background and aims: Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native species is affected by their soil legacies and by the presence of an additional species.In our two-phase plant-soil-feedback experiment, soils were first conditioned by eight herbaceous species, four of which are naturalized and four of which are native to Germany. We then grew all 16 pairwise alien-native species combinations on soil conditioned by the respective alien or native species, on a mixture of soils conditioned by both species or on control soil. Each pair of test plants was grown on these soils without or with an additional alien or native species.Soil conditioning, and particularly conspecific soil conditioning, reduced growth of the alien and native test plants. The addition of another species also reduced growth of the test plants. However, the negative conspecific soil-legacy effect on alien test plants was reduced when the additional species was also alien.The negative conspecific plant-soil feedback for alien and native plants in our study could promote their coexistence. However, as partial alleviation of negative conspecific effects on alien plants occurred with an additional alien species, the chances of coexistence of alien and native species might decrease when there are multiple alien species present.Methods: Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native species is affected by their soil legacies and by the presence of an additional species.In our two-phase plant-soil-feedback experiment, soils were first conditioned by eight herbaceous species, four of which are naturalized and four of which are native to Germany. We then grew all 16 pairwise alien-native species combinations on soil conditioned by the respective alien or native species, on a mixture of soils conditioned by both species or on control soil. Each pair of test plants was grown on these soils without or with an additional alien or native species.Soil conditioning, and particularly conspecific soil conditioning, reduced growth of the alien and native test plants. The addition of another species also reduced growth of the test plants. However, the negative conspecific soil-legacy effect on alien test plants was reduced when the additional species was also alien.The negative conspecific plant-soil feedback for alien and native plants in our study could promote their coexistence. However, as partial alleviation of negative conspecific effects on alien plants occurred with an additional alien species, the chances of coexistence of alien and native species might decrease when there are multiple alien species present.Results: Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native species is affected by their soil legacies and by the presence of an additional species.In our two-phase plant-soil-feedback experiment, soils were first conditioned by eight herbaceous species, four of which are naturalized and four of which are native to Germany. We then grew all 16 pairwise alien-native species combinations on soil conditioned by the respective alien or native species, on a mixture of soils conditioned by both species or on control soil. Each pair of test plants was grown on these soils without or with an additional alien or native species.Soil conditioning, and particularly conspecific soil conditioning, reduced growth of the alien and native test plants. The addition of another species also reduced growth of the test plants. However, the negative conspecific soil-legacy effect on alien test plants was reduced when the additional species was also alien.The negative conspecific plant-soil feedback for alien and native plants in our study could promote their coexistence. However, as partial alleviation of negative conspecific effects on alien plants occurred with an additional alien species, the chances of coexistence of alien and native species might decrease when there are multiple alien species present.Conclusion: Naturalized alien and native plants can impact each other directly when they grow next to each other, but also indirectly through their soil legacies. These alien-native interactions can also be modified by the presence of a third alien or native species. However, it is unknown how the performance of co-growing alien and native species is affected by their soil legacies and by the presence of an additional species.In our two-phase plant-soil-feedback experiment, soils were first conditioned by eight herbaceous species, four of which are naturalized and four of which are native to Germany. We then grew all 16 pairwise alien-native species combinations on soil conditioned by the respective alien or native species, on a mixture of soils conditioned by both species or on control soil. Each pair of test plants was grown on these soils without or with an additional alien or native species.Soil conditioning, and particularly conspecific soil conditioning, reduced growth of the alien and native test plants. The addition of another species also reduced growth of the test plants. However, the negative conspecific soil-legacy effect on alien test plants was reduced when the additional species was also alien.The negative conspecific plant-soil feedback for alien and native plants in our study could promote their coexistence. However, as partial alleviation of negative conspecific effects on alien plants occurred with an additional alien species, the chances of coexistence of alien and native species might decrease when there are multiple alien species present. [ABSTRACT FROM AUTHOR]

Aims: Biological invasions have historically been addressed mostly from an aboveground perspective, so little is known about the impacts of belowground invasions. We studied the impact of belowground invasions on growth of native tree species and test the possibility of novel interactions between native and non-native hosts and native and non-native belowground symbionts. Methods: We combined field and growth chamber studies. With a growth chamber bioassay we compared growth and root colonization percentage of native Nothofagus and non-native invasive pine species, both highly dependent on ectomycorrhizal fungi (EMF), growing in pine invaded and non-invaded soils from native Nothofagus forest. We evaluated the identity of EMF species associated with both hosts in the different soil sources from the bioassay and we performed an in situ root sampling in the field. Results: We found that both hosts grew equally well in both soil sources in terms of biomass, with high percent of root colonization, and no cross-host colonization of symbiotic EMF except for one species of Sistotrema found on both hosts. Conclusions: Soil where invasive hosts are absent is already conditioned by the presence of non-native invasive EMF. Native trees may be able to remain in the invaded area due to the presence of native EMF. The presence of native hosts is not hindering the invasion of non-native hosts and the presence of native belowground fungal mutualists seems not to hinder the spread of their non-native counterparts. [ABSTRACT FROM AUTHOR]

Aims: Plant invasion can alter the soil microbial community and carbon cycling in terrestrial ecosystems; however, shifts in soil autotrophic bacterial communities and their driving environmental factors after plant invasion remain largely unknown. This study examined the relationship between Moso bamboo (Phyllostachys pubscens) invasion into broadleaf forests and autotrophic bacterial community composition-function at two field sites.Methods: The abundance and composition of autotrophic bacteria were characterized by real-time PCR, terminal restriction fragment length polymorphism, and clone library based on the cbbL gene that encodes ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO).Results: On average, the cbbL gene abundance was 89% higher and RubisCO enzyme activity 110% higher in the bamboo forest than in the broadleaf forests across the two field sites. The cbbL gene abundance was positively correlated with the RubisCO enzyme activity. The cbbL-containing communities were dominated by the order Rhizobiales, and their composition differed between the forest types and between the two sites, with the effect of site location being greater. Soil readily-oxidizable carbon concentration was a critical factor determining the site location effect on the diversity and activity of the cbbL-containing community.Conclusion: Greater abundance and activity of autotrophic bacteria were associated with bamboo invasion into broadleaf forests, implying that such invasions are expected to increase the CO2 fixation potential. [ABSTRACT FROM AUTHOR]

Aims: Soil fungi play an important role in decomposing soil organic matter and facilitating nutrient uptake by plants, however, the relationship between fungal community and soil biogeochemical cycling during plant invasion is poorly understood. The objective of this study was to investigate the effects of Moso bamboo ( Phyllostachys edulis) invasion into broadleaf forests on the soil organic C (SOC) chemical composition, fungal community and mineral N production. Methods: We collected soil samples in evergreen broadleaf forests, mixed bamboo-broadleaf forests and bamboo forests. Soil fungal community and SOC chemical composition were determined. Results: Bamboo invasion decreased alkyl C but increased O-alkyl C contents. Soil fungal abundance (18S rRNA) was decreased, while their alpha diversity was increased by bamboo invasion. Additionally, bamboo invasion enhanced net N mineralization rate but reduced gross nitrification rate. The fungal community composition strongly correlated with alkyl C content, and alkyl C content explained 32% of the variation in the fungal abundance. Fungal community composition correlated with gross nitrification rate, with 43% of the variation in gross nitrification rate attributable to soil fungal abundance. Conclusions: Changes in soil fungal community caused by bamboo invasion into broadleaf forests were closely linked to changed soil organic C chemical composition and decelerated nitrate production. [ABSTRACT FROM AUTHOR]

Aims: Recently, much attention has been paid to the plant-mediated effects of aboveground herbivory on soil ecosystems. However, studies about the herbivore-induced effects of invasive plants on soil ecosystem are still lacking. In this study, we aimed to examine the soil biota and nutrient availability to an invasive plant under aboveground herbivory stress, and compare the soil responses with a native plant. Methods: We subjected an invasive plant ( Spartina alterniflora) and a native plant ( Phragmites australis) to herbivory by caterpillars of native moth Laelia coenosa, and measured soil microbes, nematodes, inorganic nitrogen (N), plant biomass and N content. Results: Soil microbial biomass, nematode abundance, ammonium N concentrations and N mineralization rates were significantly stimulated by herbivory of the invasive S. alterniflora. Besides, the stimulation of bacteria: fungi ratio, abundance of bacterivorous nematodes, and ammonium N availability were significantly higher for S. alterniflora than for P. australis. Conclusions: In general, aboveground insect herbivory of the invasive S. alterniflora enhanced the abundance of soil biota, and the soil N availability. The greater soil responses associated with S. alterniflora suggest stronger positive soil feedback than those with the native P. australis, which might facilitate the invasive plant to successfully invade its new range under biotic stress. [ABSTRACT FROM AUTHOR]

Aims: Plant invasion has been reported to alter ecosystem carbon (C) and nitrogen (N) cycling processes and pools. The mechanisms involved in how plant invasion affects the soil microbial community-the primary mediator of soil C and N cycling-remain poorly understood. The objective of this study was therefore to evaluate the effect of plant invasion on the soil microbial community in a coastal wetland of eastern China. Methods: We investigated the impact of an exotic C perennial grass, Spartina alterniflora, on the soil microbial community structure based on phospholipid fatty acids (PLFAs) analysis and chloroform fumigation-extraction by comparing it to that of bare flat and native C plants Suaeda salsa and Phragmites australis communities. Results: Spartina alterniflora invasion significantly increased soil microbial biomass C and the total and various types of PLFAs compared with bare flat, Suaeda salsa and Phragmites australis communities. Increased concentrations of soil moisture, electrical conductivity, water-soluble organic carbon (WSOC), and total, labile and recalcitrant soil organic C and N, and decreased soil pH in Spartina alterniflora community explained 65.9 % of the total variability in the PLFAs. WSOC and soil labile organic N were strongly correlated with PLFAs, whereas soil pH was negatively related to PLFAs. Conclusions: A 10-year Spartina alterniflora invasion significantly altered soil microbial biomass and community structure by increasing available substrate. The changes in soil microbial biomass and community structure may in turn enhance soil C and N sequestration in a coastal wetland of eastern China. [ABSTRACT FROM AUTHOR]

Background and Aims: Lespedeza cuneata is a non-native invasive legume that alters the soil bacterial community, associates promiscuously with rhizobia, and benefits more from rhizobial interactions compared to coexisting native Lespedeza in North America. We tested the hypothesis that native congeners differ in their nodule bacteria associations compared to L. cuneata. Methods: Plots with high L. cuneata invasion, low L. cuneata invasion with native Lespedeza species present, and uninvaded plots where native Lespedeza species existed without L. cuneata were sampled. Nodules were collected from all Lespedeza species present, and Chamaecrista fasciculata, a common native annual legume. Bacterial DNA from nodules was isolated and sequenced. Results: Nodule bacterial composition differed significantly between hosts. L. cuneata nodules contained high frequencies of rhizobial DNA and low bacterial diversity, while native Lespedeza nodules contained lower rhizobial frequencies and higher non-rhizobial bacterial diversity. Specific non-rhizobial bacterial groups exhibited strong associations with native legumes and uninvaded sites. Conclusions: Significant differences exist in the nodule bacterial composition between native legumes and an introduced congener. The mechanism(s) and ecological importance of these differences remain unknown. These differences in bacterial associations could influence not only the competitive ability of the invader, but recovery of invaded sites as well. [ABSTRACT FROM AUTHOR]

Background and aims: Feedback between plant and soil microbial communities plays a key role in plant invasions. We examined feedback in native and invasive plants growing in monoculture and mixture, to determine soil microorganisms' role in Bromus diandrus invasion. Methods: Four native forb species were grown in monoculture and in competition with Bromus and with different microbial inocula. Inoculum consisted of 20 g of soil collected from the rhizosphere of native or invasive plants used to create treatments of (1) whole soil, (2) filtrate containing non-mycorrhizal microbes, and (3) arbuscular mycorrhizal fungi (AMF) spores. Results: Native species in monoculture experienced neutral to positive feedback with whole soil and filtrate inoculum. Feedback in Bromus grown in monoculture varied in direction and magnitude with different soil microbial fractions. Fine AMF ( Glomus tenue) in filtrate inoculum appeared to cause observed positive feedback effect in native and invasive species, even with pathogenic fungi in roots. Feedback in mixture was more positive than in monoculture for some species. Conclusions: Our study highlights the difficulty of extending feedback results in monoculture to the community level, and the importance of fine AMF, which has received little attention, interacting with pathogens in plant invasion. [ABSTRACT FROM AUTHOR]

Background and aims: Increasing atmospheric nitrogen (N) deposition and biological invasion have become major concerns with global environmental change. This study aimed to determine the effects of an exotic species on a native one under increasing N deposition. Methods: We conducted a greenhouse experiment in which the exotic species Robinia pseudoacacia and the native species Quercus acutissima were grown in mixture and monocultures under four levels of simulated N deposition (0, 3, 6, 12 g m year). After 12 weeks of treatment, plant growth, leaf physiological traits and soil chemical properties were determined. Results: With its strong capability for nutrient absorption and carbon assimilation, R. pseudoacacia dominated in competition. R. pseudoacacia reduced the growth of Q. acutissima, but the relative competition index decreased with increasing N deposition. At the end of the experiment, the soil available phosphorus (P) in mixture was significantly lower than that in the monoculture of Q. acutissima, while the soil available N in the two cultivations did not show obvious differences. Conclusions: Increased N deposition alleviated the competitive effects of R. pseudoacacia on Q. acutissima. In the future, besides N, increased P availability should also be considered in the interaction between the two species. [ABSTRACT FROM AUTHOR]

Background and aims: Successful invasion by exotic plant species can modify the abundance and composition of soil microbial communities. Eupatorium adenophora and Chromolaena odorata are exotics that have become highly invasive plants in China. Several studies have investigated mechanisms of their successful invasions including phenotypic plasticity, genetic differentiation, and allelopathy, but little is known about their effects on soil microorganisms. Moreover, whether soil microbial community changes could cause feedback effects on these plant species is also not known. We seek a belowground microbiological mechanism supporting successful invasions by these exotic plants. Methods: In this study, two invasive ( E. adenophora and C. odorata) and two native plant species ( Eupatorium japonicum and Eupatorium heterophyllum) were used to compare the soil feedback (on plant growth) before and after soil sterilization and from plant-root exudates. Bacterial and fungal biomass and community composition were also examined. Results: We found that soil sterilization significantly increased biomass of native species and did not affect the invasive species' biomass. After root exudates from these plants had acted on the soil biota for 10 months, soil sterilization significantly decreased the growth of E. adenophora and C. odorata and continued to significantly increase the biomass of two native species. Denaturing gradient gel electrophoresis revealed that these four plant species modified fungal rather than bacterial communities in soil. Conclusions: Higher abundance of Paraglomus sp. in soil with C. odorata is likely to provide C. odorata roots with more soil nutrients. Considered together, these results strongly suggest that invasive E. adenophora and C. odorata created a belowground feedback that may be a mechanism contributing to their success as invasive species. [ABSTRACT FROM AUTHOR]

Background and aims: Anthropogenic nitrogen (N) and phosphorus (P) input has changed the relative importance of nutrient elements. This study aimed to examine the effects of different nutrient conditions on the interaction between exotic and native plants. Methods: We conducted a greenhouse experiment with a native species Quercus acutissima Carr. and an exotic species Rhus typhina L. grown in monocultures or mixtures, under three N:P ratios (5, 15 and 45 corresponding to N-limited, basic N and P supply and P-limited conditions, respectively). After 12 weeks of treatment, traits related to biomass allocation, leaf physiology and nutrient absorption were determined. Results: R. typhina was dominant under competition, with a high capacity for carbon assimilation and nutrient absorption, and the dominance was unaffected by increasing N:P ratios. R. typhina invested more photosynthate in leaves and more nutrients in the photosynthetic apparatus, enabling high biomass production. Q. acutissima invested more photosynthate in roots and more nutrients in leaf persistence at the expense of reduced carbon assimilation capacity. Conclusions: Different trade-offs in biomass and nutrient allocation of the two species is an important reason for their distinct performances under competition and helps R. typhina to maintain dominance under different nutrient conditions. [ABSTRACT FROM AUTHOR]

Background and aims: Through recruitment, plants establish in novel environments. Recruitment also is the stage where plants undergo the highest mortality. We investigate the recruitment niche for Microstegium vimineum, an annual grass from East Asia spreading throughout eastern North American forests. Methods: Current observational and greenhouse research indicates that M. vimineum recruitment may be inhibited by leaf litter and promoted by soil moisture; we use field studies to experimentally test how these factors influence M. vimineum germination, seedling survival and reproduction. Specifically, we introduce M. vimineum seeds into forest microhabitats with experimentally varied levels of soil moisture and leaf litter. Results: Soil moisture increases M. vimineum germination regardless of leaf litter thickness and ameliorates seedling mortality in deep leaf litter. Seed production per m increases with watering, reflecting higher germination and survival, whereas per capita seed production increases with leaf litter thickness, reflecting density-dependent limits on seed production. Conclusions: The interactive effects of varied levels of soil moisture and leaf litter thickness on key M. vimineum life history stages highlight the need to consider multiple drivers, such as rainfall and local forest disturbance, when assessing how soil properties influence the establishment of invasive plants. [ABSTRACT FROM AUTHOR]

lteration of soil nutrient dynamics has recently garnered more attention as both a cause and an effect of plant invasion. This project examines how nutrient dynamics are affected by native ( Elymus elymoides, Pseudoroegneria spicata, and Vulpia microstachys) and invasive ( Aegilops triuncialis, Agropyron cristatum, Bromus tectorum, and Taeniatherum caput-medusae) grass species. This research questions whether natives and invasives differ in their effects on nutrient dynamics. A greenhouse study was conducted using two field-collected soils. Effects on nutrient dynamics were compared using an integrated index that evaluates the total nutrients in soil and in plant tissue compared to an unplanted control. With this index, we evaluated whether soil nutrients increased or decreased as a result of plant growth, controlling for plant uptake. We found no consistent support for our hypothesis that invasive grass species as a group influence nutrient dynamics differently than native grass species as a group. Our results indicate species-specific effects on nutrient dynamics. Alteration of nutrient dynamics is not a trait shared by all of the invasive grass species in our study. However, alteration of nutrient dynamics may be a mechanism by which some individual species increase their invasive potential. [ABSTRACT FROM AUTHOR]

Although invasions by non-native species represent a major threat to biodiversity and ecosystem functioning, little attention has been paid to the potential impacts of these invasions on methane (CH4) emission and its 13C-CH4-isotope signature in salt marshes. An invasive perennial C4 grass Spartina alterniflora has spread rapidly along the east coast of China since its introduction from North America in 1979. Since its intentional introduction to the Jiuduansha Island in the Yangtze River estuary in 1997, S. alterniflora monocultures have become the dominant component of the Jiuduansha’s vegetation, where monocultures of the native plant Scirpus mariqueter (a C3 grass) used to dominate the vegetation for more than 30 years. We investigated seasonal variation in soil CH4 emission and its 13C-CH4-isotope signature from S. alterniflora and S. mariqueter marshes. The results obtained here show that S. alterniflora invasion increased soil CH4 emissions compared to native S. mariqueter, possibly resulting from great belowground biomass of S. alterniflora, which might have affected soil microenvironments and /or CH4 production pathways. CH4 emissions from soils in both marshes followed similar seasonal patterns in CH4 emissions that increased significantly from April to August and then decreased from August to October. CH4 emissions were positively correlated with soil temperature, but negatively correlated with soil moisture for both S. alterniflora and S. mariqueter soils (p < 0.05). The δ13C values of CH4 from S. alterniflora, and S. mariqueter soils ranged from -39.0‰ to -45.0‰, and -37.3‰ to -45.7‰, respectively, with the lowest δ13C values occurring in August in both marshes. Although the leaves, roots and soil organic matter of S. alterniflora had significantly higher δ13C values than those of S. mariqueter, S. alterniflora invasion did not significantly change the 13C- isotopic signature of soil emitted CH4 (p > 0.05). Generally, the CH4 emissions from both invasive S. alterniflora and native S. mariqueter soils in the salt marshes of Jiuduansha Island were very low (0.01–0.26 mg m-2 h-1), suggesting that S. alterniflora invasion along the east coast of China may not be a significant potential source of atmospheric CH4. [ABSTRACT FROM AUTHOR]

Plant invasions have the potential to significantly alter soil microbial communities, given their often considerable aboveground effects. We examined how plant invasions altered the arbuscular mycorrhizal fungi of native plant roots in a grassland site in California and one in Utah. In the California site, we used experimentally created plant communities composed of exotic ( Avena barbata, Bromus hordeaceus) and native ( Nassella pulchra, Lupinus bicolor) monocultures and mixtures. In the Utah semi-arid grassland, we took advantage of invasion by Bromus tectorum into long-term plots dominated by either of two native grasses, Hilaria jamesii or Stipa hymenoides. Arbuscular mycorrhizal fungi colonizing roots were characterized with PCR amplification of the ITS region, cloning, and sequencing. We saw a significant effect of the presence of exotic grasses on the diversity of mycorrhizal fungi colonizing native plant roots. In the three native grasses, richness of mycorrhizal fungi decreased; in the native forb at the California site, the number of fungal RFLP patterns increased in the presence of exotics. The exotic grasses also caused the composition of the mycorrhizal community in native roots to shift dramatically both in California, with turnover of Glomus spp., and Utah, with replacement of Glomus spp. by apparently non-mycorrhizal fungi. Invading plants may be able to influence the network of mycorrhizal fungi in soil that is available to natives through either earlier root activity or differential carbon provision compared to natives. Alteration of the soil microbial community by plant invasion can provide a mechanism for both successful invasion and the resulting effects of invaders on the ecosystem. [ABSTRACT FROM AUTHOR]