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Soil fungal community plays an important role in forest ecosystems, and forest secondary succession is a crucial driver of soil fungal community. However, the driving factors of fungal community and function during temperate forest succession and their potential impact on succession processes are poorly understood. In this study, we investigated the dynamics of the soil fungal community in three temperate forest secondary successional stages (shrublands, coniferous forests, and deciduous broadleaf forests) using high-throughput DNA sequencing coupled with functional prediction via the FUNGuild database. We found that fungal community richness, α-diversity, and evenness decreased significantly during the succession process. Soil available phosphorus and nitrate nitrogen decreased significantly after initial succession occurred, and redundancy analysis showed that both were significant predictors of soil fungal community structure. Among functional groups, fungal saprotrophs as well as pathotrophs represented by plant pathogens were significantly enriched in the early-successional stage, while fungal symbiotrophs represented by ectomycorrhiza were significantly increased in the late-successional stage. The abundance of both saprotroph and pathotroph fungal guilds was positively correlated with soil nitrate nitrogen and available phosphorus content. Ectomycorrhizal fungi were negatively correlated with nitrate nitrogen and available phosphorus content and positively correlated with ammonium nitrogen content. These results indicated that the dynamics of fungal community and function reflected the changes in nitrogen and phosphorus availability caused by the secondary succession of temperate forests. The fungal plant pathogen accumulated in the early-successional stage and ectomycorrhizal fungi accumulated in the late-successional stage may have a potential role in promoting forest succession. These findings contribute to a better understanding of the response of soil fungal communities to the secondary forest succession process and highlight the importance of fungal communities during temperate forest succession.

The changes of microbial communities of rhizospheric soil in different ages are speculated to cause soil-borne diseases and replanting problem in American ginseng (Panax quinquefolius L.) cultivation. This study analyzed the physicochemical properties and microbial communities of rhizospheric soil during the planting of American ginseng in the Wendeng area of Weihai, China. The water content and organic matter content of American ginseng rhizospheric soil decreased year by year. A decline in the diversity of bacteria and fungi was observed in the rhizospheric soils planting American ginseng compared with the traditional crop wheat in the control group. During the later planting stage, the abundances of Proteobacteria, Actinobacteria, and Basidiomycota were lower, whereas that of Acidobacteria, Firmicutes, and Mucoromycota were higher. Through the correlation analysis between environmental factors and microbial community, it was found that the content of soil phosphorus was significantly positively correlated with the root rot pathogen Fusarium. The results of functional prediction showed that the decrease of secondary metabolite synthesis of rhizospheric soil bacteria and the increase of plant pathogenic fungi may be the important reasons for the increase of diseases in the later stage of American ginseng planting. This study revealed the evolution of rhizosphere microbial community and function in the process of American ginseng planting, which is valuable for planting management.

There is growing interest in understanding the role that plant-soil feedbacks (PSFs) may play in invasion resistance. However, recent studies have shown that there is great uncertainty in explaining community patterns by PSF studies regarding invasions. This uncertainty may be partly because soils used for PSF studies are usually collected from open areas rather than natural communities, thus ignoring the effects of community contexts that may specifically influence the soil feedbacks of community residents to invaders. We performed a two-phase pot experiment to study the soil feedback initiated by ten co-occurring native and exotic species to a forest invader, Phytolacca americana, and the experiments were performed in forest soil and open area soil. The context-dependent mechanisms were further explored by studying different components of PSF. The results showed that natives and exotics had positive and negative effects on P. americana in the open area soil, respectively, but both had negative effects in the forest soil. Nutrient limitation was more important for the PSF in open area soil, whereas biotic factors were likely the primary mechanisms explaining the PSF in forest soil. Additionally, the litter-mediated allelopathy of dominant Quercus acutissima caused the strongest inhibition of the invader. These results suggest that native species can effectively resist invasion by producing negative PSF depending on the community context. Evidence that exotic species promote invasion through positive PSFs was not obtained. This study provided preliminary insights into the possibility of bridging PSF studies and community patterns.

Re-establishment of heritable latitudinal clines in growth-related traits has been recognised as evidence for adaptive evolution in invasive plants. However, less information is known about latitudinal clines in defence and joint clinal evolution of growth and defence in invasive plants. We planted 14 native Argentinean populations and 14 introduced Chinese populations of Alternanthera philoxeroides in replicate common gardens in China. We investigated the latitudinal clines of traits related to growth and defence, and plasticity of these traits in relation to experiment site and soil nitrogen. We found that chemical defence decreased with latitude in introduced populations but increased with latitude in native populations. For growth rate, latitudinal clines were positive in introduced populations but nonexistent in native populations. There were also parallel positive latitudinal clines in total/shoot biomass and specific leaf area. Experiment site affected the occurrence or magnitude of latitudinal clines in growth rate, branch intensity and triterpenoid saponins concentration. Introduced populations were more plastic to experiment site and soil nitrogen than native populations. We provide evidence for rapid evolution of clines in growth and defence in an invasive plant. Altered herbivory gradients and trade-off between growth and defence may explain nonparallel clines between the native and introduced ranges.

The enhanced mutualism hypothesis postulates that invasive plants promote self-growth by enriching beneficial microbes to establish a positive soil feedback. However, the roles of soil microorganisms may vary with increasing time for plant growth. Research on changes in soil microbial communities over time has important implications for understanding the mechanisms underlying plant invasion. Due to the difficulty in evaluating the duration of plant growth, few studies have quantified the changes in soil microorganisms with increasing plant age. This study focuses on the invasive weed Phytolacca americana L., which has growth rings in the main root. We conducted a two-stage experiment in the field and greenhouse to explore the soil feedback changes with duration of plant growth. We determined the effects of P. americana at different ages on the soil microbial community and soil properties and performed a soil inoculation experiment to quantify the influence of soil microbes on seed germination and seedling performance. We found that the content of some soil nutrients, namely total nitrogen, total phosphorus, nitrate-N, and available phosphorus, significantly decreased with increasing growth age of P. americana, whereas the available potassium showed an opposite increasing trend. The P. americana growth age also significantly influenced the soil bacterial community structure. However, this phenomenon did not occur in the fungal community. In the bacterial community, the relative abundance of plant growth-promoting bacteria showed an increasing trend. The soil inoculation experiment had high seed germination rates and biomass accumulation when the plants were grown in conditioned soil from P. americana growth within 5 years, suggesting a positive plant-soil feedback. However, the promoting effect disappeared in conditioned soil from 10 years of age. Our findings demonstrate that plant growth-promoting bacteria significantly accumulated in the soil during the early stages of P. americana invasion, and that the strength of enhanced positive feedback may play a crucial role in facilitating P. americana invasion. This study highlights the changing nature of plant-microbe interactions during biological invasion and illustrates how bacteria could contribute to the initial success of P. americana, providing new insights into the underlying mechanisms of plant invasion.促进共生假说(Enhanced mutualism hypothesis)指出，外来入侵植物可以通过富集有益微生物建立正向土壤反馈来促进自身生长。然而，土壤微生物的作用效果可能会随植物生长时间的延长而发生变化，进一步研究这种变化对理解植物入侵机制无疑具有重要意义，但由于确定入侵植物生长时长存在诸多困难，相关研究难以开展。本研究以主根有年轮结构的多年生草本入侵植物美洲商陆为研究对象，设计了野外采样和实验室分析两部分试验以判定不同生长年限美洲商陆对土壤理化性质和土壤微生物群落的影响，并进行了土壤接种试验以量化不同生长年限美洲商陆根际土壤微生物对其自身种子萌发和幼苗生长的影响。研究结果表明，土壤中全氮、全磷、硝态氮和速效磷含量随美洲商陆生长年限的增加而显著降低，而速效钾含量则呈现明显增加趋势。研究同时发现，美洲商陆的生长年限对土壤细菌群落结构有显著影响，主要表现为一些促进植物生长的细菌类群的相对丰度呈现增加趋势，如具有解钾功能的伯克霍尔德菌属细菌，而对真菌群落结构则无明显影响。此外，土壤接种试验结果表明，接种生长1-5年生美洲商陆根际土壤的盆栽中，美洲商陆种子发芽率和幼苗生物量积累显著增加，表现出正向的植物-土壤反馈作用。然而，接种生长10年的美洲商陆根际土壤则不会产生上述促进效果。综上认为，在入侵的早期阶段，美洲商陆通过在土壤中富集生长促进菌，驱动土壤正反馈作用，从而促进其成功入侵。这项研究强调了植物入侵过程中植物-微生物相互作用效果的变化，说明了细菌在美洲商陆成功入侵中的作用，丰富了对植物入侵潜在机理的认识。.

Bacterial enteritis is an important deadly threat to farmed seahorses. However, its pathogenesis is obscure because of the paucity of reproducible experimental intestinal inflammation models. Herein, a strain of Edwardsiella tarda YT1 from farmed seahorse Hippocampus erectus was isolated and identified by morphological, phylogenetic, and biochemical analysis, and confirmed as a pathogen of enteritis for the first time by challenge experiment. Two E. tarda concentrations (1 × 105 and 1 × 107 colony forming units [cfu] ml−1) were confirmed suitable for an enteritis model by intraperitoneal injection. To develop and evaluate the experimental model, we challenged seahorses with E. tarda and found that (1) the infection inhibited body length increase, significantly decreased body weight (P

In nature some successful invasive plants grow faster and are better chemical defenders than native plants, which appears to contradict the conventional theory that plant growth and chemical defense are trade-offs in terms of the allocation of limited resources. Using greenhouse experiments we compared the growth, chemical defensive matters (condensed tannins and total phenolics) and energy-use strategies (construction cost and energy-use efficiency) of four highly noxious invasive plants to their congeneric or co-occurring native species in subtropical China. We hypothesized that the trade-offs between growth and chemical defense in invasive plants are alleviated, and this alleviation benefits from their high photosynthetic capacities and energy-use strategies. Our results showed that all the four invasive plants grew faster than their native counterparts, and three of them had higher condensed tannins and the remaining one had higher total phenolics, indicating the invasive plants achieved both faster growth and stronger chemical defense. Moreover, the growth rate positively related to condensed tannins but negatively to total phenolics in both invasive and native plants, indicating the chemical-specific pattern of the trade-offs. Our results demonstrate that the higher photosynthetic capacity and energy-use efficiency together with lower biomass construction cost facilitated the faster growth and stronger chemical defense in invasive plants, providing an insight for their chemical-specific trade-offs between growth and chemical defense.

Context The majority of ecological studies of roads have focused on their deleterious effects, and these preconceptions have hampered a full evaluation of the ecological functions of roads. As an integrated indicator, road width represents comprehensive effects, including anthropogenic and natural disturbances. Objectives We try to explore the different effects produced by various road widths by considering changes in forest vegetation and soil. Methods We selected six study forests spanning from Shandong Province in the north to Guangdong Province in the south of China, and we assessed the influences of wide and narrow roads on plant species diversity, biomass, and soil properties along transects running from the forest edges and adjacent forest interior. We used a “shape-dependent model” to explain the factors that determine the magnitude of road effects on forests. Results Three variables measured in this study changed significantly with increasing distance from the road to the forest interior along wide roads: tree biomass, herbaceous plant biomass, and soil pH. However, no measurable biological or environmental effects were found from narrow roads. The different shapes of glades in a forest may be one reason for the various effects caused by roads of different widths. Conclusions Forest roads of different widths may have quite different ecological effects. While wider roads with large glades tend to have substantial negative impacts, small-enough roads may cause little disturbance to the forest. This suggests that not all forest roads should be perceived as the same, and narrow roads may be compatible with forest conservation.

There is growing interest in understanding the role that plant-soil feedbacks (PSFs) may play in invasion resistance. However, recent studies have shown that there is great uncertainty in explaining community patterns by PSF studies regarding invasions. This uncertainty may be partly because soils used for PSF studies are usually collected from open areas rather than natural communities, thus ignoring the effects of community contexts that may specifically influence the soil feedbacks of community residents to invaders. We performed a two-phase pot experiment to study the soil feedback initiated by ten co-occurring native and exotic species to a forest invader, Phytolacca americana, and the experiments were performed in forest soil and open area soil. The context-dependent mechanisms were further explored by studying different components of PSF. The results showed that natives and exotics had positive and negative effects on P. americana in the open area soil, respectively, but both had negative effects in the forest soil. Nutrient limitation was more important for the PSF in open area soil, whereas biotic factors were likely the primary mechanisms explaining the PSF in forest soil. Additionally, the litter-mediated allelopathy of dominant Quercus acutissima caused the strongest inhibition of the invader. These results suggest that native species can effectively resist invasion by producing negative PSF depending on the community context. Evidence that exotic species promote invasion through positive PSFs was not obtained. This study provided preliminary insights into the possibility of bridging PSF studies and community patterns.

Changes in resource availability can alter plant growth, the influence of plants on soil characteristics, and, ultimately, plant–soil feedback (PSF). Previous studies often show that invasive plants can outperform native plants under high but not low resource conditions. However, it remains unclear whether under low resource conditions, invaders can outperform natives in the long term by generating more positive or less negative PSFs. Using three non-native invasive and three non-invasive native annual Asteraceae plants, we conducted a two-phase pot experiment, where in the first, conditioning generation plants were grown to induce changes in soil characteristics, and in the second, bioassay generation plants were regrown to evaluate how they respond to these soils. Half of the pots received a nutrient addition treatment in the conditioning generation. We found significant species-specific effects of conditioning on most of the soil characteristics, and some soil characteristics were significantly correlated with bioassay generation biomass of a subset of species, but neither species nor invasive or native status affected bioassay generation biomass. All invasive species generated neutral PSFs across soil nutrient conditions. The native Emilia sonchifolia tended to condition the soil that favored its own growth more than others, and under low nutrient conditions, the native Eclipta prostrata conditioned the soil that disfavored its own growth more than others. These results indicate that invaders may not outperform natives through PSFs under low resource conditions, and increasing resource availability may change the types of PSFs for some native but not invasive plants.

L., an exotic plant that is widely distributed in China, is harmful to native ecosystems; however, little is known about its effects on soil microbial communities. Therefore, we investigated the effects of R. typhina on soil bacterial communities by 16S rRNA gene sequencing and compared the effects of R. typhina and native (Rhus chinensis Mill.) and non-invasive exotic species (Amorpha fruticosa L. and Robinia pseudoacacia L.) on soil bacterial communities via a greenhouse experiment. R. typhina decreased the diversity of the soil bacterial community compared with R. chinensis, and A. fruticosa. R. typhina soil was characterized by more Actinobacteria and lesser Proteobacteria and Acidobacteria than the other soils. Among Actinobacteria members, there was a difference in the relative abundance of Nocardioides and Streptomyces, and this could be advantageous for the growth of R. typhina. However, there was no significant difference in the soil bacterial community structure associated with R. typhina and other species. Moreover, the concentrations of total carbon, potassium, and nitrate were found to be the major soil factors influencing the relative abundance of soil bacteria.

Exotic plant invasion alters the structure and coverage of terrestrial vegetation and affects the carbon (C) stocks in ecosystems. Previous studies have shown the increases in the C stocks with increasing invasive plants, but these results remain contentious. Soil microbial communities are usually altered by plant invasion, which potentially influences the C cycling underground. We hypothesized that the plant invasion-caused dynamic changes in soil microbes would lead to the corresponding change in soil C accumulation. Using greenhouse experiments we simulated different invader intensities through varying the relative abundance of invasive species Mikania micrantha and its co-occurring native species Paederia scandens. By analyzing 13C-phospholipid fatty acid we found the invasive M. micrantha assimilated more 13C and transferred faster the fixed 13C through different tissues to soils, as compared to native P. scandens. Soil microbial components, i.e., i15:0, 16:0, 10Me16:0, 18:1w9c and 18:2w6,9 were mainly using the photo-assimilated 13C. In addition, we found a hump-shaped relationship between soil net 13C accumulate rate and rhizosphere microbial biomass, indicating that the soil C accumulation may be either enhanced or reduced in invaded ecosystems, depending on microbe abundance.

Phenotypic plasticity is one of the important mechanisms relevant to exotic plant invasions, and high plasticity is likely to influence the potential invasiveness of species. Phenotypic plasticity is broadly defined as the ability of organisms to alter their morphological and/or physiological traits in response to varying environments. Morphological and physiological plasticity are thought to have different mechanisms, resource costs and ecological implications. However, our understanding on how morphological and physiological plasticity contribute to invasiveness is still limited. We explored plant growth, morphological and physiological traits to compare the plasticity in response to variations in light availability in phylogenetically related invasive and non-invasive species from South China. We hypothesized that fast-growing and poorly shade-tolerant invasive species may exhibit higher physiological but not morphological plasticity compared with non-invasive species, prompting their successful invasion with variable light resources. On average, the examined invasive species exhibited a higher biomass accumulation under high light conditions than the non-invasive species. The interaction of light and origin had no significant effect on any of the variables in the morphological traits. However, highly significant effects were found in four of the six variables in the physiological traits: the maximum photosynthesis rate, apparent quantum yield, photosynthetic nitrogen use efficiency, and photosynthetic energy use efficiency. In some cases, the invasive species displayed higher physiological but not morphological plasticity than the non-invasive species. However, contrary to the theory, higher overall mean plasticity was not observed in the invasive plants. Our data support the idea that biological invasion is a complicated process and that strong phenotypic plasticity is merely one of the possibilities leading to the successful invasion of exotic plants.

Huang Q-Q, Wang G-X, Hou Y-P & Peng S-L (2011). Distribution of invasive plants in China in relation to geographical origin and life cycle. Weed Research51, 534–542. Summary At a continental scale, research on which areas are more likely to be invaded has often found that human socio-economic factors and biogeographic factors are important. This general pattern also holds for China, where invasive plant species richness at a provincial scale has often been found to be significantly correlated with both socio-economic (e.g. human population size and total GDP) and biogeographic factors (e.g. latitude and native plant species richness). However, these patterns are based on studies that considered invasive plants collectively rather than examining patterns within major subgroups. Here, we examine the potential role of species differences in mediating these distribution patterns in Chinese provinces. We show that distribution of invaders from Central and South America, especially perennials, is mainly determined by biogeographic factors, whereas distribution of invaders from North America and Eurasia, especially annuals, is mainly determined by socio-economic factors. The predictive power of biogeographic factors for invaders from Central and South America is stronger than socio-economic factors for invaders from North America and Eurasia. The role of socio-economic and biogeographic factors is not entangled; instead, their relative importance is dependent on species characters, such as their geographical origin and life cycle. Management and prevention policies at a national scale should consider the interactions between species characters and socio-economic and biogeographic conditions of the environment. Our results indicate that by examining the role of species differences, we may get a more realistic understanding of the cause of distribution patterns of biological invaders.

Forest succession is the base of establishing restoration reference which plays an important role in forest restoration and restoration estimation. The study presented the establishment of a Markov successional model (MSM) and its application to restoration reference in lower subtropical forest in China. The compositions of successional system in MSM were divided into three species types: pioneering pine trees, heliophytic trees and mesophytic trees. The successional system was divided into three subsystems: early successional stage, mid-successional stage and late-successional stage. Based on the site survey on the changes in the species and their individuals in 25 years, the transition matrices in various subsystems were determined. The predicted results were used to establish the restoration reference of the vegetation restoration in lower subtropical China. According to the ecological restoration reference established in this study, it would take 150 years for the forest to change from pioneer to mature communities in the region. Successional change of tree composition was forecast by the model, and the scenario forecast by the model reflects the actual conditions observed through 52 years of long-term permanent site research. The restoration experience in the region matches the forecast results. The application of a restoration reference model indicates that forest restoration can be accelerated by taking measures which change forest structure. The above results imply that a restoration reference established on the rule of regional forest succession could be very useful not only in directing, but also in assessing and managing regional forest restoration. Previously, one “ideal reference ecosystem” was used as a restoration reference in all correlative studies. In this study, the restoration “process” was used as the restoration reference.

Numerous studies have examined plant responses to elevated ultraviolet-B radiation at the species level. More than 140 studies conducted within the past three decades were collected for meta-analysis to generalize and examine overall responses of two main life-forms, woody plants and herbaceous plants under two supplemental UV-B levels. The analysis suggested that both life-forms would suffer an overall negative effect in total biomass under the two UV-B levels, and the reduction was 7.0–14.6% of the value at ambient UV-B radiation. Comparing the overall responses under the high supplemental UV-B level with those under the low supplemental UV-B level, woody plants showed no significant changes in any variables. As opposed to this, decreases in herbaceous plant height and specific leaf area as well as increase in herbaceous UV-B-absorbing compounds under the higher UV-B level were significantly greater than those under the lower UV-B level. With continued increases in UV-B levels, the two life-forms would show different response strategies for their different intrinsic capabilities to resist UV-B damage. Woody plants would not invest in large additional amounts of UV-B-absorbing compounds, while herbaceous plants would need to induce stronger defense mechanisms to protect themselves from the associated detrimental effects of UV-B radiation. A higher number of response variables were significantly affected by UV-B radiation for herbaceous plants than for woody plants. Most of the studied variables were not affected significantly under elevated UV-B for woody plants and exhibited very large confidence intervals. Further studies should investigate if the response to elevated UV-B radiation varies between different functional groups of woody species. To sum up, we suggest that as UV-B radiation continues to increase, grassland ecosystems should receive more attention for future vegetation management.