Structure Of Natural Communities Research Articles

Vertical distribution of edaphic oribatid mites (Acari: Oribatida) in two artificial forests planted on temperate grasslands

Context Oribatid mites are the most abundant taxon in forest soils that rely on porosity and organic matter availability. Exotic forests of Pinus radiata and Eucalyptus globulus planted over native grasslands in the Pampas region of Argentina have produced modification in soil properties, which can affect the composition and structure of native oribatids communities. Aims To compare oribatid communities in soils under artificial woodlands of pine and eucalyptus and to assess the vertical distribution of oribatids in relation to edaphic variables. Methods In each forest, oribatids were collected from three levels of the A horizon: (1) litter layer; (2) 0–5 cm; and (3) 5–10 cm. Edaphic variables measured were penetration resistance, bulk density, total porosity, pH and water content and luminosity at soil level. Density, species richness, diversity and evenness of oribatids were calculated in each level of each forest. Comparisons were made through multivariate analyses. Key results Edaphic variables showed no significant differences between plots but litters were structurally different. Richness and diversity showed no differences between plots whereas evenness was significantly higher in plot P. Density had higher values in the litter layer of both forests. Canonical Analysis of Principal Coordinates (CAP) showed that Pine plots had a more defined vertical distribution. Conclusions The structure and composition of litters promoted differences in the vertical distribution of oribatids. In Pinus, thick unaltered litter showed a marked vertical gradient of mites along levels while in Eucalyptus, thin and easily decomposing litter, showed no vertical patterns. Implications Assessment and management of soil biodiversity in artificial woodlands.

Effect of intraspecific seed trait variation on the germination of eight tropical dry forest species

Functional traits can have intraspecific and interspecific variations essential in the structure and dynamics of natural communities. These traits may have implications in the germination and seedling establishment phases in seeds. The objective of this study was to evaluate the effect of variations in mass, volume, and nutrient content (C, N, and P) on the germination of eight species representative of the tropical dry forest (TDF). Our results showed that seed size, both in terms of mass and volume, did not predict germination rates or percentages, nor were they related to nutrient content. In contrast, N content was the most important trait in the germination phase. Larger seeds did not germinate more or faster, but they could offer better resistance against desiccation, since they had higher C/N ratios in their tissues, a characteristic of orthodox seeds. The species A. guachapele, B. arborea, H. crepitans, and V. tortuosa presented a high biological potential in terms of their regeneration capacity, particularly, because the characteristics of their seeds, as well as the nutrient content, revealed consistent implications in their reproductive success, promoting high germination percentages in less time. In general, the results obtained in this study provide basic knowledge for future research, offering starting points for further exploration of species-specific adaptations and how they may be affected by the environment.

Nutrient enrichment alters phytoplankton biomass and composition via silicon limitation

Despite management efforts, anthropogenic nutrient enrichments continue to enhance phytoplankton blooms worldwide. Release of nitrogen and phosphorus compounds not only provides surplus of nutrients but also disbalances their stoichiometry. Declines in the relative availability of dissolved silicon might induce limitation in diatoms, major primary producers with silicified shells. We studied experimentally how nutrient enrichment and resulting decline in dissolved silicon to nitrogen ratios (Si:N) affect the structure and functioning of natural plankton communities. Nitrate was added to create a range of Si:N ratios and phosphate was supplied in Redfield ratio to nitrogen. We also manipulated copepod abundance to understand the top-down effects on communities experiencing nutrient enrichment. Nitrogen and phosphorus additions resulted in a steep phytoplankton biomass increase, followed by a post-bloom decline. Phytoplankton bloom biomass was higher in high nitrogen treatments but during the post-bloom period this trend switched. Biomass was sustained longer in high Si:N treatments, indicating that silicon limitation terminates the bloom. Many diatom species did not benefit from nitrogen and phosphorus enrichment and diatom dominance ceased below Si:N of 0.4:1. Under high grazing pressure, silicate was taken up faster suggesting that silicification is important in diatom defense. Copepods shaped plankton communities via feeding on dinoflagellates, chlorophytes and the diatom Skeletonema costatum but there was no significant effect of nitrogen and phosphorus enrichment on copepod abundance. Our results, combined with previous studies, show that while nutrient concentrations define the total phytoplankton bloom biomass, resource ratios are important in sustaining biomass and determining community structure and composition.

Fish predation affects invertebrate community structure of tropical temporary ponds, with downstream effects on phytoplankton that are obscured by pesticide pollution

Aquatic biota of tropical temporary ponds typically experience a wide range of stressors that can drive the structure and dynamics of natural communities. Particularly in regions with intense agricultural activity, aquatic biota may not only experience predation pressure but also stress from pesticides that inadvertently enter the ponds. We increasingly understand how these different sources of stress affect classic model taxa under controlled laboratory conditions, but how predators and pesticides may jointly affect pond invertebrate communities is still unclear, particularly for tropical systems. Here, we conducted an outdoor mesocosm experiment to study how fish predation combined with exposure to an environmentally relevant concentration of the commonly used insecticide cypermethrin (0.8 ng/L) affects the structure of invertebrate communities, and its potential effects on leaf litter decomposition and invertebrate grazing efficiency as measures of ecosystem functioning. A total of seven invertebrate taxa were recorded in the mesocosm communities. Fish predation effectively lowered the number of invertebrate taxa, with fish mesocosms being dominated by high densities of rotifers, associated with lower phytoplankton levels, but only when communities were not simultaneously exposed to cypermethrin. In contrast, cypermethrin exposure did not affect invertebrate community structure, and neither fish predation nor cypermethrin exposure affected our measures of ecosystem functioning. These findings suggest that predation by killifish can strongly affect invertebrate community structure of tropical temporary ponds, and that downstream effects on phytoplankton biomass can be mediated by exposure to cypermethrin. More broadly, we contend that a deeper understanding of (tropical) temporary pond ecology is necessary to effectively manage these increasingly polluted systems.

Deciphering the interaction of bacteria inoculants with the recipient endophytic community in grapevine micropropagated plants.

Engineering the plant microbiome with beneficial endophytic bacteria can improve the growth, health, and productivity of the holobiont. Here, we administered two beneficial bacterial strains, Kosakonia VR04 sp. and Rhizobium GR12 sp., to micropropagated grapevine cuttings obtained via somatic embryogenesis. While both strains colonized the plant endosphere, only Rhizobium GR12 sp. increased root biomass under nutritional-deficit conditions, as supported by the plant growth promotion traits detected in its genome. Phylogenetic and co-occurrence analyses revealed that the plant native bacterial community, originally dominated by Streptococcaceae and Micrococcaceae, dramatically changed depending on the inoculation treatments, as invading strains differently affected the relative abundance and the interactions of pre-existing taxa. After 30 days of plantlets' growth, Pantoea became a predominant taxon, and considering untreated plantlets as references, Rhizobium sp. GR12 showed a minor impact on the endophytic bacterial community. On the other hand, Kosakonia sp. VR04 caused a major change in community composition, suggesting an opportunistic colonization pattern. Overall, the results corroborate the importance of preserving the native endophytic community structure and functions during plant microbiome engineering.IMPORTANCEA better comprehension of bacterial colonization processes and outcomes could benefit the use of plant probiotics in the field. In this study, we applied two different beneficial bacteria to grapevine micropropagated plantlets and described how the inoculation of these strains impacts endophytic microbiota assembly. We showed that under nutritional deficit conditions, the response of the receiving endophytic bacterial communities to the invasion of the beneficial strains related to the manifestation of plant growth promotion effects by the inoculated invading strains. Rhizobium sp. GR12 was able to preserve the native microbiome structure despite its effective colonization, highlighting the importance of the plant-endophyte associations for the holobiont performance. Moreover, our approach showed that the use of micropropagated plantlets could be a valuable strategy to study the interplay among the plant, its native microbiota, and the invader on a wider portfolio of species besides model plants, facilitating the application of new knowledge in agriculture.

The comparison of species diversity and abundance of insect natural enemies in the domesticated species of cotton using the yellow pan trap method.

India is the world's largest cotton producer and the only country that grows all four cultivated cotton species. There have been very few studies on the diversity and abundance of natural enemies of cotton insect pests in these cultivated cotton species. Therefore, the current study (2016-2018) was conducted to assess the diversity and abundance of natural enemies that cultivated cotton species harbour. Phule Dhanwantari, Suraj, Suvin, RCH-2, and DCH-32 were the five genotypes used in the study, each with a distinct genetic background. Using the adiv 2.0.1 and vegan R packages, we identified significant differences in natural enemies in terms of species diversity, richness, evenness, and abundance. Analysis of Similarity (ANOSIM) and Non-metric Multidimensional Scaling (NMDS) indicated substantial differences in the natural enemy community structure among the examined genotypes. A total of 17,279 natural enemies were collected and identified across genotypes from seven predatory families and five parasitoid families. The percentage share of these natural enemy families across genotypes and years, in descending order, is Coccinellidae (28.23%) < Tachinidae (19.23%) < Braconidae (12.68%) < Chrysopidae (11.65%) < Chalcididae (9.41%) < Aphelinidae (6.33%) < Pentatomidae (3.29%) < Ichneumonidae (2.37%) < Syrphidae (2.33%) < Vespidae (1.81%) < Asilidae (1.79%) < Geocoridae (0.89%). Coccinellidae, Tachinidae, Braconidae, Chrysopidae, Chalcididae, and Aphelinidae are the six major families that account for more than 85% of all recorded natural enemies. These six families have a higher percentage share in Phule Dhanwantary (90%) compared to the other genotypes. The conservation and better utilization of these natural enemies are crucial for the ecological and safe management of insect pests in the cotton ecosystem.

Oomycetes as damping‐off pathogens and functional plant traits associated with the susceptibility of west Australian native plant species

AbstractDamping‐off oomycete and fungal plant pathogens reduce the germination, emergence, and survival of seedlings. In agricultural systems, this poses a significant problem as it may reduce productivity; in contrast, the impact is more subtle in natural ecosystems and may be essential for maintaining the structure and diversity of plant communities. The oomycete genus Phytophthora is frequently detected in natural plant communities causing disease in mature plants, but it is rarely assessed as a damping‐off pathogen. A pathogenicity experiment was established with five oomycete treatments, three putatively native Phytophthora species, the invasive P. cinnamomi, and Pythium irregulare, to determine the damping‐off host range in selected plant species from a hyper‐diverse Mediterranean‐type ecosystem. Additionally, plant and seed traits were analysed to determine if they were correlated with susceptibility to pre‐emergent damping‐off. Phytophthora arenaria was the only putatively native generalist damping‐off pathogen, causing 12 of 19 plant species to experience significantly reduced seedling emergence or survival relative to the control treatment. Pythium irregulare and the introduced P. cinnamomi caused significant damping‐off for 12 and 13 plant species, respectively. Plant species that were slowest to germinate and emerge were the most susceptible to pre‐emergence damping‐off caused by P. arenaria. These results suggest native and invasive Phytophthora may substantially influence the structure and diversity of natural plant communities through damping‐off. While mature plant species are the most common focus in Phytophthora research, our study indicates damping‐off should be considered to determine the full impact of these soil‐borne plant pathogens.

Effects of Different Degrees of Xanthium spinosum Invasion on the Invasibility of Plant Communities in the Yili Grassland of Northwest China.

Studying the effects of different degrees of exotic plant invasion on native plants' community structure and plant diversity is essential for evaluating the harm caused to ecosystems by plant invasion. In this study, we investigated the effects of Xanthium spinosum, a widespread invasive species, on plant community species diversity and community stability in the Ili River Valley area of Xinjiang, China, under three invasion levels (no invasion and low, moderate, and heavy invasion), and the competitive advantage index, invasion intensity, and contribution of plant community species diversity to community stability and invasibility were determined for the prickly fungus under different degrees of invasion. The results show that there were significant differences (p < 0.05) in the species diversity and community stability of plant communities caused by different degrees of invasion of X. spinosum. The species diversity and stability of plant communities were negatively correlated with the community invasibility, competitive advantage, and invasion intensity of X. spinosum (p < 0.05); therefore, the competitive advantage and invasion intensity of X. spinosum increase with the increase of its invasion degree. On the contrary, community species diversity and stability decreased with the increase of its invasion degree, ultimately leading to differences in community invasibility under different invasion degrees. The Shannon-Wiener and Simpson's indices were the greatest contributors to community stability and invasibility, respectively. Moderate and heavy levels of invasion by X. spinosum reduced the diversity and stability of local plant communities, increased the invasibility of communities, and substantially affected the structures of plant communities. Therefore, the continued invasion by X. spinosum will have an immeasurable impact on the fragile ecosystems and diversity of indigenous species in Xinjiang. We recommend that this invasive species be controlled and eradicated at the early stages of invasion to prevent further harm.

36 Beyond Environmentally Adapted, Towards Ecologically Purposed: Sheep Production in the Us West

Abstract Consumer demand for sheep products is robust, the annual consumption of U.S. lamb is steadily rising, and the number of U.S. sheep farms is increasing. Nevertheless, the U.S. sheep industry continues to lose market share to foreign competitors and the breeding ewe inventory has declined 30% since 2002. This decline has been more drastic in the upper U.S. Mountain West states, where ewe inventories have declined 37% compared with the national average decline of 26%. This is problematic given the Mountain West generates one-third and one-half of the total U.S. lamb crop and wool revenue, respectively. This depopulation trend indicates obstacles unique to the Mountain West, which are not experienced elsewhere in the nation. Mountain West sheep production systems depend on both private and public rangelands for grazing, which must co-exist with many other goals for public lands, including species conservation and critical wildlife habitat. Extensive conversion of native rangeland to croplands, rural housing, and degraded grasslands has simultaneously resulted in a substantial loss of wildlife habitat, thus creating competing ideologies for how remaining rangelands should be managed. Accordingly, public land management agencies are constantly pressured to change land management plans to accommodate public agendas aimed at restricting or halting livestock grazing on public lands with the assumption wildlife habitat will automatically improve. Such exclusion of grazing from public lands has negatively impacted operational capacity of sheep ranches, thus posing serious threats to the U.S. sheep industry and its contributions towards national food security, rural communities, and rangeland conservation. Therefore, to maintain grazing access to public lands, sheep producers and land managers urgently need tools (e.g., management, genetic) to optimize both conservation and production outcomes synergistically. However, ecological and sheep genetic outcomes have thus far been considered separate rather than integrated goals. Traditional genetic improvements in sheep production are focused strictly on the sheep without regard to the ecological outcome. In other words, the “ecosystem” is only considered to achieve profitable production within that environment. With this in mind, can sheep research move beyond the traditional focus of “environmentally adapted” flocks to “ecologically purposed” flocks? We propose that heritable ecologically focused traits can be identified and used to complement the overall sheep genetic improvement goals of the industry while creating precision-based solutions for sustainable habitat management, such as mitigating catastrophic wildfire risk, halting noxious weed invasion, and shaping vegetative structure of native plant communities towards desirable rangeland and conservation goals. We believe such outcomes extend beyond shaping public opinion about sheep grazing but also towards introducing novel value-based marketable products from the sheep industry.

Shade effect on the productivity and structure of natural campos communities: Doctoral thesis abstract

The characteristics of the forest plantations determine the dynamics of photosynthetically active radiation (PAR) under the tree canopy and its area of influence. The objective of this work was to study the effect of shade on the structure and biomass production of the natural grassland (CN), analyzing the relationships between the light environment on the vegetation cover of the understory (%), the species present and their photosynthetic metabolisms. In addition, the effect of artificial shade on the production, seasonal distribution of forage and structure of a CN were analyzed for three years. P. taeda and E. grandis exhibited a similar light environment, presenting the lowest levels of plant cover. E. globulus showed a more illuminated environment, generating better conditions for plant development. C4 species increase their coverage against increases in incident photosynthetically active radiation (PARi) levels and C3 species achieve the highest coverage at intermediate levels of light interception. The composition in summer and autumn tends to become homogeneous over the years, associating with summer perennial grasses (GPE), regardless of the level of interception of solar radiation (IRS). In winter and spring the cover evolves towards a greater association with winter perennial grasses (GPI) and winter annual grasses (GAI) in the levels of greater shade. The increase in IRS levels increased the production of CN. The effect of shade over time determined different seasonal responses in biomass production and composition of functional types of plants. The shade modifies the botanical composition, increasing the coverage of GPI, GAI and reducing the GPE. The shade level modifies the seasonal distribution of forage, smoothing the annual production curve.

Differential ecomorphic analysis of urban park vegetation

The ecomorphic approach was developed to analyze the structure of natural plant communities. This method was applied to analyze the ecological structure of an artificial park plantation in an urban environment. Urban parks perform important and diverse functions in the urban environment. As anthropogenic objects, urban parks should be subject to adequate and effective management that can increase the functional value of forest plantations in the city and ensure their sustainability. In this regard, the choice of the quantitative parameters of the park plantation to be managed is crucial. We hypothesize that ecomorphic analysis can be the basis for selecting optimal quantitative criteria for parkland management. Therefore, the goal of our study was to assess the informational value of ecomorphic analysis for characterizing park plantation in urban environments. In the park, 166 species of vascular plants were found, which are represented by phanerophytes (19.9%), nannophanerophytes (8.4%), hemicryptophytes (40.4%), geophytes (11.4%), theorophytes (18.7%) and geolophytes (1.2%). Sylvants (35.5%) predominate among the coenomorphs, with slightly less pratants (22.3%), ruderants (18.7%) and stepants (14.5%). Cultivants (3.0%), psammophytes (3.0%) and paludants (3.0%) were occasionally found. The proportion of xeromesophytes and mesophytes was the highest (32.5 and 31.3% respectively). The proportion of mesoxerophytes was also relatively high (28.3%). The proportion of other hygromorphs was relatively low. The trophomorphs were represented mainly by mesotrophs (71.1%) and a slightly smaller proportion of megatrophs (22.3%). The oligotrophs were found occasionally (6.6%). Sciogeophytes (57.2%) and heliophytes (30.1%) prevailed among heliomorphs. The proportion of sciophytes and heliosciophytes was much lower (3.6 and 9.0 %, respectively). Entomophilous plant species were the most common among the vegetation cover of the park (71.7%). Anemophilous plants were significantly inferior to them (26.5%). Autogamous and hydrophilous plants were found occasionally (1.2 and 0.6% respectively). Ballistic diasporeochores prevailed among diasporeochores (39.8%). The proportion of anemochores and endozoochores was somewhat lower (27.7 and 12.0% respectively). The results obtained allow to discover the essential ecological features of the park plantation. The park plantation has many features that bring it closer to natural forests. The similarity consists in a significant proportion of silvants, shade-loving species, and mesotrophs. A significant level of anthropogenic impact can be diagnosed on the basis of information about the increased proportion of ruderants in the plant community. The differential analysis of the ecomorphic structure in the section by climorphs is of considerable value. This approach allowed to detect an increased role of the zoogenic factor in the distribution of diaspores of phanerophytes and nannophanerophytes and an increased role of wind in the dispersal of geophytes and therophytes. The role of wind is reduced in the dispersion of hemicryptophytes in the urban environment.

Changes in structure and assembly of a species-rich soil natural community with contrasting nutrient availability upon establishment of a plant-beneficial Pseudomonas in the wheat rhizosphere

BackgroundPlant-beneficial bacterial inoculants are of great interest in agriculture as they have the potential to promote plant growth and health. However, the inoculation of the rhizosphere microbiome often results in a suboptimal or transient colonization, which is due to a variety of factors that influence the fate of the inoculant. To better understand the fate of plant-beneficial inoculants in complex rhizosphere microbiomes, composed by hundreds of genotypes and multifactorial selection mechanisms, controlled studies with high-complexity soil microbiomes are needed.ResultsWe analysed early compositional changes in a taxa-rich natural soil bacterial community under both exponential nutrient-rich and stationary nutrient-limited growth conditions (i.e. growing and stable communities, respectively) following inoculation with the plant-beneficial bacterium Pseudomonas protegens in a bulk soil or a wheat rhizosphere environment. P. protegens successfully established under all conditions tested and was more abundant in the rhizosphere of the stable community. Nutrient availability was a major factor driving microbiome composition and structure as well as the underlying assembly processes. While access to nutrients resulted in communities assembled mainly by homogeneous selection, stochastic processes dominated under the nutrient-deprived conditions. We also observed an increased rhizosphere selection effect under nutrient-limited conditions, resulting in a higher number of amplicon sequence variants (ASVs) whose relative abundance was enriched. The inoculation with P. protegens produced discrete changes, some of which involved other Pseudomonas. Direct competition between Pseudomonas strains partially failed to replicate the observed differences in the microbiome and pointed to a more complex interaction network.ConclusionsThe results of this study show that nutrient availability is a major driving force of microbiome composition, structure and diversity in both the bulk soil and the wheat rhizosphere and determines the assembly processes that govern early microbiome development. The successful establishment of the inoculant was facilitated by the wheat rhizosphere and produced discrete changes among other members of the microbiome. Direct competition between Pseudomonas strains only partially explained the microbiome changes, indicating that indirect interactions or spatial distribution in the rhizosphere or soil interface may be crucial for the survival of certain bacteria.B5pQk-pebCjYS-vjJfR65XVideo

Timing of invasive species removal influences nonnative biotic resistance and trajectories of community reassembly

Abstract As biological invasions increasingly threaten biodiversity, the removal of invasive nonnative species emerges as a possibility to recover the structure and function of native communities. Yet, we have limited knowledge of how communities assemble after nonnative removals. Since most ecosystems are invaded by multiple nonnative species, the impact of their removal likely depends on the interactions among nonnative species which, in turn, are contingent on the environmental context in which they occur. We evaluated the community assembly after the targeted removal of two highly invasive shrubs, Sweetbriar rose (Rosa rubiginosa) and Scotch broom (Cytisus scoparius). The removal was performed at two different times in the growing season (early or late removal) in field and mesocosm communities. In search of general patterns across species, we modelled species responses as a function of their origin (i.e. native/nonnative) and functional traits. We found evidence for negative and asymmetric interactions between dominant invasive species that translated into changes in the abundances of the rest of the species in the community. Depending on the identity of the removed species, the removal of invasive species affected community assembly by promoting other nonnative species or hindering the performance of native species. These effects were modulated by the timing of removal and did not depend on leaf or seed traits. Synthesis. Accounting for nonnative interactions and their temporal dependency should improve our inferences about assembly processes and the effectiveness of nonnative removal aimed at reducing the accumulation of nonnatives.

Arbuscular mycorrhizal fungi inoculation exerts weak effects on species- and community-level growth traits for invading or native plants under nitrogen deposition

Nitrogen deposition and biological invasion are two major components of global environmental change. Nitrogen deposition has been considered to enhance the resource availability of recipient habitats, which influences the invasiveness of plant invader and the invasibility of recipient native communities. Nitrogen deposition has been shown to reduce the relative abundances of arbuscular mycorrhizal fungi (AMF) globally. AMF have been found to mutualistically symbiose with approximately 75% of plant species and act as a nutrient supplier. AMF may modify the structure of native plant communities, collaborate with alien plant invaders and thus promote their invasion. The alien woody invader, Rhus typhina L. has been introduced into North China as a horticultural species, invaded the native plant community and outperformed the native competitors in growth and in photosynthetic efficiency. Nevertheless, little is known about if nitrogen deposition and AMF inoculation synergistically alter the invasibility of native plant community. In this study, R. typhina was subjected to the artificial plant community assembled by four co-existing native species – Chenopodium album L., Vitex negundo var. heterophylla (Franch.) Rehd., Rhus chinensis Mill. and Acer truncatum Bunge in a mesocosm experiment. Nitrogen deposition and AMF inoculation were simulated as environmental and biotic filters respectively. Aboveground biomass and biomass proportion, reflecting plant growth and performance, and specific leaf area and chlorophyll concentration correlated with carbon use and photosynthetic capacity of both the alien invader and the native plants were measured and calculated after harvest. We found that AMF inoculation did not alter the trait variation of alien and native species to increasing nitrogen deposition level in general, although AMF inoculation impeded the increase of aboveground biomass for C. album, V. negundo and native community with increasing nitrogen deposition level. In the scenario of nitrogen deposition and AMF inoculation, a stable status of invasion dynamic may be maintained and needs to be checked with integration of traits at extended temporal scale.

Advances and perspectives of using stable isotope probing (SIP)-based technologies in contaminant biodegradation

Stable isotope probing (SIP) is a powerful tool to study microbial community structure and function in both nature and engineered environments. Coupling with advanced genomics and other techniques, SIP studies have generated substantial information to allow researchers to draw a clearer picture of what is occurring in complex microbial ecosystems. This review provides an overview of the advances of SIP-based technologies over time, summarizes the status of SIP applications to contaminant biodegradation, provides critical perspectives on ecological interactions within the community, and important factors (controllable and non-controllable) to be considered in SIP experimental designs and data interpretation. Current trend and perspectives of adapting SIP techniques for environmental applications are also discussed.

Maximum entropy models reveal spatial variation of metabolic scaling in stream fish communities.

Metabolic scaling provides valuable information about the physiological and ecological functions of organisms, although few studies have quantified the metabolic scaling exponent (b) of communities under natural conditions. Maximum entropy theory of ecology (METE) is a constraint-based unified theory with the potential to empirically assess the spatial variation of the metabolic scaling. Our main goal is to develop a novel method of estimating b within a community by integrating metabolic scaling and METE. We also aim to study the relationships between the estimated b and environmental variables across communities. We developed a new METE framework to estimate b in 118 stream fish communities in the north-eastern Iberian Peninsula. We first extended the original maximum entropy model by parameterizing b in the model prediction of the community-level individual size distributions and compared our results with empirical and theoretical predictions. We then tested the effects of abiotic conditions, species composition and human disturbance on the spatial variation of community-level b. We found that community-level b of the best maximum entropy models showed great spatial variability, ranging from 0.25 to 2.38. The mean exponent (b = 0.93) resembled the community-aggregated mean values from three previous metabolic scaling meta-analyses, all of which were greater than the theoretical predictions of 0.67 and 0.75. Furthermore, the generalized additive model showed that b reached maximum at the intermediate mean annual precipitation level and declined significantly as human disturbance intensified. The parameterized METE is proposed here as a novel framework for estimating the metabolic pace of life of stream fish communities. The large spatial variation of b may reflect the combined effects of environmental constraints and species interactions, which likely have important feedback on the structure and function of natural communities. Our newly developed framework can also be applied to study the impact of global environmental pressures on metabolic scaling and energy use in other ecosystems.

Allelopathic effects of aqueous leaf extracts of five invasive species in Côte d'Ivoire on maize (Zea mays) and rice (Oryza sativa)

Chromolaena odorata, Euphorbia heterophylla, Fleischmannia microstemon, Porophyllum ruderale and Synedrella nodiflora are five invasive plants in agrosystems in Côte d'Ivoire. They strongly influence the structure and diversity of native plant communities. In addition, they can compete for water and nutritional resources with cultivated plants, leading to a decrease in agricultural yield. This competition often occurs through the emission of allelochemicals that prevent seed germination or inhibit the development of other species. Thus, this study aims to assess the allelopathic effects of these five species on maize and rice, two crops generally used in food self-sufficiency programmes. To this end, the seed germination, root and stem growth of these crops watered with different leaf extracts of these five species were monitored in the laboratory. All five species were found to have allelopathic effects on maize and rice development. However, the action of the allelochemicals is specific to the target plant organs and increases with the concentration of the extracts. The study shows that of the five plants, C. odorata, E. heterophylla and F. microstemon are the most damaging as they have a more pronounced effect on seed germination.

Genome-resolved analyses of oligotrophic groundwater microbial communities along phenol pollution in a continuous-flow biodegradation model system.

Groundwater pollution is one of the major environmental concerns. The entrance of pollutants into the oligotrophic groundwater ecosystems alters native microbial community structure and metabolism. This study investigated the application of innovative Small Bioreactor Chambers and CaO2 nanoparticles for phenol removal within continuous-flow sand-packed columns for 6 months. Scanning electron microscopy and confocal laser scanning microscopy analysis were conducted to indicate the impact of attached biofilm on sand surfaces in bioremediation columns. Then, the influence of each method on the microbial biodiversity of the column's groundwater was investigated by next-generation sequencing of the 16S rRNA gene. The results indicated that the simultaneous application of biostimulation and bioaugmentation completely eliminated phenol during the first 42 days. However, 80.2% of phenol remained in the natural bioremediation column at the end of the experiment. Microbial diversity was decreased by CaO2 injection while order-level groups known for phenol degradation such as Rhodobacterales and Xanthomonadales dominated in biostimulation columns. Genome-resolved comparative analyses of oligotrophic groundwater prokaryotic communities revealed that Burkholderiales, Micrococcales, and Cytophagales were the dominant members of the pristine groundwater. Six-month exposure of groundwater to phenol shifted the microbial population towards increasing the heterotrophic members of Desulfobacterales, Pseudomonadales, and Xanthomonadales with the degradation potential of phenol and other hydrocarbons.

Review of the impacts of invasive alien vertebrates on biodiversity

<p indent="0mm">Alien species invasion is one of the major causes of global biodiversity loss. As the top predators of the food web, invasive alien vertebrates have dominant impacts on the native species population, community structure, and ecosystem functions. Nevertheless, within China, there is a lack of a systematic review of the impact of invasive alien vertebrates on biodiversity. Based on an intensive and systematic literature review, we summarize the direct (e.g., predation, competition, reproductive interference, and gene pollution) and indirect (e.g., disease transmission and habitat modifications) impacts of invasive alien vertebrates on the native biota across population, community, ecosystem, and biogeography levels. We particularly focus on the impacts of invasive alien species on island ecosystems, protected areas, and regions along the “Belt and Road Initiative,” which are located in biodiversity-conservation hotspots and are extremely sensitive to biological invasions. Accounting for the requirement of biosecurity system construction in China and the international frontier of discipline development, we finally summarize the recent research progress, the directions of future studies, and the potential conservation and management strategies for invasive alien vertebrates in China.

Fusarium equiseti-inoculation altered rhizosphere soil microbial community, potentially driving perennial ryegrass growth and salt tolerance

Fusarium equiseti is an effective plant growth-promoting fungi that induce systemic disease resistance in plants. However, the role of F. equiseti in regulating salt stress response and the underlying mechanisms remain largely unknown. Here, we investigated the effect of F. equiseti Z7 strain on the growth and salt stress response in perennial ryegrass. Additionally, the role of Z7 in regulating the abundance, composition, and structure of native microbial communities in the rhizosphere soil was determined. We observed that Z7 could produce indole-3-acetic acid (IAA) and siderophores. Hence, Z7 inoculation further enhanced plant growth and salt tolerance in perennial ryegrass. Inoculating Z7 increased K+ and decreased Na+ in plant tissues. Z7 inoculation also enhanced soil quality by reducing soluble salt and increasing available phosphorus. Moreover, inoculating Z7 altered the compositions of bacterial and fungal communities in the rhizosphere soil. For instance, beneficial bacterial genera, such as Flavobacterium, Enterobacter, Agrobacterium, and Burkholderiales were dominantly enriched in Z7-inoculated soil. Interestingly, the relative abundance of these genera showed significantly positive correlations with the fresh weight of perennial ryegrass. Our results demonstrate that Z7 could remarkably promote plant growth and salt tolerance by regulating ion homeostasis in plant tissues and microbial communities in the rhizosphere soil. This study provides a scientific foundation for applying microbes to improve plant growth under extreme salt stress conditions.