Changes In Community Structure Research Articles

Changes in diazotrophic community structure associated with Kuroshio succession in the northern South China Sea

Abstract. Kuroshio intrusion (KI) is a key process that transports water from the western Pacific Ocean to the northern South China Sea (nSCS), where KI-induced surface water mixing often causes variations in microbial assemblages. Yet, how interannual KIs affect the biogeography of diazotrophs and associated environmental factors remains poorly characterized. Here, by quantifying the degree of KIs in 2 consecutive years, coupled with monitoring the diversity and distribution of nitrogenase-encoding nifH phylotypes with quantitative PCR and high-throughput sequencing, we show that changes in the diazotrophic community structure in the nSCS are highly correlated with KI-induced variations in a range of physicochemical parameters. Specifically, the filamentous cyanobacteria in the genus Trichodesmium were more abundant at stations strongly affected by KI and thereby with a deeper mixed layer and higher surface salinity and temperature; the unicellular N2-fixing cyanobacteria in group B (UCYN-B) were more abundant at stations least affected by KI and correlated with nutrient availability, whereas UCYN-C and the γ-proteobacteria were prevalent at stations moderately affected by KI. The neutral community model further demonstrated that dominant diazotrophic subcommunities were significantly affected by environmental factors in 2017 when KI was stronger compared to 2018 when KI retreated. Our analyses provide insightful evidence for the role of KI in shaping the diazotrophic community structure primarily as a stochastic process, implying a potential region-scale redistribution of diazotrophs and nitrogen budget, given that KIs are projected to intensify in a future warming ocean.

Temperature-driven dynamics: unraveling the impact of climate change on cryptic species interactions within the Litoditis marina complex.

Anthropogenic climate change and the associated increase in sea temperatures are projected to greatly impact marine ecosystems. Temperature variation can influence the interactions between species, leading to cascading effects on the abundance, diversity and composition of communities. Such changes in community structure can have consequences on ecosystem stability, processes and the services it provides. Therefore, it is important to better understand the role of species interactions in the development of communities and how they are influenced by environmental factors like temperature. The coexistence of closely related cryptic species, with significant biological and ecological differences, makes this even more complex. This study investigated the effect of temperature on species growth and both intra- and interspecific interactions of three species within the free-living nematode Litoditis marina complex. To achieve this, closed microcosm experiments were conducted on the L. marina species Pm I, Pm III and Pm IV in monoculture and combined cultures at two temperature treatments of 15 °C and 20 °C. A population model was constructed to elucidate and quantify the effects of intra- and interspecific interactions on nematode populations. The relative competitive abilities of the investigated species were quantified using the Modern Coexistence Theory (MCT) framework. Temperature had strong and disparate effects on the population growth of the distinct L. marina species. This indicates temperature could play an important role in the distribution of these cryptic species. Both competitive and facilitative interactions were observed in the experiments. Temperature affected both the type and the strength of the species interactions, suggesting a change in temperature could impact the coexistence of these closely related species, alter community dynamics and consequently affect ecosystem processes and services.

Forest landscape restoration-induced changes in land cover and woody plant community structure in a degraded forest reserve in Ghana

Restoring degraded forests has become a global concern due to the high levels of forest disturbance arising from farming, logging, and mining. This study, conducted in the degraded Tain II Forest Reserve landscape in Ghana, examined the effects of forest landscape restoration (FLR) on land cover changes and woody plant community structure in the area. The study combined remote sensing, plot sampling techniques, and structured interviews in data collection. Landsat images were used to establish the land cover changes in the landscape. Plant community structure was assessed within thirty 50 m by 50 m plots that were laid randomly in equal numbers in Natural Forest (NF), Natural Regeneration (NR), and Assisted Regeneration (AR) sites. Ecosystem services and socio-economic benefits of the FLR to the local community were also assessed. To compare site attributes, one-way ANOVA analysis was used. The results showed that forestland increased from 45 to 70 % while bare land and cropland declined consistently from over 50 % to 28 % and 5 % to 0.7 %, respectively, within 10-year study period. Woody plant species totaling 120 belonging to 34 families, compared to a baseline of 61 species and 24 families, were enumerated. The NF and NR sites had higher flora diversity than the AR sites. NF composition was less homogenous compared to the NR and AR. The majority of the community is perceived to have socioeconomically gained from ecosystem services and engagement in the FLR. Effective land governance, stakeholder participation, community-led fire control, and strategic interventions positively influenced the rate of forest restoration. The FLR influenced the land cover and species composition of the landscape. The findings highlight the importance of ecological, social, and economic considerations in FLR for sustainable outcomes for people and the environment. FLR stakeholders should collaborate in planning and implementation of forest restoration to ensure sustainable outcomes.

Denaturing Gradient Gel Electrophoresis Approach for Microbial Shift Analysis in Thermophilic and Mesophilic Anaerobic Digestions.

To determine the evolution of microbial community and microbial shift under anaerobic processes, this study investigates the use of denaturing gradient gel electrophoresis (DGGE). In the DGGE, short- and medium-sized DNA fragments are separated based on their melting characteristics, and this technique is used in this study to understand the dominant bacterial community in mesophilic and thermophilic anaerobic digestion processes. Dairy manure is known for emitting greenhouse gases (GHGs) such as methane, and GHG emissions from manure is a biological process that is largely dependent on the manure conditions, microbial community presence in manure, and their functions. Additional efforts are needed to understand the GHG emissions from manure and develop control strategies to minimize the biological GHG emissions from manure. To study the microbial shift during anaerobic processes responsible for GHG emission, we conducted a series of manure anaerobic digestion experiments, and these experiments were conducted in lab-scale reactors operated under various temperature conditions (28 °C, 36 °C, 44 °C, and 52 °C). We examined the third variable region (V3) of the 16S rRNA gene fingerprints of bacterial presence in anaerobic environment by PCR amplification and DGGE separation. Results showed that bacterial community was affected by the temperature conditions and anaerobic incubation time of manure. The microbial community structure of the original manure changed over time during anaerobic processes, and the community composition changed substantially with the temperature of the anaerobic process. At Day 0, the sequence similarity confirmed that most of the bacteria were similar (>95%) to Acinetobacter sp. (strain: ATCC 31012), a Gram-negative bacteria, regardless of temperature conditions. At day 7, the sequence similarity of DNA fragments of reactors (28 °C) was similar to Acinetobacter sp.; however, the DNA fragments of effluent of reactors at 44 °C and 52 °C were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 97%) and Tepidimicrobium ferriphilum (strain: DSM 16624) (similarity: 100%), respectively. At day 60, the analysis showed that DNA fragments of effluent of 28 °C reactor were similar to Galbibacter mesophilus (strain: NBRC 10162) (similarity: 87%), and DNA fragments of effluent of 36 °C reactors were similar to Syntrophomonas curvata (strain: GB8-1) (similarity: 91%). In reactors with a relatively higher temperature, the DNA fragments of effluent of 44 °C reactor were similar to Dielma fastidiosa (strain: JC13) (similarity: 86%), and the DNA fragments of effluent of 52 °C reactor were similar to Coprothermobacter proteolyticus (strain: DSM 5265) (similarity: 99%). To authors' knowledge, this is one of the few studies where DGGE-based approach is utilized to study and compare microbial shifts under mesophilic and thermophilic anaerobic digestions of manure simultaneously. While there were challenges in identifying the bands during gradient gel electrophoresis, the joint use of DGGE and sequencing tool can be potentially useful for illustrating and comparing the change in microbial community structure under complex anaerobic processes and functionality of microbes for understanding the consequential GHG emissions from manure.

Soil organic carbon, pH, and ammonium nitrogen controlled changes in bacterial community structure and functional groups after forest conversion

IntroductionLand-use changes significantly impact soil properties in forests, which is an area of concern. Therefore, the effects of changing forest types on soil microbial communities and their functions in northern subtropical forest regions need to be further researched.MethodsWe used 16S rDNA sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX) to assess the variation of soil bacterial communities and potential functions related to carbon (C) and nitrogen (N) cycling in two soil layers (0–10 and 10–30 cm) after the conversion of the secondary masson pine (Pinus massoniana, PM) forest to plantations of slash pine (Pinus elliottii, PE) and Chinese fir (Cunninghamia lanceolata, CL) located in Jingde County, Anhui Province, China.ResultsThe study found that converting coniferous secondary forests to coniferous plantations resulted in a notable increase in soil pH and a decrease in nitrate nitrogen and organic carbon contents. Additionally, soil microbial diversity increased significantly, and microbial community structure changed, particularly in the topsoil. These changes might affect the C- and N-cycling mediated by soil bacteria. The analysis revealed a significant decrease in the abundance of functional groups associated with C-cycling and a significant increase in the abundance of functional groups associated with N-cycling, particularly those associated with denitrification. Soil organic carbon, pH, and ammonium nitrogen were the most critical variables affecting changes in the soil microbial community.DiscussionThese findings provide valuable information for ecological restoration and future sustainable forest management.

How do phytophagous insects affect phyllosphere fungi? Tracking fungi from milkweed to monarch caterpillar frass reveals communities dominated by fungal yeast.

Since a significant proportion of plant matter is consumed by herbivores, a necessary adaptation for many phyllosphere microbes could be to survive through the guts of herbivores. While many studies explore the gut microbiome of herbivores by surveying the microbiome in their frass, few studies compare the phyllosphere microbiome to the gut microbiome of herbivores. High-throughput metabarcode sequencing was used to track the fungal community from milkweed (Asclepias spp.) leaves to monarch caterpillar frass. The most commonly identified fungal taxa that dominated the caterpillar frass after the consumption of leaves were yeasts, mostly belonging to the Basidiomycota phylum. While most fungal communities underwent significant bottlenecks and some yeast taxa increased in relative abundance, a consistent directional change in community structure was not identified from leaf to caterpillar frass. These results suggest that some phyllosphere fungi, especially diverse yeasts, can survive herbivory, but whether herbivory is a key stage of their life cycle remains uncertain. For exploring phyllosphere fungi and the potential coprophilous lifestyles of endophytic and epiphytic fungi, methods that target yeast and Basidiomycota fungi are recommended.

Dynamic interplay between soil microbial communities, enzyme activities, and pear quality across planting years

Few studies have been reported on the effect of planting years on fruit quality and soil of pear trees. In this study, four planting years (T5, T20, T30, and T40) of Cuiguan pears were used to analyze fruit quality, rhizosphere soil enzymes, and microbial diversity of pear trees, and their correlations. The results showed that the content of sucrose, reducing sugar and ascorbic acid in Cuiguan Pear showed a tendency of increasing and then decreasing with the increase of planting years, in which the highest content was found in 20- and 30-year-old fruits, and the highest content of total acid was found in 5-year-old fruits. Rhizosphere soil enzyme activities varied with planting year, with the highest protease activity in 20-year-old soil, phosphatase and urease in 30-year-old soil, polyphenol oxidase in 5-year-old soil, and sucrase in 40-year-old soil. The microbial diversity index and the number of OTUs showed an increasing and decreasing trend with the increase of planting years. Among the top 11 bacteria in pear rhizosphere soil average relative abundance, with Bradyrhizobium decreasing in relative abundance at the peak pear fruiting stages (T20 and T30), while Acidothermus showed an increasing trend in relative abundance with increasing planting years. RDA analysis showed that there were differences in the microbial community structure of pear trees at different planting years, and that both sucrose and reducing sugar contents in pears were positively correlated with T20 and T30, ascorbic acid content was positively correlated with T40, whereas the total acid content was positively correlated with T5, and that T20 was positively correlated with soil protease and phosphate mono esterase activities, and that T30 was positively correlated with polyphenol oxidase and urease activities, whereas T40 was positively correlated with sucrase activity. In summary, with the increase of planting years, changes in soil microbial community structure and soil enzyme activity have a significant impact on pear quality formation, and the results of the study provide a theoretical basis for scientific management of pear orchards.

Structural and functional effects of global invasion pressure on benthic marine communities—patterns, challenges and priorities

AbstractAimRetrospective (pre‐ vs. post‐invasion) and cross‐sectional comparisons of ecosystems exposed to high and low bioinvasion pressure, provide an alternative approach to evaluate shifts in biological communities associated with non‐indigenous species (NIS) introductions. In this study, we aimed to examine general patterns of change in community composition, structure and function in six well‐studied and globally distributed marine ecosystems that had documented histories of biological invasions.LocationGlobal.MethodsBy considering a range of regional datasets and different sampling approaches, we evaluated trends within and among ecosystems by comparing paired measures of community and functional structure in either space or time.ResultsOur analyses revealed different patterns of structural and functional change at ecosystem scales, but direct comparisons across regions were hindered by confounding effects of study designs and other drivers of change. The most prominent shifts in community composition were observed in the retrospective studies, characterised by the greatest relative contribution of NIS. No uniform pattern of change in functional metrics was observed across study regions. However, functional evenness and dispersion showed a tendency to increase in systems under higher invasion pressure, refuting the hypothesis of selective accumulation of specific traits and functional homogenisation within ecosystems exposed to high invasion pressure.Main ConclusionsAccumulation of NIS within broader communities can be a subtle process, with inherent spatial and temporal variability. Nonetheless, not only do species' proportional contributions to communities change over time in areas subjected to high bioinvasion pressure, but trait profiles can incrementally shift, which alters the original ecology of an area. Planned, long‐term studies that incorporate a range of measures of environmental drivers and ecosystem response are crucial for better understanding of cumulative, community‐level and ecosystem‐scale change associated with biological invasions.

Temporal dynamics of fecal microbiota community succession in broiler chickens, calves, and piglets under aerobic exposure.

Researchers have extensively studied the effect of oxygen on the growth and survival of bacteria. However, the impact of oxygen on bacterial community structure, particularly its ability to select for taxa within the context of a complex microbial community, is still unclear. In a 21-day microcosm experiment, we investigated the effect of aerobic exposure on the fecal community structure and succession pattern in broiler, calf, and piglet feces (n = 10 for each feces type). Bacterial diversity decreased and community structure changed rapidly in the broiler microbiome (P < 0.001), while the fecal community of calves and piglets, which have higher initial diversity, was stable after initial exposure but decreased in diversity after 3 days (P < 0.001). The response to aerobic exposure was host animal specific, but in all three animals, the change in community structure was driven by a decrease in anaerobic species, primarily belonging to Firmicutes and Bacteroidetes (except in broilers where Bacteroidetes increased), along with an increase in aerobic species belonging to Proteobacteria and Actinobacteria. Using random forest regression, we identified microbial features that predict aerobic exposure. In all three animals, host-beneficial Prevotella-related ASVs decreased after exposure, while ASVs belonging to Acinetobacter, Corynbacterium, and Tissierella were increased. The decrease of Prevotella was rapid in broilers but delayed in calves and piglets. Knowing when these pathobionts increase in abundance after aerobic exposure could inform farm sanitation practices and could be important in designing animal experiments that modulate the microbiome.IMPORTANCEThe fecal microbial community is contained within a dynamic ecosystem of interacting microbes that varies in biotic and abiotic components across different animal species. Although oxygen affects bacterial growth, its specific impact on the structure of complex communities, such as those found in feces, and how these effects vary between different animal species are poorly understood. In this study, we demonstrate that the effect of aerobic exposure on the fecal microbiota was host-animal-specific, primarily driven by a decrease in Firmicutes and Bacteroidetes, but accompanied by an increase in Actinobacteria, Proteobacteria, and other pathobionts. Interestingly, we observed that more complex communities from pig and cattle exhibited initial resilience, while a less diverse community from broilers displayed a rapid response to aerobic exposure. Our findings offer insights that can inform farm sanitation practices, as well as experimental design, sample collection, and processing protocols for microbiome studies across various animal species.

Effects of Water Level Fluctuations and Vegetation Restoration on Soil Prokaryotic Microbial Community Structure in the Riparian Zone of the Three Gorges Reservoir

Riparian zones are typical fragile and sensitive ecological areas. Fluctuations in water level are the main factor affecting the soil environment in these zones, and vegetation restoration is considered an important means of soil conservation there. However, the interactive effects of water level fluctuations and vegetation restoration on the soil microbial community structure in the reservoir riparian zone remain unclear. Therefore, we selected abandoned grassland and artificial forestland at different water level elevations as research objects in the riparian zone of the Three Gorges Reservoir. We used 16S rRNA high-throughput sequencing technology to explore the composition and diversity of soil prokaryotic microbial communities and investigated the main environmental factors driving the soil microbial community structure. The results showed that the α diversity of soil prokaryotes was the highest at the low water level of the riparian zone. The Pielou_e index, Shannon index, and Simpson index at the 163 m elevation were significantly higher than those at the 168 m elevation, and the Chao1 index and Shannon index were significantly higher than those at the 173 m elevation. However, no significant difference was found in the soil microbial community α diversity between abandoned grassland and artificial forestland. At the same time, water level fluctuations and vegetation restoration had significant effects on the community composition of soil prokaryotic microorganisms, and there were significant differences in biomarker categories in different study sites. Notably, the effects of vegetation restoration types on the soil prokaryotic microbial community structure were stronger than that of water level fluctuations. In addition, the results of hierarchical segmentation showed that soil pH was the main driving factor for the change in soil prokaryotic microbial community structure in the Three Gorges Reservoir. These results deepen our understanding of the variations in microbial community structure in the reservoir riparian zone and provide scientific reference for the restoration and reconstruction of the riparian zone ecosystem.

Climatic and disturbance impacts on temperate rainforest development since ∼18 ka in central-west Isla Grande de Chiloé (42.7°S)

Understanding the role of disturbance regimes on terrestrial ecosystems is often compounded by the paucity of time series sufficiently long and detailed to capture triggering events and the sequence of changes in species composition, community structure and dynamics along a time continuum until the present. Adding complexity to this problem, disturbance regimes and the distribution/competitive interactions of participating species may vary in time with shifts in mean climatic conditions and variability. Here we present results from sediment cores we collected from small closed-basin lakes near the Pacific coast of central Isla Grande de Chiloé, a sector with the lowest seasonality and recurrence of explosive volcanic events in Northwestern Patagonia (NWP). Our aim is examining vegetation development since the last glaciation and exploring potential climatic and disturbance impacts. We found rapid establishment of closed-canopy rainforests, which have persisted with little variation in terms of physiognomy until the present. Significant changes in species composition, structure, dynamics, and rates of change are evident over the last ∼18,000 years, along with fire maxima at ∼16.7 ka, ∼12.7 ka, between ∼11.7-9 ka, from ∼2 ka to the present, and minima in the interim. Fires precede major increases in disturbance favored taxa, which correspond in timing with fire activity maxima at NWP scale. The most recent ∼2000 years coincide with the highest number and ubiquity of human occupations at central-west and NWP scale, raising the possibility that fires were driven by human activities near our study sites. We detect a conspicuous increase in disturbance-favored trees ∼150 years after deposition of the Puma Verde Tephra (∼8.3 ka) and interpret their subsequent maintenance by frequent blowdown events after ∼7.5 ka in exposed sectors of the Coastal Range. We posit that enhanced storminess driven by stronger Southern Westerly Winds since ∼7.5 ka has favored early successional opportunistic trees in detriment of old-growth forests dominated by shade-tolerant species, generating a spatial mosaic of forest patches or gaps in different stages of recovery.

Bacterial Community Structure of Typical Lake Sediments in Yinchuan City and Its Response to Heavy Metals

Lake wetlands are extremely important and special ecosystems, which are important for regional water resource storage, environmental protection, and biodiversity maintenance. Sediment bacteria are an important component of lake ecosystems and are a major driver of biogeochemical cycling in lakes. In order to investigate the community structure of bacteria in typical lake sediments in Yinchuan City and their influencing factors, three typical lakes in Yinchuan City (Yuehai Lake, Mingcui Lake, and Xiniu Lake) were selected for the study and surface sediments were collected in January, April, July, and October 2021. The composition of the sediment bacterial community was examined using 16S rDNA high-throughput sequencing technology, and the response relationships between them and heavy metals were explored. The results showed that the ecological hazard coefficient for heavy metals in the sediments of three typical lakes in Yinchuan City was far less than 40, and the ecological hazard index was far less than 150, all of which indicated a minor ecological hazard. There were no significant differences in bacterial community diversity among the three lakes, but there were significant variations in diversity among the lakes in different seasons and significant differences in community composition. The dominant phyla (top three in terms of relative abundance) in Yuehai Lake, Mingcui Lake, and Xiniu Lake were Proteobacteria, Bacteroidetes, and Chloroflexi. The dominant lower orders were Gammaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria. The main divergent species that occurred at the phylum level in typical lakes in Yinchuan were Proteobacteria, Bacteroidetes, Euryarchaeota, Firmicutes, Actinobacteria, and Acidobacteria. The sediment bacterial community structure of Yuehai Lake was significantly correlated with Cu, Fe, Mn, Zn, As, and Pb; the sediment bacterial community structure of Lake Mingcui was significantly correlated with Fe, Pb, and Cr; and the sediment bacterial community structure of Xiniu Lake was not significantly correlated with heavy metals. The types and contents of sediment heavy metals had a significant effect on the bacterial community structure of sediments in Yinchuan Yuehai Lake and Mingcui Lake and were important environmental factors that caused changes in the bacterial community structure of lake sediments.

Impact of high-altitude acclimatization and de-acclimatization on the intestinal microbiota of rats in a natural high-altitude environment.

Intestinal microorganisms play an important role in the health of both humans and animals, with their composition being influenced by changes in the host's environment. We evaluated the longitudinal changes in the fecal microbial community of rats at different altitudes across various time points. Rats were airlifted to high altitude (3,650 m) and acclimatized for 42 days (HAC), before being by airlifted back to low altitude (500 m) and de-acclimatized for 28 days (HADA); meanwhile, the control group included rats living at low altitude (500 m; LA). We investigated changes in the gut microbiota at 12 time points during high-altitude acclimatization and de-acclimatization, employing 16S rRNA gene sequencing technology alongside physiological indices, such as weight and daily autonomous activity time. A significant increase in the Chao1 index was observed on day 14 in the HAC and HADA groups compared to that in the LA group, indicating clear differences in species richness. Moreover, the principal coordinate analysis revealed that the bacterial community structures of HAC and HADA differed from those in LA. Long-term high-altitude acclimatization and de- acclimatization resulted in the reduced abundance of the probiotic Lactobacillus. Altitude and age significantly influenced intestinal microbiota composition, with changes in ambient oxygen content and atmospheric partial pressure being considered key causal factors of altitude-dependent alterations in microbiota composition. High-altitude may be linked to an increase in anaerobic bacterial abundance and a decrease in non-anaerobic bacterial abundance. In this study, the hypobaric hypoxic conditions at high-altitude increased the abundance of anaerobes, while reducing the abundance of probiotics; these changes in bacterial community structure may, ultimately, affect host health. Overall, gaining a comprehensive understanding of the intestinal microbiota alterations during high-altitude acclimatization and de-acclimatization is essential for the development of effective prevention and treatment strategies to better protect the health of individuals traveling between high- and low-altitude areas.

Experimental seabed disturbance effects on Chatham Rise deep-sea meiofaunal communities, Southwest Pacific

ABSTRACT Growing global demand for deep-sea resources may lead to increased pressure on benthic ecosystems. Here we examined changes in meiofaunal communities following an in situ physical disturbance experiment. A significant change in meiofaunal community structure in surface (0-1 cm) and subsurface (1-5 cm) sediments was observed immediately following the disturbance at both the directly and indirectly disturbed sites and adjacent potentially undisturbed/indirectly disturbed sites, reflecting a decrease in the abundance of several meiofaunal taxa. Abundance, taxon richness and diversity also decreased immediately following disturbance across all sites. Surface community parameters returned to pre-disturbance values one year post-disturbance, but only a partial recovery was observed for the subsurface community over the same period. The accumulation of recently resuspended and deposited sediment could have led to lower meiofaunal density and shifts in community structure. Passive dispersal and recolonisation from outside the study area may explain why the surface community recovered more fully than the subsurface community. We show that meiofauna were negatively affected by a relatively minor disturbance compared to proposed commercial seabed mining operations, but the finding that communities had largely recovered one year after disturbance has implications for resilience of fauna to much more pronounced impacts of potential large-scale mining.

Response of rhizosphere microbial community structure and production performance of corn and soybean to belt planting mode

Soybean and corn strip cropping takes full advantage of the root characteristics and plant height differences between soybean and corn, which can improve crop photosynthesis and nutrient uptake as well as capitalize on the marginal effect of corn. However, there is not enough in-depth research on the effects of soybean and corn strip cropping modes on inter-root microbial communities and crop yield traits and their correlations, and the functional genes of inter-root microbes. In this study, the structural composition and functional genes of soil inter-root microbial communities under different strip cropping patterns of soybean and maize, Mode 1, Mode 2, and Mode 3, were studied using macro-genome high-throughput sequencing, and the yield traits of soybean and maize were determined and the correlation was understood, taking Zhonglian Soybean 1505 and Tiyu 108 maize as test materials at the experimental base of the Research Institute of Agricultural and Livestock Sciences, Xing'anmeng, Inner Mongolia. correlation between the two. The following results were found. Redundancy analysis found that rhizosphere microorganisms are mainly bacteria, followed by viruses, followed by archaea, and fungi are the least. Relatively speaking, viruses and bacteria are more susceptible to the influence of planting patterns than fungi. Alpha diversity analysis shows that the diversity index changes significantly during the peak flowering period. There is no difference between the other two stages. The diversity of maize rhizosphere microorganisms under Mode 1 or Mode 2 modes is higher than that under Mode 3 modes, while the diversity of soybean rhizosphere microorganisms under Mode 3 modes is higher than the other two modes. Profiling analysis found that different growth periods and planting patterns lead to varying degrees of changes in community structure. The dominant bacterial phyla include Pseudomonas, Actinobacteria, Bacteroidetes, and Streptococcus. The dominant genera of bacteria are rhizobia, pseudomonas, erythrobacteria, and pseudomonas. The relative abundance of slow root rhizobia in the three growth stages of maize rhizosphere is relatively low. The results of yield traits showed that corn yield under Mode 1 and Mode 2 planting was significantly higher than that under pattern III; soybean yield under pattern III planting was significantly higher than that under the other two patterns, indicating that pattern I or II planting is suitable for corn production, while Mode 3 planting mode is more suitable for soybean production. Correlation analysis showed that S_Massilis_putida was significantly and positively correlated with maize yield, and S_lysobacter_capsici was highly significantly and significantly positively correlated with the number of soybean plants per square meter, and the number of plants in 2 square meters. This study contributes to our further understanding of the classification of inter-root microorganisms and their functional relationships in maize and soybean under different conditions.

Distinguished denitrifying phosphorus removal in the high-rate anoxic/microaerobic system for sewage treatment

This study re-evaluated the role of anoxic and anaerobic zones during the enhanced biological phosphorus (P) removal process by investigating the potential effect of introducing an anoxic zone into a high-rate microaerobic activated sludge (MAS) system (1.60–1.70 kg chemical oxygen demand (COD) m−3 d−1), i.e., a high-rate anoxic/microaerobic (A/M) system for sewage treatment. In the absence of a pre-anaerobic zone, introducing an anoxic zone considerably reduced effluent NOx−-N concentrations (7.2 vs. 1.5 mg L−1) and remarkably enhanced total nitrogen (75% vs. 89%) and total P (18% vs. 60%) removal and sludge P content (1.48% vs. 1.77% (dry weight)) due to further anoxic denitrifying P removal in the anoxic zone (besides simultaneous nitrification and denitrification in the microaerobic zone). High-throughput pyrosequencing demonstrated the niche differentiation of different polyphosphate accumulating organism (PAO) clades (including denitrifying PAO [DPAO] and non-DPAO) in both systems. Introducing an anoxic zone considerably reduced the total PAO abundance in sludge samples by 42% and modified the PAO community structure, including 17–19 detected genera. The change was solely confined to non-DPAOs, as no obvious change in total abundance or community structure of DPAOs including 7 detected genera was observed. Additionally, introducing an anoxic zone increased the abundance of ammonia-oxidizing bacteria by 39%. The high-rate A/M process provided less aeration, higher treatment capacity, a lower COD requirement, and a 75% decrease in the production of waste sludge than the conventional biological nutrient removal process.

Effects of plant diversity and community structure on ecosystem multifunctionality under different grazing potentials in the eastern Eurasian steppe

Grazing potential represents the potential carrying capacity of steppe livestock production. Understanding the impact of changes in plant diversity and community structure on ecosystem multifunctionality (EMF) at different grazing potentials is crucial for the sustainable management of steppe ecosystems. We examined the associations between plant diversity, community structure, above-ground ecosystem multifunctionality (AEMF), and below-ground ecosystem multifunctionality (BEMF) at various grazing potentials. Our assessment employed generalized linear mixed-effects models and structural equation models to determine the impact of these factors on ecosystem multifunctionality. Our study results indicated that ecosystem multifunctionality differed depending on the level of grazing potential and decreased as grazing potential declined. The impact of plant diversity and community structure on above- and below-ground ecosystem multifunctionality varied. Plant diversity and community structure correlated more with AEMF than BEMF. Plant diversity had the most significant effect on EMF under high grazing potential, while community structure had the greatest effect on EMF under moderate and low grazing potential. These improve our understanding of the correlation between steppe plant diversity, community structure, and above- and below-ground ecosystem multifunctionality. This understanding is necessary to develop strategies to increase plant diversity or regulate community structure and the sustainability of steppes.

Synergistic effects of peracetic acid and free ammonia pretreatment on anaerobic fermentation of waste activated sludge to promote short-chain fatty acid production for polyhydroxyalkanoate biosynthesis: Mechanisms and optimization

Peracetic acid (PAA) combined with free ammonia (FA) pretreatment can be utilized to promote anaerobic fermentation (AF) of waste activated sludge (WAS) to produce short-chain fatty acids (SCFAs), and the resulting SCFAs are desirable carbon sources (C-sources) for polyhydroxyalkanoate (PHA) biosynthesis. This work aimed to determine the optimum conditions for PAA + FA pretreatment of sludge AF and the feasibility of using anaerobic fermentation liquor (AFL) for PHA production. To reveal the mechanisms of integrated pretreatment, the impacts of PAA + FA pretreatment on different stages of sludge AF and changes in the microbial community structure were explored. The experimental results showed that the maximum SCFA yield reached 491.35 ± 6.02 mg COD/g VSS on day 5 after pretreatment with 0.1 g PAA/g VSS +70 mg FA/L, which was significantly greater than that resulting from PAA or FA pretreatment alone. The mechanism analysis showed that PAA + FA pretreatment promoted sludge solubilization but strongly inhibited methanogenesis. According to the analysis of the microbial community, PAA + FA pretreatment changed the microbial community structure and promoted the enrichment of bacteria related to hydrolysis and acidification, and Proteiniclasticum, Macellibacteroides and Petrimonas became the dominant hydrolytic and acidifying bacteria. Finally, after alkali treatment, the AFL was utilized for batch-mode PHA production, and a maximum PHA yield of 55.05 wt% was achieved after five operation periods.

The Influence of Forest Litter Characteristics on Bacterial and Fungal Community Diversity in the Picea crassifolia Ecosystem on the Qinghai–Tibet Plateau

The biodiversity and activity of microorganisms are crucial for litter decomposition, but how litter traits at different stages of decomposition drive changes in microbial communities has yet to be thoroughly explored. In the typical alpine hilly area of the Qinghai–Tibet Plateau, three types of litter at different decomposition stages were selected under a natural Picea crassifolia (Picea crassifolia Kom.) forest: undecomposed (A-1), partially decomposed (A-2), and fully decomposed (A-3). By measuring physicochemical indicators, microbial diversity, and the composition of the litter at different decomposition stages, this study investigates the community changes and responses of bacteria to litter characteristic changes at different decomposition levels. The results show that with the increase in decomposition level, bacterial diversity increases, community structure changes, and network complexity gradually increases, while the changes in fungal communities are insignificant. Structural equation modeling indicates that the first principal component (PC1) of litter properties is significantly negatively correlated with bacterial diversity and positively correlated with bacterial community composition. There is no significant correlation between fungal diversity and community composition, indicating a closer relationship between bacteria and litter characteristics than fungi. In summary, with an increase in litter decomposition level, the diversity and network complexity of bacterial and fungal communities will significantly increase, which is related to the changes in various litter characteristics. This study provides a scientific basis for the regulatory mechanism of litter decomposition and turnover in the alpine hilly area of the Qinghai–Tibet Plateau, specifically in Picea crassifolia forests.

Changes in soil bacterial community structure in a short-term trial with different silicate rock powders

BackgroundThe use of rock powders in soil has emerged as a nature-based technology to improve soil properties relevant to crop development and for atmospheric carbon dioxide removal (CDR) via enhanced rock weathering (ERW). Although modeling this process is crucial, the soil microbiome has been identified as the main reason why several experimental and field results do not fit the geochemical and kinetic theoretical models. Here, the hypothesis that the bacterial community structure is modulated by the application of different silicate rock powders was tested. One phonolite, three basalt variations and one granite, as well as KCl treatments, were applied to a Ferralsol cultivated with Brachiaria in short-term pedogeochemical experiments and assessed after 1 (1M), 4 (4M) and 8 (8M) months.ResultsThe main changes in soil bacterial structure were observed at 8M and found to be modulated according to rock type, with petrochemistry and mineralogy acting as the main drivers. The content of microbial biomass carbon tended to decrease over time in the Control and KCl treatments, especially at 4M, while the rock treatments showed constant behavior. The sampling time and treatment affected the richness and diversity indices. The Si, Ca and Fe from mafic minerals were the main chemical elements related to the soil bacterial changes at 8M.ConclusionsThe type (acidity) of silicate rock powder modulated the soil bacterial community (SBC) in a pot experiment with tropical soil. The specificity of the SBC for each rock type increased with time until the end of the experiment at 8 months (8M). The carbon content in the microbial biomass was lower in the rock powder treatments in the first month (1 M) than in the control and KCl treatments and was equal to or higher than that in the 8 M treatment. This result illustrates the challenge of modeling rock powder dissolution in soil since the soil medium is not inert but changes concurrently with the dissolution of the rock.Graphical