Habitat Niche Breadth Research Articles

Alteration of soil microbiomes in an arsenic and antimony co-contamination zone after dam failure

Arsenic (As) and antimony (Sb), two toxic metal(loid)s, behave similarly and commonly occur in mine tailings. Yet, responses of microbes to As and Sb co-contamination in tailings dam failure-affected area remain limited. Herein, soil microbiomes (archaea, bacteria and fungi) across two contrasting sites (tailing-contaminated farmland and nearby undisturbed forestland) at a Sb-Au mining district in Chizhou, China were investigated by high-throughput sequencing. Results showed that As and Sb occurred mainly in the residual form, accounting for 55.82% and 52.04%, respectively. The bioavailable form was 12.77% and 10.39% in contaminated farmland compared to 13.31% and 11.66% in undisturbed forestland, respectively. Contrary to archaea and fungi, bacterial alpha-diversity significantly increased in contaminated farmland. The taxa-taxa interactions in archaea were most robust, followed by bacteria; and fungi were the weakest, which was corresponding to the habitat niche breadth. Microbial communities were affected by the deterministic processes with a modified stochasticity ratio (MST) value of 36.36%, whereas more stochasticity (MST = 49.71%) was raised in contaminated farmland than in undisturbed forestland (MST = 36.98%). The microbial function based on taxonomy-based inference indicated that nitrogen and carbon metabolisms associated with archaea and bacteria increased in contaminated farmland, as well as plant pathogen, wood saprotroph and endophyte related with fungi. The turnover of soil microbiomes was tightly correlated with As and Sb speciation. Collectively, this study reveals that the soil microbial survival strategies to As-Sb co-contamination after dam failure, providing guidance for the development of bioremediation and tailings management strategies.

Niche breadth and divergence in sympatric cryptic coral species (Pocillopora spp.) across habitats within reefs and among algal symbionts.

While the presence of morphologically cryptic species is increasingly recognized, we still lack a useful understanding of what causes and maintains co-occurring cryptic species and its consequences for the ecology, evolution, and conservation of communities. We sampled 724 Pocillopora corals from five habitat zones (the fringing reef, back reef, and fore reef at 5, 10, and 20 m) at four sites around the island of Moorea, French Polynesia. Using validated genetic markers, we identified six sympatric species of Pocillopora, most of which cannot be reliably identified based on morphology: P. meandrina (42.9%), P. tuahiniensis (25.1%), P. verrucosa (12.2%), P. acuta (10.4%), P. grandis (7.73%), and P. cf. effusa (2.76%). For 423 colonies (58% of the genetically identified hosts), we also used psbA ncr or ITS2 markers to identify symbiont species (Symbiodiniaceae). The relative abundance of Pocillopora species differed across habitats within the reef. Sister taxa P. verrucosa and P. tuahiniensis had similar niche breadths and hosted the same specialist symbiont species (mostly Cladocopium pacificum) but the former was more common in the back reef and the latter more common deeper on the fore reef. In contrast, sister taxa P. meandrina and P. grandis had the highest niche breadths and overlaps and tended to host the same specialist symbiont species (mostly C. latusorum). Pocillopora acuta had the narrowest niche breadth and hosted the generalist, and more thermally tolerant, Durusdinium gynnii. Overall, there was a positive correlation between reef habitat niche breadth and symbiont niche breadth-Pocillopora species with a broader habitat niche also had a broader symbiont niche. Our results show how fine-scale variation within reefs plays an important role in the generation and coexistence of cryptic species. The results also have important implications for how niche differences affect community resilience, and for the success of coral restoration practices, in ways not previously appreciated.

Aridity shapes distinct biogeographic and assembly patterns of forest soil bacterial and fungal communities at the regional scale

Climate change is exacerbating drought in arid and semi-arid forest ecosystems worldwide. Soil microorganisms play a key role in supporting forest ecosystem services, yet their response to changes in aridity remains poorly understood. We present results from a study of 84 forests at four south-to-north Loess Plateau sites to assess how increases in aridity level (1- precipitation/evapotranspiration) shapes soil bacterial and fungal diversity and community stability by influencing community assembly. We showed that soil bacterial diversity underwent a significant downward trend at aridity levels >0.39, while fungal diversity decreased significantly at aridity levels >0.62. In addition, the relative abundance of Actinobacteria and Ascomycota increased with higher aridity level, while the relative abundance of Acidobacteria and Basidiomycota showed the opposite trend. Bacterial communities also exhibited higher similarity-distance decay rates across geographic and environmental gradients than did fungal communities. Phylogenetic bin-based community assembly analysis revealed homogeneous selection and dispersal limitation as the two dominant processes in bacterial and fungal assembly. Dispersal limitation of bacterial communities monotonically increased with aridity levels, whereas homogeneous selection of fungal communities monotonically decreased. Importantly, aridity also increased the sensitivity of microbial communities to environmental disturbance and potentially decreased community stability, as evidenced by greater community similarity-environmental distance decay rates, narrower habitat niche breadth, and lower microbial network stability. Our study provides new insights into soil microbial drought response, with implications on the sustainability of ecosystems under environmental stress.

Deciphering the environmental adaptation and functional trait of core and noncore bacterial communities in impacted coral reef seawater

Microorganisms play pivotal roles in different biogeochemical cycles within coral reef waters. Nevertheless, our comprehension of the microbially mediated processes following environmental perturbation is still limited. To gain a deeper insight into the environmental adaptation and nutrient cycling, particularly within core and noncore bacterial communities, it is crucial to understand reef ecosystem functioning. In this study, we delved into the microbial community structure and function of seawater in a coral reef under different degrees of anthropogenic disturbance. To achieve this, we harnessed the power of 16S rRNA gene high-throughput sequencing and metagenomics techniques. The results showed that a continuous temporal succession but little spatial heterogeneity in the bacterial communities of core and noncore taxa and functional profiles involved in nitrogen (N) and phosphorus (P) cycling. Eutrophication state (i.e., nutrient concentration and turbidity) and temperature played pivotal roles in shaping both the microbial community composition and functional traits of coral reef seawater. Within this context, the core subcommunity exhibited a remarkably broader habitat niche breadth, stronger phylogenetic signal and lower environmental sensitivity when compared to the noncore taxa. Null model analysis further revealed that the core subcommunity was governed primarily by stochastic processes, while deterministic processes played a more significant role in shaping the noncore subcommunity. Furthermore, our observations indicated that changes in function related to N cycling were correlated to the variations in noncore taxa, while core taxa played a more substantial role in critical processes such as P cycling. Collectively, these findings facilitated our knowledge about environmental adaptability of core and noncore bacterial taxa and shed light on their respective roles in maintaining diverse nutrient cycling within coral reef ecosystems.

Long-term cover crop monocultures and mixtures improve soil multifunctionality and shift microbial communities and functions

Long-term cover crops are an emerging approach for achieving sustainable agriculture by reducing fertilizer use and enhancing soil quality. However, soil microbial communities, multifunctionality (i.e., the ability of soil ecosystems to simultaneously provide and maintain multiple ecological functions), and their relationships in cover crops remain poorly understood, especially in cover crop mixtures. To address these issues, here, we conducted a 15-year field experiment under different cover crop deployments (one legume and one brassica grown in monoculture or in mixture) in Carya cathayensis plantations. We found that cover crops significantly increased soil microbial diversity and multifunctionality, especially in mixtures. The bacterial and fungal compositions was significantly affected by cover crops. Interestingly, some taxa may serve as potential indicator species for nutrient status (i.e., bacterial Subgroup_2, Subgroup_6 and Subgroup_17). Cover crops significantly increased beneficial microbial functions (e.g., nitrogen fixation) but decreased pathogen-related functions (e.g., pathotroph). Bacterial and fungal community assemblages under cover crops were dominated by stochastic processes. Cover crops, especially mixtures, had a higher habitat niche breadth (Bcom). In addition, cover crops have more complex and stable bacterial and fungal networks. Partial least squares path modeling further confirmed that the variations in soil multifunctionality were largely related to nutrient resources. Importantly, the relative abundance of rare microbial taxa was also highly correlated with soil multifunctionality. Overall, our study illustrates that the use of cover crops in the long term can foster soil microbial specific taxa and contribute to improved soil multifunctionality. Our study provides support for the benefits of a legume-brassica mixture over monocultures of either and a theoretical basis for exploring cover crops as an ecological management model.

Dynamics of the soil microbial community associated with Morchella cultivation: diversity, assembly mechanism and yield prediction.

The artificial cultivation of morels has been a global research focus owing to production variability. Understanding the microbial ecology in cultivated soil is essential to increase morel yield and alleviate pathogen harm. A total of nine Morchella cultivation experiments in four soil field types, forest, paddy, greenhouse, and orchard in Shanghai city were performed to determine the potential ecological relationship between Morchella growth and soil microbial ecology. Generally, significant variation was observed in the soil microbial diversity and composition between the different experimental field types. The niche width analysis indicated that the bacterial habitat niche breadth was significantly greater than the fungal community width, which was further confirmed by a null model that revealed that homogeneous selection could explain 46.26 and 53.64% of the variance in the bacterial and fungal assemblies, respectively. Moreover, the neutral community model revealed that stochastic processes dominate the bacterial community in forests and paddies and both the bacterial and fungal communities in orchard crops, whereas deterministic processes mostly govern the fungal community in forests and paddies and both the bacterial and the fungal communities in greenhouses. Furthermore, co-occurrence patterns were constructed, and the results demonstrated that the dynamics of the soil microbial community are related to fluctuations in soil physicochemical characteristics, especially soil potassium. Importantly, structural equation modeling further demonstrated that the experimental soil type significantly affects the potassium content of the soil, which can directly or indirectly promote Morchella yield by inhibiting soil fungal richness. This was the first study to predict morel yield through soil potassium fertilizer and soil fungal community richness, which provides new insights into deciphering the importance of microbial ecology in morel agroecosystems.

Effects of an efficient straw decomposition system mediated by Stropharia rugosoannulata on soil properties and microbial communities in forestland

Cultivation of Stropharia rugosoannulata with straw in forestland is effective for straw biodegradation and can prevent the waste of straw resources and environmental pollution and generate economic benefits. However, there is a lack of systematic evaluation of spent mushroom substrate (SMS) input into forestland, such as soil properties and microbial succession. In this experiment, 0 (CK), 10 (SA), 20 (SB), 30 (SC), 40 (SD), and 50 (SE) kg/m2 straw were used to cultivate S. rugosoannulata, and two soil layers (0–10 cm, 10–20 cm) of the cultivated forestland were analyzed. The results indicated that SMS significantly promoted nutrient accumulation in forestland. The bacterial alpha diversity in the SC treatment group was greater than that in the control and gradually decreased to the control level with interannual changes, while the trend of fungal alpha diversity was opposite to that of bacterial alpha diversity. Furthermore, the SC treatment group positively affected soil nitrogen metabolism-related microorganisms for two consecutive years and significantly promoted tree growth. Habitat niche breadth and null model analysis revealed that bacterial communities were more sensitive than fungal communities after SMS input. Linear mixed model (LMM) analysis revealed that SMS supplementation significantly positively affected bacteria (Gammaproteobacteria and Bacteroidota) and significantly negatively affected fungi (Coniochaetales). The constructed fungal-bacterial co-occurrence networks exhibited modularity, and the five types of bacteria were significantly correlated with soil organic matter (SOM), soil organic carbon (SOC), available potassium (AK), available phosphorus (AAP) and available nitrogen (AN) levels. The structural equation model (SEM) showed that bacterial diversity responded more to changes in soil nutrients than did fungal diversity. Overall, 30 kg/m2 of straw decomposition and 2 years of continuous cultivation were beneficial to soil health. This study provides new insights into the rational decomposition of straw and maintenance of forestland ecological balance by S. rugosoannulata.

Assembly processes and ecological dynamics of root-associated bacterial communities during phytoremediation of vanadium-titanium mine tailings using Millettia pinnata

The vanadium-titanium magnetite (V–Ti) mine tailings are a reservoir of heavy metals, posing a grave peril to the adjacent soil environment. Millettia pinnata has emerged as a proficient pioneer tree species for the purpose of phytoremediation of V–Ti tailings. In the course of phytoremediation, the soil microbiota play an indispensable role within the rhizosphere ecosystem. The aim of this study was to dissect the underlying mechanisms governing the assembly processes of the bacterial community. The βNTI and RCbray analyses revealed that while the overall community assembly manifested deterministic attributes, rare taxa were chiefly impacted by stochastic processes (73.7%), inclusive of dispersal limitation and undominated mechanisms. In contrast, the abundant subcommunity was primarily subject to deterministic forces (84.3%), notably heterogeneous selection. Mantel test, regression analysis and ecological niche analysis showed that soil nitrogen availability emerged as a pivotal driver of the microbial assembly processes, exerting substantial influence on both rare (Mantel's r = 0.6817, p = 0.0001) and abundant taxa (Mantel's r = 0.5103, p = 0.0001) by amplifying their diversity and community turnover, constricting habitat niche breadth and overlap, and fostering the proliferation of ecological specialists. However, the heavy metal content was not found to wield significant influence in shaping the structure and assembly of the rhizosphere community (p > 0.05). The present results affirm the proposition that rare taxa are important in upholding ecological stability and providing essential microbial ecosystem services, while abundant taxa serve to fortify the entirety of the community. These insights advance our understanding of the community dynamics pertaining to the rhizosphere community associated with M. pinnata, holding paramount theoretical implications for the endeavour of plant-assisted ecological restoration in polluted tailings sites.

Microbial community and enzyme activity respond differently to seasonal and edaphic factors in forest and grassland ecosystems

Although microbial community and function patterns have been extensively studied, little is known about whether the patterns are consistent in different ecosystems and how they are influenced by seasonality or other environmental factors. To test the driving factors of microbial communities and potential functions, we collected soil samples from five forests (mixed broadleaved-Korean pine forest, mixed pine and oak forest, deciduous broadleaved mixed forest, subtropical evergreen broad-leaved forest and tropical rainforest) and three grassland ecosystems (meadow steppe, semi-arid grassland and arid grassland) across China in three seasons (spring, summer and autumn). Microbial diversity based on the sequencing of 16S rRNA gene for bacteria and internal transcribed spacer (ITS) genes for fungi were measured, and potential functions represented by soil extracellular enzyme activities (EEAs) were analyzed. The results found that soil EEAs were significantly higher in summer than in spring and autumn, and both bacterial and fungal richness indices showed greater seasonal fluctuations than the diversity. Fungal richness indices were highest in summer in both forest and grassland ecosystems, while the lowest were observed in spring for forest and in autumn for grassland, respectively. In addition, fungal communities were closely related to ecosystem types, while bacterial communities were not significantly different across ecosystems and exhibited a broader habitat niche breadth, but the relative abundance of dominant bacterial phyla showed stronger correlations with environmental variables (including climate, soil properties and nutrients) in grassland than in forest ecosystems. The decoupling of microbial community and EEAs was observed in both forest and grassland ecosystems, indicating the function redundancy of soil microorganisms. The present study provided crucial information about the effects of ecosystem types, seasonality and edaphic factors on soil microbial communities and EEAs, and could advance the understanding of soil potential function responses to environmental changes.

May microbial ecological baseline exist in continental groundwater?

BackgroundMicrobes constitute almost the entire biological community in subsurface groundwater and play an important role in ecological evolution and global biogeochemical cycles. Ecological baseline as a fundamental reference with less human interference has been investigated in surface ecosystems such as soils, rivers, and ocean, but the existence of groundwater microbial ecological baseline (GMEB) is still an open question so far.ResultsBased on high-throughput sequencing information derived from national monitoring of 733 newly constructed wells, we find that bacterial communities in pristine groundwater exhibit a significant lateral diversity gradient and gradually approach the topsoil microbial latitudinal diversity gradient with decreasing burial depth of phreatic water. Among 74 phyla dominated by Proteobacteria in groundwater, Patescibacteria act as keystone taxa that harmonize microbes in shallower aquifers and accelerate decline in bacterial diversity with increasing well-depth. Decreasing habitat niche breadth with increasing well-depth suggests a general change in the relationship among key microbes from closer cooperation in shallow to stronger competition in deep groundwater. Unlike surface-water microbes, microbial communities in pristine groundwater are predominantly shaped by deterministic processes, potentially associated with nutrient sequestration under dark and anoxic environments in aquifers.ConclusionsBy unveiling the biogeographic patterns and mechanisms controlling the community assembly of microbes in pristine groundwater throughout China, we firstly confirm the existence of GMEB in shallower aquifers and propose Groundwater Microbial Community Index (GMCI) to evaluate anthropogenic impact, which highlights the importance of GMEB in groundwater water security and health diagnosis.ALYCGLN5KzhFnoJfDo9dQRVideo

Soil Phosphorus Availability Controls Deterministic and Stochastic Processes of Soil Microbial Community along an Elevational Gradient in Subtropical Forests

Revealing the assembly mechanisms of the soil microbial community, which is crucial to comprehend microbial biodiversity, is a central focus in ecology. The distribution patterns of microbial elevational diversity have been extensively studied, but their assembly processes and drivers remain unclear. Therefore, it is essential to unravel the relationship between the deterministic and stochastic processes of the microbial community assembly and elevational gradients. Here, our study built upon previous physicochemical analyses of soil samples collected along an elevational gradient (900–1500 m) in Daiyun mountain, a subtropical forest located in southeastern China. Using the phylogenetic-bin-based null model analysis (icamp) and multiple regression on matrices approach, we explored the major drivers that influence the assembly processes of soil bacterial and fungal community across elevations. The results showed that: (1) bacterial rare taxa exhibited a broad habitat niche breadth along the elevational gradient; (2) homogeneous selection and homogenizing dispersal proved to be the most important assembly processes for the bacterial and fungal community; (3) soil phosphorus availability mediated the relative importance of deterministic and stochastic processes in the soil microbial community. Notably, the relative abundance of dominant microbial taxa controlled by homogeneous selection and homogenizing dispersal increased with increasing soil phosphorus availability. Collectively, the assembly processes of microbial elevational communities of the subtropical mountains in China can be explained to some extent by variations in the soil phosphorus availability. This conclusion provides valuable insights into the prediction of soil microbial diversity and phosphorus nutrient cycling in subtropical montane forests.

Niche breadth explains the range size of European-centred butterflies, but dispersal ability does not.

The breadth of ecological niches and dispersal abilities have long been discussed as important determinants of species' range sizes. However, studies directly comparing the relative effects of both factors are rare, taxonomically biased and revealed inconsistent results. Europe. Cenozoic. Butterflies, Lepidoptera. We relate climate, diet and habitat niche breadth and two indicators of dispersal ability, wingspan and a dispersal tendency index, to the global range size of 369 European-centred butterfly species. The relative effects of these five predictors and their variation across the butterfly phylogeny were assessed by means of phylogenetic generalized least squares models and phylogenetically weighted regressions respectively. Climate niche breadth was the most important single predictor, followed by habitat and diet niche breadth, while dispersal tendency and wingspan showed no relation to species' range size. All predictors together explained 59% of the variation in butterfly range size. However, the effects of each predictor varied considerably across families and genera. Range sizes of European-centred butterflies are strongly correlated with ecological niche breadth but apparently independent of dispersal ability. The magnitude of range size-niche breadth relationships is not stationary across the phylogeny and is often negatively correlated across the different dimensions of the ecological niche. This variation limits the generalizability of range size-trait relationships across broad taxonomic groups.

Stochastic processes shape the functional and phylogenetic structure of bird assemblages at the mine area in southwest China.

Understanding the mechanisms of community assembly is a key question in ecology. Metal pollution may result in significant changes in bird community structure and diversity, with implications for ecosystem processes and function. However, the relative importance of these processes in shaping the bird community at the polluted area is still not clear. Here, we explored bird species richness, functional, and phylogenetic diversity, and the assembly processes of community at the mine region of southwest China. Our results showed that the 3 dimensions of diversity at the mine area were lower than that at the reference sites. In the community assembly, the result was 0 < NRI/ NFRI < 1.96, which indicated deterministic processes (environmental filtering) might drive community clustering. The results of the neutral community model, and normalized stochasticity ratio, showed the dominant role of stochastic processes in shaping the bird community assembly. We further quantified the community-level habitat niche breadth (Bcom), and we found that there was no difference in Bcom-value between the mine area and reference sites. This indicates that the bird communities at the mine area and 3 reference sites were not subjected to extreme environmental selection (same or different resource allocation) to form a highly specialized niche. These findings provide insights into the distribution patterns and dominant ecological processes of bird communities under metal exposure, and extend the knowledge in community assembly mechanisms of bird communities living in the mine area.

Moso bamboo invasion changes the assembly process and interactive relationship of soil microbial communities in a subtropical broadleaf forest

Moso bamboo (Phyllostachys edulis) invasion into adjacent broadleaf forests has been widely observed across subtropical China, and has induced negative effects on aboveground biodiversity. However, how bamboo invasion influences soil microbial community structure and assembly process remains largely unknown. We investigated the changes in diversity, structure and assembly processes of bacterial and fungal communities in an evergreen broadleaf forest following Moso bamboo invasion. Soil samples were collected from three forests (a pure Moso bamboo forest, an adjacent mixed bamboo-broadleaf forest, and a non-invaded broadleaf forest) along twelve invasion transects. Our results showed that bamboo invasion increased soil pH and decreased the contents of soil organic carbon (SOC), dissolved organic carbon (DOC), total and available nitrogen and phosphorus nutrients. Bamboo invasion significantly increased the diversity indices (i.e., OTU richness and Shannon index) of both bacteria and fungi and changed their community compositions (P < 0.05). Bamboo invasion significantly decreased the relative abundance of Actinobacteria and Basidiomycota whereas increased those of Ascomycota and Mortierellomycota. The co-occurrence network analysis displayed more connected and complex relationships of both bacterial and fungal communities in bamboo forest. Bamboo invasion increased the community-level habitat niche breadths of both bacterial and fungal communities due to increased abundances of generalists. The stochastic process of bacterial and fungal community assembly weakened and the deterministic process enhanced generally as a result of bamboo invasion. The migration rate of bacterial communities (0.615) was higher than that of fungal communities (0.037), indicating that dispersal limitation less affect bacteria taxa. Random forest model demonstrated that DOC content, followed by mineral N, were the most important factors mediating the bacterial and fungal community assembly. Taken together, our results suggest that bamboo invasion strongly altered the assembly of bacterial and fungal communities by regulating the deterministic-stochastic balance, which deepens our understanding of the role of bamboo invasions on ecological processes.

Phytoplankton and Microzooplankton Community Structure and Assembly Mechanisms in Northwestern Pacific Ocean Estuaries with Environmental Heterogeneity and Geographic Segregation.

Phytoplankton and microzooplankton are crucial players in marine ecosystems and first responders to environmental changes, but their community structures and how they are shaped by environmental conditions have rarely been studied simultaneously. In this study, we conducted an eDNA metabarcoding sequencing combined with multiple statistical methods to simultaneously analyze the phytoplankton and microzooplankton in Liaohe (LH) and Yalujiang (YLJ) estuaries. The major objective was to examine how plankton community structure and assembly mechanism may differ between two estuaries with similar latitudinal position and climate but geographical segregation and differential level of urbanization (more in LH). Clear differences in diversity and composition of phytoplankton and microzooplankton communities between LH and YLJ estuaries were observed. Richness of phytoplankton was significantly higher in LH than YLJ, while richness of microzooplankton was higher in YLJ. The magnitude of intrahabitat variations in phytoplankton communities was significantly stronger than that of microzooplankton. Some phytoplankton and microzooplankton taxa also showed interhabitat differences in their relative abundances. Phytoplankton showed a stronger geographic distance-decay of similarity than microzooplankton, while significant environmental distance-decay of similarity in microzooplankton was found in the less urbanized YLJ estuary. Community assembly of phytoplankton was, based on the neutral community models, driven primarily by stochastic processes, while deterministic processes contributed more for microzooplankton. Furthermore, we detected wider habitat niche breadths and stronger dispersal abilities in phytoplankton than in microzooplankton. These results suggest that passive dispersal shapes the phytoplankton community whereas environmental selection shapes the microzooplankton community. IMPORTANCE Understanding the underlying mechanisms shaping a metacommunity is useful to management for improving the ecosystem function. The research presented in the manuscript mainly tried to address the effects of habitat geography and environmental conditions on the phytoplankton and microzooplankton communities, and the underlying mechanisms of community assembly in temperate estuaries. In order to achieve this purpose, we developed a metabarcoding sequencing method based on 18S rRNA gene. The phytoplankton and microzooplankton communities from two estuaries with similar latitude and climatic conditions but obvious geographical segregation and significant environmental heterogeneity were investigated. The results of our study could lay a solid foundation for ascertaining phytoplankton and microzooplankton communities in estuaries with obvious environmental heterogeneity and geographic segregation and mechanisms underlying community assembly.

Control factors of soil diazotrophic community assembly and nitrogen fixation rate across eastern China

Biological nitrogen (N) fixation is an essential N input into terrestrial ecosystems and plays a critical role in global N cycling. However, the driving factors of the diazotrophic community composition and soil N fixation rate at the regional scale remain largely unclear, especially in different land-use types. Here, we explored the environmental adaptation of diazotrophic communities and controlling factors of N fixation in maize, rice, and forest soils across eastern China. Results showed that the diversity, composition, and co-occurrence network differed significantly among these habitats, with a relatively higher alpha diversity and network complexity in rice fields. The mean annual precipitation plays a predominant role in shaping diazotrophic community composition. Dispersal limitation, belonging to stochastic processes, contributed most to diazotrophic community assembly in terrestrial ecosystems. Habitat niche breadth analysis indicated that the environmental adaptation of diazotrophic communities was highest in rice fields, followed by forest and maize fields. The overall N fixation rate was higher in rice fields, followed by maize and forest soils. Structural equation modeling revealed that the N fixation rate was mainly affected by soil properties in maize and forest soils. In contrast, the N fixation rate was more influenced by diazotrophic community composition and climatic factors in rice habitats. Our results revealed that the environmental adaptation of the diazotrophic communities and controlling factors of the N fixation function were different among maize, rice, and forest ecosystems. These findings will help us understand and predict the N bioavailability in different ecosystem types under climate changes.

Soil salinity, not plant genotype or geographical distance, shapes soil microbial community of a reed wetland at a fine scale in the Yellow River Delta

Soil salinization is one of the most severe environmental problems restricting biodiversity maintenance and ecosystem functioning in a coastal wetland. Recent studies have well documented how salinization affects soil microbial communities along vegetation succession of coastal wetlands. However, the salinity effect is rarely assessed in the context of plant intraspecific variation. Here, we analyzed the soil bacterial and fungal communities of Phragmites australis wetland using amplicon high-throughput sequencing at a fine scale (within 1000 m) in the Yellow River Delta. Our results revealed that microbial diversity is significantly correlated to soil salinity (assessed as electrical conductivity, EC) but not to soil nutrients (N and P content) or plant intraspecific traits (leaf length, shoot height, and neutral genetic variation). Specifically, the microbial diversity tended to decrease with increased EC, and the bacterial community was more sensitive to EC change than the fungal community. The dominant bacterial phyla were Proteobacteria, Actinobacteria, and Chloroflexi, and the dominant fungal phyla were Ascomycota, Basidiomycota, and Mortierellomycota. The relative abundance of Actinobacteria was significantly negatively correlated to EC, while Proteobacteria were positively correlated to EC. In high salinity (> 1 mS/cm), the role of the stochastic processes became more important in community assembly according to habitat niche breadth estimation, neutral community model, C-score metric, and normalized stochasticity ratio. Additional common garden and microcosm experiments provided evidence that the genotype effect of P. australis on soil microbiome might only occur between lineages from different regions but not from the same region like the Yellow River Delta. Our findings provide new insights into soil microbial community assembly processes with the intraspecific variation of host plants in the wetland ecosystem and offer a scientific reference for salinity mitigation and vegetation management of coastal wetlands under future global changes.

Dispersal limitation dominates the community assembly of abundant and rare fungi in dryland montane forests.

The assembly mechanisms and drivers of abundant and rare fungi in dryland montane forest soils remain underexplored. Therefore, in this study, we compared the distribution patterns of abundant and rare fungi and explored the factors determining their assembly processes in a dryland montane forest in China. Stronger distance-decay relationships (DDRs) were found in abundant sub-communities than in rare sub-communities. In addition, abundant fungi exhibited greater presence and wider habitat niche breadth than rare fungi. Both the null model and variation partitioning analysis indicated that dispersal limitation and environmental selection work together to govern both abundant and rare fungal assembly, while dispersal limitation plays a dominant role. Meanwhile, the relative influence of dispersal limitation and environmental selection varied between abundant and rare sub-communities, where dispersal limitation showed greater dominance in abundant fungal assembly. Mantel tests demonstrated that soil pH and phosphorus played critical roles in mediating abundant and rare fungi assembly processes, respectively. Our findings highlight that the distinct biogeographic patterns of abundant and rare fungi are driven by different assembly mechanisms, and the assembly processes of abundant and rare fungi are determined by diverse ecological drivers in dryland montane forest soils.

Aridity differentially alters the stability of soil bacterial and fungal networks in coastal and inland areas of Australia.

Despite the importance of soil bacterial and fungal communities for ecosystem services and human welfare, how their ecological networks respond to climatic aridity have yet been evaluated. Here, we collected soil samples from 47 sites across 2500 km in coastal and inland areas of eastern Australia with contrasting status of aridity. We found that the diversity of both bacteria and fungi significantly differed between inland and coastal soils. Despite the significant differences in soil nutrient availability and stoichiometry between the inland and coastal regions, aridity was the most important predictor of bacterial and fungal community compositions. Aridity has altered the potential microbial migration rates and further impacted the microbial assembly processes by increasing the importance of stochasticity in bacterial and fungal communities. More importantly, ecological network analysis indicated that aridity enhanced the complexity and stability of the bacterial network but reduced that of the fungal network, possibly due to the contrasting impacts of aridity on the community-level habitat niche breadth and overlaps. Our work paves the way towards a more comprehensive understanding of how climate changes will alter soil microbial communities, which is integral to predicting their long-term consequences for ecosystem sustainability and resilience to future disturbances.

Functional bacterial consortium responses to biochar and implications for BDE-47 transformation: Performance, metabolism, community assembly and microbial interaction

The influence of biochar on the biodegradation of persistent organic pollutants (POPs) has been extensively studied. However, the underlying mechanisms behind the response of functional microbial consortia to biochar remain poorly understood. Herein, we systematically explored the effect of biochar on 2,2′,4,4′-tetrabrominated ether (BDE-47) biodegradation, and investigated the interaction and assembly mechanism of the functional bacterial consortium QY2. The results revealed that the biodegradation efficiency of QY2 for BDE-47 increased from 53.85% to 94.11% after the addition of biochar. Fluorescence excitation-emission matrix and electrochemical analysis showed that biochar-attached biofilms were rich in redox-active extracellular polymeric substances (EPS, 3.03-fold higher than free cell), whose strong interaction with biochar facilitated the electron transfer of the biofilm, thus enhancing the debromination degradation of BDE-47. Meanwhile, the assembly model and molecular ecological networks analysis indicated that bacterial community assembly in biofilms was more driven by deterministic processes (environmental selection >75.00%) upon biochar stimulation and exhibited closer interspecific cooperative interactions, leading to higher biodiversity and broader habitat niche breadth for QY2 in response to BDE-47 disturbance. Potential degraders (Methylobacterium, Sphingomonas, Microbacterium) and electrochemical bacteria (Ochrobactrum) were selectively enriched, whose role as keystone bacteria may be participated in biofilm formation and redox-active EPS secretion (r > 0.5, P < 0.05). These findings deepen the understanding of the mechanisms by which biochar promotes microbial degradation of PBDEs and provided a theoretical basis for better regulation of functional bacterial communities during environmental remediation.