Nutrients addition decreases soil fungal diversity and alters fungal guilds and co-occurrence networks in a semi-arid grassland in northern China

Synergistic effects of nanoplastics and graphene oxides on microbe-driven litter decomposition in streams

The increasing production and release of plastics and graphene nanomaterials pose risks to the ecological environment. However, little is known regarding the interactive effects of nanoplastics (NPs) and graphene oxide (GO) on ecological processes in aquatic ecosystems. To address this knowledge gap, we conducted an indoor experiment to investigate the effect of NPs and GO alone, as well as their combined effects on litter decomposition and associated microbial community structure and function in streams. The combined treatments with GO and NPs significantly increased the relative abundance of Enterobacter (47.42-61.72 %), and the activities of leucine arylamidase and cellobiose hydrolase. Specifically, the combination of GO and NPs exerted a stronger impact on bacterial α-diversity and degradation function than on fungi, challenging the popular view. Importantly, this combination of NPs and GO inhibited litter decomposition at 5 days but promoted it at 40 days, indicating a time-dependent effect. Structural equation modeling revealed that NPs, GO, and their combined effects promoted litter carbon loss through direct breakdown and indirectly increased bacterial diversity and extracellular enzyme activities related to carbon cycling and depolymerisation. The results obtained in this study highlight the importance of considering the characteristics of pollutants interacting with NPs and their time-dependent effects when evaluating the ecotoxicological effects of NPs in aquatic ecosystems.

Ecosystem multifunctionality enhancement by short-term nitrogen addition in semi-arid saline-alkaline grassland of northern China

The vast area of saline-alkaline grasslands in the agro-pastoral ecotone of northern China has important production and ecological functions. Nitrogen (N) deposition changes the function and structure of vulnerable grasslands. However, the impacts of N deposition on ecosystem multifunctionality (EMF) remains unknown. To address this issue, a three-year in-situ study was carried out between 2018 and 2020 to assess the direct impacts of N addition on grassland ecosystem function. Eight N addition levels were applied: 0, 1, 2, 4, 8, 16, 24, and 32 g·N·m-2·yr-1. Plant-soil-microbe equilibrium properties, productivity, and plant community structure were monitored, and the impacts of N addition rate (NAR) and year (NAY) on grassland EMF were analyzed. Short-term N addition enhanced multiple individual ecosystem functions such as dominant species, aboveground biomass, soil stoichiometry, and litter, and remarkably decreased the structure of the plant community and soil physical and chemical performance. Furthermore, short-term N addition enhanced grassland aboveground multifunctionality (AGMF) and overall EMF, and had a neutral effect on belowground multifunctionality (BGMF). The primary effect of N addition was the enhancement of AGMF by increasing aboveground biomass, thereby enhancing grassland EMF; however, grassland EMF showed relatively minor fluctuations at N addition rates of >16 g·N·m-2·yr-1. The results of this study show that short-term N addition indirectly regulates grassland EMF by increasing aboveground biomass, and provide novel insights into the asynchronous response of AGMF and BGMF of grassland ecosystems to short-term N addition. The addition of an appropriate amount of N is essential to enhance grass yield and maintain grassland EMF in order to manage saline-alkaline grasslands within the agro-pastoral ecotone.

Fungal Community Complexity and Stability in Clay Loam and Sandy Soils in Mangrove Ecosystems

Soil fungi in mangroves are diverse and crucial for organic matter decomposition and element cycling. However, the drivers influencing network complexity and the stability of fungal communities across different mangrove soil habitats remain unclear. This study investigated the main factors driving the composition, diversity, complexity, and stability of fungal communities in clay loam and sandy soils in mangrove ecosystems. Results showed that Dothideomycetes and Sordariomycetes dominated in clay loam and sandy soils, respectively. Sandy soils exhibited higher alpha diversity than clay loam. Beta diversity analysis revealed significant differences in the fungal community structure between the two soil types. Network analysis demonstrated higher complexity and stability of fungal communities in clay loam than in sandy soil. Spearman's correlation analysis revealed that NH4+-N and total nitrogen were the main factors affecting complexity and stability in clay loam, respectively. Partial least squares path modeling demonstrated that alpha diversity and soil properties were closely linked to the complexity and stability of fungal communities in clay loam, whereas beta diversity was the primary driver in sandy soil. Our study enhances the understanding of the mechanisms that maintain fungal diversity and community stability in mangrove ecosystems, with important implications for restoring vegetation in degraded areas.

Prokaryotic and eukaryotic periphyton responses to warming, nutrient enrichment and small omnivorous fish: A shallow lake mesocosms experiment

Global change stressors, including climate warming, eutrophication, and small-sized omnivorous fish, may exert interactive effects on the food webs and functioning of shallow lakes. Periphyton plays a central role in the primary production and nutrient cycling of shallow lakes but constitutes a complex community composed of eukaryotes and prokaryotes that may exhibit different responses to multiple environmental stressors with implications for the projections of the effects of global change on shallow lakes. We analyzed the effects of warming, nutrient enrichment, small omnivorous fish and their interactions on eukaryotic and prokaryotic periphyton structures in shallow lake mesocosms. We performed 16S and 18S rRNA high-throughput sequencing to elucidate the effect of the abovementioned stressors. We found that warming promoted periphytic alpha diversity and network complexity, with multi-tolerant genera becoming dominating (e.g. Spirosomaceae and Azospirillaceae). Contrastingly, nutrient enrichment led to reduced prokaryotic diversity and network complexity and stability, with weak disruption of the eukaryotic structure. Small omnivorous fish were major drivers of changes eukaryotic periphyton, facilitating diversity and network complexity, and increasing prokaryotic and eukaryotic biomarker diversity. Omnivorous fish reduced the grazing pressure on periphyton mainly through selective grazing on zooplankton, contributing to periphytic structural stability and functional diversity, especially the proliferation of prokaryotic biomarkers. Nutrient enrichment counteracted the positive effects of warming on periphyton, while concerted action with omnivorous fish led to high TN and TP concentrations and accelerated the negative development of periphytic alpha diversity and network structure. The co-occurrence of the three environmental pressures ultimately resulted in a disruption of periphytic biodiversity and community structure and weakened connectivity with the environment. Our study provided new insights into the understanding of the response of prokaryotic and eukaryotic community structure and ecological functions of freshwater periphyton to global environmental change.

Nutrient Availability Shapes the Resistance of Soil Bacterial Community and Functions to Disturbances in Desert Ecosystem

Climate change has exposed desert ecosystems to frequent extreme disturbances, including wet-dry cycles and freeze-thaw events, which accelerate desertification on a global scale. The limited nutrient availability characteristic of these ecosystems may constrain microbial survival and growth, making them more vulnerable to environmental perturbations and stressors. However, how nutrient availability modulates the stability of soil ecological communities and functions in desert ecosystems remains poorly understood. In this study, we examined how nutrient addition, applied either before or after disturbances, affects the resistance of bacterial communities and multifunctionality to drought and freeze events in desert ecosystems. Our findings revealed that freeze-thaw events, rather than drought, significantly reduced bacterial diversity, with all disturbances altering the community structure. Pre-disturbance nutrient addition notably improved the resistance of soil bacterial diversity and community composition to disturbances, which played a critical role in maintaining multifunctionality in desert ecosystems. This enhanced bacterial resistance was strongly associated with increased bacterial network complexity and the enrichment of disturbance-tolerant taxa. Our results highlight the pivotal role of nutrient availability in stabilising soil bacterial communities and multifunctionality under extreme climatic conditions in desert ecosystems. These findings offer valuable insights and practical strategies for the ecological protection and management of desertification.

Long-term ammonium nitrate addition strengthens soil microbial cross-trophic interactions in a Tibetan alpine steppe

Global nitrogen (N) enrichment is modifying microbial interactions, which can be represented by network complexity. While a number of studies have explored how N addition influences the microbial intra-trophic network, its effects on the inter-trophic network have rarely been investigated. Here, we examined the effects of 8 years of multilevel N additions (i.e., 0, 1, 2, 4, 8, 16, 24 and 32 g N m-2 year-1) on inter-trophic interactions of soil microbial communities (i.e., protist-fungi, protist-prokaryote and fungi-prokaryote) in a Tibetan alpine steppe. Generally, there was a first increasing and then saturated trend of the complexity of inter-trophic networks along the N-addition gradient, which contrasts with the simplified or minimal response of intra-trophic network complexity reported previously. The intensified cross-trophic interactions were mainly explained by increased plant and litter biomass, which indicates that the N-induced increases in carbon supplies may have alleviated microbial energy limitations and thus resulted in more active metabolic processes, consequently stimulating various biotic interactions (e.g., predation, competition, and commensalism). Further, the enhanced inter-trophic network relationships were found to be associated with increased soil carbon and N mineralization processes. Overall, these findings highlight the importance of microbial cross-trophic interactions and indicate that they should be considered in predictions of ecosystem functioning under global N enrichment.

Shifts in Soil Fungal Community and Trophic Modes During Mangrove Ecosystem Restoration

Mangrove ecosystems are valuable coastal ecosystems; however, studies on the diversity and functional features of their soil fungal communities during restoration are limited. In this study, we examined fungal diversity and trophic modes across mudflat, young mangrove, and mature mangrove stages. We found that Ascomycota and Basidiomycota were the dominant phyla, with saprotrophs as the most abundant trophic mode. The abundance of the major phyla and trophic modes significantly varied across restoration stages. Although fungal alpha (α)-diversity remained stable among the stages, beta (β)-diversity showed significant differentiation. Spearman's analysis and partial Mantel tests revealed that total nitrogen and inorganic phosphorus significantly influenced the fungal α-diversity, whereas temperature and pH primarily shaped the fungal β-diversity. Total nitrogen and carbon were key factors affecting the trophic mode α-diversity, whereas total phosphorus and inorganic phosphorus were the main drivers of the trophic mode β-diversity. Variation partitioning analysis confirmed that nutrients, rather than soil properties, were the primary factors shaping fungal communities and trophic modes. Random forest analysis identified key bioindicators, including species such as Paraphyton cookei, and trophic modes such as saprotrophs, both of which were strongly influenced by soil carbon. These findings advance our understanding of fungal ecology in mangrove restoration.

Grazing increases the complexity of networks and ecological stochastic processes of mycorrhizal fungi

Arbuscular mycorrhizal fungi (AMF) form extensive symbiotic relationships with plants, which are critical for plant-driven biogeochemical cycles and ecosystem functions. Grazing and mowing, which are common grassland utilization patterns globally, significantly alter plant community characteristics as well as soil nutrients and structure, thereby potentially influencing AMF communities. However, the effects of these grassland managements on AMF community structure and ecological processes remain unclear. Here, we investigated AMF communities in cattle grazing, sheep grazing, and mowing grasslands. We examined AMF community diversity, composition, assembly processes, and network interactions. Our results revealed distinct AMF compositions across different grassland managements. In cattle and sheep grazing grasslands, the AMF community assembly processes were determined by dispersal limitation and drift, with increased importance of stochasticity. Although AMF abundance did not alter by grassland managements, AMF diversity decreased under sheep grazing, associated with reduced pH levels compared to cattle grazing or mowing. AMF formed more complex (higher average degree and graph density) and integrated (lower modularity) networks in grazing grasslands than mowing grasslands. The AMF network in cattle grazing grasslands showed the highest stability, associated with a broader habitat niche, balanced interspecies competition, and higher soil AP and MBN. Meanwhile, some species with high adaptability to grazing became key nodes in the AMF network, such as Funneliformis. Our findings highlight significant AMF responses to grazing, including increased network complexity and ecological stochasticity, providing new insights into how grassland managements influence the composition and assembly patterns of soil symbiotic microbial communities.

Phosphate-enhanced Cd stabilization in soil by sulfur-doped biochar: Reducing Cd phytoavailability and accumulation in Brassica chinensis L. and shaping the microbial community

To explore the potential of livestock manure-derived biochar for the remediation of Cd-contaminated soil, a pot experiment was conducted to explore the stabilization efficiency of cattle manure biochar (T2, BC), sulfur-doped biochar (T3, SBC), and SBC combined with phosphate (T4, SBC-PF) on Cd in contaminated soil and their effects on Cd accumulation in Chinese cabbage (Brassica chinensis L.) and soil microorganisms. The results showed that soil available phosphorus (AP), available potassium (AK), and organic matter (OM) significantly increased in T3 and T4, and the biomass of Chinese cabbage also increased from 0.46 g/pot to 0.57 and 1.05 g/pot, respectively. The DTPA-extractable Cd in T3 and T4 dramatically reduced by 78.6% and 91.4% (p < 0.05); the acid-soluble Cd decreased by 11.3% and 13.2%; and the residual Cd increased by 30.0% and 10.0%. Most importantly, the Cd contents in T2, T3, and T4 decreased by 2.2%, 89.7%, and 93.1% in the shoots of Chinese cabbage and 21.3%, 82.2%, and 86.2% in the roots of Chinese cabbage, respectively. Moreover, SBC-PF obviously changed the bacterial community and enhanced the interactions among microbes in the soil. Structural equation modeling revealed that microbial interspecific mutualistic relationships were the key factor in the pathway for reducing Cd phytoavailability. Mantel tests and random forest analyses further revealed that biochar enhanced the interactions among microorganisms by increasing the AP content in the soil. These findings demonstrated that SBC combined with phosphate is appropriate for stabilizing Cd and improving soil quality.

Tree species-dependent effects of afforestation on soil fungal diversity, functional guilds and co-occurrence networks in northern China

Afforestation exerts a profound impact on soil fungal communities, with the nature and extent of these changes significantly influenced by the specific tree species selected. While extensive research has addressed the aboveground ecological outcomes of afforestation, the nuanced interactions between tree species and soil fungal dynamics remain underexplored. This study investigated the effects of afforestation with Caragana microphylla (CMI), Populus simonii (PSI), and Pinus sylvestris var. mongolica (PSY) on soil fungal diversity, functional guilds, and co-occurrence networks, drawing comparisons with neighboring grasslands. Our findings reveal a significant increase in soil fungal Chao1 richness following afforestation, though the degree of enhancement varied across tree species. Specifically, CMI and PSI forests showed notable increases in fungal richness, whereas the response in PSY forests was comparatively modest. Saprotrophic fungal groups, integral to organic matter decomposition, showed a substantial increase across all afforested sites, with CMI forests exhibiting an impressive 205.58% rise. Conversely, pathogenic fungi, which can negatively impact plant health, demonstrated a marked decrease within plantation forests. Symbiotic groups, particularly ectomycorrhizal fungi, were notably enriched solely in PSI forests. Co-occurrence network analysis further indicated that afforestation alters fungal network complexity: CMI forests displayed increased network interactions, while PSI and PSY forests exhibited a reduction in network connectivity. Soil bulk density and organic carbon content emerged as key factors influencing network complexity, whereas tree species identity played a crucial role in shaping soil fungal community composition. Collectively, these results emphasize the importance of adopting a species-specific strategy for afforestation to optimize soil fungal diversity and network structure, ultimately enhancing the ecological resilience and sustainability of forest plantation ecosystems.

Co-application of sheep manure and commercial organic fertilizer enhances plant productivity and soil quality in alpine mining areas

Background and aims

The addition of organic fertilizers and sheep slat manure have important effects on soil quality in alpine mining areas, but how they affect soil physicochemical properties and microorganisms is not yet known.

Methods

The current study employed field-controlled experiments and high-throughput sequencing technology to investigate differences in soil physicochemical properties, microbial community structures, and diversity under four treatments: no fertilization (CK), 100% sheep manure (SM), a combination of 50% sheep manure and 50% commercial organic fertilizer (MF), and 100% commercial organic fertilizer (OF).

Results

Aboveground biomass increased by 191.93, 253.22, and 133.32% under SM, MF and OF treatments, respectively, when compared to CK treatment. The MF treatment resulted in significantly higher soil total nitrogen, total phosphorus, organic matter, and available nitrogen content compared to other treatments. Soil total nitrogen content, total phosphorus content, organic matter, available nitrogen content and available phosphorus content were 211, 120, 380, 557, and 271% higher, respectively, under the MF treatment than the CK treatment. Different nutrient additions significantly influenced soil microbial community composition. The SM and MF treatments notably increased soil bacterial and fungal community Operational Taxonomic Units (OTUs) indices and Chao 1 indices, while nutrient addition had no meaningful effect on the Simpson indices for microbial communities. There was a highly significant positive correlation between aboveground biomass and observed soil nutrient content.

Conclusion

The combined application of sheep manure and commercial organic fertilizer is more conducive to improving soil quality and enhancing plant productivity in alpine mining areas.

Evaluation of the microbial community in various saline alkaline-soils driven by soil factors of the Hetao Plain, Inner Mongolia

Soil microbial communities play a crucial role in maintaining diverse ecosystem functions within the saline-alkali soil ecosystems. Therefore, in this study, we collected various saline-alkaline soils from across the Inner Mongolia Hetao irrigation area. The soil chemical properties were analyzed, and the microbial diversity of bacteria and fungi was measured using 16 S rRNA and ITS rRNA amplicon sequencing. The dynamic relationship between the soil microbial community and soil factors was analyzed using the ABT (Aggregate Enhanced tree) model, the co-occurrence network, and the structural equation model. The results indicated that electrical conductivity (EC) was the biggest driving force of various saline-alkaline soils, affecting the community structure of bacteria (22.80%) and fungi (21.30%). The soil samples were categorized into three treatment levels based on their EC values: the low-salinity group (L, EC: 0-1 ms/cm, n = 10), the medium-salinity group (M, EC: 1-2 ms/cm, n = 8), and the high-salinity group (H, EC > 2 ms/cm, n = 6). The results demonstrated a negative correlation between microbial abundance and salinity-alkalinity, while revealing an enhanced interrelationship among species. The alterations in bacterial (12.36%) and fungal (22.92%) communities in various saline-alkali soils were primarily driven by saline-alkali ions, which served as the principal direct factors. The negative correlation between EC and SOM exhibited the highest magnitude, whereas the positive correlation between soil organic carbon and EC demonstrated the greatest strength. Therefore, it was further substantiated that EC played a pivotal role in shaping the distinct microbial communities in saline-alkali soils.

Effect of Nitrogen on Microbial Communities of Purple Mudstone Weathering Products in Southwest China: A Column Experiment

Nitrogen application significantly affects microorganisms in agricultural ecosystems. However, it is still unclear how nitrogen application affects soil chemical properties and microbial communities in purple mudstone weathering products. In this study, a field soil column experiment was conducted in a typical purple soil area with four nitrogen fertilizer application gradients of 0 [CK], 280 [N1], 560 [N2], and 840 [N3] N kg ha-1. Nitrogen addition decreased the bacterial chao1 value and increased the bacterial evenness index. For both α- and β-diversity, the effect of nitrogen addition on bacteria was much greater than that on fungi. Nitrogen addition significantly increased the relative abundance of Proteobacteria, Gemmatimonadetes, Bacteroidetes, and Ascomycota and decreased the relative abundance of Actinobacteria, Cyanobacteria, and Basidiomycota. Both pH and TC are the most important soil chemical properties influencing the bacterial and fungal communities. With the increases in the nitrogen application rate, the co-occurrence network complexity increased and then decreased. In summary, nitrogen fertilizer application could significantly change the soil chemical properties, microbial community diversity, composition, and co-occurrence network of purple mudstone weathering products. Among them, the N2 treatment (560 N kg∙ha-1) can more effectively stimulate the soil nutrients, enhance microbial network complexity, and promote further weathering of purple mudstone.

Nitrogen addition changed soil fungal community structure and increased the biomass of functional fungi in Korean pine plantations in temperate northeast China

Nitrogen (N) deposition is a global environmental issue that can have significant impacts on the community structure and function in ecosystems. Fungi play a key role in soil biogeochemical cycles and their community structures are tightly linked to the health and productivity of forest ecosystems. Based on high-throughput sequencing and ergosterol extraction, we examined the changes in community structure, composition, and biomass of soil ectomycorrhizal (ECM) and saprophytic (SAP) fungi in 0-10 cm soil layer after 8 years of continuous N addition and their driving factors in a temperate Korean pine plantation in northeast China. Our results showed that N addition increased fungal community richness, with the highest richness and Chao1 index under the low N treatment (LN: 20 kg N ha-1 yr-1). Based on the FUN Guild database, we found that the relative abundance of ECM and SAP fungi increased first and then decreased with increasing N deposition concentration. The molecular ecological network analysis showed that the interaction between ECM and SAP fungi was enhanced by N addition, and the interaction was mainly positive in the ECM fungal network. N addition increased fungal biomass, and the total fungal biomass (TFB) was the highest under the MN treatment (6.05 ± 0.3 mg g-1). Overall, we concluded that N addition changed soil biochemical parameters, increased fungal activity, and enhanced functional fungal interactions in the Korean pine plantation over an 8-year simulated N addition. We need to consider the effects of complex soil conditions on soil fungi and emphasize the importance of regulating soil fungal community structure and biomass for managing forest ecosystems. These findings could deepen our understanding of the effects of increased N deposition on soil fungi in temperate forests in northern China, which can provide the theoretical basis for reducing the effects of increased N deposition on forest soil.