Microbial Taxa Distribution Is Associated with Ecological Trophic Cascades along an Elevation Gradient

Deciphering the crop-soil-enzyme C:N:P stoichiometry nexus: A 5-year study on manure-induced changes in soil phosphorus transformation and release risk

Carbon:nitrogen:phosphorus (C:N:P) stoichiometry plays a vital role in regulating P transformation in agriculture ecosystems. However, the impact of balanced C:N:P stoichiometry in paddy soil, particularly regarding relative soil P transformation, remains unknown. This study explores the response of C:N:P stoichiometry to manure substitution and its regulatory role in soil P transformation, along with the associated release risk to the environment. Based on a 5-year field study, our findings reveal that replacing 30 % of chemical P fertilizer with pig manure (equal total NPK amounts with chemical P fertilizer treatment, named CFM) increased soil total C without altering soil total P, resulting in an elevated soil C:P ratio, despite the homeostasis of crop stoichiometry. This increase promoted microbial diversity and the accumulation of organic P in the soil. The Proteobacteria and Actinobacteria produced lower C:PEEA metabolism together, and enhanced in vivo turnover of P. Additionally, by integrating high-resolution dialysis (HR-Peeper), diffusive gradients in thin films (DGT), DGT-induced fluxes in the soil (DIFS), and sediment P release risk index (SPRRI) models, we observed that, in addition to organic P, CFM simultaneously increased soil Al-P, thereby weakening the diffusion and resupply capacity of P from soil solids to the solution. Consequently, this decrease in P release risk to the environment was demonstrated. Overall, this study establishes a connection between crop-soil-enzyme C:N:P stoichiometry, soil microorganisms, and soil P biogeochemical processes. The study further evaluates the P release risk to the environment, providing a novel perspective on both the direct and indirect effects of manure substitution on soil P cycling.

A general pattern of plant traits and their relationships with environmental factors and microbial life-history strategies

The trait-based unidimensional plant economics spectrum provides a valuable framework for understanding plant adaptation strategies to the environment. However, it is still uncertain whether there is a general multidimensionality of how variation of both leaf and fine root traits are influenced by environmental factors, and how these relate to microbial resource strategies. Here, we examined the coordination patterns of four pairs of similar leaf and fine root traits of herbaceous plants in an alpine meadow at the community-level, and their environmental driving patterns. We then assessed their correlation with microbial life-history strategies, as these exhibit analogous resource strategies with plants in terms of growth and resource utilization efficiency. Results exhibited an analogous multidimensionality of the economics spectrum for leaf and fine root traits: the first dimension, collaboration gradient, primarily represented a tradeoff between lifespan and resource foraging efficiency; the second dimension, conservation gradient, primarily represented a tradeoff between conservation and acquisition in resource uptake. Climate variables had a stronger impact on both dimensions for leaf and fine root traits than soil variables did; whereas, the primary drivers were more complex for fine root traits than for leaf traits. The collaboration gradient of leaf and fine root traits exhibited consistent relationships with soil microbial life-history strategies, both showed negative and positive correlation with bacterial and fungal strategies, respectively. Our findings suggest that both leaves and fine roots have general multidimensional strategies for adapting to new environments and provide a solid basis for further understanding the relationships between the adaptive strategies of plants and microbes.

Amendments affect the community assembly and co-occurrence network of microorganisms in Cd and Pb tailings of the Eucalyptus camaldulensis rhizosphere

Mining tailings containing large amounts of Pb and Cd cause severe regional ecosystem pollution. Soil microorganisms play a regulatory role in the restoration of degraded ecosystems. The remediation of heavy metal-contaminated tailings with amendments and economically valuable Eucalyptus camaldulensis is a research hotspot due to its cost-effectiveness and sustainability. However, the succession and co-occurrence patterns of these microbial communities in this context remain unclear. Tailing samples of five kinds of Cd and Pb were collected in E. camaldulensis restoration models. Physicochemical properties, the proportions of different Cd and Pb forms, microbial community structure, and the co-occurrence network of rhizosphere tailings during different restoration process (organic bacterial manure, organic manure, inorganic fertilizer, bacterial agent) were considered. Organic and organic bacterial manures significantly increased pH, cation exchange capacity, and the proportion of residual Pb. Still, there was a significant decrease in the proportion of reducible Pb. The changes in microbial communities were related to physicochemical properties and the types of amendments. Organic and organic bacterium manures decreased the relative abundance of oligotrophic groups and increased the relative abundance of syntrophic groups. Inorganic fertilizers and bacterial agents decreased the relative abundance of saprophytic fungi. B. subtilis would play a better role in the environment improved by organic manure, increasing the relative abundance of beneficial microorganism and reducing the relative abundance of pathogenic microorganism. pH, cation exchange capacity, and the proportion of different forms of Pb were the main factors affecting the bacterial and fungi variation. All four amendments transformed the main critical groups of the microbial network structure from acidophilus and pathogenic microorganisms to beneficial microorganisms. Heavy metal-resistant microorganisms, stress-resistant microorganisms, beneficial microorganisms that promote nutrient cycling, and copiotrophic groups have become critical to building stable rhizosphere microbial communities. The topological properties and stability of the rhizosphere co-occurrence network were also enhanced. Adding organic and organic bacterium manures combined with E. camaldulensis to repair Cd and Pb tailings improved (1) pH and cation exchange capacity, (2) reduced the biological toxicity of Pb, (3) enhanced the stability of microbial networks, and (4) improved ecological network relationships. These positive changes are conducive to the restoration of the ecological functions of tailings.

Residue quality drives SOC sequestration by altering microbial taxonomic composition and ecophysiological function in desert ecosystem

Plant residues are important sources of soil organic carbon in terrestrial ecosystems. The degradation of plant residue by microbes can influence the soil carbon cycle and sequestration. However, little is known about the microbial composition and function, as well as the accumulation of soil organic carbon (SOC) in response to the inputs of different quality plant residues in the desert environment. The present study evaluated the effects of plant residue addition from Pinus sylvestris var. mongolica (Pi), Artemisia desertorum (Ar) and Amorpha fruticosa (Am) on desert soil microbial community composition and function in a field experiment in the Mu Us Desert. The results showed that the addition of the three plant residues with different C/N ratios induced significant variation in soil microbial communities. The Am treatment (low C/N ratio) improved microbial diversity compared with the Ar and Pi treatments (medium and high C/N ratios). The variations in the taxonomic and functional compositions of the dominant phyla Actinobacteria and Proteobacteria were higher than those of the other phyla among the different treatments. Moreover, the network links between Proteobacteria and other phyla and the CAZyme genes abundances from Proteobacteria increased with increasing residue C/N, whereas those decreased for Actinobacteria. The SOC content of the Am, Ar and Pi treatments increased by 45.73%, 66.54% and 107.99%, respectively, as compared to the original soil. The net SOC accumulation was positively correlated with Proteobacteria abundance and negatively correlated with Actinobacteria abundance. These findings showed that changing the initial quality of plant residue from low C/N to high C/N can result in shifts in taxonomic and functional composition from Actinobacteria to Proteobacteria, which favors SOC accumulation. This study elucidates the ecophysiological roles of Actinobacteria and Proteobacteria in the desert carbon cycle, expands our understanding of the potential microbial-mediated mechanisms by which plant residue inputs affect SOC sequestration in desert soils, and provides valuable guidance for species selection in desert vegetation reconstruction.

Response of sediment microbial communities to the flow effect of the triangular artificial reef: A simulation-based experimental study

Artificial reefs (ARs), as an important tool for habitat restoration, play significant impacts on benthic microbial ecosystems. This study utilized 16S rRNA gene sequencing technology and computational fluid dynamics (CFD) flow simulation to investigate the effects of flow field distribution around ARs on microbial community structure. The results revealed distinct regional distribution patterns of microbial communities affected by different hydrodynamic conditions. Flow velocity and flow regime of water in sediment-water interface shaped the microbial community structure. The diversity and richness in R-HF were significantly decreased compared to other five regions (p < 0.05). At the phyla and OUT levels, most abundant taxa (1>%) showed an enrichment trend in R-HB. However, more than half of differentially abundant taxa were enriched in R-HB, which was significantly correlated with organic matter (OM). Bugbase phenotypic predictions indicated a low abundance of the anaerobic phenotype in R-HF and a high abundance of the biofilm-forming phenotype in R-HB.

Changes in soil oxidase activity induced by microbial life history strategies mediate the soil heterotrophic respiration response to drought and nitrogen enrichment

Drought and nitrogen deposition are two major climate challenges, which can change the soil microbial community composition and ecological strategy and affect soil heterotrophic respiration (Rh). However, the combined effects of microbial community composition, microbial life strategies, and extracellular enzymes on the dynamics of Rh under drought and nitrogen deposition conditions remain unclear. Here, we experimented with an alpine swamp meadow to simulate drought (50% reduction in precipitation) and multilevel addition of nitrogen to determine the interactive effects of microbial community composition, microbial life strategy, and extracellular enzymes on Rh. The results showed that drought significantly reduced the seasonal mean Rh by 40.07%, and increased the Rh to soil respiration ratio by 22.04%. Drought significantly altered microbial community composition. The ratio of K- to r-selected bacteria (BK:r) and fungi (FK:r) increased by 20 and 91.43%, respectively. Drought increased hydrolase activities but decreased oxidase activities. However, adding N had no significant effect on microbial community composition, BK:r, FK:r, extracellular enzymes, or Rh. A structural equation model showed that the effects of drought and adding nitrogen via microbial community composition, microbial life strategy, and extracellular enzymes explained 84% of the variation in Rh. Oxidase activities decreased with BK:r, but increased with FK:r. Our findings show that drought decreased Rh primarily by inhibiting oxidase activities, which is induced by bacterial shifts from the r-strategy to the K-strategy. Our results highlight that the indirect regulation of drought on the carbon cycle through the dynamic of bacterial and fungal life history strategy should be considered for a better understanding of how terrestrial ecosystems respond to future climate change.

The application of entomopathogenic nematode modified microbial communities within nesting mounds of the red imported fire ants, Solenopsis invicta

Entomopathogenic microorganisms (e.g., fungi, bacteria, nematodes) have been widely used in biological control of soil-dwelling pests, including the red imported fire ant (RIFA), Solenopsis invicta, a notorious invasive pest worldwide. The application of large amounts of entomopathogenic microorganisms to soil may affect the indigenous soil microbial communities. However, reports about the effect of entomopathogenic nematodes (EPN) on soil microbial communities are very few. In this study, the effects of EPN on RIFA populations and microbial communities in mounds were investigated. Our results showed that the application of the EPN Steinernema carpocapsae. All strain on mounds efficaciously suppressed RIFA worker populations, without forming significantly more satellite mounds compared with the control treatment. The application of EPN did not impact the bacterial and fungal diversity in soils derived from the RIFA mounds. However, it slightly altered the taxonomic make-up of the bacterial communities, but significantly altered the taxonomic composition of fungal communities at the phylum, family, and genus levels. The abundances of some beneficial bacteria and fungi, such as Streptomyces, decreased, while those of plant and animal pathogenic bacteria and fungi, dramatically increased, after EPN treatment. On the other hand, the abundances of some entomopathogenic fungi, such as Fusicolla, Clonostachys, and Mortierella, increased. Redundancy analysis or canonical correspondence analysis revealed a positive correlation between the efficacious EPN control and the presence of the insect-resistant bacteria, Sinomonas, as well as entomopathogenic fungi Fusicolla and Mortierella. This suggests that the interactions between EPN and entomopathogenic fungi may play a role in the biological control of RIFA. Our discoveries shed light on the interactions among EPN, RIFA, and soil microbial communities, and emphasize a possible mutualistic relationship between EPN and entomopathogenic fungi in the biological control of RIFA.

Soil bacterial succession with different land uses along a millennial chronosequence derived from the Yangtze River flood plain

Wetlands reclamation has been a traditional and effective practice for obtaining new land to alleviate the pressure induced by population growth. However, the evolution of soil-dwelling microorganisms along with reclamation and the potential influence of land-use patterns on them remain unclear. In this study, a soil chronosequence derived from Yangtze River sediments was established, comprising of circa 0, 60, 160, 280, 2000, and 3000 years, to examine the succession of soil bacterial communities across different land uses. Our analysis revealed obvious development in soil properties and orderly bacterial succession along reclamation gradients. Over time, reclaimed land suffered from varying degrees of abundance loss and biodiversity simplification, with dryland being the most sensitive to reclamation duration changes, whereas woodland and paddies showed slight reductions. Bacterial communities tended to shift from oligotrophs (K-strategist) to copiotrophs (r-strategist) at the phylum level as reclamation proceeded for all land use types. The relative abundance of certain bacterial functional groups associated with the carbon (C) and nitrogen (N) cycles were significantly increased, including those involved in Aerobic chemoheterotrophy, Chitinolysis, Nitrate reduction, Nitrate respiration, and Ureolysis, while other groups, such as those related to Fermentation, Methylotrophy, Nitrification, and Hydrocarbon degradation, exhibited decreased expression. Notably, prolonged reclamation can also trigger ecological issues in soil, including a continuous increase of predatory/exoparasitic bacteria in dryland and woodland, as well as a significant increase in pathogenic bacteria during the later stages in paddy fields. Overall, our study identified the impact of long-term reclamation on soil bacterial communities and functional groups, providing insight into the development of land-use-oriented ecological protection strategies.

Outdoor climate drives diversity patterns of dominant microbial taxa in caves worldwide

The cave microbiota is assumed to be shaped by indoor microclimate, biotic and abiotic factors, which are largely dependent from outside environmental conditions; however, this knowledge is available at local or regional scales only. To address this knowledge gap, we reanalyzed over 1050 bacterial and fungal communities of caves worldwide, and found that outdoor temperature and rainfall play a critical role in explaining differences in microbial diversity patterns of global caves, selecting specific dominant taxa across gradients of growing aridity conditions with arid climate leading to a reduction in total cave microbial diversity. Moreover, we found that fungal (from 186 to 1908 taxa) and bacterial (from 467 to 1619 taxa) diversity increased under temperate-tropical and temperate-continental climatic regions, respectively, highlighting an opposite preference for the two microbial compartments. We hypothesized that outdoor geographical, climatic variables and lithology are critical epistatic drivers in assembling microbial communities and their dominant taxa, whose ecological responses could be useful to predict the fate of these subterranean environments in the context of climate change. Our work elucidates the intimate connection between caves microbiota and surface ecosystems highlighting the sensitivity of cave microbial communities to climatic changes and environmental degradation. This work also provides a natural benchmark for the biogeographic information for caves globally and for protection strategies aiming at conservation of underground environments.

Habitat-specific responses of soil organic matter decomposition to Spartina alterniflora invasion along China's coast

Plant invasions cause a fundamental change in soil organic matter (SOM) turnover. Disentangling the biogeographic patterns and key drivers of SOM decomposition and its temperature sensitivity (Q10 ) under plant invasion is a prerequisite for making projections of global carbon feedback. We collected soil samples along China's coast across saltmarshes to mangrove ecosystems invaded by the smooth cordgrass (Spartina alterniflora Loisel.). Microcosm experiments were carried out to determine the patterns of SOM decomposition and its thermal response. Soil microbial biomass and communities were also characterized accordingly. SOM decomposition constant dramatically decreased along the mean annual temperature gradient, whereas the cordgrass invasion retarded this change (significantly reduced slope, p < 0.05). The response of Q10 to invasion and the soil microbial quotient peaked at midlatitude saltmarshes, which can be explained by microbial metabolism strategies. Climatic variables showed strong negative controls on the Q10 , whereas dissolved carbon fraction exerted a positive influence on its spatial variance. Higher microbial diversity appeared to weaken the temperature-related response of SOM decomposition, with apparent benefits for carbon sequestration. Inconsistent responses to invasion were exhibited among habitat types, with SOM accumulation in saltmarshes but carbon loss in mangroves, which were explained, at least in part, by the SOM decomposition patterns under invasion. This study elucidates the geographic pattern of SOM decomposition and its temperature sensitivity in coastal ecosystems and underlines the importance of interactions between climate, soil, and microbiota for stabilizing SOM under plant invasion.

Application of nitrogen-rich sunflower husks biochar promotes methane oxidation and increases abundance of Methylobacter in nitrogen-poor soil

The area of sunflower crops is steadily increasing. A beneficial way of managing sunflower waste biomass could be its use as a feedstock for biochar production. Biochar is currently being considered as an additive for improving soil parameters, including the ability to oxidise methane (CH4) - one of the key greenhouse gases (GHG). Despite the high production of sunflower husk, there is still insufficient information on the impact of sunflower husk biochar on the soil environment, especially on the methanotrophy process. To fill this knowledge gap, an experiment was designed to evaluate the effects of addition of sunflower husk biochar (produced at 450-550 °C) at a wide range of doses (1-100 Mg ha-1) to Haplic Luvisol. In the presented study, the CH4 oxidation potential of soil with and without sunflower husk biochar was investigated at 60 and 100% water holding capacity (WHC), and with the addition of 1% CH4 (v/v). The comprehensive study included GHG exchange (CH4 and CO2), physicochemical properties of soil (pH, soil organic carbon (SOC), dissolved organic carbon (DOC), nitrate nitrogen (NO3--N), WHC), and the structure of soil microbial communities. That study showed that even low biochar doses (5 and 10 Mg ha-1) were sufficient to enhance pH, SOC, DOC and NO3--N content. Importantly, sunflower husk biochar was significant source of NO3--N, which soil concentration increased from 9.40 ± 0.09 mg NO3--N kg-1 for the control to even 19.40 ± 0.26 mg NO3--N kg-1 (for 100 Mg ha-1). Significant improvement of WHC (by 11.0-12.4%) was observed after biochar addition at doses of 60 Mg ha-1 and higher. At 60% WHC, application of biochar at a dose of 40 Mg ha-1 brought significant improvements in CH4 oxidation rate, which was 4.89 ± 0.37 mg CH4-C kg-1 d-1. Higher biochar doses were correlated with further improvement of CH4 oxidation rates, which at 100 Mg ha-1 was seventeen-fold higher (8.36 ± 0.84 mg CH4-C kg-1 d-1) than in the biochar-free control (0.48 ± 0.28 mg CH4-C kg-1 d-1). CO2 emissions were not proportional to biochar doses and only grew circa (ca.) twofold from 3.16 to 6.90 mg CO2-C kg-1 d-1 at 100 Mg ha-1. Above 60 Mg ha-1, the diversity of methanotrophic communities increased, with Methylobacter becoming the most abundant genus, which was as high as 7.45%. This is the first, such advanced and multifaceted study of the wide range of sunflower husk biochar doses on Haplic Luvisol. The positive correlation between soil conditions, methanotroph abundance and CH4 oxidation confirmed the multifaceted, positive effect of sunflower husk biochar on Haplic Luvisol. Sunflower husk biochar can be successfully used for Haplic Luvisol supplementation. This additive facilitates soil protection against degradation and has the potential to mitigate GHG emissions.

Carbon amendments in soil microcosms induce uneven response on H2 oxidation activity and microbial community composition

High-affinity H2-oxidizing bacteria (HA-HOB) thriving in soil are responsible for the most important sink of atmospheric H2. Their activity increases with soil organic carbon content, but the incidence of different carbohydrate fractions on the process has received little attention. Here we tested the hypothesis that carbon amendments impact HA-HOB activity and diversity differentially depending on their recalcitrance and their concentration. Carbon sources (sucrose, starch, cellulose) and application doses (0, 0.1, 1, 3, 5% Ceq soildw-1) were manipulated in soil microcosms. Only 0.1% Ceq soildw-1 cellulose treatment stimulated the HA-HOB activity. Sucrose amendments induced the most significant changes, with an abatement of 50% activity at 1% Ceq soildw-1. This was accompanied with a loss of bacterial and fungal alpha diversity and a reduction of high-affinity group 1 h/5 [NiFe]-hydrogenase gene (hhyL) abundance. A quantitative classification framework was elaborated to assign carbon preference traits to 16S rRNA gene, ITS and hhyL genotypes. The response was uneven at the taxonomic level, making carbon preference a difficult trait to predict. Overall, the results suggest that HA-HOB activity is more susceptible to be stimulated by low doses of recalcitrant carbon, while labile carbon-rich environment is an unfavorable niche for HA-HOB, inducing catabolic repression of hydrogenase.

Dominant influence of plants on soil microbial carbon cycling functions during natural restoration of degraded karst vegetation

The impacts of natural restoration projects on soil microbial carbon (C) cycling functions have not been well recognized despite their wide implementation in the degraded karst areas of southwest China. In this study, metagenomic sequencing assays were conducted on functional genes and microorganisms related to soil C-cycling at three natural restoration stages (shrubbery, TG; secondary forest, SG; old-growth forest, OG) in the southeast of Guizhou Province, China. The aims were to investigate the changes in microbial potentials responsible for soil C cycling and the underlying driving forces. The natural restoration resulted in vegetation establishment at all three restoration stages, rendering alterations of soil microbial C cycle functions as indicated by metagenomic gene assays. When TG was restored into OG, the number and diversity of genes and microorganisms involved in soil C cycling remained unchanged, but their composition underwent significant shifts. Specifically, microbial potentials for soil C decomposition exhibited an increase driven by the collaborative efforts of plants and soils, while microbial potentials for soil C biosynthesis displayed an initial upswing followed by a subsequent decline which was primarily influenced by plants alone. In comparison to soil nutrients, it was determined that plant diversities served as the primary driving factor for the alterations in microbial carbon cycle potentials. Soil microbial communities involved in C cycling were predominantly attributed to Proteobacteria (31.87%-40.25%) and Actinobacteria (11.29%-26.07%), although their contributions varied across the three restoration stages. The natural restoration of degraded karst vegetation thus influences soil microbial C cycle functions by enhancing C decomposition potentials and displaying a nuanced pattern of biosynthesis potentials, primarily influenced by above-ground plants. These results provide valuable new insights into the regulation of soil C cycling during the restoration of degraded karst vegetation from genetic and microbial perspectives.

High Ammonium Addition Changes the Diversity and Structure of Bacterial Communities in Temperate Wetland Soils of Northeastern China

The soil microbiome is an important component of wetland ecosystems and plays a pivotal role in nutrient cycling and climate regulation. Nitrogen (N) addition influences the soil's microbial diversity, composition, and function by affecting the soil's nutrient status. The change in soil bacterial diversity and composition in temperate wetland ecosystems in response to high ammonium nitrogen additions remains unclear. In this study, we used high-throughput sequencing technology to study the changes of soil bacterial diversity and community structure with increasing ammonium concentrations [CK (control, 0 kg ha-1 a-1), LN (low nitrogen addition, 40 kg ha-1 a-1), and HN (high nitrogen addition, 80 kg ha-1 a-1)] at a field experimental site in the Sanjiang Plain wetland, China. Our results showed that except for soil organic carbon (SOC), other soil physicochemical parameters, i.e., soil moisture content (SMC), dissolved organic nitrogen (DON), total nitrogen (TN), pH, ammonium nitrogen (NH4+), and dissolved organic carbon (DOC), changed significantly among three ammonium nitrogen addition concentrations (p < 0.05). Compared to CK, LN did not change soil bacterial α-diversity (p > 0.05), and HN only decreased the Shannon (p < 0.05) and did not change the Chao (p > 0.05) indices of soil bacterial community. Ammonium nitrogen addition did not significantly affect the soil's bacterial community structure based on non-metric multidimensional scaling (NMDS) and PERMANOVA (ADONIS) analyses. Acidobacteriota (24.96-31.11%), Proteobacteria (16.82-26.78%), Chloroflexi (10.34-18.09%), Verrucomicrobiota (5.23-11.56%), and Actinobacteriota (5.63-8.75%) were the most abundant bacterial phyla in the soils. Nitrogen addition changed the complexity and stability of the bacterial network. SMC, NO3-, and pH were the main drivers of the bacterial community structure. These findings indicate that enhanced atmospheric nitrogen addition may have an impact on bacterial communities in soil, and this study will allow us to better understand the response of the soil microbiome in wetland ecosystems in the framework of increasing nitrogen deposition.

Ecosystem multifunctionality and soil microbial communities in response to ecological restoration in an alpine degraded grassland

Linkages between microbial communities and multiple ecosystem functions are context-dependent. However, the impacts of different restoration measures on microbial communities and ecosystem functioning remain unclear. Here, a 14-year long-term experiment was conducted using three restoration modes: planting mixed grasses (MG), planting shrub with Salix cupularis alone (SA), and planting shrub with Salix cupularis plus planting mixed grasses (SG), with an extremely degraded grassland serving as the control (CK). Our objective was to investigate how ecosystem multifunctionality and microbial communities (diversity, composition, and co-occurrence networks) respond to different restoration modes. Our results indicated that most of individual functions (i.e., soil nutrient contents, enzyme activities, and microbial biomass) in the SG treatment were significantly higher than in the CK treatment, and even higher than MG and SA treatments. Compared with the CK treatment, treatments MG, SA, and SG significantly increased the multifunctionality index on average by 0.57, 0.23 and 0.76, respectively. Random forest modeling showed that the alpha-diversity and composition of bacterial communities, rather than fungal communities, drove the ecosystem multifunctionality. Moreover, we found that both the MG and SG treatments significantly improved bacterial network stability, which exhabited stronger correlations with ecosystem multifunctionality compared to fungal network stability. In summary, this study demonstrates that planting shrub and grasses altogether is a promising restoration mode that can enhance ecosystem multifunctionality and improve microbial diversity and stability in the alpine degraded grassland.

Microbes drive metabolism, community diversity, and interactions in response to microplastic-induced nutrient imbalance

The impact of conventional and biodegradable microplastics on soil nutrients (carbon and nitrogen) has been widely examined, and the alteration of nutrient conditions further influences microbial biosynthesis processes. Nonetheless, the influence of microplastic-induced nutrient imbalances on soil microorganisms (from metabolism to community interactions) is still not well understood. We hypothesized that conventional and biodegradable microplastic could alter soil nutrients and microbial processes. To fill this knowledge gap, we conducted soil microcosms with polyethylene (PE, new and aged) and polylactic acid (PLA, new and aged) microplastics to evaluate their effects on the soil enzymatic stoichiometry, co-occurrence interactions, and success patterns of soil bacterial communities. New and aged PLA induced soil N immobilization, which decreased soil mineral N by 91-141 %. The biodegradation of PLA led to a higher bioavailable C and wider bioavailable C:N ratio, which further filtered out specific microbial species. Both new and aged PLA had a higher abundance of copiotrophic members (Proteobacteria, 35-51 % in PLA, 26-34 % in CK/PE treatments) and rrn copy number. The addition of PLA resulted in a lower alpha diversity and reduced network complexity. Conversely, because of the chemically stable hydrocarbon structure of PE polymers, the new and aged PE microplastics had a minor effect on soil mineral N, bacterial community composition, and network complexity, but led to microbial C limitation. Collectively, all microplastics increased soil C-, N-, and P -acquiring enzyme activities and reduced the number of keystone species and the robustness of the co-occurrence network. The PLA treatment enhanced nitrogen fixation and ureolysis, whereas the PE treatment increased the degradation of recalcitrant carbon. Overall, the alteration of soil nutrient conditions by microplastics affected the microbial metabolism and community interactions, although the effects of PE and PLA microplastics were distinct.

Transmission mechanisms of antibiotic resistance genes in arsenic-contaminated soil under sulfamethoxazole stress

Numerous studies have revealed the spread mechanism of antibiotic resistance genes (ARGs) in single antibiotic-contaminated soils. However, the comprehensive impacts of heavy metals and antibiotics on ARGs and the underlying mechanisms are still unknown. Here, high-throughput quantitative PCR and high-throughput sequencing were used to investigate changes in ARGs and bacterial communities under various sulfamethoxazole (SMX) regimes (0, 1, 10, 50 mg kg^-1) in arsenic (As) contaminated soils. The study found that the abundances of ARGs, mobile genetic elements (MGEs), and heavy metal resistance genes (HMRGs) significantly increased in the soil fortified at 10 and 50 mg kg^-1 SMX concentrations. The ARGs abundance increased with the increase in the MGEs abundance. Many significant positive correlations between various ARGs subtypes and HMRGs subtypes were found. These results indicate that the HMRGs and MGEs positively contributed to the enrichment of ARGs in As-contaminated soils under SMX stress. Meanwhile, the abundance of copiotrophic (Actinobacteriota) reduced and oligotrophic (Gemmatimonadota) increased, indicating that the life history strategy of the community changed. In addition, Gemmatimonadota was positively correlated to ARGs, HMRGs, and MGEs, suggesting that Gemmatimonadota, which can cope with As and SMX stress, was the host for resistance genes in the soil. Finally, the study found that MGEs play a determinant role in ARGs proliferation due to the direct utilization of HGT, and the indirect effect for ARGs spread under a co-selection mechanism of ARGs and HMRGs, while the bacterial community showed indirect influences by altering environmental factors to act on MGEs. Collectively, this study revealed new insights into the mechanisms of resistance gene transmission under combined SMX and As contamination in soil ecosystems.

Explore the soil factors driving soil microbial community and structure in Songnen alkaline salt degraded grassland

Introduction

Saline-alkali degradation in grassland significantly affects plant community composition and soil physical and chemical properties. However, it remains unclear whether different degradation gradients affect soil microbial community and the main soil driving factors. Therefore, it is important to elucidate the effects of saline-alkali degradation on soil microbial community and the soil factors affecting soil microbial community in order to develop effective solutions to restore the degraded grassland ecosystem.

Methods

In this study, Illumina high-throughput sequencing technology was used to study the effects of different saline-alkali degradation gradients on soil microbial diversity and composition. Three different gradients were qualitatively selected, which were the light degradation gradient (LD), the moderate degradation gradient (MD) and the severe degradation gradient (SD).

Results

The results showed that salt and alkali degradation decreased the diversity of soil bacterial and fungal communities, and changed the composition of bacterial and fungal communities. Different degradation gradients had different adaptability and tolerance species. With the deterioration of salinity in grassland, the relative abundance of Actinobacteriota and Chytridiomycota showed a decreasing trend. EC, pH and AP were the main drivers of soil bacterial community composition, while EC, pH and SOC were the main drivers of soil fungal community composition. Different microorganisms are affected by different soil properties. The changes of plant community and soil environment are the main factors limiting the diversity and composition of soil microbial community.

Discussion

The results show that saline-alkali degradation of grassland has a negative effect on microbial biodiversity, so it is important to develop effective solutions to restore degraded grassland to maintain biodiversity and ecosystem function.

Understory ferns promote the restoration of soil microbial diversity and function in previously degraded lands

Microorganisms facilitate the recovery of previously degraded soils, such as degraded lands experiencing vegetation restoration and understory expansion, through vital soil functions like nutrient cycling and decomposing organic matter. Despite the role of microorganisms in recovery, little is known about the effects of the process on microbial diversity and function. Here, we performed an understory fern, Dicranopteris dichotoma (Thunb.) Berhn removal treatments nested within three Masson pine (Pinus massoniana L.) plantations with different restoration years in subtropical China. Three ferns treatments including no ferns cover, with ferns cover, and the ferns removal treatments were established to assess the impact of the ferns on soil microbial diversity and function during revegetation and drivers of observed changes. We combined high-throughput sequencing, network structure modeling, and function prediction of soil bacterial and fungal communities to determine microbial diversity and functions. Our results showed that soil bacterial and fungal diversity increased with restoration time. Understory ferns significantly increased soil microbial diversity in the un-restored land but the effect became smaller in two restored sites. Understory ferns significantly increased the relative abundance of bacterial phyla Proteobacteria and Acidobacteria, but decreased that of Chloroflexi and Firmicutes. Furthermore, the presence of ferns increased the abundance of Basidiomycota, but increased the abundance of Ascomycota. Co-occurrence network analysis revealed that the presence of ferns leads to more complex of bacterial networks with more connections, nodes, average degrees, betweenness, and degrees. The functional predictions indicate that aerobic chemoheterotrophy, chemoheterotrophy, and nitrogen fixation functional groups play key roles in the nutrient cycling of soils with ferns cover. The bacterial and fungal community compositions were strongly affected by revegetation and understory ferns as litter biomass and soil nitrogen were identified as the key environmental factors. Our study highlights the role of understory in facilitating microbial diversity and function recovery during degraded lands restoration.

Linking between soil properties, bacterial communities, enzyme activities, and soil organic carbon mineralization under ecological restoration in an alpine degraded grassland

Soil organic carbon (SOC) mineralization is affected by ecological restoration and plays an important role in the soil C cycle. However, the mechanism of ecological restoration on SOC mineralization remains unclear. Here, we collected soils from the degraded grassland that have undergone 14 years of ecological restoration by planting shrubs with Salix cupularis alone (SA) and, planting shrubs with Salix cupularis plus planting mixed grasses (SG), with the extremely degraded grassland underwent natural restoration as control (CK). We aimed to investigate the effect of ecological restoration on SOC mineralization at different soil depths, and to address the relative importance of biotic and abiotic drivers of SOC mineralization. Our results documented the statistically significant impacts of restoration mode and its interaction with soil depth on SOC mineralization. Compared with CK, the SA and SG increased the cumulative SOC mineralization but decreased C mineralization efficiency at the 0-20 and 20-40 cm soil depths. Random Forest analyses showed that soil depth, microbial biomass C (MBC), hot-water extractable organic C (HWEOC), and bacterial community composition were important indicators that predicted SOC mineralization. Structural equal modeling indicated that MBC, SOC, and C-cycling enzymes had positive effects on SOC mineralization. Bacterial community composition regulated SOC mineralization via controlling microbial biomass production and C-cycling enzyme activities. Overall, our study provides insights into soil biotic and abiotic factors in association with SOC mineralization, and contributes to understanding the effect and mechanism of ecological restoration on SOC mineralization in a degraded grassland in an alpine region.

Microbial assemblies with distinct trophic strategies drive changes in soil microbial carbon use efficiency along vegetation primary succession in a glacier retreat area of the southeastern Tibetan Plateau

Soil microbial carbon use efficiency (CUE) is a vital physiological parameter in assessing carbon turnover. Yet, how the microbial assemblies with distinct trophic strategies regulate the soil microbial CUE remains elusive. Based on the oligotrophic-copiotrophic framework, we explored the role of microbial taxa with different trophic strategies in mediating microbial CUE (determined by a ¹³C-labeled approach) along the vegetation primary succession in Hailuogou glacier retreat area of the southeastern Tibetan Plateau. Results showed that soil microbial CUE ranged from 0.54 to 0.72 (averaging 0.62 ± 0.01 across all samples) and increased staggeringly along the vegetation succession. Microbial assemblies with distinct trophic strategies were crucial regulators of soil microbial CUE. Specifically, microbial CUE increased with microbial oligotroph: copiotroph ratios, oligotroph-dominated stage had a higher microbial CUE than copiotroph-dominated ones. The prevalence of oligotrophic members would be the underlying microbial mechanism for the high microbial CUE. Given that oligotrophs predominate in more recalcitrant carbon soils and their higher microbial CUE, we speculate that oligotrophs are likely to potentially enhance carbon sequestration in soils. In addition, the responses of the microbial CUE to fungal oligotroph: copiotroph ratios were higher than bacterial ones. Fungal taxa may play a dominant role in shaping microbial CUE relative to bacterial members. Overall, our results constructed close associations between microbial trophic strategies and CUE and provide direct evidence regarding how microbial trophic strategies regulate microbial CUE. This study is a significant step forward for elucidating the physiological mechanisms regulating microbial CUE and has significant implications for understanding microbial-mediated carbon cycling processes.

Soil properties and root traits are important factors driving rhizosphere soil bacterial and fungal community variations in alpine Rhododendron nitidulum shrub ecosystems along an altitudinal gradient

Both soil properties and plant root traits are pivotal factors affecting microbial communities. However, there is still limited information about their importance in shaping rhizosphere soil microbial communities, particularly in less-studied alpine shrub ecosystems. To investigate the effects of altitude (3300, 3600, 3900, and 4200 m) on the diversity and composition of rhizosphere soil bacterial and fungal communities, as well as the factors shaping rhizosphere soil microbial communities, we conducted this study in alpine Rhododendron nitidulum shrub ecosystems from the Zheduo mountain of the eastern Tibetan Plateau. Results demonstrated that bacterial community diversity and richness decreased to the lowest value at 3600 m and then increased at higher altitudes compared with 3300 m; whereas fungal richness at 3300 m was much lower than at other altitudes, and was closely related to soil properties and root traits. The composition of rhizosphere soil bacterial and fungal communities at the low altitude (3300 m) was different from that at high altitudes. Permutational multivariate analysis of variance and redundancy analysis indicated that soil properties (soil water content, pH, NO₃^--N, and available phosphorus) and root traits (surface area, and maximum depth) were the major factors explaining the variations of rhizosphere soil bacterial and fungal communities. Specific bacterial and fungal taxa along altitudes were identified. The bacterial taxa Planctomycetota was dominant at 3300 and 3600 m with low soil nutrient availability and high root surface area, whereas the fungal taxa Mortierellomycota was abundant at 3900 and 4200 m with high soil nutrient availability and low root surface area. These results suggested that different soil microbes can respond differently to altitude. This study provides a novel insight into factors driving rhizosphere soil bacterial and fungal community variations, which could improve our understanding of microbial ecology in alpine R. nitidulum shrub ecosystems along altitude.

Distinct microbial communities across a climatically versatile summit in the Lesotho highlands

Most studies investigating the effects of climatological factors on microbial community composition and diversity focus on comparisons of geographically distinct environments (e.g., cold vs hot deserts) or across various temporal scales. Mountain regions provide unique environments to explore relationships between various environmental factors and soil microorganisms given their range of microclimatic conditions and vegetation types. This study investigated micro-topographically (i.e., north-/south-facing slope aspects and flat plateau between them) controlled microbial diversity and community structures across a Lesotho mountain summit. Amplicon sequence analysis revealed that the north- and south-facing slopes were dominated by more Proteobacteria and Bacteroidetes, while the plateau was dominated by more Acidobacteria. Fungi from the phylum Chytridiomycota more strongly dominated the plateau and the north-facing slope than the south-facing slope. Slope aspect, through its direct influence on air and soil micro-climatology and plant diversity, significantly affects bacterial and fungal community structures at this location. These results provide original insight into soil microbial diversity in the Lesotho highlands and offer an opportunity to project the likely response of soil microorganisms to future climate warming in highly variable mountain environments such as the Lesotho highlands.

Untangling the Effects of Plant Genotype and Soil Conditions on the Assembly of Bacterial and Fungal Communities in the Rhizosphere of the Wild Andean Blueberry (Vaccinium floribundum Kunth)

Microbial communities in the rhizosphere influence nutrient acquisition and stress tolerance. How abiotic and biotic factors impact the plant microbiome in the wild has not been thoroughly addressed. We studied how plant genotype and soil affect the rhizosphere microbiome of Vaccinium floribundum, an endemic species of the Andean region that has not been domesticated or cultivated. Using high-throughput sequencing of the 16S rRNA and ITS region, we characterized 39 rhizosphere samples of V. floribundum from four plant genetic clusters in two soil regions from the Ecuadorian Highlands. Our results showed that Proteobacteria and Acidobacteria were the most abundant bacterial phyla and that fungal communities were not dominated by any specific taxa. Soil region was the main predictor for bacterial alpha diversity, phosphorous and lead being the most interesting edaphic factors explaining this diversity. The interaction of plant genotype and altitude was the most significant factor associated with fungal diversity. This study highlights how different factors govern the assembly of the rhizosphere microbiome of a wild plant. Bacterial communities depend more on the soil and its mineral content, while plant genetics influence the fungal community makeup. Our work illustrates plant-microbe associations and the drivers of their variation in a unique unexplored ecosystem from the Ecuadorian Andes.

Crop diversity promotes the recovery of fungal communities in saline-alkali areas of the Western Songnen Plain

Introduction

Phytoremediation is an effective strategy for saline land restoration. In the Western Songnen Plain, northeast China, soil fungal community recovery for saline phytoremediation has not been well documented among different cropping patterns. In this study, we tested how rotation, mixture, and monoculture cropping patterns impact fungal communities in saline-alkali soils to assess the variability between cropping patterns.

Methods

The fungal communities of the soils of the different cropping types were determined using Illumina Miseq sequencing.

Results

Mixture and rotation promoted an increase in operational taxonomic unit (OTU) richness, and OTU richness in the mixture system decreased with increasing soil depth. A principal coordinate analysis (PCoA) showed that cropping patterns and soil depths influenced the structure of fungal communities, which may be due to the impact of soil chemistry. This was reflected by soil total nitrogen (TN) and electrical conductivity (EC) being the key factors driving OTU richness, while soil available potassium (AK) and total phosphorus (TP) were significantly correlated with the relative abundance of fungal dominant genus. The relative abundance of Leptosphaerulina, Alternaria, Myrothecium, Gibberella, and Tetracladium varied significantly between cropping patterns, and Leptosphaerulina was significantly associated with soil chemistry. Soil depth caused significant differences in the relative abundance of Fusarium in rotation and mixture soils, with Fusarium more commonly active at 0-15 cm deep soil. Null-model analysis revealed that the fungal community assembly of the mixture soils in 0-15 cm deep soil was dominated by deterministic processes, unlike the other two cropping patterns. Furthermore, fungal symbiotic networks were more complex in rotation and mixture than in monoculture soils, reflected in more nodes, more module hubs, and connectors. The fungal networks in rotation and mixture soils were more stable than in monoculture soils, and mixture networks were obviously more connected than rotations. FUNGuild showed that the relative proportion of saprotroph in rotation and mixture was significantly higher than that in monocultures. The highest proportion of pathotroph and symbiotroph was exhibited in rotation and mixture soils, respectively.

Discussion

Overall, mixture is superior to crop rotation and monocultures in restoring fungal communities of the saline-alkali soils of the Western Songnen Plain, northeast China.

Vertical Distribution of Soil Bacterial Communities in Different Forest Types Along an Elevation Gradient

Microorganisms inhabit the entire soil profile and play important roles in nutrient cycling and soil formation. Recent studies have found that soil bacterial diversity and composition differ significantly among soil layers. However, little is known about the vertical variation in soil bacterial communities and how it may change along an elevation gradient. In this study, we collected soil samples from 5 forest types along an elevation gradient in Taibai Mountain to characterize the bacterial communities and their vertical patterns and variations across soil profiles. The richness and Shannon index of soil bacterial communities decreased from surface soils to deep soils in three forest types, and were comparable among soil layers in the other two forests at the medium elevation. The composition of soil bacterial communities differed significantly between soil layers in all forest types, and was primarily affected by soil C availability. Oligotrophic members of the bacterial taxa, such as Chloroflexi, Gemmatimonadetes, Nitrospirae, and AD3, were more abundant in the deep layers. The assembly of soil bacterial communities within each soil profile was mainly governed by deterministic processes based on environmental heterogeneity. The vertical variations in soil bacterial communities differed among forest types, and the soil bacterial communities in the Betula albo-sinensis forest at the medium elevation had the lowest vertical variation. The vertical variation was negatively correlated with mean annual precipitation (MAP), weighted rock content, and weighted sand particle content in soils, among which MAP had the highest explanatory power. These results indicated that the vertical mobilization of microbes with preferential and matrix flows likely enhanced bacterial homogeneity. Overall, our results suggest that the vertical variations in soil bacterial communities differ along the elevation gradient and potentially affect soil biological processes across soil profiles.

How nutrient loads influence microbial-derived carbon accumulation in wetlands: A new insight from microbial metabolic investment strategies

Excessive anthropogenic nutrient inputs often lead to the degradation of wetland ecosystems and a decrease in carbon sink capacity. Microbial-derived carbon is increasingly recognized as an important precursor for organic carbon formation, which is controlled by the balance between microbial anabolic and catabolic processes. Shifts in microbial metabolic investment under nutrient load disturbance are key, but understudied, components of microbial-derived carbon turnover. Here, the roles of the distinct life-history traits and cooperation degree of key microbial assemblies in regulating microbial-derived carbon accumulation in a wetland receiving treated wastewater were firstly assessed by combining microbial biomarkers and genomic approaches. It was found that microbial-derived carbon was an important source of organic carbon in wetlands, and strongly associated with several microbial assemblies with specific trait strategies. Further analysis demonstrated that high growth yield strategists were mainly associated with microbial necromass accrual, while microbial biomass was more dominated by resource acquisition strategies in nutrient-imbalanced wetlands. A significant positive relationship between positive cohesion and microbial-derived carbon indicated that cooperative behavior among taxa promoted the production and accumulation of microbial-derived carbon. Moreover, resource stoichiometric balance, including C:N and C:P, was identified as an important driver of shifts in microbial metabolic investment strategies. The decreased C:N ratio led to a shift from resource acquisition strategies to high growth yield strategies for the microbial community, which facilitated microbial necromass accrual along the N-limited wetland, while the increased C:P ratio caused by excessive P deposition in sediments limits microbial cooperative growth to some extent. This study highlighted the importance of stoichiometric balance in mediating microbial growth metabolism and, in turn, enhancing the carbon sink capacity of wetlands.

Dual regulatory effects of microplastics and heat waves on river microbial carbon metabolism

Rivers play a critical role in the global carbon cycle, but the processes can be affected by widespread microplastic (MP) pollution and the increasing frequency of heat waves (HWs) in a warming climate. However, little is known about the role of river microbes in regulating the carbon cycle under the combined action of MP pollution and HWs. Here, through seven-day MP exposure and three cycles of HW simulation experiments, we found that MPs inhibited the thermal adaptation of the microbial community, thus regulating carbon metabolism. The CO₂ release level increased, while the carbon degradation ability and the preference for stable carbon were inhibited. Metabonomic, 16 S rRNA and ITS gene analyses further revealed that the regulation of carbon metabolism was closely related to the microbial r-/K- strategy, community assembly and transformation of keystone taxa. The random forest model revealed that dissolved oxygen and ammonia-nitrogen were important variables influencing microbial carbon metabolism. The above findings regarding microbe-mediated carbon metabolism provide insights into the effect of climate-related HWs on the ecological risks of MPs.

Mixing planting with native tree species reshapes soil fungal community diversity and structure in multi-generational eucalypt plantations in southern China

The continuous planting pattern of eucalypt plantations negatively affects soil quality. A mixed planting pattern using native species implanted in pure plantations has been considered a preferable measure for this problem. However, the impact of this approachon the structure and function of fungal communities is not clear. Here, harvesting sites that had undergone two generations of eucalypt plantations were selected to investigate soil fungal community structure and the co-occurrence network characteristics in response to two silvicultural patterns involving the third generation of eucalypt plantations (E) and mixed plantations of Eucalyptus. urograndis × Cinnamomum. camphora (EC) and E. urograndis × Castanopsis. hystrix (EH). Compared with the first generation of eucalypt plantations (CK), E markedly weakened enzyme activities associated with carbon-, nitrogen-. and phosphorus-cycling. Reduced soil fungal alpha diversity, and elevated the relative abundance of Basidiomycota while decreasing the abundance of Ascomycota. In contrast, EC and EH not only enhanced fungal alpha diversity, but also reshaped fungal composition. At the class level, E caused an enrichment of oligotrophic Agaricomycetes fungi, classified into symbiotroph guild, while EC markedly decreased the abundance of those fungi and increased the abundances of Sordariomycetes, Dothideomycetes, Eurotiomycetes, and Tremellomycetes fungi, which were classified into saprotroph or pathotroph guild. Moreover, fungal network complexity and robustness topological attributes were higher or significantly higher in mixed plantations soils compared with those of pure eucalypt plantation E. Furthermore, fungal diversity, structure, and functional taxa were significantly affected by soil organic matter, pH, total nitrogen, and nitrate nitrogen.

Photovoltaic panels have altered grassland plant biodiversity and soil microbial diversity

Introduction

Human concerns about fossil fuel depletion, energy security and environmental degradation have driven the rapid development of solar photovoltaic (PV) power generation. Most of the photovoltaic power generation plants are concentrated in desert, grassland and arable land, which means the change of land use type. However, there is still a gap in the research of the PV panel layout on grassland plant species diversity and ecological function.

Methods

In this study, Illumina high-throughput sequencing technology was used to investigate the effects of PV panel arrangement on grassland plant species diversity and soil microbial diversity. In view of the differences in the microclimate at different sites of the PV panels, quadrates were arranged in front edge (FE), beneath the center of each panel (BP), back edge (BE), the uncovered interspace adjacent to each panel (IS) and the undisturbed grassland around the PV panels (Control), respectively.

Results

PV panels (especially FE) significantly increased the total aboveground productivity (total AGB) and plant species diversity in grasslands. FE increased precipitation accumulation and plant species diversity directly and indirectly changed the diversity of soil bacterial and fungal communities. PV panels decreased the relative abundance of Actinobacteriota, while increased the relative abundance of Proteobacteria, Acidobacteriota, and Methylomirabilota. EC, Margalef' s richness and total AGB were the main factors affecting the composition of bacterial communities, while alkaline hydrolysis nitrogen (AN) and available phosphorus (AP) were the main factors affecting the composition of fungal communities.

Discussion

In conclusion, the arrangement of PV panels increased the plant species diversity and soil microorganisms in grassland. This study provides important information for further understanding the impact of PV panels on grassland ecosystem function and is of great significance for maintaining grassland ecosystem function.

Seasonal Influence of Biodiversity on Soil Respiration in a Temperate Forest

Soil respiration in forests contributes to significant carbon dioxide emissions from terrestrial ecosystems but it varies both spatially and seasonally. Both abiotic and biotic factors influence soil respiration but their relative contribution to spatial and seasonal variability remains poorly understood, which leads to uncertainty in models of global C cycling and predictions of future climate change. Here, we hypothesize that tree diversity, soil diversity, and soil properties contribute to local-scale variability of soil respiration but their relative importance changes in different seasons. To test our hypothesis, we conducted seasonal soil respiration measurements along a local-scale environmental gradient in a temperate forest in Northeast China, analyzed spatial variability of soil respiration and tested the relationships between soil respiration and a variety of abiotic and biotic factors including topography, soil chemical properties, and plant and soil diversity. We found that soil respiration varied substantially across the study site, with spatial coefficients of variation (CV) of 29.1%, 27.3% and 30.8% in spring, summer, and autumn, respectively. Soil respiration was consistently lower at high soil water content, but the influence of other factors was seasonal. In spring, soil respiration increased with tree diversity and biomass but decreased with soil fungal diversity. In summer, soil respiration increased with soil temperature, whereas in autumn, soil respiration increased with tree diversity but decreased with increasing soil nutrient content. However, soil nutrient content indirectly enhanced soil respiration via its effect on tree diversity across seasons, and forest stand structure indirectly enhanced soil respiration via tree diversity in spring. Our results highlight that substantial differences in soil respiration at local scales was jointly explained by soil properties (soil water content and soil nutrients), tree diversity, and soil fungal diversity but the relative importance of these drivers varied seasonally in our temperate forest.

Seasonal variations of soil fungal diversity and communities in subalpine coniferous and broadleaved forests

Soil fungi have essential roles in ecosystems, but the seasonal dynamics of soil fungal communities in forests remain unclear. To explore the pattern and variation of soil fungal community diversity and structural composition across forest types and seasons, and identify the main contributors to soil fungal communities, we collected soil samples from subalpine coniferous (Picea asperata and Larix gmelinii) and broadleaved plantations (Betula albosinensis and Quercus aquifolioides) in southwest China in different seasons. Soil fungal community structural composition was determined using the Illumina MiSeq sequencing platform. The results showed that soil fungal diversity and richness in broadleaved forests were higher than in conifer forests. From heatmap cluster analysis, distinct differences in fungal community composition among forest types (coniferous and broadleaved forests) and seasons (May and July, September) were observed. Fungal communities were dominated by Basidiomycota and Ascomycota regardless of forest type and season. Helotiales and Atheliales were abundant in coniferous forests, while Agaricales, Russulales and Thelephorales predominated in broadleaved forests. Fungal community diversity and composition were significantly driven by soil pH, moisture, organic carbon, ammonium (NH₄⁺-N), fine root biomass and root tissue density, when controlling for the effects of forest type and season. Thus, forest type and season significantly affected soil fungal community diversity and composition by altering soil properties and root variables.

Changes in litter input exert divergent effects on the soil microbial community and function in stands of different densities

Soil microbial communities influence soil biogeochemical cycling by affecting the production of extracellular enzymes and the release of carbon dioxide. Changes in litter input or stand density due to thinning can affect soil microbial communities and their function by altering soil biochemical properties. However, it is unclear how or to what extent different amounts of litter input affect soil microbial communities and their function in forest stands with different densities. Therefore, we simulated litter removal, 50 % litter reduction, normal litter input, and double litter increase under field conditions by applying different amounts of litter to soils with different stand densities in the laboratory. We then measured soil biochemical properties, microbial communities, enzyme activity, and respiration rate. Our results revealed that the responses of soil dissolved organic carbon and total nitrogen to litter input were more pronounced in the high-density forest stand with poor soil than in the low-density forest stand with nutrient-rich soil, which was mainly reflected in that the addition of litter significantly decreased the concentration of dissolved organic carbon while increasing the content of total nitrogen in the soil of the high-density forest stand. In comparison to the soil carbon component, the nitrogen component of the soil was more affected by stand density. The responses of soil fungal and bacterial communities to leaf litter treatment varied with stand density, as reflected primarily in changes in the relative abundances of Ascomycota, unclassified_K_fungi, and Proteobacteria, and changes in the relative abundances of their functional groups (ectomycorrhizal fungi, saprophytic fungi, pathogens, parasites, and bacteria involved in the nitrogen cycle). Soil fungal community responses to changes in litter input are more sensitive in the high-density forest with nutrient-poor soil than in the low-density forest stand. Furthermore, litter input inhibited the activities of soil β-glucuronidase, N-acetyl-β-d-glucosaminidase, and acid phosphatase more strongly in the low-density forest stand. Litter manipulation primarily affected enzymatic activity in the high-density forest stand by changing the diversity and composition of the soil fungal community. However, in the low-density forest stand, litter treatment affected soil enzyme activity, primarily through changes in soil bacterial and fungal community composition, as well as soil respiration through changes in bacterial richness (Chao 1) and community composition. We conclude that how the change in litter input impacts the soil microbial community and its function, or the magnitude of the effects, is largely dependent on soil quality. Relationships among soil variables, microbial communities, and function differ between stand densities. Our study contributes to an enhanced understanding of the impact of changes in litter input due to climate change or anthropogenic activities on soil biogeochemical cycles and can also guide rationally formulating forest management approaches to improve microbial function under climate change.

Linkages and key factors between soil bacterial and fungal communities along an altitudinal gradient of different slopes on mount Segrila, Tibet, China

Soil microbes are of great significance to many energy flow and material circulation processes in alpine forest ecosystems. The distribution pattern of soil microbial community along altitudinal gradients is an essential research topic for the Tibetan Plateau. Yet our understanding of linkages between soil microbial communities and key factors along an altitudinal gradient of different slopes remains limited. Here, the diversity, composition and interaction of bacterial and fungal communities and in response to environmental factors were compared across five elevation sites (3,500 m, 3,700 m, 3,900 m, 4,100 m, 4,300 m) on the eastern and western slopes of Mount Segrila, by using Illumina MiSeq sequencing. Our results showed that microbial community composition and diversity were distinct at different elevations, being mainly influenced by soil total nitrogen and carbonate. Structural equation models indicated that elevation had a greater influence than slope upon the soil microbial community. Co-occurrence network analysis suggested that fungi were stable but bacteria contributed more to among interactions of bacterial and fungal communities. Ascomycota was identified as a key hub for the internal interactions of microbial community, which might affect the soil microbial co-occurrence network resilience of alpine forest ecosystems on the Tibetan Plateau.

Soil Fungal Community Structure and Function Shift during a Disease-Driven Forest Succession

Forest succession is important for sustainable forest management in terrestrial ecosystems. However, knowledge about the response of soil microbes to forest disease-driven succession is limited. In this study, we investigated the soil fungal biomass, soil enzyme activity, and fungal community structure and function in forests suffering succession processes produced by pine wilt disease from conifer to broadleaved forests using Illumina Miseq sequencing coupled with FUNGuild analysis. The results showed that the broadleaved forest had the highest fungal biomass and soil enzyme activities in C, N, and S cycles, whereas the conifer forest had the highest enzyme activity in the P cycle. Along the succession, the fungal diversity and richness significantly increased (P < 0.05). The fungal communities were dominated by Ascomycota (42.0%), Basidiomycota (38.0%), and Mortierellomycota (9.5%), among which the abundance of Ascomycota significantly increased (P < 0.05), whereas that of Basidiomycota and Mortierellomycota decreased (P < 0.05). The abundance of species Mortierella humilis, Lactarius salmonicolor, and Russula sanguinea decreased, whereas that of Mortierella minutissima increased (P < 0.05). The forests in different succession stages formed distinct fungal communities and functional structures (P < 0.05). Functionally, the saprotrophs, symbiotrophs, and pathotrophs were the dominant groups in the conifer, mixed, and broadleaved forests, respectively. Soil pH and soil organic carbon were the key factors influencing the fungal community and functional structures during the succession. These findings provide useful information for better understanding the plant-microbe interaction during forest succession caused by forest disease. IMPORTANCE The studies on soil fungal communities in disease-driven forest succession are rare. This study showed that during the disease-driven forest succession, the soil enzyme activity, soil fungal diversity, and biomass increased along succession. The disease-driven forest succession changed the soil fungal community structure and function, in which the symbiotrophs were the most dominant group along the succession. These findings provide useful information for better understanding the plant-microbe interaction during forest succession caused by forest disease.

Bacterial diversity changes in response to an altitudinal gradient in arid and semi-arid regions and their effects on crops growth

The microbiome of soil has a fundamental role in maintaining the health of soil and plants. While the diversity of microbes is one of the most important factors in the environment, little is known about the effects of elevation on the microbiome and the impact of the affected microbiome on plants. The main goal of this study is to expand our knowledge of what happens to the soil bacterial community along an altitudinal gradient and investigate their possibly different impacts on plant growth. Bacteria from soils at various altitudes have been isolated, characterized, and identified by Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) to determine the effects of an elevational gradient on the microbiome and plant growth. Furthermore, their effects have been investigated by isolates assessment on maize, wheat, and canola. Based on our results, higher altitude results in a higher diversity of the microbiome and lower bacteria biomass. Bacillus cereus is found in abundance in arid and semi-arid samples. Interestingly, enhanced diversity in higher altitudes shows similarity in response to environmental stress and tolerates these factors well. Furthermore, the inoculation of these bacteria could enhance the overall growth of plants. We prove that bacterial communities could change their biomass and diversity in response to altitude changes. These indicate evolutionary pressure as these bacteria could tolerate stress factors well and have a better relationship with plants.

Levels and variations of soil bioavailable nitrogen among forests under high atmospheric nitrogen deposition

To examine the perturbation of atmospheric nitrogen (N) deposition on soil N status and the biogeochemical cycle is meaningful for understanding forest function evolution with environmental changes. However, levels of soil bioavailable N and their environmental controls in forests receiving high atmospheric N deposition remain less investigated, which hinders evaluating the effects of enhanced anthropogenic N loading on forest N availability and N losses. This study analyzed concentrations of soil extractable N, microbial biomass N, net rates of N mineralization and nitrification, and their relationships with environmental factors among 26 temperate forests under the N deposition rates between 28.7 and 69.0 kg N ha^-1 yr^-1 in the Beijing-Tianjin-Hebei (BTH) region of northern China. Compared with other forests globally, forests in the BTH region showed higher levels of soil bioavailable N (NH₄⁺, 27.1 ± 0.8 mg N kg^-1; NO₃^-, 7.0 ± 0.8 mg N kg^-1) but lower net rates of N mineralization and nitrification (0.5 ± 0.1 mg N kg^-1 d^-1 and 0.4 ± 0.1 mg N kg^-1 d^-1, respectively). Increasing N deposition levels increased soil nitrification and NO₃^- concentrations but did not increase microbial biomass N and N mineralization among the study forests. Soil moisture and C availability were found as dominant factors influencing microbial N mineralization and bioavailable N. In addition, by budgeting the differences in soil total N densities between the 2000s and 2010s, atmospheric N inputs to the forests were more retained in soils than lost proportionally (84% vs. 16%). We concluded that the high N deposition enriched soil N without stimulating microbial N mineralization among the study forests. These results clarified soil N status and the major controlling factors under high anthropogenic N loading, which is helpful for evaluating the fates and ecological effects of atmospheric N pollution.

Salt-tolerant plant moderates the effect of salinity on soil organic carbon mineralization in a subtropical tidal wetland

Although salinization is widely known to affect cycling of soil carbon (C) in tidal freshwater wetlands, the role of the presence or absence of plants in mediating the responses of soil organic carbon (SOC) mineralization to salinization is poorly understood. In this study, we translocated soils collected from a tidal freshwater wetland to sites with varying salinities along a subtropical estuarine gradient and established unplanted and planted (with the salt-tolerant plant Cyperus malaccensis Lam.) mesocosms at each site. We simultaneously investigated cumulative soil CO₂ emissions, C-acquiring enzyme activities, availability of labile organic C (LOC), and structures of bacterial and fungal communities. Overall, in the planted mesocosm, the soil LOC content and the activities of β-1,4-glucosidase, cellobiohydrolase, phenol oxidase, and peroxidase increased with salinization. However, in the unplanted mesocosm, soil LOC content decreased with increasing salinity, whereas all the C-acquiring enzyme activities did not change. In addition, salinization favored the dominance of bacterial and fungal copiotrophs (e.g., γ-Proteobacteria, Bacteroidetes, Firmicutes, and Ascomycota) in the planted mesocosms. Contrarily, in the unplanted mesocosms salinization favored bacterial and fungal oligotrophs (e.g., α-Proteobacteria, Chloroflexi, Acidobacteria, and Basidiomycota). In both planted and unplanted mesocosms, cumulative soil CO₂ emissions were affected by soil LOC content, activities of C-acquiring enzymes, and microbial C-use trophic strategies. Overall, cumulative soil CO₂ emissions increased by 35% with increasing salinity in the planted mesocosm but decreased by 37% as salinity increased in the unplanted mesocosm. Our results demonstrate that the presence or absence of salt-tolerant plants can moderate the effect of salinity on SOC mineralization in tidal wetland soils. Future C prediction models should embed both planted and unplanted modules to accurately simulate cycling of soil C in tidal wetlands under sea level rise.

Altitudinal Variation Influences Soil Fungal Community Composition and Diversity in Alpine–Gorge Region on the Eastern Qinghai–Tibetan Plateau

Soil fungi play an integral and essential role in maintaining soil ecosystem functions. The understanding of altitude variations and their drivers of soil fungal community composition and diversity remains relatively unclear. Mountains provide an open, natural platform for studying how the soil fungal community responds to climatic variability at a short altitude distance. Using the Illumina MiSeq high-throughput sequencing technique, we examined soil fungal community composition and diversity among seven vegetation types (dry valley shrub, valley-mountain ecotone broadleaved mixed forest, subalpine broadleaved mixed forest, subalpine coniferous-broadleaved mixed forest, subalpine coniferous forest, alpine shrub meadow, alpine meadow) along a 2582 m altitude gradient in the alpine–gorge region on the eastern Qinghai–Tibetan Plateau. Ascomycota (47.72%), Basidiomycota (36.58%), and Mortierellomycota (12.14%) were the top three soil fungal dominant phyla in all samples. Soil fungal community composition differed significantly among the seven vegetation types along altitude gradients. The α-diversity of soil total fungi and symbiotic fungi had a distinct hollow pattern, while saprophytic fungi and pathogenic fungi showed no obvious pattern along altitude gradients. The β-diversity of soil total fungi, symbiotic fungi, saprophytic fungi, and pathogenic fungi was derived mainly from species turnover processes and exhibited a significant altitude distance-decay pattern. Soil properties explained 31.27−34.91% of variation in soil fungal (total and trophic modes) community composition along altitude gradients, and the effects of soil nutrients on fungal community composition varied by trophic modes. Soil pH was the main factor affecting α-diversity of soil fungi along altitude gradients. The β-diversity and turnover components of soil total fungi and saprophytic fungi were affected by soil properties and geographic distance, while those of symbiotic fungi and pathogenic fungi were affected only by soil properties. This study deepens our knowledge regarding altitude variations and their drivers of soil fungal community composition and diversity, and confirms that the effects of soil properties on soil fungal community composition and diversity vary by trophic modes along altitude gradients in the alpine–gorge region.

Plant invasion reconstructs soil microbial assembly and functionality in coastal salt marshes

Microbiologically driven ecosystem processes can be profoundly altered by alien plant invasions. The understanding of ecological mechanisms orchestrating different microbial constituents and their roles in emerging functional properties under plant invasions is limited. Here, we investigated soil microbial communities and functions using high-throughput amplicon sequencing and GeoChip technology, respectively, along a chronological gradient of smooth cordgrass invasion in salt marshes located in the Yellow River Estuary, China. We found a positive correlation between microbial diversity and the duration age of invasion, and both bacterial and fungal communities exerted orderly changes with invasion. Soil microbial metabolic potential, as indicated by the abundance of microbial functional genes involved in biogeochemical cycling, decreased in response to invasion. As a consequence, declined soil microbial metabolisms by plant invasion facilitated the carbon accumulation in invaded salt marshes. Bacteria and fungi exhibited distinct contributions to assembly processes along the invasion gradient: bacterial communities were mainly driven by selection and dispersal limitation, while fungi were dramatically shaped by stochastic processes. Soil microbial-mediated functions were taxon-specific, as indicated by community-function relationships. This study demonstrates the distinct contributions of microbial constituents to microbial community assembly and functions and sheds light on the implications of plant invasion on microbiologically driven ecosystem processes in coastal wetlands.

The Diversity of Soil Bacteria and Fungi Under Altered Nitrogen and Rainfall Patterns in a Temperate Steppe

The response of soil microorganisms to altered nitrogen (N) and rainfall patterns plays an important role in understanding ecosystem carbon and nitrogen cycling processes under global change. Previous studies have separately focused on the effects of N addition and rainfall on soil microbial diversity and community composition. However, the combined and interactive impact of N addition and rainfall on soil microbial diversity and function mediated by plant and soil processes have been poorly investigated for grassland ecosystems. Here, we conducted a field experiment with simulated N addition (N addition: 10 g N m^–2yr^–1) and altered rainfall pattern [control, rainfall reduction (compared to control –50%); rainfall addition (compared to control + 50%)] to study their interactive effects on soil microbial diversity and function in a temperate steppe of Inner Mongolia. Our results showed that N addition and rainfall addition significantly increased soil bacterial diversity, and the bacterial diversity was positively correlated with soil microbial biomass nitrogen, inorganic nitrogen, and Stipa krylovii root exudate C:N ratio, Allium polyrhizum root exudate C and N, and A. polyrhizum root exudate C:N ratio. N addition and rainfall reduction significantly reduced fungal diversity, which correlated closely with soil microbial biomass carbon and the C:N ratio of A. polyrhizum root exudates. Bacteria were mainly eutrophic r-strategists, and the responses of bacterial function guilds to the interaction between N addition and rainfall pattern were not significant. However, the arbuscular mycorrhizal fungi (AMF), in the functional classification of fungi, were significantly reduced under the condition of N addition and rainfall reduction, and the absolute abundance of the phylum Glomeromycota increased under rainfall addition, suggesting that AMFs are sensitive to altered N and rainfall patterns over short timescales (1 year). Collectively, our results have important implications for understanding the plant–soil–microbe system of grasslands under climate change.

Fungal communities in European alpine soils are not affected by short-term in situ simulated warming than bacterial communities

The impact of global warming on biological communities colonizing European alpine ecosystems was recently studied. Hexagonal open top chambers (OTCs) were used for simulating a short-term in situ warming (estimated around 1°C) in some alpine soils to predict the impact of ongoing climate change on resident microbial communities. Total microbial DNA was extracted from soils collected either inside or outside the OTCs over 3 years of study. Bacterial and fungal rRNA copies were quantified by qPCR. Metabarcoding sequencing of taxonomy target genes was performed (Illumina MiSeq) and processed by bioinformatic tools. Alpha- and beta-diversity were used to evaluate the structure of bacterial and fungal communities. qPCR suggests that, although fluctuations have been observed between soils collected either inside and outside the OTCs, the simulated warming induced a significant (p < 0.05) shift only for bacterial abundance. Likewise, significant (p < 0.05) changes in bacterial community structure were detected in soils collected inside the OTCs, with a clear increase of oligotrophic taxa. On the contrary, fungal diversity of soils collected either inside and outside the OTCs did not exhibit significant (p < 0.05) differences, suggesting that the temperature increase in OTCs compared to ambient conditions was not sufficient to change fungal communities.

Does Shift in Vegetation Abundance After Nitrogen and Phosphorus Additions Play a Key Role in Regulating Fungal Community Structure in a Northern Peatland?

Soil fungal communities are key players in biogeochemical processes of peatlands, which are important carbon stocks globally. Although it has been elucidated that fungi are susceptible to environmental changes, little is known about the intricate and interactive effect of long-term nitrogen (N) and phosphorus (P) enrichment on fungal community structure in northern peatlands. In this study, we compared a short- (2 years) with a long-term (10 years) fertilization experiment in a peatland complex in northeastern China to assess how N and/or P additions influence fungal community structure. The results showed that fungal community composition and diversity were altered by N addition, without a significant interactive effect with P addition. Not only the long-term but also the short-term nutrient addition could change the abundance of different plant functional types. However, there were no strong cascading effects on the fungal community in any of the fertilization experiments. Long-term nutrient addition showed a stronger effect on the relative abundance of different fungal functional guilds; an increase in the relative abundance of saprotrophs after fertilization did not jeopardize mycorrhizal fungi. Moreover, the decline in Sphagnum cover after long-term N addition did not parallel changes in the relative abundance of Sphagnum-associated fungi (Clavaria sphagnicola, Galerina tibiicystis, G. sphagnicola, and G. paludosa). Given that short- and long-term fertilization showed strongly contrasting effects on fungal community structure, our study highlights the necessity of assessing the long-term effects of nutrient enrichment on the association between vegetation and fungal community in peatland ecosystems. Future research priorities should emphasize the connection between the community structure of fungal functional guilds and their functionality, which is of paramount importance to better understand their influences on C storage in the face of uncertain N and P deposition regimes.

Microbial assemblies associated with temperature sensitivity of soil respiration along an altitudinal gradient

Identifying the drivers of the response of soil microbial respiration to warming is integral to accurately forecasting the carbon-climate feedbacks in terrestrial ecosystems. Microorganisms are the fundamental drivers of soil microbial respiration and its response to warming; however, the specific microbial communities and properties involved in the process remain largely undetermined. Here, we identified the associations between microbial community and temperature sensitivity (Q₁₀) of soil microbial respiration in alpine forests along an altitudinal gradient (from 2974 to 3558 m) from the climate-sensitive Tibetan Plateau. Our results showed that changes in microbial community composition accounted for more variations of Q₁₀ values than a wide range of other factors, including soil pH, moisture, substrate quantity and quality, microbial biomass, diversity and enzyme activities. Specifically, co-occurring microbial assemblies (i.e., ecological clusters or modules) targeting labile carbon consumption were negatively correlated with Q₁₀ of soil microbial respiration, whereas microbial assemblies associated with recalcitrant carbon decomposition were positively correlated with Q₁₀ of soil microbial respiration. Furthermore, there were progressive shifts of microbial assemblies from labile to recalcitrant carbon consumption along the altitudinal gradient, supporting relatively high Q₁₀ values in high-altitude regions. Our results provide new insights into the link between changes in major microbial assemblies with different trophic strategies and Q₁₀ of soil microbial respiration along an altitudinal gradient, highlighting that warming could have stronger effects on microbially-mediated soil organic matter decomposition in high-altitude regions than previously thought.

Biochar dose determines methane uptake and methanotroph abundance in Haplic Luvisol

Biochar promotes C sequestration and improvement of soil properties. Nevertheless, the effects of biochar addition on soil condition are poorly understood, especially with respect to greenhouse gas (GHG) emissions. A large proportion of GHG emissions derive from agriculture and, thus, recognition of the effect of biochar addition to soil on GHG emissions from terrestrial ecosystems is an important issue. The purpose of our study was to evaluate the short- and long-term effects of biochar application on soil in aspects of: GHG exchange (CH₄ and CO₂), basic physicochemical soil properties and structure of microbial communities in Haplic Luvisol. Soil was collected from fallow fields enriched with three doses of wood offcuts biochar (10, 20 and 30 Mg ha^-1) and incubated at two moisture levels (60 and 100% WHC) with the addition of 1% CH₄. To evaluate the influence of biochar aging in soil, the samples were analysed directly (short-term response) and five years (long-term response) after amendment. Generally, biochar addition increased soil pH, redox potential (Eh), organic carbon (SOC) and dissolved organic carbon (DOC) contents. Under 60% WHC, direct biochar application to the soil resulted in a clear improvement in the CH₄ uptake rate. In contrast to that (at 100% WHC) methane uptake rates were twofold decreased. The positive effect was reduced due to biochar aging in the soil, but five years after application, at 60% WHC and the highest biochar dose (30 Mg ha^-1) still significantly enhanced CH₄ oxidation. From a short-term perspective, biochar application increased CO₂ emissions, but after five years this effect was not observed. Microbial tests confirmed that the improvement in CH₄ oxidation was correlated with methanotroph abundance in the soil. Moreover, an increase of Methylocystis abundance in the soil enriched with biochar along with enhanced CH₄ uptake rates confirm the positive biochar influence on methanotrophic communities.

Fertilization and Soil Microbial Community: A Review

The present paper reviews the most recent advances regarding the effects of chemical and organic fertilizers on soil microbial communities. Based on the results from the articles considered, some details are presented on how the use of various types of fertilizers affects the composition and activity of soil microbial communities. Soil microbes have different responses to fertilization based on differences in the total carbon (C), nitrogen (N) and phosphorus (P) contents in the soil, along with soil moisture and the presence of plant species. These articles show that the use of chemical fertilizers changes the abundance of microbial populations and stimulates their growth thanks to the nutrient supply added. Overall, however, the data revealed that chemical fertilizers have no significant influence on the richness and diversity of the bacteria and fungi. Instead, the abundance of individual bacterial or fungal species was sensitive to fertilization and was mainly attributed to the changes in the soil chemical properties induced by chemical or organic fertilization. Among the negative effects of chemical fertilization, the decrease in enzymatic activity has been highlighted by several papers, especially in soils that have received the largest amounts of fertilizers together with losses in organic matter.

Heterotrophic Bacteria Play an Important Role in Endemism of Cephalostachyum pingbianense (Hsueh & Y.M. Yang ex Yi et al.) D.Z. Li & H.Q. Yang, 2007, a Full-Year Shooting Woody Bamboo

The previous studies show soil microbes play a key role in the material and nutrient cycles in the forest ecosystem, but little is known about how soil microbes respond to plant distribution, especially in the soil bacterial community in woody bamboo forests. Cephalostachyum pingbianense (Hsueh & Y.M. Yang ex Yi et al.) D.Z. Li & H.Q. Yang, 2007 is known as the only bamboo species producing shoots all year round in natural conditions. Endemic to the Dawei mountain in Yunnan of China, this species is a good case to study how soil bacteria respond to plant endemic distribution. In this work, we assayed the soil chemical properties, enzyme activity, changes in the bacterial community along the distribution range of the C. pingbianense forest. The results showed that soil nutrients at the range edge were nitrogen-rich but phosphorus-deficient, and soil pH value and soil urease activity were significantly lower than that of the central range. No significant difference was detected in soil bacterial diversity, community composition, and function between the central and marginal range of C. pingbianense forest. Notably, the relative abundance of heterotrophy bacteria, such as Variibacter and Acidothermus, in the soil of the C. pingbianense forest was significantly higher than that of the outside range, which may lead to a higher soil organic carbon mineralization rate. These results imply that abundant heterotrophy bacteria were linked to the endemism and full-year shooting in C. pingbianense. Our study is amongst the first cases demonstrating the important role of heterotrophy bacteria in the distribution formation of endemic woody bamboos in special soil habitats, and provides insight into germplasm conservation and forest management in woody bamboos.

K-strategy species plays a pivotal role in the natural attenuation of petroleum hydrocarbon pollution in aquifers

The natural attenuation of petroleum hydrocarbons is inseparable from the action of microorganisms, while the degradation methods and ecological strategies of microorganisms in petroleum-contaminated aquifers are still under debate. In the present study, 16 S rRNA sequencing and quantitative real-time polymerase chain reaction were used to assess the potential microbial degradation of petroleum hydrocarbons, and the ecological strategy of microorganisms under petroleum stress was analyzed through a co-occurrence network. The results showed that the microbial community in sediments exhibit higher efficiency and stability and stronger ecological function than that in groundwater. Keystone species coordinated with the community to execute ecosystem processes and tended to choose a K-strategy to survive, with the aquifer sediment being the main site of petroleum hydrocarbon degradation. Under natural conditions, the presence of petroleum hydrocarbons at concentrations higher than 126 μg kg^-1 and 5557 μg kg^-1 was not conducive to the microbial degradation of polycyclic aromatic hydrocarbons and alkanes, respectively. These results can be used as a reference for an enhanced bioremediation of contaminated groundwater. Overall, these findings provide support to managers for developing environmental management strategies.

Different patterns of belowground fungal diversity along altitudinal gradients with respect to microhabitat and guild types

Fungi are key components of belowground ecosystems with various ecological roles in forests. Although the changes in the richness and composition of belowground fungi across altitudinal gradients have been widely reported, only a few studies have focused on the microhabitat types along altitudinal gradients. Here, we analysed the effect of altitude on the ectomycorrhizal and non-ectomycorrhizal fungal communities in belowground microhabitats. We collected root and soil samples from 16 Pinus densiflora forests at various altitudes across Korea, and measured the soil properties as potential factors. Fungal communities were analysed by high-throughput sequencing of the internal transcribed spacer 2 (ITS2) region. We found that altitude negatively affected the species richness of root-inhabiting fungi but did not influence that of soil-inhabiting fungi. In addition, the composition of ectomycorrhizal (ECM) fungi was less influenced by altitude than non-ECM fungi. Most of the soil properties did not show a significant relationship with altitude, but the effect of soil properties was different across microhabitat types and ecological roles of fungi. Our results reveal that microhabitat types and altitudinal gradients differently affect the richness and composition of fungal communities associated with P. densiflora, providing a better understanding of plant-associated fungal communities.