Patterns Of Soil Microbial Communities Research Articles

Effects of Different Wheat Varieties on Soil Bacterial and Fungal Communities

ABSTRACTThe diversity and stability of soil microbial communities are indispensable components for maintaining the functions and services of agricultural ecosystems and play crucial roles in wheat production. However, the effects of different wheat varieties on soil microbial diversity, network complexity, stability, and assembly mechanisms remain largely unexplored. To bridge this research gap, we conducted field experiments in Chuzhou, China, to study the yield and soil microbial community composition of six different wheat varieties. The soil bacterial and fungal communities were investigated using high‐throughput sequencing of the 16S rRNA and ITS gene regions. Our findings indicated that, compared to common wheat, high‐yielding and disease‐resistant (HD) wheat increased both bacterial and fungal α‐diversity by regulating soil nitrogen and phosphorus concentrations, significantly affecting community structure (Adonis, p < 0.001). HD wheat significantly altered the co‐occurrence network patterns of soil microbial communities. Network analyses revealed that HD wheat increased the complexity of fungal networks while exhibiting the opposite trend for bacterial networks. However, both the bacterial and fungal networks demonstrated increased stability. Furthermore, HD wheat may increase microbial migration rates, influencing assembly processes by promoting stochastic processes in bacterial and fungal communities. Overall, this study provides valuable insights into the ecological functions and driving factors of soil microbes, offering information for the development of ecological management strategies to achieve sustainable wheat cultivation and improve soil quality. Furthermore, HD wheat significantly modified the co‐occurrence network patterns of the soil microbial communities. Network analysis revealed increased fungal network complexity in HD wheat, whereas bacterial networks showed the opposite trend. However, both the bacterial and fungal networks exhibited enhanced stability. Additionally, HD wheat likely increased microbial migration rates, influencing assembly processes by promoting stochastic processes in both bacterial and fungal communities. Overall, this study provides valuable insights into the ecological functions and driving factors of soil microbes, providing information for the development of ecological management strategies to achieve sustainable wheat cultivation and improve soil quality.

Parental material and climate jointly determine the biomass and diversity of soil microbial communities along an elevational gradient on a subtropical karst mountain

AbstractAimClimate is widely understood to determine elevational patterns of soil microbial communities, whereas the effects of parental material are uncertain. Changes in the composition of parental materials along elevational transects could also affect soil microbial communities by influencing soil pH and nutrient availability. Here, we aim to illustrate the combined effects of climate and parental material on the biomass and composition of soil microbial communities along an elevational transect.LocationA subtropical forest on a karst mountain (Mt. Jinfo), China.TaxonBacteria and Fungi.MethodsWe use phospholipid fatty acid analysis (PLFA) and DNA amplicon high‐throughput sequencing to determine biomass and diversity patterns of soil microbial communities along a subtropical elevational gradient with contrasting parental materials (limestone and clasolite).ResultsWe observed that the microbial communities were more diverse (α‐diversity) and productive (biomass) on limestone than on clasolite. Additionally, we found that parental material played a role in shaping the composition (β‐diversity) of soil microbial communities along the elevational gradient. The impact of climate on soil microbial communities was found to be significant, albeit relatively weak. Structural equation models provided evidence for both direct and indirect effects of climate and parental material on microbial biomass and α‐diversity along the elevational gradient. Notably, the changes in soil pH, influenced by both parental material and climate, were identified as a key factor driving these effects.Main ConclusionsOur results underline the importance of both climate and parental material variations in space‐for‐time studies investigating soil microbial communities along elevational gradients.

The assembly process and co-occurrence patterns of soil microbial communities at a lead smelting site

The potential toxic elements of the site are diverse and complex, seriously threatening the land utilization potential and soil ecological function. Microbial community is critical to maintaining ecosystem function, their assembly processes and diversity play an essential role in predicting changes in soil ecological function. However, our understanding of the mechanisms that shape community composition and successional direction in complex polluted environments is very limited. In this study, to explore the mechanisms driving community assembly and symbiosis in different contaminated regional environments, the biological characteristics of bacterial and fungal communities in four different polluted areas of a typical lead smelting site were studied. Contamination by PTEs appears to increase microbial networks, as well as altering microbial community composition, with relative abundance of dominant phyla such as Actinomycetes and Acidobacteria decreasing, whilst Proteobacteria and Ascomycota increased, this indicated that communities may shift from K-strategy to r-strategy and become opportunistic. Dispersal limitation (DL, 42 %–86 %), drift (Dr, 8 %–37 %) and homogeneous selection (HoS, 1 %–31 %) proved to be the important community assembly process. The top ten bins controlling the contribution of different biological processes were identified, and the relative abundance of these bacterial and fungal taxa varied with CPI. Collectively, our results suggest that CPI and nutrient availability regulate soil bacterial and fungal community assembly processes. The results of this study provide potential guidance for community regulation in the process of ecological restoration and mitigating degraded soils at smelting sites.

Regenerated woody plants influence soil microbial communities in a subtropical forest

Forests are critical for supporting multiple ecosystem services such as climate change mitigation. Microbial diversity in soil provides important functions to maintain and regenerate forest ecosystems, and yet a critical knowledge gap remains in identifying the linkage between attributes of regenerated woody plant (RWP) communities and the diversity patterns of soil microbial communities in subtropical plantations. Here, we investigated the changes in soil microbial communities and plant traits in a nine hectare Chinese fir (Cunninghamia lanceolata; CF) plantation to assess how non-planted RWP communities regulate soil bacterial and fungal diversity, and further explore the potential mechanisms that structure their interaction. Our study revealed that soil bacterial richness was positively associated with RWP richness, whereas soil fungal richness was negatively associated with RWP basal area. Meanwhile, RWP richness was positively correlated with ectomycorrhizal (ECM) fungal richness but negatively correlated with the richness of both pathogenic and saprotrophic fungi, suggesting that the RWP-fungal richness relationship was trophic guild-specific. Soil microbial community beta diversity (i.e., dissimilarity in community composition) was strongly coupled with both RWP beta diversity and the heterogeneity of RWP basal area. Our study highlights the importance of community-level RWP plant attributes for the regulation of microbial biodiversity in plantation systems, which should be considered in forest management programs in the future.

Specialist species of fungi and bacteria are more important than the intermediate and generalist species in near-urban agricultural soils

Near-urban farmland is an important component of agricultural soils in China. Understanding the distribution and functional patterns of soil microbial communities is essential for accurate fertilization and disease control in this area. By considering the generalists, intermediates, and specialists of soil microbiota, we studied the soil microbial community assembly process and functional transformations characteristics in near-urban farmlands. We found that the intermediate group has the highest relative abundance with 66.24 % and 50.33 % for fungi and bacteria, respectively. A steeper geographic distance decay relationship (DDR) was found for the specialist bacteria than the generalist and intermediate taxa in the near-urban farmlands. However, the generalist species of fungi showed a steeper DDR than the intermediate and specialist. Both bacterial and fungal generalists have the widest niche, followed by the intermediate and specialists, respectively. The null model indicated that the deterministic processes dominate the community assembly process for bacteria (56%) and fungi (54 %). Variation partitioning analysis (VPA) showed that both the specialists and intermediate groups were more susceptible to geospatial distance than the generalists. Soil water content, C and N nutrients were the main factors driving the changes in the community structure of dominant generalist, intermediate and specialist species. The main functional groups of the generalists and specialist bacteria were chemoheterotrophy. Moreover, specialist bacteria have much more functions related to nitrogen transformation and organic matter degradation than generalist species. For fungi, the specialist species mainly are responsible for saprophytic, pathotrophic_saprotrophic and symbiotrophic nutritional types. Interestingly, the specialist fungi also consisted of a higher number of saprophytic, pathotrophic and symbiotic trophic functions. Thus, fungal and bacterial specialist species, rather than the intermediate or generalist groups support the soil microbial ecosystem functions in the near-urban farmland.

The neglected role of micronutrients in predicting soil microbial structure

Predicting the distribution patterns of soil microbial communities requires consideration of more environmental drivers. The effects of soil micronutrients on composition of microbial communities are largely unknown despite micronutrients closely relating to soil fertility and plant communities. Here we used data from 228 agricultural fields to identify the importance of micronutrients (iron, zinc, copper and manganese) in shaping structure of soil microbial communities (bacteria, fungi and protist) along latitudinal gradient over 3400 km, across diverse edaphic conditions and climatic gradients. We found that micronutrients explained more variations in the structure of microbial communities than macronutrients in maize soils. Moreover, micronutrients, particularly iron and copper, explained a unique percentage of the variation in structure of microbial communities in maize soils even after controlling for climate, soil physicochemical properties and macronutrients, but these effects were stronger for fungi and protist than for bacteria. The ability of micronutrients to predict the structure of soil microbial communities declined greatly in paddy soils. Machine learning approach showed that the addition of micronutrients substantially increased the predictive power by 9–17% in predicting the structure of soil microbial communities with up to 69–78% accuracy. These results highlighted the considerable contributions of soil micronutrients to microbial community structure, and advocated that soil micronutrients should be considered when predicting the structure of microbial communities in a changing world.

Diversity and Distribution Characteristics of Soil Microbes across Forest-Peatland Ecotones in the Permafrost Regions.

Permafrost peatlands are a huge carbon pool that is uniquely sensitive to global warming. However, despite the importance of peatlands in global carbon sequestration and biogeochemical cycles, few studies have characterized the distribution characteristics and drivers of soil microbial community structure in forest-peatland ecotones. Here, we investigated the vertical distribution patterns of soil microbial communities in three typical peatlands along an environmental gradient using Illumina high-throughput sequencing. Our findings indicated that bacterial richness and diversity decreased with increasing soil depth in coniferous swamp (LT) and thicket swamp (HT), whereas the opposite trend was observed in a tussock swamp (NT). Additionally, these parameters decreased at 0-20 and 20-40 cm and increased at 40-60 cm along the environmental gradient (LT to NT). Principal coordinate analysis (PCoA) indicated that the soil microbial community structure was more significantly affected by peatland type than soil depth. Actinomycetota, Proteobacteria, Firmicutes, Chloroflexota, Acidobacteriota, and Bacteroidota were the predominant bacterial phyla across all soil samples. Moreover, there were no significant differences in the functional pathways between the three peatlands at each depth, except for amino acid metabolism, membrane transport, cell motility, and signal transduction. Redundancy analysis (RDA) revealed that pH and soil water content were the primary environmental factors influencing the bacterial community structure. Therefore, this study is crucial to accurately forecast potential changes in peatland ecosystems and improve our understanding of the role of peat microbes as carbon pumps in the process of permafrost degradation.

Soil fungal communities show more specificity than bacteria for plant species composition in a temperate forest in China

BackgroundSoil microbiome is an important part of the forest ecosystem and participates in forest ecological restoration and reconstruction. Niche differentiation with respect to resources is a prominent hypothesis to account for the maintenance of species diversity in forest ecosystems. Resource-based niche differentiation has driven ecological specialization. Plants influence soil microbial diversity and distribution by affecting the soil environment. However, with the change in plant population type, whether the distribution of soil microbes is random or follows an ecologically specialized manner remains to be further studied. We characterized the soil microbiome (bacteria and fungi) in different plant populations to assess the effects of phytophysiognomy on the distribution patterns of soil microbial communities in a temperate forest in China.ResultsOur results showed that the distribution of most soil microbes in different types of plant populations is not random but specialized in these temperate forests. The distribution patterns of bacteria and fungi were related to the composition of plant communities. Fungal species (32%) showed higher specialization than bacterial species (15%) for different types of plant populations. Light was the main driving factor of the fungal community, and soil physicochemical factors were the main driving factor of the bacterial community.ConclusionThese findings suggest that ecological specialization is important in maintaining local diversity in soil microbial communities in this forest. Fungi are more specialized than bacteria in the face of changes in plant population types. Changes in plant community composition could have important effects on soil microbial communities by potentially influencing the stability and stress resistance of forest ecosystems.

Heterogeneity and its drivers of microbial communities and diversity in six typical soils under two different land uses in tropical and subtropical southern China

Soil microenvironment is a combination of climate, biological matter, and earth parent material, which has unique characteristics and is considered to have distinctive microbial resources. In this study, we collected soil samples from farmland and woodland of six soil types in southern China to explore the soil microbial structure and functional characteristics of different soil types and land use via a high-throughput sequencing technology. The soil microbial composition was greatly affected by soil types (Adonis, P < 0,001) and land-use types (Adonis, P < 0,01). Furthermore, the network analysis indicated the different interaction patterns of soil microbial communities in different soil types. The keystone taxa identified by the network analysis were highly correlated soil N, S, and P-cycle, and soil microbial correlation may link to activation of soil functional profile. Edaphic variables such as soil pH and total phosphorus (TP) had contrasting effects on microbial diversity. The results further highlighted the importance of the niche-based habitat and function-oriented control on the structure of six typical soil microbial communities under two different land uses in southern China.

Vertical and temporal variations of soil bacterial and archaeal communities in wheat-soybean rotation agroecosystem.

Soil microbes are an essential component of terrestrial ecosystems and drive many biogeochemical processes throughout the soil profile. Prior field studies mainly focused on the vertical patterns of soil microbial communities, meaning their temporal dynamics have been largely neglected. In the present study, we investigated the vertical and temporal patterns of soil bacterial and archaeal communities in a wheat-soybean rotation agroecosystem at a depth of millions of sequences per sample. Our results revealed different vertical bacterial and archaeal richness patterns: bacterial richness was lowest in the deep soil layer and peaked in the surface or middle soil layer. In contrast, archaeal richness did not differ among soil layers. PERMANOVA analysis indicated that both bacterial and archaeal community compositions were significantly impacted by soil depth but unaffected by sampling time. Notably, the proportion of rare bacteria gradually decreased along with the soil profile. The rare bacterial community composition was the most important indicator for soil nutrient fertility index, as determined by random forest analysis. The soil prokaryotic co-occurrence networks of the surface and middle soil layers are more connected and harbored fewer negative links than that of the deep soil layer. Overall, our results highlighted soil depth as a more important determinant than temporal variation in shaping the soil prokaryotic community and interspecific interactions and revealed a potential role of rare taxa in soil biogeochemical function.

Spatial patterns of soil microbial communities and implications for precision soil management at the field scale

Spatial patterns of soil microbial communities and implications for precision soil management at the field scale

Variations in soil microbial communities in the sedge-dominated peatlands along an altitude gradient on the northern slope of Changbai Mountain, China

The mechanisms that shape soil microbes in peatlands along the altitude gradient remain unresolved due to limited data and inconsistent findings along different vertical vegetation belts from investigations. In this study, we present results of soil phospholipid fatty acids (PLFAs) profiles from an altitude gradient survey (300–1500 m) in Changbai Mountain aimed at determining the elevational patterns of soil microbial communities and their driving forces in the sedge-dominated peatlands. The results showed that the total microbial lipid biomass in the sedge-dominated peatlands increased with altitude. However, there were no obvious trends with altitude in ratios of the fungi to bacteria (F/B), the Gram positive bacteria to Gram negative bacteria (G+/G-), and the bacteria to actinomycetes (B/ACT). Redundancy analysis indicated that the dissolved organic carbon (DOC) explained most variation in soil microbial groups, while mean annual temperature (MAT) explained most variation in microbial community structure. Variation partitioning analysis revealed that climatic factors had greater influences on soil microbial community structure than soil physical and chemical properties, and 53% of the total variance was explained by MAT, mean annual precipitation (MAP) and their combined effects. This finding challenges the prevailing view that local soil properties, but not climate, control soil microbial community structure along the altitude gradient, and enhances our understanding of the role of soil microbes as carbon pumps in sedge-dominated peatlands in the process of global warming.

Assessing soil microbial biodiversity as affected by grazing and woody vegetation cover in a temperate savannah

AbstractAlthough it is well established that land use and management affects soil microbial biodiversity, with consequences for soil‐mediated ecosystem services, knowledge on human‐induced variability in soil bacterial and fungal communities is more abundant for cropping than for livestock systems. In particular, grazing management affects vegetation cover and light availability to lower vegetation layers, particularly in wooded grazing ecosystems. Our objective was to evaluate the use of T‐RFLP analysis to characterise soil microbial community patterns. We worked in a grazed temperate savannah in Entre Ríos (Argentina) and focused on two farms with different grazing management, resulting in different vegetation cover. At each farm, we sampled soils from four conditions forming a two shrub cover conditions (open and close) by two light availability conditions (high and low) factorial set with three replicates. T‐RFLP data for bacteria and fungi were used to characterise biodiversity patterns (diversity indexes, relative abundance of operational taxonomic units and community structure). Analyses were performed, between and within farms, using nonmetric multidimensional scaling analysis, non‐parametric multivariate analysis of variance and network analysis. Variation patterns of soil microbial communities were detected using T‐RFLP analysis in savannah soils from these two livestock farms. Farm, light and shrub conditions were statistically significant factors shaping variation patterns. For bacterial communities, light availability and shrub cover affected biodiversity and community structure respectively, but this impact was detected only for the farm with lower grazing intensity. For fungal communities, light availability was the factor shaping community structure, also with slightly higher impact on the farm with lower grazing intensity. These results suggest that in temperate woodlands lower grazing intensity, associated with higher vegetation cover, increases bacterial biodiversity while it decreases fungal community structure. Soil bacterial and fungal communities, showed contrasting patterns, and appear as sensitive indicators to monitor grazing management effects. We showed that T‐RFLP analysis is a cost‐effective methodology (compared to Illumina sequencing) that would be useful to disentangle impact of grazing intensity and vegetation cover in grazed temperate savannah.

Differences in microbial communities from Quaternary volcanic soils at different stages of development: Evidence from Late Pleistocene and Holocene volcanoes

Volcanic eruptions are a universal cause of ecological and geological disturbance; however, the differences in microbial communities from Quaternary volcanic soils at different stages of development in Inner Mongolia are little known. Microbial communities were investigated in Quaternary volcanic soils from Late Pleistocene volcano and Holocene volcano with the objective of elucidating their differences. The composition and potential functionality of soil microbial communities was significantly diverse between Late Pleistocene volcanic soils and Holocene volcanic soils. Although the richness, diversity and evenness of microbial communities at older volcanic soils were significantly greater than at younger volcanic soils, younger volcanic soils possessed a more complex microbial community network than older volcanic soils. The soil bacterial community was more sensitive to Quaternary volcanic soils than the fungal community, exhibiting significant differences at the phylum level and possessing more biomarkers. Quaternary volcanic soils may have enriched some specific microorganisms, i.e., biomarkers and generalists, closely related to the metabolism of soil carbon, nitrogen and phosphorus. Quaternary volcanic soils first directly mediated soil carbon, nitrogen and phosphorus, and then guided microbial multifunctionality. These results clarify the difference patterns of soil microbial communities in support of better ecological management of volcanic area in Inner Mongolia.

Soil depth matters: shift in composition and inter-kingdom co-occurrence patterns of microorganisms in forest soils.

ABSTRACTSoil depth represents a strong physiochemical gradient that greatly affects soil-dwelling microorganisms. Fungal communities are typically structured by soil depth, but how other microorganisms are structured is less known. Here, we tested whether depth-dependent variation in soil chemistry affects the distribution and co-occurrence patterns of soil microbial communities. This was investigated by DNA metabarcoding in conjunction with network analyses of bacteria, fungi, as well as other micro-eukaryotes, sampled in four different soil depths in Norwegian birch forests. Strong compositional turnover in microbial assemblages with soil depth was detected for all organismal groups. Significantly greater microbial diversity and fungal biomass appeared in the nutrient-rich organic layer, with sharp decrease towards the less nutrient-rich mineral zones. The proportions of copiotrophic bacteria, Arthropoda and Apicomplexa were markedly higher in the organic layer, while patterns were opposite for oligotrophic bacteria, Cercozoa, Ascomycota and ectomycorrhizal fungi. Network analyses indicated more intensive inter-kingdom co-occurrence patterns in the upper mineral layer (0–5 cm) compared to the above organic and the lower mineral soil, signifying substantial influence of soil depth on biotic interactions. This study supports the view that different microbial groups are adapted to different forest soil strata, with varying level of interactions along the depth gradient.

Diversity patterns of soil microbial communities in the Sophora flavescens rhizosphere in response to continuous monocropping

BackgroundContinuous monocropping can affect the physicochemical and biological characteristics of cultivated soil. Sophora flavescens is a valuable herbal medicine and sensitive to continuous monocropping. Currently, diversity patterns of soil microbial communities in soil continuous monocropping with S. flavescens have not been extensively elucidated.ResultsIn this study, comparative 16S rDNA and internal transcribed spacer (ITS) MiSeq sequencing analyses were used to examine the taxonomic community structure and microbial diversity in nonrhizosphere soil (CK) and rhizosphere soils (SCC, TCC, and FCC) sampled from fields that had undergone two, three, and five years of continuous monocropping, respectively. Among the microbial communities, a decreased abundance of Acidobacteria and increased abundances of Proteobacteria and Bacteroidetes were found with the increase in monocropping years of S. flavescens. As the continuous monocropping time increased, the diversity of the bacterial community decreased, but that of fungi increased. Redundancy analysis also showed that among the properties of the rhizosphere soil, the available phosphorus, organic matter, total nitrogen, and sucrase had the greatest impacts on the diversity of the rhizosphere microbial community. Moreover, a biomarker for S. flavescens soil was also identified using the most differentially abundant bacteria and fungi in soil samples.ConclusionsOur study indicates that long-term monocropping exerted great impacts on microbial community distributions and soil physicochemical properties. The relationship between microbial community and physicochemical properties of rhizosphere soil would help clarify the side effects of continuous S. flavescens monocropping. Our study may aid in uncovering the theoretical basis underlying obstacles to continuous monocropping and provide better guidance for crop production.

Phylogenetic Structure of Soil Bacterial Communities along Age Sequence of Subtropical Cunninghamia Lanceolata Plantations

Despite increasing investigations having studied the changing patterns of soil microbial communities along forest plantation development age sequences, the underlying phylogenetic assemblages are seldom studied for microbial community. Here, the soil bacterial taxonomic and phylogenetic diversity as well as the phylogenetic structure were examined to elucidate the community diversity and assembly in three typical ages (young, middle and mature) of Cunninghamia lanceolata plantations, a dominant economic tree species in southern China. Results indicated that the soil bacterial phylogenetic not taxonomic diversity increased with the increasing in stand age. The bacterial community composition differed significantly among the young, middle and mature plantations. Phylogenetic signals showed that bacterial communities were phylogenetically clustered and structured by environmental filtering in all studied plantations. In mature plantation, the effect of environmental filtering becomes stronger and bacteria taxa tend to intraspecific interact more complexly as characterized by co-occurrence network analysis. This suggests that ecological niche-based environmental filtering could be a dominant assembly process that structured the soil bacterial community along age sequences of Cunninghamia lanceolata plantations.

Soil microbial communities in alpine grasslands on the Tibet Plateau and their influencing factors

As an indicator and regulator of climate and environmental change, the Tibet Plateau is an important barrier for ecological security. However, despite the importance of soil microbial communities in almost all soil biochemical processes and ecosystem functions, the biogeography of soil microbial communities on the Tibet Plateau is poorly understood, especially at large scales over different ecosystem types. In this study, we collected samples from 64 sampling sites representing different grassland ecosystem types and spanning 2121 km across on the Tibet Plateau. We then used next generation high-throughput sequencing to investigate the soil prokaryote community (i.e. bacteria and archaea) diversity and spatial patterns and to explore their relationship with biotic (e.g. plant functional group diversity and biomass) and abiotic (e.g. aridity index, soil carbon and nitrogen levels) factors. Among the four alpine grassland types (i.e. alpine meadow, alpine steppe, alpine shrub and alpine desert) sampled in this study, alpine meadow had the highest soil microbial biomass and alpine desert had the lowest soil microbial richness and Shannon diversity. The soil microbial diversity in the alpine grassland correlated with plant diversity and climate factors. Soil microbial diversity negatively correlated with the annual average air temperature, but was not correlated with the annual average precipitation, indicating that temperature, rather than precipitation, may be more important in controlling the soil microbial diversity in alpine grassland ecosystems at cold temperatures. Higher air temperature likely led to an intensified aridity under limited precipitation, and thus decreased microbial diversity. As a result, the aridity index combined with temperature and precipitation explained more of the variance in the soil microbial diversity than air temperature or precipitation did individually. Moreover, after separating plant species into four functional groups (grass, forb, legume and sedge), microbial diversity positively correlated with plant functional group diversity, explaining more of the variance in microbial diversity than plant species diversity did. Results of structural equation modeling revealed that the aridity index and annual air temperature affected soil microbial diversity, directly or indirectly, through influencing plant functional group diversity and aboveground biomass; while aboveground biomass changed the soil carbon to nitrogen ratio in the upper soil layers and thus impacted soil microbial diversity. However, in contrast to microbial diversity, soil microbial biomass carbon was not correlated with plant functional group diversity, plant species diversity, or the climate factors annual average air temperature, annual precipitation and aridity index, but were linked to soil nutrient status (e.g. soil dissolved organic carbon, ammonia, available phosphorus, and carbon to nitrogen ratio) and plant biomass of sedges and forbs, demonstrating that microbial biomass and diversity were likely controlled by different factors. In summary, this study investigated the spatial patterns of soil microbial communities across different alpine grassland ecosystem types on the Tibet Plateau and enhanced our understanding of biotic and abiotic factors controlling microbial biomass and diversity, which will be important in predicting microbial changes on the Tibet Plateau under future climate change. Under future warming and wetting scenarios on the Tibet Plateau, it is possible that the aridity index would decrease, leading to increased soil microbial diversity. Results of this study also suggest a focus on the aridity index and plant functional group diversity in future microbial biogeography studies in order to further determine their roles in controlling or mediating soil microbial biomass and diversity.

Large-scale distribution of bacterial communities in the Qaidam Basin of the Qinghai-Tibet Plateau.

Many studies have investigated patterns of soil microbial communities over large spatial scales. However, these studies mainly focused on a few sites. Here, we studied the near‐surface (0–30 cm) soil microbial communities of 35 soil samples collected from most of the areas of the Qaidam Basin, which is the largest basin on the Qinghai–Tibet Plateau. A total of 32 phyla and 838 genera were detected from all the samples, in which Actinobacteria, Proteobacteria, Bacteroidetes, and Acidobacteria were the most dominant and cosmopolitan phyla. The most abundant phyla (relative abundance > 5%) detected in all 35 soil samples were also the most dominant, which could be explained by their great dispersal ability. The microbial community structures correlated strongly with variations in pH and Mg2+ and were distinct between the high Mg2+ content (>20 g/kg) samples and other samples (Acidobacteria, Actinobacteria, and Chloroflexi were significantly less abundant in the high Mg2+ content group, but the abundance of Firmicutes was significantly greater). Finally, the microbial spatial pattern was influenced by both the local environment and spatial distance, but environmental factors were the primary drivers of microbial spatial patterns in the Qaidam Basin.

Elevational Distribution Characteristics of Soil Bacterial Community and Enzyme Activities in Mount Huangshan

Mount Huangshan has a well-preserved ecosystem and obvious differences in vertical geography, which provide a natural laboratory for studying the altitudinal distribution patterns of soil microbial communities in a mid-subtropical forest ecosystem. The soil bacterial community structure and diversity of the samples collected every 100 m from 670 to 1870 m on the south slope of Mount Huangshan were examined using Illumina MiSeq high-throughput sequencing technology. The soil physicochemical properties and soil enzyme activities of the samples were also measured to explore the relationship between bacterial communities and soil properties as well as enzyme activities. The results showed that ① The contents of soil total nitrogen, available nitrogen, total potassium, and total organic carbon were significantly different across the altitudes (P<0.01) and generally increased as altitude increased. The soil sucrase activities across altitudes were significantly different (P<0.01), and generally increased as altitude increased. However, there was no significant difference in acid phosphatase and urease activities between different altitudes (P>0.05). ② The 12 elevational gradients were divided into three groups:low altitude (670-875 m), medium altitude (1080-1370 m), and high altitude (1460-1780 m). The OTUs in low altitude sites were greater than in high altitude sites but lower compared to medium altitude sites. However, the differences in OTUs across altitude sites were not significant. ③ The soil bacterial community diversity showed a unimodal pattern in a small range of altitudes from 875-1370 m, although no apparent trend was observed at the altitudes from 670-1780 m. ④ There were 7 dominant phyla and 15 dominant orders with a relative abundance of more than 3% in all soil samples. ⑤ Correlation heat map analysis between the top 15 bacterial phyla and soil physicochemical properties as well as enzyme activities showed that soil pH had the greatest effect on the differences in soil bacterial community structure across the different altitudes. Pearson correlation analysis and Partial Mantel test also showed that bacterial community α-diversity (P<0.01) and β-diversity (Partial Mantel r=0.560, P=0.001) were mainly affected by soil pH. Consequently, soil pH was the key environmental factor determining the soil bacterial community structure and diversity across the different altitudes on Mount Huangshan.