Soil microbial distribution and assembly are related to vegetation biomass in the alpine permafrost regions of the Qinghai-Tibet Plateau

Biodiversity in mountain soils above the treeline

Biological diversity in mountain ecosystems has been increasingly studied over the last decade. This is also the case for mountain soils, but no study to date has provided an overall synthesis of the current state of knowledge. Here we fill this gap with a first global analysis of published research on cryptogams, microorganisms, and fauna in mountain soils above the treeline, and a structured synthesis of current knowledge. Based on a corpus of almost 1400 publications and the expertise of 37 mountain soil scientists worldwide, we summarise what is known about the diversity and distribution patterns of each of these organismal groups, specifically along elevation, and provide an overview of available knowledge on the drivers explaining these patterns and their changes. In particular, we document an elevation-dependent decrease in faunal diversity above the treeline, while for cryptogams there is an initial increase above the treeline, followed by a decrease towards the nival belt. Thus, our data confirm the key role that elevation plays in shaping the biodiversity and distribution of these organisms in mountain soils. The response of prokaryote diversity to elevation, in turn, was more diverse, whereas fungal diversity appeared to be substantially influenced by plants. As far as available, we describe key characteristics, adaptations, and functions of mountain soil species, and despite a lack of ecological information about the uncultivated majority of prokaryotes, fungi, and protists, we illustrate the remarkable and unique diversity of life forms and life histories encountered in alpine mountain soils. By applying rule- as well as pattern-based literature-mining approaches and semi-quantitative analyses, we identified hotspots of mountain soil research in the European Alps and Central Asia and revealed significant gaps in taxonomic coverage, particularly among biocrusts, soil protists, and soil fauna. We further report thematic priorities for research on mountain soil biodiversity above the treeline and identify unanswered research questions. Building upon the outcomes of this synthesis, we conclude with a set of research opportunities for mountain soil biodiversity research worldwide. Soils in mountain ecosystems above the treeline fulfil critical functions and make essential contributions to life on land. Accordingly, seizing these opportunities and closing knowledge gaps appears crucial to enable science-based decision making in mountain regions and formulating laws and guidelines in support of mountain soil biodiversity conservation targets.

Exploring prokaryotic diversity in permafrost-affected soils of Ladakh's Changthang region and its geochemical drivers

Global warming due to climate change has substantial impact on high-altitude permafrost affected soils. This raises a serious concern that the microbial degradation of sequestered carbon can result in alteration of the biogeochemical cycles. Therefore, the characterization of permafrost affected soil microbiomes, especially of unexplored high-altitude, low oxygen arid region, is important for predicting their response to climate change. This study presents the first report of the bacterial diversity of permafrost-affected soils in the Changthang region of Ladakh. The relationship between soil pH, organic carbon, electrical conductivity, and available micronutrients with the microbial diversity was investigated. Amplicon sequencing of permafrost affected soil samples from Jukti and Tsokar showed that Proteobacteria and Actinobacteria were the dominant phyla in all samples. The genera Brevitalea, Chthoniobacter, Sphingomonas, Hydrogenispora, Clostridium, Gaiella, Gemmatimonas were relatively abundant in the Jukti samples whereas the genera Thiocapsa, Actinotalea, Syntrophotalea, Antracticibcterium, Luteolibacter, Nitrospirillum dominated the Tsokar sample. Correlation analyses highlighted the influence of soil geochemical parameters on the bacterial community structure. PCoA analyses showed that the bacterial beta diversity varied significantly between the sampling locations (PERMANOVA test (F-value: 2.3316; R2 = 0.466, p = 0.001) and similar results were also obtained while comparing genus abundance data using the ANOSIM test (R = 0.345, p = 0.007).

Spartina alterniflora Ecosystem Stability: Insights Into the Interplay Between Soil Bacteria and Their Functional Traits

The relationship between soil microbiome stability and diversity remains a topic of debate. Our study aims to investigate the relationship between soil microbiome stability and diversity in different wetland types invaded by Spartina alterniflora and to reveal the mechanisms driving functional influences on this relationship during the later-stage development of the S. alterniflora invasion system. To investigated the structure, diversity, and functional traits of soil bacteria associated with S. alterniflora and their impact on bacteriome stability we conducted 16S rRNA sequencing of soils from two types of wetlands dominated by the invasive plant S. alterniflora at different growth stages, situated in temperate (salt marsh wetland) and subtropical (mangrove wetland) regions, and assessed bacteriome stability and its driving factors. Subsequently, we analyzed environmental and bacterial changes between the two sites and constructed co-occurrence networks among taxonomic groups and functional traits. The differences in the late-stage development of the two S. alterniflora-invaded wetland systems suggest that bacterial communities with higher diversity tend to exhibit greater stability. Keystone genera play both direct and indirect roles in regulating bacteriome stability, and all belong to dominant phyla. Furthermore, biological factors significantly outweigh nonbiological factors in driving stability. In contrast, core functions (broad functions) and specialized functions such as "nitrogen metabolism" and "sulfur metabolism" decrease bacteriome stability. Their enhancement of these metabolic processes correlates with reduced community stability, which is the key to the differences observed in the two invaded systems. This study advances our understanding of the relationship between soil microbial diversity and ecosystem stability, highlighting the importance of keystone taxa and functional traits for soil microbiome stability. It enhances our ability to predict microbial community transitions. It enhances a scientific basis for the management of S. alterniflora invasion.

Roles of the soil microbiome in sustaining grassland ecosystem health on the Qinghai-Tibet Plateau

Soil microbes, as intermediaries in plant-soil interactions, are closely linked to plant health in grassland ecosystems. In recent years, varying degrees of degradation have been observed in the alpine grasslands of the Qinghai-Tibet Plateau (QTP). Addressing grassland degradation, particularly under the influence of climate change, poses a global challenge. Understanding the factors driving grassland degradation on the QTP and developing appropriate mitigation measures is essential for the future sustainability of this fragile ecosystem. In this review, we discuss the environmental and anthropogenic factors affecting grassland degradation and the corresponding impacts on soil microbe community structure. We summarize the current research on the microbiome of the QTP, in particular the effect of vegetation, climate change, grazing, and land use, respectively on the alpine grassland microbiome. The results of these studies indicate that microbially mediated soil bioprocesses are important drivers of grassland ecosystem functional recovery. Therefore, a thorough understanding of the spatial distribution characteristics of the soil microbiome in alpine grasslands is required, and this necessitates an integrated approach in which the interactions among climatic factors, vegetation characteristics, and human activities are evaluated. Additionally, we assess and summarise current technological developments and prospects for applying soil microbiome technologies in sustainable agriculture, including: (i) single-strain inoculation, and (ii) inoculation of synthetic microbial communities, (iii) microbial community transplantation. Grassland restoration projects should be carried out with the understanding that each restoration measure has a unique effect on the soil microbial activity. We propose that the sustainable development of alpine grassland ecosystems can be achieved by adopting advanced microbiome technologies and integrating microbe-based sustainable agricultural practices to maximise grassland biomass, increase soil carbon, and optimise soil nutrient cycling.

The Three-Dimensional Structure of the Genome of the Dark Septate Endophyte Exophiala tremulae and Its Symbiosis Effect on Alpine Meadow Plant Growth

The establishment of artificial grassland is a good pathway for resolving serious social and economic problems in the Qinghai-Tibet Plateau. Some beneficial indigenous microbes may be used to improve productivity in artificial grassland. The genome of the indigenous dark septate fungus, Exophiala tremulae CICC2537, was sequenced and assembled at the chromosome level using the PacBio sequencing platform, with the assistance of the Hi-C technique for scaffolding, and its 3D genome structures were investigated. The genome size of E. tremulae is 51.903848 Mb, and it contains eight chromosomes. A total of 12,277 protein-coding genes were predicted, and 11,932 genes (97.19%) were annotated. As for the distribution of exon and intron number and the distribution of gene GC and CDS GC, E. tremulae showed similar distribution patterns to the other investigated members of the genus Exophiala. The analysis of carbohydrate-active enzymes showed that E. tremulae possesses the greatest number of enzymes with auxiliary activities and the lowest number of enzymes with carbohydrate-binding modules among the investigated fungi. The total number of candidate effector proteins was 3337, out of which cytoplasmic and apoplastic effector proteins made up 3100 and 163, respectively. The whole genome of E. tremulae contained 40 compartment As and 76 compartment Bs, and there was no significant difference in GC content in its compartment As and Bs. The whole genome of E. tremulae was predicted to contain 155 topologically associating domains (TADs), and their average length was 250,000 bp, but there were no significant differences in the numbers of genes and the GC content per bin localized within the boundaries and interiors of TADs. Comparative genome analysis showed that E. tremulae diverged from Exophiala mesophila about 34.1 (30.0-39.1) Myr ago, and from Exophiala calicioides about 85.6 (76.1-90.6) Myr ago. Compared with all the investigated fungi, the numbers of contraction and expansion gene families in the E. tremulae genome were 13 and 89, respectively, and the numbers of contraction and expansion genes were 14 and 670, respectively. Our work provides a basis for the use of the dark septate fungus in alpine artificial grassland and further research into its symbiosis mechanisms, which may improve the growth of plant species used in the Qinghai-Tibet Plateau.

Diversity, functionality, and stability: shaping ecosystem multifunctionality in the successional sequences of alpine meadows and alpine steppes on the Qinghai-Tibet Plateau

Recent investigations on the Tibetan Plateau have harnessed advancements in digital ground vegetation surveys, high temporal resolution remote sensing data, and sophisticated cloud computing technologies to delineate successional dynamics between alpine meadows and alpine steppes. However, these efforts have not thoroughly explored how different successional stages affect key ecological parameters, such as species and functional diversity, stability, and ecosystem multifunctionality, which are fundamental to ecosystem resilience and adaptability. Given this gap, we systematically investigate variations in vegetation diversity, functional diversity, and the often-overlooked dimension of community stability across the successional gradient from alpine meadows to alpine steppes. We further identify the primary environmental drivers of these changes and evaluate their collective impact on ecosystem multifunctionality. Our analysis reveals that, as vegetation communities progress from alpine meadows toward alpine steppes, multi-year average precipitation and temperature decline significantly, accompanied by reductions in soil nutrients. These environmental shifts led to decreased species diversity, driven by lower precipitation and reduced soil nitrate-nitrogen levels, as well as community differentiation influenced by declining soil pH and precipitation. Consequently, as species loss and community differentiation intensified, these changes diminished functional diversity and eroded community resilience and resistance, ultimately reducing grassland ecosystem multifunctionality. Using linear mixed-effects model and structural equation modeling, we found that functional diversity is the foremost determinant of ecosystem multifunctionality, followed by species diversity. Surprisingly, community stability also significantly influences ecosystem multifunctionality-a factor rarely highlighted in previous studies. These findings deepen our understanding of the interplay among diversity, functionality, stability, and ecosystem multifunctionality, and support the development of an integrated feedback model linking environmental drivers with ecological attributes in alpine grassland ecosystems.

Distinct influences of altitude on microbiome and antibiotic resistome assembly in a glacial river ecosystem of Mount Everest

The profound influences of altitude on aquatic microbiome were well documented. However, differences in the responses of different life domains (bacteria, microeukaryotes, viruses) and antibiotics resistance genes (ARGs) in glacier river ecosystems to altitude remain unknown. Here, we employed shotgun metagenomic and amplicon sequencing to characterize the altitudinal variations of microbiome and ARGs in the Rongbu River, Mount Everest. Our results indicated the relative influences of stochastic processes on microbiome and ARGs assembly in water and sediment were in the following order: microeukaryotes < ARGs < viruses < bacteria. Moreover, distinct assembly patterns of the microbiome and ARGs were found in response to differences in altitude, the latter of which shift from deterministic to stochastic processes with increasing differences in altitude. Partial least squares path modeling revealed that mobile genetic elements (MGEs) and viral β-diversity were the major factors influencing the ARG abundances. Taken together, our work revealed that altitude-caused environmental changes led to significant changes in the composition and assembly processes of the microbiome and ARGs, while ARGs had a unique response pattern to altitude. Our findings provide novel insights into the impacts of altitude on the biogeographic distribution of microbiome and ARGs, and the associated driving forces in glacier river ecosystems.

Elevational distribution patterns and drivers factors of fungal community diversity at different soil depths in the Abies georgei var. smithii forests on Sygera Mountains, southeastern Tibet, China

Introduction

Soil fungal communities play a crucial role in maintaining the ecological functions of alpine forest soil ecosystems. However, it is currently unclear how the distribution patterns of fungal communities in different soil layers of alpine forests will change along the elevational gradients.

Material and methods

Therefore, Illumina MiSeq sequencing technology was employed to investigate fungal communities in three soil layers (0-10, 10-20, and 20-30 cm) along an elevational gradient (3500 m to 4300 m) at Sygera Mountains, located in Bayi District, Nyingchi City, Tibet.

Results and discussion

The results indicated that: 1) Soil depth had a greater impact on fungal diversity than elevation, demonstrating a significant reduction in fungal diversity with increased soil depth but showing no significant difference with elevation changes in all soil layers. Within the 0-10 cm soil layer, both Basidiomycota and Ascomycota co-dominate the microbial community. However, as the soil depth increases to 10-20 and 20-30 cm soil layers, the Basidiomycota predominantly dominates. 2) Deterministic processes were dominant in the assembly mechanism of the 0-10 cm fungal community and remained unchanged with increasing elevation. By contrast, the assembly mechanisms of the 10-20 and 20-30 cm fungal communities shifted from deterministic to stochastic processes as elevation increased. 3) The network complexity of the 0-10 cm fungal community gradually increased with elevation, while that of the 10-20 and 20-30 cm fungal communities exhibited a decreasing trend. Compared to the 0-10 cm soil layer, more changes in the relative abundance of fungal biomarkers occurred in the 10-20 and 20-30 cm soil layers, indicating that the fungal communities at these depths are more sensitive to climate changes. Among the key factors driving these alterations, soil temperature and moisture soil water content stood out as pivotal in shaping the assembly mechanisms and network complexity of fungal communities. This study contributes to the understanding of soil fungal community patterns and drivers along elevational gradients in alpine ecosystems and provides important scientific evidence for predicting the functional responses of soil microbial ecosystems in alpine forests.

Drought-induced assembly of rhizosphere mycobiomes shows beneficial effects on plant growth

Beneficial interactions between plants and rhizosphere fungi can enhance plant adaptability during drought stress. However, harnessing these interactions will require an in-depth understanding of the response of fungal community assembly to drought. Herein, by using different varieties of wheat plants, we analyzed the drought-induced changes in fungal community assembly in rhizosphere and bulk soil. We demonstrated that drought significantly altered the fungal communities, with the contribution of species richness to community beta diversity increased in both rhizosphere and bulk soil compartments during drought stress. The stochastic processes dominated fungal community assembly, but the relative importance of deterministic processes, mainly homogeneous selection, increased in the drought-stressed rhizosphere. Drought induced an increase in the relative abundance of generalists in the rhizosphere, as opposed to specialists, and the top 10 abundant taxa that enriched under drought conditions were predominantly generalists. Notably, the most abundant drought-enriched taxon in rhizosphere was a generalist, and the corresponding Chaetomium strain was found capable of improving root length and activating ABA signaling in wheat plants through culture-based experiment. Together, these findings provide evidence that host plants exert a strong influence on rhizospheric fungal community assembly during stress and suggest the fungal communities that have experienced drought have the potential to confer fitness advantages to the host plants.

IMPORTANCE

We have presented a framework to integrate the shifts in community assembly processes with plant-soil feedback during drought stress. We found that environmental filtering and host plant selection exert influence on the rhizospheric fungal community assembly, and the re-assembled community has great potential to alleviate plant drought stress. Our study proposes that future research should incorporate ecology with plant, microbiome, and molecular approaches to effectively harness the rhizospheric microbiome for enhancing the resilience of crop production to drought.

Spatial variations of fungal community assembly and soil enzyme activity in rhizosphere of zonal Stipa species in inner Mongolia grassland

Rhizosphere soil fungal and enzyme activities affect the nutrient cycling of terrestrial ecosystems, and rhizosphere fungi are also important participants in the ecological process of vegetation succession, responding to changes in plant communities. Stipa is an excellent forage grass with important ecological and economic value, and has the spatial distribution pattern of floristic geographical substitution. In order to systematically investigate the synergistic response strategies of fungal communities and enzyme activities in the rhizosphere under the vegetation succession. Here we explored the turnover and assembly mechanisms of Stipa rhizosphere fungal communities and the spatial variation of metabolic activity under the succession of seven Stipa communities in northern China grassland under large scale gradients. The results indicated that the composition, abundance and diversity of fungal communities and microbial enzyme activities in rhizosphere soil differed among different Stipa species and were strikingly varied along the Stipa community changes over the geographic gradient. As the geographical distribution of Stipa community changed from east to west in grassland transect, Mortierellomycetes tended to be gradually replaced by Dothideomycetes. The null models showed that the rhizosphere fungal communities were governed primarily by the dispersal limitation of stochastic assembly processes, which showed decreased relative importance from S. grandis to S. gobica. Moreover, the MAT and MAP were the most important factors influencing the changes in the fungal community (richness, β-diversity and composition) and fungal community assembly, while SC and NP also mediated fungal community assembly processes. These findings deepen our understanding of the responses of the microbial functions and fungal community assembly processes in the rhizosphere to vegetation succession.

Monotonic trends of soil microbiomes, metagenomic and metabolomic functioning across ecosystems along water gradients in the Altai region, northwestern China

To investigate microbial communities and their contributions to carbon and nutrient cycling along water gradients can enhance our comprehension of climate change impacts on ecosystem services. Thus, we conducted an assessment of microbial communities, metagenomic functions, and metabolomic profiles within four ecosystems, i.e., desert grassland (DG), shrub-steppe (SS), forest (FO), and marsh (MA) in the Altai region of Xinjiang, China. Our results showed that soil total carbon (TC), total nitrogen, NH4+, and NO3- increased, but pH decreased with soil water gradients. Microbial abundances and richness also increased with soil moisture except the abundances of fungi and protists being lowest in MA. A shift in microbial community composition is evident along the soil moisture gradient, with Proteobacteria, Basidiomycota, and Evosea proliferating but a decline in Actinobacteria and Cercozoa. The β-diversity of microbiomes, metagenomic, and metabolomic functioning were correlated with soil moisture gradients and have significant associations with specific soil factors of TC, NH4+, and pH. Metagenomic functions associated with carbohydrate and DNA metabolisms, as well as phages, prophages, TE, plasmids functions diminished with moisture, whereas the genes involved in nitrogen and potassium metabolism, along with certain biological interactions and environmental information processing functions, demonstrated an augmentation. Additionally, MA harbored the most abundant metabolomics dominated by lipids and lipid-like molecules and organic oxygen compounds, except certain metabolites showing decline trends along water gradients, such as N'-Hydroxymethylnorcotinine and 5-Hydroxyenterolactone. Thus, our study suggests that future ecosystem succession facilitated by changes in rainfall patterns will significantly alter soil microbial taxa, functional potential, and metabolite fractions.

Strong bacterial stochasticity and fast fungal turnover in Taihu Lake sediments, China

Understanding the assembly and turnover of microbial communities is crucial for gaining insights into the diversity and functioning of lake ecosystems, a fundamental and central issue in microbial ecology. The ecosystem of Taihu Lake has been significantly jeopardized due to urbanization and industrialization. In this study, we examined the diversity, assembly, and turnover of bacterial and fungal communities in Taihu Lake sediment. The results revealed strong bacterial stochasticity and fast fungal turnover in the sediment. Significant heterogeneity was observed among all sediment samples in terms of environmental factors, especially ORP, TOC, and TN, as well as microbial community composition and alpha diversity. For instance, the fungal richness index exhibited an approximate 3-fold variation. Among the environmental factors, TOC, TN, and pH had a more pronounced influence on the bacterial community composition compared to the fungal community composition. Interestingly, species replacement played a dominant role in microbial beta diversity, with fungi exhibiting a stronger pattern. In contrast, stochastic processes governed the community assembly of both bacteria and fungi, but were more pronounced for bacteria (R2 = 0.7 vs. 0.5). These findings deepen the understanding of microbial assembly and turnover in sediments under environmental stress and provide essential insights for maintaining the multifunctionality of lake ecosystems.

Distribution, assembly, and interactions of soil microorganisms in the bright coniferous forest area of China's cold temperate zone

The bright coniferous forest area in the cold temperate zone of China is a terrestrial ecosystem primarily dominated by low mountain Larix gmelinii trees. Limited information is available regarding the assembly mechanisms and interactions of microbial communities in the soil in this region. This study employed high-throughput techniques to obtain DNA from myxomycetes, bacteria, and fungi in the soil, evaluated their diversity in conjunction with environmental factors, associated them with the assembly process, and explored the potential interaction relationships between these microorganisms. The findings of our study showed that environmental factors had a more significant influence on the α and β diversity of bacteria compared to myxomycetes and fungi. Microbial communities were influenced by environmental selection and geographical diffusion, although environmental selection appeared to have a more significant impact than geographical diffusion. Our study suggested that different microorganisms exhibited unique evolutionary patterns and may have different assembly modes within phylogenetic groups. Myxomycetes and fungi exhibited a similar assembly process that was mainly influenced by stochastic dispersal limitation and drift. In contrast, bacteria's assembly process was primarily influenced by stochastic drift and deterministic homogeneous selection. The community of myxomycetes and fungi is greatly influenced by spatial distribution and random events, while bacteria have a relatively stable population composition in specific regions and may also be subject to environmental constraints. Finally, this study revealed that Humicolopsis cephalosporioides, a fungus that exclusively resided in cold environments, may play a critical role as a keystone species in maintaining molecular ecological networks and was considered a core member of the microbiome.

Responses of compositions, functions, and assembly processes of bacterial and microeukaryotic communities to long-range voyages in simulated ballast water

Ballast water is one of the main vectors for the spread of harmful organisms among geologically isolated waters. However, the successional processes of microbial functions and assembly processes in ballast water during the long-term shipping voyage remain unclear. In this study, the compositions, ecological functions, community assembly, and potential environmental drivers of bacteria and microeukaryotes were investigated in simulated ballast water microcosms for 120 days. The results showed that the diversity and compositions of the bacterial and microeukaryotic communities varied significantly in the initial 40 days (T0∼T40 samples) and then gradually converged. The relative abundance of Proteobacteria showed a distinct tendency to decrease (87.90%-41.44%), while that of Ascomycota exhibited an increasing trend (6.35%-62.12%). The functional groups also varied significantly over time and could be related to the variations of the microbial community. The chemoheterotrophy and aerobic chemoheterotrophy functional groups for bacteria decreased from 44.80% to 28.02% and from 43.77% to 25.39%, respectively. Additionally, co-occurrence network analysis showed that the structures of the bacterial community in T60∼T120 samples were more stable than those in T0∼T40 samples. Stochastic processes also significantly affected the community assembly of bacteria and microeukaryotes. pH played the most significant role in driving the structures and assembly processes of the bacterial and microeukaryotic communities. The results of this study could aid in the understanding of variations in the functions and ecological processes of bacterial and microeukaryotic communities in ballast water over time and provide a theoretical basis for its management.

Effects of different grassland use patterns on soil bacterial communities in the karst desertification areas

Soil bacteria are closely related to soil environmental factors, and their community structure is an important indicator of ecosystem health and sustainability. A large number of artificial grasslands have been established to control rocky desertification in the karst areas of southern China, but the influence of different use patterns on the soil bacterial community in artificial grasslands is not clear. In this study, three grassland use patterns [i.e., grazing (GG), mowing (MG), and enclosure (EG)] were used to investigate the effects of different use patterns on the soil bacterial community in artificial grassland by using 16S rDNA Illumina sequencing and 12 soil environmental indicators. It was found that, compared with EG, GG significantly changed soil pH, increased alkaline hydrolyzable nitrogen (AN) content (P < 0.05), and decreased soil total phosphorus (TP) content (P < 0.05). However, MG significantly decreased the contents of soil organic carbon (SOC), total phosphorus (TP), available nitrogen (AN), ammonium nitrogen (NH4+-N), β-1,4-glucosidase (BG), and N-acetyl-β-D-glucamosonidase (NAG) (P < 0.05). The relative abundance of chemoheterotrophy was significantly decreased by GG and MG (P < 0.05). GG significantly increased the relative abundance of Acidobacteria and Gemmatimonadota (P < 0.05) and significantly decreased the relative abundance of Proteobacteria (P < 0.05), but the richness index (Chao 1) and diversity index (Shannon) of the bacterial community in GG, MG, and EG were not significantly different (P > 0.05). The pH (R2 = 0.79, P = 0.029) was the main factor affecting the bacterial community structure. This finding can provide a scientific reference for ecological restoration and sustainable utilization of grasslands in the karst desertification areas.

Grass-microbial inter-domain ecological networks associated with alpine grassland productivity

Associations between grasses and soil microorganisms can strongly influence plant community structures. However, the associations between grass productivity and diversity and soil microbes, as well as the patterns of co-occurrence between grass and microbes remain unclear. Here, we surveyed grass productivity and diversity, determined soil physicochemical, and sequenced soil archaea, bacteria and fungi by metabarcoding technology at 16 alpine grasslands. Using the Distance-decay relationship, Inter-Domain Ecological Network (IDEN), and Mantel tests, we investigated the relationship between grass productivity, diversity and microbial diversity, and the patterns of co-occurrence between grass and microbial inter-domain network in alpine grassland. We found the archaea richness, bacteria richness and Shannon, and fungi α-diversity were significantly negatively correlation with grass diversity, but archaea and bacteria diversity were positively correlation with grass productivity. Moreover, an increase in microbial β-diversity was observed along with increased discrepancy in grass diversity and productivity and soil variables. Variance partitioning analysis suggested that the contribution of grass productivity on microbial community was higher than that of soil variables and grass diversity, which implies that microbial community was more related to grass productivity. Inter-Domain Ecological Network showed that the grass species formed complex and stable ecological networks with some bacterial, archaeal, and fungal species, and the grass-fungal ecological networks showed the highest robustness, which indicated that soil fungi could better co-coexist with aboveground grass in alpine grasslands. Besides, the connectivity degrees of the grass-microbial network were significantly positively correlated with grass productivity, suggesting that the coexistence pattern of grasses and microbes had a positive feedback effect on the grass productivity. The results are important for establishing the regulatory mechanisms between plants and microorganisms in alpine grassland ecosystems.

Response of methanogenic community and their activity to temperature rise in alpine swamp meadow at different water level of the permafrost wetland on Qinghai-Tibet Plateau

Wetlands are an important source of atmospheric methane (CH₄) and are sensitive to global climate change. Alpine swamp meadows, accounting for ~50% of the natural wetlands on the Qinghai-Tibet Plateau, were considered one of the most important ecosystems. Methanogens are important functional microbes that perform the methane producing process. However, the response of methanogenic community and the main pathways of CH₄ production to temperature rise remains unknown in alpine swamp meadow at different water level in permafrost wetlands. In this study, we investigated the response of soil CH₄ production and the shift of methanogenic community to temperature rise in the alpine swamp meadow soil samples with different water levels collected from the Qinghai-Tibet Plateau through anaerobic incubation at 5°C, 15°C and 25°C. The results showed that the CH₄ contents increased with increasing incubation temperature, and were 5-10 times higher at the high water level sites (GHM1 and GHM2) than that at the low water level site (GHM3). For the high water level sites (GHM1 and GHM2), the change of incubation temperatures had little effect on the methanogenic community structure. Methanotrichaceae (32.44-65.46%), Methanobacteriaceae (19.30-58.86%) and Methanosarcinaceae (3.22-21.24%) were the dominant methanogen groups, with the abundance of Methanotrichaceae and Methanosarcinaceae having a significant positive correlation with CH₄ production (p < 0.01). For the low water level site (GHM3), the methanogenic community structure changed greatly at 25°C. The Methanobacteriaceae (59.65-77.33%) was the dominant methanogen group at 5°C and 15°C; In contrast, the Methanosarcinaceae (69.29%) dominated at 25°C, and its abundance showed a significant positive correlation with CH₄ production (p < 0.05). Collectively, these findings enhance the understanding of methanogenic community structures and CH₄ production in permafrost wetlands with different water levels during the warming process.

Effects of autumn diurnal freeze-thaw cycles on soil bacteria and greenhouse gases in the permafrost regions

Understanding the impacts of diurnal freeze-thaw cycles (DFTCs) on soil microorganisms and greenhouse gas emissions is crucial for assessing soil carbon and nitrogen cycles in the alpine ecosystems. However, relevant studies in the permafrost regions in the Qinghai-Tibet Plateau (QTP) are still lacking. In this study, we used high-throughput pyrosequencing and static chamber-gas chromatogram to study the changes in topsoil bacteria and fluxes of greenhouse gases, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), during autumn DFTCs in the permafrost regions of the Shule River headwaters on the western part of Qilian Mountains, northeast margin of the QTP. The results showed that the bacterial communities contained a total of 35 phyla, 88 classes, 128 orders, 153 families, 176 genera, and 113 species. The dominant phyla were Proteobacteria, Acidobacteria, Actinobacteria, Chloroflexi, and Gemmatimonadetes. Two DFTCs led to a trend of increasing bacterial diversity and significant changes in the relative abundance of 17 known bacteria at the family, genus, and species levels. These were predominantly influenced by soil temperature, water content, and salinity. In addition, CO2 flux significantly increased while CH4 flux distinctly decreased, and N2O flux tended to increase after two DFTCs, with soil bacteria being the primary affecting variable. This study can provide a scientific insight into the impact of climate change on biogeochemical cycles of the QTP.