Different microbial functional traits drive bulk and rhizosphere soil phosphorus mobilization in an alpine meadow after nitrogen input

Enhanced nitrogen (N) input is expected to influence the soil phosphorus (P) cycling through biotic and abiotic factors. Among these factors, soil microorganisms play a vital role in regulating soil P availability. However, the divergent contribution of functional microorganisms to soil P availability in the rhizosphere and bulk soil under N addition remains unclear. We conducted an N addition experiment with four N input rates (0, 5, 10, and 15 g N m-2 year-1) in an alpine meadow over three years. Metagenomics was employed to investigate the functional microbial traits in the rhizosphere and bulk soil. We showed that N addition had positive effects on microbial functional traits related to P-cycling in the bulk and rhizosphere soil. Specifically, high N addition significantly increased the abundance of most microbial genes in the bulk soil but only enhanced the abundance of five genes in the rhizosphere soil. The soil compartment, rather than the N addition treatment, was the dominant factor explaining the changes in the diversity and network of functional microorganisms. Furthermore, the abundance of functional microbial genes had a profound effect on soil available P, particularly in bulk soil P availability driven by the ppa and ppx genes, as well as rhizosphere soil P availability driven by the ugpE gene. Our results highlight that N addition stimulates the microbial potential for soil P mobilization in alpine meadows. Distinct microbial genes play vital roles in soil P availability in bulk and rhizosphere soil respectively. This indicates the necessity for models to further our knowledge of P mobilization processes from the bulk soil to the rhizosphere soil, allowing for more precise predictions of the effects of N enrichment on soil P cycling.

Thermal structure regulates the dynamics of carbon dioxide flux in alpine saline lake on the Qinghai-Tibet Plateau, China

Thermal stratification and mixing play important roles in the physicochemical composition of lakes and affect the geochemical cycle. However, the regulation of lake carbon exchange at the water-air interface by seasonal thermal structures remains unclear, especially for alpine saline lake on the Qinghai-Tibet Plateau (QTP). Based on continuous field sampling, carbon dioxide flux (FCO2) at the water-air interface in Qinghai Lake during the ice-free period was quantitatively analyzed by thin boundary layer model, as well as the driving factors of the change in FCO2 at the water-air interface. The findings revealed that the FCO2 was -22.16 ± 11.73 mmol m-2d-1 during the stratification period, and - 45.32 ± 29.67 mmol m-2d-1 during the mixing period. We found that thermal stratification limits the matter-energy exchange between the upper and bottom water columns, and carbonate precipitation results in a higher FCO2 than during mixing stage. However, the mixing process reduces the limiting effect of thermal stratification. During the carbonate process, water with higher salinity and pH at the bottom of the water column enters the upper part of the water column, reducing the partial pressure of carbon dioxide (pCO2) in the water column and causing the absorption of CO2 by the lake. Thermal stratification affects the vertical material-energy exchange and atmospheric CO2 uptake of lake. The present study further explains the possible underlying regulation of CO2 uptake in saline lake on the QTP involving the varied thermal structure.

Effect of plant-soil system on the restoration of community stability after wildfire in the northeast margin of Qinghai-Tibet plateau

Wildfires, as an environmental filter, are pivotal ecological disturbances that reshape plant communities and soil dynamics, playing a crucial role in regulating biogeographic patterns and ecosystem services. In this study, we aim to explore the effects of wildfires on forest ecosystems, specifically focusing on the plant-soil feedback mechanisms within the northeastern margin of the Qinghai-Tibet Plateau (QTP). Utilizing Partial Least Squares Path Modeling (PLS-PM), we investigated the interrelationships among soil physicochemical properties, enzyme activities, species diversity, and community stability at varying post-fire recovery stages (5, 15, and 23 years). Results indicated that in the early recovery stages, rapid changes in soil properties such as decreased pH (p < 0.001) and increased nutrient availability facilitate the emergence of early successional species with high resource utilization traits. As the ecosystem evolved toward a climax community, the soil and vegetation exhibit increased stability. Furthermore, soil enzyme activities displayed dynamic patterns that corresponded with changes in soil nutrient content, directly influencing the regeneration and diversity of plant communities. Importantly, our study documented a transition in the influence of soil properties on community stability from direct positive effects in initial recovery phases to negative impacts in later stages, while indirect benefits accrue through increased species diversity and enzyme activity. Vegetation composition and structure changed dynamically with recovery time during community succession. Plant nutrient absorption and accumulation affected nutrient dynamics in the soil, influencing plant regeneration, distribution, and diversity. Our results underscore the complex interactions between soil and vegetation that drive the recovery dynamics post-wildfire, highlighting the resilience of forest ecosystems to fire disturbances. This study contributes to the understanding of post-fire recovery processes and offers valuable insights for the management and restoration of fire-affected forest ecosystems.

The impact of mixed planting of Poaceae species in the Qinghai-Tibet plateau region on forage yield, soil nutrients, and soil microbial communities

Establishing cultivated grassland in the Qinghai-Tibet Plateau region is an effective method to address the conflict between vegetation and livestock. However, the high altitude, low temperature, and arid climate in the region result in slow regeneration and susceptibility to degradation of mixed cultivation grassland containing perennial legumes and gramineous plants. Therefore, we aim to through field experiments, explore the feasibility of establishing mixed cultivation grassland of Poaceae species in the region by utilizing two grass species, Poa pratensis L. and Puccinellia tenuiflora. By employing a mixture of P. pratensis and P. tenuiflora to establish cultivated grassland, we observed significant changes in forage yield over time. Specifically, during the 3rd to 6th years of cultivation, the yield in the mixed grassland was higher than in monocultures. It exceeded the yield of monoculture P. tenuiflora by 19.38% to 29.14% and surpassed the monoculture of P. pratensis by 17.18% to 62.98%. Through the analysis of soil physicochemical properties and soil microbial communities in the cultivated grassland, the study suggests that the mixed grassland with Poaceae species can enhance soil enzyme activity and improve soil microbial communities. Consequently, this leads to increased soil nutrient levels, enhanced nitrogen fixation efficiency, and improved organic phosphorus conversion efficiency. Therefore, establishing mixed grasslands with Poaceae species in the Qinghai-Tibet Plateau region is deemed feasible.

Multilevel ecological compensation policy design based on ecosystem service flow: A case study of carbon sequestration services in the Qinghai-Tibet Plateau

Ecological compensation is an effective means to reconcile the imbalance of eco-social development between regions and promote enthusiasm for ecological environmental protection. There is some conformity between the theory of ecosystem service flow and ecological compensation, which provides new technical support for the formulation of ecological compensation policy. This study took the Qinghai-Tibet Plateau as the research area, adopted the breaking point model to obtain the spatial characteristics of carbon sequestration flow, and formulated a multilevel ecological compensation policy with Tibet as the design object. The results showed that most of the Qinghai-Tibet Plateau has a carbon sequestration surplus; the central and eastern Qinghai-Tibet Plateau, western Sichuan are successively carbon sequestration supply areas; the Chengdu Plain and Xinjiang were listed as carbon sequestration benefit areas; and the carbon sequestration tended to flow more closely between supply and benefit areas in proximity to each other. Nyingchi, Chamdo, Naqu and Shannan in Tibet need to receive a total ecological compensation of 393.21 million USD, of which 93.71 % is from the national level, 6.02 % is from carbon sequestration benefit areas in other provinces; furthermore, Lhasa and Shigatse in Tibet need to provide the remaining ecological compensation. This study offers innovations for the formulation of ecological compensation policies and provide a new theory for ecological environment management.

Temporal genetic variation mediated by climate change-induced salinity decline, a study on Artemia (Crustacea: Anostraca) from Kyêbxang Co, a high altitude salt lake on the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is one of the areas the richest in salt lakes and Artemia sites. As a result of climate warming and wetting, the areas of salt lakes on the plateau have been increasing, and the salinities have decreased considerably since 1990s. However, the impact of salinity change on the genetic diversity of Artemia is still unknown. Kyêbxang Co is the highest (4620 m above sea level) salt lake currently with commercial harvesting of Artemia resting eggs in the world, and harbors the largest Artemia population on the plateau. Its salinity had dropped from ∼67 ppt in 1998 to ∼39 ppt in 2019. Using 13 microsatellite markers and the mitochondrial cytochrome oxidase submit I (COI) gene, we analyzed the temporal changes of genetic diversity, effective population size and genetic structure of this Artemia population based on samples collected in 1998, 2007 and 2019. Our results revealed a steady decline of genetic diversity and significant genetic differentiation among the sampling years, which may be a consequence of genetic drift and the selection of decreased salinity. A decline of effective population size was also detected, which may be relative to the fluctuation in census population size, skewed sex ratio, and selection of the declined salinity. In 2007 and 2019, the Artemia population showed an excess of heterozygosity and significant deviation from Hardy-Weinberg Equilibrium (p < 0.001), which may be associated with the heterozygote advantage under low salinity. To comprehensively understand the impact of climate warming and wetting on Artemia populations on the plateau, further investigation with broad and intensive sampling are needed.

The contribution of microbial necromass to soil organic carbon and influencing factors along a variation of habitats in alpine ecosystems

A growing consensus is reached that microbes contributes to regulating the formation and accumulation of soil organic carbon (SOC). Nevertheless, less is known about the role of soil microbes (necromass, biomass) in SOC accumulation in different habitat conditions in alpine ecosystems. To address this knowledge gap, the composition and distribution of amino sugars (ASs) and phospholipid fatty acids (PLFAs) as biomarkers of microbial necromass and biomass were investigated in forest, meadow and wetland soil profile (0-40 cm) of Mount Segrila, Tibet, China, as well the contribution of bacterial and fungal necromass to SOC. The results revealed that microbial necromass carbon contributed 45.15 %, 72.51 % and 78.08 % on average to SOC in 0-40 cm forest, meadow and wetland soils, respectively, and decreased with microbial biomass. Fungal necromass contributed more to SOC in these habitats than bacterial necromass. Microbial necromass increased with microbial biomass and both of them decreased with soil depth in all habitats. The necromass accumulation coefficient was significantly correlated with microbial necromass and biomass, affected by habitat and soil moisture. Structural equation model indicated that soil abiotic factors indirectly mediated the accumulation of SOC through microbial necromass and biomass. This study revealed that different habitats and soil depths control considerably soil physicochemical properties and microbial community, finally influencing SOC accumulation in alpine ecosystems, which emphasized the influence of abiotic factors on microbial necromass and biomass for SOC accumulation in alpine ecosystems.

Soil quality assessment in low human activity disturbance zones: a study on the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau, located at the Third Pole and known as the "Asian water tower," serves as a crucial ecological barrier for China. Grasping the soil quality on the Qinghai-Tibet Plateau holds paramount importance for the rational and scientific exploitation of soil resources within the region and is essential for vegetation restoration and ecological reconstruction. This study, conducted in Maqin County, Qinghai Province, collected 1647 soil samples (0-20 cm) within a study area of 6300 km2. Sixteen soil indicators were selected that were split into beneficial (N, P, S, and B), harmful (Cr, Hg, As, Pb, Ni, and Cd), and essential (Cu, Zn, Se, Ga, K, and Ca) elements. The Soil Quality Index (SQI) was computed to assess soil quality across diverse geological contexts, land cover classifications, and soil profiles. The results indicate that the overall SQI in the study area was comparatively high, with most regions having an SQI between 0.4 and 0.6, categorized as moderately to highly satisfactory. Among the different geological backgrounds, the highest SQI was found in the Quaternary alluvium (0.555) and the lowest in the Precambrian Jinshuikou Formation (0.481). Regarding different land-use types, the highest SQI was observed in glacier- and snow-covered areas (0.582) and the lowest in other types of grassland (0.461). The highest SQI was recorded in typical alpine meadow soil (0.521) and the lowest in leached brown soil (0.460). The evaluation results have significant reference value for the sustainable utilization and management of soil in Maqin County, Qinghai Province, China.

Soil microbial diversity and composition response to degradation of the alpine meadow in the southeastern Qinghai-Tibet Plateau

With the interaction between global climate change and unreasonable human utilization, the alpine meadows on the Qinghai-Tibet Plateau have suffered various weathering degrees. Uncovering the degradation mechanism and restoration strategies can be facilitated by gaining insights into the diversity of soil microflora during meadow degradation. Therefore, we used Illumina sequencing technology to investigate the patterns of soil microbial diversity, microbial community composition, and the driving factors of microbial change in all non-degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD) alpine meadows in the southeastern Qinghai-Tibet Plateau. Our results pointed out that with the intensification of degradation, vegetation characteristics were significantly reduced, and soil parameters significantly varied among all degraded meadows. The contents of soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AN), and total phosphorous (AK) in soils decreased with the increase of degradation. The dominant bacterial phyla were the same regardless of the meadow degradation level with Actinobacteria (37.67%) and Proteobacteria (20.62%) having the highest relative abundance. Meanwhile, the dominant fungi were Ascomycota (49.9%). Based on the linear discriminant analysis (LDA) and effect size (LEfSe) method, 38 bacterial and 49 fungal species were found to be affected in the degraded alpine meadow, most of which belonged to Actinobacteria and Ascomycota, respectively. Mantel test analysis illustrated that the bacterial community was mainly significantly dependent on below-ground biomass, pH, soil organic carbon, and total nitrogen, while the fungal community was significantly dependent on soil organic carbon, total nitrogen, available nitrogen, and available potassium. These results suggest that the degeneration of alpine meadows contributes to the variability of the diversity and composition of microflora on the Tibetan plateau. Yet this effect is mainly dependent on soil factors.

Soil microbial community are more sensitive to ecological regions than cropping systems in alpine annual grassland of the Qinghai-Tibet Plateau

Introduction

Modern agriculture emphasizes the design of cropping systems using ecological function and production services to achieve sustainability. The functional characteristics of plants (grasses vs. legumes) affect changes in soil microbial communities that drive agroecosystem services. Information on the relationship between legume-grass mixtures and soil microorganisms in different ecological zones guides decision-making toward eco-friendly and sustainable forage production. However, it is still poorly understood how cropping patterns affect soil microbial diversity in alpine grasslands and whether this effect varies with altitude.

Methods

To fill this gap in knowledge, we conducted a field study to investigate the effects of growing oats (Avena sativa L.), forage peas (Pisum sativum L.), common cornflower (Vicia sativa L.), and fava beans (Vicia faba L.) in monocultures and mixtures on the soil microbial communities in three ecological zones of the high alpine zone.

Results

We found that the fungal and bacterial community structure differed among the cropping patterns, particularly the community structure of the legume mixed cropping pattern was very different from that of monocropped oats. In all ecological zones, mixed cropping significantly (p  < 0.05) increased the α-diversity of the soil bacteria and fungi compared to oat monoculture. The α-diversity of the soil bacteria tended to increase with increasing elevation (MY [2,513 m] < HZ [2,661 m]  < GN [3,203 m]), while the opposite was true for fungi (except for the Chao1 index in HZ, which was the lowest). Mixed cropping increased the abundance of soil fungi and bacteria across ecological zones, particularly the relative abundances of Nitrospira, Nitrososphaera, Phytophthora, and Acari. Factors affecting the bacterial community structure included the cropping pattern, the ecological zone, water content, nitrate-nitrogen, nitrate reductase, and soil capacity, whereas factors affecting fungal community structure included the cropping pattern, the ecological zone, water content, pH, microbial biomass nitrogen, and catalase.

Discussion

Our study highlights the variation in soil microbial communities among different in alpine ecological regions and their resilience to cropping systems. Our results also underscore that mixed legume planting is a sustainable and effective forage management practice for the Tibetan Plateau.

Data-driven assessment of soil total nitrogen on the Qinghai-Tibet Plateau

The investigation of soil total nitrogen (STN) holds significant importance in the preservation and sustainability of Earth's ecosystems. The Qinghai-Tibet Plateau (QTP), renowned as the world's most expansive plateau and characterized by its exceptionally delicate ecosystem, demands an in-depth exploration of its STN content. In this study, we use a machine learning approach to extrapolate point-scale measured STN stocks to the entire QTP and calculated STN storage from 0 to 2 m. Our results show that the XGB algorithm performs well in modeling STN despite variations in simulation accuracy for specific depth ranges. The spatial distribution of STN across the QTP exhibits pronounced heterogeneity, especially for the 0-50 cm soil layer, with relatively higher STN stocks in the southeast and lower stocks in the northwest of QTP. The vertical distribution reveals a gradual decrease in STN storage with increasing depth. The 0-50 cm soil layer holds the highest STN stocks, averaging around 0.78 kg/m2, which is almost the sum of STN stocks in the 50-100 cm and 100-200 cm soil layers. Meanwhile, the STN stocks are smaller in permafrost zone than that in non-permafrost zone. We also investigate the impact factors that control the spatiotemporal distribution of STN. It indicates that vegetation, precipitation, temperature, and elevation are the major factors for STN distribution, while physical properties of the soil have a relatively smaller impact. These findings are crucial for understanding the distribution and evolution of STN on the QTP.

Trophic relationships between protists and bacteria and fungi drive the biogeography of rhizosphere soil microbial community and impact plant physiological and ecological functions

Rhizosphere microorganisms play a vital role in enhancing plant health, productivity, and the accumulation of secondary metabolites. Currently, there is a limited understanding of the ecological processes that control the assembly of community. To address the role of microbial interactions in assembly and for functioning of the rhizosphere soil microbiota, we collected rhizosphere soil samples from Anisodus tanguticus on the Tibetan Plateau spanning 1500 kilometers, and sequenced the bacteria, fungi, archaea, and protist communities. We observed a significant but weak distance-decay relationship in the microbial communities of rhizosphere soil. Our comprehensive analysis of spatial, abiotic, and biotic factors showed that trophic relationships between protists and bacteria and fungi predominantly influenced the alpha and beta diversity of bacterial, fungal, and protistan communities, while abiotic factors had a greater impact on archaeal communities, including soil pH, available phosphorus, total phosphorus and mean annual temperature. Importantly, microbial interactions had a more significant influence on Anisodus tanguticus physiological and ecological functions compared to individual microorganisms. Network analyses revealed that bacteria occupy a central position of the co-occurrence network and play a crucial role of connector within this community. The addition of protists increased the stability of bacterial, fungal, and archaeal networks. Overall, our findings indicate that trophic relationships play an important role in assembly and for functioning of the rhizosphere soil microbiota. Bacterial communities serve as a crucial link between different kingdoms of microorganisms in the rhizosphere community. These findings help us to fully harness the beneficial functions of rhizosphere microorganisms for plants and achieve sustainable use of biological resources.

The maturity, humus content, and microbial metabolic function of sheep manure compost on the Qinghai-Tibet Plateau can be significantly improved by reducing the moisture content

The Qinghai-Tibet Plateau (QTP) is characterized by an extreme hypoxia, which may lead to lack of sufficient oxygen for compost production, and thus seriously affecting the compost quality. The moisture content (MC) has a direct effect on the oxygen content of composting pile. At present, the research on the optimum moisture content of compost production on the QTP is still lacking. This study aimed to investigate the influences of MC on fermentation quality of sheep manure composting on the QTP and to further analyze the changes of microbial metabolic function and enzyme activity under different MC. Composting experiment with low MC (45%) and conventional MC (60%) was conducted in both summer and autumn. The results showed that the composting efficiency of 45% MC was better than 60% in both seasons, which was mainly manifested as longer high-temperature period (summer:16 d vs 14 d, autumn: 7 d vs 2 d), higher germination index (summer:136.1% vs 128.6%, autumn:103.5% vs 81.2%), and more humus synthesis (summer:159.8 g/kg vs 151.2 g/kg, autumn:136.1 k/kg vs 115.5 k/kg). The 45% MC can improve microbial metabolism, including increasing the abundance of functional genes involved in carbohydrate metabolism, amino acid metabolism, and nucleotide metabolism and improving the activities of cellulase, β-glucosidase, protease, polyphenol oxidase, and peroxidase. In conclusion, 45% MC can improve the fermentation efficiency and products quality of sheep manure compost on QTP.

Distribution of rhizosphere fungi of Kobresia humilis on the Qinghai-Tibet Plateau

Kobresia humilis is a major species in the alpine meadow communities of the Qinghai-Tibet Plateau (QTP); it plays a crucial role in maintaining the ecological balance of these meadows. Nevertheless, little is known about the rhizosphere fungi associated with K. humilis on the Qinghai Tibet Plateau. In this study, we used Illumina Miseq to investigate the fungal diversity, community structure, and ecological types in the root and rhizosphere soil of K. humilis across eight areas on the QTP and analyzed the correlation between rhizosphere fungi of K. humilis and environmental factors. A total of 19,423 and 25,101 operational taxonomic units (OTUs) were obtained from the roots and rhizosphere soil of K. humilis. These were classified into seven phyla, 25 classes, 68 orders, 138 families, and 316 genera in the roots, and nine phyla, 31 classes, 76 orders, 152 families, and 407 genera in the rhizosphere soil. There were 435 and 415 core OTUs identified in root and rhizosphere soil, respectively, which were categorized into 68 and 59 genera, respectively, with 25 shared genera. Among them, the genera with a relative abundance >1% included Mortierella, Microscypha, Floccularia, Cistella, Gibberella, and Pilidium. Compared with the rhizosphere soil, the roots showed five differing fungal community characteristics, as well as differences in ecological type, and in the main influencing environmental factors. First, the diversity, abundance, and total number of OTUs in the rhizosphere soil of K. humilis were higher than for the endophytic fungi in the roots by 11.85%, 9.85%, and 22.62%, respectively. The composition and diversity of fungal communities also differed between the eight areas. Second, although saprotroph-symbiotrophs were the main ecological types in both roots and rhizosphere soil; there were 62.62% fewer pathotrophs in roots compared to the rhizosphere soil. Thirdly, at the higher altitude sites (3,900-4,410 m), the proportion of pathotroph fungi in K. humilis was found to be lower than at the lower altitude sites (3,200-3,690 m). Fourthly, metacommunity-scale network analysis showed that during the long-term evolutionary process, ZK (EICZK = 1) and HY (EICHY = 1) were critical sites for development of the fungal community structure in the roots and rhizosphere soil of K. humilis, respectively. Fifthly, canonical correspondence analysis (CCA) showed that key driving factors in relation to the fungal community were longitude (R2 = 0.5410) for the root community and pH (R2 = 0.5226) for the rhizosphere soil community. In summary, these results show that K. humilis fungal communities are significantly different in the root and rhizosphere soil and at the eight areas investigated, indicating that roots select for specific microorganisms in the soil. This is the first time that the fungal distribution of K. humilis on the QTP in relation to long-term evolutionary processes has been investigated. These findings are critical for determining the effects of environmental variables on K. humilis fungal communities and could be valuable when developing guidance for ecological restoration and sustainable utilization of the biological resources of the QTP.

Mechanism of polyethylene and biodegradable microplastic aging effects on soil organic carbon fractions in different land-use types

Microplastics (MPs) are widely present in terrestrial ecosystems, but knowledge about the aging characteristics of MPs in different land-use types and their impact on soil organic carbon fractions is still limited. Polyethylene (PE) and biodegradable MPs (Poly propylene carbonate and Polybutylene adipate terephthalate synthetic material (PPC + PBAT, Bio)), at 0 %, 0.03 %, and 0.3 % (w/w) dosages, were added to grassland, farmland, and facility soils for eight-week incubation. The aging degree of MPs was explored by quantifying the carbonyl index (CI). Soil organic C fractions such as SOC, particulate organic carbon (POC), mineral-associated organic carbon (MAOC), and microbial-derived C were analyzed. MPs underwent rapid aging after incubation, and the CI value for 0.03 % PE-MPs increased from 0.05 to 0.27 (farmland) and 0.26 (facility) (p < 0.05). The aging degree of 0.03 % and 0.3 % Bio-MPs was most significant in grassland, with CI decreasing by 46.6 % and 69.0 %, respectively. The CI of MPs were negatively correlated with their dosage. The 0.03 % and 0.3 % PE-MPs decreased soil organic carbon (SOC) content by 7.4 % and 8.2 % in grassland, and 3.0 % and 6.0 % in the facility (p < 0.05). POC content of farmland and facility soil was negatively correlated with PE-MPs' CI (p < 0.05). The 0.03 % PE and Bio-MPs decreased fungal necromass C (FNC) by 0.40 and 0.05 g kg-1 in grassland and 0.48 and 0.21 g kg-1 in farmland. Besides, the dosage of MPs regulated FNC content through soil pH, nutrients, and extracellular enzyme activity, either directly or indirectly, ultimately affecting the soil C pool. Therefore, this study demonstrates that MPs strongly affect SOC dynamics by influencing soil microbial enzyme activity and fungal necromass.

Population genetics of Artemia urmiana species complex (Crustacea, Anostraca): A group with asymmetrical dispersal and gene flow mediated by migratory waterfowl

Bird-mediated dispersal of resting eggs is the main mechanism for Artemia dispersal among catchments. The bisexual populations of Artemia urmiana species complex, which is here considered to be a collection of Artemia genetically close to the so-called "Western Asian Lineage", are mostly distributed in central and western Asia (i.e., in regions falling into the Central Asian Flyway of migratory birds) and live in diversified habitats. Little is known about the genetic relationships among these populations. Aiming to understand the population genetic characteristics and the roles of migratory birds on the dispersal and gene flow of this Artemia group, we evaluated the genetic diversity, genetic differentiation, and gene flow among 14 populations, with their altitudes ranging from 540 to 4870 m above sea level, using 13 microsatellite markers. Almost all populations exhibited high genetic diversity and heterozygote excess, which may be a consequence of combined effects of dispersal and hybridization. The global genetic differentiation (FST) value was 0.092, the pairwise FST values were 0.003-0.246. Discriminant analysis of principal components identified three genetic clusters, consisting of Urmia Lake (Iran), Zhundong (Xinjiang, China), and 12 Qinghai-Tibet Plateau populations, respectively. The among-population genetic differentiation seems to be a consequence of isolation by distance and adaptation to diversified habitats induced by altitudinal gradient. Historical gene flows are asymmetrical, and show an evolutionary source-sink dynamics, with Jingyu Lake (Xinjiang, China) population being the major source. These results support our hypothesis that in Qinghai-Tibet Plateau and surrounding areas the bird-mediated dispersal of Artemia may be biased towards from north to south and/or from higher altitude to lower altitude.

Investigating the long-term response of plateau vegetation productivity to extreme climate: insights from a case study in Qinghai Province, China

Over the past three decades, there has been a significant global climate change characterized by an increase in the intensity and frequency of extreme climate events. The vegetation status in Qinghai Province has undergone substantial changes, which are more pronounced than other regions in the Qinghai-Tibet Plateau. However, a clear understanding of the response characteristics of plateau vegetation to extreme climate events is currently lacking. In this study, we investigated the response of net primary productivity (NPP) to different forms of extreme climate events across regions characterized by varying levels of aridity and elevation gradients. Specifically, we observed a significant increase in NPP in relatively arid regions. Our findings indicate that, in relatively arid regions, single episodes of high-intensity precipitation have a pronounced positive effect (higher correlation) on NPP. Furthermore, in high-elevation regions (4000-6000 m), both the intensity and frequency of precipitation events are crucial factors for the increase in regional NPP. However, continuous precipitation can have significant negative impacts on certain areas within relatively wet regions. Regarding temperature, a reduction in the number of frost days within a year has been shown to lead to a significant increase in NPP in arid regions. This reduction allows vegetation growth rate to increase in regions where it was limited by low temperatures. Vegetation conditions in drought-poor regions are expected to continue to improve as extreme precipitation intensifies and extreme low-temperature events decrease.

The influence of low-temperature resistant lactic acid bacteria on the enhancement of quality and the microbial community in winter Jerusalem Artichoke (Helianthus tuberosus L.) silage on the Qinghai-Tibet Plateau

Jerusalem Artichoke (Helianthus tuberosus L.), an emerging "food and fodder" economic crop on the Qinghai-Tibet Plateau. To tackle problems such as incomplete fermentation and nutrient loss occurring during the low-temperature ensilage of Jerusalem Artichokes in the plateau's winter, this study inoculated two strains of low-temperature resistant lactic acid bacteria, Lactobacillus plantarum (GN02) and Lactobacillus brevis (XN25), along with their mixed components, into Jerusalem Artichoke silage material. We investigated how low-temperature resistant lactic acid bacteria enhance the quality of low-temperature silage fermentation for Jerusalem Artichokes and clarify its mutual feedback effect with microorganisms. Results indicated that inoculating low-temperature resistant lactic acid bacteria significantly reduces the potential of hydrogen and water-soluble carbohydrates content of silage, while increasing lactic acid and acetic acid levels, reducing propionic acid, and preserving additional dry matter. Inoculating the L. plantarum group during fermentation lowers pH and propionic acid levels, increases lactic acid content, and maintains a dry matter content similar to the original material. Bacterial community diversity exhibited more pronounced changes than fungal diversity, with inoculation having a minor effect on fungal community diversity. Within the bacteria, Lactobacillus remains consistently abundant (>85%) in the inoculated L. plantarum group. At the fungal phylum and genus levels, no significant changes were observed following fermentation, and dominant fungal genera in all groups did not differ significantly from those in the raw material. L. plantarum exhibited a positive correlation with lactic acid and negative correlations with pH and propionic acid. In summary, the inoculation of L. plantarum GN02 facilitated the fermentation process, preserved an acidic silage environment, and ensured high fermentation quality; it is a suitable inoculant for low-temperature silage in the Qinghai-Tibet Plateau.

Comparative Study of Potential Habitats for Simulium qinghaiense (Diptera: Simuliidae) in the Huangshui River Basin, Qinghai-Tibet Plateau: An Analysis Using Four Ecological Niche Models and Optimized Approaches

The Huangshui River, a vital tributary in the upper reaches of the Yellow River within the eastern Qinghai-Tibet Plateau, is home to the endemic black fly species S. qinghaiense. In this study, we conducted a systematic survey of the distribution of the species in the Huangshui River basin, revealing its predominant presence along the river's main stem. Based on four ecological niche models-MaxEnt with parameter optimization; GARP; BIOCLIM; and DOMAIN-we conduct a comparative analysis; evaluating the accuracy of AUC and Kappa values. Our findings indicate that optimizing parameters significantly improves the MaxEnt model's predictive accuracy by reducing complexity and overfitting. Furthermore, all four models exhibit higher accuracy compared to a random model, with MaxEnt demonstrating the highest AUC and Kappa values (0.9756 and 0.8118, respectively), showcasing significant superiority over the other models (p < 0.05). Evaluation of predictions from the four models elucidates that potential areas of S. qinghaiense in the Huangshui River basin are primarily concentrated in the central and southern areas, with precipitation exerting a predominant influence. Building upon these results, we utilized the MaxEnt model to forecast changes in suitable areas and distribution centers during the Last Interglacial (LIG), Mid-Holocene (MH), and future periods under three climate scenarios. The results indicate significantly smaller suitable areas during LIG and MH compared to the present, with the center of distribution shifting southeastward from the Qilian Mountains to the central part of the basin. In the future, suitable areas under different climate scenarios are expected to contract, with the center of distribution shifting southeastward. These findings provide important theoretical references for monitoring, early warning, and control measures for S. qinghaiense in the region, contributing to ecological health assessment.

Nitrogen addition enhances seed yield by improving soil enzyme activity and nutrients

Nitrogen (N) addition is a simple and effective field management approach to enhancing plant productivity. Nonetheless, the regulatory mechanisms governing nitrogen concentrations and their effect on soil enzyme activity, nutrient levels, and seed yield in the Festuca kirilowii seed field have yet to be elucidated. Therefore, this study sought to investigate the effect of N fertilizer application on soil enzyme activities, soil nutrients, and seed yield of F. kirilowii Steud cv. Huanhu, the only domesticated variety in the Festuca genus of the Poaceae family, was investigated based on two-year field experiments in the Qinghai-Tibet Plateau (QTP). Results showed that N input significantly affected soil nutrients (potential of hydrogen, total nitrogen, organic matter, and total phosphorus). In addition, soil enzyme activities (urease, catalase, sucrase, and nitrate reductase) significantly increased in response to varying N concentrations, inducing changes in soil nutrient contents. Introducing N improved both seed yield and yield components (number of tillers and number of fertile tillers). These findings suggest that the introduction of different concentrations of N fertilizers can stimulate soil enzyme activity, thus hastening nutrient conversion and increasing seed yield. The exhaustive evaluation of the membership function showed that the optimal N fertilizer treatment was N4 (75 kg·hm-2) for both 2022 and 2023. This finding provides a practical recommendation for improving the seed production of F. kirilowii in QTP.

Comparative responses of carbon flux components in recovering bare patches of degraded alpine meadow in the Source Zone of the Yellow River

The patchy degradation of alpine grasslands is a common phenomenon on the Qinghai-Tibetan Plateau, and the presence of bare patches (BP) in degraded grasslands significantly affects the functioning of the alpine meadow ecosystem. The succession of vegetation-recovered BP may lead to significant changes in ecosystem carbon (C) cycling. To date, it is unclear whether different components of net ecosystem carbon exchange (NEE) respond similarly or differently to the succession of recovering BP. Here, we conducted a field monitoring experiment in a degraded alpine meadow, and selected three successional stages for recovering BP to study the response of NEE and its components. We found that the succession of recoevering BP increased ecosystem respiration (ER) during the growing season and decreased ER during the off-growing season, with the differences in annual carbon output between different successional stages being insignificant. However, gross primary productivity increased with the successional gradient, and carbon input at the later stage of succession was significantly greater than that at the middle stage of succession. The succession of recovering BP promoted the carbon sequestration function of the alpine grassland, with the grassland acting as a carbon sink when it reached the state of healthy alpine meadow, while it acted as a carbon source during the middle stage of succession. Compared with BP, the amount of carbon sequested by healthy alpine meadows increased significantly by 219 g·C·m-2·yr-1. We also found that the responses of other components to the succession of recovering BP were inconsistent. In addition, the effects of succession of recovering BP on carbon flux were related to field-monitored variables (soil temperature and water content) and other considered variables (biomass, organic carbon, and microbial biomass carbon). These research findings highlight the importance of restoring vegetation in BPs, and are crucial for predicting the carbon balance in the future and formulating sustainable grassland management strategies.

The unique climate shapes distinct life-history traits of abundant bacteria in Tibetan Plateau grassland soil

The unique geographical patterns of the Qinghai-Tibet Plateau have shaped the different climatic characteristics of the Lhasa and Nyang River watersheds. However, our understanding of climate-dependent life history strategies in riparian grasslands is very limited. In this research, we have compared the causes and consequences of variations in the composition of soil abundant and rare bacterial taxa in the Nyang and Lhasa River watersheds. The results showed that the abundant bacteria, rather than the rare bacteria, exhibited distinct life history strategies between the Lhasa and Nyang watersheds that were a consequence of climate patterns. The wetter climate of the Nyang watershed led to a high ratio of r-strategists among the abundant bacteria (Abundant K:r = 0.323), while in the less favourable climate of the Lhasa watershed, K-strategists were more common among the soil abundant bacteria (Abundant K:r = 0.542). The assembly processes of abundant and rare bacteria in the Lhasa region under relatively harsh climatic conditions seemed to be more affected by variable selection than those in the Nyang region. Moreover, abundant bacteria in the Lhasa region developed stronger potentially cooperative relationships and exhibited a stronger metabolic capacity than those in the Nyang region. The 26 different functional genes identified in LS were highly associated with 38 abundant bacterial species. In contrast, the 16 identified functional genes in NY were highly correlated with 16 abundant bacterial species. These results provide new insights into climate-dependent life history strategies of soil bacterial communities with different abundances in riparian grasslands of the Tibetan Plateau. Contrasting the life history strategies of bacterial taxa with different abundances contributes to a better mechanistic knowledge of their impact on ecosystem functioning under current and future effects of global climate change.

Diazotrophic abundance and community structure associated with three meadow plants on the Qinghai-Tibet Plateau

Symbiotic diazotrophs form associations with legumes and substantially fix nitrogen into soils. However, grasslands on the Qinghai-Tibet Plateau are dominated by non-legume plants, such as Kobresia tibetica. Herein, we investigated the diazotrophic abundance, composition, and community structure in the soils and roots of three plants, non-legume K. tibetica and Kobresia humilis and the legume Oxytropis ochrocephala, using molecular methods targeting nifH gene. Diazotrophs were abundantly observed in both bulk and rhizosphere soils, as well as in roots of all three plants, but their abundance varied with plant type and soil. In both bulk and rhizosphere soils, K. tibetica showed the highest diazotroph abundance, whereas K. humilis had the lowest. In roots, O. ochrocephala and K. humilis showed the highest and the lowest diazotroph abundance, respectively. The bulk and rhizosphere soils exhibited similar diazotrophic community structure in both O. ochrocephala and K. tibetica, but were substantially distinct from the roots in both plants. Interestingly, the root diazotrophic community structures in legume O. ochrocephala and non-legume K. tibetica were similar. Diazotrophs in bulk and rhizosphere soils were more diverse than those in the roots of three plants. Rhizosphere soils of K. humilis were dominated by Actinobacteria, while rhizosphere soils and roots of K. tibetica were dominated by Verrumicrobia and Proteobacteria. The O. ochrocephala root diazotrophs were dominated by Alphaproteobacteria. These findings indicate that free-living diazotrophs abundantly and diversely occur in grassland soils dominated by non-legume plants, suggesting that these diazotrophs may play important roles in fixing nitrogen into soils on the plateau.

Bacterial and Microeukaryotic Community Compositions and Their Assembly Processes in Lakes on the Eastern Qinghai-Tibet Plateau

Bacterial and microeukaryotic community compositions and their assembly processes have remained challenging and remained unclear in lake ecosystems on the Qinghai-Tibet Plateau (QTP). We revealed the diversity and community compositions, driving factors, ecological assembly processes, and co-occurrence networks of bacterial and microeukaryotic communities in water bodies of the eight lake ecosystems across the Eastern QTP. The results demonstrated that the predominant bacteria in most samples were Proteobacteria, with an average relative abundance of 41.78%, whereas the most abundant of microeukaryotes differed among the sample sites. The redundancy analysis revealed that latitude and pH were the most important driving factors in shaping the bacterial and microeukaryotic community compositions. Homogeneous selection (56.40%) was the dominant process in assembling the bacterial communities, whereas dispersal limitation (67.24%) was the major process in governing the microeukaryotic communities. Furthermore, dissolved organic carbon and salinity were the major factors mediating the balance of deterministic and stochastic assembly processes in the bacterial and microeukaryotic communities. Both the bacterial and microeukaryotic community co-occurrence networks exhibited topological features of modularity and non-random topological features. The results offer insights into the mechanisms underpinning bacterial and microeukaryotic diversities and communities in the lake ecosystems on the QTP.

Ecological risk assessment and transmission of soil heavy metals in pastoral areas of the Tibetan plateau based on network environment analysis

The Qinghai-Tibet Plateau is distinguished by its diverse ecosystems and biodiversity, which are highly dependent on their soil. In this study, a comprehensive analysis was conducted to assess the ecological risks in Maqin County, located on the Qinghai-Tibet Plateau, along with the local background values of soil elements, level of element enrichment, and source appointment of soil elements. The findings show that the background soil element levels in Maqin County were greater than the average soil content values in China. The soils in the study area exhibited pollution levels ranging from weak to moderate. The positive matrix factorization (PMF) model was employed to successfully categorized soil elements into four sources: F1 (natural sources), F2 (grazing sources), F3 (volcanic and rock fracture sources), and F4 (intrusive and deep rock source). Based on the characteristics of the ecological communities and the network environmental analysis model, ecological risks were directly introduced through vegetation and soil microorganisms, with subsequent transmission to other components of the ecosystem through the food chain. The integrated risks associated with vegetation, herbivores, soil microorganisms, and carnivores were 0.0106, 0.00193, 0.0282, and 0.00132, respectively. Notably, soil microorganisms were found to be the primary contributors to the total ecological risk in the study area. Furthermore, network environmental analysis and human health risk models revealed that F1, F2, F3, and F4 accounted for 16.85 %, 8.90 %, 21.76 %, and 52.49 % of the input risk of vegetation and soil microorganisms, respectively. Particularly, F4 emerged as the largest contributor to human health risks. This study provides valuable information for the preservation of the ecological environment in pastoral areas, contributing to the global promotion of sustainable ecological practices.

Habitat-specific environmental factors regulate the spatial variability of biological soil crust microbial communities on the Qinghai-Tibet Plateau

Biological soil crusts (BSCs) are an important biological component of the soil surface, covering approximately 12 % of the Earth's land surface. Although BSCs are closely related to habitats, the microbial diversity and spatial variability of BSCs in different ecosystems are still unclear, especially on the Qinghai-Tibet Plateau (QTP), where climate is changeable and habitats are complex. Here, we investigated the diversity, assembly processes, spatial distribution pattern and driving factors of prokaryotic and eukaryotic microbial communities in BSCs in four habitats on the QTP. It was found that habitat-specific environmental factors regulated the composition, diversity and spatial variability of BSC microbial communities. Soil organic carbon and soil water content were the most important factors (R2 = 0.9024, P = 0.001; R2 = 0.8004, P = 0.001) affecting the spatial differences in prokaryotes and eukaryotes, respectively. Under the specific climate of the QTP, the spatial pattern of microbial communities in BSCs was controlled by precipitation rather than temperature. In addition, ecological processes further explained the effects of habitat specificity, and environmental filtering explained microbial community differences better than dispersal limitation. The results of the neutral community model and the normalized stochastic ratio index revealed that the assembly of prokaryotic communities was determined by deterministic processes at the regional scale, and at the local scale, the assembly process was mainly determined by habitat type, while the assembly of eukaryotic communities was determined by stochastic processes at both the regional and local scales. This study provided a scientific reference for the prediction of BSC distribution and resource conservation under future climate change scenarios.

Constraining the sources and cycling of dissolved inorganic carbon in an alpine river, eastern Qinghai-Tibet Plateau

It is generally acknowledged that riverine dissolved inorganic carbon (DIC) behaviors play a critical role in global carbon cycling and hence have an impact on climate change. However, little is known about the intricate DIC dynamics under various meteorological conditions in the alpine areas. Here, we investigated DIC biogeochemical processes in the Bailong River catchment, eastern Qinghai-Tibet Plateau (QTP), by combining measurements of major ions, stable and radioactive isotopic compositions of DIC (δ13CDIC and Δ14CDIC), and physiographic parameters in the Bailong River catchment. Statistics and stoichiometry analyses suggest that multiple biogeochemical processes could affect carbon cycling in the Bailong River catchment. The "old" DIC with low Δ14C values (-472.4 ± 127.8 ‰, n = 3) and stoichiometry analysis of dissolved ions showed clear evidence that carbonate weathering is primarily responsible for water chemistry in the upstream (elevation >2000 m). However, upstream samples showed that δ13CDIC increased between 5 ‰ and 11 ‰ from the theoretical mixing line, concomitant with increasing pH and decreasing pCO2, suggesting that isotopic fractionation of DIC due to CO2 outgassing may be the primary cause of the increased δ13CDIC values. Additionally, the higher Δ14C values (-285.4 ± 123.5 ‰, n = 12) in the downstream region below 2000 m suggest that allochthonous modern carbon had a great impact on DIC variations. The presence of younger DIC may have important implications for the interpretation of inorganic carbon age in downstream rivers. Our study demonstrates that physiographic conditions can regulate DIC behaviors, which can improve estimations of carbon yield and comprehension of global carbon cycle.

Grazing practices affect phyllosphere and rhizosphere bacterial communities of Kobresia humilis by altering their network stability

The primary utilization strategy for meadow grasslands on the Qinghai-Tibet Plateau (QTP) is livestock grazing. This practice is considered as one of the major drivers of plant-associated bacterial community construction and changes in soil properties. The species of Kobresia humilis is considered as the most dominant one in grasslands. However, how different grazing practices affect the phyllosphere and rhizosphere bacterial communities of K. humilis is unknown. To address this issue, the effects of the grazing enclosure (GE), single-species grazing (YG and SG, representing yak only and sheep only, respectively), and different ratios of grazing (ratio of yak to sheep is 1:2, 1:4, and 1:6, represented by MG1:2, MG1:4, and MG1:6, respectively) on the dominant plant of K. humilis, it's phyllosphere and rhizosphere bacteria, and soil properties were investigated using artificially controlled grazing and grazing enclosure. Our data showed that grazing enclosure enhanced vegetation coverage, and rhizosphere bacterial richness and diversity, while reduced plant number and bacterial network stability of K. humilis. The NO3--N, K+, and Cl- concentrations were lower under grazing compared to GE. SG reduced the concentration of NH4+-N, TN, K+, and Na+ compared to YG. Moderate grazing intensity had a lower relative abundance of the r-strategists (Bacteroidota and Gammaproteobacteria) with higher bacterial network stability. Yak and sheep grazing showed reversed impacts on the bacterial network stability between the phyllosphere and rhizosphere of K. humilis. Proteobacteria and Actinobacteriota were identified in the molecular ecological network analysis as keystone taxa in the phyllosphere and rhizosphere networks, respectively, under all treatments. This study explained why sheep grazing has more adverse effects on grazing-tolerant grass species, K. humilis, than yak grazing, and will contribute to a better understanding of the impacts of different grazing practices and grazing enclosure on alpine grassland ecosystems on the QTP.

Trends in air pollutants emissions in the Qinghai-Tibet Plateau and its surrounding areas under different socioeconomic scenarios

The Qinghai-Tibetan Plateau (QTP) and its surrounding areas are undergoing rapid changes in socioeconomic conditions, activity sectors, and emission levels. These changes underscore the significance of conducting local environmental assessments in the future and generating air pollutant emission forecasts necessary for effective evaluation. Current pollutants emissions pathways exhibit regional limitation since their based historical inventory could not accurately reflect the emission characteristics in QTP. This study constructed a high spatial resolution (0.1° × 0.1°) atmospheric pollutant emissions dataset in the Qinghai-Tibet Plateau and its surrounding Areas (QTPA) based on updated emission inventory and various socioeconomic scenarios. We found that the pollutant emissions levels are distinct among different social development scenarios, with SSP3-7.0 demonstrating the highest magnitude of emissions. Regional and sectoral contributions exhibit substantial variations. Notably, solid fuel combustion originating from residential sectors in Northeast India and open fires in Myanmar are identified as high-density sources of PM2.5 emissions. Current pollutant emission patterns in the QTPA are more akin to SSP2-4.5, however, specific regions such as Qinghai and Tibet have exhibited more pronounced trends of emission reduction. The comparison with previous datasets reveals that the predicted pollutant emissions in this study are lower than Scenario Model Intercomparison Project (SMIP) dataset but higher than Asian-Pacific Integrated Model (AIM) dataset due to the revised inventory data and model variations, in which the latter might be the main obstacle to accurate emissions prediction.

Characterization of heavy metal content distribution and evaluation of soil pollution in Maqin County, Qinghai Province, China

The Qinghai-Tibet Plateau stands as the loftiest geographical area on our planet, frequently denoted as the "Crown of the Globe." To acquire an exhaustive comprehension of the heavy metal contamination situation in the topsoil of Maqin County, Qinghai Province, a total of 1616 surface soil specimens were gathered across a 6300 km2 area. An examination was carried out on 12 metallic elements to investigate the impact of diverse geological contexts, soil categorizations, and land utilization practices on the levels of heavy metals. Additionally, the fundamental factors contributing to these trends were probed. The findings unveiled that the mean levels of the 12 metallic elements in the topsoil of Maqin County surpassed or equaled the baseline values of soil heavy metal concentrations within the research region. The coefficients of variation (CV) values for Hg, Sb, Ni, and Pb exceeded 30%, with Hg showing strong variation. The overall pollution level in the study area was classified as mild, posing a moderate ecological risk. In this study, we performed a multi-factor analysis of the significant differences in heavy metal concentrations among different geological backgrounds, soil types, and land-use types. The results showed that geological background had extremely significant impacts on elements such as Ba, Be, Cd, Cr, Cu, Hg, Ni, Sb, Tl, and Zn (p < 0.01). Soil type had an extremely significant influence on Be, Cd, Cu, and Zn (p < 0.01), as well as a significant influence on Ba (p < 0.05). Land-use type had an extremely significant impact on Ba (p < 0.01) and a significant impact on Cd (p < 0.05). Building upon the amalgamation of the outcomes from the Pearson correlation analysis, it was inferred that the main source of heavy metals in Maqin County, Qinghai Province, was the geological background.

Structure and Metabolic Characteristics of Intestinal Microbiota in Tibetan and Han Populations of Qinghai-Tibet Plateau and Associated Influencing Factors

Residents of the Qinghai-Tibet Plateau might experience shifts in their gut microbiota composition as a result of the plateau environment. For example, high altitudes can increase the abundance of obligate anaerobic bacteria, decrease the number of aerobic bacteria and facultative anaerobic bacteria, increase probiotics, and decrease pathogenic bacteria. This study aimed to determine the structure and metabolic differences in intestinal microbial communities among the Tibetan and Han populations on the Qinghai-Xizang Plateau and shed light on the factors that influence the abundance of the microbial communities in the gut. The structural characteristics of intestinal microorganisms were detected from blood and fecal samples using 16S rRNA sequencing. Metabolic characteristics were detected using gas chromatography-time-of-flight mass spectrometry (GC-TOFMS). The influencing factors were analyzed using Spearman's correlation analysis. Bacteroides and Bifidobacterium were dominant in the intestinal tract of the Han population, while Bacteroides and Prevotella were dominant in that of the Tibetan population, with marked differences in Pseudomonas, Prevotella, and other genera. Ferulic acid and 4-methylcatechol were the main differential metabolites between the Tibetan and Han ethnic groups. This may be the reason for the different adaptability of Tibetan and Han nationalities to the plateau. Alanine aminotransferase and uric acid also have a high correlation with different bacteria and metabolites, which may play a role. These results reveal notable disparities in the compositions and metabolic characteristics of gut microbial communities in the Tibetan and Han people residing on the Qinghai-Tibet Plateau and may provide insights regarding the mechanism of plateau adaptability.

First description of the male of Oecobiusprzewalskyi Hu & Li, 1987 (Araneae, Oecobiidae) from Shigatse City, Tibet, China

Background

With 90 described species, the genus Oecobius Lucas, 1846 is the largest genus of the family Oecobiidae Blackwall, 1862, five of which are known from China. Since Oceobiusprzewalskyi was described by Hu & Li in 1987, no males of this species have ever been reported.

New information

The male of Oceobiusprzewalskyi is described for the first time, based on the specimens collected in Tibet Autonomous Region. Morphological description and illustrations are given.

A bibliometric analysis of research trends and hotspots in alpine grassland degradation on the Qinghai-Tibet Plateau

A bibliometric analysis of current research, hotspots, and development trends was used to develop an overall framework of mechanisms of alpine grassland degradation on the Qinghai-Tibet Plateau. This investigation includes data from 1,330 articles on alpine grassland degradation on the Qinghai-Tibet Plateau, acquired from the Chinese Science Citation Database (CSCD) and Web of Science Core Collection (WOS). Research was divided into three themes: spatial scope and management of typical grassland degradation problems, dynamic mechanisms of grassland degradation and effects of ecological engineering, and grassland degradation risk based on remote sensing technology. The results of the analysis showed that the research can be summarized into three aspects: typical grassland degradation identification, dynamic mechanism analysis of grassland degradation, and grassland ecosystem stability strategy. The main findings can summarized, as follows: (1) Ecological analyses using the river source as a typical region defined the formation of "black soil beach" type degraded grasslands in the region, and promoted the ecological environment management and protection of the alpine grassland by discussing the causes of regional ecological environment changes; (2) Dynamic mechanism analyses of climate change and characteristics analyses of grassland vegetation-soil degradation revealed that alpine grassland degradation is the result of multiple main factors; and (3) Risk prediction methods for grassland degradation, methods of grassland management and sustainable countermeasures for agriculture and animal husbandry development, and the development of a comprehensive index of influencing factors on grassland degradation all indicate that selecting the right grassland restoration measures is the key to grassland restoration. Remote sensing monitoring and high-throughput sequencing technology should be used in future research on grassland ecosystems. In addition, multiscale, multidimensional, and multidisciplinary systematic research methods and long-term series data mining could help identify the characteristics and causes of alpine grassland system degradation. These findings can help identify a more effective coordination of landscape, water, lake, field, forest, grass, and sand management for the prevention of alpine grassland degradation.

Legume-grass mixtures increase forage yield by improving soil quality in different ecological regions of the Qinghai-Tibet Plateau

Introduction

Information on the relationship between soil quality and forage yield of legume-grass mixtures in different ecological regions can guide decision-making to achieve eco-friendly and sustainable pasture production. This study's objective was to assess the effects of different cropping systems on soil physical properties, nitrogen fractions, enzyme activities, and forage yield and determine suitable legume-grass mixtures for different ecoregions.

Methods

Oats (Avena sativa L.), forage peas (Pisum sativum L.), common vetch (Vicia sativa L.), and fava beans (Vicia faba L.) were grown in monocultures and mixtures (YS: oats and forage peas; YJ: oats and common vetch; YC: oats and fava beans) in three ecological regions (HZ: Huangshui Valley; GN: Sanjiangyuan District; MY: Qilian Mountains Basin) in a split-plot design.

Results

The results showed that the forage yield decreased with increasing altitude, with an order of GN (3203 m a.s.l.; YH 8.89 t·ha-1) < HZ (2661 m; YH 9.38 t·ha-1) < MY (2513m; YH 9.78 t·ha-1). Meanwhile, the forage yield was higher for mixed crops than for single crops in all ecological regions. In the 0-10 cm soil layer, the contents of total nitrogen (TN), microbial biomass nitrogen (MBN), soil organic matter (SOM), soluble organic nitrogen (SON), urease (UE), nitrate reductase (NR), sucrase (SC), and bacterial community alpha diversity, as well as relative abundance of dominant bacteria, were higher for mixed crops than for oats unicast. In addition, soil physical properties, nitrogen fractions, and enzyme activities varied in a wider range in the 0-10 cm soil layer than in the 10-20 cm layer, with larger values in the surface layer than in the subsurface layer. MBN, SON, UE, SC and catalase (CAT) were significantly and positively correlated with forage yield (P < 0.05). Ammonium nitrogen (ANN), nitrate nitrogen (NN), SOM and cropping systems (R) were significantly and positively correlated with Shannon and bacterial community (P < 0.05). The highest yields in the three ecological regions were 13.00 t·ha-1 for YS in MY, 10.59 t·ha-1 for YC in GN, and 10.63 t·ha-1 for YS in HZ.

Discussion

We recommend planting oats and forage peas in the Qilian Mountains Basin, oats and fava beans in the Sanjiangyuan District, and oats and forage peas in Huangshui valley. Our results provide new insights into eco-friendly, sustainable, and cost-effective forage production in the Qinghai Alpine Region in China.

Bioprospecting for the soil-derived actinobacteria and bioactive secondary metabolites on the Western Qinghai-Tibet Plateau

Introduction

The increase in incidence of multidrug-resistant bacteria and the inadequacy of new antimicrobial drugs have led to a widespread outbreak of bacterial antimicrobial resistance. To discover new antibiotics, biodiversity, and novelty of culturable actinobacteria dwelled in soil of the Western Qinghai-Tibet Plateau were investigated. By integrating antibacterial assay with omics tools, Amycolatopsis sp. A133, a rare actinobacterial strain and its secondary metabolites were further studied.

Method

Culture-dependent method was used to obtain actinobacterial strains from two soil samples collected from Ali region in Qinghai-Tibet Plateau. The cultural extractions of representative strains were assayed against "ESKAPE" pathogens by paper-disk diffusion method and the double fluorescent protein reporter "pDualrep2" system. An Amycolatopsis strain coded as A133 was prioritized and its secondary metabolites were further analyzed and annotated by omics tools including antiSMASH and GNPS (Global Natural Social Molecular Networking). The predicted rifamycin analogs produced by Amycolatopsis sp. A133 were isolated and identified by chromatographic separation, such as Sephadex LH-20 and HPLC, and spectral analysis, such as NMR and UPLC-HRESI-MS/MS, respectively.

Results

A total of 406 actinobacteria strains affiliated to 36 genera in 17 families of 9 orders were isolated. Out of 152 representative strains, 63 isolates exhibited antagonistic activity against at least one of the tested pathogens. Among them, 7 positive strains were identified by the "pDualrep2" system as either an inhibitor of protein translation or DNA biosynthesis. The cultural broth of Amycolatopsis sp. A133 exhibited a broader antimicrobial activity and can induce expression of TurboRFP. The secondary metabolites produced by strain A133 was annotated as rifamycins and zampanolides by antiSMASH and GNPS analysis. Five members of rifamycins, including rifamycin W, protorifamycin I, rifamycin W-M1, proansamycin B, and rifamycin S, were purified and identified. Rifamycin W-M1, was found as a new member of the naturally occurring rifamycin group of antibiotics.

Discussion

Assisted by omics tools, the successful and highly efficient discovery of rifamycins, a group of clinically used antibiotics from actinobacteria in Ali area encouraged us to devote more energy to explore new antibiotics from the soils on the Western Tibetan Plateau.

Typical heavy metals accumulation, transport and allocation in a deglaciated forest chronosequence, Qinghai-Tibet Plateau

Understanding heavy metals (HMs) accumulation and transportation is the foundation to assess the ecological risks caused by the pollution of HMs in terrestrial ecosystems. There are large knowledge gaps regarding impacts of vegetation succession on shaping the HMs accumulation, transportation and allocation in the remote alpine regions. Herein, we comprehensively investigated the distribution and source contribution of mercury (Hg), cadmium (Cd) and chromium (Cr) along with vegetation succession in a deglaciated forest chronosequence of Qinghai-Tibet Plateau. Results showed that Hg and Cd were highly enriched in organic soils, while Cr concentrations and pool sizes decreased significantly with the vegetation succession. Atmospheric Hg deposition contributed to the dominant Hg sources in topsoil (74 - 87%), whereas moraine weathering was the main source of Cr (73 - 76%). Both moraine (18 - 48%) and atmospheric deposition inputs (52 - 82%) affected Cd accumulation in topsoil. Over the last century, the accumulation rate of Hg and Cd showed the distinctly decreasing trends due to the vegetation leading to the elevated atmospheric depositions at the earlier deglacial sites. The negative accumulation rate of Cr along with the vegetation succession reflected the formation of organic soil diluting the geogenic inputs of Cr.

Plateau pikas near roads are bold and silent when facing a potential predator

Human disturbance, particularly road traffic, is one of the greatest threats to wildlife. Considering the association between alerting behavior and the survival of animals, it is important to study the effects of road traffic on alerting behavior of wildlife. Previous studies assessing the short-term impact of road traffic on alerting behavior of wildlife have focused on vigilance distances. However, studies on the use of alarm calls are scarce, and it is unclear whether such behavioral responses change after repeated exposure to road traffic. We assessed the alerting behavior of plateau pikas (Ochotona curzoniae) who were near or far from roads when facing a potential predator. We found that pikas near roads exhibited shorter vigilance and tolerance distances, and produced fewer alarm calls than those relatively far away from roads. Furthermore, both vigilance and tolerance distances of plateau pikas were significantly positively correlated with the distance from the burrow to the road. Road traffic reduced antipredator responses and shaped alerting behavior; that is, pikas near roads were bolder and more silent compared to those far away from roads. Our findings suggest that increasing urbanization will have corresponding effects on animal behavior, which may have significant fitness effects in the future.

Effects of Climatic Change on Phylogeography and Ecological Niche of the Endemic Herb Elymus breviaristatus on the Qinghai-Tibet Plateau

Past climatic and topographic variations have created strong biogeographic barriers for alpine species and are key drivers of the distribution of genetic variation and population dynamics of species on the Qinghai-Tibet Plateau (QTP). Therefore, to better conserve and use germplasm resources, it is crucial to understand the distribution and differentiation of genetic variation within species. Elymus breviaristatus, an ecologically important rare grass species with strong resistance, is restricted to a limited area of the QTP. In this study, we investigated the phylogeography of E. breviaristatus using five chloroplast genes and spacer regions in natural populations distributed along the eastern QTP. We identified a total of 25 haplotypes among 216 individuals from 18 E. breviaristatus populations, which were further classified into four haplogroups based on geographical distribution and haplotype network analysis. Notably, we did not observe any signs of population expansion. High genetic diversity was exhibited at both species and population levels, with precipitation being the main limiting factor for population genetic diversity levels. Higher genetic diversity was exhibited by populations located near the Mekong-Salween Divide genetic barrier, suggesting that they may have served as a glacial refuge. The significant pattern of genetic differentiation by environmental isolation highlights the influence of heterogeneous environments on the genetic structure of E. breviaristatus populations. Additionally, the results of ecological niche models indicated that the geographic distribution of E. breviaristatus populations has decreased rapidly since the Last Glacial Maximum but is not threatened by future global warming.

The fusion of multiple scale data indicates that the carbon sink function of the Qinghai-Tibet Plateau is substantial

BACKGROUND

The Qinghai-Tibet Plateau is the "sensitive area" of climate change, and also the "driver" and "amplifier" of global change. The response and feedback of its carbon dynamics to climate change will significantly affect the content of greenhouse gases in the atmosphere. However, due to the unique geographical environment characteristics of the Qinghai-Tibet Plateau, there is still much controversy about its carbon source and sink estimation results. This study designed a new algorithm based on machine learning to improve the accuracy of carbon source and sink estimation by integrating multiple scale carbon input (net primary productivity, NPP) and output (soil heterotrophic respiration, Rh) information from remote sensing and ground observations. Then, we compared spatial patterns of NPP and Rh derived from the fusion of multiple scale data with other widely used products and tried to quantify the differences and uncertainties of carbon sink simulation at a regional scale.

RESULTS

Our results indicate that although global warming has potentially increased the Rh of the Qinghai-Tibet Plateau, it will also increase its NPP, and its current performance is a net carbon sink area (carbon sink amount is 22.3 Tg C/year). Comparative analysis with other data products shows that CASA, GLOPEM, and MODIS products based on remote sensing underestimate the carbon input of the Qinghai-Tibet Plateau (30-70%), which is the main reason for the severe underestimation of the carbon sink level of the Qinghai-Tibet Plateau (even considered as a carbon source).

CONCLUSIONS

The estimation of the carbon sink in the Qinghai-Tibet Plateau is of great significance for ensuring its ecological barrier function. It can deepen the community's understanding of the response to climate change in sensitive areas of the plateau. This study can provide an essential basis for assessing the uncertainty of carbon sources and sinks in the Qinghai-Tibet Plateau, and also provide a scientific reference for helping China achieve "carbon neutrality" by 2060.

Avian malaria parasite infections do not affect personality in the chestnut thrush (Turdus rubrocanus) on the Qinghai-Tibet Plateau

Personality traits, the consistent individual behavioral differences, are currently gaining much attention in studies of natural bird populations. However, associations between personality traits and parasite infections are not often investigated. Even less attention has been given to studies of birds in the high-elevation region such as the Tibetan plateau. This research aims to examine the relationship between avian malaria parasites and two personality traits in a population of the Chestnut Thrush (Turdus rubrocanus) breed in the Tibetan plateau. Our results revealed no evidence of sex bias in malaria parasite prevalence. Furthermore, we found no effect of infection status on two personality scores: activity and boldness. Additionally, no effects on the activity level or boldness were observed for different parasite lineages of Haemoproteus, Leucocytozoon, the sex of the birds, or their interactions. Similarly, we did not find any relationship between activity level and boldness with nestling numbers, sex, or their interactions. Notably, individuals with a larger number of offspring tended to display greater boldness. Our findings indicate that blood parasite infections are common in this population but do not significantly impact the personality of the birds.

Prediction of soil moisture using BiGRU-LSTM model with STL decomposition in Qinghai-Tibet Plateau

Ali Network data based on the Qinghai-Tibetan Plateau (QTP) can provide representative coverage of the climate and surface hydrometeorological conditions in the cold and arid region of the QTP. Among them, the plateau soil moisture can effectively quantify the uncertainty of coarse resolution satellite and soil moisture models. With the objective of constructing an "end-to-end" soil moisture prediction model for the Tibetan Plateau, a combined prediction model based on time series decomposition and a deep neural network is proposed in this article. The model first performs data preprocessing and seasonal-trend decomposition using loess (STL) to obtain the trend component, seasonal component and random residual component of the original time series in an additive way. Subsequently, the bidirectional gated recurrent unit (BiGRU) is used for the trend component, and the long short-term memory (LSTM) is used for the seasonal and residual components to extract the time series information. The experiments based on the measured data demonstrate that the use of STL decomposition and the combination model can effectively extract the information in soil moisture series using its concise and clear structure. The proposed model in this article has a stable performance improvement of 5-30% over a single model and existing prediction models in different prediction time domains. In long-range prediction, the proposed model also achieves the best accuracy in the shape and temporal domains described by using dynamic time warping (DTW) index and temporal distortion index (TDI). In addition, the generalization performance experiments show that the combined method proposed in this article has strong reference value for time series prediction of natural complex systems.

Regional distribution and migration potential of antibiotic resistance genes in croplands of Qinghai Tibet Plateau

Agricultural activities have recently disturbed the ecosystem of the Qinghai-Tibet Plateau and the shift of antibiotic resistance genes (ARGs) in the different types of farmlands is not well understood, so more comprehensive ecological barrier management measures cannot be provided for the region. This research was performed to exploring ARG pollution in cropland soil on the Qinghai-Tibet Plateau to obtain information on the geographical and climatic factors shaping the ARG distribution. Based on high-throughput quantitative PCR (HT-qPCR) analysis, the ARG abundance in farmland ranged from 5.66 × 105 to 6.22 × 107 copies per gram of soil higher than previous research at soil and wetland in Qinghai-Tibet plateau, and it was higher in wheat and barley soils than in corn soil. The distribution of ARGs exhibited regional features as ARG abundance was adversely affected by mean annual precipitation and temperature with lower temperature and less rainfall at high altitude. According to network analysis and structural equation modeling (SEM), mobile genetic elements (MGEs) and heavy metals are the key drivers of ARG dissemination on the Qinghai-Tibet Plateau as they show negative relationship with ARGs, and selection copressure from heavy metals in cropland soil increases the horizontal gene transfer (HGT) potential of ARGs through synergistic selection effects, each contribution to the ARGs was 19% and 29% respectively. This research suggests the need to focus on controlling heavy metals and MGEs to constrain the dissemination of ARGs, as arable soil is already slightly contaminated by heavy metals.

High-Throughput Sequencing Technology Assisted Investigation of the Correlation between Intestinal Flora, Serum Biochemistry, Blood Lipids, and Tumour Markers in Patients with Gastric Cancer and Healthy Plateau Residents

Aim The goal is to use high-throughput sequencing technology to compare and study the structure and variety of intestinal flora in people with gastric cancer and healthy people in the Qinghai-Tibet Plateau. Background Recent research has connected gut flora structure to numerous disorders. Metabolites, endotoxins, and immunomodulatory modulation might cause gastrointestinal or other systemic diseases and affect gastric cancer treatment and prognosis. We used the correlation study to uncover biomarkers associated with good intestinal flora and gastric cancer groups on the plateau to investigate their involvement in gastric cancer development. Objectives To investigate the possible links between intestinal flora and gastric cancer in the Qinghai Plateau region using a variety of clinical phenotypic data and to investigate the flora that may be linked to gastric cancer. Methods The 22 Qinghai Province tertiary hospital gastric cancer patients and 30 healthy people had their fresh faeces collected. To examine intestinal flora diversity and composition, 52 patients underwent 16S rDNA high-throughput gene sequencing of intestinal bacteria. The correlation between clinical phenotypes and the top 15 dominant intestinal flora at the phylum level was analyzed. Results The difference in total protein TP between the healthy group and the gastric cancer group was statistically significant (P<0.001). Globulin was significantly different (P<0.05), TC of total cholesterol was significantly different (P<0.05). High-density lipoprotein showed statistical significance (P<0.05).The difference in low-density lipoprotein was statistically significant (P<0.001). Alpha-fetoprotein was significantly different (P<0.05). CA72-4 carbohydrate antigen (P<0.05). Conclusion There were significant differences in total protein, globulin, total cholesterol, high density lipoprotein, low-density lipoprotein, alpha-fetoprotein and carbohydrate antigen CA72-4 in patients with gastric cancer in the plateau area compared with the healthy group, and the different clinical variables were correlated with intestinal flora at some phylum and genus levels.

Ecological risks induced by consumption and emission of Pharmaceutical and personal care products in Qinghai-Tibet Plateau: Insights from the polar regions

As the third pole of the world and Asia's water tower, the Tibetan Plateau experiences daily release of pharmaceutical and personal care products (PPCPs) due to increasing human activity. This study aimed to explore the potential relationship between the concentration and composition of PPCPs and human activity, by assessing the occurrence of PPCPs in areas of typical human activity on the Qinghai-Tibet Plateau and evaluating their ecological risk. The results indicate that 28 out of 30 substances were detected in concentrations ranging from less than 1 ng/L to hundreds of ng/L, with the average concentration of most PPCPs in the Tibet Autonomous Region being higher than that in Qinghai Province. Among the detected substances, CAF, NOR, CTC, CIP, TCN, OTC, AZN, and DOX accounted for over 90% of the total concentration. The emission sources of PPCPs were identified by analyzing the correlation coefficients of soil and water samples, with excess PPCPs used by livestock breeding discharged directly into soil and then into surface water through leaching or runoff. By comparing the concentration and composition of PPCPs with those in other regions, this study found that CIP, ENR, LOM, NOR, CTC, DOX, OTC, and TCN were the most commonly used PPCPs in the Qinghai-Tibet Plateau. To assess the ecological risk of PPCPs, organisms at different trophic levels, including algae, crustaceans, fish, and insects, were selected. The prediction of the no effect concentration of each PPCP showed that NOR, CTC, TCN, CAF, and CBZ may have deleterious effects on water biota. This study can assist in identifying the emission characteristics of PPCPs from different types and intensities of human activities, as well as their occurrence and fate during the natural decay of aquatic systems.

Flavonoid synthesis in Lamiophlomis rotata from Qinghai-Tibet Plateau is influenced by soil properties, microbial community, and gene expression

Lamiophlomis rotata is a medicinal plant in Qinghai-Tibet Plateau, in which flavonoid compounds are the major medicinal components. However, it remains unclear how flavonoid metabolism of L. rotata is influenced by soil properties and microbial community. In this study, we collected L. rotata seedlings and rhizosphere soils from five habitats ranging from 3750 to 4270 m of altitude and analyzed the effects of habitat conditions on flavonoid metabolism. The activities of peroxidase, cellulase, and urease were increased with altitude, while those of alkaline phosphatase, alkaline protease, and sucrase were decreased with altitude. Analysis of OTUs showed that the total number of bacterial genera was higher than that of fungal genera. The highest number of fungal genera was 132, and that of bacterial genera was 33 in Batang (BT) town in Yushu County at an altitude of 3880 m, suggesting that the fungal communities may play a critical role in L. rotata rhizosphere soils. Flavonoids in leaves and roots of L. rotata shared a similar pattern, with a trend of increasing levels with altitude. The highest flavonoid content measured, 12.94 mg/g in leaves and 11.43 mg/g in roots, was from Zaduo (ZD) County at an altitude of 4208 m. Soil peroxidases affected quercetin content in leaves of L. rotata, while the fungus Sebacina affected flavonoid content in leaves and roots of L. rotata. The expression of PAL, F3'H, FLS, and FNS genes showed a declining trend in leaves with altitude, while F3H showed an increasing trend in both leaves and roots. Overall, soil physicochemical properties and microbial community affect flavonoid metabolism in L. rotata in Qinghai-Tibet Plateau. The variations in flavonoid content and gene expression as well as their associations with soil factors revealed the complexity of the growth conditions and genetic makeup in L. rotata habitats of Qinghai-Tibet Plateau.

Prediction of the potentially suitable areas of Ligularia virgaurea and Ligularia sagitta on the Qinghai-Tibet Plateau based on future climate change using the MaxEnt model

Ligularia virgaurea and Ligularia sagitta are two species of poisonous plants with strong invasiveness in natural grasslands in China that have caused considerable harm to animal husbandry and the ecological environment. However, little is known about their suitable habitats and the key environmental factors affecting their distribution. Although some studies have reported the distributions of poisonous plants on the Qinghai-Tibet Plateau (QTP) and predicted their potential distributions at local scales in some regions under climate change, there have been few studies on the widespread distributions of L. virgaurea and L. sagitta. In this study, we recorded 276 and 118 occurrence points of L. virgaurea and L. sagitta on the QTP using GPS, and then used the MaxEnt model to predict the distribution of suitable habitats. Results showed that (1) under current climate conditions, L. virgaurea and L. sagitta are mainly distributed in southern Gansu, eastern Qinghai, northwestern Sichuan, eastern Tibet, and southwestern Yunnan, accounting for approximately 34.9% and 39.8% of the total area of the QTP, respectively; (2) the main environmental variables affecting the distribution of suitable habitats for L. virgaurea and L. sagitta are the Human Footprint Index (52.8%, 42.2%), elevation (11%, 4.4%), soil total nitrogen (18.9%, 4.2%), and precipitation seasonality (5.1%, 7.3%); and (3) in the future, in the 2050s and 2070s, the area of habitat of intermediate suitability for L. virgaurea will spread considerably in northwest Sichuan, while that of high suitability for L. sagitta will spread to eastern Tibet and western Sichuan.

Unexpectedly high nitrate levels in a pristine forest river on the Southeastern Qinghai-Tibet Plateau

River nitrate (NO₃^-) pollution is a global environmental issue. Recently, high NO₃^- levels in some pristine or minimally-disturbed rivers were reported, but their drivers remain unclear. This study integrated river isotopes (δ¹⁸O/δ¹⁵N-NO₃^- and δD/¹⁸O-H₂O), ¹⁵N pairing experiments, and qPCR to reveal the processes driving the high NO₃^- levels in a nearly pristine forest river on the Qinghai-Tibet Plateau. The river isotopes suggested that, at the catchment scale, NO₃^- removal was prevalent in summer, but weak in winter. The pristine forest soils contributed more than 90 % of the riverine NO₃^-, indicating the high NO₃^- backgrounds. The release of soil NO₃^- to the river was "transport-limited" in both seasons, i.e., the NO₃^- production/stock in the soils exceeded the capacity of hydrological NO₃^- leaching. In summer, this regime and the NO₃^--plentiful conditions in the soils associated with the strong NO₃^- nitrification led to the high riverine NO₃^- levels. While the in-soil nitrification was weak in winter, the leaching of legacy NO₃^- resulted in the consistently high NO₃^- levels. This study provides insights into the reasons for high NO₃^- levels in pristine or minimally-disturbed rivers worldwide and highlights the necessity to consider NO₃^- backgrounds when evaluating anthropogenic NO₃^- pollution in rivers.

Elevational patterns of seed plants and the driving mechanisms in the Himalaya

The Himalaya is an important biodiversity hotspot on earth, which is of great significance to study the elevational gradients in plant diversity and its influencing factors for further revealing the formation of biodiversity and conservation. In this study, we measured the elevational range of 11886 seed plant species and different growth-forms (7918 herbaceous species, 2587 shrub species, and 1388 tree species) in the Himalaya. Using the optimal fitted regression models, we found that species richness and phylogenetic diversity of seed plants in the Himalaya mainly showed unimodal curves with the increases of elevation. The species richness and phylogenetic diversity of all species, trees, shrubs and herbaceous species reached the maximum value at the elevation of about 2000, 1000, 1600 and 3000 m, respectively. The results of partial regression and hierarchical partitioning analysis showed that climate and topography together drove the elevational gradient in plant diversity. Among these, mean annual temperature and annual precipitation contributed greatly to the elevational pattern, while surface area ratio and topographic heterogeneity had little influence. Compared with all species and herbaceous species, the elevational gradients of trees and shrubs plants were affected to a greater extent by the interaction between climate and topography.

Effects of grazing and nitrogen application on greenhouse gas emissions in alpine meadow

Overgrazing and injudicious nitrogen applications have increased emissions of greenhouse gases from grassland ecosystems. To explore the effects and potential mechanisms of grazing, nitrogen application, and their interaction with greenhouse gas (GHG) emissions, field experiments were conducted on the Qinghai-Tibet Plateau for three consecutive years. Alpine meadow plots were subjected to light (8 sheep ha^-1) and heavy (16 sheep ha^-1) stocking rates, with or without ammonium nitrate (NH₄NO₃) (90 kg N ha^-1 yr^-1) treatment to simulate soil nitrogen deposition. During early warm growth season (May-June), peak growth season (July-September), and early cold season (October-November), static-chamber gas chromatography was used to analyze the soil's greenhouse gas emissions (CO₂, N₂O, and CH₄). Results indicated that light stocking rate (LG) led to an increase in cumulative CO₂ and N₂O emissions, while also promoting CH₄ uptake. Conversely, heavy stocking rate (HG) produced contrasting outcomes. Additionally, nitrogen applications significantly increased the short-term CO₂ and N₂O fluxes peaks. Combined treatment of nitrogen application and light stocking rate (LG + N) resulted in increased CO₂ and N₂O emissions while decreased CH₄ uptake, consequently leading to a significant increase in global warming potential. According to the structural equation model, we discovered that nitrogen application and grazing affected GHG fluxes both directly and indirectly through their impact on the environmental factors. Our findings suggest that in the context of increasing nitrogen deposition in the Qinghai-Tibet Plateau, a moderate increase in stocking rate is more effective than reducing grazing intensity for mitigating global warming potential in alpine meadow.

Oxygen stress on age-stage, two-sex life tables and transcriptomic response of diamondback moth (Plutella xylostella)

Elucidating the genetic basis of local adaption is one of the important tasks in evolutionary biology. The Qinghai-Tibet Plateau has the highest biodiversity for an extreme environment worldwide, and provides an ideal natural laboratory to study adaptive evolution. The diamondback moth (DBM), Plutella xylostella, is one of the most devastating pests of the global Brassica industry. A highly heterozygous genome of this pest has facilitated its adaptation to a variety of complex environments, and so provides an ideal model to study fast adaptation. We conducted a pilot study combining RNA-seq with an age-stage, two-sex life table to study the effects of oxygen deprivation on DBM. The developmental periods of all instars were significantly shorter in the hypoxic environment. We compared the transcriptomes of DBM from Fuzhou, Fujian (low-altitude) and Lhasa, Tibet (high-altitude) under hypoxia treatment in a hypoxic chamber. Some DEGs are enriched in pathways associated with DNA replication, such as DNA repair, nucleotide excision repair, base excision repair, mismatch repair and homologous recombination. The pathways with significant changes were associated with metabolism process and cell development. Thus, we assumed that insects could adapt to different environments by regulating their metabolism. Our findings indicated that although adaptive mechanisms to hypoxia in different DBM strains could be similar, DBM individuals from Tibet had superior tolerance to hypoxia compared with those of Fuzhou. Local adaptation of the Tibetan colony was assumed to be responsible for this difference. Our research suggests novel mechanisms of insect responses to hypoxia stress.