Warming has a minor effect on surface soil organic carbon in alpine meadow ecosystems on the Qinghai-Tibetan Plateau.

The alpine meadow ecosystem on the Qinghai-Tibetan Plateau (QTP) is very sensitive to warming and plays a key role in regulating global carbon (C) cycling. However, how warming affects the soil organic carbon (SOC) pool and related C inputs and outputs in alpine meadow ecosystems on the QTP remains unclear. Here, we combined two field experiments and a meta-analysis on field experiments to synthesize the responses of the SOC pool and related C cycling processes to warming in alpine meadow ecosystems on the QTP. We found that the SOC content of surface soil (0-10 cm) showed a minor response to warming, but plant respiration was accelerated by warming. In addition, the warming effect on SOC was not correlated with experimental and environmental variables, such as the method, magnitude and duration of warming, initial SOC content, mean annual temperature, and mean annual precipitation. We conclude that the surface SOC content is resistant to climate warming in alpine meadow ecosystems on the QTP.

Ambient climate determines the directional trend of community stability under warming and grazing.

Changes in ecological processes over time in ambient treatments are often larger than the responses to manipulative treatments in climate change experiments. However, the impacts of human-driven environmental changes on the stability of natural grasslands have been typically assessed by comparing differences between manipulative plots and reference plots. Little is known about whether or how ambient climate regulates the effects of manipulative treatments and their underlying mechanisms. We collected two datasets, one a 36-year long-term observational dataset from 1983 to 2018, and the other a 10-year manipulative asymmetric warming and grazing experiment using infrared heaters with moderate grazing from 2006 to 2015 in an alpine meadow on the Tibetan Plateau. The 36-year observational dataset shows that there was a nonlinear response of community stability to ambient temperature with a positive relationship between them due to an increase in ambient temperature in the first 25 years and then a decrease in ambient temperature thereafter. Warming and grazing decreased community stability with experiment duration through an increase in legume cover and a decrease in species asynchrony, which was due to the decreasing background temperature through time during the 10-year experiment period. Moreover, the temperature sensitivity of community stability was higher under the ambient treatment than under the manipulative treatments. Therefore, our results suggested that ambient climate may control the directional trend of community stability while manipulative treatments may determine the temperature sensitivity of the response of community stability to climate relative to the ambient treatment. Our study emphasizes the importance of the context dependency of the response of community stability to human-driven environmental changes.

Shifting plant species composition in response to climate change stabilizes grassland primary production.

The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.

Alpine grassland plants grow earlier and faster but biomass remains unchanged over 35 years of climate change.

Satellite data indicate significant advancement in alpine spring phenology over decades of climate warming, but corresponding field evidence is scarce. It is also unknown whether this advancement results from an earlier shift of phenological events, or enhancement of plant growth under unchanged phenological pattern. By analyzing a 35-year dataset of seasonal biomass dynamics of a Tibetan alpine grassland, we show that climate change promoted both earlier phenology and faster growth, without changing annual biomass production. Biomass production increased in spring due to a warming-induced earlier onset of plant growth, but decreased in autumn due mainly to increased water stress. Plants grew faster but the fast-growing period shortened during the mid-growing season. These findings provide the first in situ evidence of long-term changes in growth patterns in alpine grassland plant communities, and suggest that earlier phenology and faster growth will jointly contribute to plant growth in a warming climate.

Diet simplification selects for high gut microbial diversity and strong fermenting ability in high-altitude pikas.

The gut microbiota in mammals plays a key role in host metabolism and adaptation. However, relatively little is known regarding to how the animals adapts to extreme environments through regulating gut microbial diversity and function. Here, we investigated the diet, gut microbiota, short-chain fatty acid (SCFA) profiles, and cellulolytic activity from two common pika (Ochotona spp.) species in China, including Plateau pika (Ochotona curzoniae) from the Qinghai-Tibet Plateau and Daurian pika (Ochotona daurica) from the Inner Mongolia Grassland. Despite a partial diet overlap, Plateau pikas harbored lower diet diversity than Daurian pikas. Some bacteria (e.g., Prevotella and Ruminococcus) associated with fiber degradation were enriched in Plateau pikas. They harbored higher gut microbial diversity, total SCFA concentration, and cellulolytic activity than Daurian pikas. Interestingly, cellulolytic activity was positively correlated with the gut microbial diversity and SCFAs. Gut microbial communities and SCFA profiles were segregated structurally between host species. PICRUSt metagenome predictions demonstrated that microbial genes involved in carbohydrate metabolism and energy metabolism were overrepresented in the gut microbiota of Plateau pikas. Our results demonstrate that Plateau pikas harbor a stronger fermenting ability for the plant-based diet than Daurian pikas via gut microbial fermentation. The enhanced ability for utilization of plant-based diets in Plateau pikas may be partly a kind of microbiota adaptation for more energy requirements in cold and hypoxic high-altitude environments.

[Effect of Naoshuantong capsule on change of SSQOL index in patients with ischemic stroke in six mouths follow-up].

To evaluate the effect of Naoshuantong capsule on the life quality of patients with ischemic stroke in six months of follow-up studies, and observe the adverse events. The results would provide reference for the secondary prevention on the recovery stage of ischemic stroke. 696 patients from 12 Class III Grade I hospitals nationwide were divided into 2 groups by central randomization system. The study group, 344 cases, were treated with Naoshuantong capsule plus Aspirin, and the control group, 352 cases, were treated with Aspirin. The patients were treated for 6 months. At the end of treatment, SS-QOL used for evaluating the quality of life was observed. The safety index was defined by adverse observation event. The incidence of adverse events and laboratory tests results were observed before and after treatment at the same time. The results indicated that compared to the control group, the treatment group had significant statistical difference in the impact of effort, self-care ability and the the work or labor ability of patients (P < 0.05). No serious adverse events were observed. Naoshuantong capsule showed some superiority to Asprin on improving the quality of life on patients with ischemic stroke, and it could be used in secondary prevention on the recovery stage of ischemic stroke. Naoshuantong capsule is safe and effective in the treatment of convalescence ischemic stroke.

Inhibition of inducible nitric oxide synthase expression and nitric oxide production in plateau pika (Ochotona curzoniae) at high altitude on Qinghai-Tibet Plateau.

Nitric oxide (NO), a potent vasodilator, plays an important role in preventing hypoxia induced pulmonary hypertension. Endogenous NO is synthesized by nitric oxide synthases (NOSs) from l-arginine. In mammals, three different NOSs have been identified, including neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS). Plateau pika (Ochotona curzoniae) is a typical hypoxia tolerant mammal that lives at 3000-5000 m above sea level on the Qinghai-Tibet Plateau. The aim of this study was to investigate whether NOS expression and NO production are regulated by chronic hypoxia in plateau pika. Quantitative real-time PCR and western blot analyses were conducted to quantify relative abundances of iNOS and eNOS transcripts and proteins in the lung tissues of plateau pikas at different altitudes (4550, 3950 and 3200 m). Plasma NO metabolites, nitrite/nitrate (NO(x)⁻) levels were also examined by Ion chromatography to determine the correlation between NO production and altitude level. The results revealed that iNOS transcript levels were significantly lower in animals at high altitudes (decreased by 53% and 57% at altitude of 3950 and 4550 m compared with that at 3200 m). Similar trends in iNOS protein abundances were observed (26% and 41% at 3950 and 4550 m comparing with at 3200 m). There were no significant differences in eNOS mRNA and protein levels in the pika lungs among different altitudes. The plasma NO(x)⁻ levels of the plateau pikas at high altitudes significantly decreased (1.65±0.19 µg/mL at 3200 m to 0.44±0.03 µg/mL at 3950 m and 0.24±0.01 µg/mL at 4550 m). This is the first evidence describing the effects of chronic hypoxia on NOS expression and NO levels in the plateau pika in high altitude adaptation. We conclude that iNOS expression and NO production are suppressed at high altitudes, and the lower NO concentration at high altitudes may serve crucial roles for helping the plateau pika to survive at hypoxic environment.

Multi-omics reveal the gut microbiota-mediated severe foraging environment adaption of small wild ruminants in the Three-River-Source National Park, China.

The Tibetan antelope (Pantholops hodgsonii), blue sheep (Pseudois nayaur), and Tibetan sheep (Ovis aries) are the dominant small ruminants in the Three-River-Source National Park (TRSNP). However, knowledge about the association between gut microbiota and host adaptability remains poorly understood. Herein, multi-omics sequencing approaches were employed to investigate the gut microbiota-mediated forage adaption in these ruminants. The results revealed that although wild ruminants (WR) of P. hodgsoni and P. nayaur were faced with severe foraging environments with significantly low vegetation coverage and nutrition, the apparent forage digestibility of dry matter, crude protein, and acid detergent fiber was significantly higher than that of O. aries. The 16s rRNA sequencing showed that the gut microbiota in WR underwent convergent evolution, and alpha diversity in these two groups was significantly higher than that in O. aries. Moreover, indicator species, including Bacteroidetes and Firmicutes, exhibited positive relationships with apparent forage digestibility, and their relative abundances were enriched in the gut of WR. Enterotype analysis further revealed that enterotype 1 belonged to WR, and the abundance of fatty acid synthesis metabolic pathway-related enzyme genes was significantly higher than enterotype 2, represented by O. aries. Besides, the metagenomic analysis identified 14 pathogenic bacterial species, among which 10 potentially pathogenic bacteria were significantly enriched in the gut microbiota of O. aries. Furthermore, the cellulolytic strains and genes encoding cellulase and hemicellulase were significantly enriched in WR. In conclusion, our results provide new evidence of gut microbiota to facilitate wildlife adaption in severe foraging environments of the TRSNP, China.

Influences of elevational gradient on flower size and number of Gentiana lawrencei var. farreri.

Plants can adapt to environmental changes by adjusting their functional traits and biomass allocation. The size and number of flowers are functional traits related to plant reproduction. Life history theory predicts that there is a trade-off between flower size and number, and the trade-off can potentially explain the adaptability of plants. Elevation gradients in mountains provide a unique opportunity to test how plants will respond to climate change. In this study, we tried to better explain the adaptability of the alpine plant Gentiana lawrencei var. farreri in response to climate change. We measured the flower size and number, individual size, and reproductive allocation of G. lawrencei var. farreri during the flowering period along an elevation gradient from 3200 to 4000 m, and explored their relationships using linear mixed-effect models and the structural equation model. We found that with elevation increasing, individual size and flower number decreased and flower size increased, while reproductive allocation remained unchanged. Individual size positively affected flower number, but was not related to flower size; reproductive allocation positively affected flower size, but was not related to flower number; there is a clear trade-off between flower size and number. We also found that elevation decreased flower number indirectly via directly reducing individual size. In sum, this study suggests that G. lawrencei var. farreri can adapt to alpine environments by the synergies or trade-offs among individual size, reproductive allocation, flower size, and flower number. This study increases our understanding of the adaptation mechanisms of alpine plants to climate change in alpine environments.

Secondary formation of oxygenated and nitrated polycyclic aromatic compounds under stagnant weather conditions: Drivers and seasonal variation.

Severe air pollution tends to occur under stagnant weather conditions. This study focused on the occurrence and formation of PM2.5-bound polycyclic aromatic compounds (PACs) under stagnant weather conditions, in consideration of their adverse human health effect and ecological toxicity. The concentrations of PACs were higher under stagnant weather conditions than in other situations with averaged values of 46.0 ng/m3 versus 12.3-39.9 ng/m3 for total PACs. Secondary formation contributed to over half of the oxygenated and nitrated polycyclic aromatic compounds (OPAHs and NPAHs). Further analyses revealed different formation mechanisms for secondary OPAHs and NPAHs. Secondary production of OPAHs was sensitive to the variations of both temperature (T) and O3 concentration at T < 22 °C but sustained at a high level despite the fluctuation of temperature and O3 concentration at T > 22 °C. Elevated NO2 concentrations favored the formation of inorganic nitrogen-containing products over NPAHs under lower temperature and higher humidity. Stagnant weather events, accompanied by raised PAC levels occurred in all seasons, but their effects on secondary processes differed among seasons. The elevated temperature, lowered humidity, and increased NO2 level facilitated the secondary formation of OPAHs and/or NPAHs during the stagnant weather events in spring and summer. While under the temperature and humidity conditions in autumn and winter, increased NO2 levels during stagnant weather events promoted the production of secondary inorganic nitrogen-containing compounds over organic products. This study raised concern about the toxic organic pollutants in the atmosphere under stagnant weather conditions and revealed different formation mechanisms between secondary oxygenated and nitrated pollutants as well as among different seasons.

The impacts of climate change and human activities on biogeochemical cycles on the Qinghai-Tibetan Plateau.

With a pace of about twice the observed rate of global warming, the temperature on the Qinghai-Tibetan Plateau (Earth's 'third pole') has increased by 0.2 °C per decade over the past 50 years, which results in significant permafrost thawing and glacier retreat. Our review suggested that warming enhanced net primary production and soil respiration, decreased methane (CH(4)) emissions from wetlands and increased CH(4) consumption of meadows, but might increase CH(4) emissions from lakes. Warming-induced permafrost thawing and glaciers melting would also result in substantial emission of old carbon dioxide (CO(2)) and CH(4). Nitrous oxide (N(2)O) emission was not stimulated by warming itself, but might be slightly enhanced by wetting. However, there are many uncertainties in such biogeochemical cycles under climate change. Human activities (e.g. grazing, land cover changes) further modified the biogeochemical cycles and amplified such uncertainties on the plateau. If the projected warming and wetting continues, the future biogeochemical cycles will be more complicated. So facing research in this field is an ongoing challenge of integrating field observations with process-based ecosystem models to predict the impacts of future climate change and human activities at various temporal and spatial scales. To reduce the uncertainties and to improve the precision of the predictions of the impacts of climate change and human activities on biogeochemical cycles, efforts should focus on conducting more field observation studies, integrating data within improved models, and developing new knowledge about coupling among carbon, nitrogen, and phosphorus biogeochemical cycles as well as about the role of microbes in these cycles.

A functional metagenomics study of soil carbon and nitrogen degradation networks and limiting factors on the Tibetan plateau.

Introduction: The Three-River Source Nature Reserve is located in the core area of the Qinghai-Tibetan Plateau, with the alpine swamp, meadow and steppe as the main ecosystem types. However, the microbial communities in these alpine ecosystems, and their carbon and nitrogen degrading metabolic networks and limiting factors remain unclear. Methods: We sequenced the diversity of bacteria and fungi in alpine swamps, meadows, steppes, and their degraded and artificially restored ecosystems and analyzed soil environmental conditions. Results: The results indicated that moisture content had a greater influence on soil microbial community structure compared to degradation and restoration. Proteobacteria dominated in high moisture alpine swamps and alpine meadows, while Actinobacteria dominated in low moisture alpine steppes and artificial grasslands. A metabolic network analysis of carbon and nitrogen degradation and transformation using metagenomic sequencing revealed that plateau microorganisms lacked comprehensive and efficient enzyme systems to degrade organic carbon, nitrogen, and other biological macromolecules, so that the short-term degradation of alpine vegetation had no effect on the basic composition of soil microbial community. Correlation analysis found that nitrogen fixation was strong in meadows with high moisture content, and their key nitrogen-fixing enzymes were significantly related to Sphingomonas. Denitrification metabolism was enhanced in water-deficient habitats, and the key enzyme, nitrous oxide reductase, was significantly related to Phycicoccus and accelerated the loss of nitrogen. Furthermore, Bacillus contained a large number of amylases (GH13 and GH15) and proteases (S8, S11, S26, and M24) which may promote the efficient degradation of organic carbon and nitrogen in artificially restored grasslands. Discussion: This study illustrated the irrecoverability of meadow degradation and offered fundamental information for altering microbial communities to restore alpine ecosystems.

Trophic niche and adaptation in highland lizards: sex has greater influences than species matching.

The plateau environments are typically arid, cool, and high altitude, posing formidable challenges to wildlife survival due to resource scarcity and harsh conditions. Unraveling ecological adaptability in severe conditions requires a deeper understanding of the niche characteristics of plateau species. Trophic niche, which is a comprehensive indicator describing the energy acquisition strategy of animals, remains relatively understudied in plateau species. Here, by combining stable isotopes and morphological data, we quantified the trophic niches of two allopatric lizard species (Phrynocephalus vlangalii and P. erythrurus) that live in the hinterland of the Qinghai-Tibetan Plateau, and explored how their trophic niches correlate with morphological and environmental factors. While both trophic niche and morphological traits were similar between species, noteworthy distinctions were observed between male and female Phrynocephalus lizards. The morphological traits associated with predation (i.e. limb length and head size) and reproduction (i.e. abdomen length), annual mean temperature, and sex played influential roles in shifting trophic niches. These results imply that sexual dimorphism may facilitate inter-sex divergence in resource utilization, leading to trophic niche variations in the highland lizards. Furthermore, extreme environmental stress can constrain interspecific divergence in morphological and trophic traits. Our findings illustrate the dynamic variations of trophic niches in highland lizards, contributing to a more comprehensive understanding of the adaptation strategies employed by lizard species in plateau environments.

Herbivore assemblages affect soil microbial communities by altering root biomass and available nutrients in an alpine meadow.

Three different herbivore grazing assemblages, namely, yak grazing (YG), Tibetan sheep grazing (SG) and yak and Tibetan sheep co-grazing (MG), are practiced in alpine meadows on the Qinghai-Tibetan Plateau (QTP), but the effects of the different herbivore assemblages on soil microbes are relatively unknown. The microbial community plays an important role in the functional stability of alpine grassland ecosystems. Therefore, it is important to understand how the microbial community structure of grassland ecosystems changes under different herbivore grazing assemblages to ensure their sustainable development. To fill this gap, a field study was carried out to investigate the effects of YG, SG, and MG on plant communities, soil physico-chemical properties and microbial communities under moderate grazing intensity in alpine meadows. Grazing increased the ß-diversity of the bacteria community and decreased the ß-diversity of the fungal community. The herbivore assemblage affected the microbial community diversity, but not the plant community diversity. Total phosphorus, soil bulk density, root biomass, and plant α-diversity were correlated with both the bacterial and fungal community composition, available phosphorus and soil moisture were correlated only with the bacterial community composition, while available potassium and above-ground net primary production (ANPP) were correlated only with the fungal community composition. Soil available nitrogen, soil available phosphorus and soil bulk density were highest in SG, while ANPP was highest in MG. It was concluded that MG can improve ANPP and stabilize the soil microbial community, suggesting that MG is an effective method for sustainable use and conservation of alpine meadows on the QTP.

An early warning signal for grassland degradation on the Qinghai-Tibetan Plateau.

Intense grazing may lead to grassland degradation on the Qinghai-Tibetan Plateau, but it is difficult to predict where this will occur and to quantify it. Based on a process-based ecosystem model, we define a productivity-based stocking rate threshold that induces extreme grassland degradation to assess whether and where the current grazing activity in the region is sustainable. We find that the current stocking rate is below the threshold in ~80% of grassland areas, but in 55% of these grasslands the stocking rate exceeds half the threshold. According to our model projections, positive effects of climate change including elevated CO2 can partly offset negative effects of grazing across nearly 70% of grasslands on the Plateau, but only in areas below the stocking rate threshold. Our analysis suggests that stocking rate that does not exceed 60% (within 50% to 70%) of the threshold may balance human demands with grassland protection in the face of climate change.

Vegetation structural shift tells environmental changes on the Tibetan Plateau over 40 years.

Structural information of grassland changes on the Tibetan Plateau is essential for understanding alterations in critical ecosystem functioning and their underlying drivers that may reflect environmental changes. However, such information at the regional scale is still lacking due to methodological limitations. Beyond remote sensing indicators only recognizing vegetation productivity, we utilized multivariate data fusion and deep learning to characterize formation-based plant community structure in alpine grasslands at the regional scale of the Tibetan Plateau for the first time and compared it with the earlier version of Vegetation Map of China for historical changes. Over the past 40 years, we revealed that (1) the proportion of alpine meadows in alpine grasslands increased from 50% to 69%, well-reflecting the warming and wetting trend; (2) dominances of Kobresia pygmaea and Stipa purpurea formations in alpine meadows and steppes were strengthened to 76% and 92%, respectively; (3) the climate factor mainly drove the distribution of Stipa purpurea formation, but not the recent distribution of Kobresia pygmaea formation that was likely shaped by human activities. Therefore, the underlying mechanisms of grassland changes over the past 40 years were considered to be formation dependent. Overall, the first exploration for structural information of plant community changes in this study not only provides a new perspective to understand drivers of grassland changes and their spatial heterogeneity at the regional scale of the Tibetan Plateau, but also innovates large-scale vegetation study paradigm.

Effects of warming and grazing on soil N availability, species composition, and ANPP in an alpine meadow.

Uncertainty about the effects of warming and grazing on soil nitrogen (N) availability, species composition, and aboveground net primary production (ANPP) limits our ability to predict how global carbon sequestration will vary under future warming with grazing in alpine regions. Through a controlled asymmetrical warming (1.2/1.7 degrees C during daytime/nighttime) with a grazing experiment from 2006 to 2010 in an alpine meadow, we found that warming alone and moderate grazing did not significantly affect soil net N mineralization. Although plant species richness significantly decreased by 10% due to warming after 2008, we caution that this may be due to the transient occurrence or disappearance of some rare plant species in all treatments. Warming significantly increased graminoid cover, except in 2009, and legume cover after 2008, but reduced non-legume forb cover in the community. Grazing significantly decreased cover of graminoids and legumes before 2009 but increased forb cover in 2010. Warming significantly increased ANPP regardless of grazing, whereas grazing reduced the response of ANPP to warming. N addition did not affect ANPP in both warming and grazing treatments. Our findings suggest that soil N availability does not determine ANPP under simulated warming and that heavy grazing rather than warming causes degradation of the alpine meadows.

Biodiversity and Ecosystem Function under Simulated Gradient Warming and Grazing.

Biodiversity and ecosystem functions and their relationship with environmental response constitute a major topic of ecological research. However, the changes in and impact mechanisms of multi-dimensional biodiversity and ecosystem functions in continuously changing environmental gradients and anthropogenic activities remain poorly understood. Here, we analyze the effects of multi-gradient warming and grazing on relationships between the biodiversity of plant and soil microbial with productivity/community stability through a field experiment simulating multi-gradient warming and grazing in alpine grasslands on the Tibetan Plateau. We show the following results: (i) Plant biodiversity, soil microbial diversity and community productivity in alpine grasslands show fluctuating trends with temperature gradients, and a temperature increase below approximately 1 °C is beneficial to alpine grasslands; moderate grazing only increases the fungal diversity of the soil surface layer. (ii) The warming shifted plant biomass underground in alpine grasslands to obtain more water in response to the decrease in soil moisture caused by the temperature rise. Community stability was not affected by warming or grazing. (iii) Community stability was not significantly correlated with productivity, and environmental factors, rather than biodiversity, influenced community stability and productivity.

Cropping practices manipulate soil bacterial structure and functions on the Qinghai-Tibet Plateau.

There is an increasing awareness of the adverse environmental effects of the intensive practices used in modern crop farming, such as those that cause greenhouse gas emissions and nutrient leaching. Harnessing beneficial microbes by changing planting practices presents a promising strategy for optimizing plant growth and agricultural sustainability. However, the characteristics of soil microorganisms under different planting patterns remain uncertain. We conducted a study of soil bacterial structure and function under monoculture vs. polyculture planting regimes using 16S rRNA gene sequencing on the Qinghai-Tibet Plateau. We observed substantial variations in bacterial richness, diversity, and relative abundances of taxa between gramineous and leguminous monocultures, as well as between gramineae-legume polycultures. The number of operational taxonomic units and alpha and beta diversity were markedly higher in the leguminous monocultures than in the gramineous monocultures; conversely, network analysis revealed that the interactions among the bacterial genera in the gramineous monocultures were more complex than those in the other two planting regimes. Moreover, nitrogen fixation, soil detoxification, and productivity were increased under the gramineous monocultures; more importantly, low soil-borne diseases (e.g., animals parasitic or symbiont) also facilitated strongly suppressive effects toward soil-borne pathogens. Nevertheless, the gramineae-legume polycultures were prone to nitrate seepage contamination, and leguminous monocultures exhibited strong denitrification effects. These results revealed that the gramineous monoculture is a more promising cropping pattern on the Qinghai-Tibetan Plateau. Understanding the bacterial distribution patterns and interactions of crop-sensitive microbes presents a basis for developing microbial management strategies for smart farming.

The Gut Microbiota Determines the High-Altitude Adaptability of Tibetan Wild Asses (Equus kiang) in Qinghai-Tibet Plateau.

It was acknowledged long ago that microorganisms have played critical roles in animal evolution. Tibetan wild asses (TWA, Equus kiang) are the only wild perissodactyls on the Qinghai-Tibet Plateau (QTP) and the first national protected animals; however, knowledge about the relationships between their gut microbiota and the host's adaptability remains poorly understood. Herein, 16S rRNA and meta-genomic sequencing approaches were employed to investigate the gut microbiota-host associations in TWA and were compared against those of the co-resident livestock of yak (Bos grunnies) and Tibetan sheep (Ovis aries). Results revealed that the gut microbiota of yak and Tibetan sheep underwent convergent evolution. By contrast, the intestinal microflora of TWA diverged in a direction enabling the host to subsist on sparse and low-quality forage. Meanwhile, high microbial diversity (Shannon and Chao1 indices), cellulolytic activity, and abundant indicator species such as Spirochaetes, Bacteroidetes, Prevotella_1, and Treponema_2 supported forage digestion and short-chain fatty acid production in the gut of TWA. Meanwhile, the enterotype identification analysis showed that TWA shifted their enterotype in response to low-quality forage for a better utilization of forage nitrogen and short-chain fatty acid production. Metagenomic analysis revealed that plant biomass degrading microbial consortia, genes, and enzymes like the cellulolytic strains (Prevotella ruminicola, Ruminococcus flavefaciens, Ruminococcus albus, Butyrivibrio fibrisolvens, and Ruminobacter amylophilus), as well as carbohydrate metabolism genes (GH43, GH3, GH31, GH5, and GH10) and enzymes (ß-glucosidase, xylanase, and ß-xylosidase, etc.) had a significantly higher enrichment in TWA. Our results indicate that gut microbiota can improve the adaptability of TWA through plant biomass degradation and energy maintenance by the functions of gut microbiota in the face of nutritional deficiencies and also provide a strong rationale for understanding the roles of gut microbiota in the adaptation of QTP wildlife when facing harsh feeding environments.