Elymus sibiricus L., a member of the Triticeae tribe, is a grass widely used for forage and restoring degraded grasslands in the Qinghai-Tibetan Plateau (QTP) region. Here, we present a high-quality reference genome assembly of allotetraploid E. sibiricus, consisting of 14 pseudochromosomes. Our findings suggest that large-scale bursts of retrotransposon activity, especially by Gypsy elements and unclassified retrotransposon elements, have played a critical role in the genome expansion of E. sibiricus as compared with other Triticeae. We identified a translocation between chromosomes Es4H and Es6H with a low recombination rate. Population genomic analysis of 90 E. sibiricus accessions and 25 diploid accessions of proposed ancestors from different habitats revealed four distinct groups, although they are of monophyletic origin. Our population analysis supports the idea that the QTP is likely the center of origin and genetic diversity of E. sibiricus. Selective sweep analysis identified significant pathways related to photosynthesis and metabolism, which are likely associated with the multiple environmental adaptations of this species to the climatic conditions of the QTP. Collectively, our study not only provides genomic resources for genetic improvement of the Elymus genus, but also provides important insights on the evolutionary history of E. sibiricus from population genomic analysis and the evolution of the tribe Triticeae.

Elymus nutans Griseb. (Poaceae: Triticeae, 2n=6x=42) is a dominant perennial plant species in the Qinghai-Tibetan Plateau in China, which is an important forage resource in high-altitude and cold regions and is the most popular species used for high yield artificial grassland planting because of its rich nutritional value and good palatability for herbivorous ruminant animals. In this study, using advanced sequencing technology, we generated an allohexaploid reference genome for E. nutans , representing the three sets of chromosomes (subgenomes St, Y, and H). This is the first study to our knowledge to confirm the origin of the Y subgenome, which shares a close relationship with the V subgenome. We predict that E. nutans arose via two-step hybridization and that its speciation occurred ∼3.16 MYA. The whole genome in this study will update the Triticeae family genomics information and provide theoretical basis for the evolutionary of its related speicies. ### Competing Interest Statement The authors have declared no competing interest.

IntroductionThe grassland degradation and harsh climate in the Qinghai-Tibet Plateau (QTP) have constrained forage production, thereby impeding the development of animal husbandry in pastoral areas of China. The effective cultivation of high-yielding Avena sativa could help alleviate this constraint.MethodsThis study comprehensively evaluated the forage yield and related agronomic traits of 62 A. sativa germplasms. Additionally, the introducing adaptability of different germplasms was predicted across various regions of the QTP.ResultsThe results indicated that: (1) 43 of 62 germplasms could successfully completed the fertility period in the eastern edge of the QTP; (2) Fresh and hay grass yield were significantly positively correlated with absolute plant height, flag leaf length, flag leaf width, flag leaf area, flag-second leaf length, flag-second leaf width, flag-second leaf area, number of total tiller, number of vegetative tiller, stem to leaf ratio of hay, thick of second stem internode, spike length, and root depth, while significantly negatively correlated with thousand kernel weight; (3) Fresh and hay grass yield were directly affected by flag-second leaf length, flag-second leaf width, flag-second leaf area, number of total tiller, number of fertile tiller, and stem to leaf ratio of hay; (4) A. sativa germplasm AS55 exhibited the highest comprehensive forage performance under field conditions, followed by AS39, AS48, AS28, AS41, and AS20; (5) The potential spatial distribution of A. sativa was concentrated in the southeastern QTP, with its distribution being significantly affected by hydrothermal conditions. Moreover, the potential distribution pattern of high suitability regions showed an expanding trend over time; (6) 15 A. sativa germplasms had varying degrees of introduction adaptability in 23 municipal-level administrative regions within the QTP. The potential suitable area for introducing different germplasms was 7.81×105 km2 in the current period and 2.68×105 km2 in the future period. the area of regions with high introduction adaptability increased from 1.60×103 km2 in the current period to 1.38×104 km3 in the future period.DiscussionIn this study, evaluations of forage production performance and predictions of introduction adaptability were conducted for 62 A. sativa germplasms at the eastern edge of the QTP. The findings aim to provide a theoretical basis for the collection, preservation, and utilization of A. sativa germplasm resources, as well as valuable insights for the cultivation and protection of plants in the QTP.

In recent years, the Pelton turbine has shown an increasing inclination toward harnessing ultra-high head hydropower resources. However, its hydraulic efficiency faces a significant decline under non-design heads. Unlike traditional methods, the entropy production method provides a quantitative and intuitive framework for understanding the spatial distribution of energy losses. This study employs the entropy production method to analyze the energy loss characteristics of a six-nozzle Pelton turbine at various operating heads. The results affirm that the entropy production method is a feasible method for evaluating energy losses in the Pelton turbine. Within the Pelton turbine, increased entropy production rate primarily results from wall friction, secondary flow, flow separation, jet expansion, jet impact, and flow interference. Under varying operating heads, the energy losses within the runner notably exceed those in other components. At the design head (Hr), the proportions of energy losses within the runner, stator domain, nozzle, and distribution tube constitute 50.28 %, 18.06 %, 28.32 %, and 3.34 % of the total losses, respectively. Nevertheless, under non-design heads, flow interference leads to a significant increase in energy losses within the runner and stator domain. The proportion of energy losses within the runner rises to 59.55 % and 68.40 % at 0.7Hr and 1.3Hr. Moreover, the energy losses within the stator domain surpass those in the nozzle, reaching 28.28 % and 18.64 % at 0.7Hr and 1.3Hr.

Siberian wildrye (Elymus sibiricus L.), a model Elymus Gramineae plant, has high eco-economic value but limited seed and forage yield. TCP transcription factors are widely regarded as influencing yield and quality and being crucial for growth and development; still, this gene family in Siberian wildrye remains unexplored. Therefore, this study looked at the Siberian wildrye TCP gene family’s reaction to several abiotic stresses, its expression pattern, and its potential evolutionary path. Fifty-four members of the EsTCP gene family were discovered. There are two major subfamilies based on the phylogenetic tree: 27 of Class I (PCF) and 27 of Class II (12 CIN-type and 15 TB1/CYC-type). Gene structure, conserved motif, and sequence alignment analyses further validated this classification. Cis-elements found in the promoter region of EsTCPs are associated with lots of plant hormones and stress-related reactions, covering drought induction and cold tolerance. EsCYC5, EsCYC6, and EsCYC7 may regulate tillering and lateral branch development. EsPCF10’s relative expression was significant under five stresses. Additionally, eight EsTCP genes are potential miR319 targets. These findings highlight the critical significance of the TCP gene family in Siberian wildrye, laying the groundwork for understanding the function of the EsTCP protein in abiotic stress studies and high-yield breeding.

Anaerobic fermentation is a critical approach for the efficient recycling of herbal medicinal waste. During fermentation, micro aeration, feedstock properties, and additives significantly influence performance. This study investigated strategies to enhance lactic acid production during the anaerobic fermentation of red clover by incorporating herbal waste Anisodus tanguticus (AT) and Rhodiola rosea (RS) and Lactiplantibacillus plantarum (LP), combined with micro aeration during the bottleneck phase of fermentation. Results showed that LP and AT exhibited a synergistic effect, increasing lactic acid content by 14.35%. Conversely, RS promoted the growth of lactic acid-consuming bacteria (e.g., Hafnia alvei), reducing lactic acid production, although this inhibitory effect was alleviated by LP inoculation, resulting in an 11.11% increase in lactic acid yield. Targeted micro aeration significantly enhanced carbohydrate metabolism increased the abundance of polysaccharide-degrading enzyme genes and boosted lactic acid content by 38.49%-74.33%. However, prolonged aeration activated aerobic bacteria, leading to decreased lactic acid production. These findings highlight the potential of combining targeted micro aeration with herbal waste interventions to overcome fermentation bottlenecks, enhance lactic acid production, and provide innovative solutions for sustainable herbal waste management.

Abstract Pelton turbines are emerging as a primary means for exploiting ultra-high water head resources. The hydraulic performance of a Pelton turbine is determined by the design of its runner/bucket. Among the critical parameters that affect the hydraulic performance of multi-nozzle Pelton turbines is the bucket offset angle (α). To investigate the influence of bucket offset angle on the flow field of Pelton turbines with six nozzles, this study conducted unsteady numerical simulations of gas-liquid two-phase flow for various bucket offset angles, employing the VOF multiphase model combined with the SST k-ω turbulence model. The results reveal that as the bucket offset angle increases, the axial width of the water sheet formed by the current jet progressively widens, with a tendency to catch up with the water film formed by the previous jet during the torque rising stage. Moreover, the increased bucket offset angle causes the water sheet to distribute more closely to the bucket cutout, raising the risk of leakage from the cutout. Notably, at α= 10°, some of the water sheet has already flowed out of the cutout and collided with the subsequent jet.

Abstract The stability of Francis turbine under low load conditions has become the focus in the power grid dominated by variable renewable energy. In this paper, the variable-speed approach is used to explore the operating characteristics of the Francis turbine, the RANS/LES hybrid turbulent model is adopted to investigate the fluid structure evolution process, and using the Q-criterion depicts the vortex cores. The results show that the numerical simulation agrees well with the experimental data acquired from the model test. It is found that the variable-speed operation can effectively eliminate the vortex ropes in the draft tube. Unexpectedly, the vortices in the runner will evolve from the separated vortices at the runner outlet for the fixed-speed Francis turbine to the inter-blade vortices at the runner inlet for the variable-speed Francis turbine in the case of small guide vane opening. It is concluded that the optimum operating range of a variable-speed Francis turbine (VSFT) should be within ±30% rated speed and 60% to 100% opening, and the pressure pulsation coefficient in the draft tube can be reduced from 7% to 1% at minimum water head, the output and efficiency of the turbine are increased by about 30% and 10% respectively.

IntroductionElymus nutans holds ecological and pastoral significance due to its adaptability and nutritional value, the Qinghai-Tibet Plateau (QTP) is a key hub for its genetic diversity. To conserve and harness its genetic resources in highland ecosystems, a thorough assessment is vital. However, a comprehensive phylogeographic exploration of E. nutans is lacking. The objective of this study was to unravel the genetic diversity, adaptation, and phylogenetics of E. nutans populations.MethodsEncompassing 361 individuals across 35 populations, the species' genetic landscape and dynamic responses to diverse environments were decoded by using four chloroplast DNA (cpDNA) sequences and nine microsatellite markers derived from the transcriptome.Results and discussionThis study unveiled a notable degree of genetic diversity in E. nutans populations at nuclear (I = 0.46, He = 0.32) and plastid DNA levels (Hd = 0.805, π = 0.67). Analysis via AMOVA highlighted genetic variation predominantly within populations. Despite limited isolation by distance (IBD), the Mekong-Salween Divide (MSD) emerged as a significant factor influencing genetic differentiation and conserving diversity. Furthermore, correlations were established between external environmental factors and effective alleles of three EST-SSRs (EN5, EN57 and EN80), potentially linked to glutathione S-transferases T1 or hypothetical proteins, affecting adaptation. This study deepens the understanding of the intricate relationship between genetic diversity, adaptation, and environmental factors within E. nutans populations on the QTP. The findings shed light on the species' evolutionary responses to diverse ecological conditions and contribute to a broader comprehension of plant adaptation mechanisms.

Elymus sibiricus L. (Siberian wildrye, Es ), a species belonging to the wheat tribe, is extensively employed as forage and for the reclamation of degraded grasslands within the Qinghai-Tibet Plateau (QTP). This study provides a high-quality reference genome assembly for the allotetraploid Es , which is composed of 14 pseudomolecules with the total genome size of 6.57 Gb. Our finding suggest that large-scale bursts of retrotransposons are critical for the genome expansion of Es . We discovered a translocation event between the Es 4H and Es 6H chromosomes with a low frequency of combination. Phylogenetic analyses of 90 Es accessions and 25 diploid accessions representing proposed ancestors from various habitats revealed the existence of four distinct populations. We further provided support for the hypothesis that the QTP is the center of origin and genetic diversity for Es . Collectively, our study offers valuable insights into the evolution of Es , as well as providing genomic resources for genetic enhancement in the Elymus genus and wheat tribe.### Competing Interest StatementThe authors have declared no competing interest.

为揭示野生老芒麦形态变异特征和遗传背景,对我国野生老芒麦主要分布区域不同生态类型的104个居群520份野生老芒麦种质进行了23个形态指标测定和遗传多样性分析.结果表明:不同生境老芒麦材料的形态特征存在显著差异,数量性状变异系数为9.49％～49.56％;聚类分析将104个居群分为具有各自明显特征和开发利用潜力的4类;形态特征与地理环境因子的相关性分析发现,野生老芒麦抽穗早晚及茎秆叶鞘基部小刺等特殊性状与其海拔呈显著相关;主成分分析发现,株高、抽穗、茎节数、单株干鲜重、旗叶长宽等指标代表了老芒麦67.79％形态多样性,是造成老芒麦形态特征变异的主要因素,可作为老芒麦形态分化的重要参考指标.

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.

本研究开展了短芒型老芒麦(Elymus sibiricus L.)种质的筛选和综合评价,以筛选优质种质.基于55个形态学指标和SCoT分子标记对川西北地区24份短芒型老芒麦种质以及两份老芒麦对照材料进行形态变异及遗传亲缘关系分析.形态学指标在26份材料之间表现出丰富的遗传多样性,Shannon-Wiener's多样性指数(H)范围为0.66～2.01;变异系数(CV)范围为4.62％～45.93％,聚类分析将26份老芒麦资源分为5个大类.基于SCoT分子标记,共扩增出多态性条带96条,多态性比率为67.61％.平均有效等位基因数为1.46,平均Nei's基因多样性指数为0.27,平均Shannon's多样性指数为0.38,供试材料的DICE遗传相似性系数为0.67～0.87.通过遗传相似系数的聚类分析,可将26份材料分为四大类.群体遗传结构分析将供试材料划分为两个类群,Q2类群来源单一,Q1类群拥有混合来源.Esdm24,Esdm6,Esdm22这3份种质的芒等相关性状具有优异的性状,可以作为短芒型老芒麦的选育的后备材料.

为进一步评价川西短芒披碱草在大田生产条件下的生产性能,课题组于2015～2018 年,以国审品种同德短芒披碱草为对照,分别在四川红原县、道孚县和青海海晏县开展了川西短芒披碱草多年多点的大田生产试验.连续 3 年的生产试验结果表明,川西短芒披碱草在各试验点生长良好,生产性能表现优良,综合评价优于对照品种同德短芒披碱草.川西短芒披碱平均鲜草产量为17760kg/hm2,较对照增产 14.7％,增产显著;干草产量平均为 6469kg/hm2,较对照增产 13.2％,增产极显著.川西短芒披碱草较对照同德短芒披碱草具有突出的丰产性和一定的稳定性,在四川省阿坝州红原县、甘孜州道孚县和青海省海北州海晏县均能很好的适应,适宜在类似生态区推广种植.

In order to make better use of the wild resources of Elymus sibiricus germplasm, in this study the 1 723 materials of wild Elymus species resources from the Qinghai-Tibet Plateau, Northwest of China, North China and Northeast of China and some foreign regions were collected, from which, total of 990 wild E. sibiricus germplasm were identified by phenotypic characteristics and the Flow Cytometry detection. The results showed that the DNA content of E. sibiricus was between 5.86～7.30 Gb with average of 6.66Gb. The DNA content of Elymus nutans Griseb was between 9.50～10.36 Gb with average of 9.97Gb. It was found out that dorsal hair appeared in the basal leaf sheath of some wild E. sibiricus materials from Northwest of China, North China and Northeast of China, which was different from the description of the morphological characteristics of E. sibiricus in Chinese Flora,which was positively correlated with longitude and latitude（P ＜ 0.01）,and negatively correlated with altitude, annual mean temperature and annual mean rainfall（P＜0.01）,indicating that there was an inevitable relationship between the existence of the dorsal hair in the basal leaf sheath of E. sibiricus and its environmental factors and which possibly was one of the adaptive mechanisms of E. sibiricus germplasm to its environment. The results of this study provided a new basis for the morphological identification of E. sibiricus,and for the exploring E. sibiricus germplasm resources and breeding application.

Alfalfa is cultivated throughout the world, but its preservation remains challenging to small farms in cold climates. This study aimed to investigate the effects of small-scale silo types and additives on the silage quality of high moisture alfalfa on the Qinghai-Tibetan Plateau. Alfalfa with moisture of about 80% was ensiled in small farm bucket silos (FBS) or wrapped bale silos (WBS) at ambient temperature (5-15 degrees C) for 180 days. At ensiling, forage was treated without any additive (CK) or with a chemical additive (SB; a mixture of sodium benzoate, potassium sorbate, and sodium nitrite) or a lactic acid bacteria (LAB) inoculant (PBB; a mixture of Lactiplantibacillus plantarum, Bifidobacterium brevis and Pediococcus pentosaceus). Among the CK silages, higher (P < 0.05) acetic acid levels, bacterial diversity indices and relative abundance of L. plantarum were found in WBS vs FBS. Overall, silage treated with SB had the highest crude protein (CP) content, the lowest amylase-treated neutral detergent fiber (aNDF) and acid detergent fiber (ADF) contents and dry matter (DM) loss. Compared with CK, treatments with SB and PBB increased (P < 0.05) lactic acid content and decreased (P < 0.05) final pH value and butyric acid content of silage. In addition, treatment with PBB reduced (P < 0.05) the relative abundance of Lactilacto-bacillus sakei and increased (P < 0.05) the similarity of silage samples from different silos. There was negligible difference in fermentation quality of silage occurred between the types of silos. However, small WBS tended to increase the relative abundance of L. plantarum for more desirable silage fermentation. Application of additives at ensiling enhanced the preservation of silage nu-trients with low DM loss. Based on the above results, small WBS were recommended for pro-ducing high-quality alfalfa silage on the Qinghai-Tibetan Plateau.

为进一步提高燕麦(Avena sativa L.)饲草生产性能,降低生产成本,本试验以梦龙燕麦(Avena sativa L.cv.Magnum)为研究对象,采用裂区试验设计,通过综合分析燕麦牧草产量和营养品质相关指标,探究不同播量、播种方式对燕麦饲草产量与品质的影响.结果表明:播种方式与鲜草产量、鲜干比、生殖枝数以及分蘖数呈极显著正相关,与倒伏率呈负相关;播种量与牧草产量有一定相关性,但差异不显著.播种方式为撒播时,梦龙燕麦的鲜草产量、干草产量以及分蘖数随播种量的增加呈先升高后降低的趋势.当播种量为 120kg/hm2 时,其鲜、干草产量和分蘖数最高,分别为 83.87t/hm2、20.93t/hm2 和811 个/m2,其NDF(48.57%)和ADF(27.03%)均达到特级燕麦干草水平,且粗蛋白(9.97%)也有显著提升(P<0.05).灰色关联度分析表明,该组合与标准处理关联系数关系最大(r =0.7643),可以获得较高的牧草产量和营养价值,适宜在生产中推广.

Landslides induced by rainfall pose a notable threat to post-earthquake reconstruction in mountainous areas. Taking Qingliu landslide as an example, this paper reveals the potential failure mechanism and range of the landslide mass through field investigation and monitoring data, and further uses the improved computational fluid dynamics method to simulate and predict the disaster range after landslide destabilization. The results show that the landslide was initially deformed and cracked under the influence of strong earthquakes and formed seepage channels for water infiltration. The circulation of surface recharge of groundwater in rainy season and long-distance recharge of groundwater from melting ice and snow in winter season leads to the continuous softening and reduction of sliding resistance in the sliding zone. Under the action of this change chain, the cracks along the back edge and boundary of the landslide continue to develop and expand and finally will lead to landslide collapse failure. The equivalent fluid method can better simulate the movement process and accumulation process of landslide, since the Qingliu landslide is a soil landslide with fluid characteristics in the process of landslide movement. The results indicate that the maximum speed of the mass flow could reach 49 m/s, which could destroy the infrastructures along the sliding path, besides, both of the two landslides could bury Xiameng town below and block the Mengtun River to form a landslide-dammed lake. The research results could provide a reference for further comprehensive treatment of landslides and the formulation of emergency plans.

To better utilize poorly fermented oat silage on the Qinghai Tibetan Plateau, 239 samples of this biomass were collected from the plateau temperate zone (PTZ), plateau subboreal zone (PSBZ), and nonplateau climatic zone (NPCZ) in the region and analyzed for microbial community, chemical composition and in vitro gas production. Climatic factors affect the bacterial α-diversity and β-diversity of poorly fermented oat silage, which led to the NPCZ having the highest relative abundance of Lactiplantibacillus plantarum. Furthermore, the gas production analysis showed that the NPCZ had the highest maximum cumulative gas emissions of methane. Through structural equation modeling analysis, environmental factors (solar radiation) affected methane emissions via the regulation of lactate production by L. plantarum. The enrichment of L. plantarum contributes to lactic acid production and thereby enhances methane emission from poorly fermented oat silage. Notably, there are many lactic acid bacteria detrimental to methane production in the PTZ. This knowledge will be helpful in revealing the mechanisms of environmental factors and microbial relationships influencing the metabolic processes of methane production, thereby providing a reference for the clean utilization of other poorly fermented silage.