The objective of this study was to reveal the effects of different forms of nitrogen fertilizers on perennial alpine cultivated grassland plant communities and soil properties. A 4-year-old perennial mixed-seeded grassland established in 2019 at Qinghai University’s comprehensive experimental demonstration base of plateau specialty agriculture and animal husbandry was used as the research object. Four treatments of control （CK）， amide nitrogen fertilizer （U）， ammonium nitrogen fertilizer （A） and nitrate nitrogen fertilizer （N） were set up to determine and analyze treatment effects on the plant community structure， soil physicochemical properties and microbial biomass. The results showed that application of different forms of nitrogen fertilizers significantly affected plant productivity， soil physicochemical properties and microbial biomass of artificial grassland， while the effect on plant diversity was not significant. Different forms of nitrogen fertilizers showed U>N>A in promoting plant productivity， with an increase of 62.60%， 53.71% and 25.85% over control. respectively. Application of amide nitrogen fertilizer significantly increased soil water content and soil conductivity and significantly decreased soil bulk density and pH value. Application of ammonium nitrogen fertilizer significantly increased total phosphorus and decreased soil microbial biological carbon to nitrogen ratio. Application of nitrate nitrogen fertilizer significantly increased soil quick phosphorus， total nitrogen， microbial biochar and microbial biochar-phosphorus ratio. Redundancy analysis showed that soil pH value and bulk weight were key soil factors influencing perennial alpine cultivated grassland plant communities. In summary， it is recommended that amide nitrogen fertilizers should be given priority in the development of nitrogen application programs for perennial alpine cultivated grassland productivity maintenance and soil improvement.

To investigate codon usage bias of Persicaria odorata， we sequenced the chloroplast genome of P. odorata using the Next-Generation Sequencing. The raw sequencing data were quality control filtered， assembled， annotated and constructed a physical map. Furthermore， we systematically analyzed the codon usage bias of 52 protein-coding sequences. Our comprehensive analysis shows that the chloroplast genome was 159 897 bp in length， with a typical quadripartite structure consisting of a large single-copy region （LSC）， a small single-copy region （SSC）， and two inverted repeat regions （IR）. The overall GC content of codons in the P. odorata chloroplast genome was 38.88%， with GC1>GC2>GC3， showing a preference for codons ending with A/U. The effective number of codons （ENC）， the codon adaptation index （CAI）， the codon bias index （CBI） and the frequency of optimal codons （Fop） ranged from 36.29 to 54.14， 0.10 to 0.30， -0.26 to 0.19， and 0.26 to 0.53， respectively. These analysis collectively indicated weak codon usage bias in the chloroplast genome of P. odorata. Neutrality plot analysis， ENC-plot analysis， and PR2-plot analysis revealed that codon usage bias in the P. odorata chloroplast genome resulted from both mutation pressure and selection pressure and was primarily determined by the selection pressure. A total of 10 optimal codons were identified. Our study established a fundamental framework for functional genomics and molecular breeding of P. odorata by providing：（i） theoretical foundations and molecular marker resources for further functional analysis of chloroplast genes， （ii） evolutionary studies， and （iii） molecular breeding within Polygonaceae.

This study aimed to evaluate the salt-alkali tolerance of Elymusdahuricus accessions during germination and early seedling stages. Three preliminary accessions were first screened under gradient salt-alkali stress （NaCl∶NaHCO₃=3∶1） to determine appropriate treatment levels； 100 and 150 mmol·L^-1 were selected for subsequent experiments based on germination rate. Ten wild accessions originating from diverse regions and habitats were then subjected to these two stress concentrations in a pot trial， with water as the control. Germination and agronomic traits were measured to comprehensively assess salt-alkali tolerance.Salt-alkali stress significantly inhibited seed germination and seedling growth， and the inhibitory effects intensified with increased concentration. Under 100 mmol·L^-1 stress， accession E5 exhibited the highest values for all germination parameters and was identified as the most tolerant one， whereas E6 showed the poorest performance， with 0% germination at 150 mmol·L^-1， indicating lowest tolerance. The ten accessions were consequently ranked as E5>E2>E9>E1>E10>E4>E3>E7>E8>E6， and classified into five categories： highly tolerant， tolerant， moderately tolerant， weakly tolerant and non-tolerant. These results provide valuable germplasm resources and a theoretical basis for breeding salt-alkali-tolerant E. dahuricus cultivars and for elucidating the molecular mechanisms underlying salt-alkali tolerance.

To elucidate the genetic diversity and adaptive evolutionary mechanisms of different geographical populations of the plateau zokor （Eospalax baileyi）， in this study PCR was conducted to amplify and clone the MHC-DRB gene exon 2 in 121 individuals from eight distinct geographical populations. The results showed that the MHC-DRB exon 2 of the plateau zokor exhibits high polymorphism， with significant genetic differentiation among populations. Geographical isolation was identified as the primary factor driving population divergence. Codon usage bias was observed in nucleotide composition. Neutral tests indicated that the plateau zokor population had not undergone recent expansion， and the maintenance of genetic polymorphism was primarily driven by natural selection. The findings of this study will provide a theoretical basis for further investigating the genetic adaptation of MHC genes in Eospalax baileyi and their effective population management.

Plant hormones play important regulatory roles in crop growth， but the relationship and mechanism by which exogenous hormones induce the growth and development of Caucasian clover root tillers are still unclear. In this study， the effects of indole acetic acid （IAA）， cytokinin （CTK） and kinetin （KT） on the growth and development， endogenous hormone content and expression of related genes in Caucasian clover root tillers were compared. The results showed when the concentration of IAA was 8.0 mg·L^-1， exogenous IAA treatment had the strongest effect on the growth of Caucasian clover root tillers. And when CTK concentration was 100.0 mg·L^-1， exogenous CTK treatment had the strongest inhibitory effect on the growth of Caucasian clover. Exogenous KT treatment had the greatest effect on the growth of Caucasian clover root tillers while KT concentration was 0.5 mg·L^-1. Compared with the control group， exogenous hormone treatment had a significant effect on BRI1， AP2/ERF， KNOX， MAPK gene family， PAL， POD and other related genes. In conclusion， 8.0 mg·L^-1 IAA and 0.5 mg·L^-1 KT work best. This study provides a practical guidance for the artificial propagation and rapid grassland planting of Caucasian clover.

To clarify the basic characteristics of single-copy nuclear gene sequences in Littledalea racemosa and obtain effective single-copy nuclear gene molecular markers， the single-copy homologous genes were identified using OrthorFinder software based on third-generation full-length transcriptome data of L. racemosa in this study. And then through PCR amplification and population testing experiments， 10 pairs of single-copy nuclear gene molecular marker primers for L. racemosa were successfully developed. The results showed that a total of 48 219 CDS （coding sequence） regions were detected in the L. racemosa transcriptome， with an average of 1.57 coding regions per transcript. A total of 301 single-copy nuclear gene sequences were obtained based on the amino acid sequences of transcriptome CDS and finally， 10 pairs of single-copy nuclear gene primers were obtained， which demonstrated effective amplification performance and exhibited intraspecific variation. A total of 64 individuals of L. racemosa were successfully amplified through all 10 pairs of single-copy nuclear genes primers. The gene sequences exhibited extensive variation in polymorphism. The number of segregating sites （S） ranged from 13 to 42， with an average of 24.4. The number of haplotypes （h） ranged from 16 to 32， with an average of 23.7. The average number of nucleotide differences （k） ranged from 2.275 to 16.497， with an average of 7.686. The haplotype diversity （H_d） ranged from 0.776 to 0.896， with an average of 0.841. The nucleotide diversity （π） ranged from 3.05×10^-3 to 15.61×10^-3， with an average of 10.50×10^-3， and the Watterson’s estimator （θw） ranged from 3.27×10^-3 to 9.92×10^-3， with an average of 6.21×10^-3. The genetic differentiation results showed that the genetic variation of 15 populations of L. racemosa mainly existed within populations. Phylogenetic trees constructed using the 10 single-copy nuclear genes demonstrated congruent relationships among five Poaceae species. The 10 pairs of L. racemosa single-copy nuclear gene primers developed in this study， providing abundant candidate markers for future research on phylogeny， and resource conservation and utilization for Littledalea species.

Spatial patterns of soil water content are fundamental to regional ecosystem stability and the sustainable use of water resources. Focusing on the Qinghai Lake Basin， this study integrated field measurements and remote-sensing imagery with statistical and geospatial analyses to investigate the spatial distributions of soil water content and soil water storage at multiple depths. Machine-learning models—Random forest （RF） and Extreme gradient boosting （XGBoost）—were applied to simulate soil water content and storage at varying depths across the basin. The results indicated that soil moisture content in the Qinghai Lake Basin gradually decreased with increasing soil depth （32.06%， 27.17%， and 24.99%， respectively）， while soil water storage increased with depth （29.72 mm， 32.07 mm， and 32.34 mm， respectively）. Spatially， soil moisture in the basin exhibited a general pattern of high values in the north and east and low values in the south and west， with higher values in the upper reaches of rivers than in the lower reaches， and higher values in the mountainous areas surrounding the lake than in the lakeshore zones. Across different vegetation types， alpine meadows had the highest soil moisture content and water storage. Model simulation results revealed that air temperature， precipitation， and the Normalized Difference Vegetation Index were the primary influencing factors of the soil moisture spatial model. This study elucidates the spatial distribution patterns and environmental response mechanisms of soil moisture in the Qinghai Lake Basin， providing a scientific basis for regional ecological restoration and water resource management.

To explore the effects of nitrogen （N） deposition on interspecific associations and niches of grassland plants， this study was conducted in the Horqin typical steppe. Nine treatments were set up， including the addition of inorganic N （I） and organic N （O） at three rates （0， 4， and 8 g·m^-2·a^-1） and their combinations（I₀O₀， I₄O₀， I₈O₀， I₀O₄， I₀O₈， I₄O₄， I₈O₄， I₄O₈， and I₈O₈）. The results showed that the plant community exhibited a random distribution under the treatments without inorganic N addition， a positive association under the I₄O₀ treatment and a negative association under the I₈O₀ treatment. Niche responses were species-specific： the niche breadth of Bassia prostrata in the I₈O₄ treatment was 58.3% higher than that in the I₄O₈ treatment （P<0.05）； Agropyron cristatum maintained a relatively high and stable niche breadth （0.32~0.36） across all treatments， and the proportion of high niche overlap of this species reached 87% under the I₈O₈ treatment. The ecological response rate （R=2.65-2.97） and niche overlap index （ΔO_ik=0.120~0.138） of A. cristatum were relatively stable； the R value of Artemisia scoparia surged to 140.50 under the I₈O₀ treatment； the R value of Lespedeza davurica remained negative （-1.62 to -0.66） with ΔO_ik<0. In conclusion， N addition enhances the negative interspecific associations of the community and niche differentiation， leading to variations in resource use efficiency among species.

To analyze the genetic diversity characteristics of the phenotypic traits and identify germplasm with superior traits in oats （Avena sativa L.）， this study conducted a comprehensive evaluation of 24 phenotypic traits in 465 oat accessions collected from 26 countries. The results showed that the coefficient of variation for 13 quantitative traits ranged from 13.19% to 46.70%， while the genetic diversity index for 11 qualitative traits varied between 0.12 and 1.00. Correlation analysis revealed significant positive correlations （P<0.01） between plant growth traits （e.g.， plant height， stem diameter） and yield-related or panicle traits， whereas a significant negative correlation （P<0.05） was observed between lodging resistance and thousand-kernel weight. Cluster analysis classified the accessions into six distinct groups： Group I， high-biomass hulled oats suitable for forage breeding； Group II， accessions combining high yield and lodging resistance； Group III， naked oats ideal for grain use； Groups IV-VI， accessions with distinctive characteristics， which can serve as a specialized gene bank. Based on principal component analysis （cumulative contribution rate of 65.05%） and comprehensive evaluation scores （F value）， five elite accessions （174， Y586， Y1062， Y341， 150） with high yield and lodging resistance were identified， demonstrating potential as excellent parental lines or fundamental research materials.

The changes in the carbon pool of alpine grasslands of the Qinghai-Tibet Plateau play an irreplaceably significant role in promoting regional ecological balance and sustainable development. This study focused on the alpine grasslands of the Qinghai-Tibet Plateau and analyzed the effects of winter warming， clipping， and their interactions on soil organic carbon components and the stability of carbon pool. The results indicated that winter warming significantly increased the content of easily oxidisable organic carbon in the soil. Clipping significantly increased the content of soil particulate organic carbon and decreased the content of mineral-bound organic carbon （P<0.05）. The interaction between winter warming and clipping significantly reduced the content of mineral-bound organic carbon （P<0.05）. Winter warming significantly enhanced soil carbon pool activity， the carbon pool activity index， and the carbon pool management index （P<0.05）. Soil moisture content showd a highly significant positive correlation with the content of mineral-bound organic carbon （P<0.01）， while it exhibited a significant negative correlation with the carbon pool activity and the carbon pool activity index （P<0.05）. Redundancy analysis and hierarchical partitioning revealed that soil moisture content and nitrate nitrogen concentration significantly influenced the components of soil organic carbon and the stability of the carbon pool. This study provides fundamental data for understanding the changes in soil organic carbon pools under the effects of climate change and human activities in the alpine grasslands of the Qinghai-Tibet Plateau.