Grassland plants achieve species coexistence through differentiated resource utilization， which directly affects the community structure and stability. To explore the impacts of grassland utilization patterns on the coexistence mechanism of community species under the background of nitrogen deposition， four nitrogen addition levels （0，2，5，10 g·m^-2·a^-1） were set up in the moving and fenced grasslands of the Huihe River Basin in Hulun Buir， and the response patterns of plant community diversity， overall interspecific association and niche characteristics to grassland utilization patterns and nitrogen deposition were investigated. The results indicated that mowing grassland was more sensitive to nitrogen addition. Under high nitrogen conditions， species diversity significantly decreased（P<0.05）， and the overall community association weakened and turned negative. The proportion of high niche overlap decreased from 56.06% under N₂ to 31.82% under N₅， while the proportion of low overlap increased to 53.03%. The overall correlation of the fenced grassland was relatively stable； the niche breadth of Leymus chinensis and Stipa baicalensis expanded to 2.77 and 2.67 in the medium nitrogen stage， respectively， but contracted and the overlapping ratio decreased in the high nitrogen stage. Nitrogen addition reshaped interspecific relationships by altering resource availability， while the utilization method of grasslands determined the stability of the community and the ability of ecological niche adjustment； the grassland steppe community exhibited a response of low nitrogen promoting and high nitrogen inhibiting to nitrogen addition.

Seed heteromorphism is a critical adaptive strategy for invasive plants to cope with environmental heterogeneity. To investigate the response mechanisms of heteromorphic seeds of Cenchrus spinifex， we examined germination characteristics of its two seed types （M-type： larger； P-type： smaller） under varying light （complete darkness vs. 12 h light/12 h dark） and moisture conditions （simulated by PEG gradients）. Subsequent seedling growth， biomass allocation， and phenotypic plasticity were analyzed in response to the interaction between water availability （normal， mild， and severe drought） and light intensity （high and low intensity）. The results showed that germination was unaffected by light but strongly inhibited by water stress； under severe drought， M-type seeds outperformed P-types in root length， bud length， and biomass. As seedlings， M-type plants showed higher phenotypic plasticity in morphological traits （plant height， tiller number， leaf area）， favoring increased aboveground resource investment for rapid life cycle completion， whereas P-type plants exhibited greater plasticity in biomass allocation， enhancing stress tolerance through increased root biomass proportion. In summary， the complementary germination and growth strategies of heteromorphic seeds in C. spinifex represent an effective “bet-hedging” mechanism， which is crucial for its successful invasion and spread across environmentally stressful and variable habitats.

To investigate the physiological regulation mechanisms of plant growth-promoting bacteria on the drought， cold， and saline-alkali stress tolerance of perennial ryegrass （Lolium perenne L.）， this study used Bacillus paralicheniformis （NCBI ID： PRJNA1402526） as the test strain. A pot inoculation experiment was conducted under three abiotic stress conditions-drought， cold， and saline-alkali stress—to analyze the effects of rhizosphere inoculation on the growth indices， physiological characteristics， and root morphology of perennial ryegrass. The results showed that inoculation with B. paralicheniformis significantly alleviated the growth inhibition caused by abiotic stresses. Compared to the non-inoculated control， the inoculated plants exhibited significantly increased plant height， above-ground and below-ground biomass， along with markedly reduced leaf relative conductivity and malondialdehyde content. Additionally， the activities of superoxide dismutase， peroxidase， and catalase， as well as the contents of proline and soluble sugars， were significantly enhanced （P<0.05）. Moreover， root system architecture was notably improved. In conclusion， inoculation with B. paralicheniformis can significantly enhance the resistance of perennial ryegrass to drought， cold， and saline-alkali stresses by synergistically strengthening its antioxidant defense capacity， osmoregulatory function， and root morphological configuration.

To investigate the effects of different grazing intensities on soil enzyme activities in a Stipa breviflora desert steppe and the driving factors， this study was based on a Stipa breviflora desert steppe and established four grazing intensity levels： no grazing （CK）， light grazing （LG）， moderate grazing （MG）， and heavy grazing （HG）. The effects of different grazing intensities on the activities of β-D-cellobiohydrolase， β-1，4-N-acetylglucosaminidase， and alkaline phosphatase were analyzed， along with species richness， aboveground net primary productivity （ANPP）， and soil pH， saturated water content， bulk density， organic carbon， available nitrogen， and available phosphorus. The results showed that with the increase of grazing intensity， the three soil enzyme activities， species richness， aboveground net primary productivity， soil organic carbon， available nitrogen， and available phosphorus all significantly decreased （P<0.05）， whereas soil bulk density was significantly increased. The Random Forest model indicated that available nitrogen and available phosphorus were the primary drivers regulating soil enzyme activities. Grazing suppresses soil enzyme activities primarily by decreasing available nutrients. This study provides a theoretical basis for the conservation and ecological restoration of desert steppes. In grassland management and utilization， measures such as controlling stocking rates and implementing seasonal grazing exclusion can be adopted.

By collecting 11 forage species from the desert steppe of Siziwang Banner， Ulanqab City， Inner Mongolia， we separately determined and calculated their crude protein， ether extract， crude ash， neutral detergent fiber， acid detergent fiber， total digestible nutrients， dry matter intake， dry matter digestibility， relative feeding value， and relative forage quality. A comprehensive evaluation of the nutritional value of different forages was conducted. The study employed a combined approach utilizing the CRITIC objective weighting method and the GRA-TOPSIS comprehensive evaluation model. The results of the study showed that the three forage grasses in the grass group， in descending order of nutritional value， were Leymus chinensis > Stipa breviflora > Cleistogenes songorica； the five forage grasses in the shrub and semi-shrub group， in descending order of nutritional value， were Bassia prostrata > Krascheninnikovia ceratoides > Caragana microphylla > Artemisia frigida > Caragana stenophylla； and the three forage grasses in the weedy group， in descending order of nutritional value， were Phlomoides umbrosa > Convolvulus ammannii > Astragalus membranaceus.

In this study， four typical patches under the conditions of shoaly land and sloping land， including bare patches， short-term restoration patches， long-term restoration patches and healthy alpine meadow， were selected. Through plant quadrat survey， the changes of community characteristics in different types of patches during natural restoration and succession were analyzed， and their correlation with soil factors was discussed. The differences of plant community characteristics and key soil limiting factors in different types of patches were revealed. The results showed that with the restoration succession， the plant diversity of shoaly land and sloping land increased significantly， and the functional group coverage and aboveground biomass were significantly different. The quantitative characteristics， diversity， coverage of functional groups （except Fabaceae） and aboveground biomass of plant communities in shoaly land were higher than those in sloping land. Plant community indexes were positively correlated with soil water content， temperature， conductivity， organic carbon， total nitrogen， total phosphorus， nitrate nitrogen and ammonium nitrogen， and negatively correlated with pH value. Organic carbon， total phosphorus， total nitrogen and ammonium nitrogen were the key limiting factors of plant community characteristics in shoaly land， and pH， ammonium nitrogen and organic carbon were the key limiting factors of plant community characteristics in sloping land. In short， the soil conditions of the patchily degraded alpine meadow had been improved and restored， which in turn promoted the positive succession of plant communities.

To investigate the key traits influencing the seed setting rate of hulled oats （Avena sativa L.） and their regulatory pathways in the alpine habitat of northwestern Sichuan， this study utilized 27 hulled oat accessions as experimental materials. Measurements were taken for growth period， agronomic traits， photosynthetic characteristics， as well as panicle and grain traits. Multi-trait association analysis was conducted using variance analysis， correlation analysis， multiple linear regression， and path analysis. The results indicated that maturity is a key factor regulating the seed setting rate. The growth period of the tested accessions ranged from 118 to 178 d， with seed setting rates varying between 32.47% and 84.72%. The average seed setting rate of early-maturing accessions （66.93%） was significantly higher than that of late-maturing ones （56.51%， P<0.05）. Mid-maturing accessions showed the highest coefficient of variation， suggesting the existence of specific germplasms with high seed-setting potential. Traits such as panicle number， awn length， and tiller number exhibited considerable variation （CV>30%）， indicating rich genetic diversity. The seed setting rate showed a highly significant negative correlation （P<0.01） with six traits， including plant height and flag leaf length. Path analysis revealed that plant height， effective tiller number， and panicle length are key direct factors regulating the seed setting rate of hulled oats in northwestern Sichuan， primarily through the direct inhibitory effect of plant height and the direct promoting effect of effective tillers. Therefore， for this region， it is advisable to select medium-early maturing varieties with moderate plant height and a high number of effective tillers.

This study implemented no-till reseeding of alfalfa （Medicago sativa） with irrigation （applied only in the establishment year） to restore degraded grassland in Yuyang district， Shaanxi Province. By investigating vegetation characteristics of enclosure， irrigation， the first year and the fourth year of alfalfa reseeding grasslands， the effects of restoration measures were evaluated to provide technical supports for the restoration of degraded grasslands in this region. The results showed that： （1） irrigation， as well as the first year and the fourth year of reseeding， significantly increased vegetation biomass and plant diversity compared to enclosure alone， while irrigation alone significantly increased the dry weight proportion （DWP） of annual grass and forb in the vegetation and decreased that of perennial grass， posing a potential threat to grassland ecosystem stability； （2） compared to irrigation alone， reseeding in the first year significantly increased the DWP of legume and decreased that of annual grass in the vegetation， indicating an optimized community structure； （3） as for reseeding in the fourth year， the community biomass reached 5321 kg·hm^-2， which was 5.58 and 2.63 times that of the enclose and irrigation， respectively， and there was 67.78% of the biomass contributed by the reseeded alfalfa， demonstrating high production potential while maintaining plant diversity. In conclusion， the reseeded alfalfa could be maintained in the improved grassland over the long term and reseeding alfalfa with irrigation （applied only in the establishment year） can be served as a primary measure for restoring the degraded grassland in this region.

This study established gradient stress treatments of pH， NaCl， NaHCO₃， and Na₂CO₃ to compare the stress tolerance differences between Leymus chinensis and Elymus dahuricus. Evaluated parameters included growth indices such as seedling leaf length， root length， and fresh weight， as well as physiological indicators including chlorophyll content， relative electrical conductivity， malondialdehyde （MDA） content， superoxide anion （O₂^-·） content， antioxidant capacity， and osmoregulatory substance levels in mature leaves. A comprehensive evaluation was conducted using principal component analysis （PCA） in conjunction with the membership function value （MFV） method. The results demonstrated that alkaline salts （NaHCO₃， Na₂CO₃） exhibited significantly stronger inhibitory effects compared to neutral salt （NaCl） and high pH conditions. With increasing Na⁺ concentration and pH levels， the growth inhibition of L. chinensis was less pronounced than E. dahuricus. Additionally， L. chinensis exhibited a smaller reduction in chlorophyll content， lower increase in relative electrical conductivity and malondialdehyde （MDA） levels， less accumulation of superoxide anion radicals （O₂^-·）， and stronger antioxidant capacity compared to E. dahuricus. Additionally， L. chinensis accumulated higher levels of osmoregulation substances （soluble sugars， soluble proteins， proline）. The PCA-MFV comprehensive evaluation confirmed consistent conclusions between seedling phenotype and mature plant physiological indices， demonstrating that L. chinensis possessed significantly superior comprehensive saline-alkali tolerance compared to E. dahuricus. This research provides a theoretical foundation for vegetation selection and breeding in saline-alkali soil.

A single-factor randomized block design was used to measure the dry matter yield， dry-to-fresh ratio， crude protein content， and relative feed value of spring-sown ‘WL’ series alfalfa （Medicago sativa） varieties in the Horqin Sandy Land during the year of establishment. Multivariate analysis was employed to explore the effects of fall dormancy grade and type on the production performance. The results showed that the dry matter yield of the first and second cuttings accounted for over 60% of the total annual yield for all tested varieties， and the yield of the fourth cutting was significantly lower than that of the other cuttings （P<0.05）. ‘WL366HQ’and ‘WL349HQ’exhibited the highest total annual dry matter yield. Fall dormancy grade and type had no significant effects on dry weight or crude protein content， with negligible effect sizes， but significantly influenced relative feed value （P<0.05）. In conclusion： （1） For spring-sown alfalfa varieties in the Horqin Sandy Land， production performance during the year of establishment varied significantly among varieties and was not related to fall dormancy rating. （2） ‘WL349HQ’and ‘WL366HQ’ demonstrated the best production performance. The first and second cuttings contributed 60% of the total annual yield. Therefore， variety selection should prioritize total annual forage yield （i.e.， production performance） rather than fall dormancy rating.