To investigate the response mechanism of terpenoid root exudates to salt stress in halophytes， Elytrigia elongata was used as a model species. Gradients of NaCl solutions were applied to soil to simulate control， light， moderate， and severe salt stress conditions. A non-targeted metabolomics approach was employed to identify the profiles and relative abundances of terpenoid compounds in root exudates， and correlations between terpenoid abundance， root morphological traits， and rhizosphere soil physicochemical properties were analyzed. The results showed that compared with the control， the relative abundance of sesquiterpenes， monoterpenes， diterpenes and other terpenoids in root exudates significantly decreased by 8.61%-16.41% under light， moderate and severe salt stress treatments. Triterpenoids and triterpene saponins significantly decreased by 24.54% and 12.43% respectively only under light salt stress. Soil pH emerged as the primary factor influencing terpenoid exudation in Elytrigia elongata. As soil salinity increased， pH decreased， thereby suppressing the secretion of sesquiterpenoids， monoterpenoids， diterpenoids， and other terpenoid classes. These findings provide critical insights into the physiological mechanisms underlying plant adaptation to saline environments.

Grass mulching has been proven to effectively enhance soil organic carbon accumulation and improve soil fertility in orchard systems. However， the mechanisms regulating the dynamics of labile organic carbon and humified carbon fractions remain unclear. From 2021 to 2023， a field experiment was conducted in an apple orchard with four grass mulching treatments established in both interrow and tree disk areas： perennial ryegrass （Lolium perenne L.）， sweet clover （Melilotus officinalis L.）， perennial ryegrass + alfalfa （Medicago sativa L.）， with traditional clean tillage as the control （CT）. We analyzed soil labile organic carbon fractions， humic carbon fractions， carbon-cycling enzyme activities， and the carbon pool management index. The results showed that sweet clover significantly increased soil organic carbon content by 14.38% and elevated the carbon pool management index by 89.55% in the interrow area compared to CT in 2022 （P<0.05）. In 2023， sweet clover further reduced soil pH in the interrow areas and the bulk density of the tree disk areas. Meanwhile， the perennial ryegrass + alfalfa mixture treatment increased soil organic carbon by 19.19% in the tree disk area， with concurrent rises in dissolved organic carbon and microbial biomass carbon （P<0.05）. Mantel tests and partial least squares path modeling revealed distinct responses of the interrow and tree disk areas to grass mulching. Increased labile organic carbon fractions primarily characterized the interrow areas， while the tree disk areas showed a strong positive response in humified carbon accumulation. In conclusion， sweet clover performed the best in interrow areas， while the perennial ryegrass + alfalfa mixture was the most effective in tree disk zones. Grass mulching in apple orchards can positively regulate the soil carbon pool through improvements in soil physical structure， activate carbon-cycling enzymes， and increase soil carbon fractions.

Drought and phosphorus deficiency are key factors limiting oat （Avena sativa） production in the Qinghai-Tibet Plateau. In order to elucidate the effects of water and phosphorus stress on oat growth， identify the primary limiting factors， and screen for key indicators of oats’ synergistic adaptation to water and phosphorus constraints. This study utilized 14 oat cultivars in pot experiments， with treatments including a control （CK）， low phosphorus stress （-P）， drought stress （-W）， and combined drought and low phosphorus stress （-W-P）. Additionally， this experiment measured 18 indicators， including agronomic traits， biomass， and phosphorus accumulation， among others. Results indicated that stress treatment significantly suppressed oat aboveground biomass and biomass of individual aboveground organs， spikelet number， grain per spike， and phosphorus accumulation at the 0.05 level. Moreover， the degree of inhibition is greater under combined stress than under single stress. Different indicators exhibited varying degrees of susceptibility to each factor， with water availability being the primary growth-limiting factor. Methods such as grey relational analysis and principal component analysis jointly identified grain biomass， aboveground biomass， spikelet number， grain per spike， belowground biomass， flag leaf area， and phosphorus accumulation in plants and grains as key indicators reflecting oats' tolerance to water and phosphorus stress. The findings of this study provide theoretical foundations and methodological guidance for the breeding and evaluation of drought-tolerant and low-phosphorus-tolerant oat cultivars on the Qinghai-Tibet Plateau.

Grassland ecological governance is a critical measure for ensuring ecological security and promoting the sustainable development of pastoral areas. Based on the theory of social embeddedness， this study utilizes survey data from 410 herder households in Inner Mongolia constructed a five-dimensional framework comprising policy， cognitive， cultural， structural， and relational embeddedness， empirically analyzed the mechanisms influencing herders’ willingness to participate in grassland ecological governance and their willingness to pay （WTP）. The findings indicated that cognition and relationship embedding positively affected the willingness to participate， while cultural embedding exerted a significantly negative effect. Conversely， the WTP was driven positively by cognitive and relationship embedding alone. Furthermore， the ISM model revealed that resource endowments-including years of experience in animal husbandry， total number of family members， grassland contract area， and livestock inventory-constitute the underlying root factors. Their influence was channeled through the key mediating variables of awareness of governance policies and expenditure on forage， which subsequently indirectly affected socially embedded factors such as the perception of policy impacts， recognition of governance necessity， and perceived attitudes of peers. This pathway ultimately shapes both the willingness to engage in neighborhood cooperation and the overall willingness of herders. Heterogeneity analysis showed that the effects of social embeddedness factors varied significantly across different grassland types. It was recommended to implement differentiated policies based on grassland types， enhance economic compensation， strengthen policy communication and community atmosphere building， and effectively leverage social norms to boost herders’ participation motivation.

This study focused on the wetland ecosystem of the Black-necked Crane National Nature Reserve in the Lhasa River Basin， systematically explores the niche characteristics， interspecific associations， and community stability of the dominant populations in the shrub layer and herb layer， analyzes the survival strategies， resource competition， and symbiotic relationships of dominant species in the alpine wetland environment， aiming to promote the positive associations between dominant species and companion species and optimize the community structure； The results show that： the average value of the Levins index in the herb layer （7.97） is higher than that in the shrub layer （3.27）， and the average value of the Shannon index （2.03） is also higher than that in the shrub layer （1.20）， indicating that herbaceous plants have better breadth and uniformity of resource utilization. The niche overlap index shows that the average value in the herb layer （0.22） is higher than that in the shrub layer （0.18）， with more intense resource competition. The interspecific association analysis shows that the shrub-herb layer presents a positive association as a whole （all VR values are greater than 1）. The overall symbiosis of plants in the shrub layer is stronger than competition， while the resource competition among species in the herb layer is more intense than that in the shrub layer. The community stability model shows that the Euclidean distances between the shrub layer， the herb layer and the theoretical stable point （20， 80） are 7.98 and 22.77 respectively， and the herb layer is in an unstable state. The study suggests optimizing vegetation configuration by screening species with matching ecological habits to enhance community stability， so as to provide a theoretical basis for the vegetation management of the reserve and the protection of the Qinghai-Xizang Plateau ecosystem.

To explore the distribution pattern and influencing factors of plant communities in the desert zone of the Aksu River basin’s landscape engeneering area， this study used field survey results as the research object. The TWINSPAN method was used for quantitative classification of communities， and the CCA （canonical correspondence analysis） method was emplyed to screen significant influencing factors. The structural equation modeling was used to investigate the interactive relationship between the distribution patterns of plant communities and environmental variables. The results showed that the TWINSPAN hierarchical classification classified the 30 survey locations into 6 association types. The Simpson and Shannon-Wiener diversity indices showed that association II and III had the highest values， while association I and V had the lowest. The Mrgalef richness index showed that association II had the highest value， which was significantly higher than association V by 1.02 times （P<0.05）. The Pielou index showed that association IV had the highest value， with relatively uniform distribution. The similarity of each community type was highest between association I and II， with the highest Jaccard’s index and Sorenson’s index values of 0.478 and 0.393. CCA ranking results indicated that the primary environmental factors influencing community distribution patterns were multi-year average precipitation， elevation， soil organic matter， and soil bulk density （P<0.001）. Further analysis of the interaction between environmental factors and association distribution patterns revealed that topographic factors， consisting of elevation and slope， had the greatest influence， with a total effect size of 0.852. These factors significantly influenced meteorological and soil factors such as annual average precipitation， evaporation， and soil organic matter， thereby influencing association spatial distribution patterns. This research provides a scientific theoretical foundation and empirical support for setting ecological restoration targets， vegetation selection， and measurement formulation for the Aksu River Basin landscape engineering project.

Investigating the effects of grazing on the ecological chemometric characteristics of carbon （C）， nitrogen （N）， and phosphorus （P） in the plant-soil continuum of long-term enclosed grasslands is crucial for sustainable grassland management. This study investigated a 38-year-old enclosed grassland in Yunwu Mountain， Ningxia， by systematically analyzing ecological-metabolic ratios and their coupling relationships at the community level （community-weighted average） for leaves and soil across four grazing intensities of Gansu Cervus canadensis （Cervus elaphus kansuensis）： ungrazed， light grazing， moderate grazing， and heavy grazing. Results indicated： （1） Moderate grazing most effectively promoted N and P accumulation. Plant growth shifted from P limitation under no grazing and combined N-P limitation under light/moderate grazing to N limitation under heavy grazing； （2） With increasing grazing intensity， both topsoil soil organic carbon （SOC） and C∶N ratio in the topsoil （0~10 cm） showed an initial increase followed by a decrease， peaking at moderate grazing levels at 40.40 g·kg^-1 and 12.08， respectively. Conversely， soil N， C∶P， and N∶P ratios were the lowest at light grazing levels at 3.22 g·kg^-1， 48.15， and 4.43， respectively. All soil parameters decreased with increasing soil depth. （3） Leaf C and N contents showed negative correlations with most soil SOC， N， P， and their ratios， while leaf P content was correlated positively with these parameters. Soil depth influenced both plant leaf and soil chemical parameters， whereas grazing intensity primarily affected soil-related indicators. In summary， grazing significantly influenced the chemical-nutrient characteristics of the plant-soil system in the long-term enclosed grassland of Yunwu Mountain. Moderate grazing promoted plant growth and soil nutrient accumulation， representing a critical grazing intensity threshold for maintaining regional grassland health. These findings provide data support and theoretical basis for further optimizing grazing management and promoting the sustainable use of long-term closed-pasture grasslands.

To investigate the effects of different composite improvement measures on soil enzyme activities and microbial communities in degraded meadow steppes， this study set up four treatments： root cutting+organic fertilizer+microbial inoculant （YQJ）， root cutting+organic fertilizer （YQ）， root cutting+foliar fertilizer （YY）， and control （CK）. High-throughput sequencing was used to determine the community structure and diversity of soil bacteria and fungi.The results showed that the YQJ treatment had a significant effect on increasing the activities of soil catalase， invertase， urease， and alkaline phosphatase， followed by the YY treatment. The composition of dominant bacterial and fungal species among different composite improvement treatments was basically similar， but the relative abundance of dominant fungal community species varied greatly. The YQJ treatment significantly reduced the relative abundance of Basidiomycota； the YY treatment significantly increased the relative abundance of Ascomycota （P<0.05）. The root cutting+foliar fertilizer treatment significantly increased the Alpha diversity indices of soil bacteria and fungi （P<0.05）. Correlation analysis results showed that soil catalase， urease， and invertase were closely related to changes in the bacterial community； soil urease and aboveground biomass were closely related to changes in the fungal community. In conclusion， composite improvement measures could improve soil enzyme activities and grassland productivity by regulating and improving the structure of soil bacterial and fungal communities， and the root cutting+foliar fertilizer treatment had the best improvement effect.

To clarify the occurrence trends of poisonous weeds in grasslands under future climate change， and to scientifically prevent their spread and reduce economic losses in the livestock industry， this study based on the distribution data of five frequently occurring grassland poisonous weeds in the Ili River Valley： Sophora alopecuroides， Aconitum leucostomum， Xanthium spinosum， Rumex thianschanicus， and Peganum harmala—and combined with 55 influencing factors， employed the Maximum Entropy model to explore the impact of climate change on the occurrence trends of these five grassland poisonous weeds. The results showed that the prediction models for the five grassland poisonous weeds all had an accuracy greater than 0.8， indicating high precision. Under four future climate scenarios， the total potential occurrence area of Aconitum leucostomum decreased， while that of the other four grassland poisonous weeds increased. Under the medium-to-high emission scenario （SSP370）， grassland poisonous weeds were more prone to expansion and posed greater risks. In terms of migration direction， in the future， Aconitum leucostomum， Rumex thianschanicus， and Peganum harmala would mainly migrate southward， Sophora alopecuroides would migrate eastward， and Xanthium spinosum would migrate toward the southeast and northeast， with an overall trend of grassland poisonous weeds migrating toward lower latitudes. Under the four future climate scenarios， the area of overlapping zones for multiple grassland poisonous weed species increased， with the largest overlapping area occurring under the high-emission scenario （SSP585）. In conclusion， continuous increases in carbon emissions will exacerbate the spread and harm of grassland poisonous weeds.

This study aimed to clarify the potential suitable habitats of three Orinus species， including O. thoroldii， O. kokonoricus and O. intermedius， under the background of climate change. Based on the data of species distribution records and climate variables， MaxEnt model and ArcGIS were applied to conduct spatial simulation and prediction of three Orinus species. The results showed that the predictive accuracy was high （AUC>0.95）. The key environmental factor influencing habitat suitability was altitude for O. thoroldii， the mean temperature of the wettest quarter was the main factor for O. kokonoricus， while the mean diurnal temperature range was the key one for O. intermedius. From the Last Interglacial to the Mid-Holocene， the suitable area for O. thoroldii and O. kokonoricus decreased， while that for O. intermedius increased. Under the future climate scenarios， the suitable area of O. thoroldii and O. kokonoricus showed an initial increase followed by a decrease， whereas the opposite trend was observed for O. intermedius. Currently， the high suitable area of O. thoroldii was mainly located in the southwest of the Qinghai-Xizang Plateau， that of O. kokonoricus was in the east of the Qinghai-Xizang Plateau， while that of O. intermedius was in the central part and northeast of the Qinghai-Xizang Plateau. We thought that the high suitable habitat of Orinus species was in the southwest， east， northeast and central parts of the Qinghai-Xizang Plateau. It is suggested to strengthen in situ protection to cope with the pressure brought by future climate change.