Analysis of plant community characteristics and soil characteristics of alpine grassland along Jiuma Expressway

Alpine grassland is the primary vegetation type in China's alpine regions, which has a significant impact on ecosystem services such as climate regulation, water conservation, soil formation and protection. This study investigated grassland communities along the Jiuma Expressway, conducting surveys in 24 plots. The results showed a total of 68 herbaceous plant species within the surveyed plots, belonging to 22 families and 54 genera. Dominant species included Carex tibetikobresia, Carex alatauensis, Carex muliensis, Medicago archiducis-nicolai, Poa pratensis, Argentina anserina, Blysmus sinocompressus, with Asteraceae and Ranunculaceae species widely distributed along the route. The Patrick Richness Index (5−20) and Shannon-Wiener Diversity Index (3.68−5.48) indicated that the species diversity of the community in this area was good. The species cover of grasslands along the route was relatively high, with above-ground biomass being higher in the 3,400−3,600 m elevation zone. The vegetation was dominated by shallow-rooted plants, with root biomass primarily distributed in the 0−15 cm soil layer (accounting for 71.15–87.90%).The soil was weakly acidic (pH 5.10−6.10) and showed a significant negative correlation (p < 0.05) with the Shannon-Wiener diversity index and soil available phosphorus content, indicating that soil pH influenced phosphorus availability and vegetation diversity. The soil contained high levels of total nitrogen and available potassium, with significant fluctuations in available phosphorus content and relatively low organic carbon content.Further analysis revealed that total nitrogen, available potassium, and organic carbon in the soil were significantly positively correlated with the average community height (p < 0.05), and organic carbon content was significantly positively correlated with above-ground biomass (p < 0.05).These results indicated that in alpine grassland ecosystems, plant diversity was jointly regulated by surface soil nutrients and pH, and soil fertility structure was crucial for the composition and growth of plant communities.In ecological restoration practices, the thickness of turf removal was recommended to be controlled between 10−15 cm to maintain root system integrity. Vegetation restoration should have prioritized enhancing soil organic matter and balancing available nutrients (especially phosphorus), and improving soil structure and carbon-nitrogen levels through organic amendments to promote plant health and ecosystem sustainability.This study provided essential baseline data for the ecological protection and restoration of alpine grasslands along the Jiuma Expressway and offered scientific guidance and technical support for ecological impact assessments and vegetation restoration techniques in similar alpine regions during highway construction.