Abstract: ObjectiveUnder the background of global climate change, ecosystems in high-altitude regions are becoming increasingly fragile and sensitive to both natural and anthropogenic disturbances. Railway construction, as a major form of infrastructure development, further intensifies ecological stress in these areas. The Lalin Railway, located on the Qinghai–Tibet Plateau, passes through zones characterized by extreme environmental conditions, including low temperatures, strong radiation, and poor soil development. Shrub–grass plant communities in this region play a critical role in maintaining ecological stability, conserving soil and water, and supporting regional biodiversity. However, these communities are easily disturbed and difficult to restore once degraded. Therefore, this study aims to investigate the altitudinal distribution patterns and diversity characteristics of shrub–grass plant communities along the Lalin Railway corridor, in order to provide a scientific basis for ecological restoration and soil and water conservation in high-altitude railway ecosystems.MethodsThe study was conducted along the Lalin Railway corridor, where ten representative sampling plots were established across an elevation gradient ranging from 3,000 to 3,900 meters. Field surveys were carried out during the peak growing season to ensure accurate observation of vegetation conditions. Within each plot, detailed vegetation investigations were performed to record species composition, floristic characteristics, plant cover, height, and community structure. Species richness and abundance data were systematically collected. To quantitatively evaluate biodiversity, multiple α-diversity indices were calculated, including the Shannon–Wiener index, Simpson index, and Pielou’s evenness index, which reflect species diversity, dominance, and distribution uniformity. In addition, β-diversity indices such as the Cody index and Sørensen index were used to assess species turnover and community differentiation along the altitudinal gradient. The Jaccard similarity coefficient was also applied to evaluate the similarity of species composition among different plots at varying elevations.ResultsThe results revealed several significant patterns in the shrub–grass communities along the Lalin Railway. First, in terms of floristic composition, the plant communities were dominated by cosmopolitan and North Temperate distribution types, indicating a strong influence of temperate elements. Endemic species were present but accounted for a relatively small proportion, suggesting that the harsh environmental conditions limit local specialization. Second, α-diversity exhibited a clear unimodal pattern along the altitudinal gradient. Species richness, diversity, and evenness all reached their peak at mid-elevations, particularly between 3,300 and 3,500 meters, where environmental conditions such as temperature and moisture were relatively favorable. In contrast, at higher elevations, plant communities became increasingly simplified, with fewer species and lower evenness, as extreme environmental factors restricted species survival and distribution. Third, β-diversity increased with increasing altitudinal differences. As the elevation gap between sampling plots widened, community similarity decreased significantly, and species turnover became more pronounced, indicating strong environmental filtering effects along the gradient.ConclusionsAltitude is a key factor influencing the structure, composition, and diversity of shrub–grass plant communities along the Lalin Railway corridor. The observed unimodal pattern of α-diversity and the increasing trend of β-diversity highlight the importance of environmental gradients in shaping community dynamics. These findings suggest that ecological restoration strategies in high-altitude railway regions should fully consider altitudinal variation. Restoration efforts should prioritize mid-elevation zones with higher biodiversity potential while adopting adaptive and site-specific measures for high-altitude areas with harsher conditions. Overall, this study provides important scientific support for optimizing vegetation restoration strategies and implementing effective soil and water conservation practices in fragile alpine ecosystems.