Abstract: Vegetation restoration in railway engineering construction areas is a critical component of alpine grassland rehabilitation on the Qinghai-Tibet Plateau. To explore effective restoration strategies, a railway engineering site was selected as the experimental area. Based on 19 native species from three functional groups, 15 treatments with different species assemblage were set. We assessed community aboveground biomass, root morphological traits, and species diversity to determine the effectiveness of each assemblage. The results showed that multi-species mixtures significantly enhanced community aboveground biomass (up to 512.4 g·m^-2) and species richness (maximum Shannon index of 2.31). Among the treatments, the 15-species mixture comprising Elymus nutans, Phalaris arundinacea, Festuca sinensis, Festuca rubra, Dactylis glomerata, Poa pratensis, Poa crymophila, Trifolium pratense, Onobrychis viciifolia, Vicia unijuga, Medicago sativa, Vicia sativa, Melilotus officinalis, Plantago lanceolata, and Cosmos bipinnatus performed best. This assemblage exhibited root traits characterized by lower specific root length and higher root tissue density, indicating greater capacity in stress resistance and resource acquisition. Our findings demonstrate that diverse native species mixtures can substantially enhance ecological restoration outcomes in linear engineering construction sites. This study provides theoretical and empirical support for efficient grassland rehabilitation on the Qinghai-Tibet Plateau as well as in other ecologically fragile alpine regions.

Key words: species configuration, ecological restoration, mixed species seeding, species diversity, grassland productivity