Ecological restoration treatments enhanced plant and soil microbial diversity in the degraded alpine steppe in Northern Tibet

Plant community structure and microbial ecological functions of alpine steppe in Northern Tibet are susceptible to variations in the natural environment and anthropogenic activities. In recent times, the alpine steppe in Northern Tibet has been severely degraded, that is, plant biodiversity was reduced and plant coverage declined. It is crucial to restoring the degraded alpine steppe in Northern Tibet to maintain the sustainable development of the environment and social economy. This study aimed to evaluate the ecological engineering benefits of four types of ecological restoration treatments: (a) independent treatment of sowing plant seeds; (b) combined treatments with (a) and fertilized microbial inoculum; (c) combined treatments with (a) and spraying hydrophilic polyurethane (which can enhance the ability of moisture retention, fertility, and temperature in the soil subsystem); and (d) the comprehensive treatments with (a) and fertilized microbial inoculum and spraying hydrophilic polyurethane. Noting their effect on plant growth performance, plant taxonomic and functional diversity, soil physicochemical properties, and soil microbial diversity in the degraded alpine steppe. Plots where no seeds were planted and no other amendments were applied were selected as experimental controls. Plant height, leaf size, plant taxonomic and functional diversity, total carbon and nitrogen contents, soil bacterial and fungal diversity were significantly enhanced under the four ecological restoration treatments. Plant growth performance (in particular, competitiveness for sunlight acquisition and leaf photosynthetic area), and soil fertility were significantly enhanced under the four treatments. The improved plant taxonomic and functional diversity and soil microbial diversity could facilitate the biological communities in degraded alpine steppe to develop better ecological functions, especially community stability. Meanwhile, the combination of all three treatments was found to be the best among all treatments applied in this study. This can help restore the degraded alpine steppe in Northern Tibet.