Effects of concrete content on seed germination and seedling establishment in vegetation concrete matrix in slope restoration

The Vegetation Concrete Base Spraying technique (VCBS) is an ecological slope restoration technique to strengthen slope stability and restore slope vegetation in the meantime. It restores vegetation on slopes by spreading a mix of concrete, greening additives, mulching materials and plant seeds on to slope surfaces. However, vegetation establishment on slopes is likely affected by concrete content in the vegetation concrete matrix. Here we conducted experiments with various concentrations of concrete content in vegetation concrete matrices to test the effect of concrete content on seed germination and seedling establishment for three pioneer species, Festuca arundinacea, Magnolia multiflora and Medicago sativa. We aimed to determine the appropriate concrete content to be used in the vegetation concrete matrix. Variations in seed germination, seedling survival and seedling growth were monitored. The results showed that the concrete content had significant effects on seed germination, seedling survival and growth of all three species. Seed germination of F. arundinacea and M. sativa decreased with increased concrete content. The germination of M. multiflora seeds peaked at 4% concrete content. The seedling survival of F. arundinacea and M. sativa increased, then decreased with increased concrete content, but the seedling survival of M. multiflora continually decreased. F. arundinacea and M. multiflora are more suitable than M. sativa for application in VCBS. Concrete content significantly influenced seedling growth of all three species. The leaf number, plant height, aboveground biomass, belowground biomass and root length, root crossing number of plants all increased with increased concrete content between the range of 0-8%, but decreased significantly when concrete content was over 8%. We concluded that 8% concrete content in the vegetation concrete matrix is appropriate in terms of seed germination and seedling establishment of the three studied species in the VCBS.