Conclusion

An appropriate proportion of gravels in the soil can improve the availability of soil water and promote plant growth, but the lower TN and SOC contents in soils with 30% and 50% gravel content also limit the plant growth. In addition, the introduced and domesticated plantsFestuca elata and Medicago sativa had better short-term ecological restoration effects than native plants Elymus dahuricus . However, if Festuca elata plus Elymus dahuricus were mixed with different species and niche plants, the same life history strategy and similar soil resource requirements would enhance the competitiveness of plants for nutrients and water in gravel soils. With the participation of ecologic niche plants, the ecological factors of each component have a relatively reasonable proportion, which can make the space complimentary. Gravel soil can increase the availability of water and nutrients, and promote the community yield in the short term. Therefore, in the process of ecological restoration on the Qinghai-Tibet Plateau, TN and SOC should be added for coarse soil textures with high gravel content, and ecologic niche plants should be mixed to achieve an ideal ecological restoration effect.