Abstract: Desert steppe in Inner Mongolia that is located in arid areas plays an important ecological function, including wind prevention, sand fixation, and biodiversity conservation. However, the desert steppe has been seriously degraded in recent years, due to human activities and climate change. How to effectively restore the ecological function of desert grassland is an urgent problem to be solved. Scientific and reasonable man-made directional cultivation is an important measure for the restoration and reconstruction of desert steppe plant community. In this study, we examined the responses of plant community structure and aboveground biomass of the desert steppe in Wulat Middle Banner to different restoration measures based on a manipulation experiment. The results showed that in the severely degraded desert steppe, short-term enclosure increased the relative coverage of forbs and increased community aboveground biomass by 2.11 times. The addition of organic fertilizer increased the richness of grass species and community aboveground biomass by 3.97 times. Supplementary sowing significantly increased the coverage and density of plant community, and increased community aboveground biomass by 9.76 times. In severely desertified steppe, supplementary sowing significantly enhanced the coverage, density and aboveground biomass of plant communities, but did not affect species diversity. In the moderately degraded area, the addition of compound fertilizer significantly reduced the number of forbs in Stipa breviflora community and increased the aboveground biomass of grasses and plant community. The addition of compound fertilizer significantly improved the grass species richness in Caragana korshinskii and bunchgrass community, but did not affect the coverage, density and aboveground biomass of plant community. Foliar fertilizer spraying significantly reduced the coverage and density of forbs in Caragana  tibetica shrubgrass community and increased the aboveground biomass of grasses. Our results can provide data support for the restoration and management of degraded desert steppe in the semi-arid area.

Key words: species composition, species diversity, aboveground biomass.