Abstract: [Objective] To ascertain the effects of improvement strategy on severely desertified grassland, and to provide references for management, development and rational use of grassland. [Method] From the year of 2015 to 2017, mixed seeding of 6 varieties of high-quality forages sowed with drilling method, including Medicago sativa, Astragalus adsurgens, Melilotus officinalis, Hedysarum laeve, Elymus dahuricus and Elymus sibiricus, were set in a severely desertified grassland area. Using free-grazing area as control, the plant species were investigated by chessboard-sampling method; the abundance, frequency, coverage, height and yield of the plants were determined; the CO₂ absorption rate, photosynthetic rate, transpiration rate and stomatal conductance of the plants were assessed and subjected to multivariate correlation analysis. Furthermore, the Shannon-Wiener diversity index of the plants was calculated, and the soil nutrient contents and electrical conductivity were determined. [Result] The number of plant species in severely desertified grassland increased from 14 before improvement （in the year of 2015） to 72, 83 and 97 in the years of 2018, 2019 and 2020 after improvement, respectively; compared with free-grazing area, the average abundance, frequency, coverage, height and yield of the forages in the improvement area were significantly （P<0.05） increased; this area had significantly （P<0.05） higher CO₂ absorption rate, photosynthetic rate, transpiration rate and stomatal conductance in comparison with free-grazing area, and there were significantly or extremely significantly positively correlations between transpiration rate and photosynthetic rate （P<0.05）, stomatal conductance and transpiration rate （P<0.05）, forage yield and photosynthetic rate （P<0.05）, as well as forage yield and transpiration rate （P<0.01）; significant （P<0.05） differences in Shannon-Wiener diversity index of the main forage species between improvement area and free-grazing area were observed; the soil contents of organic matter, available phosphorus and available potassium as well as soil electrical conductivity in improvement area were significantly （P<0.05） higher than those in free-grazing area. [Conclusion] After improvement, the severely desertified grassland has dramatically increased number of plant species, greatly improved forage production level and grassland ecological benefit, and significantly ameliorated soil nutrients.

Key words: severely desertified grassland, free grazing, mixed seeding of forages, improvement effect