Abstract: [Objective] To explore the variation characteristics of trace elements and nutrients contents of forage grasses and main dominant forage grasses in desert steppe under different grazing intensities. [Method] Field investigations were conducted in areas with different grazing intensities （moderate grazing area, no-grazing area and heavy grazing area） in desert steppe in Otog Banner, Ordos City, Inner Mongolia Autonomous Region for 3 consecutive years. Combined with laboratory analysis, the effects of different grazing intensities on the contents of trace element and nutrient of forage grasses and three kinds of main dominant forage grasses （Cleistogenes songorica, Allium mongolicum, Stipa breviflora） in desert steppe were assessed. [Result] The selenium content of Cleistogenes songorica and Allium mongolicum as well as the copper content of forage grasses in moderate grazing area were significantly （P<0.05） higher than those in no-grazing area and heavy grazing area, and the selenium and copper contents of forage grasses in no-grazing area and heavy grazing area were nearly equal to or lower than the safe content standard in this region. The iron content of Allium mongolicum in moderate grazing area was significantly （P<0.05) higher than that in no-grazing area. The magnesium content of forage grasses in heavy grazing area was significantly （P<0.05) higher than that in no-grazing area and moderate grazing area, and exceeded the safety content standard in this region. The sodium content of Stipa breviflora, Cleistogenes songorica and Allium mongolicum in moderate grazing area was significantly （P<0.05) higher than that in no-grazing area and heavy grazing area. The contents of crude protein, crude fat, crude ash, phosphorus and calcium of forage grasses in moderate grazing area were higher than those in no-grazing area by 60.71%, 69.00%, 47.62%, 28.57% and 347.85%, respectively. The contents of crude fiber, neutral detergent fiber and acid detergent fiber of forage grasses in moderate grazing area were lower than those in no-grazing area by 13.93%, 24.80% and 6.35%, respectively. The crude protein content of Stipa breviflora in moderate grazing area was higher than that in no-grazing area by 11.50%. The contents of crude fat, crude ash and calcium of Cleistogenes songorica in moderate grazing area was higher than those in no-grazing area by 24.12%, 87.56% and 116.86%, respectively. The calcium content of Allium mongolicum in moderate grazing area was higher than that in no-grazing area by 24.03%. [Conclusion] Due to the long-term grazing prohibition and overgrazing, the selenium and copper deficient grassland moves into the desert steppe in Otog Banner. Only by moderate grazing intensity can forage grasses maintain good quality.

Key words: desert steppe, grazing intensity, trace element, nutritional component