The changes of the vegetation characteristics of alfalfa grasslands under different fertilization schemes were analyzed with the trial of plot experiments.The results indicate that the species richness index of the continuous cropping alfalfa grassland did not significantly change under different fertilizer treatments,along with considerably increased community coverage,and significantly raised community heights. Fertilization could maintain species diversity and community stability and enhance alfalfa grassland productivity.After the application of fertilizer,the niche breadth of alfalfa population significantly increased and the competitiveness strengthened relatively.However,the niche breadth of forbs decreased and relatively weakened.No significant niche overlap was found between alfalfa population and other species under continuous cultivation and fertilization.Greater niche overlap was found among the forbs,between which the competition was more intense and dominant.Fertilization could improve the quality and economic value of alfalfa grasslands,while the invasion of forbs functional groups such asSetaria viridiswas one of the most important factors degrading the grasslands.