The characteristics of soil and vegetation of degenerated alpine steppe in the Yellow River Source Region

In recent years,the alpine steppe in the Yellow River Source Region has shown obvious trends of degradation and desertification.We studied the different plant communities,biomass and soil characteristics of the Stipa purpurea alpine steppe at different degradation stages.With an increase of alpine steppe degradation,the vegetation coverage,grassland quality index and the proportion of excellent aboveground biomass forage gradually declined and the grassland similarity index decreased.As degradation increased,the plant diversity index and evenness index trend were both single-peak type curves.With increased degradation,grass aboveground biomass was significantly reduced and that of forbs was significantly increased at the beginning,but it was reduced during the mid-late period.The sedge above-ground biomass was not influenced by grassland degradation.The below-ground biomass of alpine steppe plant roots in the 0-20 cm soil profile was increasingly reduced as soil depth increased while the root biomass changed into an inverted V type.The V shape,with increased degradation,the relationship between species richness and productivity converted significant positive correlation of soil organic matter,available phosphorus,nitrate nitrogen,available potassium and soil compactness concentrations were reduced.With the succession of alpine grassland degradation,soil degradation became more serious.In the severe degradation stage,desert plants appeared,and the landscape developed a desert appearance.