Changes of community characteristics in the degradation process of the alpine swamp wetland in the Yellow River Source area

Based on the method of replacing time series with spatial sequence, the changes of plant community spatial distribution characteristics in the degradation process of the alpine swamp wetland were investigated in the Yellow River Source area in QinghaiTibetan Plateau of China. The results showed that the degradation process of the wetland experienced from swamp meadow to alpine meadow, and to degraded grassland. During this progress, the species component in plant communities had succession and hygrophytes were replaced by mesophytes and xerophytes, the dominant plants, Kobresia tibetica, gradually disappeared and forbs became constructive species. Species richness index, evenness index and diversity index firstly increased and then decreased whereas dominance index inversely decreased and then increased which peaked at the alpine meadow stage. As the succession proceeded, the aboveground biomass showed a unimodal decreased curve, the proportion of perennial forbs increased dramatically and the speciesabundance distribution gradually changed into a ZipfMandelbrot model from the early lognormal model.