Comparison of the plant community characteristics in the headwater region of the Yellow River

Plant communities of Potentilla fruticosa shrub,native Kobresia pygmaea meadow and severely degraded Kobresia pygmaea meadow in Maqin County,which are located at the headwater region of the Yellow River,were investigated.The diversity index,richness,evenness and similarity index of the communities were compared.The results indicated the diversity index was in the order of Potentilla fruticosa shrub(3.609) native Kobresia meadow(3.475) severely degraded meadow(2.809).Species evenness was ranked by native Kobresia meadow(0.924)Potentilla fruticosa shrub(0.918) severely degraded meadow(0.778).The species number of Potentilla shrub,native Kobresia meadow and severely degraded Kobresia meadow was 51,43 and 37 respectively.The native Kobresia meadow and severely degraded meadow had high similarity.Species composition and dominance varied with meadow degradation and the dominance of Kobresia pygmaea decreased with degradation.Aboveground biomass was in the order of Potentilla shrub(197.90 g /m2) severe degraded neadow(125.68 g/m2)native Koresia meadow(103.78 g/m2).Belowground biomass was mainly distributed in the 0-20cm of soil and much less in the 20~40cm of soil.