Effect of Different Vegetation Types on Soil Amelioration in Lowlands of the Yellow River Delta

In order to investigate the effect of different vegetation types on soil amelioration in lowlands of the Yellow River Delta,soil physics-chemistry property,microbial biomass of tree soil,shrub soil and grass soil in Hekou County,Dongying,Shandong province were studied by taking farmland as the control.The results showed that: ①There was obvious effect of different vegetation types on soil physical and chemical properties,microorganism,and it was better in topsoil than in subsoil.② The soil bulk density,pH value and salt content of topsoil was lower than that of 20-50 cm soil depth.Soil porosity,permeability and the effect of controlling soil salinity and alkaline content of tree were better than that of shrub soil,and grass soil and farmland were poor.③Soil organic matter,available N,P,K and the amount of microorganisms were mostly distributed by the topsoil(0-20 cm soil depth),and these indexes showed this order: tree soilfarmlandshrub soilgrass soil.The largest number of bacteria accounted for over 97% of total number of microorganisms,and the number of actinomyces was higher than that of fungi.④The correlation among soil microorganism quantity and soil physics-chemistry property was significant,and the correlation coefficient of 20-50 cm soil depth was better than that of topsoil.With the improvement of soil alkali salt and the increase of soil available nutrient,the number of microorganisms was increasing in salina lowland.