| Soil is one of the most diverse microbial habitats on earth. The rhizosphere, the zone of the soil directly influenced by plant roots, is a biologically complex and distinct microhabitat within the terrestrial ecosystem. And it is also a door of the plant roots where the nutrient and moisture and various beneficial or harmful substances in and out off the plant roots. Rhododendron chrysanthum Pall.is a kind of herb on Changbai Mountain, it can conserve soil and water, to maintain the ecological balance.It has a significant role in Changbai Mountain.We collected rhizosphere and non-rhizosphere soil of Rhododendron chrysanthum Pall.on four different altitudes. Then, we measured soil microorganism quantity, soil enzyme activity, soil physical and chemical properties and the correlation among them. Results show that bacteria count is most in all samples.Rhizosphere bacteria count:2000m> 1580m> 2614m> 2300m non-rhizosphere bacteria count:1580m> 2300m> 2000m>2614m;there are more numbers of rhizosphere bacteria than non-rhizosphere bacteria at 1580m and 2300m, and less number of rhizosphere bacteria than non-rhizosphere bacteria at2000m and 2614m.there are more number of fungi and actinomycete in non-rhizosphere soil than rhizosphere soil except at 2614m. Rhizosphere fungi count:2614m>1580m>2300m > 2000m, non-rhizosphere fungi count:2300m> 1580m> 2000m> 2614m. Rhizosphere actinomycete count:2614m>2000m>2300m> 1580m, non-rhizosphere actinomycete count:2300m>2614m>2000m>1580m。there are different in soil enzyme activity at different altitude. Rhizosphere invertase activity:1580m>2614m >2300m>2000m, non-rhizosphere invertase activity:1580m>2300m>2000m> 2614m, rhizosphere invertase activity> non-rhizosphere invertase activity. Rhizosphere urease activity:2000m> 2614m> 2300m> 1580m, non-rhizosphere urease activity:2000m> 2300m> 2000m> 2614m, the non-rhizosphere urease activity are higher than rhizosphere urease activity, except at 2614m. Rhizosphere acidic phosphatase activity:2614m> 2000m> 2300m> 1580m, non-rhizosphere acidic phosphatase activity:1580m>2300m>2000m>2614m, the non-rhizosphere acidic phosphatase activity are higher than rhizosphere acidic phosphatase activity at 1580m and 2300m, the rhizosphere acidic phosphatase activity are higher than non-rhizosphere acidic phosphatase activity at 2000m and 2614m.Rhizosphere hydrogenperoxidase activity:2614m> 1580m> 2300m> 2000m, non-rhizosphere hydrogenperoxidase activity reduced with the altitude rise, the non-rhizosphere hydrogenperoxidase activity are higher than rhizosphere hydrogenperoxidase activity at 1580m and 2300m, hydrogenperoxidase activity are equal at 2000m, the rhizosphere hydrogenperoxidase activity are higher than non-rhizosphere hydrogenperoxidase activity at 2614m. Rhizosphere cellulase activity:2300m> 2000m> 2614m> 1580m, non-rhizosphere cellulase activity:2300m> 1580m> 2000m> 2614m, the rhizosphere cellulase activity are higher than non-rhizosphere cellulase activity, except at 1580m.The correlation analysis results indicate, there are Significant correlation among microbial population and soil quality, soil enzyme activity and Soil physical and chemical properties. The rhizosphere fungi and actinomyce count highly correlated with the content of NO3-N and pH value; and rhizosphere bacteria count highly correlated with the content of S. non-rhizosphere bacteria count almost have high correlation with all soil quality which we determined; non-rhizosphere actinomyce count have high negative correlation with soil physical and chemical properties, except pH and content of total K. Rhizosphere actinomyce count highly correlated with acidic phosphatase activity; non-rhizosphere bacteria count highly correlated with activity of invertase, acidic phosphatase and hydrogenperoxidase; non-rhizosphere fungi count highly correlated with urease activity and cellulase activity. Invertase activity highly correlated with content of organic matter; acidic phosphatase activity highly correlated with content of rapidly-available-P, rapidly-available-K and Slowly-available-K.Through the analysis of the results, we found:the root of Rhododendron chrysanthum Pall. significant effect on Soil properties, microbial populations and soil enzyme activity. In different growth period, microbial populations and soil enzyme activity have a certain degree of change. Plant residues and the type and quantity of litter seriously affected the number of non-rhizosphere microbial and soil enzyme activity. By measuring soil properties, the number of culturable microorganisms, soil enzyme activity and analysis of the correlation among the three, we can conclude that the root of Rhododendron chrysanthum Pall. can change the community structure of soil microorganisms, to maintain high enzyme activity, to improve its rhizosphere soil physical and chemical properties, so that Improve soil fertility, bioavailability enhancement, to create a soil environment suitable for their growth. Therefore, the strong influence of roots on the soil may be the main reason that Rhododendron chrysanthum Pall.distribution expansion in Changbai Mountain and become one of the main dominant species in tundra.
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