Objective  In order to provide a theoretical basis for the introduction and promotion of mangroves in freshwater areas, we explored the micro-ecological changes and adaptability of mangrove plants in freshwater environments.

  Method  To explore the microbial community structure characteristics of rhizosphere soil of 5 different mangrove plants, including Rhizophora stylosa(Rs), Avicennia marina(Am), Laguncularia racemose(Lr), Kandelia candel(Kc) and Aegiceras corniculatum(Ac), we performed the study by using Biolog-ECO micro plate (BIOLOG) and phospholipid fatty acid (PLFA) for revealing the response of microbial community structure to freshwater stress.

  Result  The results showed that the soil physical and chemical properties were significantly different among 5 mangrove plants. The average well color development (AWCD) values from high to low were as follows:Am > Kc > Ac > Rs > Lr, and value of Am was the highest among 5 treatments. Ploymers was the most utilized carbon source. The PLFAs analysis was performed to explore the changes in the abundance of soil microbes. The results showed that a total of 17 kinds of PLFA were detected in 5 mangrove plants, and the highest content of PLFAs was 16:0, moreover, the total PLFAs content of Am was significantly higher than the other plants; the group-specific PLFAs in 5 soil samples showed the same trend that content of bacteria reached the maximum. Principal component analysis showed that Lr and Am soils distributed in the same principal component, which was similar to the results of BIOLOG.

  Conclusion   The results indicated that soil of 5 plants was significantly better than unplanted mangrove soil (CK). The microbial community structure of rhizosphere soil was significantly different among mangrove plants. Soil microorganisms of 5 treatments showed the highest utilization of polymers, moreover, biomarkers of bacteria showed the same trend in 5 treatments.