Study On The Community Structure And Functions Of The Rhizospheric Microorganisms Of Phragmites Australis Grown In Wetlands

The wetlands are degenerating even vanishing attended the decline of wetland plant, which make the wetland quality downgrade unceasingly. The microbe-assisted phytoremediation make the two parts which consists it, plant and microbes, become complementary to each other, which makes this technology is one of the promising remediation methods to the contaminated wetlands. Phragmites australis is commonly used in the phytoremediation of contaminated environments. However, the decline of Phragmites australis in wetlands is aggravating unceasingly. Based on this background, this dissertation took the reed wetland ecosystem as the object, comparisons of the rhizosphere soil properties, growth situations, AMF (Arbuscular Mycorrhizal Fungal) colonization, the transportation and accumulation levels of 14 chemical elements in the reeds between different seasons and habitats were made. Investigations of the genetic and metabolic diversity of rhizosphere microorganisms through the DGGE and BIOLOG methods were also made.The analyses demonstrated that different rhizosphere soil properties could affect the chemical elements transportation and accumulation in reeds in different ways, such as changing the concentrations, proportion and bioavailability of chemical elements, promoting/inhibiting reed growth and AMF colonization, affecting the diversity and activity of rhizosphere microorganisms. Compared with other factors, pH brought stronger influence over the chemical element transportation and accumulation in reeds. Compared with the metabolic diversity and activity, the genetic diversity of rhizosphere microorganisms, especially of the fungi, had a closer relation to the chemical element transportation and accumulation in reeds. The Pearson correlation with the latter, such as the enrichment coefficients of Zn, Mn and Mg etc., are over 9, significantly. Between the growth season and the maturity season, the richness, diversity, and activity of rhizosphere microorganisms decreased; Such variations in the community structures and activities of the rhizosphere microorganisms followed the rules of intermediate disturbance hypothesis and edge effect. The soil organic matter content and the carbon nitrogen ratio had a close relation to the microorganism diversity.The oxygen content in the soil of wetlands is relatively low, which unfavorable to AMF growth, so the AMF infection rates of different seasons and habitats were not high, not exceeding 20%. However, the AMF infection rate was positively related to the soil water content. It was because of the growth inhibitory factors of AMF (such as P, Mg), which had a negative correlation with the soil water content. Compared with AMF vesicle, AMF hypha had a higher infection rates, and between the growth season and the maturity season, both of them decreased.Cluster Analysis of the elements showed that there were 7 clusters of 14 chemical elements; In the nonmetallic elements, C and S was respectively a separate one, N and P were grouped together; In the metallic elements, K was a separate group, Mg, Fe, Zn, Mn were classified into the same group, Ca and Cu were grouped together, Cr, Ni, Pb were grouped together.Through investigating the 17 universal microorganisms, to wit, the microbes which are well-adapted to the changes of various environmental factors, in Phragmites australis rhizosphere soil, it was found that there were more universal species of bacteria than fungi in the rhizosphere. In addition, most of them are uncultured. Principal Component Analysis showed that wetland type was the dominating factor affecting the variations in the community structures of Phragmites australis rhizospheric bacteria and actinomycetes; Both of seasonal change and wetland type were the dominating factor affecting the variations in the community structures of Phragmites australis rhizospheric fungi; Wetland type was the dominating factor affecting the variations in the metabolic diversity of the Phragmites australis rhizosphere microorganisms.In this dissertation, the relationships among the three parts, soil, rhizosphere microorganism and reed, which consist the wetland ecosystem were explored by Correlation Analysis, Cluster Analysis and Principal Component Analysis, and the universal microorganisms were investigated by DNA sequencing, which both provided instructions for the microbe-assisted phytoremediation to the contaminated wetland ecological systems.