| The functional diversity of the rhizosphere microbial community of dominant plants in the drawdown area of the Three Gorges Reservoir was explored. Rhizosphere soil of three typical dominant plants, Xanthium sibiricum, Cynodon dactylon, Hemarthria altissima and soil of bare land as control soil. Then the soil physical and chemical properties and cultured soil microorganisms on the Biolog-Eco culture plate, then measured and analyzed their carbon source dynamics, microbial diversity and functional diversity of microbial community. The results showed that organic matter content of the four soils was between 13-27 g/kg; the available nitrogen was less than 60 mg/kg; the available potassium was less than 50 mg/kg; the available phosphorus was between 5-20 mg/kg; the total nitrogen was less than 0.75 g/kg; total potassium was less than 2.5 g/kg; total phosphorus was less than 0.4 g/kg. The overall carbon source utilization capacity of the rhizosphere microbial community was: cocklebur>control>Bermudagrass ≈ Verbena. There was no significant difference in the utilization activity of amino acids and carboxylic acid carbon sources by microbial communities (P>0.05), but there were significant differences in the utilization of carbohydrates, polymers, phenolic acids and amine carbon sources (P<0.05). Component 1 of the principal component analysis showed that 5 carbohydrates, 3 polymers, and 1 carboxylic acid have a high positive reciprocity with component 1. These carbon sources were all sugar derivatives or aromatic compounds containing benzene rings, represented the degree of difference in the use of carbon sources by microbial communities. Based on the redundancy analysis of microbial community functions and environmental factors, the environmental factors that have significant impacts on the utilization of microbial carbon sources were pH, available potassium, available nitrogen and organic matter (P<0.01). The reciprocity between the function of rhizosphere microbial community and soil nutrients of several dominant plants was stronger than that of the control group. The soil nutrients in drawdown zone were at a medium to deficient level. The plant rhizosphere microorganisms could be affected by regulating soil nutrients (organic matter, total phosphorus, total nitrogen) or carbon sources of carbohydrates, polymers, phenolic acids and amines. And then this could provide theoretical guidance significance for the vegetation restoration of the degenerated ecosystem in the drawdown area. |
