Effects Of Alternanthera Philoxeroides (Mart.) Griseb Invasion On Soil Microbial Community Structure And Enzyme Activity

Alternanthera philoxeroides (Martius) Grisebach, native to South America, is a perennial herbaceous plant. It invaded China in 1892, then spread rapidly and had a negative effect on the ecology enviroment. To make sure the effect of Alligator weed on soil microorganism, this study measured the changes of soil microbial community and diversity, and soil chemical property, soil enzyme activity (dehydrogenase, urease and acid phosphatase). This study aslo aimed at providing scientific support for prevention and controlling of Alligator weed. The results are as follows:1. The number of soil bacteria and fungi increased after the invasion of Alternanthera philoxeroides. The number of both culturable bacteria and fungi detected by plate counts increased significantly. The results of fatty acid analysis also suggested that the biomass of Gram positive bacteria and fungi in the sample of Xiantao had increased significantly (p<0.05), while that of Gram negative bacteria, actinomycetes and AM fungi in the sample of Wuhan also increased significantly (p<0.05).2. The community structure of AM fungi and bacteria in soil changed after the invasion of Alternanthera philoxeroides. The DGGE profile showed that the number, mobility and density of the bands changed, but the Shanon-Wiener Index of AMF and bacteria all did not changed significantly, but microorganisms changed. The data showed that all the AM fungi was belonged to Glomus in the phylogenetic tree.3. The changes of soil physical and chemical properties had been investigated. After Alligator weed invading, total nitrogen of soil and nitrate-nitrogen increased. Available phosphonium increased and available kalium decreased.4. The activity of soil enzymes had changed after Alligator weed invading. The urease activity of soils increased significantly (p<0.05). The dehydrogenase activity decreased significantly in the acidic soils (p<0.05). The acid phosphatase activity increased significantly in alkaline soils (p<0.01).In a word, the main nutrients in soil were significantly changed after invasion of Alligator weed, the diversity of bacteria and AM fungi declined during the interaction between Alligator weed and soil microbes, which resulted in a lower stability of plant communities and Alligator weed became a dominant specie finally.