Effects Of Composite Invasive Plants On Soil Microbial Community Structures

Recently, the interaction between invasive plants and soil microorganisms becomes a hotspot to research the relationship of invasive plants and their invasive habitat. However, soil microbe is the key factor to affect the invasive ability of plants and available invasion of ecological system. Phospholipids fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) are used in this paper. According to the different invasive stages of the three composite invasive plants, Ageratina adenophora, Ambrosia artemisiifolia L. and Flaveria bidentis, we studied the soil microbe and discussed the possible invasive methods of invasive plants.The main results are as follows:1. Effects of A. adenophora, A. artemisiifolia L. and F. bidentis to the physical and chemical characteristic of the soils.Changes of soil pH value: the invasion of A. adenophora and F.bidentis improve the pH value while the invasion of A. artemisiifolia L. has an different effect. A. adenophora of Sichuan and Yunnan heavily invaded soil' pH value is 0.52 and 0.18 higher than it in native plants soil, respectively; F.bidentis of Baoding and Hengshui highly invaded soil' pH value is increased by 0.70 and 0.57 than it in native plants soil; while the pH value in Liaoning and Jiangsu is 1.08 and 1.06, which are lower than in native plants soil, respectively.Changes of organic carbon: the contents of soil organic carbon are increased by the invasion of A. adenophora, A. artemisiifolia L. and F. bidentis, respectively. The contents of organic carbon in the soil invaded heavily by A. adenophora in Sichuan and Yunnan is 48.6% and 30.3% higher than it in native plants soil, respectively; in Baoding and Hengshui, they are increased by 16.2% and 11.8 than them in native plants soil; while the contents in Liaoning and Jiangsu is 10.8% and 25.3% higher than it in the native plants soil.Changes of Total N, Total P and Total K: the contents of Total N are increased by the invasion of A. adenophora, A. artemisiifolia L. and F. bidentis, respectively. The contents of Total N in the soil invaded heavily by A. adenophora in Sichuan and Yunnan are 10.5% and 61.6% higher than the contents in native plants soil, respectively. In Liaoning and Jiangsu, the percentages are increased by 88.1% and 16.2%, while the contents are only 7.6% and 8.9% higher than them in the native plants in Baoding and Hengshui.The invasion of the three plants does not influence contents of Total P and Total K much.2. Effects of A. adenophora, A. artemisiifolia L. and F. bidentis to the soil microbial community structures.The invasion of A. adenophora leads to reduce the number of fungi in the soil, while it caused the increase of the number of the Vesicular-arbuscular mycorrhizas fungi (VAM) and actinomyces.In Yunnan heavily invaded soil, the contents of fungi are decreased by 27.7% and the percentages of VAM and actinomyces are increased by 43.2% and 12.1%. The ratio of cy19:0/18:1ω7c will be lessened clearly when the invasion of A. adenophora becomes heavier. The ratios of fungi/bacteria and G-/G+ have the different results. The ratio of cy19:0/18:1ω7c of Yunnan heavily invaded soil is lowered by 31.6%; In Sichuan, The ratios of fungi/bacteria and G-/G+ are increased by 20% and 55.3%, respectively.The invasion of A. artemisiifolia L. leads to a reduce of the number of fungi and actinomyces in the soil, while in Liaoning the invasion increases of the number of the VAM and the result is on the contrary in Jiangsu.In Jiangsu heavily invaded soil , the contents of the fungi are decreased by 33.8% and in Liaoning the percentages of actinomyces are reduced by 20%. According to the contents of VAM, they are increased by 96.7% in Liaoning and reduced by 34.1% in Jiangsu.The ratios of cy19:0/18:1ω7c, fungi/bacteria and G-/G+ will be lessened gradually when the invasion of A.artemisiifolia L. becomes heavier. The ratios of fungi/bacteria and G-/G+ have the different results. The ratio of cy19:0/18:1ω7c in Liaoning heavily invaded soil is lowered by 57.8%; In Jiangsu, The ratios of fungi/bacteria and G-/G+ are increased by 31.5% and 27.2%, respectively.The invasion of F. bidentis leads to reduce the number of fungi and actinomyces in the soil, while the number of VAM increases. In Baoding heavily invaded soil, the contents of the fungi are decreased by 46.9% and in Hengshui the percentages of actinomyces are reduced by 26.8%. According to the contents of VAM, they are increased by 22.3% in Baoding.The ratios of fungi/bacteria and G-/G+ will increase gradually with the invasion of F. bidentis heavier. The ratio of cy19:0/18:1ω7c has the different result. The ratio of cy19:0/18:1ω7c in Baoding heavily invaded soil is lowered by 49.1%; while the ratios of fungi/bacteria and G-/G+ are increased by 59.8% and 62%, respectively.3. PCR-DGGE of bacteria in different stages soil which are invaded by A.adenophora, A. artemisiifolia L. and F. bidentisThis research used total DNA of the soil in different stages as the template, hoose 27f/1492r and 338F-GC/518R as two primer pairs, using nested-PCR to amplification V3-fragment of the bacteria.Then we used the amplification to separate DGGE and sequencing. Finally, DGGE graph shows that it is very different in the bacteria community structures of different stages and the bacteria types in the heavily invaded soil are more than types in the newly invaded soil and the native plants soil.The results from the recovery bacteria bands show that the main dominant bacteria groups in the heavily invaded soil are Bacillus, among which groups that have 100% homology are the common good bacteria in the soil, such as Bacillus megaterium, Bacillus flexus, Bacillus anthracis, Bacillus pumilus, Bacillus subtilis and so on.