Effects Of Invasive Plant Flaveria Bidentis On Soil Ecosystem

Flaveria bidentis (L.) Kuntze, an annual exotic weed invaded China in recent years, has caused huge damage to the ecological environment with its strong ability to reproduce and invasive nature.this research based on the interaction between Flaveria bidentis and soil. Through the field sampling and greenhouse experiments, we study the soil mechanism of the invasion of Flaveria bidentis, different invasion levels from the effects of Flaveria bidentis on soil's physical, chemical properties and bacteria activity. The main results are summarized as follows:1. Comparing with native plant soils, the F. bidentis- invaded soils had obviously higher contents of soil organic carbon, total nitrogen, NO₃^-, and NH₄⁺, but lower contents of soil total and available phosphorous. However phosphorous did an opposite trend which is bland>native>slight>heavily.2. The urease activity of heavily-invaded soil and newly-invaded were higher than those in non-vegetated and native plant soils. phosphatase activity changed with invading. The following order was heavily-invaded>slight-invaded>native>blank. Heavily-invaded has a significantly difference with blank soil in polyphenol oxidase.3. Shannon–Weaver diversity index (H') and number of DGGE bands showed that rhizosphere bacterial diversity of F. bidentis decreased along the invasion gradient. The species richness and components was further evaluated by 16S rDNA sequences. Compared with the native vegetation soils, the slightly invaded soils contained almost the same bacterial community except for a few from Proteobacteria. In the heavily invaded soil, bacterial species in Proteobacteria, Chloroflexi and Actinomycetes were all affected, the most reduction occurred in the Proteobacteria. In the barren land soils, Proteobacteria was the dominant species and Bacteroidetes were only found in this type of soils. As the progression of F. bidentis invasion, soil microbial biomass concurrently increased.4. In present study, F. bidentis seeds from four different habitats were tested for their drought resistance under different osmotic potentials induced by PEG-6000. The result suggests that seed germination rates, GI, Vi and Germination Stress Index of F. bidentis were reduced with increasing PEG concentrations, but the drought sensitivity varied among populations significantly. Embryo root and embryo shoot increased and reduced with increasing PEG concentrations. Based on the comprehensive evaluation index, the drought resistance of four populations decreased in the following order as fruit>roadside> river>wasteland.