| Solidago canadensis was introduced as ornamental flowers in Shanghai,China in 1935. Then it spread to the eastern and central regions becoming one of the larger range expansion of alien invasive plants. Currently, the studies on Solidago canadensis mainly focused on the morphological description, infestation, biological characteristics, quarantine and control treatment, while only a few studies addressed to the soil micro-ecology. To understand the invasive plants impact on the soil environment, is beneficial to enucidate mechanism of alien species invasion, manage invasive alien species and restore ecological land system. In order to compare the difference invaded by this weed, the research plots in the field was selected according to invasive sevetiry of Solidago canadensis including three kind of communities with not invaded habitat, moderate and severe invasion of this weed. We detect rhizosphere soil N,P,K nutrient status, soil enzyme activity,and analyze the soil microbial community structure using traditional culture method and vegetation absorbed N,P,K content and seasonal dynamics changes in those community of Solidago canadensis. The results are showed as follows.1.In the early stage, invasion of Solidago canadensis changes the soil microbial community structure:soil bacteria, actinomycetes and fungi respectively increasing 89.37%, 83.25% and 154.47%,compared with the control plots. Meanwhile, phosphatase activity increased by 29.22%; the early invasion of Solidago canadensis also significantly increased soil pH value (P<0.01) and soil potassium, phosphorus, soil organic matter, total nitrogen and nitrate content were increased by 25%,89.39%,47.36%,41.8%and 194.63%,respectively.2. In the late invasion stage of Solidago canadensis, the soil bacteria, actinomycetes and fungi increased 58.62%,22.93% and 77.24%,respectively and soil invertase, phosphatase, catalase activity decreased by 8.3% 29.23%,12.21%, compared to the control plots, while compared with the control plots urease activity increased 74.46%. Soil pH value is still significantly lower than the control plots(P<0.01), meanwhile soil available K, soil nitrate content, activity phosphorus, soil organic matter content have a decline trend, nevertheless total nitrogen, compared with the control plots, had no significant difference. 3. In florescence of Solidago canadensis, it absorbed the amount of N, P, K, is 2.01 times,1.26 times and 2.02 times respectively, compared with control plots.At the same time we surveyed 12 sites of Solidago canadensis invasion and sampled and detected soil, including three types of:loam, sandy loam and clay. Loam includes the following sites:Bengbu, Hefei, Shanghai Baoshan, Xiema;:sandy loam Jinhua, Ningbo, Zhangjiagang and clay Jiaxing, Yangzhou, Changsha, Shangrao. The results showed that Solidago canadensis invasion had a significant effect.on soil active K compared to the control plots. Other indicators of soil nutrients:phosphorus, organic matter, total nitrogen, nitrate and soil pH had no great impact in general, professedly. But considering sparse and low vegetation in the control plots, biomass of Solidago canadensis in invasive plots was much higher. These results incadte that Solidago canadensis could activate soil nutrients and absorbed much greater amount than that of vegetation in the control plots. Thus, after the invasion of Solidago canadensis, deficiency of soil nutrients due to its rapid growth did not cause soil barren in invaded habitats. On the contrary Solidago canadensis accelerated the activation and release of soil nutrients to meet their high demand for its growth, making a sustainable and stable soil nutrient supply. Solidago canadensis could grew well inspite of the soil nutrient levels varied greatly in 12 different sites, which indicates that Solidago canadensis may not be sensitive to soil nutrient status, and adapte to different soil nutrient conditions, The result further reflects its strong invasibility.In conclusion, the invasion of Solidago Canadensis changed rhizosphere microbial community structure, and broke the balance between local species of plants and soil microbial, which had formed over a long period of time. At one time, Solidago Canadensis inhibited the growth of local plants, resulting in the reduction of local plant biomass; Solidago canadensis could accelerat soil nutrient cycling, increase soil active nutrient levels by increasing soil enzyme activity, change the soil environment and the balance between soil nutrient supply and demand, improve effectivness of resources utilization, so as to achieve its own rapid growth, improve the competitiveness, and finally reseach a successful invasion. |
