| Soil microbes, as an important and active part in ecological system, were very sensitive to the changes of environmental factors. Increasing atmospheric temperature would have a very important influence on soil microorganisms of wetland ecosystem. By applying Open Top Chamber to simulate long term temperature enhangcement, this paper studied the soil microbes of different soil depth levels in different seasons, and rhizosphere soil microbial quantity and diversity of reeds, including Imperata cylindrica and Phragmites australis in Chongming dongtan Phragmites australis coastal wetland, as well as non-rhizosphere soil microbial number and diversity with the response to rising atmosphere temperature. It showed with the following results:(1)The warming effect of OTC:After 8-yeas simulating temperature continuously, atmospheric temperature rose about 1.53 degrees significantly, leading to the rise of 1.04 degrees of soil temperature and no significant change in soil moisture at the same time. Long-term simulation of rising temperature increased TOC significantly, in soil surface (0-20cm layer) in July, and had no effect on the content of TN and TP.(2) 8-years long-term simulation of rising temperature leaded to the increasing of total number of soil microorganisms by 45.21% significantly. With a dramatic increasing in the number of bacteria (48.99%), it made the biggest contribution to the growth of soil microorganism quantity, and the contribution rate was 98.93% in warming group. Compared with the control, fungi had a 21.38% increase in the number. The increase of actinomycetes number was not significant.(3) In the vertical level, the increasing rate of 0-10 cm layer soil microbial total quantity was the largest, as a result of long-term simulated temperature enhancement. The increasing rate of 58.22% made the contribution rate of 45% largest in general increasing of the number of microorganism. Among them, the biggest increasing rate of bacteria (63.81%), had the largest contribution rate of 44.64%. The fungi total quantity reached the biggest increasing rate (36.45%) in 0-10cm layer after long-term simulated temperature enhancement. Actinomycetes had the biggest increasing amplitude in the 10-20cm layer, with an increasing rate of 22.68%.(4) The seasonal change of soil microorganisms presented the highest increasing rate of 103.31% in July, with the biggest contribution of 67.50% in the total number of soil microorganisms, under the condition of long-term simulated temperature enhancement. The warming had the largest effects on bacteria, leading to the biggest increasement of bacteria number in July, with the biggest contribution rate of 68.29%. Warming made no difference in actinomycetes number.(5) During the entire study, the effect of long-term simulated temperature enhancement on the number of soil bacteria of plant rhizosphere was the most significant. The number of plant rhizosphere fungi increased highest at a rate of 80.14%. Warming showed no significant impact on the number of changes of plant rhizosphere actinomycetes. Temperature enhancement increased the number of non-rhizosphere fungi significantly in the 0-10 cm soil layer, with the increasing rate of 111.22%. The number of non-rhizosphere actinomycetes increased significantly in July, especially in the 30-40 cm layer.(6) Long-term simulation of the temperature enhancement resulted in plant rhizosphere soil bacteria diversity of different layers increased obviously. Because of the difference of plant species between Phragmites australis and Imperata cylindrica, the increase of the number and species of flora also were not identical in different soil layers between warming and control group. Instead, the diversity of non-rhizosphere bacteria under the action of raising temperature decreased obviously. |
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