| Beach land bond with river and inland was a special ecosystem and very sensitive to surrounding environmental variation due to remarkable edge-effect . Because of seasonal changes and opened environment, the beachs around of Yangtze River were the main high endemic area for snails ,which were the intermediate host of Schistosoma Japonicum.Traditional methods had little effect on breeding ground for snails control, so the beachs were received much concern,especially for the reed beach.But in recent years ,many artifical poplar plantation were constructed to control snail and prevent disease,the ecological environment of the reed beach was great improved.Soil microorganisms as an important component of ecosystems, controlled soil ecosystem's many processes.However microbial diversities are very sensitive to changes of soil physical-chemical properties, and it was usually uesd as a biological indicator to evaluate soil quality and ecosystem sustainability .This article focused on the study of changes in the structure and amount of bacterial population in reed beach , and anticipated to assess the effects of artificial poplar plantation on soil bacterial population on a molecular level .Test samples were collected at position of Yueyang city, in Hunan province, in the reaches of middle Yangtze River, in July of 2008. The soils under the artificial poplar plantation with three-year-old were specially choosed and the soil under the reed were also selected as contract ,with the same altitude and soil type. All those soils were collected from surface down to 65cm with three layers such as 0-10 cm,10-25 cm and 25-65 cm .in addition, rhizosphere and root-surface soil were collected together. PCR–DGGE technique and traditional microbial counting method with isolation and culture were used to analyze the effects of artificial poplar plantation on bacterial diversity in soils selected.The main results showed as follow.The soil pH ranged in 6.0- 6.5, weak acid. The contents of nitrogen, effective phosphorus and organic carbon in the rhizosphere, root-surface and surface soil (the 0-10 cm layer) in the artifical poplar plantation were significantly lower than in the reed.The abundance of microrganism in the artificial poplar plantation was lower in the rhizosphere soil ,compared with the reed.The trend followed by bacteria,fungi and ammonia oxidizing bacteria in the root-surface soil ,but the opposite condition appeared in the actinomyces,cellulolytic bacteria,nitrite oxidizing bacteria and denitrifying bacteria.The distributions of four kinds of soil functional bacteria in different soil layers were as follow:in the 0-10 cm layer, the counts of cellulolytic bacteria and nitrite oxidizing bacteria were higher than these in the reed, the rest was lower.In 10-25 cm layer, the counts of the cellulolytic bacteria with nitrite oxidizing bacteria were lower than these in the reed, the opposite trend appeared in the denitrifying bacteria and the counts of ammonia oxidizing bacteria were the same. Except cellulose bacteria, the counts of three other kind of functional bacterial were lower than the reed in 25-60 cm layer.PCR-DGGE banding patterns and Shannon index were both indicated that the bacterial diversities were higher in rhizosphere soil and the soil layers of 10-25 cm and 25-60 cm, and were lower in root-surface soil and 0-10 cm layer, compared with these in the reed.The analysis of phylogenetic tree indicated thatβ-proteobacteria,Nitrospirae andα-proteobacteria were dominant bacteria community in beach land selected. Some respective and exclusive bacterial populations were found in rhizosphere soil, root-surface soil and 0-10cm layer.All these results showed that artificial poplar plantation has a certain impact on the soil bacterial populations in reed beach. |
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