This study was carried out in order to investigate the variations of the soil archaeal community structure in fields with continuous cotton cropping in Xinjiang Region, China. Soil samples were collected from four depths in fields with 7-year continuous cotton cropping. 16S rRNA-polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) was used to analyze the archaeal community structure in soil. The archaeal diversity indices of the soil samples at the same depth exhibited

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... ilar patterns of changes with the period of continuous cotton cropping. Cluster analysis indicated that although various timeframe of succession cropping had great effect on archaeal communities in the samples of soils at various depths, they all had the trend to restore spontaneously. Principal component analysis showed that the archaeal community structure varied similarly regardless of the period of continuous cotton cropping. Homology comparison of sequences recovered from the DGGE bands showed that the obtained sequences all originated from the archaea organisms not cultured. Continuous cotton cropping exerted significant influences on the structure of soil archaeal community in Xinjiang Region, which were largely determined by the soil depth and the period of continuous cotton cropping. The microbial diversity of soil archaeal communities gradually recovered after 5-year continuous cropping.