Abstract
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 reaction-denaturing 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 similar 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. Key words: Cotton monoculture, Archaeal communities, 16S ribosomal RNA, denaturing gradient gel electrophoresis (DGGE).
Highlights
Xinjiang is one of the regions in which cotton was planted in the earliest time, and the only one planting base for long stapled cotton in 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 three diversity indices of soil archaea gradually stabilized at levels slightly lower than those of uncultivated soils after 10 year continuous cropping, except that with the depth of 21-30 cm, no DNA band was amplified from the soil samples collected in the 0 planting year
Summary
Xinjiang is one of the regions in which cotton was planted in the earliest time, and the only one planting base for long stapled cotton in China. Xinjiang region has all the natural environmental conditions suitable for planting cotton, which include rich heat energy, abundant sunshine, little rainfall, dry air, substantial differences between day and night temperature, and artificial irrigation of snow water (Zhu, 2013). A great amount of wasteland was reclaimed to plant cotton in the eighties of the last century; the seven indices such as planting area, total productivity, mean productivity per acre, and so on with Xinjiang cotton ranked first for 21 continuous years. In Xinjiang, classes of crops are simple, and especially in the planting area within localities, the main cotton producing areas accounts for over 95%, and rotation cropping is almost impossible.
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