Characteristics of cultivable microbial community number and structure at the southeast edge of Tengger Desert

Desertification is a common environmental challenge for humans, which restricts social and economic development. Biotechnologies have been used for the management of soils in areas of desertification and the use of microorganisms has shown potential benefits, but such research is still in the initial stages. Here, we have studied the microbial distribution and diversity in soil crust and in the soil under the crust along sand dunes of different fixed ages at the southeast edge of the Tengger Desert, China. The Shapotou and Yiwanquan regions were selected as sampling sites, which represented an artificial restoration region and a natural restoration region, respectively. The results showed that the number of culturable bacteria varied between 3.7 x 10 super(3) to 2.8 x 10 super(6) CFU/g, which was similar with other deserts worldwide. The number of culturable bacteria increased with the degree of sand dune fixation, and decreased with depth, which was similar to the trend of soil improvement in areas of desertification. Such characteristics did not show any significant differences between the artificial restoration region and the natural restoration region (P>0.05). The genera Arthrobacter and Bacillus were the dominant bacteria at the southeast edge of the Tengger Desert. The genus Arthrobacter comprised 12.8% --69.5% and the genus Bacillus comprised 4.7%--60.7% of the total culturable bacteria, and these percentages increased and decreased with the degree of sand dune fixation, respectively. This result implied that Arthrobacter may play a significant role during preliminary soil crust formation. The results also showed that the quantity of culturable bacteria was positively correlated with the concentration of total soil carbon and total soil nitrogen (P