Abstract: Soil microbial biomass, community structure and microbial diversity were analyzed by using phospholipid fatty acid(PLFA)methods, based on the soil of oasis field typical basins (Manas River Basin, Jimsar river, Sangong river, Sigong river, shuimo River) and the adjoining desert in the southern Gurbantunggut Desert. The result of the ecological evaluation showed that: The total PLFAs, Fungi PLFA, Bacteria PLFA, Gram-positive bacteria PLFA(G⁺) and Gram-negative bacteria PLFA(G^-) had generally increased after reclamation of desert; Microbial community structure has undergone significant changes: In the early desert reclamation (3 a), fungal PLFA/bacterial PLFA ratio decreased 48%, G⁺ PLFA/G^- PLFA ratio (Gram-positive bacteria and Gram-negative bacteria PLFA ratio) reduce 67%. But with the extension of cultivation years, these two ratios did not change significantly, suggesting that compared with reclamation years, desert reclamation behavior have a more intense effect on the soil microbial community. In addition, the overall trend of the soil wicrobial diversity is rising with years of use. The diversity index showed a slight decrease after reclamation of 50 years but still higher than the desert soil. The total soil microbial PLFA and most bacteria PLFA content had significant negative correlation with soil conductivity while they had significant positive correlation with total nitrogen and organic carbon. Desert in the reclamation process due to irrigation increased soil moisture and reduces soil salinity, while total nitrogen and organic carbon content increased, these changes are the main reasons for the change of soil microbial communities. This study suggested that desert reclamation helped to improve soil microbial PLFA content, improve soil microbial community structure, and enrich diversity of soil microbial communities. Finally it contributed to improve soil quality.

Key words: Gurbantunggut Desert, reclamation years, microbial community, phospholipid fatty acid