Studies On Soil Microbial Community Structure Diversity In Different Degrees Of Saline-alkaline Soil

Three saline-alkali soils(slightly salinity soil, intensively salinity soil and saline soil) collected from Hetao Irrigation District(Bayannur City, Inner Mongolia) were analyzed by PLFA(phospholipid fatty acid) analysis, DGGE(denaturing gradient gel electrophoresis) and QPCR(real-time fluorescent quantitative PCR) techniques in this study. We investigated saline-alkali soil environment characters and their relation to soil microbial diversity, bacteria diversity and ecosystem functions with the line of soil microbial community structure. The main results were as follows:(1) Quantitative PLFA analysis showed that total soil microbial PLFA,bacteria and fungi PLFA contents as well as diversity index declined with the intensity of soil salinity. Soil phospholipid fatty acid markers were significantly correlated with soil total phosphorus, total nitrogen and soil organic matter.(2) DGGE results demonstrated that bacterial community structure and diversity in 0~20 cm and 20~30 cm soil layers decreased with the intensity of soil salinity: slightly salinized soil>intensively salinized soil>saline soil.Bacterial communities in 0~20 cm and 20~30 cm soil layers were different,community diversity and abundance decrease with soil depth.Shannon-Wiener index was significantly negatively correlated with w(EC)(r=-0.542,P<0.05)、p H(r=-0.526,P<0.05) and soil bulk density(r=-0.523,P<0.05), and significantly positively correlated with w(SOC)(r=0.700,P<0.01) and w(TP)(r=0.805,P<0.01). Bacterial diversity and abundance were mainly affected by EC, p H, total nitrogen(TN),SOC, total phosphorus(TP)and soil bulk density, especially w(EC) and p H. Proteobacteria dominated bacterial communities. DGGE revealed that bacteria in saline-alkali soils were salt tolerant, besides sulphate tolerant.(3) Real-time fluorescent quantitative PCR showed that the number of bacteria was as follows: slightly salinized soil>intensively salinizedsoil>saline soil. The numbers of bacteria in saline-alkali soil were negatively correlated with conductivity(r =-0.904, P <0.01), p H(r =-0.804, P <0.01),and water content(r =-0.786, P <0.05), and positively correlated with TP(r =0.772, P <0.05) and SOC(r = 0.732, P <0.05), but the correlation between bacteria number and soil total nitrogen was not significant(r = 0.481, P>0.05).(4) Combined PLFA and PCR-DGGE analysis might be an effective complementary way to elucidate microbial communities in different saline-alkali soils. PLFA method manifested no species difference in soil bacteria communities, PCR-DGGE technique showed detailed species changes, con?rming that the main bacterial species were different in different saline-alkali soils, with dominant proteobacteria bacteria of salt tolerance. The DGGE related diversity indices were suitable to discuss the microbial diversity of saline-alkali soils.