Study On Soil Microbial Molecular Diversity And Organic Matter Transformation Under Soil Salinization Condition

[Objective] Soil salinization is an important limit factor to the development of agriculture in arid and semi arid areas. Chloride and sulfate saline soil are two typical kinds of saline soil in Xinjiang. In this paper, microbial biomass, microbial activity and microbial community structure and function diversity responded to the chloride and sulfate saline salt concentration gradient has been studied. At the some time, studied the effects of salt on the utilization and transformation of soil organic matter, part of the soil carbon cycle processes. The results played a theory supporting role to determine the threshold impact of salt concentration on soil biological quality and to maintain soil microbial diversity, also provide reference and information for the local brackish water use to maintain the sustainable and healthy use of agricultural farmland.[Method] Set different salinity levels by the brackish water irrigation and with simulation methods set different concentrations of chloride and sulfate salts. Use soil enzymology and microbial culture methods to determined soil enzyme activities, microbial biomass carbon and microbial activity under different types and concentrations of salt. Microbial diversity was studied by using extracting soil DNA, PCR-DGGE methods. Soil organic matter utilization, transformation were studied through the use of soil CO2 flux in situ detection, Biolog and different C/N material degradation analysis.[Result]1) The use of brackish water can lead to significantly increasing of surface soil salinity, the use of brackish and salt water drip irrigation caused significant difference of soil electrical conductivity between fresh water, brackish water, salt water treatment (P<0.05).2) A certain level of soil salinity has little effect on soil microbial biomass (EC1:5= 0.85), but the soil enzymes, AWCD and other indicators of soil biological activity was significantly reduced, leading to significantly changes of soil biological functions and structure, soil biological functions diversity index decreased. Finally soil biological quality reduced.3) Soil microbial biomass, microbial quotient decreases with the salt concentration gradient increase, and metabolic quotient with the salt concentration gradient increases.4) Compared Chloride and sulfate two different salt types, the inhibition of chloride on soil microorganisms, soil biological activity, and microbial functional structure were more than sulfate. Chloride saline soil at the salt content of 8 g kg-1, sulfate saline soil at the salt content 10 g kg-1, because Soil biological characteristics, functional diversity and biological soil microbial community structure changes significantly, it can be used as the key value of salt content. 5) Brackish water drip irrigation significantly reduced carbon dioxide emissions under cotton membrane, and the 31 kinds of soil microbial carbon substrate use were obvious differences, but the degradation of organic material had no significant effect between these treatments.【Conclusion】Soil salinity accumulated significantly under Brackish water irrigation, which directly affect soil biological activity, reduce soil enzyme activity and soil microbial community structure and functional diversity. Prolonged use will result in a decline of soil biological quality. Different salt types affected soil quality in varying degrees, chloride had significantly greater effects on soil biological traits than the sulfate. Soil salinity significantly affected soil organic carbon utilization, and reduced the carbon dioxide release of intramembrane soil under drip irrigation.