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Journal of Arid Land

Article Title

Soil microbial activity and community structure as affected by exposure to chloride and chloride-sulfate salts

Abstract

Mixed or chloride salty ions dominate in saline soils, and exert wide-ranging adversely affect on soil biological processes and soil functions. The objectives of this study were to (1) explore the impacts of mixed (0, 3, 6, 10, 20 and 40 g Cl–/SO42– salt/kg dry soil) and chloride (0, 1.5, 3, 5, 8 and 15 g Cl– salt/kg dry soil) salts on soil enzyme activities, soil physiological functional (Biolog) profiles and microbial community structure by using soil enzymatic, Biolog-Eco microplates as well as denaturing gradient gel electrophoresis (DEEG) methods, and (2) determine the threshold concentration of soil electronic conductivity (EC1:5) on maintaining the functional and structural diversity of soil microbial community. The addition of either Cl– or mixed Cl–/SO42– salt obviously increased soil EC, but adversely affected soil biological activities including soil invertase activity, soil microbial biomass carbon (MBC) and substrate-induced respiration (SIR). Cl– salt showed a greater deleterious influence than mixed Cl–/SO42– salt on soil enzymes and MBC, e.g., the higher soil MBC consistently appeared with Cl–/SO42– instead of Cl– treated soil. Meanwhile, we found that SIR was more reliable than soil basal respiration (SBR) on explaining the changes of soil biological activity responsive to salt disturbance. In addition, microbial community structures of the soil bacteria, fungi, and Bacillus were obviously affected by both salt types and soil EC levels, and its diversity increased with increasing of mixed Cl–/SO42– salt rates, and then sharply declined down after it reached critical point. Moreover, the diversity of fungal community was more sensitive to the mixed salt addition than other groups. The response of soil physiological profiles (Biolog) followed a dose-response pattern with Cl– (R2=0.83) or mixed Cl–/SO42– (R2=0.89) salt. The critical threshold concentrations of salts for soil physiological function were 0.45 dS/m for Cl– and 1.26 dS/m for Cl–/SO42–, and those for soil microbial community structural diversity were 0.70 dS/m for Cl– and 1.75 dS/m for Cl–/SO42–.

First Page

737

Last Page

749

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