Abstract: To reveal the response of soil microbial community to changes of micro-ecological environment, five monitoring transects were set up in Xiaolinghe estuarine wetland of Liaodong Bay, with four monitoring plots in each transect. The transect G was close to the polder embankment of the culture pond, while the other four transects (Transects A, B, C, D) were situated in proper sequence towards the water area with an interval of 100 m. Phospholipid fatty acids (PLFA) analysis was applied to determine soil microbial community structure. Results showed that the polder embankment significantly affected soil microbial community structure and microecological environmental factors. Abundance of soil microbes of the tidal flat outside the polder embankment increased first and then decreased along the direction from the shore towards the water area. Total bacteria, Gram-positive bacteria, Gram-negative bacteria and fungi of transect C were significantly 33.33%, 22.00%, 50.07% and 35.65% higher than that in transect D (close to water area). PLFA signatures were significantly correlated with soil K⁺, Ca²⁺, total N, Mg²⁺ and NO₃^--N concentrations. Results of variation partitioning analysis showed that soil base ion contents together explained 72.9% of the variation of microbial community structure. Abundance of fungi, actinomyces and Gram-positive bacteria significantly decreased by means of a negative power function with increasing Mg²⁺/Ca²⁺. In summary, polder embankment and base ion content had significant effects on soil microbial community structure.

Key words: export coefficient method, measured data, slope gradient., Hujiashan small watershed, non-point source pollution,