Abstract: Taking the Quercus liaotungensis forest soil in Dongling Mountain of Beijing as the object, and by using chloroform fumigationextraction and phospholipid fatty acid (PLFA) analysis methods, this paper studied the variation characteristics of soil microbial community along an altitudinal gradient in the tree growth season. With increasing altitude, the soil microbial biomass carbon and nitrogen and the quantities of various soil microbial groups in the forest had definite differences but not significant. The ratio of soil bacteria to  fungi increased, but the ratio of G⁺ to G^- bacteria decreased. The soil microbial biomass carbon and nitrogen and the quantities of soil bacteria, fungi, and G⁺ and G^- bacteria had significant positive correlations with the contents of soil moisture, organic carbon, and total nitrogen, and the quantity of soil fungi was positively correlated with soil carbon/nitrogen ratio. The variations of the soil microbial community structure (bacteria/fungi and G⁺/G^-  bacteria) were mainly affected by soil temperature and moisture content, which meant that the soil microbial community structure was sensitive to the environmental conditions. Along with the  global warming, the proportions of soil fungi and G⁺ bacteria in the Q. liaotungensis forests in warm temperate zone would have an increase.

Key words: altitude, soil microbial biomass, soil microbial community structure, PLFA, Dongling Mountain.