中文摘要：

通过选取大兴安岭岭北部的兴安落叶松林重度、轻度火烧迹地以及为过火样地，运用磷脂脂肪酸分析方法（PLFAs），研究了火烧对0～5和5-10cm土层的土壤理化性质和土壤微生物群落的结构特征的影响，并探讨了火烧当年土壤微生物群落生物量和群落结构的变化规律与影响因素。研究结果表明：0-5和5-10cm土层的土壤pH、全钾、有效磷、黏砂比等土壤理化指标受到了火烧的显著性影响；不同火烧程度对微生物类群的生物量有影响，但不显著；重度火烧迹地的土壤微生物的群落结构指标革兰氏阳性菌-／革兰氏阴性菌（G＋／G-）以及真菌／细菌（F／B）与轻度和未过火样地具有显著差异。RDA分析指出，G＋／G-受土壤含水量影响最大，F／B受pH影响最大。说明在火烧迹地的当年，土壤水分和pH是影响土壤微生物群落结构的最重要因素。

英文摘要：

We studied theeffects of fire intensity on the soil microbial community of larch forests by selecting three kinds of sites including high intensity burned site, light intensity burned site and unburned site in the current year burning in the Daxing＇ an Mountain. Soils were sampled from 0 - 5 and 5 - 10 cm, separately in each site, and the soil microbial characteristics were analyzed by phospholipid fatty acid （PLFAs）. The pH, total potassium, available phosphorus and clay and sand content were significantly compared with burned and unburned sites. The total soil microbial biomass, bacteria biomass, fungus biomass and Frankia biomass were influenced by fire, there was no significant difference in three sites. However, the structure of soil microbial community indictors, such as G ＋/G - and F/B, were significantly different compared high intensity burned site and other two sites. By RDA analysis, G ＋/G - was influenced by soil water content, and F/B was influenced by soil pH. Therefore, the current year of burning, soil water content and pH are critical factors in affecting the structure of soil microbial community.