大兴安岭火烧迹地恢复初期土壤微生物群落特征

The characteristics of soil microbial communities at burned forest sites for the Great Xingan Mountains

对大兴安岭兴安落叶松2003年重度和中度火烧迹地以及未过火样地的土壤微生物群落进行了考察,旨在揭示火烧迹地恢复初期土壤微生物群落变化特征。研究结果表明火烧迹地土壤养分(全氮、全碳、土壤有机质、有效氮)和土壤水分与未过火对照样地存在显著差异;火烧迹地土壤微生物量碳氮、微生物代谢活性以及碳源利用能力均显著高于对照样地;但火烧迹地与对照样地土壤微生物群落结构指标土壤微生物量碳氮比(MBC/MBN)以及多样性指数没有显著差异。相关分析结果表明:土壤微生物量、代谢活性和碳源利用能力与土壤养分指标(全碳、全氮、速效氮、有机质)和土壤水分含量有显著相关性。主成分分析的结果表明火烧与否是火烧样地与对照样地土壤微生物对碳源利用能力差异的原因。所有样地土壤微生物群落真菌比例较高,可能与该地区土壤酸碱度有关(pH=4.12—4.68)。经过6a的恢复,重度和中度火烧迹地的土壤养分和水分、土壤微生物群落的生长、代谢、以及群落多样性仍存在差异,但均不显著,表明此时火烧程度对土壤微生物群落的影响已很微弱。

The Great Xingan Mountain is one of the biggest forest regions in China and serves as an important wood resource base. However, in recent years, frequently experienced severe forest fires have caused great losses in this area. Forest restoration is a very important problem that draws attention from many scientific disciplines. Restoration of soil quality in burned areas could affect vegetation restoration directly. It is thus important to monitor soil quality. Soil microorganisms are one of the most useful indicators of soil quality. Here we focus on the response of microbial populations to changes in the soil environment of recently burned areas in the Great Xingan Mountain, in which the restoration was at the early regeneration stage. The purpose of this study is to examine the effects of a range of fire severities on soil microbial biomass distribution, soil microbial community structure, and soil microbial functional diversity in these areas. Soil samples were collected from high and moderate severity burned forest sites （2003 fires）, and an unburned site.Standard experimental methods were used to measure total carbon （ TC ） , soil organic carbon （ SOC ） typical physical and chemical indicators, such soil moisture （SM）, soil available nitrogen conductance （EC）. Fumigation, extraction, and Biolog methods were used to detect soil microbial community structure, and soil microbial functional diversity, respectively. as total nitrogen （TN） , （ AN ） , and electrical biomass, soil microbial Our results showed that there were significant differences in soil nutrients （total nitrogen, total carbon, soil organic carbon, available nitrogen） and soil water content between burned and unburned sites. Soil microorganism biomass carbon on a high severity burned site and moderate severity burned site had values of （3143.93＋381. 020） mg/kg and （3204.19＋ 54. 798 ） mg/kg, respectively, which are significantly higher than those on the unburned site （ （ 1639.60 ＋468.818 ） mg/ kg）. Soil microorganism biomass nitrogen on burned sites yielded （313.56±103. 599） mg/kg on the high severity burned site and （383.12±43. 509） mg/kg on the moderate severity burned site; these values were also higher than the value on the unburned site （（ 165.22±29. 752） mg/kg）. However, only the difference between moderate severity burned site and unburned area reached a statistically significant level. Soil microorganism metabolic activities and carbon use capacities of microorganism community, which are assessed by average well-color development （AWCD）, also showed the same pattern, that is, the values of AWCD were 1.45 on high severity burned site, 1.44 on moderate severity burned site, and 0.77 on the unburned site, respectively. However, the diversity of soil microorganism community among the three types of sites was not significantly affected. The results of statistical analysis indicate that the changes in soil microorganisms of burned sites compared with the unburned site were closely related to the soil nutrients （ e. g. , soil carbon, soil nitrogen, available nitrogen and soil organic carbon） and soil water contents. The Principle Component Analysis showed that fire had a major effect on carbon use by soil microorganisms. The higher fungi ratio among study sites may be due to soil acidity, with soil pH values at the Great Xingan Mountain ranging from 4.12 to 4.68. Soil nutrients, soil water contents, and soil microbial community characteristics, such as the soil microorganism biomass （carbon and nitrogen）, metabolic activities, and diversity of microorganism community, were not statistically significantly influenced by the extent of fire （high or moderate severity fire） after 6 years. We only found the different carbon use by soil microorganism between high severity burned and moderate severity burned sites.