土壤微生物是土壤生态系统的重要组成成分，又是土壤肥力的重要评价指标之一，在生态系统物质循环和能量流动中起着重要作用。氮沉降影响土壤微生物生长和繁殖，使其结构和功能发生改变，从而影响土壤物质循环和能量流动。通过室内模拟自然氮沉降，运用磷脂脂肪酸技术，研究氮沉降对不同树种（荷木Schima superba、马尾松Pinus massoniana、马占相思Acacia mangium、海南红豆Ormosia pinnata）土壤微生物的影响。结果表明：自然氮沉降条件下，细菌是土壤微生物的主要类群，占土壤微生物总量的40%以上。采样时间和树种均对总土壤微生物生物量、细菌生物量有显著影响。同一树种10月土壤微生物生物量（总土壤微生物、细菌、真菌、放线菌）高于4月。4月土壤微生物生物量马占相思最高（总土壤微生物生物量76.78 nmol·g-1、细菌生物量33.94 nmol·g-1、真菌生物量6.91 nmol·g-1、放线菌生物量8.38 nmol·g-1），荷木最低（总土壤微生物生物量57.89 nmol·g-1、细菌生物量24.79 nmol·g-1、真菌生物量4.16 nmol·g-1、放线菌生物量5.57 nmol·g-1）；10月海南红豆最高（总土壤微生物生物量92.67 nmol·g-1、细菌生物量38.85 nmol·g-1、真菌生物量8.09 nmol·g-1、放线菌生物量9.27 nmol·g-1），荷木最低（总土壤微生物生物量71.10 nmol·g-1、细菌生物量30.79 nmol·g-1、真菌生物量4.90 nmol·g-1、放线菌生物量7.04 nmol·g-1）。采样时间和树种的交互作用对放线菌生物量有显著影响。总土壤微生物生物量与铵态氮显著正相关，而真菌生物量与土壤有机质显著正相关。结果对全球变化条件下生态系统健康管理具有重要意义。%Soil microbes are important components of soil ecosystem, and they are also one important index for soil fertility, and they can play great roles in material circulation and energy flow in ecosystem. Nitrogen deposition can influence the growth and proliferation of microorganisms, which can change the community structure and function, and then affect the material circulation and energy flow of soil ecosystem. Nitrogen deposition was simulated in laboratory, and the effects of nitrogen deposition on the soil microbes were examined with phospholipid fatty acids technique with different tree species, namely Schima superba, Ormosia pinnata, Pinus massoniana and Acacia mangium. The results showed that bacteria, over 40%of soil microbial biomass, was the main component of soil microbial biomass at current nitrogen deposition. Both sampling times (P<0.01) and tree species (P<0.05) had significant effects on the total soil microbial biomass and bacteria biomass. Soil microbial biomass (the total soil microorganisms, bacteria, fungi and actinomycetes) in October were higher than those in April for the same tree species, with the highest for Acacia mangium (total soil microbial biomass was 76.78 nmol·g-1, bacteria biomass was 33.94 nmol·g-1, fungi biomass was 6.91 nmol·g-1, actinomycetes biomass was 8.38 nmol·g-1) and the lowest for Schima superba (total soil microbial biomass was 57.89 nmol·g-1, bacteria biomass was 24.79 nmol·g-1, fungi biomass was 4.16 nmol·g-1, actinomycetes biomass was 5.57 nmol·g-1) in April, and the highest for Ormosia pinnata (total soil microbial biomass was 92.67 nmol·g-1, bacteria biomass was 38.85 nmol·g-1, fungi biomass was 8.09 nmol·g-1, actinomycetes biomass was 9.27 nmol·g-1) and the lowest for Schima superba (total soil microbial biomass was 71.10 nmol·g-1, bacteria biomass was 30.79 nmol·g-1, fungi biomass was 4.90 nmol·g-1, actinomycetes biomass was 7.04 nmol·g-1) in October. Actinomycete was effected significantly by the interaction of tree species and sampling times (P<0.05). The result also indicated that the total microbial biomass had significantly positive correlation with ammonium nitrogen (P<0.05), however, fungi biomass showed significantly positive correlation with soil organic matter (P<0.01). The results have significant roles on management on the health of ecosystem under global change.
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