山西太岳山不同林龄华北落叶松林土壤微生物群落结构特征

  目的  分析不同林龄华北落叶松人工林土壤微生物结构特征变化规律，阐明土壤微生物群落结构特征对林龄变化的响应机制及关键影响因子，为人工林可持续经营和探讨土壤微生物群落对环境变化反馈机制提供理论依据。  方法  以不同林龄华北落叶松人工林为研究对象，基于土壤微生物群落结构、土壤理化性质和林下植被特征等指标，采用冗余分析探讨土壤理化性质和林下植被特征对土壤微生物群落结构的驱动机制。  结果  研究结果表明林龄变化对土壤理化性质和微生物群落结构特征均存在显著影响，其中土壤温度、含水率、pH值、全碳、全氮、全磷、铵态氮和硝态氮含量均随着人工林年龄的增加而显著增加，土壤有效磷含量则表现出相反的变化规律（P < 0.05）。林龄增长也提高了土壤革兰氏阳性细菌、革兰氏阴性细菌、真菌和放线菌含量，但真菌与细菌以及革兰氏阳性细菌与革兰氏阴性细菌的比值呈下降趋势。林下灌木、草本层物种多样性也表现出随林龄增加而增长的变化趋势，不同林龄间差异则均未达显著水平。冗余分析结果表明本研究选取的土壤理化性质和林下植物物种多样性指标共同解释了土壤微生物群落总变异的86.1%，土壤含水率、温度、有效磷、硝态氮含量、灌木层丰富度指数和草本层丰富度指数则分别解释了微生物群落结构变异程度的22.7%、18.4%、11.8%、10.6%、7.9%和5.6%。  结论  土壤微生物群落结构特征、土壤理化性质和林下植物物种多样性（灌木层和草本层）均受到林龄变化的影响，并且土壤温度、含水率、有效磷、硝态氮和林下植物物种多样性是引起不同林龄人工林土壤微生物群落结构变化的关键驱动因子。 

Characteristics of soil microbial community structure with different plantation ages in larch forest in Taiyue Mountain of Shanxi Province,northern China

  Objective  This paper aims to analyze the variation of soil microbial community structure characteristics of larch plantation at different plantation ages, clarify the response mechanism of soil microbial community structure to the changes of plantation age and its key influencing factors, provide theoretical basis for sustainable management of the plantation and feedback effect of soil microbial community to environmental changes.  Method  Based on the characteristics of soil microbial community structure, soil physical and chemical properties and understory vegetation characteristics database, this study explored the regulation mechanism of soil physical and chemical properties and understory vegetation characteristics on the formation of soil microbial communities by redundancy analysis.  Result  The change of plantation age had a significant impact on soil physical and chemical properties and microbial community structure, such as soil temperature, water content, pH, total carbon, total nitrogen, total phosphorus, ammonium nitrogen and nitrate nitrogen content increased significantly with the increase of plantation age, but the soil available phosphorus content showed the opposite trend (P < 0.05). Meanwhile, the growth of the plantation age also significantly increased the abundance of gram-positive bacteria, gram-negative bacteria, fungi and actinomycetes in the soil, while the ratio of fungi: bacteria and gram-positive bacteria: gram-negative bacteria showed a downward trend. The diversity of understory shrubs and herb layers also showed a trend of increasing with the increase of forest age, and the differences between different forest ages did not reach a significant level. The results of redundant analysis showed that the soil physical and chemical properties and the understory vegetation diversity index explained 86.1% of the total variation of the soil microbial community, while the soil water content, soil temperature, available phosphorus, nitrate nitrogen content, and the richness index of shrub and herb layer explained 22.7%, 18.4%, 11.8%, 10.6%, 7.9% and 5.6% of the variation of microbial community structure, respectively.   Conclusion  The structural characteristics of soil microbial community, soil physical and chemical properties, and understory plant diversity (ie shrub layer and herb layer) are all affected by changes of plantation age. Notably, soil temperature, water content, available phosphorus, nitrate nitrogen, and understory vegetation diversity are key factors to drive the changes of soil microbial community structure in different plantation ages.