长白山土壤微生物群落结构及酶活性随海拔的分布特征与影响因子

Soil microbial community structure, enzyme activities, and their influencing factors along different altitudes of Changbai Mountain

长白山是由火山喷发形成的山地生态系统,是研究生态系统重建和演替过程的天然实验室。以长白山西坡垂直带中的亚高山针叶林带、亚高山岳桦林带、高山草甸带、高山苔原带土壤为研究对象,采用磷脂脂肪酸法(PLFA)和微孔板法分别测定土壤微生物群落结构及酶活性,探讨(1)长白山西坡微生物群落结构及酶活性沿海拔的分布特征;(2)垂直带植被因子、土壤因子对微生物群落结构及酶活性的影响。结果表明:土壤有机碳、全氮、全磷含量均随海拔升高先增加再减少,有机碳和全氮最高值出现在岳桦林带;随海拔升高,土壤微生物总PLFA和各类群微生物PLFA呈现出先增加后减少的变化特征,表现为亚高山岳桦林带>亚高山针叶林带>高山草甸带>高山苔原带;在对土壤微生物总PLFA的贡献率上,表现为细菌>真菌>放线菌,G^->G^+;微生物PLFA相关性方面,细菌、放线菌、G^+、G^-之间的关联性较大,真菌与这四者之间的关联性较小;土壤全氮含量与各微生物类群均表现为显著正相关,而C/N则与各微生物类群均表现为负相关,二者是调控土壤微生物沿海拔变化的主要因子;土壤水解酶βG和AP活性随海拔升高而逐渐增加,其中AP活性对高山苔原带生态系统表现出很好的响应;土壤含水量、C/N和土壤温度是调控土壤酶活性垂直变化的主要因子;高山苔原带草甸化过程对土壤含水量、全磷含量、水解酶AP活性产生重要影响,而对土壤微生物PLFA含量和其他酶活性影响不大。长白山垂直带土壤微生物群落结构和酶活性除了受到土壤环境因子和水热条件的影响,还与植被群落组成及凋落物性质具有紧密联系。

The Changbai Mountain is a mountainous ecosystem strongly affected by volcanic eruptions and with distinct vegetation zonations along different altitudes. This region offers a natural laboratory for studying post-volcanic ecosystem reconstruction and forest succession. Owing to the existence of elevation change in the vertical direction, ecological factors in mountainous ecosystems occur in a series of changes over a relatively small space. Therefore, mountainous ecosystems have become an important area to study correlation mechanisms among soil microbes, enzyme activities, and ecological factors. The objectives of the present study were to：（1） examine the distribution of microbial phospholipid fatty acids （PLFA） and enzyme activities of soils along different altitudes of Changbai Mountain and investigate factors affecting the PLFA and enzymes, and （2） explore the effects of influencing factors, vegetation, and soil on the microbial community structure and enzyme activities in four vertical zones. We sampled soils in the coniferous forest zone, ermans birch forest zone, alpine meadow zone, and alpine tundra zone along the altitudinal gradient. We determined soil microbial community structure with the PLFA method and enzyme activities with the microplate method. The results demonstrated that three environmental factors, the concentration of soil organic carbon, total nitrogen （TN）, and total phosphorus increased and then decreased as elevation increased. Soil organic carbon and TN varied with altitude, with the highest value detected in the ermans birch forest zone. Both the total microbial PLFA and various types of microbes PLFA initially increased and then decreased as elevation increased. The rank of the PLFA amount was ermans birch forest zone 〉 coniferous forest zone 〉 alpine meadow zone 〉 alpine tundra zone. The rank of the contribution rate of total microbial PLFA was bacteria 〉 fungi 〉 actinomycetes, and Gram-negative bacteria （G-） 〉 Gram-positive bacteria （G＋）. In terms of microbial PLFA correlation, bacteria, actinomycetes, Gram-positive bacteria （G＋）, and Gram-negative bacteria （G-） were significantly correlated, while fungi was poorly correlated with these microbes. TN showed a significant positive correlation with various types of microbes while the C/N ratio was negatively correlated with various types of microbes. Thus, it can be seen that TN and C/N ratio were the two main factors differentiating soil microbial community structure along the altitudinal gradient. Both soil β-glucosidase and acid phosphatase （AP） activities increased with increased elevation. The AP activity showed high response to the alpine tundra ecosystem. Soil water content, soil organic carbon, and C/N ratio were the main factors affecting the vertical distribution of soil enzyme activities. The meadow processes of alpine tundra strongly affected the soil water content, soil total phosphorus, and AP activity; however, had little effect on soil microbial PLFA and other enzyme activities. In conclusion, the soils microbial community structure and enzyme activities along different altitudes of Changbai Mountain were not only affected by soil environmental factors and hydrothermal conditions, but were also closely related to the vegetation community composition and litter chemical quality.