摘要:黄帚橐吾（Ligularia virgaurea）是高寒草甸常见的毒杂草，被认为是指示一个地区草地植被退化的重要物种，研究其根际/非根际土壤微生物在不同海拔梯度上的群落特征具有重要意义。以甘南州高寒草甸不同海拔梯度黄帚橐吾根际/非根际土壤可培养微生物为研究对象，采用稀释涂布平板法和最大可能数法（MPN）测定了土壤微生物的数量及土壤理化因子的变化。结果表明：细菌在微生物总数中占比最大，根际微生物数量随海拔升高呈先增加后减小的变化，非根际则表现为递增的趋势，微生物功能群在根际和非根际土壤中均逐渐增加；根际土壤的微生物和功能群数量均高于非根际土壤。RDA分析发现，土壤温度、有机碳、电导率、pH、全氮、全磷、速效氮及脲酶对根际/非根际土壤微生物数量及功能群变化影响较大。通径分析可知：根际土壤中，细菌和真菌受速效氮和有机碳影响较大，放线菌主要受土壤温度和电导率的影响；根际土壤固氮菌和氨化细菌决策系数速效氮 > 有机碳 > 全氮；根际和非根际土壤中硝化细菌的影响因子各不相同，根际土壤决策系数最大和最小分别为全磷和全氮，非根际则是pH和脲酶。



Abstract:Ligularia virgaurea is a common poisonous weed in alpine meadows, which is considered to be an important species indicating grassland vegetation degradation in an area. It is of great significance to study the community distribution characteristics of rhizosphere soil microorganisms at different altitude gradients. As one of the main types of soil microdomain structure, rhizosphere has high biological enzyme activity and plays an important role in maintaining regional ecosystem cycle due to the influence of plant roots, environmental factors and microbial activities. Soil microorganisms are the most important biological driving force of soil nutrient cycling, organic degradation and other biological processes. A wide variety of soil microorganisms and a large number of characteristics also maintain the functional integrity of the ecosystem. At the same time, its biodiversity is also affected by soil enzyme activities and physical and chemical properties, so the study of soil microorganisms is also an effective means to maintain ecosystem services. In this study, the cultivable microorganisms in rhizosphere/non-rhizosphere soil of Ligularia virgaurea at different altitudes in Maqu County of Gannan Prefecture were studied. The number of soil microorganisms and changes in soil physical and chemical factors were measured by the spread plate method and the maximum possible number method (MPN). The results showed that bacteria accounted for the largest proportion of the total number of microorganisms. The number of rhizosphere microorganisms increased first and then decreased with elevation, while the non-rhizosphere showed an increasing trend. The microbial functional groups gradually increased in both rhizosphere and non-rhizosphere. The number of microorganisms and functional groups in rhizosphere soil was higher than that in non-rhizosphere soil. Redundancy analysis (RDA) shows that the quantity changes are significantly correlated with soil temperature, organic carbon, electrical conductivity, pH, total nitrogen, total phosphorus, available nitrogen, and soil urease. Path analysis shows that in rhizosphere soil, bacteria and fungi are most affected by available nitrogen and organic carbon. Actinomycetes are mainly affected by soil temperature and electrical conductivity. Rhizosphere soil azotobacter and ammonifier decision coefficient available nitrogen>organic carbon>total nitrogen. The influencing factors of nitrifier in rhizosphere and non-rhizosphere soil are different. The largest and smallest decision coefficients of rhizosphere soil are total phosphorus and total nitrogen, and those of the non-rhizosphere are pH and urease. This study is helpful to understand the response mechanism of soil microorganisms in alpine meadows on Qinghai-Tibet Plateau to the invasion of poisonous weeds, and to provide theoretical basis and technical support for ecological environment protection and high-quality development of Qinghai-Tibet Plateau.





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