呼伦贝尔沙地樟子松人工林土壤细菌群落结构与功能预测

为揭示呼伦贝尔沙地樟子松人工林土壤细菌群落结构和功能特征，以3种林龄（25 a、34 a和43 a）沙地樟子松人工林为研究对象，沙质草地为对照，采用野外调查、Illumina Miseq高通量测序和PICRUSt功能预测相结合的研究方法，鉴定分析土壤细菌群落结构，阐明土壤理化因子对土壤细菌群落结构的影响，预测土壤细菌功能特征。研究结果显示：（1）呼伦贝尔沙地樟子松人工林共获得土壤细菌35门92纲109目210科267属，主要细菌优势门为变形菌门（Proteobacteria）（24.29%±3.39%）、放线菌门（Actinobacteria）（23.72%±4.10%）和酸杆菌门（Acidobacteria）（23.40%±2.55%）。人工林与沙质草地的变形菌门和酸杆菌门相对丰度存在显著差异（P<0.05），人工林间土壤细菌多样性指数不存在显著差异（P>0.05）。（2）研究区土壤细菌群落的主要影响因子是速效钾、全磷和全氮。（3）PICRUSt功能预测共获得5个一级功能层和31个二级功能层，主要涉及环境信息处理、代谢和遗传信息处理等功能。43 a人工林土壤细菌代谢功能活跃，有利于植物对养分的吸收和利用。在呼伦贝尔沙地种植樟子松人工林有助于改善土壤细菌群落结构，促进土壤细菌代谢功能，且表层土壤细菌群落对土壤环境变化更为敏感。

Soil bacterial community structure and functional prediction of Pinus sylvestris var. mongolica plantations in the Hulun Buir Sandy Land

As a fundamental and active component of soils, soil bacteria substantially affect the above-ground and underground ecosystems. In the latest decade, the community composition and diversity of soil bacteria have been widely studied in a series of ecosystems. To date, with the blooming development of modern biotechnology, this attention on soil bacteria shifts the focus to the functional examination as well as the interactions with natural environment. Pinus sylvestris var. mongolica originated in the Hulunbuir Sandy Land. Presently, P. sylvestris plantations have been occupying at least 3.0×10⁵ ha in the desertified land of the Northern China. An increasing plantations of P. sylvestris significantly contribute to desertification combating and environmental improvement. However, the effect of P. sylvestris plantations on soil bacterial structure and function remains unclear. Therefore, understanding the mutual feedback between sand-fixing vegetation and soil bacteria is of great significance for P. sylvestris plantations in the Hulun Buir Sandy Land. In this study, three age groups of P. sylvestris plantations (25 a, 34 a, and 43 a) were selected to determine soil bacterial community composition and functional groups using 16S rRNA high-throughput sequencing and PICRUSt platform. Further, the effects of soil properties on soil bacterial community were also explored. The results indicated that (1) 35 phyla, 92 classes, 109 orders, 210 families, and 267 genera were detected in the soil bacteria of P. sylvestris plantations. The dominant phyla were Proteobacteria (24.29%±3.39%), Actinobacteria (23.72%±4.10%), and Acidobacteria (23.40%±2.55%). The relative abundances of Proteobacteria and Acidobacteria significantly differed between grassland and plantations (P<0.05). Whereas, soil bacterial diversity indices were not significantly different in the P. sylvestris plantations (P>0.05). (2) Soil bacterial communities were mainly affected by available potassium, total phosphorus, and total nitrogen. (3) PICRUSt platform predicted 5 biological metabolic pathways and 31 sub-functions in the soil bacteria of P. sylvestris plantations, mainly involving environmental and metabolism & genetic information processing. The active bacterial metabolism in 43 a plantation was conducive to nutrients absorption and utilization by plants. In conclusion, P. sylvestris plantations effectively improved soil bacterial composition and metabolism in the Hulun Buir Sandy Land, and bacterial community of the topsoil was more sensitive to environmental changes. This improved information reveals the impact of soil physical and chemical properties on soil bacterial communities, enriches the study of soil bacterial community structure, function and interaction with environmental factors. Moreover, these results are expected to provide a better understanding and scientific support for the management of P. sylvestris plantations in the sandy land.