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 3.0×10~5 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 16 S 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(P0.05).(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 co