Changes in community structure and metabolic function of soil bacteria depending on the type restoration processing in the degraded alpine grassland ecosystems in Northern Tibet

Highlights: • Plant sowing raises soil pH, and soil nitrogen and phosphorus contents. • Restoration processing does not affect the alpha diversity of soil bacteria. • Restoration processing modifies the beta diversity of soil bacteria. • Restoration processing alters the relative abundance of soil bacterial proportions. • Restoration processing changes the metabolic function of soil bacteria. The alpine grassland ecosystems in Northern Tibet is seriously degraded. The condition of the degraded alpine grassland ecosystems in Northern Tibet (DAGENT) triggers a serious threat to environmental health and ecological safety of the local society. Thus, restoring DAGENT is a pressing task presently to sustain social stability and sustainable development. Soil microorganisms act a vital role in the structure and function execution of ecosystems. Further, bacteria are sensitive to external disturbances. This study purposes to evaluate the effects of the three types of restoration processing (i.e., the separated plant sowing, the separated water-soluble polyurethane fertilization, and the combined plant sowing and water-soluble polyurethane fertilization) on soil bacterial communities in DAGENT by using high-throughput sequencing with Illumina Novaseq 6000. The separated plant sowing significantly elevations soil pH, and soil nitrogen and phosphorus contents in DAGENT. Additionally, the combined plant sowing and water-soluble polyurethane fertilization markedly improves soil nitrogen content in DAGENT. The combined plant sowing and water-soluble polyurethane fertilization antagonistically affect soil pH and soil phosphorus content in DAGENT. The three types of restoration processing have no obvious effects on the alpha diversity of soil bacteria in DAGENT. But the three types of restoration processing create obvious alterations in the beta diversity of soil bacteria and the relative abundance of soil bacterial proportions in DAGENT. The three types of restoration processing also cause significant modifications in metabolic function of soil bacteria in DAGENT. The leading reason for the altered community structure and metabolic function of soil bacteria may be attributed to the changes in plant growing condition as well as soil pH and nutrient contents in DAGENT. Consequently, the three types of restoration processing are mainly changed the community structure and metabolic function of soil bacteria, rather than the alpha diversity of soil bacteria, in DAGENT.