Impact of altitude and temperature variation on microbial communities and fermentation quality of natural oat and maize silage on the Qinghai-Tibet Plateau

To investigate the microbial community dynamics and climatic responsiveness of naturally fermented silage in the Qinghai-Tibet Plateau, 51 silages from 17 distinct geographical locations across Qinghai Province were collected and analyzed. Bacterial community profiling was conducted through high-throughput 16 S rRNA amplicon sequencing, while fermentation characteristics and nutritional composition were systematically evaluated. Significant variations were observed in both fermentation parameters and nutritional quality across samples (P < 0.05). Notably, maize silage from the BHJ.M site exhibited significantly higher acetic acid (AA) content compared to other samples (P < 0.05). Moreover, BMG.O oat had better fermentation quality, indicated by the lowest pH (3.57) and higher lactic acid (LA) content (4.50%DM). Unlike oat silage, maize silage had a lower relative abundance of Lactobacillus and a higher abundance of Lentilactobacillus. Except for the Hainan (HN), the bacterial community in all regions was dominated by Lactobacillus, but the abundance of Lactobacillus was less than 75% in all samples except BMG.O. Correlation analysis indicated that high altitude and large diurnal temperature fluctuations jointly constrained Lactobacillus dominance. This environmental filtering not only shaped the Lactobacillus community structure but may also limit the metabolic functionality of certain strains, contributing to the inconsistent fermentation quality observed in naturally fermented silage on the plateau.