Microecosystem of yak rumen on the Qinghai-Tibetan Plateau is stable and is unaffected by soil or grass microbiota.

The rumen of livestock grazing on the Qinghai-Tibetan Plateau (QTP) acts as a transfer station for the circulation of soil, grass, faecal mineral elements and nutrients. Whether the microorganisms from the soil and grass could circulate through livestock rumen and excreted faeces. We studied the structural composition and interactive networks of microbiomes (bacteria and fungi) in soil, grass, and grazing yaks (rumen and faeces) on the QTP by using 16S rRNA gene and internally transcribed spacer (ITS) sequencing technology and to calculate the contribution rate of microorganisms from one habitat to another habitat using SourceTracker analysis. The meta-co-occurrence network revealed that soil, grass, rumen, and faeces comprise four independent habitats. The bacterial and fungal composition was significantly different in these four habitats. Soil microbiota showed the highest alpha diversity and microbial network complexity. Rumen microbiota demonstrated the highest microbial network stability and synergy, while grass endophytes showed the lowest microbial network complexity, stability, and synergy. According to the SourceTracker model, grass contributes 0.02% to the rumen microbes of yaks, while soil microorganisms do not circulate in the rumen. The soil and grass microbiota originating from faeces were 4.5% and 1.2%, respectively. The contribution of soil to grass was found to be 1.1%. Overall, the rumen microbiota of yaks is relatively stable and is only minimally influenced by the microbiota inhabiting the environment under natural grazing conditions. However, the contribution of yaks to soil and grass microbiota is relatively high when compared with the contribution of soil and grass to yaks microbiota.