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The ruminant digestive system harbors a complex gut microbiome, which is poorly understood in the case of the four stomach compartments of yak. High-throughput sequencing and quantitative PCR were used to analyse microbial communities in the rumen, reticulum, omasum, and abomasum of six domesticated yak. The diversity of prokaryotes was higher in reticulum and omasum than in rumen and abomasum. Bacteroidetes predominated in the four stomach compartments, with abundance gradually decreasing in the trend rumen > reticulum > omasum > abomasum. Microorganism composition was different among the four compartments, all of which contained high levels of bacteria, methanogens, protozoa and anaerobic fungi. Some prokaryotic genera were associated with volatile fatty acids and pH. This study provides the first insights into the microorganism composition of four stomach compartments in yak, and may provide a foundation for future studies in this area.

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The recently discovered nitrite-dependent anaerobic methane oxidation (n-damo) is an important methane sink in natural ecosystems performed by NC10 phylum bacteria. However, the effect of water table (WT) gradient due to global change on n-damo bacterial communities is not well studied in peatlands. Here, we analysed the vertical distribution (0–100 cm) of n-damo bacterial communities at three sites with different WTs of the Zoige peatlands in the Qinghai-Tibetan Plateau. Using an n-damo bacterial specific 16S rRNA gene clone library, we obtained 25 operational taxonomic units (OTUs) that could be divided into Groups A, B, C, D and E (dominated by A and B). The dominant group was Group B at the high (OTU14 and OTU20) and intermediate (OTU7 and OTU8) WT sites and Group A was dominant at the low WT site (OTU6 and OTU5). Using high-throughput sequencing, we observed that n-damo bacteria mainly distributed in subsurface soils (50–60 and 20–30 cm), and their relative abundances were higher at the low WT site than at the other two sites. In addition, we found that pH and nitrate were positively correlated with Group A, while total organic carbon, total nitrogen and ammonia were positively associated with Group B. Our study provides new insights into our understanding of the response of n-damo bacteria to WT gradient in peatlands, with important implications for global change.

Alpine peatlands on the Qinghai‐Tibet Plateau are an important soil carbon pool and are extremely sensitive to global change. Duration of drainage and water table drawdown accelerate peatland degradation because the soil changes from an anaerobic to aerobic environment, and climate warming exacerbates this shift. The objective of the present study was to evaluate the effects of drainage on microbial characteristics and greenhouse gas (GHG) emissions, as well as identify the factors mediating those effects. This study also analyzed whether warming increases the variability of GHG emissions. Watertable drawdown exerted greater influence on microbial communities than duration of drainage did. Watertable drawdown significantly increased the relative abundances of Proteobacteria, Acidobacteria, Actinobacteria, and Basidiomycota, and changes in soil microbiota correlated with differences in GHG emissions across three water‐table treatments. Longer drainage was associated with lower GHG emission; watertable drawdown decreased emissions of CO2 and CH4, but increased emission of N2O. In addition, high temperature increased CO2 emission by 75% and N2O emission by 42%, without significantly affecting CH4 emission. Structural equation modelling showed that microbes, especially prokaryotes (r = 0.79, p < 0.05 for all), were the primary factor affecting GHG emissions from drained peatlands. Overall, this study indicates that the watertable exerts a greater effect on GHG emissions than duration of drainage, and that warming increases variability of GHG emissions.

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