Altitudinal Distribution Patterns of Phyllosphere Microbial Communities and Their Contribution to Silage Fermentation of Kobresia pygmaea Along the Elevation Gradient on the Tibetan Plateau

Abstract

The study aimed to reveal altitudinal distribution patterns of phyllosphere microbial communities and silage fermentation of Kobresia pygmaea along the elevation gradient on the Tibetan Plateau. The K. pygmaea was individually collected from 2,500, 3,000, 4,000, 4,500, and 5,000 m above sea level (a.s.l.) on the Tibetan Plateau and ensiled for 60 days, respectively. The phyllosphere bacterial diversity increased while fungal diversity decreased along the elevation gradient, and bacterial and fungal richness showed a unimodal distribution with peak abundance at 4,000 and 3,000 m a.s.l., respectively. After 60 days of ensiling, the bacterial and fungal community composition changed but did not exhibit clear altitudinal distribution patterns. All K. pygmaea underwent a weak fermentation indicated by pH above 5.0 and low ratio of lactic/acetic acid (LA/AA). The S5000 and S3000 showed the highest and lowest pH, respectively. Although Lactobacillus dominated S4000 after 60 days of ensiling, S4000 still exhibited poor fermentation quality as well as silages from the other four regions. The higher ammonia N concentrations in S3000 and S4000 than the other silages were consistent with the detectable butyric acid in S3000 and S4000. The silage fermentation of K. pygmaea collected from five regions exhibited poor fermentation quality, thereby inoculating lactic acid bacteria to K. pygmaea before ensiling is highly recommended to improve fermentation quality on the Tibetan Plateau.

The microbial communities and natural fermentation quality of ensiling oat (Avena sativa L.) harvest from different elevations on the Qinghai-Tibet Plateau

“… Vacher et al (2016) demonstrated that the higher dispersal ability of bacteria and higher sensitivity of fungi to temperature variations might account for the bigger response of phyllosphere fungal communities to elevation gradient than bacterial communities. In the present study, the elevation gradients did not affect the fungal Shannon index in fresh oat ( p > 0.05), which was consistent with the reports by Yang X. et al (2022) , who also detected similar soil fungal Shannon index across elevation gradients.…”

“…The inconsistency of phyllosphere microbial diversity patterns across elevations could be attributed to changing environmental factors induced by elevational variables ( Yang N. et al, 2022 ). Yang X. et al (2022) found that the phyllosphere bacterial and fungal richness showed a unimodal distribution, phyllosphere fungal diversity decreased while the phyllosphere bacterial diversity increased along the elevational gradient. We observed the bimodal distribution of fungal and bacterial richness in fresh oat along the elevation gradient (2852–4447 m a.s.l).…”

“…Wickerhamomyces , Candida , Saccharomyces , and Rhodotorula were the minor genus in fresh oat before ensiling, however, they became the major fungal community after 90 days of ensiling. Yang X. et al, (2022) studied the phyllosphere microbial communities and silage fermentation of K. pygmaea on the Tibetan Plateau and found that the fungal composition markedly changed: Schizophyllum , Phodotorula , Rhodotorula , Candida , and Issatchenkia became the most dominant fungal genera after 60 days of ensiling. Duniere et al (2017) reported that members of the Saccharomycetales including Candida , Wickerhamomyce s, or Saccharomyces were the predominant fungi in terminal silage.…”

“…The second sub-sample (20 g wet basis) was extracted with 60 ml distilled water at 4°C for 24 h. The solution was filtered through four layers of medical gauze and Whatman filter paper (Hangzhou Xinhua Co., LTD., China), followed by measuring pH immediately using a pH electrode (Hanna Instruments Italia Srl, Padua, Italy). Then silage extract (5 ml) was centrifuged at 12000× g for 10 min at 4°C, and the supernatant was filtered through a 0.45 μm membrane for organic acid and ethanol analyses according to Yang X. et al (2022) . Ammonia N of silage extract was measured by the phenol-hypochlorite method according to Broderick and Kang (1980) .…”

“…Moreover, the large elevation gradient across the Qinghai-Tibet Plateau enlarged the discrepancy in microbial and chemical composition in crops cultivated at different elevations. Previous studies revealed the altitudinal distribution patterns of phyllosphere microbial communities and silage fermentation of the wild grass of Kobresia pygmaea and Elymus nutans along the elevation gradient on the Qinghai-Tibet Plateau ( Ding et al, 2020 ; Yang X. et al, 2022 ). However, there are limited studies on the altitudinal distribution patterns of phyllosphere microbial communities and chemical composition in cultivated grass, which might be different from that of wild grass because more human activities were involved in the cultivation during the crop growth.…”