Effects of grazing on composition and concentration of polyphenols in vegetation – soil of alpine meadow in Qinghai-Tibet Plateau

As secondary metabolites of plants, polyphenols not only affect the palatability and nutritional value of forage, but also affect soil carbon stability through the accumulation of litter and root exudates in the soil. Previous studies have shown that grazing can change the content and composition of vegetation phenols, but few studies have specifically investigated the variation of vegetation-soil polyphenols under the influence of grazing. To fill this knowledge gap, an alpine meadow (grazing and grazing prohibition) in the Hongyuan county region of the Qinghai-Tibet Plateau was selected as the research object, where we analyzed the variation in vegetation community characteristics, composition, and content of polyphenols in the vegetal-soil system under winter grazing and grazing prohibition, respectively. The results showed that: 1) grazing decreased the coverage of grass, but increased the coverage of forbs such as Ranunculaceae, Rosaceae, and Polygonaceae. 2) Grazing decreased the coverage of the vegetation community (P = 0.643) and the concentration of simple phenol in the 0 – 20 cm soil layer (P = 0.190), and significantly decreased the biomass of the vegetation community (above- and belowground parts), the concentration of simple phenol in the aboveground part of vegetation, and the total phenol and tannin in the 0 – 30 cm soil layer (P < 0.05). 3) However, grazing increased the species richness of the vegetation community (P = 0.357), as well as the concentration of simple phenol in the belowground part (P = 0.369), and significantly increased the concentration of total phenol and tannin in the above- and belowground parts of the vegetation (P < 0.05). The results of this study provide a new idea for protecting and maintaining the healthy and sustainable development of alpine meadows on the Qinghai-Tibet Plateau.