Soil properties and microbiome of annual and perennial cultivated grasslands on the Qinghai-Tibetan Plateau

Efforts to enhance food, fibre, and forage yields and achieve global food security have included the conversion of natural grasslands to cultivated grasslands. The quantitative effects of a global shift in grassland management on soil properties and microbial communities critical to ecosystem function have remained largely unexplored, particularly on China's Qinghai-Tibetan Plateau. Accordingly, the distinct and contrasting effects of annual Avena grasslands (AAG) versus perennial Elymus nutans Griseb. cultivated grasslands (PEG) on the region's soil properties and microbiome were investigated in an effort to examine their contribution to maintaining soil carbon and nutrients. Across three sites per grassland type, soil moisture content (45.55%), soil organic carbon (48.97 g kg(-1)), soil total nitrogen (5.13 g kg(-1)), and soil ammonium nitrogen (298.32 mg kg(-1)) were 19%-32% greater at PEG sites than AAG sites, whereas soil pH (7.81), soil total phosphorus (0.44 g kg(-1)), and soil available phosphorus (0.81 mg kg(-1)) were 2%-31% lower. The AAG and PEG site soils had different bacterial and fungal beta-diversities but similar alpha-diversities. The relative combined abundance of Gemmatimonadetes and Chytridiomycota, and that of Rozellomycota individually, were, respectively, higher and lower in AAG versus PEG site soils. This suggests that, on the Qinghai-Tibetan Plateau, contrasting grassland cultivation practices affect soil properties and microbes differently. Given the strong interaction between a soil and its microbiome, changes in a soil's microbial community structure can be expected to substantially alter soil function. This will have important ecological service implications, particularly in terms of carbon storage and water conservation in this ecologically fragile region.