Objective This study aimed to explore the response patterns of soil microbial diversity and their functional potentials to different warming levels in an alpine ecosystem on the Qinghai-Tibet Plateau of western China.

Method We conducted a field manipulation warming experiment using infrared heating methods to set three warming treatments, including control, low-level warming (+1.5 ℃) and high-level warming (+2.5 ℃). Through soil microbial high-throughput sequencing analysis, we investigated the general patterns and mechanisms underlying soil bacterial and fungi communities in response to field warming.

Result (1) Low-level warming and high-level warming significantly increased soil temperature in the topsoil by 1.4 and 2.4 ℃, and decreased soil moisture by 11% and 17%, respectively (P < 0.05). In contrast to the control, soil nitrate nitrogen content under low-level warming and high-level warming decreased by 66% and 72% (P < 0.05), respectively, while only high-level warming significantly stimulated soil available phosphorus content by 36% (P < 0.05). (2) Compared with control, warming significantly reduced soil bacterial α diversity and phylogenetic diversity, with notable differences in bacterial community structure (P < 0.05). But soil fungi community did not show any changes in these indicators. (3) In the soil bacterial community, functional categories such as carbohydrate metabolism and global and overview were significantly improved due to warming, while the abundance of three trophic types (i.e., symbiotroph, pathtroph, and saprotroph) of soil fungi did not change under warming. (4) Soil bacterial functional potentials were mainly and positively correlated with soil total nitrogen and available phosphorus, while fungal functional potentials were positively associated with fungal Shannon diversity index.

Conclusion In conclusion, warming significantly reduces soil bacterial α diversity and phylogenetic diversity, alters its β diversity. Warming promotes the expression of functional potentials such as carbohydrate metabolism in the bacterial community by regulating soil available phosphorous. In contrast, warming does not influence soil fungal diversity, community structure, and functional potentials. Our findings highlight the differential temperature sensitivities of soil bacterial and fungal communities, which may affect ecosystem functions differently.