Long-term warming impacts grassland ecosystem function: Role of diversity loss in conditionally rare bacterial taxa

The impact of microbial communities on ecosystem function varies due to the diverse biological attributes and sensitivities exhibited by different taxonomic groups. These groups can be classified as always rare (ART), conditionally rare (CRT), dominant, and total taxa, each affecting ecosystem function in distinct ways. Thus, understanding the functional traits of organisms within these taxa is crucial for comprehending their contributions to overall ecosystem function. In our study, we investigated the influence of climate warming on the biogeochemical cycles of the ecosystem in the Qinghai-Tibet Plateau, utilizing an open top chamber experiment. Simulated warming significantly lowered ecosystem function in the grassland but not in the shrubland. This discrepancy was due to the diverse responses of the various taxa present in each ecosystem to warming conditions and their differing roles in determining and regulating ecosystem function. The microbial maintenance of ecosystem function was primarily reliant on the diversity of bacterial dominant taxa and CRT and was less dependent on ART and fungal taxa. Furthermore, bacterial CRT and dominant taxa of the grassland ecosystem were more sensitive to changing climatic conditions than grassland ART, resulting in a more pronounced negative diversity response. In conclusion, the biological maintenance of ecosystem function during climate warming is dependent on microbiome composition and the functional and response characteristics of the taxa present. Thus, understanding the functional traits and response characteristics of various taxa is crucial for predicting the effects of climate change on ecosystem function and informing ecological reconstruction efforts in alpine regions of the plateau.