Temperature thresholds drive the global distribution of soil fungal decomposers

Unraveling the biogeographic pattern of soil fungal decomposers along temperature gradients – in a smooth linearity or an abrupt jump – can help us connect the global carbon cycle to global warming. Through a standardized global field survey, we identify the existence of temperature thresholds that control the global distribution of soil fungal decomposers, leading to abrupt reductions in their proportion (i.e. the relative abundance in fungal community) immediately after crossing particular air and soil temperature thresholds. For example, small increases over the mean annual temperature threshold of ~9ºC result in abrupt reductions in their proportion, paralleling a similar temperature threshold for soil carbon content. We further find that the proportion of soil fungal decomposers is more sensitive to temperature increases under arid conditions. Given the positive correlation between the global distributions of fungal decomposers and soil heterotrophic respiration, the reported temperature-driven abrupt reductions in fungal decomposers could further suppress their driven soil decomposition processes and reduce carbon fluxes from soils to the atmosphere with implications for climate change feedback. This work not only advances the current knowledge on the global distribution of soil fungal decomposers, but also highlights that small changes in temperature around certain thresholds can lead to potential unexpected consequences in global carbon cycling under projected climate change.

Y.Z.F. is supported by National Natural Science Foundation of China (42177297), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA28010302) and the Youth Innovation Promotion Association, CAS (Member No. 2014271). M.D-B. was supported by a Ramón y Cajal grant (RYC2018-025483-I), a project from the Spanish Ministry of Science and Innovation (PID2020-115813RA-I00), and a project PAIDI 2020 from the Junta de Andalucía (P20_00879). E.G. is supported by the European Research Council (ERC Grant agreement 647038 [BIODESERT]). B.K.S. lab on microbial diversity work is supported by Australian Research Council (DP170104634).