My talk will focus on the response of soil microbial communities to global change and its consequences for soil carbon stocks. By regulating the storage and release of organic carbon through the decomposition of soil and plant organic matter, soil microorganisms play a major role in soil C fluxes. To do so, they produce a broad range of exoenzymes to depolymerise large plant derived molecules into low molecular weight compounds that they assimilate and allocate either for growth or metabolism (carbon use efficiency or CUE). Both exoenzyme activity and CUE are critical processes that relate microbial community functioning to C flux kinetics. The presentation will examine the effect of agricultural intensification and climate warming on the soil carbon cycle. Taking examples from research I conducted in the UK and in the Alpine region, I will focus on the response of microbial exoenzyme activity and CUE to global change, and how these responses relate to microbial diversity.