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Plants affect terrestrial ecosystem functioning by shaping microenvironments1 and by providing the primary production that fuels energy flow into food webs. However, how plant community properties affect ecosystem functioning via energy fluxes in food webs has been little studied, especially for the soil food webs that channel most plant-derived energy. Applying a food web energetics approach, we show that the resource economics of dominant tree species control soil food web multifunctionality across European forests. Tree communities dominated by resource-acquisitive species promoted faster rates of multiple soil trophic functions than did communities dominated by resource-conservative species. These effects were primarily driven by higher-quality litter and warmer forest microclimates, leading to increased metabolic activity of soil organisms. Accordingly, tree species composition explained a large portion of variation in soil food web multifunctionality, comparable to that explained by biogeographic differences among locations. By contrast, mixtures of three tree species had weakly negative effects relative to single-species stands, mostly due to shifts in energy channelling from living fine roots to litter and a cooling effect on forest microclimate. This occurred despite an overyielding effect in aboveground tree biomass production, suggesting contrasting diversity effects above- and belowground. Our findings emphasize the importance of plant functional traits related to resource economics as drivers of soil food web functioning and demonstrate how climate-driven shifts in tree community composition may alter forest soil functioning.