Resource economics of tree communities control soil food web multifunctionality in European forests

Plants affect terrestrial ecosystem functioning by performing the primary production that energetically sustains heterotrophic organisms, and by shaping the microenvironment. However, the influence of plant diversity and community composition on ecosystem functioning through their effects on energy flow into food webs has been little studied, especially for soil food webs that channel most of the 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. Specifically, tree communities dominated by resource acquisitive species promoted faster rates of multiple soil trophic functions simultaneously than did those dominated by resource conservative species. This was primarily driven by their production of plant litter with higher nutritional quality and their warmer forest microclimate, leading to a higher metabolic activity of soil organisms. Tree species mixing had rather weak and negative effects on soil food web multifunctionality, mostly due to a shift in the resource-based energy channeling from living plant fine roots to litter and a cooling effect on the forest microclimate. Tree diversity effects were largely outweighed by community compositional effects, which were of similar magnitude to the effects of biogeographic differences among locations. Our findings emphasize the importance of plant functional traits related to resource economics as drivers of plant community effects on soil food web functioning5,9 and highlight the consequences that climate-driven shifts in tree community composition could have for forest soil functioning.