Soil and root-associated fungal response to nitrogen and phosphorus addition from grasslands worldwide: 2011-2012.

Ecosystems across the globe receive elevated inputs of nutrients, but the consequences of this for soil fungal guilds that mediate key ecosystem functions remain unclear. We found that nitrogen and phosphorus addition to 25 grasslands distributed across four continents promoted the relative abundance of fungal pathogens, suppressed mutualists, but did not affect saprotrophs. Structural equation models suggested that responses were often indirect and primarily mediated by nutrient-induced shifts in plant communities. Nutrient addition also reduced co-occurrences within and among fungal guilds, which could have important consequences for belowground interactions. Focusing only on plots that received no nutrient addition, soil properties influenced pathogen abundance globally, whereas plant community characteristics influenced mutualists, and climate influenced saprotrophs. These guild-level responses enhance our ability to predict soil functional responses to anthropogenic eutrophication and the associated longer-term responses of plant communities to this important global change factor.