Latitudinal patterns and environmental correlates of plant root exudation.

Root exudation is a key trait involved in the plant carbon economy that exerts an important control over ecosystem functioning. Yet, our understanding of global patterns of root exudation and associated influencing factors remains limited. Here we assembled a comprehensive dataset of specific root exudation rate (that is, organic carbon exuded per unit root biomass), root traits and environmental covariates from in situ measurements and a literature synthesis. Our results show that non-woody plants have a higher specific root exudation rate than woody plants. Specific root exudation rate exhibits an increasing trend from high to low latitudes, and soil available phosphorus emerges as the primary influencing factor. We also show that specific root exudation rate primarily falls at the 'fast' end of the conservation axis of the root economics space, reflecting a trade-off between carbon allocation to root metabolism and tissue construction. These findings provide a basis for predictive understanding of plant impacts on belowground biogeochemical cycles.