Plant-soil feedbacks in monoculture do not predict feedbacks in a community
Native and exotic plants showed opposite responses to plant-soil feedbacks, when grown in monoculture. Exotics showed strong negative feedback when grown in their home soils, whereas natives benefitted from their home soil (χ2=48.81, p<0.001, Fig. 5A). Exotic plants grown in away soil were over 20% larger than exotics grown in home soil, whereas native plants grown in away soil were 12% smaller than natives grown in home soil.
However, the apparent benefit of plant-soil feedbacks to natives in monoculture were not apparent when plants were grown in communities. In communities, exotic plants were approximately 9 times larger than native plants (χ2=20.07, p<0.001, Fig. 5B). As reported in Waller et al. (2020), total plant community biomass across mesocosms was reduced in home soil, but these soil effects did not differ with provenance or the proportion of exotics planted in the community.