The Effect of Prolonged Drought Legacies on Plant-Soil Feedbacks

Background Climate changes can shift plant-soil feedbacks (PSFs) causing unexpected knock-on effects on plant community dynamics. We test the hypothesis that prolonged drought legacies cause shifts in PSFs due to changes in plant-soil biotic interactions.Methods PSFs of twelve plant species representing four functional groups (C3 and C4 grasses, forbs, and legumes) were assessed in monocultures, and communities composed of one species from each of the four functional groups, in soils collected from plots with a five-year legacy of ambient rainfall or drought conditions under laboratory conditions. Plants were grown under well-watered conditions, with observed effects, therefore, being related to field drought legacies rather than experimental drought. Sterile soil conditioning was included to assess shifts in plant-soil biotic interactions associated with field rainfall legacies explicitly.Results C3 and C4 grasses displayed negative and positive PSFs, respectively, in both rainfall legacies treatments. PSFs of Plantago lanceolata shifted from positive to negative in drought legacies, while Cichorium intybus showed neutral PSFs in both soils. PSFs of Medicago sativa shifted from negative to positive, while Biserrula pelecinus and Trifolium repens showed neutral PSFs, in prolonged drought legacies. PSFs at the community level showed a trend to shift from near-positive to neutral PSFs in soils with a drought legacy, with significant negative PSFs observed when comparing home versus sterile soils, suggesting that drought may destabilise plant communities. Conclusion Our results provide evidence that prolonged drought legacies can modify plant community dynamics due to species-specific changes in PSFs that persist after droughts are alleviated.