A plant-soil feedback (PSF) is an interaction between a plant and the biotic and abiotic components of soil that affects plant growth, reproduction, and survival. These interactions, which influence biodiversity, species coexistence, and community dynamics, are not well understood as invasion mechanisms for invasive plant species.
Eragrostis lehmanniana (Lehmann lovegrass), is an invasive, perennial C4 bunchgrass that was seeded in the southwestern United States from the 1930s through the 1980s to restore degraded rangelands, leading to extensive colonization of unseeded areas. Although phenotypic plasticity, prolific reproduction, and positive response to fire contribute to the success of E. lehmanniana in the U.S., interactions with soil biota may also facilitate invasion via PSF.
We collected soils from four sites of known invasion age at the Appleton-Whittell Audubon Research Ranch in Sonoita, AZ and used them to inoculate soils for conditioning by E. lehmanniana. We used a full factorial greenhouse plant-soil feedback experiment with live and sterile inoculum in a replacement series design to evaluate how E. lehmanniana invasion age influences intra- and interspecific PSF effects and competition outcomes between E. lehmanniana and Bouteloua gracilis (blue grama).
Results/Conclusions
Eragrostis lehmanniana developed detrimental intraspecific PSF in soils of all invasion ages, as indicated by lower above-ground biomass when grown with live inoculum. Bouteloua gracilis growth was higher in live-inoculated, invaded soils of all invasion ages, indicating a beneficial PSF effect. We found no significant differences in competition outcomes that would indicate E. lehmanniana PSF influences competitive interactions between E. lehmanniana and B. gracilis. Eragrostis lehmanniana outcompeted B. gracilis in all treatments. Despite conferring a benefit to it through PSF, E. lehmanniana outcompeted B. gracilis across all invasion ages.
Competitive ability influences invasion more strongly than PSF in E. lehmanniana invasion into B. gracilis grasslands, regardless of invasion age. Future research that investigates the influence of PSF on competitive interactions between other invasive and native plants will enhance understanding of the role of PSF in plant invasions and supply information that may be invaluable for ecosystem restoration.