Investigating the Role of Soil Legacy Effects in the Management of Lespedeza cuneata, an Invasive Legume

ABSTRACT Invasive plant species present a growing threat to biodiversity. Many invasive plants recruit microbial symbionts in their novel range that influence their growth and fitness. These soil legacy effects can linger after the removal of invasive species and impact restoration efforts. In a growth room experiment to investigate the legacy effects of an invasive legume and herbicide, Lespedeza cuneata was grown with either an intraspecific competitor or a native species in field-collected soils with and without history of an L. cuneata invasion and use of glyphosate herbicide. In separate experiments, we investigated seed germination and seed bank composition in these different soil types. Taken together, results suggest that legacy effects of L. cuneata invasion do not significantly contribute to its growth or spread in a floodplain in eastern North Carolina. The absence of soil legacy effects, which have been documented in other systems, may be attributed to frequent flooding observed in the system and the resulting homogenization of soil biota. Study findings also suggest that the application of glyphosate herbicide creates areas where L. cuneata can readily reinvade, as it significantly reduced the number and diversity of seedlings to emerge from the seed bank while increasing the aboveground biomass and nodule formation of L. cuneata. Concerning the restoration of native flora, data suggest that Chasmanthium latifolium may be negatively impacted by a L. cuneata invasion or glyphosate herbicide, while Solidago altissima and Chamaecrista nictitans could be successful in preventing areas from being reinvaded.