Invasive success of Lespedeza cuneata: allelopathy and competition

Abstract

Lespedeza cuneata is an Asian legume introduced to the U.S. in the 1930s as erosion control and forage, but it can also have strong negative effects on native species and in some cases form dense monocultures. One proposed explanation for this invasive success is that L. cuneata produces allelopathic chemicals that either directly suppresses native species or indirectly alters soil chemistry or microbial communities in ways that give L. cuneata a competitive advantage. Additionally, L. cuneata may have competitive advantages over native species that operate independently or in conjunction with these allelopathic mechanisms. To test these hypotheses, I collected soil from a previous three-year field experiment in which L. cuneata was established in or excluded from randomly selected plots in a common soil type and site history. A series of greenhouse experiments were designed to isolate putative allelopathic effects, resource competition and effects of neighbor identity on native plants. Invaded soil had positive effects on L. cuneata biomass while native biomass decreased for several native species. Additionally, water manipulation resulted in significant interactions with soil history or neighbor identity for a subset of the native species, indicating that resource competition may impact invasive success of sericea. These results support the hypothesis that L. cuneata can create a positive feedback that may increase invasion potential, as well as directly impacting growth of natives,and these effects may be intensified by low water conditions.