Title: Invasive knotweed affects native plants through allelopathy
Abstract: There is increasing evidence that manyplant invaders interfere with native plants through allelopathy.This allelopathic interference may be a key mechanism of plantinvasiveness. One of the most aggressive current plant invadersis the clonal knotweed hybrid Fallopia x bohemica, which oftenforms monocultures in its introduced range. Preliminary resultsfrom laboratory studies suggest that allelopathy could playa role in this invasion. We grew experimental communities of Europeanplants together with F. x bohemica. We used activated carbonto test for allelopathic effects, and we combined this withsingle or repeated removal of Fallopia shoots to examine howmechanical control can reduce the species’ impact. Addition of activated carbon to the soilsignificantly reduced the suppressive effect of undamaged F.x bohemica on native forbs. The magnitude of this effect wassimilar to that of regular cutting of Fallopia shoots. Regularcutting of Fallopia shoots efficiently inhibited the growthof rhizomes, together with their apparent allelopathic effects. The ecological impact of F. x bohemica onnative forbs is not just a result of competition for sharedresources, but it also appears to have a large allelopathiccomponent. Still, regular mechnical control successfully eliminatedallelopathic effects. Therefore, allelopathy will create anadditional challenge to knotweed management and ecological restorationonly if the allelochemicals are found to persist in the soil.More research is needed to examine the mechanisms underlyingFallopia allelopathy, and the long-term effects of soil residues.[Craig Murrell, Esther Gerber, Christine Krebs, Madalin Parepa, Urs Schaffner and Oliver Bossdorf (2010). Invasive knotweed affects native plants through allelopathy. American Journal of Botany. on-line Dec 2, 2010, doi:10.3732/ajb.1000135].