Contrasting response to clipping in the Asian knotweeds Fallopia japonica and Fallopia x bohemica

Invasive species are often managed with the objective of population control or eradication. Here we tested whether clipping techniques influenced the aboveground and belowground structures of 2 closely related invasive taxa: Fallopia japonica and Fallopia x bohemica. We compared the aboveground response (plant height, number of stems, and number of leaves) of rhizome fragments to clipping of both taxa. The second experiment was aimed at comparing the belowground response of both taxa to the same clipping disturbance. Rhizome fragments were planted in rhizoboxes and subjected to a clipping disturbance after 4 weeks of growth. Regrowth, belowground biomass, specific root length, total root length, and distribution of roots in 3 soil layers were measured. Aboveground plant traits of both taxa were unaffected by clipping. On the other hand, clipping induced a reduction in belowground dry mass and an increased proportion of roots in the upper layer of soil in F. japonica. Both taxa of Asian knotweeds are highly tolerant to clipping because they are able to cope with aerial biomass loss. Nevertheless, this tolerance seems to be lower in F. japonica. The potential implications for the impact of these invasive species are discussed.