Three invasive Fallopia taxa are present in Belgium: F. japonica (FJ), F. sachalinensis (FS) and their hybrid F. 9 bohemica (FB). FS is the least invasive of the three taxa. In this study, we compared the taxa, in sites where they co-occur, for differences in functional traits that might influence their competitive ability and invasiveness-shoot height and ramification, leaf size, specific leaf area (SLA) and foliar nitrogen (N) concentration. The three taxa exhibited similar growth kinetics and similar SLA. However, FS differed in its architecture and allocation of leaf area, having less ramified shoots and a steeper gradient of decreasing leaf size along the main shoot. Also, FS had greater foliar N and less efficient N resorption from senescing leaves. These traits values may result in lower competitive ability of FS for light and nitrogen. For the same traits, FB was generally intermediate between FS and FJ, but often closer to the latter. FB was more variable than FS and FJ, possibly due to larger genetic variation. SLA and ramification varied greatly amongst sites for all taxa, due in part to plastic response to contrasting light regimes. Variation in functional traits values may in part explain the variation in invasiveness amongst the members of the Fallopia complex in Belgium.

No abstract