Figure 1.
Japanese knotweed structures and life cycle.
Japanese knotweed line drawing (A) showing above- and belowground structures relevant to population spread. Visible on the rhizome is a lateral bud. Drawing created by Suphannika Intanon. The life cycle diagram (B) of Japanese knotweed, showing the 2 stages considered in the integral projection model and the processes affecting individuals in each stage. Arrows represent a one-year time step.
Figure 2.
Shoot height and dry shoot biomass.
Japanese knotweed biomass is strongly related to shoot height in both years of the study. Constant, linear, and quadratic models were fit to data for each site and the best fit was selected based on the lowest Akaike Information Criteria (AIC).
Figure 3.
Survival, growth, and fecundity relationships.
Shoot survival from year 1 to year 2 (A & B), shoot height at end of year 2 (C & D), and number of rhizomes connected to the shoot (E & F) as predicted by shoot height in year 1 and ln dry shoot biomass at end of year 1, respectively. Response curves are only shown for range of data at each site. Complete data representations are available in Appendix A.
Figure 4.
Elasticity (A) of IPM matrix for Sleepy Hollow show shoots with low to medium heights (approximately 30-80 cm) have the greatest impact on the population growth rate. Sleepy Hollow is used as an example, see Appendix B for elasticity analysis for other sites. Generally, there was a greater contribution of the P object (B, survival and growth) than the F object (C, fecundity) to the population growth rate, as determined by the area under the curve. The exception is the Bath site where the F object had a greater contribution.
Figure 5.
Contributions of Vital Rate Changes.
Median absolute value of potential contribution a change in a vital rate could have on population growth rates (λ) across all sites based on final plant height (A) and dry shoot biomass (B). Contributions were calculated using each site as a reference location for every other site, and varying a single vital rate at a time. Fecundity is separated into rhizome production (Rhiz. Prod.), number of new shoots in year 2 per rhizome (New/Rhiz), and the shoot height of new, connected shoots (New Size). See Appendix C for complete data.
Figure 6.
The number of visible lateral and terminal buds present on excavated rhizomes (solid symbols). Snapped rhizomes’ lengths (open symbols) are approximate because they could not be followed to their terminal bud.