Effects of forest age and disturbance on population persistence in the understory herb, <Emphasis Type="Italic">Arisaema triphyllum</Emphasis> (Araceae)

Long-lived understory herbs experience a highly dynamic forest over space and time, yet can persist for more than a century. To understand how these populations persist, we examined effects of forest age and disturbance on potential sexual reproduction and clonal growth in the sexually labile perennial, Arisaema triphyllum. Potential sexual reproduction female:male ratio was significantly greater in the Young and Old-Gap forest states compared with Old, closed-canopy sites, where it was virtually absent. In contrast, clonal growth estimated by cormlet production did not differ significantly among the three forest states. Of seven environmental variables measured, only light positively and plant density negatively contributed significantly to the variation in potential sexual reproduction, while no measured variables contributed significantly to the variation in number of cormlets. The larger sexual reproductive effort flower stalk biomass/total biomass for males in the undisturbed, 100 yr old forest may explain the absence of females in these sites, while the invariant vegetative reproductive effort cormlet biomass/total biomass may explain the similarity in average number of cormlets per individual per season across forest states. These results suggest that potential sexual reproduction is resource-limited, while clonal growth may be resource-independent. By maintaining ramet production during unfavorable periods, A. triphyllum populations disperse temporally, “waiting” for conditions under which sexual reproduction may resume.