Persistent effects of the seedbank on the dynamics of wild sunflower populations.
Pilson, Diana*,1, Alexander, Helen2, 1 University of Nebraska, Lincoln, NE2 University of Kansas, Lawrence, KS
ABSTRACT- In wild sunflower, Helianthus annuus, population size (and seed production) in one year is positively correlated with population size in the following year. This result indicates that at least some sunflower populations are seed limited. Now we show that this effect persists, through the survival of dormant seeds in the seed bank, for at least four years. In 2000 and 2001 we initiated experimental populations that dispersed between 2000 and 20,000 seeds in the year of establishment, but that were prevented from dispersing additional seeds in the following years. In populations initiated in 2000 population size in 2001, 2002, 2003, and 2004 were all positively correlated with seed dispersal in 2000. In the 2001 populations, which dispersed fewer seeds, there was almost no germination in 2002 (due to a severe drought), but population size in 2003 and 2004 were both positively correlated with seed dispersal in 2001. Thus, the dynamics of local sunflower populations are controlled by seed production, and this effect persists for several years. Because sunflower requires a recent disturbance to germinate, our results suggest that the larger-scale dynamics of sunflower are a complex function of disturbance pattern, environmental conditions, and population size (and seed production) in (at least) the previous four years. Although long survival in the seedbank is common, this study is the first to document such long-lasting effects of the seedbank on the dynamics of a wild plant population.
Key words: Helianthus annus, population dynamics, seedbank, sunflower
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