Dispersal limitation of temperate forest herbs is now a widely accepted idea, but there are few published experiments featuring replication and controls. Extant studies on annual forest herbs trace up to a few hundred seeds to map their dispersal curves, but this is not sufficient for mapping rare dispersal events. We established twenty 3-meter-by-3-meter plots, with ten being experimental plots and ten being control plots. We scattered Phacelia purshii seed into the experimental plots in May 2012.
Results/Conclusions
By 29 April 2018, Phacelia were established in all of the experimental plots, and were not detected in any of the control plots. The mean maximum Phacelia dispersal distance from the original experimental planting plot was 25 m. The maximum distance dispersed on any experimental plot was 59 m. Our results demonstrate that dispersal limitation is preventing establishment of annual forest herbs like Phacelia purshii in forests sites where they would otherwise thrive.