During the last 20 years there has been a substantial increase in our understanding of wind-driven seed dispersal.  One form of wind-driven dispersal that has received very little attention in the literature is tumbling, whereby all or part of a plant detaches and rolls along the ground.  However, this mechanism has evolved in a number of taxonomically diverse plant families and is common among important invasive or agricultural weeds.  We developed models of tumbling dispersal of Centaurea diffusa seed based on wind tunnel experiments and tested them against field data. 

Results/Conclusions

Seeds were commonly dispersed 200 to 300 m and one plant had an estimated 3 seed remaining after traveling 1,039 m.  Though a linear model better captured field observations, both linear and negative exponential models overpredicted seed dispersal distances.  Overpredictions are probably largely attributable to differences in fecundity between plants used in the wind tunnel and those in the field.  That a linear model outperformed a negative exponential model in describing seed dispersal is contrary to common expectations.  However, the process of seed being deposited from a moving plant may indeed be linear and fecundity may be a critical factor determining dispersal distances.  To our knowledge, there is currently only one published work that explicitly addressed seed dispersal by tumbling and more research is needed.  If seed is commonly dispersed 200 to 300 m, this process is an important contributor to the rapid spread of an important invasive plant.