Field Observations of Carpinus (Betulaceae) Demonstrate High Dispersal Asymmetry and Inform Migration Simulations with Implications for Times of Rapid Climate Change

Abstract

Premise of research. Propagule dispersal allows for the movement of plants across landscapes, establishing spatial structure and driving geographic range expansions and shifts. Because this movement is critical to the survival of plant populations and species, particularly during times of rapid and large-scale climate change, dispersal patterns and potential are important to consider when both exploring the past and predicting the future.Methodology. This study analyzes wind dispersal patterns in the genus Carpinus using field collections of dispersed fruits, sampled with high spatial resolution over two complete dispersal seasons and in multiple directions away from parent plants. These detailed collections, with direction-specific information, were then used in an observation-based migration simulation developed to identify the impact of dispersal patterns on population movement.Pivotal results. Field observations indicate short dispersal distances for the vast majority of fruits as well as a high level of directional asymmetry for both species of Carpinus. This asymmetry was intensified in the environment with an open vegetative structure, consistent with wind variability being the primary driver of dispersal distances. Migration simulations that incorporate local dispersal processes suggest low migration potential with a high level of directional asymmetry.Conclusions. Results stress the importance of rare long-distance-dispersal events in circumventing dispersal limitation in Carpinus and identify an important directional aspect to the process of wind dispersal. Because of the significant relationship found between dispersal patterns and wind directionality, the addition of a direction parameter to dispersal analyses and models could enhance the understanding of historic tree population dynamics, more accurately predict future movements, and inform conservation strategies of abiotically dispersed organisms. The enhanced asymmetry found in open forest structures makes it even more important to consider wind direction for predictive methods and conservation approaches as environments become more open due to forest clearing and other human disturbances.