Dispersal is vital to a variety of ecological processes and its importance has increased in the face of dramatic habitat loss and fragmentation. Loss and fragmentation not only increases isolation of plant populations, it alters the physical structure of the landscape. There are several ways in which spatial and individual heterogeneity might interact to affect wind dispersal. The physical structure of the habitat itself may influence wind dynamics thereby affecting a plant's dispersal ability simply as a function of where it occurs in the environment. The plant might respond differently to different habitats in terms of growth. Diaspore production, quality, or morphology might also vary with habitat. We quantified wind-dispersed plant abundance and diaspore production along transects that progressed from forest clearings through edges and into the forest matrix and measured diaspore terminal velocity and mass; traits that are key for wind dispersal. We have also conducted seed release experiments and extensive wind measurements.
Results/Conclusions
Plant abundance and seed production was lower in the forest matrix compared to the clearings. However, diaspore terminal velocity and mass did not vary in a predictable way with habitat type. Our work as well as others has shown that habitat structure has a strong influence on wind dynamics and, hence, wind-driven dispersal. Similarly, our experimental seed releases have demonstrated that the location from which seeds are released in the landscape has a dramatic affect on dispersal distances; even at the center of relatively small clearings, seeds travel much greater distances than at habitat edges. Taken as a whole, these results suggest that spatial variability in habitat structure and diaspore production, rather than individual variability of diaspore traits, are the important sources of heterogeneity for wind dispersal in this landscape.
