Increasing wind dispersal with informed conservation corridor and connectivity design

Background/Question/Methods . Widespread human-induced changes in landscape structure such as habitat loss, landscape fragmentation, and climate instability can alter movement abilities and dispersal trajectories of organisms and affect populations, communities, and ecosystems. Conservation corridors, strips of habitat connecting two otherwise isolated habitat patches, have long been used in conservation planning as a tool to promote movement among remaining fragments of suitable habitat in fragmented landscapes. However, little is known about how their presence and attributes affect movement, especially for wind-dispersed organisms such as seeds. We expanded upon recent advances in spatially explicit, mechanistic dispersal modeling and conservation corridor research to determine the effects of differing corridor length, width, and continuity (i.e. continuous vs. ‘stepping stones’) on wind dispersal of species with varying dispersal ability (i.e. high vs. moderate vs. low; based on terminal velocity). Simulations were carried out in hypothetical landscapes of open habitat – where wind-dispersed plants are commonly found – surrounded by closed-canopy habitat.

Results/Conclusions . In general, continuous corridors between patches were most effective at promoting dispersal of seeds of both high and moderate dispersal ability, rivaling or exceeding dispersal in single long, open patches. High dispersal ability seeds also showed strong dispersal when a stepping stone was present between patches. Turbulence and updraft drove most of the dispersal of high dispersal ability seeds, however, this was rarely sufficient to eject lower (moderate and low) dispersal ability seeds; for these, horizontal wind speed was a more important factor. Consequently, corridors that proportionally increased in width as they increased in length, reducing the drag created by the ‘walls’ of longer corridors, were most effective at maximizing wind speed and promoting dispersal of lower dispersal ability seeds. The substantial effects of differing corridor attributes not only on rare, long distance events, but also on common dispersal events have strong implications for a variety of important ecological processes. Importantly, our results suggest that species’ dispersal abilities should be considered by conservation planners when designing corridors for wind-dispersed organisms. Furthermore, conversion of open habitats to closed-canopy habitats (e.g. through fire suppression) may disproportionately affect species of lower dispersal ability.