Anticipatory restoration of coastal communities in the face of climate change
Migrating the leading edge of a species distribution in advance of climate change effects could be useful where dispersal is limited and rate of climate change is predicted to increase beyond the capacity of species to keep pace. Species occupying the seaward end of coastal gradients may be capable of establishing landward with the removal of biological filters. In August 2011, we initiated a reciprocal transplant experiment in which a series of 4 m2 plots (n=135) was established spanning coastal assemblages across the East River estuary in northwestern Florida. Vegetation was removed (treatment) or left undisturbed (control). Individuals of the dominant graminoids representing the gradient from salt marsh to upland pine savanna assemblages (Spartina alterniflora, Juncus roemerianus, Cladium mariscus, and Aristida stricta) were harvested. Each plot was subdivided into four 1m2 subplots, which were randomly assigned to a species. Ten individuals of the assigned species were planted into each of the subplots. Plots were surveyed biannually in 2012, 2013, and 2014 to quantify survival of transplants and assess the long-term efficacy of moving coastal species upslope.
All species successfully established in plots located in their source assemblages. In seaward plots, the upland grass A. stricta was the only species that did not survive, and the fresh marsh dominant C. mariscus had low survival, suggesting that abiotic stress limited these intolerant species. In all other parts of the gradient, the four species successfully established and survived at least one growing season. The most dramatic colonization result was that of J. roemerianus, the brackish marsh dominant, which survived in all freshwater wetland and upland habitats and appeared quite healthy. J. roemerianus and C. mariscus resprouted following each of two prescribed fires in the more inland pine savanna. S. alterniflora did not survive beyond the first year outside of the brackish marsh. There were no differences in plant survival between control vs. treatment plots, but in some cases initial survival was enhanced in control plots, possibly due to protection from herbivory. These results suggest that assisted colonization of downslope species into assemblages farther inland and upslope of their original source populations is feasible. Not only did some of the downslope species survive different physical conditions but they also show resilience to disturbances more prevalent in upslope communities, suggesting these populations may be capable of long-term persistence in their new habitats.