Community disassembly and reassembly following experimental storm surge and wrack application

Abstract

Questions The structure of coastal vegetation could be altered by a regime of more intense hurricanes stemming from global climate change: (1) How do plant communities and environmental conditions across an estuarine gradient change in relation to simulated storm surge and wrack deposition? and; (2) Are there differences in the magnitude of compositional shifts along an underlying soil water conductivity gradient? Location Coastal northwest Florida, USA. Methods Four plant communities spanning an estuarine gradient (brackish marsh, freshwater marsh, wetland forest and pine savanna) were surveyed prior to and following flooding with artificial seawater and manual application of wrack. Environmental data (soil water conductivity and light transmission to soil surface) were also collected before and after treatment applications. Soil samples for texture analysis were collected prior to experimental treatments. Results The storm surge treatment reduced cover of most species, causing browning and eventual loss of leaves, particularly in pine savanna species. Soil water conductivity remained elevated for 6 mo following the experimental storm surge in the wetland forest and pine savanna. Wrack deposition resulted in substantial mortality of underlying vegetation and reduced species richness in all communities. The composition of the pine savanna plant community shifted in response to experimental storm surge and wrack application, with ‘hardy’ species capable of resprouting becoming more abundant and sensitive species dropping out of the assemblage. Vegetation zones with high background soil salinity were more resilient to the effects of storm surge and wrack deposition. Conclusions The results suggest that the combined effects of storm surge and wrack deposition can drive compositional shifts, particularly in more upland assemblages. We conclude that vegetation consisting of species ‘naïve’ to increased salinity and/or burial by wrack are highly vulnerable to tropical storm intensification.

Hurricane wrack generates landscape‐level heterogeneity in coastal pine savanna

“…Only trees and larger shrubs tended to survive burial by wrack deposits generated by major hurricanes, as also noted by Tate and Battaglia (2013). Th e wrack buried groundcover vegetation in sizable bands, leaving few aboveground legacies.…”

“…In the fall of 2008 wrack was deposited at GBNERR during storm surges of hurricanes (Gustav, Ike) crossing the Gulf of Mexico in September 2008 (also see Tate and Battaglia 2013). Some culms of Spartina patens and Panicum virgatum grew through our experimental wrack deposits and were present as sparse culms in plots.…”

Persistence of Coastal Vegetation in Supratidal Zones of Northern China

“…We try elucidating how their seeds are dispersed among such coasts (Figure 3). When storm surges arise, they inundate coastal specialists on supratidal zones, where they may thrive [1,20,22]. During the inundation, approximately 90% of their seeds are dispersed locally with shore currents, and approximately 10% are carried away by offshore currents into open seas [16].…”

“…Supratidal zones, by their nature, are different from hinterlands for occasional inundation of storm surges [16,19,20]. Once storm surges take place, seawater may surge up beyond average high tide lines in form of violent waves, so as to wash supratidal zones and coastal vegetation temporarily.…”

Home advantage? Decomposition across the freshwater-estuarine transition zone varies with litter origin and local salinity

“…Any significant changes in the intensity and frequency of seawater inflows into estuaries and rainfalls into rivers of the kind expected through climate change, are likely to modify the overall local abiotic conditions, with possible alteration of the decomposition process (Mendelssohn et al, 1999). Detritus from marine sources could be moved further inland and upstream through catchments (see Tate and Battaglia, 2013 for an example), whilst estuarine and marine systems might be expected to receive increased quantities of terrestrial leaf litter. The consequence of such perturbation could be that detritus processing is due to local mismatch between the salinity regime.…”