Community disassembly and reassembly following experimental storm surge and wrack application

Abstract

AbstractQuestionsThe 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?LocationCoastal northwest Florida, USA.MethodsFour 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.ResultsThe 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.ConclusionsThe 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.