Cooperative Ecosystem Studies Unit, South Florida/Caribbean CESU

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The USGS Southeast Ecological Science Center (SESC) seeks to provide financial assistance for research on the effects of global climate change (GCC) and sea level rise (SLR) on coastal vegetation, including transitions from freshwater vegetation communities to communities associated with more marine or brackish conditions. This will be a consequence not only of gradual SLR, but also of storm surges that can deposit large amounts of saline water far inland and possibly trigger major regime shifts to more salinity-tolerant vegetation. A model currently exists to examine mangrove/ hammock interaction and regime shift (the MANHAM model, Sternberg et al. 2007, Teh et al. 2008) and has been used for projecting ecotone movement and changes in salinity. This model demonstrates that acute increases in salinities of the vadose zone, induced by storm surge overwash events, might reduce the growth rate of the salinity intolerant hardwood hammock trees. This could promote regime shifts toward mangroves at sites that are far inland, but reachable by storm surges. This model is too simple, however, and needs to be improved and broadened. Another broad impact of GCC will be the effects on the habitats of many wildlife species, in the Greater Everglades and other areas of southern Florida. Many of the listed (threatened and endangered) species are highly sensitive to the annual temporal and spatial patterns of the landscape hydrology in the Everglades. These hydrology patterns are likely to change under projected climate scenarios.Research objectivesOne of the overarching objectives of the work will be to modify and improve existing models and develop new models to help project the effects of climate change on coastal vegetation patterns and habitats in southern Florida. The following components of competition modeling between freshwater (glycophytic) vegetation and salinity-tolerant (halophytic) coastal vegetation in relation SLR need to be improved. (1) Model the water and salinity fluxes in the vadose zone and the ground water zones in multiple vertical layers so that vertical movement of water and salinity can be simulated more realistically. (2) Model a realistic distribution of roots from glycophytic and halophytic plants in the vadose zone. (3) Include evaporative losses of water from the soil surface. (4) Model the dispersal of reproductive propagules and seedling survival more realistically. (5) Link the MANHAM model to existing USGS and other models of groundwater flow in southern Florida, such as TIME. A second overarching objective will be to utilize the existing set of models that were developed to address CERP’s needs to evaluate ecological effects; the USGS’s Across Trophic Level System Simulation (ATLSS) Program. The ATLSS ecological models are all linked through a common framework of vegetative, topographic, and land use maps that allow for the necessary interaction between spatially explicit information on physical processes and the dynamics of organism response across the Greater Everglades landscape. The simplest ecological models in the ATLSS family are the Spatially Explicit Species Index (SESI) models, which compute indices for breeding or foraging potential for key species across the southern Florida region. These models use both fine resolution maps of vegetation and fine resolution output of hydrologic models, combining several attributes of hydrology that are relevant to the well-being of particular species to derive an index value for every 500 x 500 spatial cell in the landscape. This can be done for hydrology data for any given year under any alternative water management scenario. All of these models depend critically on hydrologic input, and thus on precipitation and temperature, which may undergo changes in the future. Therefore, the application of this set of models to climate change scenarios will provide an indication of the potential effects of climate change.

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