Hydrology, salinity, nutrition, biotic factors, and physical disturbance all influence structure in coastal forested wetlands. Hydrologic rehabilitation in South Florida may affect all of these parameters in mangrove communities, as s system once characterized by seasonal sheet flow over freshwater marshes is returned to its historic condition. Through a series of greenhouse and field experiments, I isolated the effects of particular hydrologic metrics, especially flood duration and frequency, on mangrove vegetation. As nutrient level and salinity were held constant in a greenhouse experiment, growth potential tended to improve at moderate flood durations for Avicennia germinans and Rhizophora mangle. Growth increased proportional to flood duration for Laguncularia racemosa. Patterns for A. germinans and R. mangle were similar to that of a subsidy-stress model, and studies indicate that hydroperiod alone has potential to influence forest growth according to this model. However, field diameter increment did not conform to the subsidy-stress model in two-year studies conducted in South Florida on sites with different flood durations and frequencies. If a hydroperiod signature was evident, it was masked by the restricted range of observed flood durations on specific field sites, unrelated to flood frequency, but strongly related to tidal amplitude. Furthermore, growth patterns were related to soil total phosphorus concentrations, which were linked strongly to flood duration, and were suggestive of a growth benefit from water-borne phosphorus subsidies. While no long-term-imposed hydroperiod proved to be a significant stress to any one species, assessments of seedling and sapling leaf gas exchange conducted during short-term flooding revealed various alterations, including reduced carbon assimilation and increased demand from dark respiration. In addition, naturally established trees on field sites had a 20% reduction in xylem sap flux density when soils were flooded versus drained. Such reductions were not evident for saplings in the field if floods were maintained for long time periods to allow acclimation. Overall, stand-level water use was very conservative. Mangroves appear resilient to a range of hydroperiods as long as changes are imposed incrementally to avoid reductions in growth, leaf gas exchange, and whole-tree transpiration that may eventually lead to mortality.

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