Changes in plant communities relative to hydrologic conditions in the Florida Everglades

Distribution and percent cover of plant species in relation to hydroperiod (i.e., depth and duration of flooding) were examined along eight vegetation transects in Water Conservation Area 3A of the Everglades where water-level recorders were either present or subsequently installed. Transects were monitored between 1978 and 1984 to detect changes in plant communities resulting from the operation of water-control structures to improve distribution of water to WCA 3A. Hydroperiod increased significantly at four transects where long-term hydrologic data were available. Distribution of some obligate wetland species such as Sagittaria lancifolia increased significantly with longer flooding duration. Several taxa, including Nymphaea odorata and Utricularia spp., showed significant positive relationships with annual increases in water depth. Typha domingensis increased in frequency and cover at two transects close to the northernmost water-control structure despite showing no significant relationship with increased hydroperiod. Therefore, it seems that some other environmental factor, such as inputs of phosphorus enriched water through the structure, may be encouraging the encroachment of this species. Improved hydroperiod may be inadequate for Everglades restoration without water quality improvements since it will likely result in monotypic stands of T. domingensis.