The Ecology of Hydric Hammocks - USGS National Wetlands ...

Upper Myakka Lake/-HAMMOCKINVASION0.5 kmFigure 31. Expansion of hydric hammock(Shep's Island) into freshwater marsh, MyakkaRiver State Park, 1957-1972.hammock is composed of cabbage palmand live oak, the invading vegetationconsists of swamp laurel oak, Floridaelm, and, closer to the marsh, waterlocust and pop ash (Figure 32). Severeflooding during the summer of1982 killed many swamp laurel oaks,but not 1 ive oaks. Apparently thelatter species can withstand occasionaldeep inundation but not prolongedsoi 1 saturation.3.3.3 Eda~hic ConditionsParticular plant species may be favoredin some hydric hammocks becauseof variations in soil type. Changesin soil texture, organic content, andpH can markedly affect drainage andnutrient avail abil i ty, and therefore,the growth and survival of variousspecies. For example, sweetbay generallyis associated with organic soils(Wharton et a7. 1976). This speciesis most abundant in hydric hammockssuch as the Wekiva Springs forest(Table 5) that are characterized byseepage of ground water and organicrichsoils. The abundance of lob101 lypine in the northern gulf coastal hammocksi s negatively correl ated wi thsoil pH (Thompson 1980). Among thehydric hammocks sampled in Table 5,loblolly pine was most important inthe Silver Springs forest; the clayeysoils in that region are more acidthan the fine sands common to most hydrichammocks. The abundance patternsof water oak, both within the northernGulf Hammock and among hydric hammocks,parallel those of loblollypine, suggesting that growth of bothspecies is favored by similar conditions.CABBAGE PALMLIVE OAKSWAMP LAURELOAKFLORIDA ELMWATER LOCUSTPOP ASHFigure 32. Profile of expanding hydric hammock, Myakka River State Park.