Changes in a South East Florida Coastal Ecosystem After Elimination of Casuarina equisetifolia

As we have become more aware of the value of vegetation in the stabilization of coastal sand dunes, there has been an increasing desire to protect valuable native species in coastal habitats. In Florida, introduced exotic species have tended to crowd and eventually replace native vegetation, resulting in the establishment of monocultures. The Australian pine (Casuarina eguisetifolia) introduced to south Florida in 1898 by Fairchild, has become a weed species on beaches, supressing the native grasses associated with dune formation by its exudation of allelopathic substances. A Casuarina eradication project in Jupiter Island (Martin County), Florida was conducted in an attempt to slow beach erosion by allowing reestablishment of native dune forming grasses. Empirical data was obtained from this area to determine: 1. the effects of the loss of a dominant tree species, 2. the changing of the floristics of the area demonstrating subsequent growth of native vegetation, 3. the species reactions to different degrees of soil\u27s salinity and pH. Throughout the study area (Casuarina stand), the elimination of Casuarina resulted in an immediate growth of four species (Ipomoea pes-caprae –railroad vine, Paspalum vaginatum -salt joint grass, Panicum amarulum -panic grass, Uniola paniculata -sea oats ). I. pes-caprae is an opportunistic species representing an early stage of succession while P. vaginatum, P. amarulum, and U. paniculata are members of the climax community. Diversity indices declined after Casuarina eradication due to the initial rapid growth of I. pes-caprae, however significant linear or exponential growth of the native grasses was observed. It was found that the growth rates vary significantly with season. Away from the immediate shore line, maximum growth for all species occurred from mid to late summer. Highest growth rates for the majority of species occurred on a nearby natural dune (control) site, except for two species (I. pes-caprae and P. vaginatum) which were found to be most abundant throughout the (Casuarina stand) disturbed site