PLANT SUCCESSION AND THE INFLUENCE OF DISTURBANCE IN THE OKEFENOKEE SWAMP, GEORGIA

Okefenokee Swamp is a mosaic of dynamically related vegetation patches which represent different stages of temporal succession. This mosaic is continually changing from within as patches undergo succession. In the absence of disturbances, succession generally proceeds from open marsh to either cypress or shrub swamp then to either climax broad-leaved evergreen or mixed hardwood swamp.; Patches within the vegetation mosaic are created by localized disturbances such as fire and logging. Severe burns are spotty in Okefenokee but can kill all or most vegetation in a given area. Post-fire communities generally resemble earlier successional stages. Secondary succession will recapitulate the original successional development and eventually restore approximate pre-fire floristic composition. Most fires, however, are light surface fires which tend to maintain existing vegetation communities and thereby arrest the process of succession. Logging operations removed over 90% of the merchantable cypress in Okefenokee Swamp. Most logged areas are now dominated by climax mixed hardwood or broad-leaved evergreen swamps, a transition historically prevented by recurrent fires. Re-establishment of cypress is not, in general, evident and return to pre-logging floristic composition is unlikely even if frequent severe fires occur.; Characteristics of the Okefenokee vegetation mosaic are therefore determined by the intensity, frequency, and spatial distribution of disturbances which create patches versus the direction and rate of patch succession following disturbances. The relative lack of "climax" vegetation patches in Okefenokee indicates disturbances, primarily fires, are frequent relative to the rate of plant succession. The result of this recurrent disturbance regime is maintenance of a heterogeneous, disclimax ecosystem.; If the disturbance regime under which a plant community evolved is altered or if the community is subjected to disturbances it has never encountered, then the behavior and structure of that community may change. Such changes in the Okefenokee Swamp are evident in logged areas. Modification of the recurrent fire regime could also result in permanent alteration of many of the unique characteristics of Okefenokee Swamp that its inclusion in the National Wilderness System and National Refuge System was designed to preserve.