Vegetation zones and diagnostic pollen profiles of a coastal peat swamp, Bocas del Toro, Panama

A survey of the dominant vegetative cover of a large domed coastal swamp near Changuinola in the Province of Bocas del Toro, Panama, has been undertaken as an initial step in reconstructing the Holocene history of peat accumulation on this coast. Seven phasic communities of peat-forming vegetation are defined and mapped: (1) Rhizophora mangle mangrove swamp; (2) mixed back-mangrove swamp; (3) Raphia taedigera palm swamp; (4) mixed forest swamp; (5) Campnosperma panamensis forest swamp; (6) Sawgrass +/- stunted forest swamp; (7) Myrica-Cyrilla bog-plain. Pollen extracted from surface peat samples and collected from dominant vegetation, at representative sites, is used to prepare a pollen profile of each phasic community. These profiles are then compared to pollen distribution in 2 peat cores, one from the deep central part of the deposit and the second from a site near the marine margin, in order to construct a history, by floral succession, of the 4000 year evolution of the deposit. The Changuinola mire originated as freshwater palm and hardwood forest swamps that developed in close proximity to both the Changuinola River mouth, probably behind a barrier bar and freshwater lagoon system adjacent to a low energy, mangrove-dominated bay. The early swamp was likely drained to the southeast by brackish blackwater creeks much as it is today, and formerly extended considerably farther in the direction of Almirante Bay. The palm swamp was succeeded by hardwood forest swamp dominated by a very limited number of specialized species, only one of which (Campnosperma panamensis) is prone to forming monospecific stands. Increasing accumulation of woody peat promoted by the everwet climate impeded drainage of the mire, leading to doming, increased oligotrophy, and establishment of bog-plain conditions in a manner similar to that described by the Anderson model of succession in the coastal swamps of Malaysia and Indonesia. Development of the Changuinola mire did not require the initial mangrove phase which is common to the peat swamps of southeast Asia, as the palm Raphia taedigera is able to colonise and institute peat accumulation in a variety of freshwater and brackish environments.