Mangrove Ecology and Deltaic Geomorphology: Tabasco, Mexico

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Abstract
The relationships between microtopography characteristic of a non-tidal tropical delta and mangroves was studied. High salinities in the abandoned distributaries and coastal lagoons during the drier months of the year (March to Aug.) are correlated with well-developed mangrove forests (up to 30 m tall). The segregation of mangrove species according to landform type is well marked. Monospecific zones of Avicennia nitida occur on low levees and mudflats. Rhizophora mangle characterizes moist sites such as the shorelines of lagoons which are relatively stable and the edges of deteriorating and abandoned distributary channels. Together with Laguncularia racemosa, these species form a tall mixed forest in broad interdistributary basins. The dynamic ecology of mangroves and associated flora in this delta is considered to reflect habitat change induced by continually changing, geomorphic processes. Freshwater plants dominate those areas where fresh water debouches into lagoons or the Gulf of Mexico. When the center of active sedimentation and discharge shifts elsewhere, increasingly saline conditions encourage the spread of mangroves. Subsidence in the mangrove region facilitates peat development, the spread of mangroves inland, and the enlargement of lagoons. This process will cease when the distributary outlets return to the mangrove region with the result that freshwater plants will invade the mangrove community, and new landforms colonized by plants less tolerant of saline conditions, will be initiated.