FACTORS INFLUENCING RHIZOPHORA MANGLE L. SEEDLING DEVELOPMENT IN EVERGLADES CARBONATE SOILS

Nutrient limitation, soil waterlogging, and soil salinity have been hy pothesized as the principal factors limiting the development of neotro pical mangrove forests. A mesocosm experiment was initiated to investi gate these alternative factors, using low-nutrient soils from the sout h Florida Everglades. Nitrogen (N), phosphorus (P), aeration, and sali nity treatment effects on Rhizophora mangle L. seedling leaf area, ste m elongation, and biomass development were determined. Phosphorus rath er than nitrogen was the important macro-nutrient limiting R. mangle l eaf area, and root and leaf biomass development in the mesocosm experi ment. A subsequent P enrichment experiment was conducted in the field to substantiate mesocosm findings. Under P enrichment in the field, se edling stem elongation rates increased from 0.03 mm d(-1) to 0.20 mm d (-1) and leaf area increased from 25 cm(2) to 75 cm(2), relative to un fertilized controls. Soil aeration stimulated root biomass development 40% in the mesocosm experiment. Sodium chloride at 32 parts per thous and resulted in branch initiation with no leaf response; however, hype rsaline conditions greater than 45 parts per thousand caused denaturin g of terminal buds. Thus, without hypersalinity stress, P is identifie d as a dominant factor limiting R. mangle foliar and stem development in low nutrient carbonate soils. Soil anoxia also influences root deve lopment and may moderate stem elongation responses to P fertilization in the field. (C) 1997 Elsevier Science B.V.