DISTRIBUTIONAL PATTERNS OF FLORA SPECIES IN RESPONSE TO SALINITY GRADIENTS IN A PALUSTRINE WETLAND

Abstract

This study investigated the distributional patterns of species in response to salinity gradients. The vegetation was systematically sampled using a quadrat of 50 x 10 m. Vegetation variables were measured. At depths of 0 – 15 and 15 – 30 cm, sediment samples were dug and analyzed using standard methods. Fourteen species were encountered. Rhizophora mangle and Mytragyna ciliata had highest and least density values of 6664±687.16 and 3.00±0.42 st/ha. The most frequent species were Rhizophora mangle and Nypa fruticans (100 %). Rhizophora mangle and Mytragyna were tallest (12.45±1.20 m) and shortest species (3.11±0.24 m). Elaeis guineensis and Alchornea cordifolia had the largest (1.79±0.05 m2/ha) and least (0.008±0.0002 m2/ha) basal area values. Highest crown cover value was recorded by Rhizophora mangle (9.14±0.08 m2/ha) while by Alchornea cordifolia had the least value (0.04±0.001 m2/ha). Gradient analysis revealed that Ipomoea involucrata, Paspalum vaginatum, Dracaena mannii, Piptadeniastrum africanum, Elaeis guineensis, Staudtia stipitata, Alchornea cordifolia, Terminalia superba and Mytragyna ciliata belonged to ecological group 1 with ecological optima of 8.14, respectively. Acrostichum aureum (ecological optimum of 29.32), Avicennia africana (ecological optima of 19.56 and 30.12) and Phoenix reclinata (ecological optima of 8.14 and 29.32) belonged to ecological group 4 while Nypa fruticans (ecological optima of 8.14 and 29.32) and Rhizophora mangle (ecological optima of 19.56 and 30.12) belonged to ecological group 0. This study provides information on species adaptation and performance in relation to environmental stress and will form the basis for the future and effective management of this ecosystems.

Keywords

• Salinity
• Palustrine wetland
• Mangrove
• ecological amplitude
• gradient analysis.