SOIL-VEGETATION INTERRELATIONSHIPS OF MANGROVE SWAMPS AS REVEALED BY MULTIVARIATE ANALYSES

Vegetation and soil of mangrove swamps were studied with the aim of understanding the interrelationships of the mangrove ecosystem. Principal components analysis (PCA) was used to generate a hypothesis that the distribution patterns of mangrove vegetation were influenced by variation in soil properties. The hypothesis, tested by simple correlations of vegetation components and soil variables, revealed a primary nutrient/salinity factor as explaining species variation on the first principal component, while the second was explained by physical site quality and micronutrients. Canonical correlation analysis (COR) was also used to relate both subsystems directly. The primary relationship between vegetation and soil was confirmed to be in terms of nutrient and salinity variation. Several species, e.g. Avicennia africana and Rhizophora spp., indicated little or no relation to soil calcium and magnesium levels. A spatial segregation of species was also apparent due to selective tolerance and adaptation of the species to levels of salt concentrations. Field moisture, associated with tidal flooding, was observed to affect both subsystems through their effect on nutrient supply, chloride concentrations and organic carbon.