RELATIONSHIPS BETWEEN VEGETATION GRADIENTS AND SOIL VARIABLES OF MANGROVE SWAMPS IN SOUTHEASTERN NIGERIA

The vegetation and soils of mangrove swamps were studied in order to determinine the relationship between species variation and soil variables. The basic premise was that the vegetation and the soils are multivariate and could be viewed in terms of gradients. Principal components analysis, an eigenvector multivariate analytical technique, was used in the interpretation of the structure within the correlation matrix of the vegetation and soil data. The principal components analysis indicated the first four components of the soil system as: salinity (complex hydrochemical gradient); nutrient gradient; soil moisture gradient; and substrate texture gradient. The first four components of the vegetation system were indicated as: competition gradient; adaptation gradient; residual competition gradient; and site preference gradient. The soil salinity gradient was negatively correlated with vegetation competition and adaptation gradients (r= -0.38; r= -0.35), while the nutrient gradient was positively correlated with the residual competition gradient (r= 0.56). It was observed that non-mangroves were more sensitive to soil nutrient levels than true mangrove species.