RELATIONSHIP BETWEEN VEGETATION AND SOIL CHARACTERISTICS IN INYANG ETIM EKPO RIVER VALLEY, SOUTH-SOUTH NIGERIA 0 0

Abstract

Vegetation and soil are widely understood to exhibit a circularly causal relationship, in which soil supplies the anchorage, nutrients, moisture, and habitat that vegetation requires to thrive, while vegetation in turn protects soil against erosion and replenishes soil nutrients through litterfall and the mineralisation of litter, yet this reciprocal relationship has rarely been examined using a multivariate approach in the riparian valleys of South-South Nigeria. This study examined the relationship between vegetation parameters and soil characteristics in the Inyang Etim Ekpo River Valley, Akwa Ibom State, Nigeria. Data on floristic and structural composition of the riparian vegetation and on soil physico-chemical properties at topsoil (10-15 cm) and subsoil (15-30 cm) depths were obtained through direct field observation, measurement, and enumeration from ten composite sampling points systematically and randomly delineated along forty quadrats laid out on both banks of the river valley, and were analysed using descriptive statistics and canonical correlation analysis (CCA). The omnibus multivariate tests of significance, Wilks' Lambda, Pillai's Trace, Hotelling-Lawley Trace, and Roy's Greatest Root, were all non-significant (p > .05), indicating no significant overall relationship between the full sets of vegetation and soil variables. However, examination of the canonical cross-loadings and redundancy indices, which reveal the amount of variance shared between individual variables independently of the overall test of significance, showed that herbaceous species composition loaded strongly and positively with topsoil exchangeable cation on the first canonical function, girth loaded strongly and positively with subsoil acidity on the second canonical function, and basal cover loaded strongly and positively with topsoil nutrient on the third canonical function, with the vegetation variable set accounting for 40.3% of the variance in the soil variable set and the soil variable set accounting for 20.1% of the variance in the vegetation variable set. The study concludes that, at the level of specific variable pairs, vegetation attributes exert a positive influence on soil nutrient status in the Inyang Etim Ekpo River Valley, and recommends that deforestation be discouraged through policy regulation and that government gazette the valley for conservation in collaboration with the local communities.