Geospatial Variability and Ecological Amplitudes of Plants along Nutrient Gradients in Imo River Wetland

Abstract

This study assessed the geospatial variability and ecological amplitudes of plants along nutrient gradients in Imo River Wetland. Systematic sampling was employed for the vegetation and soil using ten 10 m x 10 m quadrat spaced at 20 m interval along established belt transects. Soil samples were obtained using a soil auger at two rooting depths (0 – 15 cm and 15 – 30 cm) and were analyzed using standardized methods. Eight (8) species belonging to six (6) families were found. Nypa fruticans was the most dominant (541.78±155.90 st/ha) and frequent (75%) species while Phoenix reclinata, Rhizophora mangle, Laguncularia racemosa and Pandanus candelabrum were the species with the least frequency of 25%, respectively. Laguncularia racemosa also had the least density value of 25.00±0.00 st/ha. The ecological amplitudes showed that species responded differently to nutrients and environmental gradients. Nypa fruticans showed peak density values at pH and available phosphorus values of log 1.64 and log 0.77 mg/kg respectively. Phoenix reclinata and Rhizophora mangle showed a strong affinity for organic carbon and total nitrogen reaching peak density values at log 2.69% and log – 0.99%, respectively. Nypa fruticans recorded wide adaptability with increasing Ca concentration reaching a peak density value at log 2.44 cmol/kg. Generally, Nypa fruticans was the most successful of all species having recorded the highest density values at different nutrient gradients. By and large, this study showed overlapping occurrences of species in response to varying levels of nutrients across the plots and lends credence to wetland conservation and appropriate environmental monitoring against invasive species.