Diversity of Nematodes and Earthworms Associated with Tropical Trees in An African Arboretum

In order to maintain soil fertility and quality, sustainable agriculture, and ecosystem processes, the population and diversity of soil organisms are crucial. This study was carried out at the Arboretum of the Faculty of Agriculture, University of Port Harcourt, and examined the diversity and population of nematodes and earthworms under a few chosen trees. Samples of soil, roots, and earthworms were randomly taken from the rhizosphere of trees at a depth of 0–30 cm using a spade and hand trowel. The extraction tray method was used to extract nematodes, the hand sorting and ethological method was used to collect and count earthworms, and the analysis of variance was performed on the data collected, and least significant difference was used to separate the means. Results showed significant difference in earthworm population across all trees with the highest earthworm population observed under Annona muricata (25.8), while lowest earthworm population was recorded under Irvingia gabonensis. Nematode population ranged from 3.0 – 53.0 while earthworm population ranged from 7 – 25.8 under the various tree species. Four (4) nematode species were identified, and Dorylaimida spp was the most predominant nematode. All five selected tropical tree species had effect on nematode community structure and earthworm population but Tectona grandis exerted the greatest effect. These impacts may be due to passive byproducts of nutrient intake, root shape, shearing habitat preference by trees and soil organisms, or active selection for soil microbes by plants through root exudates. These trees could be used in sustainable agriculture and agroforestry.