M.U. Marcus’s scientific contributions

Studies have shown that microbial community structure is influenced by tree species identity thus the objective of this study was to determine microbial community structure in the rhizosphere of five selected tropical trees. This research was conducted at the Forestry Arboretum of the Faculty of Agriculture, University of Port Harcourt. Random sampling was used to collect soil samples from the rhizosphere of selected trees at a depth of 0-30cm for microbial analysis and identification in the laboratory using standard procedures. Results showed significant difference in microbial population across all trees with the highest microbial population observed under Tectona grandis (4.6x106 cfu/g) and the lowest microbial population recorded under Irvingia gabonensis. Ranges of microbial population were, total heterotrophic bacteria 0.88x106cfu/g – 4.6x106 cfu/g, and total heterotrophic fungi 3.0x103 cfu/g – 15.0 x103 cfu/g. Microbial diversity showed variation across all tree species, a total of 11 Bacteria and 9 fungi species were isolated and identified. Bacillus spp was the most predominant bacterium; Aspergillus spp was the most predominant fungus, highest microbial diversity was observed under Tectona grandis and Gmelina arborea, and lowest microbial diversity was found under Nauclea diderrichii. All five selected tropical tree species had effect on the microbial community structure but Tectona grandis exerted the most effect. This tree can therefore be utilized in agroforestry to boast nutrient availability and sustainable agriculture.

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.