Microbial Population Dynamics under Tropical Trees in an Arboretum

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.