Microbial populations were isolated and counted in agar-plated composite soil samples collected from stands of three different species and an adjacent natural forest in Akure forest reserve. The plantations were mature and unthinned stands of Nauclea didderrichi, Gmelina arborea and Tectona grandis. This was to assess the role of microbes in humus formation and soil fertility enhancement and to compare their population and species diversity in the monoculture stands and the natural forest. Soil pH and organic matter contents of the soil samples were also obtained, compared and correlated with microbial population. The results show that the soil samples consisted 33 species of bacteria and 23 species of fungi. The population of bacteria ranged between 26.14 x 106 and 360 x 106 MPN g-1 dried soil while that of fungi ranged between 2.50 x 106 and 23.34 x 106 MPN g-1 dried soil. Highest species diversity and population of the microbes were isolated in soil samples from the natural forest and the least from Tectona grandis stand. The correlation and regression results show that microbial diversity and abundance is highly influenced by soil pH and organic matter. There was no significant difference in organic matter and pH values of the samples from the different forest ecosystem (p = 0.05) but significant difference was discovered to exist in bacterial and fungal population (p = 0.05). The number and species diversity obtained for bacteria were more than that of fungi but there was close association in the abundance of the microbes obtained for all the soil samples.
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V.A.J. Adekunle, H.B. Dafiewhare and O.F. Ajibode, 2005. Microbia Population and Diversity as Influenced by Soil pH and Organic Matter in Different Forest Ecosystems . Pakistan Journal of Biological Sciences, 8: 1478-1484.