Browsing Okavango Research Institute (ORI) by Author "Mubyana-John, T."
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Siele, M.P.; Mubyana-John, T.; Bonyongo, M.C. (Global Science Books http://www.globalsciencebooks.com/index.php?page=shop.product_details&category_id=1&flypage=shop.flypage&product_id=5&option=com_virtuemart&Itemid=56&vmcchk=1&Itemid=56, NaN, 2008)[more][less]
Abstract: Soil cover influences soil biological and chemical processes in various ways. The effects of soil cover (bare soil without litter, litter cover, Mopane tree canopy and grass cover) on soil respiration and microbial population at four sites in the Mopane woodland of north western Botswana were investigated. Soil respiration rates were measured using an infrared gas analyzer. Nitrifying bacterial populations were quantified by MPN on ammonium and nitrite calcium carbonate media, oligotrophs on 1% nutrient agar, actinomycetes on starch casein agar, bacteriovorous protozoans by MPN on sodium chloride agar baited with Enterobacter, and fungal biomass carbon using buried slides were also determined. Soil respiration in different habitats was significantly influenced by type of cover, diurnal temperature variations and soil moisture. Soils under cover showed significantly higher soil respiration than the bare soils. Autochthonous bacterial populations in the Mopane woodland soils consisted mostly of oligotrophs which varied insignificantly between seasons. Fungi were the most dominant microorganisms in all the Mopane woodland soils, with biomass of 162.05 to 282.14 μg C/g soil in the wet season and 11.84 to 44.16 μg C/g soil in the dry season. Microscopic observation of buried slides revealed that fungi play a vital role in holding soil particles together in these soils. The results showed a strong positive relationship between changes in fungal biomass and fluctuation of soil respiration. However, no clear correlation was observed between the variation of soil respiration and other microbial populations (oligotrophic bacteria, actinomycetes, and nitrifying bacteria). Overall these results indicate that in soils under Mopane tree canopy, fungi contribute significantly to soil structure and soil respiration. Other microbial populations consist mostly of oligotrophs which show minimal seasonal variations. Soil moisture significantly influences seasonal fluctuation in soil respiration. URI: http://hdl.handle.net/10311/292 Files in this item: 1
The Effects of Soil Cover.pdf (6.625Mb) -
Mubyana-John, T.; Wutor, V.C.; Yeboah, S.O.; Ringrose, S. (Academic Journals. http://www.academicjournals.org/SRE, NaN, 2007)[more][less]
Abstract: The influence of wild fires on microbial community structure, soil organic matter, sulphur oxidising and nitrifying microbial populations in the floodplains of the Okavango Delta of Botswana was assessed. Microbial community structure was assessed by phospholipids ester-linked fatty acids (PLFA) quantification while microbial sulphur oxidisers were assessed by Most Probable Number (MPN). Community structure assessment showed that burning shifted the microbial community structure from single cellular bacteria being the dominant groups to filamentous fungi and actinomycetes being the most dominant groups. Generally burning increased the fungal component (18:2 w6) matrix from 3.40 to 8.35 while the actinomycetes and sulphur reducing bacterial (10 Me 16:0) component also increased from 1.02 to 1.70 mostly in the floodplains. Generally, the organic matter content declined with burning. However, the influence of burning on soil pH was non conclusive. Soil microbial biomass carbon increased slightly after the fire. The number of heterotrophic and nitrite-oxidizing and sulphur reducing bacteria increased. Overall, these results indicate that burning significantly alters the microbial community structure as large above ground losses of nutrients during and after burning often results in low quantities of nutrients released into the soil. URI: http://hdl.handle.net/10311/349 Files in this item: 1
Fire and.pdf (2.461Mb)
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