Department of Botany
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Item A Quantitative Study of the Ecology of the Serengeti Short Grasslands(1976) Banyikwa, Feetham F.Item Studies on Soil Erosion Control and Land Reclamation in Kondoa District, Tanzania: An Evaluation of the HADO Project(1979) Banyikwa, Feetham F.; Kikula, I. S.; Mohamed, S. A.; Rugumamu, SeverineItem Soil Erosion and Land Degradation in Tanzania: The Case of Kondoa Irangi Highlands, Dodoma, Tanzania.(1981) Banyikwa, Feetham F.; Kikula, I. S.Item Loss of Ascorbic Acid Due to Wilting in Some Green Leafy Vegetables(1983) Seeramulu, N.; Banyikwa, Feetham F.; Srivastava, V.Item Growth Analysis of Groundnuts (Arachis Hypogea) In Competition with Ageratum Conyzoides.(1985) Banyikwa, Feetham F.; Rulangaranga, Z. K.Item The Geographical Distribution of Mangrove Forests along the East African Coast.(UNESCO, 1986) Banyikwa, Feetham F.Item Endangered Mangrove Ecosystems. The Case of the Kunduchi and Mbweni Mangrove Forests(1986) Banyikwa, Feetham F.; Semesi, A. K.Item The Physical and Chemical Characteristics of a Phycocolloid from the Red Alga Sarcodia Montagneana j. Agardh of Tanzania(1987) Semesi, A. K.; Banyikwa, Feetham F.A phycocolloid from Sarcodia montagneana has been evaluated by chemical and physical analyses. The study has revealed that the phycocolloid has a yield of 39.6 per cent (percentage dry weight of alga), an IR spectrum similar to that reported for .lambda.-type carrageenan, an SO4-2 content of 22.5 per cent, a 3, 6-anhydrogalactose content of 5.1 per cent, a galactose content of 51.5 per cent (percentage dry weight of phycocolloid) and a negative optical rotation. The polysaccharide does not form a gel and cannot be modified by alkaline borohydride. It may be used in the food industry as an emulsifying agent.Item The Growth Response of Two East African Perennial Grasses to Defoliation, Nitrogen Fertilizer and Competition(Wiley, 1988) Banyikwa, Feetham F.Two East African perennial grasses, Digitaria macroblephara (Hack) Stapf. and Sporobolus ioclados (Trin.) Nees, were grown in pure and mixed culture in a factorial treatment design of defoliation, nitrogen fertilizer and plant density for a period of 90 d. With regard to controls, defoliation reduced total yield of both species per plant by 81%; higher density decreased total yield per plant by 56%; and intraspecific compe- tition decreased total yield per plant 24% more than interspecific competition. High nitrogen promoted total yield per plant by 168%. Total yield per plant of D. macro- blephara was 3.2 times greater than that of S. ioclados. With defoliation, density dependent competition decreased total yield per plant by 42% while, without defolia- tion, density dependent competition decreased total yield per plant by 601%. With defoliation, high nitrogen increased yield per plant by 9% while without defoliation high nitrogen increased yield per plant by 315%. The results suggest that the magni- tude of the negative aspects of density dependent competition may be lessened by defoliation and growing plants in mixed culture. It is concluded that in grazing ecosystems it may be advantageous to grow plants in mixed culture since the negative effects of interspecific competition are less than those arising from intraspecific competition.Item Optimal Weeding Period for Groundnuts (Arachis Hypogea L.)(1988) Rulangaranga, Z. K.; Banyikwa, Feetham F.Item The Growth Response of Two East African Perennial Grasses to Defoliation, Nitrogen Fertilizer and Competition(1988) Banyikwa, Feetham F.Two East African perennial grasses, Digitaria macroblephara (Hack) Stapf. and Sporobolus ioclados (Trin.) Nees, were grown in pure and mixed culture in a factorial treatment design of defoliation, nitrogen fertilizer and plant density for a period of 90 d. With regard to controls, defoliation reduced total yield of both species per plant by 81%; higher density decreased total yield per plant by 56%; and intraspecific competition decreased total yield per plant 24% more than interspecific competition. High nitrogen promoted total yield per plant by 168%. Total yield per plant of D. macroblephara was 3.2 times greater than that of S. ioclados. With defoliation, density dependent competition decreased total yield per plant by 42% while, without defoliation, density dependent competition decreased total yield per plant by 601%. With defoliation, high nitrogen increased yield per plant by 9% while without defoliation high nitrogen increased yield per plant by 315%. The results suggest that the magnitude of the negative aspects of density dependent competition may be lessened by defoliation and growing plants in mixed culture. It is concluded that in grazing ecosystems it may be advantageous to grow plants in mixed culture since the negative effects of interspecific competition are less than those arising from intraspecific competition.Item Species-Habitat Relationships in The Serengeti Short Grasslands, Tanzania(1989) Banyikwa, Feetham F.An improved principal components analysis ordination is used to study grass-habitat relationships in the Serengeti short grasslands. Species distribution is found to be influenced by soil factors along a topographic gradient.Item Fuzzy Set Ordination and Classification of Serengeti Short Grasslands, Tanzania(Wiley, 1990) Banyikwa, Feetham F.; Feoli, Enrico; Zuccarello, VincenzoSpecies abundance data from 32 representative stands are used to evaluate the vegetation in the heavily grazed Serengeti short grasslands. The abundant species are: Kyllinga nervosa, Sporobolus ioclados, S. kentrophyllus and Eustachys paspaloides, all occurring in elevated areas, and Hypoestes forskalei, which is found in the drainage areas. Numerical classification and fuzzy set ordination revealed four main grassland communities associated with a topographic gradient. The communities are considered distinct since their niches, as computed in the community and environmental fuzzy system space are not overlapping. Leaching, erosion and animal disturbance effects correlated with the topographic gradient are found to determine species composition and overall community structure in the grasslands.Item Plant Communities and Herbivory(1995) McNaughton, S. J.; Banyikwa, Feetham F.Item Promotion of the Cycling of Diet-Enhancing Nutrients by African Grazers(1997) McNaughton, S. J.; Banyikwa, Feetham F.; McNaughton, M. M.Experiments in Serengeti National Park, Tanzania, provide direct evidence that large, free-ranging mammalian grazers accelerate nutrient cycling in a natural ecosystem in a way that enhances their own carrying capacity. Both nitrogen and sodium were at considerably higher plant-available levels in soils of highly grazed sites than in soils of nearby areas where animal density is sparse. Fencing that uncoupled grazers and soils indicated that the animals promote nitrogen availability on soils of inherently similar fertility and select sites of higher sodium availability as well as enhancing that availability.Item Ecosystem Catalysis: Soil Urease Activity and Grazing in the Serengeti Ecosystem(Wiley, 1997) McNaughton, S. J.; Zuniga, Gina; McNaughton, M. M.; Banyikwa, Feetham F.The activity of soil ureases was evaluated in the laboratory in soils from three locations in the Serengeti National Park, Tanzania, differing in the grazing intensities that the grasslands there support. Urease activity was assayed by the instantaneous release of NH4 as soon as soils drained to field capacity after application of an aqueous urea solution approximating N concentrations in ungulate urine. The appearance of NO3 and S04 in extracts was used as an index of biological activity and pH changes; neither responded to urea addition. Ammonium appearance in extracts of soils to which water but not urea was applied was low and identical; appearance in extracts where urea had been added was high and differed between sites, increasing with the level of grazer activity at a site. The data document ecologically meaningful levels of soil urease in Serengeti soils and a positive associa- tion of those levels with grazing intensity.Item Ecosystem Catalysis: Soil Urease Activity and Grazing in the Serengeti Ecosystem(1997) McNaughton, S. J.; Zuniga, Gina; McNaughton, M. M.; Banyikwa, Feetham F.The activity of soil ureases was evaluated in the laboratory in soils from three locations in the Serengeti National Park, Tanzania, differing in the grazing intensities that the grasslands there support. Urease activity was assayed by the instantaneous release of NH4 as soon as soils drained to field capacity after application of an aqueous urea solution approximating N concentrations in ungulate urine. The appearance of NO3 and SO4 in extracts was used as an index of biological activity and pH changes; neither responded to urea addition. Ammonium appearance in extracts of soils to which water but not urea was applied was low and identical; appearance in extracts where urea had been added was high and differed between sites, increasing with the level of grazer activity at a site. The data document ecologically meaningful levels of soil urease in Serengeti soils and a positive association of those levels with grazing intensity.Item Promotion of the Cycling of Diet-Enhancing Nutrients by African Grazers(1997) McNaughton, S. J.; Banyikwa, Feetham F.; McNaughton, M. M.Experiments in Serengeti National Park, Tanzania, provide direct evidence that large, free-ranging mammalian grazers accelerate nutrient cycling in a natural ecosystem in a way that enhances their own carrying capacity. Both nitrogen and sodium were at considerably higher plant-available levels in soils of highly grazed sites than in soils of nearby areas where animal density is sparse. Fencing that uncoupled grazers and soils indicated that the animals promote nitrogen availability on soils of inherently similar fertility and select sites of higher sodium availability as well as enhancing that availability.Item Temporally Variable Rainfall Does Not Limit Yields of Serengeti Grasses(Wiley, 1998) Williams, Kevin J.; Wilsey, Brian J.; McNaughton, Samuel J.; Banyikwa, Feetham F.Temporally variable rainfall, on scales ranging from intraseasonal to decadal, is characteristic of the climate of dry grassland ecosystems. A growth chamber experi- ment indicated that the Serengeti ecosystem's most abundant and widespread grass, red oat grass (Themeda triandra), collected at locations with different rainfalls, growing seasons, and grazing intensities, is insensitive to an ecologically realistic range of rainfall events if the total amount of rain is constant. The result was confirmed under field conditions since plots did not respond to different temporal variances in water supply, although they did respond to levels of water supply. The results suggest that these grasses are water "spenders", using it as fast as they can when it is abundant, and then being semi-dormant in intervals between downpours. This characteristic could provide a competitive advantage in environments character- ized by infrequent thundershowers. The ability to tolerate intervals between showers without losing living tissues, or dying, can contribute to the success of grasses in highly variable climates, and will tend to quench potentially drastic fluctuations of energy flow through the food web.