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Dynamics of Sudanian savanna-woodland ecosystem in response to disturbances

Savadogo, Patrice (2007). Dynamics of Sudanian savanna-woodland ecosystem in response to disturbances. Diss. (sammanfattning/summary) Umeå : Sveriges lantbruksuniv., Acta Universitatis Agriculturae Sueciae, 1652-6880 ; 2007:64
ISBN 978-91-576-7363-3
[Doctoral thesis]

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Grazing, fire and selective tree cutting are major disturbances shaping species diversity and productivity in savanna-woodland ecosystems. Their effects, however, are highly variable and poorly understood. Structural and functional responses of the Sudanian savanna-woodland ecosystem to such disturbances were investigated, with particular emphasis on the herbaceous vegetation. Fuel and fire behaviour were characterized in relation to grazing, dominant grass type and wind direction. The results indicated that fuel consumption by fire was significantly reduced by moderate livestock grazing intensity; rate of spread was faster and flame height shorter in head fire than back fire. The average maximum temperature was high on: non-grazed areas; areas dominated by annual grasses; plots subjected to head fire; and at the soil surface. Residence time of temperatures above 60ºC, considered lethal for plant tissues, exhibited a similar trend to that for fire temperature. Examination of structural responses of herbaceous vegetation to disturbances revealed that grazing favoured the diversity of perennial grasses. Fire favoured annual and perennial grasses richness. Selective cutting had no effect on any of the vegetation attributes assessed. The combined effect of grazing, fire and selective cutting increased the diversity of forbs. Structural responses exhibited significant temporal variation, which could be related to inter-annual variation in rainfall, stocking rate and fire intensity. Principal Response Curves analysis provided further evidence that their effects were species-specific. Functional responses of the ecosystem were characterized by soil physico-chemical and hydrological properties, aboveground biomass production and chemical concentration. High grazing intensity reduced soil water infiltration and aboveground biomass through increased trampling and herbage removal. Annual early fire tended to reduce steady state infiltration rate due to its effect on soil organic matter that explained 34% of the steady state infiltration rate. Long-term frequent fire affected neither soil physico-chemical properties nor total aboveground herbaceous biomass. Further analysis of fire effects on biomass production and nutrient composition of four grass species indicated that it significantly reduced above-ground dry matter, crude protein, neutral detergent insoluble crude protein and Ca, Fe, and Mn concentrations. In conclusion, moderate grazing intensity could be used to modify fire behaviour, to reduce susceptibility to erosion and to maintain sufficient biomass production. For vegetation management, back fires are recommended as they are less intense. The variation in structural responses between sites highlights the importance of landscape-scale approaches for understanding the impacts of disturbances on Sudanian savanna-woodland ecosystems that seems to follow the non-equilibrium theory of disturbance dynamics.

Authors/Creators:Savadogo, Patrice
Title:Dynamics of Sudanian savanna-woodland ecosystem in response to disturbances
Series Name/Journal:Acta Universitatis Agriculturae Sueciae
Year of publishing :2007
Number of Pages:53
ALLI. Patrice Savadogo, Didier Zida, Louis Sawadogo, Daniel Tiveau, Mulualem Tigabu and Per Christer Odén. 2007. Fuel and fire characteristics in a savanna-woodland of West Africa in relation to grazing and dominant grass type. (Submitted manuscript). II. Patrice Savadogo, Daniel Tiveau, Louis Sawadogo and Mulualem Tigabu. 2007. Herbaceous species responses to long-term effects of prescribed fire, grazing and selective tree cutting in the savanna-woodland of West Africa. (Submitted manuscript). III. Patrice Savadogo, Mulualem Tigabu and Louis Sawadogo. 2007. Multivariate analysis of dynamic responses of herbaceous vegetation communities to disturbances in the Sudanian savanna-woodland using Principal Response Curves. (Manuscript). IV. Patrice Savadogo, Louis Sawadogo and Daniel Tiveau. 2007. Effects of grazing intensity and prescribed fire on soil physical and hydrological properties and pasture yield in the savanna woodlands of Burkina Faso. Agriculture Ecosystems & Environment, 118: 80-92. V. Patrice Savadogo, Mulualem Tigabu, Louis Sawadogo and Per Christer Odén. 2007. Dry matter production and nutrient composition of four grass species in a Sudanian savanna-woodland subjected to repeated early fire. (Submitted manuscript).
Place of Publication:Umeå
ISBN for printed version:978-91-576-7363-3
Publication Type:Doctoral thesis
Full Text Status:Public
Agrovoc terms:savannas, woodlands, ecosystems, wildfires, grazing, selective felling, biomass, biodiversity, burkina faso
Keywords:Fire, herbivory, selective tree cutting, biomass production, herbaceous diversity, soil water infiltration, nutrient contents, Burkina Faso, West Africa.
Permanent URL:
ID Code:1454
Department:(S) > Dept. of Forest Genetics and Plant Physiology
Deposited By: Patrice Savadogo
Deposited On:09 May 2007 00:00
Metadata Last Modified:02 Dec 2014 10:12

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