scholarly journals Determinants of fire intensity in working landscapes of an African savanna

Fire Ecology ◽  
2020 ◽  
Vol 16 (1) ◽  
Author(s):  
Paul Laris ◽  
Rebecca Jacobs ◽  
Moussa Koné ◽  
Fadiala Dembélé ◽  
Christine M. Rodrigue
Keyword(s):  
Ambient Air ◽  
Dry Season ◽  
West African ◽  
Ecological Impacts ◽  
Fire Intensity ◽  
African Savanna ◽  
Seasonal Timing ◽  
Working Landscapes ◽  
Fire Type ◽  
Visual Efficiency

Abstract Background An often cited rule of savanna fire ecology is that early dry-season fires burn less intensely than late dry-season ones; however, few studies base their experimental design on the practices of fire managers in working landscapes. The objective of this research was to study the factors influencing fireline intensity, combustion, and patchiness for a West African savanna under common vegetation and land management practices. We conducted 97 experimental fires by selecting burn plots and seasonal timing (early, n = 33; middle, n = 44; or late, n = 20) based on local practices in a typical working landscape. We collected data for biomass consumed, grass type, scorch height, speed of fire front, visual efficiency (patchiness), fire type, and ambient air conditions. We used multiple regression analysis to determine the key factors affecting fire intensity. Results Mean intensity was lowest for the middle season fires and highest for the late season fires. Minimum fire intensity increased over the fire season except for a sharp drop mid season, while maximum intensity progressively decreased. Seasonal values were highly variable. Fire intensity was moderately positively correlated with scorch height and more modestly correlated with visual efficiency, but only marginally correlated with combustion completeness. Average combustion completeness increased weakly as the dry season progressed. Intensity of back-fires was determined primarily by seasonal timing and the associated ambient humidity and wind and, to a lesser extent, grass characteristics. Head-fire intensity was only feebly responsive to wind speed. Conclusions We found that, at the peak time of West African savanna burning, the intensity of fires decreased. Fire behaviors in working West African landscapes were more dependent on fire type and wind than seasonality. Finally, we found that fire intensity values were lower than those reported elsewhere due to the more representative conditions of the fire setting (under lower afternoon winds) and fuel loads (lower biomass on working landscapes). Future research should focus on the ecological impacts of fires set under such conditions on growth and death rates of savanna trees.

scholarly journals Methane gas emissions from savanna fires: What analysis of local burning regimes in a working West African landscape tell us

2021 ◽  
Author(s):  
Paul Laris ◽  
Moussa Koné ◽  
Fadiala Dembélé ◽  
Lilian Yang ◽  
Rebecca Jacobs
Keyword(s):  
Ambient Air ◽  
Methane Emissions ◽  
Dry Season ◽  
West African ◽  
Biomass Composition ◽  
Fire Intensity ◽  
Methane Cycle ◽  
Gas Emissions ◽  
Savanna Fires ◽  
Fire Type

Abstract. Savanna fires contribute significantly to greenhouse gas emissions. While it is recognized that these fires play an important role in the global methane cycle, there are too few accurate estimates of emissions from West Africa, the continent's most active fire region. Most estimates of methane emissions contain high levels of uncertainty because they are based on generalizations of diverse landscapes that are burned by complex fire regimes. To improve estimates we used an approach grounded in the burning practices of people who set fires to working landscapes. We conducted 97 experimental fires collecting data for savanna type, grass type, biomass composition and amount consumed, scorch height, speed of fire front, fire type and ambient air conditions for two sites in Mali. We collected smoke samples for 36 fires using a canister method. We report values for fire intensity, combustion completeness, patchiness, modified combustion efficiency (MCE) and emission factor (EF). Our study finds that methane EFs ranged from 3.71 g/kg in the early dry season (EDS) to 2.86 in the mid-dry season (MDS). We found head fires had nearly double the CH4 EF of backfires (4.89 g/kg to 2.92). Fires during the MDS have the lowest intensity values and the lowest methane emissions 0.981 g/m2 compared with 1.030 g/m2 for EDS and 1.102 g/m2 for the late dry season (LDS). We conclude that policies aimed at shifting the burning regime earlier to reduce methane emissions will not have the desired effects, especially if fire type is not considered. We recommend using the adjusted mean value of 0.862 g/m2—based on the carbon content for West African grasses—for calculating emissions for West African savannas.

scholarly journals Methane gas emissions from savanna fires: what analysis of local burning regimes in a working West African landscape tell us

2021 ◽  
Vol 18 (23) ◽  
pp. 6229-6244
Author(s):  
Paul Laris ◽  
Moussa Koné ◽  
Fadiala Dembélé ◽  
Christine M. Rodrigue ◽  
Lilian Yang ◽  
...  
Keyword(s):  
Methane Emission ◽  
Ambient Air ◽  
Methane Emissions ◽  
Dry Season ◽  
Fire Intensity ◽  
Gas Emissions ◽  
Significant Difference ◽  
Savanna Fires ◽  
Fire Type ◽  
Emission Density

Abstract. Savanna fires contribute significantly to greenhouse gas emissions. While it is recognized that these fires play a critical role in the global methane cycle, there are too few accurate estimates of emissions from West Africa, the continent's most active fire region. Most estimates of methane emissions contain high levels of uncertainty as they are based on generalizations of diverse landscapes that are burned by complex fire regimes. To improve estimates we used an approach grounded in the burning practices of people who set fires to working landscapes. We collected and analyzed smoke samples for 36 experimental fires using a canister method for the early dry season (EDS) and mid-dry season (MDS). We also collected data for savanna type, grass type, biomass composition and amount consumed, scorch height, speed of fire front, fire type, and ambient air conditions for two sites in Mali. We report values for fire intensity, combustion completeness, patchiness, modified combustion efficiency (MCE), emission factor (EF) and methane emission density. Our study found that mean methane EFs ranged from 3.83 g kg−1 in the EDS to 3.18 g kg−1 in the MDS, but the small sample did not provide enough power for this effect to be significant. We found head fires had nearly double the CH4 EF of backfires (5.12 g kg−1 to 2.74), a significant difference. Byram's fire intensity was a significant driver of CH4 EF but with weak effect. Methane emission density increased marginally from 0.839 g m−2 in the EDS to 0.875 g m−2 in the MDS, a difference that was not significant. Head fires, however, had much higher emission densities than backfires – 1.203 vs. 0.708 g m−2 – respectively, a significant difference. We suggest the reason for the higher methane emissions from head fires, which have higher intensity, is the longer flame lengths that burn green leaves on trees, releasing methane. We conclude that policies aimed at shifting the burning regime earlier to reduce methane emissions will not have the desired effects, especially if fire type is not considered. Future research should consider the state and amount of leafy biomass combusted in savanna fires.

The Mecca Pilgrimage By West African Pastoral Nomads

1977 ◽  
Vol 15 (1) ◽  
pp. 47-58 ◽  
Author(s):  
J. S. Birks
Keyword(s):  
West Africa ◽  
Dry Season ◽  
West African ◽  
The West ◽  
African Savanna ◽  
Pastoral Nomads ◽  
West Africans

Each dry season many Um Borroro or nomadic Fulani set off eastwards to Mecca. They are some of the 5,000 or so West Africans who make the pilgrimage (the haj) each year by travelling along the savannas through Cameroun, Chad, and the Sudan.1 About four-fifths of them come from what is generally called Hausaland and Bornu in Nigeria and Niger, but some pilgrims from all the West African savanna countries travel overland.2 Although they comprise only about six per cent of the total arriving in Mecca from West Africa (the majority come by air and sea), they represent an important relict movement which earlier this century involved more than 15,000 migrants per annum.3

Uncovering cryptic species diversity of a termite community in a West African savanna

2011 ◽  
Vol 61 (3) ◽  
pp. 964-969 ◽  
Author(s):  
Barbara Hausberger ◽  
Dorothea Kimpel ◽  
Abbo van Neer ◽  
Judith Korb
Keyword(s):  
Species Diversity ◽  
Cryptic Species ◽  
West African ◽  
African Savanna

Mineral fertilizer management of maize on farmer fields differing in organic inputs in the West African savanna

2006 ◽  
Vol 96 (2-3) ◽  
pp. 355-362 ◽  
Author(s):  
M.C.S. Wopereis ◽  
A. Tamélokpo ◽  
K. Ezui ◽  
D. Gnakpénou ◽  
B. Fofana ◽  
...  
Keyword(s):  
Mineral Fertilizer ◽  
West African ◽  
Fertilizer Management ◽  
The West ◽  
African Savanna

The breeding season and diet of Arvicanthis in northern Nigeria

1989 ◽  
Vol 5 (4) ◽  
pp. 375-386 ◽  
Author(s):  
Safianu Rabiu ◽  
Martin Fisher
Keyword(s):  
Breeding Season ◽  
Food Supply ◽  
Rainy Season ◽  
Dry Season ◽  
Northern Nigeria ◽  
East African ◽  
African Savanna ◽  
Seasonal Differences ◽  
Sudan Savanna ◽  
Semi Arid

ABSTRACTThe breeding season and diet of the rat Arvicanthis was monitored from December 1983 to November 1985 in the semi-arid Sudan savanna at Kano, Nigeria, West Africa. Breeding began 1–2 months before the start of the rainy season and ceased at the beginning of the dry season. The diet of Arvicanthis was omnivorous, but with seasonal differences. Monocotyledons and dicotyledons predominated in the diet in the dry season, with seeds and insects increasing in the diet in the rainy season. The major differences between the ecology of Arvicanthis at Kano and on the East African savanna were that in East Africa the breeding season is longer and begins after the start of the rainy season. These and other dissimilarities between the biology of Arvicanthis in the two areas could be due to the effect of climatic differences on food supply and to the possible existence of different taxonomic groupings of Arvicanthis in the two regions.

scholarly journals The Environmental Effects of Policy Change in the West African Savanna: Resettlement, Structural Adjustment and Conservation in Western Mali

1998 ◽  
Vol 5 (1) ◽  
pp. 23 ◽  
Author(s):  
Dolores Koenig ◽  
Tiéman Diarra
Keyword(s):  
Structural Adjustment ◽  
Study Data ◽  
West African ◽  
The West ◽  
African Savanna ◽  
Policy Initiatives ◽  
River Basin Development ◽  
Case Study Data ◽  
Simultaneous Implementation

This article broadens analytic perspectives on the effects of government interventionsby looking at the interaction of two distinct but simultaneous policy initiatives: involuntary resettlement and structural adjustment. Case study data from the Bafing valley in Mali show that simultaneous implementation of these two initiatives reinforced the economic growth of the zone but increased negative environmental effects.Key Words: Mali, resettlement, structural adjustment, sahel, environmental degradation, economic development, river basin development, privatization, liberalization.

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