The Pyrogeography of Methane Emissions from Seasonal Mosaic Burning Regimes in a West African Landscape
Abstract
:1. Introduction
1.1. Methane Emissions and Savanna Spatiotemporal Complexity
- Vegetation desiccation (fuel drying) generally causes an increase in combustion efficiency as drier fuels combust more completely, which theoretically results in a drop in the EFs of CO and CH4 since they are products of incomplete combustion.
- As fuel drying progresses further, there is an increase in fire intensity (a measure of the energy emitted by a fire, which affects the flame and scorch height), as well as fire severity (the amount of vegetation affected by a fire), which theoretically increases the amount of fuel consumed and increases the emission density.
- As grasses (fuels) become more uniformly dry as the season progresses, there is less patchiness in terms of fuel moisture, typically resulting in an increase in burn size and completeness (both the CC and BAC) at the plot and landscape scale, theoretically increasing the emission density (Figure 2).
1.2. Seasonal Emission Equations
2. Methods
2.1. The Local Fire Regime
2.2. Data Collection
2.3. Plot Design
2.4. Field Data Analysis
2.5. Gas Emissions Sampling and Analysis
2.6. Statistical Analysis
3. Results
3.1. General Fire Characteristics by Season
3.2. Emissions by Season
3.3. Regression Analyses
3.4. Comparison of Local and Random Fires in the MDS
4. Discussion
4.1. Causes of Elevated Methane Emission Parameters and Seasonal Differences
4.2. Local (Systematic) vs. Random Fire
4.3. Policy Implications
5. Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Mean Plot Characteristics (n = 107) | Annual Mean | Head (51) | Back (56) | Early (25) | Middle (42) | Late (40) |
---|---|---|---|---|---|---|
Dry biomass (tons/hectare) | 4.1 | 4.0 | 4.2 | 3.8 | 4.2 | 4.1 |
Grass biomass (percent) | 78.1 | 76.1 | 80.0 | 91.1 | 72.5 | 75.9 |
Temperature (Celsius) | 33.3 | 33.3 | 33.3 | 32.8 | 31.2 | 35.8 |
Relative humidity (percent) | 22.1 | 22.1 | 22.7 | 29.1 | 23.9 | 15.9 |
Wind speed (meters/second) | 1.19 | 1.18 | 1.20 | 1.01 | 1.45 | 0.86 |
Spread rate (meters/second) | 0.030 | 0.043 | 0.018 | 0.032 | 0.026 | 0.034 |
Byram’s Fire Intensity (Kw/m) | 214.1 | 314.9 | 124.5 | 229.6 | 179.5 | 249.7 |
Scorch Height (meters) | 1.5 | 1.7 | 1.3 | 1.4 | 1.3 | 1.7 |
Fuel Moisture (%) | 8.9 | 10.1 | 7.9 | 8.6 | 14.3 | 3.5 |
Burn Area Completeness (%) | 91.8 | 93.1 | 90.7 | 84.2 | 90.4 | 98.0 |
Combustion Completeness (%) | 85.6 | 85.8 | 85.4 | 83.7 | 83.2 | 89.5 |
Emissions and Fire Data n = 107 Values in Parentheses Have Outliers Removed (n = 86) | CH4 Density g/m2 | CH4 (EF) g/kg | MCE | Total Combustion (BAC + CC) | Byram’s Fire Intensity kW/m |
---|---|---|---|---|---|
All Fires (mean) | 2.27 (2.09) | 6.96 (6.93) | 90.1 (91.1) | 0.77 (0.78) | 224.5 (165.6) |
Early Fires | 2.15 (1.60) | 6.52 (5.90) | 94.9 (93.1) | 0.71 (0.69) | 229.6 (154.5) |
Middle Fires w/random burns | 2.87 (2.73) | 9.53 (9.76) | 89.5 (95.1) | 0.77 (0.75) | 162.2 (138.8) |
Middle Fires wo/random burns | 3.16 (3.14) | 8.88 (10.35) | 85.0 (93.8) | 0.77 (0.75) | 170.9 (117.9) |
Late Fires | 1.72 (1.82) | 4.53 (4.93) | 87.7 (87.7) | 0.82 (0.87) | 249.7 (199.5) |
Head Fires | 2.39 (1.86) | 7.12 (6.86) | 88.6 (92.4) | 0.79 (0.79) | 296.4 (232.2) |
Backfires | 2.16 (2.24) | 6.80 (6.98) | 91.5 (91.6) | 0.75 (0.78) | 120.1 (119.8) |
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Laris, P.; Koné, M.; Dembélé, F.; Rodrigue, C.M.; Yang, L.; Jacobs, R.; Laris, Q.; Camara, F. The Pyrogeography of Methane Emissions from Seasonal Mosaic Burning Regimes in a West African Landscape. Fire 2023, 6, 52. https://doi.org/10.3390/fire6020052
Laris P, Koné M, Dembélé F, Rodrigue CM, Yang L, Jacobs R, Laris Q, Camara F. The Pyrogeography of Methane Emissions from Seasonal Mosaic Burning Regimes in a West African Landscape. Fire. 2023; 6(2):52. https://doi.org/10.3390/fire6020052
Chicago/Turabian StyleLaris, Paul, Moussa Koné, Fadiala Dembélé, Christine M. Rodrigue, Lilian Yang, Rebecca Jacobs, Quincy Laris, and Facourou Camara. 2023. "The Pyrogeography of Methane Emissions from Seasonal Mosaic Burning Regimes in a West African Landscape" Fire 6, no. 2: 52. https://doi.org/10.3390/fire6020052