Seasonality of carbon emissions from biomass burning in a Zambian savanna

Hoffa, Erica Ann.; Ward, Darold E.; Hao, Wei Min; Susott, Ronald A.; Wakimoto, Ronald H.

doi:10.1029/1999jd900091

Cited by 129 publications

(201 citation statements)

References 27 publications

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“…We estimated fuel wood collection and herbivory as in van der Werf et al (2003). The main result of including these two processes was a decrease in fuel loads in savanna ecosystems, in better agreement with measured fuel loads (e.g., Shea et al, 1996;Hoffa et al, 1999). Within tropical forest ecosystems, aboveground biomass levels from the model were broadly consistent with published estimates.…”

Section: Fuel Loadssupporting

confidence: 75%

“…Several generalities about CC have emerged from studies that have measured CC's in a wide range of vegetation types (e.g., Shea et al, 1996;Hoffa et al, 1999;Carvalho et al, 2001). First, CC of fine fuels is usually very high, up to 1 (complete combustion) for dry surface litter.…”

Section: Combustion Completenessmentioning

confidence: 99%

“…CC has been measured in the field for various biome and fuel types (e.g., Carvalho et al, 1995;Shea et al, 1996;Hoffa et al, 1999), and varies over the course of the fire season with more complete combustion at the end when fuels have had more time to dry out, as shown by Hoffa et al (1999) for savanna ecosystems. In general, fine and dry fuels burn more completely than coarse and wet fuels, although a paucity of data makes it challenging to quantitatively link CC with climate in global models.…”

Section: G R Van Der Werf Et Al: Interannual Variability In Globalmentioning

confidence: 99%

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Interannual variability in global biomass burning emissions from 1997 to 2004

et al. 2006

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Abstract. Biomass burning represents an important source of atmospheric aerosols and greenhouse gases, yet little is known about its interannual variability or the underlying mechanisms regulating this variability at continental to global scales. Here we investigated fire emissions during the 8 year period from 1997 to 2004 using satellite data and the CASA biogeochemical model. Burned area from 2001-2004 was derived using newly available active fire and 500 m. burned area datasets from MODIS following the approach described by Giglio et al. (2006). ATSR and VIRS satellite data were used to extend the burned area time series back in time through 1997. In our analysis we estimated fuel loads, including organic soil layer and peatland fuels, and the net flux from terrestrial ecosystems as the balance between net primary production (NPP), heterotrophic respiration (R h ), and biomass burning, using time varying inputs of precipitation (PPT), temperature, solar radiation, and satellite-derived fractional absorbed photosynthetically active radiation (fA-PAR). For the 1997-2004 period, we found that on average approximately 58 Pg C year −1 was fixed by plants as NPP, and approximately 95% of this was returned back to the atmosphere via R h . Another 4%, or 2.5 Pg C year −1 was emitted by biomass burning; the remainder consisted of losses from fuel wood collection and subsequent burning. At a global scale, burned area and total fire emissions were largely decoupled from year to year. Total carbon emissions tracked burning in forested areas (including deforestation fires in the tropics), whereas burned area was largely controlled by savanna fires that responded to different environmental and human factors. Biomass burning emissions showed large interannual variability with a range of more than 1 Pg C year −1 , Correspondence to: G. R. van der Werf (guido.van.der.werf@falw.vu.nl) with a maximum in 1998 (3.2 Pg C year −1 ) and a minimum in 2000 (2.0 Pg C year −1 ).

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Section: Fuel Loadssupporting

confidence: 75%

Section: Combustion Completenessmentioning

confidence: 99%

Section: G R Van Der Werf Et Al: Interannual Variability In Globalmentioning

confidence: 99%

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Interannual variability in global biomass burning emissions from 1997 to 2004

et al. 2006

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“…Given lower fuel consumption rates achieved under EDS-dominated fire regimes, (Russell-Smith, Murphy et al 2009) have estimated that EDS fires in this study area typically emit 48% of the Kyoto-accountable greenhouse gases (CH 4 , N 2 O) per hectare burnt, compared with LDS fires. This calculation incorporates the finding that emission ratios of greenhouse gasses do not vary throughout the season in Australian savannas (Meyer and Cook 2010), even though they have been shown to increase as the dry season progresses in Zambian savanna grassland (Hoffa, Ward et al 1999).…”

Section: Discussionmentioning

confidence: 99%

The influence of prescribed fire on the extent of wildfire in savanna landscapes of western Arnhem Land, Australia

Price

Russell‐Smith

Watt

2012

Int. J. Wildland Fire

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Fire regimes in many north Australian savanna regions are today characterised by frequent wildfires occurring in the latter part of the 7-month dry season. A fire management program instigated from 2005 over 24 000 km2 of biodiversity-rich Western Arnhem Land aims to reduce the area and severity of late dry-season fires, and associated greenhouse gas emissions, through targeted early dry-season prescribed burning. This study used fire history mapping derived mostly from Landsat imagery over the period 1990-2009 and statistical modelling to quantify the mitigation of late dry-season wildfire through prescribed burning. From 2005, there has been a reduction in mean annual total proportion burnt (from 38 to 30%), and particularly of late dryseason fires (from 29 to 12.5%). The slope of the relationship between the proportion of early-season prescribed fire and subsequent late dry-season wildfire was ~-1. This means that imposing prescribed early dry-season burning can substantially reduce late dry-season fire area, by direct one-to-one replacement. There is some evidence that the spatially strategic program has achieved even better mitigation than this. The observed reduction in late dry-season fire without concomitant increase in overall area burnt has important ecological and greenhouse gas emissions implications. This efficient mitigation of wildfire contrasts markedly with observations reported from temperate fire-prone forested systems.

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“…Hoffa et al (1999) computed fire emissions in Zambian grasslands and woodlands using PGREEN, defined as the proportion of green grass biomass to total (green+dead) grass biomass. Ito and Penner (2005) applied three different EF scenarios that accounted for both seasonal and spatial variability.…”

Section: T T Van Leeuwen and G R Van Der Werf: Spatio-temporal Vamentioning

confidence: 99%

Spatial and temporal variability in the ratio of trace gases emitted from biomass burning

Leeuwen¹,

Werf²

2011

Atmos. Chem. Phys.

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Abstract. Fires are a major source of trace gases and aerosols to the atmosphere. The amount of biomass burned is becoming better known, most importantly due to improved burned area datasets and a better representation of fuel consumption. The spatial and temporal variability in the partitioning of biomass burned into emitted trace gases and aerosols, however, has received relatively little attention. To convert estimates of biomass burned to trace gas and aerosol emissions, most studies have used emission ratios (or emission factors (EFs)) based on the arithmetic mean of field measurement outcomes, stratified by biome. However, EFs vary substantially in time and space, even within a single biome. In addition, it is unknown whether the available field measurement locations provide a representative sample for the various biomes. Here we used the available body of EF literature in combination with satellite-derived information on vegetation characteristics and climatic conditions to better understand the spatio-temporal variability in EFs. While focusing on CO, CH 4 , and CO 2 , our findings are also applicable to other trace gases and aerosols. We explored relations between EFs and different measurements of environmental variables that may correlate with part of the variability in EFs (tree cover density, vegetation greenness, temperature, precipitation, and the length of the dry season). Although reasonable correlations were found for specific case studies, correlations based on the full suite of available measurements were lower and explained about 33%, 38%, 19%, and 34% of the variability for respectively CO, CH 4 , CO 2 , and the Modified Combustion Efficiency (MCE). This may be partly due to uncertainties in the environmental variables, differences in measurement techniques for EFs, assumptions on the ratio between flaming and smoldering combustion, and incomplete information on the location and timing of EF Correspondence to: T. T. van Leeuwen (thijs.van.leeuwen@falw.vu.nl) measurements. We derived new mean EFs, using the relative importance of each measurement location with regard to fire emissions. These weighted averages were relatively similar to the arithmetic mean. When using relations between the environmental variables and EFs to extrapolate to regional and global scales, we found substantial differences, with for savannas 13% and 22% higher CO and CH 4 EFs than the arithmetic mean of the field studies, possibly linked to an underrepresentation of woodland fires in EF measurement locations. We argue that from a global modeling perspective, future measurement campaigns could be more beneficial if measurements are made over the full fire season, and if relations between ambient conditions and EFs receive more attention.

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Seasonality of carbon emissions from biomass burning in a Zambian savanna

Cited by 129 publications

References 27 publications

Interannual variability in global biomass burning emissions from 1997 to 2004

Interannual variability in global biomass burning emissions from 1997 to 2004

The influence of prescribed fire on the extent of wildfire in savanna landscapes of western Arnhem Land, Australia

Spatial and temporal variability in the ratio of trace gases emitted from biomass burning

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