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important driver of ecosystem structure in savanna ecosystems (Beringer et al. 2007;
Knicker 2007) in which reducing fire frequency increases carbon stocks in woody
biomass (Beringer et al. 2007).
After the combustion of organic matter in the surface mat layer, SOC recupera-
tion follows with decomposition of roots of dead or burned plants, which overtime
attains a balance with the unburned plot (Oluwole et al. 2008). However, increases
in SOC content have also been reported in response to an increased deposition of
dry leaves and charred plant materials in fires that affect the tree canopy (Yan et al.
2012).
The role of fire in managing extensive rangelands remains controversial. Some
have found controlled fire to provide positive effects in terms of control of invasive
species (Fuhlendorf and Smeins 1997; Winter et al. 2011), while others have reported
negative effects on vegetative composition (Nicholas et al. 2009). Teague et al. (2010)
reported minimal impacts of burning on soil physical properties of southern Great
Plains prairie rangelands. They found instead that rotational grazing provided ben-
efits of less bare ground, greater SOC and nitrogen, and lower soil temperatures
compared with continuous grazing on either burned or unburned areas.
Although regular burning has been reported to have a consistent short-term nega-
tive effect on SOC in grassland soils (Ansley et al. 2006; Piñeiro et al. 2010), the
immediate and long-term effects of burning on SOC remain unclear. For instance,
Bird et al. (2000) reported greater SOC in unburned plots in subhumid savanna in
Zimbabwe, whereas Oluwole et al. (2008) found lower SOC in unburned plots than
in frequently burned plots in South African dry savanna.
Fire not only influences the total biomass of savanna systems but it also mark-
edly influences the vegetation structure of savannas (Higgins et al. 2007). Vegetation
structural changes influence the microclimate and distribution of resources such
as nutrients and moisture (Ludwig et al. 2002; Higgins et al. 2007). Fire distur-
bances can lead to ecosystem degradation associated with the disruption of the fun-
damental environmental cycles such as carbon and other nutrients (Corvalan et al.
2005), although managed fire is also a tool to intentionally manipulate rangeland
ecosystems.
Large carbon inputs to the soil occur via photosynthesis, plant growth, and litter
decomposition (Fynn et al. 2003), while a disturbance such as fire can alter plant spe-
cies diversity and dominance by changing microclimate and the availability of limit-
ing resources (light, water, and nutrients). These changes in ecosystem structure and
the abiotic environment often modify key functional characteristics of ecosystems
(primary productivity, hydrology, and nutrient fluxes) that have the potential to alter
the storage and turnover of carbon in plants and soils (Ansley et al. 2006).
Management that enhances SOC generally results in increased protection of the
soil from erosion. Conversely, poor management such as intensive burning can result
in SOC losses and the land being vulnerable to soil erosion, especially on steeply
sloping land (Ansley et al. 2006; Piñeiro et al. 2010). A significant contribution to
SOC by the litter is only in the top few centimeters of soil and therefore its removal
by fire reduces the organic matter content near the surface. The effect of fire is neg-
ligible at deeper levels because most of the organic matter in deep soils originates
from root turnover (Fynn et al. 2003).
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