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Genomics and Applied Biology, 2010, Vol.1, No.1
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Both harvesting treatments created significantly more
100 hours fuels than measured in the control, and the
50% stocking treatment created more 1 000 hours
fuels than the 70% stocking treatment and the control.
Heavy fuels take longer to ignite, spread slower, burn
longer and throw off large volumes of heat when dry.
Typically heavy fuels are less available than light
fuels.
Heavy fuels in eastern hardwood forests will not
typically be a fire behavior factor during a prescribed
burn. These heavy fuels would become more available
under drought or dry conditions, and if the rate of fire
spread is slow. The accumulation of fine fuels around
the heavy fuels could also cause these heavy fuels to
become involved by allowing prolonged contact with
heat. If heavy fuels become involved, they would burn
and smolder longer, and produce greater output of heat,
thus creating sources of firebrands and continued
heating during the smoldering phase. This creates
potential rekindling issues during the mop up phase of
a prescribed burn. Slow moving fires through heavy
fuels can transfer large amounts of heat to mineral soil
or oil organisms (Rollins et al., 1993). During forest
fires, maximum ground temperatures may reach
200~300
℃
; However under heavy fuels ground
temperatures may exceed 1 500
℃
while the surface
temperatures in these locations is 500~700
℃
(Neary
et al., 1999). Surface temperatures ranging from
175~275
℃
have been recorded for prescribed burns
in Southern Ohio, depending on season of burn, slope
position, and slope aspect (Schwe- mlein and
Williams, 2007).
It is most likely that a prescribed burn performed in
these forests would consume the 1 hour and 10 hours
fuels. It would be rare that the 100 hours and 1 000
hours fuels would become involved in most prescribed
burns in eastern hardwood forests. With this
assumption, along with the assumption of average
combustion efficiency and fuel moisture during a
prescribed burn when applying emission factors
reported by Battye and Battye (2002; http://www. epa.
gov/ttn/chief/ap42/ch13/related/firerept.pdf), and the
estimated carbon emissions from a prescribed burn are
reported in table 5. It is apparent that prescribed
burning would emit lower amounts of carbon than if
all surface fuels were consumed in a wildfire event.
Narayan et al. (2007) found this to be the case when
analyzing wildfire and prescribed burn data in Europe.
Prescribed burning, although itself a carbon source,
can be an effective management tool for reducing fuel
loads and preventing greater emissions as the result of
wildfire.
The amount of fuel consumed during a fire is a key
variable in modeling fire effects (Peterson et al., 1987).
The amount of fuel consumed will vary, based on fuel
load, ecosystem type (fuel type), fuel moisture,
weather, and fire behavior. It was found that the
variability in fuel consumption during burning in
Alaska is the main driver of uncertainty in the
emission of carbon-based greenhouse gases from
wildland fires (French et al., 2004), and this variability
is both spatial and temporal in nature.
2.3 Conclusions
Forest harvesting in eastern hardwood forests
contributes significantly to fuel loading. Harvesting
created significantly more total surface fuels
compared to the control, with the largest percentage of
these fuels contained in the deadwood material (>5 cm
Table 5 The estimated mean of carbon emissions resulting from the consumption of 1 hour and 10 hours fuels during a prescribed
burn within the harvest treatments and control in the Richland Furnace State Forest, Southern Ohio
Carbon emission component (t/ha)
CO
2
CO
CH
4
Total carbon
emissions (t/ha)
Treatment
Mean
Standard
deviation
Mean
Standard
deviation
Mean
Standard
deviation
Mean
Standard
deviation
50% stocking
38.15a 40.04
3.61a
3.79
0.17a
0.18
41.93a
44.01
70% stocking
35.70a 20.43
3.38a
1.93
0.16a
0.09
39.24a
22.45
Control
21.42a
3.85
2.03a
0.36
0.10a
0.02
23.55a
4.23
Note: Lowercases mean followed by the same letter aren't significantly different between forest floor fuels (Duncan's MRT, p=0.05)