More info for the terms:
backfire,
basal area,
competition,
fire management,
flame length,
forest,
fuel,
hardwood,
litter,
prescribed fire,
series,
successionPrescribed fire is used in loblolly pine stands for seedbed preparation,
hardwood control, fuel reduction, and thinning. Unless thinning of
seedlings is desired, stands should not be burned before they are large
enough to withstand injury. To avoid crown scorch, loblolly pine should
be 10 to 15 years old, 15 to 20 feet (4.6-6.1 m) tall, and have a bark
thickness of 0.3 to 0.4 inch (0.8-1.0 cm) before being burned for the
first time [
2,
7,
41,
37,
59,
65]. To avoid mortality but not crown scorch,
trees smaller than 8 feet (2.4 m) tall or less than 2 inches (5 cm) in
diameter at groundline should not be burned [
11]. The first fire is
difficult because of excess fuel build-up and danger to young pines. A
backfire should be used in cool weather and high moisture conditions.
Hardwood control: Hardwoods smaller than 4 inches (10 cm) in diameter
can usually be controlled by frequent fire [
62]. Hardwood recovery
takes 5 to 10 years, depending on the site quality. Using prescribed
fire every 5 years or when 25 percent of the largest hardwood stems are
approaching 1 inch (2.5 cm) in diameter is recommended [
41,
42].
A single winter fire is effective at controlling 1-inch-diameter (2.5
cm) hardwoods [
41]; periodic winter fires can control hardwoods up to 2
inches (5 cm) in diameter; and a summer fire can control hardwoods up to
4 inches (10 cm) in diameter [
59]. Although prescribed burns are
usually conducted during winter to avoid injury to loblolly pine, summer
burning is a more effective control of hardwood competition [
23].
Twenty years of annual summer burning completely eradicated hardwoods
from a loblolly pine forest in South Carolina [
62,
63]. However, a
series of annual winter fires will not eradicate hardwoods because root
stocks are not killed. Three annual summer fires at mid-rotation,
followed by periodic winter fires may be an effective means of hardwood
control [
42]. Infrequent low-severity surface fires may speed up
succession to hardwoods by increasing the number of hardwood sprouts
[
14].
Seedbed preparation: A low-severity summer prescribed fire,
approximately 1 month before seedfall, is the most effective seedbed
preparation [
19,
41,
42,
57]. If only a winter fire is used, hardwoods
have an entire growing season before loblolly pine seedfall [
41,
57]. A
winter fire 1 to 2 years prior to a summer fire is suggested to reduce
fuel buildup. A winter fire, followed by three annual summer fires just
before harvest, was very effective [
52]. Brown and burn treatments have
also proven effective [
6].
Thinning: Prescribed burning has been used successfully to thin young
loblolly pine stands. However, the forest manager risks damaging the
entire stand and reducing the growth rate. A prescribed fire in South
Carolina resulted in a 58 percent reduction in stems per acre and near 0
percent mortality in 1 inch (2.5 cm) diameter and larger saplings [
61].
Thinning with fire should only be done in stands with a wide range of
diameters [
45].
Disease and insects: In the Coastal Plain, prescribed burning before
and after thinning reduced infection by root rot (Heterobasidion
annosum). The fire destroyed litter which is associated with sporophore
development of H. annosum. A fungal competitor (Trichloderma spp.)
increased in the soil after burning and may have contributed to the
reduced infection [
25].
Fire wounds 4 to 6 inches (10-15 cm) wide and larger can result in cull
from fungi, insect action, or high amounts of resin [
26]. The black
turpentine beetle (Dendroctonus terebrans) attacked trees with fire
wounds in east Texas [
24].
Nutrients: It is unclear whether prescribed fire on loblolly pine sites
will increase or decrease the available nitrogen. Fire volatilizes
nitrogen in the soil, and repeated burning on infertile sites may limit
productivity [
33]. However, decomposition of burned material increases
the available nitrogen content of soil. Consequently, light prescribed
fire may be a low-cost alternative to fertilizer [
50,
64].
FIRE CASE STUDY
SPECIES: Pinus taeda
FIRE CASE STUDY CITATION : Carey, Jennifer H., compiler. 1992. Hardwood control for loblolly pine seedbed
preparation in Georgia. In: Pinus taeda. In: Fire Effects Information System,
[Online]. U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).
Available: https://www.fs.fed.us
/database/feis/ [
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REFERENCE : Brender, Ernst V.; Cooper, Robert W. 1968. Prescribed burning in
Georgia's Piedmont loblolly pine stands. Journal of Forestry. 66(1):
31-36. [
8].
SEASON/SEVERITY CLASSIFICATION : Summer strip head fire/low- to moderate-severity
Summer backfire/low-severity
Winter strip head fire/low- to moderate-severity
Winter backfire/low-severity
STUDY LOCATION : The study was conducted in the Hitchiti Experimental Forest near Macon,
Georgia, in the rolling hills of the lower Piedmont.
PREFIRE VEGETATIVE COMMUNITY : The overstory consisted of 100 square feet basal area per acre (23 sq
m/ha) of 40-year-old loblolly pine (Pinus taeda). Small understory
hardwoods included flowering dogwood (Cornus florida), sweetgum
(Liquidambar styraciflua), blackgum (Nyssa sylvatica), hawthorn
(Crataegus spp.), oak (Quercus spp.), hickory (Carya spp.), and winged
elm (Ulmus alata). There were 750 small hardwoods per acre (1,850/ha)
from 0.6 to 6.5 inches (1.5-16.5 cm) in diameter and approximately 5,000
smaller stems per acre (12,000/ha). Hardwoods made up 22 square feet
basal area per acre (5 sq m/ha).
TARGET SPECIES PHENOLOGICAL STATE : NO-ENTRY
SITE DESCRIPTION : The terrain was gently rolling with 10 to 20 percent slope. Litter
accumulation was 4 to 8 tons per acre (9-18 metric tons/ha) of which
approximately 10 to 45 percent was hardwood litter. The humus type was
shallow duff-mull.
FIRE DESCRIPTION : Twenty plots of 1.5 acres (0.6 ha) each were randomly assigned to 5
different treatments: summer backfire, summer strip head fire, winter
backfire, winter strip head fire, and no fire. Backfires were run down
slope and head fires up slope. A complete stand inventory by species
and 1 inch (2.5 cm) diameter classes, a tally of stems less than 0.6
inches (1.5 cm) on 15 milacre quadrants, and litter fuel weights and
moisture were taken before and after the fire. The following
fire-weather measurements were taken: wind direction and speed, air
temperature, relative humidity, rate of flame spread, flame length,
depth of fire front, and time-temperature relationships at 1- and 4-foot
(0.3-1.2 m) heights. Soil erosion and seedling regeneration in milacre
quadrants were evaluated after the fire. Each plot was further
subdivided for repeat fires. The repeat fire data will not be discussed
here because of difficulties and inconsistencies encountered with the
fires.
The following tables present fire data:
fire rate of spread litter consumption energy release
ft/min percent Btu/min/ft
winter back 1.4 38 1232
summer back 1.2 46 1200
winter strip 8.8 40 8448
summer strip 10.0 53 11200
fire temperature duration
deg. C
winter strip-1 ft 255 24 seconds above 200 degrees
winter strip-4 ft 130 43 seconds above 100 degrees
summer strip-1 ft 480 22 seconds above 400 degrees
summer strip-4 ft 220 27 seconds above 200 degrees
FIRE EFFECTS ON TARGET SPECIES : Summer fires top-killed more hardwoods than winter fires. The following
table shows the percentage of hardwoods top-killed by summer and winter
fires:
d.b.h. class summer kill winter kill
inches percent percent
1 96 73
2 64 73
3 33 12
4 18 7
5 15 8
6 13 0
There was no significant difference in percent hardwoods top-killed
between backfires and strip head fires.
Fuel consumption was greater in the summer than in the winter.
Loblolly pine seedlings were more abundant and better distributed on burned
plots than unburned plots. Seedlings were also more abundant on plots burned in
the summer than in the winter. The percent milacre stocking of
seedlings was 57 percent on the control, 77 percent on the winter fire
plots, and 90 percent on the summer fire plots.
Soil erosion was minimal, and no difference was found between season or
method of burning.
FIRE MANAGEMENT IMPLICATIONS : A single strip fire in the summer is the best method for removing
hardwoods and preparing an adequate seedbed. Although there were no
significant differences between head strip fires and backfires, head
strip fires were cheaper and easier to control. A summer strip fire
should only be conducted, however, if fuel accumulation is less than 10
tons per acre (22 metric tons/ha). Optimum summer fire conditions were
a litter moisture content of 10 to 20 percent, a relative humidity of 20
to 60 percent, and a steady wind speed of 1 to 5 miles per hour (1.6-8
km/h).