FIRE EFFECTS
SPECIES: Pinus palustris | Longleaf Pine 



IMMEDIATE FIRE EFFECT ON PLANT : 
Open-grown grass-stage seedlings with root collar diameters smaller than
0.3 inch (0.8 cm) can be killed by light fire [7,29].  Under a pine
overstory, light fire can kill seedlings smaller than 0.5 inch (1.3 cm)
in diameter, because excess pine litter under the canopy makes the fire
hotter [3,18,44].  In a prescribed winter fire in Alabama, 1-year-old
seedlings with exposed root collars were more susceptible to fire than
seedlings with root collars at or near the soil surface [33].  Larger
grass-stage seedlings are highly resistant to fire.

In the height-growth stage, seedlings 1 to 3 feet (0.3-0.9 m) tall are
extremely vulnerable to fire [20,29].  If the terminal bud is destroyed,
the seedling will die [37].  Once a seedling is about 3.3 feet (1 m)
tall, it is likely to survive low-severity ground fires [38].  After the
sapling is 10 feet (3 m) tall, it is very fire tolerant [54].  Trees 10
inches (25 cm) in diameter and larger survive all but the most severe
fires [10].  A high-severity crown fire kills some mature trees and
nearly all trees smaller than 10 inches (25 cm) in diameter [20].

Longleaf pine needles were killed instantly when immersed in water at
147 degrees Fahrenheit (64 deg C) but survived 11 minutes at 126 degrees
Fahrenheit (52 deg C) [14].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Fire can stimulate height-growth initiation of grass-stage seedlings.
After three annual spring fires in Louisiana, most grass-stage seedlings
had initiated height growth.  It is thought that height growth is
initiated because fire reduces competition and brown-spot needle blight
infection.  Late spring or summer fires are more effective at promoting
height growth than winter fires [12,13,23].  However, annual fires begun
only 1 year after germination stunt height growth [20].

Once a seedling has entered the height-growth stage, fire damage can
decrease growth.  Annual fires have reduced basal area growth of young
longleaf pine by 22 to 44 percent [54].  In Alabama, prescribed biennial
fires begun in 14-year-old stands averaging 22 feet (6.7 m) in height
and 3.2 inches (8.1 cm) in diameter reduced growth, even though no crown
scorch was observed.  The impact on growth of biennial fires worsened
with time.  The season of fire had no effect [6].

Older longleaf pine shows no growth loss if there is little or no needle
scorch [29].  Seed production of mature trees is not affected by
frequent fire.

Seed will germinate on mineral soil exposed by fire [7].

Trees in regularly burned stands develop a buttressed trunk which
results in stump taper [1].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Prescribed burning in longleaf pine stands is used to control brown-spot
needle blight, stimulate height growth, reduce excess fuel, control
understory hardwoods, improve wildlife habitat, thin stands, and prepare
a mineral seedbed [18,54].

Fire consumes foliage infected by brown-spot needle blight as well as
inoculum in fallen leaves [29,54].  Burning is recommended when
infection levels are greater than 20 percent and grass-stage root
collars are larger than 0.3 inches (0.8 cm) in diameter or height-growth
stage seedlings root collars are greater than 1.5 inches (3.8 cm).  If
the infection rate is higher than 20 percent, a high percentage of
affected seedlings will die from the fire [18,35,45].

Annual spring fires are recommended to initiate height growth once
grass-stage seedlings are large enough to withstand fire.  In the
spring, the green grass keeps the fire cool, and buds are protected by
long sheaths of needles.  However, grass-stage seedlings grown on poor
sites may not tolerate light fire [12].  Once height growth begins, the
stand should not be burned for several years and then burned less
frequently [23].

Late annual spring fires are recommended to gain control of hardwoods.
Summer fires are also effective, but the risk of pine mortality is
increased [8].  Hardwoods are susceptible to fire in the late spring and
summer because root reserves are low.  Once hardwood populations are
reduced, winter fire at 5-year intervals maintains longleaf pine stands,
and enables a single fire in the spring or summer before seedfall to
expose the necessary mineral soil seedbed [18,53].

Although longleaf pine regeneration is rarely excessive [2], a stand can
be thinned by fire.  In Alabama, a prescribed winter fire thinned a
1-year-old stand from 177,000 seedlings per acre (437,000/ha) to 6,300
per acre (15,600/ha) [33].

Frequent late spring or early summer fires are necessary to recreate the
longleaf pine-grassland savannahs that were common in presettlement
times [44].

Related categories for Species: Pinus palustris | Longleaf Pine