KUCHLER TYPE FIRE ECOLOGY AND MANAGEMENT
KUCHLER TYPE: Subtropical Pine Forest



FUELS, FLAMMABILITY, AND FIRE OCCURRENCE : 
Fuels:  Most fires in subtropical pine forest are surface fires that
consume only litter and understory vegetation.  Fuel conditions are
favorable to fire.  Slash pine needles accumulate and decompose only
slowly.  The grassy herb layer, which contributes a small amount of
fuel, keeps pine needles from forming a dense mat.  The open canopy
allows fuels to dry rapidly; fire is possible within a day after rain
[33].  Wade [42] assigned a figure of 6,000 Btu per pound of fuel for
all slash pine ecosystem fuels.  The rates of fuel accumulation and
decomposition reach equilibrium within about 10 years in southern
Florida [33,42].  Frequent fire (every 2-3 years) keeps fuels from
accumulating to levels which support fire severe enough to damage and
kill overstory south Florida slash pine.  Fires within subtropical pine
forest are usually extinguished at interfaces with hardwood hammocks:  A
fire with flame lengths greater than 3.3 feet (1 m) burning through pine
can reach a hammock margin and die out in seconds [33].

Fire Occurrence:  Big Cypress National Preserve and Everglades National
Park are probably the most fire prone units within the National Park
Service system.  From 1948 to 1979, Everglades National Park fire
records include 682 fire reports and 451,082 acres burned.  The first 21
months of Big Cypress fire records (after its establishment in 1974)
documented 131 fires that burned 40,370 acres [36].  In 1979, 81
reported fires burned 23,140 acres in Big Cypress Swamp.  Nearly all of
the fires in Big Cypress Swamp ocurred in sawgrass prairies, dwarf
cypress (Taxodium distichum var. nutans) savannas, and pinelands.  Much
of the pineland in Big Cypress Swamp is pine flatwoods, which probably
constitutes most of the pineland area burned, but some of the area
burned was probably subtropical pine forest [40].

Much detail concerning the fire history of Everglades National Park is
reported by Taylor [38].  Between 1948 and 1979 there were 682 recorded
fires that burned 451,082 acres (257,246 ha) within park boundaries (an
additional 251 fires burned 480,080 acres (192,032 ha) outside park
boundaries but within the Everglades Fire Protection Zone in the same
period).  Lightning fires accounted for 22 percent of all fires in the
protection zone (both within and outside of the park), but only about 10
percent of the burned area.  Peak lightning fire incidence was in June.
During the same period within the protection zone, 89,607 acres (35,842
ha) were burned by prescribed fire and 747,839 acres (299,136 ha) were
burned by fires started either intentionally, but outside of official
management plans, or accidentally.  Of all the unauthorized fires
started by humans, 41 percent were ignited on a Sunday, which coincided
with peak hunting or recreational use [38,40].

Presettlement Fire Frequency:  Hoffmeister [17] suggested that
limestones in southern Florida were most recently exposed around 5,000
years before present.  Other evidence indicates, however, that emergence
may have been much earlier.  Archeological materials found in the area
have been dated at 8,000 years before present, which is also consistent
with evidence from the rate of sea level rise [27].  In addition,
several calciphilic plants are unique to the rocklands of southern
Florida; many have no apparent adaptations for long-distance dispersal
which suggests a period of evolution in situ [33].  It is generally
assumed that lightning fire has always been important in southern
Florida fire regimes [32,36,38].  There is much evidence supporting the
idea that fires were common [36].  Based on current ecological
relationships, Snyder and others [33] inferred that Miami Rock Ridge
pine forests were maintained by fire at 3- to 15-year intervals: longer
intervals would have resulted in succession to hardwoods, shorter
intervals would have limited south Florida slash pine regeneration.
Wade [42] suggested that southern pinelands probably burned every 2 to 3
years in presettlement times.  Both Robertson [29] and Taylor [36]
believe that historic natural fires were lightning caused, occurred
during the summer months, and burned several thousand acres during
drought intervals of about 8 years.  It is likely, however, that
aboriginal fires substantially increased fire frequency over some
background level and fires occurred in the dry season [32,36].

Current Fire Regime:  In the Everglades lightning fires have little
chance to spread because of roads, canals, and artificially high water
levels maintained in Shark Slough during the dry season.  The present
annual average of 2,540 acres burned by lightning fires would result in
a burning cycle of more than 200 years for the fire-prone communities of
Everglades National Park [36].  Based on 10 years of fire records for
all fire types (presumably including incendiary and accidental fires),
Snyder [32] estimated that Big Cypress pinelands currently have a 7-year
fire return interval.


FIRE EFFECTS ON SITE : 
Surface fire in subtropical pine forest consumes aboveground organic
matter and often leaves bare rock substrate [43].  Prescribed fires in
subtropical pine fores in Dade County volatilized 1-1.5 kg/sq m of
organic matter and 5.7-9.5 g/sq m of nitrogen (as N).  Losses of
phosphorus, potassium, calcium, and magnesium were not detectable,
except for potassium in one plot.  After the fires, litter mass and
nutrients often showed an initial decrease before recovery began.  At 1
year, litter mass was 42-62 percent of the prefire amount.
Meteorological inputs and symbiotic plus nonsymbiotic fixation should
easily replace the nitrogen lost to fire [56].

Prescribed fire is used for seedbed and site preparation:  Germination
and survival of slash pine is best on mineral soil, although mineral
soil exposure is not an absolute requirement [42].


FIRE EFFECTS ON VEGETATION : 
Fire Effects on South Florida Slash Pine:  South Florida slash pine is
more resistant to fire than the typical variety of slash pine (Pinus
elliottii var. elliottii) [21].  South Florida slash pine seedlings have
a grasslike, almost stemless stage lasting from 2 to 5 years, a thick
taproot, and heavy wood [1,34].  Less than 0.1 percent of typical slash
pine seedlings survived a wildfire that occurred 2 years after they were
planted.  In contrast, 23 percent of south Florida slash pine seedlings
survived a head fire and 56 percent survived a backing fire [21].  There
has been, however, a lack of seedling establishment in Everglades
National Park subtropical pine forests, even with 3-to 7-year fire-free
intervals.  Loope and Dunevitz [24] speculated that this lack of
establishment may be caused by an absence of favorable sites (i.e., all
sites are occupied by long-established vegetation).  They believe that
less frequent but more severe fire may be necessary to create conditions
favorable for south Florida slash pine establishment [24].

Recruitment of south Florida slash pine in subtropical pine forest is
usually limited to open areas where the pine overstory has been killed
by fire.  Reduction of the overstory in even-sized stands by thinning or
fire is likely to be important for regeneration [8].  A comparison of
stand characteristics among subtropical pine forest stands that were
virgin and unmanaged (i.e. no prescribed fire); second-growth and
managed; and virgin and managed showed the highest degree of similarity
between the two managed stands.  These stands are both composed of
medium-sized trees and have lower species diversity than the virgin
stand that has been fire free for a number of years.  Uniformity of tree
size could be explained by the formation of a dense population of
seedlings which would prevent further seedling establishment.  The
second-growth stand was established as an even-aged stand in the large
openings left after logging, and the virgin stand was speculated to have
lost large trees to fire which created openings for seedling
establishment [8].  Season of fire may have a critical effect on
seedling establishment.  Snyder [56] reported that there was a
pronounced increase in the establishment of new south Florida slash pine
seedlings after a wet season prescribed fire.  Wet season burn plots had
much higher seedling densities 1 year after the fire than did plots
burned in the dry season.  Seedfall occurs from September into November;
prescribed fires in the dry season after seedfall destroy the current
year's seed crop and by the following year conditions are less favorable
for seedling establishment [56].

Small south Florida slash pine, 6.6 to 19.8 feet (2-6 m) tall, have a
greater than 50 percent probablilty of surviving a hot surface fire
[34].  In mature trees, the long needles shield vulnerable apical buds
from fire and the bark is thick and insulating [33].  Although fires do
not normally kill overstory south Florida slash pine, wildfires during
drought years can cause high mortality [39].  Wade and Johansen [44]
reported that older south Florida slash pine were killed by a prescribed
fire in southern Florida dry prairie even though no scorch was observed,
and there was no outward evidence of injury or infestation.  They
speculated that the fire killed the upper feeder roots of all trees;
younger trees were able to produce new rootlets quickly and thus
survived [44].  Doren and others [8] suggested that the absence of large
trees from managed virgin stands of subtropical pine forest was a result
of introducing fire after a long fire-free interval.  They speculated
that the large trees were killed by fire because fuels built up around
the bases during the long period without fire that occurred prior to the
institution of prescribed fire management in Everglades National Park.
Similar mortality was observed after the application of prescribed fire
during a drought year in areas that had not experienced fire for decades
[8].  Mature south Florida slash pine seldom ignite at the base when
struck by lightning (even though the tree may be killed) and stands are
usually too open to carry crown fire [34].

Fire Effects on Understory Vegetation:  Recovery after fire occurs first
among the herbaceous plants, which sprout quickly from underground
organs.  Fire stimulates many species to bloom, particularly firegrass.
In many cases, this stimulation also results in synchronous blooming
among all members of the same species.  Other grasses following fire are
bushy bluestem (Andropogon glomeratus), pullup muhly (Muhlenbergia
filiformis), and lopsided indiangrass (Sorghastrum secundum) [30].  Many
herbs flower infrequently except in recently burned areas; these include
Florida mock grama (Tripsacum floridanum), Brazilian satintail (Imperata
brasiliensis), shortleaf gayfeather (Liatris tenuifolia var.
quadrifolia), sweet shaggytuft (Stenandrium dulce), and bejuco colorado
(Ipomoea microdactyla).  Fire can shift the blooming period for some
species, but this is usually only noticeable for species with short
flowering periods.  For example, summer fire shifted the flowering
period of slender gayfeather (Liatris gracilis) from September-October
to December-January [33].  Coontie, which has been reported to reproduce
following fire, did not flower after a severe prescribed fire on a study
plot that had gone two decades without fire [35].  

The grass-dominated stage of postfire succession usually lasts for one
season [29,30].  After 2 or 3 years, the shrub understory largely
recovers dominance [30].  Seedlings of hopbush and shining sumac have
been observed in the first year after a fire and therefore are probably
derived from soil seedbanks [33].  False tamarind and trema (Trema
micranthum) are weedy species that pioneer on burned pinelands [41].
Most hardwoods regenerate by sprouting after fire.  Fruiting is
typically eliminated for 1 to 2 years but sprouting usually results in
an increase in stem numbers over prefire conditions [33].

In Long Pine Key (a region of the Everglades containing subtropical pine
forest), prescribed fires have been conducted since 1958 and their
effects have been monitored.  In a study spanning 1958 to 1980, there
were 8 recorded wildfires and 26 prescribed fires.  By 1980, the number
of shrub stems (all species) was 92 percent of the original number of
stems over all the study plots.  On some plots, stem numbers had
increased.  The most common shrubs on burned plots were saw-palmetto,
velvetseed, and Guianese colicwood (Myrsine floridana).  Silverpalm
increased by 82 percent on burned plots.  Saw-palmetto was within 7
percent of original numbers.  Other species increasing with prescribed
fires included hopbush, shining sumac, tetrazygia, and southern
bayberry.  Poisonwood showed an overall decline of 41 percent;
poisonwood spreads easily in the absence of fire [39].

Fire Effects on Successional Processes:  Fire maintains subtropical pine
forest by reducing hardwood competition [6,7,10,30,33,44].  There are
usually few changes in species occurrence, but relative importance
shifts after fire [33].  A single fire kills few hardwoods because roots
are deep in the limestone substrate.  There is some evidence that
hardwoods are killed with annual or biennial fire, and are replaced by
an understory of low palms, especially saw-palmetto [39].  This would
effectively shift species composition from subtropical pine forest to
pine flatwoods.  Palms are rarely killed by fire; usually all expanded
leaves are consumed or killed but apical buds are unaffected.  New leaf
and flowerstalk production is uninterrupted by fire [33].

Effects of Fire Exclusion:  Fire exclusion usually allows understory
hardwoods to attain subcanopy status [39].  Understory hardwoods grow
6.6 to 13.2 feet (2-4 m) in the 3- to 7-year intervals between
prescribed fires in Everglades National Park [24].  The herbaceous
understory is shaded out by hardwood growth in as little as 15 to 25
years without fire [39].  In a subtropical pine forest that had not
experienced fire for 35 years, the hardwood understory formed dense
growth 10 to 26 feet (3-8 m) tall with emergents up to 43 feet (13 m)
tall [24].

Fire exclusion in Big Pine Key was associated with a doubling in the
number of slash pine stems over an 18-year period, most of which were
under 12 feet (3.6 m) tall.  Interpretation of the vegetation response
in the study was complicated by drought conditions and the nearby
construction of mosquito-control ditches, which altered the hydroperiod
[2].  Nearby, No Name Key was heavily invaded by hardwood hammock
species with fire exclusion over the same period [3].


FIRE EFFECTS ON RESOURCE MANAGEMENT : 
Vertebrates are rarely killed by prescribed fire in Miami Rock Ridge
pine forests.  Fire reduces cover and shade, and creates conditions
where temperatures are more extreme at and near ground level.  Animals
that require sheltered conditions move out after a fire, whereas those
that use exposed stands move in.  Following a fire in Long Pine Key,
populations of hispid cotton rat decreased but those of cotton mouse
(Peromyscus gossypinus) increased [18].  Emlen [52] recorded no
difference in resident bird species compositon or abundance after
prescribed fire on Long Pine Key.

Many pinelands in the southern Atlantic Coastal Plain are managed for
game birds, particularly northern bobwhite (Collinus virginianus) and
wild turkey (Meleagris gallopavo).  Quail production in southern Florida
is enhanced by burning one-third to one-half of a management block per
year (a 2-3 year rotation).  It is recommended that prescribed fires be
completed before the nesting period begins in March [25].

Little is known about habitat use by Big Cypress fox squirrels which
occupy subtropical pine forest.  It has been speculated that protection
from fire has had a negative effect.  Many pinelands in Big Cypress
Swamp have a dense understory of saw-palmetto, which is undesirable
habitat for Big Cypress fox squirrels [20].  Lack of fire in subtropical
pine forest and other pinelands may have contributed to the decline of
American kestrel (Falco sparverius paulus) in Florida [16].

Red-cockaded woodpecker habitat is maintained by fire.  They abandon
tree cavities if the understory vegetation grows to the height of the
cavity, they do not forage in areas where the understory vegetation is
dense, and the pines they depend on for cavity trees establish only in
openings created by fire [54].


FIRE USE CONSIDERATIONS : 
The original plans for prescribed fires in pinelands in the Everglades
included mostly backing fires, with headfires to be used where hardwood
succession was more advanced [39].  However, 15 to 20 years of fire
exclusion in Miami Rock Ridge pine forests allows hardwoods to become
large enough to create conditions that limit fire spread (i.e., high
humidity coupled with a lack of ground-level vegetation and fuels);
high-intensity fire can carry in these hardwoods but usually damages
surrounding pine.  Backfires can be used to reintroduce fire to pine
stands with overgrown hardwoods.  Wherever the hardwood understory was
dense, Werner [45] was successful in employing repeated backing fires to
open up the understory.  The first several burns were patchy and left
pockets of dense hardwoods untouched.  Very frequent (2 year) burning as
soon as fuels are adequate to carry fire eventually allowed hardwood
control [22,44].

Once hardwoods are controlled, fires should be somewhat less frequent:
annual and biennial fires may result in a decrease in understory species
diversity and domination by saw-palmetto [29].  Backing fires have
little or no adverse effect on south Florida slash pine, providing the
trees are over 12 feet (3.8 m) tall [14].  Light backing fires generate
sufficient heat to top-kill most hardwoods up to 0.75 inch in basal stem
diameter.  Backfires, however, are often impractical for large areas
because of the time required; therefore, short running headfires are
considered the best method for prescribed fire in pine understories
where hardwoods are not overgrown [39].

Wade [42] reported a range of fireline intensities and predicted effects
on slash pine.  The optimum range for the typical variety is 21 to 75
Btu's per foot per second (73-260 kW/m) with flame lengths of 0.5 to 2.5
feet (0.2-0.8 m).  At this level of intensity, there are usually no fire
control difficulties and scorch heights are generally below 15 feet (4.6
m).  With moderate, persistent in-stand winds and low ambient
temperatures, scorch heights will be lower.  South Florida slash pine
can withstand higher fireline intensities than the typical variety [42].


FIRE MANAGEMENT CONSIDERATIONS : 
Human activity has greatly increased the number and destructiveness of
fires because drainage of southern Florida has intensified and prolonged
the normal dry season [6] and because fire suppression has allowed a
heavy buildup of fuels.

Recognition of the abnormal conditions created by fire exclusion led to
prescribed fire plans for Everglades pine forests by 1956.  Until 1981,
prescribed fires were conducted primarily in the winter dry season
[5,18,19,39] at 3- to 7-year intervals [5,24].  Since 1981, wet-season
fires have been conducted in order to create conditions that are similar
to the presettlement fire regime [5,32,33,39].  Summer fires are more
effective at killing hardwoods than winter fires but are twice as
damaging to the overstory pines [13].  A series of summer fires at short
intervals will generally eradicate many hardwood rootstocks [12].  Fires
after south Florida slash pine seedfall in early autumn kill seed crops
and young seedlings.  If pine reproduction is lacking, however, fire
should be conducted before the next seed fall.  Good seed crops can be
predicted by numbers of maturing cones [43].

Brazilian pepper has the potential to dominate the understory of
subtropical pine forests.  Brazilian pepper-dominated understories
prevent south Florida slash pine seedling establishment.  Most Brazilian
pepper survive fire once they are 3.3 feet (1 m) tall or more by
sprouting after top-kill.  Fire-free intervals greater than 7 years,
considered as possibly necessary for south Florida slash pine
establishment after severe fire, could create conditions allowing
Brazilian pepper establishment.  Should this occur, the use of
herbicides to kill Brazilian pepper may be necessary [24].


REHABILITATION OF SITES FOLLOWING WILDFIRE : 
NO-ENTRY

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