KUCHLER TYPE FIRE ECOLOGY AND MANAGEMENT
KUCHLER TYPE: Cypress savanna



FUELS, FLAMMABILITY, AND FIRE OCCURRENCE : 
Fuels:  On the driest sites, rapid decomposition and occasional flooding
prevent organic matter accumulation [17].  Most of Big Cypress Swamp,
however, is covered with sufficient fuel to carry fire.  Occasional
freezes may influence fuel characteristics by killing back the
cold-sensitive vegetation and increasing litter [39].  Mean standing
stock of litter in a dwarf cypress savanna was 344 (+/- 94) grams per
square meter [3].

In years of average precipitation, fires may burn in grasslands and
dwarf cypress savanna, but will not burn very far into the middle of
cypress domes or strands.  Conversely, in a drought year fire may be
more severe in the centers of domes and strands than on the edges.  When
peat is dry enough to burn, the larger amount of litter and organic
material in the center will support a more severe fire than on the
edges.  Fires that consume peat may kill trees due to root damage and
loss of structural support.  Fires are rarely severe enough to kill
trees in dwarf cypress savanna because of sparse organic matter [3,6].

Flammability:  In cypress swamps, ericaceous evergreen shrubs are
particularly flammable community members [17].  

Cypress domes and strands and hardwood swamps probably constituted
natural barriers to the spread of wildfire in presettlement times; fire
burning in grasslands and savannas around cypress domes would burn into
the dome only as far as soil and vegetation moisture levels would
permit.  Drainage of these wetlands has increased the flammability of
cypress domes [42].

Fire During Presettlement Human Occupation:  Human occupation occurred
within a few hundred years of vegetation establishment in southern Florida
[39,24].  Most cypress swamps in southern Florida contain evidence of past
fires [42].  It is generally assumed that lightning fires have always
been an important factor in southern Florida fire regimes.  Prior to
European settlement, human-caused fire may have substantially increased
fire frequency over the background frequency of lightning fires
[14,38,39].  It is likely that most Native American-caused fires were
set in the dry season, as soon as fuels could carry fire [39].

Fire in the Postsettlement Period:  The frequency of fires increased
with European settlement of southern Florida.  Fires were set for numerous
reasons and many fires were started through carelessness or accident.
Drainage of swamps increased the frequency and intensity of fires, with
concomitant severe damage to peat exposed by drainage [41].

Fire Frequency:  The Everglades and Big Cypress National Preserve are
the most fire-prone ecosystems in the National Park Service system.
Southern Florida experiences 70 to 90 thunderstorm days per year, the
highest number of any area in the United States.  The mean annual number
of ground strikes is from 4 to 12 per square kilometer.  Most of the
cloud-to-ground strikes occur during the wet season and 87 to 93 percent
of lightning fires occur from May to August; lightning fires have been
recorded in all months except January and February.  Fewer strikes but
more lightning fires occur in the Everglades than in Big Cypress Swamp
[39,41].  Taylor [41] estimated that the interval between extreme fire
years (years in which a very large number of fires or large number of
acres burned) in the Everglades is 5.8 to 7.5 years, and that there is a
moderate fire season every 3.2 years.

In southern Florida, widespread and severe fires occurred in more than
one-third of the years between 1900 and 1952.  In very dry years,
organic soil fires occasionally burned from one dry season to the next,
through the normally wet summer months.  Between 1948 and 1979, there
were 682 fire reports and 451,082 burned acres in the Everglades.  For
the first 21 months of fire records for Big Cypress (starting in 1979),
there were 131 reported fires, which burned 40,370 acres (16,716 ha).

Many fires in Big Cypress burn out before discovery.  Both Parks have
been disturbed by drainage, logging, farming, off-road vehicle use, and
invasion by exotic species, all of which affect fire frequency to some
extent.  Other changes in fire intensity, frequency, and type have come
from fire suppression, prescribed fire programs, and incendiary fire.
Wildfires and incendiary fires are extinguished [41].  Wet-season
prescribed fires have replaced dry season lightning fires in many
grasslands.  Drainage has decreased hydroperiods and increased
flammability of peat [5,41].

In Big Cypress Swamp, lightning-caused fire is minor relative to
human-caused wildfire and prescribed fire.  Human-caused wildfires occur
in the dry season, and are strongly correlated with moisture conditions
[39].  Of the 1,068 fires recorded in Big Cypress Swamp from 1979 to
1988, about four-fifths were incendiary or accidental [39].  The number
of fires is positively correlated with peak backcountry use during wild
turkey season in March and concides with dry conditions.  "Sunday is a
particularly popular day for starting fires" [39].
  
The average fire return interval for all community types in Big Cypress
is approximately 12 years [39].  Cypress in dwarf cypress savanna show
fire scars and may reveal fire frequency in the dwarf cypress type;
however, the slow growth of the trees makes interpretation of rings
difficult [41].  Snyder [39] estimated the fire return interval for
dwarf cypress savanna as 24 years.  Wade and others [42] reported an
estimate of seven to nine fires per century in dwarf cypress savanna.
Cypress-mixed hardwood strands and cypress domes have a fire return
interval of 110 years according to Snyder [39], but Ewel [17] stated
that they experience three to five fires per century.  Strands appear to
have longer fire rotations than domes or dwarf cypress savanna [42].


FIRE EFFECTS ON SITE : 
Peat based habitats such as cypress domes and strands can support both
ground and surface fires.  Fire may remove aboveground vegetation only
or may also consume peat.


FIRE EFFECTS ON VEGETATION : 
The effects of fire on southern Florida ecosystems are compounded by
changing hydrologic relationships.  Presettlement fires had different
effects than current fires due to human-caused changes in drainage
patterns, fire frequency, and the introduction of exotic species [42].

Cypresses survive surface fires better than competing hardwoods [20].
Low-severity surface fires therefore tend to maintain monospecific
cypress stands by suppressing hardwood regeneration and killing young
hardwoods [9,17].  For example, in Okefenokee Swamp, woody species
invade peat islands between fires but most are killed by fire [12].
Young cypress trees (less than 200 years old) may sprout after fire if
damage to roots is slight.  Sprout production and viability decline with
tree age [5].

The characteristic rounded shape of cypress domes and strands appears to
be related to peat depth, fire frequency, and site conditions.  In
Corkscrew Swamp, trees are generally larger and older on sites with deep
peat.  The deeper peat is in contact with water for longer periods and
dries out more slowly.  Fires are therefore more frequent and more
severe on the edges of domes and strands than in the center where peat
is deepest.  The less frequent the fire on a microsite, the more likely
cypresses will survive to larger size.  Outside the strand, hydrologic
conditions favor fire that is frequent enough to kill young cypress
trees before they can grow large enough to survive low-severity fire;
the community is therefore maintained as grassland.  In Gordon Swamp, a
small cypress strand on the edge of Corkscrew Swamp Sanctuary, a
different pattern was recorded.  Peat depth increased towards the center
of the strand, but tree size was uniform (rather than increasing in the
center) and trees were younger in the center of the strand.  This
situation was probably caused when fire killed trees in the center but
not the edges.  Following fire, newly established cypresses grew faster
than the trees on the edges of the strand.  Better site conditions in
the center may have contributed to faster tree growth; relative sizes of
trees may be partly due to the poor condition of fire-damaged trees on
the strand edge.  Strands and domes probably expand and contract in
response to fire occurrence and hydrologic conditions.  During extreme
drought, even large strands and domes may experience stand-replacing
fire [12].

In a north-central Florida cypress dome, a wildfire killed most shrubs,
hardwoods and pines, but killed less than 50 percent of the dominant
cypress trees.  By 3 years after the fire, the study site flora was
composed almost completely of cypress, but the site was being colonized
by hardwoods and shrubs [20].

Gunderson [25] proposed a conceptual succession model for southern
Florida swamps that shows the effects of logging and fire on cypress and
mixed hardwood swamps.  After logging, mixed hardwoods and remnant
cypress are maintained in the absence of fire.  With a severe fire,
willow (mostly Coastal Plain willow) colonizes open areas.  Willows are
maintained by repeated fire, but in the absence of fire succeed to mixed
hardwoods.  After logging, stands of mixed hardwoods and remnant cypress
may experience low-severity fires, which favor cypress over hardwoods,
and could return the stand to conditions approximating the prelogging
conditions.  In the absence of fire, cypress regeneration returns the
stand to a mixed swamp (cypress and hardwoods, but with continued lack
of fire succession to mixed hardwoods occurs).  Cypress and mixed
hardwood stands may be converted to monospecific cypress forests by
surface fires; in the absence of fire, monospecific cypress stands are
invaded by hardwoods.  With severe fire, monospecific cypress stands and
cypress and mixed hardwood stands are converted to willow and remnant
cypress stands.  Willow-remnant cypress stands may develop to
monospecific cypress stands with occasional surface fires, if cypress
regeneration occurs.  More frequent or more severe fire that eliminates
cypress regeneration will maintain a willow-remnant cypress stand [25].
Since cypress seed dispersal in limited, recovery from severe fires that
consume peat may be very slow, particularly where water flow is slow to
negligible.  In areas where severe fires have burned old-growth cypress
stands, there is little sign that communities are recovering to prefire
conditions [5].


FIRE EFFECTS ON RESOURCE MANAGEMENT : 
Prescribed fire in and near cypress swamps is used mainly to enhance
wildlife habitat, particularly for endangered species [39].


FIRE USE CONSIDERATIONS : 
Dye [13] reported on firing techniques in the Everglades and Big Cypress
Swamp.  In the past, prescribed fire in Big Cypress was usually
conducted in the cooler months:  November to April [39].  The current
trend is to conduct prescribed fire in May and June during the "natural"
lightning fire season, which fulfills the goal of approximating original
conditions.  Most fires are set as headfires; burn plots are small
(600-1,000 ac [243-405 ha]); blacklines are wide; and multiple firing
patterns are employed.  Dye [13] recommended staggered headfires after
the establishment of backing and single flankfires within zone
perimeters.  Plowing lines and the use of firing patterns leading to
development of broad coalescing fire fronts are not recommended.


FIRE MANAGEMENT CONSIDERATIONS : 
Low-severity fires do no apparent damage to dwarf cypress savannas and
prevent invasion by hardwood species.  Fuel build-up could result in
crown scorch and cypress mortality.  It is unlikely that wet season
lightning fires ever occurred with any regularity in presettlement
times; fuels were either inundated or too sparse to carry fire.
Lightning fires were probably common whenever the water table dropped.
Low-intensity, prescribed headfires are recommended for this type at
approximately 10-year intervals [42].

Fire management in cypress domes and strands will be an incidental
effect of prescribed fire in dwarf cypress savanna.  Some domes will be
moist enough to prevent fire spread, while others (in the same year)
will carry fire.  Prescribed fire in dwarf cypress savanna will,
therefore, create a patchwork of fire that burns into domes to some
extent.  Because of reduced hydroperiods, however, some prescribed fires
may burn severely in cypress domes.  

Fire management in cypress swamps must be "fine-tuned".  Fire cannot be
excluded, but cypress is vulnerable to severe fire [42].  In northern
Florida, periodic fire in seasonally dry cypress domes will perpetuate
cypress at the expense of pine [20].  An intense fire every 2 or 3
decades kills most pine and hardwoods, but leaves cypress.  The removal
of a thin layer of organic soil appears to be tolerated by cypresses and
other species.  It is possible that more frequent, low-intensity fires
(every 2-3 years) could be used to achieve the same goal, although this
has not been demonstrated [42].

The nature of fires in both northern and southern Florida has changed
[17].  Drainage of southern Florida has resulted in soils that are dry
early in spring which contributes to wildfires that are more destructive
than fires that occurred before widescale drainage.  Under current
conditions, fires consume large amounts of organic soil and kill the
roots of most fire-adapted plant species (as well as fire sensitive
species) [42].  Fire in logged cypress swamps is more severe than in
unlogged swamps due to remaining slash and the presence of dense
regrowth.  Fires burn hotter, destroy cypress seeds and roots in the
soil, and eliminate cypress sprouts.  This situation favors the
replacement of cypresses by willows which are followed by mixed
hardwoods [25].  The detrimental effects of severe fires in cypress
swamps include smoke production (hazardous to health), loss of organic
soils, loss of vegetation, damage to wildlife habitat, loss of esthetic
value, and scars and damage caused by suppression efforts [42].

Melaleuca invasion occurs on sites that have been drained and severely
burned.  The flammability of melaleuca increases the probability of
crown fires in cypress stands, particularly where melaleuca has invaded
the ecotone between cypress stands and pine flatwoods [39,41].

Fire management programs in southern Florida will probably be designed
to bring about desired effects rather than recreate a specific fire
regime.  Prescribed fire use is limited by public tolerance; visible
smoke is produced, and high intensity fires are feared [39].


REHABILITATION OF SITES FOLLOWING WILDFIRE : 
NO-ENTRY

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