KUCHLER TYPE FIRE ECOLOGY AND MANAGEMENT
KUCHLER TYPE: Palmetto prairie



FUELS, FLAMMABILITY, AND FIRE OCCURRENCE : 
Fuels:  In cut-over south Florida flatwoods, pineland threeawn comprised
about 20 percent of the total biomass, other species 10 percent, and
mulch constituted at least 50 to 60 percent of the total biomass 2 years
after prescribed winter fire.  Biomass yields at 3 to 4 years following
fire averaged between 5,500 and 7,000 pounds per acre (6,188-7,875
kg/ha) [42].  After 3 to 4 years, a steady state was reached where a
relatively constant 70 percent of the total biomass was mulch [42].

Flammability:  Fire travels unevenly through the mosaic of palmetto
prairie, flatwoods (various phases), and scrubs, reflecting the varying
flammability of the different communities [2].  Pine flatwoods and
palmetto prairie typically burn vigorously and completely (excepting
overstory pines), leaving few unburned patches [3].  Swale and flatwoods
transects ranged from 96 to 100 percent burned after a series of
prescribed fires and one wildfire at the Archbold Biological Station
[2].  The two most dominant species of palmetto prairie, pineland
threeawn and saw-palmetto, are highly flammable, as is gallberry, even
though saw-palmetto and gallberry remain green all year [3,48].
Abrahamson and others [4] rated pine flatwoods second in flammability
among the seven community types occurring at Archbold Biological
Station.  Flammability appears to be related to the amount of grasses,
saw-palmetto, pine duff, and litter [4].

Fire Occurrence:  Southern Florida has the highest number of
thunderstorm days per year (70-90) [45] and the highest frequency of
lightning strikes of any region of the United States [3].  The National
Oceanographic and Atmospheric Administration estimated that there are 10
to 12 cloud to ground lightning strikes per square kilometer per year in
Highlands County, Florida.  Only a small percentage of those strikes
actually ignite fires:  In one area, 30 fires resulted from an estimated
2,100 to 2,600 strikes in 14 years.  At the Archbold Biological Station,
a majority of the 56 lightning strikes recorded between 1967 and 1980
occurred between May and September, with peak lightning activity
occurring in July.  Almost all (97%) lightning fires occurred between
May and September, most frequently at the beginning of the rainy season,
since vegetation moisture content of many dominant species is lowest in
spring [4,45].  In the presettlement period, fires were not restricted
by roads, canals, and other structures, and many spring and summer
wildfires probably burned over very large areas [3].

Fire Frequency:  Christensen [9] estimated a natural fire frequency for
Coastal Plain savannas (which probably includes palmetto prairie) as
approximately every 2 to 8 years, based on the life history and fire
adaptations of the dominant species, including pineland threeawn and
saw-palmetto.  Menges and others [37] estimated that flatwoods and
southern ridge sandhills in central peninsular Florida burned an average
of once in 3 to 10 years.  Within a climatic region, fire frequency is
often correlated with site fertility:  Fires are more frequent on
nutrient-limited or oligotrophic sites than on eutrophic sites [10].
The nutrient-poor soils of Coastal Plain savannas result in production
of ligneous herbaceous fuels with a low nutrient content.  Decomposition
is slow, litter accumulates rapidly, and therefore the probability of
another fire increases rapidly.

Fire History:  Fires have occurred in southern Florida for at least
50,000 years, as evidenced by the charcoal present in lakebeds [45].
Watts and Hansen [61] speculated that fires were relatively frequent
between 50,000 and 20,000 years ago, then decreased in frequency, and
increased again approximately 12,000 years ago.  The earliest aboriginal
occupation of Florida has also been estimated at about 12,000 years BP
[45].  However, the flat terrace of extreme southern Florida has only
been above sea level for a few thousand years [64].  Lightning fires
were probably the main selective force driving the fire adaptations of
palmetto prairie vegetation; however, extensive consistent burning by
Native Americans, in a pattern different from that of lightning fires
(increased frequency and in different seasons or habitats) constituted a
strong selective force.  There are, for example, instances where local
genetic adaptations have arisen in time spans of only a few hundred
years [45].  It is therefore quite conceivable that either Native
American burning practices, or burning and other management practices
implemented since European settlement, have combined to enhance fire
adaptations in palmetto prairie species [45].


FIRE EFFECTS ON SITE : 
The nutrient budget of palmetto prairies and pine flatwoods is closely
tied to fire regime.  Over long periods of time, the average annual loss
of carbon in many frequently burned communities may exceed 0.18 pounds
per square yard (100 g/sq m).  In pine flatwoods, 10 to 30 percent of
the biomass produced each year may be recycled by fire.  In addition,
soil conditions favor vegetation characteristics that increase the
probability of low intensity, frequent fire.

Nitrogen and phosphorus are the nutrients most frequently limiting to
plant growth in Coastal Plain communities [10].  Fire causes an overall
loss of nutrients, but increases short-term nutrient availability as a
consequence of mineralization, addition of nutrients as ash, changes in
microbial activity, or alteration of soil ion exchange.  Most nutrients
are not present in available form immediately after fire; there is a
delay during which nutrients are converted to available forms.  Direct
addition of mineral nutrients in the ash is not as important as changes
in mineralization rates to postfire soil fertility.  Nutrient loss to
surface runoff is negligible due to the lack of topographic relief.
Most nutrient loss is due to volatilization and leaching into
groundwater.  Annual prescribed fire could result in overall loss of
nutrients and effectively lower productivity [10].  However, Wells [58]
reported that annual burning of pine flatwoods in South Carolina did not
reduce nitrogen.

Following prescirbed fire for fuel reduction in a slash
pine/saw-palmetto-gallberry type, nutrients remaining in unburned and
partially burned plant materials were measured.  Carbon was found to
have been largely volatilized.  Nitrogen, phosphorus, magnesium, and
sulfur loss had a significant positive correlation with fuel weight loss
(i.e., much of those nutrients were volatilized); potassium, calcium,
and manganese were not as strongly correlated.  Copper, aluminum, and
molybdenum increased following fire; iron, strontium, boron, barium, and
zinc loss was medium to large [25].

Temperatures at the soil surface, measured 5 days after prescribed fire
in palmetto prairie near Archbold Biological Station, were up to 20
degrees Fahrenheit (11 deg C) higher than on unburned sites [2].


FIRE EFFECTS ON VEGETATION : 
The vegetation of palmetto prairie is highly adapted to fire; most of
the species are usually found only in frequently burned (less than 50
years without fire, most less than 20 years) ecosystems [3].  Many
species sprout from underground stems or roots [3].  Gallberry, for
example, sprouts from roots and saw-palmetto sprouts from stems that are
partly to completely underground.  On southern Florida range, gallberry
burned in January was visibly sprouting by late February, exhibited the
most rapid growth from mid-April to mid-May, and was 2 feet tall (0.6 m)
by November.  Saw-palmetto burned in November produced one fully
expanded leaf by January, seven to eight leaves by the end of 1 year,
and three or four more leaves by the end of the second year.  Unburned
saw-palmetto produce an average of five to six leaves per year.
Saw-palmetto burned in late fall is stimulated to grow all winter
whereas unburned saw-palmetto is relatively dormant in winter.  Postfire
sprout numbers of both saw-palmetto and gallberry usually exceed prefire
stem numbers, though a number of sprouts die the second year.  Foliage
cover per stem increases gradually with protection from fire [20].

Blades of pineland threeawn appear within 3 days of a winter fire; this
species comprised at least half of the herbaceous vegetation through a
2-year period following fire on south Florida pinelands [20].  The date
of burning affects the number and density of pineland threeawn
reproductive tillers; pineland threeawn burned in late spring (May)
produces substantially more seed than that burned in early spring (March
or April) [42].

Fire occurrence in a particular season also initiates or enhances the
flowering of other herbs inhabiting palmetto prairie.  Cutthroat grass
(Panicum abcissum) and beardgrasses (Andropogon spp.) do not flower
unless burned in the spring or summer.  Catesby's lily (Lilium
catesbaei), yellow bachelor's button (Polygala rugelii), deer tongue
(Carphephorus paniculatus), and white-topped aster (Aster tortifolius)
flower more conspicuously following fire [1,4,42].

Robinson [46] compiled a list of the fire effects on 30 proposed,
threatened, and endangered plant species occurring in pine flatwoods
communities.  Fire is rated beneficial for all of the listed species
[46].

Gallberry flatwoods recovered to near prefire vegetative cover in less
than 6 months following prescribed winter fire.  Pineland threeawn
flatwoods whose prefire cover averaged 82 percent had recovered to 56
percent cover at approximately postfire year 1, 60 percent cover by year
2, and 79 percent cover by year 3.  Burning produced no appreciable
change in vascular plant community composition, although there was some
shift in the relative abundance of woody species.  In gallberry
flatwoods, there was a decrease in the importance value of fetterbush,
gallberry, and saw-palmetto; and an increase in the importance value of
dwarf huckleberry (Gaylussacia dumosa) and ground blueberry [2].  A
discussion of species specific responses is available [1].

Effects of Fire Exclusion:  Some species decline with fire exclusion.
Ground blueberry increases in shoot density and dominance following
fire, but rapidly declines in density as it is overtopped by taller
species during intervals without fire.  In intervals without fire,
ground blueberry can survive with little aboveground biomass.  When fire
releases nutrients and decreases shade and competition for moisture,
ground blueberry responds with renewed vigorous growth [3].  Herbs are
also less common in pineland threeawn flatwoods that have not
experienced recent fire than in recently burned stands, largely due to
shading by tall shrubs [4].  Little bluestem (Schizachyrium scoparium),
and slender bluestem (S. tenerum) are suppressed by the accumulation of
litter in unburned stands; they remain vigorous on burned stands.
However, little bluestem decreases with burning on grazed lands [16].

The relative abundance of species may be altered by fire exclusion as
well.  The understory of a South Florida slash pine stand that was last
burned in 1941 had greatly reduced pineland threeawn cover by 1963 [20].
Pineland threeawn may survive 2 to 4 decades of fire suppression but
with a decline in vigor and cover.  A longleaf pine flatwood that had
not experienced fire for 25 years was overgrown with saw-palmetto and
gallberry.  Even though pineland threeawn had not been observed on the
site, it sprouted from dormant tussocks within a few weeks of a winter
precribed fire.  It was, however, eliminated from a longleaf pine site
over 34 years of fire exclusion [11].

In infrequently burned pine flatwoods, saw-palmetto, gallberry, and
fetterbush increase in dominance (largely due to height growth) [11,20].
Other species increasing with fire exclusion include sand live oak
(Quercus geminata), southern bayberry, and dahoon (Ilex cassine), all of
which grow rapidly to small tree size if not top-killed by fire [53].

At Archbold Biological Station, changes in vegetative composition with
fire exclusion have been recorded.  There have been no fires on the
study sites since 1926 or 1927; prior to that fire frequency in the
southern ridge sandhill area was about once every 9 years.  It was
reported that flatwoods/bayheads sites (lumped together for the purposes
of the study) showed some degree of convergence towards bayheads; sites
formerly dominated by flatwoods shrubs have bayhead trees such as redbay
(Persea borbonia) emerging as dominant species [37].  Monk [38] also
suggested that bayheads may develop from low pine flatwoods in the
absence of fire.


FIRE EFFECTS ON RESOURCE MANAGEMENT : 
Palmetto prairie forage production was 65 pounds per acre (73 kg/ha) 3
weeks following burning, 1 ton per acre (2,250 kg/ha) 1 year following
burning, and 1.75 tons per acre (3,938 kg/ha) after 2 years.  Species
included pineland threeawn, panicums, and bluestems [21].  Forage
quality is highest immediately after a fire, but declines rapidly to
borderline for cattle nutrition by 3 months after a fire [20].  Cattle
will graze pineland threeawn for 2 to 3 months after burning, but then
seek other forage plants [21].  Pineland threeawn remained vigorous
under heavy grazing when burned at intervals longer than 1 year, but
decreased slightly in cover on ranges that were burned annually and
heavily grazed [18].  In southern Florida, pineland threeawn cover was
unchanged when burned biennially and grazed heavily [20].  Month of
burning affects early forage production.  Ranges burned in March or May
averaged two and four times as much herbage, respectively, in the 60
days after fire as ranges burned in October or November [34].  Cattle
grazed newly emerged saw-palmetto leaves following fire [22].  Treeless
ranges produced three times as much early growth herbage when burned in
May than on ranges burned in November.  Yields by 2 years after fire
were not affected by season of prescribed fire.  The difference in
season of burning was much less pronounced on ranges with trees present,
since ranges with trees produce less forage than open sites [28].

Gallberry top-killed by fire does not produce flowers or fruit until the
second year, but then bears profusely.  Burned saw-palmetto blooms and
produces a few fruits the first year, but at a lower than normal rate.
Full fruit productivity for gallberry is regained in 8 to 10 fire-free
years after biennial burning [20], although the fruit production of most
other shrubs in open pine flatwood peaks at 3 to 5 years after burning [29].

Direct Fire Effects on Wildlife:  In longleaf pine flatwoods on the St.
Marks National Wildlife Refuge no dead herpetiles were found in an area
where severe fire consumed vegetation down to bare sand, although a
later search resulted in the discovery of one dead box turtle.  Several
living box turtles had fire scars on the carapace.  Twenty-six species
of herpetiles were active in the burned area 3 weeks after the fire.  In
adjacent slash pine/saw-palmetto flatwoods, the flatwoods salamander
occurred at similar activity levels in the winter and spring of 1979 on
sites that were either unburned since 1977 or burned in January 1979 (at
the start of the sampling program).  The fact that the salamanders
survived a winter fire during the active breeding season makes it
extremely likely that they can survive summer fire when they are dormant
and protected in soil burrows [36].  Herpetiles that appear to be most
at-risk from fire are reptiles in mid-ecdysis (i.e.  are actively
shedding skin) [36].  Wood [59] reported no fire-caused mortality of
tree squirrels, furbearers, or black bears (Ursus americanus).  Taylor
[54] however, reported that a fast moving grass fire killed five marsh
rabbits (Silvilagus palustris), although eastern cottontails (S.
floridanus) easily escaped.

Indirect Fire Effects on Wildlife:  Prescribed fire is widely used by
wildlife managers in the Southeast.  White-tailed deer have been
observed to lick the nutrient-rich ash on fresh burns.  In winter,
white-tailed does use freshly burned areas; the extra nutrients may be
beneficial during early gestation.  April through July lightning fires
are thought to provide nutrient-rich ash that is beneficial during late
gestation [15].  Mourning doves (Zenaida macroura) have been observed
foraging on fresh burns [32].  At Myakka River State Park, palmetto
prairie that had been overgrown by shrubs was prescribed burned in
winter and summer to compare season of fire on bird densities.  Bird
abundance on the winter burn was not different from the unburned
control, but was lower on the summer burn [13].  

Managers of hunting plantations burn ranges annually to improve northern
bobwhite habitat.  Time of burning has an important effect on food
availability to northern bobwhite.  Normally, late winter and early
spring are critical periods when food is relatively scarce.  Spring
fires are detrimental to food production for game birds.  Production of
northern bobwhite food is delayed 1 month on ranges burned in January, 2
months on March burns, and 3 months on May burns [28].  Hughes [28]
recommends that managers burn separate parts of the range area in
different seasons to keep forage green and palatable all year.  Fall
burning is best where wildlife habitat is desirable because burning in
fall favors spring production of food plants.  However, fall prescribed
fire involves increased risks, and there is potential for loss of nest
sites for birds.  

Hughes [28] recommends that for wildlife use, cattle should be kept off
of ranges for approximately 6 weeks following fall prescribed fire, and
4 weeks after spring fires to maintain wildlife forage availability.

Prey availability for raptors is altered by fire; most hawks and owls in
palmetto prairie depend on hispid cotton rat (Sigmodon hispidus) and
eastern cottontail.  Frequent fire maintains habitats suitable for many
common mammalian prey species, but temporarily exposes them when cover
is consumed.  The fulvous harvest mouse (Reithrodomys fulvescens) and
the cotton mouse (Peromyscus gossypinus) increase after fire; the hispid
cotton rat, eastern harvest mouse, and round-tailed muskrat (Neofiber
alleni) decrease after fire; oldfield mouse (P. polionotus) and Florida
mouse (P. floridanus) populations remain unchanged [32,54].  Cooper's
hawk (Accipiter cooperii) and sharp-shinned hawk (A. striatus) are the
primary predators of northen bobwhite and the larger passerines that are
abundant in fire-maintained game lands including palmetto prairie [32].


FIRE USE CONSIDERATIONS : 
Temperatures as high as 977 degrees Fahrenheit (525 deg C) have been
recorded at Archbold Biological Station prescribed surface fires in
flatwoods [4].  In south Florida cutover pine flatwoods with low
coverage of saw-palmetto, aboveground temperatures measured in both
headfires and backfires averaged 415 degrees Fahrenheit (212 deg C),
with no significant differences between the headfires and backfires.
Only two of five sites showed temperatures as high as 120 degrees
Fahrenheit (49 deg C) at 0.125 inch (0.3 cm) below the surface; all
other sites were cooler at that level and deeper [42].  These data
indicate that fire in palmetto prairie, as in other grassy ecosystems
usually passes over the surface too rapidly to heat the soil to any
great degree.

Nelson and Adkins [41] report on a laboratory study of flame height,
length, and tilt angle in relation to wind speed for slash
pine/saw-palmetto-gallberry fuels.  They also provide comparable field
data on winter fire in a longleaf pine-slash pine/saw-palmetto-gallberry
type.

Hough and Albini [26] characterized the fuel complex of a
palmetto-gallberry type, adjusting parameters so that use of the
Rothermel model of fire spread and intensity is practical for this type.
This type is a complex association of saw-palmetto and gallberry beneath
slash pine or slash pine and longleaf pine; it appears to be very
similar to palmetto prairie in most respects.  In this complex, live and
dead fuels accumulate so rapidly that in 5 years wildfire can seriously
damage the pines [26].  McNab and others [35] estimated fuel weights in
slash pine/saw-palmetto stands, and developed equations to be used to
estimate the dry weight of total fuels and fuels by size class.  They
concluded that most of the components of this fuel complex can be
estimated by the age of the rough, understory height, and saw-palmetto
cover [35].

Hough [24] reported a proposed method for estimating the weight of fuel
burned by prescribed fire, and also measured the caloric value of some
fuels as determined by oxygen-bomb calorimetry [23].  Sackett [47]
published a schedule of fuel accumulation rates for palmetto prairie
species.  Specific burning guidelines for fuel reduction prescribed fires
are available [47].


FIRE MANAGEMENT CONSIDERATIONS : 
The natural fire season for palmetto prairie in presettlement times was
spring and summer.  Humans have added a second fire season in winter,
using prescribed fires which burn with lower severity.  Currently,
wildfires are much smaller than they were before European settlement,
leaving many areas (particularly those not managed for cattle) unburned.

The impact of winter prescribed fire on vegetative composition is
different from that of the natural fire regime (spring and summer fire)
and has resulted in an alteration of the relative abundance of many
species [14].  Palmetto prairie and pine flatwoods are prescribed burned
for many reasons including forage improvement for cattle, maintenance of
open conditions, shrub control, fuel reduction, and wildlife habitat
improvement [14,48].

Many cattle ranges in southern Florida, which are grazed all year long,
are burned as often as there is sufficient vegetation to carry fire;
fire is the primary tool for manipulating vegetation [3,28].  Areas are
burned in rotation through the burning season to extend the period of
quality herbage production and to reduce gallberry and saw-palmetto
competition [3].  Fire will not eliminate saw-palmetto, however, and
very frequent winter fire may increase it [31,49,57].  Fire effects on
palmetto prairie include a stimulation of new growth, an increase in the
nutrient content and palatability of grasses and forbs, and increased
accessibility to forage plants [3].  However, frequent burning has led
to the decline of lopsided indiangrass (Sorghastrum secundum), chalky
bluestem (Andropogon capillipes), creeping bluestem, and goobergrass,
which are the major preferred and palatable native forage grasses.
These grasses are also sensitive to grazing [49].  Sievers [49]
recommended that range managers burn pastures no more often than every
third year, and then only between January and March when the preferred
grasses are dormant.  He also recommended that grazing on ranges in
excellent condition be deferred for 60 to 90 days following fire.  On
ranges already dominated by pineland threeawn grazing can occur
immediately after fire, but cattle should be removed in 6 to 8 weeks to
allow creeping bluestem establishment [49].

In areas to be managed as nature preserves or natural areas, such as
Myakka River State Park, fire has been used to preserve the original
character of plant communities.  Myakka River State Park was
predominantly open (nonforested) in the 1940's.  By the 1980's, oaks
(Quercus spp.) expanded into palmetto prairie where fire was excluded.
These oaks have a dense understory of saw-palmetto.  With the
introduction of winter prescribed fire in the 1960's, the expansion of
oaks was halted, but the existing trees survive the winter fire regime.
A summer prescribed fire was sufficiently intense to kill oak overstory
trees, but left south Florida slash pine and the dense understory of
saw-palmetto.  It is therefore suggested that summer fire is needed for
canopy reduction (where oaks have invaded); however, the danger posed by
heavy fuel accumulations may require fuel reduction fires prior to
summer prescribed fire [27].

Sackett [47] recommended a 3-year interval for prescribed fire as
optimum for fuel reduction and reduction of wildfire damage risk.

Fire consumes much aboveground biomass and litter, and appreciably
increases the rate of nutrient turnover.  Phosphorus and cations in
phytomass are mineralized.  Soil pH is raised, stimulating
nitrogen-fixing bacteria.  Some nitrogen is lost to volatilization, and
the amount varies with fire intensity [3].  Frequent low-intensity fires
release small pulses of nitrogen and volatilize only 20 to 40 percent of
the forest floor nitrogen.  This much is replaced in about 5 years from
atmospheric precipitation alone, not counting what is added through
nitrogen fixation [17].  Very frequent burning could result in
sufficient nutrient loss to decrease plant production.  Walker and Peet
[65] reported that biomass production in annually burned mesic pine/wiregrass
(Sporobolus teretifolius, Muhlenbergia expansa, and others) savannas was
lower than in pine/wiregrass savannas that were burned infrequently.

The long-term effects of prescribed fire may be small compared to the effects
of grazing; grazing results in increased grass production and floristic changes
(which vary with grazing intensity and precipitation, and are compounded by
fire).  Grazing animals also cause soil compaction and a concomitant
reduction in water infiltration and percolation [63].  Soil compaction
coupled with trampling reduces the growth and survival of pine seedlings [8].


REHABILITATION OF SITES FOLLOWING WILDFIRE : 
NO-ENTRY

Related categories for Kuchler Type: Palmetto prairie