KUCHLER TYPE FIRE ECOLOGY AND MANAGEMENT
KUCHLER TYPE: Oak-hickory forest



FUELS, FLAMMABILITY, AND FIRE OCCURRENCE : 
Fuels and Flammability:  In the Sand Prairie Scrub Oak Nature Preserve,
Illinois, estimated fuel loads were highest in closed forest, moderate
in savanna, and lowest in prairie.  When blackjack oaks in savanna reach
sufficient size, grass growth under their crowns is reduced and wind
action sweeps away litter; this reduces the amount of fuel near the tree
trunk and prevents fire from reaching the tree base.  Following a spring
prescribed fire, a study of patterns of fuel consumption around isolated
blackjack oak savanna trees showed that fire never reached their bases.
In closed forest, tree mortality was high, and trees experienced more
scorch at stem bases than trees on the forest-prairie edge [5].

In hardwood stands in the north-central states, fire danger is high in
both the spring and fall and low in the summer months when the
vegetation is green [64].  At Indian Creek Nature Center, Iowa,
prescribed fires were conducted in spring under moist conditions in
grassland and adjacent oak-hickory woodlots.  In the woods, fires were
generally patchy and left large areas unburned [73].

Oak leaf litter affects the likelihood of fire and increase fire
intensity [54].  Oak leaves crinkle up when they dry and are therefore
held above the ground surface creating a loose, porous fuel bed that
carries fire easily [54,73].  In contrast, leaves of locust (Robinia
spp.), maple, and elm lie flat, stay damp, and do not burn well [73].
Oak leaf litter is easily carried by wind; burning leaves can ignite
spot fires and increase fire spread.  Dead leaves of black oak often
remain on the tree, creating deep layers of dry fuels in young stands
[54].  Wildfire hazard has increased due to fuels buildup and fire
exclusion on the Hercules Glades Wilderness Area in southwestern
Missouri since its designation as wilderness.  Management-ignited fire
and prescribed natural fire have been recommended [56].

Fire Occurrence:  It is widely accepted that along the western boundary
of the deciduous forest Native Americans set many fires that kept
oak-hickory forests open, helped determine the grassland-forest
boundary, and limited the range of maple-basswood forests [73,97].
Nearly every acre in the Midwest probably experienced at least
occasional fire [73].  There are numerous reports of Native Americans
burning Missouri savannas and grasslands on an annual basis, usually in
the autumn after leaf-fall [22,56].  Northern Missouri was virtually
fire-free soon after settlement; southern Missouri continued to be
burned by early settlers, but fires were of lower severity than
presettlement, aborigine-set fires.  In 1936, the state Conservation
Commission began a concerted effort to suppress fire throughout the
state [22].  In the Missouri Ozarks, fire history of a post oak savanna
growing on a ridge was reconstructed for 1734 to 1991 using tree ring
analysis.  The mean fire return interval from 1740 to 1850, the period
of greatest fire frequency, was 2.8 years.  After 1850, the fire return
interval increased to 24 years [26].

In southern Wisconsin (the area mapped by Kuchler as oak savanna [K081]
but containing virtually the same species as oak-hickory forests and
bluestem prairie-oak-hickory mosaic), oak savannas were widespread and
common in presettlement times and disappeared rapidly as soon as fires
ceased.  It was therefore estimated that presettlement fire frequency
was very high and in some areas fire occurred annually [54].

In the north-central states, there were more than 11,000 fires reported
between 1970 and 1972.  Many fires were caused by debris burning
(approximately 33%), many were incendiary (20%), and only a very few
(1%) were started by lightning.  More than 50 percent of the fires
burned in hardwood stands [64].  Boerner and Cho [10] estimated fire
return intervals for heavily forested sites in southeastern Ohio from
1923 to 1978.  They calculated an average fire return interval of 643
years given current conditions.  Average fire intervals of 900 years
were estimated for the Shawnee National Forest, Illinois [54].



FIRE EFFECTS ON SITE : 
In Missouri seasonal rates of nonsymbiotic nitrogen fixation in surface
soils of oak-hickory forests were measured on plots exposed to 30 years
of annual or periodic prescribed fire.  Fire treatments had no
influence on fixation rates, which averaged 0.1 kg/ha/year, or on the
proportion of samples showing nitrogen fixing activity [93].

In Missouri annual fire in oak-hickory forests may reduce nutrient
availability and water infiltration.  Burning significantly reduced
quantities of extractable ammonium in the soil; annual burning resulting
in lower amounts than burning every 4 years [92].  In Missouri, oak
forests were prescribed burned annually or periodically (every 5th year)
in spring.  Annual fires were patchy and of low severity due to lack of
surface fuels.  Soils of annually burned plots became increasing
compacted and had little or no earthworm and insect activity compared to
unburned soils and litter.  After seven annual fires, water infiltration
rates were 4.5 times faster on unburned soils than on burned soils [73].
Arend [111] reported reductions in infiltration rates after prescribed
fire for some soils under mixed upland oaks in Missouri.


FIRE EFFECTS ON VEGETATION : 
Fire is an important factor in establishing and maintaining vegetation
patterns in the Ozark Mountains [2,74].  The closed-canopy oak-hickory
forest that now predominates in the Missouri Ozarks is thought by some
authors to be an artifact of fire suppression and other anthropogenic
disturbances.  People travelling in the area in presettlement times
described a wide variety of plant communities ranging from grassland, to
oak savannas, to oak-pine forests [26].  Repeated fires create open,
parklike stands of oak [90].

Drought is the primary agent controlling the frequency and severity of
fire and the impact of fire on trees in oak-hickory forests.  Drought
contributes to low fuel moistures and therefore high fireline intensity,
resulting in more severe fire.  Individual trees stressed by drought are
more susceptible to pathogens after fire wounding and sprout less
vigorously after top-kill.  Stands affected by insects or pathogens also
have high amounts of fine fuels [17].

Species Responses:  Most oaks are resistant to fire to some extent; fire
resistance generally increases with stem diameter [54,78].  Most oaks
sprout from dormant basal buds after top-kill.  Sprouting species are
favored over other hardwoods by occasional fires [23].  Boerner and Cho
[10] hypothesized that large, emergent oaks in an old-growth forest in
southeastern Ohio were established following one or more large-scale
disturbances such as fire or windstorm.  After oak establishment on good
sites, severe fire maintains oak dominance [54].

Rouse [78] listed the following oaks in order of decreasing bark
thickness:  chestnut oak, black oak, northern red oak, and white oak.
Lorimer [53] rated upland oaks slightly differently in order of
decreasing bark thickness:  bur oak, black oak, white oak, and northern
red oak.  The thinner bark of northern red oak may acount for its
susceptibility to top-kill by fire.  Bur oak and white oak are often
maintained in oak savannas, whereas frequent fire reduces northern red
oak to shrubby clumps of sprout origin.

Black oak is a short-lived (less than 150 years) tree, intermediate in
shade tolerance.  It sprouts after injury or top-kill.  Susceptibility
to fire is intermediate in larger individuals and high in young
seedlings and sprouts [42].  Both mature [110] and young black oak
seedlings sprout [54].

Fire-caused basal wounding provides entry for wood-rotting fungi and
insects [74].  Loomis [52] published a method for predicting tree
mortality and estimating basal wound size for surviving trees.
Mortality equations were derived for black oak, white oak, post oak, and
scarlet oak.  The black oak formula also applies to hickories and to
northern red oak.  Mortality depends on tree species, diameter at breast
height, height of bark blackening, and the width of bark blackening at 1
foot above the ground [52].

Prescribed spring fire in grasslands and adjacent woods in Iowa resulted
in a great increase in flowering of forbs, and reduced woody species such
as common prickly-ash (Zanthoxylum americanum), black locust, barberry,
buckthorns, and maples [73].

Survival of lichens after fire in a Michigan oak savanna was summarized
by Wetmore [105].  Many species showed lower cover after fire on the
part of tree trunks closest to the soil; cover reduction was less
pronounced high on the tree trunks, even at high fire frequencies [105].
 
Effects of Fire on Species Composition:  Fire influences species
composition towards oak-hickory and away from maple-beech dominated
forest [15].  After a severe wildfire in West Virginia, oaks increased
from 9.3 percent of the dominant trees to almost 30 percent of the
total, mostly due to top-kill of mesic hardwoods [54].  Frequent fire
reduces tree and shrub cover in favor of prairie species.  In the
Driftless Area (Wisconsin and Minnesota), almost pure stands of northern
red oak occur on moist sites that would be suitable for sugar maple.
These are even-aged stands that probably established after severe fires
[23].  In many oak-hickory forests, sugar maple and other shade-tolerant
and fire susceptible species are increasing in number and cover.
Evidence that this is a result of fire exclusion includes the tendency
of sugar maple and other fire-susceptible species to co-occur on
protected sites that show no evidence of past fire [67].  In southern
Wisconsin oak forests (which experienced fire in presettlement times but
have not burned recently), oak regeneration is scarce.  McCune and
Cottam [59] suggested that since none of the understory species in
southern Wisconsin (hackberry, boxelder, American elm, butternut, black
cherry, and red maple) are true climax species, the absence of
disturbance is an historic anomaly and the future composition of these
forests is unclear.

Henderson [42] compared two black oak stands in Indiana with differing
fire  histories.  The stand which had experienced frequent, low-severity
surface fires was dominated by black oak and a few northern red oak, and
there were few other woody species.  The stand that had experienced more
severe fire less frequently was also dominated by  black oak, but had
less fire-tolerant species present as well:  red maple (Acer rubrum),
sassafras (Sassafras albidum), and black tupelo (Nyssa sylvatica) [42].

In Illinois grassy openings with few trees were burned annually with
prescribed fire from 1969 to 1973.  They were not burned again until
1990, 1991, and 1992.  With annual fire, prairie forbs increased and
woody species declined.  In the 15-year fire-free interval, the number of
shrub species increased.  When prescribed fire was resumed, prairie
willow (Salix humulis) and silky dogwood (Cornus amomum) sprouted
vigorously after fire; prairie forbs also increased [3].

Effects of Fire on Stand Structure:  Fire was important in maintaining
oak savannas at the forest-prairie ecotone.  There are numerous
historical references to the rapid conversion of savanna to oak forest
following European settlement and cessation of fire [23].  Anderson and
Brown [5] proposed that the mosaic of presettlement vegetation types was
strongly influenced by fire patterns that tended to limit closed forests
to areas protected from most fires.  In Tennessee annual and periodic
prescribed surface fires were conducted in upland oak-dominated
vegetation.  Upland stands were mostly post oak-blackjack oak, southern
red oak-scarlet oak, or white oak [30].  After 25 years, understory
cover of woody plants was irregular but more or less constant in
annually burned plots.  Overstory cover was open, with few trees per
acre.  In periodically burned plots, woody understory cover increased
irregularly.  In unburned control plots, woody understory plant cover
first decreased but then increased over the 25-year period [29].

In presettlement Indiana grass-dominated openings were maintained by
annual burning after autumn frost.  These frequent fires prevented the
growth of trees and "permanent vegetation".  In less than 50 years
without fire, former openings were converted to forest [49].  Repeated
fires are thought to be responsible for scrub oak lands (stands of
scrubby oaks of sprout origin) in the Midwest [23].

In the Sand Prairie Scrub Oak Nature Preserve, a March 1977 prescribed
fire in closed forest consumed 95 to 99 percent of the surface litter in
study plots.  Numerous trees had fire scars up to 3.3 feet (1 m) above
the ground.  In the savanna the fire did not reach within 1 foot (30
cm) of the base of any of the 14 trees.  Surface area burned ranged from
7.1 percent to 52.4 percent in different plots.  None of the savanna
trees showed any deterioration in 3 years after the fire even though
some had scorching of the lower branches [4].

Black oak sand savannas at Hoosier Prairie Nature Preserve, Indiana, are
maintained by prescribed fire.  One area has been burned four times in 8
years, three times in the spring, and once in the fall.  The number of
woody stems increased after the first fire, but decreased thereafter.
Postfire sprouting of smooth sumac occured at the same rate through four
fires, but black oak and prairie willow sprouting rates declined.
Another area of oak savanna at Hoosier Prairie was burned five times in
8 years.  Allowing plots to rest from fire for least 2 years resulted in
an increase in the numbers of woody stems, but the number of woody stems
decreased after two consecutive fires [7].


FIRE EFFECTS ON RESOURCE MANAGEMENT : 
Few instances of direct mortality from fire have been recorded for
wildlife species in oak-hickory forests.  In Oklahoma, Bigham and others
[9] observed many dead eastern box turtles immediately after severe
fires in post oak-blackjack oak woods and adjacent pasture and range.
They also observed living turtles, snakes, northern bobwhites, and a
rabbit on the burned area 4 days after the fire [9].


FIRE USE CONSIDERATIONS : 
Moore [66] published a method for field measurement of fuel moisture to
assess burning conditions in oak-hickory forests.


FIRE MANAGEMENT CONSIDERATIONS : 
Fire was once an important factor in the oak-hickory ecosystem and
maintained the open character of most stands in the Midwest [15,54].
Many historians and ecologists feel that the midwestern oak-hickory
forests evolved with frequent fire and remain fire-dependent [73].
Prescribed fire is useful for maintaining the diversity of oak-hickory
forests, and is being used in Indiana, Illinois, Missouri, Wisconsin,
and Iowa with good results.  Prescribed fire use continues in hardwood
and mixed forests as a wildlife management tool [106] and to modify
understory composition or size class structure [35,99].

Unfortunately, few short- or long-term ecological studies of fire
perturbations have been conducted on oak-hickory forests [15].
Implications for fire in management of currently existing closed-canopy
forests are unclear.  Regeneration problems associated with these
forests are similar to problems occurring in forests farther east.

Prescribed fire is being considered as a silvicultural tool in oak
forests.  It seems likely that several low- to moderate-severity
prescribed fires will reduce the number of shade-tolerant competitors,
and it is possible that such fires may encourage establishment of oaks.
A single fire will have little lasting impact, and in some cases may be
detrimental to oak regeneration.  Several fires are probably necessary
to select against less fire-resistant competitors [54].  Lorimer [54]
commented that experiments with medium-severity fire are to be
encouraged; low-severity fire may not kill competing species at rates
high enough to be beneficial to oak regeneration.  In some areas
silvicultural approaches may be as least as successful as prescribed
burning programs [54] because basal wounding by fire allows entry of
fungi and insects and reduces the value of timber trees [74].

In an attempt to improve oak regeneration in an upland hardwood forest
in northern Alabama, a prescribed fire was conducted in 4- to 6-year-old
oak stands that appeared to be in danger of replacement by other
species.  One fire in these stands did not substantially alter the trend
to replacement of oaks by other species.  Stands recovered rapidly from
fire; density of browse species and herb cover increased, resulting in
improved wildlife habitat [45].

With increasing age of forests, regeneration of oaks after disturbance
tends to decrease.  Sprouting tends to decrease with age.  Established
shade-tolerant species in the understory and subcanopy are more
competitive than low-vigor oak sprouts [15].

In the Midwest many savanna and grassland areas have been prescribed
burned on a regular basis.  These fires have been prevented from
spreading into adjacent forests, with the result that there are no
transitional areas.  Under presettlement conditions, grassland fires
sometimes spread into adjacent oak-hickory forests, depending on local
conditions.  These fires maintained savanna and ecotonal communities in
irregular mosaics.  It has been recommended, therefore, that prescribed
fires for grassland maintenance be allowed to burn into adjacent forest
and reestablish savanna vegetation and ecotones [73].

In Indiana fire management policies are based on the premise that oak
savanna and prairie communities will best be maintained by a fire
interval of 2 to 8 years, depending on unit history and specific goals.
Annual fires are not recommended for either restoration or maintenance
of oak savanna because there is usually not enough fuel to carry fire,
and annual fires may damage some herbs.  Remnants of oak savanna prairie
need to be burned at least every 15 years or they will develop into dense
forest.  Spring fires are thought to be the most effective [32].

In Indiana black oak sand savannas, maintenance and restoration of
vegetational mosaics was initiated with prescribed fire.  Plots were
burned biennially, three times in the spring and once in the fall, for a
total of four times in 8 years [7].

On the Grand Prairie, Illinois, U.S. Forest Service personnel are
attempting to restore the transition landscape (as savanna) by allowing
firewood removal until approximately 10 trees are left per acre (25
trees/ha); tree removal is followed by annual prescribed fire [58].

There has been some debate over the choice of sites and appropriate
methodology for restoration of presettlement vegetation including
savannas [60,72].  Mendelson and others [60] contend that savanna
vegetation represents an ecotonal and therefore not unique vegetation
type and should not be created by artificial means.  Packard [72] and
his colleagues believe that, since the presettlement vegetation has been
grossly disturbed by humans, drastic measures (i.e., prescribed fire
and tree thinning) are necessary to restore savanna and other
presettlement vegetation types.


REHABILITATION OF SITES FOLLOWING WILDFIRE : 
NO-ENTRY

Related categories for Kuchler Type: Oak-hickory forest