KUCHLER TYPE DESCRIPTION
Kuchler Type: Oak-hickory forest


PHYSIOGRAPHY : 
Oak-hickory forests are found on all topographic positions including dry
rocky ridges, deep coves, and well-drained valley floors [81].  West of
the Appalachian Mountains, deciduous forests occupy areas geologically
classified as plateaus, although erosion has produced rolling to
mountainous topography [44].


CLIMATE : 
The climate of the north-central forest region (Minnesota, Wisconsin,
Michigan, Iowa, Illinois, Indiana, Ohio, Missouri, and Kentucky) is
continental and ranges from humid to subhumid.  Winters are cold and
summers hot.  Temperatures differ greatly from north to south through
the region, both in summer and winter.  Temperature, growing season, and
precipitation increase from north to south; at a given latitude,
precipitation increases from west to east [44].

In the southeastern United States along the eastern edge of the
oak-hickory forest, mean annual precipitation is approximately 45 inches
(1,140 mm); at the western edge, annual precipitation averages 39 inches
(980 mm).  Lower precipitation in the western parts of this area is
exacerbated by an episodic pattern of rainfall and more frequent
drought.  In southeastern oak-hickory forest, average annual
precipitation increases from 42 inches (1,060 mm) in Indiana to 55
inches (1,400 mm) in Alabama [15].

At the southwestern limit of oak-hickory forest, central Texas has an
average annual precipitation of 22 inches (560 mm) and mean annual
temperatures around 65 degrees Fahrenheit (18.3 deg C).  In eastern
Texas mean annual temperatures are 62.6 to 66.2 degrees Fahrenheit
(17-19 deg C), and the growing season is approximately 225 days [15].


SOILS : 
Oak-hickory forests occur on soils ranging from cool-moist Boralf and
Orthod Spodosols to warm-dry Millisols and Alfisols.  Soils range from
clay to loam and are derived from glacial material, residual
sandstones, shales, limestones, gneisses, schists, and granites [81].

In southeastern oak-hickory forests, soils encompass a wide range of
physical and chemical features, ranging from shallow to deep, infertile
to rich, and high clay fraction to very little clay.  Soils are formed
in residuum, primarily from limestone parent materials, but also from
sandstones and shales.  Soils in oak-hickory forests are fertile
compared to other southeastern soils and represent some of the most
productive agricultural land on these uplands [15].

Parent materials on the Ozark plateau are predominantly limestones,
cherts, and dolomites. In Arkansas, soil parent materials in the eastern
Ouachita province are mostly shales, sandstones, quartzites, and cherts,
and in the western Ouachita province are mostly sandstones and shales [12].


VEGETATION : 
Classification:  There is much debate over the most useful
classification for the eastern deciduous forests including oak-hickory
forest.  Oak-hickory forest is not uniform across its range; dominants
vary with climatic and edaphic conditions.  The many differing
interpretations of oak-hickory forest are probably a function of its
vegetational complexity [15].  The most extensive area of unequivocal
oak-hickory forest is found in the Ozark Mountains, where it covers most
upland sites [15].  Hicks and Chabot [44] described oak-hickory forest
that is largely equivalent to Kuchler's oak-hickory type, but Braun [12]
characterized the central and eastern portions of K100 as western
mesophytic forest.  She defined the oak-hickory forest as the most
westerly part of the deciduous forest region.  Some authors use a
definition of oak-hickory forest that is broader than either Kuchler's
or Braun's, and include all forests dominated by oaks and having at
least some hickory component as oak-hickory.  These definitions usually
include Kuchler's oak-hickory forest (K100), oak-hickory-pine (Pinus
spp.) (K111), Appalachian oak forest (K104), and Braun's mixed
mesophytic forest [37,81].

Monk and others [65] divided the eastern deciduous forest into three
regions:  the northern region, occupied by eastern hemlock (Tsuga
canadensis), eastern white pine (Pinus strobus), and northern hardwood
forests; the central region which included oak-hickory; and the southern
region, occupied by pine and oak-pine forests.  They defined oak-hickory
as inclusive of Braun's oak-hickory, oak-chestnut (Castanea spp.), and
about half of her western mesophytic forest; this definition is
inclusive of Kuchler's oak-hickory forest but somewhat broader [65].

The Forest and Range Ecosystems of Garrison and others [37] include FRES
15, the oak-hickory ecosystem.  This ecosystem includes Kuchler's
oak-hickory but also the mosaic of oak-hickory and bluestem prairie
(K082), Cross Timbers (K084), Appalachian oak (K104), oak-pine-hickory
(K111), and oak savanna (K081) types [37].

This write-up includes mostly information about communities within
Kuchler's [51] oak-hickory forest region as it was mapped, with the
major focus on oak-hickory communities in the Ozarks.  Communities
further north (in Wisconsin and Michigan) are included where information
is deemed relevant.  An oak savanna type was mapped by Kuchler as a
potential type for Wisconsin and Michigan (K081), but forests of similar
structure and containing mostly the same species occurred widely in
presettlement times throughout the prairie-forest interface.  Savannas
in the central states are therefore included because of their relevance
to the fire ecology of oak-hickory forests.

Other classifications describing oak-hickory forest include the following:

The central hardwood forest [20]
Plant geography--with special reference to North America [28]
Ordination and classification of western oak forests in Oklahoma [31]
A classification of the deciduous forest of eastern North America [65]
The study of plant communities [71]
Classification and evaluation of forest sites in the Cumberland
  Mountains [86]
The natural vegetation of North America [97]

Flora:  Oak-hickory forests as described by Kuchler [51] are dominated
by white oak, black oak, northern red oak, bitternut hickory (Carya
cordiformis), and shagbark hickory (C. ovata).  Other trees in
alphabetical order of scientific name include pignut hickory (C.
glabra), white ash (Fraxinus americana), black walnut (Juglans nigra),
black cherry (Prunus serotina), chinquapin oak (Q. muehlenbergii), and
basswood (Tilia americana).  In the northern parts of the oak-hickory
forest, other components are northern pin oak (Q. ellipsoidalis), and
shingle oak (Q. imbricaria).  In the southern parts of the oak-hickory
type, forest tree species include black hickory (C. texana), mockernut
hickory (C. tomentosa), southen red oak (Q. falcata), overcup oak (Q.
lyrata), blackjack oak (Q. marilandica), Shumard oak (Q. shumardii),
and post oak (Q. stellata) [51].  Occasional eastern white pine and
eastern hemlock also occur [44].

Burkman and others [17] described oak-hickory forests as the largest and
most diverse forest type in the eastern United States.  Cover types
include post oak-blackjack oak, bur oak (Q. macrocarpa), bear oak (Q.
ilicifolia), northern pin oak, chestnut oak (Q. prinus), white oak-black
oak-northern red oak, white oak, black oak, and northern red oak [17].
Oak-hickory forest sensu Kuchler is approximately equivalent to the
Society of American Foresters white oak (Q. alba)-black oak (Q.
velutina)-northern red oak (Q. rubra), white oak, and northern red oak
forest cover types [39].

Braun's description of the oak-hickory forest flora resembles Kuchler's.
In northern stands, bur oak has great prominence.  Northern pin oak is
confined to the northern division.  Flowering dogwood is a common
understory tree.  Blueberries and huckleberries (Vaccinium spp.) are
abundant shrub layer components, as is ceanothus (Ceanothus spp.).  The
herb layer often contains poverty oatgrass (Danthonia spicata),
bird's-foot viola (Viola pedata), Appalachian mountainmint (Pycnanthemum
flexuosum), stone-mint (Cunila origanoides), clasping aster (Aster
patens), flax-leaved aster (A. linariifolius), and legumes including
downy trailing lespedeza (Lespedeza procumbens), round-leaved
tick-trefoil (Desmodium rotundifolium), wild sensitive plant
(Chamaecrista nictitans), goat's rue (Tephrosia virginiana),
pencil-flower (Stylosanthes biflora), and Sampson's snakeroot (Orbexilum
pedunculatum) [12].

The Texas Plant and Wildlife Department published a list containing
current information on the stability and distribution of plant
communities occurring in Texas.  They listed a post oak-black hickory
series and post oak-blackjack oak series which occur within Kuchler's
oak-hickory forest.  In each of these community types, woody species
diversity is highest to the east, where closed canopies may form.  Post
oak-black hickory forms open woodlands over deep sands in the western
portion of its Texas range; species composition varies with soil texture
and depth and herbs have higher species diversity than stands farther
east.  Components of this type include white oak, southern red oak,
blackjack oak, pines, other hickories, flowering dogwood, yaupon (Ilex
vomitorium), and beautyberry (Callicarpa americana).  Common components
of the post oak-blackjack oak series include cedar elm (Ulmus
crassifolia), southern red oak, yaupon, beautyberry, water oak (Q.
nigra), black hickory, eastern redbud, and deciduous holly (I. decidua),
but composition is variable [89].

Savanna:  Some authors define oak savanna as open-grown oaks with 10 to3
80 percent crown cover, with or without a shrub layer, and with a ground
cover of grasses and forbs [23].  The understory vegetation of savanna
is a mixture of both prairie and forest species, with prairie forbs and
grasses more abundant in areas of high light, and forest forbs and woody
species more abundant in areas of low light [13,69].  Early descriptions
of Missouri savannas are of very open woodlands with ground covers of
grasses and forbs and no underbrush or small timber [22].

The herb layer in oak savannas consists mostly of bluestem prairie
species, namely big bluestem (Andropogon gerardii), little bluestem
(Schizachyrium scoparium), Indian grass (Sorghastrum nutans),
switchgrass (Panicum virgatum), and many prairie forbs [97].  In Indiana
typical savanna herbs include little bluestem, butterfly weed (Asclepias
tuberosa), flax-leaved aster, and yellow sedge (Carex pensylvanica) [7].
Savanna trees are oak-hickory dominants; bur oak is common in northern
savannas and post oak and blackjack oak are dominant in southern
savannas.  In Texas junipers (Juniperus spp.) and mesquites (Prosopis
spp.) are common associates [97].  Indiana black oak sand savannas are
dominated by black oak and white oak.  Understory trees include black
cherry, sassafras (Sassafras albidum), shining sumac (Rhus copallina),
and smooth sumac (R. glabra) [7].

No species is known to be endemic to oak savannas, and relatively few
species are modal (i.e., have their highest occurrence in this habitat)
[69].  In Wisconsin only six species are considered modal in oak savanna
(K081):  sunflower-everlasting (Heliopsis helianthoides), kitten-tails
(Besseya bullii), cancer-root (Orobanche uniflora), smooth phlox (Phlox
glabberima), thick-root buttercup (Ranunculus fascicularis), and
mountain deathcamas (Zigadenus elegans) [25].

Geographic Trends:  Major vegetational trends from east to west include
an increasing importance of oaks, particularly post oak, and a reduction
in canopy tree species diversity.  Mesic sites and vegetation are more
restricted in the western part of the range, particularly with decreased
precipitation and increased incidence of drought and fire.  Pines
increase in importance from north to south [15].  Oak-hickory merges
with oak-hickory-pine (K111) in eastern Texas, grades into post
oak-blackjack oak savanna (Cross Timbers [K084]) farther south and west
in Texas, and alternates with tallgrass prairie on the western edges of
its distribution (within the region mapped as mosaic of bluestem prairie
and oak-hickory forest) [12].


WILDLIFE : 
Birds:  Few bird species can be considered distinctive of oak-hickory
forests.  Species frequently encountered in oak-hickory forests include
red-bellied woodpecker (Melanerpes carolinus) and cerulean warbler
(Dendroica cerulea) [61].  Avian species richness is well documented
within the southeastern portion of the oak-hickory forest.  Breeding
bird communities within southeastern oak-hickory forests range from
about 120 species in western Tennessee to about 93 species in the
southern extreme [38].  Dominant members of the avifauna of southeastern
oak-hickory forests include downy woodpecker (Picoides pubescens),
great-crested flycatcher (Myiarchus crinitus), red-bellied woodpecker,
eastern wood-pewee (Contopus virens), tufted titmouse (Parus bicolor),
Kentucky warbler (Oporornis formosus), red-eyed vireo (Vireo olivaceus),
and summer tanager (Piranga rubra) in the Bluegrass region of Kentucky.
On the Highland Rim and Knobs of Kentucky and Tennessee, dominant
avifauna also include ovenbird (Seiurus aurocapillus), black-throated
green warbler (Dendroica virens), black-and-white warbler (Mniotilta
varia), blue jay (Cyanocitta cristata), red-eyed vireo, wood thrush
(Hylcichla mustelina), Carolina chickadee (Parus carolinensis), hairy
woodpecker (Picoides villosus), and eastern wood-pewee.  In the Central
Basin, Tennessee, dominant avifauna include most of the abovementioned
species and yellow-billed cuckoo (Coccyzus americanus).  In the Ozark
Plateau blue-gray gnatcatcher (Polioptila caerulea) and northern
cardinal (Cardinalis cardinalis) occur in addition to previously
mentioned species; on the Coastal Plain additional species include
Carolina wren (Thryothorus ludovicianus), northern parula (Parula
americana), and hooded warbler (Wilsonia citrina).  In lowland
communities the avifauna is dominated by prothonotary warbler
(Protonotaria citrea), American redstart (Setophaga ruticilla), wood
duck (Aix sponsa), red-eyed vireo, American woodcock (Scolopax minor),
yellow-throated vireo (Dendroica dominica), northern parula, hooded
warbler, Acadian flycatcher (Empidonax virescens), pileated woodpecker
(Dryocopus pileatus), white-breasted nuthatch (Sitta carolinensis),
Carolina chickadee, and tufted titmouse [15].

Probst [75] summarized oak forest bird communities for the eastern
United States, including both oak-hickory forests and oak-pine forests.
The blue jay and the brown-headed cowbird (Molothrus ater) are species
of generalized habitat requirements that are found in almost every
stand, regardless of age or structure.  However, most birds require
particular habitat features.  Five categories of birds that are present
in oak-hickory forest, based on response to habitat feature include:  1)
bark foragers such as northern flicker (Colaptes auratus),
white-breasted nuthatch, downy woodpecker, and hairy woodpecker, 2)
active gleaners feeding in the tree canopy such as chickadees (Parus
spp.), tufted titmouse, and red-eyed vireo, 3) pursuers feeding in tree
canopy with a sit-and-wait hunting strategy such as flycatchers
(Empidonax spp.) and tanagers (Piranga spp.), 4) ground species
associated with shrub and sapling layers such as thrushes (family
Muscicapidae), rufous-sided towhee, and ovenbird, and 5) species
associated with dense growth of saplings and small trees, mostly
warblers (Emberizidae) [75].

Mammals:  Southeastern oak-hickory forests generally are low in
mammalian species richness with the exception of bats (Chiroptera).
The limestone-based geology of the region has fostered a rich cave fauna
including little brown myotis (Myotis lucifugus), big brown bat
(Eptesicus fuscus), and pipistrelles (Pipistrellus spp.).  The
white-footed mouse (Peromyscus leucopus) is very common in southeastern
oak-hickory forest; other common species include short-tailed shrews
(Blarina brevicauda and B. carolinensis), eastern chipmunk (Tamias
striatus), eastern gray squirrel (Sciurus carolinensis), eastern fox
squirrel (S. niger), gray fox (Urocyon cinereoargenteus), raccoon
(Procyon lotor), opossum (Didelphis virginiana), striped skunk (Mephitis
mephitis), and white-tailed deer (Odocoileus virginianus) [15].

Reptiles:  The garter snake (Thamnophis sirtalis) is very common in
oak-hickory forests of the Southeast; other common reptiles include
black racer (Coluber constrictor), black rat snake (Elaphe obsoleta),
five-lined skink (Eumeces fasciatus), fence lizard (Sceloporus
undulatus), rough green snake (Opheodrys aestivus), ring-necked snake
(Diadophis punctatus), eastern hognose snake (Heterodon platyrhinos),
and eastern box turtle (Terrapene carolina).  Reptile species richness
generally increases to the south and east of the southeastern
oak-hickory region.

Amphibians:  Moist sites within oak-hickory forest support amphibians,
most commonly slimy salamander (Plethodon glutinosus), dusky salamander
(Desmognathus fuscus), American toad (Bufo americanus), Fowler's toad
(B. woodhousei), spring peeper (Hyla crucifer), and gray treefrogs (H.
versicolor and H. chrysoscelis) [15].


ECOLOGICAL RELATIONSHIPS : 
Species Distribution:  Oak-hickory associates tend to clump together on
ridges and upper slopes.  In grassy openeings and on steep slopes and
other dry exposures oak-hickory associates cooccur with plant species
such as eastern redcedar (Juniperus virginiana) that are tolerant of
xeric conditions [15].  On the Ozark Plateau dry ridges and south-facing
slopes are usually occupied by open communities of post oak and
blackjack oak.  Locally, shortleaf pine (Pinus echinata) may form mixed
stands with the oaks.  White oak is usually more abundant on
north-facing slopes, entering some ridge forests.  In the western border
area, deep ravines and gorges are occupied by mesophytic species; sugar
maple (Acer saccharum), white oak, and northern red oak are abundant.
Open forests of low-statured trees with sparse herbs occur on xeric
plateaus [12].  On the Ozark Plateau in southeastern Missouri,
ordination of forest stands showed a clear separation of upland forests
into two groups.  Acid upland stands were dominated by black oak, black
hickory, and white oak.  Other stands (intermediate in elevation and
soil acidity) tended to be dominated by chinkapin oak, sugar maple,
eastern redcedar, and basswood.  White ash and slippery elm (Ulmus
rubra) were sometimes present [101].

The eastern deciduous forest reaches its western limit in the central
portion of Oklahoma as oak forest and oak savanna.  Farther west,
occasional stands occur in sandstone canyons in west-central Oklahoma
and in the Wichita Mountains of southwestern Oklahoma [31].  These
forests are attributed to climatic fluctuations which favored the
westward migration of eastern species [12].  Prior to European
settlement oak savanna was common in western Oklahoma; these stands now
have a closed canopy developed with the advent of grazing and fire
suppression.  Ordination of forests in this area demonstrated that the
vegetation pattern corresponded to a complex moisture gradient.  Post
oak and blackjack oak codominated forests occuping the xeric end of the
gradient, post oak dominated stands located in the middle (slightly more
mesic), and forests at the mesic end of the gradient included sugar
maple, elm, and Shumard oak-dominated stands [31].  Post oak and black
hickory appear to require relatively high levels of nutrients and
moisture, while blackjack oak is tolerant of drier, less fertile sites
[47].

Phenology:  The understory herbs begin growth earliest in spring; the
herb stratum is dominated by species that overwinter as rosettes or
underground perennating organs [44].

Disturbance and Succession:  Oak-hickory forests have a long history of
disturbance; the presettlement pattern was a mosaic of seral stands,
many due to Native American activities.  Continuing and overlapping
disturbances in the range of oak-hickory forest arise from the high
value of the land for agriculture [15].  In some regions in the eastern
United States, current oak dominance is similar to and is related to the
importance of oaks in presettlement forests.  In other regions,
particularly in the Midwest, the current distribution of oaks exceeds
that of presettlement vegetation [1].  Much development of oak forests
has occurred through a variety of ecological pathways and disturbance
patterns [2].  In northern Michigan sites on upland sandy soils that
were dominated by eastern white pine, red pine, or mixtures were
converted to northern red oak stands after disturbance by logging and
fire [46].  In Missouri stands that were oak-pine or pine at the turn
of the century are now dominated by scarlet oak (Quercus coccinea) and
black oak following heavy cutting of the pine and post-harvest fires
[24].

Most oaks are considered early to mid-successional species; there is
recent evidence of a widespread potential for oak replacement by more
shade-tolerant tree species in mature forests [53,68].  This phenomenon
seems to be more prevalent on mesic than on xeric sites [1,2].  There is
a strong successional trend to shade-tolerant species such as sugar
maple and American beech (Fagus grandifolia) on moist sites [15].  The
persistence of relatively shade-intolerant oaks in mesic forests may be
related to cycles of synchronous tree death similar to the fir (Abies
spp.) waves seen in New England, or shifting mosaic conditions caused by
climate changes and/or large-scale disturbance [102].  Changes in fire
frequency have had an impact on the species composition and structure of
many forests [15].  For further discussion, see FIRE ECOLOGY AND
MANAGEMENT.

Old-field Succession:  Species composition and the successional role of
species may vary geographically.  Generally, the first 3 years following
the last crop are dominated by herbaceous members of the Asteraceae such
as fleabanes (Erigeron spp.), asters (Aster spp.), ragweeds (Ambrosia
spp.), and goldenrods (Solidago spp.), and grasses such as crabgrasses
(Digitaria spp.), bristlegrasses (Setaria spp.), threeawns (Aristida
spp.), and panic grasses (Panicum spp.).  In many instances, woody
species such as persimmon (Diospyros virginiana), elms (Ulmus spp.),
hackberries (Celtis spp.) and junipers seed in but are not dominant for a
number of years.  Broomsedge (Andropogon virginicus) is a common
dominant from the fourth year on, and may be a component for over 20
years.  On limestone soils, eastern redcedar is a major old-field
inhabitant.  Oak-hickory and dry open forests of post oak, junipers,
blackjack oak, and black hickory eventually develop on at least 50
percent of the relatively dry uplands.  Other forest types develop in
mesic coves and in bottomlands [15].

Old-field succession occurred on abandoned fields in western Illinois
following a period in which the area was heavily cultivated and suffered
severe erosion, then converted to pasturage and hay fields.  Early
succession was dominated by cool-season grasses including Kentucky
bluegrass (Poa pratense).  Early establishing woody species included
boxelder (Acer negundo) and elms.  Trees with heavy seeds only later
invaded the edges of fields.  The most rapid tree development took place
in gullies [16].

Savanna Vegetation:  Depending on local conditions including fire
regime, climate, and settlement patterns, very different descriptions of
the same area were sometimes recorded within a few years [69].  The
structure of most savannas is highly dependent on fire frequency;
savannas are converted to more closed forest in less than 50 years
without fire.  Further discussion of the relationship of savanna and
fire is in FIRE ECOLOGY AND MANAGEMENT [15].

Nuzzo [69] distinguished between open savanna and scrub savanna.  Open
savanna is a parklike community with widely spaced trees, virtually no
shrub layer, and an herbaceous ground layer.  Scrub savanna is made up
of moderate to dense thickets of oak sprouts within a prairie matrix,
with a few fairly dwarfed open-grown trees.  Open savannas usually occur
on flatter, usually mesic areas, and scrub savannas are generally
located on the dry to dry-mesic areas of steeper topography,
particularly hillsides, dunes, and ridges.  Both kinds of savanna vary
in structure through time and space, depending on fire occurrence [69].

The persistence of some high-quality savannas may be related to the
droughty soils on which they occur.  Some savannas, in particular those
located on thin soil or rocky substrates, have survived moderate
grazing, exclusion of fire, and competition with alien and woody
species.  Light grazing may have helped maintain the savanna.  Some
stands have survived because they have been burned relatively frequently
[69].

The roots of savanna trees may show morphological responses to growing
in dry soils; bur oak taproots are at least 13.2 feet (4 m) deep in dry
soils but are not as deep in moist soils [103].

Related categories for Kuchler Type: Oak-hickory forest