BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus rubra | Northern Red Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Northern red oak is a medium to large, variable deciduous tree [39,47].
It is the tallest and most rapidly growing of the oaks [20] and commonly
reaches 65 to 98 feet (20-30 m) in height and 2 to 3 feet (61-91 m) in
diameter [101].  On extremely favorable sites plants may grow to 160
feet (49 m) and up to 8 feet (2.4 m) in diameter [24].  Trees are tall,
straight, and columnar with a large crown in forested stands but are
characterized by a short bole and spreading crown in openings [101].
Plants generally have a strongly developed taproot and a network of
deep, spreading laterals [47,56].  The gray to grayish-brown bark has
shallow vertical furrows and low ridges and becomes checkered with age
[39].

Northern red oak is monoecious.  Staminate catkins are borne in leaf
axils of the previous year's growth, whereas pistillate catkins occur in
two- to many-flowered spikes in the axils of leaves [101].  The acorns
are approximately 0.8 to 1.3 inch (20-33 mm) in length, with a shallow,
saucer-shaped cup [26,39,47].  Acorns are borne singly or in clusters of
two to five [101].  The nut contains a large, white, bitter kernel [20].

The variety borealis is characterized by smaller acorn cups [93].


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (megaphanerophyte)
   Undisturbed State:  Phanerophyte (mesophanerophyte)
   Undisturbed State:  Phanerophyte (nanophanerophyte)
   Burned or Clipped State:  Chamaephyte
   Burned or Clipped State:  Hemicryptophyte
   Burned or Clipped State:  Cryptophyte (geophyte)


REGENERATION PROCESSES : 
Seed:  Northern red oak generally first bears fruit at 25 years of age,
although most trees do not produce acorns in abundance until 50 years of
age [101].  On extremely favorable sites trees as young as 10 years may
bear some fruit [53].  Northern red oak produces good crops every 2 to 5
years [101].  Yields vary by individual as well as with weather
conditions and site factors.  Relatively large, dominant or codominant
individuals with open crowns typically produce more acorns than do trees
with small, restricted crowns.  Trees with a 16 inch (41 cm) d.b.h. can
yeild 800 acorns per year, and trees with a d.b.h. of 20 to 22 inches
(51-56 cm) can yield 1,600 acorns per year [33].  Larger trees tended to
be less productive.  Total acorn production may range from 100 to more
than 4,100 per tree [111].  In a single year, northern red oak trees
produced a combined total of nearly 14,000 sound acorns per acre in a
mixed oak stand in southern Michigan [33].  Cold, rainy weather during
flowering can result in poor seed production [43].

Under carefully controlled conditions, acorns can be stored for up to 2
or 3 years [127].  After 52 months in storage, only a few acorns
remained viable.  In good acorn years up to 80 percent of the crop is
commonly destroyed, and in poor years virtually the entire acorn crop
can be eliminated by birds, mammals, and insects [101].

Germination:  Acorns of northern red oak are characterized by variable
dormancy which requires stratification for germination [11].  Dormancy
varies by the individual seed [114], but northern seeds often require
longer stratification [11].  Under natural conditions, acorns generally
germinate in the spring after dormancy is broken by over-wintering [24].
Delayed germination may occur but is very rare [114].  Seeds can be
stratified at 35 to 41 degrees F (2-5 degrees C) for several months
[11].

Acorns germinate best in soil which is covered by a layer of leaf litter
[101].  In one study, 80 percent of all planted acorns germinated
compared with less than 1 percent of acorns left on the soil surface.
Domestic animals such as pigs and cows may promote germination by
trampling the soil and "planting" the acorns, and by reducing competing
herbaceous vegetation [25].  Seeds on the soil surface are particularly
vulnerable to rodent predation [24].  In an Iowa study all seeds present
on top of the litter layer were destroyed by rodents compared with 68
percent of buried seeds [33].

Seed dispersal:  Seeds of northern red oak are primarily dispersed by
birds and mammals.  Scatter-hoarders such as the gray squirrel are
particularly important dispersal agents in some areas [111].  Gray
squirrels bury as much as 19 percent of the available acorn crop and
fail to recover many seeds over the winter [65].  Scatter-hoarders
typically disperse seed a few yards from the source tree.  Mice and
chipmunks are short-distance dispersers and usually move seeds 33 to 98
feet (10-30 m) [25].  Blue jays are effective long-distance dispersal
agents and can transport seed from several hundred yards to 2 or 3 miles
(4-5 km) [25,53,57].  Evidence suggests that blue jays prefer to cache
acorns on open sites or at forest margins [25].  Gravity may aid in seed
dispersal [101].

Seedling establishment:  Seedling establishment is generally limited to
years of abundant acorn production [101].  However, advance regeneration
is usually present.  In mature stands, seedlings may number up to 7,000
per acre (2,824/ha), but few survive more than a few years or grow to
more than 6 or 8 inches (15-20 cm) in height [52].  Seedlings require
adequate soil moisture for survival and good early development [24].
Early growth may be reduced by a combination of shade, low soil
fertility, and competing herbaceous vegetation [60,61].  Shading alone
has little effect on initial seedling establishment [60].

Vegetative regeneration:  Northern red oak commonly sprouts vigorously
after plants are damaged or killed by fire or mechanical injury [101].
Small poles, saplings, and even seedlings can sprout if cut or burned
[43].  Although young oaks typically stump sprout more readily than do
older or larger individuals, northern red oaks up to 22 inches (56 cm)
in diameter have produced sprouts [33].  Stump sprouts derived from
larger stems tend to grow faster than those derived from smaller,
damaged stems.  Individuals 20 to 25 years of age regardless of size
produce an average of four or five sprouts [101].

Repeated sprouting is common in northern red oak [122]; many seedlings
die back to the ground level periodically.  Seedling sprouts with root
collars up to 2 inches (5 cm) in diameter often develop after repeated
damage [46].  After repeated fires, these stems may develop "stools" or
areas comprised of callus tissue filled with dormant buds.  Seedlings
often develop an "s"-shaped curve at ground level which helps protect
dormant buds from fire [98].  Cycles of dying back and resprouting can
result in crooked, flat-topped, or forked stems [101].

Root sprouting also occurs [46].  Sprouts that develop at or below the
ground level are less likely to decay than are sprouts that develop
relatively high on the parent stump [101].  Epicormic buds located
beneath the bark of older oaks commonly sprout when older trees are
damaged or after openings are created by heavy thinning [101,122].

Bud dormancy is largely controlled by auxins rather than by levels of
carbohydrate reserves [122].  Apical dominance can restrict the
development of belowground buds when buds survive on aboveground
portions of the plant.  Sprouting is reduced by low light levels [122]
and decreases as the stand ages [75].  The number of sprout groups
decreases from poor to good sites [75].  Initial sprout growth is
typically rapid [98].


SITE CHARACTERISTICS : 
Northern red oak grows on a variety of dry-mesic to mesic sites [3].  It
occurs in rich, mesic woods, on sandy plains, rock outcrops, stable
interdunes, and at the outer edges of floodplains [29,124,126].
Northern red oak is most common on north- and east-facing slopes
[30,101].  It typically grows on lower and middle slopes, in coves,
ravines, and on valley floors [101].

Plant associates:  Overstory associates of northern red oak are numerous
and include white oak (Quercus alba), black oak, scarlet oak, southern
red oak, post oak (Q. stellata), eastern white pine (Pinus strobus),
American beech (Fagus grandifolia), sugar maple, red maple (Acer
rubrum), black cherry (Prunus serotina), American basswood (Tilia
americana), sweet gum (Liquidambar styraciflua), white ash (Fraxinus
americana), green ash (F. pennsylvanica), aspen (Populus tremuloides),
hickories (Carya spp.), black gum (Nyssa sylvatica), black walnut
(Juglans nigra), jack pine (Pinus banksiana), eastern hemlock (Tsuga
canadensis), and elm (Ulmus spp.) [12,76,82,101].  Flowering dogwood
(Cornus florida), holly (Ilex spp.), eastern hophornbeam (Ostrya
virginiana), sassafras (Sassafras albidum), American bladdernut
(Staphylea trifolia), redbud (Cercis canadensis), persimmon (Diospyros
virginiana), and serviceberry (Amelanchier spp.) are frequent small tree
associates [101].  Common understory shrubs and vines include greenbrier
(Smilax spp.), blueberries (Vaccinium spp.), mountain-laurel (Kalmia
spp.), leatherwood (Dirca palustris), witch-hazel (Hamamelis
virginiana), beaked hazel (Corylus cornuta), spice bush (Lindera
benzoin), poison-ivy (Toxicodendron radicans), grape (Vitis spp.), and
rosebay rhododendron (Rhododendron maximum) [101].  Numerous herbaceous
species occur with northern red oak.

Climate:  Annual precipitation averages 30 inches (76 cm) at the
northwestern edge of northern red oak's range and 80 inches (203 cm) in
the southern Appalachians [101].  Mean annual temperatures range from 40
degrees F (4 deg C) in the North to 60 degrees F (16 deg C) in the South
[24].  Growing season length varies from 100 to 220 days.  Northern red
oak reaches its best development in the Ohio Valley and along the west
slope of the Allegheny Mountains where precipitation averages 40 inches
(102 cm) annually and average annual temperature is 52 degrees F (11
degrees C) [101].

Soils:  Northern red oak grows on clay, loam, and sandy or gravelly
soils [20,101].  Soils may be deep and free of rocks, or shallow and
rocky [33].  Plants generally exhibit best growth on deep, fertile,
well-drained, finely textured soils with a relatively high water table
[26,39,101].  Soils are derived from a variety of parent materials
including glacial outwash, sandstone, shale, limestone, gneiss, schist,
or granite [101].

Elevation:  Northern red oak grows at relatively low elevations in the
Smoky Mountains.  The variety rubra typically grows at lower elevations
than does the variety borealis [129].  Generalized elevations ranges by
geographic location are as follows [73,101,113]:

        Location          Elevation                           

        s Appalachians    up to 5,500 feet (1,680 m)           
        White Mtns. NH    up to 1,476 feet (450 m)             
        IN                700 to 850 feet (214-259 m)         
        MO                800 to 1,300 feet (244-397 m)        
        MI                600 to 700 feet (182-214 m)         
        NY                900 to 1,400 feet (275-427 m)       
        NC                2,300 to 5,000 feet (702-1,525 m)    
        WV                1,800 to 3,500 feet (549-1,070 m)    
        WI                800 to 1,000 feet (244-305 m)       


SUCCESSIONAL STATUS : 
Northern red oak is intermediate in shade tolerance [101].  It is
generally considered a midseral species, but its successional status is
poorly known.  Crow [25] reported that it is "neither an aggressive
colonizer that is characteristic of early successional species nor an
enduring shade-tolerant, slow-grower . . . typical of late successional
species."  Even-aged stands are common; northern red oak is unable to
establish beneath its own canopy.  Advanced regeneration provides a mode
by which northern red oak can reoccupy a site following disturbances
such as fire, wind damage, or herbivory.  In most areas, advanced
regeneration persists for no more than a few years [85].  Parker and
others [88] reported that some seedlings persisted for approximately 25
years despite repeated die-backs.  These seedlings did not reach sapling
or pole size unless gaps were created in the forest canopy; most
ultimately died [88].  Limited evidence suggests that northern red oak
may have maintained itself in some mature forests through gap-phase
replacement [25].  Northern red oak is often replaced by more
shade-tolerant species such as sugar maple and American basswood [6,17].

The Upper Midwest:  In parts of the Upper Midwest, northern red oak
dominates early seral to midseral stages following clearcutting but is
replaced by sugar maple and American basswood [51].  Northern red oak
assumes prominence after early succession in which bigtooth aspen
(Populus grandidentata) dominates in upland pine-hardwood forests of
Michigan [102] and persists in some old-growth oak-hickory forests of
southern Michigan [42].  Even-aged stands found in parts of the
Driftless Area may have originated after intense, stand-replacing fires
that began in nearby prairies and savannas.  With frequent fires, sugar
maple forests are replaced by northern red oak stands [25].

New England:  In New England, logging and slash fires in the late 1800's
and early 1900's replaced pine-hemlock forests with stands made up of
oak and maple [83].  In central New England, where advance regeneration
is present prior to disturbance, northern red oak often assumes
dominance between 10 to 40 years after disturbance and often persists
for 100 years or more [46].  Forests are often replaced by sugar maple,
red maple, or gray birch (Betula populifolia) [46,83].

Central Midwest:  Northern red oak is present in old growth floodplain
forests of Illinois [96] and in "postclimax" stands on mesic sites in
Nebraska [2].  In parts of Indiana, it is generally regarded as a
midseral to late seral species in mesophytic forests and is often
replaced by species such as sugar maple, Ohio buckeye (Aesculus glabra),
shagbark hickory (Carya ovata), American beech, and white ash in climax
stands [86,88].


SEASONAL DEVELOPMENT : 
The timing of annual budbreak varies with the genetic composition of the
plant and with site characteristics such as elevation and soils [8,62].
Budbreak tends to be delayed at higher elevations [62] and on sites with
copper, lead, or zinc mineralized soil [8].  Plants often undergo
relatively rapid vegetative growth from May through June [23].  Episodic
or recurrent shoot growth, in which periods of shoot elongation
alternate with resting periods, can occur throughout the growing season
[25].  Growth of leaves and roots is also often cyclic [27].  However,
under natural conditions, seedlings typically produce a single flush of
leaves during a relatively short period of growth which often lasts only
2 to 3 weeks.  The shoot becomes dormant during early summer despite
seemingly favorable growing conditions [25].

Flowering occurs in April or May, during or before leaf development
[33].  Acorns require two seasons for development and ripen in September
and October [24].  Phenological development by geographic area follows:

Area              Flowering         Fruit ripe        Reference

Adirondacks       May               September         [20]
Blue Ridge Mtns.  April-May         ----              [130]
WI                May               ----              [26]
var. rubra
NC,SC             April             August            [93]
var. borealis:
NC,SC             May               Sept.-Oct.        [93]

Related categories for Species: Quercus rubra | Northern Red Oak