BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus marilandica | Blackjack Oak



GENERAL BOTANICAL CHARACTERISTICS : 
Blackjack oak is a small to medium-sized, slow-growing, native,
deciduous tree.  It is often shrubby with a low, rounded crown.  The
contorted, down-sweeping branches remain on the tree several years after
they die [46].  Leaves are tenacious after having turned brown, often
clinging to the tree throughout the winter [50].  The acorns are about
0.4 inches (1 cm) long [41].  On poor xeric sites or in drier climates,
blackjack oak is rarely taller than 30 feet (9 m) [49,50].  On better
sites, it grows 45 to 50 feet (14-15 m) in height [15,49].  Blackjack
oak has lived to be as old as 230 years in Oklahoma [23].

Dwarfed forms of blackjack oak exist on Buzzard's Roost, Missouri, and
in the Pine Plains of New Jersey.  In Missouri, the trees are extremely
stunted (4.5 feet [1.4 m] tall), leaves and acorns are miniature, and
there is rosetting of the leaves [44].  In the New Jersey Pine Plains,
the dwarfed blackjack oaks are multistemmed with large, irregularly
shaped stools that are considerably older than the current stems.  The
height is usually less than 11 feet (3.4 m) [33].  Blackjack oak in the
Pine Plains exhibit rosetting of leaves and buds in stems roughly 10
years old or older [58].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual:  Blackjack oak is monoecious [50].  It bears seeds at a younger
age than many associated arborescent oaks.  In a study in West Virginia,
acorn crops of blackjack oaks that averaged 0.87 inch (2.2 cm) d.b.h.
failed 2 out of 4 years [39].

Dissemination is by gravity and animals.  Germination is hypogeal.
Blackjack oak grows more slowly than many associated trees, including
post oak [51].  Average annual height growth of seedlings in Missouri
during a 6-year period was 1.7 inches (4.3 cm) [26].

Excessive soil moisture and inundation cause severe stress and often
high mortality of blackjack oak seedlings [9].

Vegetative:  If top-killed or cut, blackjack oak sprouts vigorously from
the root crown [59].  Sprouts grow faster than seedlings.  Average
annual height growth of sprouts in Missouri during a 6-year period was
4.4 inches (11.2 cm) [26].  Root crown sprouts as young as 3 to 4 years
old can produce mature acorns [30].


SITE CHARACTERISTICS : 
A semixeric species, blackjack oak is found on xeric sand deposits and
on extremely dry upper slopes and ridges [56].  It generally occurs on
southerly or westerly aspects [34].  Blackjack oak is found to about
2,500 feet (760 m) in the Appalachian Mountains [16,57].

Blackjack oak typically occurs on dry, nutrient-poor soils [12].  Soils
are sandy, gravelly, or clayey, and may contain a fragipan subhorizon
[7,49].  Blackjack oak usually occurs in sand only if it is heavily
impregnated with clay or shallowly overlies clay [35].  In the Piedmont,
blackjack oak occurs on serpentine soils which are typically eroded,
shallow, and stony [7,22].  The stunted condition of blackjack oaks in a
plant community on Buzzard's Roost in Missouri [see General Botanical
Characteristics] is thought to be caused by the poor soil conditions
which include low pH, very low calcium and magnesium, and high aluminum
[44].

Blackjack oak occurs on sites too dry for southern red oak, northern red
oak, or white oak (Quercus alba) [37,44].  It often survives on more
xeric sites than post oak [14].  In Oklahoma, blackjack oak seedlings
occupied the xeric end of the moisture gradient, whereas on more mesic
sites, blackjack oak, post oak, and eastern redcedar (Juniperus
virginiana) seedlings codominated the seedling layer [13].  However,
during a severe drought in Oklahoma, there was higher mortality of
mature blackjack oak than post oak [46].  The dominance of blackjack oak
on less favorable sites may be due to its tolerance of soil infertility
rather than to its drought tolerance [23,46].

Overstory associates not mentioned in Distribution and Occurrence
include pignut hickory (Carya glabra), black hickory (C. texana),
mockernut hickory (C. tomentosa), scarlet oak (Q. coccinea), shingle
oak, winged elm (Ulmus alata), blackgum (Nyssa sylvatica), and sourwood
(Oxydendrum arboreum).  Understory associates include blueberry
(Vaccinium spp.), huckleberry (Gaylussacia spp.), mountain-laurel
(Kalmia latifolia), sumac (Rhus spp.), and hawthorn (Crataegus spp.).
Herbaceous plant associates include bluestems (Andropogon spp.), little
bluestem (Schizachyrium scoparium), and sedges (Carex spp.) [7,16,58].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Blackjack oak is shade intolerant [15].  Because of slow growth, it is
probably overtopped by other species, including most oaks.  It probably
persists and becomes dominant on sites too poor for faster growing
species.

Blackjack oak is common in the understory of pine (Pinus spp.)-hardwood
forests.  In the absence of fire, blackjack oak may become dominant
depending on site conditions and competition from associated species
[17].  In upland longleaf pine (Pinus palustris) savannas and longleaf
pine sandhills in the west Gulf Coastal Plain, blackjack oak, along with
post oak, bluejack oak, and black hickory, become dominant and
eventually replace longleaf pine [6].

Blackjack oak, along with post oak, will expand into adjacent prairies
in the absence of fire [17].  The post oak-blackjack oak association may
be an edaphic climax on dry sites [16].  Because of its longevity,
blackjack oak may be found as a dominant in climax oak-hickory forests
[46]. 

In a study in central Illinois, dry sandy sites were dominated by
blackjack oak and black oak.  The two species also dominated the
seedling and sapling layers.  However, an influx of shade tolerant,
mesophytic species such as American elm (Ulmus americana) and hackberry
(Celtis occidentalis) in the seedling strata suggest that at least a
partial takeover is likely in the continued absence of fire.  The xeric
nature of the site will probably prevent complete takeover [1].


SEASONAL DEVELOPMENT : 
Blackjack oak flowers from March to May depending on latitude and
elevation.  Acorns ripen from September to November of the second
growing season after flowering, drop in the fall, and germinate in the
spring [15,41,50].

Related categories for Species: Quercus marilandica | Blackjack Oak