The Iroquois considered Quercus ilicifolia very helpful in treating gynecological problems (D. E. Moerman 1986).
Control
Fall fire
Spring fire
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g. [30,31,48,107,116,129]).
Aboveground description: Bear oak is a deciduous gangly shrub or small tree that often forms dense thickets. It ranges from 3 to 30 feet (1-8 m) tall and 2 to 6 inches (5-15 cm) in diameter [30,31,48,107,116,129]. Stems are short-lived and grow slowly [109,134]. The typical stem life span is 20 to 30 years; however, the bear oak root system is reportedly long lived and may support several generations of short-lived stems [99,134].
Leaves are arranged alternately. Leaf length measures 2 to 6 inches (5-15 cm), and the width is 1 to 4 inches (3-10 cm) [30,31,48,101,116,129]. Bear oak is monoecious, with both male and female flowers on the same plant. Male flowers are catkins and female flowers are borne in clusters or singly. Female flowers are produced on current-year's growth [31,107,116,135]. Acorns are egg-shaped and measure 0.4 to 0.8 inch (1-2 cm) long. The acorn cup is saucer shaped with large scales and covers about 1/2 the nut. Bear oak requires 2 growing seasons to produce fruit [31,48,55,107,116].
Belowground description: Underground bear oak structures carefully excavated from the New Jersey pine barrens revealed that bear oak stems arise from a "massive" irregularly shaped taproot. The taproot is commonly 2 to 4 inches (5-10 cm) thick but may measure as thick as 7 inches (20 cm). Three common root structures were observed. One type had a single main taproot that reached 20 to 36 inches (51-91 cm) deep and lateral roots that lay just below the soil surface. Another had 2 main taproots and several well-developed lateral roots. Root systems with 2 or more main roots growing vertically or obliquely were also common. Two other root types were observed but were less common. One had a single main taproot that extended obliquely, and the other had 1 taproot that forked within a few inches of the soil surface allowing 2 taproot branches to extend horizontally at a depth of 4 to 8 inches (10-20 cm) [75].
Bear oak roots did not reach into the water table even when it was shallow (1 to 2 feet (0.3-0.6 m), and bear oak was absent or scarce on imperfectly to poorly drained soils. Bear oak roots are intolerant of saturated conditions, which may explain some of the variation in root structure in the New Jersey pine barrens [75].
Fire adaptations: Bear oak aggressively produces sprouts from the root crown following top-kill by fire [2,63]. While some seedlings may emerge following fire, vegetative regeneration is predominant [15,17].
FIRE REGIMES: Frequent fires are characteristic of bear oak habitats. Dwarf mixed pine-shrub oak vegetation in the New Jersey pine barrens are consistently recognized as fire-maintained communities [79,83,91,136]. A fire frequency of 6 to 8 years is suggested by Bucholz and Gallagher [16] to preserve dwarf pitch pine-bear oak and blackjack oak forests on New Jersey's pine barren plains. Reasons for frequent fires in bear oak habitats are described for southern New Jersey's pitch pine forests. Bear oak communities are highly flammable because of long growing seasons, high maximum temperatures, strong dry winds, and level to rolling topography that favor ignition and extensive fire spread [83].
Fire occurrence and return intervals: Bear oak communities may burn as frequently as every 5 years, and the longest mean fire return interval reported for bear oak habitat is 60 years [128]. Wade and others [121] suggest that the bear oak cover type burns in understory fires at intervals of 35 years or less in eastern forests. Likely the type of vegetation that invades bear oak communities and the speed at which it comes to dominate the canopy affects bear oak's longevity in fire-free communities.
In pitch pine forests of southern New Jersey, Lutz [83] estimated that prior to 1923, fires burned in plains vegetation an average of once every 8 years. "Transition" communities burned every 12 years, and barren vegetation types burned every 16 to 26 years, on average. For a brief description of these community types, see the New Jersey: section of Habitat Types and Plant Communities.
In the New Jersey pine plains, bear oak is present in several community types with mean fire return intervals ranging from 5 to 60 years. In open shrublands dominated by low-growing blackjack oak, bear oak, and pitch pine, surface and crown fires are common at 5- to 15-year intervals. In mature closed shrublands where vegetation composition is the same as in open pine plain shrublands but grows slightly taller, the mean fire return interval is 15 to 60 years. Fires are sporadic, and a mix of crown and surface fires is common. In pitch pine-shrub oak barrens that support tree-sized pitch pine burn, crown fires are more common than surface fires, and the average fire frequency is 15 to 25 years. Pitch pine-post oak/shrub oak woodlands typically burn in crown fires that occur every 25 to 30 years, on average. Pitch pine-tree oak/shrub oak and pitch pine-shortleaf pine-tree oak/shrub oak vegetation types support a mixture of crown and surface fires at 30- to 40-year intervals [128].
In Cape Cod, eastern Massachusetts, signs of past fire were evident in most bear oak habitats. Fire scars and/or macroscopic charcoal were found in over 70% of pitch pine/bear oak and oak-pine/huckleberry communities and in nearly 50% of manzanita (Arctostaphylos spp.)-bear oak communities. Because of the methods used in this study, the evidence of past fire has likely been underestimated. Underestimates were likely greatest for shrub-dominated communities, which lack trees [94].
Fire behavior: Severe fires were typical in bear oak communities. In the Connecticut Valley of Massachusetts, large, severe, summer fires were predominant in pitch pine/scrub oak vegetation early in and through the middle of the 20th century [93]. Spring fires before leaf out were most common in Suffolk County, New York, between 1938 and 1995. The "high-intensity, top-killing" fires burned when winds were high, humidity was low, and litter and fine fuels were readily combustible. However, the deep duff layer was normally moist, so deep-penetrating fires were unlikely. Researchers suggest mimicking historical FIRE REGIMES in the Connecticut Valley and Suffolk County today is difficult given the highly fragmented nature of the vegetation and its proximity to wildland urban interfaces [63].
Changes in fire frequency over time: Fire frequency changes in bear oak habitats are often the result of anthropogenic influences. In the pitch pine forests of southern New Jersey, fires were common, but natural fire ignitions were rare. Anthropogenic fire starts were common, and since these woodlands were not valued for timber production large areas were allowed to burn. However, successful fire exclusion in the area led to reduced fire frequencies beginning in 1932 [83]. Historical fire records indicate that fire size and area burned annually has decreased since 1940 in the 1,400,000-acre (550,000-ha) New Jersey pine barrens. From 1906 to 1939, an average of 55,275 acres (22,369 ha) burned per year, and the average fire size was 112 acres (45.5 ha). During the early 1900s, the fire return interval for the area was an estimated 20 years. From 1940 to 1980, an average of 20,050 acres (8,115 ha) burned annually, fire size averaged 16 acres (6.4 ha), and the estimated fire return interval was 65 years. Most fires in the pine barrens were stand replacing [42].
The species composition of pitch pine barrens in Suffolk County, New York, has changed with fire exclusion practices. Aerial photographs revealed that from 1938 to 1995 average fire size has significantly (p=0.001) decreased. From 1938 to 1996, approximately 55% of the study area was unburned. Barren communities including dwarf pine plains, pitch pine/scrub oak, heath, pitch pine/heath, and scrub oak shrublands made up 87% of the study area in 1938 but just 36% in 1994. Bear oak shrublands decreased by 84% (857 acres (347 ha)) from 1938 to 1994, and pitch pine/bear oak woodlands decreased by 72% (5,100 acres (2,065 ha)) from 1938 to 1994. A severe wildfire in 1995, however, mitigated the loss of bear oak shrublands by creating 2,000 acres (820 ha) of this vegetation type. Fire return intervals of more than 30 years allow tree oaks to establish and persist [63].
In Suffolk County, New York, European settlement increased the amount of area occupied by pine barrens vegetation through logging and burning in the 17th, 18th, and 19th centuries. Logging typically involved the selective removal of deciduous hardwoods for building material and fuel. Fires were used to clear areas for farming, came from railroad engine sparks, and occurred through human carelessness. Fire exclusion in the 20th century has led to the conversion of a lot of once barren vegetation to tree oak-hardwood forests in north-central Suffolk County and tree oak-pitch pine woodlands in south-central Suffolk County [69]. However, research in the Pocono till barrens of Pennsylvania indicates that areas were bear oak-dominated prior to settlement. These areas are thought to have been maintained through periodic fire, fire-adapted species dominance, low-nutrient soils, and microclimates [74].
On Martha's Vineyard Island of Massachusetts, historical records indicate that fire size has decreased since the late 1940s. Between 1855 and 1990, over 20 fires burned that were 990 acres (400 ha) or larger, and 9 or more fires exceeded 5,000 acres (2,000 ha) in size. More than 90% of fires burned in the spring. However, since the late 1940s there was only 1 fire larger than 1,000 acres (600 ha), and since 1965 no fires have exceeded 100 acres (40 ha) in size [44].
The following table provides fire return intervals for plant communities and ecosystems where bear oak is important. Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Community or ecosystem Dominant species Fire return interval range (years) shortleaf pine Pinus echinata 2-15 shortleaf pine-oak Pinus echinata-Quercus spp. <10 Table Mountain pine Pinus pungens <35 to 200 [121] pitch pine Pinus rigida 6-25 [17,59] eastern white pine Pinus strobus 35-200 [117,121] eastern white pine-northern red oak-red maple Pinus strobus-Quercus rubra-Acer rubrum 35-200 Virginia pine Pinus virginiana 10 to <35 Virginia pine-oak Pinus virginiana-Quercus spp. 10 to <35 [121] quaking aspen-paper birch Populus tremuloides-Betula papyrifera 35-200 [28,121] oak-hickory Quercus-Carya spp. <35 northeastern oak-pine Quercus-Pinus spp. 10 to <35 southeastern oak-pine Quercus-Pinus spp. <10 white oak-black oak-northern red oak Quercus alba-Q. velutina-Q. rubra <35 [121] bear oak Quercus ilicifolia 5-60 [83,128] chestnut oak Quercus prinus 3-8 northern red oak Quercus rubra 10 to <35 post oak-blackjack oak Quercus stellata-Q. marilandica <10 black oak Quercus velutina <35 [121]Throughout its range, bear oak occupies dry mountain, upland, barren, and slope sites [101,116,129]. Bear oak is sensitive to salt spray in areas with low water availability and is likely restricted from extreme coastal locations [54].
Climate: Bear oak habitats have very similar climate regimes; however, temperature extremes are typically less pronounced in more coastal habitats. On Martha's Vineyard, Massachusetts, the climate is mild. Average winter and summer temperatures are 30 °F (0 °C) and 70 °F (20 °C), respectively. Average annual precipitation is 47 inches (1,200 mm), and thunderstorms commonly occur about 20 times a year [44]. In southern New Jersey, average temperatures are similar. The coldest month is typically February when temperatures average 29 to 34 °F (-1.7-1.1 °C). The warmest month is July when temperatures average 73 to 77 °F (23-25 °C). However, the record high as of 1934 was 107 °F (42 °C), and the record low was -16 °F (-27 °C) [83]. In Maryland's Appalachian Province, there are commonly 120 to 150 days with below freezing temperatures, and the average annual precipitation is 43 inches (1,100 mm), most of which falls in June [14]. In central Pennsylvania, late spring frosts are common [60].
Elevation: The bear oak forest cover type occupies elevations from near sea level to 3,000 feet (1,000 m) throughout its range [60]. Bear oak is restricted to elevations of less than 1,000 feet (300 m) in the Adirondacks of New York [68] and from 1,500 to 2,500 feet (460-760 m) in North Carolina [4].
Soils: Bear oak grows on sandy, rocky, well-drained, nutrient-poor soils [30,31,48,60,127]. In northern Virginia's Blue Ridge Province, Table Mountain pine/bear oak/heath woodlands are found in infertile soils with low pH, calcium, and magnesium levels but high iron and aluminum levels [41]. In the Appalachians, bear oak is common on shallow soils [21].
Bear oak thickets provide food and shelter for many wildlife species [31]. Black bears, white-tailed deer, small mammals, game birds, and songbirds eat acorns [23,25,57,116]. Early successional pine barren habitats where bear oak abundance is high are correlated with many rare and declining bird and moth populations in southeastern Massachusetts [52].
Bear: Acorns provide important fall weight gain for prehibernating black bears [25].
Deer: Bear oak stems and acorns are eaten by white-tailed deer [23,57]. Browse utilization may be related to season and stem age. White-tailed deer browsing was greater on burned than unburned bear oak-dominated woodlands in central Pennsylvania. In the summer of 1971, white-tailed deer browsed 43% of bear oak stems on plots burned the previous spring but browsed fewer stems, 23% to 26%, on unburned and 3-year-old burned plots. In 1972 white-tailed deer browsed 57% of bear oak stems on 1-year-old burned plots and browsed 25% or less on unburned and 2-year-old burned plots [56]. Following low-severity, early spring, prescription fires in scrub oak communities of Centre County, Pennsylvania, white-tailed deer browsed 3.6% of all new sprouts [108].
In central Pennsylvania, white-tailed deer utilization of bear oak was heaviest in the late winter months. White-tailed deer browsed bear oak stems rarely (trace-0.7%) from April through November. Utilization in December, January, February, and March was 2.7%, 1.8%, 5.7%, and 9.9%, respectively. Percent utilization was averaged over 3.5 years of data collection [11].
Little and others [82] observed few white-tailed deer browsing on 1-year-old bear oak stems in southern New Jersey pitch pine forests. However, white-tailed deer did feed on the acorns of low-growing scrub oaks. The researchers predicted that scrub oak acorns likely fed deer for just 6 weeks of the year, but in good mast years acorns may be available for several months. For information on acorn production in southern New Jersey, see Seed production. Several other researchers indicate that acorns are palatable to white-tailed deer and an important source of fat through the fall and winter [23,25].
Small mammals: A number of small mammals feed on acorns. Small mammal browsing occurs but is likely affected by bear oak stem age and seasonality. A 2-year study of eastern and New England cottontail feeding habits in Connecticut revealed bear oak utilization was low. Based on 170 winter (January-March) observations, researchers observed feeding on bear oak 5 times. In the summer (April-October), cottontails did not feed on bear oak in 27 total observations [24].
Eastern chipmunks, eastern gray squirrels, red squirrels, southern flying squirrels, and northern flying squirrels all feed on acorns and commonly cache nuts for overwinter use [25].
Birds: Bear oak habitats and acorns are important for a diversity of game and songbird species. Great crested flycatchers are common in dry pitch pine barrens, pine warblers utilize pitch pine woodland habitats, and brown thrashers and eastern towhees are common in pitch pine/scrub oak forests of New England [25]. In the Barrens Grouse Habitat management Study Area in Centre County, Pennsylvania, Yahner [137] found that species richness, species diversity, and total density of the ground-shrub foraging bird guild were positively correlated with bear oak, dwarf chinkapin oak, and black cherry (Prunus serotina) densities. Birds characteristic of this guild included gray catbirds, golden-winged warblers, chestnut-sided warblers, and field sparrows [137]. The number of bird species observed in bear oak was 17 in the spring and 2 in the winter from 1981 to 1984 [138]. In Plymouth County, Massachusetts, ruffed grouse were associated with sites having high bear oak coverage in pitch pine/bear oak communities [51].
In pitch pine/bear oak barrens in southeastern Massachusetts, 31 breeding bird species were observed in the study area. Rufous-sided towhees, common yellowthroats, and prairie warblers made up 49% to 70% of the total breeding bird density. Rufous-sided towhees used bear oak vegetation when foraging above ground, and common yellowthroats and prairie warblers had a "pronounced preference" for bear oak when foraging [92].
A number of birds feed on acorns, so it is likely that when bear oak and bird habitats overlap, bear oak acorns would be utilized. Red-bellied and other woodpeckers, jays, white-breasted nuthatches, and brown thrashers feed on acorns. Acorns are also eaten by wild turkeys [25,57] and are preferred over other available natural foods [113]. In the Nathaniel Mountain Refuge of southern Hampshire County, West Virginia, bear oak together with dogwood (Cornus spp.) and fox grape (Vitis labrusca) made up the bulk of wild turkey diets. The researcher indicated that wild turkeys were competing with white-tailed deer and squirrels for bear oak acorns [49].
Insects: Bear oak supports a rich insect fauna that includes several rare moth species. A diverse community of Coleoptera and Lepidoptera insect herbivores feeds on bear oak [2], and planthoppers of the Homoptera order also utilize bear oak as a host [126]. Surveys of pitch pine/bear oak barrens from Maine to Virginia revealed that 44 Miridae insect species were associated with bear oak. The researcher noted that insect associations in bear oak were more diverse than insect associations in other northeastern oak communities [125].
Bear oak is the only or primary larval host for 16 of 56, or 29%, of the rare or endangered Lepidoptera species in southern New England and southeastern New York. However, this likely underestimates bear oak's importance, as 12 polyphagous species utilized bear oak and/or low sweet blueberry (Vaccinium angustifolium) as hosts, as well [122]. In southeastern Massachusetts, bear oak is host for Lepidoptera species that include daggermoths, pine barrens itames, Melsheimer's sack-bearers, spiny oakworms, and Gerhard's underwing moths. These moths were associated with early successional pine barrens habitats with a high abundance of bear oak [52].
In bear oak, black jack oak, and pitch pine pygmy forests of New Jersey's Burlington and Ocean counties, pitfall trapping of 2 tiger beetles (Cicindelidae unipuncata and Megacephala virginica) was more successful than expected, suggesting that these species may be more common than realized [10].
Palatability/nutritional value: Foliar and acorn nutrient concentrations of bear oak in Pennsylvania are provided below. The nutrients available in dry and fresh bear oak acorns that were collected in late September from Pennsylvania are as follows [123]:
Percent content (dry) Percent content (fresh) Moisture NA 42 Crude protein 10.3 5.9 Ether extract 20 11.6 Crude fiber 3 1.7 Total ash 2.1 1.2 N-free extract 64.6 37.5 Available protein 9.6 5.6 Lignin 4 2.3 Cellulose 3.8 2.2 Tannin 11.3 6.6 Ca trace trace Mg 0.14 0.08 P 0.19 0.11In Centre County, Pennsylvania, the foliar nutrient concentrations of bear oak on unburned, once-burned, and twice burned plots were compared. For information on the fires see Effects of repeated fire. For the data below, values in the same column that are followed by different letters were significantly (p<0.05) different [56]:
Treatment Years since fire P (%) Crude protein (%) K (%) Ca (%) Mg (%) Unburned NA 0.17a 13.6a 0.51a 0.50a 0.10a Once burned 4 0.18a 15.4b 0.57b 0.50a 0.11a Twice burned 1 0.18a 15.8b 0.51a 0.80b 0.12b Twice burned 2 0.26b 15.7b 0.56b 0.46a 0.11aCover value: Bear oak thickets provide "excellent" cover for many wildlife species year round [130]. For additional information on the importance of bear oak in wildlife habitats, see the species group of interest in Importance to livestock and wildlife.
Much of the literature refers to a group of scrub or shrub oaks describing
a community of shrubby oak species. This group may include any or all of the following species: bear oak, blackjack
oak, and dwarf chinkapin oak (Quercus prinoides). In this review, all
scrub or shrub oak communities mentioned included bear oak.
Bear oak is a dominant species in the following vegetation classifications:
United States
―
Maine (southern):
mixed deciduous forests dominated by red maple (Acer rubrum), gray birch (Betula populifolia), and
quaking aspen (Populus tremuloides) with a lesser amount of pitch pine (Pinus rigida)
pitch pine/bear oak vegetation
bear oak communities with dense bear oak thickets and scattered pitch pine [22]
chestnut oak (Q. prinus)/bear oak vegetation in the Appalachian Province of Allegheny County [14]
pitch pine-bear oak communities dominate the
area immediately surrounding Halfway Pond in Plymouth County [33]
black huckleberry (Gaylussacia baccata)-bear oak tall
shrublands on Nantucket Island and Martha's Vineyard, less common on Martha's Vineyard [35]
pitch pine/bear oak/broom crowberry (Corema conradii) and pitch pine/bear
oak-northern bayberry (Morella pensylvanica) communities of the Cape Cod National Seashore [36]
pitch pine/bear oak, manzanita (Arctostaphylos spp.)-bear oak,
mixed oak-pine/huckleberry (Quercus-Pinus-Gaylussacia spp.) vegetation types on Cape Cod [94]
pitch pine woodlands in the central part of the state with shortleaf pine (Pinus echinata) and
Virginia pine (P. virginiana) possible [53]
pitch pine-post oak (Q. stellata) and chestnut oak forests of the central pine barrens [85]
pitch pine/bear oak communities in the pine barrens region [98]
plains community type with a pitch pine overstory and post oak and
sassafras (Sassafras spp.) occasionally present, all vegetation is less than 11 feet (3.4 m) tall
transition community dominated by same species as the plains community, but trees are larger with
"poor" forms or shapes
barrens community with an open canopy dominated by pitch pine but
with some shortleaf pine, Virginia pine, white oak (Q. alba), chestnut oak, scarlet oak, and black oak possible [83]
open-canopy community dominated by stunted pitch pine, shrub oaks, and a dense layer of ericaceous shrubs in the Hudson
Valley [106]
barrens communities dominated by pitch pine with some scattered white oak and
chestnut oak on Long Island
transition communities dominated by bear oak; plains communities
with dwarfed pitch pine, bear oak, and low-growing huckleberry and blueberry (Vaccinium spp.) on Long Island [99]
woodlands with a mixed canopy of pitch pine, northern red oak, and eastern
white pine (P. strobus) in the northeast [7]
Table Mountain pine (P. pungens)/bear oak/heath woodlands in the Blue Ridge Province [41]
dry slope and ridge forests of the valley and ridge Appalachian provinces [86]
granite and sand barrens in the southern part of the province [20]
Information on specific historical, medicinal, or ethnobotanical uses of bear oak is lacking. Acorns of the red oak group are bitter, and the bitter flavor is typically removed by leaching before consuming the nutmeat [37].
In a review, bear oak was reportedly used by menstruating Iroquois women [89].
Bear oak flowers from May to June in the southeastern U.S. [31], and flowering is often earlier in southern and coastal bear oak habitats than in northern and continental habitats.
Flowers are produced prior to leaf out [57]. A single flush of leaves is produced over a 7- to 10-day period in mid- to late May in eastern Massachusetts [2]. Leaves persist through the winter [116].
Bear oak is capable of producing a 2nd growth flush if defoliated severely by herbivores or if plants experience a killing frost [2]. May and Killingbeck [84] studied the 2nd set of bear oak leaves produced following severe defoliation by gypsy moths in Rhode Island. They found that the 2nd flush of leaves had increased specific mass. This may indicate an increase in tannins and phenols that may result in "tougher" leaves and decreased subsequent herbivory.
Microclimate and site conditions may also affect the seasonal development of bear oak. Along a north-facing slope gradient in Plymouth County, Massachusetts, bear oak flowering and leaf out was delay by nearly a month in the bottom of a depression as compared to the top of a slope [1].Prolific root crown sprouting following fire makes bear oak an important species in early postfire communities [2]. Bear oak quickly reestablishes on burned sites following frequent top-killing fires, severe humus-consuming fires, and growing-season fires [128].
On a burned site in eastern Massachusetts, an estimated 50% of bear oak stems were produced within 2 years of the fire. Fire characteristics were not described [2]. Bear oak sprout density following fire can be 50,000 to 100,000 stems/acre [87]. While repeated severe fires are tolerated, a fire frequency of less than 5 years reportedly decreases bear oak size and "vigor." When plots in Massachusetts burned in a severe drought-season fire and then reburned for several successive years in summer fires, bear oak was eliminated [63].
Vegetative regeneration predominates on burned sites. Following a May wildfire in dwarf pitch pine-mixed oak forests of New Jersey, just 2 oak (bear or blackjack oak) seedlings occurred in a 40-m² area in the 3rd postfire month [15]. Bear oak's established root system may be more effective than seedlings in capturing the short-lived flush of nutrients that occurs following fire and may explain the lack of seedling emergence [17]. Following an "intense crown fire" in mixed oak-red maple forests of north-central Pennsylvania, bear oak sprout and seedling density averaged 883±883 (sx)/ha and 16±16/ha, respectively on 12 burned stands. The 6 unburned stands had no sprouts or seedlings [105].
Bear oak reproduces sexually through acorn production [132,135] but is capable of prolific asexual regeneration through sprout production following top-killing disturbances [2,60,75]. Wolgast and Zeide [134] indicate that asexual regeneration occurs even in the absence of top-killing disturbances.
Pollination: Flowers are wind pollinated [31].
Breeding system: Bear oak is monoecious [31], but male and female flowers produced on the same plant are not compatible [29]. Female flowers are borne only on current-year's growth [135].
Seed production: Mature bear oak acorn production requires 3 growing seasons. Flower buds are produced in the 1st growing season, flowering occurs in the 2nd growing season, and immature acorns are produced in the fall but are not mature until the following growing season [135]. The 1st bear oak sprouts to produce acorns were 3 years old on a clearcut area of New Jersey's Coastal Plain. The 1st bear oak sprouts to flower were 2 years old. Female flower production was greatest in the 5-year-old bear oak age class, lowest in the 13-year-old age class, and intermediate in the 9-year-old age class when the 3 age classes were compared [132,135].
Numerous studies have found that acorn production can be affected by stem age, weather, site condition, and/or herbivory. Cumming [23] indicates that bear oak acorn production is sporadic. However, in a review, Halls [57] reports that bear oak produces good acorn crops annually and that yields are greatest for bear oak stems between 4 and 9 years old, although 24-year-old stems may still produce acorns. Wolgast [135] found that acorn production decreased with age in 5-, 9-, and 13-year age classes in the pine barrens of New Jersey. Acorn number and acorn weight were greatest in the 5-year-old age class. Below are the acorn weights and production by age class. Bear oak abundance on the 0.01-ha plots was not provided [134].
Age class (years) 5 9 13 Average acorn number/0.01-ha plot 4,599 2,574 1,356 Average acorn weight (kg)/0.01-ha plot 4.57 3.16 1.53In southern New Jersey pitch pine forests, however, 30-year-old bear oak stems produced more acorns than 7-year-old stems. Researchers collected acorns from 0.4-ha quadrats. No acorns were collected from sites dominated by 3-year-old bear oak stems. Regardless of stem age, however, acorn production was greatest on sites free of pitch pine shading. Data are summarized below [82].
7-year-old bear oak stems 30-year-old bear oak stems shade open shade open # acorns found 2 97 36 140 # sound acorns 0 64 25 98 Production (lbs./acre) 0 87 34 133On the University of Rhode Island campus, bear oak plants entirely defoliated by gypsy moths produced a 2nd flush of leaves 2 to 3 weeks following defoliation but had "strongly reduced" acorn production [84].
In controlled experiments, randomly selected bear oaks from the New Jersey pine barrens were subjected to high (61%-71%) and low (38%-50%) humidity levels at the time of flowering. Significantly (p<0.01) fewer immature acorns were produced under high humidity conditions [133,135].
Measurements of stem height, flowering, and acorn production along a 574-foot (175-m) slope in Plymouth County, Massachusetts, revealed that generally the greatest number of flowers and mature acorns were produced on the tallest stems, which grew at the top of the gradient. The lowest point along the gradient was at the bottom of a 70-foot (20-m) deep depression. See the table below for a summary of the data [1].
Relative elevation Female flowers Male inflorescences Proportion of stems producing mature acorns Stem height(m)
(average number ± s)
(cm ± s)
11.75 281±209 816±666 0.84 1.88±0.38 11.75 63±51 145±217 0.70 1.92±0.61 11.5 98±75 230±187 0.44 1.31±0.16 10.75 69±71 193±133 0.05 1.43±0.36 8.25 68±58 90±89 0 1.68±0.43 7.25 33±29 67±78 0.07 1.38±0.43 5.25 48±54 62±89 0 1.49±0.40 2.75 35±31 84±84 0 1.31±0.45 0 25±26 50±45 0 1.48±0.40Based on the results of 2 separate studies, Wolgast [131,135] concluded that genetic factors were more important than soil site conditions in determining acorn productivity of bear oak. The 1st study measured soil and moisture characteristics beneath 9-year-old open-grown plants that were producing acorns at high, intermediate, and low levels. Site quality was not significantly (p=0.1) different beneath the plants. To better evaluate site influences, 18 of the highest, 18 of the lowest, and 18 of the intermediate acorn producers were transplanted onto a common site in Ocean County, New Jersey. Yields remained relatively the same for the high, low, and intermediate producers, and a significant (p<0.05) genotype difference was observed [131,135].
Seed dispersal: Small mammals and birds may aid in the dispersal of oak acorns by abandoning caches. American and European jays often cache acorns a few meters apart in open environments and cover them with debris or soil [29].
Seed banking: Bird and small mammal caches suggest that a bear oak seed bank may exist, but to date (2006), information regarding the longevity and viability of bear oak seed banks is lacking. However, Lanner [73] reports that American and European jays are "vital" to oak establishment, as acorns in their unused winter caches have a high probability of germinating.
Germination: Cold stratification followed by warm temperatures encourages bear oak germination. Bear oak seed collected in the fall from southwestern Virginia was treated to 6 weeks of cold temperatures. The cold temperatures successfully broke bear oak shoot dormancy that exists after emergence of the radicle. Cold stratification also increased the range of temperatures required for successful germination. Below are the germination percentages, shoot lengths, and number of leaves produced per shoot of stratified and unstratified seed under different temperature regimes [3].
Unstratified
Stratified
45-61 °F 64-75 °F 45-61 °F 64-75 °F Average percent germination with shoot elongation 3% 17% 47% 63% Average shoot length (inches) 3.7 2.7 2.8 3.5 Number of leaves/shoot 2.8 4.1 3.7 6.2Seedling establishment/growth: Bear oak seedling growth, closely monitored for 3 years, revealed rapid 1st season growth that slowed in subsequent years. Seed collected in North Carolina and Virginia was planted in nursery beds in Tennessee. By the end of the 1st growing season, average seedling height was 16 inches (41 cm), mean leaf number was 40, leaf size averaged 9 cm², and an average of 4.5 growth flushes was produced. Seedlings were fertilized [39]. The 1-year-old seedlings were planted onto clearcut or old-field sites in the southern Appalachians. The average initial height of bear oak seedlings planted on the sites ranged from 12 to 14 inches (30-36 cm), and after 3 years the average height was 16 to 23 inches (41-58 cm). Survival of bear oak seedlings ranged from 74% to 86%. A severe late frost in the winter of 1977 to 1978 may have affected seedling survival and/or growth [40].
Asexual regeneration: Bear oak produces vegetative sprouts from the root crown [2,75]. While asexual regeneration is abundant following top-kill [2,57,60,75], bear oak reproduces vegetatively in the absence of aboveground damage as well.
Bear oak sprout densities can be as high as 50,000 to 100,000 stems/acre following fire or cutting. In Pennsylvania bear oak stems were persistent following consistent cutting. Sprouts were clear cut on two 25 ft² plots twice a year between early June and late September. Twelve cuttings were required to eliminate sprouting. The researcher did not indicate whether sprouting ever resumed following the 12 cuttings [87].
As sexual reproduction reaches its peak at 6 to 7 years of age, sprout production declines "sharply." A switch in reproductive strategies was observed between 5 and 13 years of age in bear oak plants of the New Jersey pine barrens. The average number of acorns produced per 0.2-acre (0.01-ha) plot was 4,599 for 5-year-old bear oak, and the average fresh weight of sprouts was 0.25 kg/0.01 ha. Thirteen-year-old bear oak plants produced an average of 1,356 acorns/0.01 ha plot, while the average fresh weight of sprouts was 12.29 kg/0.01 ha [134]. However, Buchholz [15] reported that in the dwarf pitch pine-mixed oak forests of New Jersey's pine barrens plains, vegetative reproduction dominates, and seedling establishment is rare even in the absence of fire.
Bear oak's persistence depends on periodic disturbances. Bear oak is intolerant of dense shade, rapidly recolonizes clearcut or burned sites, and is most typical of early seral communities.
General: The bear oak forest cover type is maintained by frequent top-killing disturbances [60]. In New York's Albany Pine Bush, bear oak was most common on recently disturbed sites. The recent disturbances included fire and/or land clearing [88]. Pine barren habitats with high bear oak abundance are considered early seral communities in southeastern Massachusetts [52].
Other researchers describe bear oak habitats as fire-maintained "subclimax" types [91,124]. Buchholz and Good [17] consider dwarf pitch pine-mixed oak forests of New Jersey steady state, early seral communities that resist change following disturbances.
Observations of the succession of old-field sites in southern New Jersey indicate that recolonization is more rapid on sites where bear oak was established prior to the disturbance than on sites without bear oak coverage at the time of disturbance. Old-field sites, in the beginning, are sedge (Carex spp.) and forb dominated, but soon shortleaf pine, bear oak, and pitch pine invade. When pines are 15 to 20 years old, tree oak species such as white oak, scarlet oak, black oak, and/or chestnut oak begin to invade the understory. As the oaks mature the site is considered a mixed oak-pine vegetation type. Once the pines mature and die, hardwood species dominate the stand. The climax vegetation for these old fields is thought to be hardwood dominated. Frequent "killing" fires arrest successional advancement of the vegetation and maintain subclimax pitch pine/bear oak stands [80,81].
On disturbed sites, bear oak abundance is related to disturbance type and connectivity of suitable habitat. In the Connecticut Valley of Massachusetts, bear oak has not colonized previously plowed old-field sites that were abandoned 50 to 100 years earlier. The researchers suggest that seed dispersal opportunities may be limited in the highly fragmented landscape [93]. However, on the Montague Plain of central Massachusetts, bear oak frequency was equal on plowed and unplowed sites, although abundance was greater on unplowed sites. Agriculture was abandoned 50 to more than 100 years prior to the study [96]. On the Cape Cod National Seashore, bear oak frequency was equal on old woodlots, areas where vegetation was logged but never completely eliminated, and old-field sites that were plowed in the past [36].
A single study of vegetation change in the Lebanon State Forest of New Jersey revealed a decrease in bear oak coverage as succession progressed. There were 8 years, free of major disturbances, between the 2 vegetation surveys. The largest decrease in bear oak cover, 13.1%, occurred in the pitch pine-mixed oak/scrub oak vegetation type, and the smallest decrease, 2%, occurred in mixed oak-pine/scrub oak vegetation [114].
Shade relationships: Bear oak is described as extremely shade intolerant and "light demanding" [57,110]. In a Table Mountain pine stand in North Carolina, shaded bear oak shrubs were less than 3 feet (1 m) tall and produced no flowers or acorns during the year observed [4].
Early postdisturbance responses: Disturbances normally increase bear oak frequency, cover, and/or density. Relative bear oak cover increased on an often-disturbed power line right-of-way in the Hudson Valley Sand Belt of New York. Treatments to the right-of-way included mowing, herbicide applications, and combinations of the 2 treatments. Bear oak average relative cover before treatments was 2.9% and after treatments averaged 4.5%. Frequency was unchanged [43].
In the New Jersey pine barrens, bear oak was present in 88% of continuous forest stands and 53% of fragmented forests. A significantly (p<0.025) greater proportion, 50%, of continuous forests than fragmented stands, 10.5%, were burned since 1979. Increased burned area may explain the greater bear oak abundance in continuous stands. However, researchers considered fragments more disturbed than continuous forest stands [47].
Bear oak coverage decreased slightly on repeatedly mowed heathland sites on Nantucket Island, Massachusetts. Coverage increased slightly on untreated sites. Mowing left only 2 inches (5 cm) of aboveground vegetation. Sites were mowed in the fall and winter 4 times in 13 years on a nearly biennial schedule and were evaluated 2 years after the last mowing. Bear oak frequency and cover on mowed and control sites are provided below [34]. For information on bear oak recovery on repeatedly burned sites in Nantucket see Effects of repeated fire.
Control Fall/winter mowing Years since treatment NA NA Prefire 2 Cover (%) 26 31 12 9 Frequency (%) 60 67 50 50The scientific name of bear oak is Quercus ilicifolia Wangenh. (Fagaceae) [30,31,48,50,64,107,116,129].
When habitats overlap, bear oak hybridizes with several species within the red
oak group (Erythrobalanus) [100].
The following hybrids are recognized [48,50,77,90,129]:
Quercus ÃÂ brittonii W.T. Davis, a cross with blackjack oak (Q. marilandica)
Quercus ÃÂ caesariensis Moldenke, a cross with southern red oak (Q. falcata)
Quercus ÃÂ fernaldii Trel., a cross with northern red oak (Q. rubra)
Quercus ÃÂ giffordii Trel., a cross with willow oak (Q. phellos)
Quercus ÃÂ rehderi Trel., a cross with black oak (Q. velutina)
Quercus ÃÂ robbinsii Trel., a cross with scarlet oak (Q. coccinea)
Q ÃÂ brittonii hybrids studied in New Jersey had
morphological characteristics intermediate between
bear oak and blackjack oak [112].
In New Jersey, a hybridization study revealed that although occupying a common
area, bear oak and
blackjack oak were hybridizing but bear oak and black oak were not [61].
Quercus ilicifolia, commonly known as bear oak or scrub oak, is a small shrubby oak native to the Eastern United States and, less commonly, in southeastern Canada. Its range in the United States extends from Maine to North Carolina, with reports of a few populations north of the international frontier in Ontario.[3] The name ilicifolia means "holly-leaved."
Quercus ilicifolia is a deciduous tree or shrub growing occasionally reaching a height of 6 meters (20 feet) but usually much smaller.[4][5] It is gangly and can form a dense thicket. The plant grows from a large taproot, which reach 20 centimeters (8 inches) in thickness. The taproot lives a long time, producing several generations of above ground parts. The alternately arranged leaves are each up to 15 cm (6 in) in length by 10 cm (4 in) in width. The species is monoecious with plants bearing both male catkins and solitary or clustered female flowers. The egg-shaped acorn is 1 to 2 cm (1⁄2 to 3⁄4 in) long with a saucer-shaped cap. The plant reproduces sexually by seed and also vegetatively by sprouting new stems.[5][4]
Quercus ilicifolia is a dominant plant species in a number of regions and habitat types. In Maine, it is found in deciduous forests alongside red maple (Acer rubrum), gray birch (Betula populifolia), and quaking aspen (Populus tremuloides). In Massachusetts, it codominates with black huckleberry (Gaylussacia baccata) on the shrublands of Nantucket and Martha's Vineyard. On Cape Cod, it occurs with pitch pine (Pinus rigida) and broom crowberry (Corema conradii). It is common in New Jersey's Pine Barrens and the pine barrens of Long Island. It also occurs in fire barrens on granite and gneiss further north in Canada.[6] Quercus ilicifolia is also present in the Piedmont of North Carolina, where it is listed as a state endangered plant.[7]
It is an oak that is adapted to disturbance in the habitat, such as wildfire and browsing. As a result, it does not tolerate shade and requires disturbance to remove other plant species so it can receive sunlight. It sprouts prolifically after fire burns away its above ground parts.[5]
Quercus ilicifolia provides food and shelter for many animal species. Bears consume the bitter acorns,[8] especially when preparing for hibernation. White-tailed deer eat the acorns and the stems and foliage. Many types of squirrels cache the acorns. Many birds depend on them; wild turkeys prefer them over other types of food. A large number of insect species live on the oak. This oak species is the main food plant for 29% of the rare or endangered Lepidopterans in southern New England and southeastern New York.[5]
Quercus ilicifolia has been used in revegetation projects on the Fresh Kills Landfill on Staten Island.[5]
Quercus ilicifolia, commonly known as bear oak or scrub oak, is a small shrubby oak native to the Eastern United States and, less commonly, in southeastern Canada. Its range in the United States extends from Maine to North Carolina, with reports of a few populations north of the international frontier in Ontario. The name ilicifolia means "holly-leaved."
