Fagus grandifolia E h rh
Fagus grandifolia Ehrh.
American Beech
Fagaceae — Beech family
Carl H. Tubbs and David R. Houston
American beech (Fagus grandifolia) is the only species of
this genus in North America. Although beech is now confined to
the eastern United States (except for the Mexican population) it
once extended as far west as California and probably flourished
over most of North America before the glacial period (39). This
slow-growing, common, deciduous tree reaches its greatest size in
the alluvial soils of the Ohio and Mississippi River Valleys and
may attain ages of 300 to 400 years. Beech wood is excellent for
turning and steam bending. It wears well, is easily treated with
preservatives, and is used for flooring, furniture, veneer, and
containers. The distinctive triangular nuts are eaten by people
and are an important food for wildlife.
Nội Dung Chính
Habitat
Native Range
American beech is found within an area from Cape Breton Island,
Nova Scotia west to Maine, southern Quebec, southern Ontario,
northern Michigan, and eastern Wisconsin; then south to southern
Illinois, southeastern Missouri, northwestern Arkansas,
southeastern Oklahoma, and eastern Texas; east to northern
Florida and northeast to southeastern South Carolina. A variety
exists in the mountains of northeastern Mexico.
-The native range of American beech.
Climate
Within the range of beech, annual precipitation usually is from
760 mm to 1270 mm (30 to 50 in) (39); however, some beech is
found in Michigan where precipitation is about 580 mm (23 in),
and in Canada where about 640 mm (25 in) fall annually.
Precipitation during the growing season varies from 250 mm to 460
min (10 to 18 in). Beech is a mesophytic species; it uses twice
as much water for transpiration and growth processes annually,
compared to some drought resistant oaks and even lesser amounts
by some pines.
The growing season for beech varies from 100 to 280 days; the
species is found in one county in Michigan where the growing
season is only 92 days.
Mean annual temperatures range from 4° to 21° C (40°
to 70° F). Beech can exist under temperature extremes lower
than -42° C (-44° F) and 38° C (100° F).
Higher than average summer temperatures may be unfavorable for
beech growth.
Soils and Topography
Beech is found generally within two principal soil groups: the
gray-brown podzolic (Hapludalf) and the laterite (Acrorthox) and
is prevalent on podzols; it is seldom found on limestone soils
except at the western edge of its range. These soils are
contained in the orders Alfisols, Oxisols, and Spodosols. Soils
of loamy texture and those with a high humus content are more
favorable than lighter soils (39). The largest trees are found in
the alluvial bottom lands of the Ohio and the lower Mississippi
River valleys, and along the western slopes of the southern
Appalachian Mountains.
Beech populations frequently are higher on coarse-textured,
dry-mesic soils in the northern part of its range (38). In
Indiana, beech is more sensitive to reduced soil moisture than is
white oak (Quercus alba), sugar maple (Acer
saccharum), American elm (Ulmus americana), and
slippery elm (U. rubra). It will grow on poorly drained
sites not subjected to prolonged flooding and may grow where the
water table is within 15 cm to 25 cm (6 to 10 in) of the surface.
It is markedly less tolerant of such conditions than are red
maple (Acer rubrum) and sweetgum (Liquidambar
styraciflua). Beech trees on poorly drained sites have
shallower root systems than those on better drained sites (39).
‘Ember stands containing considerable numbers of beech are found
on soils ranging from pH 4.1 to 6.0 (39), but seldom where pH
exceeds 7.0.
Beech is found at low elevations in the North and relatively high
elevations in the southern Appalachians. Local soil and climatic
factors probably determine whether beech grows at the higher
elevations. In the Adirondacks of New York, low temperatures and
wind keep beech below 980 m (3,200 ft), in contrast to the
southern mountains where on the warmer slopes it grows at
elevations up to 1830 m (6,000 ft). At latitudes in the middle of
its range, however, beech is more abundant on the cooler and
moister northern slopes than on the southern slopes (39).
Associated Forest Cover
Within its wide range in eastern North America, beech is
associated with a large number of trees. Some of the principal
associates are sugar maple, red maple, yellow birch (Betula
alleghaniensis), American basswood (Tilia americana),
black cherry (Prunus serotina), southern magnolia
(Magnolia grandiflora), eastern white pine (Pinus
strobus), red spruce (Picea rubra), and several
hickories (Carya spp.) and oaks Quercus spp.). Beech
is included in 20 forest cover types and is a major component in
the following three (5): Sugar Maple-Beech-Yellow Birch (Society
of American Foresters Type 25), Red Spruce-Sugar Maple-Beech
(Type 31), and Beech-Sugar Maple (Type 60). Beech is a minor
species in 17 other cover types.
Life History
Reproduction and Early Growth
Flowering and Fruiting- In the Northern and Central
States, beech flowers appear in late April or early May when the
leaves are about one-third grown; the species is monoecious. The
flowers are quite vulnerable to spring frosts. Male flowers occur
in long-stemmed heads; female flowers in clusters of two to four
(40). Beechnuts require one growing season to mature and they
ripen between September and November. Two or (rarely) three nuts
may be found within a single bur. The first nuts to fall are
usually wormy or aborted.
Seed fall begins after the first heavy frosts have caused the burs
to open and is completed within a few weeks. Some empty burs
remain on the trees throughout the winter.
Seed Production and Dissemination- Beech ordinarily begins
to produce a substantial amount of seeds when about 40 years old,
and by the time it is 60 years old may produce large quantities.
Good beech seed crops are produced at 2- to 8-year intervals
(40).
Beech seeds, averaging about 3,500/kg (1,600/lb), are relatively
heavy. Most of the seeds simply drop to the ground under the
parent trees. Rodents may carry some of them short distances and
on steep terrain a few may roll down slopes, but dispersal is
quite restricted. Bluejays may transport many beech seeds several
kilometers (16,17).
Seedling Development- Beech seeds germinate from early
spring to early summer. Germination is epigeous and chilling is
required to break dormancy. On either mineral soil or leaf
litter, germination is good, but on excessively wet sites it is
poor. Both germination and survival tend to be better on mor
humus than on mull humus soil (39,40).
Beech seedlings develop better under a moderate canopy or in
protected small openings than they do on larger open areas where
the surface soil may dry out below the depth of the shallow
roots. Height growth of seedlings is about the same in dense (87
percent) or moderate (55 percent) shade, but total dry weight and
root development are greatest under moderate shade. Height
growth, dry weight, and root development in the open are less
than in shade (25). Seedlings are found in large numbers beneath
even the densest stands, but under such conditions their growth
is slow. Beech reproduction can start under, and come through,
fern and raspberry cover.
Dormancy of beech seedlings can be broken in spring and growth can
be prolonged in fall by supplemental light. Decreasing day length
plays the major role in inducing dormancy in the fall, but day
length may be secondary to temperature in controlling resumption
of growth in the spring. That is, day length probably becomes
adequate for growth to resume in the spring before temperatures
are high enough for growth to occur. Temperature, therefore,
exerts the final control over growth resumption.
Beech continues growing all winter in a greenhouse when daylight
is supplemented by continuous artificial light.
The height of beech seedlings growing in the intense competition
of a virgin hemlock-hardwood stand in northern Pennsylvania (39)
was as follows:
Age
Total
height
(yr)
(m)
(ft)
6
0.3
1
10
0.6
2
14
0.9
3
17
1.2
4
18
1.4
4.5
20
1.5
5
22
1.8
6
25
2.1
7
When forest stands are heavily cut, beech reproduction tends to
grow more slowly than that of most associated hardwood species.
This is especially true in clearcuttings. Here the beech
reproduction may be overtopped by less tolerant species, such as
the birches and white ash (Fraxinus americana), that
respond vigorously to increased light. A number of studies have
shown that heavy cutting or clearcutting results in fewer beech
in the new stand than in the old (39). Repeated clearcutting on
short rotations may nearly eliminate beech. Under partial
cuttings, especially single-tree selection cuttings, intolerant
species offer little competition and the tolerant beech
reproduction is able to develop. The beech may be further favored
by its virtual immunity to deer browsing.
Vegetative Reproduction- Beech sprouts well from the
stumps of young trees, but this ability diminishes after trees
reach 10 cm (4 in) in d.b.h. Sprouts from stumps 25 cm to 38 cm
(10 to 15 in) in diameter usually are short lived and do not
attain tree stature. Numerous sprouts may develop on the trunk of
beech immediately below a wound, and from the tops of stumps;
here adventitious buds develop in callus tissue of the cambial
region.
Beech trees may develop large numbers of root sprouts or suckers.
Studies (30) have shown that reproduction is almost exclusively
by suckering in the “beech gaps” and is abundant in the
Adirondack Mountains of New York, in Maine (13), and in many
other areas, often those near the northern and western limits of
its range (11,42) where environments are severe (27). Suckering
is stimulated only slightly by removal of the stem (18). Injury
to roots appears to be necessary for the initiation of root
sprouts in beech (19). Root sprouts arise from adventitious buds
that form within callus tissues associated with wounds.
Experimental injuries to roots in November resulted in fewer
sprouts than did injuries inflicted in spring (20). Sometimes
root sprouts develop where no apparent injury has occurred (39).
There were relatively more root sprouts on southerly slopes in
areas where freeze-thaw action tended to injure shallow or
exposed roots and stimulate sprout formation, and where late
spring frosts tended to injure or kill young seedlings. In Ohio,
seedling regeneration was positively associated with northerly
exposures and root sprout regeneration with southerly exposures
(11).
In an undisturbed stand of mature beech in the Adirondacks, 1,730
to 2,220 root sprouts per hectare (700 to 900/acre; 7 to 12/tree)
were counted (39). Casual observations elsewhere indicate that
the number per tree may greatly exceed this figure.
Root sprouts can develop into desirable trees. Isozyme genetic
studies have shown that some groups of overstory beech trees with
similar phenotypic traits are clones (14). Sometimes root sprouts
are ephemeral. In one reproduction study, made after a
60-year-old stand of beech was cut, all of the root sprouts died
within 4 years. On the other hand, the trees in a 40-year-old
beech stand of sprout origin averaged 10 cm (4 in) in d.b.h. and
11.6 in (38 ft) in height.
Beech limbs root in a single year when layered. Interspecific root
grafting is common.
Sapling and Pole Stages to Maturity
Growth and Yield- Beech’s period of radial growth may
continue for 80 to 89 days in the Georgia Piedmont and for
approximately 60 days in Indiana (39). Annual height growth of
beech saplings is complete in about 60 days; 90 percent of this
growth occurs between May 10 and June 10, American beech has a
lower site index than any associated hardwood in the northern
Lake States.
The radial growth period is influenced by available soil moisture.
Under normal conditions, it may end in the middle of July, but
drought may end it in mid-June. A few individual trees may
continue their growth into August and September. In dry years,
annual rings may not grow in the basal sections of some beech
trees. In general, radial growth of beech begins when the leaves
are fully expanded.
The annual diameter increment of beech of pole and small saw-log
size averages from around 1.8 to 2.3 mm (0.07 to 0.09 in) in
undisturbed second-growth stands to 3.8 to 4.8 min (0.15 to 0.19
in) in trees released by partial cuttings (35,39). Annual growth
of poles for 5 years after heavy release, leaving from 1.1 to 4.6
m/ha (5 to 20 W/acre) of basal area, ranged from 5.6 mm (0.22 in)
to 7.6 min (0.30 in); growth was better in the most heavily
stocked stands and on trees with good crown development (26).
Under optimum conditions, beech trees may become 37 in (120 ft)
high; however, they generally average 18 to 24 in (60 to 80 ft).
Growth data for beech in the Lake States are shown in table 1.
Table 1- Characteristics of American beech
growing in the lake states.
Age
D.b.h.
Height
Volume
(yr)
(cm)
(m)
(m³)
20
2
4
—
40
6
8.5
—
60
10
11.9
0.03
80
14
14.6
0.1
100
18
17.4
0.22
150
29
22.9
0.76
200
40
25.6
1.58
250
51
26.8
2.69
(yr)
(in)
(ft)
(ft³)
20
0.7
13
—
40
2.3
28
—
60
3.8
39
1
80
5.4
48
3.7
100
7.1
57
7.9
150
11.5
75
27
200
15.7
84
56
250
19.9
88
95
Among 12 broad-leaved species rated according to their longevity,
beech was exceeded only by white oak and sugar maple. Beech trees
older than 366 years have been found in Pennsylvania. The
distribution of numbers of trees by age is “J” shaped,
typical of tolerant long-lived species (21). One of the largest
beeches on record, growing in Michigan, is 135 cm (53.2 in) in
d.b.h., 49 m (161 ft) tall, and has a crown 32 in (105 ft) wide.
Beech trees prune themselves in well-stocked stands. Open-grown
trees, however, develop short, thick trunks with large, low,
spreading limbs terminating in slender, somewhat drooping
branches that form a broad, round-topped head.
Beech trees that have been injured or suddenly exposed by stand
cuttings often develop epicormic branches. In one stand where 65
percent of the basal area had been cut, 40 percent of the
remaining beech trees had epicormic branches 5 years later,
whereas in a similar but uncut stand, only 17 percent of the
trees had such branches (39). Epicormic branching of beech trees
has also been observed after glaze damage and after
low-temperature injury (27). One report on winter injury showed
epicormic branches to be restricted largely to trees with d.b.h.
of 10 cm (4 in) or less (2).
Rooting Habit- Young seedlings have a taproot that gives
way to a heart root system as the tree matures (41). The root
system is generally shallow but may penetrate to 1.5 m (5 ft) or
more in deep soils. The fine roots form a dense mat in our soil
types. Beech root systems are more shallow than the associated
yellow birch and sugar maple. Few tree species are less tolerant
of flooding during the growing season than American beech.
Root exudates of beech contain more organic acids than those of
sugar maple or yellow birch.
Reaction to Competition- Beech is classed as very tolerant
of shade. In some parts of its range, beech is the most tolerant
species. Its tolerance is partly due to its very low respiration
rate (24) and the quick response of the stomata, which open when
light suddenly increases and rapidly close when light intensity
diminishes. Beech stomata are more responsive than those of red
maple, red oak Quercus rubra), or yellow-poplar (Liriodendron
tulipifera), which are less tolerant (43). On very poor soils
or in very cold climates, beech may be less tolerant. The
tolerances of beech and associated sugar maple are about the same
(25), although locally one species or the other may predominate
in the forest understory. Factors other than the ability to
endure shade appear to govern the relative success of beech and
its common tolerant competition, sugar maple, eastern hemlock
(Tsuga canadensis), and balsam fir (Abies balsamea).
Beech may be more competitive under somewhat adverse site and
climate conditions (39).
Beech and sugar maple are recognized as climatic climax species in
the northern hardwood types of the Northeast, Lake States, and
Appalachian Mountains. In the Southeast, relict areas of beech
suggest that an original maple-beech association has been
displaced by the once subclimax oak-hickory community.
Damaging Agents- In regions with low winter temperatures,
long frost cracks often appear in the tree trunks. These cracks
are sometimes superficial but sometimes extend deep into the
bole. In the Northeast, beech has been damaged or killed by
temperatures of -40° to -45° C (-40° to -50°
F) preceded by severe droughts (39). Injured trees died the
following summer and winter. Beech can be severely damaged by
late spring frosts.
In a Kentucky study of effects of flooding, beech was one of the
more sensitive species. Beech trees were killed by 2 weeks of
submergence of their root crowns in summer. An 18-day period of
flooding in winter had no apparent adverse effect, however.
Beech’s susceptibility to glaze-storm breakage is no greater than
that of its associated hardwoods and may be somewhat less than
the average for a mixed stand (39). Except on shallow soils,
beech is rather windfirm.
The thin bark of beech renders it highly vulnerable to injury by
fire (large shallow roots are especially vulnerable), sunscald,
logging, pruning, or disease. When large branches are broken they
heal comparatively slowly (38) and serve as entrance courts for a
host of decay fungi (12,32).
More than 70 decay fungi (a record for a hardwood species) have
been reported for beech (12). The most important include Daedalea
unicolor, Ganoderma applanatum, Fomes fomentarius, Phellinus
igniarius, Hericium erinaceus, H. coralloides, Steccherinum
septentrionale, Inonotus glomeratus, and Ustilina
vulgaris. The shoestring fungus, Armillaria sp., the
most important root pathogen, attacks and girdles roots of
weakened trees. Beech roots are also parasitized by the
broomrapes, Conopholis americana and Epifagus
virginiana. The latter, beech drops, is specific to beech
(8,34).
The thinness of beech bark also makes it vulnerable to an
unusually large number of sucking insects, including the beech
blight aphid, Fagiphagus imbricator, and the giant bark
aphid, Longistigma caryae. Continuous heavy outbreaks of
the oystershell scale, Lepidosaphes u1mi, have resulted
in severe crown dieback and even in the death of entire stands
(1). Xylococculus betulae, another scale, causes
roughened spots on stems of young trees and is especially
devastating to the sprout thickets that have emerged in the
aftermath of beech bark disease , the most serious problem of
this species (13,31).
Beech bark disease is initiated when yet another scale insect, the
beech scale, Cryptococcus fagisuga, attacks the bark of
beech trees and renders it susceptible to bark canker fungi of
the genus Nectria (3,33). The insect component of this
scale-Nectria “complex” was introduced to Nova
Scotia from Europe around 1890 and is now found throughout New
England, New York (15) and northern Pennsylvania (37). In 1981, a
70,000-acre infestation was detected in northeastern West
Virginia, many miles south of the nearest previously known
infestation (28). More recently, the disease has been reported as
far west as Toronto, Ontario, and the scale is now present in
northeastern Ohio and northwestern Virginia (29). In North
America, Nectria coccinea var. faginata is the
fungus most commonly associated with the disease in the Maritime
Provinces, New England, and northern New York. In western
Pennsylvania, West Virginia, and some New York stands however, N.
galligena is the predominant associated species. As the
disease and forest interact for the first time, mortality may be
so severe that a large proportion of the big, mature beech trees
are killed. Mortality is now especially high in some southern and
western areas of the Adirondack Mountain region. The percent
stocking of beech was reported (7) to remain the same after the
killing front of the beech bark disease moved through a managed
stand; the disease mainly affected the larger trees. Although
such mortality is rare in stands emerging in the aftermath of the
disease, severe defect may be caused by the now-endemic causal
complex together with Xylococculus betulae (13).
Defoliation by insects can occasionally be a serious problem (1).
The most damaging is the saddled prominent, Heterocampa
guttivitta, although the forest tent caterpillar (Malacosoma
disstria), gypsy moth (Lymantria dispar), fall
cankerworm. (Alsophila pometaria), and the Bruce
spanworm. (Operophtera bruceata) occasionally cause heavy
defoliation in local areas. Insect defoliation often renders
trees susceptible to attack by the shoestring root fungus.
Beech is seldom severely browsed by white-tailed deer. When other,
more desirable tree species are available, beech is usually
nipped only sparingly (36).
Special Uses
Beech mast is palatable to a large variety of birds and mammals,
including mice, squirrels, chipmunks, black bear, deer, foxes,
ruffed grouse, ducks, and bluejays. Beech is the only nut
producer in the northern hardwood type. Beech wood is used for
flooring, furniture, turned products and novelties, veneer,
plywood, railroad ties, baskets, pulp, charcoal, and rough
lumber. It is especially favored for fuelwood because of its high
density and good burning qualities.
Creosote made from beech wood is used internally and externally as
a medicine for various human and animal disorders. (It is
important to note that coal tar creosote, the kind used to
protect wood from rots, is highly toxic to humans.)
Genetics
Fagus grandifolia Ehrh. is the only type species of
American beech now recognized in North America (9,10,23). Some
botanical authorities hold that Northern and Southern beeches
vary, and have described the southern form as F grandifolia
var. caroliniana (Loud.) Fern. & Rehd., Carolina
beech (4,6). A previously named species in the mountains of
Mexico (39) has been renamed a variety, F grandifolia var.
mexicana (Martinez) Little (22).
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