Gray Birch

Betula alleghaniensis is a characteristic tree of the northern Appalachians and the hemlock hardwoods forest of the Great Lakes region. It was formerly widely known by the illegitimate (superfluous) name B . lutea F. Michaux.

Native Americans used Betula alleghaniensis medicinally as an emetic or cathartic, to remove bile from intestines, as a blood purifier, as a wash for "Italian itch," and as a diuretic (D. E. Moerman, as Betula lutea ).

Betula alleghaniensis is very closely related to B . lenta , which it resembles in many features (T. L. Sharik and R. H. Ford 1984). A distinctive feature is usually its freely exfoliating bark, although in certain populations the bark remains close and dark (B. P. Dancik 1969; B. P. Dancik and B. V. Barnes 1971).

Betula alleghaniensis Britton × B . papyrifera Marshall has seldom been reported, but it may actually be more common than realized in the northeastern states. In most features it is intermediate between the parents (B. V. Barnes et al. 1974).

Betula × purpusii Schneider (= Betula alleghaniensis Britton × B . pumila Linnaeus, 2 n = 70) is a rather common hybrid wherever the parent species occur together. The large shrubby plants show strikingly intermediate leaf characteristics.

Trees , to 30 m; trunks straight, crowns narrowly round. Bark of young trunks and branches dark reddish brown, in maturity tan, yellowish, or grayish, lustrous, smooth, irregularly exfoliating, or sometimes darkening and remaining close; lenticels dark, horizontally expanded. Twigs with odor and taste of wintergreen when crushed, glabrous to sparsely pubescent, usually covered with small resinous glands. Leaf blade narrowly ovate to ovate-oblong with (9--)12--18 pairs of lateral veins, 6--10 × 3--5.5 cm, base rounded to cuneate or cordate, margins sharply doubly serrate, teeth coarse, rather irregular, apex acuminate; surfaces abaxially usually moderately pubescent, especially along major veins and in vein axils, often with scattered, minute, resinous glands. Infructescences erect, ovoid, 1.5--3 × 1--2.5 cm, generally remaining intact after release of fruits in late fall; scales sparsely to moderately pubescent, lobes diverging proximal to middle, central lobe tapering to narrow tip, lateral lobes ascending or partially extended, broader, rounded. Samaras with wings narrower than body, broadest near summit, not or only slightly extended beyond body apically. 2 n = 84.

St. Pierre and Miquelon; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Conn., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., W.Va., Wis.

Flowering late spring.

Stream banks, swampy woods, and rich, moist, forested slopes; 0--500m.

Betula alleghaniensis var. fallax (Fassett) Brayshaw; B. alleghaniensis var. macrolepis (Fernald) Brayshaw; B. lutea F. Michaux; B. lutea var. macrolepis Fernald

More info for the term: swamp

yellow birch
swamp birch
silver birch
gray birch

More info for the terms: forest, fruit, monoecious, tree

Yellow birch is a native, deciduous tree. It usually ranges from 60 to
75 feet (18-23 m) in height and up to 2 feet (0.6 m) in diameter, and
occasionally grows to 100 feet (30 m) in height and 4 feet (1.2 m) in
diameter [14,44,53]. Open-grown yellow birch crowns are long and wide
spreading; in more dense forest crowns are short and irregularly rounded
[53]. The trunk usually divides into a few spreading branches but
lateral shade produces a straight trunk that extends nearly to the top
of the tree. In dense stands the trunk is free of branches for over
half the height of the tree [53]. The bark is somewhat lustrous,
separating in thin layers [14] which exfoliate and result in a finely
shaggy appearance [44]. On old trunks, the bark is deeply grooved and
about 0.5-inch (1.2-cm) thick [25]. The root system of yellow birch is
generally shallow but variable. There is a well-developed extensive
lateral root system; roots spread horizontally or may penetrate more
than 5 feet (1.5 m). Yellow birch is monoecious [32]. The fruit is a
winged nutlet 0.13- to 0.14-inch (3.2-3.5-mm) long (not including
the wings) [14].

Yellow birch is slow growing [32]. Average longevity is approximately
150 years, but maximum longevity is over 300 years [58].

The range of yellow birch extends from southern Newfoundland, Cape
Breton Island, Nova Scotia, New Brunswick, Anticosti Island, the Gaspe
peninsula, and Maine west to southern and southwestern Ontario and
Minnesota; south to northern New Jersey, northern Ohio, extreme northern
Indiana and Illinois; and south in the mountains to South Carolina,
extreme northeastern Georgia, and eastern Tennessee [76].

More info for the terms: fire frequency, fire regime, forest, frequency, fuel, hardwood, mesic, presence, surface fire, tree

Yellow birch is susceptible to fire injury due to its thin bark [32];
young yellow birch do not usually survive fire. Mature trees may
survive because the thin forest floor under large yellow birch does not
usually support severe or persistent surface fire [90]. Yellow birch
germinates readily on early postfire sites [91,92,115].

Forest Type: Heinselman [52] suggested that the presence of yellow
birch in old mixed forests is hard explain without fire disturbance;
however, other authors describe yellow birch as opportunistic with
respect to fire but not fire dependent [90]. Lorimer [77,78] reported
that the presence of yellow birch (in land survey records) is not a
reliable indicator of previous fire. In Massachusetts, a beech-hemlock
forest containing yellow birch developed on an island where fire had not
occurred for many years. The land surrounding the island is occupied by
fire-dependent pitch pine (Pinus rigida) and scrub oak types. In the
1940's the island forest was broken up by a hurricane, which corresponds
with the age of many yellow birch [30].

Fire Frequency: Yellow birch typically occurs in forests with fire-free
intervals of at least 150 to 300 years; the fire regime is characterized
by crown and severe surface fires in combination [52]. The
presettlement hemlock-northern hardwood forests experienced fire
infrequently [2]. In Wisconsin, mesic hemlock-northern hardwood forests
north and east of the transition zone between the fire-dependent
prairie-savanna mosaic and nonfire-dependent forest probably experienced
fire periodically prior to the fire-suppression era. The presence of
large, late-successional species indicates that the average interval
between stand-replacing fires was longer than the average lifespan of
major tree species in the region [20]. In the Great Lakes States and
Acadian Forest region, presettlement northern hardwoods-pine-spruce-fir
forests probably had a semieven-aged structure where less shade-tolerant
components were maintained by long-return interval disturbances such as
fire or windstorms. Most fires in these forests were severe surface
fires, occurring only after prolonged drought, and usually affecting
forests that were breaking up due to other factors (and thus had heavy
fuels). Estimates for Maine presettlement fire return intervals range
from 806 to 1,923 years [77].

In the twentieth century, forest types containing yellow birch in New
Brunswick have either experienced no fires or have had very long
fire-free intervals. For sugar maple-yellow birch-fir in New Brunswick,
the mean annual area burned between 1931 and 1970 was about 0.16 percent
of the total area of that type [119]. A similar study for Nova Scotia
reported that 0.03 percent of the total area (of sugar maple-yellow
birch-fir) burned annually between 1915 and 1975 [120]. In northern
Maine, hardwood forests were estimated to have a fire return interval of
approximately 800 years [2]. Northern hardwood forests had estimated
fire return intervals (from data spanning 1903-1956) of 910 years for
Maine and 770 years for New Hampshire [35].

Fire Season and Conditions: At low elevations in the southern
Appalachians, lightning-caused fires occur less often in the hardwood
forests than in pine-hardwood forests. Fire frequency by forest type is
related to the month of occurrence. Fires that occur before May usually
start at higher elevations; after May, more fires start at lower
elevations and are concentrated in the pine-hardwood type, possibly
because after hardwoods have leafed out fuel moistures are too high to
support fire [8]. In Maine, northern hardwoods are less likely to burn
than other forest types, and are more susceptible to fire damage.
Ignition and spread of fire are unlikely except during the most severe
droughts [89].

FIRE REGIMES :
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".

More info for the term: litter

Regression coefficients relating bark thickness to diameter at breast height
have been published for yellow birch [51].

The moisture content of the inner bark of yellow birch ranges from 44 to
65 percent, depending on season of sampling. The heat of combustion
of dry yellow birch bark is 9,200 Btu [129].

Site Preparation: Fire has been used to create suitable seedbed
conditions for yellow birch regeneration [1]. In New York, the number
of yellow birch seedlings was higher on postharvest plots that had been
prescribed burned and scarified than on plots that had either been
prescribed burned or scarified, or on control plots [11]. Prescribed
fires have been used for yellow birch seedbed preparation in Ontario.
The fires were conducted in late fall, after sugar maple and beech leaf
and seedfall and before the major portion of yellow birch seeds were
dispersed. Low-intensity surface fires consumed litter and killed
advance regeneration of sugar maple. These fires did not significantly
reduce the number of stems (all species) greater than 0.6 inch (1.5 cm)
d.b.h., though basal scarring was evident. Fire-prepared plots resulted
in higher stocking of yellow birch than unburned plots, and reduced the
development of sugar maple [6,16].

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More info for the term: phanerophyte

Phanerophyte

More info for the term: forest

Soils: Yellow birch occurs on moist, well-drained soils of uplands and
mountain ravines [32]. It occurs on various soil types including
glacial tills, outwash sands, lacustrine deposits, shallow loess, and
residual soils derived from sandstone, limestone, igneous, and
metamorphic rock [32]. In the Adirondacks, yellow birch occurs on soils
derived from limestone, gneiss, anorthosite, sandstones, shales, and
conglomerates [67]. The best growth occurs on well-drained fertile
loams and moderately well-drained sandy loams [32]. Even though growth
is poor, yellow birch is often abundant where drainage is restricted.
Yellow birch occurs on muck soils with pH 7.5 to 8.0 [9]. In New York,
yellow birch occurred on wetland soils with soil surface pH ranging from
4.0 to 6.8 [59]. Birches (Betula spp.) are sensitive to soil phosphorus
[90].

Periodic droughts are damaging to yellow birch because of its shallow
roots [55].

Elevation: In the Adirondacks and the Appalachians, yellow birch
reaches its maximum importance in the transition zone between low
elevation deciduous forest and montane spruce-fir forests. In the
Adirondacks, it occurs at elevations ranging from 100 feet (30 m) to
3,413 feet (1040 m), but is uncommon above 3,000 feet (914 m)
[10,39,61,67]. The lower slopes to about 2,310 feet (700 m) are
dominated by sugar maple, American beech, and yellow birch. Between
2,310 feet and 2,970 feet (700-900 m) is a transition zone to spruce and
spruce-fir forests. In the southern Appalachians the highest importance
value for yellow birch occurs at mid- to high-elevations from 2,800 to
3,000 feet (853-914 m) [19,23]. In western Great Smoky Mountains
National Park, yellow birch tends to be more concentrated in protected
coves at lower elevations, and spreads out of the coves at higher
elevations [19].

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

5 Balsam fir
16 Aspen
17 Pin cherry
18 Paper birch
19 Gray birch - red maple
20 White pine - northern red oak - red maple
21 Eastern white pine
22 White pine - hemlock
23 Eastern hemlock
24 Hemlock - yellow birch
25 Sugar maple - beech - yellow birch
26 Sugar maple - basswood
27 Sugar maple
28 Black cherry - maple
30 Red spruce - yellow birch
31 Red spruce - sugar maple - beech
32 Red spruce
33 Red spruce - balsam fir
34 Red spruce - Fraser fir
35 Paper birch - red spruce - balsam fir
37 Northern white-cedar
39 Black ash - American elm - red maple
50 Black locust
57 Yellow-poplar
58 Yellow-poplar - eastern hemlock
59 Yellow-poplar - white oak - northern red oak
60 Beech - sugar maple
107 White spruce
108 Red maple

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES10 White - red - jack pine
FRES11 Spruce - fir
FRES15 Oak - hickory
FRES16 Oak - gum - cypress
FRES17 Elm - ash - cottonwood
FRES18 Maple - beech - birch

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: forest

K093 Great Lakes spruce - fir forest
K096 Northeastern spruce - fir forest
K097 Southeastern spruce - fir forest
K102 Beech - maple forest
K106 Northern hardwoods
K107 Northern hardwoods - fir forest
K108 Northern hardwoods - spruce forest

More info for the terms: forest, presence, tree

Yellow birch seedlings and saplings are killed by even low-severity
fires [32]. Small trees were killed by fire that left large trees in a
northern hardwoods forest unharmed [105]. Large trees usually survive
fire; Martin [85] mentioned the presence of large, old yellow birch that
predate a fire that initiated a red maple-paper birch stand in Ontario.

A subjective ranking of tree fire resistance compiled by Starker [106]
listed yellow birch as twelfth out of twenty-two species rated.

Yellow birch is browsed by moose, white-tailed deer, and snowshoe hare.
Deer consume large numbers of seedlings in summer, and prefer green
leaves and woody stems in fall [32,104]. Yellow birch seeds are
consumed by common redpoll, pine siskin, chickadees, and other songbirds
[104]. Ruffed grouse feed on seeds, catkins, and buds. Red squirrel
cut and store mature strobili, eat yellow birch seeds, and also feed on
birch sap. The yellow-bellied sapsucker uses yellow birch as a summer
food source [32,104]. Beaver and porcupine chew the bark of yellow
birch [104].

More info for the terms: codominant, forest, natural, shrubs

Yellow birch is usually found singly or in small groups [32], growing
with American beech (Fagus grandifolia), maples (Acer spp.),
particularly sugar maple (A. saccharum), ashes (Fraxinus spp.), aspens
(Populus spp.), other birches (Betula spp.), eastern white pine (Pinus
strobus), red spruce (Picea rubens), and balsam fir (Abies balsamea)
[25]. In the Great Lakes-St. Lawrence forest region, yellow birch
occurs in mixed forests with red pine (P. resinosa) and eastern white
pine, and with eastern hemlock (Tsuga canadensis) [1]. Yellow birch is
a dominant, codominant, or important species in northern hardwoods-red
spruce forest, northern hardwoods, transition hardwoods-eastern white
pine, and in central hardwoods-eastern hemlock-eastern white pine [28].
Yellow birch is codominant with yellow buckeye (Aesculus octandra) in
western Great Smoky Mountains National Park [19]. In the Catskill
Mountains of New York, yellow birch is dominant in some spruce-fir
stands and codominant in most others. It occurs as nearly pure stands
on steep slopes at higher altitudes, or mixed with black cherry (Prunus
serotina), mountain maple (Acer spicatum), red maple (A. rubrum) and
paper birch (B. papyrifera) in open, scrubby stands on ridgetops [86].

Small trees and shrubs associated with yellow birch include sweet birch
(B. lenta), ironwood (Ostrya virginiana), American hornbeam
(Carpinus caroliniana), striped maple (A. pensylvanicum), mountain
maple, alternate-leaved dogwood (Cornus alternifolia), beaked hazelnut
(Corylus cornuta), Atlantic leatherwood (Dirca palustris), witch-hazel
(Hamamelis virginiana), American fly honeysuckle (Lonicera canadensis),
American mountain-ash (Sorbus americana), Canada elderberry (Sambucus
canadensis), Canada yew (Taxus canadensis), and mapleleaf viburnum
(Viburnum acerifolium) [32].

The largest concentrations of yellow birch are found in Quebec, Ontario, New
Brunswick, Maine, upper Michigan, and New York. About 50 percent of the
growing stock volume of yellow birch is in Quebec [32].

Publications listing yellow birch as a dominant or codominant species in
vegetation classification schemes include:

The natural forests of Maryland: an explanation of the vegetation map of
Maryland [15]
Field guide: Habitat classification system for Upper Peninsula of
Michigan and northeast Wisconsin [24]
White Mountain landscapes [36]
A forest classification for the Maritime Provinces [79]
A classification of the deciduous forest of eastern North America [88]
Vegetation-environment relations in virgin, middle elevation forests
in the Adirondack Mountains, New York [101]
Vegetation of the Great Smoky Mountains [123]
Classification of forest ecosystems in Michigan [126]

More info for the term: tree

Tree

More info for the terms: forest, hardwood, scarification, seed, selection

Numerous management guidelines for yellow birch and yellow
birch-containing types [43,46,73,111], and recommendations for
silvicultural treatments [68,98,113,114] are available in the
literature. Shaw [104] reported on management considerations for
wildlife in northern hardwoods.

Harvest System and Regeneration: Yellow birch regenerates primarily by
germination; very little advance regeneration is usually present
[38,60]. Early twentieth century logging practices that favored shade
tolerant species resulted in a decrease in yellow birch [84]. The
effects of different harvesting systems and conditions on yellow birch
regeneration have been studied and reviewed [70,92,109]. Harvest should
coincide with good seed years [99]. Clearcutting small patches or
strips provides suitable conditions for yellow birch seedling
establishment in the Northeast [32,38,74,82,84]. Yellow birch
reproduces well on patch cuttings of up to 0.3 acre (0.12 ha) [43]. In
New Hampshire, strip cutting failed to increase the proportion of yellow
birch in the stand but it did increase the percentage of yellow birch
likely to become crop trees [47]. Group selection can significantly
increase the proportion of yellow birch by creating openings for yellow
birch regeneration [27,83]. In New Hampshire, after 38 years of group
selection yellow birch comprised one-quarter to one-third of the trees
in the 4- to 12-inch d.b.h. class. The pretreatment proportion was not
reported; however, under single-tree selection yellow birch will usually
decline to less than 20 percent, and sometimes to less than 10 percent,
of stocking [27,72]. In the Great Lakes States, 20 years after group
selection yellow birch had not increased in proportion to other species
[34]. Shelterwood systems designed to increase the proportion of yellow
birch have been investigated [46,49,64,115].

Seedbed Preparation: Scarification of seedbeds improves yellow birch
seedling establishment [38], although the effects may be short-lived if
organic matter is scraped away rather than mixed in with the mineral
soil [64]. Yellow birch can be direct seeded after harvest in the
northern hardwood forest zone [45].

Harvesting Considerations: Yellow birch is windfirm on deep,
well-drained loam and sandy loam soils, but is subject to windthrow on
shallow, poorly drained soils. It is susceptible to winter sunscald
[32]. Yellow birch is sensitive to high soil temperatures and sudden
exposure [43]. It is also susceptible to root, stem, and crown injury
due to logging and is subject to insect attack as a consequence of
injury. Top dieback and some mortality occur after heavy cuts in mature
and overmature stands [32].

Damaging Agents: Yellow birch is susceptible to ice and snow load
damage, and young trees are vulnerable to late spring frosts. Yellow
birch is susceptible to injury at 3.5 ppm sulfur dioxide but is tolerant
of ozone at 0.25 ppm [32]. Hacker and Renfro [48] rated yellow birch as
slightly sensitive to ozone. Top dieback sometimes occurs following
heavy seed crops [32]. Heavy or repeated browsing by deer and moose
kills small yellow birch. Sometimes browsing prevents regeneration
[62]. In New York, growth of yellow birch was not detected on
postharvest plots that were unfenced [11]. Porcupine feeding damages
birch crowns, reduces wood quality, and is sometimes fatal. Red
squirrel cut new germinants [32]. Heavy feeding by yellow-bellied
sapsucker reduces growth, lowers wood quality, and is sometimes fatal
[32]. Yellow birch has relatively few species-specific insect pests,
but is frequently attacked by pests typically associated with other
northern hardwood species [5]. Insect and disease damaging agents are
listed [32].

CT GA IN IL IA KY ME MD MA MI
MN NH NJ NY NC OH PA RI SC TN
VT VA WV WI NB NF NS ON PQ

Yellow birch can be tapped for sap which is used to make an edible
syrup. Tea can be made from the twigs and/or inner bark [31].

Yellow birch chips can be used to produce ethanol and other products [13].

More info for the term: hardwood

Yellow birch was listed as a highly preferred browse species in northern
hardwood forests [110]. In New Hampshire, white-tailed deer browsed
birch twigs (both yellow birch and paper birch) at a browse index rate
of approximately 4 (i.e., four times the expected rate based on
availability) [104].

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More info for the terms: fruit, phenology, seed

The pistillate catkins of yellow birch form in the fall, and finish
development from late May to early June. The fruit ripens from late
August to early September [32]. The phenology of yellow birch in
northern Minnesota was reported as follows [4]:

flower appearance April 2 to May 16
initial bud swell April 6 to May 1
leaf out May 3 to May 25
anthesis May 13 to May 29
seed fall (initiation) August 6
leaf fall September 26 to October 4

More info for the terms: density, hardwood, seed, succession, surface fire, top-kill

Yellow birch is a poor sprouter following top-kill by fire. Seed
germination and seedling establishment are enhanced by fire disturbance.
Yellow birch frequently forms pure patches following fire. In Wisconsin
northern hardwood forests it often comprises 60 percent of the hardwood
thickets [80]. Most of the research on yellow birch regeneration is
associated with logging regimes, so it is not clear what role fire plays
in yellow birch regeneration in unmanaged stands. It is likely that a
low-intensity, patchy fire would create conditions that favor yellow
birch regeneration by reducing the hardwood leaf mat and exposing
mineral soil, but leaving mature trees as a seed source [1].

In northern hardwood forests, postfire regeneration is likely to include
at least a small proportion of yellow birch. Major postfire species in
this area are paper birch, gray birch (Betula populifolia), aspens, red
spruce, and pines (Pinus spp.) [32,89]. In the Laurentian Highlands of
central Quebec, yellow birch is present in low numbers in early postfire
succession on well-drained sites in montane mixed forests. The main
colonizers are balsam fir and paper birch [22]. In North Carolina
spruce-fir forests, which rarely burn, yellow birch was important in
postfire regeneration [103]. Gibson [42] reported that former Atlantic
white-cedar (Chamaecyparis thyoides) swamps developed into red maple or
red maple-yellow birch stands following fire. In northwestern
Pennsylvania, a ridge that supported a dense stand of eastern hemlock
and mixed hardwoods was converted by fire to a stand composed of red
maple, black cherry, yellow birch, and water birch (B. occidentalis) [54].

In northern hardwood types in Wisconsin, low-severity surface fires seem
to favor sugar maple over yellow birch and beech. Severe fires,
however, destroy existing sugar maple reproduction and create openings
in the canopy, favoring yellow birch. The composition of a northern
hardwood stand was traced to three distinct fires, each of which was
followed by an increase in the proportion of yellow birch [80]. Birches
(yellow birch, sweet birch, and paper birch) exhibited a pulse of
reproduction after a surface fire in Connecticut, peaking in density
around 25 years. By 55 years after the fire birch density on burned and
unburned stands was similarly low [117].

More info for the term: root crown

Tree without adventitious-bud root crown
Initial-offsite colonizer (off-site, initial community)

More info for the terms: cover, duff, hardwood, litter, natural, seed, stratification, tree

Yellow birch reproduces primarily by seed; seedlings and young saplings
will sprout but sprouts are weak and short lived. Older trees do not
sprout [32,74].

Reproductive Age and Seed Crop Production: Under normal conditions,
yellow birch first reproduces at about 40 years. Optimum seed
production occurs at about 70 years of age. However, seeds have been
produced by 7-year-old open-grown saplings, and heavy seed crops have
been produced by 30- to 40-year-old yellow birch in open-grown positions
or in thinned stands. Yellow birch produces good seed crops at 1- to
4-year intervals, usually with very little seed produced in intervening
years [1,32]. Out of every 10 years, yellow birch averages 1 heavy seed
year, 3.5 medium years, 4.5 light or very light years, and 1 year of
seed failure [82]. The maximum number of successive good crops was 4
years [45]. Yellow birch is a prolific seed producer, and viability is
usually good [32], although seed quality is variable from year to year
[60,82]. Seed longevity up to 8 years has been achieved under
laboratory conditions; under natural conditions viability drops off
rapidly the second year [58,60]. However, Roberts and Dong [99]
reported that a substantial amount of yellow birch regeneration was
derived from 2-year-old seed.

Seed Dispersal: Yellow birch seed is disseminated by wind, most of the
seed falling after cold weather begins. The winged nutlets may travel
up to 1,320 feet (400 m) over crusted snow [32]. Effective dispersal is
approximately 2 to 4 times tree height [74]. Korstian [65] estimated
that if yellow birch seeds are released from 50 feet (15 m),
in a 5 mile per hour wind, 50 percent will fall within 700 feet (213 m)
of the release point, and 90 percent within 820 feet (250 m).

Seed Germination: Yellow birch seeds contain a water-soluble
germination inhibitor. This inhibitor is inactivated by light. Under
artificial conditions, seed dormancy is broken by stratification or by
exposure of imbibed seed to cool-white fluorescent light [32]. Yellow
birch seeds germinate and grow best on moist mineral soil enriched with
humus; bare mineral soil and duff alone are unsuitable substrates
[16,64,82,124]. However, in undisturbed stands, germination of yellow
birch seeds usually occurs on mossy logs, decayed wood, in cracks in
boulders and on windthrown tree hummocks [32,67]. Optimum germination
of yellow birch occurs at 59 to 61 degrees Fahrenheit (15-16 deg C)
[27]. A substrate pH of 2.4 completely inhibited germination, and pH
3.0 partly inhibited germination (50.7 percent) [94,96].

Seedling Establishment and Growth: Yellow birch seedlings require
overhead light, crown expansion space, and plentiful soil moisture and
nutrients to compete with faster growing associates; conditions found in
gaps are conducive to yellow birch seedling establishment [1,32]. Some
shade improves seedling survival [82]. In one study, heavily shaded
(14-25% of full sun) yellow birch seedlings grew taller and had more
leaf area than those in full sun, but unshaded seedlings accumulated
more biomass [127]. Mortality of yellow birch seedlings is usually very
high [121]. In one study, minimum mortality was estimated as 97 percent
14 months after germination. Seedling survival is better on disturbed
microsites; seedlings that germinate on litter are unlikely to survive
[26,40]. Seedlings surviving their first year survive to sapling and
larger stages only where there is sufficient light [121]. Surviving
seedlings in hemlock-northern hardwood forests occur on microhabitats
with slightly lower canopy cover than in the surrounding area, primarily
under coniferous rather than mixed canopies [26]. Growth is better on
humus over sandy loams than on decayed logs, mineral soil, or litter
[124].

Vegetative Reproduction: Greenwood cuttings of yellow birch have been
successfully rooted and overwintered. Propagation by grafting is also
possible [32].

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More info for the terms: climax, cover, density, forbs, forest, hardwood, presence, seed, succession, tree

Facultative Seral Species

Yellow birch is intermediate in shade tolerance. Leak [71] assigned
yellow birch to the category of persistent successional species. Yellow
birch is described as opportunistic due to its habit of producing
abundant small seed [40]. Yellow birch seeds comprised a higher than
expected proportion (compared to the abundance of mature trees) of the
seed rain and seedbank of a mixed forest [56]. The presence of yellow
birch in mid- to late-successional stands depends on local disturbance
[28,71]; it cannot reproduce under a closed canopy and requires soil
disturbance and light for seedling survival [32]. Birches respond to
gaps of all sizes, with a peak density found in gaps of about 2,800
square feet (250 sq m) in Pennsylvania. In the southern Appalachians,
birches exhibited a peak density in 10-year-old gaps [102]. In southern
Appalachian spruce-fir forests, yellow birch seedlings were the most
abundant species in gap plots but not in closed-canopy plots. They
exhibited the highest growth rate of any species in gaps [122]. The
origin of the gap is apparently important; in upper Michigan, yellow
birch apparently failed to establish readily in gaps formed by stem
breakage because soil was undisturbed [87]. Yellow birch decreased
between 1964 and 1986 in red spruce-Fraser fir (Abies fraseri) stands,
even though there was loss of the Fraser fir to insect attack [18].

Yellow birch seedlings do not successfully compete with advance
regeneration of other northern hardwood species, grasses, and forbs
[32]. However, in sugar maple-beech-yellow birch forests, seedlings of
the three dominants were approximately equally abundant [40]. In mature
hemlock-hardwood forests in New York, yellow birch was the third most
common seedling species, distributed randomly as to canopy type [26].
Yellow birch seedlings tend to occur in clumps. The abundance of yellow
birch seedlings in Quebec was almost always negatively correlated to
that of other tree species even though its seed abundance was positively
related to that of other species [57]. Sugar maple seedlings produce an
allelopathic substance that inhibits the root growth of yellow birch
seedlings [112].

Early Successional Stands: Yellow birch is a common early to
mid-successional associate in aspen-birch stands [28]. In northern
hardwood ecosystems, yellow birch reaches maximum importance levels
within 15 years of disturbance, and those levels are maintained for at
least 100 years [81]. On Isle Royale, Michigan, a paper birch-dominated
stand that originated after fire early in this century is undergoing
canopy invasion by sugar maple and yellow birch [50]. In New Hampshire,
succession was monitored after experimental deforestation and 3 years of
vegetation suppression. Yellow birch comprised 0.6 percent of total
biomass in the first year of succession, and increased to 11.8 percent
in the nineteenth year [97]. Second-growth stands usually contain
approximately the same percentage of yellow birch as virgin stands [32].
Yellow birch occurs on fine till with importance peaking at about 80
years. On sandy soils, the trend is indistinct, probably declining over
time [71]. On old fields in Tennessee, succession included small
amounts of yellow birch in 15-year-old stands. Yellow birch occurred at
maximum density on 42- and 48-year-old plots, was present in lower
numbers on the 63-year-old plot, and was not present in the old-growth
plots [21].

Mid- to Late-Successional Stands: Yellow birch is abundant in mid- to
late-successional balsam fir-yellow birch-paper birch-white spruce
(Picea glauca) stands on Isle Royale [50]. It is a major gap-phase
component of sugar maple-beech-yellow birch and hemlock-yellow birch
cover types [32]. The age distribution of yellow birch in a virgin
northern hardwoods forest was somewhat irregular: There were many
10-year-old saplings, no 40-year-old trees, and many 100-year-old trees
[69]. In Wisconsin, even-aged northern hardwoods contain a high
proportion of yellow birch and uneven-aged stands tend towards pure
sugar maple [80]. In many old-growth stands, yellow birch gradually
decreases in importance as the stand ages. In Tennessee, in both
hemlock-mixed forest and mixed deciduous forest, yellow birch decreased
between 1935 and 1987 in undisturbed stands [17].

Climax Stands: Cary [128] described a climax forest in Maine consisting
of red spruce, American beech, maples, and yellow birch. Hansen and
others [50] described a yellow birch-sugar maple type as the climax
forest on Isle Royale, Michigan. These forests have not experienced
major disturbances for more than 120 years and include yellow birch of
up to 150 years of age [50]. Yellow birch was present in old-growth
forests in New York. The average ages of yellow birch trees in two
stands were 200 and 250 years [75]. Forcier [40] explained the presence
of yellow birch in climax stands as a combination of longevity and
micro-succession. At the single tree level, yellow birch is replaced by
sugar maple which is replaced by beech, which, following a small-scale
disturbance, is replaced by yellow birch [40].

Betula lutea Michx. [76]
B. alleghaniensis var. macrolepis (Fern) Brayshaw [76,131]

More info for the term: backcross

The currently accepted scientific name of yellow birch is Betula
alleghaniensis Britt. [14,76]. A recognized form is B. a. forma fallax
(Fassett) Brayshaw [131].

Yellow birch hybridizes with low birch (B. pumila L. var. glandulifera
Reg.). The hybrid is named B. xpurpusii C. K. Schneid [76]. An
additional entity formed by a backcross of B. xpurpusii and B.
alleghaniensis has also been named: B. xmurrayana Barnes & Dancik [44].

Early colonizers of a site denuded of vegetation by brine (used for
well-injection fluid) included yellow birch. Soil salinity levels had
returned to slightly above normal when initial colonization occurred [7].

Yellow birch is an economically important source of lumber. The wood is
heavy, strong, and close-grained. It is used for furniture, cabinetry,
charcoal, pulp [14], interior finish, veneer, tool handles [29], boxes,
woodenware, and interior doors [32].

Yellow birch grows in cool areas with abundant precipitation. Its northern limit coincides with the 2° C (35° F) average annual temperature isotherm, and its southern and western limits coincide with the 30° C (86° F) maximum temperature isotherm (31). Although the average annual temperature is about 7° C (45° F) throughout its range, temperature extremes range from -40° C to 38° C (-40° F to 100° F) (45). Annual precipitation rtinges from about 1270 mm (50 in) in the East to 640 mm (25 in) in central Minnesota at its western limit. More than half of the precipitation may be snow. Snowfall ranges from 152 to 356 cm (60 to 140 in) and averages 229 cm (90 in) in the north. The growing season ranges from 60 to 150 days and averages about 120 days.

Yellow birch is a very sensitive species that is more susceptible to injury than its common associates. It is windfirm on deep, well-drained loam and sandy loam soils but is subject to windthrow on shallow, somewhat poorly drained soils. Thin-barked yellow birch is susceptible to fire injury. Seedlings and saplings are killed outright by even light surface fires. The fine branching habit of yellow birch makes it susceptible to damage from accumulating ice or snow loads. Large trees are frost hardy (91) but late spring frost can kill 10-year-old seedlings, especially on litter seedbeds under full and partial shade. Winter sunscald can be a problem on the south and southwest sides of birch boles. Birch foliage and twigs are injured by wind-borne salt spray. Seed germination is also greatly reduced by 0.20-percent salt concentrations in the soil (6). Simulated acid rain at pH values from 3 up to 4 stimulated birch germination (80) but foliar damage occurs at pH levels of 3 or less and seedling growth reductions at pH 2.3 (127). Yellow birch seedlings are tolerant to atmospheric pollution of ozone at 0.25 p/m (67) and sensitive to 3.5 p/m of sulfur dioxide (66).

Post-logging decadence is a localized decline from which most trees recover. It consists of top dying and some mortality following heavy cutting in mature and overmature stands. Yellow birch is more susceptible to root, stem, or crown injury and more severely affected than its common hardwood associates. Weakened trees are often attacked and eventually killed by the bronze birch borer.

A decline of yellow birch and paper birch trees, called birch dieback, caused widespread mortality between 1932 and 1955 in eastern Canada and northeast United States. It affected yellow birches of all sizes, even in undisturbed virgin stands. The first visible symptoms of dieback are similar to those of decadence. Foliage in the upper crown appears small, curled, cupped, yellowish, and thin. Following this, tips of branches die, then dying progresses downward, involving entire branches and often more than half the crown within 2 or 3 years. Trees are usually killed within 3 to 5 years by the bronze birch borer, which with root rot fungi, the gold ring spot virus, and other pests have been considered secondary agents associated with birch dieback. Many researchers have attributed birch dieback to adverse climatic conditions, drought, and increased soil temperature, over an extended period, which caused rootlet mortality that weakened the trees and predisposed them to attacks by the borer. Others have considered over-maturity, past cutting practices, killing of associated trees by disease and the spruce budworm, and defoliating insect outbreaks on birch as initially responsible for weakening the trees. More recently the apple mosaic virus (49) and the "frozen soil" theory (59) have been suggested as the possible triggering mechanisms for birch dieback. Under the "frozen soil" theory, shallow-rooted birch trees in years without snow cover are apparently unable to replace moisture losses from their stems through both frozen rootlets and those broken from frost heaving. To date, no single "triggering" cause of birch dieback has been widely accepted, but the condition is probably the result of one or more of the indicated stress factors.

Top-dying and reduced growth of yellow birch crowns have also been associated with heavy birch seed crops (51). This dieback occurs the year after bumper seed crops and is limited to the peripheral 0.6 to 0.9 m (2 to 3 ft) of branch tips on mature trees and usually just the past season's growth on younger trees.

Discoloration and decay are the major causes of defect and loss in wood quality of yellow birch (75,92). Discoloration and decay develop more rapidly in yellow birch than other diffuse-porous northern hardwood species (60,107). Some of the nonhymenomycetes most frequently isolated from discolored wood associated with birch wounds are Libertella betulina, Trichocladium canadense, Phialophora spp., Phialocephala spp., Hypoxylon spp., and Nectria spp. (32,103,104,107).

Mechanical wounds with more than 320 cm² (50 in²) of exposed wood are important entrance courts for decay fungi (92). Pholiota limonella, P. aurivella, Polyporus versicolor, Daldinia concentrica, and Hypoxylon spp. are aggressive invaders of these larger wounds (76,104,106). D. concentrica and Hypoxylon spp. also invade branch stubs. Extensive decay is usually associated with larger mechanical injuries more than 20 years old and frost cracks more than 10 years old. Species of Phialophora are often found in tissues near frost cracks (33). Bacteria, Graphium spp., Phialophora spp., Polyporus spp., Pholiota spp., and Nectria are the microorganisms most frequently associated with increment-bore wounds in birch (60). Increment-bore wounds cause reddish-brown decay columns from 74 to 213 cm (29 to 84 in) long within 2 years following boring.

Nectria galligena is the most common and damaging stem disease of yellow birch. It causes perennial targetlike cankers, a twig blight, and subsequent crown dieback (59). The fungus can penetrate saplings, small branches, buds, and wounds but usually enters the host through cracks originating at branch axils from heavy snow or ice loads (7). Nectria cankers cause localized defects that reduce stem quality and weaken the stem, increasing the chances for wind breakage (45).

Diaporthe alleghaniensis causes a black sunken canker and shoot blight of yellow birch (1). Natural infections probably enter through bud scale scars, frost cracks, leaf scars, wounds, and other injuries (2). Cankers appear on shoots, stems, and petioles of seedlings in the spring and summer and foliage wilts and browns in the summer. Outbreaks of D. alleghaniensis occur only when conditions are optimum for infection and growth (70). Normally the fungus is weakly pathogenic and thins out less vigorous and overtopped seedlings.

Gnomonia setacea causes a canker, shoot blight, and leaf spot disease of yellow birch seedlings (71).

Stereum murrayi causes elongated, sunken, bark-covered stem cankers and a yellow-brown stringy trunk rot of yellow birch. Cankers are common on branch stubs and decay usually extends about 0.3 m (1 ft) above and below cankers on pole-sized trees (106). Decay can be extensive in overmature yellow birch. Phellinus laevigatus also produces characteristic sunken, bark-covered cankers on mature and over-mature trees. Single cankers indicate extensive decay. It is more common on dead than living trees. Inonotus obliquus produces black, clinker-like, sterile conks that develop in trunk wounds and branch stubs. Sometimes conks of L. obliquus and Phellinus igniarius occur on dead branch stubs in the center of Nectria cankers. A sterile conk indicates from 50 to 100 percent cull (59) and decay extends from 1.5 to 2.1 m (5 to 7 ft) above and below each conk. Inonotus obliquus is an aggressive decay fungi that can invade and kill tissues around these sterile conks (106).

Armillaria mellea, the shoestring root rot, is the most common and important root and butt decayer of yellow birch trees (106). The fungus causes a white root rot with black rhizomorphs on the roots.

Inonotus obliquus, Pholiota spp., Phellinus igniarius, and P. laevigata are the principal decay fungi of yellow birch trunks (45,76,106). The false tinder fungus (P. igniarius) causes a common white trunk rot of yellow birch. A single conk indicates extensive decay that extends 2.4 to 3.0 m (8 to 10 ft) above and below the conk. Pholiota aurivella is an aggressive decayer of centers of larger birches and Pholiota limonella causes a yellow-brown stringy trunk rot.

Ganoderma applanatum usually occurs on dead birches but sometimes rots the centers of trunks and infects roots and butts through wounds (106). Perennial, hoof-shaped conks of Fomes fomentarius, the tinder fungus, are common on dead birch. The fungus also has been associated with decay in living and dead branches of dieback birches. Piptoporus betulinus, Fomitopsis pinicola, and Polyporus lucidus also are primarily decayers of dead wood but they may extend into centers of living trees (59).

Coniothyrium spp., common twig-inhabiting fungi, injure yellow birch seeds and seedlings (108). They are associated with weevils that tunnel through the cones and destroy or injure the seeds.

The bronze birch borer (Agrilus anxius) is the most serious insect pest of yellow birch. It attacks both healthy and weakened birches (83) but apparently can normally complete its life cycle only in dead or dying wood in weakened trees. Mature and overmature trees left severely exposed after logging and in lightly stocked stands are more subject to attack then trees in well-stocked stands. Adults deposit their eggs in bark crevices of upper branches. Grubs hatch, bore meandering tunnels underneath the bark that cause top dying, then move progressively lower down the stem and kill the tree within 2 or 3 years. The Columbian timber beetle (Corthylus columbianus) bores deep into the sapwood of vigorous birches of all sizes (3). A flatheaded borer (Chrysobothris sexsignata) occurs commonly on birch in the East. The ambrosia beetle (Xyloterinus politus) is a secondary insect that attacks weakened and wounded birches. Adults bore holes through lenticles in the bark and make galleries (105).

In outbreaks, the birch skeletonizer (Bucculatrix canadensisella) completely destroys foliage by August. Successive attacks reduce host vigor and may predispose birches to bronze birch borer attacks.

Although yellow birch is not a preferred host of the forest tent caterpillar (Malacosoma disstria), the gypsy moth (Lymantria dispar), the elm spanworm (Ennomos subsignarius), the hemlock looper (Lambdina fiscellaria), or the saddled prominent (Heterocampa guttivitta), caterpillars of these species defoliate birch in severe outbreaks. Two to three years of successive defoliation can kill birch trees (122). Dusky birch sawfly larvae (Croesus latitarsus) prefer small saplings of gray birch but also defoliate yellow birch saplings by feeding inward along leaf edges (3). The lace bug, Corythucha pallipes, can be a very injurious insect, especially on young birch (25). A treehopper (Carynota stupida), a stink bug (Elasmuche lateralis), an aphid (Euceraphis betulae), a lygaeid bug (Kleidocerys resedae germinatus), and a scale insect (Xylococculus betulae) are other commonly to abundantly occurring sucking insects of yellow birch (3). E. lateralis and Kleidocerys resedae germinatus also feed on catkins. The birch seed midge (Oligotrophus betheli) lives in birch seed and makes it infertile.

Yellow birch is a preferred food of the snowshoe hare and the white-tailed deer. White-tails are especially fond of browsing seedlings during the summer, and green leaves and woody stems in the fall, and they favor succulent sprouts over slower growing seedlings. Heavy or repeated browsing often kills seedlings. Moose often severely browse it. Porcupine feeding often damages birch crowns, reduces wood quality, and sometimes kills the trees. Red squirrels cut new germinants, eat seeds, store mature strobiles, and feed on birch sap.

Yellow birch is a favorite summer food source of the yellow-bellied sapsucker on its nesting grounds. Heavy sapsucker feeding can reduce growth, lower wood quality, or even kill birch. The common redpoll and many other songbirds eat yellow birch seed. Ruffed grouse feed on the catkins, seeds, and buds.

Yellow birch is generally considered intermediate in shade tolerance and competitive ability (45). It is more shade tolerant than the other native birches, but less tolerant than its major associates, sugar maple (Acer saccharum), beech (Fagus grandifolia), and hemlock (Tsuga). Yellow birch is the major gap-phase component of the forest cover types Sugar Maple- Beech-Yellow Birch and Hemlock-Yellow Birch. It cannot regenerate under a closed canopy; it must have soil disturbance and an opening in the canopy (125). It tends to be stable on moist sites but gives way with age to more tolerant species on dry sites.

Yellow birch is often a pioneer species following fires but is usually less abundant than aspen (Populus), pin cherry (Prunus pensylvanica), and paper birch (Betula papyrifera). Birch seedlings cannot compete successfully with advance regeneration, grass, and herbaceous plants. An allelopathic relation between yellow birch and sugar maple seedlings has been noted (118). Advance sugar maple regeneration offers the stiffest competition in the Sugar Maple-Beech-Yellow Birch cover type, while red maple (Acer rubrum) sprouts are the most serious problem on wetter sites in the Lake States.

Yellow birch has an adaptable well-developed, extensive lateral root system. Its roots are capable of either spreading horizontally through shallow soils or penetrating to depths of more than 1.5 rn (5 ft) under favorable conditions. Roots often follow old root channels in compacted soil layers. Rooting patterns of older trees in unmanaged stands may be modified by their origin on decayed wood and stumps (fig. 3). Within- and between-tree root grafting is common in birch (42).

Irregularly distributed lateral roots of sapling and pole-size trees often extend well beyond their crown perimeters (120). Most root systems have irregular circular or oval shapes. Roots of trees on slopes are usually concentrated along the contour and the uphill side of the stem. Main laterals are close to the soil surface and usually have one or two sinker roots within 1.8 m (6 ft) of the stem. These sinkers often penetrate to impervious layers (53). Replacement root growth is active from leafout (May 5) until late October in southern New Hampshire (99).

Normally, 40 years is considered the minimum and 70 years the optimum seed-bearing age for yellow birch (45), but heavy seed crops are also produced by 30- to 40-year-old trees in either open-grown positions or thinned stands. However, open-grown progeny test saplings with large crowns bear viable seed at 7 years and male catkins at 8 years (21). Germinable seed has also been obtained from 16-year-old trees 5 to 10 cm (2 to 4 in) in d.b.h. and 6.7 to 7.6 rn (22 to 25 ft) tall.

Good seed crops usually occur at about 2 to 3 year intervals but the frequency of good or better seed crops varies-every 1 to 4 years in northeastern Wisconsin (47), and every 2 to 3 years in Maine, and every 3 years in Ontario (10). Consecutive good or better seed crops only occurred once in the 26-year Wisconsin study; 60 percent of the intervening crops failed or were poor. Seed-crop failures are often caused by hard frost in late spring or early fall or by insects and disease. The percentage of viable seeds produced varies each year and can be very low due to a high proportion of seedcoats without embryos, probably caused by parthenocarpy (14). Seed viability is often affected by weather conditions during pollination, fertilization, and seed development. It also varies by locality, stand, and individual trees within the same stand.

Although some seeds fall shortly after they mature in August, the first heavy seedfall in Canada and the northern United States comes with cold weather in October. Contrary to earlier reports, larger seeds are not shed first nor is their germination capacity any better than that of smaller filled seeds (17).

Yellow birch seeds are light, averaging 99,200/kg (45,000/lb) (8). They are dispersed by the wind and blown up to 400 m (1,320 ft) over crusted snow (10). Dispersal of adequate amounts for regeneration is at least 100 m (330 ft) from the edge of a fully stocked mature northern hardwood stand.

Yellow birch is a prolific seeder, producing between 2.5 and 12.4 million seeds per hectare (1 to 5 million/acre) in good seed years (45), and up to 89 million/ha (36 million/acre) in a bumper seed year (52). Seed viability is usually good in years with heavy seed crops and poor in years with light crops. Germinative capacity in good seed years is still low, however, averaging about 20 percent under natural conditions.

The next seed crop can be estimated from the abundance of the overwintering male catkins (88). Fairly reliable estimates of the fall yellow birch seed crop can also be obtained from the size of the spring-maturing red maple crop (47).

Yellow birch seedcoats contain a water-soluble germination inhibitor that is inactivated by light (17). Seed dormancy can be broken down artificially either by stratifying the seed in moist peat or sand at 5° C (41° F) for 4 to 8 weeks or by germinating unchilled seeds in a water medium under "cool-white" fluorescent light for more than 20 days. Germination test results are always higher when unchilled rather than stratified seeds are used (8). Following stratification, seeds are germinated at alternating day and night temperatures of 32° C and 15° C (90° F and 59° F) for 30 to 40 days, and alternating temperature of 30° C and 20° C (86° F and 68° F) with at least 8-hour light periods are used for unchilled seeds. Germination percentages exceeding 90 percent are common in good seed years.

Seeds can be stored in tightly closed bottles at from 2 to 4° C (36 to 40° F) for 4 years without losing viability (17). Some seed lots stored well for 8 years and one lot still had 65 percent germination after 12 years (19).

Yellow birch seeds dispersed in the fall and winter germinate at warm temperatures in early June. Germination is epigeal. In undisturbed stands, yellow birch can only regenerate on mossy logs, decayed wood, rotten stumps, cracks in boulders, and windthrown hummocks because hardwood leaf litter is detrimental to its survival elsewhere (45). In June most seeds germinate in compacted leaf litter that birch radicals and hypocotyls cannot pierce (10). Drying of the litter during the growing season kills most germinants. The remaining seedlings later succumb to frost damage or are smothered by the next leaf fall.

Unless stands have been burned or heavily disturbed by blowdowns or logging, abundant birch regeneration is normally restricted to edges of skidroads or landing areas on well-drained sites. On less-well-drained soils, sufficient moisture remains in the leaf litter to result in adequate establishment if advance regeneration of other species is removed (117).

The most important factors affecting the catch of yellow birch seedlings are an adequate seed supply, favorable weather, proper seedbed conditions, adequate light, and control of competition.

Removing advance regeneration is at least as important as preparing proper seedbeds (121). Scarification fulfills both requirements and, when coupled with opening of the canopy, can greatly increase the initial catch of birch seedlings (45). Optimum seedling survival and growth, however, occur on disturbed humus or mixed humus mineral soil seedbeds in the absence of advance regeneration (126).

Mechanical scarification and prescribed burning are used to prepare receptive seedbeds and eliminate advance regeneration. Scarification should be shallow to mix humus and mineral soil and to expose 50 to 75 percent of the area (46,88). Spring burning during and shortly after leafout in years with abundant male birch catkins may also control competition from advanced regeneration and provide seed for successful birch regeneration. Treatments should coincide with good seed crops because the effects of scarification are largely lost after two or three growing seasons.

Under dense forest canopies (13 and 15 percent of full sunlight) yellow birch roots grow slower than sugar maple seedlings (81). As a result, few yellow birch become established under selection cutting (43).

The optimum light level for top growth and root development of birch seedlings up to 5 years old is 45 to 50 percent of full sunlight (43). The best root-to-shoot ratios are also produced at similar light levels (86). In field studies, the greatest 2-year height growth occurred at the lowest canopy density of 0 to 14 percent, and on mixed humus and mineral soil seedbeds it occurred under canopy densities between 29 and 50 percent (123). Moderate side shade is beneficial to birch seedlings during their first 5 years (124).

Clearcutting small patches or strips provides suitable conditions for yellow birch seedling establishment in the Northeast where rainfall is abundant. Scarified clearcut patches of 0.04 to 0.24 ha (0.1 to 0.6 acre) produce good catches of birch regeneration. Patches are difficult to manage but can be used in uneven-aged management to increase the proportion of birch (43) when groups of mature or defective trees are harvested (85).

In the dry western part of the species range, success with strip clearcutting to regenerate birch has been too variable to generally recommend its use. In Upper Michigan success depends on a good seed crop, favorable weather, and control of advance regeneration (89). Although strips 20 and 40 in (66 and 132 ft) wide were equally well stocked with birch seedlings after 6 or 7 years in Michigan, strips 20 in (66 ft) wide are about optimum in Canada (10), and strips 15 in (50 ft) wide are recommended in the Northeast (43).

Clearcuttings of 2 to 4 ha (5 to 10 acres) and uniform selection cuttings are not as effective as smaller patches or the shelterwood method for establishing yellow birch stands (87,90). In the western part of its range, birch regenerates best under shelterwood cuttings (48,121). Ten well-distributed yellow birch seed trees per hectare (4/acre) provide an adequate seed supply (88). Otherwise, 0.56 kg/ha (0.5 lb/acre) of stratified (6 to 8 weeks at 5' C (41' C) birch seed can be applied about a week after site preparation in May (46) or unstratified seed can be sown before January (48).

Yellow birch can also be successfully established by planting 2-0 stock 15 to 50 cm (6 to 20 in) tall on 0.08 ha (0.2 acre) clearcut patches (97).

Yellow birch seedling growth in the Northeast is limited by inadequate soil fertility in acid sandy subsoils and can be greatly improved by deep fertilizing with phosphorus and lime to correct phosphorus deficiency and aluminum toxicity (61). Aluminum is toxic to roots, especially in subsoils, deficient in magnesium and sulfur. Seedling roots are tolerant of aluminum concentrations or up to 80 p/m but concentration of 120 p/m or more are toxic (84).

Manganese toxicity in seedlings occurs above foliar concentrations of more than 1,300 p/m; concentrations of less than 60 p/m are deficient; and 440 p/m are optimum (64).

Optimum nursery seedbed density is about 160 seedlings per square meter (15/ft²) (45). Normally 2-0 stock averaging 28 cm (11 in) tall with roots 23 cm (9 in) long and 5 mm (0.2 in) in stem caliper is large enough for dormant spring planting. For early starts in the greenhouse, seedlings require at least 2 months of cold storage to break dormancy (34). Containerized planting is feasible (11,50,115). In 3 months seedlings 40 to 50 cm (16 to 20 in) tall can be produced in the greenhouse using 20-hour days with supplemental cool-white fluorescent and incandescent light (17). Growth can also be accelerated by using plastic greenhouses (94).

After 5 years, yellow birch seedlings are normally overtopped by faster-growing species and require complete release from overstory shading for best survival, growth, and quality development. Photosynthetic rates of overtopped seedlings are only 54 to 70 percent of those grown in full sunlight and their dry weights are 66 percent lower (82).

Birch crop trees in Vermont and Michigan seedling stands (up to 2.5 cm or 1 in d.b.h.) have benefited from cleaning or early release (40,55). After 9 years, trees cleaned to within a 2.4 in (8 ft) radius of the bole radius in Michigan exhibited the best stem, crown, and branch characteristics. They averaged 2 cm (0.8 in) larger in d.b.h. and 0.5 rn (1.6 ft) taller than the control trees. Shoot growth of yellow birch partly depends upon current photosynthate (73). The shoot elongation period for released saplings (1.5-m or 5-ft radius) can be extended up to 30 days by making more light and moisture available to them (55).

Yellow birch grows over a large area with diverse geology, topography, and soil and moisture conditions. In Michigan and Wisconsin it is found on glacial tills, outwash sands, lacustrine deposits, shallow loess deposits, and residual soils derived from sandstone, limestone, and igneous and metamorphic rock (95). Soils are also derived from granites, schists, and shales in other parts of its range.

Growth of yellow birch is affected by soil texture, drainage, rooting depth, stone content in the rooting zone, elevation, aspect, and fertility. Yellow birch grows best on well-drained, fertile loams and moderately well-drained sandy loams within the soil orders Spodosols and Inceptisols and on flats and lower slopes (45). It also grows on Alfisols typical of the humid temperature forest region. Rootlet development is profuse in loam but poor in sand. Even though its growth is poor, yellow birch is often abundant where drainage is restricted because competition from other species is less severe.

In the Lake States birch grows best on well- and moderately well-drained soils and on lacustrine soils capped with loess. Its growth is poor on poorly-drained lacustrine soils, shallow soils over limestone, and coarse-textured sandy loams without profile development (95). Site quality between the best and poorest sites differs by more than 9 m (30 ft) at 50 years.

In the Green Mountains of Vermont birch grows on unstratified glacial till up to 792 m (2,600 ft) (109). Here, thickness of the upper soil horizon as influenced by elevation and aspect have been used to estimate site index-birch grows better at lower elevations than higher elevations and on northeast aspects than southwest aspects.

Yellow birch seedlings and small saplings reproduce from sprouts when cut, but sprouting from larger stems is very poor (93,111).

Greenwood cuttings of birch have been successfully rooted (45) and overwintered (56). The species can also be propagated by grafting (17).

Betulaceae -- Birch family

G. G. Erdmann

Yellow birch (Betula alleghaniensis) is the most valuable of the native birches. It is easily recognized by the yellowish-bronze exfoliating bark for which it is named. The inner bark is aromatic and has a flavor of wintergreen. Other names are gray birch, silver birch, and swamp birch. This slow-growing long-lived tree is found with other hardwoods and conifers on moist well-drained soils of the uplands and mountain ravines. It is an important source of hardwood lumber and a good browse plant for deer and moose. Other wildlife feed on the buds and seeds.

Yellow birch ranges from Newfoundland, Nova Scotia, New Brunswick, and Anticosti Island west through southern Ontario to extreme southeastern Manitoba; south to Minnesota and northeastern Iowa; east to northern Illinois, Ohio, Pennsylvania to northern New Jersey and New England; and south in the Appalachian Mountains to eastern Tennessee and northeastern Georgia. Southward yellow birch grows at higher elevations, appears more sporadically, and finally is restricted to moist gorges above 914 m (3,000 ft).

The largest concentrations of yellow birch timber are found in Quebec, Ontario, Maine, Upper Michigan, New York, and New Brunswick (96). About 50 percent of the growing stock volume of yellow birch in North America is in Quebec.


-The native range of yellow birch.

Betula alleghaniensis, the yellow birch, golden birch, or swamp birch, is a large tree and an important lumber species of birch native to northeastern North America. Its vernacular names refer to the golden color of the tree's bark. In the past its scientific name was Betula lutea.

Betula alleghaniensis is the provincial tree of Quebec, where it is commonly called merisier, a name which in France is used for the wild cherry.