VALUE AND USE
SPECIES: Populus tremuloides | Quaking Aspen 



WOOD PRODUCTS VALUE : 
Quaking aspen is one of the most important timber trees in the East.
Its wood is used primarily for particleboard, especially waferboard and
oriented strandboard, and for pulp.  In the Great Lakes States, quaking
aspen is the preferred species for making oriented strandboard.  Quaking
aspen fibers are well suited for making fine paper.  Some quaking aspen
is used for lumber.  Quaking aspen lumber is used for making boxes,
crates, pallets, and furniture.  A small but growing volume is made into
studs.  Quaking aspen wood is little used in the West, except in
Colorado, where it is used for pulp and particleboard [125].  Specialty
products from quaking aspen wood include excelsior, matchsticks, and
tongue depressors.  Quaking aspen pellets are used for fuel [125,170].

The wood of quaking aspen is light, soft, and straight grained.  It has
good dimensional stability and it turns, sands, and holds glue and paint
well.  It has relatively low strength, however, and is moderately low in
shock resistance.  Both sapwood and heartwood have low decay resistance
and are difficult for preservatives to penetrate [125,170].  Quaking
aspen wood warps with conventional processing, but saw-dry-rip
processing controls warping [101].


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Quaking aspen forests provide important breeding, foraging, and resting
habitat for a variety of birds and mammals.  Wildlife and livestock
utilization of quaking aspen communities varies with species composition
of the understory and relative age of the quaking aspen stand.  Young
stands generally provide the most browse.  Quaking aspen crowns can grow
out of reach of large ungulates in 6 to 8 years [116].  Although many
animals browse quaking aspen year-round, it is especially valuable
during fall and winter, when protein levels are high relative to other
browse species [159].

Large wild ungulates:  Elk browse quaking aspen year-round in much of
the West, feeding on bark, branch apices, and sprouts [38,42,102].  In
some areas, elk use it mainly in winter [116].  In northwestern Wyoming,
elk begin browsing quaking aspen as soon as they move onto winter ranges
in November and continue to use it through March [6].

Quaking aspen is important forage for mule and white-tailed deer.  Deer
consume the leaves, buds, twigs, bark, and sprouts [42,102,158].  New
growth on burns or clearcuts is especially palatable to deer [42,43].
Deer in many areas use quaking aspen year-round [23], although in some
western states, deer winter below the aspen zone [42,43].  Quaking aspen
communities are described as the major "deer-producing forest type" in
the north-central United States [31].  In the Great Lakes States,
quaking aspen is primary browse for white-tailed deer and moose [23].
Stands less than 30 years of age provide optimum forage for deer in
Minnesota [31].  In some locations, sprouts provide key summer forage
for deer after herbaceous species have cured [42,43].  Quaking aspen is
one of the most important items in the summer diet of mule deer on the
Kaibab National Forest of Arizona [159,161], and comprises up to 27
percent of the summer diet of mule deer in parts of central Utah [113].
However, it is relatively unimportant deer browse in parts of South
Dakota [159].  Mule deer in Utah have been observed consuming large
amounts of quaking aspen leaves after autumn leaf fall [42,161].

Quaking aspen is valuable moose browse for much of the year [23].  Moose
utilize it on summer [42] and winter ranges [23,42,135].  Quaking aspen,
paper birch (Betula papyrifera), and willows (Salix spp.) make up more
than 95 percent of the winter hardwood browse utilized by moose on
Alaska's Kenai Peninsula [149].  Relatively high levels of moose use
have been reported from early summer through late fall in Minnesota [84]
and Idaho [135].  Young stands generally provide the best quality moose
browse [42].  However, researchers in Idaho found that in winter, moose
browsed mature stands of quaking aspen more heavily than nearby
clearcuts dominated by quaking aspen sprouts [135].

Bison once favored quaking aspen-grassland transition zones in Manitoba
and Saskatchewan [32,102].  However, little is known about the historic
importance of quaking aspen browse to bison.  Meagher [105] found that
woody plants made up only 1 percent of the diet of bison in Yellowstone
National Park, and she did not list quaking aspen as one of the woody
species bison used.

Bears:  Black and grizzly bears feed on forbs and berry-producing shrubs
in quaking aspen understories.  Quaking aspen forests in Alberta provide
excellent denning and foraging sites for black bear [42].

Lagomorphs:  Rabbits and hares feed on quaking aspen in summer and
winter [42,43].  In winter, shoeshoe hare and cottontail rabbits eat
quaking aspen buds, twigs, and bark [42,43].  Quaking aspen is one of
the most important and nutritious summer browse species for rabbits in
Alberta [42], and is a preferred winter food of snowshoe hare in
Manitoba [20].  Pikas also feed on quaking aspen buds, twigs, and bark
[158].  Lagomorphs may girdle suckers or even mature trees [23,102].  In
some parts of Canada, fairly high quaking aspen mortality has been
attributed to rabbits and hares [20,102].

Rodents and shrews:  Small rodents such as squirrels, pocket gophers,
mice, and voles feed on quaking aspen during at least part of the year
[43,88,158].  Mice and voles frequently consume quaking aspen bark below
snow level, and can girdle suckers and small trees [23,43,88,152].  The
southern red-backed vole, deer mouse, and white-footed mouse are
dominant small mammals in quaking aspen communities of northern
Minnesota and upper Michigan.  Small mammal populations in quaking aspen
generally fluctuate widely with stand age and annual variation in animal
population size.  Highest densities typically occur in mature quaking
aspen stands.  Field mice (Peromyscus spp.), for example, are most
abundant in mature quaking aspen communities [129].  The red-backed
vole, however, is most abundant in sapling stands, somewhat less
abundant in mature stands, and least common in clearcuts.

Quaking aspen provides food for porcupine in winter and spring
[23,42,43].  In winter, porcupine eat the smooth outer bark of the upper
trunk and branches.  Porcupine girdling of quaking aspen has killed
large tracts of merchantable trees in Minnesota.  In spring, porcupine
eat quaking aspen buds and twigs [43].

Beaver comsume the leaves, bark, twigs, and all diameters of quaking
aspen branches [43].  They use quaking aspen stems for constructing dams
and lodges [42,102].  At least temporarily, beaver can eliminate quaking
aspen from as far as 400 feet (122 m) from waterways [6,23].  An
individual beaver consumes 2 to 4 pounds (1-2 kg) of quaking aspen bark
daily, and it is estimated that as many as 200 quaking aspen stems are
required to support one beaver for a 1-year period [42,43].

Birds:  Quaking aspen communities provide important feeding and nesting
sites for a diverse array of birds [39].  Bird species using quaking
aspen habitat include sandhill crane, western wood pewee, six species of
ducks, blue, ruffed, and sharp-tailed grouse, band-tailed pigeon,
mourning dove, wild turkey, red-breasted nuthatch, and pine siskin.
Quaking aspen is host to a variety of insects that are food for
woodpeckers and sapsuckers [42].  Generally, moist to mesic quaking
aspen sites have greater avian species diversity than quaking aspen
stands on dry sites [40,42].

Many bird species utilize quaking aspen communities of only a particular
seral stage.  Research at a northern Utah site suggests that blue
grouse, yellow-rumped warbler, warbling vireo, dark-eyed junco, house
wren, and hermit thrush prefer mature quaking aspen stands.  The
MacGillivray's warbler, chipping and song sparrows, and lazuli bunting
occur in younger stands [39,42].  Bluebirds, tree swallow, pine siskin,
yellow-bellied sapsucker, and black-headed grosbeak favor quaking aspen
community edges [39].

Ruffed grouse:  Through most of its range, ruffed grouse depends on
quaking aspen for foraging, courting, breeding, and nesting sites
[23,42,70].  It uses quaking aspen communities of all ages.  Favorable
ruffed grouse habitat includes quaking aspen stands of at least three
different size classes [23,70].  Young (2- to 10-year-old) stands
provide important brood habitat, and 10- to 25-year-old stands are
favored overwintering and breeding areas [122].  Quaking aspen leaves
and buds are readily available in abundant quantities in stands greater
than 25 years of age, and such older stands are used for foraging
[70,122].

Ruffed grouse chicks find protection in dense, young aspen suckers as
early as 1 year after fire or other disturbance [70].  Pole-size stands
appear to offer the best breeding habitat and may support one breeding
bird per 3 to 4 acres (1.2-1.6 ha).  Breeding generally does not occur
in stands exceeding 25 years of age or with a density less than
approximately 2,000 stems per acre [23].

Quaking aspen buds, catkins, and leaves provide an abundant and
nutritious, year-long food source for ruffed grouse [23,70].  Vegetative
and flower buds are the primary winter and spring foods of the ruffed
grouse.  Ruffed grouse eat 6 times more quaking aspen buds than buds
from all other species combined [70].  It is estimated that ruffed
grouse can consume more than 45 quaking aspen buds per minute and can
satisfy their daily winter food needs in as little as 15 to 20 minutes
[23].  Ruffed grouse generally begin feeding on staminate flower buds
from several weeks prior to the period of snow accumlation, and continue
well into early spring [23,70].  Male ruffed grouse feed on staminate
catkins until at least early May [70].  Nesting hens consume large
quantities of new quaking aspen leaves early in the spring [23,70].
Ruffed grouse consume quaking aspen leaves throughout the summer [23],
and the leaves are considered to be the second most important food
source during the fall.  Ruffed grouse appear to prefer certain clones.
Buds from some clones may be up to 30 percent richer in protein than
buds from neighboring clones [70].

Livestock:  Most classes of domestic livestock use quaking aspen.
Domestic sheep and cattle browse the leaves and twigs [158,161].
Domestic sheep browse quaking aspen more heavily than cattle [158,161].
It is estimated that domestic sheep consume 4 times more quaking aspen
sprouts than cattle.  Heavy livestock browsing can adversely impact
quaking aspen growth and regeneration [42,43,161].


PALATABILITY : 
Quaking aspen is palatable to all browsing livestock and wildlife
species [38,23,42,84,161,169].  The buds, flowers, and seeds are
palatable to many bird species including numerous songbirds and ruffed
and sharp-tailed grouse [42,168].

Palatability of quaking aspen for livestock and wildlife species has
been rated as follows [48]:

                       CO       MT       ND       OR       UT       WY
Cattle                Fair     Fair     Fair     ----     Fair     Fair
Domestic sheep        Fair     Good     Good     ----     Fair     Good
Horses                Fair     Fair     Fair     ----     Fair     Fair
Pronghorn             ----     ----     Poor     ----     Fair     Fair
Elk                   Good     Fair     ----     ----     Good     Good
Mule deer             Good     Fair     Fair     ----     Good     Good
White-tailed deer     Good     Fair     Fair     ----     ----     Good
Small mammals         ----     Fair     ----     ----     Fair     Good
Small nongame birds   ----     Fair     Fair     ----     Fair     Fair
Upland game birds     ----     Good     Good     ----     Fair     Good
Waterfowl             ----     ----     ----     ----     Poor     Poor


NUTRITIONAL VALUE : 
Overall energy and protein values of quaking aspen are rated "fair"
[48].  Nutritional content of quaking aspen browse varies seasonally, by
plant part, and by clone [11,40,159].  Protein content drops as the
growing season progresses [42,179].  On a Utah site, average leaf
protein dropped from 17 percent in early June to 3 percent at
abscission.  Clonal variation in leaf protein ranged from 13.4 to 20.9
percent in June and from 10.1 to 14.6 percent in September.  Average
twig protein dropped from 17 percent in spring to 6 to 7 percent in
winter.  Twig nitrogen, phosphorus, and potassium levels dropped from
spring to winter, but twig calcium, magnesium, sodium, and fat levels
increased.  Phosphorus values in September averaged only 58 percent of
those in June [159].

Mean composition of quaking aspen terminal shoots, collected in March
and April in Soldotna, Alaska, was as follows [149]:

     dry matter (%)                       43.6
     gross energy (kcal/g)                 5.1
     crude protein (%)                     7.9
     neutral-detergent fiber (%)          54.9
     acid-detergent fiber (%)             40.1
     lignin (%)                           10.5
     ash (%)                               1.9
     in-vitro digestibilty for moose (%)  42.0


COVER VALUE : 
Wild and domestic ungulates use quaking aspen for summer shade, and
quaking aspen provides some thermal cover for ungulates in winter
[42,35,152].  Seral quaking aspen communities provide excellent hiding
cover for moose, elk, and deer [42,161].  Deer use quaking aspen stands
for fawning grounds in the West [94].  Ungulates generally do not use
quaking aspen much in winter.  Perala [122] reported that in the Great
Lake States, pure quaking aspen stands provided white-tailed deer with
relatively poor insulation and protection from winter winds compared to
adjacent stands of conifers.

Quaking aspen provides good hiding and thermal cover for many small
mammals [152].  Snowshoe hare use it for hiding and resting cover in
summer [42,43].  Beaver use quaking aspen branches for dams and lodges.

A variety of bird species use quaking aspen for hiding, nesting, and
roosting cover [42].  Sapling and pole-size stands provide especially
good winter cover for birds [23].  Snow tends to accumulate earlier and
deeper in quaking aspen than in adjacent conifer stands, and ruffed
grouse use the deep snow for burrowing cover in winter [122].  Dense
stands of fairly small diameter stems (<6 inches [15cm]) provide the
best protection from predators.  Overall cover value for ruffed grouse
is enhanced in stands containing several size classes [70].
        
Over 4 years, 22 to 65 pairs of breeding birds were found in 10 acres (4
ha) of quaking aspen in nothern Utah.  Species nesting in quaking aspen
included the broad-tailed hummingbird, northern flicker, house wren,
American robin, warbling vireo, yellow-rumped warbler, junco, western
wood pewee, and lazuli bunting [39].  The following other species also
nest in mature quaking aspen communites [42]:

       canopy nesters -  pewees, vireos, western tanager, Cassin's finch,
         least flycatcher
       ground nesters -  hermit thrush, Townsend`s solitaire, dark-eyed junco,
         white-crowned and Lincoln`s sparrows, veery, ovenbird, nighthawk,
         Connecticut and mourning warblers
       shrub nesters - flycatchers (Empidonax spp.), rose-breasted and
         black-headed grosbeaks, chipping, clay-colored, and song sparrows,
         yellow and MacGillivray`s warblers, rufous-sided and
         green-sided towhees, black-billed cuckoo
       cavity nesters - chickadees, nuthatches, woodpeckers, owls,
         sapsuckers, hairy and downy woodpeckers

General cover value of quaking aspen has been rated as follows [48]:

                       CO       MT       ND       OR       UT       WY
Pronghorn             ----     ----     Poor     ----     Poor     Poor
Elk                   Fair     Good     ----     ----     Good     Good
Mule deer             Fair     Good     Poor     ----     Good     Good
White-tailed deer     Fair     Good     Fair     ----     ----     Good
Small mammals         ----     Good     ----     ----     Good     Good
Small nongame birds   Good     Good     Good     ----     Good     Good
Upland game birds     Poor     Good     Good     ----     Good     Good
Waterfowl             ----     ----     ----     ----     Poor     Poor


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Aspens (Trepidae) are unique in their ability to stabilize soil and
watersheds.  Fire-killed stands are promptly revegetated by root sprouts
(suckers).  The trees produce abundant litter that contains more
nitrogen, phosphorus, potash, and calcium than leaf litter of most other
hardwoods.  The litter decays rapidly, forming a nutrient-rich humus
that may amount to 25 tons per acre (oven-dry basis).  The humus reduces
runoff and aids in percolation and recharge of ground water.  Litter and
humus layers reduce evaporation from the soil surface.  Compared to
conifers, more snow accumulates under quaking aspen and snowmelt begins
earlier in the spring.  Soil under quaking aspen thaws faster and
infiltrates snow more rapidly than soil under conifers [23].

Wide adapability of quaking aspen makes it well-suited for restoration
and rehabilitation projects on a wide range of sites.  Seedlings
transplanted onto disturbed sites have shown good establishment [33].
Seedlings have some advantages over vegetative cuttings.  In large-scale
greenhouse production, quaking aspen seedlings are more economical to
establish and grow [57].  Seedlings grow a taproot and secondary roots
quickly, while quaking aspen cuttings can be slow to establish an
adequate root system [145].  Also, genetic diversity is greater among
seedlings than cuttings [146].  Seed stored at 4 degrees Fahrenheit (-20
deg C) has retained viability for at least 2 years.  Fung and Hamel [57]
and Schier and others [145] provide procedures for collecting and
processing quaking aspen seed.

The major advantage of using quaking aspen cuttings is that clones with
desirable traits can be selected as parent stock.  Quaking aspen
vegetative cuttings are difficult to root, however [123,146].  Stem
cuttings are especially difficult to root unless taken from young
sprouts.  Root cuttings taken from young sprouts are generally most
successful.  Schier and others [146] provide information on growing
quaking aspen cuttings in the greenhouse.

Case examples - Riparian:  In riparian and lodgepole pine (Pinus
contorta) zones of Lost Canyon near Fresno, California, restoration was
needed after a hydroelectric plant pipe broke, scouring part of the
canyon.  Quaking aspen seedlings showed 99.2 percent survival (or 357
live seedlings) and had a mean height of 10.6 inches (26.6 cm) 1 year
after transplant [33].

Strip-mined sites:  Some old strip-mined sites in Pennsylvania, Ontario,
and elsewhere have not revegetated due to extreme acidity of the soil.
Quaking aspen is one of the first native tree species to volunteer on
these soils after application of lime [81,168].    

Mine spoils:  Quaking aspen transplants were successfully established on
phosphate mine spoils in southeastern Idaho that received only 18 inches
(450 mm) of annual precipitation [145].


OTHER USES AND VALUES : 
Mountain slopes covered by quaking aspen provide high yields of
good-quality water.  Quaking aspen intercepts less snow than conifers,
so snowpack is often greater under quaking aspen [44].

Well-stocked quaking aspen stands provide excellent watershed
proctection.  The trees, the shrub and herbaceous understories, and the
litter of quaking aspen stands provide nearly 100 percent soil cover.
Soil cover and the intermixture of herbaceous and woody roots protect
soil except during very intense rains [44].

Quaking aspen is valued for its aesthetic qualities at all times of the
year.  The yellow, orange, and red foliage of autumn particularly
enhances recreational value of quaking aspen sites [85].

Quaking aspen is widely used in ornamental landscaping [85].


MANAGEMENT CONSIDERATIONS : 
It is somewhat unclear why some quaking aspen stands break up and die
while others remain stable.  The age at which quaking aspen clones begin
to die probably has a genetic component.  Site quality can also be a
major factor [143].  Is it well documented in the Great Lakes States
that environmental variables affect quaking aspen longevity [63,93].
Stands in this region may deteriorate* rapidly; more than half the trees
in a well-stocked stand may die in 6 years [63].  In Utah, however,
clone deterioration was found to occur over a number of generations of
sprouts [141].  Schier and Campbell [143] found that on the Wasatch
National Forest near Logan, Utah, concentrations of phosphorus and
percent silt were significantly lower on soils with deteriorating clones
than on soils with healthy clones.  Ten deteriorating clones and ten
healthy clones were studied.

*Deteriorating stands are defined as those stands with a low density of
stems that are younger and smaller in size, and with poorer form and
higher crown:stem ratios, than healthy stands [143].

Cryer and Murray [36] speculated that both soil type and disturbance are
important in quaking aspen stability.  As a quaking aspen stand matures,
a humus-rich (mollic) soil layer develops.  Quaking aspen thrive for a
time, but without disturbance gradually begin to age and deteriorate.
With deterioration, the soil loses organic matter and thickness.  With
loss of humus and litter, rapid percolation leaches the soil, which
becomes thinner, more acidic, and lower in nutrients.  Acidic,
low-nutrient soils support conifers more readily than quaking aspen.
Disturbances such as burning or clearcutting tend to maintain quaking
aspen.  If soil is already thin and acidic, however, clearcutting will
probably convert the site to conifers.  Quaking aspen on such sites has
been observed to sprout, grow to about 3 feet (0.9 m) in height, and
begin to die.  A deteriorating stand that is burned may be more likely
to revert to quaking aspen because burning increases soil pH and adds
organic carbon and nutrients to the soil.  However, fire will probably
not rejuvenate the stand if quaking aspen biomass is so low that burning
does not appreciably raise soil pH and nutrient levels.  Sucker vigor
will probably be low.

Range:  There is increasing concern that in the West, poor quaking aspen
regeneration is due, at least in part, to wildlife overbrowsing young
sprouts [67].  Where browsing pressure is heavy, ungulates may remove
quaking aspen regeneration before it grows above browseline.  To provide
for quaking aspen regeneration in such areas, enough quaking aspen must
be removed to create an unbrowsed surplus of new growth [122].  A few
areas of the West have such large elk populations that even after
large-scale wildfires, quaking aspen sprouts attained little height
growth because of intense browsing.  In such areas, quaking aspen
sprouts probably require protection from browsing [90].

Promoting quaking aspen:  Prescribed burning is one method of promoting
quaking aspen (see FIRE MANAGEMENT).  When prescribed burning is not
desired or feasible, clearcutting or bulldozing is recommended [77,177].

Clearcutting often results in a sucker stand of 50,000 to 100,000 stems
per hectare [17,35,49].  A basal area of less than 4 trees/sq m/ha is
recommended to promote sprouting [87,122].  Partial cuttings seriously
inhibit sprouting because apical dominance is retained in standing
stems, and shade from standing stems reduces vigor of the few suckers
that do appear [49].

Clearcutting in southeastern boreal forest:  Lavertu and others [98]
found that in balsam fir-northern white-cedar (Abies balsamea-Thjua
occidentalis) forest in Quebec, quaking aspen showed strong sprouting
response regardless of forest seral stage, number of quaking aspen
present before cutting, quaking aspen stem age, or quaking aspen root
density.  After clearcutting on sites that had burned 46, 74, 143, 167,
and 230 years earlier, quaking aspen sprouted vigorously even on the
site that had not burned for 230 years, had only a single, living
quaking aspen stem, and the lowest quaking aspen root density of all
five site types.  Initial sprouting densities were greater in younger
stands, but due to greater mortality of sprouts in younger stands,
differences in sprouting density between different-aged stands were not
significant 3 years after clearcutting.

Bulldozing:  Carefully done, whole-tree bulldozing can stimulate quaking
aspen suckering [177,178].  Operations that cause deep cutting or
compaction of soil will reduce sprouting [177].  Shepperd [178] obtained
good quaking aspen regeneration by pushing over whole trees using a
rubber-tire skidder with the blade positioned above ground level.  This
technique severed large roots to a distance of 3.3 to 5 feet (1-1.5 m)
from the stem.  Five years after treatment, quaking aspen suckers
averaged 37,888 per hectare when slash was removed and 10,131 per
hectare with slash intact.  In contrast, sites that were clearcut
averaged 17,544 stems per hectare (no slash) and 7,038 stems per hectare
(slash) [178].

Quaking aspen control:  On some sites, it may be desirable to convert
quaking aspen to another vegetation type.  Stand conversion may be
relatively easy on dry or poorly drained sites, or on sites were quaking
aspen is exposed to snow damage.  Quaking aspen production is usually
low on such sites to begin with, and such stands are prone to breakup.
On other sites, it may not be possible to eliminate quaking aspen, but
quaking aspen can probably be reduced [49].  Very small clearcuts reduce
quaking aspen abundance because sprouting response is weak after such
treatment [114].  Girdling also reduces adundance; sprouting occurs
after girdling, but shade provided by standing dead stems increases
sprout mortality.  Also, it is thought that girdling promotes decay of
the root system [147].  Use of glyphosate after cutting has been shown
to control quaking aspen regeneration for some time [122,123].

In Quebec, quaking aspen in a quaking aspen-paper birch stand
originating after a 1944 fire was partially controlled by removing
overtopping quaking aspen when the stand was 7 and 14 years of age.
Stocking varied as follows at postfire year 34 [96].

_______________________________________________________________________________
         Treatment            |                   Stocking
______________________________|________________________________________________
control (no treatment)        |  5% paper birch; 90% aspen;  5% mixed hardwoods
Aug. 1951 cut & Nov. 1958 cut | 90% paper birch; 10% aspen
Nov. 1951 cut & Nov. 1958 cut | 44% paper birch; 41% aspen; 15% mixed hardwoods
Nov. 1951 cut & May 1959      |  
  herbicide (injection in     | 32% paper birch; 63% aspen;  5% mixed hardwoods
____aspen only)_______________|________________________________________________

Related categories for Species: Populus tremuloides | Quaking Aspen