Index of Species Information
SPECIES: Picea pungens
Introductory
SPECIES: Picea pungens
AUTHORSHIP AND CITATION :
Pavek, Diane S. 1993. Picea pungens. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
https://www.fs.usda.gov/database/feis/plants/tree/picpun/all.html [].
ABBREVIATION :
PICPUN
SYNONYMS :
Picea parryana Sarg.
Picea commutata Horton
SCS PLANT CODE :
PIPU
COMMON NAMES :
blue spruce
Colorado blue spruce
Colorado spruce
silver spruce
pino real
TAXONOMY :
The currently accepted scientific name of blue spruce is Picea pungens
Engelm. [68,125]. It is a member of the pine family (Pinaceae). There
are no recognized subspecies, varieties, or forms.
Blue spruce does not readily hybridize with other conifers [105].
Throughout its range, it occurs with Engelmann spruce (Picea engelmannii
Parry), but few if any natural hybrids are ever produced [22,105].
Artificial crosses have produced small amounts of seed with low (0.3
percent) germination [34,46]. Blue spruce, Engelmann spruce, and white
spruce (Picea glauca) are sympatric in the Sweetgrass Hills of
north-central Montana. Putative hybrids among all three spruce species
have been reported [113].
Approximately 38 horticultural varieties of blue spruce have been
developed [37,122].
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
DISTRIBUTION AND OCCURRENCE
SPECIES: Picea pungens
GENERAL DISTRIBUTION :
Blue spruce is restricted to the central and southern Rocky Mountains.
Its range extends from scattered populations in eastern Idaho and
western Wyoming to better developed populations in Utah and Colorado.
The range of blue spruce continues southward into Arizona and New Mexico
[22,38,77,103,104]. It occurs rarely in north-central Montana [113].
ECOSYSTEMS :
FRES20 Douglas-fir
FRES21 Ponderosa pine
FRES23 Fir - spruce
FRES26 Lodgepole pine
FRES28 Western hardwoods
STATES :
AZ CO HI ID MT NM UT WY
BLM PHYSIOGRAPHIC REGIONS :
6 Upper Basin and Range
7 Lower Basin and Range
9 Middle Rocky Mountains
10 Wyoming Basin
11 Southern Rocky Mountains
12 Colorado Plateau
13 Rocky Mountain Piedmont
KUCHLER PLANT ASSOCIATIONS :
K012 Douglas-fir forest,
K018 Pine - Douglas-fir forest
K019 Arizona pine forest
K020 Spruce - fir - Douglas-fir forest
K021 Southwestern spruce - fir forest
K022 Great Basin pine forest
K025 Alder - ash forest
SAF COVER TYPES :
206 Engelmann spruce - subalpine fir
210 Interior Douglas-fir
211 White fir
216 Blue spruce
217 Aspen
218 Lodgepole pine
219 Limber pine
235 Cottonwood - willow
237 Interior ponderosa pine
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Blue spruce occurs as dominant or codominant in small stands or as
scattered individuals. In riparian settings, blue spruce is codominant
with cottonwoods such as narrowleaf cottonwood (Populus angustifolia) or
balsam poplar (P. balsamifera) [7,85,117]. Blue spruce is more
important in habitat type series of the central Rocky Mountains. Blue
spruce series are restricted to cool, moist areas thoughout the
southwestern mixed-conifer forests [1,26,120]. Common codominants are
Engelmann spruce, white fir (Abies concolor), and Douglas-fir
(Pseudotsuga menziesii) [3,26,88].
Blue spruce is often a long-lived seral species. It is seral in white
fir, corkbark fir (Abies lasiocarpa var. arizonica), or fir phases of
Engelmann spruce habitat types [3,39]. It infrequently occurs in the
spruce-fir subalpine zone [31].
Some of the many publications that list blue spruce as an indicator or
dominant in habitat or community types are:
(1) Classification of the forest vegetation on the National Forests of
Arizona and New Mexico [3]
(2) Classification of riparian vegetation of the montane and subalpine
zones in western Colorado [7]
(3) Aspen community types of Utah [88]
(4) A physical and biological characterization of riparian habitat and
its importance to wildlife in Wyoming [91].
MANAGEMENT CONSIDERATIONS
SPECIES: Picea pungens
WOOD PRODUCTS VALUE :
Blue spruce is not an important timber tree because it occurs
infrequently, and the wood is brittle with many knots [38,65]. The wood
is light, soft with numerous resin canals, close-grained, and weak
[104,122]. When it is harvested, it is often cut and marketed with
Engelmann spruce [77].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Blue spruce provides cover for a variety of bird and animal species
[29]. Big game forage is good throughout blue spruce habitat types in
northern New Mexico and southern Colorado [26]. Numerous birds eat blue
spruce seeds [122]. Blue spruce cones are cached by red squirrels in
Utah [128].
In a mixed-conifer forest in the White Mountains of Arizona, nongame
birds moderately preferred blue spruce for cover and gleening for
insects. In a comparison of usage in logged and control areas, mountain
chickadee and ruby-crowned kinglet preferred blue spruce in unlogged
areas only; yellow-rumped warbler preferred it in both treatment areas;
and gray-headed junco preferred blue spruce in logged areas only [47].
PALATABILITY :
Blue spruce is not a highly preferred food for either wildlife or
domestic animals [10,103]. Deer browse blue spruce infrequently [122].
In mixed-conifer forests, blue spruce is the least desired browse
species by elk and deer [67]. White-tailed deer in Conneticut browsed
ornamental blue spruce an average of 0.5 percent throughout the summer
[18]. Blue spruce can be used an an index of mule deer population size;
young blue spruce are severely damaged by browsing during times of
overpopulation [64].
NUTRITIONAL VALUE :
The protein value of blue spruce is rated as poor, and its energy value
is fair [29].
COVER VALUE :
Blue spruce provides good environmental protection for elk, mule deer,
white-tailed deer, small mammals, and small nongame and upland game
birds in Colorado, Utah, and Wyoming. It gives poor cover for pronghorn
in Colorado and Wyoming, and fair to poor cover for waterfowl in Utah
and Wyoming [29].
Blue spruce was one of several species in a commercial conifer nursery
used by white-tailed and mule deer for hiding and thermal cover during a
severe winter in southeastern Wyoming [56]. Moose use blue spruce for
shelter [75]. In Wyoming, moose used the blue spruce climax association
an average of 5 percent over 4 years [63]. Where blue spruce occurred
in a ponderosa pine forest in Colorado, cavity nesting birds showed no
preference in tree species selection for nest sites [100].
Mixed-conifer forests of Arizona and New Mexico that blue spruce occur
in are valuable summer habitat for game and nongame animals and birds
[44,73].
Sensitive and endangered species use mixed-conifer stands in which blue
spruce occurs. Such species include flammulated owls in Colorado, Jemez
Mountain salamander of New Mexico, and northern goshawks in Arizona
[20,94,98,99]. Bald eagle breeding areas at intermediate elevation in
Wyoming are dominated by blue spruce and narrowleaf cottonwood. In the
Snake River Unit, 28 percent of the nests were in blue spruce trees
[114].
VALUE FOR REHABILITATION OF DISTURBED SITES :
Blue spruce has been included in roadside reclamation on U.S. Highway 89
south of Afton, Wyoming. One year after grasses had been planted,
container-grown blue spruce were planted [23]. Data on establishment
success were not given.
Blue spruce was chosen as one of several species to provide cover and
foraging area for wildlife. This reclamation planting mediated habitat
loss due to increased water levels in Rufus Woods Lake, Washington [17].
No data on establishment success were given.
Blue spruce was planted in Canada as a part of shelterbelts to prevent
wind erosion [54].
OTHER USES AND VALUES :
Blue spruce is planted extensively as an ornamental in North America and
Europe [13,77,104,]. Blue spruce are used as Christmas trees [38,65].
It is the state tree of Colorado and Utah [77,65].
OTHER MANAGEMENT CONSIDERATIONS :
Silviculture: Blue spruce has an intermediate tolerance for single-tree
selection harvesting [55]. Single-tree selection and diameter-limit
harvest methods were compared on a Southwestern old-growth mixed-conifer
stand in which blue spruce occurred. The single-tree selection method
left the stand satisfactorily stocked with 54 percent damage to advance
regeneration. Diameter-limit method left the stand understocked with 71
percent loss of advance regeneration [51]. Conifer regeneration by
small patch clearcutting was also recommended for these forests [42,52].
Effective seeding distance to obtain adequate natural regeneration of
blue spruce is about 3 to 4 times the height of the tree [80]. Because
blue spruce is considered a late successional species, it is not
suitable as a seed tree in clearcuts [53,106]. Silvicultural practices
for mixed-conifer stands are reviewed in detail [67].
Blue spruce ranged from 2 to 28 inches (5.1-71.1 cm) d.b.h. with most
trees at 2 inches (5.1 cm) in stand inventories of virgin mixed-conifer
forest; no blue spruce died during the 5 years of monitoring. Initial
blue spruce volume was 360 board feet per acre; final volume was 391
board feet per acre. Average annual growth of blue spruce was less than
0.2 inch (0.5 cm) [50]. In east-central Arizona, blue spruce were 3.05
square feet per acre (0.7 sq m/ha) basal area in a total 177.7 square
feet per acre (40.8 sq m/ha) for the mixed-conifer forest. Blue spruce
annual basal growth of 2.9 percent was the highest growth rate for all
tree species present [33]. In blue spruce habitat series in central
Colorado, total basal areas ranged from 169 to 300 square feet per acre
(49-83 sq m/ha) with all size classes of blue spruce present [60,61].
Other Uses: In wet sites with well-developed soil, blue spruce timber
potential is high; however, the timber value may be low. Blue spruce is
often more valuable for wildlife habitat and food and for recreation
[70].
Blue spruce is a component of mixed-conifer forests that have been a
part of browse studies [41]. Equations exist for predicting forage
production [12,40,76]. Forage production estimates include hiding and
thermal cover for wildlife management. Since these mixed-conifer
clearcuts require 50 to 100 years to regenerate, clearcut areas are a
long-term forage resource for deer and elk [118]. Quaking aspen
(Populus tremuloides) is often associated with blue spruce on upland
sites. Treatment of conifers in these systems depends on whether aspen
is to be maintained for livestock forage or wildlife habitat [25].
Blue spruce is a part of mixed-conifer stands that are managed for
watershed [52]. Clearcuts in these forests increase water yield almost
in proportion to the area cleared [24].
Artificial vegetative propagation of blue spruce is possible using short
cuttings, grafting, and air layering [28,38,123]. Breeding commercial
stock has been successful; however, interspecific crosses rarely yield
viable hybrids [34,46,90,105]. Blue spruce pollen used in artificial
crosses is viable for almost 3 years when stored at cold temperatures
[36]. Methods for cone harvesting and seed extraction are discussed in
detail [32,103].
Blue spruce have been planted in a wide range of environments. It has
been a part of state nursery programs to stock oldfields in Ohio [93].
Blue spruce nursery stock is more drought resistant than other spruce
species, and it can withstand temperatures to -40 degrees Fahrenheit
(-40 deg C) [38]. It can tolerate some flooding. Forty percent of
3-year-old blue spruce seedlings survived 21 days under aerated,
submerged conditions; all died after 28 days [82].
Blue spruce was included in a 30-year shelterbelt project in the
northern Great Plains. Blue spruce was 13 feet (4 m) tall at 20 years
with 32 percent of the original trees surviving [49]. It has been
successfully used in shelterbelts in Montana, North Dakota, and South
Dakota [9,119]. Planting recommendations have been discussed in detail
[4,107].
Damaging Agents: Insects and disease reduce growth, viability, and
vigor of blue spruce [37,124]. Heart and root rots, cone rusts,
nematodes, snow molds, canker, and tip blight have an impact on blue
spruce [38,89]. Silvicultural methods that minimize pathologic and
insect problems are discussed in detail [2,45,106]. Calibrated
ecosystem models that correlate microclimate with blue spruce stand
information are useful for predicting the behavior of forest pathogens
[83]. Tree ring patterns of blue spruce have been used to construct
past occurrence of insect attacts [69].
Blue spruce is a host of western spruce budworm (Choristoneura
occidentalis); outbreaks and symptoms are discussed in detail [16,78].
Blue spruce is an infrequent host of mountain pine beetle (Dendroctonus
ponderosae) and spruce beetle (D. rufipennis), which kill other conifers
[5,62]. Trees surviving infestation are more susceptible to other
pathogens, insects, and windthrow [45,57].
Blue spruce is the principal host of western spruce dwarf mistletoe
(Arceuthobium microcarpum) and minor host of other dwarf mistletoe
species [58,59,124]. Infected blue spruce seedling mortality under a
heavily infested canopy was twice that of the control [79].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Picea pungens
GENERAL BOTANICAL CHARACTERISTICS :
Blue spruce is a native evergreen tree with a dense, pyramidal to
spire-shaped crown [75,116,122]. It can be 70 to 115 feet (21-35 m)
tall with a diameter up to 3 feet (0.91 m) [103,104,115,122]. The bark
is 0.75 to 1.5 inches (1.9-3.8 cm) thick [104]. Branches are stout and
horizontal to drooping [65,122]. The leaves are four-angled, stiff with
sharp points, and 1 to 1.25 inches (2.5-3.2 cm) long [37,68]. Cones are
2.5 to 4 inches (6.4-10.2 cm) long with thin, flexible scales [77]. The
seeds are 0.13 inch (0.3 cm) long, about half the length of the wings
[104].
The largest blue spruce recorded was from Colorado at 126 feet (38.4 m)
tall with 60.8 inches (154.4 cm) d.b.h. [38]. The oldest blue spruce
was 600 years [86].
RAUNKIAER LIFE FORM :
Phanerophyte
REGENERATION PROCESSES :
Blue spruce reproduces sexually. Natural vegetative reproduction does
not occur, although epicormic shoots sometimes sprout on the trunks
[38].
Seed production begins at about 20 years and peaks at 50 to 150 years
[38,122]. Blue spruce is a good to prolific seed producer, producing
full cone crops every 2 to 3 years [32,38,122]. Cones mature in August
of the first year and have 85 to 195 seeds per cone [37]. Seeds are
wind disseminated, falling within 300 feet (90 m) of the upwind timber
edge [38].
Most germination occurs on exposed mineral soil; however, seeds
germinate on a variety of substrates [37]. Natural germination rates
usually are low; however, one study reported 80 percent germination
[28,38]. Seeds germinate without stratification under a wide range of
temperature and light conditions [38,103]. Blue spruce seedlings will
establish beneath parent or other conifer canopies if understory
vegetation is lacking or sparse [71].
Overall tree growth is slow [65]. In a nursery, blue spruce were 19.1
to 23.3 inches (48.5 to 59.2 cm) tall after 5 years [38]. Seedlings are
susceptible to frost heaving and may be susceptible to drought due to
shallow roots [2,66]. Blue spruce transplanted into the ponderosa pine
(Pinus ponderosa) zone in the southern Rocky Mountains all died due to
drought conditions [21]. Blue spruce was collected throughout its range
and grown in a Michigan nursery. Growth rates slightly decreased as
latitude of origin increased [13]. In a study in North Dakota, 73.6
percent of all blue spruce roots were in the top 2 feet (0.61 m) of the
Fargo clay soil [127]. Despite its shallow roots, blue spruce is
windfirm [122].
SITE CHARACTERISTICS :
The shallow roots of blue spruce restrict it to moist sites where water
is close to the surface [75]. Blue spruce occurs on montane
streambanks; well-drained floodplains or cobble flats; first-level
terraces; ravines; intermittent streams; or subirrigated, gentle slopes
[37,60,75,104].
Throughout much of its range, blue spruce grows in cool climates that
are subhumid to humid, characterized by low summer temperatures and low
winter precipitation [37]. In the southern end of its range, it may be
restricted to riparian areas in arid and semiarid climates;
precipitation occurs bimodally with dry springs [92]. Average annual
precipitation in blue spruce habitats varies from 18 to 24 inches
(460-610 mm) [37].
Blue spruce typically occurs at mid-elevations. In Wyoming, blue spruce
is abundant along streams at 6,750 feet (2,057 m) in elevation and
extends up into subalpine zones to 10,499 feet (3,200 m) [37,61]. In
Utah, blue spruce occurs from 6,500 to 8,400 feet (1,981-2,560 m) in
elevation, where often the parent material is limestone or calcareous
sandstone [15,38,65]. In Colorado, blue spruce occurs in canyons from
6,700 to 8,530 feet (2,042-2,600 m) in elevation and on canyon slopes
from 9,800 through 11,500 feet (2,987-3,505 m) in elevation [61,70,74].
Blue spruce occurs from 7,500 to 9,842 feet (2,285-3,000 m) in elevation
in Arizona and New Mexico [1,84,116].
Blue spruce grows on a variety of soil types. Usually, soils are young
and undeveloped; however, soil textures may be deep sandy to gravelly
loams that are well drained [37,61]. Soils are commonly derived from
fluvium, alluvium, and colluvium [60,110]. Soils may have a litter
layer up to 3.5 inches (9 cm) thick [61]. Soil temperature regimes are
frigid in montane canyons to cryic at higher elevations [26,85]. Blue
spruce stands are often associated with areas of cold air drainage
[60,128]. Blue spruce occurs on flat to moderate (12 to 20 percent)
slopes that often are north- to south- or southeast-facing [38,70].
Common associates not mentioned in Distribution and Occurrence are Rocky
Mountain maple (Acer glabrum), thinleaf mountain alder (Alnus incana
ssp. tenuifolia), wax currant (Ribes cereum), Utah honeysuckle (Lonicera
utahensis), Gambel oak (Quercus gambelii), Saskatoon serviceberry
(Amelanchier alnifolia), and common juniper (Juniperus communis)
[3,37,70,88]. Other associated species are hairy goldenaster
(Chrysopsis villosa), Fendler meadowrue (Thalictrum fendleria), Arizona
fescue (Festuca arizonica), bluejoint reedgrass (Calamagrostis
canadensis), and field horsetail (Equisetum arvense) [3,37,115,128].
SUCCESSIONAL STATUS :
Facultative Seral Species
Blue spruce occurs in various seral stages from pioneer to climax. Its
successional status depends on location and associated species [38].
Blue spruce is a pioneer species in riparian communities that are
subject to periodic disturbances, such as scouring and flooding
[8,38,116]. It is present in all size classes along the riparian
systems and on the lower slopes in the southwestern United States, where
it may be a topoedaphic climax species [37].
Blue spruce is an intermediate to late, long-lived seral or climax
species in montane or subalpine zones [6,38,106]. Blue spruce is
intermediate in shade tolerance [38,111]. It may be seral to or climax
with any of the conifer species in the mixed-conifer forests [30,37].
Quaking aspen and lodgepole pine (Pinus contorta) can be seral to blue
spruce [87].
SEASONAL DEVELOPMENT :
Reproductive buds of blue spruce form on shoots of the previous year
[103]. Pollen is shed from April to June, depending on altitude. Cones
mature during August or September of their first year; seeds disperse in
fall and winter [37,103]. Some cones drop the first winter; however,
most are retained 2 to 3 years [37]. Seeds germinate in the spring or
summer after dispersal [38].
FIRE ECOLOGY
SPECIES: Picea pungens
FIRE ECOLOGY OR ADAPTATIONS :
Blue spruce is easily killed by fire [67,126]. It has thin bark and
shallow roots which make it susceptible to hot surface fires [14]. Blue
spruce is slow to self-prune lower branches; therefore, surface fires
can crown [19]. Blue spruce foliage has moderately volatile oils [109].
Crowns are dense and highly flammable [106,109]. However, surviving
blue spruce remain windfirm in stands opened by fire [14].
In riparian areas where blue spruce occurs, intervals between fires are
about 350 to 400 years. Severe fires occur infrequently, and succession
back to the original community is often relatively rapid (15 to 35
years). Depending on the site, blue spruce may be the dominant seral
tree [19].
Successive fires may prevent blue spruce from dominance because it is
fire intolerant. Historical fire frequency in mixed-conifer forests was
about 22 years, based on fire-scarred trees in the White Mountains of
Arizona [27]. Fire suppression during the past 100 years has made the
mixed-conifer forest in which blue spruce occurs more susceptible to
fire; however, blue spruce may be dominant in some areas because of the
longer fire-free intervals.
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".
POSTFIRE REGENERATION STRATEGY :
Tree without adventitious-bud root crown
Secondary colonizer - off-site seed
FIRE EFFECTS
SPECIES: Picea pungens
IMMEDIATE FIRE EFFECT ON PLANT :
Fire kills blue spruce. Low severity fires will kill saplings and
seedlings [2]. Slow burning of fine fuels will kill the shallow roots
of blue spruce [14].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
NO-ENTRY
PLANT RESPONSE TO FIRE :
Blue spruce does not sprout after fire [109]. Rates of establishment
will vary depending on proximity of seed trees and moisture. Seed must
be transported from off-site. Blue spruce will establish by
wind-dispersed seed that readily germinates on the mineral soil exposed
by fire. Small mammals and birds may also carry cones or seeds into a
burn.
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
NO-ENTRY
FIRE MANAGEMENT CONSIDERATIONS :
Fire is less frequent in montane mixed-conifer forests at lower
elevations where Douglas-fir is dominant with blue spruce than in
ponderosa pine types. Quaking aspen is seral and present because of
fire in these forests. Prescribed fire here would increase habitat and
browse for wildlife [108].
Blue spruce is not recommended for fire shelterbelts based on studies in
Victoria, Australia. Fuel ladders form from persistent dead low
branches [109].
Fuel prediction is difficult because of the large variation in natural
fuel loadings in the forests where blue spruce occurs [101]. Therefore,
Sackett [102] determined average squared diameters and specific
gravities of blue spruce and seven other conifer species in Arizona and
New Mexico. This established weight and volume of fuels using planar
intersect method. Greatest accumulations on the mixed-conifer forest
floor come from fermentation and humus layers [43]. One fuel loading
estimate was an average of 44 tons per acre (98 t/ha) [128].
References for species: Picea pungens
1. Alexander, Billy G., Jr.; Fitzhugh, E. Lee; Ronco, Frank, Jr.; Ludwig, John A. 1987. A classification of forest habitat types of the northern portion of the Cibola National Forest, New Mexico. Gen. Tech. Rep. RM-143. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 35 p. [4207]
2. Alexander, Robert R. 1974. Silviculture of central and southern Rocky Mountain forests: a summary of the status of our knowledge by timber types. Res. Pap. RM-120. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 36 p. [15586]
3. Alexander, Robert R.; Ronco, Frank, Jr. 1987. Classification of the forest vegetation on the National Forests of Arizona and New Mexico. Res. Note RM-469. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station. 10 p. [3515]
4. Alspach, Lyle K. 1989. Dazomet use for seedbed fumigation at the PFRA Shelterbelt Centre, Indian Head, Saskatchewan. In: Landis, Thomas D., technical coordinator. Proceedings, Intermountain Forest Nursery Association; 1989 August 14-18; Bismarck, ND. Gen. Tech. Rep. RM-184. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 40-42. [17052]
5. Amman, Gene D.; Cole, Walter E. 1983. Mountain pine beetle dynamics in lodgepole pine forests. Part II. Population dynamics. Gen. Tech. Rep. INT-145. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station. 59 p. [8315]
6. Baker, William L. 1988. Size-class structure of contiguous riparian woodlands along a Rocky Mountain river. Physical Geography. 9(1): 1-14. [9269]
7. Baker, William L. 1989. Classification of the riparian vegetation of the montane and subalpine zones in western Colorado. The Great Basin Naturalist. 49(2): 214-228. [7985]
8. Baker, William L. 1990. Climatic and hydrologic effects on the regeneration of Populus angustifolia James along the Animas River, Colorado. Journal of Biogeography. 17(1): 59-73. [13236]
9. Barnes, Thomas G.; Keyser, Emmett J., III; Linder, Raymond L. 1989. Survey of animal damage and feeding selectivity of rabbits in eastern South Dakota shelterbelts. In: Bjugstad, Ardell J.; Uresk, Daniel W.; Hamre, R. H., tech. coords. 9th Great Plains wildlife damage control workshop proceedings; 1989 April 17-20; Fort Collins, CO. Gen. Tech. Rep. RM-171. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Forest and Range Experiment Station: 154-159. [9816]
10. Beetle, Alan A. 1962. Range survey in Teton County, Wyoming: Part 2. Utilization and condition classes. Bull. 400. Laramie, WY: University of Wyoming, Agricultural Experiment Station. 38 p. [418]
11. Bernard, Stephen R.; Brown, Kenneth F. 1977. Distribution of mammals, reptiles, and amphibians by BLM physiographic regions and A.W. Kuchler's associations for the eleven western states. Tech. Note 301. Denver, CO: U.S. Department of the Interior, Bureau of Land Management. 169 p. [434]
12. Betters, David R. 1983. Overstory-understory relationships: aspen forests. In: Bartlett, E.T.; Betters, David R., eds. Overstory-understory relationships in Western forests. Western Regional Research Publication No. 1. Fort Collins, CO: Colorado State University Experiment Station: 5-8. [3309]
13. Bongarten, B. C.; Hanover, J. W. 1986. Provenance variation in blue spruce (Picea pungens) at eight locations in the northern United States and Canada. Silvae Genetica. 35(2-3): 67-74. [9836]
14. Bradley, Anne F.; Noste, Nonan V.; Fischer, William C. 1991. Fire ecology of forests and woodlands in Utah. Gen. Tech. Rep. INT-287. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 128 p. [18211]
15. Buchanan, Hayle. 1960. The plant ecology of Bryce Canyon National Park. Salt Lake City, UT: University of Utah. 136 p. Thesis. [3364]
16. Carlson, Clinton E.; Fellin, David G.; Schmidt, Wyman C. 1983. The western spruce budworm in northern Rocky Mountain forests: a review of ecology, past insecticidal treatments and silvicultural practices. In: O'Loughlin, Jennifer; Pfister, Robert D., eds. Management of second-growth forests: The state of knowledge and research needs: Proceedings of a symposium; 1982 May 14; Missoula, MT. Missoula, MT: University of Montana, School of Forestry, Montana Forest and Conservation Experiment Station: 76-103. [7097]
17. Carson, Robert G.; Edgerton, Paul J. 1989. Creating riparian wildlife habitat along a Columbia River impoundment in northcentral Washington. In: Wallace, Arthur; McArthur, E. Durant; Haferkamp, Marshall R., compilers. Proceedings--symposium on shrub ecophysiology and biotechnology; 1987 June 30 - July 2; Logan, UT. Gen. Tech. Rep. INT-256. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station: 64-69. [5924]
18. Conover, M. R.; Kania, G. S. 1988. Browsing preference of white-tailed deer for different ornamental species. Wildlife Society Bulletin. 16: 175-179. [8933]
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