Index of Species Information

SPECIES:  Picea rubens


SPECIES: Picea rubens
AUTHORSHIP AND CITATION : Sullivan, Janet. 1993. Picea rubens. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: [].
ABBREVIATION : PICRUB SYNONYMS : Picea rubra (Du Roi) Link Picea australis Small Picea nigra var. rubra Engelmann. SCS PLANT CODE : PIRU COMMON NAMES : red spruce yellow spruce West Virginia spruce eastern spruce he-balsam blue spruce TAXONOMY : The accepted scientific name for red spruce is Picea rubens Sarg. There are no subspecies, varieties, or forms [48,64]. Natural hybrids with black spruce (P. mariana) have been reported [9,48]. LIFE FORM : Tree FEDERAL LEGAL STATUS : No special status


SPECIES: Picea rubens
GENERAL DISTRIBUTION : Red spruce occurs from Cape Breton Island, Nova Scotia, and New Brunswick, west to Maine, southern Quebec, and southeastern Ontario, and south to central New York, northeastern Pennsylvania, northern New Jersey, and northeastern Massachusetts. Its range extends south in the Appalachian Mountains of extreme western Maryland, eastern West Virginia, northern and western Virginia, western North Carolina, and eastern Tennessee [48]. ECOSYSTEMS : FRES10 White - red - jack pine FRES11 Spruce - fir FRES18 Maple - beech - birch FRES19 Aspen - birch STATES : CT ME MD MA NH NJ NY NC PA TN VT VA WV NB NS PE PQ BLM PHYSIOGRAPHIC REGIONS : NO-ENTRY KUCHLER PLANT ASSOCIATIONS : K096 Northeastern spruce - fir forest K097 Southeastern spruce - fir forest K108 Northern hardwoods - spruce forest SAF COVER TYPES : 5 Balsam fir 12 Black spruce 16 Aspen 17 Pin cherry 18 Paper birch 21 Eastern white pine 22 White pine - hemlock 23 Eastern hemlock 24 Hemlock - yellow birch 25 Sugar maple - beech - yellow birch 27 Sugar 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 60 Beech - sugar maple 107 White spruce 108 Red maple SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : Red spruce is a common dominant or codominant in the red spruce and the spruce-fir forests of the northeastern United States and adjacent Canada. Shrub associates of red spruce in the Adirondack Mountains of New York include red raspberry (Rubus idaeus), dwarfed blackberry (R. pubescens), hobblebush (Viburnum alnifolium), Canada yew (Taxus canadensis), and American fly honeysuckle (Lonicera canadensis). Ground layer herbs include wild sarsaparilla (Aralia nudicaulis), Aster acuminatus, yellow beadlily (Clintonia borealis), and common wood-sorrel (Oxalis montana). Common bryophytes found in old-growth red spruce forests in the Adirondacks include Brotherella recurvans, Schreber's moss (Pleurozium schreberi), Polytrichum ohioense, mountain fern moss (Hylocomium splendens), Bazzania trilobata, ptilium (Ptilium crista-castrensis), Drepanocladus uncinatus, Dicranum scoparium, and D. montanum [47]. In the southern Appalachian Mountains, arboreal associates include Fraser fir (Abies fraseri), yellow buckeye (Aesculus octandra), sweet birch (Betula lenta), and black cherry (Prunus serotina) in addition to those found in the northern part of its range [59,79,87]. Understory associates in openings include rhododendrons (Rhododendron spp.), American mountain-ash (Sorbus americana), and wild raisin (Viburnum cassinoides). Other understory associates include highbush cranberry (Viburnum edule), mountain holly (Ilex montana), mountain laurel (Kalmia latifolia), speckled alder (Alnus rugosa), pin cherry (Prunus pensylvanica), serviceberry (Amelanchier spp.), raspberries (Rubus spp.), and blueberries and huckleberries (Vaccinium spp.). In closed red spruce stands, mosses, lichens, and clubmosses predominate in the understory along with wood sorrel (Oxalis spp.), trillium (Trillium spp.), and checkerberry wintergreen (Gaultheria procumbens) [79]. Publications describing habitat or cover types in which red spruce is dominant or codominant include: (1) Proceedings of the Region 9 Land Systems conference on the White Mountain National Forest [5] (2) The Hubbard Brook ecosystem study: composition and dynamics of the tree stratum [11] (3) Ground vegetation patterns of the spruce-fir area of the Great Smoky Mountains National Park [14] (4) Spruce-fir forests of the coast of Maine [16] (5) Forest type studies in the Adirondack region [31] (6) The classification and evaluation of site for forestry [33] (7) The identification and description of forest sites [34] (8) Old-growth forests of Adirondack Park, New York [47] (9) Vegetation-environment relationships in virgin, middle elevation forests in the Adirondack Mountains, New York [68] (10) Natural ecological communities of New York State [71]


SPECIES: Picea rubens
WOOD PRODUCTS VALUE : Red spruce is one of the more important timber species in the northeastern United States. The wood is light in weight, straight grained, and resilient. It is used for paper, construction lumber, and is highly preferred for musical instruments [9,29]. IMPORTANCE TO LIVESTOCK AND WILDLIFE : Spruce grouse browse the leaves and twigs of red spruce [62]. Mice and voles consume and store significant amounts of spruce seeds, preferring red and white spruce to balsam fir [2]. Birds (particularly crossbills or grosbeaks) will clip the terminal buds of young spruce, as will porcupines, bears, snowshoe hares, and, rarely, deer [7,55,78]. Red squirrels clip twigs and terminal buds and also eat reproductive and vegetative buds [7,72]. In the southern part of its range, red spruce forests are used by only a few wildlife species. Many of these species are usually only found farther north, such as snowshoe hare, wood warblers and other songbirds, rodents, and salamanders [79]. PALATABILITY : Red spruce is unpalatable to white-tailed deer [78]. NUTRITIONAL VALUE : NO-ENTRY COVER VALUE : Red spruce provides thermal and loafing cover for spruce grouse in winter [62]. VALUE FOR REHABILITATION OF DISTURBED SITES : Red spruce is occasionally used for revegetation of coal mine sites in West Virginia, primarily at high elevations, but it is of limited value for this purpose [82]. OTHER USES AND VALUES : Red spruce gum was formerly collected and processed for chewing gum [29]. OTHER MANAGEMENT CONSIDERATIONS : Silviculture: Various silvicultural systems may be used to manage red spruce. Single tree selection, group selection, shelterwood, and strip clearcut are all practical harvesting methods. Red spruce is subject to windthrow; partial cuttings are recommended not to exceed half of the basal area, and a lighter harvest is usually better. Seed tree cuts are not recommended [6,9]. Frank and Blum [23] recommend a selection silviculture where net growth is maximized by a 10-year, intensive selection system. Clearcuts are contraindicated for many soil types and fertility levels [35]. Postharvest red spruce regeneration is entirely dependent on advance reproduction. If seedlings are not present at the time of logging, any new spruce seedlings will be quickly overtopped and suppressed by faster growing hardwoods [17]. Leaf litter may aid in red spruce regeneration. Harvesting during the dormant season or allowing harvested trees to dry on site has been recommended to increase litter [35]. Loucks [53] noted that in the Maritime Provinces of Canada, red spruce regeneration is usually good following partial cuts but may be lacking in clearcuts. The extent of red spruce forests has decreased following extensive logging practices and subsequent fire [3]. In the mountains of central West Virginia, it is estimated that approximately 500,000 acres (200,000 ha) of red spruce present in the late 19th century had been reduced to less than 60,000 acres (24,000 ha) by 1975, and as little as 17,500 acres (7,000 ha) in 1978 [10,73]. Management for wildlife: Harvest practices have an effect on the resulting stand structure, and therefore on the numbers and species of birds that use red spruce habitats. Crawford and Titterington [15] identified five seral stages and the corresponding bird species, and made associated recommendations for management of spruce-fir stands. They also determined that spruce budworm infestation increases both the number and diversity of birds. Dense, young stands of red spruce support a higher population of birds but with less diversity than in older forests. Insects and disease: Red spruce is relatively free from insects and diseases until it is mature. Mature trees are susceptible to the following insects: spruce budworm (Choristoneura fumiferana), eastern spruce beetle (Dendroctonus rufipennis), European spruce sawfly (Diprion hercyniae), yellowheaded spruce sawfly (Pikonema alaskensis), and eastern spruce gall adelgid (Adelges abietis) [9,22,23,30]. Diseases of red spruce have been detailed [9,22,23,30,47]. Red spruce decline: Throughout its range, growth rates of red spruce have declined and mortality has increased [36]. This decline is apparently more severe at higher elevations, in older stands, and on more exposed sites. This decline is not limited to red spruce; balsam fir and associated white and black spruce appear to be affected also [85]. A number of studies on the causes of red spruce decline have failed to make a definitive case for any single cause. There may be no single cause or the complexity of the situation may not lend itself to a clear cause-effect relationship [36,42,47]. The combination of climatic stress and atmospheric pollution is probably the major cause of this decline, according to a number of researchers [19,36,41,42]. Numerous other causes have been proposed as well, including a natural cycle of dieback and recovery [3, 36,]. A survey of the extent and identifiable causes of mortality and decline was published in 1985 [85].


SPECIES: Picea rubens
GENERAL BOTANICAL CHARACTERISTICS : Red spruce is a native, evergreen conifer. It is a medium-sized tree, attaining a maximum height of 115 feet (35 m); the average mature height is 60 to 75 feet (18-23 m). The ovulate cones are 1.3 to 1.5 inches (3-4 cm) long, with rigid rounded scales that are often slightly toothed on the edges. Red spruce is very shallow rooted; most of the feeding roots occur in the duff and top few centimeters of soil. In Maine, the average depth of roots was 13 inches (33 cm), with a maximum depth of 22 inches (56 cm) [9]. Red spruce is long-lived, often achieving ages greater than 350 years [1]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : Red spruce reproduces exclusively by seed. The first cone crop is usually produced when the crown first reaches direct light [27,39]. Therefore, red spruce can bear cones as early as 15 to 20 years of age; cone production peaks about 15 years later. In dense, even-aged stands, full cone crops are rare until the trees are 40 to 50 years old [39]. Good seed crops are produced every 3 to 8 years, with light crops in intervening years. Cones are dropped shortly after they are mature [9]. The seeds are wind or rain disseminated. The maximum distance for dispersal by wind is approximately 201 feet (61 m) [27]. Seeds do not exhibit dormancy. Most germinate the spring following dispersal; occasionally germination will occur in the fall soon after seeds drop from the tree. Seeds are usually not viable after 1 year. Germination is largely controlled by moisture availability. Seeds will germinate in almost any medium except sod. Seeds that germinate in thick duff are subject to overheating and/or drought mortality. Drought and frost-heave are the major causes of seedling mortality the first year [9]. Successful reproduction appears to depend more on seedling survival than on germination requirements [9]. Seedling establishment is usually best on shallow, less fertile soils that discourage competitive hardwoods [87]. The primary roots of red spruce seedlings do not penetrate litter and forest duff to any depth [38]. Red spruce seedlings have a root system of finely branched rootlets and no strong laterals; they depend entirely on the humus for nutrients and water [57]. SITE CHARACTERISTICS : Red spruce grows in climates with cool, moist summers and cold winters [74]. In the northeastern United States, the mean annual precipitation ranges from 36 to 52 inches (910-1,320 mm) and is often higher in the mountainous terrain where red spruce occurs, due to fog drip. Snow cover averages 80 to 160 inches (203-406 cm), with 100 to 140 days of snow cover per year [9]. Most of the soils on which red spruce occurs are developed from glacial deposits. The most productive soils are derived from parent materials of unsorted glacial drift and till deposited on the midslopes of hills and mountains. Soils on red spruce sites are usually acid Spodosols, Inceptisols, and sometimes Histosols with thick mor humus and a well-defined A2 horizon. Soil pH ranges from 4.0 to 5.5. Red spruce is often found on sites that are unfavorable for other species, such as organic soils overlying rocks in mountainous locales, on steep rocky slopes with thin soils, and in wet bottomlands [9]. In the northern part of its range, red spruce occurs at elevations ranging from sea level to 4,500 feet (0-1,370 m), above which it is usually replaced by balsam fir (Abies balsamea). The elevational zonation of species is defined as follows [67]: up to 1,485 feet (450 m) northern hardwoods (hemlock phase) 1,486 to 2,508 feet (451- 760 m) northern hardwoods (spruce phase) 2,508 to 4,026 feet (761-1,220 m) subalpine (spruce-fir phase) 4,027 to 4,785 feet (1,221-1,450 m) subalpine (fir phase) In the southern Appalachian Mountains, red spruce occurs at elevations from about 3,200 feet to 6,200 feet (980-1,890 m); above 6,200 feet (1,890 m), red spruce tends is usually replaced by Fraser fir (Abies fraseri) [59]. SUCCESSIONAL STATUS : On shallow, acidic, glacial till soils, red spruce is considered climax. It is usually subclimax on fertile, well-drained slopes and on abandoned fields and pastures where is is replaced by shade-tolerant hardwoods such as sugar maple and beech. Other types, such as red spruce-balsam fir and red spruce-yellow birch are usually climax [20]. Red spruce is tolerant of shade. Seedlings of red spruce can establish in as little as 10 percent of full sunlight, but for optimum growth, at least 50 percent of full sunlight is needed [9,75,81]. Growth tends to be suppressed in shade, but such suppression can persist for many years without killing the tree. For example, suppressed understory individuals may be 4 to 5 feet (1.2-1.5 m) tall, and be more than 50 years old. In comparison, open-grown red spruce can reach sawtimber size at 50 years [9,29]. Red spruce responds to canopy removal even after many years of suppression. The taller and older a seedling or sapling is, the greater is its response to release, up to about 55 years of age after which response to release starts to decline. However, the amount of response does not revert to seedling levels until the tree is around 100 years of age. Umbrella-shaped saplings 40 to 80 years old that have been suppressed will respond to release after a delay of several years, and in fact have an advantage because they are taller than smaller, healthier saplings which respond more quickly to canopy opening. More than half of mature red spruce second growth arises from larger but suppressed advance growth, as opposed to having arisen from small advance growth or new seedlings [16]. Upon release, 60-year-old red spruce growth exceeds that of same-age balsam fir and therefore tends to dominate the canopy [56]. Leak [44] defined red spruce in New Hampshire as a dominating climax species on shallow, dry, wet, or poorly aerated soils; it is a minor component in young stands but increases markedly over time until it is a canopy dominant. He estimated that, if undisturbed, red spruce can reach densities of 70 to 80 percent in a minimum of 250 years. Red spruce is a long-lived species and, once established, persists as a dominant for a long time. Davis [16] observed young spruce-fir stands in coastal Maine originating in open sites and as the understory to early seral hardwoods such as paper birch. The young, open-grown stands may be dominated by white spruce, red spruce, or balsam fir in any proportions. A spruce-fir stand originating as understory tends to be dominated by red spruce and/or balsam fir, though white spruce is often present. Moore [58] found red spruce forests to be even-aged in groups, indicating that establishment and/or canopy achievement tends to occur in openings. Red spruce and red spruce-fir cover types are self-maintaining. Stand composition may vary with stand age. Both red spruce and its two fir associates (balsam and Fraser) are shade tolerant, and both spruce and fir reproduction are found under spruce-fir canopies [6,16]. In the Catskill Mountains of New York, balsam fir reproduction predominated under both spruce and balsam fir stands. Both red spruce and balsam fir reproduction occurred at low densities under hardwood stands (mostly yellow birch) [55]. McIntosh and Hurley [55] do not believe that red spruce forests form a self-perpetuating climax in this area. Their conclusion may be biased, however, since balsam fir outcompetes red spruce in early stages, but is usually overtopped or outcompeted by red spruce in more mature forests [16]. Flieger [21] described 350-year-old stands of red spruce which were characterized by irregular stocking and variable crown heights and widths, with at least two age classes apparent. Most virgin red spruce forests are uneven-aged, indicating that the forests did no originate following stand-destroying disturbances, and that red spruce is able to reproduce under its own canopy [52]. SEASONAL DEVELOPMENT : Red spruce vegetative buds begin growth from May 26 to June 3 [8]. Needles are shed early in summer [12]. Reproductive cones open in late April to early May [29,72]. Red spruce cones mature the first autumn from mid-September to mid-October [29,39]. Dissemination of seeds begins soon after cones are ripe and continues until March [29].


SPECIES: Picea rubens
FIRE ECOLOGY OR ADAPTATIONS : Red spruce forests persist without fire. Red spruce is easily killed by fire due to its thin bark, shallow roots, flammable needles, and lack of self-pruning [9,23,39]. Its slow early growth rate delays the formation of a corky layer, which increases the fire susceptibility of young trees [39]. In a study based on a survey of foresters, Starker [76] rated the fire resistance of 22 New England tree species based on fire mortality and fire avoidance (occurrence in habitat that does not burn very often). Red spruce was not resistant in terms o fire mortality but moderately or very resistant in terms of fire avoidance, and was ranked 13th overall. Red spruce habitat is subject to few fires; fires that occurred in presettlement times were usually of low severity [1]. Saunders [73] noted that old-timers claimed that forest fires would stop when they reached the spruce-fir forest boundary. Electrical storms are common in this area but are usually accompanied by sufficient rain, and fuels are usually moist [32]. Severe surface fires probably occurred infrequently, during periods of prolonged drought, and usually affected forests that were breaking up due to wind, ice storm damage, or similar events that generate surface fuels [25,32,60,61,87]. The estimated natural fire return intervals for the northeastern United States and adjacent Canada range from 330 to 3,300 or more years [25,32,51,52,84]. Estimates of natural fire frequency have been complicated by human activities. Logging in these forests has resulted in an increase in fire frequency and intensity, particularly in logging slash [18,32,52]. The catastrophic fires of the 19th and 20th centuries can be attributed to human activities [21,32,52]. However, even with the increase in fires due to human activity, most fires are small and quickly suppressed. There should be sufficient time between fires for red spruce to regain dominance on most sites unless deliberately and/or repeatedly burned. It has been suggested that, in presettlement forests, the increase of dead fuels following spruce budworm outbreaks increased the likelihood of fire [21,25,32]. Such outbreaks are more common in balsam-fir-dominated forests than in red-spruce-dominated forests, but the two species usually occur together, in varying proportions. Before settlement by Europeans, forests in northern New England, the Adirondack Mountains, and the hillier sections of southern New England and Pennsylvania were not deliberately burned by Native Americans as were other areas in the northeastern United States [18]. 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


SPECIES: Picea rubens
IMMEDIATE FIRE EFFECT ON PLANT : Red spruce is easily killed by fire [49]. Surface or ground fires that consume the litter and organic layers covering the superficial roots of red spruce are almost certain to severely injure the roots [39]. Fire kills mature trees by exposing roots, subjecting the tree to water stress and/or windthrow, which may result in the eventual death of the tree [39,87]. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : Red spruce does not sprout. Seed germination is greater on burned areas with exposed mineral soil than in duff; mortality, however, is also greater due to increased surface temperature and drought [63]. Burned red spruce or spruce-fir stands are initially restocked by aspen (Populus spp.) or birch (Betula spp.) via wind-disseminated seed; paper birch (Betula papyrifera)-aspen stands are particularly diagnostic of fire in upland red spruce forests [52]. Red spruce seedlings appear a few years after fire, developing as an understory in the aspen-birch complex, and eventually penetrate the overstory after 50 or 60 years. Birch and aspen become decadent after 75 to 80 years and red spruce or red spruce and balsam fir regain dominance if left undisturbed [49,52,65]. On better sites, northern hardwoods, chiefly sugar maple and American beech, may replace red spruce, and in some areas, balsam fir will dominate the late postfire succession. Postharvest/postfire restocking by red spruce is extremely slow where the organic layers are destroyed by severe fire (particularly where harvest has been heavy) [49]. In Nova Scotia, mature spruce forests have few herbs and shrubs in the understory. After a fire, herbs increase in the first 6 years and dominate for 40 or more years while conifers slowly establish [54]. After fire in the southern Appalachians, blackberry (Rubus ursinus) and red raspberry colonize the site. Pin cherry and yellow birch follow. Blackberry and raspberry are too competitive for red spruce and must be shaded out by the hardwoods before red spruce can establish [39]. In West Virginia, postlogging and postfire succession in red spruce forests follows a similar pattern: ferns and raspberry are followed by other shrubs, then hardwoods (particularly hawthorn [Crataegus spp.]), and eventually spruce. In many areas, this successional pattern has been extremely slow; heaths or barrens form that do not appear as if they will ever return to forest [13]. Martin [54] studied postlogging/postfire succession in Nova Scotia and found that red spruce was present on most sites after the second postfire year, becoming more numerous and dominant in the later seres. He concluded that repeated heavy cuttings and light fires on the poorer soils of the southern upland of Nova Scotia encourages the invasion of heath plants, which limits the rate and amount of tree regeneration. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : NO-ENTRY FIRE MANAGEMENT CONSIDERATIONS : Some managers believe that prescribed fire may be a useful silvicultural tool for managing red spruce on some sites. On such sites, the exposed mineral soil must have plentiful moisture, soil temperatures must be moderate, and competition must be minimal [65]. In general, however, fires in red spruce habitat are of little silvicultural value [87]. Slash burning following logging kills advance reproduction and creates rank postfire vegetation that delays any new seedling establishment [39]. The fire management plan for Acadia National Park, Maine, dictates the suppression of natural fires. Prescribed fires may be used on occasion to reduce fuels [61]. Patterson and others [60] estimated fuel loadings for a number of stands in Acadia National Park that contained red spruce. They concluded that fire exclusion was probably resulting in increased fuel loads. Alexander [4] compiled slash fuel indices for red spruce and compared actual fire spread, intensity, and slash and organic layer depletions with those predicted by the Canadian Forest Fire Danger Rating System. Freeman and others [24] developed equations to determine average crown weight per tree as a function of tree height and diameter for use in a method to predict slash weight after logging red spruce.


SPECIES: Picea rubens
REFERENCES : 1. A. D. Revill Associates. 1978. Ecological eff. of fire and its mgmt. in Canada's national parks: a synthesis of the literature. Vols 1&2. Lit. Rev. & Annot. Bibliography. Ottawa, ON: Parks Canada, National Parks Branch, Natural Resources Division. 345 p. [3416] 2. Abbott, Herschel G. 1962. Tree seed preferences of mice and voles in the Northeast. Journal of Forestry. 60: 97-99. [20402] 3. Adams, Harold S.; Stephenson, Steven L. 1989. Old-growth red spruce communities in the mid-Appalachians. Vegetatio. 85: 45-56. [11409] 4. Alexander, Martin E. 1984. Prescribed fire behavior and impact in an eastern spruce-fir slash fuel complex. Canadian Forestry Service Research Notes. 4(1): 3-10. [8661] 5. Fay, Stephen C.; Alvis, Richard. 1993. White Mountain landscapes. Laconia, NH: U.S. Department of Agriculture, Forest Service, Region 9, White Mountain National Forest. 76 p. Working draft. [21663] 6. Benzie, John W.; Blum, Barton M. 1989. Silviculture of northeastern conifers. In: Burns, Russell M., compiler. The scientific basis for silvicultural and management decisions in the National Forest System. Gen. Tech. Rep. WO-55. Washington, DC: U.S. Department of Agriculture, Forest Service: 18-30. [10243] 7. Blum, Barton M. 1977. Animal damage to young spruce and fir in Maine. Res. Note NE-321. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 4 p. [13653] 8. Blum, Barton M. 1988. Variation in the phenology of bud flushing in white and red spruce. Canadian Journal of Forest Research. 18: 315-319. [8662] 9. Blum, Barton M. 1990. Picea rubens Sarg. red spruce. In: Burns, Russell M.; Honkala, Barbara H., technical coordinators. Silvics of North America. Volume 1. Conifers. Agric. Handb. 654. Washington, DC: U.S. Department of Agriculture, Forest Service: 250-259. [13388] 10. Bones, James T. 1978. The forest resources of West Virginia. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. [Pages unknown]. [21944] 11. Bormann, F. H.; Siccama, T. G.; Likens, G. E.; Whittaker, R. H. 1970. The Hubbard Brook ecosystem study: composition and dynamics of the tree stratum. Ecological Monographs. 40(4): 373-388. [21173] 12. Chandler, Robert F.; Jr. 1943. Amount and mineral nutrient content of freshly fallen needle litter of some northeastern conifers. Proceedings, Soil Science of America Society. 8: 409-411. [21599] 13. Core, Earl L. 1929. Plant ecology of Spruce Mountain, West Virginia. Ecology. 10(1): 1-13. [9218] 14. Crandall, Dorothy L. 1958. Ground vegetation patterns of the spruce-fir area of the Great Smoky Mountains National Park. Ecological Monographs. 28(4): 337-360. [11226] 15. Crawford, Hewlette S.; Titterington, Richard W. 1979. Effects of silvicultural practices on bird communities in upland spruce- fir stands. In: DeGraaf, Richard M.; Evans, Keith E., compilers. Management of north central and northeastern forests for nongame birds: Proceeding of the workshop; 1979 January 23-25; Minneapolis, MN. Gen. Tech. Rep. NC-51. St. Paul, MN: U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station: 110-119. [18083] 16. Davis, Ronald B. 1966. Spruce-fir forests of the coast of Maine. Ecological Monographs. 36(2): 79-94. [8228] 17. Davis, William C. 1991. The role of advace growth in regeneration of red spruce and balsam fir in east central Maine. In: Simpson, C. M, ed. Proceedings of the conference on natural regeneration management; 1990 March 27-28; Fredericton, NB. Fredericton, NB: Forestry Canada, Maritimes Region: 157-168. [17197] 18. Day, Gordon M. 1953. The Indian as an ecological factor in the northeastern forest. Ecology. 34(2): 329-346. [15744] 19. DeHayes, D. H.; Waite, C. E.; Ingle, M. A.; Williams, M. W. 1990. Winter injury susceptibility and cold tolerance of current and year-old needles of red spruce trees from several provenances. Forest Science. 36(4): 982-994. [13608] 20. Eyre, F. H., ed. 1980. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters. 148 p. [905] 21. Flieger, B. W. 1971. Forest fire and insects: the relations of fire to insect outbreak. In: Proceedings, annual Tall Timbers fire ecology conference; 1970 August 20-21; Fredericton, NB. No. 10. Fredericton, NB: Tall Timbers Research Station: 107-114. [18936] 22. Frank, Robert M.; Bjorkbom, John C. 1973. A silvicultural guide for spruce-fir in the northeast. NE-6. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 29 p. [8686] 23. Frank, Robert M.; Blum, Barton M. 1978. The selection system of silviculture in spruce-fir stands--procedures, early results, and comparisons with unmanaged stands. Res. Pap. NE-425. 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