Index of Species Information

SPECIES:  Picea glauca

Introductory

SPECIES: Picea glauca
AUTHORSHIP AND CITATION : Uchytil, Ronald J. 1991. Picea glauca. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [].
ABBREVIATION : PICGLA SYNONYMS : NO-ENTRY SCS PLANT CODE : PIGL COMMON NAMES : white spruce Canadian spruce western white spruce Alberta spruce Black Hills spruce skunk spruce cat spruce Alberta white spruce Porsild spruce TAXONOMY : The currently accepted scientific name of white spruce is Picea glauca (Moench) Voss [40]. The genus Picea consists of about 30 species of evergreen trees found in cool, temperate regions of the northern hemisphere. Seven species of Picea, including white spruce, are native to North America. White spruce is widely distributed across northern North America and exhibits considerable geographic variation. However, Little [40] thinks it unnecessary to distinguish varieties, although up to four have been recognized by various other authorities. Natural hybridization between species of Picea is common. Engelmann spruce (P. engelmannii) x white spruce hybrids are common where the ranges of these species overlap. Natural crosses between these species occur from central British Columbia as far south as eastern Washington and Yellowstone National Park [15]. Within this area trees at low elevations closely resemble pure white spruce, while pure Engelmann spruce tends to dominate at higher elevations. Hybrids between the species are concentrated on intervening slopes. Sitka spruce (P. sitchensis) and white spruce are sympatric in northwestern British Columbia and southwestern Alaska. Hybrids occur in this area of sympatry, and have been classified as Picea X lutzii Little. Hybrids between black spruce (P. mariana) and white spruce are relatively rare [45]. LIFE FORM : Tree FEDERAL LEGAL STATUS : No special status OTHER STATUS : NO-ENTRY


DISTRIBUTION AND OCCURRENCE

SPECIES: Picea glauca
GENERAL DISTRIBUTION : White spruce has a transcontinental distribution.  It grows from Newfoundland, Labrador, and northern Quebec west across Canada along the northern limit of trees to northwestern Alaska, south to southwestern Alaska, southern British Columbia, southern Alberta, and northwestern Montana, and east to southern Manitoba, central Minnesota, central Michigan, southern Ontario, northern New York, and Maine.  An isolated population also occurs in the Black Hills of South Dakota and Wyoming [45]. ECOSYSTEMS :    FRES10  White - red - jack pine    FRES11  Spruce - fir    FRES18  Maple - beech - birch    FRES19  Aspen - birch    FRES20  Douglas-fir    FRES23  Fir - spruce    FRES28  Western hardwoods STATES :      AK  ME  MI  MN  MT  NH  NY  SD  VT  WI      WY  AB  BC  LB  MB  NB  NF  NS  NT  ON      PE  PQ  SK  YT BLM PHYSIOGRAPHIC REGIONS :     8  Northern Rocky Mountains    15  Black Hills Uplift KUCHLER PLANT ASSOCIATIONS :    K012  Douglas-fir forest    K093  Great Lakes spruce - fir forest    K095  Great Lakes pine forest    K096  Northeastern spruce -fir forest    K102  Beach - maple forest    K106  Northern hardwoods    K107  Northern hardwoods - fir forest SAF COVER TYPES :      1  Jack pine      5  Balsam fir     12  Black spruce     15  Red pine     16  Aspen     18  Paper birch     21  Eastern white pine     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     37  Northern white cedar     38  Tamarack     39  Black ash - American elm - red maple    107  White spruce    201  White spruce    202  White spruce - paper birch    203  Balsam poplar    204  Black spruce    206  Engelmann spruce - subalpine fir    217  Aspen    218  Lodgepole pine    251  White spruce - aspen    252  Paper birch    253  Black spruce - white spruce    254  Black spruce - paper birch SRM (RANGELAND) COVER TYPES : NO-ENTRY HABITAT TYPES AND PLANT COMMUNITIES : Climax white spruce forests are widespread across Alaska and northwestern Canada.  They consist almost entirely of white spruce, but may have scattered black spruce, paper birch (Betula papyrifera), aspen (Populus tremuloides), and balsam poplar (P. balsamifera) present [41]. Climax stands are often broken up by extensive seral communities resulting from forest fires. In eastern Canada and the northeastern United States, white spruce occurs as a climax species in pure or mixed stands.  Within the fog belt of Quebec and Labrador, white spruce forms pure stands near the seaboard [22].  At climax, it often codominates or forms a significant part of the vegetation in mixed stands with red spruce (Picea rubens), balsam fir (Abies balsamea), and black spruce. In the Black Hills, white spruce habitat types occur at high elevations and in cool canyon bottoms [33].  Published classifications listing white spruce as an indicator species or dominant part of the vegetation in habitat types (hts), community types (cts), or ecosystem associations (eas) are presented below:         Area                Classification          Authority AK                         general veg. cts     Viereck & Dyrness 1980 nw AK                      general veg. cts     Hanson 1953 interior AK                postfire cts         Foote 1983 SD, WY: Black Hills        forest hts           Hoffman & Alexander 1987 AB                         general veg. cts     Moss 1955 w-c AB                     forest cts           Corns 1983                            general veg. eas     Corns & Annas 1986 BC: Prince Rupert Forest      Region, Interior      Cedar-Hemlock Zone    general veg. eas     Haeussler & others 1985     Prince Rupert Forest      Region, Subboreal      Spruce Zone           general veg. eas     Pojar & others 1984 PQ: Gaspe Peninsula        forest veg. cts      Zoladeski 1988 ON                         forest eas           Jones & others 1983

MANAGEMENT CONSIDERATIONS

SPECIES: Picea glauca
WOOD PRODUCTS VALUE : White spruce wood is light, straight-grained, and resilient.  It is an important commercial tree harvested primarily for pulpwood and lumber for general construction [45].  Logs are used extensively for cabin construction [60].  It has also been used for specialty items such as sounding boards, paddles and oars, cabinets, boxes, and food containers [44,60]. IMPORTANCE TO LIVESTOCK AND WILDLIFE : Browse:  Livestock and wild ungulates rarely eat white spruce.  Snowshoe hares sometimes feed heavily on white spruce saplings and seedlings.  On a cut-over site in northern Alberta, 40 percent of 2- and 3-year-old white spruce seedlings were browsed by hares [62].  In Alaska, white spruce needles, bark, and twigs comprise a major portion of the snowshoe hare's winter diet.  During this time of the year, snow covers many other foods, leaving only trees and shrubs above snowline available for hares to browse [64].  Mice and voles eat spruce seedlings [62].  Red squirrels clip twigs and feed on vegetative and reproductive buds in the spring [9].  Consumption of leaders and the ends of upper branches by red squirrels tends to be greatest during poor cone crop years.  Spruce grouse feed entirely on spruce needles during winter [20]. Seed:  Numerous seed-eating birds and mammals feed on white spruce seed. White spruce seed is a primary food of red squirrels [9].  White spruce habitats are favored by red squirrels because of the highly palatable seeds; squirrel density is much greater in white spruce stands than black spruce stands [9].  Red squirrels are so dependent on this food source that population density is directly related to the periodicity of good seed crops [69].  Mice, voles, shrews, and chipmunks consume large quantities of white spruce seeds off the ground [45].  Chickadees, nuthatches, crossbills, and the pine siskin extract seeds from open spruce cones and eat seeds off the ground [29]. PALATABILITY : White spruce is not a preferred browse.  Its palatability is low for moose, elk, white-tailed deer, and mule deer, but it may be moderately palatable to bighorn sheep [11,21].  Red squirrels prefer white spruce seed over black spruce seed [9]. NUTRITIONAL VALUE : White spruce seeds are nutritious and are a good energy source for red squirrels which can survive the winter on a diet consisting entirely of white spruce seeds.  In Alaska, white spruce seeds averaged 6,615 cal/g [9]. Data from a nutritional study of white spruce needles collected in the winter on the Kenai Peninsula, Alaska, are presented below [20]:              (percent chemical composition and caloric content)                                range           mean        protein                      5.5 - 8.1         6.32 fat                          2.8 - 4.1         3.34 crude fiber                 21.0 - 25.9       23.5 ash                          2.6 - 4.4         3.27 nitrogen free extract       61.4 - 65.0       63.51 Kilogram calories/100 g       486 - 506        494.8 COVER VALUE : White spruce provides good wildlife cover.  It may be particularly important as winter shelter [45,52], especially to caribou which use it for protection from strong winter winds [30]. VALUE FOR REHABILITATION OF DISTURBED SITES : White spruce is useful for long-term revegetation of coal mine overburden.  In Alberta, it is considered one of the best conifers for this purpose [63].  White spruce x Engelmann spruce hybrids have been observed naturally invading coal mine spoils at high elevations in west-central Alberta [51].  White spruce has also naturally invaded coal mine overburden in south-central Alaska.  At this location, the overburden had a clay content of 42 to 44 percent, and was redeposited on the mined area and graded back to the original contour [18].  On anthracite strip mine spoils, however, survival of planted white spruce seedlings was poor to adequate after 5 years [63]. Results of direct seeding of white spruce onto logged-over areas and abandoned farmland has been variable [53].  The fact that it naturally invades mine spoils indicates, however, that direct seeding may be useful on some disturbed sites.  White spruce seed remains viable for up to 10 years when stored in sealed containers in a cool, dry environment [53].  The seed requires moist, cool stratification for 60 to 90 days to break dormancy [53].  Seed from Alberta is an exception, and requires no presowing treatment. Two-year-old or older white spruce nursery stock has been planted in disturbed areas with relatively good success.  Bareroot stock is recommended for harsh subalpine sites in Alberta where frost heaving may occur [63].  It is not recommended for planting on steep slopes subject to erosion.  In northeastern Alberta, overwinter survival of container-grown and transplanted white spruce seedlings was satisfactory on amended oil sand tailings [23]. White spruce can be readily propagated by rooted cuttings [45].  Methods for collecting, processing, storing, and planting white spruce seed have been described [52]. OTHER USES AND VALUES : White spruce can be planted as an ornamental and used in shelterbelt plantings [45]. White spruce was important to native peoples of interior Alaska [45]. Poles were used to construct dwellings, and bark was used as roofing material.  Thin, straight, pliable roots were used as rope.  Pitch, watery sap, and extracts from boiled needles were used for various medicinal purposes.  Boughs were used for bedding, and rotten wood for smoking moose hides [34,45]]. OTHER MANAGEMENT CONSIDERATIONS : Regeneration following timber harvest:  Natural regeneration of white spruce following timber harvest is unreliable [53].  Spruce seedlings are, therefore, commonly planted following timber harvest.  For adequate natural regeneration mineral soil seedbeds are required.  Mechanical treatments or broadcast burning may be used to expose mineral soils. Following timber harvest in Alaska, white spruce seedling density was 10 times greater, frequency 2 times greater, and cover 4 times greater on scalped versus unscalped surfaces [67].  White spruce seedlings die when shrub competition becomes severe [17]. Pests and diseases:  The most common insect pests and diseases of white spruce include needle and stem rusts, root diseases, trunk rots, mistletoe (Arceuthobium pusillum), bark beetles, wood-boring insects, weevils, the spruce budworm, and the yellowheaded spruce sawfly, all of which have been discussed in detail [45,53].

BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Picea glauca
GENERAL BOTANICAL CHARACTERISTICS : White spruce is a native, coniferous, evergreen tree.  It typically grows as a medium-sized upright tree with a long, straight trunk, and narrow, spirelike crown.  Because of poor growing conditions at the northern portion of its range, it may grow as a short, single-trunked tree, or assume a mat or krummholz form [60].  In Alaska, white spruce is typically 40 to 70 feet (12-21 m) tall and 6 to 18 inches (15-42 cm) in diameter [60].  Throughout much of Canada, white spruce's average height is about 80 feet (24 m) [36].  On good sites throughout the range of white spruce, individual trees may grow to a height of 100 feet (30 m) or more and attain diameters of 24 to 36 inches (60-90 cm) [45]. The bluish-green needles are 0.75-inch-long (1.9 cm), stiff, and four-sided [36].  Bark on mature trees is thin, usually less than 0.3 inch (8 mm) thick [53], scaly or smooth, and light-grayish brown.  White spruce is shallow-rooted.  Rooting depth is commonly between 36 and 48 inches (90-120 cm), but taproots and sinker roots may descend to 10 feet (3 m) [45].  On northern sites, large roots are usually concentrated within 6 inches (15 cm) of the organic-mineral soil interface [45]. Trees often retain lower branches, but in dense stands lower branches are gradually shed, so that eventually the crown occupies about one-half of the tree's height [36].  Light-brown cones are about 2 inches (5 cm) long and hang from the branches of the upper crown [36]. RAUNKIAER LIFE FORM : Phanerophyte REGENERATION PROCESSES : Cone and seed production:  Plants can begin producing seed at 4 years of age but generally do not produce seed in quantity until they are 30 years of age or older [44].  Good to excellent seed crops occur every 2 to 6 years on good sites [45], but in many areas, good seed crops are produced only every 10 to 12 years [46,65].  In natural stands cone production occurs primarily on dominant and codominant trees, with sporadic production from intermediate and suppressed trees [45].  Seeds are about 0.12 inch (3 mm) long, with a 0.25- to 0.33-inch-long (6-9 mm) wing [53].  There are approximately 226,000 seeds per pound [52]. Cone and seed predation:  Red squirrels can reduce cone crops significantly.  In interior Alaska, they have harvested as much as 90 percent of a cone crop [45].  Their impact on cone and seed production is greatest during poor or medium cone crop years [69].  Numerous insects also reduce seed yields.  The spruce cone maggot, the fir cone worm, and the spruce seed moth are responsible for most loss.  Following dispersal, small mammals consume considerable amounts of seed off the ground [45]. Dispersal:  The winged-seeds are dispersed by wind and travel primarily in the direction of prevailing winds.  Most seed falls within about 300 feet (91 m) of a source, but seeds have been found as far as 1,300 feet (400 m) from a seed source [6,66].  Seeds found considerable distances from a source probably travel over crusted snow.  A study in Alaska found that 50 percent of seed fell within 90 feet (27 m), and 90 percent of seed fell within 210 feet (64 m) of a 60-foot-tall tree [65].  Red squirrels disperse seeds also.  White spruce reproduction is common at squirrel middens [62]. Viability and germination:  White spruce seeds remain viable for only about 1 to 2 years.  Under natural conditions, seeds overwinter under snow and germinate in the spring or summer when there is adequate moisture and soil temperatures have warmed [45].  In Alaska seeds do not begin germinating until temperatures become favorable, usually in mid-May [69].  If June is a rainy month, most seeds will germinate.  If June precipitation is low and seedbeds dry out, germination is delayed until it rains in July and August [69].  Germinative capacity is 50 to 70 percent [52]. Seedling establishment:  Seedling establishment is best on mineral soil. White spruce may also establish on shallow organic seedbeds, but rarely establish where organic layers are thicker than 2 to 3 inches (5-8 cm) [55].  Seedlings are frequently found on rotten wood. Growth:  Seedlings grow best in full sunlight, but are tolerant of low light, and can withstand many years of suppression [6].  First-year seedlings are normally less than 1 inch ( 2.5 cm) tall.  After 4 to 6 years, seedlings are less than 20 inches ( 50 cm) tall [45]. Vegetative reproduction:  At the northern treeline in Alaska and much of Canada, white spruce reproduces almost exclusively by layering [19,45]. In these far north habitats, seed viability is at best low, and seedlings are rare or absent [19].  Layering may also occur further south when the lower branches touch the ground and become covered with moss, litter, or soil. SITE CHARACTERISTICS : White spruce occupies boreal forests.  It is largely confined to well-drained uplands or river terraces and floodplains.  In interior Alaska and the Northwest Territories, white spruce forests are usually found on stream bottoms, river terraces and lake margins, and on warm, well-drained, south-facing slopes within 5 miles (8 km) of major river valleys [24,45].  Seral stands of white spruce and aspen, and white spruce and birch, are common on relatively dry slopes with a south or southwest exposure, and on dry, excessively drained outwash or deltaic soils [41].  Across northern Alaska, white spruce grows at the northern limit of tree growth where it forms open communities on dry exposed sites [57].  At arctic timberline, white spruce grows in well-drained soils, often along streams where permafrost has been melted away by flowing water [73].  In British Columbia and Alberta, white spruce is widely distributed, occupying floodplains, foothills, and mountains from 2,500 to 5,000 feet (762-1,524 m) in elevation [43,45].  In northeastern Alberta, open, parklike white spruce forests occur on high ridges, stony beaches, and dune habitats [43].  In eastern Canada, the Lake States, and the northeastern United States, white spruce occurs in many coniferous and mixed coniferous-hardwood forests.  Pure stands or mixed stands where it is dominant are not widespread.  Conifers, including white spruce, tend to occupy shallow outwash soils on upper slopes and flats, while hardwoods or mixtures of hardwoods and spruce are found on deep glacial till soils of lower slopes [72]. Associated trees:  Alaska associates include paper birch, quaking aspen, black spruce, and balsam poplar.  In western Canada, associates include subalpine fir (Abies lasiocarpa), balsam fir, Douglas-fir (Pseudotsuga menziesii), jack pine (Pinus banksiana), and lodgepole pine (P. contorta).  In eastern Canada and the northeastern United States associates include black spruce, paper birch, quaking aspen, red spruce, balsam fir, northern white-cedar (Thuja occidentalis), yellow birch (Betula alleghaniensis), and sugar maple (Acer saccharum) [22,45].  In Wisconsin, white spruce commonly grows with balsam fir [14], and in Maine, with red spruce [22]. Understory:  In Alaska and across much of western Canada, climax stands have understories dominated by a well-developed layer of feather mosses. The total depth of the live moss-organic mat is frequently 10 to 18 inches (25-46 cm) or more [45].  Mixed stands of white spruce and seral hardwoods have shallower moss layers.  Understory shrubs include green alder (Alnus viridis ssp. crispa), willows (Salix spp.), mountain cranberry (Vaccinium vitis-idaea), prickly rose (Rosa acicularis), highbush cranberry (Viburnum edule), bog birch (Betula glandulosa), twinflower (Linnaea borealis), black crowberry (Empetrum nigrum), bearberry (Arctostaphylos uva-ursi), and soapberry (Shepherdia canadensis) [22,45].  In the Prairie Provinces, common understory shrubs include snowberry (Symphoricarpos albus), red-osier dogwood (Cornus stolonifera), serviceberry (Amelanchier alnifolia), and western chokecherry (Prunus virginiana) [45]. Stand characteristics:  In Alaska and western Canada, climax stands are usually closed, except near treeline [22].  White spruce stands can be either even-aged or uneven-aged.  Even-aged stands result from rapid invasion of white spruce into burned areas.  Uneven-aged stands result from the slow invasion of spruce seedlings into seral birch or aspen stands [41]. Soil:  White spruce grows on a wide variety of soils of glacial, lacustrine, marine, or alluvial origin.  It grows well on loams, silt loams, and clays, but rather poorly on sandy soils [22].  It is somewhat site demanding, and often restricted to sites with well-drained, basic mineral soils.  White spruce grows poorly on sites with high water tables and is intolerant of permafrost [22].  In the Lake States and northeastern United States, it grows mostly on acid Spodosols, Inceptisols, or Alfisols, with a pH ranging from 4.0 to 5.5 [72].  In the Northeast, it grows well on calcareous and well-drained soils but is also found extensively on acidic rocky and sandy sites, and in some fen peatlands in coastal areas [22]. SUCCESSIONAL STATUS : White spruce is a long-lived climax tree that gradually replaces pine, aspen, birch, and/or poplar on well-drained sites.  Less frequently it occurs as an early successional species, forming pure stands or mixing with seral hardwoods immediately after fire.  Its ability to successfully establish following fire depends on fire severity and intensity, and seed production during the year of the fire [see Plant Response to Fire]. Following stand destroying fires, dense stands of aspen, birch, and/or poplar tend to develop quickly, and these successional species are often scattered throughout all but the oldest white spruce stands [56].  White spruce seedlings establish under these seral hardwoods, develop and grow slowly, and eventually replace them.  White spruce-aspen, white spruce-birch, and white spruce-balsam poplar are common mid-successional communities that, with the continued absence of fire, will gradually be replaced by essentially pure stands of white spruce.  Foote [24] outlined six postfire successional stages for sites capable of supporting climax white spruce stands in interior Alaska:   1.  Newly burned (0-1 year after fire) - Following stand destroying       fires, shoots of prickly rose, highbush cranberry, willows,       quaking aspen, and birch appear within a year.  White spruce       seedlings are rare.   2.  Moss-herb stage (1-5 years after fire) - Herbs cover about 30       percent of the ground; fireweed (Epilobium angustifolium) is the       most common.  Mosses cover about 30 percent of the ground.       Quaking aspen and paper birch each average about 12,150 stems per       acre (30,000 stems/ha), originating from both sucker shoots and       seedlings.  Limited white spruce establishment occurs at this       time.   3.  Tall shrub-sapling stage (3-30 years after fire) - Tall shrubs or       tree saplings dominate the overstory, with herbs, tree seedlings       and litter below.  White spruce seedlings are often present at       this stage, but not conspicuous.   4.  Dense tree stage (26-45 years after fire) - Young trees, mostly       aspen and/or birch dominate the overstory.  The understory is       dominated by highbush cranberry, prickly rose, twinflower,       mountain-cranberry, and Labrador-tea.  Willows and herbs decline.   5.  Hardwood stage (46-150 years) - This stage has well developed       stands of quaking aspen, paper birch, or mixtures of hardwoods and       hardwood-white spruce.  As the hardwoods begin to die, codominant       or understory white spruce form the overstory.   6.  White spruce stage (150-300+ years) - White spruce eventually       replaces the hardwoods to form an open to closed canopy.  Some       hardwoods remain, but the oldest stands tend to be nearly pure       spruce. Following fire in upland spruce-fir stands in New England, early seral stages are dominated by aspen and birch, sometimes pine, and occasionally pure white spruce [6].  White spruce has invaded much abandoned agricultural land in this region, forming essentially even-aged stands.  In northwestern Quebec, white spruce is considered a long-lived, shade-tolerant climax species.  However, probably due to spruce budworm outbreaks, white spruce often declines after about 200 years, while paper birch remains abundant [7].  In Wisconsin, white spruce commonly replaces trembling aspen and paper birch.  White spruce and balsam fir are the major dominants of the oldest boreal forest stands in Wisconsin [14]. White spruce is a climax species on the floodplains of large rivers of interior Alaska and northwestern Canada.  Willows are the first to colonize siltbars and are in turn replaced by the mid-successional balsam poplar.  The long-lived white spruce becomes established in low numbers early on and survives to dominate the climax stage [10,49].  The climax type on river terraces in southeastern British Columbia is dominated by white spruce and trembling aspen [25]. In Glacier National Park, white spruce x Engelmann spruce hybrids have invaded ponderosa pine (Pinus ponderosa) savannas as a result of fire exclusion [27]. SEASONAL DEVELOPMENT : Pollen shedding may occur in May, June, or July, with southern areas having earlier dispersal than northern areas.  Pollen shedding is temperature dependent and may vary yearly by as much as 4 weeks at any given location.  Cones ripen in August or September, about 2 to 3 months after pollen shed. Timing of seedfall varies yearly depending on climatic conditions.  Cool, wet weather delays seedfall, but under warm and dry conditions cones open and seeds disperse early [45,69].  In general seedfall begins in late August or September [45].  Nienstadt and Teich [44] reported that most seeds are shed within about 5 weeks after cones open; however,, Zasada and others [69] reported that over several years in interior Alaska, 90 percent of white spruce seeds were dispersed by late December.  Following dispersal, cones remain on the tree for 1 to 2 years.

FIRE ECOLOGY

SPECIES: Picea glauca
FIRE ECOLOGY OR ADAPTATIONS : Plant adaptations to fire:  White spruce relies on wind-dispersed seeds which readily germinate on fire-prepared seedbeds to colonize burned sites.  However, it is not adapted to colonize large burns because (1) most fires in boreal regions occur in the summer before white spruce seeds are mature, and thus little or no seed is available for fall dispersal, and (2) seeds in cones on surviving trees are dispersed over relatively short distances [55,65].  Since fire-killed trees generally do not contribute to seedfall, seed for colonizing burns must come from nearby surviving trees.  Survivors include the occasional mature tree which survives fire damage, trees escaping fire in small, unburned pockets, and trees adjacent to burned areas [41].  Occasionally trees that are severely injured by a summer fire will continue to develop and disperse viable seed in the fall, even though the trees will die within 1 to 2 years [66].  Because seeds in trees are mature and ready for dispersal by fall, white spruce can quickly invade areas after fall burns, especially during good seed crop years [1]. Many researchers report that white spruce is not well adapted to regenerate following fire because it has nonserotinous cones [1,2,41,65].  Nearly all seed is dispersed in the fall or winter, but cones remain on trees for 1 to 2 years after this peak dispersal period [45].  However, in northern Saskatchewan, Archibold [3,4] found that some seed remains in cones for up to 2 years and is an important factor in postfire seedling establishment.  In these studies, an April wildfire burned through a mixed spruce-hardwood stand containing 1,080 white spruce trees per acre (2,667/ha) averaging 40 years old.  During the first postfire year, fire-killed white spruce trees released 540,000 seeds per acre (1,338,000/ha).  During the 2nd postfire year, these dead trees released 50,000 seeds per acre (123,500/ha), of which 70 percent germinated in the laboratory. Fire regime:  Across its range, few white spruce stands are older than 200 years.  The oldest are floodplain white spruce stands, some of which are older than 300 years [32].  Fire frequency in white spruce forest types is generally between 60 and 200 years [45].  In Alaska, Foote [24] observed that fire in white spruce forest types was less common than in black spruce types.  She found numerous white spruce stands older than 100 years, but most black spruce stands sampled were less than 100 years old. White spruce stands typically have well-developed organic soil layers. The depth to which this organic mat is consumed varies depending on the type of fire.  Sometimes the organic mat is consumed, and mineral soil exposed [24]. POSTFIRE REGENERATION STRATEGY :    off-site colonizer; seed carried by wind; postfire years 1 and 2

FIRE EFFECTS

SPECIES: Picea glauca
IMMEDIATE FIRE EFFECT ON PLANT : White spruce is easily killed by fire.  Its thin bark provides little insulation for the cambium, and the shallow roots are susceptible to soil heating.  Surface fires can burn deep into litter and duff, charring or sometimes consuming roots up to 8 to 9 inches (20-23 cm) in diameter [41].  Surface fires often spread to white spruce crowns because the highly flammable fine fuels concentrated under the trees often produce flames that reach the low-growing, flammable, lichen-draped branches [1,37]. White spruce seeds on the ground are usually killed by fire because they have little or no endosperm to protect the embryo from high temperatures [55].  Cones are not necessarily destroyed by summer fires, but immature seeds will not ripen on fire-killed trees. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : Viereck and Schandelmeier [61] reported that most fires in spruce stands in interior Alaska are either crown fires or ground fires intense enough to kill overstory trees.  The needles of white spruce trees often remain green following ground fires, but the boles are usually scorched to the extent that most trees die [24].  In interior Alaska, 100 percent of 40- to 140-year-old white spruce were killed by a high-severity, low-intensity surface burn that consumed the entire organic mat, estimated to be 1 to 5 inches (3-13 cm) thick [31]. Following a late May-early June wildfire in Interior Alaska, Zasada [66] observed that fire effects on white spruce varied considerably depending upon fire intensity and severity.  This fire occurred when white spruce flowering was complete, but fertilization was not.  Fire effects varied as follows:  Crowns destroyed - within the zone of the highest fire intensity, crowns were completely destroyed by fire. Crowns scorched - near the intense zone tree crowns were scorched by the heat of the fire.  All these trees were killed.  Small cones did not develop any further. Boles scorched or girdled - where underburning consumed most of the forest floor, tree crowns were hardly affected, but trees received so much damage to the bole that most died by the end of the first or second summer after the fire.  Although these trees were severely injured, the cones and seeds continued to develop.  When seed matured, viability was about equal to seed from adjacent unburned stands. PLANT RESPONSE TO FIRE : Following fire, white spruce reestablishes via wind-dispersed seeds from surviving trees in protected pockets or from trees in adjacent unburned areas.  Within a few years after a fire, white spruce reproduction is often localized and centered around areas of surviving trees. Establishment is quite variable, depending on the proximity of surviving cone-producing trees, seed production during the year of the fire and immediate postfire years, and amount of mineral soil exposed by the fire.  Under most circumstances, it can rapidly invade burned sites only when (1) fire consumes the organic mat and exposes mineral soil and (2) surviving trees provide a seed source.  When these conditions are met, white spruce begins to establish seedlings 1 or 2 years after fire. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : White spruce seedling establishment is rapid following fall wildfires that expose mineral soil but do not burn into the tree crowns.  These hot surface fires usually kill the trees, but the mature seeds are not harmed and soon begin dispersing onto the mineral soil.  One year following a late-August wildfire of this type in interior Alaska, white spruce frequency was 100 percent, and seedling density was 12,150 per acre (30,000/ha) [31].  White spruce is less likely to regenerate following high-severity, low-intensity surface fires in the spring or summer, because seeds will not develop on the fire-killed trees. However, if not all trees are killed, some seed will develop over the summer.  This occurred on portions of a late May-early June burn in interior Alaska.  One year following this fire, white spruce seedlings were numerous on portions of the burn where underburning consumed most of the forest floor, but crowning did not occur.  Although the trees were severely injured, seeds matured within the cones, so that by fall 1,100 viable seeds were dispersed per square meter.  Seedling frequency was 100 percent, and density 290 per square meter one growing season after the fire [66]. In British Columbia and Alberta, in areas where white spruce or white spruce x Engelmann spruce hybrids are abundant and lodgepole pine scarce, spruce will establish quickly following fire if sufficient numbers of seed trees survive or are near the burn.  If lodgepole pine is present before burning, it usually seeds in aggressively and assumes a dominant role, quickly overtopping any spruce seedlings [16,35]. However, because of its shade tolerance, white spruce can establish under a developing pine canopy.  Day [16] sampled lodgepole pine-white spruce x Engelmann spruce hybrid stands in southern Alberta that initiated from fires that occurred 29 and 56 years before sampling.  He found that both pine and spruce initiated large numbers of seedlings immediately after the fire.  Pine, however, established greater numbers of seedlings, which rapidly outgrew the spruce and formed a canopy that was 3 to 4 times the height of the spruce.  Pine seedling establishment ceased about 30 years after fire, but the shade-tolerant spruce continued to establish.  Given a sufficient disturbance-free interval, white spruce will eventually dominate sites where spruce and pine seed in together following fire. The Research Project Summary of Van Wagner's [74] study provides information on prescribed fire use and postfire response of plant community species, including white spruce, that was not available when this species review was originally written. FIRE MANAGEMENT CONSIDERATIONS : Broadcast burning can be used for fuel reduction and site preparation following logging of white spruce [68].  Survival and early growth of planted white spruce is enhanced by burning.  Four years after outplanting of container-grown stock in northeastern British Columbia, leader length was 36 percent longer on burned versus unburned sites; however, foliar nutrient content was much lower.  Improvements in growth on burned sites have been observed for 15 years [5]. Frequent fires can eliminate white spruce from an area because it does not produce seed in quantity until it is 30 years old or older. 

References for species: Picea glauca


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