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Forest Products

Commercial Species

White Spruce (Picea glauca)

White Spruce

Written By: Eugene E. Wheeler, Retired USDA Forest Service Program Manager for Cooperative Forestry Programs, (Alaska) Region 10. Currently a consultant for Idaho Panhandle Forestry.

Introduction

This site contains a brief discussion of botanical and wood structural characteristics, forest associations, major pests, fire problems, and some of the commercial uses of white spruce. The booklet is nontechnical and provides an introduction to white spruce and the Alaska forest environment in which it grows. White spruce (Picea glauca) is the most valuable component of Alaska's interior boreal (taiga) forests that stretch from the Kenai Peninsula across the Alaska Range to the southern slopes of the Brooks Range including the drainages of the Yukon, Kuskokwim and Copper River systems. Boreal (taiga) forests cover most of the land in that area up to 5,000 feet (1,524.5 meters) elevation, and white spruce is the dominant species up to 3,500 feet (1,067.2 meters). White spruce is one of the more versatile species grown in Alaska. Its nearly white wood is moderately light weight and easily milled to a fine lustrous finish. In the past, its primary use was for houselogs in Alaska. It now has international acclaim for such uses as sounding boards for musical instruments, lumber, and quality pulp.

The Climate

Interior Alaska is a moderately dry area with extreme temperatures. Precipitation ranges from 6 to 26 inches (15.2 to 63.5 centimeters) annually. Summer temperatures are from 35°-100° (2°38°), while winter temperatures can drop below -70° (-57°). The growing season is short (90 to 125 frost free days). However, long periods of daylight (20-24 hours) provide the solar energy required for optimum tree growth.

Tree growth is rapid in well-drained soils which are free of permafrost. Eighteen inch leaders are not uncommon on white spruce. At the other extreme, dbh (diameter at breast height - 4.5 feet or 1.4 meters) can be as small as 3 inches (7.6 centimeters). As a comparison, larch, which is important in the eastern boreal forests, rarely reaches 5 inches (12.7 centimeters) dbh. Permafrost, forming under moss and timber mats that inhibit solar energy from reaching the soils, acts as a physical barrier to root penetration, limiting access to soil nutrients and impeding tree growth.

The Forest

The boreal forest (taiga) of Alaska occurs from the Kenai Peninsula to the southern slopes of the Brooks Range and from the Canadian border to the Bering Sea. White spruce (Picea glauca), paper birch (Betula papyrifera) and aspen (Populus tremuloides) are the main species on the warmer, well-drained sites. Mixtures of balsam poplar (Populus balsamifera), black cottonwood (Populus trichocarpa), white spruce, black spruce (Picea mariana) and eastern larch (Larix laricina) develop on the bottomlands and flood plains of the many rivers. Various willows and small alders also grow throughout the forest.

Approximately 105.8 million acres (42.8 million hectares), or nearly one third of Alaska, are classified as boreal forest. Of this, 22.5 million acres (9.1 million hectares) are presently considered commercial forest (capable of producing 20 cubic feet or more of wood per acre, per year). The total net sawtimber volume of all species in interior Alaska is estimated at 31 billion board feet (5.4 billion cubic feet), with white spruce accounting for 81% of this volume.

Bottomland Spruce-Hardwood Association

The bottomland spruce-hardwood forest types, consisting of variable width strips along the major rivers, account for approximately 17% (18 million acres or 7.3 million hectares) of the boreal forest. These are the most productive sites of that vast forest area. The high productivity of these sites is due in part to the frequent flooding of the rivers, which adds nutrients to the soil and removes the accumulated litter layer. Very little permafrost exists in the river bottom soils which are well drained and support vigorous vegetation. However, productivity of the bottom land spruce-hardwood forest sites does vary considerably throughout the boreal forest area. The most productive commercial forest sites are located near Fairbanks on the Tanana River.

Upland Spruce-Hardwood Forest Types

The upland spruce-hardwood forest types account for approximately 61% of the boreal forest (64.4 million acres or 26 million hectares). These types occupy sites to 1,000 feet (304.9 meters) in elevation along the lower Yukon River and up to 3,500 feet (1,067.2 meters) near the Alaska-Yukon Territory border. The average productivity of upland forests is less than that of the bottomland forest sites. Factors which contribute to this lower productivity include lower soil nutrient levels, cooler soil temperatures, and lower precipitation.

The Tree

White spruce (Picea glauca) is the most significant tree of Alaska's taiga or boreal forest. It grows in pure stands or in association with black spruce, larch, birch, aspen and balsam poplar on the deeper well-drained soils. It generally does not compete with other species on soils which have a high water table or are poorly drained and are subjected to prolonged periods of standing surface water, or those soils with permafrost. White spruce reaches heights of 40-70 feet (12.2-21.3 meters) tall, and dbhs of 6-13 inches (15.2-45.7 cm.). Under optimum conditions, it can reach heights of 80-115 feet (24.4-35.1 meters) and dbhs of 30 inches (76.2 cm.).

Wood Properties

The heartwood and the sapwood of white spruce are both practically white and, consequently, are not readily distinguishable when dry. The wood is classified as nonporous, having a fine, moderately uneven texture, and is easily machined and worked. The tree is relatively slow growing in Alaska, resulting in growth rings which are closer together and a slightly denser wood than that found in the white spruce of other areas.

In comparison with other commonly known construction species such as Douglas fir, the wood of white spruce is moderately light in weight, weak in bending and compression strength, moderately limber, moderately soft, moderately low in shock resistance, and has moderately large shrinkage. It is ranked as easy to kiln dry, stable and easy to glue.

White spruce lumber gives good service in ordinary construction, although it has a low resistance to decay. The wood is easy to work in all hand and machine operations and has little dulling effect on cutting edges. White spruce is almost tasteless and odorless when seasoned, making it especially well suited for food containers. It takes paint and varnish well and can be easily stained. The wood is readily sliced to a smooth silky finish, which is advantageous for the manufacture of veneers and plywood. It has a long slender, colorless fiber that is especially desirable in making pulp and paper.

Seasoning

White spruce is generally easy to dry and can be air dried to some extent in the interior region where it grows. Kiln schedules are slightly milder than those for Sitka spruce. Kiln drying times vary from 60 hours to six days.

Other Properties

The following wood properties are averages derived from previous reports concerning white spruce. Many figures have been derived from tests on Alaskan white spruce, while others are more general with data coming from white spruce and other spruces from other areas. They are published herein as guidelines. Variables are caused by growing and handling conditions.

I. Weights
A. Solid Wood - Average weight in pounds per cubic foot (kilograms per cubic meter).
Wood lbs./cu.ft. kg./cu. m.
Green 36 768.9
Seasoned (15-19% moisture content) 31 497.9
Seasoned (12% moisture content) 30 480.3
B. Logs (Approximated)

1. Average weight per log in pounds. (Kilograms)

Log Lengths Sealing Diameter
8" (20.3cm)
Sealing Diameter
12" (30.5cm)
Sealing Diameter
16" (40.6cm)
Sealing Diameter
20" (50.8cm)
8 feet
(2.4 meters)
225 lbs. (102.1 kg.) 400 lbs. (181.4 kg.) 750 lbs. (340.2 kg.) 1,200 lbs. (544.3 kg.)
12 feet
(307 meters)
400 lbs. (181.4 kg.) 750 lbs. (340.2 kg.) 1,100 lbs. (499.2 kg.) 1,800 lbs. (816.5 kg.)
16 feet
(4.9 meters)
500 lbs. (226.8 kg.) 950 lbs. (430.9 kg.) 1,600 lbs. (725.8 kg.) 2,400 lbs. (1,088.6 kg.)
20 feet
(6.1 meters)
625 lbs. (283.5 kg.) 1,200 lbs. (544.3 kg.) 2,000 lbs. (907.2 kg.) 3,000 lbs. (1,360.8 kg.)

2. Average log weight per MBF using Scribner Decimal "C" Log Rule Scale.

Scaling Diameter Weight Per MBF
8" (20.3 cm.) 14,500 lbs. (6,577.2 kg.)
12" (30.5 cm.) 11,500 lbs. (5,216.4 kg.)
16" (40.6 cm.) 9,500 lbs. (4,309.2 kgs)
20" (50.8 cm.) 8,500 lbs. (3,855.6 kg.)
24" (60.9 cm.) 7,800 lbs. (3,538.1 kg.)
30" (71.0 cm.)
C. Lumber - Average weight in pounds (kilograms) per MBF.
Wood Rough Lumber
Avg. Weight/MBF
Surfaced Lumber**
Avg. Weight/MBF
Green 3,000 - 3,200 lbs.
(1,360.8 - 1,451.5 kgs.)
2,300 - 2,500 lbs.
(1,043.3 - 1,134.0 kgs.)
Seasoned (15-19 MC*) 2,600 - 2,700 lbs.
(1,179.4 - 1,224.7 kgs.)
1,950 - 2,100 lbs.
(884.5 - 952.6 kgs.)
II. Specific Gravity
Wood Specific Gravity
Green 0.37
Seasoned (12% MC) 0.40
III. Shrinkage - Percent from green to seasoned, based on original green dimensions.
Wood Tangential* Thickness (Radial*) Length Volume
Green to 12% MC 2.9 2.4 0.1 5.7
Green to 15-19% MC 2.6 1.8 0.1 4.5

* Moisture Content - MC
** Based on lumber standards for dimension lumber. Data from local Alaska producers.
*** Flat-grain board. Reverse for quarter-sawn or edge grain board.

IV. Basic Strength Values and Mechanical Properties of Red Cedar and Alaska Cedar.

(Strength properties of white spruce increase as the wood is dried out.)

A. Hardness - Load required to embed a 0.444 inch (1.1 cm.) ball to 1/2 its diameter.
Wood End Grain Side Grain
Green 370 lbs. (167.8 kgs.) 320 lbs. (145.2 kgs.)
Seasoned 640 lbs. (290.3 kgs.) 480 lbs. (217.7 kgs.)
B. Static Bending
Wood Fiber Stress at Elastic Limit psi* (ksc**)
Green 3,200 psi (225.0 ksc)
Seasoned 6,700 psi (471.1 ksc)
Modulus of Rupture
Wood Fiber Stress at Elastic Limit psi* (ksc**)
Green 5,600 psi (393.7 ksc)
Seasoned 9,800 psi (689.0 ksc)
Modulus of Elasticity
Wood psi* (ksc**)
Green 1,070 psi (75.2 ksc)
Seasoned 1,340 psi (94.2 ksc)
Work to Elastic Limit
Wood Work to Elastic Limit
(in.-lb. per cu. in.)
Work to Elastic Limit
(cm.-kg. per cu. in.)
Green .51 .006
Seasoned 1.83 .020
Work to Maximum Load
Wood Work to Maximum Load
(in.-lb. per cu. in.)
Work to Maximum Load
(cm.-kg. per cu. in.)
Green 6.0 .065
Seasoned 7.7 .084
C. Impact Bending - Height of drop causing complete failure - 50 lb. (22.7 kg.) hammer.
Wood Height Inches (Centimeters)
Green 22 in. (55.9 cm.)
Seasoned 20 in. (50.8 cm.)
D. Compression Parallel to the Grain Fiber
Wood Stress at Elastic Limit Maximum Crushing Strength
Green 2,150 psi (151.2 ksc) 2,570 psi (180.7 ksc)
Seasoned 4,750 psi (334.0 ksc) 5,470 psi (304.6 ksc)
E. Shearing Strength
Wood Parallel to Grain
Green 690 psi (48.5 ksc)
Seasoned 1,080 psi (75.9 ksc)
F. Tension
Wood Perpendicular to the Grain
Green 220 psi (15.5 ksc)
Seasoned 360 psi (25.3 ksc)
G. Compression (Perpendicular to grain, fiber stress at elastic limit)
Wood psi (ksc)
Green 240 psi (16.9 ksc)
Seasoned 460 psi (32.3 ksc)

* Pounds per square inch - psi
** Kilograms per square centimeter - ksc

Uses of the Tree

The Pacific Rim countries place high-value on white spruce for use in the light construction industries, especially house construction, and for specialty products such as chopsticks and sounding boards for pianos. White spruce pulp was very important in the dissolving pulp industry until the decline in the world rayon market. However, the international market shows some increasing demand for the world supply of spruce sawlogs, cants and bolts. White spruce also has a growing domestic market. Traditional domestic uses are houselogs, fuelwood, and rough lumber and timbers. More recent uses include kitchen cabinets, dried and finished lumber, and dimension material for buildings of light and medium construction. Because of its many favorable wood characteristics, its uses are nearly as limitless as are the potential uses of wood itself.