tr% Division of Agricultural Sciences UNIVERSITY OF CALIFORNIA CALIFORNfA AGRICULTURAL EXPERIMENT STATION BULLETIN 854 This bulletin reports the results of strength tests, density, shrinkage, and fiber measurements on wood of young- and old-growth giant sequoia trees from the southern Sierra. It compares these values with those of coast redwood and Sierra white fir and concludes that the wood of the young-growth trees is satis- factory for use as construction material and pulpwood. October, 1971 THE AUTHORS: Robert A. Cockrell is Professor of Forestry at the School of Forestry and Conserva- tion, Berkeley, and Wood Technologist at the Forest Products Laboratory, Richmond. Robert M. Knudson is Research Assistant at the Forest Products Laboratory, Rich- mond. Alan G. Stangenberger is Research Assistant at the School of Forestry and Con- servation, Berkeley. MECHANICAL PROPERTIES OF SOUTHERN SIERRA OLD- AND SECOND-GROWTH GIANT SEQUOIA 1 INTRODUCTION Giant sequoia [Sequoia gigantea (Lindl.) Decne.], which is famous for its size and longevity, is restricted to more or less iso- lated small groves of large old trees in the central and southern Sierra Nevada moun- tains of California. Although S. gigantea has been essentially overlooked as having potential value as a timber-producing spe- cies, its relatively limited second-growth stands have good rate of growth (Wensel and Schoneheide, 1971), good tree form and freedom from insect and disease at- tack (Fowells, 1965). Accordingly, it seemed worthwhile to assemble data on mechanical and certain related phvsical properties of the wood, such as density, shrinkage and fiber length, in order to assess suitability of the species for com- mercial forest planting. Old-growth giant sequoia has long been regarded as lighter and more brittle than the coast redwood but, as reported by Sudworth (1908), "it is said not to be less valuable for lumber." It was among the indigenous woods tested by S. P. Sharpies and reported by C. S. Sargent (1884). He described bending specimen failures as "square break on tension side" and his data showed seasoned wood of giant sequoia to be definitely weaker than coast redwood and white fir in bending and stiffness but equivalent to them in maxi- mum crushing strength along the grain. (These were exploratory tests quite differ- ent from present ASTM procedures, 1952.) Although no data on mechanical prop- erties of native-grown second-growth giant sequoia were available, R. Keyl- werth (1954) reported on tests of wood from five planted trees grown and tested in Germany using DIN procedures. These trees averaged 26.6 meters high and test material came from sections 28 to 38 cm in diameter with 38 to 44 rings. Keyl- werth stated that, in comparison with coast redwood, Douglas fir, and spruce, this wood was inferior only with respect to tensile strength, and that wood of both sequoias is inferior to Douglas fir and spruce in resistance to impact loading. His tests showed little difference in strength between heartwood and sapwood, and a high variability which he attributed to grain deviation resulting from presence of many small sound knots. He indicated that the wood was suitable for construc- tion, furniture, boxes, small casks, boat building and core veneer, and that the high natural durability of the heartwood recommended it for hot-bed frames. E. J. Martin (1958) reports "That the grain and the color of Sequoiadendron giganteum (giant Sequoia) wood are also of interest to the wood-working industry may be seen from the fact that, in Rheydt, a veneer plant offered DM 600 (about $150) for the trunk of a 75-year-old tree. Since the wood can be excellently pol- ished, it is useful for many purposes in interior architecture, for inlays, and for furniture." MATERIALS AND METHODS Second-growth wood for testing was ob- tained from several trees in young-growth stands which had grown up after logging in the 1870's (Biswell, et al, 1966) in Whitaker's Forest (a 320-acre University of California research tract adjacent to the western edge of Sequoia National Park with elevation range of 5200 to 6200 feet). These trees had been either knocked to the ground by old-growth 1 Submitted for publication February 26, 1971. Fig. 1. Cross sections of old-growth giant sequoia planks trees that fell, or had been damaged or blown down by winter storms. Table 1 (tables start page 9) gives information on trees and location of test logs. Opportunity to obtain some of the old- growth material used for testing came un- expectedly when it was learned that the Sequoia Forest Products Company of Dinuba was about to saw some logs from fallen trees in the Mountain Home State Forest located east of Porterville. Planks 3 inches x 12 inches x 8 feet in length were obtained from eight different quarter-log sections in the course of 1/2 days' sawing at the mill. Location of test planks in the trees could not be deter- mined, nor could it be ascertained how many different trees were represented. The logs from which the planks came were between 8 to 12 feet in diameter and had well over 1,000 rings. Figure 1 shows cross sections of the planks; table 2 shows the number of growth rings in each plank. Bolts approximately 4 feet long were cut from logs of the younger trees and sawn into 2% x 2M inch test blanks follow- ing generally the procedure presented in ASTM designation D 143-52 (ASTM). Exploratory tests of specific gravity, shrinkage and bending were made on green material from tree E. Test blanks from 4-foot bolts of all other trees were divided arbitrarily into two groups, one to be tested green and the other at the air- dry condition (approximately 12 per cent moisture content). The presence of many small knots and the small diameter of some logs limited the amount of clear 2x2 inch test blanks. Where only limited clear material was available, a larger num- ber of blanks was tested green. Each plank from old-growth logs was divided into four test-blank strips some- what larger than 2/2 x 2 l A inches in cross section. Two of these provided specimens for green tests and the other two for dry tests. At least one specimen was selected from each strip for each of the tests. All mechanical tests and the specific gravity and volumetric shrinkage deter- minations conformed to ASTM D 143-52. Tangential, radial and longitudinal shrink- age was determined by measuring dimen- sional changes to the nearest 0.001-inch on 1 x 1 x 4-inch specimens cut with the growth rings aligned so as to permit exact measurements in the tangential and radial directions. Tangential and radial measure- ments were taken in the middle of the 4-inch blocks, and longitudinal measure- ments were taken in the 4-inch direction. Fiber-length data were obtained by macerating matchstick-size samples of wood with an aqueous solution of 10 per cent nitric and 10 per cent chromic acids, staining with Bismark brown and mount- ing directly on slides in dilute polyvinyl acetate. Averages were based on 40 meas- urements of fibers selected at random from slides of each sample (Echols, 1969). RESULTS AND DISCUSSION Table 3 (page 10) lists basic data for the various mechanical and physical prop- erties of green second-growth wood; table 4 lists the same for dry second-growth wood. Since the number of tests for each property varied for different trees, mean values were determined from trees means rather than individual test values to give each tree equal weight (Cockrell, 1959). Table 5 gives data for both green and dry wood of old-growth. Moisture content. Moisture content of second-growth green wood averaged well over 100 per cent. Some sapwood ex- ceeded 200 per cent, while some heart- wood was as low as 60 per cent. Dry wood was tested at approximately 12 per cent moisture content, with actual values rang- ing from 11 to 16 per cent. Adjustment to 12 per cent was made with the U. S. Forest Products Laboratory exponential formula, using the intersection point (Mp) 25 as suggested in the Wood Handbook (1955). The old-growth material, all heart- wood, had moisture content ranging be- tween 85 and 165 per cent, with most specimens from 5 of the 8 planks being over 120 per cent. Dry tests were made at Fig. 2. Cross section of second-growth tree number 2 at height of 16 feet Fig. 3. Cross sections of second-growth tree number 3 at heights of 8.5 and 14 feet a moisture content between 11 and 11.5 per cent. Growth rate. The growth pattern of young trees had the ring width decreasing from the pith outward as is typical for dominant forest-grown conifers. Growth rate in the central core (within 25 rings from pith) was consistently about 7 to 10 rings per inch. Out toward the bark the number of rings per inch increased from 10 to 20, or even higher in the case of tree number 3 whose outer 50 rings ranged from 18 to 40 rings per inch. All trees had zones of sapwood 2 to 4 inches thick containing 25 to 45 growth rings (about 60 rings in tree number 3). Figures 2 and 3 show the ring pattern and sap- wood zones for trees 2 and 3. Individual old-growth test specimens ranged from 17 to 44 rings per inch with the exception of a few from plank number 7, one of which had only 11 rings per inch (see figure 1 and table 2). Structural qualities. Table 6 compares second-growth and old-growth giant se- quoia with second-growth and old-growth coast redwood [Sequoia sempervirens (D. Don) Endl.] and white fir [Abies concolor (Gord. and Glend.) Lindl.] on the basis of selected mechanical properties. It is evi- dent that second-growth giant sequoia is slightly heavier and stronger than second- growth coast redwood, and decidedly heavier and stronger than most of the wood of old-growth giant sequoia tested in this study. (Specific gravity of heart- wood specimens tested by Sharpies [Sar- gent, 1884] averaged 0.32 [based on oven- dry volume and weight], the same as that in table 5.) Second-growth test specimens were preponderantly sapwood, and the static bending specimens failed consis- tently in splintering tension. This con- trasted sharply with the brash type of failures characteristic of most of the old- growth specimens in this study. The one dense specimen of old-growth, plank number 7 with a specific gravity of 0.37, had a splintering tension flexural failure and its strength values approached sec- ond-growth values; it had green values of 3800 psi maximum crushing strength, 6450 psi modulus of rupture, and 830,000 psi modulus of elasticity. By contrast, plank number 3, with the lowest specific gravity (0.27) had values of 1800, 4000, and 325,000 respectively. Second-growth sapwood test blanks used in this study machined satisfactorily, and superficially resembled white fir. They had essentially the same average specific gravity, shrink- age, and green moisture content as the German-grown material tested by Keyl- werth (1954) and previously mentioned. Since this study shows second-growth giant sequoia to be equal to or somewhat superior to white fir and second-growth redwood in most of its mechanical prop- erties, it can be recommended as accept- able for dimension grades of lumber to be 6 used for light construction. Shrinkage. Table 7 present data on lon- gitudinal, tangential, radial, and volume- tric shrinkage and compares them to some shrinkage data for heartwood of coast redwood. Heartwood specimens showed appreciably lower tangential, radial, and volumetric shrinkage than did sapwood, with the old-growth figures be- ing decidedly lower than the second- growth. The great majority of the second- growth specimens elongated slightly when air-dried (12 to 15 per cent moisture con- tent) but showed some shrinkage (most of them under 0.10 per cent) at the oven-dry condition. There was considerable varia- tion in shrinkage among the eight old- growth quarter logs sampled, as there also was in mechanical properties. Dense ma- terial from plank number 7 showed higher radial, tangential, and volumetric shrink- age, and lower longitudinal shrinkage than did the others. Shrinkage of second- growth heartwood of giant sequoia in gen- eral resembled that of coast redwood. Fiber length. Figure 4 (below) shows the relationship of fiber length to rings from pith in cross sections about 18 feet above the ground for three young-growth trees. The fibers averaged about 3.5 mm in length at 20 rings from the pith, and approached 4 mm at 50 rings. Maximum values for individual fibers 20 rings and farther out ranged from 4.3 to 5.6 mm, with most of them being close to 5 mm. Average fiber length for the eight old- growth specimens was 4.5 mm, with in- dividual averages ranging from 4.1 to 4.8. Maximum individual fiber lengths ranged from 5.7 to 7.0 mm, with six specimens having a maximum above 6.0; specimen number 7 had the lowest maximum (5.7 mm). Separate averages were calculated for springwood and summerwood fiber length for this specimen and were almost identical, being respectively 4.37 mm and 4.41 mm. A comparison with fiber-length char- acteristics of coast redwood presented by Resch and Arganbright (1968) reveals that both young-growth and old-growth giant sequoia have significantly shorter fibers, and that the rate of increase of length with rings from pith resembles more the typical conifer pattern that "tapers off after the first 10 to 30 years of tree life," rather than remaining high like coast red- wood during the first 50 years of growth. Fig. 4. Relationship of fiber length to rings from pith of three second-growth giant sequoias 4 _____ -A - —y* A- — " • ■ -^ ^^ y ^^ •_ / *& /* — -—-__ / E E 3 - z r * • TREE 1 X .J A A TREE 2 O 2 a a TREE 3 z // LU -J /< at uu CO 1 u- i i i __j i i 1— 1 10 20 30 40 50 RINGS FROM PITH 60 SUMMARY Strength and certain other related physical properties data are reported for second- growth and old-growth giant sequoia wood grown under natural forest conditions in the southern Sierra. Second-growth wood, much of it sapwood, was distinctly superior to old-growth (all heartwood), which proved to be much lighter and more brittle. Wood from the young trees was equal in most strength properties to second-growth redwood and old-growth white fir and is recommended for use in light construction. Shrinkage properties of heartwood of both second-growth and old-growth giant Se- quoia are quite similar to comparable categories of coast redwood; sapwood has much higher shrinkage values than heartwood. Fibers of giant sequoia wood are shorter than coast redwood; their length averages 4 to 4.5 mm which is slightly higher than the average length for conifers generally. ACKNOWLEDGMENTS The authors wish to acknowledge the assistance of Richard Benner in obtaining test material from Whitaker's Forest and R. M. Echols of the Pacific Southwest Forest and Range Experiment Station in making available fiber projection and measuring ap- paratus. LITERATURE CITED American Society for Testing and Materials 1952. Standard methods for testing small clear specimens of timber. D 143-52. Philadel- phia, Pennsylvania. Bendtsen, B. A. 1966. Strength and Related Properties of a Randomly Selected Sample of Second-Growth Redwood. U.S.F.S. Res. Paper FPL 53, For. Prod. Lab., Madison, Wise. Biswell, H. H., H. Buchanan, and R. P. Gibbens 1966. Ecology of the vegetation of a second-growth Sequoia forest. Ecology 47(4): 630-34. Cockrell, R. A. 1959. Mechanical properties of California-grown Monterey pine. Hilgardia 28(8): 227-38. Echols, Robert M. 1969. Permanent slides of stained wood fibers without dehydration or cover glasses. Forest Science 15(4): 411. Fowells, H. A. 1965. Silvics of forest trees of the United States. U. S. Dept. of Agr., Agr. Handbook No. 271. Jaroslavcev, G. D. and T. N. Visnjakova 1964. Physical and mechanical properties of the wood of Sequoia gigantea. Lesn. Khoz. 17(11):70. Keylwerth, R. 1954. Das Holz der Sequoia gigantea. Holz als Roh- und Werkstoff 12(3): 105-07. Markwardt, L. J. and T. R. C. Wilson 1935. Strength and related properties of woods grown in the United States. U. S. Dept. of Agr. Tech. Bui. 479. Martin, E. J. 1958. Die Sequoien und ihre Anzucht Mitteilungen der Deutschen Dendrologischen Gesell- schaft No. 60 Jahrbuch 1957-1958. Resch, Helmuth and D. G. Arganbright 1968. Variation of Specific Gravity, Extractive Content, and Tracheid Length in Redwood Trees. Forest Science 14(2): 148-55. 8 Sargent, Charles S. 1884. Report on the Forest in North America, Vol. 9 of the 10th Census, Census Office, Dept. of Interior, Washington, D.C. Schniewind, A. P. 1963. Comparison of young-growth and old-growth redwood machinability, fastening strength, and shrinkage. California Forestry and Forest Products No. 33. Sudworth, George B. 1908. Forest Trees of the Pacific Slope. U. S. Dept. of Agr., Washington, D.C. U. S. Department of Agriculture 1955. Wood Handbook. Agriculture Handbook No. 72. Wensel, L. C. and R. Schoenheede Young Growth Gross Volume Tables for Sierra Redwood [Sequoia gigantea (Lindl.) Decne.] University of California Agr. Expt. Sta. Bui. Series (unpublished). Tarle 1 AGE AND SIZE OF TREES AND LOCATION OF TEST BOLTS IN TREES Rings at stump D.B.H.t Total height Bolt Bolt location and size Tree number Large end Small end Height D.I.B.H Height D.I.B. E 84 80+ 84 83 86 86* 86* inches 11.7 19.9 19.4 10.5 15.1 15.7 20.6 feet 67J 85 § 113 94 811 96 109 A B A B C D A B A A B A feet 3.0 16.0 20.0 3.0 16.0 28.0 51.5 8.5 13.8 8.0 10.0 14.5 31.0 inches 10.7 14.4 14.0 18.4 13.8 13.2 11.2 8.5 8.2 12.0 13.4 12.6 13.9 feet 8.0 20.0 24.0 7.5 20.5 32.5 56.0 13.6 18.2 12.5 14.5 19.0 35.5 inches 8.9 1 14.0 2 13.8 15.2 3 4 13.7 12.9 10.8 8.2 7.8 11.6 5 . . 12.6 6 12.0 13.3 ♦Estimated since from same stand as Tree No. 4. fDiameter outside bark 4.5 ft. above ground. ^Broken top. §9" D.O.B. at 85' where top broken off and not possible to reconstruct. ISpike top rubbing against pine tree for 33 yrs. I Diameter inside bark. 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