Tension wood in southern red oak quercus falcata michx.https://scholarworks.sfasu.edu/texas_forestry_papers/1013/thumbnail.jp

Burkart, Leonard F.

Cano-Capri, Jorge

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Stephen F. Austin State UniversitySFA ScholarWorksTexas Forestry Papers, No. 1-29, 1970-1976 Journals4-1974Texas Forestry Paper No. 25Leonard F. BurkartStephen F. Austin State UniversityJorge Cano-CapriStephen F. Austin State UniversityFollow this and additional works at: http://scholarworks.sfasu.edu/texas_forestry_papersPart of the Other Forestry and Forest Sciences CommonsTell us how this article helped you.This Book is brought to you for free and open access by the Journals at SFA ScholarWorks. It has been accepted for inclusion in Texas Forestry Papers,No. 1-29, 1970-1976 by an authorized administrator of SFA ScholarWorks. For more information, please contact cdsscholarworks@sfasu.edu.Recommended CitationBurkart, Leonard F. and Cano-Capri, Jorge, "Texas Forestry Paper No. 25" (1974). Texas Forestry Papers, No. 1-29, 1970-1976. Book14.http://scholarworks.sfasu.edu/texas_forestry_papers/1411s.-~l¥ SCHOOL OF FORESTRY lr~4< STEPHEN F. AUSTIN STATE UNIVERSITY Nacogdoches, Texas Tension Wood In Southern Red Oak Quercus falcata Michx. by Leonard F . Burkar t ' and Jorge Cano-Capri' Tension wood, which causes degrade in hardwood lumber and veneers, c not be readi ly identified in the log once a tree is cut. A basis for estimating tem wood content in standing t rees could help sawm ill and plywood operators pro< their logs for maximum yield and quality. To establish if easily measu parameters can be used for such predictions, we have determined the amount • location of tension wood in red oak trees having varying degrees of lean . A leaning tree or a straight tree that has a one-sided or eccentric crown ca ed by prevailing winds, injury, competition or some other reason is stressed gravity a nd has a natural tendency to fall. To offset or react against such stres: trees produce a chemically, physically, and anatom ically abnormal type wood c ed " reaction wood." Tension wood, the form of reaction wood produced hardwood trees. is characterized by cells (gelatinuous fibers). with thickened walls and lower lignin-to-cellulose ratio than normal cells, that tend to pull agai the d isrupting stress (8}. In conifers, on the other ha nd, reaction to stress cond iti produces compression wood, which tends to push against the stress. Compres! wood is located primarily on the lower side of the lean while tension wood tend concentrate in the upper or tension side (8). The presence of tension wood in lumber is often associated with longit ud shrinkage, warping, collapse, splitting, rough or fuzzy planing, and low resista to shock. Equally deleterious effects occur in veneers and pulps. Gelatinous fiber tension wood can occur singly, in isolated groups, or in broad bands or pate within a growth ring (11). As a rule, tension wood cannot be recognized wi th certainty by visual ins1 tion of the ends of logs. Wahlgren (11), Lassen (7), Hale (4), Koch (6), and oll 1 Associnlc Profcti6Ur, School of f'oresiry. Stephen F. Aul:itin Suut• Univen&it)l, Nncotednches. 1'exn:.. l Former Graduate St\ldem . School or Fori!S[J)'. Sttphcn F. J-\U'IIin SlAte UniHI"lity. Nncof{doche1'., Tt>XIU•, point out that growth ring eccentricity is an unreliable indicator of the presence of reaction wood. Sorensen and Wilson (9) found maximum tension wood on the upper side of the lean regardless of eccentricity. Kaiser and Pillow (5) found higher concentrations of gelatinous fibers on the upper side of leaning cottonwood trees. Frequency of gelatinous fibers was highly correlated with degree of lean. Goeble (3) on the other ha.nd, reported more tension wood in a non-leaning hickory than in the leaning trees he examined. Zanker (12) and Terrel (10), working with poplar and aspen respectively, found that. frequency of gelatinous fibers increased with height in the tree. MATERIALS AND METHODS A 23-acre plot of typical upland mixed pine-hardwood forest in the Stephen F. Austin Experimental Forest, Nacogdoches County, Texas, was selected for the field work. All southern red oaks seven inches or greater dbh with at least sixteen feet of defect-free log below major branching were assigned to lean classes as follows: Class I, o• -2.5°; Class II, 3.0•-6.0•; Class ill, 7 .o•-lo.o•; and Class fV, 11.0• and greater. The degree of lean was read to the nearest 0.5° with a simple instru-ment consisting of a protractor with an attached plumb bob. Table 1 shows dis-tribution of trees among these classes. Table 1. Number and classification of red oak trees on a 23-acre plot of mixed pine-hardwood forest in East Texas. Lean Trees Class (Degrees) (Number) Percent I 0.0- 2.5 114 53.0 n 3.0- 6.0 79 36.7 m 7.0-10.0 15 7.0 IV 11.0-greater 7 3.3 T hree trees were randomly selected from each lean class and prepared for laboratory examination. The lower side of the lean was marked and the degree and direction of lean at selected heights along the trunk were recorded. The selected trees were felled and 2-inch thick disks were cut from just above butt swell, just below major branching, and midway between these two points. The disks were stored in a freezer until examined. Each disk was measured for stem eccentricity and then divided into four quadrants relative to Lhe lean (Fig. 1). Enough three-quarter-inch squares were randomly located and marked on each quadrant to occupy approximately 10 percent of the total cross-sectional area. The squares were then cut from the sections and prepared for microtomy. Neut.ral side Upper side Lower side Neutral side Figure /. Cross section of tree stem showing quadrants, as related to lean direction. Squares were softened for microtome sectioning by the triethylene glycol method described by Burkart (2). An AO Spencer 860 sl iding microtome was used to cut cross sections 30 microns thick for microscope examination. The sections were stained with a 1:9 solution of Safranin-0 in water, followed by counter-staining with a four percent alcoholic solution of Fast Green . This treatment stains normal fibers bright red and gelatinous fibers blue-green. A Leitz Orthoplan microscope fitted with a photograming eyepiece was used to define 60 observation areas on each microscope sl ide. Under 160x magnification, the percentage of gelatinous fibers was determ ined as an index to tension wood oc-curence in sampled tree segments. RESULTS Table 2 summarizes the relative frequencies of gelatinous and normal cells. Contrary to the findings of Arganbright and Bensend (1) who found the largest number of gelatinous fibers concentrated in the earlywood portions of soft maples. our study of southern red oaks found such fibers confined almost exclusively to the latewood portion of the growth rings with greatest amounts usually in the wider growth increments. No gelatinous fibers were found in the last row oflatewood cells within any growth ring. Table 2. Frequency of gelatinous fibers in relation to total fibers. Location with respect to lean o.e Total •· b Upper Neutral Lower Class cross section quadrant quadrant quadrant - -- - - · - · · · · - - - · - - · · · - - - percent - - - - - - -- - - - -- -........ . I 11.16 18.74** 11 .35 3.38 II 12.04 18.71 12.05 5.37** m 14.62 29.31*'" 14.21 ** o.33** IV 15.63 34.88** 12.01 ** 0.00** Mean 13.36 25.41 ** 12.41** 2.27** n. Avtro~~ li>r !) LI'\'6 and aU height~!> within t he treet>. IJ. 'l'otal crus~ geclion w11s n nuly:r.ed ,;eJN}ra tcly. No !iig nificnnl difference was found hel\.,.CCll lvWI t:'tt)!Qo; St>t·•iouul uwnt){l!:-.. c. t-... igures noi underscored by 1he same line were signilic-unt ly differen1 at the f.pfi- level. •• Si~nificantly different aL the 11 ( level. Horizontal comJ>Misons. Within individual growth rings, gelatinous fibers were found scatl·ered individually, in isolated groups, in narrow and broad tangentia I or radial bands. and in solid patches. Bands and patches of gelatinous fibers occured most freq uent.-ly in the upper sides of Class ill and IV trees, a lthough a number of solid patches were found in one Class I tree which showed an exceptionally large amount of ten-sion wood. Individual gelatinous [ibers were usually scattered more or less evenly throughout the sample section. Bands were found as tangent ia l or radial rows of cells, often confined between the broad rays. In some extensive patches, con-siderable amounts of collapse were observed. Frequency of gelatinous fibers tended to increase with increased lean, but standard "t" tests showed no significan t differences between class means at. t he 5''r level. As the degree of lean increased , the concentratio~and aggregat.ion oJ gelatinous fibers increased in the upper quadrant and~t~' the lower quadrant. Conversely, with decreasing lean, the distribution of such fibers became uniformly scattered throughout the entire tree cross section. Though the total oum ber ol gelatinous fibers did not significantly increase with increasing lean, the concentra-tion in the upper side increased and that in the lower side decreased significantly. No significant differences were found between means of the neutral s ides. CONCLUSIONS Only 10 percent of the red oak trees on the study area fell into Classes nr or IV, the upper sides of which contained 29 to 34 percent tension wood fibers. Such leaning trees are usually not harvested or if harvested produce lumber, furniture blanks, or veneer of low or cull grade. Trees in Classes I and n, in which gelatinous fibers are more uniformly distributed, contain few concentrations of tension wood that would degrade lumber or other products. Grading standing southern red oak trees according to lean class and marking lean class and upper s ide of lean on each log should aid I urn ber and veneer mill operators to maximize product quality by reducing degrade due to tension wood. Class I and lllogs can be processed normally for high quality products. Class Ill and IV logs s hould not be used for rotary cut veneers. T he neutral 8Jld lower sides of such logs contain relatively small amounts of tension wood and could be sawn for grade in the usual manner. Lumber from the upper portion should probably be marked and segregated at the green chain for use in pallets or other products not requiring kiln drying or planing. LITERATURE CITED l. Arganbright, D.G. and D.W. Bensend. 1968. Relationship of gelatinous fiber development to tree lean in soft maple. Wood Sci. 1(1 ):37-40. 2. Burkart, L.F. 1968. Triethylene glycol as a woody tissue softener in preparation for microtome sectioning. Stain Technology. 41(5). 3. Goeble, N .B. 1960. Ten.~ ion wood and its relation to splitting in Hickory. S.C. Agr. Exp. Sta. Bul. 480. 21 pp. 4. Hale, J.D. 1961. importance of compression wood and tension wood in ap-praising wood quality. Ca n. Dept. of For. Bul. 0-186. 7 pp. 5. Kaiser, M. and M.Y. Pillow. 1955. T ension wood in eastern cottonwood. Cen-tral States For. Exp. Sta. Tech. Paper No. 149. 6. Koch, C. B. 1968. The nature of tension wood in black cherry. W.V. Univ. Agr. Exp. Sta. Bul. 561. 14 pp. 7. Lassen, L.E. 1959. Tension wood in cottonwood. For. Prod. Jour. 9(3):116-120. 8. Pahshin, A.J. and C. deZeeuw. 1964. Textbook of wood technology. McGraw-Hill Book Co., Inc. , New York. pp. 300·306. 9. Sorensen, W.S. and B. F. Wilson. 1964. The position of eccentric stem growth and t ension wood in leaning red oal~ trees. Harvard For. Paper No. 12. 10. Terrell, B.Z. 1952. Distribution of tension wood and its relation to longitudinal shrinkage in aspen. U.S.D.A., For. Serv. Bul. R-1917. 25 pp. 11. Wahlgren, H.E. 1957. Effect of tension wood in a leaning eastern cottonwood. For. Prod. Jour. 7(6):4. 12. Zenker, R. 1968. Ten:;iM wood percent and fiber length £n the stemwood of different poplar varieties. Translated from Faserforshung und Textiltechnik. Vol. 19. 

Texas Forestry Paper No. 25

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Texas Forestry Paper No. 25

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