|Table of Contents|
Front Cover 1
Front Cover 2
Selection and preparation of test material
Characteristics of tension wood in Aspen
Variability of longitudinal shrinkage
Tables and figures
UNITED STATES DEPARTMENT OF AGRICULTURE
FORESTS i PRODUCTS TS LABORATORYT OR
Madison 5, Wisconsin
In Cooperation with the Univerity of Wisconsinl
IDISTUMDUTICS CF NSICS WCCI
ASID ITS PATICS TC MCITUIDINAIL
SPINIAGE~ is AsiptsN
Digitized by the Internet Archive
T T'T Ac ,T'~~
! dstr,-'- ition o tcrnsicn od an a~v~a '~ ~wv 'a- Z'l"
tw '. c C :-Iuo flY r,, sr > Yi IwhI&ct, tom tl,( OC
l~'r, noat,& i, :;l of' a--'- ( x -' ~>'~~o) s from 1c -'! r- tr s
The irterri ~ ati-On 'hi -)f ion -'tn I]~i to o i fu.
-~lat. Lnou, '4 -,Vs a s: c al Wis A t c', trr M sue 1 n c r c)
woo,.d Ka >t niVrn:ala]on- F I rain. 7-'i ,,a ,ni W art
o nv e t> a~in t t 11 cF r0 SDc T o r -t 7 on th,- oc- -Urrcence an"
sat-isfactor, Kal~ as waru i~~ :, a-i nin qual t io in c(3rtabin
hardwoo l sp(i2.
Akins; 7,nd -illow l~found t' at. to-ion ;-oin w',7t- oak has Freater
t a ~ lo. itu]i. -1c-f.r i n,: t to 1fO n C Jr, ctl, w All t-e iirr
of 1 atino;- Pi: -'s I-"n th, t. .t n ~rs. *;um r-)us cxa~r-_*nat ions 7)f u r
at, t-c 17- rtc_-t r- 1,ic' s a 'r or av h t .nt r L I. 's cause byD t'.-
ret *Y. of t.-2iLo )f -!i tiOVT' 30 t Yat of nr m.al in
VIC nik C ,; ""J io~.kt n L~'nts~ U dl'ari J-- inf- ol t,- --r-).
S. !-. Clai ( r 'or~ t _o o n > cKo t c LY
mi ~n-,f i'~..'ut~:aon of c-rta ; o n cott. nwo-.-) lo 7, at ti'e 7nr~
YItlot:onn 'rI1. i lo .'*n,- j u' oi t c n :ba
t itia t i :~r r'r il sC t' ca' 11,,w v a''l
Sntn in ,)a t Y2+ -- rc1,,. to- hi+, ratllr'c, at c,11 of
2 t.h.1>17Ai-i~ ultui-(- 7. a l~on
concentration on the upper side of leaning trees. Hence, there is a need
for basic information on thp distribution of tension wood and the relation
of the number of its gelatinous fibers to longitudinal shrinkage of the
Selection and Preparation of Test Material
The aspen test specimens were taken from two butt logs that were selected
because their appreciable sweep indicated that they originated in leaning
trees. From these logs, 1-inch-thick 1-oards were sawed that represented
the upper (concave), lower (convex), and lateral surfaces of the trees as
they originally stood. dhen freshly sawed from the logs, these boards gen-
erally were bowed with the concave surface toward the bark, because longi-
tudinal stresses were greatest at that surface (fig. 1). Frequently, the
boards showin,- the greatest deformation also were extremely fuzzy, a
characteristic that often seems to be, associated with the presence of
tension wood (1, 5).
Samples for determinations of longitudinal shrinkage were cut from the full
width and from each end of the boards and thereby represented wood from
heights, respectively, of about 1 to 2 feet and 8to 9 feet above the ground.
Each sample was about 12 inches long and planed on both surfaces. One edge
of each was jointed before consecutive specmens, about 1 inch square in
cross section'. were ripped from the full idth of the sample. The ripping
was done with a smooth-cutting saw that, ordinarily produced exceptionally
smooth surfaces. On some surfaces, however, considerable torn grain
occurred, apparently because of the presence of tension wood. Both ends
of the specimens were trimed, so that. lhe finished lengths of the speci-
mens were about 9-1/2 inches.
Each test specimen was designated b, the following: The letter L or N to
distinguish the two logs; the letter A or B to indicate a specimen from the
butt or top, respectively, a sample nmber to indicate the side of the log
with respect to lean oil the tree; and a spec-men nmber. The boards from
lo, L were numbered 1, 31 5<, and 7, and those from log M were numbered 11,
13, iand 17. A designation for a t Tical sp~ecmen, LA-7-1, would there-
fore. mean lo- 1, !,utt region, sample 7 (upper side), specimen 1. Figure 2
shows positions of the test specimens with respect to upper, lower, and
lateral sides of the two leaning aspen trees. The 8 boards from the 2 logs
produced 77 specimens, on which longitudinal hrinkage, specific gravity,
and com,,arative number of gelatinous fibers were deterined.
After the specimens were cut to final size, they were evacuated of air under
distilled water by, a water suction pur-TI and then soaked about 12 hours at
room tem erature. This treatment replaced small amounts of moisture in the
wood that were lost during storage and processing of the specimens and
thereby approximated the green condition of the wood for the first measure-
Rept. No. R1917
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regions of the logs, while considerably fewer of the se fibers were found on
th lower sides. This area of greatest corncertrtion of these abnormal
fibers was also corr, ated with the groat st longitudinal shrinkage,
At the tops of both logs, the gelatinous fibers were more uniformly dis-
tributed on all sides than at the butts. The upp:-er sides, however, showed
greater concentrations. of gelatinious fibers arnd greater lon!7itu( inal
sl-rinka'e than the lower sides. The average number of gelatinous fibers
at the tors of the logs was slip-htl- f-reater than the average number at
the butt re _ions,. but the difference was not statistically significant in
either log. In a comparison of avera-e values for log L and log !j, loC L
had ignificantly, hi-her value-- for both com,-)arative number of gelatinous
f il c11 an,,, lonw 'Ltudinal shrink: -e than Log "i. Table 1 shows values for
lon--.tu,,ina1 -hrin.'a, e. s.pecific ravit ,,w nu-iber of 7elatinous fibers
lor al.]-dc of I)Cth lo-'s as wall as toru, 1utt, and lo~z avera,,es.
Values for Ion, itu dinal shrinka ,e in all the te 7t1 sncimens were concen-
tr~t'. in _-',e lo-fer end of the ran ,, althou .h some slirin,'ae values were
,,.rrcciabl,, a'-ov,- t-,he aver'a e (fig,. ) Aconsldera'7o number of specimens
had ~ ~ ~ 0 hh rvlstanIohr 5~) coa cr to ',ec tie u~ual ranro of
lon!-itu( inlal s!hrin1h.--, namely, 7.1 to -.3 Dentof the g-reen dimensions.
Lon'-itu 1.1nal shrinkage was gr --_tcst for tic uper sidc,.s of both logs but fell
within the usual .ranlre -or shrlinkape for t, lo,.eir sides. Lor L ha(I
significantly hi-he.- values for lo~tdalshrinkage than lo-- 1. (tale 1).
Variability of Longitudinal Sihrinkage
Longitudinal shrinkage did not appear to be closely correlated with specific
gravity, which had about the same range in both logs (fig. 7). Longitudinal
shrinkage was correlated to a moderate extent, -,ith the comparative number
of gelatinous fibers, but varied widely, expecially with large numbers of
gelatinous fil-ers (fig. 2).
The relations between one variable and too oth rs operating jointly can be
shown in a thre,_ -dimensional graph ('1), For this work, the values for the
test specimens w re classified b-, specifics gravity and by number of gelati-
nous fibers. Z Se ries of an-11roximrations were made alternately of relation-
ships of lonritul.inal shrinkage to nu;-n')(r of gelatinous fibers and to
spe cific gravity> That )rocedlurc incl-ded successive approx imat ions until
thc=~ was os5-. t-iall no chan-c in the estimated relationship of longitu-
dinal shrln:a7-e to either number of -,latinous fibers or specific gravity.
The j data we-e combined in a thrc o2.im -.: onal -r,,.,h that' shows trends of
lon.,itudinal shrinka-e of ason var-in with '.)oth nU7,'-cr of F.elatinous
f~csand s-ocific ra)Vit7' fi' 2)
Th(: thlr,_,Gdimensional graph -ho,,s L'iat lo n--tuin-1 irink-i-e is in direct
li~r rl-,tion to the nutrc_ of ge-,lat-i'nous fib ,,rs in each of the specific
gravity classes. Jhon specific gravity is held approximately constant, an
iucrca.-X i nutr-er of gelatinous fiors is accompanied by an increase, in
longitudinal shrinkage. On the oth,--r h:nd., the general relationship of
Re~Pt. I'l. P1917 -i
(i~ ~ !T:, '1Tj'TIA and T1 IT OI I III
io5r) O(,TTr1,1,7< fF rC'FT!,TT JOTJS FTRB,,F "'"i TMEbTH .FFECT UFO"T
EI,T E7 Ti 11')S T) T ~D f TCIL7S.
F-~oc. For s t Pr~oducts Research. Societ Vol. L
1'- 3 0. 'R 7t 7, TL TL:-: TER A.ATO7 CI TITFL l)TTS
Lr To: j iJY-'3C1 -T TTO SW. EL-2.
For. -Frod. Pes.'Full. 1 o. 7. Forest Products Research
Laboratnry, A, lesbury, England.
1)37. 'HEDSR'IKI STWTCT=R, R ? TITZS OF TE*-STO ,
r~1 mc~(as s,,lvat- ca U.0
Foirestr-- Vol. 11L, '.o. 2.
1947. 1'T T D T,- Fr-1 C(-,?~ AL!,,TTO AA'iJi
LO--!ITUD!i"- ,L ST17,I~c- DTQI
Forest Products Laboratory Pept. T1o. 7 ,093-
(0 ILLO ,T1 N:. Y.
195c). IJSCEOF T77TSICT1 W00)I PT AHOG,'- ,Y IN KRL A T I O, TO
LONG IT T) A.Ih S F-,ITJE A-
Forest Prod,,Icts Laboratory Roopt. No. DlTSK3.
ft~ 4* To 2917
Table'I ~gt1ra 'lrinkage-, sec"lific gravitY, and comparative' numbtro u' geliatinou 'lh!r !'A't,
mns 1' r f) twu apen logo from leaning trees
Des ignat i n: S,i 11 : .Nu:-ber I .witudlnal shrIn~ulge~- S pecific gravity- C mpa ra t Ive f~~e P !li I.
o f Pf - - - - - - - - - - - - - - - - - - - - - -
specimen i. I.'- :Av.'rnge :Minimnum :Maximnum :Average :Minlimum :Maximnumi Average Miinum. Y'IX ir.
* r.,, n.
: percent: Percent: Percent:
ljitt rnl: 7
ave rage ..........
L-B-i L atf*ral
L-B-5 :... d-
L-B-5 : owtr
b-B- I : 14per
M-A-11 L att ral f
M-A-i5 d ,.
H-A-i15 Lwer 4
average ............. 2
M-B-1' : '
ave ragt ...............I
.251, .2 76
Btwed I i green 11c. mi. i :f
-bat,' ) r' Ln andI weight when yev(n dry.
L late Pr.m th, f~requon y find district ion Pf gelatinous Pfibers no estlimatedI by inicr oio i ipl al X~It
Rept. No. BI)i'7
H lil4' P
ul th- ouu-,--Ie of an as-)en lo
-e I .--,',owerj, 1 oards Cut
ccnca,,-c,. sui-face, Is to-: ,:,rQs t',lo bark.
7i of ? -Vi gr r' >e~ t .-sr, t o ane
anid ccnc~a,, sides of th,-, lor,-.
t. o. -:I" ?17
M i 7"b,71 11
c;!F ar v v
i I I'(,
Fp,)rl 4 .--P~hotomrnocrgaph of a section of spr, Iowln -
gelatincuo fiber-, scattc~r, K aj-iong normal
t-un, o' vali, c, for
of f,,c latinous fi, ,er-,- from thle t(;st
A VERA GEI
COMPARATIVE NU11BER OF
M 87467 IP
clz-tril-ution of valu-s for lon-it-u ,In-']-
in, all t(, -t L pc,,--im-ns.
-A VI Rl
LONG/TUOINAL SHRINKAGE (PERCENT)
W 874648 F
--------------- I .... ....
-U--r of lon, ituclinal shr-"-n',-a-c w*th r-,,--rcet to
in ':Ir, t,,--t Sj),-C mcr s o' -,--n.
An / OG L
o LOG M4
0. 40 -
0.36 0. 3 7
Fi, u--c 8.--R=n'-e of lon tuc inal shrinkage with respect to the
comparative rnml -or of gelatinous fiber-q in the
test specimens of aspen.
TDt. ,Jo. T1917
LS do o
COMPARE /VE NUMBER OF GELATINOUS
7 N 87670 F
-r--nh s owing tl cox-tincd
ff c t o C n c i o a t i r i s f r s -- n 0. S P, c i
gravIt:,, on lon -itudin l sqrinkal--, -, ln a,--n,-,,n.
( Z' -1 114 7
R c ', t, 0 lo PI 917
ONVER ,,ITY OF FLORIDA
31262 08866 6093