n_
i
r u,l ..
:·· --·
· ,.. .,
__
i.._,.1) •r.<·1
Forest
L.i
offi :ial use
._,_;
'
• .
Service fer
Roy R.
Use of Temperature Pellets in
Regeneration Research
IIrnH TE::iIPERATURES at the ground
at the surfaee of the soil.
surface are a 111ajor cause of seed­
come in the form of
ling 1nortality for ruany conifers.
1/8-inch
tablets
accurate,
'l'hey
7/16-inch by
are inex­
which
dis­
Critic-al te1nperatures are believe<l.
pensiYe,
to oce11r in a tissue-thin layer at
tinctively colored, g·enerally water­
Fro1n this layer, ten1­
proof for at least a year, easily
the.surface.
peratnres decrease g-reatly in the
first fe,v milli1neters upvv-ard
into
do1v11\varrl jn_to tht!
I.o:):; s of J)ougL15-fir see<L
.'/J_ll_ 1lings begin 'vhen sur.facp. teu1pera­
tures exceed 123° F.,3··' bnt the
th•_· air
tln·eshold
ind
is
not
shm·p.
Newly
gern1inated seedlings of such thin­
stemn1ed species as Douglas-fir and
hemlock generally die at tempera­
tures between 123° F. and 140° F.,
b11t
occasional
individuals
that
n1auage to escape heat injury early
in the season inay survive ten1per.
at.ures in cxers.s of 150°
F.
Until very recN1tly it was diffi­
cult
to measure te1nperatnres in
this
thin
line
of
surface
heat.
Available i11!=-;trun1ents "·ere, 1nore­
over1
costlv
i
and rnost
investio·a­
;
tions of so l surface te111peratn es
were neees.-;arily limited to a rela­
tively few samples.
Connnerc·ial temperature pellets5
are 110\\' available which in some
\rays are superior to n1ore expen­
siYe instru 111 rnts such as ther1non1­
eters, thern1ographs, and thermo­
couples.
'l1hey are cheap enough
to pel'n1it extensive sampling, and
they proYide an accurate rneasnre
insoluble,
to any desired size,
fraginented
and available in useful intervals. oE
1neltin­
(110°
t.einpern.tnres
.l:2;J'·' F . . 1::i;,1G:J0 Ji'., error
F._,
1''
1.'";0' Jo' ..
aHi1
± l
p rcent).
l e·
suits of stttdies on natural seedbeds
thousands
many
with
pellets
of
over three seasons have sno\Yll thl'.'n1
to be highly· useful 1rhe11 there is
ten1pe1·aturc
maxin1u1n
for
need
records at about 12° intervals.
I\Iany temperature-measuring in­
strun1ents SUC!h as n1ercnry ther·
mon1eters and thermogrnph bulbs
are so -large that their readings ac··
tually represent an integration of
a range of te1npc.ratures near the
couples
overcome
thern10­
fine
1\.lthough
Sllrface.
difficulty,
this
they can conduct appreciable heat
dO\Yn
cooler
inetal \Yires .to
the
layers,6 and may easily be installed
or becon1e shifted aboYe or belo\Y
the plane of highest te1nperature.
temperature· pellet,
'l'he
trast,
intersects
soil
the
con­
in
surface
and provides a n accurate recor(l of
the
location
exact
of
the
plane
where the temperature exceeds the
melting point of the pellet.
There
iR only slight conduction of heat
of the tcn1peratnre in the hairline
throug·h the pellet to cooler Javers.
The clin1atc near the
groulld. (2n<l cil.) llarvartl Cnivcr::;ity
fa:;s. 1950.
Pre:<>s, Cun1bridge,
"'-Sn1ith, D. ir. •rhe in.fiuencc of sf'cd­
bed conditions on the regeneration of
Connecticut ,_i\gric.
eastcn1 >vhite pine.
Expt. Stn.. Bul. 54;), 61 pp. Illus. 19;"51.
3] aker, F. S. Pri11ei11le8 of. silvieul·
ture. ).fcGnn\·-I-fill Book Co., Inr., _Kew
-York. 44 pp. Illus. 1950.
ls:ine, L. A. H eprodu t iYc hn.Lits of
])ougl:is-flr. Charles L:ltltH•P Pack For­
l'.Stry Foundfttion, \Vnsl1iu ton, 1). C. 107
I'P· Il\1u.;:;. 1fJ:i3.
T}::-0.tPH.::; !'iOl !l h." the 'J'einpil C0q1ora·
tion, :l\cw Y nrk, New York, were used. iu
1"t a fine addition to the instrn­
1G eigcr1
tl11°:;e trials.
R.
These chara teristics n:ake the pel­
1ncnts conitnonly used for measur­
ing snrface soil te1nperatures.
If a pal'th111y buried pellet is
expo cd t•J sun's radiation, it \Yill
begin to softe n
in
a
thin line at
the soil surface \Yhc•n t11 P. n1elti11p:
tc1npcratnrt·
Silen
Pacific Northwest Fo rc t and H.ange
Experiinent Station I:'ort!st $,,n·ice,
U. S. Departinent of A6rkultur1 ,
Portiaud, On•gon
is
r0aC'licd.
Shonlcl
the ten1peratnre then drop, the pel­
let \vill reharden, but a thin eroded
as
face
a record.
continue
up.
the portion above
the
Hyuartnj:l, 0. 'L'L·!llJ>ernture and e\·:qJll·
l
Rll
should
tempern.LnTe
nll
ward,
surface will melt, but the part he­
]o\v the surface \vill generally rc­
n1ain intact.
fcr::.:.t ·1:":r:1J n­ th
;tr:;1::;nrz 11.L
provi \
seec1be<ls reaching lethal tempera·
P! ll".'t
·,\·1 1"-
nuthnr tu
clearcuttino·
on Douglas-fir
tures
IL J. Andrews Exper
n1ental F orest. .!_\_ large ntnnber
within the
each
\rithin
points
sa1np1in­
of
clearcut area \\'ere first chosen at
Pellet
random or syste1naticaUv.
l
frag1nents of several ine ting tc1n­
peratnres \Vere then placed at ea.ch
point to pLovide n. range o.-f maxi­
ml1m ten!peratures.
Sinte seedh,_.,d
te1nperatures inay vary· ronsicler­
ably even
over an ineh of snr£acP
th e pc1Jet. \Vi.th the n1ost ilr:.portan
i
p]ar e<l on
the exact point. On the II. ,T. An­
dre\YS Experimental Forest, pel­
lets n1elting at 138° F. \vere n<:;ed
n1elting temperature \Y11.S.
the
at
heat loss
this
because
point
exact
correlates best.
te1nperature
,vith
of Dough1.s.fir seedlln s.
h
Fragments of pellets having hig er
or lrnver inelting- points \Yl'l'8 then
placed
and
1/.i,
to the east
E!asf.-\\·est Orit•nta.
to 0- t-inch
\Yest.
'I'he
lion of the line
of pellet fra"ments
\Vas adopted to preYent
to ;t11pick
inarkers on either end fro1n :'had·
ing the fragn1rnts.
In placing
the
spot
Pach pellet frHg1nent,
\Yas
first.
prepared
hy
probing t.he po.int of a prueil about
one-half inch jnto the
soil
lo
fc1r111
a s111al1 coni(•al hole. rrhe .frrq:;1nent
\Vas thC'n
inseriell "'itl1
t\Yt:E'7.1_!rs.
thi1·tl or
above the grn:11JL1.
point first, so that ouly a
less sl10\Vl'd
ra t.on at a 1 ll lt>.'ar gn_1u11 1 level 011 CL·r·
i!t•:>. Can: dian .Tourn::il of
tn.in fo rc ::;t
Bot:111y ;.-: : 7\.0- ;.s:::. 1 r1;J-L
its sur­
If instead the
line \vill ren1ain etched on
'l'his
t\VO
liroee-durc
re>a on s .
\\·as
fnl!u,vl·1.1 for
}; a d
] xpl'rienc••.'
Hho1rn that consiclcrab1e u1<Y\'1_ u1ent
JOUR'1 AL
312
OF
ten1perature
areas,
FORESTRY
also
pellets
proved admirably suited for sam­
l
p i ng ten1peratures of the soil next
to the steins of ne1vly germinated
scerllings (Fig.
1).
When seedlings
are under- continuous obserYation,
pellet fragments even as fine ai::; a
dus t can be used effectively but are
easil r lost. For intern1ittent obser­
"'i'ation over JonO' periods relatively
;
long splinter-lil e fragtne ts of
s111ail
d i a 1nete r are better. These n1av be
placed Yery close to a tiny
ten1
'-ri t hout actually touching or shad­
ing it.
Long fragn1ents are e spe­
ci al ly desirable \rhere loose seed­
be d:-; such as cl uff or lnoss Jnake it
hard to }1redict at \rh:i.t. snrfaee
'. ·iI!
L,.,-1_·] tl1•:- l-:i.'..!·1;;•.:.:t ti=-·r!-1fF 1·:1.i.n:·
u;_,1:!11.
i.'i\;_'
1 .::I'' f:·0.':'..·nJ-?nt
iio1Ll<l
be used so1ne distance a\vay fro1n
FIG. 1.-Temperature pellets insta;Jed near the t:t.;111 of a Doug!a,,·fir :>e tlling.
sceclling st0111s because of sooting.
Tl1e
133° F. pellet fragn1eut is closest to the stem; 1 5° P. :uuJ 1;)(1° .P. fragntents are
on either side. Snu1ller splinter-like frng1nents 'vould 11onnal!y he used, but ]1:i.if
pellets are shown here for clarity. \Vhoie 150° pell ts and tl1t:ir ahuuinuin container
are
shown at right.
jects by rain1 'vind, gravity or bi­
ot ic actiYity· took p lace C\'Cn on
relative]:- flat surfac es during snn1­
This
n10Yen1ent \Yas
n1uch
rnore prononnce1l on steep slopes.
Pellet frag:n1entg
1n r.r ely plneecl on
the surface often becan1e lost, but
partially buricU frnµ-1nents nsually
re111ainecl in place. In ar1c1ition a
pellet fraginent partiall:v b nrie cl
\vould usually h_�avc an unmelted
portion beJo,v ground 1evr.l to pro­
vide positive e \· id ence
t11at the sur­
face te1nperatnre hncl exceeded tbe
melting point of the pellet. Other­
' 'ise there \Vas no
ertain \ray to
e
detern1inc \Vhether the absen ce of
a pell e t meant it had completely
1neltcd, or had si1npl · beron1e 1o8t.
lialf pellets \Ycre the 1110:..t f.:ntis­
factory size of fragn1ent \Vhen the
tests
o\·er seYi_·r[ll
\\Thole p .,11cts p r0v r cl un­
\\·ere
moni lis .
necessarily
carric d
large
1nun1 surface te1npcratures nea r a
see dlin g
te1n
be accurately
ran
Incasured \ \· i t h prac:tically JlO dis­
of soil particles and o ther small ob­
mer.
\\ ith these preeautions, t he 1na::s:i­
for point
sara­
pl i ng anJ £r ag 1nents sn1a11er thrnt
a half pellet took too long to find.
pell e t
of the niicrosite.
T\\'O further precautions
hould
js an exce ption .
its n 1 t l ting
point, it pa rt ly vaporizc·s, l eavi ng;
hel1lnd a hlaek s1Jnt. '.L' hi bhH:kPns
thr ac1jarrnt soil nrfac:e ancl 111a ­
in;:r
(:ha11g·l thP t.c1npcraturc c:haracter­
le!s freq nrn tl y melt "·lien left 1rn­
1rhe
J2S0 Ji1•
turbance of the natural con dition s
h eat ed
\\Thc>n
abo\'
istie:::: of: sn rfa c·r. 1nat0rials. 1'1or
thi reason. a s1nal l fra 1ncnt ( .-811c•llet or s1nallcr) of the 1:25° P. pc1lr.t. \ras nsrcl and 'ras placed at 1Past ou e-ha lf ineh
a\ray fr01n frag-n1cnt of other p llcts. 1\ tooth­
pirk 111arker \Yas t he n insf"!rtrd in the soil beside it. TJpon n1elrin 1". the l26° F. pP1lc t leaYes a pc-r.;;.;ist.­
ing ba n d o.f sriot on the toothpick. Ji1rag111e11ts of oth f ·r pcllrts ran be placell
c1ose
together,
should not touch
and
(\l'
1n1t
they n1('_\· llll:t)' .Fnse 1nakc it aiffieult
to i n t r rpret result:::. T11
cl ll it ion to t he i L· 11scf:uln0ss
in large sral e san1pling of clearcut
a
be taken in h8ndling-
nr
transport­
p ·ll Pts. 'fo guard against ac­
c:idental n1f'ltjng. thPy should be
ea Tr i ed in an insn1ated bag.
protcctr d inside
in the
an
auto 11arked
Since the
sunshine.
cl­
123°
pel lets react chcm ie olly with the
others.
they should be
separnit·ly.
becon1e
packaged
The 125° pellets also
oily from
prolonged
ex­
p o snrP tti bod y- heat ,.,·hen carried
in the pockets of clothing-.
'i'\Thpther nsetl for extensive sau1­
pli.ng
to find the percent of seed­
bt ds re1v_dtinf?_' 1eth;ll te1nperatnre5
or for dctrr:1-:iti_i· g Jnaxi1nu1:n tcn1pernturrs ir;. t11e n;innte nren near
a scPtlling- :-:tern, icmperatnre p 1­
l•.>t:::: sho,\· pron1isc
as a ncvt and rr­
linhlc r e r-arc h tool.