University of Montana
ScholarWorks at University of Montana
Theses, Dissertations, Professional Papers
Graduate School
1984
Water stress response after thinning Pinus contorta
stands in Montana.
Bryan L. Donner
The University of Montana
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Donner, Bryan L., "Water stress response after thinning Pinus contorta stands in Montana." (1984). Theses, Dissertations, Professional
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B Y T H E AU T HOR.
MANSFIELD L i b r a r y
Un i v e r s i t y
Date :
of
Mo n t a n a
19 8 4___
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approved
W A T E R STRESS RESPONSE AFT ER THINNING
PINÜS CQNTORTA STANDS IN MONTANA
By
Bryan L. Donner
B.S.r
Northern Arizona University^
1981
Presented in partial fulfillment of the requirements
for the degree of
Master of Science
UNIVERSITY OF MONTANA
1984
Approved by:
.
Chairman,
L
4
Board of Examiner^
Dean,
Graduate School
Date
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Page ii
Donner, Bryan L . , M.S., May 1984
Water Stress Response After
Montana (49 pp.)
Director:
Thinning
Forestry
Finns
contorts
Stands
in
Dr. Steven W. Running
This study compared the leaf water potential of thinned
stands
of
lodgepole pine
(Finns contorts var.
latifolia Engelm.) to
adjacent controls at three sites in Montana.
The even-aged stands
had average
ages
of 48, 58, and 60 years with initial stocking
densities
of 2000,
2500, and
12,000
stems
per
hectare,
respectively.
Each stand was
thinned
to different units of
varying densities in the fall of 1982.
Fre-dawn
leaf water
potential measurements were
taken monthly in the summer of 1983
using the pressure chamber technique to determine plant moisture
stress differences between the thinned and unthinned stands.
Late
summer leaf water potential was
significantly greater
in the
thinned
stands
than in the controls.
Furthermore, the increased
leaf water potentials were proportional to the basal area removed
with the greatest level of thinning exhibiting the greatest water
potentials.
These water potentials developed in the
late summer
to
levels near
those documented
in the literature for similar
stands even with greater than normal
early summer precipitation
and soil moisture contents.
Measurements of radial increment and
height growth of the sample trees in subsequent years will help
determine
if the phenomenon of thinning
shock
is related to
moisture stress conditions in recently thinned stands.
Page iii
Acknowledgements
I would like to express
individuals
project.
Keane,
my
appreciation
Steve
Running
all
Bob
deserve special thanks for
the
middle
of
the
Thanks to Emily Chesick for boring trees and digging
soil pits
hel ping
the
Ramakrishna Nemani,
running around in the woods with me in
night.
all
who helped contribute to the completion of this
Jeff Graham, Rob Ethridge,
and
to
in the snow;
with
the
Liz Easterling and Mark Bakeman
soil
analysis
for
and classification;
and
Dianne Daley for providing the soil moisture data.
Va luable consultation in
organizing
provided by Roger Hungerford,
Jim Faurot,
Bob Pfister.
Running,
for
My most sincere
simultaneously
the
was
George Briggs,
appreciation
keeping
project
goes
to
and
Steve
me amused and on the
right track.
This project was
supported
Rese arch Project grant number 47.
by
the
Mission
Oriented
Page iv
TABLE OF CONTENTS
A b s t r a c t ...................................................Page ii
Ac k n ow ledgements
............................................
iii
Table of C o n t e n t s ............................................. iv
List of T a b l e s ................................................. ..
List of I l l u s t r a t i o n s ..........................................
Introduction
...................................................
1
Methods
Study A r e a s ...................................................5
Sampling P r o c e d u r e s ........................................ 10
Statistical A n a l y s i s ........................................ 15
Results
Climate M e a s u r e m e n t s ........................................ 17
Leaf Water Potential and T h i n n i n g ........................ 19
Soil Moisture and T h i n n i n g ................................. 25
D is c ussion and C o n c l u s i o n s ................................... 27
A p p e n d i c e s ...................................................... 32
Literature C i t e d ............................................... 46
Page v
LIST OF TABLES
1.
Study area stand c h a r a c t e r i s t i c s
Page 11
2.
Study area site c h a r a c t e r i s t i c s ........................ 12
3.
Sample tree dimensional characteristics
.............. 14
LIST OF ILLUSTRATIONS
1.
Study site l o c a t i o n s ................................. Page 6
2.
Lubrecht Experimental Forest site photography
3.
Rattling Gulch site photography
4.
West Dry Fork site p h o t o g r a p h y ............................ 9
5.
Study area total m onthly precipitation
6.
Seasonal
Leaf Water P o t e n t i a l , L u b r e c h t ............... 20
7.
Seasonal
Leaf Water Potential,
Rattling Gulch
8.
Seasonal
Leaf Water Potential,
West Dry F o r k ...........23
9.
Soil moisture
depletion,
• . . • 7
....................
8
................. 18
. . . .22
L u b r e c h t ..................... 26
INTRODUCTION
Lodgepole pine
(Pinus contorta var.
latifolia Engelm.)
constitutes one of the major timber species harvested in the
Northern Rocky Mountains.
hectares
north
in Montana,
into
Pure
stands
cover
Idaho, Wyoming, Washington,
Canada.
The
serotinous
cones
millions
of
Oregon,
and
allow
for
reproduction in large numbers after a major disturbance such
as fire or c l e a r c u t t i n g .
The overabundent reproduction
ev entually
stagnant
form
dense,
Unlike many other conifer species,
not
become
dominance
stratified
and
into
outcompete
stands
in
later years.
these stands generally do
crown classes.
weaker
may
trees,
No trees take
thus
naturally
thinning the stand to distribute plant requirements to a few
healthy individuals
(Alexander
1960).
Many
thousands
hectares are covered with overstocked, mid dle aged
years)
lodgepole pine stands.
small
to
of
(30 to 70
Trees in these stands are too
be of commercial sawlog value and are unlikely to
grow to a m e rc hantable size.
Prescribed,
artificial
thinning
of
overstocked
lodgepole pine stands to desired densities is an alternative
for the forest land m a n a g e r .
the
Thinning offers
a
means
for
redistribution of plant requirements to a few trees per
Page 2
hectare
(Alexander 1960)
allowing for the best possible
of a site for wood production.
Commercial thinning is often
possible with post and poles as the product
Improvements
in
other
rangeland forage
quality,
and
beetle
(Wellner
1975).
forest resources y such as increased
(Phillips
1973,
watershed runoff
Other benefits
use
Dealy
1975),
(Goodell 1952)
aesthetic
are possible.
include increased resistance to mountain pine
(Mitchell
et
al.
1983)
and
decreased
wildfire
potential•
Silviculture
excellent
literature
growth
response
m id dle-aged stands
Lotan
1967,
1971).
to
thinning
and
following
1967
and
1973,
Yerkes
reported
(1960)
transfer
whole
stands
no
release
of
first thinning in
Schubert 1971,
may
in
capacity
respond
Seidel
differently
not respond at all,
(Staebler
(Reukema
1964).
reported on
thinning
Do u gl a s- f ir
plantation.
1956).
Lane
white
pine.
50-year-old
shock
It
50-year-old
and
Douglas-fir
Harrington and Reukema
in
a
is
55-year-old
difficult
f requency of thinning shock because most
responses
a
not
to fewer stems through thinning.
Crown expansion was reduced in
favorable
examples
found that 110-year-old Douglas-fir could
growth
Was hi n gt o n
a
individual trees will
condition known as "thinning shock"
(1963)
many
(Alexander 1960, Barrett 1961, Gary 1978,
Dahms
However,
offers
discount
or
to
reports
ignore
in
(1983)
Washington
assess the
emphasize
unfavorable
Page 3
responses,
Litera ture
limited.
pertaining
to
this
specific
topic
is
Thi nning shock itself has only been reported as to
its occurrence but no li terature has been
found
concerning
research into the cause of thinning shock.
The water status
of the site is a possible explanation
water
but
studies of thinned stands are also limited.
(1974)
reported
plantation.
on
work
in
an
relations
Sucoff and Hong
18-year-old
red
pine
This study showed greater leaf water potential
and soil moisture content in
the
u nthinned stand.
(1975)
Lopushinsky
data by Seidel in Oregon
that
thinned
stand
than
the
reported on unpublished
thinned
lodgepole
pine
at
mi dday had slightly higher moist ure stress than an unthinned
plot.
Lopushinsky attributed this to increased exposure
the residual trees.
The effects of basal area reductions on
seasonal soil moisture
frequently.
depletion
1968),
stands
have
been
studied
more
An increase in soil moisture content following
a silvicultural treatment has
pine
of
(Johnston
red pine
larc h/Douglas-fir
stands
stands
ponderosa pine stands
been
1975^
(Bay
reported
in
lodgepole
Dahms 1971 and 1973, Herring
and
(Newman
(Orr 1968,
Boelter
and
1963),
Schmidt
Helvey 1975).
western
1980)
and
Page 4
The growing season in Montana is usually
by long periods of little precipitation.
dry periods
is
requirements
frequently
for
growth,
adequate temperatures,
months.
It
is
thus
reduced
Tree growth during
(Zahner
1968)•
such as nutrients,
are normally met
reasonable
characterized
radiation,
during
to
Other
the
examine
and
summer
the
water
relations of a site when first investigating thinning shock.
Thinning
m ay
improve site water relations by reducing both
overall stand transpiring surface area and live root density
within the s o i l , potentially altering water availability for
the residual trees.
for
Canopy interception is reduced allowing
a greater amount of rainfall to reach the soil surface.
Thinning m a y also adversely affect site water
relations.
A
reduction in stand leaf biomass would increase the amount of
radiation in the lower canopies and could possibly
canopy
loss.
temperatures,
increase
thus increasing transpirational water
Higher radiation loads reaching the ground could also
increase
soil
Therefore,
the primary hypothesis for this
thinning
temperatures
overstocked,
Montana will either
and
surface
evaporation.
study
was
that
middle-aged lodgepole pine stands in
improve or adversely
effect
the
water
relations of the residual trees from the unthinned stand.
METHODS
Criteria for study area selection were the presence
of
a control and mor e than one treatment^ middle age with crown
closure
before
thinning,
easy
access,
and
sufficiently
different from other sites in initial stocking density.
three study areas chosen are
refered
Experimental Forest, Rattling Gulch,
to
as
the
Lubrecht
and West Dry Fork.
study areas were thinned in the fall of 1982 under
not
origi nally associated with this study.
provided
an
potential
op portunity
responses
in
to
1983
measure
under
The
The
research
These thinnings
initial
this
leaf
water
project.
One
treatment at West Dry Fork was thinned in the spring of 1983
but
this
was
early
enough
in the growing season so that
responses should not have been affected.
was
thinned
of
Project
Forestry.
of
the
University
Forest
Service,
Expe riment Station.
1.
Photographs
of
Montana
The Rattling Gulch and West Dry Fork
sites were thinned to two different densities
U.S.
site
to three di fferent densities under the Mission
Oriented Research
School
The Lubrecht
Intermountain
each
Forest
and
Site locations are presented in
showing
representative
treatment at each site are presented
control
by
the
Range
Figure
and
one
in Figures 2, 3, and 4.
Page 6
Lu b rech t E x p e rim e n ta l
Forest
Great
Moccasin
Missoula
Neihart ^
* philipsburg
9
Rattling
Gulch
®Dillon
locations.
Figure
1.
Falls
Study site
West Dry
Fork
Page 7
(ft***
{A )
( B)
Figure 2. Lubrecht Ejg^erimental Fbrest.
meter treatment.
( A ) Control.
(
b
) 6.1
Page 8
f
f
f;
(A )
( B)
Figure 3.
treatment.
Rattling Gulch.
( A ) Control.
( B) 5.3 meter
Page 9
(A
)
4
(B )
Figure 4. West Dry Fork.
treatment.
( A ) Control.
( B ) 2.9 meter
Page 10
The Lubrecht Experimental
Garnet
Range
Forest
is
located
in
the
approximately 50 kilometers east of Missoula.
The lodgepole pine study area originated from a post-logging
fire
in
1932.
deposits.
The
Philipsburg
The stand grows on glacial lake sedimentary
Rattling
Gulch
site
is
located
kilometers
northwest
of
Montana in the Upper Wi llow Creek drainage.
on a mid-slope alluvial fan.
located
on
the
Philipsburg^
The stand grows
The West Dry Fork
of
central
Montana.
study
The
approximately six kilometers east of Monarch,
Dry Fork Belt Creek drainage.
deposit
area
of
is
West Dry
Pseudotsuoa
Fork
(Pfister et al.
is
limestone.
a
mid-slope
The
climax
m e n z i e s i i / V a c c ipium
Pseudotsuoa
1977).
Stand
summarized in Tables 1 and 2,
is
Montana in the
The stand is on
weathered
site
vegetation habitat type for the Lubrecht and Rattling
sites
It
Lewis and Clark National Forest in the
Little Belt Mountains
Tertiary
the
Ranger D i s t r i c t y Deerlodge National Forest.
is approximately 25
is
on
Gulch
and
menzi es i i/ L in n aea
borealis
and site characteristics are
respectively.
Sampling PlLQggdujgg
Lubrecht has 40 sample trees
West
Dry
and
Rattling
Fork have 30 sample trees each:
were selected in each of the treatments or
Gulch
and
ten sample trees
control.
Forty
samples were determined to be the max imum number possible in
Page 11
Table 1.
Study area stand characteristics.
Study Area
Lubrecht
Exp. For.
Feature
5.1
5.5
6.3
29.3
33.5
27.2
Initial Leaf
Area Index
Initial Basal
Area (sq. m/ha)
Basal Area
Reductions
42,
50, 72
Ave. Stand Age
3.4,
one pre-dawn sampling session.
for
their
percent
and
Individual sample trees were
live crown ratios
25 to 45 percent.
sample trees in each unit fell in one of
Care
in
immediate
2.9
58
cont rasting live crown ratio categories were
75
1.7,
5.3
60
49
primarily
1210
3600
350
900
270, 560
1090
3.0, 4.3,
6.1
Averag e Spacings
(meters)
to
66
12,000
2500
2000
Residual Stocking
De nsities (s/ha)
55
33,
33, 66
(%)
Initial Stocking
De nsity (s/ha)
chosen
West Dry
Fork
Rattling
Gulch
(LCR).
selected
Two
for:
Half of the ten
these
categories.
sample tree selection was taken to assure that the
area
around
each
sample
tree
consisted
of
representatively distributed trees of average size and crown
Page 12
Table 2.
Study area site characteristics.
Complete soil
p rofile des criptions are located in the Appendix.
Study Area
Lubrecht
Exp. For.
Rattling
Gulch
West Dry
Fork
1250
1700
1600
5-15
0-10
30 - 35
Asp ect
NW
W
NNE
Mean Annual P r e ­
cipitation (cm)
45
46
Feature
Elevation
Slope
(m)
(%)
Mean Min. January
Temperature (C)
Mean Max. July
T emperature (C)
-13.5
-12.5
-14.4
27.6
26.2
25.4
Typic
Eutroboralf
Soil Subgroup
Typic
Cryochrept
volume so extremes of shading or open
Study
50
areas
Typic
Cryoboralf
were
avoided.
site layout and sample tree locations are depicted in
Appendices G, H/ and I.
Sample tree dimensional characteristics
before
leaf
b reast height
the
base
of
water
(DBH,
potential
were
readings began.
1.37 m ) , total height,
measured
Diameter at
and the height to
the crown were measured using standard forest
inventory equipment.
Crown width at the greatest point
was
Page 13
estimated.
The
live
crown
ratio was calculated from the
p er c entage of crown length to total tree height.
boring s
for
age
Increment
and sapwood area were conducted after all
leaf water potential measure ments were completed.
taken
at
the
base.
The
DBH
to
calculate
sapwood
basal
area.
height were
Current
year's
increment was not great enough to affect calculations.
area
index
of
the
al.
Leaf
stands before thinning were determined
using regression equations based on DBH developed
et
was
measure ments and length of
sapwood on increment borings taken at breast
used
Age
(1979)
in
Oregon.
Average
characteristics for each LCR category
at
by
Gholz
dimensional
the
three
study
were
taken
areas are presented in Table 3.
Pre-dawn leaf water potential measurements
four
times
on
a
monthly
basis
beginning
mon th l y data collection for the three sites
wit h in
five
days.
all me asure ments at
session.
in June.
were
All
conducted
With the exception of Lubrecht in June,
a
site
were
taken
in
one
pre-dawn
Each tree was only sampled once per session and no
regard was given to canopy position when the sample twig was
removed.
A pressure chamber device was used for estimation
of leaf water potential using standard
and
H in ckley 1975) .
techniques
An additional five sample trees of low
LC R in the control at Lubrecht were selected
A ugust diurnal leaf
(Ritchie
water
potential
for
July
measurements.
and
These
Page 14
T able 3.
Sample tree dimensional characteristics.
Cha racteristic
n
DBH
(cm)
Height
(m)
Crown Width
(m)
Lubrecht E.F.
LCR:
>55%
<45%
20
20
20.4
12.9
16.1
14.7
4.0
1.8
62
30
Rattling Gulch
LCR:
>55%
<45%
15
15
18.6
12.6
15.7
14.6
3.2
1.3
62
39
Wes t Dry Fork
LCR:
>55%
<45%
15
15
11.9
7.1
10.6
2.2
1.1
63
44
Study Area
altern ate sample trees were
twigs
on
the
primar y
8.5
chosen
in
sample trees.
order
to
LCR
(%)
conserve
Diurnal measurements
were not taken at Rattling Gulch and West Dry Fork.
Meteorological data were obtained from U.S.
of
Commerce
Experim ent
(1984)
Station
and
(1983)
Montana
Forest
publications.
un published 1983 data for Lubrecht.
as
possible.
and Conservation
Goetz
provided
Precipitation data were
selected from weather stations located
areas
Department
as
near
the
A weather station at the Lubrecht Camp
is approximately 600 m from the Lubrecht study area.
Forest
Service
study
weather
station
at
A U.S.
Philipsburg
is
Page 15
a p p r o x im a te l y 25 km southeast of the
Another
U.S.
Forest
Service
Rattling
weather
Gulch
station
is
n or t h-northwest of Neihart and approximately 5 km
of
the
pan
West
Dry Fork site.
ev aporation
Experim ent
data
Station
13 km
southwest
In addition to precipitation,
were
west
site.
selected
of
from
the
Moccasin
Lewistown and Western Montana
Col lege at Dillon.
An as sociated study conducted by
Montana
School
of
other
University
Forestry researchers concerned seasonal
soil moisture depletion at the Lubrecht study
data
collected
soil
contents
moisture,
as
water potential.
Nine
located
response
in
each
to
the
measured
neutron
from
These
unit
May 1 to November
from 0.15 m to 1.52 m.
tree's
ability
to
by the pre-dawn leaf
probe
access
tubes
were
and an adjacent clearcut.
Soil mo isture by percent volume was
basis
site.
can be used in the present study to compare
actual soil moisture
utilize
of
me asured
on
a
weekly
8, 1983 at six depths ranging
Data were not available from July 14
to Aug ust 2 due to equipment failure.
An^lysjg
Mean mont h ly leaf water potentials for each study
response
Initial
unit
were
stocking
elevation,
and
area
compared for statistical significance.
densities,
climatic
stand
differences
age,
did
slope,
not
aspect,
allow
for
Page 16
contrasts between sites and me asurement
analysis
of
treatme nts
variance
established
individual
T-tests
with
a
a
factorial
pooled
between
dates.
one-way
arrangement
variance
groups.
A
estimate
These
of
for
one-tailed
contra sts suggested significance between treatments with the
criteria
of
the
water potential.
greater
densities
having the least leaf
A two-tailed T-test suggested significance
between live crown ratio categories and leaf water potential
wi thin each response unit on a given date.
tested
at the 95% confidence level.
using the SPSSx
(1983)
Batch System.
Significance was
Analysis was conducted
RESULTS
May and June total precipitation
sites
were relatively normal.
at
three
study
The distribution of rainfall
in late May and early J u n e y howeverr was
rain
all
such
that
little
fell immediately before the first me asurement session.
July was uncommonly wet,
with
several
periods
compared
of
to
intense
historical
rainfall
averages,
at each s i t e .
Total precipitation for July was 240% greater than normal at
Lubrecht,
170%
greater at Rattling Gulch,
at West Dry Fork.
and 120% greater
Total monthly pr ecipitation
returned
to
normal at Wes t Dry Fork in August and September but remained
higher at
both
Lubrecht
and
Rattling
Gulch.
Figure
5
summarizes precipitation at the three sites.
Pan
evaporation
the
measurements
indication
of
Radiation,
temperature,
évapotranspiration
evaporative
and
correlations cannot be
betw een
the
two
wind,
can
demand
and
give
a
placed
humidity
on a tree.
affect
still water evaporation,
made
due
evaporating
to
physical
surfaces.
relative
but direct
differences
Seasonal
evaporation can possibly indicate greater than or less
normal
seasonal leaf water potential.
17
both
pan
than
A pan evaporator at
MONTHLY PRECIRTATION, Philipsburg
MONTHLY PRECIPITATION, Lubrecht
VI
Î
E
I
o
10-
£
o
c
o
"5
0
I
c
o
o
Û.
Ü
I
U tosirtm tnis front
MAY
JUN
JUL
AUG
MAY
SEP
JUN
JUL
AUG
SEP
MONTHLY PRECIRTATION, Neihart 8 NNW
15
Figure 5. Stucty area monthly total
precipitation, ( ----- ) indicates
yearly historical average. ( ---- )
indicates 1983 average.
to
CL
5
£L
1*0 I^iuiom ents (fo m
0
*—
MAY
JUN
JUL
AUG
SEP
I
H
00
Page 19
the M o ccasin Experiment Station near West Dry Fork
c on s i stently
summer.
lower
than
normal evaporation throughout the
A pan evaporator at Dillon
southwest
Montana
to
measured
showed
evaporation
in
be near normal for 1983 except for a
lower than normal July.
Leaf Water Potential and Thinning
Pre-dawn leaf water potential at all sites were usually
lower
in
in
the
the control than in the treatments.
late
treatment
summer
had
were
always
significantly
lower.
The controls
At
least
greater leaf water potentials
than the adjacent control for all measurement dates at
site
one
each
except for West Dry Fork in June and Lubrecht in July.
Statistical analysis is summarized for the
three
sites
in
Appendixes A, B, and C.
Leaf water potential
increased
in
July
0.15 to 0.20 MPa from June
had stat istically similar water
August
at
session
showed
the
potentials
greatest
treatments
August.
Leaf
water
decreased
from
August
control actually increased.
July.
the
Both the 3.0 and 6.1
greater
potential
to
The
in water
0.37 MPa less in
than the 4.3 meter treatment.
in
in
site
All units
difference
m eter treatments were also signif icantly
control
Lubrecht
(Figure 6).
potent ials recorded during the study:
control
the
in
September
than
the
all three
but
the
Significant differences between
D
CL
0)
>
O
U)
0)
/
D
C
Q)
O
CL
CD
O
Response Units
C ontrol
5 0 m spacing
O
CD
m m «
m m m m m
4 .5 m sp acing
6 1 m sp acing
200
250
300
Julian Dote
Figure 6. Seasonal leaf water potential by response unit, Lubrecht Bçerimental
Forest.
I
ro
o
Page 21
treatment units always occurred with the treatment that
the
least
basal
area
removed
having
the
had
lowest
water
Rattling
Gulch
potential.
Water potentials in the three units at
responded
similarly throughout the s u m m e r .
The control and
treatment water potentials increased from an
unusually
June reading to higher levels in July and August
Leaf water p o t e n t i a l ,
September.
The
less than the
throughout
control
3.4
the
however^
decreased
meter
less
treatment in all
these
two
treatment
The
water
cases.
groups
in
water potential was significantly
summer.
had
(Figure 7)•
dramatically
in
every
greatest
potential
Significant
occurred
in
Significant differences between
the
measurement
difference between
these two groups was 0.23 MPa in September.
treatment
low
than
The
3.4
the
5.3 meter
differences
June
and
control
meter
between
September.
and
the
5.3
meter treatment only occurred in August and September.
The West
significant
summer
Dry
Fork
site
consistently
had
the
differences of the three study areas.
most
No early
increase in leaf water potential occurred here as did
the other two sites
potential
slightly
markedly
from
(Figure 8)•
in
August
the
to
early
Except for
summer
September.
remained at about the same water
progressed.
The control decreased water
June
The
potential
but
increased
two treatments
as
the
summer
when the control was greater
1.2-1
O
CL
Q)
>
O
1
-
u>
Q)
C
'ô
c
0
o
CL
0
O
0.6
Response Units
Control
O
0
5 4 m spacing
0.4-'
150
?.AIT.
200
250
300
Julian Date
Figure 7. Seascmal leaf water potential by respcmse unit. Rattling Gulch.
I
K)
to
o
CL
Q)
>
O
O)
0)
c
[5
c
Q)
O
CL
L
Q)
O
Response Units
Control
O
CD
1.7 n spacing
....
200
250
300
Julian Dote
Figure 8. Seasonal leaf water potential by response unit, West Dry Fork.
I
ro
w
Page 24
than the 1.7 meter treatment,
potentials
had
increasing proportional to density.
significantly
treatments
1.7 meter
all measurements showed
in
less
July,
treatment
leaf
August,
in
water
July.
The control
potential
and September,
The
two
water
than
both
except for the
treatments
were
significantly different from each other in all cases.
The live crown ratio
effect
on
the
pre-dawn
does
not
seem
to
leaf water potential.
differences between the two LCR categories on
date
and response
unit were few.
differences at Rattling Gulch.
The
five
significant
contradictory.
The
<45%
have
an
Significant
a
particular
There were no significant
West Dry Fork only had
differences
LCR
had
category
at
one.
Lubrecht
sometimes
were
had
a
greater mean leaf water potential than the >55% LCR category
and
visa-versa.
Statistical
analysis
is
summarized
in
Ap pendices J, K, and L.
The two diurnal leaf water potential measurements taken
at
the
Lubrecht
results.
less
than
morning.
Experimental
Forest gave fairly similar
The August pre-dawn water potential was
0.20
MPa
July but did not decrease as quickly in the late
The mid-afternoon minimum was -1.51
and -1.63 MPa in August.
MPa
in
July
Page 25
M9i9tup9 and Thinning
Soil moisture depleted in the upper
over
unit
lower
the
course
(Figure 9).
depths
soil
at
Lubrecht
of the summer was greatest in the control
Little soil moisture was depleted
from
May
until
September
at
the
and the clearcut
actually accumulated soil moisture at a depth of 1.2 meters.
The
4.3
meter
treatment had the greatest depletion of all
the mod ified units.
depletion
The
6.1
meter
of the forested units.
had
the
least
Less depletion occured at
0.15 meters than at
0.30 meters in
sparsely
clearcut.
vegetated
unit
all
Informal
cases
except
analysis
cores during access tube installation showed tree
be concentrated in the 0.25 to 0.75 meter depths.
the
of soil
roots
to
20-1
0)
E
o
15-
JD
c
10
-
0)
o
0)
CL
(D
Legend
3
learcut
Control Plot
5 0 m s p acing
O
(f)
4.3^ m sjDocing
-5-
0
0.5
1.5
Depth, meters
Figure 9. Seasonal soil moisture depletion, lA±>recht Experimental Forest.
taken on May 15 and September 24, 1983.
Measurements
I
lO
DISCUSSION AND CONCLUSIONS
I
would
immediately
speculate
after
leaf
thinning
water
potentials
measured
in similar stands and sites in
years of normal or less than normal rainfall and evaporative
demand
would
probably
results reported here.
probably
be
higher
be significantly different from the
Overall leaf water potentials
in
would
the early summer and progressively
decrease through September.
I also believe a
greater
leaf
water potential difference between the thinned and unthinned
units would exist.
about
the
The treatments
would
probably
exhibit
same pre-dawn measurements as my results but the
controls would have lower overall water potentials.
these
predictions with some caution,
however,
I
make
since on-site
me teo rological data were not collected.
The initial stocking density at
was
relatively light.
size
s/ha)
in
a
total
forest
thinning
A large number of the trees were already at sawlog
(greater than 16.8 cm).
trees
in
size.
It is interesting
leaf
(2000
A forest land manager would probably
give this stand low pri ority
program.
Lubrecht
water
the
4.3
Almost
all
of
the
residual
and 6.1 meter treatments were of sawlog
that
significant
differences
in
potential developed even under thinnings from a
27
Page 28
low density stand.
Gulch,
This same situation exists
these
same
spacings
I
suspect
that
West
Dry
Fork
(12,000 s/ha)
spacing
is
less
site,
than
control.
A
1,7
meter
what forest land managers generally
differences
water
the
but was thinned lightly,
occurred
this high density treatment.
leaf
to
however, was a relatively dense
thin to in stands of this age and height.
significant
thinning
from a stand of greater density would
result in even lower leaf water potentials in
stand
Rattling
The stand was at 2500 s/ha and about one quarter of
the trees were sawlog sized,
The
at
potential
in
between
The
Again,
however,
the control and
significantly
increased
lightly thinned stands or stands
thinned from low initial densities indicates the sensitivity
of
the
residual
tree's
water
relations to reduced basal
area.
Soil moisture depletion trends at the Lubrecht site are
similar
to
results found in other studies
1963, Dahms 1971 and
Helvey
1975,
Newman
Response units with
greatest
amount
late summer.
(1980)
1973,
and
the
Herring
Schmidt
greatest
1968,
1980,
basal
Johnston
and
area
Orr
1975,
1968),
showed
the
of depletion from spring field capacity to
Bay and Boelter
(1963)
and Newman and
Schmidt
sampled soil moisture in a range of depths and found
almost equal depletion for all depths down
Since
(Bay and Boelter
the
majority
of
to
1.5
meters.
depletion was above 0,75 meters at
Page 29
Lubrechty
I
believe
shallower
than
the
rooting
depth
the
Lubrecht
in the soils of the other two studies.
greatest amount of water depleted in the
at
at
shallowest
depth
(0.15
clearcut
meters),
surface.
indicating
to
the clearcut,
the
the
at
The reason for the large amount of depletion
in the 4.3 meter spacing over the 3.0 meter spacing
attributed
The
occurred
importance of shading in reducing direct solar radiation
the
is
slope positions,
soil differences,
access tubes
can
be
side radiation loading from
and the
grid
placement
of
(as opposed to carefully placing the tubes
in relation to residual t r e e s ) .
The two most significant
soil
moisture
to
the late summer,
Standard silvicultural thinnings,
Under the higher
treatment
stress
conditions
control unit leaf water potentials were
always lower than the treatments and,
Gulch,
leaf
except
for
soil
moisture
m e a s u r e d by the tree's
availability
ability
to
after
use
p r ob abl y
increase
removed.
The lower leaf water potentials
Gulch
5.3
meter
Rattling
water potentials increased over the
controls proportional to the level of thinning.
residual
available
those conducted in the study sites, will reduce
both of these factors.
of
affecting
in thinned stands is canopy interception and
transpiring surface area.
similar
factors
soil
Therefore,
thinning,
water,
as
will
proportional to the degree of basal area
in
the
Rattling
treatment than in the 3.4 meter treatment
Page 30
cannot be explained*
the
Zahner
(1968)
growth
of
division and
trees.
He concluded
enlargement are reduced
stress
is
of the
tissue
Assessing
summarized the effects of water stress on
the rates
when
internal
Running
leaf
containing
"stress"
mother
conditions
cells
is
and
(1980), and Graham
potential
approximately
-1.6
restricts
water
restricts
carbon
photosynthesis.
(1983)
MPa.
loss
at
mid-afternoon
closure
to
be
conductance
transpiration
exchange
(1975)r
but
also
necessary
for
summer growth may have been moisture
stress limited at each study
treatment
found
stomatal
through
gas
mid-afternoon
Lopushinsky
stomatal
Reduced
dioxide
Late
all
at near
derivatives.
difficult but comparing
moisture stresses is possible.
water
meter
water
severe enough to cause dehydration and shrinkage
pre-dawn leaf water potential measurements to
ma x i m u m
of cell
site's
Lubrecht.
control
Water
and
the
3.0
stress probably had
little effect on growth in all other treatments.
In conclusion,
to
after
thinning to avoid moisture stress conditions at three
sites
Montana.
utilize
Furthermore,
increased
soil
able
moisture
in
immediately
residual lodgepole pine trees were
the decrease in
moisture stress
was proportional to the basal area removed with the greatest
level
of
potential.
thinning
Late
exhibiting
summer
moisture
the
highest
stresses
leaf
water
developed
in
Page 31
denser
units at the three sites even with much greater than
normal early summer precipitation.
stress
cannot
1972)
time y
be related to thinning s h o c k .
pos sib ly affecting thinning shock,
(Eis
At this
or
nitrogen
such
deficiencies
as
moisture
Other factors
root
caused
grafting
by
quantities of thinning residues with high C;N ratios
et
al.
1976) may be involved.
large
(Miller
Dimensional analysis of the
sample trees in subsequent years will help determine if
time
required
after thinning.
for
release
is
the
related to moisture stress
APPENDICES
32
Page 33
APPENDIX A
Leaf W ater Potential Treatment Contrast T-Tests
Lubrecht Experimental Forest
One-tailed, Pooled Variance Estimate
36 degrees of freedom
Ho: There is no leaf water potential difference between
the units.
Ha: The denser unit has a lower leaf water potential.
Statistic
Contrast
T-value
June 21,22
Control Control Control 3.0 m —
3.0 m —
4.3 m —
(std. error = 0.034)
3.0 m
3.108
4.3 m
2.220
6.1 m
2.072
4.3 m
0.148
6.1 m
1.036
6.1 m
0.888
Prob. value
Significant?
0.002
0.017
0.023
0.442
0.154
0.191
yes
yes
yes
no
no
no
July 21
Control
Control
Control
3.0 m
3.0 m
4.3 m
(std. error = 0.060)
- 3.0 m
-0.531
- 4.3 m
0.059
- 6.1 m
0.197
— 4.3 m
0.256
- 6.1 m
0.727
— 6.1 m
0.472
0.300
0.477
0.423
0.400
0.236
0.320
no
no
no
no
no
no
Aug. 19
Control
Control
Control
3.0 m
3.0 m
4.3 m
(std. error = 0.056)
- 3.0 m
6.186
- 4.3 m
6.544
- 6.1 m
3.487
— 4.3 m
3.057
- 6.1 m
2.700
— 6.1 m
-0.358
0.000
0.000
0.001
0.002
0.006
0.362
yes
yes
yes
yes
yes
no
0.000
0.014
0.099
0.168
0.002
0.020
yes
yes
no
no
yes
yes
Sept. 24
Control
Control
Control
3.0 m
3.0 m
4.3 m
(std.
- 3.0
- 4.3
- 6.1
- 4.3
— 6.1
— 6.1
error
m
m
m
m
m
m
= 0.044)
4.420
2.289
1.315
0.975
3.106
2.131
Page 34
APPENDIX B
Leaf Water Potential Treatment Contrast T-Tests
Rattling Gulch
One-tailedf Pooled Variance Estimate
27 degrees of freedom
Ho: There is no leaf water potential difference between
the units.
Ha: The denser unit has a lower leaf water potential.
Statistic
Contrast
T-value
Prob. Value
Significant?
June 23
Control
Control
3.4 m
(std. error = 0.029)
— 3.4m
6.061
— 5.3 m
— 0.561
— 5.3 m
— 6.622
0.000
0.290
0.000
yes
no
no *
July 22
Control
Control
3.4 m
(std. error = 0.037)
- 3.4 m
2.068
- 5.3 m
1.496
— 5.3 m
— 0•571
0.024
0.073
0.287
yes
no
no
Aug. 22
Control
Control
3.4 m
(std. error = 0.031)
— 3.4m
4.423
— 5.3m
3.53 9
— 5.3 m
— 0•885
0.000
0.001
0.192
yes
yes
no
0.000
0.000
0.010
yes
yes
no *
Sept. 25 (std. error = 0.025)
Control - 3 . 4 m
9.486
Control — 5.3 m
7.002
3.4 m — 5.3 m
— 2.483
* Did not meet one-tailed requirements.
Page 35
APPENDIX C
Leaf Water Potential Treatment Contrast T-Tests
Wes t Dry Fork
One-tailed, Pooled Variance Estimate
27 degrees of freedom
Ho: There is no leaf water potential difference between
the units.
Ha: The denser unit has a lower leaf water potential.
Statistic
Contrast
T-value
June 25
Control
Control
1.7 m
(std. error = 0.017)
- 1.7 m
-2.741
- 2.9 m
1.371
4.112
— 2.9 m
0.006
0.091
0.000
no *
no
yes
July 24
Control
Control
1.7 m
(std. error = 0.027)
- 1.7 m
1.661
4.228
- 2.9 m
2.567
- 2.9 m
0.054
0.000
0.008
no
yes
yes
Aug. 23
Control
Control
1.7 m
(std. error = 0.029)
6.969
- 1.7 m
12.222
- 2.9 m
5.253
- 2.9 m
0.000
0.000
0.000
yes
yes
yes
0.000
0.000
0.002
yes
yes
yes
Sept. 27 (std. error = 0.028)
4.415
Control - 1.7 m
7.620
Control - 2.9 m
3.205
1.7 m — 2.9 m
Prob. Value
Did not meet one-tailed requirements.
Significant?
Page 36
APPENDIX D
Soil Profile Description,
Lubrecht Experimental Forest
LOCATION:
Section
12
study
area,
Lubrecht
Experimental
Forest.
Approximately
1050
meters
northeast
of
the
southwest corner of Section 12, T13N, R15W.
PHYSIOGRAPHY:
Dissected
percent slope.
terrace,
northeast
aspect,
10
PARENT MATERIAL:
Tertiary-aged siltstone
residuum
with
a
surface
mantle
of younger lacustrine sediments (probably
Glacial Lake M i s s o u l a ) .
DRAINAGE:
Well-drained;
moderately
slow
150 centimeters and very slow below.
ELEVATION:
permeability
to
1250 meters.
NATIVE VEGETATION:
SOIL CLASSIFICATION:
frigid.
PSME/VACA habitat type.
Typic Eutroboralf,
fine-silty,
mixed,
PROFILE DESCRIPTION:
Colors are for dry soil unless otherwise noted.
01
A21
2 - 0 cm
0 - 2 0
A22
20 - 43
A&B
43 - 69
Forest Litter, mostly undecomposed.
Brown (lOYR 5/3) silt loam, dark brown (lOYR
4/3) moist; weak fine granular structure;
soft, very friable, slightly sticky and nonplastic; many very fine, fine and medium
roots, common coarse roots; gradual wavy
boundary.
Pale brown (lOYR 6/3) silt loam, brown (lOYR
5/3) moist; weak fine granular structure;
soft, very friable, slightly sticky and non­
plastic; man y very fine, fine and medium
roots, common coarse roots; gradual wavy
boundary.
A portion : pale brown (lOYR 6/3), brown
(lOYR 5/3) moist, B portion: brown (lOYR
5/3), dark brown (lOYR 4/3) moist silt loam;
me dium subangular blocky structure; slightly
plastic; many very fine and fine roots,
common medium and coarse roots;
moderately
thick clay films on ped faces and in pores;
gradual wavy boundary.
Page 37
B2
69 -
97
B3
97 -
152
Cr
152
Pale brown (lOYR 6/3) silty clay loam, brown
(lOYR 5/3) moist; moderate, medium subangu­
lar blocky structure; slightly hard, fri­
able sticky and slightly plastic; many fine
and very fine roots, common medium and
coarse roots ; gradual wavy boundary*
Pale brown (lOYR 6/3) silt loam, brown (lOYR
5/3) moist; weak, medium subangular blocky
structure; slightly hard, friable, slightly
sticky and nonplastic; common very fine and
fine roots; few medium and coarse roots,
gradual wavy boundary.
Fractured siltstone with roots and clay
films in cracks*
Page 3 8
APPENDIX E
Soil Profile Description,
Rattling Gulch
LOCATION:
Rattling Gulch
Study
Site,
Deerlodge
National
Forest,
approximately
15 kilometers north on FS road No.
88
from
state
route
348.
Approximately
550
meters
northeast
of
the
southwest
corner. Sec.
4, T8N, R15W,
Montana P.M.
PHYSIOGRAPHY:
slope•
Straight mid-slope,
PARENT MATERIAL:
DRAINAGE:
west
aspect,
5
-
10%
Mixed stream deposited old sediments.
Moderately to well drained.
ELEVATION:
1700 m e t e r s .
NATIVE V E G E T A T I O N : PSME/VACA habitat type.
Dominant
serai
species is PICO with a V A C A and CARU dominated understory.
SOIL CLASSIFICATION:
Typic Cryochrept,
loamy skeletal.
PROFILE DESCRIPTION:
Colors are for moist soil unless otherwise noted.
O
A1
3 - 0
0 - 5
A3
5 - 2 2
cm
32
22 - 50
33
50 - 100
Forest litter, mostly
undecomposed.
Very dark brown
(lOYR 2/2) gravelly loam,
brown, (lOYR 4/3) dry.
Weak granular struc­
ture; loose, firm, nonsticky and slightly
plastic; clear boundary and pH 5.8.
Dark yellowish brown (lOYR 3/6) gravelly
loam, light yellowish brown (lOYR 6/4) dry.
Basically structureless; loose, friable,
slightly sticky and plastic; clear boundary
and pH 6.2.
Yellowish brown
(lOYR 5/4) gravelly loam,
very pale brown
(lOYR 7/4) dry.
Weak gran­
ular structure; loose, firm, slightly
sticky and very plastic; gradual boundary
and pH 5.4.
Yellowish brown (lOYR 5/6) gravelly sandy
loam, very pale brown (lOYR 5/6) dry.
Weak,
subangular blocky s t r u c t u r e ; loose, firm,
slightly sticky and plastic; gradual b oun ­
dary and pH 4.2.
Page 3 9
APPENDIX F
Soil Profile Description^ West Dry Fork
LOCATION:
West
Dry
Fork
Study
Site^
Lewis
and
Clark
National
Forestr
approximately
6.5
kilometers
east of
Mon arc h on FS road No.
120.
Approximately
400 meters
east-southeast
of
the northwest corner of Sec.
6, T15N,
R8E, Montana P.M.
PHYSIOGRAPHY:
slope.
Straight m i d - s l o p e y north aspect,
PARENT MATERIAL:
DRAINAGE:
30
-
35%
Weathered l i m e s t o n e .
Well drained.
ELEVATION:
1650 meters.
NATIVE VEGETATION:
PSME/LIBO - CARU habitat type.
Dominant
serai
species
is PICO, with a CARU, ASCO, SPBE, and ROAC
understory.
SOIL C L A S S I F I C A T I O N :
Typic Cryoboralf,
loamy skeletal.
PROFILE DESCRIPTION:
Colors are for moist soils unless otherwise noted.
Oe
A1
3 - 0 cm
0 - 3
Bit
3 - 7
B2t
7 - 1 6
B3ca 16 - 50+
Forest litter, mostly undecomposed.
Dark
yellowish brown (lOYR 3/4) silty clay
loam, dark brown (lOYR 4/3) dry.
Moderate
granular structure; loose friable, sticky
and plastic; clear boundary and pH 5.0.
Dark yellowish brown (lOYR 3/6) silty clay,
dark yellowish brown (lOYR 3/6) dry.
Moder­
ate granular structure, loose firm, sticky
and plastic ; clear boundary and pH 6.5.
Dark
yellowish brown (lOYR 3/4) cobbly clay,
dark yellowish brown (lOYR 3/4) dry.
Moder­
ate granular, structure ; loose, firm, very
sticky and plastic; granular boundary and
pH 6.2.
Dark yellowish brown (lOYR 3/4) cobbly clay
loam, dark yellowish brown (lOYR 4/6) dry.
Loose, friable, sticky and plastic; very
violent effervescence; lower boundary not
found and pH 6.8.
Page 4 0
APP END IX G
L u br ech t Experimental Forest — S t u dy Site Layout and Sample
Tree Locations.
4.3
M spacing
6.1
3.0
M spacing
M spacing
Control
1 cm
24
meters
Page 41
APPENDIX H
Rattling Gulch — S t u d y S i t e Layout and Sample Tree
Locations.
5.3
3.4
M spacing
M spacing
V
\
Control
V
\ \
\ '
\
\
\
\
\ \
1 cm
sr 12 m e t e r s
Page 42
a p pe n d i x
I
Vfest Dry Fork - S t u d y S i t e Layout and S a m p l e Tree Locations.
'
y
1.7
C on tr o l
1 cm
55
la
N
M spacing
Page 43
APPENDIX J
Live Crown Ratio and Leaf Water Potential T-Tests
Lubrecht Experimental Forest
Two-tailedf Pooled Variance Estimate
8 degrees of freedom
Ho: There is no difference in the leaf water potential of
trees of high live crown ratio versus trees of low live
crown ratio.
Ha: There is no difference.
Statistic
Contrast
Significant?
T-value
Prob. Value
June 21,22
Control
3.0 m spacing
4.3 m spacing
6.1 m spacing
3.58
1.13
1.00
-1.57
0.007
0.291
0.347
0.156
yes
no
no
no
July 21
Control
3.0 m spacing
4.3 m spacing
6.1 m spacing
1.44
-0.42
1.68
0.32
0.187
0.684
0.131
0.759
no
no
no
no
A u g . 19
Control
3.0 m spacing
4.3 m spacing
6.1 m spacing
2.75
— 0 .64
0.38
-3.76
0.025
0.53 9
0.717
0.006
yes
no
no
yes
Sept. 24
Control
3.0 m spacing
4.3 m spacing
6.1 m spacing
2.47
-0.32
-0.59
-2.41
0.039
0.760
0.574
0.041
yes
no
no
yes
Positive T-value
<45% LCR mean.
indicates a greater >55% LCR mean than the
Page 44
AP PENDIX K
Live Crown Ratio and Leaf Water Potential T-tests
R a ttling Gulch
Two-tailed, Pooled Variance Estimate
8 degrees of freedom
Ho: There is no difference in the leaf water potential of
trees of high live crown ratio versus trees of low live
crown ratio.
Ha: There is no difference.
Statistic
Contrast
T-value
Prob. Value
Significant?
June 23
Control
3.4 m spacing
5.3 m spacing
0.41
0.46
0.23
0.694
0.656
0.821
no
no
no
July 22
Control
3.4 m spacing
5.3 m spacing
0.74
0.15
0.34
0.480
0.886
0.740
no
no
no
Aug. 22
Control
3.4 m spacing
5.3 m spacing
1.06
0.89
0.15
0.320
0.400
0.882
no
no
no
Sept. 25
Control
3.4 m spacing
5.3 m spacing
-0.28
0.81
0.33
0.790
0.440
0.753
no
no
no
Positive T-value
<45% L CR mean.
indicates a greater
>55% LCR mean than the
Page 45
APPENDIX L
Live Crown Ratio and Leaf Water Potential T-Tests
W est Dry Fork
Two-tailed, Pooled Variance Estimate
8 degrees of freedom
Ho; There is no difference in the leaf water potential of
trees of high live crown ratio versus trees of low live
crown ratio.
Ha; There is no difference.
Statistic
Contrast
T-value
Prob. Value
Significant?
June 25
Control
1.7 m spacing
2.9 m spacing
0.00
-3.13
0.77
1.000
0.014
0.462
no
yes
no
July 24
Control
1.7 m spacing
2.9 m spacing
— 0.06
0.93
-0.43
0.953
0.381
0.679
no
no
no
A u g . 23
Control
1.7 m spacing
2.9 m spacing
1.03
0.11
-1.10
0.334
0.919
0.302
no
no
no
Sept. 27
Control
1.7 m spacing
2.9 m spacing
-2.04
1.31
-2.26
0.076
0.228
0.053
no
no
no
Positive T-value indicates a greater
<45% LCR mean.
>55% LCR mean than the
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