SOIL COMPACTION:
CONCERNS, CLAIMS, AND EVIDENCE
Dick Miller and Harry Anderson
ABSTRACT
Soil resistance to penetration was measured in ten 7­
to 27-acre operational units in overstocked mixed-conifer
stands at the Fritz Timber Sale in Northeast Washington.
Different combinations of felling and yarding equipment
were used to thin eight of these units; no combination
was replicated. Two other units remained nonharvested
controls. Using a recording penetrometer, resistance was
measured to the 33-cm depth (13 inches) at ten stations
on 5–17 100-foot long, randomly oriented transects in
each unit. Ground-based harvesting equipment operated
on and off designated trails. Although trails occupied 6–
57% of the harvested units, total area of strong compac­
tion on these trails varied greatly (0–42%). Consequences
of soil compaction for tree performance at this sale area
are unknown. In fact, consequences of soil disturbance
for trees have seldom been measured in the Northwest.
At the relatively few places where trees were measured,
response to compaction ranged from mostly negative
through none to positive. Therefore, current claims about
dire consequences of compaction for long-term site pro­
ductivity must be based largely on limited sampling, as­
sumptions about the consequences of compaction for tree
performance, and speculation. We assert that uncertainty
about the consequences of compaction and other forms
of soil disturbance will remain until long-term tree perfor­
mance is correctly measured over a wide range of regional
soils and climatic.
Point 2. But, the consequences of soil disturbance for
subsequent tree performance have been measured only at
a limited number of locations, and usually for short peri­
ods.
Point 3. Yes, uncertainty about the actual consequences
of compaction (and other forms of soil disturbance) will
continue until tree performance is reliably measured over a
wide range of regional soils and climatic conditions and
for a long period of time. That is our concern and we will
suggest ways to collect such direct evidence.
POINT 1.
HARVESTING EQUIPMENT DISTURBS
THE SOIL (FRITZ TIMBER SALE)
Methods
• Sale layout. The eight harvested units and the two
nonthinned control units were 7–27 acres in size (Figs.
1 and 2). The dots represent starting points for randomly
oriented transects used to sample soil compaction.
Figure 1.—Units on flat terrain. Dots
are starting points for transects.
Keywords: commercial thinning, harvesting equip­
ment, soil bulk density, penetration resistance, penetrom­
eter, Northeast Washington
INTRODUCTION
We suspect that many of you have observed soil distur­
bance by heavy equipment used to harvest trees. You and
others are probably concerned that soil compaction, rut­
ting, or displacement of topsoil could reduce future tree
survival or growth. The scientific literature shares your con­
cern (Greacen and Sands 1980; Froehlich and McNabb
1984; Geist et al. 1989; Page - Dumroese et al. 1993; Wronski
and Murphy 1994).
In this presentation, we address concern about longterm soil capacity by supporting the following points:
Point 1. Yes, ground-based harvesting equipment used
to thin overstocked forests disturbs the soil over much of
the harvested area—to varying severity. To support this
point, we will report results from a soil investigation in
the recent Fritz Timber Sale on the Colville National For­
est.
Figure 2.—Units on steep
terrain. Cots are starting
points for transects.
Published in Small Diameter Timber: Resource Management, Manufacturing, and Markets proceedings from conference held February 25-27, 2002 in
Spokane, Washington. Compiled and edited by D.M. Baumgartner, L.R. Johnson, and E.J. DePuit. Washington State University Cooperative
Extension. (Bulletin Office, WSU, PO Box 645912, Pullman, WA 99164-5912. MISC0509. 268 pp.
98 Miller and Anderson
• Stand description. All units on flat terrain were in the
subalpine-fir type with about 900–1100 stems per acre
that averaged 5.0–5.9 inches d.b.h (Table 1). Of these
trees, 24–57% were cut. Units on steep terrain gener­
ally exceeded 30% slopes; the timber type was either
Douglas-fir or lodgepole pine. Before-thinning density
in steep units was about 440–800 trees per acre, less
than in the flat units, but mean d.b.h. averaged about
1 inch larger. About 53–69% of these trees were cut.
• Soils. Units on flat terrain included several soil series,
which ranged from low to high in their susceptibility
to compression when subjected to a load (Table 2). High
compressibility was related to finer soil textures (silt
loams); conversely low compressibility was associated
with sandy loam textures. Sandy loam textures were
more prevalent in the steep units.
• Harvesting methods. Different combinations of felling
or yarding equipment were used in each of the eight
commercially thinned units; no combination was rep­
licated (Table 3). Trees were felled by chain saw in only
one unit; trees in the remaining units were felled by
machines. Ground-based yarding equipment was used
on flat units and on one of the four steep units. Desig­
nated trails were spaced at either 40 or 130 feet (center­
to-center distance). Corridors for skyline cables re-used
some of the trails used earlier by either a feller-buncher
(that bunched whole trees) or a tracked harvester that
felled and processed cut-to-length logs for retrieval by
cable. Both the harvester and the feller-buncher had
extendable booms that enabled the operator to cut trees
within a 30-foot radius.
• Theoretical coverage of trail/corridors. Designated
trails were about 14 feet wide. Therefore, with a center­
to-center spacing of 40 feet, designated trails would
cover about 35% of the harvested area (Table 4). At this
trail spacing, both the feller-buncher and harvester
could fell nearby trees, yet remain on the trail. With a
designated trail spacing of 130 feet, however, the edge­
to-edge distance between trails was 116 feet (130 mi­
nus 14 feet). This would require equipment operators
either to move off designated trails or leave about a 60­
foot wide portion nonthinned. Note that fewest trees
were cut on Unit 2, where chainsaws were used to fell
trees.
• Measurement of soil strength (resistance to cone pen­
etration). Resistance to penetration was measured to
the 33-cm depth (13 inches) at ten systematically lo­
cated stations on 100-foot long, randomly oriented
transects (Fig. 3). There were 5–17 transects in each unit.
At nearly all stations, three profiles of soil resistance
were registered by a Rimik CP-20 cone penetrometer.
Data from these subsamples were averaged to obtain a
station mean for each 1.5 cm depth. Post-harvest mea­
surements were made that same summer or fall shortly
after each unit was harvested in 1998 on steep terrain
and in 1999 on flat terrain. The two control units were
sampled concurrently. The location of each station rela­
tive to skid trails was documented: Code 2 = skid trial
rut, Code 6 = beside or between ruts, and Code 0 = nontrail location. Some Code 6 sampling points could have
been on displaced soil.
• Measurement of soil bulk density. Fine-soil bulk den­
sity near the midpoint of the 0- to 7.5-cm depth was
measured before (summer 1997) and after harvest (fall
1999). Soil cores (68.7 cm3, 5.4 cm diameter) were col­
lected at systematic locations along transects but only
within units on flat terrain.
Table 1.—Site and stand characteristicsa
Unit
No.
Before
thinning
Mean
Area
slope
Forest type
Trees
ac
-1
Cut
b
Dq
in.
Trees
BA
Ac.
%
—%—
27
24
20
17
7
15
7
13
10
12
Subalpine fir
Subalpine fir
Subalpine fir
Subalpine fir
—
1101
1080
879
1025
—
5.2
5.9
5.0
5.9
—
24
49
33
57
34
56
46
54
8
12
16
18
17
31
36
33
25
40
Douglas-fir
Douglas-fir
Lodgepole pine
Lodgepole pine
Lodgepole pine
802
438
701
537
—
6.1
7.1
6.4
6.4
—
53
69
64
66
—
56
54
56
55
—
Flat terrain:
2
3
4
19
Control
Steep terrain:
8
9
16
17
Control
a
Trees 1.0-in. d.b.h. and larger. Source: Camp, A. Nonpublished data, Pacific Northwest Research
Station. Wenatchee Forestry Sciences Lab.
b
Dq = quadratic mean diameter = diameter of tree of average basal area; BA = basal area
Miller and Anderson 99
Table 2.—Soil series in flat and steep terrain, by unit; based on a soil survey by Zulauf
and Starr (1979).
Unit
No.
Parent material
Area
Series name
Cap
Base
Compressibilitya
%
Flat terrain:
2
3
4
19
Control
60
40
45
30
20
5
75
25
100
50
50
Neuske silt loam
Scar sandy loam
Nevine loam
Scar sandy loam
Gahee loam
Neuske silt loam
Neuske silt loam
Scar sandy loam
Scar sandy loam
Nevine loam
Gahee loam
silty till
till
ash
till
ash
silty till
silty till
till
till
ash
ash
silty till
till
compact till
till
outwash
silty till
silty till
till
till
compact till
outwash
H
L
M
L
L
H
H
L
L
M
L
Merkel sandy loam
Merkel sandy loam
Rock land
Merkel sandy loam
Rock land
Merkel sandy loam
Nevine loam
Merkel sandy loam
ash
ash
—
ash
—
ash
ash
ash
granitic till
granitic till
—
granitic till
—
granitic till
granitic till
granitic till
L
L
L
L
L
L
M
L
Steep terrain:
8
9
16
17
Control
a
100
50
50
50
50
80
20
100
H=high, M=moderate, L=low
Table 3.—Harvesting equipment; designated trails corridors were 14-feet wide with center-to-center spacings of 40 or
130 feet.
Terrain and
unit
No.
Area
Ground-based
Tree felling
Processing to logs
Equipment
ac
Flat (7-15 % mean slopes):
2
3
4
19
27
24
20
17
Chain saw
Harvester
Feller-buncher c
Feller-buncher
Forwarding-yarding
Cable system
Spacing
Skylinea
ft
Corridor spacing
ft
Harvester b
Harvester
Whole tree
Harvester
Forwarder c
Forwarder
Skidder c
Forwarder
130
40
130
130
--­
---
-­
Harvester
Harvester
Whole tree
Harvester
-Forwarder c
---
40
40
40
40
Uphill
—
Downhill
Downhill
80
-­
40
80
-­
-­
Steep (25-36 % mean slopes):
8
9
16
17
a
8
12
16
18
Harvester f
Harvester
Feller-buncher d
Harvester
Skagit model 333 yarder, adapted with a third drum; Christy haul-back carriage
Tracked Kabelco model 200 single-grip harvester with Kato 500 saw head; cut logs to length (CTL)
c
Rubber-tired Valmet model 892 forwarder (14-ton capacity)
d
Tracked Timbco model 445 B feller-buncher with Quadco Hot-Saw felling head on an extendable boom
e
Rubber-tired Cat model 518 skidder with swinging grapples
f
Tracked Valmet model 500T single-grip harvester (with tilting cab); cut logs to length (CTL)
b
100 Miller and Anderson
Table 4.—Designated trails: theoretical coverage
Spacing between
Width
Centerline
Edges
Needed
Percentage of harvest area
reach
(width ÷ CL distance)
- - - - - - - - - - - - - - - Feet - - - - - - - - - - - - - - ­
14
%
40
26
13
35
130
116
58
11
Figure 3a.—Designated trail with slash place by a trackedharvester.
Figure 3b.—Soil strength was measured by a cone penetrometer.
Figure 3c.—The general terrain of the Fritz Timber Sale.
Miller and Anderson 101
• Bulk density in surface soil of flat terrain (trail vs.
non-trail portions). Among the four harvested units
on flat terrain, fine-soil bulk density on trails averaged
3–14% greater than that in non-trail portions (Table 6).
Note that the USFS. Northwest Region’s standard for
judging compaction as detrimental is a 20% or more
increase in BD of soils derived from volcanic ash or pum­
ice (USFS 1998). By this standard, average compaction
on the trails in flat units was not detrimental. Because
some of the non-trail portions also could have been
compacted, we calculated a 20% increase in the mean
before-harvest BD as our threshold standard. Based on
this standard, 15% of unit 19 had “detrimental” com­
paction.
Results (from Fritz)
• Percentage of area in trails, by equipment combina­
tions. We have two independent estimates of the com­
bined area in designated and supplemental trails (Table
5). The first is based on the percentage of all sampling
stations (10 per transects) that fell in or near trail ruts
(Codes 2 and 6). By this estimate, 6–57% of the unit
areas were in trails. The second estimate was based on a
similar number, but different 100-foot long transects
in each unit. Where these transects crossed machine
trails, the intercepted distance was expressed as a per­
centage of total transect length (Tepp, in review). Trails
occupied 12–38% of the harvested area based on this
second estimate.
Table 5.—Percentage of thinned area in trails, by unit.
Terrain
Harvesting equipment
and unit
Trail
Penetrometer
Monitoring transects a
spacing
transects
Trails
No. % of stations
No.
Difference
% of total length
Flat:
2
3
4
19
Chain saw, harvester, forwarder
Harvester, forwarder
Feller-buncher, whole-tree skidder
Feller-buncher, harvester, forwarder
130
40
130
130
13
14
10
8
21
57
17
39
13
14
10
8
12
29
28
38
-10
-13
3
-1
Harvester, uphill skyline
Harvester, forwarder
Feller-buncher, whole-tree, downhill
Harvester, downhill skyline
40
40
40
40
10
15
14
18
6
18
27
13
14
16
14
17
19
28
25
30
13
10
-1
17
Steep:
8
9
16
17
a
Total transect lengths per unit range from 800 to 1700 feet. Adapted from Tepp (in review).
Table 6.—Fine-soil bulk density after harvest in the 0- to 7.5-cm mineral soil depth in trails (ruts and adjacent soil) vs.
other portions, in flat terrain.
Visual strata
Trails
Unit
No.
Sta.
No.
Non-trail
Mean
SE a
-3
— Mg m —
%
Sta.
No.
Difference
Mean
SE a
-3
— Mg m —
%
Absol
Mg m-3
Rel
%
2
Chain saw, harvester, forwarder
25
0.851
0.000
0.0
100
0.782
0.024
3.1
0.069
8
3
Harvester, forwarder
74
0.695
0.015
2.2
57
0.676
0.020
3.0
0.019
3
Feller-buncher, whole-tree skidder
29
0.816
0.044
5.4
65
0.701
0.025
3.6
0.115
14
Feller-buncher, harvester, forwarder
30
0.823
0.046
5.6
48
0.763
0.029
3.8
0.060
7
4
19
a
Equipment
SE = standard error of mean; derived from nested ANOVA (2-stage sampling)
102 Miller and Anderson
• A few 70-year-old trails of a former fire-salvage sale
were readily identifiable in some units on steep terrain
by paucity of vegetation and shallow ruts. Lateral berms
were absent or indistinct, so topsoil displacement was
less evident. Soil in trails remained compacted, espe­
cially below the 5-cm depth (Fig. 4); however, maxi­
mum resistance was less than 1500 kPa. Note that 2000–
3000 kPa is generally considered detrimental to root
growth (Powers et al. 1998).
kPa. Our sample size was large, 32–58 sampling sta­
tions per coded condition.
* Figure 6. Trails in unit 4 were designated at 130-foot
intervals. Therefore, the feller-buncher had to leave
designated trails to fell intervening trees, which were
then yarded as whole trees with a rubber-tired skidder.
About 75% of the unit was Neuske silt loam, a highly
compressible soil. Note the large difference in soil re­
sistance at stations associated with trails (ruts and
adjacent soil) compared with off-trail stations. Note
also that resistance generally exceeded 2000 kPa at
lower depths, but this root-restricting resistance was
close to the surface in the trails.
Figure 4.—Average soil resistance in steep unit 17, by location of
sampling station (3 subsamples per station). Note the residual
mean compaction in 70-year-old trails of a former salvage sale.
• Soil resistance increased after recent thinning in the
Fritz Sale (Figs. 5 and 6). The increase was greater in the
finer textured soils of the flat terrain than in sandier
textures on slopes.
* Figure 5. Unit 3 had designated trails at 40-foot spac­
ing; therefore, the harvester could readily cut trees in
the intervening portions and pile logs along the trail.
A rubber-tired forwarder transported these logs to the
landing. Note the much greater resistance in the ruts
(tracks) especially at 5-cm and lower depths. Note also
that below 20 cm, average resistance exceeded 2000
Figure 5.—Average soil resistance in flat unit 3 after harvester-for­
warder combination and 40-foot trail spacing (center-to-center).
Note greater resistance in the tracks than in adjacent soil, some
of which could be displaced berm.
Figure 6.—Average soil resistance in flat unit 4 after combination
of felling by a feller-buncher and whole-tree skidding; 130­
foot trail spacing. Note resistance at stations in trails (ruts and
nearby soil) exceeded 2000 kPa close to surface.
* Note that different combinations of equipment were
assigned to each unit. This lack of true replication pre­
cludes statistical testing to indicate which equipment
provides the least impact on soil. Although we used
different methods to assess soil compaction after har­
vesting (Landsberg et. al., pending review), we pro­
vide only the post-harvest comparisons in this pre­
sentation.
* Trail vs. nontrail. This method of comparison equals
the usual, retrospective (after-harvest) monitoring in
which one samples soil on trails and compares these
estimates of soil resistance or bulk density to corre­
sponding estimates from non-trail portions. When
interpreting retrospective results, one must verify or
assume (1) that trails were placed on soils representa­
tive of the remaining portions (soils were similar), (2)
that soil moisture conditions on and off trails were
similar when sampled, hence (3) that differences can
be explained by equipment impact (a typical moni­
toring question). Based on this after-harvest moni­
toring, we note that average resistance in trails of only
one of eight units exceeded the proposed standard
defining detrimental resistance (Table 7). Of the sta­
tions located on trails, 0–70% had penetration resis­
tance equal to or exceeding 2000 kPa on the 15- to
25-cm depth. This equated to as much as 40% of Unit
3 being detrimentally compacted (Fig. 7).
Miller and Anderson 103
Table 7.—Average difference in after-harvest soil resistance on trails (ruts and adjacent soil) versus non-trail portions, by
unit and depth in mineral soil.
Terrain
and
Unit
Equipment
Trail
Flat:
2
3
4
19
Standard zone a (15-25 cm)
Surface soil (0-10 cm)
Non-trail
Difference
———— kPa————
Chain saw, harvester, forwarder
Harvester, forwarder
Feller-buncher, whole-tree skidder
Feller-buncher, harvester, forwarder
All
Mean
%
Trail
Non-trail
Difference
———— kPa ——— —
%
1682
1257
1890
1514
852
1092
890
1058
830
165
1000
456
97
15
112
43
1926
2258
2976
2198
1720
2192
1803
1714
206
66
1173
484
12
3
65
28
1586
973
613
63
2340
1857
483
26
627
887
790
717
816
754
-90
71
36
-13
9
5
794
1416
1058
888
989
850
-94
427
208
-11
43
24
1046
757
289
38
1396
986
383
35
838
761
77
10
1166
928
238
26
Steep:
8
9
16
17
All
a
Harvester, uphill skyline
Harvester, forwarder
Feller-buncher, whole-tree,
downhill skyline
Harvester, downhill skyline
Mean
Dr. Robert Powers (PSW Research Station, USFS) has proposed to the U.S. Forest Service (Pacific Southwest Region, Region 5) that
detrimental soil damage be defined as a 500 kPa or more increase in soil strength (15- to 25-cm depth in mineral soil).
Figure 7.—Percentage of harvested area in
trails (ruts and nearby soil) and with pen­
etration resistance of 2000kPa or more in
the 15- to 25-cm depth of trails, by unit
number. Additional non-trail area could
have compacted soil.
Conclusions from the Fritz Timber Sale
1. Among the eight thinned units that we investigated, 6–57% of the harvested area was in designated and supplemen­
tal trails. Supplemental trails were made where equipment had to leave widely spaced (130 ft) designated trails to fell
intervening trees.
2. Extent and severity of compaction was greater on flat units, where all yarding was by forwarders or skidders and
where three of four units had soils of silt loam or loam textures.
3. Consequence of this disturbance to tree performance is unknown. Will this be assessed in the future?
104 Miller and Anderson
• The linkage between soil disturbance and tree performance (the variable needed for economic analysis) must
be quantified to know the practical consequences of
soil compaction.
POINT 2.
THE CONSEQUENCES OF SOIL
DISTURBANCE FOR SUBSEQUENT
TREE PERFORMANCE ARE
SELDOM MEASURED
• East of the Cascades. All east-side studies are based on
data collected 8–64 years after overstory removal or
clearcutting (Table 8). Effects of trails in eastside com­
mercial thinnings on residual tree growth have not been
reported. Note that all investigations are retrospective
rather than controlled-treatment.
Table 8.—Eastside: Investigations of tree growth on skid trails vs. off skid trails, by type of harvesta.
Area and species
Locations
Soil texture
No.
Tree age
Source
years
Thinning: no reports
0
—
Overstory removal:b
WA, ponderosa pine
3
loamy (ash)
9-18
WA, lodgepole pine
OR, ponderosa pine
1
1
ashy
sandy loam
11
64
Clear cutting:
OR, ponderosa pine
1
loamy
8
a
Results
—
N. ID, ponderosa pine 1
silt loam (ash)
20-25
N. ID, lodgepole pine 2
silt loam (ash)
15-19
BC, conifers
BC, conifers
BC, conifers
BC, Engleman spruce
4
5
3
3
loam to silt loam 16-18
loamy (calcareous) 9-22
sandy (acid)
9-22
sandy loam
9-10
BC, lodgepole pine
3
sandy loam
9-10
—
-20 % stem volume
-5 % tree height
0 % volume, tree height
-6 % to -12 % tree BA growth
- 38 % tree height
(at + 20 % increase in BD)
-20 % d.b.h. (displacement)
-10 % d.b.h. (compaction)
-22 to-25 % d.b.h. (compaction)
15 to -25 d.b.h. (displacement)
-14 to +4 % tree height
-12 to-15 % height
+18 to 22 % height
tree volume least on track,
most on berm
tree volume least on track
at two locations and most
at one location
None
Froehlich et al. (1986)
Froehlich et al. (1986)
Froehlich (1979)
Cochran and Brock (1985)
Clayton et al. (1987)
Clayton et al. (1987)
Smith and Wass (1980)
Smith and Wass (1979)
Smith and Wass (1979)
Senyk (2001)
Senyk (2001)
Skidroads, not trails, were investigated in BC. These roads are bladed into steep slopes. Growth usually differs with position on
running surface and sidecost (cut, track, fill).
b
The influence of residual overstory trees on growth of younger, measured trees complicates inferences about skid-trail effects.
Miller and Anderson 105
POINT 3.
WHAT EVIDENCE IS RELIABLE
FOR JUDGING RISK TO
LONG-TERM SITE PRODUCTIVITY?
• Conventional soil monitoring (“effectiveness” moni­
toring of USFS) has an area and severity standard. Sev­
eral types of soil disturbance are recognized in addition
to compaction. Compaction severity that exceeds a
specified threshold (e.g., 20% increase in bulk density)
is considered “detrimental” compaction; this “counts”
as a risk to soil capacity or quality (Fig. 8). The com­
bined, estimated area of “detrimental” disturbances
should not exceed 20% of the total (gross) harvested
area, including the permanent roads which obviously
remove land from production (USFS 1998).
* Tree monitoring (termed “validation” monitoring by
the USFS) would test this assumed linkage between tree
performance and changed soil properties.
* For example, one would measure:
• Seedling survival and early growth; this is simplest
to do and indicative of short-term effects
• Growth of residual trees after thinning or partial
cutting; this is more difficult to accomplish
• Cubic volume yields per acre in mature stands; the
most difficult to estimate, but the definitive mea­
sure
* We assert that monitoring tree growth
• Provides the necessary direct evidence for judging
risk to long-term site productivity
• Can indicate which type, severity, and pattern of
soil disturbance really affects tree performance
SUMMARY
Point 1.
Increased soil resistance after harvesting at the Fritz Tim­
ber Sale are consistent with results from other investiga­
tions. Ground-based harvesting equipment used to thin
these overstocked forests disturbed soil over much of the
harvested area. Estimated combined area of severe com­
paction (> 2000 kPa) varied greatly among the eight units
(0–42%).
Point 2.
Relative to the millions of acres of commercial forest in
the Inland West, the consequences of soil disturbance for
subsequent tree performance have seldom been measured.
Without local experience and longer periods of observa­
tion, current claims about dire consequences of soil com­
paction to long-term site productivity must be based largely
on assumptions, circumstantial evidence, and speculation.
Point 3.
Figure 8.—Percentage of harvested area in trails and with a 20% or
more increase over average preharvest bulk density (0 to 7.5
cm depth) in specified harvest unit.
* At Fritz (8 units)
• 6 to 42 % of the thinned area was in trails and cor­
ridors
• We detected compaction (increased soil resistance)
on these trails, but was it really “detrimental” to soil
capacity to grow trees?
* Soil monitoring:
• Provides numbers indicating the types, severity, and
coverage of soil disturbance
• Provides indirect evidence: soil properties are
changed. From this circumstantial evidence, many
assume that tree performance will be reduced; But
performance can also be increased on compacted soil
in some situations (Powers and Fiddler 1997)
Uncertainty about the consequences of soil compaction
and other forms of soil disturbance will remain until tree
performance is reliably measured over a wide range of re­
gional soils and climatic conditions, and over a long pe­
riod of time.
Take-away Message:
If you are concerned about tree performance,
then collect direct evidence—measure trees.
ACKNOWLEDGMENTS
We became involved with the Creating Opportunities
project (CROP) after Dr. Joan Landsberg retired from USFS.
We summarized data (collected by Forest Service crews from
Wenatchee Lab) and are preparing reports for publication.
We thank the CROP and Dr. Landsberg for the opportu­
nity to complete this work. We are also grateful to Jeffery
Tepp for the orderly transfer of data files and assorted
records, to John Senyk and Andrew Youngblood for tech­
nical review, and to Sherry Dean for helping prepare our
visual presentation.
106 Miller and Anderson
LITERATURE CITED
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clearcuts. Res. Note INT-372. U.S. Department of Agri­
culture–Forest Service, Intermountain Research Station,
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Froehlich, H.A. 1979. Soil compaction from logging equip­
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Froehlich, H.A., D.W.R. Miles, and R.W. Robbins. 1986.
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on compacted soils in central Washington. Forest Ecol­
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physical conditions of some Pacific Northwest volca­
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soils: A review. Australian Journal of Soil Research 18:
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Long-Term Soil Productivity Study: progress through
the first 5 years. In: Proceedings, Eighteenth Annual
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Management Conference, Redding, CA.
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cent to contour skidroads in the subalpine zone, south­
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BC. 26 pp.
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Ouwerkerk, C. (eds.). Soil compaction in crop produc­
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Authors
Dick Miller, Retired
USDA Forest Service-PNW Research Station
Forestry Sciences Laboratory
3625 93rd Ave. SW
Olympia, WA 98512-9193
360-956-2345 ext 669
millersoils@aol.com
Harry Anderson
USDA Forest Service-PNW Research Station
Forestry Sciences Laboratory
3625 93rd Ave. SW
Olympia, WA 98512-9193
The use of trade or firm names in this publication
is for reader information and does not imply
endorsement by the US Department of Agriculture
of any product or service.