United States

Department of

Agriculture

Forest Service

Pacific Northwest

Research Station

General Technical

Report

PNW-GTR-510

April 2001

Log and Lumber Grades as

Indicators of Wood Quality in

20- to 100-Year-Old DouglasFir Trees from Thinned and

Unthinned Stands

R. James Barbour and Dean L. Parry
Authors R. James Barbour is a research forest products technologist and Dean L. Parry is a

forester, Forestry Sciences Laboratory, P.O. Box 3890, Portland, OR 97208.
Barbour, R. James; Parry, Dean L. 2001. Log and lumber grades as indicators of

wood quality in 20- to 100-year-old Douglas-fir trees from thinned and unthinned

stands. Gen. Tech. Rep. PNW-GTR-510. Portland, OR: U.S. Department of

Agriculture, Forest Service, Pacific Northwest Research Station. 22 p.

This report examines the differences in wood characteristics found in coastal Pacific

Northwest Douglas-fir (Pseudotsuga mensziesii (Mirb.) Franco) trees harvested at the

age of 70 to 100 years old to wood characteristics of trees harvested at the age of 40

to 60 years. Comparisons of differences in domestic log grades suggest that the proportion of log volume in the higher grades (Special Mill and No. 2 Sawmill) increased

with both stand age and tree size. Simulation of lumber grade yields based on log

characteristics suggests that yields of higher grades of lumber increased until about

age 60 to 70, and then leveled off over the rest of the age range examined in this

analysis. We included structural lumber products in the analysis but not higher value

appearance grade products, and some evidence suggests that yields of these products might have begun to increase in the oldest trees. The analysis also showed that

the younger trees had larger branches and more juvenile wood, possibly because

they had been grown in stands that received a higher level of early stand management than the older trees. If these young trees were grown to the ages of 70 to 100,

they likely would not produce the same log and lumber grade yields found in the older

trees we examined.

Keywords: Wood quality, log grade, lumber grade, thinning, Douglas-fir, Pseudotsuga

mensziesii, ecosystem management, sustainable forestry.

Abstract
Contents 1 Introduction

2 Objectives

3 Methods

4 Source of Data

4 Method of Comparison

5 Field Data Collection

6 Estimated Log Grade Yields

7 Estimates of Lumber Grades

8 Results and Discussion

8 Log Grades

14 Relative Importance of Log Grading Criteria

16 Lumber Yields

18 Conclusions

20 Acknowledgments

20 Literature Cited
1

Introduction In recent years, most landowners in the coastal Pacific Northwest have begun to

place greater emphasis on conserving biodiversity in their management practices.

There are, however, important distinctions in the objectives of the various landowners.

Whereas most federal lands and some other public lands are now managed primarily

to maintain or restore ecological function, with wood production being a secondary

objective, wood production is still the primary objective for most private landowners of

industrial and large nonindustrial land. There are many variations on these broad

themes, but in general, this divergence in objectives results in relatively long rotations

to promote old-forests characteristics on public land and relatively short rotations to

enhance the economic returns from wood production on large private land holdings.

Most managers of industrial and large nonindustrial land holdings have adopted stand

management practices that involve planting and precommercial thinning1 followed by

either a commercial thinning or clear felling by about age 40. The first commercial

entry is highly dependent on market conditions. It may replace a precommercial thinning at about age 20 if pulp or chip markets are good, or it may not occur until about

age 40, but in most cases, clear felling usually occurs no later than age 60. Port Blakely

Tree Farm in Seattle, Washington, is a moderate size, private owned company that

uses a different strategy. On some of the Port Blakely land, Douglas-fir (Pseudotsuga

menziesii (Mirb.) Franco) is managed on 70- to 100-year rotations under silvicultural

regimes that may involve multiple thinnings. The regimes used by Port Blakely are

similar to management activities anticipated for some USDA Forest Service and USDI

Bureau of Land Management (BLM) land designated as “matrix” or during the period

when active management is allowed in “late-successional reserves” under the

Northwest Forest Plan (NWFP) for the recovery of the northern spotted owl (USDA

and USDI 1994).2 These management techniques also might interest other landowners,

of both large and small parcels, who want to create stand characteristics that differ

from those found in typical industrial plantations but who still consider timber harvest

an important land management objective (Curtis and others 1998).

The analysis described here was undertaken as a cooperative project between Port

Blakely Tree Farm and the USDA Forest Service, Pacific Northwest (PNW) Research

Station. We evaluated those differences in wood characteristics likely to exist in

Douglas-fir stands managed on shorter (40- to 60-year) and longer (70- to 100-year)

rotations. Potential log and lumber quality for trees removed as early as 20 years,

which might be expected during early commercial thinning, and trees removed at up

1 Under some market conditions, thinned material is sold for chips,

whereas under others it is left on the site.

2 The matrix land allocation under the Northwest Forest Plan for

the recovery of the northern spotted owl (NWFP) “...is the area in

which most timber harvest and other silvicultural activities will be

conducted.” Late-successional reserves are intended to “...maintain

a functional, interactive, late-successional and old-growth forest

ecosystem. They are designed to serve as habitat for late-successional and old-growth related species including the northern

spotted owl.”
to 100 years are considered. Economic analysis is not performed in this report

because (1) the economics of wood production is not a primary concern under the

NWFP, and (2) firms interested in this information will conduct their own economic

analyses using proprietary financial data. This report should, however, provide sufficient information about wood characteristics for those interested in conducting economic analyses.

Data for the analysis came from two sources: (1) new data, collected from a sample

of trees harvested from two Port Blakely thinning trials in naturally regenerated

Douglas-fir stands on site II+ (King 1966) land in southwestern Washington and (2)

existing data drawn from a database of tree, log, and lumber characteristics maintained by the Ecologically Sustainable Production (ESP) of Forest Resources team of

the PNW Research Station (Stevens and Barbour 2000). The trees used for this

analysis came from studies conducted by the ESP team in collaboration with a consortium of public and private landowners known as the Stand Management Cooperative (SMC) (see Fahey and others 1991). These trees are referred to as the SMC

trees.

Curtis (1995) and Stinson (1999) give details about the stand characteristics and the

treatment history for the Port Blakely thinning trials. The older installation, designated

by Port Blakely as XT-1, was established in a 47-year-old stand in 1948 and harvested at age 95. Curtis (1995) characterizes the thinning regime as light. The younger

installation, known as XT-7, was established in a 42-year-old stand in 1958 and harvested at age 80. Curtis (1995) characterizes the treatment of this installation as a

heavy thinning. Trees were removed from the Port Blakely thinning trials in summer

1996 to determine various wood characteristics. The sample of SMC trees represents

trees that are about the same age as the Port Blakely trees. In addition, the SMC

trees include a sample of younger trees intended to provide a comparison with

current management practices being used on private land in western Washington

and Oregon.

The objectives of this analysis were developed to provide information that is useful to

both public and private resource managers interested in understanding the influence

of stand age and management history on wood characteristics. The objectives were to:

1. Make qualitative comparisons of the characteristics of trees grown on Port

Blakely’s XT-1 and XT-7 thinning trials to trees in various age classes that represent typical management practice on industrial forest land in western Washington

and Oregon (SMC trees). We compared:

a. Log and lumber grade yields of thinned and unthinned portions of each XT 

thinning trial

b. The characteristics of trees grown on the XT thinning trial to those of SMC 

trees of similar ages

c. The characteristics of both the Port Blakely trees and older SMC trees (80 to 

100 years) to those of younger SMC trees (20 to 60 years)

2. Develop a better understanding of the likely wood characteristics of trees grown

under the longer rotation mandated for some lands under the NWPF for matrix

land (USDA and USDI 1994).

2

Objectives
3

Methods The three measures of wood quality considered in this analysis are (1) log grade, 

(2) visual lumber grades, and (3) machine stress-rated (MSR) lumber grades. These

measures were chosen because they can be evaluated directly to compare product

potential of each group, and because price series are readily available for each product (Anderson 2000, Barr 1998, Warren 1998), thereby making it easy for others to

conduct economic analyses by using the product yield information provided in this

analysis. Only structural products were considered because self-pruning does not

typically occur in Douglas-fir stands until age 60 to 80 (Kachin 1940), and thus even

the oldest trees used in this analysis had insufficient time to produce appreciable

amounts of clear wood.

The available data sets are not ideal for this analysis because many of the trees were

originally collected for other purposes. Not all of the records for the trees included in

the analysis contained all the information needed to produce grades under all three

systems. The data sets are, however, adequate to make reasonable estimates of log

grades by using techniques developed by Christensen (1997). Christensen’s (1997)

techniques use diameter at each buck point, measurements of branch size by using a

modified height pole and caliper, and estimations of growth rate. Simulation of lumber

grade yield is also possible by using regression models developed by Fahey and others

(1991). Although estimated log grades and simulated lumber yields do not provide an

exact description of wood characteristics in these trees, they do allow reasonable

comparisons among the various age classes and management intensities.

At each of the two Port Blakely installations, 25 sample trees were selected systematically across the full range of diameters present on the unthinned and thinned permanent sample plots. This process resulted in selection of 50 trees from each thinning

trial for a total of 100 Port Blakely trees. An additional 289 trees were selected from

two earlier SMC studies (Barbour 1995,3 Fahey and others 1991) by using the ESP

tree quality database (table 1).

The criteria used for selecting an SMC tree were that (1) tree age (from 21 to 100

years) and (2) sufficient data (enough data had to be available about a tree to estimate the log or lumber grades used in the analysis). The two previous SMC studies

included trees from 20 locations throughout western Washington and Oregon. The

objectives of these studies and the tree selection criteria were similar in that they

focused on site class I or II land and trees grown in either natural stands or plantations managed for rapid wood volume production. We believe this sample represents

the existing resource on private land, but most Forest Service and BLM land has a

much lower site class. Consequently, site class should always be considered

before extrapolating results to federal ownerships. We believe that the similarity in

sites, management history, and selection criteria made it reasonable to combine trees

from the two studies. Trees included in these two studies were selected systematically

to represent the range of variation in diameter and branch size and should not be

regarded as random samples. For this reason, generalized inferences should not be

Source of Data

3 Study conducted in cooperation with the SMC.
4

made from analyses presented here. The analyses do, however, provide a qualitative

description of the way wood characteristics change in different-aged trees and how

the trees from the Port Blakely installations fit into the continuum of changing quality

with age that can be constructed from the trees in the ESP tree quality database

(Stevens and Barbour 2000).

Data were organized into a set of eight analytical groups, the thinned and unthinned

sample from each of the two Port Blakely XT installations and the SMC trees divided

into four age classes (table 1). The designations used for the Port Blakely trees are

95-UT, 95-TH, 80-UT, and 80-TH. They refer to the approximate age at which the

installation was harvested4 and type of treatment, thinned (TH) or unthinned (UT).

The SMC age classes are designated as 21-40, 41-60, 61-80, and 81-100 to reflect

the harvest ages of the trees included in each class.

The treatments at the Port Blakely installations were unreplicated, and the grouping

of the SMC trees is by age class rather than by stand. Although artificial, these groupings are thought to represent the population of Douglas-fir managed under similar

conditions. The response variables for this analysis were generated either by combining empirical data on the morphological characteristics of logs or by using regression

models developed elsewhere to estimate lumber grades. Consequently, comparisons

described in this analysis are based on interpretations of tables and graphs of the

averages for each group rather than statistical analysis of the variation among the

groups.

4 Based on estimated stand initiation date. Average stump ring

counts for the sample trees are shown in table 1.

Method of Comparison

Table 1—Source, naming, average age, and sample size of trees used to make

up the analytical groups compared in this analysis

Source of 

trees and Treatment or Mean 

analytical groupa age class (years) stump age Number of trees

Years

Port Blakely:

95-UT XT-1 (UT) 91 25

95-TH XT-1 (TH) 93 25

80-UT XT-7 (UT) 72 25

80-TH XT-7 (TH) 73 25

Stand 

Management 

Cooperative:

21-40 21-40 32 124

41-60 41-60 49 113

61-80 61-80 64 41

81-100 81-100 86 11

a UT = untinned; TH = thinned.
5

Field Data Collection

The Port Blakely trees were compared by installation and treatment. The type of

grouping used for the SMC trees was chosen because commercial thinnings tend to

fall into the 21- to 40-year age class, second thinnings and clear felling on private

land tends to coincide with the 41- to 60-year age class, and one of the Port Blakely

installations falls into each of the next 20-year age classes. On national forests and

BLM land, the final thinning in late-successional reserves will occur between ages 60

and 80, and harvests from the “matrix” land could fall into any of these classes

(USDA and USDI 1994).

When the Port Blakely trees were felled and bucked, each log was labeled with a

unique number that identified the treatment (TH or UT), tree from which the log came,

and position the log came from within the tree. Stump ring counts were taken to

determine tree age. Woods length logs were moved to a paved log yard where additional measurements were made including large-end diameter, small-end diameter

(SED), and midpoint diameter inside bark, as well as diameter inside bark 4 feet from

the large end of each butt log. Large-end, small-end, and juvenile wood diameter for

each log were measured according to standard scaling procedure, which uses the

average of the smallest cross-sectional diameter and a diameter measured at 90° to

the smallest diameter. Midpoint diameter of the Port Blakely logs was measured outside the bark. Bark thickness was measured to the nearest 0.1 inch and subtracted

from the diameter outside the bark to obtain diameter inside the bark. Other measurements included bark thickness at each buck point, number of rings on the large and

small ends of each log, branch index (BIX) for each mill length log, and juvenile core

diameter on the large and small ends of each woods length log. Branch index was

calculated as the average of the largest diameter knot in each of the four quadrants

(90°s of circumference) of the log surface. The juvenile wood core was estimated as

the diameter of the first 20 growth rings from the pith on each end of each woods

length log. This method was used to estimate juvenile wood because it is a required

input for the Fahey and others (1991) MSR lumber grade yield models.

Port Blakely trees were bucked to preferred woods length logs of 35 feet to an 8-inch

top. Stand Management Cooperative trees were bucked into 40-foot woods length

logs with a minimum top diameter of 4 inches. Lengths differed because Port Blakely

manufactured their logs for export, whereas the SMC trees were processed for the

domestic market. Analysis of log grades is based on woods length logs. Analyses of

lumber grade yields are based on mill length logs. The Port Blakely logs were sold

full length so data for the lumber analysis was taken on “pencil-bucked” mill length

logs. This was generally one 20- and one 14-foot log except when a short woods

length log was produced because of a falling break, some other defect, or short top

logs. Stand Management Cooperative woods length logs were bucked into mill length

logs and sawn into lumber (Fahey and others 1991; Barbour and others [see footnote

3]). In both SMC studies, the preferred mill length log was 20 feet, but shorter logs

also were produced when woods length logs were not full length or contained a

break or defect.
6

Log grades were not recorded in the field, but estimated grades were developed for

each woods length log. Methods for log grade assignment basically follow those

developed by Christensen (1997) for estimating log grade in standing trees.

Christensen’s (1997) methods are similar to those pioneered by Gaines (1962) and

refined by Lane and Woodfin (1977), except that Christensen (1997) includes actual

measurement of branch size in the lower portion of the stem and growth rate at

breast height. Differences in the methods used in this analysis included direct

measurement of branch size and growth rate for all logs because the trees were

felled, which made log ends and branch stubs accessible. Estimated grades were

based on the small-end diameter, branch size, growth rate in the outer portion of

the log, and minimum length (table 2).

Growth rate in the outer portion of the log was estimated for both Port Blakely and

SMC woods length logs by subtracting the radius of the juvenile core (first 20 rings

from the pith) from the total radius and dividing the result by the number of rings in

the mature wood portion of the log (equation 1). This was done for both ends of the

log and averaged. Although this is not exactly how growth rate is defined in the log

grading rules (Northwest Log Rules Advisory Group 1998), it is sufficient to obtain

an adequate estimate of the growth rate (GR),

GR = Total ring count - 20, (1)

rm

where

Total ring count is the number of rings in the large or small end of the mill length log,

20 is the number of rings in the juvenile core, and

rm is the radius of the mature wood portion of the log calculated as the radius of the

log minus the radius of the juvenile core.

Estimated Log Grades

Table 2—Criteria used to estimate log gradesa

Log grade

No. 2 No. 3 No. 4

Grading criteria Special Mill Sawmill Sawmill Sawmill

Minimum rings per inch

outer portion 6 rings per inch None None None

Minimum scaling diameter 16 inches 12 inches 6 inches 5 inches

Maximum branch diameter 1.5 inches 2.5 inches 3 inches None

Minimum length 17 feet 12 feet 12 feet 12 feet

a These criteria follow the Northwest Log Rules Advisory Group (1998) rules except for the branch frequency

requirements for Special Mill and net scale requirements for all grades. Failure to include the net scale

requirement is most important for No. 4 Sawmill logs because in practice, larger logs with high defect levels

are placed in this grade. In this analysis, only small logs or those with large branches were graded as No.

4 Sawmill.
7

The maximum branch diameter was taken as the largest of the four measurements

made on each woods length log segment for calculating BIX. The Special Mill grade

has an additional branch frequency requirement (Northwest Log Rules Advisory

Group 1998, p.11). This feature could not be included in this analysis because no

branch frequency data were collected. We may therefore have overestimated the

number of Special Mill logs.

An SAS program (SAS 1995) was written to sort and grade logs. There was insufficient information to grade either peelers or No.1 Sawmill logs. The protocol was to

first sort logs by diameter (those 16 inches and greater for Special Mill) then by knot

size. Those that met both the diameter and knot size restrictions for Special Mill were

then tested to ensure that growth rate was less than six rings per inch and that logs

met the appropriate length requirement. Logs failing to meet requirements for Special

Mill were tested as No. 2 Sawmill logs and so on (table 2).

No adjustment in log grade was made for net scale because the logs from the Port

Blakely trees were not scaled. Field observations revealed little defect or deformation

in these logs, but because the defects were not recorded, they could not be included

in the log grading protocol. The methods used to assign grade restricted the No. 4

Sawmill grade to logs with an SED of less than 6 inches. In reality, larger defective

logs, with low net scale volumes, also are placed in this grade. This illustrates a shortcoming in the analysis because some defective larger logs could in theory have been

graded as other than No. 4 Sawmill. On the other hand, even the oldest stands in this

study are relatively young in terms of the biological capability of Douglas-fir. Stands in

this age range typically would not display high levels of defect. The PNW Research

Station over the past 30 years has analyzed many logs from several Douglas-fir wood

product recovery studies to evaluate the importance of the net scale requirement.

This evaluation was accomplished by using the database described by Stevens and

Barbour (2000). The results suggest that the average defect in trees younger than

100 years old is always less than 5 percent of the gross scale volume and usually

much less than that. So we feel that the grading system used here adequately represents log grade for the purposes of this analysis.

Estimates of visual and MSR lumber grade yields for each mill length log (8 to 20

feet) from both the Port Blakely and the SMC trees were made by using grade recovery models developed by Fahey and others (1991). These estimates are based on the

BIX for visual grades and BIX and juvenile wood percentage for MSR grades.

Selection of lumber grades—The visual lumber grades reported in this analysis

are those included in the structural joists and planks for 6-inch and wider lumber or

Structural Light Framing grades for 4-inch wide lumber (WWPA 1991). The MSR lumber grades are 2100 fb, 1650 fb, 1450 fb, Utility (or No. 3 depending on the width of

the lumber), and Economy (WWPA 1991). This set of grades is not the same one that

a mill would choose when processing Douglas-fir. Mill managers typically select a mix

of grades that maximizes their value recovery. The optimization process includes

information about current markets, orders, and the technical capability of the mill. The

grade recovery models in Fahey and others (1991) attempt to generalize a set of

grades useful for describing the characteristics of a resource.

Estimates of Lumber

Grade Yields
8

In practice, mills that visually grade lumber under the Structural Light Framing or the

Joists and Planks rules also use other visual rules to increase value. Sometimes various laminating grades are sorted to capture the increased value of higher quality

lumber. In other cases, grading rules are mixed to minimize production of low-value

grades. For example, 2 by 4 lumber that would be downgraded to No. 3 and sold for

as little as $180 per thousand board feet5 under the Structural Light Framing rules

often qualifies as Standard under the Light Framing Rules (WWPA 1991) and can be

sold for $335 per mbf. This ability to mix grading systems could make a considerable

difference in the profitability of a mill.

The situation for MSR lumber is somewhat different. Fahey and others (1991) chose

to represent MSR lumber as a set of three MSR grades and two visual grades. In

reality, mills produce a much more complex mix of grades. Grading rules allow visual

restricted grading options for lumber that fails to make the lowest MSR grade manufactured by a mill. The rules require placing this lumber in visual grades with mechanical properties below the lowest MSR grade the mill produces. The 1450 fb grade

estimated by the Fahey and others (1991) model has design values rated lower than

any Douglas-fir visual grade except Utility. If a Douglas-fir mill actually produced the

1450 fb grade, it would preclude manufacture of all other visual grades except Utility

and Economy. For the same reasons given in the example for No. 3 mentioned earlier,

it is unlikely Douglas-fir mills actually would produce the mix of MSR grades reported

in this analysis. This grade mix does, however, provide a good profile of the distribution of properties within the resource.

The data used to discuss quality at the log level are presented in three tables. Table 3

contains information on the proportion of log volume in each grade for each analytical

group. Table 4 includes data about the relative importance of morphological characteristics (diameter, knot size, and growth rate) and processing decisions (length) in

determining log grade. These data also are used to demonstrate how some log or

stumpage purchasers may benefit by going beyond log grade when making processing decisions. Table 5 summarizes details on the relative importance of each gradedetermining characteristic.

Port Blakely thinning trials—All four Port Blakely analytical groups produced good

quality logs. Special Mill and No. 2 Sawmill were the two predominant log grades on

all four areas. The Port Blakely installations yielded almost no No. 4 Sawmill logs

because the utilization standards set by the company (8-inch minimum SED) effectively precluded their manufacture under the grading protocol used in this analysis.

A small volume of No. 4 Sawmill logs was manufactured from the 95-UT trees, but

otherwise the lowest grade was No. 3 Sawmill (table 3).

Results and

Discussion

5 Based on prices reported by Anderson (2000) from September

2000.

Log Grades
9

Table 3—The proportion of total log volume in each analytical group meeting

various log grades displayed by analytical group

Log grade Stand averageb

Analytical Special No. 2 No. 3 No 4 quadratic mean 

groupa Mill Sawmill Sawmill Sawmill Age diameter

- - - - - - - - - - Proportion - - - - - - - - - - Years Inches

95-UT .41 .45 .13 .01 91 24.9

80-UT .41 .44 .15 .00 72 22.6

95-TH .56 .36 .08 .00 93 26.9

80-TH .40 .54 .06 .00 73 29.3

21-40 .00 .20 .74 .06 32 14.5

41-60 .04 .38 .53 .05 49 19.7

61-80 .03 .48 .48 .00 64 16.7

81-100 .37 .38 .19 .06 86 22.4

a UT = unthinned; TH = thinned.

b Quadratic mean diameter at breast height of sample trees.

Table 4—Reason why logs were not placed in the next higher log grade by

analytical group and log grade

Average

Total grading

Grading criteria grading criteria

Analytical Log Growth Total criteria exceeded

groupa grade Diameter Knots rate Lengthb logs exceeded per log

- - - - - - - - - - Numbersc - - - - - - - - - -

95-UT No. 2 Sawmill 25 17 0 0 36 42 1.17

80-UT No. 2 Sawmill 29 17 4 0 39 50 1.28

95-TH No. 2 Sawmill 29 22 1 2 38 54 1.42

80-TH No. 2 Sawmill 22 36 31 1 50 90 1.80

21-40 No. 2 Sawmill 14 8 13 1 14 36 2.57

41-60 No. 2 Sawmill 39 45 24 0 55 108 1.96

61-80 No. 2 Sawmill 20 7 1 1 23 29 1.26

81-100 No. 2 Sawmill 9 3 0 0 10 12 1.20

95-UT No. 3 Sawmill 24 0 0 0 24 24 1.00

80-UT No. 3 Sawmill 31 0 0 0 31 31 1.00

95-TH No. 3 Sawmill 17 0 0 0 17 17 1.00

80-TH No. 3 Sawmill 14 0 0 0 14 14 1.00

21-40 No. 3 Sawmill 137 8 0 0 138 145 1.05

41-60 No. 3 Sawmill 151 23 0 0 156 174 1.12

61-80 No. 3 Sawmill 58 1 0 0 58 59 1.02

81-100 No. 3 Sawmill 10 1 0 0 10 11 1.10

95-UT No. 4 Sawmill 0 1 0 0 1 1 1.00

80-UT No. 4 Sawmill 0 0 0 0 0 0 0

95-TH No. 4 Sawmill 0 0 0 0 0 0 0

80-TH No. 4 Sawmill 0 0 0 0 0 0 0

21-40 No. 4 Sawmill 22 2 0 0 23 24 1.04

41-60 No. 4 Sawmill 12 4 0 0 16 16 1.00

61-80 No. 4 Sawmill 0 0 0 0 0 0 0

81-100 No. 4 Sawmill 1 1 0 0 1 2 2.00

a UT = unthinned; TH = thinned.

b Length depends on merchandising decisions by individual companys.

c Entries represent number of times this grading criteria was exceeded.
10

Both thinned areas had a somewhat better log grade distribution (more Special Mill

and No. 2 Sawmill volume) than the corresponding unthinned areas. About 85 percent

of the volume from both unthinned areas was in Special Mill and No. 2 Sawmill grade

logs, whereas the thinned areas yielded 94 percent (95-TH) and 92 percent (80-TH)

in these grades. Although no precise records are available, the strategy was to thin

from below and attempt to remove mortality and defective trees (Curtis 1995). This

practice presumably improved log grade in the residual stand, thereby eliminating the

trees that would later yield low-grade logs. Stinson (1999) reports data for the volume

removed from the XT-1 (95-TH here) installation during the various entries but not the

quality of this material.

The log grade distributions in the two unthinned areas were virtually identical, but the

log grade distributions in the thinned areas differed from one another, thereby suggesting that the intensity of the thinning and possibly harvest age may have affected

log grade distribution. The Port Blakely 95-TH trees were older at harvest and received

a lighter thinning treatment than the trees on the 80-TH area. Both of these factors

are consistent with the observed log grade yield results. Proportional volume of Special

Mill grade logs was about one-third higher for the 95-TH analytical group than any of

the three other Port Blakely analytical groups (fig. 1). Although it is not possible to use

the available information to say conclusively why these differences occurred, sufficient

information exists to rule out some possibilities and highlight others. The most likely

explanations for these types of differences are (1) tree size, (2) spacing at stand initiation, (3) timing of thinning, (4) thinning intensity, and (5) age at harvest. Of these,

thinning intensity seemed the most likely cause for the differences in log grade

observed for the Port Blakely trees.

Table 5—Proportion of logs downgraded from Special Mill to No. 2 Sawmill or

No. 3 Sawmill by analytical groupa

Grading criteria

Analytical Log Growth

group grade Diameter Knots rate Length

95-UT No. 2 Sawmill 0.69 0.47 0.00 0.00

80-UT No. 2 Sawmill .74 .44 .10 .00

95-TH No. 2 Sawmill .76 .58 .03 .05

80-TH No. 2 Sawmill .44 .72 .62 .02

21-40 No. 2 Sawmill 1.00 .57 .93 .07

41-60 No. 2 Sawmill .71 .82 .44 .00

61-80 No. 2 Sawmill .87 .30 .04 .04

81-100 No. 2 Sawmill .90 .30 .00 .00

95-UT No. 3 Sawmill 1.00 .00 .00 .00

80-UT No. 3 Sawmill 1.00 .00 .00 .00

95-TH No. 3 Sawmill 1.00 .00 .00 .00

80-TH No. 3 Sawmill 1.00 .00 .00 .00

21-40 No. 3 Sawmill .99 .06 .00 .00

41-60 No. 3 Sawmill .97 .15 .00 .00

61-80 No. 3 Sawmill 1.00 .02 .00 .00

81-100 No. 3 Sawmill 1.00 .10 .00 .00

a Proportions sum to greater than 1.0 because some logs exceed more than one grade determining criteria.
11

Tree size is not the reason. The 80-TH trees were larger yet yielded a lower proportion

of volume in Special Mill (table 3), the most diameter-sensitive grade (table 2). The

stands also were thinned at about the same age, so it is unlikely that age at thinning

led to the observed difference in grade yield.

Spacing at stand initiation is important because it is one of the major factors determining branch size (Larson 1969). Little information is available about the conditions

in these stands at the time they were established, but Curtis (1995) concluded that

both Port Blakely installations were probably initially widely spaced. Curtis bases this

conclusion on the number of trees present when the stands were first thinned as

well as evidence of mortality before thinning. Although it is unknown if the stocking in

one stand was heavier than in the other, the closeness of proportional grade yields

for the unthinned areas supports the idea that the stocking levels were similar and

that the thinning treatment, not initial conditions, created the differences between

installations. Curtis also rates both sites as II+ so differences in site quality were

probably not a factor.

Thinning intensity may have influenced log grade yield. The 95-TH area was thinned

frequently but lightly at 47, 55, 60, 74, and 77 years old. The 80-TH area was thinned

heavily at ages 42 and 54 then lightly at age 62. The relative density of the 80-TH

area had not recovered to a point where suppression-related mortality was anticipated

by the time it was remeasured at age 76 (Curtis 1995). Data presented in table 4

show that growth rate and knot size were much more important in limiting log grade

for the logs from the 80-TH analytical group than for those from any of the other Port

Blakely analytical groups. This is consistent with expectations for stands maintained in

relatively open conditions.

SM

2S

3S

Proportion of total

4S

Average tree age and treatment

80-UT 80-TH 95-UT 95-TH

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

Figure 1—Proportion of total woods length log volume in each log grade from each Port Blakely analytical

group (UT = unthinned; TH = thinned). SM = Special Mill, 2S = No. 2 Sawmill, 3S = No. 3 Sawmill, and

4S = No. 4 Sawmill.
The differences in treatment appear to have promoted rapid branch and stem diameter growth in the trees from the 80-TH area but only moderate branch growth and

stem diameter growth in the trees from the 95-TH area. Information collected on BIX

supports this idea even though it was not possible to reconstruct histories of branch

size over time. Change in branch size with tree height provides a surrogate for this

information. Lower branches provide a picture of conditions before treatment, whereas the upper branches provide a snapshot of treatment effects. The average BIX for

each 17.5-foot log from each Port Blakely analytical group is plotted in figure 2.

Although it is not possible to say which logs grew before or after the thinning, it is reasonable to generalize the influence of thinning from the height trends. On both installations, BIX was smaller in the lower logs from the thinned areas than the lower logs

from the unthinned areas, thereby suggesting that either these differences existed

before thinning or some trees with large branches were removed during thinning. The

latter is consistent with the goal of improving both growth and quality of the residual

trees by removing small, poorly formed, and branchy trees. Regardless of the cause

of this initial difference, the height trend indicates a response to thinning. As log

height increased, the BIX on both thinned areas became larger than the BIX on the

corresponding unthinned areas. The lighter thinning treatment received by the trees in

the 95-TH area seems to have increased stem diameter enough to improve yield of

Special Mill logs without increasing either branch size or growth rate enough to disqualify many of those larger logs from the higher grade. In contrast, the heavier thinning received by the trees in the 80-TH area increased both branch diameter and ring

width beyond the allowable limits, thereby disqualifying many large logs from the

Special Mill grade (table 5).

Trees from the 95-TH area were 15 years older at harvest than those from the 80-TH

area, but it is unclear if age was an important factor in the observed differences in log

grade yield. Proportional log grade yields from the two unthinned areas were virtually

identical (table 3). Trees from the younger 80-TH area were larger (table 3), yet yielded

about one-third less of their total volume in Special Mill grade logs than the older

95-TH trees (fig. 1). This happens because growth rate and branch size were more

important factors in determining grade in the younger trees than in the older ones

(table 4). Extending the rotation without additional thinning could result in slower

diameter growth, which in turn might allow more logs to meet the growth rate criteria

for Special Mill. The 95-TH trees were also old enough to begin branch stub occlusion

after natural pruning (Kachin 1940). Occlusion also might result in reduction in number of knots counted by the scaler during grading because they become less obvious

as they are overgrown. Using the methods developed by Christensen (1997) for projecting stand developmental trajectories might help to evaluate the importance of

these potential changes and answer questions about how the characteristics of the

80-TH trees might change were they grown for another 15 years.

Stand Management Cooperative trees—Age does, however, seem to explain much

of the change in proportional log grade when the full 20- to 100-year age range is

examined. The proportion of No. 3 Sawmill log volume declined with age, whereas the

proportion of volume in No. 2 Sawmill and Special Mill logs increased over this age

range (fig. 3). An exception to this trend was seen in the age class 41 to 60 years and

61 to 80 years where there was a slight decline in the proportional volume of Special

12
13

Figure 2— Change in branch index (BIX) with mill length log height (17.5 feet per log) for the trees from

each Port Blakely analytical group. Branch index (inches) Branch index (inches)

Log number (no. 1 = butt)

Log number (no. 1 = butt)

A

B
Mill logs (table 3). This is apparently linked to the diameter of the two groups (proportion of logs downgraded to No. 2 sawmill for diameter, table 5). The trees from the 41-

to 60-year age class had a quadratic mean breast height diameter (QMD) of 19.7

inches. The trees from the 61- to 80-year age class had a smaller QMD of only 16.7

inches. The Special Mill grade requires a minimum SED of 16 inches, so in at least

half of the trees in the 61- to 80-year age class, a 34-foot butt log was unlikely to

yield a Special Mill log. This decline in the proportion of Special Mill logs occurred

even though the younger 41- to 60-year age class trees had an average BIX that was

nearly one and one-half times as large as the 61- to 80-year age class trees (1.41

inches vs. 0.97 inch). Thus, the No. 2 Sawmill logs produced from the younger 41- to

60-year age class trees would be noticeably “rougher” than those from the 61- to 80-

year age class (table 4). This is evident from the higher number of grading criteria

exceeded per log. Although it is impossible to completely separate diameter from age

in this analysis, diameter was always an important factor in determining log grade in

all analytical groups. All but 33 of the 362 logs from the SMC database graded as No.

3 Sawmill, and all those from the Port Blakely thinning trials placed in that grade were

downgraded only for diameter (table 4).

Table 4 contains information about the reasons logs failed to qualify for the next highest log grade. Even though two groups of logs may be assigned to the same grade,

their “quality” can be quite different. The latitude in quality allowed within a single grade

is apparent when the number of grading criteria exceeded per log is compared among

all analytical groups for the No. 2 Sawmill grade (table 4, final column in rows 1-8).

14

Proportion of total volume

Average group age, age class, and group average diameter

21-40/32

41-60/49

61-80/64

81-100/86

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

SM

2S

3S

4S

Figure 3—Proportion of total woods length log volume in each log grade for analytical groups of SMC trees

arranged by age class (x-axis label also shows average age and quadratic mean diameter for the tree in

each group). SM = Special Mill, 2S = No. 2 Sawmill, 3S = No. 3 Sawmill, and 4S = No. 4 Sawmill.

Relative Importance of Log

Grading Criteria
The logs from trees in the younger two SMC age classes exceeded more grading

criteria than either those from the older SMC age classes or the Port Blakely trees.

The 95-UT No. 2 Sawmill logs (row one, last column in table 4) exceeded an average

of 1.17 grading criteria per log, and those from SMC age class 21-40 exceeded an

average of 2.57 grading criteria per log (row 5, table 4). This means that for the 95-UT

trees, about 17 percent of the No. 2 Sawmill logs contained features that exceeded at

least two grading criteria. The other 83 percent of the No. 2 Sawmill logs only exceeded one grading criterion. The No. 2 Sawmill logs from the SMC age class 21-40 typically exceeded two grading criteria, but 57 percent of them exceeded three. All of

these logs were nonetheless assigned to the No. 2 Sawmill grade under existing

rules (Northwest Log Rules Advisory Group 1998). This means that at least the

appearance of the logs from the two groups would be noticeably different. Some differences in the types of products manufactured from them also might be expected,

and in fact, the market currently recognizes the range of quality within some log

grades because different prices are reported for old- and young-growth Special Mill,

No. 2, and No. 3 Sawmill grades (Log Lines 1999).

More subtle but possibly important differences also are seen among the Port Blakely

analytical groups. For example, the data presented in table 3 suggest that, based on

log grade alone, the trees from thinned areas have higher quality than those from

unthinned areas. When the data are reexamined by using the techniques presented in

table 4, a different, more complex picture develops. Although the trees from thinned

stands produce larger proportional volumes in the higher grades, the No. 2 Sawmill

logs from the thinned stands exceed more grading criteria per log than those from the

unthinned stands. This suggests that at least by some measures, the logs within the

No. 2 Sawmill grade from the unthinned stands are of higher quality. This result is

consistent with more general information on branch size and quality seen after thinning reported for both Douglas-fir (Maguire and others 1991, Riou-Nivert 1989) and

other species (Alazard 1994, Barbour and others 1994, Colin and others 1992).

Consequently, more demanding log grading systems, such as those used for proprietary export grades, might reveal greater differences between trees from the thinned

and unthinned area, than are apparent here.

Comparison of Port Blakely trees and SMC database trees—The proportion of

logs that exceeded each grading criterion for each analytical group is shown in table

5. This representation of the data shows the influence of the heavy thinning received

by the 80-TH trees on the criteria used to evaluate log grade. The 80-TH analytical

group is the only Port Blakely analytical group where growth rate was an important

factor in disqualifying logs from the Special Mill grade. Knot size was also more

important for this group than for the other three Port Blakely analytical groups. Based

on the data in table 5, the No. 2 Sawmill logs from the 80-TH trees are most similar to

those from the SMC 41- to 60 year age class. Or, in other words, No. 2 Sawmill logs

from this 80-year-old stand might closely resemble those from stands one half to twothirds that age. It is important to keep in mind, however, that although the logs graded

as No. 2 Sawmill from these two groups had similar characteristics, 40 percent of the

volume from the 80-TH group qualified as Special Mill, but only 4 percent of the volume from the age class 41- to 60 year SMC trees made that grade (table 3).

15
Estimated yields of visually graded and MSR lumber for the trees from the Port

Blakely thinning trials and the SMC trees are presented in tables 6 and 7. These are

composite results for all logs from all trees in each analytical group. Lumber grade

yields are reported as a percentage of the total board-foot lumber tally for each analytical group. Lumber tally is dependent on log diameter and was estimated by using

the lumber recovery factor model of Fahey and others (1991).

16

Table 6—Average volume percentage of yields of visually graded lumber by

grade from each analytical groupa

Lumber grade

Analytical Select Utility or No. 2 and Branch

group Structural No. 1 No. 2 No. 3 Economy Better. index

- - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - Inches

95-UT 21 20 46 10 4 86 0.89

80-UT 17 21 46 11 5 84 .90

95-TH 25 17 45 10 4 87 .87

80-TH 17 19 48 12 5 83 1.05

21-40 5 15 53 19 8 73 1.32

41-60 5 12 51 22 11 67 1.41

61-80 16 20 47 12 5 83 .97

81-100 25 21 43 9 4 88 .88

a Lumber grade yields were estimated by using grade prediction models developed by Fahey and others

(1991) for WWPA Structural Light Framing and Joists and Planks grade rules (WWPA 1991).

Table 7—Average volume percentage of yields of machine stress rated (MSR)

lumber grades for each analytical groupa

Lumber grade

Analytical Utility or Juvenile

group 2100fb 1650fb 1450fb No. 3 Economy wood

- - - - - - - - - - - - - - - - - - - - Percent - - - - - - - - - - - - - - - - - - - -

95-UT 25.0 37.2 18.0 13.4 6.3 28.2

80-UT 23.3 36.9 18.2 14.9 6.6 35.0

95-TH 24.9 36.5 20.0 12.3 6.3 24.1

80-TH 22.5 35.7 18.3 16.0 7.4 24.8

21-40 9.1 26.0 24.1 29.4 10.7 83.3

41-60 8.6 23.5 21.6 29.1 17.2 57.5

61-80 22.0 37.3 16.3 15.9 8.5 39.0

81-100 28.8 40.7 13.2 10.5 6.8 33.8

a Grades were estimated by using equations developed by Fahey and others (1991) for MSR lumber.

The "grades" are approximations based on edge knot size and stiffness.

Lumber Yields
The average BIX for each analytical group is included in table 6 because the visual

lumber grade yield models developed by Fahey and others (1991) use BIX as their

only independent variable. These relations are independent of log diameter. Branch

index varied in the narrow range between 0.89 and 1.05 inches for all the analytical

groups except the SMC age classes 21 to 40 years and 41 to 60 years, which had

much larger branches (BIX 1.32 and 1.41 inches). As mentioned earlier, these trees

probably grew in stands that were either established at wider spacings or respaced

earlier than either the older SMC stands or the Port Blakely thinning trials.

The recovery models for MSR lumber include both BIX and percentage of juvenile

wood as independent variables (Fahey and others 1991) and so percentage of juvenile wood is included in table 7. The MSR grade yield models have a slight dependence on diameter because the juvenile wood diameter is fixed once trees reach 20

years old at a given height. As total diameter increases, the proportion of juvenile

wood slowly declines, and MSR grade yield improves.

Port Blakely trees—The results for visual lumber grade yield were consistent with

the log grade results already presented. Estimates of visual lumber grade yield for the

trees from all the Port Blakely thinning trials were similar regardless of whether the

area was thinned, although the older (95-TH and 95-UT) trees had slightly higher

yields of Select Structural lumber. The results for MSR lumber agreed with those for

visually graded lumber (table 7). The similarity between trees from the thinned and

unthinned areas indicates that when middle-aged stands are thinned, there is little

influence on quality if structural lumber is the intended product. This result is consistent with Christensen’s (1997) findings for the Hoskins level-of-growing-stock installation. The Port Blakely thinning trials were thinned when stands were 40 years old or

older and, by this time, the branches in the lower portions of the stems, where the

greatest volume is concentrated, were almost certainly dead. Branch size was therefore fixed so faster growth after thinning would not necessarily substantially alter

lumber grade distributions.

Stand Management Cooperative trees—The results for visually graded and MSR

lumber for the SMC database trees are different than those for the Port Blakely thinning trials (tables 6 and 7). The distribution of both visual and MSR grades indicates a

considerable change in quality in the trees that are older than 60 years as compared

to those younger than 60 years. At this level of analysis, it is not clear if these results

reflect some quirk in the data or if these differences actually represent differences in

quality related to changing silvicultural practices over the past 40 years. Initial spacing

or precommercial thinning seems to have influenced the characteristics of the SMC

database trees where the younger trees have considerably larger branches (table 6)

and higher percentage of juvenile wood (table 7). The observed increases in branch

size and proportion of juvenile wood are consistent with results reported in the literature for widely spaced and early thinned Douglas-fir and other species (Barbour and

others 1997, Briggs and Smith 1986). It therefore seems likely that the information in

tables 6 and 7 actually reflects differences in young stand management. This is not

surprising because the SMC trees were intentionally selected to represent trees

grown by using silvicultural practices designed to favor rapid wood production.

17
Conclusions

If this assumption is correct, these data indicate that the practices used to grow the

younger trees have put them on a trajectory for lower quality that will influence their

characteristics and consequently their market value under any economically viable

rotation. Even if the trees from the SMC age classes 21 to 40 and 41 to 60 years

were grown until they reached age 80, they still would have large branches in their

lower boles as well as higher in the stem if rapid growth is maintained during the

entire rotation. The BIX reported for these trees in table 6 is fixed and will not decline

with age. The relation between growth rate and the proportion of juvenile wood is

complex because at any height, the volume of juvenile wood is fixed once trees make

the transition to mature wood production. The longer the trees grow, therefore, the

less juvenile wood they will contain as a proportion of their total volume. Given two

trees of equal size, the one that grew more slowly when young will tend to have a

lower proportion of juvenile wood than the one that grew more quickly when young.

Although the proportion of juvenile wood will slowly decline with increased diameter,

large branches will still negatively influence MSR lumber grade yields. The important

point is that simply growing the younger trees longer would not lead to the same

product yields as are seen in the trees from the Port Blakely thinning trials or the two

older age classes of SMC trees.

Management history seemed to influence the characteristics of the trees examined

here. Analysis of the SMC trees by age class reveals a gradual increase in log and

lumber grades with increasing stand age. The Port Blakely trees fit into this continuum

fairly well. Log grade, visual lumber grade, and MSR lumber grade results suggest

that Douglas-fir wood quality increases fairly rapidly until about stand age 60 and then

apparently levels off. The trees from the five oldest analytical groups had similar log

and lumber grade yields although the SMC trees in this age class came from the

central Cascade Range in Oregon, and the Port Blakely thinning trials were on the

Olympic Peninsula in western Washington. The evaluation of lumber grades performed

in this analysis did not, however, recognize increasing clear wood volume because

only structural lumber was considered in the estimated grade yields. Data available in

the literature on natural pruning suggest that quality may begin to increase again at

about age 100 when recoverable amounts of clear wood have formed. The log grade

results tend to account for this because the Special Mill grade is intended to capture

the potential yield of Select and Better lumber. Even so, there was little difference in

log grade between the older and younger Port Blakely thinning trial that could be

attributed to age.

The differences in quality between trees from thinned and unthinned Port Blakely areas

were relatively small. The trees from thinned areas tended to yield larger proportions

of higher graded logs than from unthinned areas. For logs of equal grade, however,

logs from the unthinned areas tended to have fewer characteristics that prevented

them from being placed in the next higher grade than the logs from the thinned areas.

So, some processors might consider logs of equal grade from unthinned areas as

higher quality than the logs from thinned areas. There were essentially no differences

in estimated grade yields of visually graded or MSR structural lumber among the

trees from the various analytical groups from the Port Blakely thinning trials. This

analysis did not, however, include estimates of grade yields for appearance grade

lumber, which might have revealed greater differences in quality between the logs

from thinned and unthinned areas.

18
19

Diameter was always an important factor in determining if logs were placed in all

grades; however, two of the other grading criteria, that is, knot size and growth rate,

were as important or more important than diameter in determining if logs met the

criteria for the Special Mill grade. Even when young trees are large enough to make

Special Mill logs, they rarely do because either their branches are too large or their

growth rate is too high. Branch size and growth rate also are related to stand tending;

for example, initial spacing and the timing and intensity of thinning, as well as site

quality.

A continuum of improving log and lumber grade yield was apparent with tree age, and

this was common across analytical groups. For example, the trees from the SMC age

class 81 to 100 years yielded similar proportions of logs and lumber in the various

grades as did the Port Blakely trees. As the age of the SMC trees declined, branch

size and juvenile wood dimensions changed in ways that could not be accounted for

simply by tree or stand age, and these changes also influenced log and lumber grade.

This probably reflects a shift from more extensive to more intensive forestry practices

on industrial land in western Oregon and Washington over the past 50 years, but in

most cases, we have insufficient plot level treatment histories to say this conclusively.

Practices such as use of genetically improved planting stock, herbicides to reduce

vegetative competition in young stands, wide initial spacing, precommercial thinning,

and commercial thinning all are consistent with the trend toward the larger branches

and wider juvenile wood cores observed in the younger trees. It is, for example, clear

from the analyses presented here that trees grown by using the long rotation forestry

and relatively late thinnings practiced in Port Blakely’s XT-1 and XT-7 thinning trials

had different wood characteristics than trees grown by using the high-yield forestry

techniques practiced for the two youngest SMC age classes and that those differences would persist even if the SMC trees were grown to the same age as the Port

Blakely trees.

The potential importance of site quality, however, should be considered when interpreting the results from this study. All of the trees analyzed here came from either

site I or site II land, and yet much of the land owned by the federal government is at

higher elevations and lower site classes where slower growth is expected even with

earlier and heavier thinnings. This might tend to mitigate branch size, growth rate,

and juvenile wood diameter, but it would reduce total diameter, thereby making the

effect on log grade yield difficult to predict.

These results do, however, suggest that the longer rotations used under the NWFP

“matrix” land specifications could result in trees with different wood characteristics

than those grown either in industrial plantations or of older trees grown under past

forest management practices. This, of course, depends on the timing and intensity of

thinnings used to alter structure in the existing stands. The earlier and heavier the

thinnings, the more the trees from longer rotations will resemble trees from plantations

managed for rapid growth. If late heavy thinnings like the regime used on the Port

Blakely XT-7 installation (80-TH analytical group) are used, large trees with moderate

branch size and growth rates should result. The positive effect of diameter will lead to

some improvement in the domestic log grade mix from the older stands but little, if

any, change in the proportions of various lumber products manufactured from them.

On the other hand, late light thinnings, similar to those used by Port Blakely on the

XT-1 thinning trials (95-TH analytical group), will result in trees that are somewhat
Acknowledgments

smaller for a given age but with characteristics that might make them more desirable

for certain wood products with higher market value. If early, heavy thinnings are used,

the negative effect on proportional log and lumber grades probably will be more pronounced than that seen for the two Port Blakely installations. These differences still

need to be quantified, but it is apparent from the difference in knot size, juvenile wood

proportion, and growth rate between the more intensively managed SMC trees and

the Port Blakely trees that longer rotations that result in larger trees will not necessarily result in trees with significantly higher market value for wood removed from these

stands.

We thank all of the technical experts who reviewed and commented on this report and

who provided information used in conducting the study. We are particularly grateful to

Mike Mosman and Garret Eddy from Port Blakely Tree Farm who provided partial

funding for the study and many technical comments; Steve Stinson from the University

of Washington, who assisted with fieldwork and provided data from his own study;

and Sue Willits, Bob Curtis, Dean DeBell, Dave Marshall, and Glenn Christensen all

from the PNW Research Station, and Jim Stevens from the Campbell Group who

provided technical input and reviewed the manuscript at various stages.

Alazard, P. 1994. Stand density and spacing of Pinus pinaster: consequences for

growth and tree quality. Moulis-en-Medoc, France Afocel Sud-Ouest. InformationsForet,-Afocel-Armef. 2: 129-144.

Anderson, J.P. 2000. Random Lengths: the weekly report on North American forest

products markets September 8, 2000. Eugene, OR: Random Lengths: 55(1): 5.

Barbour, J. 1995. The Stand Management Cooperative annual report. In: Wood

quality project progress report. Seattle, WA: University of Washington, College of

Forest Resources: 20-25.

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density and radial growth in mature jack pine (Pinus banksiana) for 38 years after

thinning. Canadian Journal of Forest Research. 24(12): 2439-2447.

Barbour, R.J.; Johnston, S.; Hayes, J.P.; Tucker, G.F. 1997. Simulated stand characteristics and wood product yields from Douglas-fir plantations managed for

ecosystem objectives. Forest Ecology and Management. 91: 205-219.

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Publishing.

Briggs, D.; Smith W.R. 1986. Effects of silvicultural practices on wood properties. In:

Oliver, C.D.; Hanley, D.P.; Johnson, J.A., eds. Douglas-fir: stand management for

the future. Contribution No. 55. Seattle, WA: University of Washington, College of

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Christensen, Glenn A. 1997. Development of Douglas-fir log quality, product yield,

and stand value after repeated thinnings in western Oregon. Corvallis, OR: Oregon

State University. 176 p. M.S. thesis.

Colin, F.; Monchaux, P.; Houllier, F.; Leban, J.M. 1992. Growth, branching and

wood quality of Norway spruce: first results for trees harvested at a third thinning.

Paris, France. Association Foret-Cellulose (AFOCEL); Annales-de-RecherchesSylvicoles,-AFOCEL,-1991: 251-296.

20

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21
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22
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of program information (Braille, large print, audiotape, etc.)

should contact USDA’s TARGET Center at (202) 720-2600

(voice and TDD).

To file a complaint of discrimination, write USDA, Director,

Office of Civil Rights, Room 326-W, Whitten Building, 14th

and Independence Avenue, SW, Washington, DC 20250-9410

or call (202) 720-5964 (voice and TDD). USDA is an equal

opportunity provider and employer.

Pacific Northwest Research Station 

333 S.W. First Avenue 

P.O. Box 3890 

Portland, OR 97208-3890

Pacific Northwest Research Station

Web site http://www.fs.fed.us/pnw

Telephone (503) 808-2592

Publication requests (503) 808-2138

FAX (503) 808-2130

E-mail desmith@fs.fed.us

Mailing address Publications Distribution

Pacific Northwest Research Station

P.O. Box 3890

Portland, OR 97208-3890
U.S. Department of Agriculture

Pacific Northwest Research Station

333 S.W. First Avenue

P.O. Box 3890

Portland, OR 97208-3890

Official Business

Penalty for Private Use, $300