Eric A. Simmons, Todd A. Morgan, Erik C. Berg, 

Stanley J. Zarnoch, Steven W. Hayes, and Mike T. Thompson

Logging Utilization in Idaho: 

 Current and Past Trends

United States Department of Agriculture / Forest Service

Rocky Mountain Research Station

General Technical Report RMRS-GTR-318

March 2014
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Simmons, Eric A.; Morgan, Todd A.; Berg, Erik C.; Zarnoch, Stanley J.; Hayes, Steven W.; 

Thompson, Mike T. 2014. Logging utilization in Idaho: Current and past trends. Gen. Tech. 

Rep. RMRS-GTR-318. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky 

Mountain Research Station. 15 p.

Abstract 

A study of commercial timber-harvesting activities in Idaho was conducted during 2008 and 

2011 to characterize current tree utilization, logging operations, and changes from previous 

Idaho logging utilization studies. A two-stage simple random sampling design was used to select 

sites and felled trees for measurement within active logging sites. Thirty-three logging sites 

and 815 felled trees were measured. Results of the 2008/2011 study indicated that harvesting 

efforts removed 1,011 cubic feet (cf) of timber volume from growing stock for every 1,000 cubic 

feet (mcf) delivered to the mill, created 24 cf of growing-stock logging residue, and that 13 cf 

of non-growing-stock (stump wood and tops above 4 inches diameter outside bark (dob)) were 

delivered to the mill. This compared to 1,086 cf of growing-stock removals that created 95 cf of 

growing-stock logging residue and utilized 9 cf of non-growing-stock per mill-delivered mcf in 

a 1990 study. This study confirmed two long-term timber harvesting trends in Idaho: declining 

diameter at breast height (dbh) of harvested timber, and declining amounts of logging residue 

generated per unit of mill-delivered volume. 

Keywords: growing-stock removals, logging residue, removals factors, timber harvest

Authors

Eric A. Simmons is a Research Associate, Todd A. Morgan is the Director of Forest Industry Research, Erik C. Berg is a Research Forester, and Steven W. Hayes is a Research Forester at the 

Bureau of Business and Economic Research (BBER), Gallagher Business Building, The University 

of Montana, Missoula, Montana.

Stanley J. Zarnoch is a Mathematical Statistician, USDA Forest Service, Southern Research Station, Lehotsky Hall, Clemson University, Clemson, South Carolina.

Michael T. Thompson is a Resource Analyst, USDA Forest Service, Rocky Mountain Research 

Station, Forest Inventory and Analysis, Ogden, Utah.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 1

Introduction_____________________________________________________________

Forest managers require current information on the characteristics and effects of 

timber harvesting on forest inventory. For example, they may need to know how much 

woody material remains in the forest after commercial logging operations to understand 

fuel loads or amounts of down woody material remaining for wildlife, predict potential 

feedstock for woody biomass energy, or gauge the efficiency of logging operations. 

Likewise, the characteristics of harvested trees (e.g., dbh1, total tree height, or species 

mix) and harvesting methods (e.g., mechanical vs. hand felling, merchandising at the 

stump vs. at the landing, or cable yarding vs. skidding) may be of interest for planning 

or policy purposes.

Logging utilization studies provide much of this information by identifying volumes of 

growing-stock2 (Woudenberg and others 2010) trees (fig. 1) removed from forest inventory during commercial timber harvest activities. The studies also provide information 

by developing logging utilization factors, which quantify the amount of growing-stock 

volume cut and either delivered to the mill or left as logging residue in the forest or at 

the landing (Morgan and Spoelma 2008). These logging utilization factors are used in 

the calculation of logging residue volumes that are published in the Timber Products 

Output (TPO) database (http://srsfia2.fs.fed.us/php/tpo_2009/tpo_rpa_int2.php), which is 

maintained by the Forest Inventory and Analysis (FIA) Program of the USDA Forest 

Service. These factors can be applied to historic or projected levels of timber harvest 

at various spatial scales to provide estimates of logging residue volume. Logging utilization studies also characterize timber harvest activities and equipment used and can 

also provide estimates of the distributions of trees and volume harvested by species, 

size, and logging method. When conducted in a consistent manner, these studies can 

provide a great deal of information about changes in timber harvesting through time 

and differences between states or regions of the country.

1 Diameter outside bark measured at 4.5 feet above ground on the uphill side.

2 Growing stock is defined as all live trees of commercial species that meet minimum merchantability standards or have the potential to meet these merchantability standards. In general, these trees have at least one solid 8-foot section, are reasonably free of form defect on 

the merchantable bole, and at least 34 percent or more of the volume is merchantable. For the 

California, Oregon, and Washington inventories, a 26 percent or more merchantable volume 

standard is applied, rather than 34 percent or more. 

Logging Utilization in Idaho: Current and 

Past Trends

Eric A. Simmons, Todd A. Morgan, Erik C. Berg, Stanley J. Zarnoch, 

Steven W. Hayes, and Mike T. Thompson
2 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

Idaho Timber Harvest Trends

There are more than 16.6 million acres of unreserved timberland3 potentially available for timber harvest activities in Idaho (Witt and others 2012). However, neither the 

timber resource nor harvesting activities are evenly distributed throughout the state; and 

the mere presence of forested unreserved timberland has not been a strong indicator 

of harvest activity in recent years. Markets and policy issues have influenced the geographic and ownership sources of harvested timber as well as annual harvest volumes.

Recent annual timber harvest volumes in Idaho have ranged from mid-decade highs 

of more than 1.1 billion board feet (BBF) Scribner in 2004 and 2005, to lows, not seen 

since World War II, of 760 million board feet (MMBF) Scribner during 2009 (Brandt 

and others 2012; Morgan and others 2013). The ownership mix of Idaho’s timber harvest 

has been in transition since the 1990s, with federally managed forests providing 30 to 

40 percent of the harvest volume in the early 1990s and less than 15 percent since 2000 

(fig. 2). There was a corresponding increase in the private lands proportion of the harvest throughout the 1990s and early 2000s. However, since the collapse of U.S. home 

building and markets for lumber, there was a marked decline in the harvest volume and 

proportion from private lands after 2007, and harvest volumes from state-owned lands 

have nearly doubled since mid-decade. As federal harvest volumes declined in the 1990s 

and 2000s, the geographic source of Idaho’s timber harvest made a pronounced shift 

3 Timberland is defined as unreserved forest land capable of producing 20 cubic feet per acre 

per year of wood from trees classified as a timber species on forest land designated as a timber forest type (Witt and others 2012).

Figure 1—Sections of softwood trees.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 3

to northern Idaho (i.e., north of the Salmon River), which currently accounts for 80 to 

90 percent of the annual state harvest volume. Since 1995, six of Idaho’s 44 counties 

consistently account for 65 to 75 percent of annual harvest (Brandt and others 2012).

Two prior investigations of logging utilization were conducted in Idaho during 1965 

(Wilson and others 1970) and 1990 (McLain 1996). However, because Idaho’s timber 

harvest volume, source of ownership, species mix, and milling infrastructure have 

changed substantially since the 1960s and particularly the 1990s (Brandt and others 

2012; Morgan and others 2004), managers need updated information that reflects the 

characteristics and effects of contemporary timber harvesting practices. Thus, to obtain 

updated information, a study of logging utilization across Idaho was conducted during 

the 2008 and 2011 field seasons. This study was designed to quantify the creation of 

logging residue at the state level, and characterize harvested trees and harvesting activities within Idaho. The specific objectives were to:

1. characterize Idaho’s timber harvest by tree species and dbh;

2. characterize Idaho timber harvest operations by felling, yarding, and merchandising methods;

3. compute current Idaho logging utilization factors to express:

a. volumes of growing-stock logging residue generated per mcf of mill-delivered 

volume,

b. proportions of mill-delivered volume coming from growing-stock vs. nongrowing stock portions of harvested trees, and

c. total removals (i.e., timber product and logging residue) from growing stock.

Figure 2—Idaho timber harvest by ownership 1947-2012 (source: Bureau of Business and Economic Research, The University 

of Montana-Missoula; USDA Forest Service Region One, Missoula, Montana).
4 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

Methods ________________________________________________________________

Conducting a statewide logging utilization study in Idaho presents challenges. As 

Morgan and Spoelma (2008) pointed out, it is not possible to know in advance the full 

population of logging sites in a state for a given year and simply draw a sample of those 

sites to measure. Harvest volumes and characteristics change from year-to-year and 

even scheduled harvests may not be executed as planned; so the characteristics of recent 

harvests are the best predictors of geographic location and ownership of current and 

future harvests. Publicly available information about recent timber harvests in Idaho was 

used to identify the target population and sampling design that would do the following:

1. provide the data necessary to meet the study objectives,

2. be logistically and financially feasible,

3. assure the safety of the crews conducting the field work, and

4. be consistent with methods currently used in other states and regions.

The target population for this study was active logging sites in Idaho where green 

(live) trees were being commercially harvested for conversion into wood products including lumber and veneer/plywood. Because of the need to measure harvesting impacts 

on growing stock, only green-tree sites were targeted. Salvage sales, where many or 

most trees were dead prior to harvest, were not included. Historically, 90 to 95 percent 

of Idaho’s annual timber harvest volume had been used for lumber and veneer/plywood 

production (Brandt and others 2012; Morgan and others 2004). Other timber products 

(e.g., pulpwood, posts, and fuel wood) are commonly merchandised with sawlogs. Thus, 

sites where sawlogs and veneer logs were the primary products to be harvested were 

identified, because these would account for the vast majority of annual harvest volume 

while also capturing some volume for other products.

A two-stage random sampling scheme was used to select logging sites and trees within 

logging sites for measurement (Levy and Lemeshow 1999). Logging sites with active 

harvesting of green trees for commercial products served as the stage 1 sampling units 

and were selected at random across the entire state. Annual timber harvest summaries 

provided by the Idaho Department of Lands (http://www.idl.idaho.gov/news/annual_reports/index_ar.htm) and Idaho forest industry reports (Brandt and others 2012; Morgan 

and others 2004) provided the geographic locations (i.e., county) and ownerships of 

these potential logging sites (fig. 3). Timberland owners and sawmills throughout the 

state were contacted to identify when and where logging activities would be occurring, 

and to request access to logging sites to conduct measurements. When land managers 

denied access to a site, a replacement site was selected at random from the pool of 

remaining identified sites.

The stage 2 sampling units consisted of felled trees at each selected logging site. 

To qualify as a potential measurement tree, it had to be growing stock (live prior to 

harvest, dbh ≥ 5 inches, and meet minimum merchantability standards) and the entire 

stem, including the stump and top, had to be measureable (Morgan and Spoelma 2008; 

Woudenberg and others 2010).

Sample sizes for stage 1 and 2 sample units were guided by standard errors achieved 

on previous utilization studies. Zarnoch and others (2004) found that standard errors 

for utilization ratios dropped substantially by increasing the number of measured logging sites from 10 to 20. Previous logging utilization studies in California and Montana 

garnered low standard errors by measuring 25 to 35 trees on each of 30 to 35 logging 

sites (Morgan and Spoelma 2008; Morgan and others 2005). Further, logging utilization 

studies conducted by the USDA Forest Service Southern Research Station (Bentley and 

Johnson 2004; Zarnoch and others 2004) suggested that a sample of 30 to 50 logging 

sites with 20 to 35 felled trees measured at each logging site would be sufficient to 

determine state-level utilization factors.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 5

Figure 3—Sample site distribution and harvest volumes by geographic region.
6 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

Data Collection

Logging contractors or foresters were contacted at each selected site 3 to 5 days prior 

to site visits to confirm access and outline protocols to ensure field crew safety. At each 

logging site, they provided information on tree species, products merchandised, and 

preferred and acceptable log lengths delivered to receiving mill(s). Field crews recorded 

this information along with the date, county, land ownership class, felling method, yarding/skidding method, log merchandising location and method, logging contractor name, 

equipment in use, and receiving mill(s).

Field crews randomly selected felled trees that met the specified requirements. Individual trees or piles accumulated for skidding were scattered throughout the logging 

site, depending on the operation and equipment used. A unique identification number 

was assigned to each measurement tree, and species, dbh, and primary product (e.g., 

sawlog, veneer log, etc.) information was recorded. Diameter and section length measurements were taken at the cut stump, at 1 foot above ground level (uphill side of 

the tree), at dbh, at the 7.0-inch dob (end of sawlog portion of sawtimber tree), at the 

4.0-inch dob point (end of growing stock), and at the end-of-utilization. Each tree had 

diameter (in 0.1 inch increments) and section length (in 0.1 foot increments) measurements recorded with a maximum section length of 16 feet. Thus, for each bole section, 

lower and upper dob and length were recorded. The percent cubic cull for each section 

was also recorded and each bole section was identified as utilized (delivered to the mill) 

or unutilized (logging residue).

A minimum of 25 felled live trees were measured at each of 19 logging sites during 

the 2008 field season and at 14 logging sites in 2011. These 33 active logging sites 

were spread across 10 Idaho counties and more than 825 felled trees were measured. 

Approximately 10 measurement trees were excluded from data analysis because of errors or omissions in data collection. The final sample contained 815 trees for analysis.

Data Analysis

Following the methods of Morgan and Spoelma (2008), cubic volumes of individual 

tree sections were calculated using Smalian’s formula (Avery and Burkhart 1994), section volumes were summed for each tree by category (e.g., utilized vs. unutilized stump, 

bole, and upper stem sections of the trees), and utilization factors were calculated for 

each tree and site. For the Idaho logging utilization data set, means, standard errors, and 

95 percent confidence intervals (CIs) were computed for state-level utilization factors 

based on the two-stage random sampling design using the ratios of means estimator 

(Zarnoch and others 2004) obtained from SAS PROC SURVEYMEANS (SAS 2010). 

Characteristics of the felled trees, harvest operations, and utilization factors were then 

summarized and compared with historic Idaho logging utilization studies and with recent 

studies from other western states.

Results _________________________________________________________________

Characteristics of Felled Trees

The 815 trees that were analyzed ranged from 5.0 inches to 29.3 inches dbh. About 

50 percent of the harvested trees had a dbh ≤ 12 inches and accounted for 18 percent 

of the mill-delivered (utilized) volume, 19 percent of growing-stock removals, and 20 

percent of the growing-stock logging residue (table 1). Roughly one-half of the milldelivered volume, growing-stock removals, and growing-stock logging residue came 

from trees with dbh < 16 inches.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

7

Table 1—Distribution of trees, mill-delivered volume, and growing-stock logging residue volume by dbh class. 

dbh class 

(inches)

Number 

of trees

Percent of 

sample trees

Cumulative 

percent

Percent of mill delivered volume Cumulative percent

Percent of 

growing-stock 

removals

Cumulative 

percent

Percent of 

growing-stock 

logging residue

Cumulative 

percent

6 50 60.1 6.1 00.7 0.7 00.6 0.6 1.9 1.9

8 132 16.3 22.4 30.8 4.5 30.8 4.4 5.6 7.6

10 145 17.7 40.1 80.0 12.4 70.9 12.3 8.0 15.6

12 145 17.7 57.9 12.3 24.8 12.1 24.4 9.2 24.814 104 12.7 70.6 13.1 37.8 13.0 37.4 11.7 36.516 79 90.7 80.3 13.8 51.6 14.0 51.3 18.8 55.3

18 59 70.3 87.6 13.7 65.3 13.7 65.1 13.4 68.7

20 42 50.1 92.8 11.8 77.1 11.9 77.0 10.5 79.2

22 21 20.6 95.3 70.0 84.1 70.0 84.0 6.8 86.024 24 20.9 98.3 90.2 93.3 90.2 93.2 6.2 92.126 10 10.2 99.5 40.7 98.0 40.8 98.0 5.3 97.428 3 00.4 99.9 10.2 99.3 10.3 99.3 2.5 99.930 1 00.1 100.0 00.7 100.0 00.7 100.0 0.1 100.0
8 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

A majority (55 percent) of growing-stock logging residue came from trees with dbh 

between 13 and 21 inches, roughly 35 percent of the sampled trees. In general, smaller 

trees produced less volume delivered to the mill for every mcf of timber harvested. 

As well, they produced more logging residue per mcf delivered to the mill than larger 

diameter trees, although several trees in the 28-inch dbh class were damaged during 

felling and produced more residue per mill-delivered volume (fig. 4).

Grand fir (Abies grandis (Doug Ex D. Don) Lindl.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western larch (Larix occidentallis Nutt.), and western redcedar 

(Thuja plicata Donn ex D. Donn) were the top four species in the sample. Together, 

they accounted for 82 percent of the total mill delivered volume and 87 percent of the 

growing-stock logging residue (fig. 5).

Characteristics of Logging Operations and Sites

Harvesting methods included hand (i.e., with chainsaws) and mechanical felling and 

merchandising, as well as a mix of the two. Mechanical felling methods included the use 

of equipment with accumulating heads such as a “hot saw” or feller-buncher, as well as 

cut-to-length (CTL) harvesting heads. Hand felling and merchandising was done with 

chainsaws. Mechanical merchandising methods included the use of stroke (slide-boom) 

delimbers and dangle-head processors either at the landing or as part of a CTL system. 

Ground-based skidding included the use of rubber-tired skidders or dozers, which had 

either a grapple or a winch with chokers.

Figure 4—Volume of growing-stock logging residue and residue per mill-delivered mcf by tree dbh class.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 9

Mechanized systems dominated Idaho logging operations in 2008 and 2011. 

Mechanical felling was employed nearly twice as often as hand felling, which 

was reserved for steep slopes and sensitive areas like riparian zones. Each of the 

following methods was employed at least four times as frequently as their alternative: ground based yarding, tree length skidding, merchandising at the landing, and 

merchandising with mechanical processors (table 2). Cable yarding was used on 

just 12 percent of sites, versus 88 percent of sites with ground skidding. Tree-length 

skidding was employed at 82 percent of sites. Merchandising at the landing was 

also far more common (88 percent of sites) than merchandising in the unit. CTL 

systems, where material was stacked on a forwarder in the unit and unloaded at a 

landing or transferred directly onto a logging truck, were used at only two locations 

(6 percent of sites).

Figure 5—Proportions of mill-delivered volume and growing-stock logging residue by species.
10 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 Table 2—Number of sampled sites by logging methods and ownership class. Felling Yarding Skidding Merch location Merch method Ownership Hand b Mechanical Mixed Ground Cable Tree length Log length In unit At landing Mechanical Hand b Federal 1 1 0 1 1 1 1 1 1 2 0 State 3 2 1 5 1 3 3 1 5 4 2 NIPF a 1 2 0 3 0 3 0 1 2 3 0 Industrial private 6 14 2 20 2 20 2 1 21 19 3 Total 11 19 3 29 4 27 6 4 29 28 5 a Non-industrial private forest. b With chainsaws.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 11

State-Wide Logging Utilization Factors

Logging utilization removals factors are state-wide ratios of removals volumes versus 

mill delivered volumes (Morgan and Spoelma 2008). Removals factors, quantifying 

impacts on growing stock, revealed that harvesting removed 1,011 cf of timber volume 

from growing stock for every mcf delivered to the mill; 987 cf of growing stock was 

utilized, plus 24 cf of growing stock was left in the forest or at the landing as logging 

residue (table 3). In addition, 13 cf of non-growing stock from stumps and tops went 

to the mill.

Among the major harvested species, western redcedar showed the lowest residue per 

delivered volume, with only 21 cf of growing-stock residue created per mcf delivered to 

the mill. Douglas-fir followed closely at 22 cf, and grand fir at 27 cf per mcf. Western 

larch had the highest residue factor, with 32 cf of growing-stock logging residue generated per mcf delivered to the mill.

Of the merchantable stem (i.e., portions of the tree from the cut stump to the end of 

utilization), 1.3 percent was mill-delivered volume from non-growing stock (i.e., stumps 

and tops above 4 inches dob), 96.4 percent was mill-delivered volume from growing 

stock, and 2.3 percent was unutilized growing-stock logging residue (fig. 6). Most of 

the growing-stock logging residue came from stumps cut higher than 1.0 foot above 

ground level and portions of the bole that were broken during felling. Relatively little 

logging residue came from stem sections near the end of growing-stock (i.e., the 4-inch 

dob). There is relatively less volume in the smaller-diameter (upper) portions of the 

bole, compared to stump sections. Also, with the frequent use of whole-tree harvesting 

and 23 of the 33 logging sites having pulpwood as a component, use of the smaller bole 

sections was quite common.

Table 3—Idaho 2008/2011 logging utilization removals factors.

Lower Estimate Upper

bound (ratio of bound Standard Cubic feet per

Removals factors (95% CI) means) (95% CI) error mill-delivered mcf

Non-growing stock product delivered to mills 0.009 0.013 0.018 0.002 13

(utilized non-growing stock ÷ total utilized) 

Growing-stock product delivered to mills 0.982 0.987 0.991 0.002 987

(utilized growing stock ÷ total utilized)

Growing-stock logging residue 0.017 0.024 0.032 0.004 24

(unutilized growing stock ÷ total utilized)

Removals from growing stock 1.000 1.011 1.022 0.005 1,011

((utilized + unutilized growing stock) ÷ total utilized)

Figure 6—Merchantable stem utilization.
12 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

Discussion ______________________________________________________________

Idaho Logging Utilization Through Time

Research methods, particularly site selection and volume calculation, differed between 

the current study and prior (i.e., 1965 and 1990) Idaho logging utilization investigations. 

Although methodological differences prevent comprehensive statistical tests between 

this study and earlier ones, useful and informative comparisons are still possible.

In his 1990 study, McLain (1996) allocated sample sites proportional to volume of 

harvest by ownership and volume of harvest by resource area. For this analysis, sampled 

logging sites were selected at random from the target population of all known sites across 

Idaho. Through a mill canvass, McLain estimated that National Forest System (NFS) 

lands provided approximately 45 percent of Idaho’s harvested timber volume (McLain 

1996; fig. 7). The current study’s ownership distribution is a reflection of the dwindling 

volume harvested from NFS lands over the past 20 years. Only 6 percent of Idaho’s 2006 

timber harvest came from NFS compared to 40 percent or more prior to 1995 (Brandt 

and others 2012). Geographic distribution for this study paralleled the 1990 study’s site 

distribution, in that the majority of harvest and therefore most of the sample sites were 

located in the northern Idaho resource area in both time periods.

Volume computation methods differed between this and previous investigations. 

Researchers in previous studies scaled felled tree sections using the Scribner Log Rule 

then converted board foot to cf volumes using a conversion factor of 4.5 board feet per 

cf (McLain 1996; Wilson and others 1970). Consistent with contemporary national logging utilization methods (Bentley and Johnson 2004; Morgan and Spoelma 2008), cubic 

volumes were calculated in the 2008/2011 study using large- and small-end diameters 

and section lengths with Smalian’s formula (Avery and Burkhart 1994).

Removals factors have changed substantially through time. From 1965 to 2011, there 

has been a 10 percent (112 cf) reduction in total growing-stock removals per mcf of 

mill-delivered volume, and an 80 percent (99 cf) reduction in the volume of growingstock logging residue generated per mcf harvested (table 4). Since 1990, growing-stock 

logging residue has decreased 72 percent (61 cf) per mill-delivered mcf, total removals 

from growing stock have declined 6 percent (65 cf) per mill-delivered mcf, and there 

has been a 44 percent increase in the utilization of non-growing stock components (i.e. 

stumps and tops). Contemporary logging activities generate far less growing-stock 

residue than historic practices, and have a lower overall impact on growing-stock, with 

more mill-delivered volume coming from non-growing stock portions of harvested trees.

Figure 7—Percent of sample sites by ownership class, 1990 and 2008/2011.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 13

Table 4—Removals and residues over time.

1965 1990 a 2011 Change Percent change

- - - - - - - - - - - - - - Cubic ft (cf) per 1,000 cf mill delivered - - - - - - - - - - - - - - 

Non-growing stock product delivered to mills N/A 9 13 4 44

Growing-stock product delivered to mills N/A 991 987 -4 0

Growing-stock logging residue 123 85 24 -61 -72

Removals from growing stock 1,123 1,076 1,011 -65 -6

a Base year for change comparison.

The decrease in the percentage of growing stock left in the woods as logging residue 

and the increase in the utilization of non-growing stock portions of the tree can be attributed to technological advancements in logging and milling operations. Most of the 

sites that field crews sampled were harvested with highly efficient, mechanized logging 

systems. Further, receiving mills were often equipped with computerized log profilers 

and state-of-the-art sawing capabilities, which allowed them to process logs more efficiently, especially small-diameter trees.

Over the last 20 years, timber harvests have shifted from larger to smaller diameter 

trees. In 1990, only 33 percent of felled tree volume came from trees with dbh ≤ 17 

inches, and 28 percent came from trees with dbh > 27 inches. Results from the current 

study show that 51 percent of felled tree volume came from trees with dbh ≤ 17 inches, 

and just 2 percent came from trees with dbh > 27 inches (table 5). This progressive shift 

to the use of smaller-diameter timber over time is well documented. McLain noted the 

same trend when comparing his 1990 results to those of Wilson in 1965 (McLain, 1996; 

Wilson and others 1970), and analyses of sawmill data have revealed similar trends 

toward the use of smaller-diameter timber (Keegan and others 2010 a,b) throughout 

the western United States.

Table 5—Comparison of growing-stock removals by dbh class, 1990 vs. 2008/2011.

dbh 

class

1990 GSa volume 

removed

Percent of 

GSa volume

Cumulative 

percent

dbh 

class

2008/2011 

GSa volume 

removed

Percent of 

GSa volume

Cumulative 

percent

6 5 1

33 percent 

of total 

volume

6 6 1

51 percent 

of total volume

8 25 2 8 38 4

10 55 5 10 80 8

12 71 7 12 123 12

14 110 10 14 131 13

16 97 9 16 141 14

18 135 12

72 percent of 

total volume

18 139 14

98 percent of 

total volume

20 53 5 20 120 12

22 119 11 22 71 7

24 62 6 24 93 9

26 46 4 26 48 5

28 62 6 28 percent of 

total volume

30+

28 13 1 2 percent of 

30+ 247 23 7 1 total volume

Total 

GSa

volume

1,087 100 b

Total 

GSa

volume

1,011 100 b

a Growing stock.

b Percentages may not sum to 100 due to rounding.
14 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014

Idaho’s Redcedar Phenomenon

Results indicated that western redcedar yielded somewhat smaller volumes of logging 

residue per mcf of mill-delivered volume than other Idaho tree species. Land managers 

may find this result counterintuitive because older, large-diameter cedars are typically 

found with heavy heart rot. The calculation of the growing-stock logging residue factor 

can partially explain this anomaly. This factor is a ratio of residue volume to mill-delivered 

volume, which can produce a low ratio, particularly when mill-delivered volumes are 

quite high. Although the butts of older cedar may contain much defect-related residue, 

older cedars are usually large-diameter trees with higher mill-delivered volumes that 

often dwarf the residue volumes and therefore lower the ratio. Efficient utilization of 

cedar trees in Idaho has contributed to sizeable volumes of cedar being delivered to 

mills. Brandt and others (2012) identified seven cedar product facilities operating in 

northern Idaho in 2006. A robust cedar products industry coupled with competition 

for high-value cedar products, utility poles, and cedar sawlogs have ensured that mill 

deliveries of cedar wood remain exceptionally high.

Conclusions _____________________________________________________________

Logging utilization studies can help land managers understand the impacts of commercial timber harvesting on growing-stock inventories, woody residue volumes, and 

carbon dynamics. Variables including logging method, site quality, species, diameter, 

defect, and the presence/absence of a pulp market can have profound impacts on the 

production of logging residue.

The sampling design used in this study appears to have captured the range in variability of recent Idaho logging sites and harvested trees. Site locations as a reflection 

of geographic distribution and species mix in the sample closely approximated Idaho’s 

2006 timber harvest, as reported by Brandt and others (2012). Results also suggest that 

the sampling scheme did well at capturing information on the more frequently harvested 

species, but perhaps not as well with the very infrequently harvested species. This study 

produced removals factors that enabled meaningful comparisons to historical data as 

well as stand-alone analysis of current timber harvesting activities in Idaho. Findings of 

this study support the results of previous studies that indicate technology has reduced 

the amount of growing-stock logging residues with improved utilization of non-growing 

stock material over time.

Results show that in Idaho the diameter of harvested trees has been decreasing over 

time. With less volume per tree, more small trees are required to produce the same milldelivered volume. Smaller trees have also been shown to produce more logging residue 

per unit of mill-delivered volume than larger diameter trees. This dynamic suggests that 

if the trend of harvesting smaller diameter timber continues and the total amount of 

volume delivered to the mill remains constant, then the total amount of logging residue 

generated from that harvest will increase. This growing volume of unutilized material 

could represent a potential source of material for the burgeoning woody biomass or 

biofuels industry.

Future logging utilization investigations could provide land managers with estimates 

of biomass specified by individual tree components, including unutilized tops and 

limbs. In addition, easy-to-use residue prediction models that integrate the effects of 

land ownership, logging systems, and other variables could greatly enhance the utility 

of these studies for land managers.
USDA Forest Service Gen. Tech. Rep. RMRS-GTR-318. 2014 15

Acknowledgments________________________________________________________

The authors gratefully acknowledge the financial support of: USDA Forest Service, 

Rocky Mountain Research Station, Forest Inventory and Analysis Program, Ogden, 

Utah; and the Northwest Advanced Renewables Alliance supported by the Agriculture 

and Food Research Initiative Competitive Grant no. 2011-68005-30416 from the USDA 

National Institute of Food and Agriculture. Other cooperators include: the Idaho Department of Lands; numerous private landowners, foresters, and loggers; Charles B. Gale, 

research assistant; and William H. McLain, Forest Service (Retired).

References ______________________________________________________________

Avery, T.E.; Burkhart, H.E. 1994. Forest measurements, 4th ed. New York: McGraw-Hill, Inc. 408 p.

Bentley, J.W.; Johnson, T.G. 2004. Eastern Texas harvest and utilization study, 2003. Resour. Bull. SRS97. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. 28 p.

Brandt, J. P.; Morgan, T.A.; Keegan, C. E., III; Songster, J. M.; Spoelma, T. P.; DeBlander, L.T. 2012. Idaho’s 

forest products industry and timber harvest, 2006. Resour. Bull. RMRS-RB-12. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 45 p.

Keegan, C.E., T.A. Morgan, K.A. Blatner, and J.M. Daniels. 2010a. Trends in lumber processing in the 

western United States, part 1: Board foot Scribner volume per cubic foot of timber. Forest Products 

Journal. 60 (2):133-139.

Keegan, C.E., T.A. Morgan, K.A. Blatner, and J.M. Daniels. 2010b. Trends in lumber processing in the western United States, part 2: Overrun and lumber recovery factors. Forest Products Journal. 60 (2):140-143.

Levy, P.S., and S. Lemeshow. 1999. Sampling of populations: Methods and applications, 3rd ed. New 

York: Wiley, Inc. 525 p.

McLain, W. H. 1996. Logging utilization - Idaho, 1990. Resour. Bull. INT-RB-86. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 16 p.

Morgan, T. A.; Keegan, C.E., III; Hayes, S.W.; O’Laughlin, J. R.; Taylor, R. G.; Watson, P.; Gorman, T.M.; 

Shook, S. 2013. Station Bulletin 100. Contribution No. 1074 of the Idaho Forest, Wildlife and Range 

Experiment Station, University of Idaho, Moscow, Idaho. 4 p.

Morgan, T.A.; Keegan, C.E., III; Spoelma, T.P.; Dillon, T.; Hearst, A.L.; Wagner, F.G.; DeBlander, L.T. 

2004. Idaho’s forest products industry: A descriptive analysis. Resour. Bull. RMRS-RB-4. Fort Collins, 

CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 31 p.

Morgan, T.A.; Spoelma, T.P. 2008. California logging utilization: 2004. Western Journal of Applied Forestry. 23(1):12-18.

Morgan, T.A.; Spoelma, T.P.; Keegan, C.E., III; Chase, A.L.; Thompson, M.T. 2005. Montana logging 

utilization, 2002. Res. Pap. RMRS-RP-52. Fort Collins, CO: U.S. Department of Agriculture, Forest 

Service, Rocky Mountain Research Station. 12 p.

SAS. 2010. SAS version 9.2. Cary, NC: SAS Institute Inc.

Wilson, A.K.; Green, R.E.; Choate, G.A. 1970. Logging residues on sawlog operations, Idaho and Montana. 

Res Pap. INT-77. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Forest and 

Range Experiment Station. 12p.

Witt, Chris; Shaw, John D.; Thompson, Michael T.; Goeking, Sara A.; Menlove, Jim; Amacher, Michael 

C.; Morgan, Todd A.; Werstak, Charles. 2012. Idaho’s Forest Resources, 2004-2009. Resour. Bull. 

RMRS-RB-14. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain 

Research Station. 134 p.

Woudenberg, Sharon W.; Conkling, Barbara L.; O’Connell, Barbara M.; LaPoint, Elizabeth B.; Turner, 

Jeffery A.; Waddell, Karen L. 2010. The Forest Inventory and Analysis Database: Database description 

and users manual version 4.0 for Phase 2. Gen. Tech. Rep. RMRS-GTR- 245. Fort Collins, CO: U.S. 

Department of Agriculture, Forest Service, Rocky Mountain Research Station. 336 p.

Zarnoch, S.J.; Bentley, J.W.; Johnson, T.G. 2004. Determining sample size for tree utilization surveys. 

Res. Pap. SRS-34. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research 

Station. 11 p. 


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