United States 

Department of 

Agriculture

Forest Service

Pacific Northwest 

Research Station

General Technical 

Report

PNW-GTR-790

June 2009

Characteristics of Remnant 

Old-Growth Forests in the 

Northern Coast Range of 

Oregon and Comparison to 

Surrounding Landscapes

Andrew N. Gray, Vicente J. Monleon, and Thomas A. Spies
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multiple use management of the Nation’s forest resources for sustained yields of wood, 

water, forage, wildlife, and recreation. Through forestry research, cooperation with the 

States and private forest owners, and management of the National Forests and National 

Grasslands, it strives—as directed by Congress—to provide increasingly greater service 

to a growing Nation.

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Authors 

Andrew N. Gray is an ecologist and Thomas A. Spies is a research forester, 

Forestry Sciences Laboratory, 3200 SW Jefferson Way, Corvallis, OR 97331; 

Vicente J. Monleon is a research mathematical statistician, Forestry Sciences 

Laboratory, 620 SW Main St., Suite 400, Portland, OR 97208.

Cover photograph by Andrew Gray.
Abstract

Gray, Andrew N.; Monleon, Vicente J.; Spies, Thomas A. 2009. Characteristics 

of remnant old-growth forests in the northern Coast Range of Oregon and comparison to surrounding landscapes. Gen. Tech. Rep. PNW-GTR-790. Portland, 

OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research 

Station. 45 p.

Old-growth forests provide unique habitat features and landscape functions 

compared to younger stands. The goals of many forest management plans in the 

Pacific Northwest include increasing the area of late-successional and old-growth 

forests. The goal of this study was to describe existing old-growth forests in the 

northern Oregon Coast Range that might serve as examples of desired future 

conditions and developmental pathways. In addition, the abundance of specific 

stand attributes associated with old-growth stands was estimated from regional 

inventory data. Most of the old-growth stands had experienced moderately severe 

disturbances during their development resulting in mid- and understory trees 

belonging to cohorts younger than those of overstory trees. Most of the stands had 

the full complement of old-growth attributes (large shade-intolerant trees, shadetolerant trees, snags, and down wood), although the dead wood attributes tended 

to be less abundant in drier stand types. Thresholds for at least four of the five 

old-growth attributes were met on 7 percent of the inventory plots on federal lands, 

but on only 0.4 percent of the inventory plots on nonfederal lands. Shade-intolerant 

trees in particular were low in abundance in mature stands of intermediate diameter 

class (10 to 30 in). Large-diameter class stands (>30 in) were more abundant near 

the coast than near the Willamette Valley margin. Results suggest that although 

old-growth forests can develop along multiple pathways, stand composition and 

productivity constrain development such that expecting all late-successional stands 

to have the full complement of old-growth attributes may not be realistic. 

Keywords: Old growth, late-succesional forest, inventory, habitat, disturbance.

1

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Introduction

Old-growth forests are stands dominated by trees of advanced age, and their 

abundance is important throughout the world. Old-growth forests often provide 

unique habitat features for a wide variety of organisms and unique functions on the 

landscape that are not provided as well by younger stands at earlier successional 

stages of development (Ruggiero et al. 1991). Old-growth forests have declined 

dramatically in abundance in many regions in the last several centuries, owing 

mostly to logging and land conversion, and they can take a long time to grow back 

(Gray 1998, Spies and Franklin 1996). It is important to study remaining stands 

because there are not many left, and we need to be able to describe their structure 

and composition. Many land managers are tasked with increasing the area of oldgrowth (or late-successional) stands, so it is important to define those targets 

in sufficient detail.

The current management emphasis for large portions of federal land in the 

coastal Pacific Northwest under the Northwest Forest Plan (NWFP) is the maintenance and restoration of late-successional forests (USDA Forest Service and USDI 

Bureau of Land Management 1994). Late-Successional Reserves were created to 

protect existing late-successional and old-growth forests and provide for development of new ones from younger stands. Although management was allowed in 

those younger stands to promote old-growth characteristics, the processes responsible for old-growth development, how they differ regionally, and how to encourage 

them with management, are topics of debate (Carey et al. 1999, Gray 2000, Spies 

and Franklin 1996). In the Oregon Coast Range, where evidence of the structure of 

presettlement forests across much of the landscape has been erased by subsequent 

wildfires and logging, determining the natural abundance and characteristics of oldgrowth forests is contentious as well. Some studies suggest that old-growth stands 

formed at much lower densities than those currently found in young and mature 

forests (Tappeiner et al. 1997). Other studies indicate that old-growth stands in the 

Coast Range are younger and less structurally diverse than those in other parts 

of the Pacific Northwest (Spies and Franklin 1991). Additional information on the 

structure, composition, and disturbance history of existing old-growth stands could 

provide a useful reference for desired future conditions of Coast Range forests.

A variety of approaches have been used to define, classify, and quantify the 

abundance of old-growth forests. The simplest approach is to apply a threshold 

for a single attribute to classify stands as old-growth. For example, Bolsinger and 

Waddell (1993) classified all plots in the region that sampled stands 200 years or 

older as old growth, using readily available inventory plot data. Other approaches 

to quantify old-growth forest abundance have used stand structural stages either 

The processes 

responsible for oldgrowth development, 

how they differ 

regionally, and how 

to encourage them 

with management, 

are topics of debate. 
2

GENERAL TECHNICAL REPORT PNW-GTR-790

inferred from remote sensing or assessed on inventory field plots (Moeur et al. 

2005). Additional approaches have described old-growth forests using a variety of 

stand structural attributes that tend to be present in old-growth. This was initially 

developed for Douglas-fir forests (Franklin et al. 1986), and subsequently extended 

to other forest types and refined to account for differences in site productivity 

(USDA Forest Service 1993). An alternative to describing thresholds for attributes 

is to use an index of the degree to which stands contain high-quality old-growth 

attributes (i.e., “old-growthiness”), either derived solely from stand variables 

(Spies and Cohen 1992), or through ratios of calculated stand attributes to those 

found in old-growth stands (Acker et al. 1998, Pabst 2005). It is not clear how well 

these different approaches work in a variety of forest types or how they compare 

to each other.

The objectives of this study were to (1) survey and describe the composition 

and structure of existing old-growth stands found along an east-west gradient 

across the northern Oregon Coast Range, (2) compare attributes of old-growth 

stands in the northern Coast Range with data from an earlier study conducted to 

the south, and (3) determine the abundance of old-growth stand attributes in the 

Oregon Coast Range from regional inventory data.

Our analysis of old-growth forest characteristics focuses on a variety of stand 

structural attributes found in ecological definitions of old growth. The Old-Growth 

Definition Task Group (Franklin et al. 1986) (referred to as “PNW-447" based on 

the issue number of the research paper) listed several attributes that were relatively 

easy to measure and that could be used as minimum criteria for classifying 

Douglas-fir 1 dominated stands as old-growth. Although few old-growth stands 

would meet all criteria, it was expected that most old-growth stands would meet 

most of the criteria. For Douglas-fir dominated stands on western hemlock zone 

sites, the criteria were:

a. Two or more tree species in a range of sizes and ages

b. Douglas-fir trees ≥32 in diameter at breast height (DBH) or 

≥200 yr old: eight or more per acre

c. Shade-tolerant associates (western hemlock, western redcedar, Pacific 

silver fir, grand fir, or bigleaf maple) ≥16 in DBH: 12 or more per acre

d. Deep, multilayered canopy

e. Conifer snags ≥20 in DBH and ≥15 ft tall: four or more per acre

f. Biomass of downed logs: ≥15 tons per acre

g. Downed logs ≥24 in diameter at large end and ≥50 ft long: four or 

more per acre

1 See “Common and Scientific Names” in appendix tables 9 and 10.
3

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Slightly different criteria were provided in the same publication for 

Douglas-fir-dominated stands in the drier Douglas-fir or grand fir zones:

a. Two or more tree species in a range of sizes and ages

b. Douglas-fir, ponderosa pine, or sugar pine trees ≥30 in DBH or 

≥200 yr old: eight or more per acre

c. Intermediate and small size classes of white fir, Douglas-fir, or 

incense-cedar present

d. Multilayered canopy

e. Conifer snags ≥20 in DBH and ≥15 ft tall: one or more per acre

f. Biomass of downed logs: ≥10 tons per acre

g. Downed logs ≥24 in diameter at large end and ≥50 ft long: two 

or more per acre 

Subsequent efforts developed similar criteria adjusted by stand productivity 

class (site class) for most of the vegetation zones in Oregon and Washington (USDA 

Forest Service 1993) to reflect differences in the speed of stand development with 

site class. As the purpose of this paper was not to classify stands but compare 

structural attributes of stands in different forest types, the simpler levels presented 

in PNW-447 for the western hemlock zone were used for comparison.

Methods

Study Area

The Coast Range rises between the Pacific Ocean and the Willamette Valley in 

Oregon; the study area we selected was bounded by the ocean on the west, the 

Willamette River on the east, the Columbia River on the north, and the North 

Umpqua River on the south (fig. 1). This study focuses primarily on federal lands 

in the portion of this area north of the city of Newport and is referred to as the 

“northern” Coast Range. The area between Newport and the North Umpqua River 

is referred to as the “central” Coast Range, and old-growth and inventory data from 

this area were compared with data collected in the northern area. The Coast Range 

consists of steep, dissected mountains ranging from sea level to 4,000 ft in elevation. 

Climate follows the regional pattern of cool, wet winters and warm, dry summers 

but varies significantly with elevation and distance from the coast. Forests along 

the coast are dominated by Sitka spruce and western hemlock, with most forests 

away from the coast dominated by Douglas-fir and western hemlock (Franklin and 

Dyrness 1973). Drier Douglas-fir, grand fir, and Oregon white oak communities 

occur in the eastern foothills of the range. The coastal stands are among the most 

productive forests in the world, with aboveground biomass production of 4.5 to 6.7 

tons · ac-1 · yr-1 in mature (about 100-yr-old) stands (Gholz 1982).
4

GENERAL TECHNICAL REPORT PNW-GTR-790

Figure 1—Study area showing delineation of northern and central Oregon Coast Range zones, lands managed by the 

Bureau of Land Management and the U.S. Forest Service, and selected cities.

Astoria

Tillamook

Newport

Reedsport

Portland

City

Major rivers

Bureau of Land Management

Forest Service

Central Coast Range

Northern Coast Range

0 10 20 40 Miles

Eugene o
5

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Large high-intensity fires in the mid-1800s had a significant impact on the 

northern Coast Range (Holbrook 1943, Morris 1934, Teensma et al. 1991); much 

of the heavily burned land was designated national forest in 1905. Similarly, much 

of the Tillamook Burn of 1933 reverted to state ownership and was designated 

state forest. The valley margin has changed substantially in the last 150 years, 

from being open prairie-savanna maintained by Native American burning to being 

dominated by closed forests (and agriculture) (Thilenius 1968). The federal forest 

lands in the study area are administered by the USDA Forest Service (FS) and the 

USDI Bureau of Land Management (BLM). Much of the BLM lands are mixed 

with private industrial forest land in a checkerboard pattern.

Stand Selection and Measurement

An extensive effort was undertaken to locate old-growth stands on publicly owned 

lands across the climatic and vegetation gradient from the coast to the valley 

margin. The primary selection criterion was for stands with a fairly continuous distribution of trees greater than 40 in DBH over a 1-ha (2.47-ac) area. In some cases, 

the oldest stands found in a vegetation zone were sampled, even if many of the 

old-growth structural attributes were not apparent. Small patches (i.e., patches that 

did not cover most of a 1-ha circular plot), stands where dead trees had been salvage 

logged, and stands with scattered large trees at low density were not sampled. 

Potential stands for sampling were identified by investigating a variety of sources, 

including initial models of stand size class from satellite images (Cohen et al. 2001), 

data from forest inventory plots, agency stand maps (developed from aerial photointerpretation), aerial photos, word-of-mouth from agency employees and researchers, and published studies and reports (Greene 1982, Juday 1976, Quaye 1982, 

Thomas et al. 1993, Wood 1991). Potential sites were visited, and dominant trees 

were measured for diameter and increment-cored for age. Permission was obtained 

from the land managers for plot installation in the Cascade Head Scenic Research 

Area, in the BLM research natural areas (RNAs) and areas of critical environmental 

concern, and in Oregon State University’s McDonald-Dunn Forest. Thirteen stands 

were selected and measured during the summers of 1997 and 1998 (table 1, fig. 2). 

No stands were identified in the northern half of the northern Coast Range study 

area. Within each stand, four points were identified and one was randomly selected 

as plot center; in most cases, however, stands were so small that the plot footprint 

would have overlapped substantially from any selected point. Large gaps (about 

60 ft in diameter) fell within the plot area in three of the stands (VOG, Moon, and 

ElkCk), while part of a plot (about 0.25 ac) crossed into a younger age class in one 

of the stands (Rowell2).

Large high-intensity 

fires in the mid-1800s 

had a significant 

impact on the northern 

Coast Range.
6

Table 1—Locations and site characteristics of measured old-growth plots, and groupings used in some analysesSite code Site name Ownera Latitude Longitude Elevation Precipitationb Slope Aspect Slope position Plant asso

Feet Inches Percent Degrees

Nesk Neskowin Crest USFS 45.0741 -123.9793 1,200 110 41 73 Slope, upper 3rd PISI/OXO

CliffCk Cliff Creek USFS 45.0631 -123.9830 1,500 112 30 297 Slope, upper 3rd PISI/OXOVOG Valley of Giants BLM 44.9402 -123.7108 1,300 137 11 193 Bench TSHE/OX

Bear Bear Creek USFS 44.8813 -123.8500 1,180 118 59 150 Slope, lower 3rd TSHE/OX

LtGrass Little Grass BLM 44.7479 -123.5969 1,860 145 39 154 Bench TSHE/OX

Mountain

Moon Moon Creek BLM 45.3410 -123.6623 1,320 110 71 181 Slope, lower 3rd TSHE/AC

ElkCk Elk Creek BLM 45.3050 -123.5675 1,400 107 41 200 Bench TSHE/AC

Rock Rock Creek USFS 44.9849 -123.9391 480 105 52 215 Slope, lower 3rd TSHE/GA

Rowell1 Rowell Creek BLM 44.9808 -123.5805 1,300 88 54 215 Slope, middle 3rd TSHE/RH

 #1

Rowell2 Rowell Creek BLM 44.9713 -123.5880 1,570 97 59 133 Slope, middle 3rd TSHE/MA

 #2

Dorn Dorn Peak BLM 44.9767 -123.5507 2,030 90 49 154 Slope, upper 3rd TSHE/AC

McDon1 McDonald OSU 44.6361 -123.3015 1,100 61 41 329 Slope, upper 3rd ABGR/CO

Forest #1

McDon2 McDonald OSU 44.6269 -123.3154 1,200 65 31 29 Rounded ridge top ABGR/CO

Forest #2

a USFS = U.S. Forest Service; BLM = Bureau of Land Management; OSU = Oregon State University.b Annual precipitation estimated from overlay of plot locations on PRISM maps (Daly et al. 1994).c Plant Associations determined from vegetation using McCain and Diaz (2002); species data and codes identified in appendix table 10.d Identified only for Douglas-fir-dominated stands >200 yr old.
7

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

o

Plot

City

River

Federal land

Luckiamute

Yaquina

Siletz

Nestucca

Wilson

Yamhill

Wil al mette

Tillamook

Newport

Moon

ElkCk

Nesk

CliffCk

Rock

VOG

Rowell1

Rowell2

Dorn

Bear

LtGrass

McDon2

McDon1

0 10 20 Miles

Figure 2—Location of old-growth plots sampled for this study in the northern Oregon Coast Range.
8

GENERAL TECHNICAL REPORT PNW-GTR-790

The field measurement protocol was based on the Current Vegetation Survey 

(CVS) forest inventory design used on federal lands at the time (Max et al. 1996). 

The plot design consisted of a cluster of five points within a 2.47-ac (1-ha) circle, 

with four points spaced 133.9 ft in cardinal directions from the central point. Slope, 

aspect, and slope position were recorded for each point. At each point, trees and 

snags of different sizes (<3, 3 to 12.9, and 13 to 47.9 in DBH) were measured in a 

set of three nested plots of different sizes (0.01, 0.05, and 0.19 ac, respectively). In 

addition, all trees and snags ≥48 in DBH were measured on the full 2.47 ac. Owing 

to time limitations, all sampling was done using slope distances, and actual horizontal plot areas were calculated during analysis using the slope at each point. The 

use of slope distances resulted in horizontal plot areas that ranged from 81.5 to 99.3 

percent of the nominal, 2.47-ac horizontal area for the 13 stands, with a mean of 

90.6 percent. Up to three trees of each species across the range of diameters present 

were bored for age (largest borer used was 24 in long) and cores taken back to the 

lab for analysis. If available, nearby stumps of the same size classes were examined 

for age.

Logs were tallied using the line-intercept method on two transects oriented 

north-south and east-west, that crossed the width of the 2.47-ac plot, resulting in a 

total transect slope length of 740 ft, and the slope of each transect was measured. 

This sometimes resulted in the same log being tallied on two different transects, 

and the data were used from both samples. The common concern that sampling 

with multiple transects introduces bias is unfounded; estimates derived from each 

individual transect are unbiased and the mean of two unbiased estimates can never 

be biased (Woodall and Monleon 2008). Because plot centers are usually randomly located, multiple transects are a random sample of a stand; they are exactly 

analogous to sampling with a cluster of subplots, or a cluster of prism plots that 

occasionally tally the same large tree. There is a substantial body of literature on 

line-intercept sampling in which clusters of transects are used, and they appear to 

be most efficient in both variance reduction and field implementation (e.g., Bell et 

al. 1996, Hazard and Pickford 1986). Logs, or portion of logs, ≥3 in diameter were 

selected, and the species; decay class; large-end, intersect, and small-end diameters 

(or 3 in, whichever was greater); and length between small- and large-end diameters 

were recorded. The cover of each vascular plant species was recorded on three of 

the five points (the central point and two randomly selected from the remaining 

four) using the 0.05-ac plot size.
9

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Other Data Sets

Plots were established in old-growth stands in the central Coast Range and areas 

south of the study area in the 1980s for the U.S. Forest Service, Pacific Northwest 

Research Station’s Old Growth Wildlife Habitat Program (Spies and Franklin 1991; 

referred to as “OGWH” plots). Data from the OGWH plots were analyzed to compare old-growth attributes with stands sampled in the northern Coast Range for this 

study. In the OGWH study, stands 10 to 50 ac in area were selected to span a range 

of site-moisture conditions. Within each stand, up to five points were systematically 

located 100 or 150 m (328 or 492 ft) apart, depending on stand area. At each point, 

trees and snags of different sizes (<20 or ≥20 in DBH) were measured in two nested 

plots (0.12 and 0.25 ac, respectively). Portions of down wood pieces that fell within 

the 0.12-ac plot were measured. All sampling was done using slope distances, and 

actual horizontal plot areas were calculated during analysis using the slope at each 

point. Twenty-four stands in the Coast Range that were sampled with four or five 

points were selected for analysis. Roughly half of the plots used in the analysis were 

installed south of the study area, between Coos Bay and Reedsport.

Forest inventory plots that fell within the study area were analyzed to assess the 

distribution and abundance of old-growth structural characteristics on the landscape. The CVS plots were established on FS and BLM lands using the same basic 

plot design as that used in the north coast old-growth stands. The CVS plots were 

located on a systematic 1.7-mi grid (3.4-mi in wilderness) between 1993 and 2001. 

The only differences between the CVS and north coast field protocols were that one 

51.1-ft-long line-intercept transect was used at each CVS point, resulting in a total 

transect length of 256 ft, and all lengths and plot areas were horizontally corrected 

for slope in the field. Five hundred and eighty-four CVS plots, on which at least four 

out of the five points were classified as forested plant associations (McCain and 

Diaz 2002), were selected for analysis.

In 2001, the Forest Inventory and Analysis (FIA) Program began installing a 

nationally standardized inventory across all forest lands in the region (Bechtold and 

Patterson 2004, USDA Forest Service 2006). The consistent plot design allows for 

more robust comparisons of attributes between federal and nonfederal lands than 

was possible using the CVS and earlier FIA inventories. Six-tenths of the plots on a 

systematic 3.3-mi grid were measured by FIA between 2001 and 2006 (all Western 

States are sampled on a 10-yr cycle). The plot design consisted of a cluster of four 

points within a 1-ha (2.47-ac) circle, with three points spaced 120 ft from center at 

0, 120, and 240 degrees. At each point, trees and snags of different sizes (<5, 5 to 

30, and ≥30 in DBH) were measured in a set of three nested plots of different sizes 

Forest inventory 

plots that fell within 

the study area were 

analyzed to assess 

the distribution and 

abundance of oldgrowth structural 

characteristics on 

the landscape.
10

GENERAL TECHNICAL REPORT PNW-GTR-790

(0.003, 0.04, and 0.25 ac, respectively). Woody debris was measured on two 58.9 

ft-long transects per point, resulting in a total transect length of 471 ft. All lengths 

and plot areas were horizontally corrected for slope in the field. Two hundred and 

seventy-one FIA plots, on which at least 75 percent of the plot area was forested and 

in nonfederal ownership, were selected for analysis of nonfederal lands. The same 

criterion was applied to federal lands, resulting in 99 selected plots.

Data Analysis 

All analyses of the northern Coast Range old-growth plot tree data were based 

on horizontal sample areas, calculated using the slope at each point and the (slope 

length) radius of each plot. The different plot areas were used to create a tree-level 

expansion factor (“tpa,” trees per acre), calculated as one divided by the horizontal 

sample area, in acres. Tree densities in different categories were calculated by 

summing tree tpa, and individual tree basal areas were multiplied by tpa before 

summing to the plot level. Calculations of quadratic mean diameter (QMD) and 

standard deviation of diameter used weighted means with tpa as the weight. 

Quadratic mean diameter was calculated for trees in dominant and codominant 

crown classes. Standard deviation of diameter was calculated separately as an 

indicator of canopy layering, using all live trees ≥1 in DBH; the divisor used for the 

calculation was the sum of weights (tpa) minus 1 (“vardef = wdf” in the MEANS 

procedure in SAS (1999)), which in effect provides an estimate of the standard 

deviation of DBH for a tree of mean tpa.

Descriptive statistics of forest structure and composition were calculated for 

each old-growth plot. Tree age at breast height was estimated for many of the large 

trees where the 24-in-long increment borer did not come near the pith. Missing age 

was calculated by extrapolating the growth rate of the two in nearest the pith to the 

missing distance to the pith (estimated as tree radius - core length). In cases where 

extrapolations were >100 yr, dominant or codominant trees of the same species and 

diameter as the uncored (e.g., relatively small diameter) portion of each tree were 

selected from regional inventory data (Waddell and Hiserote 2005) from plots in 

the Coast Range of similar site class, and the median age calculated. If this age 

was 25 percent different from the extrapolated age of the uncored radius, it was 

used for the age of the uncored portion instead. The ages on the smaller diameter 

trees are more accurate and may be a better indicator of maximum tree age (e.g., a 

413-yr-old, 41-in DBH Douglas-fir compared to a 296-yr-old, 71-in DBH Douglasfir on the Rock Creek plot). Some Douglas-fir trees were cored outside the stand 

being sampled to estimate timing of intermediate disturbances (ages noted with an 

asterisk in the diameter distribution graphs).
11

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

The slope of each transect and the transect slope length were used to calculate 

the horizontal length of each transect. Down log volume was calculated for each 

piece using the diameter-at-line-transect intercept. Highly decayed class-V logs 

were assumed to be flattened in cross section, with vertical diameter 0.439 times the 

measured horizontal diameter (Spies et al. 1988). Log biomass was calculated using 

the estimated log volume, species-specific wood densities from the Forest Products 

Laboratory (USDA Forest Service 1987), and decay-class biomass discounts from 

Waddell (2002). For class-V logs, the biomass discount for softwoods was based on 

the ratio for Douglas-fir (0.33), and the discount for hardwoods was based on the 

overall mean for multiple species (0.3) (Harmon and Sexton 1996). Volume per acre, 

mass per acre, and density were calculated from slope-corrected transect lengths 

(Woodall and Monleon 2008).

The variables used in the PNW-447 old-growth definition were calculated 

from the tree, snag, and woody debris data, except for the criterion of two or more 

tree species in a range of sizes and ages, which was not readily quantifiable. A few 

adjustments were made to apply the criteria to the broader range of forest composition found across the Coast Range. Because Sitka spruce often dominates early in 

succession in coastal stands, it was included in the calculation of the second criterion (“b”) as an estimate of large shade-intolerant tree density, and Pacific yew was 

included in the third criterion with the other shade-tolerant species. Because tree 

heights were only measured for a subset of trees, and crown ratio estimates were 

not very precise, the data were not suitable to assess crown layering directly. The 

standard deviation of tree DBH was used as an indicator of multilayered canopy, 

although no threshold was specified and the critierion was not included in the 

determination of old-growth status. The criterion related to down wood was split 

into two variables (mass and density) as not all of the data sets analyzed for this 

paper allowed calculation of log density.

Three indices of degree of “old-growthiness” were calculated with the northern 

Coast Range plot data: the canopy height diversity index (CHDI), (Spies and 

Cohen 1992), the old-growth index (OGI) (Acker et al. 1998), and the old-growth 

habitat index (OGHI; structure only, not using stand age) (Pabst 2005). The CHDI 

estimates crown area in different height classes, assigns weights that increase with 

height class, and sums values that result in an index ranging from 0 to 15. Tree 

heights were estimated from equations in Garman et al. (1995) assuming that all 

plots were of intermediate site class III. The OGI is based on values of standard 

deviation of DBH, density of early-seral trees >39.3 in DBH, density of all trees 

≥2 in DBH, and mean DBH; the index is based on where the calculated values lie 

between the mean for selected young and old-growth stands, and ranges from 0 
12

GENERAL TECHNICAL REPORT PNW-GTR-790

to 100. The OGHI is based on values of density of trees >39.3 in DBH, density 

of snags >19.6 in DBH and >49 ft tall, density of trees in four DBH classes (2 to 

10, 10 to 20, 20 to 40, and >40 in) combined into a diameter distribution index, 

and volume of down wood. The OGHI index for a stand is based on where the 

calculated values lie in relation to the mean for selected young, mature, and oldgrowth stands in the Coast Range, and ranges from 0 to 100.

The same calculations and procedures were used on the other data sets (OGWH 

old-growth plots, and CVS and FIA inventories within the study area). Because 

these plots span an even greater range of composition than the northern Coast 

Range old-growth plots, the species used in criteria “b” and “c” were expanded. 

Noble fir and incense-cedar were included in the shade-intolerant species category, 

and California laurel was included in the shade-tolerant species category.

For some analyses of the different old-growth and inventory data sets, data 

were grouped into three forest zones, called “spruce,” “hemlock,” or “valley.” If 

Sitka spruce or lodgepole pine made up 5 percent or more of the basal area, the plot 

was classified as a “spruce” type. Otherwise, if western hemlock made up 5 percent 

or more of the basal area or if the plot was in the Coast Range ecoregion section 

(Cleland et al. 2005), then it was classified as a “hemlock” type. All remaining plots 

(in the margins of the Willamette Valley) were classified as “valley” types.

Results

Tree Composition and Structure

The northern Coast Range old-growth plots are described and shown in all figures 

and tables in order from moist to dry sites, as inferred from plant associations and 

topography. This generally meant a progression from west to east, particularly at 

the ends of the gradient (fig. 2), and from the spruce to hemlock to valley zones. 

Abbreviated plot names (“site codes”) are used in the figures, tables, and text; 

codes are defined in table 1.

The Neskowin Crest (Nesk) and Cliff Creek (CliffCk) plots were the only plots 

that were dominated by Sitka spruce; western hemlock was the only other species 

present (table 2). Sitka spruce trees tended to be the largest trees in each plot and 

were usually in the overstory canopy layer. Although spruce were abundant in the 

seedling pool (table 3), none were found in the 1 to 20 in DBH range (fig. 3a). Live 

and dead trees spanned the range of tree sizes at Nesk, whereas at CliffCk live 

trees occurred only in the middle size classes and snags occurred in the smallest 

size classes.
13

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Table 2—Basal area of live trees and snags by site and speciesa

Site code PSME TSHE PISI THPL ABGR TABR ACMA ALRU CONU UNKN Total

Basal area (ft 2/ac)

Live trees:

Nesk 185 186 371

CliffCk 98 415 513

VOG 300 212 512

Bear 290 187 53 12 542

LtGrass 320 115 8 6 449

Moon 254 134 6 3 397

ElkCk 250 123 0.3 374

Rock 333 221 1 2 557

Rowell1 311 99 1 410

Rowell2 227 209 8 444

Dorn 356 24 2 382

McDon1 179 11 47 0.4 237

McDon2 333 2 40 376

Standing dead trees:

Nesk 80 29 16 124

CliffCk 14 10 25

VOG 190 23 23 236

Bear 162 16 24 2 7 210

LtGrass 168 14 1 7 3 192

Moon 176 27 4 207

ElkCk 103 14 17 134

Rock 121 121 17 259

Rowell1 57 12 24 93

Rowell2 168 18 12 198

Dorn 77 0.4 4 13 94

McDon1 12 9 21

McDon2 2 4 7

a Species codes are defined in appendix table 9.

The rest of the plots were dominated by Douglas-fir. For the nine plots in the 

middle of the Coast Range moisture gradient (VOG, Bear, LtGrass, Moon, ElkCk, 

Rock, Rowell1, Rowell2, Dorn), the second-most important species was western 

hemlock (table 2). The only other species to constitute more than 5 percent of the 

basal area was western redcedar at Bear. Two of these plots (Rowell1 and Rowell2) 

also had a substantial component of Pacific yew, but most of these trees had been 

killed by having their bark removed, probably the result of bark collection for 

production of taxol, a cancer-inhibiting compound (Bolsinger and Jaramillo 1990). 

Red alder was found in two of the plots that had fairly large gaps in them and were 

close to perennial streams (Bear and Moon). 
14

GENERAL TECHNICAL REPORT PNW-GTR-790

For most of the nine hemlock zone plots, Douglas-fir (and the occasional 

hemlock) was found in the largest size classes, and hemlock and other species were 

found in the intermediate and smallest size classes (fig. 3a–c). The exception was 

Dorn, where Douglas-fir occurred in all size classes. Despite its high elevation, 

abundant precipitation, and northerly aspect, this stand was located in a ravine that 

seemed to consist of exceedingly well-drained soils, and an abundance of dry-site 

shrubs grew there (e.g., vine maple, California hazel, oceanspray, and dwarf Oregon 

grape–see appendix). Except for Dorn, where Douglas-fir seedlings (trees <1 in 

DBH) were recorded, only hemlock was found in the seedling size class; no seedlings were detected at Moon or ElkCk (table 3). Snags were found across the range 

of diameter classes in most of the plots.

Figure 3 (a–d)—Density of trees by diameter class and species for sampled old-growth plots. Note the change in scale between diameter 

classes less than 20 in (left side of figure) or greater than 20 in (right side of figure). Species are designated by color (codes defined in 

appendix table 9), live trees are shown as positive values, standing dead trees (snags) as negative values, and numbers above bars are 

estimated ages for trees cored in the respective diameter class and species (indicated by color).

-100

-50

0

50

100

150

200

250

Bear

-10

-5

5

10

15

20

0

25

439 537

108

90

97,113

-100

-50

0

50

100

150

200

250

300

VOG

-10

-5

5

10

15

20

30

0

25

536 489

209

388

386 290,303

-100

-50

0

50

100

150

200

250

Trees per acre

-100

-50

0

50

100

150

200

250

300

Nesk

-10

-5

5

10

15

20

30

0

25

269

280

134

113

251

CliffCk

Diameter class (in)

-10

-5

5

10

15

20

0

25

146

91,121

116

1–5

5–10

10–2020–3030–4040–6060–80

80–105

Diameter class (in)

1–5

5–10

10–2020–3030–4040–6060–80

80–105

A

PSME

PISI

TSHE

THPL

ACMA

ALRU

ABGR

CONU

TABR

UNKN
15

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

The two plots in the Willamette Valley margin (McDon1 and McDon2) were 

dominated by Douglas-fir in the largest diameter classes, with substantial amounts 

of bigleaf maple and grand fir in the intermediate- and small-diameter classes (table 

2, fig. 3c–d). No seedlings were recorded in either plot (table 3). Very few snags 

were present, and they tended to be in the smallest size classes.

Age Structure and Intermediate Disturbance

Pit-and-mound topography was evident at the Sitka-spruce-dominated sites (Nesk 

and CliffCk), probably a result of past windstorms in these coastal locations. The 

largest spruce and hemlock trees that were aged at Nesk ranged from 251 to 280 yr 

old, suggesting stand establishment following intense disturbance around 1710 (fig. 

3a). Younger trees of both hemlock and spruce appeared to be present, raising the 

possibility that chronic wind disturbance created multiple opportunities for spruce 

Figure 3—Continued.

Rock

296,

427

126

124

252

ElkCk

402,

481

104*

413

97,

114

Moon

158

447

LtGrass

170

95

159,173

145 124

138

92

108 125

156

111 117* 433

114

218

107

237,

120 429

124*

B

-100

-50

0

50

100

150

200

250

-10

-5

5

10

15

20

0

25

-100

-50

0

50

100

150

200

250

300

-10

-5

5

10

15

20

30

0

25

-100

-50

0

50

100

150

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250

Trees per acre

-100

-50

0

50

100

150

200

250

300

-10

-5

5

10

15

20

30

0

25

Diameter class (in)

-10

-5

5

10

15

20

0

25

1–5

5–10

10–2020–3030–4040–6060–80

80–105

Diameter class (in)

1–5

5–10

10–2020–3030–4040–6060–80

80–105

PSME

PISI

TSHE

THPL

ACMA

ALRU

ABGR

CONU

TABR

UNKN
16

GENERAL TECHNICAL REPORT PNW-GTR-790

Figure 3—Continued.

McDonald 2

153,

229

191 130,

151

137 125,

125

127

0

Trees per acre

-100

-50

50

100

150

200

250

300

-10

-5

5

10

15

20

30

0

25

Diameter class (in)

1–5

5–10

10–2020–3030–40

40–6060–80

80–105

D

PSME

PISI

TSHE

THPL

ACMA

ALRU

ABGR

CONU

TABR

UNKN

Figure 3—Continued.

McDon1

218

127,

130

Dorn

91 257

83

0

Rowell2

447,

449

0

Rowell1

499

482 402

97

307 156,

286

127

128

470

124*

218

74

35,56,

98 82

138

178

198

55 72

164,

267

102 496

202

-100

-50

0

50

100

150

200

250

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-5

5

10

15

20

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25

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300

-10

-5

5

10

15

20

30

0

25

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50

100

150

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250

Trees per acre

-100

-50

50

100

150

200

250

300

-10

-5

5

10

15

20

30

0

25

Diameter class (in)

-10

-5

5

10

15

20

0

25

1–5

5–10

10–2020–3030–4040–6060–80

80–105

Diameter class (in)

1–5

5–10

10–2020–3030–4040–6060–80

80–105

C

PSME

PISI

TSHE

THPL

ACMA

ALRU

ABGR

CONU

TABR

UNKN
17

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Table 3—Density of seedlings (trees <1 in DBH)

by site and speciesa

Site code PSME PISI TSHE Total

Trees per acre

Nesk 2,502 1,470 3,972

CliffCk 63 21 84

VOG 1,304 1,304

Bear 613 613

LtGrass 22 22

Moon 0

ElkCk 0

Rock 320 320

Rowell1 920 920

Rowell2 2,213 2,213

Dorn 248 45 293

McDon1 0

McDon2 0

a Species codes are defined in appendix table 9.

Table 4—Volume of down wood by site and decay 

class groupa

Site code I and II III and IV V Total

Log volume (ft3/ac)

Nesk 5,830 1,109 407 7,346

CliffCk 364 1,719 304 2,387

VOG 6,221 19,302 532 26,055

Bear 4,916 4,283 303 9,502

LtGrass 787 4,405 180 5,371

Moon 1,660 3,557 307 5,523

ElkCk 2,170 6,786 469 9,425

Rock 5,857 4,483 1,097 11,437

Rowell1 2,001 5,084 21 7,106

Rowell2 21 4,148 1,962 6,131

Dorn 753 3,960 471 5,184

McDon1 1,928 630 0 2,559

McDon2 532 295 0 827

a Decay classes described in Woodall and Monleon 2008.

regeneration, since spruce appears to be less shade-tolerant than hemlock (Minore 

1979). The CliffCk plot was substantially younger than Nesk, with the largest aged 

trees ranging from 91 to 146 yr old. The lack of trees in small-diameter classes 

and the low volume of woody debris (table 4) suggest this stand experienced little 

mortality since establishing after an intense disturbance around 1850.
18

GENERAL TECHNICAL REPORT PNW-GTR-790

The estimated maximum tree ages for eight of the nine mid-Coast Range 

sites (excluding LtGrass) ranged from 429 to 537 yr old, suggesting these stands 

established following intense disturbances in the period 1460 to 1570 (fig. 3a–c). 

(The general stand age at VOG was corroborated by counting rings on a recent 

tree-fall that had been cut about 30 ft from the base where it crossed a trail; the 

age was estimated at 538 yr.) In most of these plots, the ages of the largest hemlock 

(and an occasional small Douglas-fir) were substantially younger than those of the 

dominant Douglas-fir; the hemlock and small Douglas-fir could have established 

following a moderate-intensity fire. If any hemlock had been present at the time of 

such a fire, most would have been killed. Char was noted on the bark of Douglas-fir 

in most of these eight plots, but not for VOG or Rock. Most of the codominant and 

intermediate hemlock at VOG appeared to have germinated on top of logs or snags, 

suggesting high levels of understory competition on the ground (Gray and Spies 

1997), which might have occurred following a windthrow event. Several large trees 

at VOG fell over in recent windthrow events, possibly with root rot as a contributing 

factor. Despite being small and surrounded by substantially younger stands, the 

Rock stand appeared to not have experienced much disturbance in its history.

The maximum age of the LtGrass plot was substantially younger, at 173 yr, 

than the other mid-Coast Range sites. The aged dominant and codominant hemlock 

and Douglas-fir ranged in age from 108 to 173 yr, and char was noted on heavilydecomposed Douglas-fir snags, suggesting generally even-aged stand establishment 

following an intense fire around 1820.

The two plots in the Willamette Valley margin (McDon1 and McDon2) had 

maximum ages of 218 and 229 yr, respectively, indicating stand establishment in the 

late 1700s. (The general stand age at McDon2 was corroborated by counting rings 

on three stumps in an adjacent clearcut; estimated ages ranged from 190 to 200 yrs.) 

Tree density was lower in these plots than in most of the other plots in this study, 

and the largest Douglas-fir had large dead limbs less than 20 ft above the ground, 

indicating a long period of growth in open conditions. The low abundance of snags 

and down wood in older decay classes (table 4) suggests these stands may have 

slowly filled in from a previously nonforest grassland/savanna condition.

Old-Growth Criteria and Indices

Most of the plots sampled for this study exceeded most of the PNW-447 criteria for 

old-growth structure (table 5, fig. 4). All except Nesk had more than eight shadeintolerant trees per ac (tpa) ≥32 in DBH (and Nesk was close at 7.8). However, 

old-growth criteria have not been developed specifically for coastal Sitka sprucewestern hemlock stands, where both species commonly establish during stand 

The estimated 

maximum tree ages 

for eight of the nine 

mid-Coast Range 

sites ranged from 

429 to 537 years old.
19

Table 5—Stand characteristics, old-growth criteria and old-growth indices by plot Old-growth Variable criteria Nesk CliffCk VOG Bear LtGrass Moon ElkCk Rock Rowell1 Rowell2 Dorn MGeneral stand structure: Maximum tree age (yr) 280 146 536 537 173 447 481 429 499 470 496 

Quadratic mean DBH 40.2 41.6 49.2 40.2 38.1 45.8 47.9 37.6 43.4 40.0 43.5 

dominants and codominants (in) Maximum tree DBH (in) 97.4 75.1 101.2 92.3 64.0 100.0 93.6 91.9 72.7 83.0 89.8 

Standard deviation 16.8 12.4 20.0 14.1 15.7 19.6 17.3 12.6 14.2 16.2 18.1 

DBH (in) Maximum tree height (ft) 244 185 258 220 219 248 241 286 223 214 179 

Herb cover (percent) 73 85 65 47 67 57 37 16 2 6 5 

Shrub cover (percent) 10 18 30 11 3 16 31 43 50 56 72 

Old-growth criteria (PNW-447): Intolerants ≥32 in 8 7.8 33.9 9.4 9.9 24.8 8.7 9.9 17.0 23.1 11.1 18.7 

DBH (n/ac) Tolerants ≥16 in 12 37.0 23.3 39.4 51.7 20.6 24.2 22.4 39.4 14.5 37.2 3.6 

DBH (n/ac) Canopy layers 2 Snags ≥20 in DBH and 4 7.5 2.2 13.0 8.9 11.6 7.9 11.1 18.4 5.9 12.6 3.0 

≥15 ft tall (n/ac) CWD mass (ton/ac) 15 71.6 18.8 270.4 91.2 37.8 56.5 93.9 112.6 67.6 41.4 37.9 

CWD ≥24 in dia. (lg. end) 4 4.1 4.2 24.5 11.4 10.4 3.8 14.6 8.3 6.2 2.5 5.2 

and ≥50 ft long (n/ac) Old-growth indices: Canopy Height Diversity Indexa 9.1 7.1 14.0 13.3 9.6 13.8 13.2 13.8 11.4 11.7 10.8 

Old-Growth Indexb 97 99 100 80 100 100 97 50 88 98 100 

Old-Growth Habitat Indexc 82 79 91 91 92 84 88 99 90 86 85 

Note: Values in boldface fall below the old-growth criteria. a Spies and Cohen 1992. b Acker et al. 1998. c Pabst 2005.
20

GENERAL TECHNICAL REPORT PNW-GTR-790

initiation or following intermediate disturbances. For both western hemlock and 

Sitka spruce, the density of trees ≥32 in DBH at Nesk was 13.6 per acre. All plots 

except Dorn and McDon2 met the criteria of ≥12 shade-tolerant tpa ≥16 in DBH. As 

mentioned above, Dorn appeared to be a very dry site despite having an understory 

plant community keying out to the hemlock zone (species are in appendix, table 

10; keys are from McCain and Diaz 2002). Both Dorn and McDon2 met the less 

Figure 4—Values for old-growth criteria in PNW-447 (Franklin et al. 1986) for old-growth plots 

sampled in this study. Horizontal dashed lines mark the thresholds for moist Douglas-fir old-growth 

forests given in PNW-447.

Logs >24 in diameter and >50 ft long

North Coast stand

Nesk

CliffCk

VOG

Bear

LtGrass

Moon

ElkCr

Rock

Rowell1Rowell2

Dorn

McDon1

McDon2

Density (n/ac)

0

5

10

15

20

25

Snags >20 in DBH and >15 ft tall

Density (n/ac)

0

5

10

15

Tolerants >16 in DBH

Density (n/ac)

0

10

20

30

40

50

Intolerants >32 in DBH

Density (n/ac)

0

10

20

30

40

Mass (tons/ac)

0

50

100

150

200

250 Coarse woody debris
21

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

stringent PNW-447 criterion for dry Douglas-fir forests by having Douglas-fir or 

grand fir present in intermediate and small size classes.

Most of the plots met the PNW-447 snag criterion (≥4 snags per acre ≥20 in 

DBH and ≥15 ft tall). The exceptions included three relatively young plots (CliffCk, 

McDon1, and McDon2) and Dorn (which did meet the less stringent one-per-acre 

criterion for dry Douglas-fir forests). All except McDon2 had more than 15 tons/

ac of down wood, but four plots did not meet the large log density criteria (Moon, 

Rowell2, McDon1, and McDon2).

Six of the thirteen plots met all five of the old-growth criteria examined here, 

while ten plots met four of the five criteria. Using the dry-site criteria for Dorn, 

McDon1, and McDon2 meant that Dorn met all criteria but McDon1 and McDon2 

still fell short of the necessary levels of down wood and snags. This is not too 

surprising given the relative youth of these plots (about 200 yr old) and their likely 

establishment in a previously nonforested site. However, the two other relatively 

young plots (CliffCk and LtGrass) met most or all of the old-growth criteria.

The standard deviation of DBH, a possible surrogate for canopy layering, 

ranged from 12.4 to 20.0 (table 5). Different plots seemed to have similar values for 

very different reasons. The three plots with the lowest values were CliffCk, Bear, 

and Rock. While CliffCk had a narrow diameter range, Rock and Bear had wide 

diameter ranges but high densities in the smallest size class and moderate densities 

in the intermediate classes, suggesting substantial canopy layering. The plots with 

the highest standard deviations were VOG, Moon, and Dorn, and all tended to have 

the most even distribution of tree densities across a wide range of size classes, suggesting high levels of canopy layering.

The Canopy Height Diversity Index (CHDI) ranged from 5.6 to 14.0, with the 

highest scores going to those plots with the highest densities of the largest Douglasfir (VOG, Moon, and Rock), reflecting the higher weights given to the largest trees 

(table 5, fig. 5). Plots with low CHDI scores either had few trees in the largest 

diameter classes or no Douglas-fir, so estimated tree heights were low (CliffCk and 

Nesk), or tree densities were low in general (McDon1 and McDon2). The Acker et 

al. (1998) Old-Growth Index (OGI) did not vary much among the plots and differed 

substantially from the other indices. The Rock plot had the lowest OGI score. The 

high density of small trees in this plot led to high total tree density and low mean 

DBH, resulting in low scores for those attributes. The Old-Growth Habitat Index 

(OGHI)(Pabst 2005) scores ranged from 56 to 99. In this case, the Rock plot had 

the highest OGHI score, caused by the high density of trees in all size classes, 

high density of snags, and high volume of down wood. The lowest scores were for 

McDon1 and McDon2, caused primarily by the low levels of down wood and snags. 

Six of the thirteen 

plots met all five of 

the old-growth criteria 

examined here, while 

ten plots met four of 

the five criteria. 
22

GENERAL TECHNICAL REPORT PNW-GTR-790

The other relatively young plots, CliffCk and LtGrass, had relatively high scores 

that were similar to older plots.

Comparison With Old-Growth Wildlife Habitat Plots

The Old-Growth Wildlife Habitat (“OGWH”) plots from the central Coast Range 

and areas to the south were grouped into moisture classes by Spies and Franklin 

(1991), based on plant assocations. Applying the same moisture classes to the 

northern Coast Range (“NCoast”) plots dominated by Douglas-fir and ≥ 200 yr 

old classified Dorn, McDon1, and McDon2 into the “dry” category; ElkCk, Rock, 

Rowell1, and Rowell2 into the “mesic” category; and VOG, Bear, and Moon into 

the “wet” category (table 1). The OGWH plots were younger on average than the 

NCoast plots, with several in the 200- to 300-yr age class and only 2 of the 24 

stands with ages greater than 450 yr old (table 6). Although we found few stands 

Figure 5—Values for three different old-growth indexes for the old-growth plots sampled in this study. CHDI = Canopy Height Diversity 

Index (Spies and Cohen 1992), OGI = Old-Growth Index (Acker et al. 1998), OGHI = Old-Growth Habitat Index (Pabst 2005). Values for 

CHDI are shown on the left axis and values for OGI and OGHI on the right axis. Canopy Height Diversity Index

Old-growth indices

16

14

12

10

8

6

4

110

100

90

80

70

60

50

40

Nesk

CliffCk

VOG

Bear

LtGrass

Moon

ElkCk

Rock

Rowell1

Rowell2

Dorn

McDon1McDon2

North Coast stand

CHDI

OGI

OGHI
23

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

in the NCoast in the 200- to 300-yr age class, it is possible that stand selection was 

more focused on older stands in the north. Stand basal areas were similar in dry 

stands, but substantially higher for NCoast wet stands than for OGWH wet stands. 

The density of shade-intolerant trees was slightly higher and the density of shadetolerant trees was substantially lower in the OGWH plots than in the NCoast plots. 

The higher standard deviation of DBH for the NCoast plots probably results from 

the higher density of shade-tolerant trees. NCoast plots in the mesic and wet classes 

had substantially greater density of snags and mass of coarse wood than the OGWH 

plots.

Comparison With Forest Inventory Plots

Most of the forests in the Coast Range were smaller in mean diameter than the 

old-growth plots. Quadratic mean diameters greater than 40 in were found on 2.7 

percent of the CVS inventory plots on federal lands, and 0.4 percent of the FIA 

plots on nonfederal lands (fig. 6). (FIA plots on federal land are not shown in fig. 6 

because the lower number of plots sampled to date [n = 99] distributed among the 

30 diameter/location classes resulted in an irregular frequency distribution.) The 

proportion of plots in different size classes on federal lands was more balanced in 

the central Coast Range than in the northern Coast Range. The proportion of plots 

in the >30 in QMD classes declined from the spruce to the hemlock to the valley 

zones. Inventory plots in the >30 in QMD classes on federal lands had substantially 

lower basal areas than those found on the old-growth plots (table 7). Mean basal 

areas by stand size class were similar between federal and nonfederal inventory 

plots, however. In addition, the federal land estimates for basal area were similar 

for the CVS and FIA inventory plot designs.

Table 6—Comparison of selected attributes of old growth stands from this study (NCoast) and from the 

stands sampled in the Old-Growth Wildlife Habitat Program (OGWH)a

Dry Mesic Wet

OGWH NCoast OGWH NCoast OGWH NCoast

Stand age (yr) 276 (48) 314 (157) 384 (98) 470 (30) 310 (55) 507 (52)

Basal area (ft2/ac) 336 (43) 331 (82) 362 (104) 446 (79) 318 (55) 483 (77)

Quadratic mean DBH of dominants (in) 38.9 (4.8) 45.4 (2.1) 38.2 (5.6) 42.2 (4.5) 41 (8.3) 45.1 (4.6)

Intolerants ≥32 in DBH (n/ac) 20.4 (5.2) 17.7 (7.8) 14.5 (10.3) 15.3 (6.1) 13.8 (7.7) 9.3 (0.6)

Tolerants ≥16 in DBH (n/ac) 4.1 (4.3) 10.3 (7.5) 18.8 (11) 28.4 (11.9) 17.6 (13.8) 38.4 (13.8)

Standard deviation DBH (in) 14.3 (3.2) 17.5 (0.8) 13.6 (3.6) 15.1 (2.1) 15.3 (3.6) 17.9 (3.3)

Snags ≥20 in DBH and ≥ 15 ft tall (n/ac) 2.7 (1.8) 1.1 (1.6) 3.6 (3.1) 12 (5.1) 4.6 (3) 9.9 (2.7)

Coarse woody debris mass (ton/ac) 19.7 (12) 24.5 (14.7) 32.6 (21.5) 78.9 (31.1) 32.1 (11.4) 139.4 (114.8)

a Means (with standard deviations in parentheses) are shown by site moisture class (n = 3 or 4 for NCoast, 8 for OGWH).
24

GENERAL TECHNICAL REPORT PNW-GTR-790

Figure 6—Distribution of Current Vegetation Survey inventory plots on federal land and Forest 

Inventory and Analysis (FIA) inventory plots on nonfederal land in the northern and central Oregon 

Coast Range by quadratic mean diameter and vegetation zone. The FIA plots on federal land are not 

shown because the lower number of plots sampled to date (n = 99) resulted in an irregular frequency 

distribution among the 30 classes in this figure.

Federal forest land

Quadratic mean diameter (in)

Percentage of plots by zone

0

10

20

30

40

50

60

70

Central

Coast

North

Coast

Nonfederal forest land

Percentage of plots by zone

0

10

20

30

40

50

60

70

Central

Coast

North

Coast

0–10

10–2020–3030–40

>40

0–10

10–2020–3030–40

>40

Quadratic mean diameter (in)

0–10

10–2020–3030–40

>40

0–10

10–2020–30

30–40

>40

Spruce

Hemlock

Valley

Spruce

Hemlock

Valley
25

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Because of differences in plot design, old-growth attributes on federal lands are 

shown for both the CVS and FIA inventories; the CVS results are most comparable 

with the northern Coast Range old-growth plots, and the FIA results are most 

comparable with the nonfederal FIA plots. On federal lands, 1.7 percent of the CVS 

inventory plots exceeded all five of the PNW-447 thresholds evaluated, while 7.0 

percent exceeded at least four of the five thresholds (for FIA plots, the figures were 

0 percent and 11.1 percent, respectively). The threshold for density of large shadeintolerant trees was exceeded on 28 percent of the CVS plots, whereas the threshold 

for density of shade-tolerant trees was only exceeded on 14 percent of the CVS plots 

(fig. 7a; for FIA plots, the figures were 25 percent and 23 percent, respectively). The 

large snag criterion was met on 22 percent of the CVS plots and 20 percent of the 

federal FIA plots. Interestingly, at least one live tree ≥48 in DBH was recorded on 

41 percent of the CVS plots and 38 percent of the federal FIA plots. Standard deviation of DBH was greater than 12 in (the lower end value for the old-growth plots) 

on 15 percent of the CVS and federal FIA plots (fig. 7b). The PNW-447 thresholds 

for coarse wood mass and density of large logs were exceeded on 35 percent and 17 

percent of the CVS plots, and 44 percent and 12 percent of the federal FIA plots, 

respectively. Five percent of the CVS and federal FIA inventory plots on federal 

lands had an OGHI score of 70 or greater.

Old-growth forest attributes were less common on nonfederal lands than on 

federal lands. None of the inventory plots met all five of the PNW-447 thresholds, 

while 1 out of 271 (0.4 percent) met four and 4.4 percent met three. The thresholds 

for large shade-intolerant tree density and large snag density were met on 2 percent 

and 6 percent of the plots, respectively, whereas the threshold for shade-tolerant 

density was met on 18 percent of the plots (fig. 7a). However, 5.5 percent of the plots 

Table 7—Mean live tree basal area on inventory plots on federal and nonfederal 

lands by inventory type and stand quadratic mean diameter class (standard 

deviation in parentheses)a

Stand Federal lands, Federal lands, Nonfederal lands,

diameter class CVSb inventory FIAc inventory FIA inventory

Inches - - - - - - - - - - - - - - Basal area (ft2/ac) - - - - - - - - - - - - - -

0–10 67 (54) 97 (58) 73 (63)

10–20 170 (63) 179 (65) 173 (67)

20–30 235 (74) 217 (83) 226 (97)

30–40 281 (85) 261 (102) —

>40 291 (63) 276 (67) 105 (0)

a Number of plots for each inventory type and owner group from left to right were 584, 271, and 99.

b CVS = Current Vegetation Survey.

c FIA = Forest Inventory and Analysis.

On federal lands, 

1.7 percent of the 

CVS inventory plots 

exceeded all five of the 

PNW-447 thresholds 

evaluated, while 7.0 

percent exceeded at 

least four of the five 

threshold.
26

GENERAL TECHNICAL REPORT PNW-GTR-790

had at least one tree ≥48 in DBH recorded on them. Standard deviation of DBH 

was greater than 12 in (the lower end value for the old-growth plots) on 1.5 percent 

of the plots (fig. 7b). Whereas the PNW-447 threshold for coarse wood mass was 

exceeded on 35 percent of the plots, the threshold for density of large logs was 

met on only 3.3 percent of the plots. One (0.4 percent) of the inventory plots on 

nonfederal lands had an OGHI score of 70 or greater.

Figure 7—Abundance of selected old-growth structural characteristics on Current Vegetation Survey (CVS) and Forest Inventory 

and Analysis (FIA) inventory plots on federal and nonfederal land in the northern and central Oregon Coast Range. Figures are 

reverse cumulative distributions; each point on the line shows the percentage of plots that exceed the value on the horizontal axis. 

The thresholds suggested for old-growth in PNW-447 (Franklin et al. 1986) are shown with an arrow.

Intolerants ≥32 in DBH

Tolerants ≥16 in DBH

Snags ≥24 in DBH and ≥15 ft tall

Trees >48 in DBH

Number per acre

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

0

0.4– 2

2– 44– 6

6– 8

8– 10

10– 1212– 16

16– 20

20– 3030– 40

Number per acre

0

0.4– 1

1– 22– 3

3– 44– 5

5– 6

6– 8

8– 10

10– 1515– 20

20– 25

Number per acre

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

0

0.4– 4

4– 8

8– 12

12– 1616– 20

20– 30

30– 40

40– 60

60– 8080– 91

Number per acre

0

0.4– 1

1– 22– 3

3– 44– 5

5– 6

6– 8

8– 10

10– 1515– 20

20– 25

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

A
27

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

There is a common perception that mature stands in the Coast Range are 

lacking in shade-tolerant mid- and under-story trees. Additional analyses were 

conducted on the abundance of shade-tolerant trees, and hemlock in particular, for 

inventory plots in the hemlock zone with QMD ≥20 in. The proportions of these 

plots with hemlock basal area less than 10 percent of the total basal area were 

estimated as 81 percent, 66 percent, and 75 percent for federal CVS, federal FIA, 

and nonfederal FIA plots, respectively (table 8). Estimates of the density of hemlock 

seedlings and saplings were 47, 58, and 23 tpa for federal CVS, federal FIA, and 

nonfederal FIA plots, respectively.

Standard deviation of DBH Logs ≥24 in diameter and ≥50 ft long

Coarse wood mass Old-Growth Habitat Index

Inches

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

0–2

2– 4

4– 66– 8

8– 10

10– 12

12– 1414– 16

16– 18

18– 2020– 22

Number per acre

0

0.4– 1

1– 22– 3

3– 44– 5

5– 6

6– 8

8– 10

10– 1515– 20

20– 25

Tons per acre

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

Plots in group (reverse cumulative percent)

0

10

20

30

40

50

60

70

80

90

100

0–5

5– 10

10– 1515– 20

20– 2525– 30

50– 75

75– 100

100– 150

150– 200200– 250

Index

0–10

10– 20

20– 3030– 40

40– 50

50– 6060– 7070– 80

80– 90

90– 100

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

Federal CVS

Nonfederal FIA

Federal FIA

B

Figure 7—Continued.
28

GENERAL TECHNICAL REPORT PNW-GTR-790

Discussion

Our study of old-growth forest in the northern Oregon Coast Range found substantial variation in stand structure, composition, and disturbance history across the 

different ecological zones from west to east. The detailed descriptions of individual 

old-growth plots could provide useful reference points for stands being managed 

for late-successional attributes in this area, where such information has been 

lacking. Our results suggest differences between stands studied in the northern 

Oregon Coast Range and areas to the south, which may result from differences 

in fire history and site productivity. Our analysis indicates that published indices 

of old-growth do not behave similarly and may be useful for different purposes. 

Finally, the analysis of inventory data indicates the overall abundance of different 

late-successional forest attributes in the region. We first discuss some of the limitations of the analyses before addressing the results in greater detail.

Limitations of the Comparisons

The attributes of a forest are rarely fully enumerated. Instead, they are measured 

with plots and are thus subject to sample error. For example, just by chance, five 

fifth-acre plots may detect no large snags in a 40-ac stand in which the true density 

is four per acre. Therefore all analyses that use individual plots as representative of 

stand conditions should be interpreted with caution. There is also some ambiguity 

for the size of area or the criteria used to delineate a “stand,” so that the true stand 

attributes could differ, depending on whether one included riparian zones or stand 

Table 8—Measures of shade-tolerant tree abundance, and of hemlock alone, on inventory plots in the 

hemlock zone with quadratic mean diameter ≥20 ina

Federal lands, Federal lands, Nonfederal lands,

Variable CVSb inventory FIAc inventory FIA inventory

Number of plots 210 35 16

Percentage of plots by amount of hemlock:

Plots with hemlock basal area = 0 38.1 45.7 56.3

Plots with hemlock basal area <10 percent 42.9 20.0 18.8

Plots with hemlock basal area ≥10 percent 19.0 34.3 25.0

Mean hemlock basal area (percent) 6.2 (0.8) 12.6 (3.4) 9.7 (5.4)

Mean shade-tolerant basal area (percent) 14.2 (1.2) 19.7 (3.9) 24.2 (9)

Mean hemlock seedling+sapling density (n/ac)d 47 (10) 58 (29) 23 (11)

Mean shade-tolerant seedling+sapling density (n/ac)d 58 (12) 58 (29) 37 (17)

a Means are shown with standard errors in parentheses.

b CVS = Current Vegetation Survey.

c FIA = Forest Inventory and Analysis.

d Seedlings and saplings are trees ≥0.5 ft tall and < 5 in DBH.
29

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

edges with reduced large-tree density. Every forest attribute that is either measured 

or calculated at the plot level is sensitive to the size of plot (or length of transect) 

with which the data were collected (Gray 2003). For example, if there was a target 

of ≥10 small trees per acre (tpa) and the plot area for small trees was one-sixth of an 

acre, the estimated densities for tallies of 0, 1, 2, or 3 trees would be 0, 6, 12, or 18 

tpa. However, the improvement in accuracy that results from using larger plot sizes 

levels off eventually, particularly for attributes that are abundant (e.g., sampling a 

tree size class present at 500 tpa will result in essentially the same estimate whether 

one uses a 1-ac plot or a 0.25-ac plot). Most sample protocols deal with this by using 

larger plots for attributes that are either rare or more important and smaller plots for 

those that are abundant or less important. These effects must be kept in mind when 

comparing individual-plot results from studies that use very different plot designs.

This paper compares estimates of stand attributes obtained from studies that 

differed in how plots were selected and in the areas and transect lengths used for 

each plot. The old-growth studies selected specific stands that met some initial 

criteria for old growth and were not randomly selected from a population of 

objectively identified candidate stands. Although researchers attempted to select 

representative stands, inference to a larger population cannot be assumed. The 

inventory plots, on the other hand, were systematically located and constitute a true 

representative sample of the population of forested lands in the Coast Range. The 

studies also differed in the amount of within-plot variability encountered. Although 

there was some randomization in where old-growth plots were located within a 

stand, stand edges were avoided; in the north coast study, many stands were so 

small that there was only one relatively confined intact area where the plot was 

placed. In contrast, systematically placed inventory plots may straddle two or more 

stand conditions, or include features that are usually avoided in a targeted sample 

like rock outcrops, streams, or roads. Indeed an early study of natural “immature” 

(average age 80 yr) Douglas-fir stands in western Oregon and Washington found 

that randomly selected “real” stands had about 85 percent of the basal area that 

would be expected from “normal” (i.e., fully-stocked) stands, and that small openings consisting of creeks, rock outcrops, and unstocked areas amounted to about 6 

percent of stand area (Meyer 1930). An alternative sampling approach that captures 

within-stand variability better than cluster plots is strip-transect sampling, which 

we have applied in large mature stands in the Coast Range (Monleon et al. 2002). 

The old-growth stands sampled for this paper were too small to be sampled well 

with strip transects, however. Thus, using the results from the old-growth plots as 

a target for management might be appropriate for a uniform, fully stocked stand 

condition, but are probably somewhat high for the average forest condition.

Using the results 

from the old-growth 

plots as a target for 

management might 

be appropriate for a 

uniform, fully stocked 

stand condition, but 

are probably somewhat 

high for the average 

forest condition.
30

GENERAL TECHNICAL REPORT PNW-GTR-790

Old-Growth Stand Characteristics

The plots measured in the northern Coast Range differed substantially, illustrating 

the role of environment and history in shaping stand structure. Eight of the plots 

could be called “mature” or “classic” Douglas-fir old-growth, with trees ≥80 in 

DBH and ≥400 yr old, multiple species in a wide range of diameters, and abundant 

large snags and down wood. Despite relatively low densities of Douglas-fir in a few 

of these plots (VOG, Bear, Moon, ElkCk), Douglas-fir still dominates the plot in 

terms of basal area and, assuming background mortality rates, likely will continue 

to do so for some time. Most of the plots appeared to have experienced at least one 

moderate-severity fire since establishment, possibly resulting in most of the hemlock being substantially younger and smaller than the dominant Douglas-fir.

The two Douglas-fir plots in the Willamette Valley margin (McDon1 and 

McDon2) might be considered “early” old-growth based on age alone, but the 

developmental history of these stands puts them in a different ecological type and 

pathway. Those stands developed from an open-grown savanna and likely underwent frequent low-severity fire early in development, followed by heavy grazing 

in the late 1800s and early 1900s. As a result, they have fairly low tree densities in 

the overstory and understory, and low amounts of dead wood (snags or logs). It is 

not clear how different these stands would be if these locations had been forested 

longer, or if the disturbance regime had been different during development. Nor is 

it clear how unique they are, although forest encroachment on old savanna could be 

quite extensive in the Willamette Valley margins (Zybach 2003).

Although younger than the other Douglas-fir plots and with fewer trees in the 

≥60 in DBH size, the LtGrass plot contained a diverse mix of species and tree sizes 

with an abundance of large snags and logs. The apparently high productivity and 

varied topography of this site, the establishment of hemlock and maple early in 

stand development, and the abundant wood legacy from a prior old-growth stand 

(14 class 4 and 5 snags ≥40 in DBH were recorded on the plot) contributed to its 

structural diversity.

The oldest of the two Sitka spruce plots shared many attributes with the 

Douglas-fir old-growth plots, although the number of large spruce was somewhat 

lower than the number of large Douglas-fir in the other plots. It is likely this plot 

experienced strong windstorms in the past that thinned the overstory sufficiently 

for spruce to establish and grow into the overstory. The younger spruce plot, despite 

having a large number of large spruce and hemlock and moderate levels of snags 

and logs, had the appearance of a mature stand rather than old growth. The lack of 

trees <30 in DBH resulted in most of the tree canopy being in a single layer, rather 

than a multilayered arrangement.

 Most of the plots 

appeared to have 

experienced at 

least one moderateseverity fire since 

establishment.
31

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Comparison With Other Coast Range Old-Growth Plots

The plots measured for this study in the northern Coast Range were older than the 

OGWH plots measured by Spies and Franklin (1991) in the central Coast Range 

and areas farther south, which may also explain the lower density of Douglas-fir 

and higher density of large shade-tolerant trees found in the north. The higher basal 

areas in the mesic and wet stands in the north might reflect differences more in 

sampling than in biology. In this study, 1-ha (2.47-ac) plots were installed in small 

remnant patches, whereas in the OGWH study, sample plots were distributed across 

larger stands, thus picking up more variation. Intermediate disturbances in the form 

of moderate-intensity fires appear to have played a role in old-growth forest composition and structure in both areas, particularly with increasing distance from the 

coast (Impara 1997).

Abundance of Old-Growth in the Coast Range

Most of the forests in the Oregon Coast Range have been heavily disturbed and are 

lacking many of the characteristics of old-growth forests. This is not surprising, 

given the large fires of the mid-1800s and 1933 (Morris 1934), the creation of public 

forests from these burns, and the extensive timber harvesting on public and private 

lands.

The 1936 forest type map made as part of the first comprehensive forest inventory of the region (Andrews and Cowlin 1940) indicates that by the 1930s, most of 

the remaining Douglas-fir old growth in the northern Coast Range was primarily 

found on private land, much of it in the Siletz River drainage (around the site of 

the town of Valsetz). Other blocks of old growth were located on BLM land in the 

upper Siletz and Rowell Creek drainages, and on land currently in state ownership 

at the southern edge of the original Tillamook Burn (the latter stands may have 

been killed in subsequent reburns). Locating enough old stands of sufficient size to 

sample for this study was challenging, although it is possible there are others; the 

part of the Moon Creek RNA which the BLM lists as old growth (Schuller 2006) 

was not reconnoitered for this study owing to washed-out roads. Another BLM 

RNA, the Butte, is found in a small block of federal land in the northern part of the 

study area and was not examined either because of oversight.

Plots with mean diameters greater than 30 in were very rare on nonfederal 

lands. On federal lands, these plots were more abundant in the central than in the 

northern Coast Range, where they were more frequent in spruce stands than in 

hemlock or valley-margin stands. Old-growth attributes that were particularly 

lacking on federal lands were shade-tolerant trees ≥16 in DBH, large logs, and deep, 

multilayered canopies (as indicated by standard deviation of DBH). The low density 
32

GENERAL TECHNICAL REPORT PNW-GTR-790

of shade-tolerant tree species, even in large-diameter mature stands, could reflect 

a general lack of seed source and be a reflection of the large historical fires that 

occurred in the area, as well as the common historical practice of primarily planting Douglas-fir after logging (Schrader 1998, Wimberly and Spies 2002). Although 

occurring at low density, the proportion of inventory plots with trees ≥48 in DBH 

on federal land (38 percent) as well as on nonfederal land (6 percent) was surprising. A related study of inventory plots in the Coast Range also found a substantial 

imprint of legacy trees on current forest structure across ownerships (Ohmann et 

al. 2007). Although one or two old trees do not contribute much to stand structure, 

they may be refugia for slow-dispersal organisms such as lichens and provide 

habitat for some organisms that can then spread into the maturing stand around 

them (Silett et al. 2000).

Old-Growth Indices

Old-growth indices can be useful tools for monitoring the abundance of old-growth 

characteristics in individual stands or across landscapes. The three old-growth 

indices calculated for this paper behaved differently across the northern Coast 

Range old-growth plots. Both the Canopy Height Diversity Index (CHDI) (Spies 

and Cohen 1992) and the Old-Growth Index (OGI) (Acker et al. 1998) are based 

solely on live trees, so do not evaluate the snag and log components of stands. The 

CHDI puts the heaviest weights on tall trees and sums the scores from different 

tree sizes, so seems to function better as an index of total crown volume in a stand 

rather than height diversity per se. The OGI was primarily developed to classify 

how closely young and mature stands resemble old growth, so it did not vary much 

among the stands. This index gave the lowest score to an old-growth stand with 

high tree densities and did not differentiate the younger stands from the older 

ones. The Old-Growth Habitat Index (OGHI) (Pabst 2005) performed quite well in 

relation to expectations based on the abundance of individual stand structure elements, giving the lowest values to the Willamette Valley margin plots that had few 

snags and down logs. The OGHI did not seem to distinguish structural differences 

between the two other younger plots and the older plots (however there is a version 

of the index that includes stand age as a criterion). It is also interesting to note that 

the standard deviation of DBH, which has been proposed as an indicator of canopy 

layering, did not always perform as expected. A high value seems to reflect layering, but the low values were caused by low layering as well as high density of small 

trees and clumpy diameter distributions.
33

Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Conclusions

Quantification of the stand characteristics in old-growth plots in the northern 

Oregon Coast Range for this study may provide useful information for management 

practices designed to restore late-successional forests in the region. Although we 

believe that we measured most of the remaining old-growth stands in the northern 

Oregon Coast Range, the stands included in this study are what were left after an 

intense selection by natural and human disturbance. Strictly speaking, each plot 

is an individual case study and inference has to be limited to the plots actually 

observed, not to the hypothetical population of historical (or potential) old-growth 

stands in the study area. Our results suggest that the composition, structure, and 

productivity of a current stand places some important constraints on the character 

of future late-successional forests; expecting all stands to have the full complement of late-successional attributes may not be realistic. Disturbance history is a 

particularly important consideration. Many of the north coast stands experienced 

moderately severe fire during their development. Although these disturbances may 

have temporarily reduced the abundance of some late-successional attributes (e.g., 

multilayered canopies and shade-tolerant cohorts), most stands had the full complement of attributes at five centuries of age.

Some stands on productive sites in the Coast Range are able to develop most 

desired late-successional attributes relatively quickly (<200 yr), particularly when 

a mix of species and an abundance of legacies from previous stands are available 

early in stand development (e.g., the Little Grass Mountain plot). However, it is not 

clear how well stands that develop old-growth characteristics early in stand development will be able to retain them, especially if the shade-intolerant Douglas-fir 

decreases in importance through natural mortality. Thus it may be important to 

have mature stands with a variety of stand compositions and structures across the 

landscape. The relatively low abundance of shade-tolerant trees, and hemlock in 

particular, in many of the mature stands in the Coast Range suggests that planting 

may be needed if accelerated development of understory tree cohorts and multiple 

canopy layers are goals.

Selecting simple thresholds for classifying stands as “old growth,” for example 

age, or quadratic mean diameter, can be useful because they are relatively easy 

to calculate and use for monitoring trends over time. Using criteria that combine 

thresholds for several late-successional attributes, or that calculate indices based 

on their amounts, can be a more powerful way to assess the attainment of the 

combination of conditions that provide wildlife habitat and ecosystem function 

in old-growth forests. However, it is important to understand the stand types to 

which the indices apply, the components that are included in them, their behavior 

Expecting all stands 

to have the full 

complement of latesuccessional attributes 

may not be realistic.
34

GENERAL TECHNICAL REPORT PNW-GTR-790

under different conditions, and their sensitivity to sampling methods—particularly 

plot size. Analysis of multiple individual late-successional attributes can provide 

a more complete understanding of the relative abundance of specific habitat and 

structural features across the landscape, or in any subset of stand types. Some of 

the late-successional forest attributes examined here are also important in natural 

early-successional stands. Current management in the Coast Range is focused on 

increasing the area of old growth on federal lands and producing commodities on 

nonfederal land, but alternative management approaches—for example, creating a 

variety of vegetation structures and habitats within and among ownerships—might 

be more effective at maintaining native biodiversity and local commodity production at the same time (Spies et al. 2007).

Acknowledgments

Thanks to Cindy McCain, Connie Harrington, Stuart Johnston, Melinda Moeur, 

and David Mladenoff for critical reviews of an earlier version of this manuscript. 

Rob Pabst provided many insightful suggestions and comments. Y. Bulatov, W. 

King, and N. Matzke assisted with field data collection. Funding was provided by 

the PNW Research Station and Northwest Forest Plan research funds (USDA Forest 

Service, Region 6; USDI Bureau of Land Management, Oregon State Office).

Metric Equivalents

When you know: Multiply by: To find:

Inches (in) 2.54 Centimeters (cm)

Feet (ft) 0.3048 Meters (m)

Acres (ac) 0.4047 Hectares (ha)

Square feet per acre (ft2

/ac) 0.2296 Square meters per hectare (m2/ha)

Cubic feet per acre (ft3/ac) 0.07 Cubic meters per hectare (m3/ha)

Tons 0.9072 Tonnes

Tons per acre 2.2417 Tonnes per ha

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Characteristics of Remnant Old-Growth Forests in the Northern Coast Range of Oregon; Comparison to Surrounding Landscapes

Appendix

Table 9—Common and scientific names for tree species,a and codes used in tables 

and figures

Common name Species name Species code

Bigleaf maple Acer macrophyllum Pursh ACMA

California laurel Umbeullularia californica (Hook. & Arn.) Nutt.

Douglas-fir Pseudotsuga menziesii (Mirb.) Franco PSME

Grand fir Abies grandis (Dougl. ex D. Don) Lindl. ABGR

Lodgepole pine Pinus contorta Dougl. ex Loud.

Noble fir Abies procera Rehd.

Oregon white oak Quercus garryana Dougl. ex Hook.

Pacific dogwood Cornus nuttallii Audubon ex Torr. & Gray CONU

Pacific silver fir Abies amabilis Doubl. ex Forbes

Pacific yew Taxus brevifolia Nutt. TABR

Ponderosa pine Pinus ponderosa Dougl. ex Laws

Red alder Alnus rubra Bong. ALRU

Sitka spruce Picea sitchensis (Bong.) Carr. PISI

Sugar pine Pinus lambertiana Dougl.

Western hemlock Tsuga heterophylla (Raf.) Sarg. TSHE

Western redcedar Thuja plicata Donn ex D. Don THPL

White fir Abies concolor (Gord. & Glend.) Lindl. ex Hildebr.

Unknown (snag or log) UNKN

a Source: Little 1979.
42

Table 10—Mean cover of understory plant species recorded at each site, sorted alphabetically by life form (n = 3 subplots) Species codea Scientific namea Common name Nesk CliffCk VOG Bear LtGrass Moon ElkCk Rock Rowell1 

Shrubs: ACCI Acer circinatum Pursh vine maple 15.3 11.7 31.3 0.3 22.7 

AMAL2 Amelanchier alnifolia (Nutt.) Saskatoon serviceberry 

Nutt. ex M. Roemer CHME Chimaphila menziesii little prince's pine 0.1 0.1 0.1 

(R. Br. ex D. Don) Spreng. COCA13 Cornus canadensis L. bunchberry dogwood 0.3 

COCO6 Corylus cornuta Marsh. beaked hazelnut 

FRPU7 Frangula purshiana (DC.) Pursh's buckthorn 0.3 0.1 Cooper GASH Gaultheria shallon Pursh salal 0.3 0.4 0.1 27.3 16.7 

HODI Holodiscus discolor (Pursh) oceanspray 

Maxim.

LONIC Lonicera L. honeysuckle 

MANE2 Mahonia nervosa (Pursh) dwarf Oregon grape 0.1 3.7 2.0 2.7 0.4 8.4 

Nutt.

MEFE Menziesia ferruginea Sm. fool's huckleberry 3.3 2.7 0.1 0.1 4.3

OPHO Oplopanax horridus Miq. devilsclub 0.7 6.7

RHMA3 Rhododendron macrophyllum Pacific rhododendron 8.0 

D. Don ex G. Don

RIBES Ribes L. currant 0.1 0.1

ROGY Rosa gymnocarpa Nutt. dwarf rose 0.3 

RUDI2 Rubus discolor Weihe & Nees Himalayan blackberry 

RUPA Rubus parviflorus Nutt. thimbleberry 0.1 

RUSP Rubus spectabilis Pursh salmonberry 0.1 0.7 7.7 6.0 0.4 0.1 0.4 RUUR Rubus ursinus trailing blackberry 0.1 0.1 0.1 0.1 

Cham. & Schlecht.

SARA2 Sambucus racemosa L. red elderberry 1.0 2.7 0.3 0.1 0.1

SYAL Symphoricarpos albus common snowberry 

(L.) Blake

TODI Toxicodendron diversilobum Pacific poison oak 

(Torr. & Gray) Greene

VAOV Vaccinium ovalifolium Sm. oval-leaf blueberry 3.3 0.1 0.1

VAPA Vaccinium parvifolium Sm. red huckleberry 5.3 11.0 4.7 1.4 1.3 1.3 0.4 18.7 0.1 

Forbs:

ACTR Achlys triphylla (Sm.) DC. deerfoot vanillaleaf 0.1 0.1 

ACRU2 Actaea rubra (Ait.) Willd. red baneberry 0.1 
43

Table 10—Mean cover of understory plant species recorded at each site, sorted alphabetically by life form (n = 3 subplots) Species codea Scientific namea Common name Nesk CliffCk VOG Bear LtGrass Moon ElkCk Rock Rowell1 

ADBI Adenocaulon bicolor Hook. pathfinder 

ADPE Adiantum aleuticum L. maidenhair fern 1.0 ANMA Anaphalis margaritacea western pearly everlasting 0.1 (L.) Benth. ANDE3 Anemone deltoidea Hook. Columbian windflower 0.1 

ANLY Anemone lyallii Britt. Lyall's anemone 

AQFO Aquilegia formosa Fisch. ex DC. western columbine 

ASCA2 Asarum caudatum Lindl. wild ginger 0.1 Asteraceae composite family 0.1 ATFI Athyrium filix-femina (L.) Roth common ladyfern 0.1 0.7 1.0 1.0 0.1 

BLSP Blechnum spicant (L.) Sm. deer fern 2.7 0.1 0.1 1.7 1.0 2.4 CASC7 Campanula scouleri Hook. Scouler's harebell 0.1 

ex A. DC. CLSI2 Claytonia sibirica L. Siberian springbeauty 9.0 22.7 0.1 0.7 0.1 0.1 0.7 

CLUN2 Clintonia uniflora (Menzies ex beadlilly 0.4 1.0 0.1 J.A. & J.H. Schultes) Kunth DIFO Dicentra formosa (Haw.) Walp. bleeding heart 0.7 0.1 0.1 DIPU Digitalis purpurea L. foxglove 0.1 DIHO3 Disporum hookeri (Torr.) Hooker fairybell 0.7 0.1 1.3 0.1 0.1 0.3 0.4 

Nichols. DREX2 Dryopteris expansa (K. Presl) mountain woodfern 0.7 1.4 0.7 0.1 0.1 0.1 Fraser-Jenkins & Jermy EPCIW Epilobium ciliatum ssp. fringed willowherb 0.1 watsonii (Barbey) Hoch & Raven FRVE Fragaria vesca L. woodland strawberry 0.1 GAAP2 Galium aparine L. stickywilly 

GATR3 Galium triflorum Michx. fragrant bedstraw 0.1 0.1 0.4 0.1 

GOOB2 Goodyera oblongifolia Raf. rattlesnake plantain 0.1 

GYDR Gymnocarpium dryopteris western oakfern 0.1 (L.) Newman HIAL2 Hieracium albiflorum Hook. white hawkweed 0.3 

HYTE Hydrophyllum tenuipes Pacific waterleaf 

A. Heller Leguminosae Pea family 

LIAP Ligusticum apiifolium (Nutt. celeryleaf licorice-root 

ex Torr. & Gray) A. Gray
44

Table 10—Mean cover of understory plant species recorded at each site, sorted alphabetically by life form (n = 3 subplots) Species codea Scientific namea Common name Nesk CliffCk VOG Bear LtGrass Moon ElkCk Rock Rowell1 

LIGR Ligusticum grayi Coult. Gray’s licorice-root 0.1 & Rose Liliaceae Lilly family 0.1 LYAM3 Lysichiton americanus Hulten American skunkcabbage 0.7 0.1 & H. St. John MADI Maianthemum dilatatum false lily of the valley 2.7 1.7 0.1 0.3 0.1 (Wood) A. Nels. & J.F. Macbr. MARA7 Maianthemum racemosum false lily of the valley 

(L.) Link feathery MAST4 Maianthemum stellatum starry false lily of the valley 0.4 0.1 

(L.) Link

MAOR3 Marah oreganus (Torr. ex coastal manroot 0.1

S. Wats.) T.J. Howell

MIDE3 Mimulus dentatus Nutt. coastal monkeyflower 1.0 0.1

ex Benth.

MOUN2 Moneses uniflora (L.) A. Gray single delight 0.1

MOHY3 Monotropa hypopithys L. pinesap 0.1

MOUN3 Monotropa uniflora L. Indianpipe 0.1 

MYMU Mycelis muralis (L.) Dumort. wall-lettuce 0.1 

OSBE Osmorhiza berteroi DC. sweetcicely 0.1 

OXOR Oxalis oregana Nutt. redwood-sorrel 32.7 31.7 46.7 16.0 46.7 28.3 5.3 0.1 0.3

POGL8 Polypodium glycyrrhiza licorice fern 0.1 0.1 0.1 0.1 0.1

D.C. Eat.

POMU Polystichum munitum western swordfern 40.0 16.7 12.3 34.0 41.3 40.0 28.3 13.7 1.4 

(Kaulfuss) K. Presl

PTAQ Pteridium aquilinum (L.) Kuhn brackenfern 6.7 0.1 

PYPI2 Pyrola picta Sm. whiteveined wintergreen 0.1 

SEJA Senecio jacobaea L. stinking willie 0.1

STCHC3 Stachys chamissonis var. coastal hedgenettle 10.3 0.4 0.1

cooleyae (Heller) G. Mulligan & D. Munro

STME2 Stellaria media (L.) Vill. common chickweed 0.1 0.1

STREP3 Streptopus Michx. twistedstalk 0.1 

STAM2 Streptopus amplexifolius claspleaf twistedstalk 0.1

(L.) DC.

TEGR2 Tellima grandiflora (Pursh) bigflower tellima 

Dougl. ex Lindl.
45

Table 10—Mean cover of understory plant species recorded at each site, sorted alphabetically by life form (n = 3 subplots) Species codea Scientific namea Common name Nesk CliffCk VOG Bear LtGrass Moon ElkCk Rock Rowell1 

THOC Thalictrum occidentale Gray western meadow-rue 

TITR Tiarella trifoliata L. threeleaf foamflower 0.7 0.1 0.4 0.1 0.4 0.3 TRBOL Trientalis borealis ssp. broadleaf starflower 0.1 0.1 0.1 

latifolia (Hook.) Hulten TROV2 Trillium ovatum Pursh Pacific trillium 0.1 0.4 1.0 0.1 0.1 0.7 0.1 0.1 

VAHE Vancouveria hexandra white insideout flower 

(Hook.) Morr. & Dcne. VEVI Veratrum viride Ait. green false hellebore 

VIOR Viola orbiculata Geyer ex Holz. darkwoods violet 1.4 

VISE3 Viola sempervirens Greene evergreen violet 0.4 0.3 0.1 

2FORB Unknown forb Forb 0.1 Graminoids: BRVU Bromus vulgaris (Hook.) Shea Columbia brome 6.0 9.3 0.1 0.1 

Unknown graminoid Graminoid 0.1 0.1 0.1 0.4 0.1 

a Species codes and nomenclature from USDA NRCS (2000).

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