103

1Dean S. DeBell is a research forester (retired), and 2Constance A. Harrington is a research forester, Forestry Sciences Laboratory, 3625-93rd Avenue SW, 

Olympia, WA 98512; 3Barbara L. Gartner is a professor, Department of Wood Science and Engineering and 4Ryan Singleton is a senior faculty research 

assistant, Department of Forest Science, Oregon State University, Corvallis, OR 97331.

Corresponding author: Constance A. Harrington, research forester, Pacific Northwest Research Station 3625-93rd Avenue SW Olympia, WA 98512, phone: 

360-753-7670, email: charrington@fs.fed.us

— Red Alder: A State of Knowledge —

Time and Distance to Clear Wood 

in Pruned Red Alder Saplings

Dean S. DeBell1, Constance A. Harrington2

Barbara L. Gartner 3, Ryan Singleton4

Abstract

Pruning trials in young alder stands were sampled to 

evaluate response to pruning. Effects of pruning (1) live 

branches on different dates, and (2) dead branches with 

or without damaging the branch collar were assessed on 

trees pruned in 3- and 6-year-old plantations, respectively. 

Six years after pruning, stem sections were collected and 

dissected in the longitudinal-radial plane to expose the 

center of the stem and branch stub. Ring counts and linear 

measurements were made for various boundaries or points, 

including time of pruning, stub length, defect, and beginning 

of clear wood formation. Pruning during the growing 

season and, to a lesser extent, late in the growing season 

when leaf abscission was beginning, resulted in shorter 

times and distances to formation of clear wood (2.1 years, 

14.5 mm) than pruning in the dormant season or just prior 

to the beginning of the growing season (2.6 years, 18.6 

mm). Cutting the branch collar on dead branches led to 

shorter times and distances to clear wood (2.8 years, 21.9 

mm) than intentionally avoiding such wounding (3.5 years, 

24.8 mm); these differences were associated with shorter 

branch stubs as there were no differences in the amount 

of defect. Epicormic branching was minimal in the two 

pruning studies, averaging less than one branch per tree in 

the date of pruning test and only two branches per tree in the 

branch collar wounding study. Assessments for comparable 

unpruned trees indicated that times to form clear wood after 

branch death would be markedly greater and that epicormic 

branching was equal to or greater than that determined for 

pruned trees. Although statistically significant differences 

occurred among different pruning dates and with branch 

collar wounding, the decision to prune or not prune is of 

much greater practical importance, regardless of when (date) 

or how it is done. Such pruning decisions can be made by 

using this information on time and distance to clear wood 

in economic analyses developed with available data on tree 

growth, log volume, lumber recovery, pruning costs, and 

price differentials for clear vs. knotty wood. 

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.
104

Introduction

Red alder (Alnus rubra Bong.) is an important 

hardwood in the coastal forests of Oregon, Washington, 

and British Columbia (Harrington 1990). For decades it 

was considered primarily a weed species that provided 

unwanted competition to conifers in these forests, but red 

alder is now recognized for some highly valued ecological 

and economic contributions. Rapid early growth and ability 

to fix atmospheric nitrogen make it a very desirable species 

for restoring and enhancing productivity of forest sites after 

natural and human-caused disturbances (Tarrant and Trappe 

1971). Its wood is desired for fuel, fiber, and solid wood 

products; as with other hardwood species, clear wood has 

the highest value and is used in furniture, cabinetry, and 

paneling. Red alder grows rapidly at young ages and recent 

silvicultural research has indicated that alder sawlogs can be 

produced in plantations on short rotations (30 years or less) 

with wide spacings (c.f., DeBell and Harrington 2002, Hibbs 

and DeBell 1994). Wide spacings, however, also lead to 

large, long-lived branches on the lower bole that can reduce 

log grade and value of lumber recovered. Such branching 

can be reduced by growing the trees at denser spacing to 

facilitate natural pruning (Hibbs and DeBell 1994) but 

diameter growth will be reduced. Another alternative is 

to grow the trees at wide spacing and manually prune the 

lower branches as is done to produce clear wood in other 

species throughout the world (Hanley et al. 1995, Haygreen 

and Bowyer 1996).

Although there is a long history of pruning hardwood 

species in other regions, there is little research or experience 

with regard to pruning red alder. Berntsen (1961) examined 

stem sections of 43-year-old alder that had been pruned 

22 years before. He found that stubs of pruned limbs 

were sometimes grown over within two years; decay was 

present in every dead or pruned stub but it rarely extended 

beyond the knot and it did not hinder the increment of clear 

wood. Berntsen (1961) also found that epicormic branches 

frequently originated, singly and in clusters, where other 

branches had been naturally or artificially pruned; these 

were apparently of such size and number to negate any 

gains in wood quality from pruning. Such branches, more 

common in hardwoods than conifers, form from suppressed 

buds located throughout the stem that are released (or 

sprout) following stand or tree disturbance. If the epicormic 

branches are abundant, persist and grow to large size, the 

resulting knots may reduce quality and value of the logs 

at harvest below that of unpruned trees. Berntsen (1961) 

therefore concluded that the desirability of pruning was 

questionable until more was learned about the cause and 

control of epicormic branching. 

Our research was conducted in young, rapidly 

growing red alder plantations. We investigated how the 

trees responded to pruning in terms of how long it took to 

form clear wood and also the degree to which epicormic 

branches were formed. Existing pruning trials (Brodie and 

Harrington 2006) offered the opportunity to assess: (1) 

effects of date (season) of pruning live branches, and (2) the 

nature of the cut for dead branch pruning (e.g., does it make 

a difference whether live tissue around the branch collar is 

wounded in the operation?). For some hardwood species, 

substantial differences in wound occlusion and subsequent 

decay may exist among seasons or dates of pruning (i.e., 

McQuilkin 1950). If such differences occur in red alder, 

pruning operations will need to be scheduled accordingly. 

If differences are negligible, however, pruning can be 

scheduled with greater flexibility. The study of pruning 

dead branches resulted from observations that some dead 

branches that broke off naturally did not occlude quickly. 

Also dead branches sometimes would break off inside the 

stem and leave a pocket or hole that filled in rather slowly. 

We hypothesized that wounding the branch collar would 

rejuvenate the tissues around the branch collar resulting 

in faster occlusion; in addition, making the pruning cut 

through the branch collar (closer to the stem) would also 

reduce stub length). We examined correlations between 

time and distance to clear wood formation and stem size 

(radius), stem (cambial) age, branch diameter, branch angle, 

and radial growth rate after pruning. We also evaluated 

epicormic branching on the pruned study trees and on 

comparable unpruned trees in the surrounding plantation.

Methods

Origin and Nature of Sample Trees

Stem samples for our investigation originated and 

represent subsamples from two trials of pruning methods 

(Brodie and Harrington 2006) that were superimposed on 

selected portions of research plantations of young red alder 

(fig. 1) at the Washington State Department of Natural 

Resources’ Meridian Seed Orchard, 12 km east of Olympia 

and near Lacey, Washington (47° 00 ‘ N, 122° 45 ‘ W). 

Detailed descriptions of the site, design and establishment 

of the research plantations, and early growth and stand 

development were reported in DeBell et al. (1990) and Hurd 

and DeBell (2001). Early results of the pruning trials are 

Figure 1—Young red alder plantation near Lacey, Washington.
105

given in Brodie and Harrington (2006). The soil at the site 

is a deep, excessively drained loamy fine sand formed in 

glacial outwashes and trees were irrigated to supplement the 

low rainfall (15 cm) falling during the May 1 – September 

30 period. Climate is mild with an average growing season 

of 190 frost-free days; mean annual temperature is 10.1°C, 

mean January minimum temperature is 0.1°C, and mean 

August maximum temperature is 25.1°C. The plantations 

were established with 1-year-old seedlings and kept 

weed-free by tilling, hoeing, and selective application of 

herbicides. 

One pruning trial (date of pruning) subsampled for our 

study was installed in a 3-year-old plantation (4 years from 

seed), spaced (after thinning) at 2 m by 2 m or 2500 trees 

per hectare. Live branches were pruned from the lower 

one-third of the crown of 10 trees without damaging branch 

collars on each of seven dates. Dead branches present 

in the same region of the stem were also removed at the 

same time. Most branches were removed by handsaw, but 

small trees or very small branches with inadequate wood 

to support a saw were cut with hand clippers. At time of 

pruning, the trees averaged 7.0 m tall and 6.7 cm in diameter 

at breast height (table 1), and were pruned to an average 

height of 3.2 m. Ten trees each from five of the pruning 

dates, representing a range of phenological stages, were 

selected for dissection and evaluation: January 1 – middormant season, March 1 – immediately prior to budbreak, 

May 1 – early growing season (leafed out), June 15 – midgrowing season (leafed out), and September 15—toward 

the end of the growing season (beginning of some leaf 

abscission). In addition, 10 trees that had not been pruned 

were selected for comparative measurements. 

 The second pruning trial (branch collar wounding) 

was installed in a 6-year-old plantation (7 years from seed), 

spaced (after thinning) at 2.8 m by 2.8 m or 1250 trees 

per hectare. All branches (dead and alive) were pruned 

on the lower bole by handsaw on May 1. At pruning, the 

trees averaged 9.4 m tall and 11.0 cm in diameter at breast 

height (table 1). Two pruning methods were tested on 

dead branches only: (1) without damaging branch collars 

(sometimes referred to as a “Shigo cut” [Shigo 1986]), and 

(2) with deliberate wounding of branch collars. Ten trees 

were randomly selected for each treatment. All trees treated 

were selected for dissection and evaluation in our study; 

an additional 10 trees (of identical age) that had not been 

pruned were also sampled in an adjacent planting of nearly 

the same spacing. 

Sample Collection, Preparation, 

and Measurement

Six years after pruning treatments were implemented, 

the trees for both studies were felled and several 

measurements taken on stem and branch characteristics. 

These included total height and diameter at breast height 

(table 1), height and diameter of every dead branch 

remaining on the bole, and the same measurements on 

live branches occurring at a height below the highest dead 

branch. Height and diameter of epicormic branches were 

also recorded. 

Five pruning scars (or branches or branch scars if 

sampling an unpruned tree) distributed between the stump 

and 4.8 m on the bole (nearly all were below 3.3 m) on 

each study tree were selected for sampling and their height 

recorded; a 15-cm thick section centered on the scar (or 

branch) was cut by chain saw. Each section was labeled by 

tree number and sample location on the bole (1=lowest and 

5=highest) and placed in a heavy plastic bag for transport to 

the laboratory. 

Two of the five sections (2 and 4) from the date of 

pruning study were used to assess presence of decay 

organisms in the branch stub. After excision from the stub, 

small samples of woody tissue were surface sterilized by 

flame; they were then pressed into malt extract agar in petri 

plate cultures, and examined over time for growth of decay 

fungi. The remaining three sections (1, 3, and 5) from each 

tree in the date of pruning study and all five sections from 

the branch collar wounding study were then kiln-dried at 

63°C for 48 hours to reduce decay. 

After drying, each section was examined visually to 

determine the location and orientation of the branch scar 

(pruned or unpruned) of interest. A band saw was used to 

dissect each section in the longitudinal-radial plane through 

the center of the branch and stem pith. Occasionally two 

Measure and time Study 1-date 

of pruning

Study 2-branch 

collar wounding

Mean Min Max Mean Min Max

DBH (cm): At pruning 6.7 4.7 9.1 11.0 7.8 13.4

 At sampling 12.4 8.2 18.9 19.2 15.3 24.7

Height (m): At pruning 7.0 5.6 8.2 9.4 8.3 10.1

At sampling 13.2 9.1 16.5 17.1 15.8 19.4

1 Number of observations is 60 trees for study 1 and 30 trees for study 2.

Table 1—Size of trees at pruning and at time of sampling (6 years later) 1.
106

or more cuts were needed to achieve good radial exposure 

through the branch. The radial surface was then sanded 

with a belt sander to aid identification of rings and various 

growth and healing (occlusion) boundaries (fig. 2).

Qualitative branch characteristics (dead or alive, pruned 

or unpruned) were recorded as were various ring counts. 

Linear measurements such as branch diameter, ring widths, 

and distances from the pith to point of branch death (branch 

collar wounding study only), end of stub, occlusion, and 

beginning of clear wood were determined to the nearest 0.1 

mm. Ring counts and distances as defined in Petruncio et al. 

(1997) plus some additional variables were calculated from 

the above measurements (table 2). For pruning treatments 

applied during the growing season, some measurements 

of ring count (CAM) and radial distance (AW, RIB) were 

adjusted as appropriate based on the phenology of stem 

cambial growth (i.e., seasonal pattern of cumulative radial 

increment) as determined in the plantations and reported in 

DeBell and Giordano (1994).

Summary and Analysis of Data

Analysis of variance procedures were used to assess 

effects of treatments (date of pruning in study 1, and 

branch collar wounding in study 2) on time and distance to 

clear wood, and treatment means were separated by least 

significant difference procedures (SAS 1994). Correlation 

matrices containing all variables were examined to evaluate 

relationships to time and distances to produce clear wood 

on pruned trees. All samples (stem sections) were assumed 

to represent independent observations. Differences 

among treatment means and correlation coefficients were 

considered significant if p<0.05. Data on live, dead, and 

epicormic branches originating on the bole below 3.3 m 

were summarized by 1.0 m height intervals above the stump 

(0.3 m).

Results 

The young trees in the plantation responded well to 

pruning. No trees died, and except for the pruning wounds, 

none were obviously injured in the pruning operation. There 

was no excessive sap flow or bleeding from wounds. At time 

of sampling, external evidence of pruning scar locations was 

still observable but occlusion was complete on all trees and 

there were no visual differences among treatments.

General Nature of Tree Characteristics 

and Pruning-Healing Variables

Values for pruning-healing variables measured on the 

stem sections for Study 1 and Study 2 are listed in table 3. 

Age and size of the stem sections and branches differed 

substantially between the two studies at time of pruning: 

cambial age of the stem section (3.6 vs. 5.0 years); its mean 

radius (25.5 vs. 48.5 mm); mean stub diameter (13.4 vs. 

17.0 mm); and stub length (13.2 vs. 18.7 mm) had much 

lower values in Study 1. Average time (ABR) and distance 

(ABW) to clear wood also differed markedly, even though 

radial growth rate after pruning (RWAP) was rather similar 

in the two studies (5.7 and 6.0 mm/yr). 

Figure 2—Diagrammatic stem sections showing branch stub immediately after pruning and 6 years later. Healing 

(occlusion) region is separated into stub length (Zone A) and region beyond the stub where defects may occur 

(Zone B). Adapted from Petruncio et al. (1997).
107

Study 1 — Date of Pruning 

Although there were no significant differences among 

pruning dates for number of rings (AR) from time of 

pruning to end of the pruned stub, significant differences 

were present among some treatment means for other 

“healing” or occlusion variables (table 4a). On average, 

fewer than 2 years (1.4 to 1.9) and no more than 15.2 

mm (AW) of radial growth were needed to reach the end 

of the branch stub. Such values are, of course, strongly 

influenced by growth rate after pruning and closeness of 

the prune to the stem (stub length). Statistically significant 

differences among pruning dates in time and distance from 

the end of the stub to formation of clear wood (BR and 

BW) reflect defects of various kinds (primarily bark or rot). 

Pruning in the dormant season (January 1) and just prior 

to the beginning of the growing season (March 1) resulted 

in longer times beyond the stub to clear wood (BR) than 

for pruning in mid-June (0.86 and 0.82 vs. 0.41 years); 

distances from the end of stubs to clear wood (BW) were, 

on average, twice as long for January pruning as those for 

any other date (5.1 vs. 2.5 mm). Because total time (ABR) 

and distance to clear wood (ABW) is the summation of both 

A and B variables (radius or time at pruning to end of stub 

plus end of stub to clear wood), they both show significant 

differences among treatment dates. In general, pruning 

during the growing season (May 1 and June 15) and, to a 

lesser degree, late in the growing season when some leaf 

abscission has started (September 15) results in shorter 

times and distances from pruning to formation of clear wood 

(average–2.1 years and 14.5 mm radial distance) than does 

pruning in the dormant season (January 1) or just prior to 

the beginning of the growing season (March 1) (average–2.6 

years and 18.6 mm radial distance). 

The relatively short time to produce clear wood after 

pruning live branches contrasts sharply with the time 

required for branches in unpruned trees to die, break off, and 

heal over. Many of the unpruned trees still had live and dead 

branches on the lower stem: one third still had live branches 

in the 1.3 to 2.3 m section and two thirds had live branches 

in the 2.3 to 3.3 m section. Dead branches were even more 

common; one third of the unpruned trees had dead branches 

in the lowest (0.3 to 1.3 m) section and all trees had some 

dead branches on the bole below 3.3 m. All trees evaluated 

in this study were components of intensively measured 

research plantations; as such, lower dead branches were no 

doubt broken off sooner and closer to the bole by activities 

of field personnel than would be typical in production 

plantations. Thus, not only is the presence of dead branches 

on the unpruned study trees likely to be lower than what 

would usually be expected, but also our assessment of times 

and distances required to produce clear wood beyond those 

branches that did break off may be biased toward the low 

end. Even so, average times and distances to clear wood 

after branch death were markedly greater in unpruned trees 

(4.2 years and 23.9 mm) than after pruning in pruned trees 

(2.4 years and 16.2 mm).

Ring counts

 CAM Number of rings from the pith to the year pruned. i.e., age of cambium when pruned

 AR Number of rings (years) to grow over zone A. i.e., since the year of pruning to the stub end

 BR Number of rings (years) to grow over zone B, i.e., from the end of stub to clear wood

 ABR Total number of rings (years) of zones A and B combined 

 DPRG Number of rings between branch death and pruning (study 2 only)

Distances (mm)

 AW Zone A width = stub length: the distance from the stem cambium at the time of pruning to the stub end (See Fig. 2)

 BRDIA Stub end diameter

 BW Zone B width: the radial distance from the end of stub to clear wood (Fig. 2) 

 ABW Width of zones A and B combined (ABW = AW + BW)

 RIB Radius from pith to year of pruning (RIB= ROS – AW)

 ROS Radius-over-stub: distance from pith to end of stub

 ROO Radius-over occlusion (ROO = ROS + BW)

 DPDIS Distance from point (ring) of branch death to prune (study 2 only)

Other measures

 BRANG Branch angle (measured from vertical)

 RWAP Average ring width (rate of growth) for the 6 years after pruning

Table 2—Definition of variables.
108

The preliminary assessment of decay organisms 

indicated that decay fungi were present in the branch stubs 

of unpruned trees to a somewhat greater extent than in the 

wound centers or branch stubs of pruned trees (29% vs. 

19%, respectively, for the average of all dates). There was a 

trend by pruning date in the percentage of stubs from pruned 

trees that contained decay fungi, however: January - 4%, 

March - 8%, May - 22%, June - 21%, and September - 39%.

Study 2 — Pruning and Branch 

Collar Wounding 

Times and distances between pruning and the end of 

the stub (AR and AW) and to the production of clear wood 

(ABR and ABW) differed significantly between sections 

with damaged and undamaged branch collars (table 4b). 

The amount of defect beyond the stub (reflected in BR 

and BW), however, was essentially the same in the two 

treatments, 0.3 years and about 5 mm of radial growth. 

The times and distances to production of clear wood after 

pruning averaged slightly more than 3 years and about 23 

mm of radial growth. Times and distances associated with 

intentional wounding of the branch collar were shorter, and 

were associated with shorter stub lengths (AW) for limbs 

pruned at the stem (damaged branch collars) rather than 

those pruned just beyond at the branch collar. 

As discussed above, estimates of remaining branches 

on unpruned trees are probably conservative. Because the 

plantation in the branch collar wounding study was older, 

no trees had live branches (except for epicormic branches) 

below 3.3 m. All unpruned trees, however, still had dead 

branches in the 1.3 to 2.3 m bole section and higher, and a 

few had a branch in the lowest 0.3 to 1.3 m section. Times 

and distances required for formation of clear wood for those 

branches in unpruned trees that did die and break off were 

at least one year longer and 5 mm greater in distance than 

those required by pruned trees. 

Other Factors that Influence 

“Healing” Variables

Correlations among all variables listed in table 2 were 

examined to determine which factors (other than date of 

pruning and branch collar wounding) might influence 

time and distance to formation of clear wood. Correlation 

coefficients for most variables that were significantly 

correlated with one or more healing variables are listed in 

tables 5a and 5b. 

Only live branches were evaluated in the date of 

pruning study (table 5a), and the factors associated with 

increased time and distance to formation of clear wood 

(ABR and ABW) were branch diameter (increased lengths 

Study 1 Study 2

Variable (unit) Code Mean Std dev Min Max Mean Std dev Min Max

Age branch was pruned (years) CAM 3.6 0.9 1.0 5.0 5.0 0.2 4.0 5.0

Rings in zone A (years) AR 1.7 1.2 0.0 6.0 2.9 1.2 1.0 7.0

Width of zone A= stub length (mm) AW 13.2 7.1 0.0 32.0 18.7 5.5 6.0 30.0

Rings in zone B (years) BR 0.6 0.8 0.0 3.0 0.3 0.5 0.0 1.0

Width of zone B (mm) BW 3.0 3.6 0.0 17.0 4.9 4.4 1.0 21.0

Rings in zones A and B (years) ABR 2.4 1.3 0.0 6.0 3.2 1.3 1.0 7.0

Width of zones A and B (mm) ABW 16.2 7.8 0.0 37.0 23.5 6.8 7.0 38.0

Radius-inside-bark (mm) RIB 25.5 8.4 8.0 51.0 48.5 7.2 29.0 69.0

Radius-over-stub (mm) ROS 38.4 8.9 16.0 60.0 67.2 8.5 46.0 90.0

Radius-over-occlusion (mm) ROO 41.4 9.8 20.0 75.0 72.0 10.2 47.0 107.0

Ring width after pruning (mm/year) RWAP 5.7 1.8 2.3 11.0 6.0 1.6 2.7 11.0

Stub diameter (mm) BRDIA 13.4 6.8 4.6 38.6 17.0 5.2 6.6 33.8

Rings between branch death 

and prune (years) DPRG N/A N/A N/A N/A 1.1 0.5 0.0 3.0

Distance between branch 

death and prune (mm) DPDIS N/A N/A N/A N/A 9.2 5.7 0.0 27.0

Branch angle (degrees) BRANG 35.3 11.4 4.0 68.0 36.7 11.4 3.0 77.0

Table 3—Values of healing-pruning variables measured on pruned branch stubs of studies 1 (date of pruning) and 2 

(branch collar wounding).
109

Date AR AW BR BW ABR ABW

yrs mm yrs mm yrs mm

January 1 1.7a 14.5bc 0.9b 5.1b 2.6ab 19.6b

March 1 1.9a 15.2c 0.8b 2.4a 2.6b 17.6ab

May 1 1.4a 10.9a 0.5ab 2.6a 1.8a 13.5a

June 15 1.7a 11.0a 0.4a 2.9a 2.2ab 13.9a

September 15 1.8a 13.8abc 0.6ab 2.2a 2.4ab 16.0ab

Table 4a—Treatment means for “healing” variables Study 1—date of pruning. Means 

in a column followed by the same letter are not significantly different at p = 0.05.

Treatment AR AW BR BW ABR ABW

yrs mm yrs mm yrs mm

Damaged 2.54a 17.0a 0.32a 4.9a 2.85a 21.9a

Undamaged 3.17b 20.2b 0.30a 4.8a 3.47b 24.8b

Table 4b—Treatment means for “healing” variables (study 2). Means 

followed by the same letter are not significantly different at p = 0.05. 

Table 5a—Correlation (r) of healing variables to other 

characteristics of stem cross sections (study 1-date of pruning). 

Based on 106 samples (all dates, live branches only): minimum 

r for statistical significance at p = 0.05 is 0.20.

Healing 

variable

Other characteristics

RIB CAM BRDIA BRANG RWAP

AW -0.37 -0.44 0.36 0.28 0.10

AR -0.43 -0.45 0.14 0.17 -0.05

BW 0.20 -0.02 0.22 0.11 0.25

BR 0.14 -0.02 0.42 0.18 -0.08

ABW -0.25 -0.41 0.43 0.31 0.20

ABR -0.29 -0.40 0.38 0.27 -0.08

Healing 

variable

Other characteristics

RIB BRDIA RWAP

AW -0.13 0.15 0.25

AR -0.03 0.32 -0.23

BW 0.24 0.33 -0.09

BR -0.20 0.07 -0.25

ABW 0.05 0.33 0.15

ABR -0.07 0.32 -0.31

Table 5b—Correlation (r) of healing 

variables to other selected characteristics of 

stem cross sections (study 2—branch collar 

wounding). Based on 88 samples (both 

treatments, dead branches only): minimum 

r for statistical significance p = 0.05 is 0.21.

of both stub [AW] and defect [BW] and time to grow over 

defect [BR]), branch angle (mainly increased stub length), 

and radial width after pruning (RWAP) (increased defect 

[BW]). Increased radius (RIB) and age (CAM) of the stem 

section at pruning were associated with decreased time 

and distance to formation of clear wood, primarily because 

stub lengths (AW) for stem sections having larger radii 

and greater numbers of rings were significantly shorter and 

fewer years were required to grow over them. 

In contrast to table 5a which examines correlations 

between distances and times to clear wood production and 

other stem and branch traits after pruning live branches 

of trees in the 3-year-old plantation used for the date-ofpruning study, table 5b shows correlations among some 

of the same plus additional variables after dead branches 

were pruned from trees in the 6-year-old plantation used 

for the branch collar wounding study. Healing variables 

for dead branches were not correlated with cambial age 

(CAM) or branch angle (BRANG) as they were for live 

branches in the date-of-pruning study (table 5a). Neither 

were distance or time from branch death to pruning (DPDIS 

and DPRG) related to any of the healing variables. Stem 

radius at pruning (RIB) and defect (BW), however, were 

positively correlated. Larger diameter branches (BRDIA) 

had slightly (though not significant statistically) longer 

stubs (AW), greater defect (BW), took more years to grow 

over stub (AR), and resulted in longer times and distances 

to clear wood (ABR and ABW). Increased radial growth 
110

after pruning (RWAP) was associated with decreased time 

to grow over stubs (AR), any defect (BR), and produce 

clear wood (ABR). Although RWAP was also significantly 

correlated with increased stub length (AW), no reasons for 

this relationship are apparent. 

Epicormic Branching (Both Studies)

Epicormic branching was minimal in the two pruning 

studies. Averaged over all pruned trees, there was less 

than one epicormic branch per tree in the date of pruning 

study and only two branches per tree in the branch collar 

wounding study (table 6). The branches averaged only 2-3 

mm in diameter at 6-7 years after pruning. Moreover, such 

epicormic branching as did occur could not be attributed 

to pruning because an examination of 10 comparable 

unpruned trees near each study revealed that incidence of 

epicormic branching was equal to or greater than in their 

pruned counterparts. The percentage of trees with epicormic 

branches and the number of branches per tree tended to be 

greater for the lowest (0.3-1.3 m) stem section than for the 

two higher stem sections (table 6); and only in this lower 

section was epicormic branching sometimes greater for 

pruned than for unpruned trees. 

Discussion and Conclusions

That vigorous red alder saplings can heal over and 

produce clear wood after only 2 to 3 years and about 25 

to 40 mm (or about 1 to 1.5 inches) of diameter growth 

following pruning (fig. 3) is good news for forest owners 

and managers who may wish to accelerate the production of 

clear wood on relatively short rotations. Berntsen’s (1961) 

earlier work on alder trees that were pruned at age 21 also 

indicated that some pruning stubs were grown over in two 

years but there was no indication as to the proportion of 

wounds that healed over in that time. In our study, clear 

wood was being laid down over about 60% of the pruning 

wounds within two years, and nearly 80% of the wounds 

within 3 years.

 Our date-of-pruning trial identified differences 

among pruning dates that were significant statistically, but 

managers will want to consider whether a difference of 0. 

8 years or 6 mm in time and radial distance is sufficient 

to warrant scheduling of operations to coincide with the 

best times for pruning. Certainly it would not if one had 

to postpone pruning operations until the next year to do it 

at the optimal time. Nevertheless, the finding that early to 

mid-growing season is, in fact, the most effective time for 

rapid healing is fortunate from the standpoint of operational 

planning because many other silvicultural activities such 

as planting and fertilizing usually must be scheduled 

before or after the growing season. Although no other 

research on date of pruning has been done for red alder, our 

results are generally consistent with findings for eastern 

hardwoods. Neely (1970), for example, found that spring 

(May) wounds healed much more rapidly than wounds 

created in summer (July), fall (October), or winter (March) 

for ash, honey locust, and pin oak. Although McQuilkin 

(1950) recommended pruning eastern hardwoods (except 

red maple) in late winter and early spring to achieve fastest 

wound occlusion, he favored pruning red maple in late 

spring or early summer to reduce excessive bleeding. Leban 

(1985) concluded that spring wounding of red maple led 

to less dieback around the wound and less decay than fall 

wounding. Colder than normal temperatures at time of the 

January pruning in our study may have been responsible 

for greater tissue damage and defect (BW or rot plus bark) 

in January than occurred for other pruning dates (decay 

associated with this pruning date, however, was low). 

Study 1 (date of pruning) Study 2 (branch collar wounding)

Stem section (ht (m) above ground) Stem section (ht (m) above ground)

0.3 to 

1.3

1.3 to 

2.3

2.3 to 

3.3

All 

heights

0.3 to 

1.3

1.3 to 

2.3

2.3 to 

3.3

All heights 

to 3.3 m

Trees with 1 or more epicormic 

branches (%)

 Pruned 16.0 6.0 12.0 20.0 55.0 20.0 25.0 65.0

 Unpruned 9.1 17.3 36.4 54.5 60.0 40.0 30.0 90.0

Mean number of epicormic branches 

per tree (number) all trees

 Pruned 0.20 0.10 0.24 0.60 1.45 0.20 0.40 2.05

 Unpruned 0.18 0.36 0.82 1.36 1.20 0.90 0.40 2.50

Mean diameter of epicormic 

branches (mm)

 Pruned 2.5 2.3

 Unpruned 3.3 2.1

Table 6—Epicormic branching in pruning studies compared with comparable unpruned trees of the same age.
111

Our study of branch collar wounding indicated that it 

is unnecessary to avoid wounds of the branch collar (i.e., 

as in a “Shigo cut”) when pruning dead branches of red 

alder. Healing times and distances to clear wood were, in 

fact, slightly shorter when branch collars were intentionally 

wounded. Most pruning studies with other hardwood species 

have involved removal of live branches, and it has been 

recommended that branch collars should not be damaged 

when live branches are pruned (cf., Shigo 1986). Shigo et 

al. (1979), working with black walnut, recommend against 

injuring the branch collar even when pruning dead branches 

because it may increase the amount of decay spreading 

inward (and upward and downward) from the dead branch. 

Ring shakes and dark vertical streaks also were associated 

with injured branch collars (flush cuts) in the black walnut 

trees. We saw little evidence of such development of decay 

(or shake and discolorization) in red alder, however. And 

years ago, Berntsen (1961) also reported that “decay rarely 

extended beyond the extremities of knots.” Recent work has 

determined that living red alder is very efficient in its ability 

to compartmentalize decay, and most decay events do not 

extend beyond the injured tissue (Allen 1993, Harrington et 

al. 1994). 

Our examination of the healing over of broken branches 

in unpruned trees indicated that times and distances to clear 

wood were substantially greater than those associated with 

pruning of either live or dead branches. Such data obviously 

applies only to the period after the branch has died and has 

broken off; if one adds the period prior to such events to 

that recorded in our comparison, one is probably looking at 

differences of 5 or more years to produce clear wood in the 

lower 3 m of stem of unpruned trees. Thus, the decision to 

prune or not prune is of much greater practical importance 

than that of when to prune live branches or how to prune 

dead ones.

Examination of correlation coefficients served mainly 

to underscore some logical relationships between stem and 

branch traits and healing. Times and distances to clear wood 

were longer as branch diameter and branch angle increased. 

Healing times and distances for trees in the 3-year-old 

plantation were shorter, however, for stem sections of 

greater cambial age and larger diameter (radius). Apparently 

it was easier to make close prunes (shorter AW) on larger 

rather than smaller stems. We suspect this finding was 

associated with use of clippers to prune branches on some of 

the smaller trees that lacked sufficient rigidity for use of the 

saw; the relationship did not occur in the larger trees in the 

6-year-old plantation pruned in the branch collar study, all of 

which were pruned by saw. Correlation coefficients for the 

date of pruning study suggested that increased growth rate 

after pruning was associated with greater defect (BW). Such 

a trend seems counter-intuitive and may be associated with 

some peculiarity or confounding relationship in our sample, 

and it was not apparent in the branch collar wounding study. 

The correlation in the latter study of increased radial growth 

rates with decreased time to grow over the stub, defect, and 

produce clear wood, however, is what one would expect.

Epicormic branching does not appear to be a problem 

when young, vigorous red alder trees are pruned. More 

than half of the pruned trees had no epicormic branches; 

those that did averaged fewer than two epicormic branches 

per tree and these were small, averaging only 2.4 mm in 

diameter. Moreover, such epicormic branching as did occur 

was just as prevalent or more so in unpruned trees in the 

same plantation. Only in the lowest section of the bole (0.3 

to 1.3 m) did the incidence of epicormic branching average 

slightly higher in pruned than unpruned trees. The tendency 

toward increased sprouting in the lowest section of both 

pruned and unpruned trees in the branch collar damage 

study (6-year-old plantation) may result from decreased 

apical control at greater distances from the terminal, and 

the much greater distance from the live crown in pruned 

than in unpruned trees may account for the slightly greater 

epicormic branching at this level in pruned trees. 

Why do our findings and interpretations with respect to 

epicormic branches differ so greatly from those of Bernsten 

(1961)? We believe at least two factors may contribute: 

(1) general vigor, and (2) other changes in the stand 

environment. Trees in Berntsen’s study were undoubtedly 

less vigorous; they were 21 years old and growing in natural 

stands when pruned whereas ours were growing in 3- and 

6-year-old plantations. Red alder grows very rapidly in 

height during the first two decades, especially so in the first 

10 years (Harrington and Curtis 1986). Beyond that time 

height growth is markedly reduced, and some studies have 

shown that response of natural alder stands to an initial 

thinning at older ages is much reduced and sometimes 

negligible (Berntsen 1962, Warrack 1964). In addition, tree 

crowns begin to lose their conical form at about the same 

time, indicating that apical control is diminishing. Skillings’ 

(1958) research on defects and healing following pruning in 

Figure 3—Stem section from tree pruned as part of the branch collar 

wounding study. Clear wood was produced after only 2 years following 

pruning.
112

northern hardwoods is consistent with our suggestion that 

tree vigor plays a role; he found epicormic branching to be 

substantial in lower crown classes, but limited in dominant 

and codominant trees. In another study (Skilling 1959) 

on yellow birch (a relative of red alder), only dominant 

and codominant trees were pruned; epicormic branching 

was slight and branches short-lived, and “for all practical 

purposes could be disregarded.” Secondly, other information 

indicates that the pruned trees examined by Berntsen 

(1961) came from a stand that was not only pruned, but 

also had been released from overtopping conifers and 

thinned at the same time (Rapraeger 1949, Berntsen 1962). 

If so, the epicormic branching may have been a response 

to sudden opening of the stand by release and thinning as 

well as pruning, and perhaps was particularly stimulated 

by the combination of these treatments at a stand age 

(21 years) when growth (particularly height growth) is 

normally decreasing. Other studies have indicated that 

epicormic branching can increase when red alder stands 

are thinned, and such observations were made primarily 

in stands thinned beyond age 15 (Warrack 1964, Smith 

1978). Some epicormic branching may occur even when 

younger stands are thinned, however (Hibbs et al. 1989). In 

another pruning trial established in a 10-year-old plantation, 

trees at the edge of the stand or near openings had greater 

numbers of epicormic branches than trees in fully-stocked 

portions of the stand (Brodie and Harrington 2006). Given 

these observations, we suggest that epicormic branching is 

unlikely to be a problem when pruning is done on interior 

trees early in the life of alder plantations—i.e., when height 

growth is in its most rapid phase (before age 15)—and at 

least a year or so after (or before) any significant thinning 

of the stand. There may be logistical as well as biological 

reasons to schedule thinning and pruning operations in 

different years.

Trees in our study were pruned by removal of about 

one-third of the live crown (retaining crown ratios of 50% or 

more) and no top breakage occurred. Pruning 50% or more 

of the total height on young trees, however, may greatly 

increase the chances that high winds will snap off the top 

during the first growing season or so after pruning. Such 

damage has been observed when operational plantations 

were pruned to that degree. Although not a problem in 

these trials, there is some anecdotal evidence that pruning 

can increase the attractiveness of the bole to sapsuckers 

(possibly because increased sugar content at base of now 

raised live crown). 

Based on this work and that reported in Brodie and 

Harrington (2006), there seem to be no major biological 

concerns about pruning live and dead branches in the lower 

one-third of crowns of young red alder. Pruning can be done 

at anytime of the year (even during the growing season; 

if anything, preferably so) and without particular concern 

about damage to branch collars. On average, clear wood will 

be produced in fewer than 3 years and less than 40 mm 

(1.5 inches) of diameter growth after pruning. Decisions on 

whether or not to prune must be based on price differentials 

for clear versus knotty wood and the costs of investments 

in pruning. Currently available data on tree growth, log 

volume, and lumber recovery can be used to evaluate the 

economic benefits (or lack thereof) of pruning stands of 

various ages on sites of different quality, and harvested at a 

range of ages.

Acknowledgements

This work was supported in part by a special USDA 

grant to Oregon State University for wood utilization 

research and also by the Wood Compatibility Initiative 

of the Pacific Northwest Research Station, Olympia, 

Washington. The alder plantations were established with 

funds provided by the U.S. Department of Energy to the 

PNW Research Station’s silviculture team at Olympia. 

Leslie Brodie and Joseph Kraft assisted with data analysis 

and tree measurement and Daniel Johnson, Marshall Murray 

and Steve Ray helped in installation of the original study. 

Mark Lavery assisted in collection and preparation of the 

stem samples, and made initial measurements. Camille 

Freitag and Jeffrey Morrell were responsible for assessment 

of decay fungi. Leslie Brodie, Alex Dobkowski, and David 

Marshall reviewed an earlier draft of the manuscript. We 

thank them all.

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red alder. Journal of Forestry 59 (6): 675-676.

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stands of red alder. Res. Note PNW-RN-219. U.S. 

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Oregon State University Press. 116-130. 
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Clendenen, G.W.; Zasada, J.C.; Harms, W.R.; 

McKevlin, M.R. 1990. Increasing the productivity of 

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Ridge National Laboratory. 

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rectangularity of planting influence 20-year growth 

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Fight, R.D. 1995. Forest pruning and wood quality 

of western North American conifers. Contrib. No. 77, 

Seattle, WA: Institute of Forest Resources. College of 

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and site index curves for red alder. Res. Pap. PNW-358. 

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Harrington, C.A.; Zasada, J.C.; Allen, E.A. 1994. 

Biology of red alder (Alnus rubra Bong.). In: Hibbs, 

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management of red alder. Corvallis, OR: Oregon State 

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wood science - an introduction (third edition). Ames, IA: 

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and dressings on the healing of tree wounds. Journal of 

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pruned branch stub occlusion in young, coastal Douglasfir. Canadian Journal of Forest Research 27: 1074-1082.

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Station, Forestry Sciences Laboratory, 3625 93rd Avenue 

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N. 1979. Internal defects associated with pruned and 

unpruned branch stubs in black walnut. Res. Pap. NE440. U.S, Department of Agriculture, Forest Service, 

Northeast Forest and Range Experiment Station. 27 p. 

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northern hardwood pruning. Journal of Forestry 56(1): 

19-22.

Skilling, D.D. 1959. Response of yellow birch to artificial 

pruning. Journal of Forestry 57(6): 429-432.

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improving the forest environment. Plant and Soil (Special 

Volume 1971): 335-348. 

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114
115

1Mariano M. Amoroso is a PhD student at the Department of Forest Sciences, University of British Columbia, email: amorosomariano@hotmail.com

2Eric C. Turnblom is an Associate Professor in Forest Biometrics at the College of Forest Resources, University of Washington, Seattle, Washington, and the 

Stand Management Cooperative Silviculture Project Leader at the same university, email: ect@u.washington.edu

— Red Alder: A State of Knowledge —

On the Effects of Tree Crop Rotation: 

Red Alder Following Alder or Douglas-fir; 

Douglas-fir Following Fir or Alder

Mariano M. Amoroso1 and Eric C. Turnblom2

Abstract

Red alder (Alnus rubra Bong.) has been proposed 

for use in crop rotation due its ability to symbiotically 

fix atmospheric nitrogen. The ability of this species for 

increasing nutrient status and ameliorating site deficiencies 

have been recognized, however whether this will have an 

effect on a subsequent “crop” or if it can be used in a crop 

rotation scheme remains unknown. A Douglas-fir – red alder 

conversion study established in 1984 may shed light on 

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.

some of these issues. Results 20 years after establishment 

showed that the previous presence of red alder resulted in 

an overall increased productivity of the site compared to the 

adjacent Douglas-fir site. 

Keywords: crop rotation, Douglas-fir, red alder, Washington 

State
116

Introduction

Crop rotation is the alternation of different crops in 

the same field in some regular sequence. It differs from 

the haphazard change of crops from time to time, in that 

a deliberately chosen set of crops is grown in succession 

in cycles over a period of years; the crop sequence is not 

randomly chosen either, but is intentionally selected with a 

specific objective. This technique appeared primarily as a 

solution to the decline in crop yields resulting from having 

the same crop continuously grown in the same place. The 

practice of crop rotation has been widely accepted and 

successfully applied in the field of the agriculture. There are 

both direct and indirect benefits from rotational practices. 

Among them are pest control, maintenance of organic 

matter and soil nitrogen, protection and complete use of soil, 

balanced used of plant nutrients, economy of labor, and risk 

reduction. However, the effectiveness of rotating crops will 

ultimately depend on the type of crops and crop rotation

timing.

When it comes to forestry, “rotation” is recognized as 

a guide for the economic age to which each stand can be 

grown before it is succeeded by the next one. It is also a 

more complex but flexible concept since rotation could also 

be understood in ecological terms. In practice the rotation 

time is set by two principles, the physical and the financial 

rotation, since one can almost never be considered without 

the other (Smith et al. 1997). In either case the goal is to 

maximize or optimize the long-term sustained yields and 

capital return respectively. Nevertheless, forestry faces some 

of the same issues as agriculture and sometimes silvicultural 

practices are needed for pest control, maintenance of 

adequate levels of organic matter and nitrogen in the soils, 

as well as soil protection. Additionally, and even though 

it has not been practically demonstrated, the repeated 

cultivation of same forest stands in some sites could 

possible result in yield declines. 

The concept of crop rotation has not been applied to 

forestry for practical reasons such as rotation lengths, lack 

of a variety in crops as well as the fact that forestry is a 

younger discipline compared to agriculture. The unmodified 

application of this agriculture concept in forestry will not 

be that simple for managerial, biological and economical 

reasons; however, there might be situations, such as in the 

case of short rotations of fast growing species, where it 

could be feasible. Other cases could also include situations 

where some kind of immediate site amelioration is needed, 

or where the presence of a particular species in the previous 

crop will result in an improvement of the site quality and 

thus an increase in the yield of the future species.

Red alder (Alnus rubra Bong.) has been proposed for 

use in both crop rotation and in mixtures with other species 

(Tarrant and Trappe 1971, Atkinson et al. 1979, DeBell 

1979). Due to its ability to symbiotically fix atmospheric 

nitrogen, this species can increase levels of nitrogen and 

organic matter to a site (Tarrant and Miller 1963, Trappe et 

al. 1968, Harrington 1990), and has been experimentally 

planted to serve as a nitrogen source for other species 

(Briggs et al. 1978), as an alternative to N fertilization in 

N-stressed forests, and on other eroded or low fertility areas 

(Tarrant and Trappe 1971, Heilman 1979). Additionally, it 

could be used in a crop rotation system or as an alternative 

in areas containing coniferous root pathogens, such as 

Phellinus weiri (Hansen 1979, Harrington 1990) or Swiss 

needle cast. The ability of this species for increasing 

nutrient status and ameliorating site deficiencies have been 

recognized (Harrington 1990) and some attempts were made 

simulating different rotation schemes (Atkinson et al. 1979); 

however, whether this will have an effect on a subsequent 

“crop” or whether it can be use in a crop rotation scheme 

remains unknown. 

A unique semi-natural experiment was established 

in 1984 at the so-called “Thompson Site” on the Cedar 

River Watershed, WA in which two adjacent stands were 

clear-cut harvested in the same year, one predominantly 

Douglas-fir (Pseudotsuga menziesii, Mirb. Franco), the 

other predominantly red alder. Each of the stands were 

divided in two and then replanted to red alder and Douglasfir respectively; representing alder plantations following 

both an alder and a fir stand, and vice versa. The goal of this 

study was to determine the effect of red alder soil nutrient 

status (leaching vs. mineralization and nitrification rates) 

on soil fertility, as well as on the growth of subsequent 

forest rotations (Van Miegroet et al. 1990, 1992). The 

authors concluded that even though the presence of red 

alder generally improves the N fertility of the site, the 

experiment was not able to demonstrate, after 4 years, an 

improvement in growth (based on height measurements 

only) of the seedlings planted on sites previously occupied 

by alder over those planted after Douglas-fir cover (Van 

Miegroet et al. 1990). Another finding of the study was a 

decrease in soil and solution pH in the upper soil horizon. 

The authors hypothesized a phosphorus deficiency and 

later, two different levels of phosphorus fertilization were 

applied as well as one level of nitrogen fertilization. No 

further aboveground analyses of this study were conducted 

since then. Based on the potential of this alternative on some 

areas, we decided to investigate the outcomes twenty years 

after study establishment with the following objectives: 

• Whether the presence of red alder improves site 

fertility and thus growth and productivity of 

subsequent rotations, or whether it may have a 

negative impact.

• Whether there are any differences in succeeding 

species in relationship to this potential growth 

change.

• Whether the supplementation with N and P may 

have an effect on productivity.
117

Methodology 

Site characteristics

The study was conducted at the Thompson Research 

Center (aka “Thompson Site”) at the Cedar River 

Watershed, King County, WA. The site has a mean annual 

temperature of 49.6°F and a mean annual precipitation of 

51.2 inches. Two adjacent stands originating after fire in the 

1930s were clear-cut harvested in 1984, one predominantly 

Douglas-fir (Pseudotsuga menziesii, Mirb. Franco), the 

other predominantly red alder (Alnus rubra Bong.). At 

the time of harvesting the stands presented the following 

characteristics: the Douglas-fir stand had approximately 445 

stems per acre (SPA) and 218 ft2 per acre of basal area with 

a Douglas-fir site index of 106 ft at 50 years breast height 

age (site class III); the red alder stand was about 324 stems 

per acre and 156 ft2 per acre of basal area with a Douglas-fir 

site index of 111 feet at 50 yr breast height age (site class 

III). Both stands were around 50 years old. 

Experimental design

The study consists of a Split-split Plot Design. In each 

of the original stands an area of 2.5 acres was cut, divided 

in two, and replanted in 1985 with 500 SPA to red alder 

and Douglas-fir respectively; this representing red alder 

plantations following both an alder and a fir stand, and vice 

versa. Eight tenth-acre experimental plots were set in each 

replanted area adding up to a total of 32 plots. Later on, in 

an effort to assess the effects of additional site amelioration, 

between two and four of the eight plots in each new 

plantation were fertilized as follows: i) 180 pounds/acre N 

as urea at 8 years where Douglas-fir was planted; and ii) 

180 and 360 pounds/acre of P at 7 years where red alder 

was planted. After the fertilization treatments were applied, 

treatment descriptions resulted as follows:

1. FF C: Cut DF stand, plant 1-1 DF, control (no 

fertilization)

2. FF N: Cut DF stand, plant 1-1 DF, fertilize 180 

pounds/acre N 

3. FA C: Cut DF stand, plant RA wildings

4. FA P360: Cut DF stand, plant RA wildings, fertilize 

360 pounds/acre P 

5. FA P180: Cut DF stand, plant RA wildings, fertilize 

180 pounds/acre P 

6. AA C: Cut RA stand, plant RA wildings

7. AA P360: Cut RA stand, plant RA wildings, 

fertilize 360 pounds/acre P 

8. AA P180: Cut RA stand, plant RA wildings, 

fertilize 180 pounds/acre P 

9. AF C: Cut RA stand, plant 1-1 DF

10. AF N: Cut RA stand, plant 1-1 DF, fertilize 180 

pounds/acre N 

We decided to include only the higher level of 

phosphorus fertilization in this analysis (RA plots with 180 

pounds/acre P were not considered).

Analysis

Data were analyzed as a linear repeated measures 

experiment with two factors, treatment and time. The 

treatment factor consisted in the combinations of rotation 

pattern and fertilization (8 levels), and the time factor in 

three times post establishment (5, 10 and 20 years). For 

purposes of the analysis, each of the eight plots representing 

a rotation pattern were considered as replicates. The authors 

recognize that in fact, the plots are not strictly independent. 

So, results obtained from hypothesis testing are likely to 

have larger p-values in reality than would first appear.

The model describing both fertilization and time is 

presented as follow:

yijk = μ + ti + hk(i) + qj + tqij + eijk

where:

yijk = (QMD, Volume, Height) for rotation / fertilization 

 combination i, time j, replicate k

μ = overall average response

ti = the fixed effect of the i-th rotation/fertilization level

hk(i) = the error accounting for variation between plots

qj = the effect of time period j

tqij = time by treatment interaction

eijk = the leftover error not accounted for by time or 

 treatment

Attempts were made to add covariates to the model to 

account for uncontrolled factors, especially density, but the 

results showed the variables not to be significant. A strong 

interaction was apparently occurring for “FA C” and “FA 

P” treatments with time. This was resolved with covariance 

adjustments in the 3rd. measurement when historical records 

revealed storm damage in those plots. Statistical differences 

among treatments were tested by using orthogonal contrasts 

(0.1 level); tables for comparisons between treatments are 

presented in what follows.

It is important to note before presenting the results that 

the domain of the study may limit the scope or range of 

conditions to which results apply (one soil type, location, 

etc.) It is important to note that some of the plots have 

suffered physical damage by weather and other abiotic 

agents, so the results must be interpreted in light of this 

knowledge. 

(1)
118

Results 

Diameter growth

Both DF and RA exhibited significantly greater QMD 

in the control plots growing after RA compared to DF 

(fig. 1). For DF these differences in growth resulted to be 

significant at age 10 (table 1). From the same figure it can 

be seen what happened with red alder through time. At age 

5 RA growing after DF had a greater QMD compared to 

the FA rotation. However, 15 years later it seems that initial 

difference no longer remains and has turned slightly in favor 

of the AA rotation. Interesting also is the effect RA has on 

both species growth patterns. When growing after DF, RA 

resulted in a greater QMD than DF after 20 years. However, 

growing after RA and despite the initial differences, DF 

resulted in a larger diameter. Interesting was also the fact 

that at initial ages alder trees growing after alder presented 

a smaller QMD compared to those growing after DF. Even 

though a toxicity effect was initially hypothesized, Van 

Miegroet et al. (1990) concluded that such response could 

have been a consequence of competition with a more intense 

understory vegetation development in the N-richer site.

The fertilization treatments also showed some 

interesting results (figs. 2 A, B). Nitrogen fertilization 

resulted in a growth increment only when DF grew after 

DF. The addition of phosphorus on the RA plots seems to 

have a small effect in the AA plots resulting in greater QMD 

although differences were not significant (table 1). 

Height growth

Height growth of DF and RA appears to be enhanced 

if RA is the previous crop (fig. 3). In addition to this, fig. 3 

shows the higher initial growth of RA compared to DF as 

it has been reported in the literature but also that the stand 

dynamics is reaching the time where attained heights of RA 

and DF are just about to reverse as a consequence of RA 

height growth slowing down.

The addition of fertilizers had also some influences 

on the height growth of both species. While nitrogen 

fertilization resulted in no added increment for DF, 

phosphorus increased the total height of RA growing after 

both RA and DF (figs. 4 A, B). It can be seen again that DF 

growing after RA resulted in taller trees but no differences 

where found between the control and the fertilization 

treatment (table 2). In the RA plots the addition of P may 

result in slightly taller trees. It is interesting that RA height 

growth slowed down sooner where RA was planted after 

DF.

Volume 

The presence of RA in a rotation scheme increased the 

total volume per acre in the DF control plots compared to 

the FF rotation (fig. 5). After 20 years DF growing after 

RA doubled the volume per acre of DF after DF. This result 

parallels those found for diameter and height. No significant 

differences were found for RA following RA or DF. 

Even though some trends can be seen and differences 

are expected to become significant with time (figs. 6 A, B), 

the fertilization treatments resulted in no significant effects 

(table 3).

Table 1—Contrast results for Quadratic Mean Diameter 

at ages 5, 10 and 20.

Contrast Age = 5 Age = 10 Age = 20

ALDER SITE VS. FIR SITE SIGNIF. SIGNIF. SIGNIF.

FFC vs. AFC NS SIGNIF. SIGNIF.

FFC vs. FFN NS NS SIGNIF.

AFC vs. AFN NS NS NS

FAC vs. AAC NS NS SIGNIF.

AAC vs. AAP NS NS NS

FAC vs. FAP NS NS NS

FAP vs. AAP NS NS SIGNIF.

Table 2—Contrast results for Mean Total Height at ages 

5, 10 and 20. 

Contrast Age = 5 Age = 10 Age = 20

ALDER SITE VS. FIR SITE NS. NS SIGNIF.

FFC vs. AFC NS SIGNIF. SIGNIF.

FFC vs. FFN NS NS NS

AFC vs. AFN NS NS NS

FAC vs. AAC NS NS SIGNIF.

AAC vs. AAP NS NS NS

FAC vs. FAP NS NS SIGNIF

FAP vs. AAP NS NS SIGNIF.

Figure 1—Quadratic mean diameter at 5, 10 and 20 years after 

establishment. Vertical bars represent standard errors. 

AF C

AA C

FA C

FF C

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QMD (inches)

Conclusions 

Results 20 years after establishment show that the 

presence of red alder resulted in an overall increased 

productivity of the site compared to the adjacent Douglas-fir 

site (table 3). The Douglas-fir plantation established after a 

red alder stand not only exhibited the greatest productivity 

measured as volume per acre but also doubled that of 

Douglas-fir growing after a Douglas-fir stand.

In a red alder – red alder rotation scheme growth is 

enhanced after an initial decline. However, without site 

amelioration red alder plantations following Douglas-fir 

yield almost as much as alder following alder. 

Results for the fertilization treatment showed that N 

fertilization in a red alder – Douglas-fir rotation scheme 

may not result in growth benefit, furthermore it might 

be detrimental. P fertilization, on the other hand, may be 

beneficial if the level of nitrogen is not limiting. These 

results follow what is known as “the law of the limiting 

factor” that states that the addition of a nutrient will only 

result in increments when all the rest of growth limiting 

factors (other nutrients in this case) are not limiting. 

Fertilization on sites that may have been already enriched by 

the presence of red alder will not result in any extra growth 

since nitrogen is no longer the limiting growth factor. 

The addition of phosphorus on the other hand, could have 

positive consequences in these situations.

The results presented here only reflect the biological 

aspect of a crop rotation scheme and the different response 

to the fertilization treatments. Since no economical analyses 

are presented and the practice of forest fertilization usually 

involves a significant capital investment, implementation 

of fertilization programs should also be evaluated by costbenefit or other appropriate analyses. 

Table 3—Contrast results for Volume per Acre at ages 5, 

10 and 20.

Contrast Age = 5 Age = 10 Age = 20

ALDER SITE VS. FIR SITE NS NS SIGNIF.

FFC vs. AFC NS NS SIGNIF.

FFC vs. FFN NS NS NS

AFC vs. AFN NS NS NS

FAC vs. AAC NS NS NS

AAC vs. AAP NS NS NS

FAC vs. FAP NS NS NS

FAP vs. AAP NS NS NS

Figure 2—Quadratic mean giameter for Douglas-fir (A) and red alder (B) after 5, 10 and 20 years of establishment. Vertical bars represent 

standard errors. 

Figure 3—Mean total height at 5, 10 and 20 years after establishment. 

Vertical bars represent standard errors. 

A B

AF C

AA C

FA C

FF C

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Some comments need to be made again with respect 

to the results of this study. The domain of this study may 

limit the scope or range of conditions to which results apply. 

For this reason results should be understood carefully since 

the outcomes can be strongly influenced by site quality. 

Further, N-fixation rates for red alder have been reported to 

vary significantly from site to site and this will undoubtedly 

affect the outcomes in other situations.

Acknowledgments

The authors wish to express their thanks to Bob Gonyea 

and Bert Hasselberg at the Stand Management Cooperative, 

University of Washington for their help with the field data 

collection and for providing insights and history about the 

study. Further insights and additional history of the study 

provided by Bob Edmonds are gratefully acknowledged. 

Figure 4—Mean total height for Douglas-fir (A) and red alder (B) after 5, 10 and 20 years of establishment. Vertical bars represent standard 

errors. 

Figure 5—Mean volume per acre at 5, 10 and 20 years after establishment. 

Vertical bars represent standard errors. 

A B

AF C

AA C

FA C

FF C

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121

Figure 6—Mean volume per acre for Douglas-fir (A) and red alder (B) respectively after 5, 10 and 20 years of establishment. Vertical bars 

represent standard errors. 

Literature Cited

Atkinson, W. A., B. T. Bormann, and D. S. DeBell. 1979.

Crop rotation of Douglas-fir and red alder: A preliminary 

biological and economical assestment. Botanical Gazzette 

140: 102-107.

Briggs, David G., Dean S. DeBell, and William A. 

Atkinson, comps. 1978. Utilization and management 

of alder: Proceedings of a Symposium. USDA Forest 

Service, General Technical Report PNW-70. Pacific 

Northwest Forest and Range Experiment Station, 

Portland, OR. 379 p. 

DeBell, Dean S. 1979. Future potential for use of symbiotic 

nitrogen fixation in forest management. In Symbiotic 

nitrogen fixation in the management of temperate forests. 

p. 451-466. J. C. Gordon, C. T. Wheeler, and D. A. Perry, 

eds. Oregon State University, Corvallis. 

Hansen, E. M. 1979. Survival of Phellinus weirii in 

Douglas-fir stumps after logging. Canadian Journal of 

Forest Research 9(4):484-488.

Harrington, C. A. 1990. Red alder. In Silvics of North 

America. R. M. Burns and B. H. Honkala, tech. cords. 

Agriculture Handbook 654, Volume 2: Hardwoods. U.S. 

Dept. of Agriculture, Forest Service, Washington, D.C. 

877 p.

Heilman, P. E. 1979. Use of alders in coal spoil reclamation 

in the Pacific Northwest. In Symbiotic nitrogen fixation 

in the management of temperate forests. p. 477. J. C. 

Gordon, C. T. Wheeler, and D. A. Perry, eds. Oregon 

State University, Corvallis. 

Tarrant, R. F., and R. E. Miller. 1963. Accumulation of 

organic matter and soil nitrogen beneath a plantation 

of red alder and Douglas-fir. Soil Science Society of 

America Proceedings 27(2):231-234. 

Tarrant, R. F., and J. M. Trappe. 1971. The role of Alnus

in improving the forest ecosystem. Plant soil, Special vol: 

335-348. 

Trappe, J. M., J. F. Franklin, R. F. Tarrant, and G. M. 

Hansen, eds. 1968. Biology of alder: Proceedings of a 

Symposium. Fortieth Northwest Scientific Association 

Meeting. USDA Forest Service, Pacific Northwest Forest 

and Range Experiment Station, Portland, OR. 292 p. 

Van Miegroet, H., D. W. Cole, and P. S. Homann. 1990.

The effect of alder forest cover and alder conversion on 

site fertility and productivity. p333-354. In S. P. Gessel et 

al., (ed) Sustained productivity of forest soils. Proc. of the 

7th. North American Forest Soil Conference. University of 

British Columbia, Faculty of Forestry publ., Vancouver, 

BC., Canada. 

Van Miegroet, P. S. Homann, and H., D. W. Cole. 

1992. soil nitrogen dynamics following harvesting and 

conversion of red alder and Douglas-fir stands. Soil Sci. 

Soc. Am. J. 56:1311-1318.

0

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Time after establishment (years) Time after establishment (years)

FFC FFN AFC AFN FAC FAP AAC AAP 

A B

123

Economics 

(Supply/Markets/Returns)
124
125

1Glenn R. Ahrens is Extension Forester, Oregon State University Extension Service, Clatsop and Tillamook County. 2001 Marine Drive, Room 210, Astoria, 

OR 97103, email: glenn.ahrens@oregonstate.edu

— Red Alder: A State of Knowledge —

Overview of Supply, Availability, 

and Regulatory Factors Affecting 

Red Alder in the Pacific Northwest

Glenn R. Ahrens1

Abstract

The inventory of red alder timber in the Pacific 

Northwest is about 265 million cubic meters (30.5 billion 

board feet), however much of this is not available due to 

economic, policy, or regulatory factors. Of the total annual 

harvest of 4.64 million cubic meters (~598 million board 

feet), 87% comes from private lands in Washington (64%) 

and Oregon (23%). The remainder comes from other lands 

in Washington and Oregon (5%), British Columbia (6%), 

and California (2%). 

The current supply of alder is a legacy of past practices, 

which increased the alder component during most of the 

1900s. Modern forest practices generally reduce the alder 

component. Regulations protecting riparian zones, unstable 

slopes, and wildlife habitat reduce the availability of alder 

timber. Declines in abundance of alder are becoming 

apparent and the rates of removal of alder in the 1990s do 

not appear sustainable. Knowledge of and management for 

alder are increasing however, and there is much potential 

for foresters to maintain or increase alder. The supply of 

alder in the future depends on the uncertain balance of these 

positive and negative factors. 

Keywords: red alder, timber supply, availability, 

management, regulatory factors.

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.
126

Introduction 

As the value and utilization of red alder have 

increased in the Pacific Northwest, so too have concerns 

about sustaining supplies of red alder timber. A previous 

assessment of hardwood supply in the Pacific Northwest 

(Raettig et al. 1995) concluded that short-term supply was 

favorable, but there was cause for concern about longterm supply due to lack of management for hardwoods. 

Since 1995, harvest volumes of red alder have declined 

and shortage of alder logs has been cited as a major 

factor limiting lumber production and sales (Washington 

Hardwoods Commission). Increasing prices for red alder 

sawlogs are also consistent with declining alder timber 

supply (fig. 1.) The last assessment of hardwood supply 

in the region was based on USFS forest inventory data for 

Oregon (federal lands 1976, non-federal lands 1986, 1987) 

and Washington (1991), with no information from other 

states or British Columbia (BC). Updated information on 

timber inventory across the range of alder is now available 

and it is important to revisit the question of alder supply 

for the International Symposium, Red Alder: A State of 

Knowledge (March 23-25, 2005, University of Washington, 

Seattle).

This paper provides an overview of red alder timber 

supply and the major factors affecting the alder resource 

across the geographic range of the species. The purpose is to 

revisit the key trends identified in the 1995 analysis (Raettig 

et al.) and provide an updated assessment of the red alder 

resource, including:

• Timber inventory, growth, and removal;

• Forest management practices and regulations, and

• Sustainable supplies in the future.

Timber Inventory 

The total inventory of about 265 million cubic meters 

(30.5 billion board feet Scribner) of red alder is welldistributed across Washington (36%), BC (35%), and 

Oregon (27%), with small amounts in California (3%) and 

Alaska (1%) (fig. 2). These inventory volumes indicate the 

relative abundance of red alder across its range and should 

not be confused with actual timber supply. 

Note that the relatively large inventory estimate for red 

alder in BC (91.9 million m3) is for all stand types in the 

coast region (Canadian National Forest Inventory System 

2001). Previously published estimates of the alder inventory 

in BC of about 33 million m3 (Massie 1996) were based 

only on the amount of alder in stands where alder was the 

most abundant species (leading species). For comparison, 

an updated estimate for the amount of alder in stands where 

alder is the leading species in coastal BC is 29.7 million m3 

(Canadian National Forest Inventory System 2001).

Timber harvest and removal 

The actual supply of alder for industrial utilization 

depends on the portion of the timber inventory that is 

made available for harvest. This is influenced by many 

factors including landowner goals, policies, regulations, 

local resource quantity and quality, access, logging costs, 

transportation costs, etc. Recent volumes of alder removal 

are used below to provide an indication of available alder 

wood volumes from forests across the range of alder (fig. 

3). Removals include some wood volume that may not 

be utilized. Consistent estimates of removal volumes are 

Red alder log price trends

Adjusted for inflation to 2004 $ 

0

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Figure 1—Price trends for red alder sawlogs (8-inch and larger at small 

end) for northwest Oregon and southwest Washington. Prices represent 

delivered log prices per 1000 board feet Scribner log scale. Source: Oregon 

Department of Forestry quarterly log price reports.

Red alder inventory volume

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Figure 2—Timber inventory volume to a 10-cm top (4-inch) of red alder 

across its range in California (CA 1995 inventory - Waddell et al. 1996), 

Oregon (OR 1997 inventory – Azuma et al. 2002), Washington (WA 2001 

inventory – Gray et al. 2005), BC (BC 2000 inventory – Canadian National 

Forest Inventory System 2001), and Alaska (AK 2000 inventory – van Hees 

2003). Inventory for federal lands in Washington and Oregon: HIserote and 

Waddell 2004.
127

provided by inventory reports for all U.S. states. For BC, 

actual harvest volumes were used. 

Annual removals of red alder totaled about 4.64 million 

m3 (598 million board feet Scribner scale) across the range 

of the species (fig. 3). About 87% of the alder removals 

were provided by private lands in Washington (64%) and 

Oregon (23%). Non-federal public forests in Washington 

and Oregon (primarily State-owned) provide about 5 percent 

of total removals, which is relatively small in proportion to 

the share of the alder resource in State ownership (14%). 

Removals of alder from federal forests in Washington and 

Oregon amount to less than 1% of the total and are not 

shown.

Annual harvest volumes of alder in coastal BC amount 

to about 6% of total alder removals, which is small in 

proportion to the amount of alder in BC (35% of the total 

inventory). Removals of alder in northern California amount 

to about 2% of the total, similar to the state’s share of the 

inventory (2.5%). Alder is being harvested and utilized in 

Northern California, particularly from Industrial Private 

lands. No estimates of harvest or removals of alder in 

Alaska were found. With less than 1% of the total alder 

resource, potential harvest and utilization of alder from 

Alaska could be locally important but it would amount to 

less than 1 % of the total alder harvest. 

Washington and Oregon are the major sources of 

alder supply, accounting for over 90% of the harvest. Total 

inventory of alder in California and Alaska are too low to 

have a major impact on the overall supply of alder. While 

there may be potential to increase supplies of alder from 

BC forests, current plans for timber supply areas and tree 

farm licenses in BC do not indicate substantial increases in 

harvest of alder in the future (BC Ministry of Forests 1999-

2004. H. Reveley, pers. Comm, BC Ministry of Forests, 

Defined Forest Area Management, Coastal Region.). 

Therefore, discussion of resource trends affecting 

alder supply will focus on Washington and Oregon. Within 

these two states, a further breakdown of the alder inventory 

shows that private owners have 60% of the resource, about 

evenly divided between industrial and non-industrial 

(small woodlands or family forestlands) ownership (fig. 4). 

Between the two states, Washington has about 2 times as 

much alder as Oregon.

Forest resource trends 

The current supply of alder is a legacy of past 

management practices, which increased the component of 

alder and other hardwoods in the Pacific Northwest (fig. 

5). During most of the 1900’s, growth and inventory of 

hardwoods increased, while rates of removal and utilization 

were low (Raettig et al. 1995, Figure 17, p. 42). Since 

the 1970’s, however, removals of alder have increased 

while forest management to favor conifers has become 

increasingly effective. This is expected to reduce both the 

abundance of hardwood-dominated forest and the proportion 

of hardwoods in conifer-hardwood mixtures. The increase 

in abundance of hardwoods seems to have stopped in the 

1990s (fig. 5). 

Declines in abundance of alder are particularly 

apparent as illustrated by decreases in estimates of growing 

stock inventory since the previous inventories in both 

Oregon (28% decrease) and Washington (24% decrease) 

(Raettig et al. 1995, Azuma et al. 2002, Gray et al. 2005). 

Likewise, estimates of the area of hardwood-dominated 

Annual removals of red alder

4.64 million cu. m (~598 million bd. ft) 

WA - Private

64%

OR - Private

23%

WA+OR State/OP

5%

BC

6%

CA

2%

Figure 3—Annual removals for red alder showing the relative proportion 

of the total removals provided by selected states and ownerships. Data 

sources for the U.S. as in Figure 1. Figures for BC are harvest volumes 

reported by the BC Harvest Billing System for 1998-2000, with board-foot 

volume computed using the average ratio of board-foot : cubic foot volume 

removals reported for alder in the U.S. (3.65 bf/cf). 

Alder sawtimber inventory by owner

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Figure 4—Inventory of red alder sawtimber (million board feet Scribner 

scale) across major land ownerships in Washington (2001 - Gray et al. 

2005) and Oregon (1997 - Azuma et al. 2002).
128

forest decreased by about one third over the last 3 periodic 

inventories in both Washington (1980, 1991, 2001) and 

Oregon (1976, 1987, 1997). The trend is apparent on both 

industrial and non-industrial private lands (fig. 6). Similar 

trends are described by Alig et al. (2000), who projected a 

35% decrease in alder timberland on forest industry lands 

and an 18% decrease on non-industrial private timberland in 

the westside Pacific Northwest for the period 1980-2010. 

During the 1990s, removals, mortality, and forest 

conversion (to non-forest) contributed to a 28% net loss of 

hardwood inventory on non-federal lands in Washington 

(fig. 7). In Oregon, both removals and mortality are lower, 

and forest conversion is negligible, so that there was 14% 

net growth in total hardwood inventory between 1987 and 

1997. Removals and mortality are proportionally higher for 

alder than other hardwoods in both states. For Washington 

and Oregon combined, red alder comprises 73% of the 

hardwood removals and mortality, but only 58% of the 

hardwood inventory. Annual removals plus mortality of 

alder in the two states exceed growth on industrial forests by 

30%; removals plus mortality are about equal to growth on 

non-industrial private forests (fig. 8). 

Since some of the forest growth occurs in areas that 

are not available for harvest, the levels of alder removal in 

Washington and Oregon during the 1990s do not appear to 

be sustainable. Future declines in available supplies of alder 

should be expected on private lands—the primary source of 

alder timber supply. 

Policy and regulatory factors 

reducing alder supply 

Availability of alder timber for harvesting is reduced 

by landowner policies and forest practices regulations. 

Forest policy clearly limits timber supply on federal lands 

in the U.S. since these lands contain about 17% of the 

alder inventory but provide less than 1% of the total alder 

timber harvest. On actively managed state forests, alder 

is harvested along with softwoods, although state forest 

policies do limit the amount of harvest more than on private 

lands. Protection of riparian areas, unstable slopes, and 

retention of trees for wildlife habitat reduces the harvestable 

portion of the alder resource on all ownerships. 

Protection of riparian areas and unstable slopes are 

expected to have a disproportionate impact on availability 

of alder compared to conifers due to the relatively high 

abundance of alder in these areas. Accurate estimates of the 

amount of alder affected are difficult to obtain due to the 

variety of protection requirements and options across the 

range of alder, along with diverse landowner behavior in 

implementation. 

Hardwood inventory

Private lands in western OR and western WA

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Figure 6—Periodic estimates of the area of hardwood forest types in 

western Oregon (a. Raettig et al. 1995, Azuma et al. 2002) and western 

Washington (b. Raettig et al. 1995, Gray et al. 2005). 

Figure 5—Hardwood inventory volume estimates on private lands in 

Washington and Oregon from 1931 to 2001 (from Haynes, tech. coord. 

2003).
129

Estimates of the amount of alder that is unavailable due 

to policy and regulation have been made for Washington, 

based on analysis using Geographic Information Systems 

(GIS) to overlay land ownership and protection (buffer) 

areas on maps of alder occurrence. A study for western 

Washington estimated about 7.6 billion board feet of red 

alder available for harvest after deducting about 46% of 

the resource as unavailable due to landowner policies and 

riparian regulations (Washington Hardwoods Commission 

2002). This same assessment estimated that while riparian 

buffers comprise about 8% of the timberland area, they 

contain 18% of the red alder sawtimber volume.

Comprehensive assessments of alder availability using 

spatial analysis (GIS) have not been published for Oregon 

or BC. General estimates of about 5-10% of the alder 

resource affected by riparian regulations have been made 

(Raettig et al. 1995, G. Lettman, Oregon Dept. of Forestry, 

pers. Comm.). Under a scenario of increasing riparian 

harvesting restrictions, Adams et al. (2002) projected a 

24.4% reduction in harvest volume (all species) on private 

timberlands in western Oregon assuming a 100-foot no cut 

buffer. Given the overall warmer, drier conditions in western 

Oregon compared to Washington, the moisture-loving red 

alder should be even more concentrated in riparian areas 

compared to upland areas in Oregon. 

Much of the alder in BC does not appear to be 

available for harvesting. The alder harvest in BC is quite 

low for the level of inventory. Review of allowable harvest 

determinations and discussions with BC Ministry foresters 

suggest a variety of factors limiting availability of alder 

(Pederson 2000, 2001, 2002, 2004. H. Reveley, pers. 

comm., BC Ministry of Forests, Coastal Region.). Much of 

the alder in BC may not be economically available due to 

difficult access and high costs of logging and transportation. 

While delivered log prices for alder in BC are comparable 

to associated conifer values (2004 prices per cubic meter 

were $70, $55, and $110 for red alder, western hemlock, 

and Douglas-fir respectively; Log Market Reports from 

BC Ministry of Forests, Revenue Branch), relatively low 

economic returns per hectare are still expected for alder, 

which discourages both harvesting and management focused 

on alder in BC. Concentration of alder in riparian protection 

zones was also indicated as a reason for relatively low 

harvest volumes. 

Riparian protection rules as implemented in Washington 

are generally more restrictive than those in Oregon and BC, 

based on the widths of no-harvest buffers along predominant 

stream types (table 1). The current emphasis on retention 

and development of a conifer component in riparian areas 

provides some potential for removal of alder in riparian 

zones, particularly under site-specific plan options in both 

Oregon and Washington. Due to the complexity of the 

riparian protection rules, private forest owners may not 

choose to harvest in riparian zones even when they have 

the option to do so. Compliance monitoring in Oregon 

showed that 60% of riparian management areas surveyed 

were treated with no-harvest prescriptions and only 2% 

were treated with a hardwood conversion/conifer restoration 

prescription (Robben and Dent 2002). In Washington, 

only 23 riparian hardwood conversion plans were filed, 

out of thousands of forest practices applications, by nonindustrial private owners during 2002-2004 (Washington 

Department of Natural Resources, Small Forest Landowner 

Office). Harvesting behavior by industrial forest owners in 

Washington has not been summarized. 

Changes in hardwood volume

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Removal

Growth

Figure 8—Annual removals and growth of red alder in western Oregon 

(1997 – Azuma et al. 2002) and western Washington (2001 – Gray et al. 

2005).

Figure 7—Changes in hardwood timber volume between inventories in 

western Washington (WA 1991-2000, Gray et al 2005) and western Oregon 

(OR 1987-1997, Azuma et al. 2002).
130

Declining timber 

harvest volumes

The declining area and volume of alder available for 

harvest does indicate decreases in supply of alder timber 

in the future. The question remains as to how soon and 

how much lower? Timber supply projections for Oregon 

and Washington in the 1990s predicted reductions in 

hardwood timber supply using various assumptions about 

forest management and harvesting behavior on private 

lands (Sessions et al. 1990, Adams et al. 1992). More 

recent timber harvest projections for western Oregon and 

Washington have not projected specific hardwood harvest 

levels (Adams et al. 2002, Zhou et al. 2005). 

While there is still no comprehensive timber supply 

assessment focused on red alder in the Pacific Northwest, 

trends in timber harvest levels between 1994 and 2003 do 

show a gradual decline in the volume of alder harvested 

annually in Washington and Oregon (fig. 9). The harvest of 

alder generally goes up or down with total harvest and the 

total timber harvest level also declined between 1994 and 

2003. The volume of alder harvested, however, declined 

about 33% while the total harvest declined only 20% (based 

on 3-year running averages). A reduced proportion of alder 

in the total timber harvest is the expected result of the 

declining hardwood component in Oregon and Washington. 

Total timber harvest projections for western Oregon and 

Washington indicate slight decreases in the overall timber 

harvest level during the next 2 decades (Zhou et al. 2005). 

Management of alder

There has been a great deal of research focused on 

management of red alder since the 1980’s, as illustrated 

by numerous presentations (OSU Hardwood Silviculture 

Cooperative, Weyerhaeuser Co., USFS PNW Research 

Station) at the 2005 Symposium, Red Alder: A State of 

Knowledge (March 23-25, 2005 University of Washington, 

Seattle). Nearly 20 years of private and public research 

focused on alder management indicate the potential for 

relatively high yields (8-12 m3/ha/year) in short rotations 

(25-35 years) in managed stands. 

In a detailed assessment of management plans and 

practices affecting alder across major forest ownerships, 

Raettig et al. (1995) identified several key issues preventing 

management for alder, including: uncertainty about 

economic returns, lack of information on growth and yield 

in managed stands, and lack of experience with alder 

management. These issues persist across the range of alder, 

even after 10 more years of alder research and continued 

increases in alder prices (fig. 1). 

 Timber harvest 

western Oregon and Washington

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

1993199419951996199719981999200020012002

t e

ef dr a

o

b

n

oilli m-l at o

T

0

100

200

300

400

500

600

700

800

t e

ef dr a

o

b

n

oilli m- r e

dl A

Alder

Total

Figure 9—Annual timber harvest rates for red alder and for all species (total) in western Oregon (Oregon Department of Forestry Timber 

Harvest reports) and western Washington (Washington Department of Natural resources timber harvest reports for all species, Washington 

Hardwoods Commission hardwood processor reports for red alder). 
131

Non-industrial private forest owners in general do 

not manage intensively to favor conifers and they are 

expected to produce an increasing share of the alder given 

the reductions in alder on industrial ownerships. While 

this generality continues to hold, alder supply from nonindustrial forests has also declined slightly and conversion 

of these ownerships to non-forest uses reduces sustainable 

alder supply in the future. 

Recent revisions of management plans for state forests 

in northwest Oregon (2001) address the potential for 

maintaining alder for both timber and habitat purposes. In 

Washington, increasing the production and harvest of red 

alder has been recommended as increased alder timber 

values are incorporated in the Washington Department 

of Natural Resources’ timber marketing program (Jon 

Tweedale, WA DNR pers. Comm.). 

Along with the growing knowledge-base for 

management of alder, on-the-ground management for 

alder appears to be increasing. Forest managers often 

leave alder during weeding and pre-commercial thinning 

of young forests when it appears to be the best crop tree. 

Nursery production and planting of alder seedlings also 

appear to be increasing. These observations are based on 

informal surveys of forest managers across private and 

state ownerships conducted in the course of producing 

and teaching alder management workshops in Oregon and 

Washington between 1997 and 2004 (45 events, ~1500 

participants). Attitudes about alder have clearly changed 

since the 1980’s, however, formal surveys have not been 

conducted to quantify increases in management for alder.

When harvests of red alder were at their highest levels 

during the 1990s, alder comprised about 6% of the total 

timber harvest in western Oregon and western Washington, 

and about 1% of the harvest in coastal BC. While a gradual 

decline in alder is now evident after decades of conifer 

forestry, management for alder on a relatively small portion 

of the landscape (~5%), along with continuing production 

of incidental alder could maintain current levels of supply. 

Raettig et al. (1995) estimated at most 1% of the managed 

forest landscape was intentionally regenerated to red alder. 

Although there are indications that this will increase, the 

question remains: will the major forest landowners manage 

more alder in the future?

Conclusions

A gradual decline in available supplies of red alder 

timber is now evident in Washington and Oregon, which 

currently provide over 90% of alder supply. Major factors 

that reduce supply of red alder include management 

favoring conifers, increased protection of riparian areas, 

shifts in public timber policy, and conversion of forest to 

non-forest land use. Knowledge of and management for 

alder are increasing and there is much potential for forest 

managers to maintain or increase alder across its range. 

Changes in policy and practice could also greatly increase 

availability of current alder inventory in BC (or federal 

lands in the US). The supply of alder in the future depends 

on the uncertain balance between these positive and 

negative factors. 

Increased management of alder timber is the key to 

sustaining alder supply. While increased log prices for alder 

have stimulated great interest, major forest landowners are 

still reluctant to invest in managing alder until management 

techniques become well-demonstrated and there is better 

information on growth and yield in managed stands.

Literature Cited

Adams, Darius M.; Schillinger, Randall R.; Latta, 

Greg; Van Nalts, Adrienne; 2002. Timber harvest 

projections for private land in western Oregon. Research 

Contribution 37. Corvallis, OR: Forest Research 

Laboratory, Oregon State University, 30 p.

Adams, D. M.; Alig, R. J.; Anderson, D. J.; (et al.). 1992.

Future prospects for western Washington’s timber supply. 

Inst. For. Resourc. Contrib. 74. Seattle: College of Forest 

Resources, University of Washington. 201 p.

Alig, R. J.; Zheng, D.; Spies, T. A.; Butler, Brett J. 2000.

Forest cover dynamics in the Pacific Northwest west side: 

regional trends and projections. Res. Pap. PNW-RP-522. 

Portland, OR: U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station. 22p.

Azuma, D. L.: Bednar, L. F.; Hiserote, B. A.; Veneklase, 

C. F. 2002. Timber resource statistics for western Oregon, 

1997. Resour. Bull. PNW-RB-237. Portland, OR: U.S. 

Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 120 p.

BC Ministry of Forests 2005. Forest Planning and 

Practices Regulations. BC Ministry of Forests, Victoria, 

B.C.

BC Ministry of Forests. Timber Supply Area analysis 

reports: Sunshine Coast (2001), Strathcona (2004), Mid 

Coast (1999), Kingcome (2004), Fraser (1998), Soo 

(1999), and North Coast (1999) Timber Supply Areas. BC 

Ministry of Forests, Victoria, B.C.

Gray, A. N.; Veneklase, C. F.; Rhoads, R.. D. Timber 

resource statistics for nonnational forest land in western 

Washington, 2001. Resour. Bull. PNW-RB-246. Portland, 

OR: U.S. Department of Agriculture, Forest Service, 

Pacific Northwest Research Station. 117 p. 

Haynes, R. W., tech. coord. 2003. An analysis of the timber 

situation in the United States: 1952 to 2050. Gen. Tech. 

Rep. PNW-GTR-560. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research 

Station. 254 p.
132

Hiserote, B. A.; Waddell, K. L. compilers 2004. A 

database of forest inventory information for California, 

Oregon, and Washington. PNW-FIA IDB Version 1.4-1. 

Portland, OR: U.S. Department of Agriculture, Forest 

Service, Pacific Northwest Research Station, Forest 

Inventory and Analysis Program. 

Kline, J. D.; Alig, R. J. 2001. A spatial model of land use 

change for western aOregon and western Washington. 

Res. Pap. PNW-RP-528. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Pacific Northwest 

Research Station. 24 p.

Massie, M. R.C. 1996. Hardwood utilization and supply 

in BC. p. 1-7 in: Comeau, Philip G.; Harper, George J.; 

Blache, Marilyn E.; Goateng, Jacob O.; Thomas, Keith 

D. 1996. Ecology and management of BC hardwoods. 

Workshop Proceedings. FRDA Report No. 255. BC 

Ministry of Forests, Victoria, BC, 246 p.

Oregon Department of Forestry, 2001. Northwest Oregon 

State Forests Management Plan. Salem, Oregon. 

Pederson, L.; 2000-2004. Rationale for allowable annual 

cut (AAC) determination. Mid Coast Timber Supply 

Area (2000). Sunshine Coast Timber Supply Area (2002). 

Kingcome Timber Supply Area (2002). . Fraser Timber 

Supply Area (2004). BC Ministry of Forests. Victoria, 

BC.

Raettig, T. L.; Connaughton, Kent P.; Ahrens, Glenn R. 

1995. Hardwood supply in the Pacific Northwest: a policy 

perspective. Res. Pap. PNW-RP-478. Portland, OR: 

U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 80 p.

Robben, J.; Dent, L.; 2002. Oregon Department of 

Forestry best management practices compliance 

monitoring project: Final report. Oregon Department of 

Forestry Forest Practice Monitoring Program Technical 

Report 15. 68 p.

Sessions, J.; Johnson, K. N.; Beuter, J. (et al.), cords. 

1990. Timber for Oregon’s tomorrow: the 1989 update. 

Corvallis, OR: Forest Research Laboratory, College of 

Forestry, Oregon State University, 183 p.

State of Oregon, 2005. Forest Practice Administrative 

Rules. OAR Chapter 629, Divisions 623, 630-660. 

State of Washington, 2005. Washington Administrative 

Code 222. 

Van Hees, W.W.S. 2003. Forest resources of southeast 

Alaska, 2000: results of a single-phase systematic sample. 

Res. Pap. PNW-RP-557. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Pacific Northwest 

Research Station. 96 p.

Waddell, K. L.: Bassett, P. M. 1996. Timber resource 

statistics for the North Coast Resource Area of 

California. Resour. Bull. PNW-RB-214. Portland, OR: 

U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 50 p.

Washington Hardwoods Commission. 2002. A hardwood 

resource assessment for western Washington. Online 

publication. On file at PO Box 1095, Camas, WA 98607

Zhou, X.; Haynes, R. W.; Barbour, R. J.. 2005. 

Projections of timber harvest in western Oregon and 

Washington by county, owner, forest type, and age 

class. Gen. Tech. Rep. PNW-GTR-633. Portland, OR: 

U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 30 p.
133

1C. Larry Mason is a research scientist and project coordinator with the Rural Technology Initiative, University of Washington, College of Forest Resources, 

Box 352100, Seattle, WA 98195-2100, email: larrym@u.washington.edu

— Red Alder: A State of Knowledge —

Red Alder Market Implications for 

Management; Reasons for Optimism 

C. Larry Mason1

Abstract

In 2000, red alder (Alnus rubra) log prices, after more 

than two decades of steady price gains, surpassed Douglasfir (Pseudotsuga menziesii) log prices for the first time in 

history and have retained a price lead ever since. Alder, once 

considered a negative value weed, is now recognized as a 

valuable commercial timber species. As a result, there is 

increasing interest among forest managers in the potential 

for investments in alder plantations. A common concern, 

however, is an uncertainty about the future reliability of 

strong alder log markets. This paper will consider available 

information on alder log and lumber market influences and 

offer speculation that alder products appear well positioned 

for continued market success.

Keywords: red alder, hardwoods, wood market economics

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.
134

Introduction

While red alder has long been recognized by tree 

farmers as a suitable species to plant in areas that are wet, 

nutrient poor, infected by Swiss needle cast or root rot, or 

in other ways unsuitable for Douglas-fir, until recently alder 

has not been widely considered as a plantation alternative 

to Douglas-fir on high quality sites. A strong performance 

by alder log prices in recent years when compared to 

Douglas-fir prices may lead some foresters to reconsider the 

potential for planting alder on their best sites. The following 

graph displays historic prices, adjusted for inflation to 2004 

dollars, for Douglas-fir and red alder saw logs (average 

price of #2 and #3 saw logs for each species) from 1970 

to 2004 in the Puget Sound region of western Washington. 

Alder log prices surpassed those for Douglas-fir for the first 

time in history in 2000 and have retained a price lead ever 

since. Historically, alder log prices have been less volatile 

than Douglas-fir prices and display a stronger upward trend 

(fig. 1). 

Financial performance simulations can help in making 

species comparisons for return on planting investment. 

For demonstration purposes, assumptions will be that 

plantations are hardy and on a good site, costs and prices are 

treated in constant dollars, 5% is the expected real rate of 

return, results are reported based upon current log prices and 

management cost estimates before taxes, and yield estimates 

in thousand board feet (MBF) and ton wood are consistent 

with expectations listed below (Mason 2003). 

• DF-45. A 45-year Douglas-fir rotation; no 

commercial thin. (30 MBF & 70 tons) 

• RA-35. A 35-year Red Alder rotation. (20 MBF& 

30 tons) 

A soil expectation value (SEV) calculation suggests 

that, due to price advantage and shorter rotation length, 

alder plantations may provide better return on investment 

than Douglas-fir plantations (fig. 2).

A common concern, however, is an uncertainty about 

the future reliability of strong alder log markets. Alder 

logs are manufactured into a number of primary lumber 

products for domestic and export markets. An examination 

of available information about alder product markets will 

provide a better understanding of the future potential 

performance of alder log prices.

Alder Lumber

In March of 2004, the Hardwood Review Weekly 

reported its North American Hardwood Outlook for 2004. 

Alder lumber sales were characterized as some of the hottest 

in the hardwood markets with strong domestic and overseas 

demand. The expectation was that demand would continue 

to exceed production for the foreseeable future. A little more 

than a year later, in spite of little to no gain for other species 

in hardwood lumber export markets, this forecast held true 

(Hardwood Review 2005). Alder export sales increased 

world wide by more than 30% in the first five months of 

2005 as compared to the first five months of 2004 (table 1)

with big gains in important international markets like China 

and the European Union (figs. 3 and 4). 

Most wood species experience fluctuating demand for 

individual lumber grades with favorable markets for some 

items coincident with poor markets for others. Alder lumber, 

however, is in increasing demand for the full spectrum of 

lumber grades with product sales limited only by supply. 

The higher grades of select, #1, and #2 have long been 

desirable for furniture and cabinet manufacture due to the 

excellent workability characteristics of this species (fig. 

5). Workability is important to manufacturers not only 

to ensure production of high quality products but also to 

reduce operation costs. Good workability minimizes unit 

production time, increases product recovery, and extends the 

life of production equipment and materials. Unique to alder, 

because of its uniform color and grain characteristics, is its 

ability to readily accept both light and dark stains which 

Figure 1— Historic prices, adjusted for inflation to 2004 dollars, for 

Douglas-fir and red alder saw logs (average price of #2 and #3 saw logs 

for each species) from 1970 to 2004 in Region 1 (Puget Sound) of western 

Washington. Source: Log Lines, Fox, U. S. Dept of Labor. 

Figure 2—Simulated soil expectation value (SEV) comparison at a 5% 

target rate of return for Douglas-fir and red alder plantations. Source: Rural 

Technology Initiative.

0

200

400

600

800

Red alder

Douglas-fir

WA Region 1 Log Prices (2004$)

Dollars ($) per million board feet

1970 1975 1980 1985 1990 1995 2000 2005

Soil expectation values (SEV) for simulated

0

200

400

600

800

1000

1200

1400

Douglas-fir 45 year rotation Red alder 35 year rotation

Dollars ($)

Douglas-fir and red alder plantations 
135

change its appearance to resemble that of more expensive 

hardwoods such as black cherry (Prunus serotina). After 

many years of serving as a low cost substitute, alder has 

gained an industry nickname of “poor man’s cherry.” 

Current wholesale kiln-dry prices for the highest quality 

alder lumber are respectably comparable to those of 

Douglas-fir with ranges from $1000/MBF to over $2000/

MBF depending upon grade (Redmond 2005). 

Recent market popularity of “southwest rustic” 

furniture and cabinets has increased industry demand for 

knotty lower grades of alder lumber such as frame, standard, 

and #3 shop. Strong markets for these grades have resulted 

in prices that currently range from $550 to $825/MBF 

(Redmond 2005). Emergence of strong demand for lower 

quality lumber for furniture and cabinet products has created 

tight supplies for pallet markets with subsequent price 

improvements for this low grade product. Pallet and crating 

manufacture is the largest hardwood end-use application 

in the United States with an estimated consumption of 3.5 

billion board feet of lumber for 2005 (Hardwood Review 

Table 1—Alder lumber export statistics for Jan-May of 2004 and 2005. Source: Hardwood Review (2005) and USDA 

Foreign Agricultural Service (2005).

Alder LBR Exports by 

Country

Jan-May 2004 

Vol. (m3)

Jan-May 2005 

Vol. (m3)

Change 

05 vs. 04

Jan-May 2004 

Value (1000 $)

Jan-May 2005 

Value (1000 $)

Change 

05 vs. 04

China 47,397 65,349 +37.9% $12,897 $19,620 +52.1%

Canada 13,467 18,515 +37.5% $3,751 $4,283 +14.2%

Mexico 11,740 12,380 +5.5% $4,065 $4,552 +12.0%

Italy 7,990 8,774 +9.9% $5,125 $6,517 +27.2%

Germany 3,031 6,657 +119.6% $2,506 $5,433 +116.8%

Spain 5,483 4,961 -9.5% $3,479 $3,601 +3.5%

Taiwan 5,504 4,049 -26.4% $1,548 $1,209 -21.9%

Philippines 1,388 2,617 +88.5% $617 $1,365 +121.2%

Vietnam 855 1,907 +123.0% $313 $746 +138.2%

Portugal 1,762 1,501 -14.8% $952 $829 -12.9%

World Total 107,159 135,315 +26.3% $40,304 $52,589 +30.5%

Figure 3—Value of alder lumber exports for total world and top markets: 

2001-2004. Source: USDA Foreign Agriculture Service. Figure 4—Top five hardwood lumber species imported to China in 2004. 

Source: USDA Foreign Agriculture Service.

Value of alder lumber exports for total world 

and top markets: 2001-2004

0

20

40

60

80

100

120

2001 2002 2003 2004

Millions $

World

China

EU-25

Canada

Working properties for selected commercial hardwoods 

Machining

Nailing

Screwing

Gluing

Finishing

Red alder

American cherry

Hard maple

Soft maple

POOR GOOD

Figure 5—Working properties for selected commercial hardwoods. Source: 

American Hardwood Export Council.

Top five hardwood lumber species exported to China in 2004 

0

5

10

15

20

25

30

35

Alder Red Oak Yellow Poplar Maple White Oak

Millions $

Species
136

2005). Alder pallet lumber has long been preferred by 

markets within the grocery industry because it imparts no 

resins or other toxins to foodstuffs. Alder pallet lumber, an 

equivalent to utility grades of other species, has seen prices 

in excess of $300/MBF during 2005 (Redmond 2005). 

With favorable markets for pallet stock, chip production 

is limited to trim and side-cut. While chip prices have been 

lackluster for all species, hardwood chips are in stable 

demand as hardwood fiber is needed to produce high quality 

paper. Given that the west produces less than 3% of the total 

U. S. supply of hardwood chips (Warren 2004), alder chip 

markets are not likely to experience price reduction due to 

oversupply or substitution. 

Discussion

Red alder log and lumber prices have demonstrated 

stable upward growth for the last several decades. 

Hardwood markets tend to be less cyclical than commoditydriven softwood markets. The use of alder in the 

manufacture of value-added wood products means that the 

demand is secured by niche-product positions with little 

risk of substitution (Eastin et al. 1999). Favorable price 

positions have been established for the full spectrum of 

alder lumber grades. Alder logs have generally been priced 

between the more expensive cherry and the lower priced 

varieties of maple species (Acer). The uniform grain pattern 

and light color of alder allow it to be stained to match 

changing consumer preferences and market trends. Alder is 

widely used as a substitute for more expensive traditional 

species like cherry. Past price relationships indicate that 

cherry and maple provide the upper and lower bounds for 

alder price fluctuations. No evidence was found in a review 

of the literature and trade publications to suggest that this 

relationship might not continue. Important to markets 

such as the European Union, alder is not an old growth or 

tropical hardwood species. Alder has well-established export 

positions and is the preferred species in the fast-growing 

China market.

Trend analysis of Pacific Northwest hardwood timber 

harvest and growing stock (dominated by alder) indicates 

that standing inventories will far exceed harvest volumes 

(Haynes 2003) through 2050. Regulatory constraints on 

harvest, however, appear to limit market supply of logs 

relative to growing domestic and international demand 

resulting in continued upward price pressure. 

 International trade data available from the USDA 

Foreign Agriculture Service show that alder export lumber 

markets are expanding faster than other international 

markets for U.S. hardwood species. The short rotation 

length and strong market position of red alder should result 

in increased interest in alder plantation establishments on 

well-drained, high sites in western Oregon and Washington 

that have previously been preferred for Douglas-fir.

Literature Cited

American Hardwood Export Council. 2005. About U.S. 

Hardwoods. Web Publication. http://www.ahec.org/

hardwoods/guide/.

Eastin, I. L., S. R. Shook, and W. Sammarco. 1999. An 

Assessment of the PNW Hardwood Lumber Industry. 

CINTRAFOR Working Paper # 72. Seattle, WA: Center 

for International Trade in Forest Products. College of 

Forest Resources, University of Washington. 45 p.

Hardwood Review. 2004. North American Hardwood 

Outlook. Hardwood Review Weekly. 20(26). 1, 21. 

Hardwood Review. 2005. Low-Grade Lumber market 

Report. Hardwood Review Weekly. 21(25). 21. 

Hardwood Review. 2005. North American Hardwood 

Exports. Hardwood Review Global. 16(3). 1, 7, 8, 28, 29, 

31. 

Haynes, R.W. 2003. An Analysis of the Timber Situation in 

the United States: 1952 to 2050. Gen. Tech. Rep. PNWGTR-560. Portland, OR: U.S. Department of Agriculture, 

Forest Service, Pacific Northwest Research Station. 254 p.

Log Lines: Log Price Reporting Service. Mount Vernon, 

WA.

Mason, C. L. 2003. After decades of Douglas-fir 

plantations, is it time for forest landowners to consider 

planting alder and cedar? RTI Fact Sheet # 22. Seattle, 

WA: Rural Technology Initiative. College of Forest 

Resources, University of Washington.

Redmond, W. 2004. pers. com. North Pacific Lumber. 

Fox, T. 2003. pers. com. Timber Management Plus.

USDA Foreign Agricultural Service. 2005. FASonline. 

http://www.fas.usda.gov/ustrade.

US Dept of Labor. 2005. Consumer Price Indexes Website 

Inflation Calculator. http://www.bls.gov/cpi/home.

htm#data.

Warren, D. D. 2004. Production, Prices, Employment, and 

Trade in the Northwest Forest Industries, All Quarters 

2002. Res. Bull. PNW-RB-241. Portland, OR: U.S. 

Department of Agriculture, Forest Service, Pacific 

Northwest Research Station. 170 p.
137

1Pete Holmberg is assistant division manager for silviculture and regeneration for Washington State Department of Natural Resources, Olympia, WA 98504 

and can be reached at 360-902-1348, email: pete.holmberg@wadnr.gov

— Red Alder: A State of Knowledge —

Red Alder—Regeneration and Stand 

Initiation: Techniques and Field Craft 

as Related to Final Returns on 

Early Investments 

Pete Holmberg1

Abstract 

Red alder (Alnus rubra Bong.) exhibits juvenile height 

growth rates that far exceed other commercially important 

conifer species in the U.S. Pacific Northwest. This rapid 

growth rate together with desirable wood characteristics 

and promising market prospects are attractive to forest 

managers. However, red alder’s silvical characteristics and 

site sensitivity imply high early investment costs as well as 

risk factors that might well be higher than for conventional 

conifer management. Relatively certain high return on 

investments require careful site selection and judicious 

management, particularly during the first decade, in ensuring 

uniform tree spacing. This detailed attention to spacing 

require substantial early investments in site preparation, 

planting and planting stock, pre-commercial thinning, and 

pruning. This paper illustrates how Hardwood Silviculture 

Cooperative studies have influenced a Washington State 

Department of Natural Resources manager’s assumptions 

about red alder cultivation in relation to silvics and expected 

returns on investments.

Keywords: Red alder, return on investment, silviculture, 

plantation, stumpage, techniques and field craft.

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.
138

Summary

Red alder (Alnus rubra Bong.) exhibits juvenile height 

growth rates that far exceed commercially important 

conifer species in the U.S. Pacific Northwest. In addition, 

the species is highly phototropic and has low apical 

dominance. Therefore, in order to secure maximum return 

on investment, spacing in red alder plantations must be 

carefully managed from the earliest stages. This requires 

substantial early investments. Although accurate growth 

simulators for managed stands of red alder are yet to be 

developed, data from natural stands as well as plantation 

growth data from Hardwood Silviculture Cooperative 

(HSC) research through year 12 are sufficient to enable 

initial projections of merchantable volume and financial 

plus-ups attributable to intensive management. HSC data 

sets are from 26 plantations initiated at varying densities 

and subjected to differing silvicultural treatments. This 

information lends itself to initial projected estimates and 

also indicates that growth (and thus yield) of intensely 

managed red alder plantations dramatically exceeds that 

of natural stands. Assessments of relative magnitudes of 

return on investments may thus be performed. If current 

red alder stumpage trends hold, return on investments from 

intensively managed red alder plantations could be on the 

order of twice or more high site mixed Douglas-fir and 

western hemlock plantations that are grown to culmination 

of periodic annual increment. A drawback of red alder 

stands is the high risk associated with frost and icestorm damage (casual observation indicates this risk may 

considerably reduced in red alder plantations); which has 

frequently caused irredeemable damage to the commercial 

value of natural red alder stands. 

Introduction

A forester considering cultivation of red alder (Alnus 

rubra Bong.) in Oregon, Washington, or British Columbia 

would be well served to take into account the Hardwood 

Silviculture Cooperative’s (HSC) red alder plantation data. 

This cutting edge research describes growth responses 

of red alder to intensive management on 26 plantations 

throughout western Oregon, Washington and British 

Columbia. Each site has four initial planting densities 

subdivided into varying treatments that cover a range of 

pruning and thinning options through year 12. From an 

operational perspective, feasible approaches gleaned form 

this research should be adapted to practical techniques 

and field craft that should be analyzed from cash flow and 

investment perspectives for a whole rotation. Facts, or in 

their absence, logical assumptions, regarding site selection, 

site preparation, stocking control, planting stock, thinning 

techniques, and pruning together with market assumptions 

and financial investment analysis must be brought together 

into a plausible and practical whole. To that end, this paper 

will present such a synthesis in the form of an optimal 

silvicultural prescription for a red alder rotation on a 

suitable, and presumably typical, site. The prescription will, 

in particular, endeavor to devise a regime for treatments 

and investments likely to best attain the desired high-value 

outcome.

The Case for Red Alder

Pros

So, why red alder? Biologically, red alder has juvenile 

height growth rates that exceed Douglas-fir (Pseudotsuga 

menziesii (Mirb.) Franco var. menziesii), western hemlock 

(Tsuga heterophylla (Raf.) Sarg.), and western redcedar 

(Thuja plicata Donn ex. D.Don) by as much as a factor 

of four during the first five decades. Figure 1 illustrates 

this situation. Not until around age 50 do most of these 

conifers overtake red alder in total height. Red alder’s 

quick accumulation of merchantable biomass implies short 

rotations and therefore relatively assured markets and 

favorable investment recovery.

Red alder occupies a special niche in domestic and 

world markets due to grain uniformity, stain acceptance, and 

workability. These markets—the Chinese furniture industry 

in particular—are likely to foster an increasing demand for 

superior quality red alder for an extended future. Probably 

adding to this trend is the fact that countries and regions 

outside the native range of red alder have not taken on their 

own cultivation programs for red alder as many have done 

with Douglas-fir. 

Thus, an image of the future begins to form in which 

red alder emerges as a market niche of potentially sustained 

high value.

Figure 1—Height growth of red alder compared to commonly associated 

commercial conifers. Source: Peterson, E.B., Ahrens, G.R., and Peterson, 

N.M. (eds). 1996. Red Alder Managers’ Handbook for British Columbia. 

FRDA Report 240.).

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70 80 90 100

Height Growth Comparison

Alder S127

Douglas-fir S130

Hemlock S126

Redcedar S118

Sitka spruce S129

Source: Green and Klinka, 1994

Height (m)

Age (yr from seed)
139

Cons

Is there a downside? As we shall see, red alder 

cultivation requires disciplined adherence to specific site 

selection criteria as well as to silvicultural regimes that 

have considerable front-end investments. Financial rewards 

will be tightly linked to specific sites that capitalize on 

red alder’s high juvenile growth rates and to regimes that 

judiciously manage red alder’s high degree of phototropism 

and low apical dominance (fig. 2). Associated risks for 

irrecoverable error might dissuade foresters to whom lower 

but more conventional returns on investment from conifer 

plantations represent their risk management comfort zone. 

More about this later. 

Red alder (rightly, at present) is touted as immune 

to most pests that affect conifer forests. However, little 

is known about pests that might yet emerge as epidemics 

should sizable acreages in pure red alder plantations begin 

to proliferate. At present, outside of susceptibility of older 

trees to white heart rot (Phellinus igniarius) and sapsucker 

(Sphyrapicus spp) bark and cambium damage, there are few 

pests known to have caused serious damage to red alder in 

forest stands. Regarding mechanical damage (and associated 

compartmentalized rot), it is well known that red alder is 

more sensitive than conifers to logging damage, and natural 

stands of red alder are also more prone to top breakage from 

ice or snow storms (with subsequent generation of multiple 

tops due to low apical dominance). One should note, 

however, that casual observation of plantation red alder 

indicates that straight and well-spaced red alders are less 

susceptible to top breakage than natural stands with their 

clumpy spacing and near-universal stem sweep.

Thus, the robust picture of red alder management 

becomes nuanced with some negative factors that must be 

minimized through judicious management and site selection. 

Next, I will discuss two of these factors, site selection and 

mechanical damage, in more detail.

Site Selection

Red alder, because of its ability through bacterial root 

nodules, to fix and use atmospheric nitrogen and thereby 

fertilize itself, grows competitively on a wide variety of 

sites. However, within this wide spectrum, there is a limited 

range of sites suitable for cultivating superior commercialgrade red alder. Characteristics of this limited range are: (1) 

moist but well drained soils; (2) northerly through easterly 

aspects, especially on steeper and drought-prone slopes; (3) 

a frost-free growing season (paying particular attention to 

avoiding localized frost pockets); and (4) a relative absence 

of elk (which may cause rubbing and trampling damage). 

One should also avoid areas prone to even rare (such as 

Natural Stand—Ample stocking as well as stem sweep

Planted 525 TPA—Straight and clear

Planted 100TPA—Branches and forks

Figure 2—The photos above show phototropic-induced stem sweep in a natural stand (upper left), excessive branching and multiple stems due to low apical 

dominance (right), and straight and clear stems with around six feet of crown lift in a stand planted at 525 trees per acre at age nine (lower left). Source: 

Hardwood Silviculture Cooperative.
140

bi- or tri-decadal) ice storms and heavy snow loads. Thus, 

sites suitable for intensive management for red alder are 

also excellent sites for Douglas-fir (or other low elevation 

westside conifers), site class I to high III. Site selection 

will most likely become less time consuming (but not less 

critical) with development of GIS site selection models such 

as the newly fielded Washington Department of Natural 

Resources pilot model.

Mechanical Damage

As regards mechanical damage from snow and ice, a 

brief digression on risk assessment is warranted. In conifer 

forestry, site characteristics are relatively easy to determine, 

and errors in judgment are often benign. Not so with red 

alder. Imagine, for example, a red alder plantation selected 

per the above site criteria but with only a casual look to rare 

historic weather. Imagine also that a more judicious look 

at rare historical weather would have revealed ice storms 

having occurred only every 10 to 20 years, and that we are 

now at a point at which our fictional red alder plantation has, 

though significant investments and treatments, progressed 

as intended to mid-rotation. Consider the effects on this 

stand of a single ice storm lasting but a few hours and 

causing a 1⁄4-inch ice build-up on this red alder plantation 

versus a similarly aged conifer stand. Personal observations 

indicate that in both red alder and conifer stands the weight 

of the ice might cause top breakage at stem diameters 

down to around 6 inches. In observed conifer stands, apical 

dominance generally re-established single new leaders, 

and the resultant future grade defect could be bucked 

out at harvest with a relatively modest loss of value. In 

observed natural red alder stands, on the other hand, high 

phototropism combined with low apical dominance caused 

broken-topped trees to often sprout multiple new leaders 

(and epicormic branches on stems around larger openings) 

to quickly dominate canopy openings. The result was 

significant loss of commercial value; only the stem portion 

below the breakage could develop future commercial 

value. Thus, careful site selection and risk assessment are 

imperative. A single brief ice event one or two decades after 

planting may render a red alder plantation nearly financially 

worthless. One must therefore carefully analyze site-related 

risks before committing to intensive and expensive red alder 

management. Next, we will consider some techniques and 

field craft that should prove useful in preparing, reforesting, 

thinning, and pruning a correctly sited red alder plantation. 

Site Preparation

When it comes to site preparation, one should realize 

that herbicide control of competing vegetation after planting 

is infeasible, because current herbicides fail to distinguish 

between red alder and undesirable vegetation. Hence, 

the site preparation stage prior to planting is the only 

feasible opportunity to control vegetation, and gambling 

with the outcome ought not be an option. Other important 

considerations regarding red alder and site preparation 

are: (1) salmonberry cannot be controlled through manual 

means, only herbicides or broadcast burning are effective; 

and (2) certain woody species, notably vine maple, may 

be “plucked out” in the course of logging the previous 

stand. The up-shot is that if vegetative suppression is 

likely to cause seedling mortality, site preparation is 

imperative. If red alder captures the site early due to 

proper site preparation and planting, rapid growth rate, 

and full stocking, it will outgrow all other vegetation, and 

further vegetation control will be unnecessary. In most 

cases, however, site preparation with herbicides capable 

of controlling targeted vegetation is necessary in order to 

assure full stocking and even spacing of planted seedlings. 

I will re-visit the importance of even spacing and full 

stocking i.e., no planting mortality, later when I discuss how 

silvical characteristics of red alder are used to produce highvalue log characteristics.

Planting Techniques and Field Craft

First, a primary activity objective for planting is a 

practically 100 (and no less than 95) percent first-year 

survival with good vigor on, or close to, a nine-foot-square 

grid pattern. Red alder seedlings are different from their 

conifer counterparts in that seed germination in a bare root 

seed bed is poor and unpredictable. (A trial is currently 

underway at Webster Nursery to study if this obstacle can be 

overcome—moisture regimes and frost control may prove 

crucial factors.) To overcome the uncertain germination rate, 

DNR’s Webster Nursery grows a so-called “plug-1⁄2” that, 

coupled with proper temperature and irrigation regimens 

and newly developed techniques for top-mowing, produces 

a relatively inexpensive high quality red alder seedling in 

eight to 10 months. The seeds are germinated in very small 

containers in an atmospherically controlled and “fertigated” 

greenhouse in April, thus achieving higher germination 

rates than with bare root sowing. These mini-plugs are 

lifted and transplanted into a bare-root bed in early summer, 

inoculated with Frankia bacteria to speed formation of 

nitrogen-fixing root nodules, lifted from the bare-root 

bed and put in freezer storage in January or February, and 

thawed and stored in a cooler approximately two weeks 

prior to out-planting. Seedling characteristics when packed 

and stored are: (1) crown height of 12 to 31 inches (30 to 

80 cm), (2) caliper of 5 mm, (3) healthy buds and branches 

along the entire length of the stem, (4) prolific root nodules, 

and (5) healthy terminal. Seedling care at out-planting must 

be extensive to prevent damage to succulent terminals and 

buds, desiccation, and root damage. Tree planters must, 

for example, avoid stuffing too many seedlings into their 

planting bags and exposing unplanted seedlings to heat and 

drying.

The planting window is short: mid-March through midApril, and after predicted last frost for the site at hand.
141

Planting Density

In determining stand establishment criteria, rotational 

stand objectives must first be clearly defined. By combining 

a defined desired end-state objective with silvical 

characteristics of red alder seedlings and saplings, one is 

positioned to chart the optimal pathway from the initial 

stand condition to the desired end state. Accordingly, I assert 

that a desired end state objective for a commercial red alder 

plantation is maximum return on investment manifested by 

full stocking at rotation’s end with each tree’s lowest 22 feet 

(6.7 meters) being a log of superior grade. A superior grade 

log is straight, clear, and with a dbh of at least 15 inches (38 

centimeters). This implies (1) even spacing to preclude stem 

sweep (fig. 2) and (2) stocking that is periodically adjusted 

to (a) induce natural pruning at branch diameters of onehalf inch or less (no “black knots”) and (b) sustain diameter 

and height growth at maximal levels when considering 

natural pruning criteria without inducing opportunities 

for phototropic stem sweep. The HSC—using 12-year 

plantation data from test plots in Oregon, Washington, and 

British Columbia—found promise in planting red alder at 

nine-foot square spacing (525 trees per acre or 1,300 trees 

per hectare). 

The HSC further tested the concept of planting 525 

trees per acre by comparing the response to pre-commercial 

thinning (PCT) at various ages. The graphs in figure 3 

compare dbh and height growth in response to PCT to 230 

trees per acre at four (“early”) versus eight (“late”) years 

since planting.

The results clearly indicate that diameter growth 

benefits from thinning as early as age four while height 

growth response is not as succinct. There are also 

indications that stands receiving the late PCT have a 

tendency to catch up with earlier thinned stands (fig. 

3). Moreover, casual observation of several red alder 

plantations aged four through 15 indicate that thinning 

at age four delays natural pruning processes and results 

in excessive branch diameters in the lower crown. 

Accordingly, one might deduce (while awaiting further 

research) that the window of consideration for PCT opens 

at age four, but the optimal time (factoring in both the value 

of clear wood and growth rate) is most likely in the eight to 

10-year range. From this author’s viewpoint, these emerging 

parameters (planting at nine-foot spacing and PCTing near 

age 10 and taking out one-half of the trees per acre) are on, 

or very near, the optimal silvicultural pathway towards the 

highest possible return on investment. As we shall soon see, 

financial analysis of the entire rotation lends credibility to 

this assumption.

Some Thoughts on Thinning Techniques 

and Field Craft as Related to Red Alder 

Silvics and the Objective of Maximum 

Return on Investment

From red alder’s extreme shade intolerance comes 

a corresponding phototropism i.e., a strong proclivity 

to bend towards direct sunlight. In natural stands of red 

alder, stocking depends entirely on the stochastic nature 

of seed and seed bed availability, germination conditions, 

etc. Stocking therefore tends to be universally clumpy, 

and phototropic stem sweep becomes nearly universal. 

Crown ratios in densely stocked clumps quickly diminish 

to the point of being too low to respond to thinning, while 

diameters are uneven (although tree height is not), and 

Figure 3—Results of diameter and height response of red alder stands planted at 525 trees per acre to early and late pre-commercial thinning through age 12. 

Source: Hardwood Silviculture Cooperative.

Age (years)

2 4 6 8 10 12 14

0

5

10

15

20

Control 525tpa

Early thin to 230tpa

Late thin to 230tpa

Age (years)

2 4 6 8 10 12 14

0

5

10

15

20

Control 525tpa

Early thin to 230tpa

Late thin to 230tpa

525 tpa = 1300 tpha

230 tpa = 570 tpha

DBH (cm)

Height (m)
142

suppression mortality occurs. More stem sweep follows 

around openings created from suppression mortality (fig 

2). From an economic standpoint, the stand has lesser 

valued, slow growing logs and makes inefficient use of 

available growing space. In intensively managed red alder 

plantations, we intend to preclude these negative factors. 

We accomplish that through very even initial spacing 

coupled with stocking controls intended to balance viable 

crown ratios (maintaining approximately 60 percent) with 

natural pruning at branch diameters of less than one inch. 

The need for even spacing may be considered proportional 

to red alder’s phototropism. Therefore, red alder’s need for 

uniform spacing in order to produce high-value logs is far 

greater than Douglas-fir or other conifers. 

Thus, a question arises of how to “plant on a grid” and 

then sustain the grid through one or more thinnings. The 

first step, of course, is to select sites with even availability 

of planting spots—good soil throughout, requisite site 

preparation, and sufficient planting contract provisions to 

ensure a seedling every nine feet in a square pattern. Such 

strict spacing arrangements may be sustained when PCTing 

by taking out every other diagonal row (thus removing onehalf of the basal area and trees per acre). PCT would shift 

the square pattern 45 degrees while widening the spacing by 

the square root of two (approximately 1.4). In other words, 

if planting is at nine foot spacing, PCT would be to 9 x 1.4 

≈ 13 foot spacing, and a subsequent commercial thinning 

would be to a spacing 13 x 1.4 ≈ 18 feet. Seen from above, 

the original grid, trees to be removed in thinning and the 

grid after thinning would appear as in figure 4.

Where Does This Take Us?

In review, we initially established a desired endstate and then devised the best way to get there from a 

silvically optimal initial stand condition. Note that we 

first established two desirable parameters for maximizing 

return on investment: full stocking and superior-grade first 

logs in practically every tree. Next we looked at planting 

as well as thinning techniques and field craft to maximize 

value potential value at final harvest. We noted that planting 

between 500 and 600 trees per acre on a uniform and square 

grid enabled us to PCT by removing one-half of the trees per 

acre and thus sustained a high and uniform rate of desirable 

stand development. The phototropic nature of alder 

compelled us to develop techniques and field craft to sustain 

uniform and square spacing before and after thinning. Thus, 

by removing every other diagonal row, we PCTed to 13-

foot square spacing (from the initial spacing of nine feet). 

A subsequent commercial thinning—if we do one—would 

be to13 x √2 ≈ 18 feet, assuming that future research will 

indicate similar desirable development for slightly older 

stands. The final stocking would be around 130 evenly 

spaced trees per acre, with each tree being straight and 

clear (through natural pruning and possibly dead branch 

knock-down) up to at least 22 feet while sustaining 

maximal diameter accrual to attain the desired 15 inches 

dbh. Although, currently available data for natural stands 

indicate 14 inches at dbh for 120 trees per acre, I anticipate 

additional growth from judicious plantation management. 

We can now flesh out these concepts with a rudimentary 

regime simulation combined with robust financial analysis 

to scope whether or not the financial outcome warrants early 

investments.

Stand Development Simulation 

and Financial Analysis

Although the HSC has thus far developed 12 years 

of information on intensive red alder management, a 

notable gap exists in the lack of a good growth and yield 

simulator for managed stands. For the interim, I will 

note that existing knowledge lends itself to mathematical 

calculations sufficient to project rough stand averages at 

important decision nodes. Growth projections are derived 

by coupling HSC plantation growth data through year 12 

with natural stand site index curves. However, growth and 

yield simulations based on site trees have inherent overestimation bias that is perpetuated when used to extrapolate 

12-year HSC plantation data to final rotation. A subjective 

downward adjustment of projections is therefore prudent. In 

order to remain financially conservative, it is also prudent 

to assume investments, such as thinning and dead branch 

knock-down, occur at the earliest possible juncture. Thus, 

growth and yield calculations with a prudent downward 

adjustment and coupled with what seems as reasonable 

future stumpage assumptions may be used for projecting 

returns on investments. The tabulation below contains 

what is, after comparison to feasible alternative regimes, 

Original grid Tree marking After thinning

Figure 4—The even-spaced thinning solution: Start with 9-foot square spacing (far left). In thinning, remove every other diagonal row (gray 

crowns, center). The post-thinning spacing is even and square, although the squares are turned 45 degrees, at 9 feet x √2 ≈ 13 feet. Even spacing 

supports uniformly vertical phototropic response in red alder.
143

thought to be both an optimal and practical rotation-length 

silvicultural prescription.

The investment value of this rotation, using a discount 

rate of four percent, results in a bare land value (BLV) of 

just under $5,000 per acre. BLV is defined as net present 

value of an infinite succession of identical rotations.1

Rotation length is therefore immaterial when comparing 

present value of silvicultural regimes of various rotation 

lengths to each other. This is because the calculated 

investment period in all cases is the same i.e., infinity. This 

would not be true if using the pure form of net present 

value (NPV), in which case comparison of different rotation 

length scenarios is invalid. Thus, comparing the BLV from 

the above stand tabulation to a likewise optimal mixed 

Douglas-fir – western hemlock regime final-harvested at 

culmination of periodic annual increment, one finds that the 

red alder regime is more than twice as profitable in terms of 

BLV.2 Although the red alder projection is admittedly crude, 

its financial advantage over mixed conifer is sufficiently 

large to confidently state that red alder cultivation merits 

serious consideration on suitable sites.

1 In the formula BLV = NFV ÷ [(1 + i) n - 1], “NFV” is net future value i.e., 

the net of all revenues and costs, each compounded until the end of the 

rotation; “i” is the compounding rate; and “n” is the number of years—

compounding periods—in the rotation. BLV, or Bare Land Value, may be 

thought of as Net Present Value (NPV) for an infinite succession of identical rotations. Since the investment period would thus be equal i.e., infinity, 

BLV lends itself to equitable financial comparison of various regimes and 

rotation lengths. 

2

 Net future value for the red alder regime when the value of all activities 

are accumulated at 5 – 1percent to year 30 is $11,117 per acre. Applied to 

the formula for calculating bare land value, the result is $4,955 per acre. 

By comparison, a similarly optimal regime for mixed Douglas-fir and 

associated conifers terminated at approximately the culmination of periodic 

annual increment (ages 40 to 60), yields a maximum bare land value in the 

$1,700 to $2,400 per acre range, depending upon species mix and other site 

specific variables and assumptions.

Conclusions

• Red alder cultivation for commercial purposes 

requires management intensity not matched by 

conifer forestry and therefore requires a level of 

investment higher than for conifer plantations.

• Site selection is of critical importance in 

intensively managed red alder; effects of error in 

this regard are not benign as in conifer plantations.

• Windows for management intervention are 

relatively short, and if not acted upon, the 

commercial value of red alder regimes go from 

potentially superior to assuredly mediocre.

• Returns on investment show potential to be on the 

order of more than twice the value of mixed conifer 

rotations, given what today seems to be reasonable 

assumptions on growth, yield, and stumpage 

values, and provided that risk is analyzed and 

judiciously managed.

• Further research is needed to develop state-of-theart growth and yield simulators for managed stands 

of red alder.

Acknowledgements

The author gratefully acknowledges peer reviews 

by Andrew A. Blum, associate program director for 

the Hardwood Silviculture Cooperative and Florian 

Deisenhofer, Washington State Department of Natural 

Resources forest scientist.

Literature cited

Bluhm, Andrew A. 2004. Red alder management: 

principles and practices. Washington State University 

Forestry Extension Summer Forestry Education Series. 

Powerpoint presentation given at Mount Vernon, WA. 

August 28, 2004. (On-line address http://www.cof.orst.

edu/coops/hsc/pubs/index.htm#present)

Harrington, C.A. 1990. Silvics of red alder. In: Silvics 

of North America, vol. 2, Hardwoods. Technically 

coordinated by: R.M. Burns and B.H. Honkala. USDA 

For. Serv. Agric. Handb. 654. Washington D.C. pps. 116-

123.

Khaddurri, Nabil. 2005. Interview with the author 

regarding red alder seedling cultivation practices at 

the Washington State department of Natural Resources 

Webster Forest Nursery.

Peterson, E.B., Ahrens, G.R., and Peterson, N.M. (eds). 

1996. Red Alder Managers’ Handbook for British 

Columbia. FRDA Report 240.

Stand chronology and cash flow tabulation:

Activity Year Cost/Revenue

Site prep (aerial herbicide) 0 ($110)

Plant (seedlings + contract) 0 ($300)

PCT 4 ($100)

Dead branch knock-down 8 ($100)

CT (3 MBF/ac @ $200/MBF) 18 $600

Final Harvest (20 MBF/ac 

@ $600/MBF) 30 $12,000
144
145

1Kevin W. Zobrist (email: kzobr@u.washington.edu) and C. Larry Mason (email: larrym@u.washington.edu) are research scientists with the Rural 

Technology Initiative, University of Washington, College of Forest Resources, Box 352100, Seattle, WA 98195-2100.

— Red Alder: A State of Knowledge —

Alternate Plans for Riparian 

Hardwood Conversion: 

Challenges and Opportunities

Kevin W. Zobrist and C. Larry Mason1

Abstract

Many riparian stands in western Washington are 

dominated by red alder and other hardwood species. 

Riparian harvest restrictions designed to protect salmon 

habitat can be problematic in these stands, as they may 

preclude establishment of desirable large conifers while also 

resulting in economic losses for landowners. Washington 

forest practices rules allow for development of “Alternate 

Plans” which are intended to provide flexibility for solutions 

to avoid unintended consequences. A case study has been 

done of a hardwood conversion alternate plan. Observations 

from this case study have identified problem areas in 

the alternate plan approval process. Approaches such as 

templates may help address these problems. 

Keywords: red alder, riparian management, economics

This paper was published in: Deal, R.L. and C.A. Harrington, eds. 2006. Red alder—a state of knowledge. General Technical 

Report PNW-GTR-669. Portland, OR: U.S. Department of Agriculture, Pacific Northwest Research Station. 150 p.
146

Introduction

The state of Washington has recently updated its 

forest practices regulations, adding new restrictions on 

timber harvesting in riparian areas. The purpose of the 

new rules, known as the “Forests and Fish Rules,” is to 

protect endangered salmon and other aquatic resources in 

compliance with the federal Endangered Species Act and 

Clean Water Act. In western Washington, the Forests and 

Fish Rules are specifically intended to put riparian stands on 

a trajectory towards desired future conditions (DFC). The 

DFC are conditions of mature, unmanaged riparian stands, 

characterized by large conifers that provide shade and a 

long-term source of large woody debris (LWD) thought to 

be important for fish habitat.

The Forests and Fish Rules for western Washington 

require a three-zone riparian buffer along fish-bearing or 

potentially fish-bearing streams. The total buffer width is 

one site potential tree height, which varies from 90 to 200 

feet depending on site class. No harvest is allowed in a 50-

foot core zone immediately adjacent to the stream. The next 

zone is the inner zone, which extends from the core zone to 

two-thirds or three-fourths of the site potential tree height 

depending on the size of the stream. Partial harvest may be 

allowed in the inner zone if the number and basal area of the 

conifers in the core and inner zones are projected to meet 

minimum requirements when the stand is 140 years old. The 

remainder of the buffer is the outer zone, in which harvest 

is allowed so long as 20 conifers per acre with a diameter at 

breast height (DBH) of 12 inches or greater are retained.

Many riparian stands in western Washington are 

dominated by red alder (Alnus rubra) and other hardwoods. 

In these situations, the Forests and Fish Rules can be 

problematic. Because of inadequate conifer density and 

basal area, no harvest will be allowed in either the core 

or inner zones. However, without active management to 

harvest some of the alder and establish a greater conifer 

component, it is unlikely that these riparian stands will 

achieve the DFC within the desired time frame. Instead, 

as the alder, which is not a long-lived species, becomes 

senescent, the riparian stand may become dominated 

by salmonberry (Rubus spectabilis) and other brushy 

vegetation. The lack of opportunity to harvest valuable 

hardwood timber in the riparian zone also means economic 

losses for landowners. The economic impacts of the riparian 

harvest restrictions can be significant, especially when no 

timber can be harvested from the inner zone (Zobrist 2003; 

Zobrist and Lippke 2003).

In order to accommodate situations where the rules 

may hinder the achievement of the DFC and to provide 

opportunities for landowners to find lower cost approaches 

for protecting riparian areas, the rules allow landowners 

to submit a site-specific alternate plan for managing a 

riparian stand. A case study has been done of one of the first 

“hardwood conversion” alternate plans to be submitted. This 

case study offers insights into some of the challenges of and 

opportunities for using alternate plans as a solution for the 

sustainable management of riparian hardwood stands.

Hardwood Conversion 

Case Study

The case study is of a hardwood conversion alternate 

plan that was submitted in 2002 by a small forest landowner 

in southwest Washington. The landowner planned to harvest 

a 26-acre stand that bordered 1,570 feet on the east side of 

a north-south stream. The stream ran dry in the summer, but 

it was identified as potential winter fish habitat and so was 

classified as fish-bearing. The stream was considered small, 

as its bankfull width was less than 10 feet. The stand was 

site class II, requiring a total riparian buffer width of 170 

feet. The first 50 feet from the stream was the no harvest 

core zone. The inner zone then extended 64 feet from the 

edge of the core zone out to two-thirds of the buffer width 

(114 feet), as required for small streams. The remaining 56 

feet was the outer zone (fig. 1).

The dominant species in the riparian zone was red alder, 

which was 30 years old, had a density of 105 trees per acre 

(TPA), and ranged in size from 6 to 18 inches DBH. There 

were also 35 TPA of 55-year-old Douglas-fir (Pseudotsuga 

menziesii) ranging in size from 6 to 40 inches DBH, along 

with a few (less than 6 TPA) other hardwoods, such as black 

cottonwood (Populus trichocarpa) and bigleaf maple (Acer 

macrophyllum) (fig. 2). The core and inner zones, which 

comprised approximately 4 acres, had an inadequate conifer 

component to allow harvesting in the inner zone under 

the default rules. The landowner proposed a hardwood 

conversion alternate plan to harvest some of the existing 

alder in both the core and inner zones to establish more 

conifers and generate some revenue. 

The alternate plan addressed the riparian zone as two 

different management units, with unit 1 bordering the 

southern 1,070 feet of stream and unit 2 bordering the 

northern 500 feet of stream (fig. 3). For unit 1, the alternate 

plan proposed leaving all of the Douglas-fir and 49 red alder 

along the stream bank in the core zone while harvesting the 

rest of the hardwoods in that zone. For the inner zone the 

plan proposed leaving 13 Douglas-fir (12 less than 9 inches 

Figure 1—A 170-ft riparian buffer is required for small streams on site 

class II. The buffer includes a 50-ft core zone, followed by a 64-ft inner 

zone and a 56-ft outer zone.

Core

Zone

Inner

Zone

Outer

Zone

Stream

bank

50 ft 114 ft 170 ft
147

DBH and one with 28 inches DBH) and harvesting the 

remaining Douglas-fir and all of the hardwoods. All trees 

would be harvested in the outer zone. For unit 2, no harvest 

would be done in the core zone. The plan proposed to leave 

8 Douglas-fir dispersed in the inner zone, while harvesting 

the remaining Douglas-fir and all of the hardwoods. All 

trees would be harvested in the outer zone.

The alternate plan called for the harvested areas to be 

replanted with 300 TPA of 1-1 seedlings. The seedlings 

would be 80 percent Douglas-fir and 20 percent western 

hemlock (Tsuga heterophylla). Brush control would be 

done at 3 years and 7 years after planting to ensure that 

the planted conifers become free to grow. To evaluate the 

expected results of the proposed alternate plan over time, 

the riparian stand was treated according the prescription 

and then projected over 140 years using the Landscape 

Management System (LMS). LMS is an analysis tool that 

integrates growth, treatment, and visualization models 

(McCarter et al. 1998). The projected stand conditions 

immediately, 10 years, 40 years, and 140 years after 

treatment are shown in fig. 4. These projections suggest that 

in the long term this alternate plan would result in a riparian 

stand dominated by large conifers and characteristic of the 

DFC.

In order for an alternate plan to be approved, it must 

be reviewed by an interdisciplinary (ID) team that includes 

representatives from the Washington Departments of 

Natural Resources, Fish and Wildlife, and Ecology, along 

with local tribes. The ID team that reviewed this alternate 

plan proposed several revisions. The ID team proposed 

a wider no-harvest area in the core zone of unit 1. They 

proposed that only the smallest Douglas-firs be harvested 

in the inner zone, and only those leaning away from the 

stream. They also proposed in-stream LWD placement of 37 

to 45 conifer logs originating from outside the riparian area 

(i.e. the upland portion of the harvest unit).

The economic costs of the revisions proposed by the 

ID team were unacceptable to the landowner. However, 

a compromise was reached in which the logs for LWD 

placement were allowed to include leave trees and downed 

wood from the core and inner zones. This eliminated the 

cost of using merchantable upland logs for LWD placement 

by allowing the placement of logs that would not otherwise 

have gone to the mill. The final revised plan included an 

additional 54 red alder and 5 cottonwood leave trees in the 

core zone of unit 1. In the inner zone of unit 1, 12 Douglasfir leave trees were to be retained with an average DBH of 

18 inches. In the inner zone of unit 2, 10 Douglas-fir leave 

trees were to be retained with an average DBH of 26 inches.

Figure 4—LMS simulation of the riparian stand conditions over time under 

the proposed alternate plan.

Figure 3—The case study riparian zone comprised two management units 

along 1,570 feet on one side of a small, north-south stream.

Figure 2—A visualization of the case study riparian stand, which is 

predominantly 30-year-old red alder with some older conifers and 

additional hardwood species present.
148

Using figures provided by the consulting forester 

who prepared the alternate plan, a breakdown of the costs 

and revenues for the original alternate plan, the proposed 

revisions, and the final, approved compromise is given in 

table 1. These are only the costs and revenues exclusive to 

the alternate plan that are above what would be expected if 

management was done according to the default rules. The 

original proposed plan would have resulted in a net return 

to the landowner of $8,775. The revisions proposed by the 

ID team would have reduced this by 94% to $495, at which 

point the landowner was no longer willing to pursue the 

alternate plan. The compromise resulted in a net return of 

$4,495, a 49% reduction from the original proposal.

Discussion

Alternate plans are potential solutions for situations 

such as hardwood-dominated riparian areas in which the 

regulatory prescription is unlikely to achieve the DFC in a 

timely manner. However, observations from this case study 

suggest that the development and approval of such plans 

may be problematic. The approval process can be long and 

costly for both the landowner and the agencies participating 

on the ID team. In this case, the plan development and 

approval process took approximately one year and involved 

three ID team field visits. The cost to the landowner was 

$1,500 for consulting fees, which was 17% of the net 

harvest revenue for the approved plan and represents 

approximately $1 per foot of stream. Agency costs included 

the personnel and equipment costs of the three field visits, 

plus the associated office time. Additional agency costs were 

expected for supervision of the LWD placement.

Another problem observed was the lack of guidelines 

for alternate plan development and approval. There were 

no objective, measurable performance criteria to gauge the 

effectiveness of the proposed plan or subsequent revisions. 

At the same time, a lack of economic guidelines almost 

resulted in a failure to reach an agreement. Without clear 

guidelines and objective, measurable performance criteria, 

the overall goals of alternate plans can easily get lost in 

the negotiation process and opportunities for “win-win” 

solutions of greater effectiveness and lower compliance 

costs can be missed.

The problems observed with this case study were 

not unexpected. This was one of the first alternate plans 

to be submitted, and as with any new process, time and 

experience are needed to work out logistical issues. The 

purpose of this case study was to identify areas of need 

and potential solutions for improving process efficiency 

and results. One such solution suggested in the rules is the 

development of alternate plan templates. These templates 

would be pre-established guidelines to expedite the 

development and approval of alternate plans for common 

situations. Conversion of predominantly hardwood riparian 

stands for conifer regeneration has been identified as a 

common situation for which a template approach would be 

appropriate.

Alternate plan templates for hardwood conversion 

present an opportunity to provide for short and long term 

riparian habitat goals while also providing economic relief 

to landowners. These templates could provide landowner 

incentives for future stewardship. They could also facilitate 

an increase in the available short term supply of red alder, 

as much of the current inventory is located in riparian areas. 

A streamlined approval process would make alternate plan 

implementation more feasible for both landowners and 

regulatory agencies, which is necessary for the large-scale 

success of alternate plans.

Several key elements will likely be needed for a 

successful hardwood conversion template. A narrow, noharvest buffer will be needed immediately adjacent to the 

stream for interim shade, bank stability, and short term LWD 

recruitment. Sufficient harvest of the remaining riparian 

hardwoods will be needed to create adequate growing 

Table 1—Itemized cash flows for the original proposed alternate plan, the plan with proposed revisions, and the 

final approved compromise. Only the additional cash flows associated with the alternate plan are included.

Cash Flow Proposed Plan Proposed Revisions Approved Compromise

Net Harvest Revenue $12,210 $8,710 $8,710

Site Preparation -$625 -$625 -$625

Planting -$810 -$670 -$670

LWD Log Value $0 -$4,000 $0

LWD Placement Cost $0 -$1,000 -$1,000

Brush Control Year 3 (discounted at 5%) -$275 -$230 -$230

Brush Control Year 7 (discounted at 5%) -$225 -$190 -$190

Consulting Fees -$1,500 -$1,500 -$1,500

Net To Landowner $8,775 $495 $4,495
149

space for conifers. Regeneration specifications (species 

mix and density) should be appropriate for the site and for 

long term growth. The template process should be simple 

and affordable and provide sufficient economic benefits to 

landowners.

The observations from the case study suggest several 

challenges that will need to be addressed in developing a 

hardwood conversion template. Short term function needs, 

such as shade and bank stability, will need to be balanced 

with the long term establishment of the DFC. Specifically, 

the appropriate width of the no-harvest buffer adjacent 

to the stream will need to be identified. Appropriate 

regeneration strategies will need to be developed. These 

strategies will need to extend beyond planting, such as brush 

control and pre-commercial thinnings. This will increase 

landowner costs but may be necessary for establishing 

conifers while preventing the subsequent development 

of too densely stocked conditions. Treatment of existing 

conifers will also need to be addressed. As was the case for 

the case study, hardwood-dominated stands often include 

some conifers—too few to achieve the DFC, but enough to 

potentially impact regeneration. Finally, it will be important 

to establish sufficient conifers to achieve the DFC while 

still maintaining a hardwood component. Hardwoods play 

an important role in riparian forest ecosystems. Ultimately 

the goal is not the eradication of riparian hardwoods in 

favor of purely coniferous stands, but rather the sustainable 

management of both conifers and hardwoods.

Literature Cited

McCarter, J.B.; Wilson, J.S.; Baker, P.J.; Moffett, J.L.; 

Oliver, C.D. 1998. Landscape management through 

integration of existing tools and emerging technologies. 

Journal of Forestry 91(12):31-42.

Zobrist, K. 2003. Economic impacts of the Forests and 

Fish Rules on small, NIPF landowners: Ten Western 

Washington case studies. RTI Working Paper 1, Revised 

Edition. Seattle, WA: Rural Technology Initiative, 

College of Forest Resources, University of Washington.

Zobrist, K.; Lippke, B.R. 2003. Case studies examining 

the economic impacts of new forest practices regulations 

on NIPF landowners. In Teeter, L.; Cashore, B.; Zhang, 

D., eds. Forest policy for private forestry: Global and 

regional challenges. Wallingford, UK: CABI Publishing. 

Chapter 19. 
150

Metric Equivalents

When you know: Multiply by: To find:

Degrees Fahrenheit (°F) (F-32)/1.8 Degrees Celsius (°C)

Inches (in) 2.54 Centimeters

Feet (ft) .3048 Meters

Acres (ac) .4047 Hectares

Trees per acre (TPA) 2.471 Trees per hectare

Thousand board feet (MBF) 2.4 Cubic meters (m3)

English Equivalents

When you know: Multiply by: To find:

Degrees Celsius (°C) (C* 9/5)+32 Degrees Fahrenheit (°F) 

Centimeters (cm) .3937 Inches (in)

Meters (m) 3.2808 Feet (ft)

Square meters per hectare (m2/ha) 4.36 Square feet per acre (ft2 /ac)

Cubic meters per hectare (m3/ha) 14.30 Cubic feet per acre (ft3 /ac)

Kilograms per hectare (kg/ha) 0.89 Pounds per acre (lb/ac)

Kilometers (km) 0.6214 Miles (mi)

Hectares (ha) 2.470 Acres 
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—as directed by Congress—to provide increasingly greater service to a growing Nation.

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Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410, or call (800) 795-

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