Condition and Deterioration 

Rate of Precommercial Thinning 

Slash at False Island, Alaska

Michael H. McClellan, Paul E. Hennon, Patrick G. Heuer, 

and Kenneth W. Coffin

Pacific Northwest 

Research Station

Research Paper

PNW-RP-594

May 2014

United States Department of Agriculture

Forest Service
Authors

Michael H. McClellan is a research ecologist and Paul E. Hennon is a research 

forest pathologist, Pacific Northwest Research Station, Forestry Sciences 

Laboratory, 11175 Auke Lake Way, Juneau, AK 99801; Patrick G. Heuer is 

a silviculturist and Kenneth W. Coffin is a wildlife biologist, Alaska Region, 

Tongass National Forest, 204 Siginaka Way, Sitka, AK 99835. Coffin currently 

is located in the Rocky Mountain Region, White River National Forest, 220 E. 

Market St., Meeker, CO 81641.

Cover photograph by Eric Winter.

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Abstract

McClellan, Michael H.; Hennon, Paul E.; Heuer, Patrick G.; Coffin, Kenneth 

W. 2014. Condition and deterioration rate of precommercial thinning slash at 

False Island, Alaska. Res. Pap. PNW-RP-594. Portland, OR: U.S. Department 

of Agriculture, Forest Service, Pacific Northwest Research Station. 29 p.

We examined slash from thinning treatments in a 21-year chronosequence of 

young-growth stands in southeast Alaska to determine the strength and persistence of slash effects on two key features of deer habitat quality: forage availability and deer mobility within thinned areas. We describe the main deterioration 

processes and their dynamics over time. We measured wood density of slash of 

various ages and present a model to estimate changes in wood density over time. 

This report also discusses factors that contribute to initial slash loading, slash 

deterioration, and effects on deer habitat. 

Keywords: Thinning, Sitka spruce, western hemlock, southeast Alaska, 

slash, decomposition, wildlife habitat, Sitka black-tailed deer.
ii

Summary

In southeast Alaska, precommercial thinning enhances timber values and 

promotes the growth of understory plants that provide forage for wildlife such 

as Sitka black-tailed deer (Odocoileus hemionus sitkensis). The dead stems and 

branches of cut trees, however, can impede deer access to the thinned stand and 

may reduce development of understory plants through shading or physically 

occupying growing sites, potentially reducing benefits to wildlife. We observed 

the condition of slash from thinning treatments in a chronosequence of younggrowth stands near False Island, Alaska, to determine how long thinning slash 

could reduce deer habitat quality. Our observations suggest that precommercial 

thinning slash can impede deer movement until about 9 years after thinning. A 

key deterioration process is the decay of side branches that are suspending the 

cut stems above the forest floor. As the branches decay, they break and allow 

the cut stems to settle to the forest floor. Between 9 and 13 years after thinning, 

slash shades some growing sites but also creates small refugia where plants 

can grow protected from browsing deer. After about 13 years, dead stems are 

still decaying and recognizable, but they have fully settled to the forest floor, 

where they occupy some growing space but no longer impede deer access. We 

measured wood density of slash in stands thinned in different years to estimate 

actual deterioration rates and loss of carbon. Decay rates of western hemlock 

(Tsuga heterophylla (Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) 

Carr.) stem wood were similar, losing approximately 32 percent of wood density after 9 to 13 years and 40 percent 24 years after thinning. This report also 

discusses factors that contribute to initial slash loading, slash deterioration, and 

effects on deer habitat: stand age at thinning, site productivity, spacing, and 

annual snow accumulation.
iii

Contents

1 Introduction

3 Methods

3 Team Observation for Consensus Building

3 Sites

4 Deterioration Rate—Measured Changes in Slash Wood Density

5 Results

5 Stand 413 Near Lindenberg Harbor, 4 Years After Thinning

7 Stand 168, 9 Years After Thinning

7 Stand 143, 10 Years After Thinning

8 Stand 522, 12 Years After Thinning, With an Unthinned Travel Corridor

10 Stand 507, 13 Years After Thinning

10 Stand 230, 13 Years After Thinning

11 Stand 582, 14 Years After Thinning

13 Stand 382, 16 Years After Gap Treatment

15 Stand 528, 21 Years After Thinning

17 Stand 529, 21 Years After Thinning

17 Changes in Wood Density of Slash

20 Discussion

23 Dynamics of Slash Deterioration and Crown Closure

24 Changes in Wood Density

25 Applicability of Results

26 Conclusions

27 Acknowledgments

27 English Equivalents

28 Literature Cited

1

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Introduction

Understory vascular plants provide forage for deer and other animals, contribute to 

biological diversity, and are used for subsistence by residents of southeast Alaska. 

Consequently, promoting diverse and abundant understory plant communities is 

often an objective of thinning treatments in dense, light-limited, young-growth 

forests. Precommercial thinning can leave large amounts of slash (foliage, branches, 

and stems) covering the ground between residual trees. The chief concerns with 

heavy slash loading relate to resources other than timber. However, the benefits of 

reducing crown cover to promote understory development by thinning or pruning 

may be reduced as long as heavy slash accumulations shade or physically occupy 

growing sites. Also, the benefits of increased forage production may be unavailable to deer and other animals if slash impedes their movement through the stand. 

Because of these concerns, slash treatment (piling, lopping, scattering, etc.) is often 

recommended when thinning is prescribed in stands having high value to wildlife.

Unfortunately, adding slash treatments can more than double the per-acre cost 

of thinning and pruning. If funds are limited, this will reduce the number of acres 

that can be treated, leading managers to question whether the greater benefit comes 

from treating more acres and tolerating the presence of slash for some time or from 

treating fewer acres and immediately reaping the benefits of reduced crown cover, 

increased forage availability, and ease of passage for large animals. In weighing 

these alternatives, managers are hampered by the absence of information on the 

persistence of slash. We have little data on how long the slash significantly affects 

understory plant abundance and animal movement. In one study in southeast 

Alaska (Doerr and Sandberg 1986), most of the thinning slash had deteriorated 

18 years after treatment and high levels of deer use were observed. The authors 

speculated that deer use may have been reduced by heavy slash accumulation 

immediately following thinning. Without better information on the early dynamics 

of slash deterioration, the relative benefits of thinning and slash treatment cannot be 

evaluated.

Slash has been shown to affect the movement of deer and other large herbivores. In Montana, elk (Cervus elaphus nelsoni), mule deer (Odocoileus hemionus), 

and white-tailed deer (Odocoileus virginianus) preferentially used clearcuts where 

slash did not impede their movement. In contrast, deer in ponderosa pine (Pinus 

ponderosa Lawson & C. Lawson) forests on Arizona’s Kaibab Plateau were 

observed to prefer areas where logging slash was untreated, even though forbs 

were more abundant in areas where the slash was removed (Reynolds 1969). This 

preference was unexplained. Parker et al. (1984) developed a model of elk and deer 
2

RESEARCH PAPER PNW-RP-594

energy expenditures for locomotion. Their model predicted that energy expenditures for moving through slash increased with the relative depth of slash (obstacle 

height in relation to animal height) and the obstacle density (number of obstacles 

encountered per unit of lineal distance). Jumping over obstacles greatly increased 

energy use, but animals could reduce that cost if they could walk around obstacles.

In several instances, slash has been shown to have a protective effect on tree 

seedlings and understory plants by preventing herbivory by deer. In Sweden, slash 

retention had no effect on total plant biomass that consisted mostly of grasses and 

sedges, but the growth of tree seedlings, shrubs, and herbs—as well as the total 

number of species—increased with slash retention (Berquist et al. 1999). Aspen 

regeneration and shrub cover were greater in South Dakota clearcuts where slash 

was retained, 19 years after cutting (Rumble et al. 1996). In Pennsylvania hardwoods, where intense deer herbivory is present, more regeneration was found in 

areas where slash was retained (Grisez 1960). In contrast, Bergquist and Örlander 

(1998) found that slash quantity was not correlated with deer browsing on conifer seedlings. Krueger and Peterson (2009) studied a gap 3 years after a major 

windthrow event and concluded the relatively light slash loading did not prevent 

browsing of herb-layer plants by deer.

From a purely scientific viewpoint, the ideal approach to the question of slash 

effects and persistence would be long-term, properly designed experimental studies that accounted for the diverse environmental and biological factors that that 

are known to affect slash decomposition and breakdown rates. Such studies would 

be worthwhile and, if broadened somewhat, could have applications beyond the 

immediate management questions—in modeling carbon storage, nutrient cycling, 

and site productivity, for example. It is likely, however, that useful findings from 

this sort of study would not be available to decisionmakers for a decade or more, so 

another approach was needed.

In southeast Alaska, thinning of young even-aged stands began roughly 30 

years ago and continues through the present. We recognized that this population 

of thinned stands could be used in an observational retrospective study of slash 

decomposition rates, so we explored the concept with a limited sample of thinned 

stands. The primary objective of this project was to observe and report on the condition of slash and its likely interference with deer and other large mammal habitat 

enhancement goals in young-growth stands that had received thinning at different 

periods in the past near False Island, Alaska. This chronosequence approach also 

allowed us to address a secondary goal of quantifying the actual deterioration rate 

of individual slash pieces up to 24 years after thinning. 
3

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Methods

Team Observation for Consensus Building

An interdisciplinary team met the week of July 17, 2006, in the False Island area to 

make observations on slash in young-growth stands that had been precommercially 

thinned.1

 Participants included wildlife biologists, a fish biologist, a research forest 

pathologist, a silviculturist, and a research forest ecologist. The False Island area of 

Chichagof Island was selected because the Tongass National Forest’s Sitka Ranger 

District had records on past thinning activities that allowed the team to view a 

series of accessible stands with a variety of thinning dates (time-since-thinning). 

A consensus-building approach was used in this project with the team making 

joint observations along this chronological sequence of past thinning. The team 

discussed observations on the condition of slash and abundance of understory while 

in these stands, and reached consensus on how slash appears to deteriorate through 

time to affect possible deer movement and understory vegetation development.

The most difficult task was judging the effect of slash on deer access. Objective 

rating of this was not possible within the constraints of this study. Access is likely 

to be affected not only by the amount and type of slash present, but also by how 

strongly a deer is motivated to access the site and the amount of effort it is willing 

to exert. Our subjective judgments on deer access were based on our collective 

ability to move through the slash and the assumption that deer would have a slightly 

easier time of it.

Sites

Thinned stands were located on the False Island road system located along Peril 

Strait on the southern portion of Chichagof Island, Alaska, at latitude 57° 31’ N, 

longitude 135° 11’ W. All were young even-aged stands that were naturally regenerated following clearcut harvesting. Thinning treatments ranged from 4.3-m to 5.5-m 

(14-ft to 18-ft) spacing 9 to 21 years before we made our observations. For a more 

recent thinning, 4 years prior, we accessed a stand near Lindenberg Harbor and the 

abandoned Todd cannery site 13 km southeast of False Island. In all cases, cut trees 

were left in place; our observations suggested that typical operational thinning had 

been implemented with no further treatment of piled, lopped, or scattered cut stems. 

1 All thinning of stands examined in this study was precommercial, i.e., done to reduce 

stocking and not to produce a product. From this point forward, use of the term “thinning” 

assumes that it was precommercial.
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RESEARCH PAPER PNW-RP-594

Deterioration Rate—Measured Changes in Slash Wood Density

A small team returned to False Island in September 2009 to make a more quantitative assessment of the rate of slash deterioration using the chronosequence of stands 

that represented time-since-thinning. Stemwood from thinning slash was collected 

in stands that represented 5 (Ocean Boulevard), 12 (stand 168), 17 (stand 582), and 

24 (stand 529) years after thinning. Because a 5-year-old thinned stand was not 

available at False Island, we used larger trees cut 5 years prior at the Ocean Boulevard site, but sampled wood pieces closer to the tops of these cut stems to represent 

the same diameter classes as pieces taken from smaller cut stems at other sites 

(see below). In addition, live trees from an unthinned stand in the same age class 

were felled and wood pieces collected as described below to represent initial wood 

density, or time zero. 

Four cut stems each for western hemlock (Tsuga heterophylla (Raf.) Sarg.) and 

Sitka spruce (Picea sitchensis (Bong.) Carrière) were sampled at each site. Three 

pieces of each cut stem, approximately 10 cm (nearly 4 in) long, were removed by 

hand sawing: one piece 1 m from the base, one from the mid-stem, and one near the 

top. These pieces averaged approximately 12 cm (5 in), 7 cm (3 in), and 3 cm (1 in) 

in diameter, respectively. Plastic bags were placed under some of the more decayed 

pieces to recover any parts of the wood pieces that would have been lost to fragmentation during the hand sawing. Six measurements were made on each piece of 

wood to the nearest millimeter: two diameters each for the top and bottom, and two 

lengths. After calculating top and bottom areas and length for these pieces, volumes 

were then derived by the formula for the frustum of a cone (Husch et al. 1972):

V = L(Ab+(AbAt

)

0.5 +At

)/3 (1)

Where

V = volume (cm3

)

L = length (cm)

Ab = area of bottom end (cm2

)

At

 = area of top end (cm2)

Wood pieces were oven-dried to a constant weight at 50 °C and then weighed. 

Existing wood density of slash, which can be used to estimate deterioration through 

time, was determined from measurements of weight and volume by the formula 

below. Density values (expressed as g/cm3) were averaged for the bottom, top, and 

middle sections to create a mean stemwood density for each cut tree.

D = W/V (2)

Where

D = dry weight density (g/cm3

)

W = oven-dry weight (g)

V = volume (cm3

).
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Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Analysis and estimation of decay rates were conducted with the nonlinear 

regression procedure (NLIN) in SAS (SAS 2009).2 A two-phase exponential decay 

function was chosen because the rate of wood decay typically tapers off through 

time as substrate quality is reduced (Harmon and Sexton 1996).

y = b1e-k1

t

 + b2e-k2t (3)

Where 

b1, b2 = coefficients for components 1 and 2

k1, k2 = decomposition rate constants for components 1 and 2

e = natural logarithm (2.7183)

t = time, in years

Results

The following observations, made by the team at each young-growth stand visited, 

are arranged in a chronology by time since thinning.

Stand 413 Near Lindenberg Harbor, 4 Years After Thinning

This stand was thinned at age 27 years to 4.9- by 4.9-m (16- by16-ft) spacing as part 

of experiment 3 of the Tongass-Wide Young-Growth Study (TWYGS) (McClellan 

2008). In addition to the thinning, parts of the unit were pruned, with either 25 

or 50 percent of the leave trees pruned. All three treatment areas were examined 

(figs. 1 and 2). The pruned branches increased the amount of small-diameter slash 

present. Four years after treatment, slash did not appear to be decayed, bark and 

twigs were still attached, and side branches kept the cut stems propped up. Withinstand variability in productivity had a major effect on slash loading and understory 

presence. In the lower productivity areas, slash stem diameters and slash loads were 

smaller. Overlapping slash stems between leave trees were 0.9 to 1.24 m (3 to 4.1 ft) 

deep in many places, and the slash likely impeded deer access to the site. Oval-leaf 

blueberry (Vaccinium ovalifolium Sm.), red huckleberry (Vaccinium parvifolium

Sm.), and salmonberry (Rubus spectabilis Pursh) stems were growing through 

some of the slash piles and their presence was probably the result of lighter slash 

loads and greater understory abundance under the more open pretreatment canopy. 

In contrast, in the more productive portion of the stand, slash was 1.8 m (6 ft) or 

more in depth with larger diameter cut stems. The general lack of understory likely 

resulted from heavy slash loads and a legacy of the sparse understory that existed 

prior to treatment under the dense pretreatment canopy.

2 The use of trade or firm names in this publication is for reader information and does not 

imply endorsement by the U.S. Department of Agriculture of any product or service.
6

RESEARCH PAPER PNW-RP-594

Figure 1—Slash and shrubs in a less productive area within stand 413, 4 years after thinning and 

pruning 50 percent of the leave trees.

Figure 2—Heavy slash in a more productive part of stand 413, 4 years after thinning and pruning 

50 percent of the leave trees.

Michael H. McClellan Michael H. McClellan
7

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Stand 168, 9 Years After Thinning

This stand was thinned at age 29 years to 4.3- by 4.3-m (14 by 14-ft) spacing. Slash 

was still suspended by side branches, which appeared firm and were not breaking. 

Stems had some external wood decay but were still sound inside. After 9 years, 

slash was still occupying growing space and limiting deer access to much of the 

stand (fig. 3). Ferns, red elderberry (Sambucus racemosa L. var. racemosa), devilsclub (Oplopanax horridus (Sm.) Miq.), and oval-leaf blueberry were the dominant 

understory plants. The limited understory response was likely attributable to both 

slash occupying growing sites and shade from the overstory canopy. The team concluded that the canopy would likely close before the slash deteriorated sufficiently 

and that this stand should have been thinned earlier to maintain a more abundant 

understory and create less slash.

Stand 143, 10 Years After Thinning

This stand was thinned to 5.5- by 5.5-m (18 by 18-ft) spacing at age 20 years. The 

stand is in a productive riparian flood plain and is dominated by Sitka spruce with 

red alder (Alnus rubra Bong.) present throughout (fig. 4). The slash loading from 

thinning appeared light given the wide spacing—probably owing to the size of the 

Figure 3—Stand 168, 9 years after thinning.

Michael H. McClellan
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RESEARCH PAPER PNW-RP-594

young conifers at the time of thinning and the lower pretreatment stocking as compared to more upland settings. Lower stocking of conifers appeared to result from 

the limited number of favorable microsites for conifer establishment and to the presence of numerous red alder in the stand. Red alder were generally retained during 

the thinning treatment. Thinning slash was mainly on the ground, partially decayed 

with limbs intact but decaying, so there was little shading of understory and movement through the stand was not restricted. The understory was well developed with 

a number of species, including salmonberry.

Stand 522, 12 Years After Thinning, With an Unthinned Travel 

Corridor

This stand was thinned to 5.5- by 5.5-m (18 by 18-ft) spacing in 1994 at age 26 

years. A portion of the stand was left unthinned to provide a travel corridor for 

deer. The slash was still impeding travel within some portions of the thinned areas, 

but many areas within the stand were accessible and the unthinned corridor had a 

well-used deer trail. The thinned area had a good understory of plants including 

oval-leaf blueberry, salmonberry, and devilsclub (fig. 5). Side lighting from the 

thinned portion allowed vegetation to develop within the margins of the unthinned 

corridor (fig. 6). There was evidence that deer were moving out into thinned areas 

with lower slash loading to browse.

Figure 4—Stand 143, 10 years after thinning.

Michael H. McClellan
9

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Figure 5—Stand 522, 12 years after thinning, in the thinned part of the stand.

Figure 6—Stand 522, 12 years after thinning, in the unthinned travel corridor.

Michael H. McClellan Greg Killinger
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RESEARCH PAPER PNW-RP-594

Stand 507, 13 Years After Thinning

This stand was thinned to 4.3- by 4.3-m (14- by 14-ft) spacing at age 20 years. 

Leave trees were mainly western hemlock with small numbers of red alder present 

(fig. 7). The slash load was moderate with most of the 2.5- to 10-cm diameter stems 

on the ground. Smaller stems were decayed and weakened, but the larger stems 

were decayed on the outside and sound inside. Primary branches were decayed and 

breaking, allowing most stems to have settled on the ground. Slash distribution 

was quite variable, with open areas as well as small piles. The understory was well 

developed, but there was concern that the canopy was beginning to close and the 

understory would soon be diminished by canopy shading. The team concluded 

that slash deterioration had progressed to the point where it no longer presented a 

problem of shading understory or limiting the mobility of deer.

Figure 7—Stand 507, 13 years after thinning.

Stand 230, 13 Years After Thinning

This stand was thinned to 5.5- by 5.5-m (18- by 18-ft) spacing at age 21 years. The 

slash was composed of 5- to 15-cm diameter stems. Primary branches of slash were 

decayed but mainly still attached. Cut stems were on the ground with the outside 

Greg Killinger
11

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

2.5 to 5.0 cm decayed and inside wood appearing mainly sound. The understory 

was well developed with good species diversity (fig. 8). Slash had deteriorated 

and settled to the point where it was probably not limiting deer mobility or 

shading understory.

Stand 582, 14 Years After Thinning

This stand was thinned at age 14 years to 4.3- by 4.3-m (14- by 14-ft) spacing. Slash 

stem diameters ranged from 2.5 to 13 cm (1 to 5.2 in) and the stems were partially 

decayed and on the ground. Slash was distributed in a more patchy fashion than 

seen in other stands; this was probably caused by within-stand variation in site 

productivity (figs. 9 and 10). Deer movement would not be restricted between the 

piles of slash. Slash was still shading understory in places, but understory plants 

were evident around the slash. Stand heterogeneity created a range of slash accumulation, which was viewed positively by the team and could be mimicked by varying 

the nominal spacing in highly uniform stands.

Figure 8—Stand 230, 13 years after thinning.

Greg Killinger
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RESEARCH PAPER PNW-RP-594

Figure 9—Stand 582, 14 years after thinning, in an area of relatively light slash accumulation.

Figure 10—Stand 582, 14 years after thinning, in an area of greater slash accumulation.

Michael H. McClellan Michael H. McClellan
13

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Stand 382, 16 Years After Gap Treatment

This stand developed after clearcutting in 1929. The 77-year-old stand was dominated by heavily fluted western hemlock and had very little understory vegetation. 

Gaps measuring 0.08 ha were cut when the stand was 61 years old to improve deer 

forage availability (fig. 11). The treatments were applied at an age far beyond the 

usual precommercial thinning age, so the slash pieces ranged up to 50-cm (19.7-in) 

diameter (fig. 12). Smaller diameter pieces were well decayed and the slash had 

largely settled to the ground, so movement through the treated area was relatively 

easy and few growing places were shaded. Despite the abundant light within the 

gaps, understory biomass appeared much lower than expected. The understory vegetation (fig. 13) showed evidence of heavy browsing by deer: herbs and half-shrubs 

were nearly absent, western hemlock seedlings were severely clipped and rarely 

over 0.3 to 0.6 m (1 to 2 ft) tall, and the only shrub that was thriving was rusty menziesia (Menziesia ferruginea Sm.), whose twigs are known to be eaten in only small 

amounts by deer (Hanley and McKendrick 1985). The intense herbivory observed 

can be explained by several factors. This stand is on a low-elevation south-facing 

slope, so deer would be expected to congregate in this area during the winter. Also, 

the untreated parts of the stand are extensive and in the stem-exclusion phase of 

development, with very little understory present. The vegetation in the gaps was the 

only good source of forage in the stand, so deer were naturally attracted to it.

Figure 11—Stand 382, 16 years after gap creation, looking across a gap into the untreated 77-year-old 

forest. Note the lack of understory vegetation in the untreated area.

Michael H. McClellan
14

RESEARCH PAPER PNW-RP-594

Figure 12—Stand 382, 16 years after gap creation in a 77-year-old stand. Note that trees felled in this 

treatment are larger than those in a typical precommercial thinning.

Figure 13—Heavily browsed western hemlock seedlings in a gap cut in stand 382.

Michael H. McClellan Greg Killinger
15

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Stand 528, 21 Years After Thinning

This stand was thinned at age 17 years to 4.3- by 4.3-m (14- by 14-ft) spacing. The 

slash was on the ground, no longer suspended, with decaying moss-covered stems. 

It would not limit movement of deer or create much shading for understory. Crowns 

have closed since this stand was thinned. There is little remaining understory cover 

in parts of the stand. Dead stems of rusty menziesia and salmonberry (fig. 14) 

are evidence of shady conditions created from canopy closure. The Sitka Ranger 

District has several other treatments in this stand. In 2003, the district installed 

30-m-diameter gaps where all trees were cut, girdled, or pruned.3

 Understory 

vegetation within the gaps responded well to these treatments (figs. 15 and 16).

Figure 14—Stand 528, 21 years after thinning with no further treatment. Note the dead stems of 

understory shrubs.

3 Mechanical girdling kills the tree by cutting through the bark and cambium around the 

circumference of the stem. Two cuts are usually made and the bark may be optionally 

removed between the cuts.

Greg Killinger
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RESEARCH PAPER PNW-RP-594

Figure 15—A 3-year-old gap created by cutting in stand 528, 21 years after thinning.

Figure 16—A 3-year-old gap created by girdling in stand 528, 21 years after thinning. Note the 

minimal amount of slash on the ground.

Michael H. McClellan Michael H. McClellan
17

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Stand 529, 21 Years After Thinning

This stand was thinned to 4.3- by4.3-m (14- by 14-ft) spacing at age 17 years. The 

remaining slash was in the form of small-diameter stems (2.5 to 10 cm [1 to 4 in]), 

on the ground, which broke easily. The small stumps from thinning were rotten. 

The canopy has closed since thinning and little understory was present at the time 

of our observations (fig. 17). Self-pruning did not occur, so there were many dead 

branches retained on leave trees.

Figure 17—Stand 529, 21 years after thinning. Note the lack of understory plants and the smalldiameter stumps from cut trees.

Changes in Wood Density of Slash

The original wood density of cut stems averaged 0.44 g/cm3 with western hemlock 

having slightly higher initial density (0.46 g/cm3) than Sitka spruce (0.42 g/cm3) 

(fig. 18). These values are very close to published specific gravity values, which are 

the same as g/cm3

 at room temperature at sea level, for these two species, which are 

0.45 and 0.40, respectively (Forest Products Laboratory 1987). Our density values 

are averages for live trees from the three stem sections taken from near the bottom, 

middle, and top of stems. Interestingly, the wood collected from near the tops of 

tree stems had slightly higher mean density than wood lower in stems (fig. 19). 

Michael H. McClellan
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RESEARCH PAPER PNW-RP-594

0.55

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

Wood density (g/cm3

)

Time since thinning (years)

0 5 10 15 20 25

Hemlock and spruce slash

Spruce

Hemlock

Figure 18—Mean wood density in young-growth thinning slash for western hemlock and Sitka 

spruce 0 to 24 years after thinning at False Island, Alaska. Error bars represent ±1 standard error.

Figure 19—Mean wood density in young-growth thinning slash of three diameter classes (from 

bottom, middle, and tops of stems) 24 years after thinning at False Island, Alaska. Error bars 

represent ±1 standard error.

0.55

0.50

0.45

0.40

0.35

0.30

0.25

0.20

0.15

Wood density (g/cm3

)

Time since thinning (years)

0 5 10 15 20 25

Slash size classes

Larger diameter (~10 cm, 4 in)

Middle diameter (~6 cm, 2.5 in)

Smaller diameter (~2 cm, 1 in)
19

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Changes in wood density after thinning followed a nonlinear pattern for the 

two species and for different wood piece sizes (figs. 18 and 19). Hemlock wood and 

smaller pieces (stem tops) had higher mean densities than spruce or wood sections 

in the middle and lower stems, but these were not significant differences. 

Because our sampling did not detect differences in initial density or deterioration rates between tree species or among piece sizes, we combined them to produce 

one model of the rate of deterioration of cut western hemlock and Sitka spruce 

young-growth tree stems. The resulting model was a two-phase exponential decay 

function (p < 0.0001):

D = 0.1794e-0.1344t + 0.2570e-0.000725t (4)

Where 

D = wood density

e = natural logarithm (2.7183)

t = time, in years

Wood density from cut tree stems after 24 years was 0.260 g/cm3

, representing 

a loss of about 40 percent from the initial wood density (fig. 20). 

Time-since-death (years)

0 5 10 15 20 25

Wood density (g/cm3)

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

y = 0.1794e-0.1344x + 0.2570e-0.000725x

Figure 20—Mean wood density of western hemlock (circles) and Sitka spruce (squares) dead tree 

stems by time since thinning near False Island, Alaska. Values are mean wood density per tree 

stem from sample pieces taken at the lower, mid, and upper stem. Resulting equation is a two-phase 

exponential decay rate (p < 0.0001) where y = wood density (g/cm3), x = years since death, and 

e = the base of the natural logarithm (2.7183).
20

RESEARCH PAPER PNW-RP-594

Discussion

Initial slash loading appeared to be determined by the stand age at time of thinning, site productivity, and the intensity of silvicultural treatments. Older and 

more productive stands contained more standing volume and generated more slash 

during thinning. As the intensity (spacing) of thinning increased, slash loading 

was observed to increase. We observed the greatest slash loading in a stand that 

was both thinned and pruned at age 27 years. The large tree size, high volume, and 

intensity of treatment yielded deep and continuous slash loads in productive parts of 

the stand (see fig. 2).

Most of the stands we observed had a lot of within-stand variability of slash 

loading. We attributed most of this to within-stand variations in productivity, not 

to variations in thinning intensity. We found that within stands with uniform age 

and thinning prescriptions, the amount of thinning slash was far greater in the 

productive areas than in less productive areas. In the riparian stand we visited, we 

concluded that two factors contributed to the highly variable slash loading: the 

distribution of favorable microsites for conifer regeneration and the presence of 

red alder, which was not cut during thinning. After observing abundant understory 

plants growing under heavy concentrations of slash, we concluded that slash piles 

may have value in protecting plants from herbivory as they develop. By impeding 

deer access, the slash could allow perennial understory plants to develop robust root 

systems and gather resources while protected from herbivory.

We observed two treatment options that appeared successful in older, more 

productive stands where thinning would be expected to generate heavy slash loads. 

Leaving a portion of a stand unthinned is sometimes done to provide a travel corridor for deer, to ease movement between landscape elements, and improve connectivity. We found evidence of heavy use of travel corridors, but also found two 

added benefits. The unthinned areas received side lighting from the thinned areas, 

allowing greater understory development within the unthinned corridor. We also 

found evidence that deer were moving from the corridors into thinned areas with 

lower slash loading in order to browse. The second treatment option is girdling, 

rather than cutting trees to be thinned (see fig. 16). The objective of girdling is to 

kill the tree and have it remain standing, so that it deteriorates slowly rather than 

immediately delivering a large amount of slash to the forest floor. We examined 

a 3-year-old gap that was created by girdling and there was a good understory 

response and very little slash within the gap. One treatment option that is unlikely 

to be used in the future is bucking the slash into shorter pieces to get them to lie 

down. Two bucking treatments are being tested in the TWYGS study, but slash 
21

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

4 Spores, S. 2012. Personal communication. Silviculture program manager, Tongass 

National Forest, Federal Building, Ketchikan, AK 99901-6591.

treatment is very expensive and thinning contractors are extremely reluctant to bid 

on contracts that include bucking or other postthinning slash treatments. In the past, 

it has been difficult for contractors to accurately predict the time and effort required 

to complete slash treatments, so there is considerable risk of underbidding.4

Immediately after operational thinning of young-growth stands, overlapping 

suspended slash stems appeared to present a serious issue for both deer mobility 

and shading of understory plants. These conditions persisted for roughly 9 years at 

False Island. From about 9 to 13 years after thinning, deterioration of side branches 

allowed slash to settle to the ground, where it became less of a barrier to animal 

movement. Slash still shaded some of the understory, but it also protected some 

plants from herbivory, thus creating understory refugia. Slash had not completely 

deteriorated after 13 years and could still be recognized on the forest floor, but there 

was negligible impairment of deer mobility and forage availability by this stage.

Visual inspection of individual cut stems in these stands helped us understand 

a general pattern of deterioration for thinning slash in the False Island area (table 

1). Fine branches were the first to deteriorate and after 9 years, they are gone. 

Bark sloughs off and is missing at about the same time. Initially, cut stems are 

propped up by their primary branches, creating tall, impenetrable layers. These 

side branches can be retained, at least as stubs, long after thinning; however, about 

10 years after thinning, branches become decayed, lose so much strength that they 

break, and allow the main stems to be pushed to the ground under their own weight 

or that of snow. Thus, the deterioration of branches is a key feature involved in the 

progression of slash from complex, deep tangles to simpler, shallow arrays of larger 

stems. The larger cut stems decay more slowly, with more decay on the outside and 

less in the stem interiors, but once they are on the ground and their branches have 

mainly deteriorated, they do not appear to produce much shading to understory 

plants or mobility issues for deer. Visual inspections of the well-decayed stems in 

the older thinned stands suggest that most of the wood decay is by white-rot fungi, 

which degrade both cellulose and lignin. This is in contrast to most of the wood 

decay occurring in dead old-growth hemlock and spruce trees, which is by brownrot fungi, primarily the red belt fungus (Fomitopsis pinicola (Swartz ex Fr.) Karst), 

which degrades cellulose but not lignin.
22

RESEARCH PAPER PNW-RP-594 Table 1—Visual condition of thinning slash 4 to 21 years after thinning at False Island, Alaska Age at Years precommercial since Stand thinning thinning Bark Fine twigs Branches Stem diameter and condition 413 27 4 Fully 90 percent Fully retained 2 to 10 cm on unproductive sites, 15 to 20 cm retained retained on productive sites, larger stems suspended, very little decay 168 29 9 Partially gone Gone Long primary 15 to 18 cm, partially suspended, outer 2 cm branches retained (sapwood) decayed, not breaking

143 20 10 Mostly gone Gone Primary retained Faster decay at this site (a riparian forest), 

 but decayed mainly on the ground and breaking

507 20 13 Mostly gone Gone Primary stubs 2 to 10 cm, stems on ground, 

 retained, decayed smaller stems decayed and breaking and broken

230 21 13 Mostly gone Gone Primary retained 5 to 15 cm, stems on the ground, small stems 

 but decayed thoroughly decayed, larger ones decayed on 

 outside 2 to 5 cm and sound inside

582 14 14 Mostly gone Gone Primary retained 2 to 13 cm, outer 5 cm 

 but decayed of wood decayed, sound in middle

382 61 16 Partially gone Gone Long primary 5 to 50 cm, small stems decaying 

 branches retained breaking, larger ones with decay in outer 

 wood, including F. pinicola

528 17 20 Gone Gone Only primary 10 cm, on the ground, partially decayed 

 stubs remain (both white and brown rots), breaking 

529 17 21 Gone Gone Mainly gone 2 to 8 cm, stems on the ground, moss covered, 

 decay penetrating, but middle sound

Note: This information is not available for stand 522. 
23

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Dynamics of Slash Deterioration and Crown Closure

The habitat benefits of thinning appear to be reduced by slash for a period of 9 

years or so. Once the thinning slash has deteriorated to the point that deer have 

unimpeded access to the stand, the full benefits of understory enhancement are 

realized. At some point, however, the crown growth will lead to canopy closure and 

subsequent losses of understory plants due to shading. The length of this “window 

of opportunity” between slash deterioration and canopy closure seems to be controlled by site productivity, intensity of thinning, and timing of thinning. In general, 

more productive sites will reach canopy closure sooner than less productive sites. 

Figures 21 and 22 illustrate the effects of thinning timing and intensity—thinning 

at younger stand ages and thinning to wider spacing should lead to delayed canopy 

closure. Properly executed girdling treatments will decrease slash accumulation, so 

for any given spacing, girdling should create a longer period of forage availability.

Figure 21—Predicted canopy cover following thinning to a 4.3- by 4.3-m (14- by14-ft) spacing at 

four different stand ages. These predicted results are from a FVS-SEAPROG “bare ground” run for 

a productive site.

Canopy Regrowth Following 14 by 14 ft Thinning

Stand age (years)

Canopy cover (percent)

100

80

60

40

20

0

PCT age 15 years

PCT age 20 years

PCT age 25 years

PCT age 30 years

0 10 20 30 40 50 60
24

RESEARCH PAPER PNW-RP-594

Changes in Wood Density

The wood density variation with height that we observed was similar to that found 

by Farr (1973) in a survey of 20 even-aged stands in southeast Alaska. The lack 

of effect on decomposition rates observed in these stands owing to tree species 

and stem diameter was unexpected, but could be explained by the relatively small 

diameter range of the stem sections. Saprophytic wood decay of dead trees tends to 

occur first on the surface of wood and progresses toward the center of stems. We 

would expect to find different decay rates by stem diameter, especially slower decay 

rates in larger pieces, if we had sampled a greater range of sizes beyond the typical 

12 cm (5 in) thinned stems.

The two-phase exponential decay function is typical for wood decay (Minderman 1968) and can be explained by a rapid early phase of deterioration when the 

wood substrate quality is high, followed by a slower deterioration phase in the 

poorer wood substrate. Note that at time zero, the decay function is simply the sum 

of the two decay coefficients, which sum to the initial wood density, 0.44 g/cm3

. 

Canopy Regrowth Following 18 by 18 ft Thinning

Stand age (years)

Canopy cover (percent)

100

80

60

40

20

0

0 10 20 30 40 50 60

PCT age 15 years

PCT age 20 years

PCT age 25 years

PCT age 30 years

Figure 22—Predicted canopy cover following thinning to a 5.5- by 5.5-m (18- by 18-ft) spacing at 

four different stand ages. These predicted results are from a FVS-SEAPROG “bare ground” run for 

a productive site.
25

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Modeling the rate of decomposition revealed that the wood was initially composed 

of 41 percent (0.1794 g/cm3) fast-decomposing material and 59 percent (0.2570 g/

cm3) more resistant to decomposition. After 24 years, 40 percent of the carbon is 

lost from the slash. Along with assessing the impact of slash on deer habitat, these 

results are useful to incorporate into carbon flux models. Once density is known, 

carbon content can be assumed to be close to 50 percent of wood, whether sound or 

decayed (Sollins et al. 1987).

Applicability of Results

Our observations were confined to a relatively limited part of southeast Alaska, 

so it is reasonable to ask whether the results and conclusions of this study apply to 

southeast Alaska as a whole. Three factors affecting deterioration rates would be 

expected to vary across southeast Alaska: temperature, moisture, and snowpack. 

Decomposition is an enzyme-mediated process and, as such, its rate increases 

with temperature once temperatures exceed 0 to 5 °C. Optimum temperatures for 

wood decomposition are between 25 and 30 °C, and wood-decomposing organisms 

are unable to grow above 40 °C. Within the Tongass, we can expect temperatures to 

be lower than the optimum and to vary with latitude, elevation, aspect, and proximity to the outer coast, glaciers and interior passes. North-south differences could 

be large: southeast Alaska spans about 5° of latitude and work in Finland showed a 

40 percent increase in conifer litter decomposition over an 8° decrease of latitude 

(Mikola 1960).

In some studies, wood decomposition occurred only when moisture contents 

were between 30 and 120 percent of the dry weight. In southeast Alaska, the 

frequent precipitation during the warmest months indicates that moisture is unlikely 

to be limiting, except possibly in the smallest diameter pieces during rare extended 

periods of dry summer weather.

Heavier snowpacks are likely to compress slash over time and reduce the 

overall depth. On the other hand, dense slash or shrubs can suspend snow above 

the forest floor and increase the effective burial depth of forage plants (Hanley et 

al. 2012), as well as make travel more difficult. Where snow cover persists into late 

spring, slash decomposition rates may be depressed. Southeast Alaska experiences 

large variations in climate over relatively short distances and weather monitoring 

stations are few and far apart, so it is unlikely we will have good data on snowpack 

persistence. Local managers, however, often have a good sense of where “snow 

holes” exist on their districts and their insights will be useful.
26

RESEARCH PAPER PNW-RP-594

Future research would be needed to judge the applicability of these results to 

more southern locations in southeast Alaska. One possibility would be to repeat 

this study on Prince of Wales Island, which has a long history of precommercial 

thinning. Another opportunity lies in the TWYGS study.5 In TWYGS experiments 

2, 3, and 4, slash depth and cover are estimated on each understory vegetation 

sample quadrat. Over time, repeated measurements on the TWYGS sites will 

yield good information on slash loading and deterioration related to a range of 

silvicultural treatments.

Conclusions

Based on our observations at False Island, discussions with silviculturists and wildlife biologists, and observations elsewhere in southeast Alaska, we have concluded 

with the following list of observations (4 and 6) and hypotheses (1, 2, 3, 5, and 7):

(1) Initial slash loading is a function of stand age at time of thinning, microsite 

productivity, and the intensity of treatment. Older and highly productive 

stands contain more standing volume that is converted to slash during thinning. Slash loads increase with wider spacing, and pruning adds additional 

slash.

(2) Very few thinned stands will have uniform loading of slash. Within-stand 

variations in productivity or availability of favorable microsites (as in riparian stands) will lead to heavy concentrations of slash in some areas and 

small amounts of slash in others. Concentrations of slash may have value in 

protecting plants from herbivory as they develop.

(3) Where heavy slash is expected—as in thinning productive older stands—

deer access to stands can be improved by leaving unthinned travel corridors 

or by using girdling rather than cutting as a means of killing trees. Slash 

treatments, such as cutting trees into smaller lengths, are unlikely to be 

done owing to resistance from thinning contractors.

(4) In the stands we observed, slash was likely to impede deer movement until 

about 9 years after thinning. From 9 to 13 years, slash no longer affected 

deer mobility, but some shading of understory occurred. Initial slash loading and winter snow accumulation could affect this timing.

5 McClellan, M.H.; De Santo, Toni L. [N.d.]. Tongass-Wide Young-Growth Studies: study 

plan and establishment report. Manuscript in preparation.
27

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

(5) Thinning creates a “window of opportunity” that lasts from the time that 

thinning slash ceases to impede deer movement through the stand to the 

time the overstory canopy closes again and the understory dies off. The 

length of this window can be controlled by the timing and intensity of thinning, or by subsequent treatments.

(6) Tree species and diameter of stem wood had little effect on decomposition 

rates observed in these stands. Modeling the rate of decomposition revealed 

that the wood was initially composed of 41 percent fast-decomposing 

material and 59 percent material more resistant to decomposition. After 24 

years, 40 percent of the carbon is lost from the slash.

(7) The landscape context is critical to predicting the potential wildlife benefits 

of silvicultural treatments. Heavy slash loads in a few stands may be of little consequence in a landscape with abundant available forage. Conversely, 

small-scale treatments set in landscapes with limited forage may create 

overly intense herbivory and destruction of the understory. Thoughtful 

placement and timing of thinning treatments can provide forage dispersed 

across the landscape by considering the location of sites during the “window of opportunity” when deer have access and forage is still available.

Acknowledgments

Thanks to Jim Russell for initiating this project and to fellow team members 

Scott Snelson, Greg Killinger, Jim Brainard, and Jeff Garnette. Pat Cunningham 

provided valuable advice on the decomposition model. We also thank Tom Hanley, 

Sheila Spores, and Greg Hayward for their reviews of this report.

English Equivalents

When you know: Multiply by: To find:

Centimeters (cm) 0.394 Inches

Meters (m) 3.28 Feet

Meters 1.094 Yards

Kilometers (km) 0.6215 Miles

Hectares (ha) 2.47 Acres

Square meters per hectare (m2/ha) 4.37 Square feet per acre

Grams (g) 0.0352 Ounces

Grams 0.0022 Pounds

Grams per cubic centimeter (g/cm3

) 62.43 Pounds per square foot

Degrees Celsius (°C) 1.8 °C + 32 Degrees Fahrenheit
28

RESEARCH PAPER PNW-RP-594

Literature Cited

Bergquist, J.; Örlander, G. 1998. Browsing damage by roe deer on Norway 

spruce seedlings planted on clearcuts of different ages: 1. Effect of slash removal, 

vegetation development, and roe deer density. Forest Ecology and Management. 

105: 283–293.

Bergquist, J.; Örlander, G.; Nilsson, U. 1999. Deer browsing and slash 

removal affect field vegetation on south Swedish clearcuts. Forest Ecology and 

Management. 115: 171–182.

Doerr, J.G.; Sandburg, N.H. 1986. Effects of precommercial thinning on 

understory vegetation and deer habitat utilization on Big Level Island in 

southeast Alaska. Forest Science. 32: 1092–1095.

Farr, W.A. 1973. Specific gravity of western hemlock and Sitka spruce in 

southeast Alaska. Wood Science. 6: 9–13.

Forest Products Laboratory. 1987. Wood handbook: wood as an engineering 

material. Agric. Handb. 72. Washington, DC: U.S. Department of 

Agriculture. 466 p. 

Grisez, T.J. 1960. Slash helps protect seedlings from deer browse. Journal of 

Forestry. 58: 385–387.

Harmon, M.E.; Sexton, J. 1996. Guidelines for measurements of woody detritus 

in forest ecosystems. Publication No. 20. Seattle, WA: University of Washington, 

College of Forest Resources, U.S. LTER Network Office. 73 p.

Husch, B.; Miller, C.I.; Beers, T.W. 1972. Forest mensuration. 2nd ed. New York: 

The Ronald Press Company. 410 p.

Hanley, T.A.; McKendrick, J.D. 1985. Potential nutritional limitations for blacktailed deer in a spruce-hemlock forest, southeastern Alaska. Journal of Wildlife 

Managment. 49: 103–114.

Hanley, T.A.; Spalinger, D.E.; Mock, K.J.; Weaver, O.L.; Harris, G.M. 2012.

Forage resource evaluation system for habitat—deer: an interactive deer habitat 

model. Gen. Tech. Rep. PNW-GTR-858. Portland, OR: U.S. Department of 

Agriculture, Forest Service, Pacific Northwest Research Station. 64 p.

Krueger, L.M.; Peterson, C.J. 2009. Effects of woody debris and ferns on 

herb-layer vegetation and deer herbivory in a Pennsylvania forest blowdown. 

Ecoscience. 16: 461–469.
29

Condition and Deterioration Rate of Precommercial Thinning Slash at False Island, Alaska

Lyon, L.J.; Jensen, C.E. 1980. Management implications of elk and deer use of 

clear-cuts in Montana. The Journal of Wildlife Management. 44: 352–362.

McClellan, M.H. 2008. Adaptive management of young stands on the Tongass 

National Forest. In: Deal, R.L., ed. Integrated restoration of forested ecosystems 

to achieve multiresource benefits: proceedings of the 2007 national silviculture 

workshop. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific 

Northwest Research Station: 225–232.

Mikola, P. 1960. Comparative experiment on decomposition rates of forest litter in 

southern and northern Finland. Oikos. 11: 161–166.

Minderman, G. 1968. Addition, decomposition and accumulation of organic 

matter in forests. Journal of Ecology. 56: 355–362.

Parker, K.L.; Robbins, C.T.; Hanley, T.A. 1984. Energy expenditures for 

locomotion by mule deer and elk. The Journal of Wildlife Management. 

48: 474–488.

Reynolds, H.G. 1969. Improvement of deer habitat on southwestern forest lands. 

Journal of Forestry. 67: 803–805.

Rumble, M.A.; Pella, T.; Sharps, J.C.; Carter, A.V.; Parrish, J.B. 1996. Effects 

of logging slash on aspen regeneration in grazed clearcuts. Prairie Naturalist. 

28: 199–209.

SAS Institute, Inc. 2009. SAS/STAT® 9.2 User’s guide. Cary, NC: SAS 

Institute, Inc.

Sollins, P.; Cline, S.P.; Verhoeven, T.; Sachs, D.; Spycher, G. 1987. Patterns 

of log decay in old-growth Douglas-fir forests. Canadian Journal of Forest 

Research. 17: 1585–1595.



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