United States 

Department of 

Agriculture 

Forest 

Service 

Northern 

Region 

200 East Broadway 

P.O. Box 7669 

Missoula, MT 59807 

Numbered Report 06-12 December 2006

CHANGES IN FIRE-KILLED WESTERN LARCH ON THE GLACIER VIEW RANGER 

DISTRICT (FLATHEAD NATIONAL FOREST), MONTANA 

YEAR FIVE REPORT 

Marcus Jackson, Plant Pathologist 

USDA Forest Service, Forest Health Protection 

Northern Region, Missoula, MT 

INTRODUCTION 

This is the third of several reports describing 

progress in a ten- or more-year study evaluating 

changes of fire-killed western larch in 

northwestern Montana. Trees included were 

killed by the Moose Fire on the Flathead 

National Forest in fall 2001. This study 

evaluates more than 350 trees (240 dissected), 

looks at a large range of sizes (Table 1), and 

evaluates fire-killed trees over an extended 

period of time. 

Table 1. Tree Locations and Site Characteristics

Number of Trees Per Size ClassA

Site 1 2 3 4 Total

Average

SlopeB

 AspectC

Habitat 

TypeD

Central 

ElevationE

1 67 30 7 1 105 25% West ABLA/CLUN 3,880 

2 2 4 5 17 28 20% Southwest ABLA/LIBO 3,880 

3 11 16 18 20 65 14% VariableF ABLA/CLUN 3,840 

4 1 22 24 42 89 35% West ABLA/CLUN 3,720 

5 5 16 38 21 80 38% Northeast ABLA/MEFE 4,100 

Total 86 88 92 101 367 

A Number of trees tagged for each size class at each site. Size Class 1 = 8 to 11.9 inches dbh, Size Class 2 

=12 to 15.9 inches dbh, Size Class 3 = 16 to 19.9 inches dbh, and Size Class 4 = 20 to 38 inches dbh. 

B

 Average percent slope across site. 

C Predominant aspect at the site. 

D Predominant habitat type (h.t.) as defined in Pfister et al. (1977). Site 1 has some trees 

 that are in ABLA/XETE h.t., Site 2 has some ABLA/XETE h.t. and PICEA/CLUN h.t., 

 and Site 5 has some in the ABLA/CLUN h.t. 

E

 Elevation in the geographic center of the site. 

F

 Mostly southwest and northeast. 
2

This report describes observations of all standing 

trees and dissections five years post-fire. For 

additional information about purpose, methods, 

and first through fourth year findings see Forest 

Health Protection Reports 04-16 (Jackson 2004) 

and 05-06 (Jackson and Bulaon 2005). More 

dissections are planned for seven and ten years 

post-fire. 

METHODS 

Standing Tree Evaluations

In early September 2006, all trees tagged in 2002 

and not yet dissected were observed to determine 

if they were standing, had broken tops, sloughed 

bark, or conks present. Bark was considered 

"sloughed" when exposed wood could be seen as 

a result of separation of bark from wood and was 

not caused by woodpecker foraging or rubbing 

from nearby fallen trees. In the year four 

evaluation (Jackson and Bulaon 2005), all 

broken tops were counted, while in the year five 

evaluation only trees with broken tops below an 

estimated four inch diameter top were considered 

broken since four inches was identified as the 

minimum disk size. When conks were observed, 

fungal species and location of conks were noted. 

Dissection Data

In mid September 2006, ten trees were dissected 

in each size class with wood borer, check, wood 

stain, and peripheral decay data collected. In the 

first two reports, the term 'sapwood decay' was 

used to describe decay around the periphery of 

the disks since almost all peripheral decay was 

confined to the sapwood during the first three 

years of dissections. Considerable decay that 

originated on the periphery of the disks moved 

into the heartwood prior to the year five 

dissections; therefore, 'peripheral decay' is a 

more appropriate term for description of post-fire 

initiated decay. Given variability in feller skill, 

breakage was not included in defects described 

in this report. Loss to breakage should be 

included in estimates of total merchantable 

volume. 

RESULTS & DISCUSSION 

Evaluation of All Standing Trees

Five years after the fire, no trees had fallen due 

to natural causes. Of the original 367 trees 

identified and tagged, one was removed from the 

data set because it was a Douglas-fir, one was 

lost to firewood cutters, 120 had been dissected, 

and the remaining 245 were still standing. Two 

hundred-sixteen (88%) of the standing trees had 

sloughing bark. 

Twenty-eight (11%) of the 245 standing trees 

had broken tops. Only 11 of the 22 broken tops 

that were reported in a previous report (Jackson 

and Bulaon 2005) were included in the 28 

identified as having broken tops in year five 

post-fire (see Methods above). Twenty-seven of 

the broken tops were at Site 1 while one broken 

top was at Site 2. The broken top at Site 2 

occurred prior to the year four evaluation of all 

standing trees. Ten (37%) of the 27 trees at Site 

1 were broken prior to the year four evaluation 

and 17 (63%) of the 27 trees were broken 

between the year four and year five standing tree 

evaluations. Although weather events (wind or 

heavy snow loads) may have been factors at Site 

1, extensive wood borer activity and peripheral 

decay probably contributed significantly to the 

large number of broken tops at that site. Eight 

broken topped trees were dissected in 2006. Six 

of the eight dissected trees had extensive 

peripheral decay (40% to 90% of disk area) and 

six of the eight contained wood borer galleries in 

the highest disk (first disk directly below the 

break). All dissected trees with broken tops had 

extensive peripheral decay, five or more wood 

borer galleries, or a combination of decay and 

wood borer galleries in the disk directly below 

the break. 

Fruiting bodies of the decay-causing fungus 

Fomitopsis pinicola (Swartz:Fr.) Karst were 

found on more than 1/3 of the trees and 

Trichaptum abietinum (Dickson:Fr.) Ryvarden 
3

and Cryptoporus volvatus (Pk.) Shear were each 

observed on less than ten trees. 

Dissection Data

Agent (wood borer, check, stain, and peripheral 

decay) data from dissections are summarized for 

each tree and size class in Table 2. 

Wood Borers 

Although no trends have developed regarding 

differences in wood-boring insect depth across 

size classes throughout this study (Jackson and 

Bulaon 2005; Table 2 of this report), wood borer 

holes per square foot of disk area decreased with 

increasing tree size every year including year 

five. The greater number of wood borer holes 

per square foot in the smaller diameter classes 

can probably best be explained by the fact that 

disk area increased exponentially as disk 

diameter increased incrementally. In previous 

years (Jackson and Bulaon 2005), it was noted 

that roughly the same number of insects attacked 

each disk; therefore, substantially more area was 

affected on smaller disks than larger disks and 

smaller trees than larger trees. 

Checks 

It's difficult to compare check data between 

years since there were no checks observed one 

year post-fire and abnormally high precipitation 

in the three months prior to data collection three 

years post-fire greatly reduced the number and 
4

 Table 2. Agent Data Summarized by Tree Five Years after the Moose Fire 

Tree 

No. 

DBHA 

(inches) 

AgeB 

(Years) SiteC

Deepest 

BorersD 

(mm) 

Borer 

Holes/Sq. 

FootE

StainF 

(Percent)

Peripheral

DecayG 

(Percent)

Deepest 

CheckH 

(mm)

No. of 

ChecksI

Sapwood 

Volume 

(Percent)J

929 8.2 91 5 18 0.7 1.3 0 119 2.1 57.9 

923 8.7 84 5 60 3.9 6.0 3.9 92 1.3 46.0 

619 8.9 87 1 20 2.5 1.7 9.7 77 0.6 38.7 

548 9.7 81 1 24 7.7 6.6 10.9 90 1.4 35.5 

583 10.3 88 3 79 10.4 0.7 0.8 68 1.3 36.7 

535 10.5 81 1 61 9.4 0.5 17.1 95 0.8 37.7 

624 10.8 81 1 40 10.0 1.3 49.8 95 0.7 44.5 

611 11.3 82 1 40 8.7 2.5 31.1 60 0.4 38.5 

683 11.6 183 3 25 3.8 1.8 2.5 40 2.4 22.8 

543 11.8 88 1 60 12.6 3.6 12.0 107 0.7 33.2 

MDCK 10.2 95 - 43 7.0 2.6 13.8 84.3 1.2 39.2 

510 12.3 91 1 44 5.6 7.2 7.2 108 1.1 24.1 

534 12.7 86 1 74 14.0 2.3 40.5 55 0.4 33.0 

547 13.0 77 1 80 3.7 5.0 9.4 120 2.2 38.7 

671 13.2 228 3 68 3.7 0.6 17.6 69 1.0 34.5 

700 13.6 95 1 92 9.3 2.0 18.5 120 1.7 40.5 

642 14.0 85 1 54 12.1 2.6 30.7 100 1.6 34.4 

509 15.2 82 1 62 5.0 0.8 31.2 124 0.8 27.2 

701 15.5 227 4 35 2.7 2.9 16.1 55 0.5 25.8 

742 15.5 214 4 85 0.4 0.7 12.2 80 0.3 28.4 

674 15.9 201 3 45 1.2 0.6 17.4 80 0.1 25.8 

MDC 14.1 139 - 64 5.8 2.5 20.1 91.1 1.0 31.2 

963 16.2 198 5 74 5.6 5.8 5.3 130 2.4 25.5 

745 16.7 220 4 50 1.3 0.5 16.0 0 0 20.3 

776 17.2 217 4 64 4.8 1.5 25.3 70 0.2 22.1 

760 17.4 204 4 38 0.9 1.2 12.5 65 1.1 24.9 

943 18.1 227 5 37 4.2 2.1 22.3 90 0.7 27.0 

941 18.2 202 5 80 3.0 1.3 16.6 122 1.5 31.7 

936 18.7 210 5 42 2.0 1.8 18.0 103 1.2 24.4 

919 19.2 232 5 40 1.6 1.5 13.1 38 0.6 22.3 

723 19.3 210 4 40 2.5 0.9 13.3 157 0.1 18.2 

912 19.9 222 5 56 2.0 0.1 19.1 32 0.1 24.2 

MDC 18.1 214 - 52 2.8 1.7 16.2 80.7 0.8 24.1 

734 20.4 174 4 40 1.7 0.9 16.3 74 2.8 20.2 

716 21.0 221 4 40 2.9 0.6 21.7 180 0.5 24.9 

913 21.2 203 5 31 1.6 3.8 23.7 75 1.2 28.6 

659 21.8 194 3 84 1.2 4.1 3.4 119 5.9 19.3 

790 22.8 192 5 57 4.2 0.1 15.0 66 0.5 28.2 

708 23.5 240 4 40 2.9 3.8 20.7 72 1.9 26.3 

755 24.0 223 4 40 2.6 1.4 14.0 81 2.7 22.8 

673 25.2 204 3 57 2.0 1.6 11.5 18 0.1 19.7 

732 26.9 184 4 42 1.8 0.2 15.6 50 1.5 17.8 

678 28.8 202 3 120 3.0 1.6 12.8 95 0.4 25.8 

MDC 23.6 204 - 55 2.4 1.8 15.5 83 1.8 23.4 

See legend on next page.
5

Legend for Table 2.

ADiameter at breast height (4.5 feet above ground level). 

B

Age-estimated by counting annual rings at the stump. 

C

 Tree location (see Jackson 2004). 

DDistance of wood borer hole that was furthest from the edge of wood on any disk from the tree. 

E

Average number of wood borer holes per square foot of disk area observed. 

F

Estimated percent cubic volume affected by sapwood stain. Estimated by calculating volume of each log 

using Smalian's Formula for a paraboloid frustum and multiplying total volume of the log by the mean of 

percent area affected by sapwood stain on disk at each end of the log. Total stain volume in the tree was 

then divided by total tree volume. 

 

GEstimated percent cubic volume affected by peripheral decay. Estimated by calculating volume of each 

log using Smalian's Formula for a paraboloid frustum and multiplying total volume of the log by the mean 

of percent area affected by peripheral decay on disk at each end of the log. Total peripheral decay volume 

in the tree was then divided by total tree volume. 

HDepth of deepest check found on any disk from the tree. 

I

Quotient when total number of peripheral checks on all disks are divided by total number of disks on that 

tree. 

J

Percent sapwood volume estimated by calculating total volume of each log and heartwood volume of 

each log using Smalian's Formula for a paraboloid frustum. Heartwood volume was then subtracted from 

total volume, with the difference divided by total volume and multiplied by 100. 

KMDC - mean for diameter class. Mean for the ten values in diameter class, except wood borer depth 

means only include trees where wood borers were found. 
6

size of visible checks for that year. Peripheral 

decay five years after the fire reduced the ability 

to adequately identify the number of small 

checks. However, the trend towards more 

checks in the largest diameter class compared to 

the three smaller diameter classes continued 

(Table 2). This may be due to greater surface 

area associated with larger disks on larger trees. 

No trend has developed regarding deepest checks 

for different size classes.

Stain 

A reduction in stain of at least 50% in all size 

classes (Table 2) compared to measurements 

three years post-fire (Jackson and Bulaon 2005) 

were observed. Others have suggested that 

sapwood stain volume decreases in fire-killed 

conifers as some of the stained wood is 

consumed by sapwood decay fungi (Kimmey 

1955; Hadfield and Magelssen 2006). This is 

probably why we observed less stain. The two 

smaller size classes contained a higher 

percentage of sapwood stain compared to the two 

larger size classes. Larger percent disk surface 

area containing sapwood in younger trees 

contributed to this difference. 

Peripheral Decay 

Peripheral decay has increasingly become a 

significant agent of change as time progressed 

(Jackson and Bulaon 2005). As with sapwood 

stain, percent peripheral decay is generally 

greater in smaller diameter trees due to a higher 

percentage of sapwood. However, peripheral 

decay accounted a greater proportion of more 

volume in the 12 to 16 inch dbh size class than 

the 8 to 12 inch dbh size class five years postfire. One possible explanation for this 

discrepancy in the data is the broken tops. Five 

trees in the 12 to 16 inch size class had broken 

tops and three of the trees in the 8 to 12 inch size 

class had broken tops. Since percent peripheral 

decay generally decreased with increasing disk 

height above approximately 20 feet (Jackson and 

Bulaon 2005) and approximately two disks were 

lost above the breaks in the 12 to 16 inch size 

class, some solid wood was probably lost from 

those trees - increasing the overall decay 

percentage. Only one or no disks were lost from 

each of the broken trees in the 8 to 12 inch size 

class. A second explanation is the rate of decay 

may be different at various sites. Of the trees in 

Size Class 1, all four of the least decayed trees 

were in sites other than Site 1. A third 

explanation for the lower decay may be the 

effect that checks have on smaller diameter trees. 

Given the deepest check length and number of 

checks are similar in the three smaller size 

classes (Jackson and Bulaon 2005; Table 2 of 

this report); a larger portion of a tree in the 

smallest size class may be drying more quickly, 

causing the tree to be a less suitable substrate for 

decay-causing fungi. Future dissections should 

show whether decay slows in the smaller size 

classes as time progresses or if this discrepancy 

is purely a result of an inadequate sample size 

and/or due to the other explanations presented 

above. 
7

REFERENCES CITED 

Hadfield, J. S., and Magelssen. R. M. 2006. 

Wood Changes in Fire-Killed Tree 

Species in Eastern Washington. USDA 

For. Serv., Okanogan and Wenatchee 

National Forests, Wenatchee, WA. 49p. 

Jackson, M.B. 2004. Changes in Fire-Killed 

Western Larch on the Glacier View 

Ranger District (Flathead National 

Forest), Montana: Establishment and 

Year One Report. USDA For. Serv. 

Forest Health Protection Rpt. 04-16. 

Missoula, MT. 13p. 

Jackson, M.B. and B. Bulaon. 2005. Changes in 

Fire-Killed Western Larch on the Glacier 

View Ranger District (Flathead National 

Forest), Montana: Years Two, Three, and 

Four Report. USDA For. Serv. Forest 

Health Protection Rpt. 05-06. Missoula, 

MT. 20p. 

Kimmey, J.W. 1955. Rate of Deterioration of 

Fire-killed Timber in California. USDA 

Circular No. 962. 22p. 

ACKNOWLEDGEMENTS 

The author thanks Marylou Zimmerman and 

Keith VanBroeke of the Hungry Horse and 

Glacier View Ranger Districts for providing 

local support. He also thanks Blakey Lockman 

and Gregg DeNitto of the Forest Health 

Protection field office in Missoula for their 

reviews and constructive comments regarding 

this report and Jen Durilla for final formatting.