United States 

Department of 

Agriculture I 

Forest Service 

Northeastern Forest 

Experiment Station 

Research Paper NE-648 

Photographic Guide of Selected 

External Defect Indicators and 

Associated Internal Defects 

in Yellow Birch 

Everette D. Rast 

John A. Beaton 

David L. Sonderman 
Abstract 

To properly classify or grade logs or trees, one must be able to correctly identify 

indicators and assess the effect of the underlying defect on possible end products. 

This guide assists the individual in identifying the surface defect indicator and 

shows the progressive stages of the defect throughout its development for yellow 

birch. Eleven types of external defect indicators and associated defects that are 

particularly difficult to evaluate are illustrated and described. 

The Authors 

EVERETTE D. RAST, forest products technologist, received a B.S. degree in 

forestry from the University of Missouri in 1960 and an M.S. degree in agricultural 

economics from The Ohio State University in 1970. He joined the USDA Forest 

Service in 1960 as a forester on the Mendocino National Forest and transferred to 

the Northeastern Forest Experiment Station, Delaware, Ohio, in 1966. From 1966 

to 1987 hie was with the log and tree grade project, and then the management and 

utilization alternatives for nonindustrial private forests. In 1987 he was transferred 

to the Station's Forestry Sciences Laboratory in Princeton, West Virginia, as a 

member of the Advanced Hardwood Processing and Technical Resource Center. 

JOHN A. BEATON, forestry technician, received a certificate as a forest technician 

from Lake City Junior College and Forest Ranger School, Lake City, Florida, in 

1964. He joined the Forest Service in October 1964 as a forestry aid at the Forest 

Insect and Disease Laboratory, Delaware, Ohio. In November 1976, he was 

transferred to Project 1351, Northeastern Forest Experiment Station, Delaware, 

Ohio, as a forestry technician. 

DAVID L. SONDERMAN, forest products technologist, joined the Northeastern 

Forest Experiment Station in 1962 and was on the staff of the Eastern Softwood 

Timber Quality project until 1972. From 1972 to 1987 he was located at Delaware, 

Ohio, with the Northeastern Station's project on management and utilization 

alternatives for nonindustrial private forests. HB is currently with the Station's 

Forestry Sciences Laboratory at Princeton, West Virginia. 

Manuscript received for publication 24 September 1990 

Northeastern Forest Experiment Station 

5 Radnor Corporate Center 

100 Matsonford Road, Suite 200 

P.O. Box 6775 

Radnor, Pennsylvania 19087 

May 1991 
Introduction 

This photographic guide on yellow birch is the seventh in a 

series designed to assist in the understanding of the relationship 

between exterior defect indicators and the underlying defect. 

In this study, like the yellow-poplar (Rast et al. 1990) and white 

oak (Rast et al. 1989) studies, bolts were sliced and photographs 

of interior defects were taken at the USDA Forest Service's 

Forest Products Laboratory in Madison, Wisconsin. In this 

publication we provide a stereo pair of photographs of the 

defect indicators to give the user a more realistic view. 

Twelve yellow birch trees on the Florence Ranger District of 

the Nicolet National Forest in northeastern Wisconsin were 

selected, felled, and bucked into twenty-three Cfoot bolts 

containing the defects selected to be studied. Many of the 

bolts contained two or more defects. The bolts were 

carefully transported to a warehouse to be photographed. 

This controlled environment enabled us to take quality 

photographs of defect indicators and provided a good 

storage area for the bolts until the film was processed and 

the prints checked. 

The ends of the bolts were marked off in quadrants using 

the geometric center as the midpoint. The quadrants were 

aligned to keep all of the defects in quadrant 1 or 2, if 

possible. A 1-inch groove was routed along the 3-4 quadrant 

line, providing an identification mark in the rotary-cut veneer 

for clipping. By clipping at this point, each sheet of veneer 

was one complete revolution qf the log. This provided a 

method for identifying thy correct defects corresponding to 

the surface defect indicators that were photographed. 

Prior to slicing, the bolts were steam-heated in a water vat 

just enough to loosen the bark. Next, the bolts were 

debarked by hand, replaced in the vats, and heated to the 

correct slicing temperature. A bolt was then removed from 

the vat, chucked in the lathe, and rotary sliced into 

1110-inch-thick veneer. Before getting a continuous sheet of 

veneer, the round-up pieces of veneer were counted and 

those necessary for photographing were saved. Once it 

began coming off in a continuous sheet, the veneer was 

clipped at the notch in the small end and stacked by bolts. 

The bolt number was put on the first and last sheet of 

veneer to identify each bolt. Only 10 to 15 bolts were sliced 

at a time so the defects could be photographed the same 

day to prevent stain or discoloration. Then the veneer was 

put in cold storage before drying. 

Discussion of Defects 

The defect indicators reported in this publication are: 

suppressed bud; adventitious bud; suppressed bud cluster; 

open bird peck; light, medium, and heavy distortions; new 

and old sound wounds; seam; and gunshot wound. We 

believe that these indicators often are difficult to identify 

and evaluate in terms of their effect on end-product quality. 

Graders normally have little difficulty recognizing and 

evaluating obvious grading defects such as limbs, forks, 

bumps, and butt scars. 

The photo format for each defect evaluated in this 

publication is, first, a pair of stereo photographs of the 

defect indicator on the log surface. Next is an enlarged set 

of prints showing the defect indicator followed by a series of 

prints of the actual defect as it appears at different depths 

below the log surface. Below the photo of the defect 

indicator (Fig. 1) is a list that describes the size of the defect 

in terms of length (along the grain), width (across the grain), 

and height (above the normal bark contour); log diameter, 

inside the bark (ib) at the defect; round-up thickness; core 

diameter; and distance of defect above the stump. The 

information listed below the interior defect (Fig. 1) indicates 

distance below the log surface (inside the bark) as well as 

the distance from the first slice of veneer to that particular 

photographed defect. The last photograph in each defect 

series also lists total veneer thickness, which is the 

distance from the initial slice of usable veneer to the veneer 

core. 

Suppressed and Adventitlous Buds 

Epicormic branches develop from two types of buds: 

suppressed or dormant buds and adventitious buds 

(Kormanik and Brown 1969 and Shigo 1986). Suppressed 

buds (Fig. 1) can persist for many years as a bud trace or 

they can sprout suddenly after some stimulus such as 

thinning or damage to the tree. After sprouting, many 

develop into small limbs that often die, but the bud trace 

usually continues to form in the cambial zone even after the 

epicormic limb dies and eventually drops off, sometimes 

forming another epicormic limb that also dies and drops off. 

Or the suppressed bud may cease all activity in the cambial 

zone following its occurrence, showing no evidence of the 

bud trace. By contrast, an adventitious bud (Fig. 2) forms 

anew from the cambium, usually following injury to the tree. 

The defect indicator for both bud types is identified by a 

slight break in the bark pattern with a small protuberance in 

the center. 
Figure 1 .-Suppressed bud and associated internal defects. 

Stereo view of defect indicator 

Defect size . 1/2 x 1/2 inches Depth belowLog.diameter at defect (ib) .............. 16.4 inches 

Round-up thickness ................... 0.0 ................................ inch Logsurface 0.Oinch 

Core ....................... ........................ diameter. 6.8 inches First sheet of veneer 0.0 inch 

Defect distance above stump. ........... 8.5 feet 
Figure 1 (Continued) 

Depth belowLog surface ......................... 4.7inches 

First sheet of veneer .................. 4.7 inches 

Total Veneer Thickness. ............... 2.8 inches 

Figure 2.-Adventitious bud and associated internal defects. 

Stereo view of defect indicator 
Figure 2 (Continued) 

Defect size ............................ I x 1 inches Depth belowLog diameter at defect (ib). ............... 12.0 inches 

Round-up thickness. .................... 0.5 inch Logsurface ................................ O.Oinch 

Core diameter ......................... 5.6 inches First sheet of veneer ........................ 0.5 inch 

Defect distance above stump ............. 19.0 feet 

Depth belowLogsurface .............................. 0.5inches 

First sheet of veneer. ...................... 1.0 inches 

Depth belowLogsurface .............................. 0.8inch 

First sheet of veneer. ...................... 1.3 inches 

Total Veneer Thickness .................... 2.8 inches 
Suppressed Bud Cluster 

As its name implies, a suppressed bud cluster is a 

group of suppressed buds (3 to 20) tightly clustered in a 

small area, normally 2 by 2 inches or less in size. Usually, 

there is evidence of concentric rings around the defect 

indicator. Figure 3 does not show the presence of the 

concentric rings around the defect indicator, but this is 

common in thin-barked trees such as yellow birch. The 

small protuberance associated with a single bud is much 

larger with this suppressed bud cluster and there is 

evidence of several individual buds. Also, two 

adventitious knots are clearly visible in the first defect photo 

(4.3 inches below log surface) and several others can be 

detected in the third defect photo (5.1 inches below log 

surface). 

Figure 3.-Suppressed bud cluster and associated internal defects. 

Stereo view of defect indicator 
Figure 3 (Continued) 

Defect size ............................ 2 x 2 inches 

Log diameter at defect (ib). ............... 18.0 inches 

Round-up thickness ..................... 0.0 inch 

Core diameter ......................... 5.9 inches 

Defect distance above stump ............. 5.0 feet 

Depth belowLog surface .............................. 4.8 inches 

First sheet of veneer. ...................... 4.8 inches 

Depth belowLogsurface .............................. 4.3inches 

First sheet of veneer. ...................... 4.3 inches 

Depth belowLog surface .............................. 5.1 inches 

First sheet of veneer. ...................... 5.1 inches 
Figure 3 (Continued) 

Depth belowLog surface. ............................. 5.3 inches 

First sheet of veneer. ...................... 5.3 inches 

Total Veneer Thickness .................... 6.5 inches 

Bird Peck 

Bird peck is evaluated by determining whether callus tissue 

is formed in the peck holes (Rast et al. 1973). If the peck 

holes are open, the pecks did not reach the cambium layer 

and there will be no damage. But if the peck holes are 

closed (callus material present), there will be damage to the 

tree. Bird pecks are sometimes considered as old or new. 

However, this classification should not be used except to 

say that new bird pecks can be disregarded in grading logs 

and trees, whether or not they reach the cambium layer, so 

long as the tree is cut shortly after injury. The rationale is 

that the peck defects will be removed during the initial 

stages of primary processing of the log (debarking, 

slabbing, or round-up). 

Figure 4 shows open bird peck that is not occluded and, 

therefore, can be disregarded. No photos of the veneer 

were taken since there were no defects in the underlying 

wood. 

In the area where our study trees were selected, we found 

only one tree with bird peck (the open bird peck shown in 

Figure 4). But this does not mean that bird peck is not a 

problem in yellow birch; in fact, it can be a major problem. 

For evidence of bird peck in the underlying wood, see other 

photo guides or publications listed in the back of this 

publication. Severe bird peck in any species can lead to a 

separation of the wood along the rings. 
Figure 4.-Open bird peck. 

Stereo view of defect indicator 

Defect size ............................ 1 x 6 inches 

Log diameter at defect (ib). ............... 13.0 inches 

Round-up thickness ..................... 0.7 inch 

Core diameter ......................... 5.6 inches 

Defect distance above stump ............. 24.5 feet 
Bark Distortions 

Bark distortions usually indicate an overgrown knot, and 

because of age they have no height measurement (flush 

with the normal contour of the bark). They are classified as 

light, medium, or heavy. A light bark distortion (Fig. 5) 

shows a slight amount of curvature in the surrounding bark 

plates, and the bark pattern varies only slightly from normal. 

Because of these features, light bark distortions are 

inconspicuous and often overlooked. Medium bark 

distortions (Fig. 6) show more of the concentric circles, but 

they are broken in several areas by the regular bark pattern 

running lengthwise through the defect indicator. Also, there 

can be present moderate to well-defined breaks in the bark 

pattern running radially from the outer edges to the center 

of the defect indicator. Heavy bark distortions (Fig. 7) are 

identified by the characteristic pattern of concentric circles 

encompassing the defect indicator and "pucker-like" 

appearance of the center. 

All bark distortions result in some product degrade, but the 

amount of degrade decreases as the depth to the initial 

defect below the log surface increases. Light bark 

distortions, because of their greater d'epth below the log 

surface, are not considered defects in grading factory 

lumber logs, but medium and heavy distortions are. 

Likewise, many of the grading systems for veneer logs 

disregard light bark distortions. The clear area between the 

log surface and the defect is important in determining 

product suitability and, therefore, the log's economic value. 

Figure 5.-Light bark distortion and associated internal defects. 

Stereo view of defect indicator 
Figure 5 (Continued) 

Defect size ............................ 1 x 1 inches 

Log diameter at defect (ib). ............... 12.5 inches 

Round-up thickness. .................... 0.3 inch 

Core diameter ......................... 6.0 inches 

Defect distance above stump ............. 20.0 feet 

Depth belowLogsurface .............................. 3.0inches 

First sheet of veneer. ...................... 3.3 inches 

Depth belowLog surface .............................. 3.5 inches 

First sheet of veneer. ...................... 3.8 inches 

Total Veneer Thickness .................... 3.0 inches 

(photograph taken V2 inch inside of core) 

10 
, . 

Figure 6.-Medium bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 3 x 3 inches Depth belowLog diameter at defect (ib) ................ 12.8 inches 

Round-up thickness. .................... 0.5 inch Log surface .............................. 2.1 inches 

Core diameter ......................... 5.7 inches First sheet of veneer. ...................... 2.6 inches 

Defect distance above stump ............. 21.5 feet 
Figure 6 (Continued) 

Depth belowLogsurface .............................. 2.3inches 

First sheet of veneer. ...................... 2.8 inches 

Depth belowLogsurface .............................. 2.9inches 

First sheet of veneer. ...................... 3.4 inches 

Depth belowLog surface. ............................. 2.5 inches 

First sheet of veneer. ...................... 3.0 inches 

Total Veneer Thickness .................... 2.9 inches 
Figure 7.-Heavy bark distortion and associated internal defects. 

Stereo view of defect indicator 

Defect size ............................ 2 x 2 inches Depth belowLog diameter at defect (ib). ............... 12.0 inches 

Round-up thickness ..................... 0.7 inch Log surface. ............................... 0.5 inch 

Core diameter ......................... 5.7 inches First sheet of veneer. ...................... 1.2 inches 

Defect distance above stump ............. 27.0 feet